• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method for operating an internal combustion engine (1), in particular with self-ignition, with at least one SCR catalytic converter (5) in the exhaust line (3) and an exhaust gas recirculation system (4) with an exhaust gas recirculation valve (8), wherein the exhaust gas recirculation amount and / or the position of the exhaust gas recirculation valve (8) is regulated as a function of the NOx concentration upstream of the SCR catalytic converter (5) such that a NOx concentration measured by at least one first NOx sensor (6) upstream of the SCR catalytic converter (5) NOxI1 corresponds to a predetermined NOx concentration target value (NOxS) In order to be able to comply with legally prescribed NOx emission limit values independently of aging phenomena, it is provided that the NOx concentration in the exhaust gas downstream of the SCR catalytic converter (5) is at least a second NOx sensor (7) and with the NOx concentration (NOxI1) of the first NOx sensor (6) upstream of the SCRKa and comparing a comparison of the NOx measured values (NOxI1, NOxI2) with an efficiency value (KNOx) of the NOx conversion SCR catalyst (5), wherein the NOx concentration target value (NOxs) is upstream the SCR catalyst (5) is adjusted when the determined efficiency value (KN O x) deviates from a predetermined efficiency setpoint (KNoxs).
    公开号:AT512760A1
    申请号:T50092/2012
    申请日:2012-03-21
    公开日:2013-10-15
    发明作者:Holger Dr Huelser；Bernhard Dipl Ing Breitegger
    申请人:Avl List Gmbh；
    IPC主号:
    专利说明:

    1 Printed: 22-03-2012 E014 u · 10 2012/50092 56362
    The invention relates to a method for operating an internal combustion engine, in particular with self-ignition, with at least one SCR catalytic converter in the exhaust system and an exhaust gas recirculation system with an exhaust gas recirculation valve, wherein the exhaust gas recirculation amount and / or the position of the exhaust gas recirculation valve in dependence on the NOx concentration upstream of the SCR catalyst is controlled so that a measured by at least a first NOx sensor upstream of the SCR catalyst NOx concentration corresponds to a predetermined NOx concentration target value.
    As the NOx conversion capability of the SCR catalyst decreases over time due to aging or detoxification effects, the engine must be operated at higher exhaust gas recirculation rates to reduce the engine's NOx emissions, and still maintain the required low levels despite reduced NOx conversion capability To achieve NOx concentrations downstream of the SCR catalyst.
    It is known to carry out the regulation of the recirculated exhaust gas on the basis of an air mass or lambda sensor. The necessary sensors are expensive. Further, the specification of a desired air mass or a desired value for lambda requires a large number of corrections, in order thereby to achieve low NOx emissions in different operating states of the internal combustion engine. This variety of corrections is complex to handle.
    From JP 2000-282958 A, an internal combustion engine with an exhaust gas recirculation system and an SCR catalyst is known, wherein the exhaust gas recirculation valve is controlled by a control unit so that a measured by a NOx sensor upstream of the SCR catalyst NOx concentration of a NOx concentration Setpoint corresponds.
    In this method, however, deterioration of NOx conversion of the SCR catalyst due to aging effects, poisoning, etc., can not be taken into consideration. 1/5 21-03-2012
    Printed: 22-03-2012 E014 10 2012/50092 2
    The object of the invention is to avoid these disadvantages and to be able to comply with the legally prescribed NOx emission limit values at the end of the exhaust gas line independently of aging phenomena in the simplest possible way.
    According to the invention, this is achieved by also measuring the NOx concentration in the exhaust gas downstream of the SCR catalytic converter with at least one second NOx sensor and comparing it with the NOx concentration of the first NOx sensor upstream of the SCR catalytic converter and from a comparison of the NO x measurement values, an efficiency value of the SCR catalyst for the NO x conversion is determined, wherein the NO x concentration target value is adjusted upstream of the SCR catalyst when the determined efficiency value deviates from a predetermined efficiency target value.
    Today's SCR catalyst systems usually have both upstream and downstream by default each a NOx sensor to monitor the NOx conversion of the SCR catalyst. Thus, no additional sensor technology is required for the realization of the method according to the invention. If the calculated efficiency value deviates from the specified efficiency setpoint, then the exhaust gas recirculation is adjusted so that the setpoint value for the NOx concentration upstream of the SCR catalytic converter, which is changed on the basis of the changed efficiency value of the SCR catalytic converter, is actually achieved. It will be readily apparent to those skilled in the art that the adjustment of the exhaust gas recirculation by adjusting a target exhaust gas recirculation rate or by adjusting a target value for the position of the exhaust gas recirculation valve or by adjusting a target value for the air / fuel ratio lambda or by a Adjustment of the desired air mass or by similar known methods can be done.
    Preferably, it is provided that the NOx concentration setpoint upstream of the SCR catalyst is reduced if the determined efficiency value is less than a predetermined efficiency setpoint.
    In accordance with the above-explained reduction of the target value for the NOx concentration upstream of the SCR catalyst with reduced efficiency of the SCR catalyst, an increase of this target value with increased efficiency is also required E014 10 2012/50092
    Subject of the method according to the invention possible. Such an increase in NOx concentration usually results in reduced fuel consumption.
    It is particularly advantageous if the setpoint specification for the efficiency of the SCR catalytic converter depends on the operating conditions of the SCR catalytic converter, in particular the temperature and / or the space velocity of the exhaust gas flow, the operating conditions of the internal combustion engine, in particular the rotational speed and / or the load and / or the NOx concentration measured by the first NOx sensor. The NOx concentration setpoint for the NOx concentration at the location of the first NOx sensor may be a function of at least one operating parameter of the internal combustion engine, preferably the speed or the load, and / or at least one environmental parameter, preferably the atmospheric pressure. Thus, the control can be adapted quickly to changing conditions, and to tolerances in the exhaust gas recirculation system.
    In order to prevent excessive formation of soot particles, it is advantageous if, in addition, an upper limit value for the exhaust gas recirculation quantity and / or for the opening position of the exhaust gas recirculation valve is specified as a function of at least one operating parameter of the internal combustion engine, preferably the rotational speed or the load. Preferably, the upper limit value for the exhaust gas recirculation quantity and / or for the position of the exhaust gas recirculation valve is predefined as a function of at least one environmental parameter, preferably the atmospheric pressure. This allows a rapid adaptation to changes even at the limit.
    The invention will be explained in more detail below with reference to FIGS.
    1 shows schematically an internal combustion engine for carrying out the method according to the invention, and FIG. 2 shows the method sequence.
    The Fig.l shows schematically an internal combustion engine 1, with an intake manifold 2, an exhaust line 3 and an exhaust gas recirculation system 4 for returning exhaust gases from the exhaust line 3 in the intake manifold 2. In the exhaust line 3, an SCR catalyst 5 is arranged, with which NOx in Exhaust gas can be reduced. Upstream of the SCR catalyst 5, a first NOx sensor 6, downstream of the SCR catalyst 5, a second NOx sensor 7 is arranged. With the two NOx sensors 6, 7, the NOx conversion of the SCR catalyst 5 can be monitored 3/5 21-03-2012
    Printed: 22-03-2012 E014 10 2012/50092 4. The NOx sensors 6, 7 are in communication with an electronic control unit ECU. Further, the electronic control unit ECU is connected to an exhaust gas recirculation valve 8 with which the exhaust gas recirculation amount can be controlled.
    The two NOx sensors 6 and 7 are included as standard in conventional SCR catalyst systems.
    With the method described here, the exhaust gas recirculation control can be made possible without further sensor in the air path with the least possible calibration effort.
    The method according to the invention is explained below with reference to FIG. 2:
    In a first step 10, a nominal value NOxs for the NOx concentration at the location of the first NOx sensor 6 is determined. In this case, it is advantageous if this specification depends on the operating parameters of the internal combustion engine 1, in particular the speed n, the load L, but also on ambient parameters such as the atmospheric pressure p. From the comparison of the first NOx-concentration measured by the first NOx-sensor NOxu and the specification NOxs of the NOx-concentration, a desired value EGRs for the position of the exhaust-gas recirculation valve 8 or the exhaust-gas recirculation rate is calculated in a further step 20. In step 30, it is examined whether the target value EGRs for the position of the exhaust gas recirculation valve 8 or the exhaust gas recirculation rate exceeds a maximum value EGRmax and equals the maximum value EGRmax when the target value EGRs is exceeded. Limiting the exhaust gas recirculation rate prevents excessive formation of soot particles. The limitation, ie the maximum value EGRmax itself, may in turn depend on operating parameters of the internal combustion engine 1, such as, for example, the rotational speed n or load L or on ambient parameters such as the atmospheric pressure p.
    In order to be able to compensate for a deterioration in the NOx conversion of the SCR catalytic converter 5 due to aging effects, poisoning, etc., the signal N0xi2 of the second NOx sensor 7 downstream of the SCR catalytic converter 5 can also be taken into account. For this purpose, an efficiency value Knqx of the SCR catalyst for the NOx conversion is first calculated in step 40 from the comparison of the signals NOxu and NOx ^ of the two NOx sensors 6, 7. Dodge the calculated 4/5 21-03-2012
    Printed: 22-03-2012 E014 10 2012/50092 5
    Efficiency value Knox from a setpoint specification KNoxs from, the NOx concentration setpoint specification NOxs is adjusted (step 50). In particular, the NOx concentration target value specification NOxs is reduced by a predefined value ΔΝΟχ if the efficiency value Knox is too low.
    It is advantageous if the setpoint specification KNOxs for the efficiency Kmx of the SCR catalytic converter depends on operating conditions of the SCR catalytic converter 5 (in particular the temperature and / or the space velocity of the exhaust gas flow in the SCR catalytic converter) and / or on operating conditions of the internal combustion engine 1 (FIG. in particular the rotational speed n and / or the load L) and / or the NOx concentration NOxn, which is measured by the first NOx sensor 6. • Through the described method, the exhaust gas recirculation recirculation can be realized without additional sensors in the air path. Compared to a pure control of the exhaust gas recirculation valve 8, there is the advantage that changes and tolerances in the exhaust gas recirculation system 4 are immediately recognized by means of modified NOx emissions from the first NOx sensor 6. Furthermore, aging of the SCR system can be compensated by reducing the NOx emissions of the internal combustion engine 1 by increasing the exhaust gas recirculation rate. Although this may lead to a slight increase in the fuel consumption of the internal combustion engine 1 with increasing aging of the SCR system, the legally required emissions can be maintained in any case. 21-03-2012
    权利要求:
    Claims (10)
    [1]
    1. Printed: 22-03-2012 E015 10 2012/50092 6 PATENT CLAIMS 1. Method for operating an internal combustion engine (1), in particular with self-ignition, with at least one SCR catalytic converter (5) in the exhaust line (3) and an exhaust gas recirculation system (4 ) with an exhaust gas recirculation valve (8), wherein the exhaust gas recirculation amount and / or the position of the exhaust gas recirculation valve (8) in dependence of the NOx concentration upstream of the SCR catalyst (5) is controlled so that by at least one first NOx sensor (6 ) upstream of the SCR catalyst (5) measured NOx concentration (NOxn) corresponds to a predetermined NOx concentration Soilwert (NOxs), characterized in that also downstream of the SCR catalyst (5) the NOx concentration in the exhaust gas with at least one second NOx sensor (7) is measured and compared with the NOx concentration (NOxn) of the first NOx sensor (6) upstream of the SCR catalyst (5) and from a comparison of the NOx measured values (NOxn, NOx ^)an efficiency value (Km0x) of the SCR catalyst (5) for the NOx conversion is determined, wherein the NOx concentration target value (NOxs) upstream of the SCR catalyst (5) is adjusted when the determined efficiency value (KNox) of a specified efficiency value (KNO * s) deviates.
    [2]
    2. The method according to claim 1, characterized in that the NOx concentration target value (NOxs) is reduced when the determined efficiency value (KNox) is smaller than the predetermined efficiency target value (KNoxs).
    [3]
    3. The method according to claim 1 or 2, characterized in that the NOx concentration-Soilwert (NOxs) as a function of at least one operating parameter of the internal combustion engine (1), preferably the speed (n) or the load (L), is specified.
    [4]
    4. The method according to any one of claims 1 to 3, characterized in that the NOx concentration-Soilwert (NOxs) as a function of at least one environmental parameter, preferably the atmospheric pressure (p), is specified.
    [5]
    5. The method according to any one of claims 1 to 4, characterized in that the predetermined efficiency setpoint (KNoxs) as a function of at least one operating parameter of the SCR catalyst (5), preferably the temperature and / or the space velocity of the Exhaust gas flow in the SCR catalyst (5), is determined.
    [6]
    6. The method according to any one of claims 1 to 5, characterized in that the predetermined efficiency setpoint (KNOxs) as a function of at least one operating parameter of the internal combustion engine (1), preferably the speed (n) and / or the load (L) is determined.
    [7]
    7. The method according to any one of claims 1 to 6, characterized in that the predetermined efficiency setpoint value (KNOxS) is determined as a function of the NOx concentration (NOxn) measured by the first NOx sensor.
    [8]
    8. The method according to any one of claims 1 to 7, characterized in that an upper limit (EGRmax) for the exhaust gas recirculation amount and / or for the position of the exhaust gas recirculation valve (8) is determined, and that the target value (EGRs) for the exhaust gas recirculation amount and / or for the position of the exhaust gas recirculation valve (8) is set equal to the limit value (EGRmax) when the setpoint value is greater than the limit value.
    [9]
    9. The method according to claim 8, characterized in that the upper limit value (EGRmax) for the exhaust gas recirculation amount and / or for the opening position of the exhaust gas recirculation valve (8) as a function of at least one operating parameter of the internal combustion engine (1), preferably the rotational speed (n) or Load (L), is specified.
    [10]
    10. The method according to claim 8 or 9, characterized in that the upper limit value (EGRmax) for the exhaust gas recirculation amount and / or for the position of the exhaust gas recirculation valve (8) as a function of at least one environmental parameter, preferably the atmospheric pressure (p), is specified. 2012 03 21 Fu / Bt
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