• 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:
    A method of degrading the elastically stored energy of a tool operated by an electric motor (20), comprising determining the rotational speed of the electric motor; Determining a limit torque for the electric motor (20) using the speed, at which limit torque the energy is at least predominantly converted into copper losses of the electric motor and driving the electric motor (20) by means of a speed control with a decreasing speed, while maintaining the limit torque as engine torque limit.
    公开号:AT519142A2
    申请号:T50808/2017
    申请日:2017-09-22
    公开日:2018-04-15
    发明作者:Essig Matthias；Spielmann Andreas
    申请人:Wittenstein Se；
    IPC主号:
    专利说明:

    The invention relates to methods for dissipating an elastically stored energy of a tool operated with an electric motor and a tool with an electric motor.
    So-called power wrenches or heavy-duty wrenches operated with an electric motor are known from the prior art, in which the electric motor drives a work spindle with the interposition of a transmission. The gear ratio is high, so that u. a. due to the rigidity of the gearbox, elastic energy is stored in the mechanical system during a screwing operation. An example of the stored elastic energy includes the torsional energy.
    During a screwing process, the work spindle rotates in a tightening direction or fastening direction of an element of the screw connection to be produced, for example a bolt or a nut. The screwing process ends when a desired tightening torque is reached. The stored elastic energy can cause the work spindle to accelerate against the tightening direction after the screwing process has ended. This can lead to the electric motor rotating at a speed that exceeds its nominal speed or design speed.
    A method for braking a heavy-duty screwdriver with an electric motor and transmission is known from US Pat. No. 5,285,857 A. In the conventional method, the rotor of the electric motor is blocked at intervals (see, for example, FIG. 3 of US Pat. No. 5,285,857 A). There is a jerky behavior of the electric motor. The energy dissipation is comparatively slow, and the jerky impacts put a heavy load on the engine and transmission.
    The object of the invention is to provide an improved method for reducing the elastically stored energy of a tool operated with an electric motor or a tool operated with an electric motor for performing the method, the energy being reduced in particular quickly or gently.
    / 28
    The object is achieved by a method according to claim 1 or by a tool according to the independent claim.
    A typical method according to the invention comprises determining the speed of the electric motor; determining the limiting torque for the electric motor using the rotational speed, at which limiting torque the energy is converted at least for the most part into copper losses of the electric motor; and driving the electric motor by means of a speed control with a decreasing speed, while maintaining the limit torque as the motor torque upper limit.
    The tool is, for example, a screwing tool, typically a power screwdriver or heavy duty screwdriver. The tool can be mains-operated or battery / rechargeable. The tool can, for example, also act on workpieces or be designed as part of a machine. Embodiments of the invention are designed as stationary machines or as part of such machines. Further embodiments are designed as hand-operated devices.
    The speed of the electric motor can be determined, for example, using a suitable speed sensor or speed encoder.
    In exemplary embodiments, the speed is determined without an encoder. An encoderless determination of the rotational speed is possible, for example, as in the document "Operation without position encoder of permanent magnet excited synchronous machines"; Dr. Karsten Wiedmann; Faculty of Electrical Engineering and Computer Science at Gottfried Wilhelm Leibniz Universität Hannover; Described in 2012.
    It is also possible to indirectly determine the speed of the electric motor, for example by determining the output speed at the output of the transmission or at the output of the electric motor.
    / 28
    The limit torque for the electric motor is determined using the speed of the electric motor. At the limit torque, the energy is at least largely converted into copper losses in the electric motor.
    In an exemplary description of the electric motor in the d / q coordinate system, the electrical power loss P v of the electric motor, in which copper losses are predominantly generated, results in the approximation to 3 -7
    Pv - Rq · where R q is the electrical resistance in the q-axis and where i q is the current in the q-axis.
    The mechanical power of the electric motor results as the product of the current motor torque M and the mechanical angular velocity UJmech. By equating this results in 3 7 M · <*> mech
    The motor torque M depends on the angular velocity and thus on the speed n.
    Using the determined speed, the torque M is typically determined as the limit torque M L i m at which the energy in the electric motor is at least for the most part, typically more than 90% or more than 95% or at least essentially complete, in copper losses is implemented. Here, “at least essentially” typically means that, in addition to the copper losses, friction losses occur in particular within the transmission and motor, so that 100% of the energy is not broken down into copper losses.
    4/28
    Apart from such losses that are not intentionally caused, in typical exemplary embodiments the energy should be converted as completely as possible into copper losses.
    The electric motor is typically driven with a speed control. Driving in the sense of the method according to the invention is typically an electrical operation of the electric motor, that is, energization or commutation of the electric motor.
    According to the method according to the invention, the speed control for reducing the elastically stored energy is operated in such a way that the speed decreases, whereby according to the method the limit torque MLim is maintained as the upper limit for the engine torque M by the speed control.
    The limit torque M Lim is typically used as a limitation in the speed control. A speed of 0 is typically specified as a reduction in the speed; However, it is also possible to specify a speed that is different from 0, as long as it is smaller in magnitude than the current speed n.
    Typically, the method is started immediately after a screwing operation has ended.
    With the method according to the invention, the stored elastic energy can be dissipated quickly without the electric motor or the transmission being excessively loaded, in particular without the electric motor or the transmission being jerkily loaded.
    The electric motor or the gear can be spared. Destruction of an intermediate motor circuit by an excessive speed and the associated high induced voltage can be avoided. It can also be achieved that no energy is fed into the intermediate circuit while the method is being carried out.
    / 28
    An advantageous, typically a continuous or homogeneous, screw feeling can be achieved.
    In the case of a tool on which the method according to the invention is used, additional components can be dispensed with, in particular additional circuits for limiting the current or the voltage.
    In typical embodiments, the method includes repeating the following method instructions until an abort criterion is met: determining the speed of the electric motor; determining the limiting torque for the electric motor using the rotational speed, at which limiting torque the energy is converted at least for the most part into copper losses of the electric motor; and driving the electric motor by means of a speed control with a decreasing speed, while observing the limit torque as the motor torque upper limit. Typically, the above-mentioned process instructions are carried out one after the other in the order given, after the execution of the last-mentioned process instruction again with the first-mentioned process instruction.
    Typically, repeating the process instructions includes executing the process instructions continuously. Typically, the electric motor with the speed control is continuously driven while maintaining the limit torque as the upper limit of the motor torque. The gentle operation of the electric motor or the transmission and / or the screw feeling can be further improved.
    In embodiments, it is determined that the termination criterion is met when the speed falls below a minimum speed.
    The speed typically refers to a speed in the opposite direction. The counter-rotation direction is opposite to the tightening direction or fastening direction. If execution of the method is started immediately after the end of a screwing operation, the actual engine speed is initially 0 and then, due to the stored elastic mechanical / 28
    Energy, in the opposite direction to a value other than 0. If it is determined as an abort criterion whether the minimum speed is undershot, this only takes place after the value other than 0 has been assumed in the opposite direction of rotation.
    The minimum speed is predetermined or can be specified, typically adjustable depending on the engine characteristics.
    In embodiments, it is determined that the termination criterion is met when the limit torque falls below a minimum torque.
    The minimum torque is predetermined or can be determined, typically adjustable depending on the engine characteristics.
    It is typically determined that the termination criterion is met if the speed falls below a minimum speed and if the limit torque falls below a minimum torque.
    In embodiments, it is determined that the termination criterion is met if the speed falls below a minimum speed during a defined period. In embodiments, it is determined that the termination criterion is met if the limit torque falls below a minimum torque during a defined period. Typically, it is determined that the termination criterion is met if the speed falls below a minimum speed during a defined period and if the limit torque falls below a minimum torque during a defined period.
    The defined period is typically set to a period longer than 20 ms or longer than 50 ms and shorter than 1 s or shorter than 500 ms. For example, the defined period is set longer than 100 ms and shorter than 200 ms.
    The termination criteria are monitored by the control device from the start of the method according to the invention. The defined period of time precludes / 28 that the process is interrupted immediately when starting at a possibly low speed or limit torque. In addition, the defined period of time can rule out that a small swing in the state variables immediately leads to the process being terminated.
    In embodiments, the minimum speed is less than 10% of a nominal speed of the electric motor. Typically, the minimum speed is less than 5% or less than 3% of the nominal speed of the electric motor. As a result, the method can be carried out, for example, until gentle operation of the electric motor or the transmission is also possible in freewheeling, and further heating of the electric motor can be reduced.
    In embodiments, the minimum torque is less than 20% of a nominal torque of the electric motor. The minimum torque is typically less than 15% or less than 10% of the nominal torque of the electric motor. As a result, the method can be carried out, for example, until gentle operation of the electric motor or the transmission is also possible in freewheeling, and further heating of the electric motor can be reduced.
    In embodiments, the limit torque is determined using a motor parameter of the electric motor, the motor parameter comprising the motor voltage constant of the electric motor. The motor voltage constant of the electric motor is typically the quotient of the voltage in the motor and the angular velocity ω of the electric motor.
    In embodiments, the limit torque is determined using a motor characteristic of the electric motor, the motor characteristic comprising the chained outer conductor resistance of the electric motor.
    The limit torque is typically determined using a motor characteristic of the electric motor, the motor characteristic comprising the motor voltage constant and the chained external conductor resistance of the electric motor.
    / 28
    For example, the limit torque M (n) is determined as a function of the mechanical speed n according to the following expression:
    M (n) = c · n ρ 2 · ψ ^ · 2 · π k 2 · π with c = τ—— 2 . 60 · 60
    2nd
    Here k e is the motor voltage constant, and R tt is the chained phase resistance. These sizes are typically available for the engine and are easy to specify.
    In embodiments, the limit torque is determined as a non-zero value that, at the particular speed of the electric motor, is in the range of 80% to 120%, typically at least substantially in the area of the intersection between the mechanical power of the electric motor and the electrical copper power loss of the electric motor .
    The mechanical power of the electric motor and the electrical copper power loss of the electric motor are plotted, for example, for the specific speed as characteristic curves over the respective torque. The intersection typically results from equating the mechanical power with the electrical copper power loss. A different intersection can result at other speeds.
    A tool according to the present invention comprises an electric motor, a typically sensorless speed determination device for determining the speed of the electric motor, a control device for controlled driving of the electric motor using the determined speed and a control device. The control device is set up to carry out a method described here for dissipating the elastically stored energy. The control device is typically set up to control the control device accordingly in order to carry out the method.
    9/28
    The electric motor is typically operated or energized in a targeted manner in such a way that the elastic mechanical energy is continuously reduced and is only converted into copper losses in the electric motor without any jerky operation.
    In embodiments, the control device is set up to carry out a method described here, which comprises: determining the rotational speed of the electric motor; determining the limiting torque for the electric motor using the rotational speed, at which limiting torque the energy is converted at least for the most part into copper losses of the electric motor; and driving the electric motor by means of a speed control with a decreasing speed, while maintaining the limit torque as the motor torque upper limit.
    Further advantages and features of preferred embodiments of the invention are explained below with reference to the accompanying drawings, the figures showing:
    Fig. 1 is a schematic perspective view of a heavy duty screwdriver to illustrate embodiments of the invention;
    2 is a block diagram for a tool configured to perform a method according to an embodiment of the invention;
    3 is a schematic controller diagram for performing a method according to an embodiment of the invention;
    4 is a combined diagram showing the torque and speed of the electric motor during a screwing operation and after a screwing operation has been completed, without carrying out a method according to an embodiment of the invention;
    5 is a combined diagram showing the torque and speed of the electric motor during a screwing process and after a screwing process has been completed, with implementation of a method according to an embodiment of the invention;
    6 is a diagram showing the determination of the limit torque in a method according to an embodiment of the invention;
    / 28
    7 is a flowchart for a method according to an embodiment of the invention.
    Typical embodiments are described below with reference to the figures, the invention being not restricted to the exemplary embodiments, but rather the scope of the invention being determined by the claims.
    1 shows a schematic perspective view of a heavy-duty screwdriver 1 to clarify embodiments of the invention. The
    Heavy duty screwdriver according to the illustration shown in FIG. 1 is shown as an angle screwdriver; however, the invention is not limited to such tools and, for example, non-angular tools can also be operated with the method according to the invention.
    In a housing 11 of the heavy-duty screwdriver 1, an electric motor (not recognizable in FIG. 1) and a gear (also not shown in FIG. 1) are accommodated together with a speed determination device, a regulating device and a control device.
    The heavy-duty screwdriver 1 is provided with a handle 16, on which an operating switch 17 is provided, with which a screwing process can be started.
    An output-side work spindle receptacle 13 serves to receive a screw head. A torque arm 14 is provided in order to be able to apply a counter torque for the screwing process. The heavy-duty screwdriver 1 shown is designed as a mains-operated tool; a feed line 15 is used to connect the heavy-duty screwdriver 1 to a voltage supply.
    During a screwing operation, a desired screwing torque can be specified for the heavy-duty screwdriver 1. A set screw torque that can be specified in a typical heavy-duty screwdriver 1 is, for example, greater than 5000 Nm or greater than 8000 Nm. During the screwing process, elastic mechanical energy is stored in the components of the heavy-duty screwdriver. For example, the / 28
    Include torsional energy (torsional energy) of the transmission or the torque arm 14 or the rotational energy in the electric motor or in the transmission.
    2 is a block diagram for a tool configured to perform a method according to an embodiment of the invention. The tool is, for example, the heavy-duty screwdriver 1 shown in FIG. 1.
    An electric motor 20 with an output-side gear 12 is shown schematically in FIG. 2.
    An encoder signal 31 from the electric motor 20 is fed to a speed determination device 30. The speed determination device 30 is set up to determine a speed signal 32 from the encoder signal 31, the speed signal 32 corresponding to the current speed of the electric motor 20. However, the invention is not limited to encoder-based speed determination. The determination of the instantaneous speed of the motor by the speed determination device can also be done without an encoder or without an encoder, for example according to the method described in the document "Position sensor-free operation of permanent magnet excited synchronous machines"; Dr. Karsten Wiedmann; Faculty of Electrical Engineering and Computer Science at Gottfried Wilhelm Leibniz Universität Hannover; 2012 is described. Further sensorless regulations can be known and used from the prior art.
    The speed signal 32 is fed to a control device 40. The control device 40 outputs an output signal 41 to the electric motor 20 and thus controls it using the instantaneous speed of the electric motor, which results from the speed signal 32.
    The speed signal 32 is also fed to a control device 50. The control device 50 is set up to use the speed from the speed signal 32 to determine a limit torque for the electric motor 20, at which limit torque the energy is converted at least for the most part into copper losses of the electric motor.
    / 28
    The control device outputs a limit torque signal 51 to the control device 40. For a method for reducing the elastically stored energy according to embodiments of the invention, the control device 40 controls the electric motor 20 in such a way that the rotational speed is reduced; at the same time, it uses the limit torque signal 51 to ensure that the engine torque does not exceed the predetermined limit torque from the limit torque signal 51.
    For example, the setpoint for the speed at which the control device 40 is to regulate the electric motor 20 is a low speed which is less than a few hundred revolutions per minute, for example less than 200min -1 or less than 100min -1 , typically of 0min -1 .
    The control device 50 determines the limit torque for the electric motor 20 regularly, typically continuously or at fixed time intervals. For example, the speed in the embodiment is determined by the speed determination device 30 with a sampling frequency of 1 kHz and supplied to the control device 50 as a speed signal 32. If the speed of the electric motor changes, then the limit torque typically also changes. The control device 50 can, for example, likewise determine the limit torque with a clock frequency of 1 kHz and feed it to the control device 40, so that the specification of the upper limit for the engine torque is continuously adjusted in the control device 40.
    In embodiments, sampling rates for the speed with, for example, at least 0.5 kHz, at least 1 kHz or at least 2 kHz are used. In typical embodiments, the limit torque is determined with a clock frequency of at least 0.5 kHz, at least 1 kHz or at least 2 kHz. Typically, steps a) to c) are carried out repeatedly at a frequency of at least 0.5 kHz, at least 1 kHz or at least 2 kHz.
    The invention is not to be understood as restrictive in that the control device 40, the speed determination device 30 and / or the control device 50 must be provided as separate components or circuits. This differentiation is made here only for reasons of clarity, / 28 and the control device 40, the speed determination device 30 and / or the control device 50 can also be embodied in an integrated manner, as a common circuit (s), etc.
    3 is a schematic controller diagram for performing a method according to an embodiment of the invention. A block 60 for determining the engine parameter c is the amount | n | the mechanical speed, for example the speed signal 32 from the speed determination device 30. The engine parameter c is determined according to the embodiment as follows:
    _ 3 P 2 · lAp 2 _ k; -π C ~ 2 60 - ^ l.6O
    2nd
    Here k e is the motor voltage constant, and R tt is the chained phase resistance. These sizes are typically available for the engine and are easy to specify.
    In a subsequent dynamic control, which is denoted overall by 70 in FIG. 3, in the embodiment shown the constants K p , Tn dictate that control to a speed of 0 within a limited period of time, for example within 3 seconds or within 1 second. From this, a limit torque Mum is determined, which is given to the control device 40 as a limit torque signal 51. The control device is set up in such a way that the value that is specified via the limit torque signal 51 is not exceeded as the upper limit of the motor torque when the electric motor 20 is activated. Typically, the control device is set up in such a way that the value that is specified via the limit torque signal 51 as the value of the upper limit of the engine torque is at least almost reached, but not exceeded. The control device 40 is also given a value of 0 as the target speed ns. The control device 40 outputs an output signal 41 to the electric motor, for which these requirements are met.
    14/28
    The transient response of the limit torque M Lim can be set with the dynamic control shown in FIG. 3. The dynamic control 70 is only exemplary, however, and the invention is not restricted to the use of a dynamic control 70. For example, dynamic control 70 can also be dispensed with in typical methods described herein. The limit torque MLim will typically be determined directly from the product of the motor parameter c and the speed n.
    FIG. 4 is a combined diagram that shows the time profile of the torque M and the speed N of the electric motor 20 during a screwing process and after a screwing process has ended, without carrying out a method according to an embodiment of the invention.
    After a short start-up phase up to approx. 177s, the speed n gradually decreases and the torque M builds up. The target torque is reached between 186s and 187s. Then no torque is applied to the motor and the stored elastic energy suddenly discharges. In the case shown in FIG. 4 without using the method according to the invention, the motor jumps from approx. -500 min -1 to 0 min -1 to a high reverse speed of approx. 5000 min -1 . This can represent a mechanical load on the electric motor or the transmission; Furthermore, such a high reverse speed can lead to undesirably high or impermissibly high voltages being induced in the intermediate circuit of the electric motor.
    The increase in speed at approx. 188s corresponds to a desired (targeted, controlled) reverse rotation of the motor in order to be able to remove the tool.
    FIG. 5 is a combined diagram that shows the temporal profile of the torque M and the rotational speed n of the electric motor 20 during a screwing process and after a screwing process has been completed, with implementation of a method according to an embodiment of the invention.
    After a short start-up phase up to approx. 138s, the speed gradually decreases and the torque builds up. The target torque is reached between 149s and 150s.
    / 28
    A method according to an embodiment of the invention is now carried out. The motor is not switched off or not supplied with current, as in the case of FIG. 4, but is regulated from approximately 149.8 s in such a way that a predetermined torque-dependent maximum reverse speed n is not exceeded. The stored elastic energy of the system is gradually converted into electrical loss energy in the form of copper losses in the engine. The torque therefore gradually decreases between about 150s and 151s.
    This can prevent a high reverse speed of the electric motor from occurring after the screwing process has ended (upper line in FIG. 5), with a good screwing feeling at the same time.
    The increase in speed at approx. 151s corresponds to a desired (targeted, controlled) reverse rotation of the motor in order to be able to remove the tool.
    The method is carried out according to the embodiment until an abort criterion is met. The termination criterion defines, for example, when the stored elastic energy has fallen below a lower threshold. According to the embodiment, the termination criterion is assumed to be fulfilled if the calculated limit torque and the speed have fallen below defined thresholds for a defined period of time.
    The termination criteria are monitored by the control device 50 from the start of the method according to the invention.
    The thresholds are typically set depending on the motor, the threshold for the limit torque being, for example, in the range 5-15% of the maximum torque of the electric motor (the nominal torque), and the threshold for the speed, for example, in the range of 1-3% of the rated motor speed lies.
    The defined period can be set to, for example, 100 ms or to, for example, 200 ms.
    / 28
    6 is a diagram showing the determination of the limit torque in a method according to an embodiment of the invention.
    In Fig. 6, the electrical power loss P V and the mechanical power Pmech of the motor are plotted against the motor torque M, at an exemplary selected speed n of 700 revolutions per minute (min -1 ).
    A non-zero intersection of the electrical power loss and the mechanical power of the motor can be seen in the example shown at 6 Nm.
    With a torque of 6 Nm at this speed of 700 min -1 the mechanical power is equal to the electrical copper power loss. In embodiments, the limit torque is determined as a non-zero value that is in the range of 80% to 120%, typically at least substantially in the range of 100% of such an intersection at the specific speed of the electric motor.
    7 is a flowchart for a method according to an embodiment of the invention.
    It is determined in 110 that the screw is tightened, that is to say the tightening torque or the tightening angle has been reached.
    In 120 the restoring torque of the transmission is released. After 120, a method according to a typical embodiment of the invention is started.
    The speed of the electric motor is determined in 130, for example measured with a sampling frequency of 1 kHz.
    At 140, a maximum torque or limit torque is determined depending on the speed and an engine parameter, as described herein.
    / 28
    In 150, the maximum torque is input into a limiting device of the control device or of the speed controller.
    In 160, an output signal to the electric motor for regulating to a speed of 0 is specified by the regulating device, the maximum torque being taken into account by the regulating device.
    In 170, it is determined whether or not a predetermined torque threshold and a predetermined speed threshold are undershot.
    In the event that it is determined in 170 that the aforementioned thresholds have not been undershot, a return is made to 130.
    In the event that it is determined in 170 that the stated thresholds have been undershot, the method continues with 180.
    The method according to the invention is ended in 180 according to the embodiment.
    The sequence of a method according to an embodiment of the invention is explained below. For the screwing process, that is to say before the start of the method for reducing the elastically stored energy according to the embodiment, a desired screwing torque is specified which is achieved in the screwing process.
    As a result, the screw is initially held in place at the start of the method for reducing the elastically stored energy according to the embodiment. At this time, the limit torque corresponds to the set screw torque. The limit torque is the output torque at which the mechanical power is in equilibrium with the copper losses of the electric motor. This in turn leads to the motor not rotating at this point in time, which is followed by n * c = 0.
    / 28
    This results in a decreasing limit torque, the decrease in the limit torque being adjustable according to the embodiment via the dynamic control 70. This results in a controlled rotation of the motor.
    In the embodiment, the rotational speed n is now continuously determined with a constant sampling frequency, for example of 1 kHz or of 2 kHz, and the corresponding limit torque is calculated from n * c.
    This limit torque is included in a limiting device of the control device 40, which is designed as a speed controller. The control device 40 specifies an upper engine torque limit for controlling to a speed of 0. The control device 40 thus now continuously reduces the rotational speed, taking into account the upper engine torque limit, which corresponds to the limit torque value last received from the control device 40. As soon as the control device 40 receives a new value for the limit torque, the control device 40 adjusts the engine torque upper limit accordingly. The limit torque corresponds to the upper engine torque limit during the degradation of the elastically stored energy according to the method according to the embodiment.
    Innsbruck, September 22, 2017
    权利要求:
    Claims (12)
    [1]
    Claims
    1. A method for dissipating the elastically stored energy of a tool operated with an electric motor (20), comprising:
    a) determining the speed of the electric motor;
    b) determining a limit torque for the electric motor (20) using the rotational speed, at which limit torque the energy is converted at least for the most part into copper losses of the electric motor;
    c) driving the electric motor (20) by means of a speed control with a decreasing speed, while observing the limiting torque as the upper limit of the motor torque.
    [2]
    2. The method according to claim 1, wherein the method instructions a) -c) are carried out repeatedly, in particular with a frequency of at least 0.5 kHz, until an abort criterion is met.
    [3]
    3. The method according to claim 2, wherein the termination criterion is met if the speed falls below a minimum speed.
    [4]
    4. The method according to claim 2 or 3, wherein the termination criterion is met when the limit torque falls below a minimum torque.
    [5]
    5. The method of claim 4, wherein the termination criterion is met when the limit torque falls below the minimum torque and the speed falls below the minimum speed.
    [6]
    6. The method according to any one of claims 3 to 5, wherein the termination criterion is reached when the speed falls below the minimum speed during a defined period or when the limit torque falls below the minimum torque during a defined period.
    20/28
    [7]
    7. The method according to any one of claims 3 to 6, wherein the minimum speed is less than 10% or less than 5% or less than 3% of a nominal speed of the electric motor (20).
    [8]
    8. The method according to any one of claims 3 to 7, wherein the minimum torque is less than 20% or less than 15% or less than 10% of the nominal torque of the electric motor (20).
    [9]
    9. The method according to any one of the preceding claims, wherein the limit torque is determined using a motor parameter of the electric motor (20), wherein the motor parameter comprises the motor voltage constant of the electric motor (20).
    [10]
    10. The method according to claim 9, wherein the motor parameter comprises the chained external conductor resistance of the electric motor (20).
    [11]
    11. The method according to any one of the preceding claims, wherein the limit torque is determined as a non-zero value that at the determined speed of the electric motor (20) in the range of 80% to 120% or at least substantially in the range of the intersection between the mechanical Power of the electric motor (20) and the electrical copper power loss of the electric motor (20) is.
    [12]
    12. Tool with:
    an electric motor (20);
    a speed determination device (30) for determining the speed of the electric motor (20);
    a control device (40) for controlled driving of the electric motor (20) using the determined speed; and a control device (50) which is set up to carry out a method according to one of the preceding claims.
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    同族专利:
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    US10411639B2|2019-09-10|
    引用文献:
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
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