Diesel engine control

专利摘要:
In the diesel engine provided with the exhaust gas recirculation valve 6, the target exhaust gas recirculation amount determined based on the engine running condition is compared with the maximum recirculation amount of the valve 6 (S28). When the target exhaust gas recirculation amount exceeds the maximum recirculation amount, the target exhaust gas recirculation amount is limited to the maximum flow rate (S28). Even after the target exhaust gas recirculation amount, the exhaust gas recirculation amount 6 keeps the opening of the exhaust gas recirculation valve 6 in accordance with the maximum recirculation amount for a predetermined time (S26), so that the exhaust gas recirculation amount accurately follows the target amount.
公开号:KR20020019546A
申请号:KR1020027000770
申请日:2001-05-15
公开日:2002-03-12
发明作者:이토야마히로유키
申请人:하나와 요시카즈；닛산 지도우샤 가부시키가이샤；
IPC主号:

专利说明:

Diesel engine control {DIESEL ENGINE CONTROL}
[2] Japanese Patent Application Laid-Open No. 8-128361 (1996) discloses an exhaust gas recirculation (EGR) apparatus that suppresses the combustion temperature of a diesel engine by a recirculation portion of exhaust gas to intake air. This EGR apparatus changes the exhaust gas recirculation amount (EGR amount) as the exhaust gas recirculation valve (EGR valve) opens. When the EGR valve is operated using an actuator, when the command signal is input to the actuator A delay occurs until the EGR valve starts operating. In connection therewith, in the above-described prior art, pre-processing corresponding to the delay is applied to the command signal of the actuator to improve the accuracy of the EGR control.
[1] The present invention relates to control of a diesel engine provided with an exhaust gas recirculation device.
[12] 1 is a schematic view of a control apparatus for a diesel engine according to the present invention.
[13] 2 is a schematic view of a common rail fuel injector installed in a diesel engine.
[14] 3 is a flowchart showing a routine for calculating a target fuel injection quantity Qsol executed by the controller according to the present invention.
[15] 4 is a chart showing the volume of the basic fuel injection quantity diagram stored by the controller.
[16] 5 is a flowchart showing a routine for calculating the EGR valve opening area (Aev) executed by the controller.
[17] 6 is a chart showing the volume of the EGR valve lift amount stored by the controller.
[18] 7 is a flowchart showing a routine for calculating the target EGR amount Tqek for the cylinder executed by the controller.
[19] 8 is a flowchart showing a routine for calculating the cylinder intake fresh-air amount Qac executed by the controller.
[20] 9 is a flowchart showing a routine for calculating the intake fresh-air flow rate Qas0 of the intake passage executed by the controller.
[21] 10 is a chart showing the volume of the intake air amount diagram stored by the controller.
[22] 11 is a flowchart showing a routine for calculating the target EGR rate Megr executed by the controller.
[23] 12 is a chart showing the volume of the plot of the basic target EGR rate (Megrb) stored by the controller.
[24] 13 is a chart showing the volume of the plot of the water temperature correction coefficient (Kegr_tw) stored by the controller.
[25] 14 is a flowchart showing the complete combustion judgment routine executed by the controller.
[26] 15 is a flowchart showing a routine for calculating the duty value (Dtyvnt) of the pressure control value of the supercharger executed by the control unit.
[27] Fig. 16 is similar to Fig. 15, but shows another embodiment of the present invention.
[28] 17 is a flowchart showing a routine for calculating the EGR rate (Megrd) of the intake valve position executed by the control unit.
[29] 18 is a flowchart showing a routine for calculating a time constant value Kkin executed by the control unit.
[30] 19 is a flowchart showing the volume of a plot of the volume efficiency equivalent basic value (Kinb) executed by the control unit.
[31] 20 is a flowchart showing a subroutine for calculating a target intake air amount tQac executed by the control unit.
[32] Fig. 21 is a chart showing the volume of a plot of the target intake air amount basic value tQacb executed by the control unit. Fig.
[33] 22 is a chart showing the volume of the plot of the correction factor ktQac stored by the control unit.
[34] Fig. 23 is a chart showing the volume of a plot of the target intake air amount tQac stored by the control unit.
[35] 24 is a flowchart showing a subroutine for calculating the actual EGR amount Qec executed by the control unit.
[36] 25 is a flowchart showing a routine for calculating a target opening (Rvnt) of the variable fuel injection nozzle executed by the control unit.
[37] 26 is a chart showing the volume of the plot of the target opening (Rvnt) stored by the control unit.
[38] Fig. 27 is similar to Fig. 25, but shows another embodiment of the present invention.
[39] 28 shows a second embodiment of the present invention, similar to FIG. 26, but different.
[40] 29 is a flowchart showing a routine for calculating the open loop control amount Avnt_f of the target opening executed by the control unit.
[41] 30 is a flowchart showing a routine for calculating a feedback control amount Avnt_fb of the target opening executed by the control unit.
[42] 31 is a flowchart showing a subroutine for executing the linearization process of the target opening executed by the control unit.
[43] 32 is a chart showing the volume of the plot of the target opening (Rvnt) stored by the control unit.
[44] 33 is a chart showing the relationship between the opening area of the variable nozzle and the boost pressure.
[45] 34 is a flowchart showing a subroutine for setting the duty value (Dtyvnt) of the pressure control valve of the supercharger executed by the control unit.
[46] 35 is a flowchart showing a subroutine for setting the duty selection signal flag fvnt2 executed by the control unit.
[47] 36 is a flowchart showing a routine for correcting the temperature correction amount (Dty_t) of the duty value executed by the control unit.
[48] Figure 37 is a chart showing the volume of a plot of the base exhaust gas temperature (Texhb) stored for the control unit.
[49] 38 is a chart showing the volume of the plot of the water temperature correction coefficient (Ktexh_Tw) stored in the control unit.
[50] 39 is a chart showing the volume of the plot of the temperature correction amount (Dty_t) stored in the control unit.
[51] 40 is a chart showing the temperature characteristic of the actuator of the supercharger.
[52] 41 is a diagram of the volume of a plot of the duty value (Duty_h) when the opening of the variable nozzle is constant or increased when the variable nozzle stored by the control unit is completely closed.
[53] Fig. 42 is a diagram of the volume of the plot of the duty value (Duty_l) when the opening of the variable nozzle is constant or increases when the variable nozzle stored by the control unit is completely opened.
[54] Fig. 43 is similar to Fig. 41, but shows a case where the opening of the variable nozzle is decreasing.
[55] Fig. 44 is similar to Fig. 42, but shows a case where the opening of the variable nozzle is decreasing.
[56] 45 is a chart showing the hysteresis phenomenon in the relationship between the command-opening linearization processing value and the duty value according to the present invention.
[57] 46 is a flowchart showing the operation check subroutine executed by the control unit;
[58] 47 is a flowchart showing a routine for calculating the duty value (Dtyvnt) executed by the control unit.
[59] Fig. 48 is a chart showing the volume of the diagram of the control pattern value (Duty_pu) stored by the control unit.
[60] 49 is a chart showing the volume of the plot of the duty value (Duty_p_ne) stored by the control unit.
[61] 50 is a flowchart showing a subroutine for calculating the EGR amount feedback correction coefficient Kqac00, the EGR flow velocity feedback correction coefficient Kqac0, and the EGR flow velocity learning correction coefficient Kqac executed by the control unit.
[62] 51 is a flowchart showing a routine for setting the feedback permission flag fefb executed by the control unit.
[63] 52 is a flowchart showing a routine for setting the learning value reflection permission flag felrn2 executed by the control unit.
[64] 53 is a flowchart showing a routine for setting the learning value tolerance flag felrn executed by the control unit.
[65] 54 is a flowchart showing a routine for calculating the EGR amount feedback correction coefficient (Qqac00) executed by the control unit.
[66] 55 is a chart showing the volume of the plot of the correction gain stored by the control unit;
[67] 56 is a chart showing the volume of the plot of the water temperature correction coefficient (KgfbTw) stored by the control unit.
[68] 57 is a flowchart showing a routine for calculating the EGR flow velocity feedback correction coefficient (Qqac0) executed by the control unit.
[69] 58 is a chart showing the volume of the plot of the correction gain (Gkfbi) of the EGR flow velocity stored by the control unit.
[70] 59 is a chart showing the volume of the plot of the water temperature correction coefficient (KgfbiTw) stored by the control unit.
[71] 60 is a chart showing the volume of the plot of the error ratio learning value (Rqac _n ) stored by the control unit.
[72] 61 is a flowchart showing a routine for updating the learning value executed by the control unit.
[73] 62 is a chart showing the volume of the plot of the learning rate Tclrn stored by the control unit.
[74] 63 is a flowchart showing a routine for calculating the EGR value flow rate Cqe executed by the control unit.
[75] Fig. 64 is a diagram showing the volume of the diagram of the EGR value flow rate Cqe stored by the control unit.
[76] 65 is a flowchart showing a routine for setting a physical limiter executed by the control unit.
[77] 66A and 66B are graphs showing changes in the amount of EGR under the control according to the present invention when the diesel engine is in the transient state.
[78] 67A to 67C are graphs showing the difference between the EGR rate, the EGR valve opening, and the EGR valve front and rear pressure when the vehicle decelerates under the control according to the present invention.
[79] Figs. 68A to 68C are graphs showing changes in the speed of the jet, the change in the EGR rate, and the amount of nitrogen oxide (NOx) emissions under the control according to the present invention.
[80] 69 is a flowchart showing a routine for calculating an EGR valve opening area (Aev) according to the third embodiment of the present invention.
[81] 70 is a flowchart showing a routine for calculating a restricted target EGR amount (Tqecf) for a cylinder according to the third embodiment of the present invention.
[82] 71 is a flowchart showing a routine for setting a physical limiter according to the third embodiment of the present invention.
[83] 72 is a flowchart showing a routine for calculating a delay processing value (RVNTE) according to the third embodiment of the present invention.
[84] 73 is a chart showing the volume of a plot of the maximum flow velocity basic value (Egmaxb) according to the third embodiment of the present invention.
[85] 74 is a chart showing the volume of the plot of the maximum flow velocity correction coefficient (Kemin) according to the third embodiment of the present invention.
[86] 75 is a chart showing the volume of an experimental drawing of the EGR valve opening area (Eaev) per unit displacement according to the third embodiment of the present invention.
[87] Figure 76 is similar to Figure 75, but shows theoretical values.
[3] The EGR control has characteristics, for example, that the EGR amount increases when the vehicle decelerates and the EGR amount decreases when the vehicle accelerates. When the diesel engine is running in an elapsed state, the EGR amount must be changed by a good response to obtain an appropriate EGR amount according to these control characteristics. In the prior art, the response delay of the actuator is compensated by pretreatment, but the required time for the exhaust gas to move from the EGR valve of the engine to the cylinder is not compensated.
[4] Further, according to the prior art apparatus, the command value of the EGR amount is calculated by the control unit, but any physical restriction is not set on the obtained command value, and the command exceeding the maximum EGR amount that can be physically reached by the EGR valve Or a command value equal to or less than the minimum EGR amount that can be physically reached by the EGR valve to be set is possible, the response of the EGR control can be deteriorated.
[5] Therefore, an object of the present invention is to eliminate the delay of the EGR valve due to the time required for the exhaust gas to flow from the EGR valve of the engine to the cylinder, and to improve the ability of the EGR amount to follow the target value.
[6] It is also an object of the present invention to prevent the command value of the EGR amount from exceeding the physical limit of the EGR valve.
[7] In order to achieve the above object, the present invention provides an engine having an engine having an exhaust gas recirculation valve for recirculating a part of an exhaust gas to an exhaust passage in a combustion chamber, an intake passage for exhausting air from the combustion chamber, Thereby providing a control device.
[8] The control device sets a target exhaust gas recirculation amount based on a sensor that detects a running condition of the engine and a running condition, determines a maximum recirculation amount of the exhaust gas recirculation valve, compares a maximum recirculation amount with a target exhaust gas recirculation amount Limits the target exhaust gas recirculation amount so as to be equal to the maximum recirculation amount when the target exhaust gas recirculation amount exceeds the maximum recirculation amount, controls the opening of the exhaust gas recirculation valve based on the target exhaust gas recirculation amount, And the opening of the exhaust gas recirculation valve is programmed to maintain an opening corresponding to a maximum recirculation amount for a predetermined time after the gas recirculation amount falls below a maximum recirculation amount.
[9] The present invention also relates to an apparatus for detecting a running condition of an engine, a mechanism for setting a target exhaust gas recirculation amount based on driving conditions, a mechanism for determining a maximum recirculation amount of the exhaust gas recirculation valve, A mechanism for limiting the target exhaust gas recirculation amount so as to be equal to the maximum recirculation amount when the target exhaust gas recirculation amount exceeds the maximum recirculation amount, a mechanism for limiting the exhaust gas recirculation amount based on the target exhaust gas recirculation amount, A control device for controlling the opening of the recirculation valve and a mechanism for maintaining the opening of the exhaust gas recirculation valve corresponding to the maximum recirculation amount for a predetermined time after the target exhaust gas recirculation amount falls below the maximum recirculation amount Lt; / RTI >
[10] The present invention also relates to a method for controlling an exhaust gas recirculation system, comprising: setting a target exhaust gas recirculation amount based on driving conditions; determining a maximum recirculation amount of the exhaust gas recirculation valve; comparing a maximum recirculation amount with a target exhaust gas recirculation amount; Limiting the target exhaust gas recirculation amount to be equal to the maximum recirculation amount when the recirculation amount exceeds the maximum recirculation amount, controlling the opening of the exhaust gas recirculation valve based on the target exhaust gas recirculation amount, And opening the exhaust gas recirculation valve for a predetermined period of time after falling to the maximum recirculation amount, maintaining an opening corresponding to the maximum recirculation amount.
[11] The description of the advantages of the invention, as well as other features, is set forth in detail in the remainder of the specification and is illustrated in the accompanying drawings.
[88] (Embodiment 1)
[89] Referring to Fig. 1, the diesel engine 1 has an intake passage 3 and an exhaust passage 2. The intake passage 3 and the exhaust passage 2 are shown in Fig. The diesel engine 1 is a multi-cylinder diesel engine in which the pattern of heat generation is configured to be single-stage combustion due to low-temperature premixed combustion. Such a diesel engine is disclosed in Japanese Patent Application Laid-Open No. 8-86251, 1999. The intake air of the intake passage 3 is supplied to each cylinder of the diesel engine through the collector 3A. The compressor 55 of the variable capacity supercharger 50 is installed upstream of the intake passage 3 of the collector 3A. The swirl control valve is installed in the intake port leading each cylinder from the intake passage (3). When the diesel engine 1 is running at a low rotational speed at a low load, it closes a portion of the passage and causes a swirl in the flow of air flowing into the combustion chamber 1A of the diesel engine 1.
[90] The combustion chamber 1A has a large-diameter annular combustion chamber. This is a combustion chamber in which a cylinder cavity of the same diameter is formed at the bottom along the cap surface on the piston. A conical portion is formed at the bottom of the cavity. Therefore, the resistance to the vortex entering from the outside of the cavity is reduced, and the mixing of the air and the fuel is enhanced. Also, due to the cavity shape, the swirl spreads from the center of the cavity to the outside as the piston is lowered.
[91] The diesel engine 1 has a fuel injection device 10 of a general rail type.
[92] 2, the fuel injection device 10 includes a fuel tank 11, a fuel supply passage 12, a supply pump 14, an accumulation chamber 16A formed in a common rail 16, (Not shown). The fuel supplied from the supply pump 14 is stored in the accumulation chamber 16A through the high-pressure fuel passage 15, and is then distributed to the respective nozzles 17. [
[93] The nozzle 17 includes a needle valve 18, a nozzle chamber 19, a fuel passage 20 for the nozzle chamber 19, a retainer 21, a hydraulic piston 22, a return spring 23, a hydraulic piston Way solenoid valve 25 horizontally inserted into the fuel passage 24 and the fuel passage 24 leading to the high-pressure fuel. The return spring 23 pushes the needle valve 18 in the closing direction of the lower portion of the figure through the retainer 21. The hydraulic piston 22 contacts the upper edge of the retainer 21.
[94] The three-way valve 25 has a port A connected to the accumulation chamber 16A, a port B connected to the fuel passage 24 and a port C connected to the drain passage 28. When the three-way valve 25 is OFF, ports A and B are connected, and ports B and C are shut off. Therefore, the fuel passages 20 and 24 are connected, and the high-pressure fuel is guided from the accumulation chamber 16A to both the upper portion of the hydraulic piston 22 and the nozzle chamber 19. [ Since the pressure receiving area of the hydraulic piston 22 is larger than the pressure receiving area of the needle valve 18, in this state, the needle valve 18 is seated on the valve seat, whereby the nozzle 17 is closed.
[95] In the state in which the three-way valve 25 is ON, the ports A and B are shut off and the ports B and C are connected.
[96] The fuel pressure of the fuel passage 24 pushing the hydraulic piston 22 downward is discharged to the fuel tank 11 through the drain passage 28 and the fuel of the nozzle chamber 19 which acts the upward direction of the needle valve The needle valve 18 is raised by the pressure, and the fuel in the nozzle chamber 19 is injected from the hole at the end of the nozzle 17. When the three-way valve 25 is returned to the OFF state, the fuel pressure in the accumulation chamber 16A again operates the hydraulic piston downward, and the needle valve 18 is seated on the valve seat, and the fuel injection is terminated.
[97] That is, the fuel injection start timing is adjusted by the conversion timing from the OFF state to the ON state of the three-way valve 25, and the fuel injection amount is adjusted by the ON state duration period. Therefore, if the pressure in the accumulation chamber 16A is the same, the fuel injection amount increases the ON time of the three-way valve 25 longer.
[98] In order to adjust the pressure in the accumulation chamber 16A, the fuel injection device 10 has a return passage 13 for returning the surplus fuel discharged by the supply pump 14 to the fuel supply passage 12 . The return passage 13 is provided with a pressure control valve 31. The pressure regulating valve 31 opens and closes the return passage 13 and adjusts the pressure of the accumulation chamber 16A by changing the fuel injection amount with respect to the accumulation chamber 16A.
[99] The fuel pressure in the accumulation chamber 16A is equal to the fuel injection pressure of the nozzle 17 and becomes higher than the high fuel pressure in the fuel injection rate accumulation chamber 16. [ The three-way valve 25 and the pressure regulating valve 31 function according to the input signal from the control unit 41.
[100] The structure of the fuel injection device 10 is known from pages 73 to 77 of the thirteenth international conference on internal combustion engines.
[101] Referring again to FIG. 1, the exhaust gas drives the exhaust gas turbine 52 of the variable capacity supercharger 50 in the exhaust passage 2, and then is discharged to the atmosphere side. The variable capacity supercharger 50 has an exhaust gas turbine 52 and a compressor 55 that compresses the air by rotation of the exhaust gas turbine 52. The intake passage 3 supplies the air supercharged by the compressor 55 to the diesel engine 1. The variable nozzle 53 driven by the pressure actuator 54 is installed at the inlet of the exhaust gas turbine 52.
[102] The pressure actuator 54 includes a diaphragm actuator 59 for driving the variable nozzle 53 in accordance with the signal pressure and a pressure control valve 56 for generating a signal pressure in accordance with the duty signal input from the control unit 41. The control unit 41 generates the duty signal so that the opening of the variable nozzle 53 is equal to the target opening Rvnt. Based on the target opening Rvnt, the control unit 41 controls the variable nozzle 53 to reduce the nozzle opening when the rotational speed of the diesel engine 1 is low. Therefore, the flow rate of the exhaust gas guided to the exhaust gas turbine 52 is increased to reach a predetermined boost pressure. On the other hand, when the rotational speed of the diesel engine 1 is high, the control unit 41 controls the variable nozzle 53 to fully open to guide the exhaust gas to the exhaust gas turbine 52 without resistance.
[103] When the gaseous fuel mixture is burned in the diesel engine 1, harmful nitrogen oxides (NOx) are formed. The amount of nitrogen oxide depends mainly on the combustion temperature, and the amount of generated nitrogen oxide can be suppressed by making the combustion temperature low. The present diesel engine 1 reduces the oxygen concentration in the combustion chamber 1A by exhaust gas recirculation (EGR), thereby realizing low-temperature combustion. For this purpose, the diesel engine 1 has an exhaust gas recirculation (EGR) passage 4 connected to the exhaust passage 2 upstream of the exhaust gas turbine 52 and a collector 3A of the intake passage 3 . A diaphragm-type exhaust gas recirculation (EGR) valve 6, which reacts to control the sound pressure provided from the sound pressure control valve 5 and the cooling device 7, is installed in the EGR passage 4. [
[104] The negative pressure control valve 5 generates a negative pressure in response to the duty signal input from the collector 41, thereby changing the exhaust gas recirculation rate (EGR rate) through the EGR valve 6. [
[105] For example, in the low rotational speed and low load regions of the diesel engine 1, the EGR rate is at most 100%, and as the rotational speed and the load of the diesel engine 1 increase, the EGR rate decreases. At a high load, since the exhaust gas temperature is high, the intake air temperature will rise if a large amount of EGR is performed. The intake air temperature rises, the nitrogen oxide (NOx) no longer decreases, the ignition delay of the injected fuel becomes shorter, and it becomes impossible to obtain premixed combustion. Therefore, the EGR rate is reduced at the same stage as the rotational speed and load of the diesel engine 1 increase.
[106] The cooling device 7 guides the portion of the engine coolant to the water jacket 8 around the EGR passage 4 and cools the exhaust gas recirculated in the EGR passage 4. [ The cooling water inlet 7A of the water jacket 8 is provided with a flow control valve 9 for regulating the recirculation amount of the cooling water according to a signal from the control unit 41. [
[107] The pressure regulating valve 31, the three-way valve 25, the negative pressure control valve 5, the pressure actuator 54 and the flow control valve 9 are controlled by signals from the control unit 41, respectively. The control unit 41 includes a microcomputer equipped with a CPU, a RAM, a ROM, and an input / output interface (I / O interface).
[108] A pressure sensor 32 for detecting the fuel pressure in the accumulator 16A, an accelerator opening sensor 33 for detecting the opening Cl of the vehicle accelerator pedal, a rotational speed Ne of the diesel engine 1, A cylinder check sensor 35 for identifying the cylinder of the diesel engine 1, a water temperature sensor 36 for detecting the coolant temperature Tw of the diesel engine 1, and a compressor 55. The crank angle sensor 34 detects the crank angle sensor 34, A signal corresponding to the detected value is input to the control unit 41 from the air flowmeter 39 for detecting the intake air flow rate upstream of the intake passage 3 of the engine.
[109] The control unit 41 calculates the target fuel injection amount of the nozzle 17 and the target pressure of the accumulation chamber 16A based on the rotational speed Ne of the diesel engine 1 and accelerator opening Cl. The fuel pressure in the accumulator 16A is feedback-controlled by opening and closing the pressure regulating valve 31 so that the actual pressure of the accumulator 16A detected by the pressure sensor 32 coincides with the target pressure.
[110] The control unit 41 controls the three-way valve 25 in accordance with the target fuel injection amount and the fuel injection start timing, which are calculated in accordance with the running condition of the diesel engine 1, (ON) time of the signal line 25 is controlled. For example, when the diesel engine 1 is in a low rotational speed and low load state under a high EGR rate, the fuel injection start timing is delayed near the top dead center of the piston so that the ignition delay of the injected fuel is long. Due to this delay, the temperature of the combustion chamber 1A at the ignition time is lowered, and the generation of soot due to the high EGR rate is suppressed by increasing the premixed combustion consumption. On the other hand, the injection start timing is advanced as the rotational speed and load of the diesel engine 1 increase. This is due to the following reasons. Specifically, even if the ignition delay period is constant, the ignition delay crank angle obtained by changing the ignition delay period increases in proportion to the engine speed increase. Therefore, in order to ignite the fuel injected at a predetermined crank angle, the injection start timing needs to be advanced at a high rotation speed.
[111] The control unit 41 also controls the supercharger pressure and the EGR amount.
[112] As mentioned before, if the EGR amount is changed, the boost pressure will also change. Conversely, if the boost pressure changes, the EGR amount changes as the exhaust gas pressure changes. Therefore, the boost pressure and the EGR amount can not be independently controlled and can cause an external control disturbance to each other.
[113] When the EGR amount is changed, if the boost pressure is to be kept constant, the opening of the variable nozzle 53 of the turbocharger 50 must be readjusted. Further, when the boost pressure is changed, if the EGR amount is to be kept constant, the opening of the EGR valve 6 must be readjusted. In this way, it is difficult to ensure precise control during the transient state of the engine.
[114] The control unit 41 according to the present invention calculates the target intake air amount tQac of the intake passage 3 in accordance with the vehicle running condition and calculates the target intake air amount tQac from the target intake air amount tQac to the openable target value of the supercharger 50 The actual EGR amount for the cylinder at the position of the intake valve of the diesel engine 1 and the EGR rate Megrd of the intake air via the intake valve of the diesel engine 1 are set. Megrd is also referred to as the actual EGR rate. The duty value Dtyvnt supplied to the pressure control valve 56 is then determined using the routine shown in Fig. 15, and the pressure control valve 56 is controlled so that the variable nozzle 53 reaches the target opening Rvnt A corresponding command signal is output. In this way, the control unit 41 controls the supercharging pressure of the supercharger 50.
[115] The control unit 41 also calculates the required EGR amount Mqec of the EGR valve 6 based on the target EGR rate Megr determined according to the running condition of the vehicle. Considering the required time for the exhaust gas to travel from the EGR valve 6 to the intake valve of the diesel engine 1 via the collector 3A, the intermediate value representing the required EGR amount for the cylinder to the intake valve position is calculated The required EGR amount (Mqec) is applied to the delay processing. The control unit 41 also preprocesses the intermediate value Rqec to correct the response delay of the negative pressure control valve 5 and the EGR valve 6 as in the prior art. The target EGR amount (Tqec) for the cylinder is calculated in this manner.
[116] However, due to the physical limitations of the negative pressure control valve 5 or the EGR valve 6, even if a command signal corresponding to the target EGR amount is outputted to the negative pressure control valve 5, the target EGR amount Tqec may not be reached have.
[117] Incidentally, the control unit 41 executes the following processes (A) to (E) which are essential features of the present invention.
[118] (A) The maximum value of the actually reachable EGR amount is set in accordance with the EGR valve flow rate Cqe as a physical upper limit (Tqelmh). The EGR valve flow rate Cqe is the flow rate of the exhaust gas passing through the EGR valve 6. [
[119] (B) The minimum value of the actual reachable EGR amount is set as the physical lower limit (Tqem1). The physical lower limit (Tqelml) is set to, for example, zero.
[120] (C) The overshoot to the physical upper limit (Tqelmh) of the target EGR amount (Tqec) or the deficiency to the physical lower limit (Tqem1) is calculated as the over / under amount (Dtqec) for each output of the command signal. The negative value Tqec1 is calculated by adding the excess / deficiency amount Dtqec _n-1 calculated in the previous preceding case in which the command signal was output and the target EGR amount Tqec calculated in the present case in which the command signal is output.
[121] (Dq) The limit target EGR amount Tqecf is computed by applying the physical upper limit Tqelmh and the physical lower limit Tqelml to the negative value Tqec1 and a command signal corresponding to the restricted target EGR amount Tqecf is calculated (5).
[122] (E) The value obtained by subtracting the restricted target EGR amount (Tqec) from the negative value (Tqec1) is calculated as the excess / deficiency amount (Dtqec _n-1 ) for outputting the signal in the following cases.
[123] The control executed by the control unit 41 is described with reference to the flowchart. Among all the routines shown in the flowchart, the independent routines are executed at the intervals described separately below, and the subroutines are executed at the execution intervals of the parent routines.
[124] Figs. 3, 4 and 8 to 14 are known from Japanese Patent Application Laid-Open No. 10-288071, 1998.
[125] First, a routine for calculating general parameters used for control of boost pressure and EGR amount is shown. The general parameters include a target fuel injection quantity Qsol of the fuel injector 10, a target EGR rate Megr of the EGR valve 6, a value Kkin such as a time constant, an actual EGR rate Megrd, The intake air fresh air flow rate Qas0 of the intake passage 3, and the actual EGR amount Qec. The value Kkin of the time constant is a value indicative of the EGR control delay due to the collector 3A inserted between the EGR valve 6 and the intake valve of the diesel engine 1. [ The actual EGR rate Megrd shows the EGR rate of the intake air passing through the intake valve of the diesel engine 1. [ The actual EGR rate Megrd changes the first order delay with respect to the target EGR rate Megr. The calculation of these parameters is executed irrespective of the boost pressure control routine and the EGR amount control routine.
[126] First, with reference to Fig. 3, a routine for calculating the target fuel injection quantity Qsol will be described. This routine is executed synchronously to the REF signal output by the crank angle sensor 34 for each reference position of each cylinder combustion cycle. In the case of a four stroke cycle engine, the REF signal is output every 180 degrees for a four-cylinder engine and every 120 degrees for a six-cylinder engine.
[127] First, in step S1, the engine speed Ne is read, and in step S2, the accelerator opening Cl is read.
[128] In step S3, the base fuel injection quantity Mqdrv is calculated by examining the diagram shown in Fig. 4 based on the engine rotation speed Ne and the accelerator opening Cl. This drawing is stored in the memory of the control unit 41 in advance.
[129] In step S4, the target fuel injection quantity Qsol is calculated by adding an increase correction based on the engine cooling water temperature Tw to the base fuel injection quantity Mqdrv.
[130] Next, with reference to Fig. 11, a routine for calculating the target EGR rate Megr will be described. This routine is also executed synchronously with the REF signal.
[131] The control unit 41 first reads the engine rotation speed Ne, the target fuel injection quantity Qsol and the engine cooling water temperature Tw at step S51.
[132] 12, the basic target EGR rate Megrb is calculated from the engine rotational speed Ne and the target fuel injection quantity Qsol. In step S52, the basic target EGR rate Megrb is calculated from the engine rotational speed Ne and the target fuel injection quantity Qsol. This drawing is stored in the memory of the control unit 41 in advance. In this figure, the basic target EGR rate Megrb is set higher in the region where the operating frequency of the engine is high. This region corresponds to a region where both the rotational speed Ne and the load are small. In this figure, since the load is represented by the target fuel amount Qsol or the like when the engine output is high and soot is likely to be generated, the basic target EGR ratio is set to have a low value in this region.
[133] In step S53, referring to the diagram shown in Fig. 13, the water temperature correction coefficient Kegr_Tw of the basic target EGR rate Megrb is calculated from the cooling water temperature Tw. This drawing is stored in the memory of the control unit 41 in advance.
[134] In step S54, the target EGR rate Megr is calculated from the basic target EGR rate Megrb and the water temperature correction coefficient Kegr_Tw by the following equation (1).
[135] Megr = Megrb · Kegr_Tw (1)
[136] In step S55, the subroutine shown in Fig. 14 for determining whether or not the diesel engine is in the complete combustion state is executed.
[137] In step S61, the engine rotational speed Ne is read. In step S62, the engine rotational speed Ne that determines the slice level NRPMK corresponding to the complete combustion rotational speed is calculated, And complete combustion are compared.
[138] The slice level NRPMK is set to, for example, 400 rpm. When the engine rotation speed Ne exceeds the slice level NRPMK, the routine proceeds to step S63.
[139] Here, when the counter value Tmrkb is larger than the predetermined time TMRKBP, the counter value Tmrkb is compared with the predetermined time TMRKBP, and the complete combustion flag is changed from ON to ON in step S64, Lt; / RTI >
[140] When the engine rotation speed Ne is equal to or lower than the slice level NRPMK in step S62, the subroutine proceeds to step S66. Here, the counter value Tmrkb is set to 0, and the complete combustion flag is turned off in the next step S67, and the subroutine is terminated.
[141] When the counter value Tmrkb is equal to or smaller than the predetermined time TMRKBP in step S63, the counter value Tmrkb is increased in step S65 and the subroutine is terminated.
[142] In this subroutine, even if the engine rotation speed Ne exceeds the slice level NRPMK, the complete combustion flag does not immediately turn on, and after this state continues for the predetermined time TMRKBP, The flag immediately changes to ON.
[143] Referring again to Fig. 11, after executing the subroutine of Fig. 14, the control unit 41 determines the complete combustion flag in step S56. When the complete combustion flag is ON, the subroutine of FIG. 11 ends. When the complete combustion flag is OFF, the target EGR rate Megr is reset to 0 in step S57, and the subroutine of FIG. 11 is ended.
[144] 17 and 18, a routine for calculating the time constant value Kkin and the actual EGR rate Megrd will be described. The actual EGR rate Megrd is changed by the first order delay with respect to the target EGR rate Megr. (Kkin) and the actual EGR rate (Megrd) are described together.
[145] FIG. 18 shows a routine for calculating a time constant value Kkin. This routine is executed synchronously with the REF signal.
[146] The control unit 41 reads the engine rotational speed Ne, the target fuel injection quantity Qsol, and the preceding leading value (Megrd _n-1 (%)) of the actual EGR rate in step S91. The previous leading value (Megrd _n-1 ) is the Megrd value calculated in the previous precedent case when the routine is executed.
[147] In step S92, the volume efficiency equivalent base value Kinb is calculated from the engine rotation speed Ne and the target fuel injection quantity Qsol by examining the figure shown in Fig. 19 stored in advance in the memory of the control unit 41 .
[148] In step S93, the volume efficiency equivalent basic value Kinb is calculated from the following equation (2). When EGR is executed, the ratio of the fresh air in the intake air decreases, and the volume efficiency decreases. This reduction is reflected in the computation of the value Kin, such as volume efficiency, through the volume efficiency equivalent base value (Kinb).
[149] (2)
[150] In step S94, the time constant value Kkin corresponding to the capacity of the collector 3A is calculated by multiplying the value Kin such as volume efficiency by a constant KVOL.
[151] The constant (KVOL) is expressed by the following equation (3).
[152] KVOL = (VE / NC) / VM (3)
[153] VE = exhaust amount of diesel engine 1,
[154] NC = number of cylinders of diesel engine 1, and
[155] VM = volume of passage from collector 3A to intake valve.
[156] FIG. 17 shows a routine for calculating the actual EGR rate (Megrd). This routine is executed at intervals of 1/100 second.
[157] The control unit 41 first reads the target EGR rate Megr in step S81.
[158] In the next step S82, the time constant value Kkin is read. The routine of Fig. 18 for calculating the time constant value Kkin is executed synchronously with the REF signal, and this routine for calculating the actual EGR rate Megrd is executed at 1/100 second intervals. Therefore, the value Kkin such as the time constant is a time constant value Kkin calculated by the routine of Fig. 18 immediately before the execution of the routine of Fig. Likewise, the previous preceding value (Megrd _n-1 ) of the actual EGR rate read by the routine of Fig. 18 is the actual EGR rate calculated by the routine of Fig. 17 just before the execution of the routine of Fig.
[159] In step S83, the actual EGR rate Megrd is calculated from the following equation (4) using the target EGR rate Megr, the previous preceding value Megrd _n-1 , and the value Kkin such as the time constant.
[160] Megrd = Megr · Ne · Ke2 # + Megrd _n-1 · (1 -Kkin · Ne · KE2 #) (4)
[161] However, KE2 # = constant.
[162] In this equation, Ne · KE2 # is a value for converting the EGR rate per intake stroke of each cylinder and the EGR rate per unit time.
[163] Next, with reference to Fig. 8, a routine for calculating the cylinder intake fresh air amount Qac will be described. This routine is executed synchronously with the REF signal. The cylinder intake fresh air quantity Qac is expressed by the intake fresh-air quantity at the intake valve position of one cylinder of the diesel engine 1. The cylinder intake fresh air amount Qac is calculated from the fresh air flow rate Qas0 of the intake passage 3 detected by the air flow meter 39 but the air flow meter 39 is located upstream of the compressor 55 The cylinder intake fresh air quantity Qac is calculated in consideration of time until air passes through the collector 3A and the air flow meter 39 adopted in the cylinder.
[164] First, in step S31, the control unit 41 reads the engine rotation speed Ne of the intake passage 3 and the fresh air flow rate Qas0.
[165] In step S32, the intake fresh-air flow rate Qas0 is converted into the intake fresh-air amount Qac0 per cylinder by the following equation (5).
[166] (5)
[167] However, KCON # = constant
[168] The constant KCON # is a constant for converting the intake fresh air flow rate Qas0 of the intake passage 3 into the intake fresh air amount Qac0 per cylinder.
[169] In a four-cylinder engine, the constant (KCON #) is 30 because the two cylinders perform air suction on each rotation. In a six-cylinder engine, the constant (KCON #) is 20, since the three cylinders perform air suction on each turn.
[170] A significant amount of time is required until the air passing through the air flow meter 39 is actually introduced into the cylinder. In order to correct this time difference, the control unit 41 executes the processing of steps S33 and S34.
[171] When considering the required time from the air flow meter 39 to the inlet of the collector 3A in step S33, the value Qac0 _nL of Qac0, which was the EGR flow velocity feedback correction coefficient before the routine in which L was executed, (Qac _n ) per cylinder. The value of L is determined experimentally.
[172] In consideration of the time difference from the collector 3A to the intake valves of the respective cylinders of the diesel engine 1 in step S34, the cylinder intake fresh-air quantity Qac is calculated by the first- do.
[173] Qac = Qac _n-1 (1 - Kkin) + QacnKkin (6)
[174] However, Kkin = value such as time constant, and
[175] Qac _n-1 = Qac operated on in the previous predecessor when the routine was executed.
[176] The signal input from the air flow meter 39 to the control unit 41 is the analog voltage signal Us and the control unit 41 supplies the analog voltage signal Us to the intake path 3 To the intake air flow rate Qas0. This routine is executed at intervals of 4/1000 seconds. In step S41, the control unit 41 reads the analog voltage signal, and in step S42, it examines the diagram shown in Fig. 10 and converts it into a flow rate Qas0_d. This drawing is stored in advance in the memory of the control unit 41. [
[177] In addition, in step S43, the weighted average processing executes the flow velocity Qas0_d, and the obtained value is regarded as the intake fresh air flow rate Qas0 of the intake passage 3.
[178] Next, with reference to Fig. 24, a routine for calculating the actual EGR amount Qec will be described. The actual EGR amount corresponds to the EGR amount per cylinder at the intake valve position. This routine is executed at intervals of 1/100 second.
[179] First, in step S111, the control unit 41 reads a value (Kkin) such as a cylinder intake air fresh air amount Qacn, a target EGR rate Megr, and a time constant according to the collector capacity at the inlet of the collector 3A . During the intake air fresh air amount per cylinder (Qac _n ) at the inlet of the collector 3A, the value calculated by the routine of FIG. 8 is used and during the time constant value Kkin, the value calculated by the routine of FIG. Is used.
[180] In the next step S112, the EGR amount Qec0 per cylinder at the inlet of the collector 3A is calculated by the following equation (7).
[181] Qec0 = Qacn · Mger (7)
[182] In the next step S113, the actual EGR amount Qec is calculated by the following equation (8), and the routine ends.
[183] Qec = Qec0 Ne KE # + Qec _n-1 (1 - Kkin Ne KE #
[184] However, KE # = constant, and
[185] Qec _n-1 = the previous operation if the preceding routine is carried Qec _n.
[186] Equation (8) allows delay processing similar to that of Equation (4).
[187] The control of the boost pressure control and the control of the EGR amount by the control unit 41 is performed based on the target fuel injection quantity Qsol, the value Kkin such as the time constant, the target EGR rate Megr, the actual EGR rate Mdgrd, Qac) and the actual EGR amount thus calculated.
[188] The boost pressure is controlled by the duty value (Dtyvnt) of the signal output to the pressure control valve (56) of the supercharger (50). When the duty value (Dtyvnt) is 0, the pressure control valve (56) is completely opened, and when the duty value is 1, it is completely closed.
[189] The routine shown in Fig. 15 determines the duty value (Dtyvnt). Therefore, this routine constitutes the main routine of boost pressure control. This routine is executed at intervals of 1/100 second.
[190] First, the control unit 41 reads the actual EGR rate Megrd in step S71. In step S72, the target intake air amount tQac is calculated using the subroutine shown in Fig.
[191] Referring to Fig. 20, first, in step S101, the control unit 41 reads the engine rotation speed Ne, the target fuel injection quantity Qsol, and the actual EGR rate Megrd. In step S102, the actual EGR rate Megrd is compared with a predetermined value MEGRLV #. The predetermined value MEGRVL # is a value for judging whether the exhaust gas recirculation is actually executed and set to, for example, 0.5%.
[192] In step S102, when Megrd> MEGRLV #, the subroutine proceeds to step S103. On the other hand, when Megrd MEGRLV #, the subroutine proceeds to step S106. (MEGRLV #) is not set to 0 in order to deal with the case of exhaust gas recirculation so small that the exhaust gas recirculation is not performed.
[193] In step S103, the target intake air amount basic value tQacb is calculated from the engine rotation speed Ne and the actual EGR rate Megrd by checking the diagram shown in Fig. When the engine rotational speed Ne is constant, this figure gives a larger actual EGR rate (Megrd) to a larger target intake air amount basic value tQacb. This drawing is stored in advance in the memory of the control unit 41. [
[194] Next, in step S104, the correction coefficient ktQac of the target intake air amount is calculated from the engine rotation speed Ne and the target fuel injection quantity Qsol by checking the diagram shown in Fig. The correction coefficient ktQac is a coefficient for setting the target intake air amount in accordance with the running condition of the vehicle.
[195] In step S105, the target intake air amount tQac is calculated by multiplying the target intake air amount basic value tQac by the correction coefficient ktQac.
[196] On the other hand, in step S106, when the exhaust gas recirculation is not performed, the target intake air amount tQac is calculated from the engine rotation speed Ne and the target fuel injection amount Qsol by checking the diagram shown in Fig. 23 .
[197] After calculating the target intake air amount tQac in this way, the subroutine ends.
[198] Next, in step S73 of Fig. 15, the control unit 41 reads the actual EGR amount Qec calculated by the routine of Fig.
[199] In step S74, the control unit 41 reads the target opening Rvnt of the variable nozzle 53. Here, the opening is a value indicating the open area of the variable nozzle 53 as a percentage of the open area when the nozzle is completely opened. Therefore, when the nozzle is fully opened, the opening is 100%, and when fully closed, the opening is 0%. Opening is used to indicate the opening of the variable nozzle 53 as a bolt that does not affect the capacity of the turbocharger 50, but of course the open area of the variable nozzle 53 can be used.
[200] The target opening Rvnt of the variable nozzle 53 is calculated by the routine shown in Fig. This routine is executed synchronously with the REF signal irrespective of the main routine of FIG.
[201] Referring to Fig. 25, in step S121, the control unit 41 first reads the target intake air amount tQac, the actual EGR amount Qec, the engine rotation speed, and the target fuel injection amount Qsol. In the next step S122, the intake air quantity value tQas0 for calculating the target opening Rvnt of the variable nozzle 53 is calculated by the following equation (9).
[202] tQas0 = (tQac + Qsol QFGAN #) Ne / KCON # (9)
[203] However, KCON # = constant.
[204] In step S123, the value Qes0 of the EGR amount is calculated by the following equation (10).
[205] Qes0 = Qec + Qsol QFGAN # Ne / KCON #
[206] In the equations (9) and (10), Ne / KCON # is a coefficient for converting the intake air amount per cylinder or the EGR amount into a value per unit time.
[207] Qsol QFGAN # is added to the target intake air amount tQac or the actual EGR amount Qec in order to change the target opening Rvnt according to the load of the diesel engine 1 in the equations (9) and (10) do.
[208] The effect of the target fuel injection quantity Qsol indicating the load of the diesel engine 1 is adjusted by the gain QFGAN #. In the following description, tQas0 calculated in this manner is referred to as a value such as an intake air amount, and Qes0 is referred to as a set value such as an EGR amount.
[209] In the next step S124, the target opening Rvnt of the variable nozzle 53 is calculated by examining the figure shown in Fig. 26 stored in advance based on the intake air amount value tQas0 and the value Qes0 such as the EGR amount .
[210] The target opening Rvnt is a value obtained by increasing the value Qes0 of the EGR amount in the right side region of the figure in which the intake air amount value tQas0 is large. . This is because of the following reasons. As the EGR amount increases, the fresh air decreases, and therefore, the air-fuel ratio becomes rich and soot easily occurs. In order to avoid such a situation, the target opening Rvnt is reduced and the fresh air intake amount is increased by raising the boost pressure of the turbocharger 50 where the EGR amount further increases.
[211] The supercharging efficiency of the turbocharger 50 is small in the region on the left side of the drawing where the value (tQas0) such as the set intake air fresh air amount is small. In the region of this figure, the target opening Rvnt is reduced as the value tQas0, such as the set intake air drawn-air amount, is decreased. This is because if the target opening Rvnt is increased in this region, the exhaust pressure required to rotate the exhaust gas turbine 52 is hardly established. This is also because, when the vehicle is accelerated by the full opening of the accelerator pedal, if the initial opening of the variable nozzle 53 is small, the acceleration effect due to supercharging is large.
[212] In this figure, the target opening Rvnt of the region indicated by Rvnt = Small is about 20%. The target opening (Rvnt) of the region indicated by Rvnt = Large is set to about 30% if the fuel efficiency is emphasized, and about 60% if the exhaust gas purification is emphasized.
[213] After reading the target opening Rvnt in step S74 of Fig. 15, the control unit 41 executes the pre-processing for the target opening Rvnt using the subroutine shown in Fig. 29 in step S75 . This preprocessing is intended to compensate for a delay operating based on the time required to actuate the pressure actuator 54 driving the variable nozzle 53. This process is required because the operation of the pressure actuator 54 using the pressure control valve 56 and the diaphragm actuator 59 has a large response delay compared with the stepper motor.
[214] 29, the control unit 41 first reads the target opening Rvnt in step S141.
[215] In step S142, when the subroutine is executed, the open estimate Cavnt _n-1 calculated in the previous preceding case is compared with the target opening Rvnt. The open estimate (Cavnt _n-1 ) is described later in step S150.
[216] When Rvnt > Cavnt _n-1 , the variable nozzle 53 is operating in the opening direction. In this case, in step S143, the subroutine sets the pre-correction gain Gkvnt as a predetermined value (GKVNTO #), and as a predetermined value (TCVNTO #) in step S144, Tcvnt), and proceeds to step S150.
[217] Here, the time constant value (Tcvnt) is the inverse of the time constant, and a large value indicates that the response is faster.
[218] On the other hand, when Rvnt Cavnt _n-1 in step S142, the subroutine determines whether or not Rvnt <Cavnt _n-1 in step S145.
[219] When Rvnt &lt; Cavnt _n-1 , the variable nozzle 53 is operating in the closing direction. In this case, the subroutine sets the pre-correction gain Gkvnt to the predetermined value GKVNTC # in step S146, and sets the pre-correction time value Tcvnt to the predetermined value TCVNTC # in step S147 And proceeds to step S150. Here, GKVNTO # <GKVNTC # and TCVNTO # <TCVNTC #.
[220] The reason for setting this when the variable nozzle 53 is closed is because the exhaust gas pressure acts as a resistive force and therefore the gain is set to be larger than when the nozzle is opened to promote the operation of the variable nozzle 53 , It is preferable to set the time constant to be smaller. Making the time constant small means to make the time constant value (Tcvnt) large as mentioned above.
[221] When the target opening Rvnt is not smaller than the open expectation Cavnt _n-1 , that is, when Rvnt is equal to Cavnt _{n-1 in} step S145, in step S148, setting the same pre-correction gain (Gkvnt) and (Gkvnt _n-1) and, by previously set a preceding value (Tcvnt _n-1) and the same pre-correction time constants value (Tcvnt), the process proceeds to step (S150).
[222] In step S150, the open prediction value Cavnt is calculated from the following equation (11) using the pre-correction time constant value Tcvnt and the target opening Rvnt.
[223] Cavnt = Rvnt 占 Tcvnt + Cavnt _n-1占 (1 - Tcvnt) (11)
[224] However, Cavnt _n-1 = Cavnt computed in the previous precedent in which the subroutine was executed.
[225] In the next step S151, the target open-loop control amount Avnt_f is calculated by the following equation (12) using the open prediction value Cavnt and the target opening Rvnt.
[226] Avnt_f = Gkvnt Rvnt- (Gkvnt-1) Cavnt _n-1 (12)
[227] 29, the control unit 41 returns to the routine of Fig. 15, and at step S76, calculates the target opening (Rvnt) feedback correction amount Avnt_fb using the subroutine shown in Fig. 30 as .
[228] 30, in step S161, the control unit 41 first determines whether or not the target intake air amount tQac, the target EGR rate Megr, the engine rotation speed Ne, the target fuel injection amount Qsol, The fresh air amount Qac is read.
[229] In step S162, the target EGR rate Megr is compared with a predetermined value MEGRLV #. The predetermined value MEGRLV # is the same as the value used in step S102 of FIG. Here, it is determined whether exhaust gas recirculation is performed by comparing the predetermined value MEGRLV # with the target EGR rate Megr.
[230] Megr MEGRLV # is an area where exhaust gas recirculation should be performed. In this case, the subroutine proceeds to step S164, and the error rate dQac of the target intake air amount tQac is calculated with respect to the actual intake air amount Qac by the following equation (13).
[231] dQac = (tQac / Qac) - 1 (13)
[232] The error rate dQac takes a positive value when the target intake air amount tQac is larger than the actual intake air amount Qac and when the target intake air amount tQac is smaller than the actual intake air amount Qac, The error rate dQac takes a negative value.
[233] If the target intake air amount tQac is equal to the actual intake air amount Qac, then the error rate dQac is zero.
[234] Megr &lt; MEGRLV # is an area where exhaust gas recirculation is not performed. In this case, the subroutine sets the error rate dQac to 0 in step S163.
[235] After setting the error rate dQac, the subroutine proceeds to step S165.
[236] The feedback gain correction coefficient Kh used for the feedback control of the target opening Rvnt is checked in advance in the control unit 41 and the engine rotational speed Ne and the target fuel injection quantity Qsol . This figure is set to further increase the load of the diesel engine 1 and the rotational speed Ne of the diesel engine 1 indicated by the target fuel injection quantity Qsol to the correction coefficient Kh.
[237] In the next step S166, the proportional feedback gain Kp, the integral feedback gain Ki and the differential feedback gain Kd are corrected by the correction coefficient Kh, the proportional constant KPB #, the integral constant KIB # (KDB #), respectively.
[238] Based on these gains, the feedback control amount Avnt_fb of the target opening Rvnt of the variable nozzle 53 is calculated using a conventionally known proportional / integral / differential control equation in step S167.
[239] After the above calculation, the control unit 41 returns to the routine of Fig. 15 and executes linearization processing on the target opening (Rvnt) using the subroutine shown in Fig. 31 in step S77.
[240] Referring to Fig. 31, in step S171, the control unit 41 reads the open loop control amount Avnt_f and the feedback control amount Avnt_fb of the target opening Rvnt.
[241] In step S172, the command opening Avnt is calculated by adding these control amounts.
[242] In the next step S173, the linearization process value Ratdty of the instruction open (Avnt) is calculated from the instruction open (Avnt) by checking the figure of Fig. 32 stored in advance in the memory of the control unit 41. Fig.
[243] After this process, the control unit 41 returns to the routine shown in Fig. 15 and determines the duty value (Dtyvnt) using the subroutine shown in Fig. 34 in step S78.
[244] 34 sets the duty value Dtyvnt of the signal output to the pressure control valve 56 of the variable nozzle 53. [ This linearization is required for the following reasons.
[245] In Fig. 33, when the EGR is not executed, the change width of the boost pressure is the same but the open areas (dA0 and dA1) are different. When EGR is executed, this difference may be even greater. In other words, it is difficult to precisely control the boost pressure by the fixed feedback gain. In order to ensure a prompt response of the boost pressure, the feedback gain Kh is set to change according to the driving condition.
[246] 34, at step S181, the control unit 41 determines whether or not the engine rotational speed Ne of the diesel engine 1, the target fuel injection quantity Qsol, the command opening linearization processed value Ratdty, The correction time constant value value Tcvnt and the water temperature Tw are read.
[247] In step S182, the duty signal change flag is set using the subroutine shown in Fig.
[248] Referring to Fig. 35, in step S201, the control unit 41 first reads the value of the command opening (Avnt) and the value (Tcvnt) of the pre-correction time constant.
[249] In step S202, the command opening prediction value Adlyvnt is calculated by the following equation (14).
[250] Adlyvnt = Avnt Tcvnt + Adlyvnt _n-1 (1 - Tcvnt) (14)
[251] Adlyvnt _n-1 = the Adlyvnt value calculated in the previous precedence in which the subroutine was performed.
[252] Here, the relationship between the command opening (Avnt) and the command opening expectancy (Adlyvnt) corresponds to the relationship between the target opening (Rvnt) and the opening expectation (Cavnt).
[253] In the next step (S203), the command opening estimate (Adlyvnt) is compared to the time (M) before the command opening calculated by the subroutine executed to estimate (Adlyvnt _nM).
[254] When Adlyvnt ≥Adlyvnt _nM , the command opening is incremental or constant. In this case, the subroutine sets the operation direction flag fvnt to 1 in step S204, and proceeds to step S206.
[255] In step S206, it is determined whether Adlyvnt = Adlyvnt _nM . When Adlyvnt = Adlyvnt _nM , in step S207, the duty maintaining flag fvnt2 is set to 1, and the subroutine ends.
[256] When Adlyvnt = Adlyvnt _nM is not satisfied, the routine proceeds to step S208.
[257] In step S203, when Adlyvnt &lt; Adlyvnt _nM , the command opening decreases. In this case, the subroutine resets the operation direction flag fvnt to 0 in step S205, and the routine proceeds to step S208.
[258] In step S208, the duty maintaining flag fvnt2 is reset to 0, and the subroutine is terminated.
[259] Therefore, after setting the two flags fvnt and fvnt2, the control unit 41 reads the duty value temperature correction amount Dty_t in step S183 of Fig. The duty value temperature correction amount Dty_t is calculated by the routine of Fig. 36 independently executed synchronously with the REF signal.
[260] 36, in step S211, the control unit 41 first reads the engine rotation speed Ne, the target fuel injection quantity Qsol, and the cooling water temperature Tw.
[261] The basic exhaust gas temperature Texhb is calculated from the engine rotational speed Ne and the target fuel injection quantity Qsol by checking the figure shown in the figure 37 previously stored in the memory of the control unit 41 in step S212. do. The basic exhaust gas temperature Texhb is the exhaust gas temperature after the completion of the preheating of the diesel engine 1. [
[262] In the next step S213, the water temperature correction coefficient Ktexh_Tw is calculated by looking up the figure shown in Fig. 38 in which the control unit 41 is stored, based on the cooling water temperature Tw.
[263] In step S214, the exhaust gas temperature Texhi is calculated by multiplying the water temperature correction coefficient Ktexh_Tw by the base exhaust gas temperature Texhb.
[264] In the next step S215, the actual exhaust gas temperature Texhdly is calculated by adding the exhaust gas temperature Texhi and the first order processing delay by the following equation (15). This value is a value considering the delay due to the thermal inertia to the change of the exhaust gas temperature.
[265] Texhdly = Texhi KEXH # + Texhdly _n-1 (1 - KEXH #) (15)
[266] However, KEXH # = constant, and
[267] Texhdly _n-1 = Texdly computed in the previous predecessor when the subroutine was executed.
[268] In the next step S216, the difference dTexh between the base exhaust gas temperature Texhb and the actual exhaust gas temperature Texhdly is calculated.
[269] In the final step S217, the duty value temperature correction amount Dty_t is calculated by examining the figure shown in Fig. 39 stored in advance in the memory of the control unit 41, based on the difference dTexh. The meaning of the processing of steps S216 and S217 will be described later in detail.
[270] After reading the value of Dty_t in step S183, the control unit 41 executes the process after step S184 in Fig. Steps S184 to S189 are steps obtained by adding the duty value and the hysteresis processing.
[271] 45, when the linearization processing value Ratdty of the command opening (Avnt) increases, the duty value becomes equal to the command signal (Duty_l_p) when the variable nozzle (53) is fully opened and the command signal 53) is changed in accordance with a straight line connecting the command signal (Duty_h_p) when fully closed. On the other hand, when the linearization process value Ratdty decreases, the duty value becomes equal to the command signal Duty_l_n when the variable nozzle 53 is fully opened and the command signal Duty_h_n when the variable nozzle 53 is fully closed, As shown in FIG. In the figure, two straight lines cross the area where the variable nozzle 53 is almost closed, but this area is an area not used for actual control of the pressure control valve 56. These characteristics are set on the assumption that the diesel engine 1 is fully preheated. When the actual exhaust gas temperature Texhdly is low, the pressure actuator 54 has a variable nozzle 53 opening characteristic higher than the same duty value, as shown in Fig. Therefore, in order to compensate for the difference in the characteristics of the pressure actuator 54 due to the exhaust gas temperature, it is necessary to apply the temperature correction amount Dty_t calculated in the steps S216 and S217 in Fig.
[272] Now, the control unit 41 determines the operating direction flag fvnt in step S184. When the operating direction flag fvnt is 1, that is, when the command opening (Avnt) increases or remains constant, the processes of steps S185 and S186 are executed. In step S185, the duty value Duty_h when the variable nozzle 53 is fully closed is calculated based on the target fuel injection quantity Qsol by examining the Duty_h_p diagram shown in Fig.
[273] In the next step S186, the duty value Duty_l when the variable nozzle 53 is fully opened is calculated by looking at the Duty_l_p diagram shown in Fig. After this processing, the subroutine proceeds to step S189.
[274] When the operating direction flag fvnt is 0 in step S184, that is, when the command opening (Avnt) decreases, the processes of steps S187 and S188 are executed. In step S187, the duty value Duty_h when the variable nozzle 53 is fully closed is calculated based on the target fuel injection quantity Qsol by examining the Duty_h_n diagram shown in Fig. In the next step (S188), the duty value (Duty_l) when the variable nozzle (53) is fully opened is calculated based on the target fuel injection quantity (Qsol) by examining the Duty_l_n diagram shown in Fig.
[275] After this processing, the subroutine proceeds to step S189.
[276] In step S189, the command duty base value Dty_h is calculated by the following equation using the duty values Duty_h and Duty_l found in the above process, the linearization processing value Ratdty of command opening Avnt, and the temperature correction amount Dty_t 16 by a linear interpolation process.
[277] Dty_h = (Duty_h - Duty_l) Ratdty + Duty_l + Dty_t (16)
[278] Since the command duty base value Dty_h is the same linearization processing value Ratdty, by changing the straight line used for the linear interpolation processing when the command open (Avnt) decreases and does not decrease, command open (Avnt) And becomes smaller than the other cases when it is decreased.
[279] In the next step S190, the duty maintaining flag fvnt2 is determined. When the duty keeping flag fvnt2 is 1, that is, when the command opening prediction value Adlyvnt does not change, the command duty value Dtyv is set to a duty value Dtyv calculated in the previous preceding case in which the subroutine was executed in step S191 (Dtyvnt _n-1 ). The duty value (Dtyvnt _n-1 ) will be described later in detail.
[280] When the duty preservation flag fvnt2 is 0, that is, when the command opening prediction value Adlyvnt changes, in step S192, the command duty value Dtyv is updated to the command duty base value Dty_h calculated in step S189 .
[281] Therefore, after judging the command duty value Dtyv in the step S191 or S192, the control unit 41 sets the subroutine of Fig. 46 based on the command duty value Dtyv in the final step S193 The operation of the variable nozzle 53 is checked.
[282] 46, in step S221, the control unit 41 reads the command duty value Dtyv, the engine rotational speed Ne, the target fuel injection quantity Qsol, and the cooling water temperature Tw.
[283] In successive steps (S222) to (S225), it is judged whether or not the operation check condition is satisfied. The operation check is executed only when all of these conditions are satisfied.
[284] In step S222, it is determined whether the target fuel injection quantity Qsol is smaller than a predetermined value QSOLDIZ #. When this condition is satisfied, it means that the diesel engine 1 executes the fuel cut-off.
[285] In step S223, it is determined whether or not the engine rotation speed Ne is smaller than the predetermined value NEDIZ #. When this condition is satisfied, it means that the rotational speed Ne of the diesel engine 1 is in the middle or low speed region.
[286] In step S224, it is determined whether or not the cooling water temperature Tw is smaller than the predetermined value TwDIZ #. When this condition is satisfied, it means that the preheating of the diesel engine 1 is not complete.
[287] In step S225, it is determined whether the operation check flag Fdiz is 0 or not. When this condition is satisfied, it means that the operation check has not yet been executed.
[288] When all the conditions are satisfied, the operation check counter value CtFdiz is increased in step S226, and the routine proceeds to step S227.
[289] When any one of the determination results of steps S222 to S224 is not satisfied, the subroutine resets the operation check flag Fdiz to 0 in step S233, and proceeds to step S234. However, when the operation check flag Fdiz is 1 in step S225, the process immediately proceeds to step S234.
[290] In step S227, the operation check counter value CtFdiz is compared with a predetermined upper limit value CTRDIZH #.
[291] When the operation check counter value CtFdiz is smaller than the upper limit value CTRDIZH #, the operation check counter value CtFdiz is compared with the predetermined lower limit value CTRDIZL # in step S228. When the operation check counter value CtFdiz is not smaller than the lower limit value CTRDIZL #, in step S229, the duty value Dtyvnt is set for the operation check using the subroutine shown in Fig.
[292] When the upper limit value CTRDIZH # is set to, for example, 7 seconds and the lower limit value CTRDIZL # is set to, for example, 2 seconds, the duty value for the operation check is set only at an interval of 5 seconds between the upper limit value and the lower limit value .
[293] Here, with reference to FIG. 47, a subroutine for setting a duty value for operation check will be described.
[294] The control unit 41 first reads the operation check counter value CtFdiz and the engine rotation speed Ne in step S241.
[295] In the next step S242, the control pattern value Duty_pu is set by checking the diagram shown in FIG. 48 based on the difference between the operation check counter value CtFdiz and the lower limit value CTRDIZL #. This figure is stored in the memory of the control unit 41 in advance. The control pattern value Duty_pu is set so that the operation check counter value CtFdiz is repeatedly changed between 0 and 1 by a short period according to the elapsed time after exceeding the lower limit value CTRDIZL #.
[296] In the next step S243, the duty value Duty_p_ne commanded to the pressure control valve 56 is checked on the basis of the engine rotational speed Ne based on the diagram shown in Fig. 49 stored in advance in the memory of the control unit 41 . The duty value Duty_p_ne is set on the assumption that the duty for examining the opening / closing operation of the variable nozzle 53 is different depending on the engine rotation speed Ne. For example, when the variable nozzle 53 is closed, it must be closed against the exhaust gas pressure. The exhaust gas pressure increases in accordance with the increase in the engine rotation speed Ne.
[297] In addition, when the engine rotation speed Ne is in the high speed region, closing of the variable nozzle 53 for the operation check has a major influence on the engine running environment. Therefore, in the high-speed region, the duty value Duty_p_ne is decreased as the engine rotation speed Ne is increased so as to reduce the influence on the engine running environment.
[298] In the next step S244, the duty value Dtyvnt is calculated by multiplying the control pattern value Duty_pu by the duty value Duty_p_ne, and the subroutine is terminated.
[299] Thus, after the setting of the duty value for checking the operation is completed in step S229 of Fig. 46, the subroutine of Fig. 46 also ends.
[300] On the other hand, when the operation check counter value CtFdiz is not smaller than the upper limit value CTRDIZ # in step S227 of FIG. 46, the process of step S230 is executed. Here, the previous precedent value CtFdiz _{n-1 of the} operation check counter value CtFdiz operation is compared with the upper limit value CTRDIZH #. If the previous preceding value CtFdiz _n-1 is smaller than the upper limit value CTRDIZH #, this means CTRDIZH # that has reached the upper limit value CTRDIZH # in the repeated execution of this subroutine, and if the duty value Dtyvnt reaches the upper limit value CTRDIZH # S231), the operation check flag Fdiz is set to 1 in step S232, and the subroutine is ended.
[301] When the operation check is completed, the duty value Dtyvnt is set to 0 in step S231, so that the variable nozzle 53 is fully opened. This operation is intended to maintain precise control during normal control that is subsequently executed. Since the operation check flag Fdiz is set to 1, the determination result of step S225 is always negative at the time of execution of the subroutine thereafter. This means that the operation check of the variable nozzle 53 is executed immediately after starting the diesel engine 1.
[302] On the other hand, when the previous precedent value CtFdiz _n-1 of the operation check counter value CtFdiz is not smaller than the upper limit value CTRDIZH # in step S230, the subroutine proceeds to step S234. In step S234, the operation check counter value CtFdiz is reset to 0, and the routine proceeds to step S235.
[303] When the operation check counter value CtFdiz is smaller than the predetermined lower limit value CTRDIZL # in step S228, the subroutine also proceeds to step S235.
[304] In step S235, the duty value Dtyvnt for the operation check is determined in step S191 or step S192, and the subroutine is terminated. In this case, therefore, the normal control of the variable nozzle 53 is executed.
[305] Particularly, when the operation of the pressure actuator 54 is unstable, such as at low temperatures, the operation check of the variable nozzle 53 smoothes the operation of the variable nozzle 53 and increases the reliability of the boost pressure control.
[306] Thus, the subroutine of Fig. 46 ends, and the processing of the subroutine of Fig. 34 and the processing of the main routine of Fig. 15 are also ended.
[307] Next, the calculation of the target opening area Aev of the EGR valve 6 will be described with reference to Fig. This routine constitutes a main feature of the present invention. This routine is executed every time the REF signal is input.
[308] First, in step S11, the control unit 41 calculates the target EGR amount Tqec of the EGR valve 6 using the subroutine shown in Fig.
[309] Referring to Fig. 7, in step S21, the control unit 41 reads the intake air amount per cylinder Qac _n at the inlet of the collector 3A. Qac _n is a value calculated in the above-described step S33 of Fig.
[310] In the next step S22, the target EGR rate Megr is read. The target EGR rate Megr is a value calculated by the routine of Fig.
[311] In the next step S23, the required EGR amount Mqec is calculated by the following equation (17). The required EGR quantity (Mqec) is also the quantity for the cylinder.
[312] Mqec = Qacn · Megr (17)
[313] In the next step S24, the delay processing uses the time constant value Kkin calculated by the routine of Fig. 18 to calculate a median value Rqec corresponding to the required EGR amount per cylinder at the intake valve position of the diesel engine 1 , The required EGR amount is executed by the following equation (18). The delay processing corresponds to the response delay of the negative pressure control valve 5 and the EGR valve 6. [
[314] Rqec = Mqec Kkin + Rqec _n-1 (1-Kkin) (18)
[315] However, Rqec _n-1 = Rqec calculated in the previous preceding case in which the subroutine was executed.
[316] In step S25, the target EGR amount Tqec per cylinder at the position of the EGR valve 6 is calculated by executing the linearization process by the following equation (19) using the median value Rqec and the required EGR amount Mqec . This linearization process compensates for the delay in the change of the EGR amount due to the time required for the exhaust gas to move from the EGR valve 6 of the diesel engine 1 to the intake valve through the collector 3A.
[317] Tqec = Mqec GKQEC + Rqec _n-1 (1 - GKQEC) (19)
[318] However, GKQEC = pre-compensation gain.
[319] In the next step S26, the negative value Tqec1 is calculated by the following equation (20).
[320] Tqec1 = Tqec + Dtqec _n-1 (20)
[321] However, Dtqec _n-1 = the excess / shortage amount (Dtqec) calculated in the previous preceding case in which the subroutine was executed.
[322] The excess / deficiency amount Dtqec is the value described in the above-mentioned processes (A) to (E). Here, the value calculated in the previous precedent case in which the subroutine of FIG. 7 is executed is used. The calculation of the excess / deficiency amount Dtqec will be described later.
[323] In the next step S27, the control unit 41 sets the physical upper limit Tqelmh and the physical lower limit Tqelml by the subroutine shown in Fig.
[324] Referring to Fig. 65, in step S401, the control unit 41 calculates the EGR valve flow rate Cqe (m / sec) by the subroutine shown in Fig. First, this calculation will be described.
[325] Referring to Fig. 63, in step S361, the control unit 41 reads the actual EGR amount Qec, the actual EGR rate Megrd, and the cylinder intake fresh air amount Qac.
[326] In step S362, the EGR flow velocity feedback correction coefficient Kqac0 and the EGR flow velocity learning correction coefficient Kqac are calculated by the subroutine shown in Fig.
[327] The control unit 41 first determines whether or not the target intake fresh air amount tQac, the cylinder intake fresh air amount Qac, the engine rotational speed Ne, and the target fuel injection amount Qsol are equal to each other, .
[328] The delay processing value tQacd of the target intake fresh air amount tQac is calculated from the target intake fresh air amount tQac and the time constant value Kkin calculated by the routine of Fig. . This value corresponds to the target intake air amount at the intake valve position of the diesel engine 1.
[329] tQacd = tQac Kkin KQA # + tQacd _n-1 (1 - Kkin KQA #) (21)
[330] However, KQA # = constant, and
[331] tQacd _n-1 = tQacd computed in the previous predecessor when the subroutine is executed.
[332] In the next step S253, the feedback permission flag fefb, the learning permission flag felrn and the learning value reflection permission flag felrn2 associated with the control of opening the EGR valve are read.
[333] These flags are set by the independent routines shown in Figs. 51, 52 and 53, respectively.
[334] Fig. 51 shows a routine for setting the feedback permission flag fefb. This routine is executed at 1/100 (second) intervals.
[335] 51, first, in step S271, the control unit 41 reads the engine rotation speed Ne, the target fuel injection quantity Qsol, the actual EGR rate Megrd, and the water temperature Tw.
[336] In successive steps (S272 to S275), the EGR amount feedback control condition is determined.
[337] In step S272, it is determined whether or not the actual EGR rate Megrd exceeds the predetermined value MEGRFB #. The predetermined value (MEGRFB #) is a value for checking whether exhaust gas recirculation is actually performed. In step S273, it is determined whether or not the cooling water temperature Tw exceeds the predetermined value TwFBL #. The predetermined value TwFBL # is set at 30 占 폚. In step S274, it is determined whether or not the target fuel injection quantity Qsol exceeds the predetermined value QSOLFBL #.
[338] The predetermined value QSOLFBL # is a value for checking whether or not the diesel engine 1 is in the fuel cut-off state. In step S275, it is determined whether or not the engine rotation speed Ne exceeds the predetermined value NeFBL #. The predetermined value NeFBL # is a value for checking whether the vehicle is in a low speed region in which the rotation of the diesel engine 1 is stopped.
[339] When all the conditions of the steps S272 to S275 are satisfied, the subroutine proceeds to step S276 and increases the timer value Ctrfb.
[340] In the next step (S278), it is judged whether or not the timer value Ctrfb is larger than the predetermined value TMRFB #. The predetermined value TMRFB # is set to a value smaller than 1 second, for example. When the determination result is affirmative, the subroutine sets the feedback permission flag fefb to 1 in step S279, and the subroutine ends. On the other hand, when any one of the conditions of the steps S272 to S275 is not satisfied, the subroutine resets the timer value Ctrfb to 0 and proceeds to the next step S280.
[341] If the determination in step S278 is negative, the subroutine also proceeds to step S280.
[342] In step S280, the feedback permission flag fefb is reset to 0, and the subroutine is terminated.
[343] According to this subroutine, the feedback permission flag fefb is set to 1 only in a state where all the conditions of the steps S272 to S275 are not satisfied, continues for a time exceeding the predetermined value TMRFB # In other cases, the feedback permission flag fefb is reset to zero.
[344] Fig. 52 shows a routine for setting the learning value reflection permission flag felrn2. This routine is also executed at intervals of 1/100 (second).
[345] 52, first, in step S291, the control unit 41 reads the engine rotation speed Ne, the target fuel injection quantity Qsol, the actual EGR rate Megrd, and the cooling water temperature Tw.
[346] In the subsequent steps (S292) to step (S295), the EGR amount learning value reflecting conditions are determined.
[347] In step S292, it is determined whether the actual EGR rate Megrd exceeds the predetermined value MEGRLN2 #. The predetermined value MEGRLN2 # is a value for checking whether the exhaust gas recirculation is actually executed. In step S293, it is determined whether or not the cooling water temperature Tw exceeds the predetermined value TwLNL2 #. The predetermined value TwLNL2 # is set to 20 占 폚. In step S294, it is determined whether or not the target fuel injection quantity Qsol exceeds the predetermined value QSOLLNL2 #. The predetermined value QSOLLNL2 # is a value for checking that the diesel engine 1 is not in the fuel cut-off state. In step S295, it is determined whether or not the engine rotation speed Ne exceeds the predetermined value NeLNL2 #. The predetermined value NeLNL2 # is a value for checking that there is no vehicle in the low speed region where the diesel engine 1 stops rotating.
[348] Only when all the conditions of steps S292 to S295 are satisfied, the subroutine proceeds to step S296 and the timer value Ctrln2 is incremented.
[349] In the next step (S298), it is judged whether or not the timer value (Ctrln2) exceeds the predetermined value TMRLN2 #. The predetermined value TMRLN2 # is set to 0.5 second. When the determination result is affirmative, the subroutine sets the learned value reflection permission flag felrn2 to 1 in step S299, and the subroutine ends.
[350] On the other hand, when either one of steps S292 to S295 is not satisfied, the subroutine resets the timer value Ctrln2 to 0 in step S297, and proceeds to the next step S300. When the determination in step S298 is negative, the routine also proceeds to step S300.
[351] In step S300, the learning value reflection permission flag felrn2 is reset to 0, and the subroutine is terminated.
[352] 53 shows a routine for setting the learning permission flag felrn. This routine is also executed at intervals of 1/100 (second).
[353] 53, first, in step S311, the control unit 41 reads the engine rotation speed Ne, the target fuel injection quantity Qsol, the actual EGR rate Megrd, and the water temperature Tw.
[354] In successive steps (S312) to (S317), the EGR amount learning permitting conditions are determined.
[355] In step S312, it is determined whether or not the actual EGR rate Megrd exceeds the predetermined value MEGRLN #. The predetermined value MEGRLN # is a value for examining whether the exhaust gas recirculation is actually performed. In step S313, it is determined whether or not the cooling water temperature Tw exceeds the predetermined value TwLNL #. The predetermined value TwLNL # is set at 70 캜 to 80 캜. In step S314, it is determined whether or not the target fuel injection quantity Qsol exceeds the predetermined value QSOLLNL #. The predetermined value QSOLLNL # is a value for checking whether or not the diesel engine 1 is in the fuel cut-off state. In step S315, it is determined whether or not the engine rotation speed Ne exceeds the predetermined value NeLNL #. The predetermined value NeLNL # is a value for checking whether there is a vehicle in a low speed region where the diesel engine 1 stops rotating. In step S316, it is determined whether the feedback permission flag fefb is 1 or not. In step S317, it is determined whether the learning value reflection allowance flag felrn2 is 1 or not.
[356] Only when all the conditions of steps S312 to S317 are satisfied, the subroutine proceeds to step S318 and the timer value Ctrln is incremented.
[357] In the next step S320, it is judged whether or not the timer value Ctrln exceeds the predetermined value TMRLN #. The predetermined value TMRLN # is set to 4 seconds. When the result of this determination is affirmative, the subroutine sets the learning permission flag felrn to 1 in step S321, and the subroutine ends. On the other hand, if any of the conditions of the steps S312 to S317 is not satisfied, the subroutine resets the timer value Ctrln to 0 in step S319, and proceeds to the next step S322 . The subroutine also proceeds to step S322 when the determination result of step S320 is negative. In step S322, the learning permission flag felrn is reset to 0, and the subroutine is terminated.
[358] The control unit 41 reads the feedback allowance flag fefb, the learning value reflection permission flag felrn2 and the learning permission flag felrn with reference to Fig. 50. Then, in step S254, (fefb) is &quot; 1 &quot;.
[359] The feedback correction coefficient Kqac00 of the EGR amount and the feedback correction coefficient Kqac0 of the EGR valve flow velocity Cqe in the step S256 are calculated in step S255 when the feedback allowable flag fefb is 1, The unit 41 proceeds to step S259.
[360] On the other hand, when the feedback allowable flag fefb is not 1 in step S254, the control unit 41 sets the feedback correction coefficient Kqac00 of the EGR amount to 1 in step S257, The feedback correction coefficient Kqac0 is set to 1, and then the flow proceeds to step S259.
[361] Now, calculation of the feedback correction coefficient Kqac00 of the EGR amount executed in step S255 and calculation of the feedback correction coefficient Kqac0 of the EGR valve flow velocity executed in step S256 will be described.
[362] The calculation of the feedback correction coefficient Kqac00 of the EGR amount is executed by the subroutine of Fig.
[363] 54, in step S331, the control unit 41 determines whether or not the target intake air amount delay processing value tQacd, the cylinder intake fresh air amount Qac, the engine rotation speed Ne, the target fuel injection amount Qsol) and the cooling water temperature Tw are read. The delay processing value tQacd is a value calculated in step S252 in Fig.
[364] In step S332, the correction gain Gkfb of the EGR flow rate is calculated based on the engine rotation speed Ne and the target fuel injection quantity Qsol, by referring to the diagram shown in Fig. 55 stored in advance in the memory of the control unit 41 . In the next step S333, the water temperature correction coefficient KgfbTw of the correction gain is calculated by looking up the figure shown in Fig. 56 stored in advance in the memory of the control unit 41, based on the cooling water temperature Tw.
[365] In the final step S334, the feedback correction coefficient Kqac00 of the EGR amount is calculated by the following equation (22) using the correction gain Gkfb and the water temperature correction coefficient KgfbTw.
[366] Kqac00 = (tQacd / Qac - 1) - Gkfb - KgfbTw + 1 (22)
[367] (tQacd / Qac-1), and the first term of the right side of the equation (22) is the error ratio of the target intake air amount delay processing value (tQacd) to the cylinder fresh air amount (Qac). Therefore, the feedback correction coefficient Kqac00 of the EGR amount is a value centered at 1.
[368] The calculation of the feedback correction coefficient Kqac0 of the EGR valve flow velocity is executed by the subroutine shown in Fig.
[369] 57, in step S341, the control unit 41 first determines whether or not the delay processing value tQacd, the cylinder intake fresh air amount Qac, the engine rotational speed Ne, the target fuel injection quantity Qsol, The water temperature Tw is read out
[370] In step S342, the correction gain Gkfbi of the EGR valve flow rate is calculated based on the engine rotation speed Ne and the fuel injection amount Qsol, by checking the diagram shown in Fig. 58 stored in advance in the memory of the control unit 41 .
[371] In step S343, the water temperature correction coefficient KgfbiTw of the correction gain is calculated by looking up the diagram shown in Fig. 59 stored in advance in the memory of the control unit 41 based on the cooling water temperature Tw.
[372] In the next step S344, the error ratio Rqac0 is calculated by the following equation (23) using the correction gain Gkfbi and the water temperature correction coefficient KgfbiTw.
[373] Rqac0 = (tQacd / Qac-1) Gkfbi KgfbiTw + Rqac0 _n-1 (23)
[374] However, Rqac0 _n-1 = Rqac0 calculated in the previous precedent in which the subroutine was executed.
[375] In the next step S345, 1 is added to the error ratio Rqac0, so that the feedback correction coefficient Kqac0 of the EGR valve flow velocity is calculated. Therefore, the feedback correction coefficient Kqac0 of the EGR valve flow velocity is proportional to the integral of the error ratio.
[376] 50, the feedback correction coefficient Kqac00 of the EGR amount and the feedback correction coefficient Kqac0 of the EGR valve flow rate are set again. Thereafter, in step S259, the control unit 41 calculates the learning correction value Kqac0 It is determined whether the allowable flag felrn2 is 1 or not.
[377] When the learning value reflection permission flag felrn2 is 1, that is, when reflection to the EGR amount control of the learned value is permitted, the control unit 41 sets the engine rotation speed Ne and the target fuel injection amount The error unearned value Rqac _n is read out by examining the diagram shown in Fig. 60 previously stored in the memory of the control unit 41, based on the error-free learning value Qsol. In the next step S261, the EGR flow velocity learning correction coefficient Kqac is calculated by adding 1 to the error ratio learning value Rqac _n .
[378] When the learning value reflection permission flag felrn2 is not 1 in step S259, the control unit 41 sets the EGR flow velocity learning correction coefficient Kqac to 1 in step S262.
[379] After the processing in step S261 or step S262, the control unit 41 determines in step S263 whether the learning permission flag felrn is 1 or not.
[380] When the learning permission flag felrn is 1, the control unit 41 subtracts 1 from the EGR flow velocity feedback correction coefficient Kqac0 in order to calculate the present value Rqacp of the error ratio in step S264. In the next step (S266), the learning value is updated using the subroutine of Fig. 61, and the subroutine is ended.
[381] When the learning permission flag felrn is not 1, the control unit 41 resets the current value Rqacp of the error ratio to 0 in step S265, and ends the subroutine of Fig.
[382] Next, the update of the learning value executed in step S266 will be described.
[383] 61, in step S351, the control unit 41 reads the engine rotation speed Ne, the target fuel injection quantity Qsol, and the error ratio Rqacp calculated in step S264.
[384] In step S352, the learning rate Tclrn is calculated by examining the diagram shown in Fig. 62 stored in advance in the memory of the control unit 41, based on the engine rotational speed Ne and the target fuel injection quantity Qsol.
[385] In step S353, the error ratio learning value Rqac _n is calculated by looking up the above-described diagram of Fig. 60 based on the engine rotation speed Ne and the target fuel injection quantity Qsol.
[386] In the next step S354, the weighted average processing by the following formula (24) is added to the error ratio Rqacp read in step S351, and the error ratio learning value is updated.
[387] Rqac _n (new) = Rqacp Tclrn + Rqac _n (old) (1 - Tclrn) (24)
[388] However, Rqac _n (new) = the error ratio learning value (Rqac _n ) written in the drawing,
[389] Rqacp = error ratio read in step S351, and
[390] Rqac _n (old) = the error ratio learning value Rqac _n read from the drawing in step S353.
[391] In the next step (S355), it is superimposed by using the values stored values thus calculated error ratio learning (Rqac _n (new)) in the drawing of Figure 60.
[392] By ending the subroutine of Fig. 61, the control unit 41 ends the processing of the subroutine of Fig.
[393] 63, the control unit 41 corrects the EGR flow velocity by using the EGR flow velocity feedback correction coefficient Kqac0 and the EGR flow velocity learning correction coefficient Kqac calculated in step S362 by the following equation (25) The actual EGR amount Qec_h is calculated in step S363.
[394] Qec_h = Qec · Kqac · Kqac0 (25)
[395] In steps S364 to S367, an initial value of the actual EGR amount Qec_h, which is corrected when the EGR operation is started, is set. In step S364, it is determined whether or not the corrected actual EGR amount Qec_h is zero. When Qec_h is 0, that is, when EGR does not operate, the corrected actual EGR amount Qec_h is set by the following equation (26) in step S365, and the routine proceeds to step S366. When the corrected actual EGR amount is not 0 in step S364, the routine bypasses step S365 and proceeds to step S366.
[396] Qec_h = Qac MEGRL # (26)
[397] However, MEGRL # = constant.
[398] In step S366, it is determined whether or not the actual EGR rate Megrd is zero. When the actual EGR rate Megrd is 0, the actual EGR rate Megrd is set equal to the constant MEGRL # at step S367, and the routine proceeds to step S368. When the actual EGR rate Megrd is not 0, the routine bypasses the step S367 and proceeds to the step S368.
[399] When the EGR valve 6 is fully closed, the EGR valve flow rate of the EGR valve 6 is zero, and the equations (25 and 26) indicate that when the EGR operation is started, that is, when the EGR valve 6 starts to open, This is an equation for setting the initial value of the parameter used in the flow velocity calculation. The constant MEGRL # may be set to, for example, 0.5.
[400] The upstream and downstream differential pressures of the EGR valve 6 at the start of the EGR operation differ depending on the running conditions of the diesel engine, and as a result, the EGR valve flow rates at the start of the EGR operation also differ. The upstream and downstream differential pressures of the EGR valve 6 when the EGR valve 6 starts to open are in accordance with the cylinder intake fresh air amount Qac. Therefore, a precise calculation of the EGR valve flow rate at the time when the EGR operation is started can be improved by making the initial value of Qec_h directly proportional to the cylinder intake fresh air amount Qac by the equation (26).
[401] Now, at step S368, the control unit 41 checks the diagram shown in Fig. 64 stored in advance in the memory of the control unit 41 based on the corrected actual EGR amount Qec_h and the actual EGR rate Mergd , The EGR valve flow rate Cqe is calculated, and the subroutine ends.
[402] After calculating the EGR valve flow rate Cqe, the control unit 41 calculates the physical upper limit Tqelmh by the following equation (27) in step S402 of FIG.
[403] Tqelmh = Cqe AEVMX K / Ne (27)
[404] However, AEVMX = EGR valve maximum opening area (m2),
[405] K = conversion coefficient, and
[406] Ne = engine speed.
[407] The right side of the equation (27) represents a value obtained by converting the maximum flow rate (m3 / sec) of the EGR valve 6 per cylinder. That is, the upper physical limit (Tqelmh) is the maximum amount of EGR per cylinder in which the cylinder can be physically reached.
[408] In the next step (S403), the physical upper limit (Tqelml) is set equal to 0, and the subroutine ends. The physical lower limit (Tqelml) is the minimum amount of EGR per cylinder that the EGR valve 6 can physically reach. Normally, the EGR amount when the EGR valve 6 is completely closed is zero. Nevertheless, the reason for setting the physical lower limit (Tqelml) is as follows.
[409] In the case of an engine constituting a mechanism for absorbing the exhaust gas normally remaining in the exhaust gas recirculation passage such as the collector 3A, or when there are conditions for making the exhaust gas flow in the reverse direction, the minimum EGR The amount may be negative (-).
[410] These conditions are satisfied in the engine constituting the mechanism provided with the diesel particulate filter in the EGR passage 4 and the exhaust gas flows backward to the EGR passage 4 under a supercharging pressure sufficient for the intake passage 3, The fine particles caught in the filter are discharged to the exhaust passage (2).
[411] In the control unit 41, step S403 of setting the physical lower limit in accordance with the present invention is provided to be handled in such a case.
[412] After this physical restriction is set by the subroutine of Fig. 65, the control unit 41 limits the value (Tqec1) added by this physical restriction in step S28 of Fig. In particular, a larger value of the added value (Tqec1) and the physical lower limit (Tqelml) is selected, and a smaller value among the selected upper limit and the upper physical limit (Tqelmh) is set to the limited target EGR amount (Tqecf) per cylinder.
[413] In the next step S29, the target EGR amount Tqek is calculated based on the target EGR amount Tqecf limited per cylinder, the EGR amount feedback correction coefficient Kqac00 calculated by the subroutine of Fig. 50, and the constant used in the routine of Fig. (28) using (KCON #).
[414] Tqek = Tqecf (Ne / KCON #) / Kqac00 (28)
[415] However, Ne = engine rotation speed.
[416] In the final step (S30), the difference between the added value (Tqec1) and the restricted target EGR amount (Tqecf) is calculated as the excess / deficiency amount (Dtqec), and the subroutine is ended. This value Dtqec is used as the preceding preceding value Dtqecn-1 of the excess or minimum amount in step S26 in the case where the subroutine is executed.
[417] The target EGR amount Tqek is calculated by the subroutine of Fig. 7, and in step S12 of Fig. 5, the control unit 41 reads the EGR flow rate Cqe calculated in the subroutine of Fig. 63 .
[418] In the next step S13, the opening area Aev of the target EGR valve is calculated by the following equation (29) using the target EGR amount Tqek and the EGR flow rate Cqe.
[419] Aev = Tqek / Cqe (29)
[420] The obtained open area Aev of the target EGR valve is converted into, for example, the lift amount or the drive signal of the EGR valve 6 using the diagram of Fig. Therefore, the control unit 41 outputs a signal based on these parameters to the pressure control valve 5 that drives the EGR valve 6, so that the control unit 41 controls the opening of the EGR valve 6 relative to the opening area Aev of the target EGR valve Control the opening.
[421] (Second Embodiment)
[422] Next, referring to Fig. 16, a second embodiment of the present invention will be described in connection with the pressure control of the supercharger 50. Fig.
[423] According to the present embodiment, the routine shown in Fig. 16 is used in place of the routine of Fig. 15 for calculating the duty value (Dtyvnt) of the pressure control valve of the supercharger. As in the case of the routine of Fig. 15, the routine of Fig. 16 is also executed at intervals of 1/100 second.
[424] 15, the target opening Rvnt of the variable nozzle 53 is calculated based on the actual EGR amount Qec, but in the routine of Fig. 16, the target opening Rvnt is calculated based on the actual EGR rate Megrd .
[425] Particularly, in the routine of Fig. 16, the processing of step S73 of Fig. 15 for calculating the actual EGR amount Qec is omitted. At the same time, the routine shown in Fig. 27 is applied instead of the routine shown in Fig. 25 in the calculation of the target opening Rvnt of the variable nozzle 53. [ The description of the residual process is the same as the process of the first embodiment.
[426] 27, in step S131, the control unit 41 reads the target intake fresh air amount tQac, the actual EGR rate Megrd, the engine rotational speed Ne, and the target fuel injection quantity Qsol .
[427] In step S132, the same calculation is performed in the same manner as the calculation in step S122 in Fig. 15, and the value tQas0, such as the set intake air fresh air amount, is calculated.
[428] In step S133, the target opening Rvnt of the variable nozzle 53 is set in the memory of the control unit 41, which is stored in advance in the memory of the control unit 41, based on the set intake air fresh air amount value tQas0 and the actual EGR rate Megrd And is calculated by looking at the drawings.
[429] In the diagram of Fig. 26 of the first embodiment, the vertical axis represents the value (Qes0) of the EGR rate, but in the diagram of Fig. 28, the vertical axis represents the actual EGR rate (Megrd). The two figures are only different for these parameters, and the characteristics of the acquired target opening (Rvnt) are the same no matter which drawing is used.
[430] In the embodiment described above, the pre-correction is performed to compensate the response delay of the sound pressure control valve 5 and the EGR valve 6, such as the conventional technology for the control unit 41 and the required EGR amount Mqec, It also compensates for the delay corresponding to the time required for the exhaust gas from the EGR valve 6 to reach the intake valve of the diesel engine 1 via the collector 3A. Further, the EGR amount is changed as shown in Figs. 66A and 66B because it carries out the above-described processes (A) to (E).
[431] In these schemes, FIG. 66A shows the change in the EGR amount when the required EGR amount is increased stepwise, and FIG. 66B shows the change in the EGR amount when the required EGR amount is reduced stepwise.
[432] 66A, when the required EGR amount Mqec is increased stepwise at the time t1, the target EGR amount Tqec corrected by the required EGR amount Mqec pre-correction and delay correction is substantially equal to the physical upper limit Tqelmh ). Therefore, the command signal corresponding to the target EGR amount Tqec is outputted to the negative pressure control valve 5 as the EGR amount.
[433] Therefore, the target EGR amount Tqec decreases by the first order delay and falls below the required EGR amount Mqec after the time t2. Therefore, when the command signal corresponding to the target EGR amount Tqec is outputted to the negative pressure control valve 5, the rate of increase of the actual EGR amount Qec after the time t2 is set to be the same as that shown by the curve X in the drawing And a certain amount of time is required for the actual EGR amount Qec to follow the required EGR amount Mqec.
[434] On the other hand, in this control device, when the target EGR amount Tqec exceeds the physical upper limit Tqelmh, the command signal corresponding to the negative value obtained by adding the excess amount Dtqec to the target EGR amount Tqec is And is outputted to the sound pressure control valve 5 in the next case where the signal is outputted. The command signal corresponding to the physical upper limit Tqelmh is equal to or higher than the negative pressure control valve 5 even after the time t2 as the negative value Tqec1 exceeds the physical upper limit Tqelmh for a time longer than the target EGR amount Tqec ). Therefore, the actual increase rate Qec of the EGR amount does not decrease even after the time t2, and the actual EGR amount Qec quickly converges to the target EGR amount Mqec as shown by the curve Y in the figure . It can be observed that the area covered by the curves X and Y in the figure corresponds to the difference in the amount of EGR.
[435] The ability of the actual EGR amount Qec following the required EGR amount Mqec in the case where the required EGR amount Mqec is reduced stepwise at the time t1 as shown in Fig. (Tqec1), and outputs a command signal corresponding to the negative value (Tqec1) to the negative pressure control valve 5.
[436] In this control device, the physical upper limit (Tqelmh) is set in accordance with the EGR valve flow rate (Cqe). The EGR valve flow rate Cqe is a value corresponding to the upstream and downstream pressure differences of the EGR valve 6. [ When decelerating the vehicle, the upstream and downstream pressure differences of the EGR valve 6 decrease as shown by the dotted line in Fig. 67C. Therefore, the EGR valve flow rate Cqe also decreases. The physical upper limit (Tqelmh) value calculated by the equation (28) at the beginning of the deceleration is represented by the value A and the physical upper limit value Tqelmh calculated by the equation (28) at the end of the deceleration is the value B, Lt; / RTI &gt;
[437] (1) when the physical upper limit (Tqelmh) is fixed to the value (A), (2) when the physical upper limit Tqelmh is fixed to the value B and (3) when it changes in accordance with the EGR valve flow velocity Cqe. The above case (3) corresponds to the present invention. In all these cases, the negative value (Tqec1) is calculated by adding the excess amount (Dtqec) to the physical upper limit (Tqelmh), respectively.
[438] 67A, in case (1), the capability of the actual EGR rate following the target EGR rate is suitable for the start of deceleration, as soon as the physical upper limit Tqelmh is large, but the immediate value (Tqec1) Tqelmh). As a result, in the latter half of the deceleration, the ability of the actual EGR rate to follow the target EGR rate decreases, such that an excess amount (Dtqec) does not occur, and the actual EGR rate to converge to the target EGR rate, Time is required.
[439] In case (2), as the physical upper limit (Tqelmh) is small, the ability of the actual EGR rate following the target EGR rate is low at the start of acceleration. Also, the negative value (Tqec1) continues to exceed the physical upper limit (Tqelmh) for a long time, so that the actual EGR rate overlaps in the latter half of deceleration. Therefore, the time required for the EGR rate to converge to the target EGR rate is substantially the same as the time in case (1).
[440] In case (3), good tracking characteristics are obtained at the start of deceleration and at the end of deceleration, such that the physical upper limit Tqelmh is large at the start of deceleration and the physical upper limit Tqelmh is small at the end of deceleration, To the target EGR rate.
[441] 68A to 68C show the relationship between a change in nitrogen oxide (NOx) emission during acceleration in the case where the soot or particulate matter is the same level, a delay correction and a pre-correction of the required EGR amount (Mqec). During acceleration, as both the engine speed Ne and the engine load Qsol increase, the EGR rate decreases as shown in the drawing of Fig. Upon completion of the acceleration, both the engine speed and the engine load (Qsol) decrease while the vehicle speed remains constant. Therefore, the EGR rate shown in FIG. 68B increases stepwise, and the NOx emission amount increases at this time as shown in FIG. 68C.
[442] 68C shows the case where the target EGR amount per cylinder Tqec is determined by adding the delay correction of step S24 in Fig. 7 to the required EGR amount Mqec, and the thin line indicates the target EGR amount per cylinder Amount Tqec is determined by adding both the delay correction of step S24 of Fig. 7 and the pre-correction of step S25 to the required EGR amount Mqec. In both cases, the restriction processing is not executed on the target EGR amount Tqec. The solid line in the figure shows the amount of nitrogen oxide (NOx) emission under the control of the present invention. As shown in the figure, the nitrogen oxide (NOx) emissions can be reduced since it provides a variable physical limit.
[443] The EGR flow rate Cqe used to determine the upper physical limit (Tqelmh) is a value that is not affected by the engine running state, that is, the steady state or transient state. Therefore, by setting the upper physical limit (Tqelmh) in accordance with the EGR flow velocity Cqe, the control delay of the EGR amount is eliminated in the transient state, and the ability to converge to the target value of the EGR amount is improved.
[444] In the above-described embodiment, the EGR flow rate Cqe is expected, and the EGR valve 6 is controlled based on the predicted value, but the EGR valve 6 upstream and downstream of the EGR valve 6, A pressure difference is also expected, and the EGR valve 6 is controlled based on this pressure difference.
[445] (Third Embodiment)
[446] Next, a third embodiment of the present invention will be described with reference to Figs. 69 to 76. Fig. Fig. 69 shows a routine for calculating the EGR valve opening area Aev in place of the routine of Fig. 5 of the first and second embodiments described above. This routine is also executed synchronously with the REF signal as in the routine of Fig.
[447] In the first and second embodiments described above, the EGR valve opening area Aev is calculated based on the target EGR amount Tqek of the EGR valve 6, but in this embodiment, the opening area of the target EGR valve (Aev Is calculated from the target opening ratio Rvnt per cylinder and the target amount of restriction EGR Tqecf.
[448] In step S411 of Fig. 69, the target amount of restriction EGR (Tqecf) per cylinder is calculated using the subroutine of Fig. Fig. 70 is the same as the routine except step (S29) of Fig. The setting of the physical upper limit Tqelmh and the physical lower limit Tqelml executed in step S27 of Fig. 70 is executed by the subroutine shown in Fig.
[449] Referring to Fig. 71, first, in step S421, the control unit 41 reads the actual EGR rate Megrd and the delayed process value RVNTE of the target opening Rvnt.
[450] Here, the delay processing value RVNTE is a value calculated by the independent routine shown in FIG. This routine is executed synchronously with the REF signal.
[451] 72, first, at step S431, the control unit 41 sets the value Tcvnt of the pre-correction time constant, which is set in step S144 of the subroutine of Fig. 29, (RVNT). The pre-correction time constant value value Tcvnt is a value for compensating the operation delay of the variable nozzle 53, as described above.
[452] In the next step S432, the delay processing value RVNTE is calculated by the following equation (30) from the target opening Rvnt and the pre-correction time constant value Tcvnt, and the routine is ended.
[453] RVNTE = Rvnt Tcvnt KVN1 # + RVNTE _n-1 (1 - Tcvnt KVN1 #) (30)
[454] However, KVN1 # = constant, and
[455] RVNTE _n-1 = RVNTE computed in the previous predecessor when the subroutine was executed.
[456] The delay processing value RVNTE calculated in the equation (30) shows the actual opening of the variable nozzle 53 based on the output of the duty signal for the pressure control valve 56 by the control unit 41.
[457] After the delay processing value RVNTE calculated by the routine of Fig. 72 is read, the control unit 41 reads the drawing shown in Fig. 73 based on the delay processing value RVNTE in step S422 of Fig. 71 And calculates the maximum EGR flow rate basic value (Eqmaxb) per unit discharge amount. This drawing is stored in advance in the memory of the control unit 41. [ Here, the maximum EGR flow rate basic value Eqmaxb per unit discharge amount is set to give a large value to the small opening delay processing value RVNTE. This is because when the opening of the nozzle 53 decreases and the boost pressure increases, the upstream and downstream pressure difference of the EGR valve 6 increases and the maximum flow velocity through the EGR valve 6 increases.
[458] In step S243, the amount of change Dregr of the actual EGR rate Megrd is calculated by the following equation (31).
[459] Dregr = Megrd-Megrd _n-1 (31)
[460] However, Megrd = Megrd computed in the previous precedent in which the subroutine was executed.
[461] In the next step S424, the maximum EGR flow velocity correction Kemin is calculated with reference to the drawing shown in Fig. 74 based on the amount of change Dregr.
[462] In step S425, the maximum amount of EGR per cylinder is calculated from the correction coefficient Kemin and the maximum EGR flow rate basic value Eqmaxb by the following equation (32).
[463] Tqelmh = Egmaxb · Kemin · SVOL # (32)
[464] SVOL # = displacement of the diesel engine (1).
[465] As shown in FIG. 74, when the EGR rate increases, that is, when Dregr &gt; 0, the maximum flow velocity correction coefficient Kmin is larger than 1.0. Conversely, when the EGR rate decreases, that is, when Dregr &lt; 0, the maximum flow velocity correction coefficient Kmin is a positive value smaller than 1.0. According to equation (32), the physical upper limit increases with increasing EGR rate, which is for the following reasons. When the EGR rate increases, the pressure difference between the upstream and downstream of the EGR valve 6 changes in the decreasing direction. The pressure difference gradually decreases as shown by the dashed line in Fig. 67C and exceeds the pressure difference as shown in the steady state, i.e., the solid line in the gradually decreasing interval. In other words, at this interval, more EGR is performed in the steady state. The reason that the physical upper limit increases with the increase of the EGR rate is that this phenomenon is reflected in actual operation. Conversely, when the EGR rate decreases, the pressure difference between the upstream and the downstream of the EGR valve 6 changes in the increasing direction, but the pressure difference gradually increases without changing stepwise, and at the gradually increasing interval, Is less than the steady state pressure difference. This is because the upper physical limit decreases with decreasing EGR rate in Eq. (32).
[466] In the final step (S426), the physical lower limit (Tqelml) is set to 0, and the subroutine ends.
[467] After the subroutine of FIG. 71 is completed, in step S28 of FIG. 70, the control unit 41 calculates the target restricted EGR amount Tqecf per cylinder in the same manner as in the first embodiment described above. In addition, in step S30, the excess / deficiency amount Dtqec is calculated, and the subroutine of Fig. 70 is terminated.
[468] 69, the control unit 41 sets the EGR amount feedback correction coefficient Kqac00, the EGR flow velocity feedback correction coefficient Kqac0, and the EGR flow velocity learning correction coefficient Kqac to the following equation . These are calculated by the subroutine of Fig. 50 of the first embodiment.
[469] In step S413, the limit target EGR amount per unit discharge amount Tqecf2 is calculated by the equation (33).
[470] Tqecf2 = Tqecf / (Kqac.Kqac0.Kqac00) / SVOL # (33)
[471] SVOL # = displacement of the diesel engine (1).
[472] In step S414, the target open delay processing value RVNTE calculated in the routine of Fig. 72 is read.
[473] In step S415, the open area Eaev of the target EGR valve per unit discharge amount is calculated based on the target EGR amount Tqecf2 per unit discharge amount and the target opening delay processing value RVNTE, . This drawing is stored in advance in the memory of the control unit 41. [
[474] 75, the delay processing value RVNTE, which is a horizontal axis, is considered to be substantially the same as the differential pressure upstream and downstream of the EGR valve 6. [ For example, when the opening of the EGR valve 6 is smaller than the delay processing value RVNTE, is larger than the opening of the variable nozzle 53, and is set to a constant larger than the boost pressure, The differential pressure between the two is increased. Conversely, if the value is larger than the retarded value RVNTE, is larger than the opening of the variable nozzle 53, and is set to a constant smaller than the boost pressure, the differential pressure upstream and downstream of the EGR valve 6 decreases.
[475] Therefore, the delayed processing value RVNTE, which is a horizontal axis, is considered to represent the differential pressure upstream and downstream of the EGR valve 6. [ Taking the EGR amount in the vertical axis, the opening of the EGR valve 6 can be classified by these parameters as can be understood from the drawing of Fig.
[476] In Fig. 75, the numeral symbol is a temporary value designated to show the relative magnitude of the opening of the EGR valve 6. [
[477] By experiment, the inventor obtained the experimental drawing of FIG. 75, but the EGR valve opening area (Aev) can also be determined using the theoretical value plot shown in FIG.
[478] In Fig. 75 and Fig. 76, although the characteristics are largely different in the right region of the drawing, no control is actually effected in this region, no matter what drawing is used.
[479] What is read from these figures is not the opening area of the EGR valve 6 but the opening area (Eaev) of the target EGR valve per piston displacement. This allows it to be applied to drawings without depending on the displacement of the diesel engine 1.
[480] The control unit 41 calculates the opening area Eaev of the target EGR valve per unit exhaust amount volume in step S415 of Figure 69 and the opening area Aev of the target EGR valve is calculated in step S416 by the diesel engine 1 ) Is multiplied by Eaev, and the routine of Fig. 69 is ended.
[481] The open area of the target EGR valve obtained by the routine of Fig. 69 is converted into, for example, the lift amount of the EGR valve 6 or the drive signal by using the diagram of Fig. The control unit 41 outputs a duty signal corresponding to the pressure control valve 5 for driving the EGR valve 6 to control the opening of the EGR valve 6 with respect to the opening area Aev of the target EGR valve.
[482] According to this embodiment, since the physical upper limit Tqelmh is calculated based on the target open delay processing value RVNTE, i.e., the target value of the boost pressure control, the physical upper limit changes according to the operating state of the turbocharger 50. [ Therefore, this embodiment also eliminates the EGR control delay during transient conditions, and the ability to follow the target value of the EGR amount is improved as in the first and second embodiments.
[483] 75, the vertical axis represents the target EGR rate per unit displacement (Tqecf2), but the target EGR amount Tqek per unit time converted by the following equation (34) can also be used as the vertical axis.
[484] Tqek = Tqecf (Ne / KCON #) / (Kqac Kqac0 Kqac00) / SVOL #
[485] However, KCON # = constant,
[486] Kqac00 = EGR amount feedback correction coefficient,
[487] Kqac0 = EGR flow velocity feedback correction coefficient,
[488] Kqac = EGR flow rate learning correction coefficient, and
[489] SVOL # = displacement of diesel engine (1).
[490] According to the results of the experiment obtained by the inventors, when the valve per unit time is used as the vertical axis, the features of the figure are much more complicated than when the valve per unit displacement is used as the vertical axis. Therefore, it is preferable to use a valve per unit displacement in the vertical axis.
[491] In Fig. 75, the target opening Rvnt may be used on the horizontal axis instead of the delay processing value RVNTE.
[492] In this embodiment, the target opening Rvnt has been used as the operating target of the supercharger 50. [ The target opening Rvnt represents the ratio of the open area to the fully open area. However, it is also possible to use the target opening area of the variable nozzle 53 instead of the target opening Rvnt.
[493] In the above embodiment, the delay processing and the preprocessing have been added to the required EGR amount Mqec, but only the delay processing may be applied.
[494] In the above embodiment, the physical upper limit Tqelmh is set to a variable value, the physical lower limit Tqelml is set to a fixed value, and the excess / deficiency amount Dtqec is added to the target EGR amount Tqec.
[495] However, a variety of variables can be created at this point. In particular, both of the physical upper limit (Tqelmh) and the physical lower limit (Tqelml) are set to the excess and deficiency amount (Dtqec) added to the fixed value and the target EGR amount (Tqec).
[496] The purpose of adding the excess or deficiency amount Dtqec to the target EGR amount Tqec is that the target EGR amount Tqec falls below the physical upper limit Tqelmh and then the EGR valve 6 is opened for a moment corresponding to the physical upper limit Tqelmh. To maintain the opening of the door. Further, after the target EGR amount Tqec falls below the physical upper limit Tqelmh without addition of the excess / deficiency amount Dtqec to the target EGR amount Tqec, the EGR amount Tqecm is maintained for a predetermined time to maintain the opening corresponding to the physical upper limit Tqelmh. The valve 6 may be directly controlled.
[497] The above embodiments illustrate the application of the present invention to diesel engine operation by low temperature premix combustion, and the heat generation pattern is single stage combustion, but the present invention is also applicable to a conventional diesel engine Lt; / RTI &gt;
[498] As described above, the present invention eliminates the delay of the EGR control due to the time required for the exhaust gas to flow from the EGR valve to the cylinder of the engine and improves the response of the EGR amount following the target value. Thus, the present invention improves exhaust emissions of diesel engine vehicles.

权利要求:
Claims (13)
[1" claim-type="Currently amended] A combustion chamber 1A, an intake passage 3 for sucking air into the combustion chamber 1A, an exhaust passage 2 for exhausting the exhaust gas from the combustion chamber 1A and an exhaust passage 2 for exhausting the exhaust passage 2 to the combustion chamber 1A. 1. A control device for an engine (1) having an exhaust gas recirculation valve (6) for recirculating a part of a gas,
Sensors (34, 39) for detecting the running condition of the engine (1), and
(S25, S26) of setting a target exhaust gas recirculation amount based on the running condition,
A step (S27) of judging the maximum recirculation amount of the exhaust gas recirculation valve 6,
A step (S28) of comparing the maximum recirculation amount and the target exhaust gas recirculation amount,
(S28) limiting the target exhaust gas recirculation amount to be equal to the maximum recirculation amount when the target exhaust gas recirculation amount exceeds the maximum recirculation amount,
(S29) controlling the opening of the exhaust gas recirculation valve (6) based on the target exhaust gas recirculation amount, and
(S26) in which the opening of the exhaust gas recirculation valve (6) maintains the opening corresponding to the maximum recirculation amount for a predetermined time after the target exhaust gas recirculation amount falls below the maximum recirculation amount is programmed to the microprocessor And a control unit for controlling the diesel engine.
[2" claim-type="Currently amended] The microprocessor according to claim 1, wherein the microprocessor (41)
The opening of the exhaust gas recirculation valve 6 for a predetermined period of time after the target exhaust gas recirculation amount falls below the maximum recirculation amount,
(S25, S26) of setting a target exhaust gas recirculation amount on the basis of the running condition in each control case,
(S30) calculating a difference between the target exhaust gas recirculation amount and the maximum recirculation amount as an excess amount when the target exhaust gas recirculation amount is larger than the maximum recirculation amount,
Further programmed to maintain an opening corresponding to a maximum recirculation amount by modifying a target exhaust gas recirculation amount by adding an excess amount to the target exhaust gas recirculation amount in the following control case.
[3" claim-type="Currently amended] The microprocessor according to claim 1, wherein the microprocessor (41)
And changing the maximum recirculation amount based on the running condition (S402, S403).
[4" claim-type="Currently amended] The microprocessor according to claim 1, wherein the microprocessor (41)
(S22) of calculating a target exhaust gas recirculation ratio based on the running condition, estimating an actual exhaust gas recirculation amount from the target exhaust gas recirculation rate and the running condition (S113), calculating the actual exhaust gas recirculation amount and the target exhaust gas recirculation amount Calculating a required exhaust gas recirculation amount from the running condition and the target exhaust gas recirculation rate (S23), calculating a flow rate of the exhaust gas recirculation valve (6) from the exhaust gas recirculation valve ) Corresponding to the exhaust gas arrival time from the exhaust gas recirculation valve 6 to the combustion chamber 1A is added to the delay processing value (step S24) (Step S25) of calculating the target exhaust gas recirculation amount obtained by adding the exhaust gas recirculation valve 6 to the exhaust gas recirculation valve 6 based on the target exhaust gas recirculation amount and the speed, Determining a target valve opening, and target a diesel engine control apparatus in accordance with the valve opening, it characterized in that the further program to step (S13) for controlling the exhaust gas recirculation valve (6).
[5" claim-type="Currently amended] The method according to claim 1,
The sensors 34 and 39 for detecting the running condition are provided with a sensor 34 for detecting the rotational speed of the engine 1 and a sensor 39 for detecting the amount of intake of the intake passage 3. [ controller.
[6" claim-type="Currently amended] The microprocessor according to claim 1, wherein the microprocessor (41)
A step S27 of judging the minimum recirculation amount of the exhaust gas recirculation valve 6, a step S28 of comparing the minimum recirculation amount and a target exhaust gas recirculation amount, and a step S28 of, when the target exhaust gas recirculation amount is smaller than the minimum recirculation amount, (S28) of limiting the gas recirculation amount to a minimum flow rate, controlling the opening of the exhaust gas recirculation valve (6) based on the target exhaust gas recirculation amount (S29), determining a target exhaust gas recirculation amount (S26) of maintaining an opening of the exhaust gas recirculation valve (6) with an opening corresponding to a minimum recirculation amount for a predetermined period of time.
[7" claim-type="Currently amended] The microprocessor according to claim 1, wherein the microprocessor (41)
(S410, S27) in which the maximum recirculation amount is set to be large as the target exhaust gas recirculation amount is increased.
[8" claim-type="Currently amended] 8. The system of claim 7, wherein the microprocessor (41)
(Step S401) of calculating the flow rate of the exhaust gas recirculation valve 6 based on the running condition, and step S27 in which the maximum recirculation amount is determined based on the flow rate of the exhaust gas recirculation valve 6 A diesel engine control device.
[9" claim-type="Currently amended] The method according to claim 1,
(50) for supercharging the intake air of the intake passage (3) in accordance with the pressure of the exhaust gas in the exhaust passage, and a step of calculating an operation target value of the supercharger (50) based on the driving condition (S124), and controlling the supercharger (50) based on the operation target value (S75 to S78).
[10" claim-type="Currently amended] 10. The system according to claim 9, wherein the microprocessor (41)
And determining the maximum recirculation amount based on the operation target value (S422, S425).
[11" claim-type="Currently amended] 10. The method of claim 9,
The exhaust gas turbine 52 provided in the exhaust passage 2 and the compressor 55 installed in the intake passage 3 for supercharging the intake air in accordance with the rotation of the exhaust gas turbine 52 and the exhaust gas turbine 52 Characterized in that the operating target is a target opening of the variable nozzle (53), and the target opening of the variable nozzle (53) is larger than the target opening of the variable nozzle Characterized in that the microprocessor (41) is further programmed to set a maximum recirculation amount with a large value.
[12" claim-type="Currently amended] A combustion chamber 1A, an intake passage 3 for sucking air into the combustion chamber 1A, an exhaust passage 2 for exhausting the exhaust gas from the combustion chamber 1A and an exhaust passage 2 for exhausting the exhaust passage 2 to the combustion chamber 1A. 1. A control device for an engine (1) having an exhaust gas recirculation valve (6) for recirculating a part of a gas,
Means (34, 39) for detecting the running condition of the engine,
Means (41, S25, S26) for setting a target exhaust gas recirculation amount on the basis of the running condition,
Means (41, S27) for determining the maximum recirculation amount of the exhaust gas recirculation valve (6)
Means (41, S28) for comparing the maximum recirculation amount and the target exhaust gas recirculation amount,
Means (41, S28) for limiting the target exhaust gas recirculation amount to be equal to the maximum recirculation amount when the target exhaust gas recirculation amount exceeds the maximum recirculation amount,
Means (41, S29) for controlling the opening of the exhaust gas recirculation valve (6) based on the target exhaust gas recirculation amount, and
And means (41, S26) for maintaining the opening of the exhaust gas recirculation valve (6) for a predetermined time after the target exhaust gas recirculation amount falls below a maximum recirculation amount, corresponding to a maximum recirculation amount Diesel engine control unit.
[13" claim-type="Currently amended] A combustion chamber 1A, an intake passage 3 for sucking air into the combustion chamber 1A, an exhaust passage 2 for exhausting the exhaust gas from the combustion chamber 1A and an exhaust passage 2 for exhausting the exhaust passage 2 to the combustion chamber 1A. 1. A control method for an engine having an exhaust gas recirculation valve (6) for recirculating a part of a gas,
Detecting a running condition of the engine (1)
Setting a target exhaust gas recirculation amount based on the running condition,
Determining a maximum recirculation amount of the exhaust gas recirculation valve (6)
Comparing the maximum recirculation amount with a target exhaust gas recirculation amount,
Limiting the target exhaust gas recirculation amount to be equal to the maximum recirculation amount when the target exhaust gas recirculation amount exceeds the maximum recirculation amount,
Controlling the opening of the exhaust gas recirculation valve (6) based on the target exhaust gas recirculation amount, and
And maintaining the opening of the exhaust gas recirculation valve (6) for a predetermined time after the target exhaust gas recirculation amount falls below a maximum recirculation amount to an opening corresponding to a maximum recirculation amount.

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同族专利:

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公开号 | 公开日

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EP1283949A1|2003-02-19|

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JP3656518B2|2005-06-08|

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KR100433924B1|2004-06-04|

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DE60124903T2|2007-05-24|

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EP1283949B1|2006-11-29|

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JP2001329876A|2001-11-30|

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CN1260470C|2006-06-21|

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DE60124903D1|2007-01-11|

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CN1380936A|2002-11-20|

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US20020170546A1|2002-11-21|

---

WO2001088358A1|2001-11-22|

---

US6502563B2|2003-01-07|

引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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法律状态:
2000-05-18|Priority to JP2000146265A

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2000-05-18|Priority to JPJP-P-2000-00146265

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2001-05-15|Application filed by 하나와 요시카즈, 닛산 지도우샤 가부시키가이샤

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2002-03-12|Publication of KR20020019546A

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2004-06-04|Application granted

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2004-06-04|Publication of KR100433924B1

优先权:

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申请号 | 申请日 | 专利标题

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JP2000146265A|JP3656518B2|2000-05-18|2000-05-18|Diesel engine control device|

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JPJP-P-2000-00146265|2000-05-18|