Vehicle motor control device

Abstract

This prevents the system from mistakenly detecting a driver circuit malfunction due to power surges. [Solution] The vehicle motor control device comprises a driver circuit, an overcurrent detection circuit, and a control unit. The driver circuit drives the electric motor by supplying power to the electric motor via a switching element. The overcurrent detection circuit detects when an overcurrent flows through the driver circuit based on the voltage across the terminals of the switching element. The control unit executes a first drive process to drive the electric motor by inputting a first control signal, which is a pulse signal, to the switching element. If the control unit detects that an overcurrent has flowed through the driver circuit during the execution of the first drive process, it terminates the first drive process and executes a second drive process to drive the electric motor by inputting a second control signal to the switching element. If the control unit detects that an overcurrent has flowed through the driver circuit during the execution of the second drive process, it determines that there is an abnormality in the driver circuit.

Description

Technical Field

[0001] The present invention relates to a motor control device for a vehicle.

Background Art

[0002] The electronic device disclosed in Patent Document 1 includes an electric motor, a driver circuit, and a microcomputer. The driver circuit has a plurality of switching elements. The driver circuit drives the electric motor by supplying power to the electric motor via the plurality of switching elements. In the driver circuit, the plurality of switching elements operate based on an instruction from the microcomputer.

[0003] By the way, when an abnormality such as a short circuit occurs in the driver circuit, an overcurrent may flow through the driver circuit. Therefore, the above-described electronic device further includes an overcurrent detection circuit. The overcurrent detection circuit detects that an overcurrent has flowed through the driver circuit based on the voltage between the terminals of the switching element. When the overcurrent detection circuit detects that an overcurrent has flowed through the driver circuit, the driver circuit stops driving the electric motor.

Prior Art Documents

Patent Documents

[0004] [[ID=*]] International Publication No. 2018 / 181815

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​In electronic devices like those described above, electric motors are sometimes driven by inputting pulse signals as control signals to switching elements. When driving electric motors in this way, surges can occur in the driver circuit, causing the voltage across the switching element terminals to fall outside the appropriate voltage detection range predetermined by the overcurrent detection circuit. In this case, even if no overcurrent is actually flowing through the driver circuit, the overcurrent detection circuit mistakenly detects that an overcurrent is flowing through the driver circuit, causing the driver circuit to stop driving the electric motor. [Means for solving the problem]

[0006] A vehicle motor control device for solving the above problems is a vehicle motor control device for controlling the drive of an on-board electric motor, comprising: a driver circuit having a switching element arranged in a power supply line connecting a power source and the electric motor, which drives the electric motor by supplying power to the electric motor via the switching element; an overcurrent detection circuit that detects when an overcurrent flows through the driver circuit based on the terminal voltage of the switching element; and a control unit that controls the drive of the electric motor by operating the driver circuit, wherein the control unit performs a first drive process which drives the electric motor by inputting a first control signal, which is a pulse signal of a reference frequency, to the switching element; a second drive process which, if the overcurrent detection circuit detects that an overcurrent has flowed through the driver circuit during the execution of the first drive process, terminates the first drive process and drives the electric motor by inputting a second control signal, which is different from the first control signal, to the switching element; and a determination process which, if the overcurrent detection circuit detects that an overcurrent has flowed through the driver circuit during the execution of the second drive process, determines that an abnormality has occurred in the driver circuit. [Effects of the Invention]

[0007] The above-mentioned vehicle motor control device has the effect of suppressing the false detection of a driver circuit malfunction caused by surges. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing a vehicle motor control device according to an embodiment and an electric motor controlled by the vehicle motor control device. [Figure 2] Figures 2(a) to 2(f) are time charts showing the operation of the judgment control when the driver circuit of the vehicle motor control device shown in Figure 1 is functioning correctly. [Figure 3] Figures 3(a) to 3(f) are time charts showing the operation of the judgment control when the driver circuit of the vehicle motor control device in Figure 1 is abnormal. [Modes for carrying out the invention]

[0009] One embodiment of a vehicle motor control device will be described with reference to Figures 1 to 3. <Vehicle Configuration> Figure 1 shows a vehicle 100 equipped with a vehicle motor control device 50. Hereafter, the vehicle motor control device 50 will be simply referred to as "motor control device 50".

[0010] As shown in Figure 1, the vehicle 100 is equipped with a battery 30 and a braking device BD. The braking device BD generates braking force in the vehicle 100 by supplying brake fluid to the wheel cylinders. In addition to the motor control device 50 described above, the braking device BD further includes an electric motor 20 and a pump 10 that discharges brake fluid when driven by the electric motor 20.

[0011] As an example of a braking device BD, the downstream unit disclosed in "Japanese Patent Publication No. 2022-55467" can be cited. In such a braking device BD, the brake fluid accumulated in the reservoir can be pumped up by the pump 10 during braking control such as anti-lock brake control.

[0012] <Motor control device configuration> The motor control device 50 includes a driver circuit 60, a control circuit 70, and a processing circuit 80.

[0013] An example of the electric motor 20 is a brushed DC motor. The electric motor 20 is driven by power supplied from the battery 30 via the driver circuit 60. In other words, the battery 30 functions as the power source for the electric motor 20.

[0014] As shown in Figure 1, the driver circuit 60 includes a first switching element 61, a second switching element 62, a third switching element 63, and a fourth switching element 64. An example of the first switching element 61 is a so-called N-channel type MOSFET. "MOSFET" is an abbreviation for "Metal-Oxide-Semiconductor Field-Effect Transistor". The first switching element 61 comprises a drain 61D, a source 61S, and a gate 61G. The drain 61D is electrically connected to the positive terminal of the battery 30. The source 61S is electrically connected to the first terminal of the electric motor 20. The gate 61G is electrically connected to the control circuit 70.

[0015] An example of the second switching element 62 is a so-called N-channel type MOSFET. The second switching element 62 comprises a drain 62D, a source 62S, and a gate 62G. The drain 62D is electrically connected to the first terminal of the electric motor 20 and the source 61S of the first switching element 61. The gate 62G is electrically connected to the control circuit 70.

[0016] An example of the third switching element 63 is a so-called P-channel type MOSFET. The third switching element 63 comprises a drain 63D, a source 63S, and a gate 63G. The source 63S is electrically connected to the source 62S of the second switching element 62. The drain 63D is electrically connected to the second terminal of the electric motor 20. The gate 63G is electrically connected to the control circuit 70.

[0017] An example of the fourth switching element 64 is a so-called N-channel type MOSFET. The fourth switching element 64 includes a drain 64D, a source 64S, and a gate 64G. The drain 64D is electrically connected to the second terminal of the electric motor 20 and the drain 63D of the third switching element 63. The source 64S is electrically connected to the negative terminal of the battery 30. The gate 64G is electrically connected to the control circuit 70.

[0018] In the motor control device 50, the first switching element 61 and the fourth switching element 64 are used when controlling the supply and cut-off of power to the electric motor 20. In other words, the first switching element 61 is an example of a switching element arranged on the power supply line connecting the battery 30 and the electric motor 20. Also, the fourth switching element 64 is an example of a switching element arranged on the power supply line connecting the power source and the electric motor 20. Furthermore, the driver circuit 60 is an example of a driver circuit that drives the electric motor 20 by supplying power to the electric motor 20 via the first switching element 61 and the like. Note that the second switching element 62 and the third switching element 63 are used, together with a monitor circuit not shown, to determine the presence or absence of on-fixing or disconnection of the first switching element 61 and the like.

[0019] The control circuit 70 is an IC chip including an overcurrent detection circuit 71 and a pre-driver circuit 72. The overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 based on the voltage between terminals, which is the voltage between the drain 61D and the source 61S in the first switching element 61. In the present embodiment, the first switching element 61 is an example of a switching element for which the overcurrent detection circuit 71 is an overcurrent detection target.

[0020] Here, it is not preferable from the viewpoint of protecting the driver circuit 60 and the electric motor 20 that the current flowing through the driver circuit 60 and the electric motor 20 is too large. And, the larger the current flowing through the driver circuit 60 and the electric motor 20 is, the higher the voltage between terminals, which is the voltage between the drain 61D and the source 61S in the first switching element 61, tends to be.

[0021] Therefore, when the voltage between terminals of the first switching element 61 is higher than the upper limit voltage, the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60. Also, if the voltage between terminals of the first switching element 61 is too low, there is a possibility that the overcurrent detection circuit 71 may not operate properly. The voltage between terminals that serves as a criterion for determining whether the overcurrent detection circuit 71 operates properly is referred to as the "lower limit voltage". And when the voltage between terminals is lower than the lower limit voltage, the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 even though no overcurrent is actually flowing.

[0022] Therefore, the range from the above-mentioned lower limit voltage to the upper limit voltage is referred to as the "voltage detection range predetermined for the overcurrent detection circuit 71". And when the voltage between terminals of the first switching element 61 is outside the voltage detection range, the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60.

[0023] The pre-driver circuit 72 can individually control the on / off of the plurality of switching elements 61 to 64 of the driver circuit 60. That is, the pre-driver circuit 72 can control the on / off of the switching elements 61 to 64 by inputting a control signal to the gates 61G to 64G of the target switching elements 61 to 64.

[0024] The pre-driver circuit 72 can communicate with the overcurrent detection circuit 71. For example, when the first switching element 61 and the fourth switching element 64 are operating to drive the electric motor 20, if the overcurrent detection circuit 71 inputs a signal indicating that an overcurrent has been detected in the driver circuit 60, the pre-driver circuit 72 stops inputting a control signal to the first switching element 61. In other words, the pre-driver circuit 72 turns off the first switching element 61 and stops driving the electric motor 20.

[0025] The processing circuit 80 can communicate with the overcurrent detection circuit 71 and the pre-driver circuit 72 of the control circuit 70. An example of the processing circuit 80 is an electronic control unit. In this case, the processing circuit 80 includes a CPU 81 and a memory 82. The memory 82 includes a read-only ROM, a read and write volatile RAM, and a read and write non-volatile storage. The memory 82 pre-stores various programs and various data. The CPU 81 executes the program in the memory 82, causing the processing circuit 80 to operate the pre-driver circuit 72.

[0026] Specifically, the processing circuit 80 can control the on / off state of multiple switching elements 61-64 via the pre-driver circuit 72. For example, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 for controlling the electric motor 20. As a result, the pre-driver circuit 72 controls the first switching element 61, etc., according to the command signal. Therefore, in the motor control device 50, the processing circuit 80 and the pre-driver circuit 72 constitute a "control unit 90" that controls the driving of the electric motor 20 by operating the driver circuit 60.

[0027] The control unit 90 performs a first drive process, a second drive process, and a determination process. The first drive process and the second drive process are processes that drive the electric motor 20. <First drive process> The control unit 90 drives the electric motor 20 by a first drive process. The first drive process is a process that drives the electric motor 20 by PWM control. "PWM" is an abbreviation for "Pulse Width Modulation".

[0028] Specifically, the processing circuit 80 of the control unit 90 inputs a command signal to the pre-driver circuit 72 for executing the first drive process. In response to the command signal, the pre-driver circuit 72 controls the first switching element 61 and the fourth switching element 64 to the ON state, while controlling the second switching element 62 and the third switching element 63 to the OFF state. At this time, the pre-driver circuit 72 inputs a first control signal S1, which is a pulse signal with a reference frequency FS, to the gate 61G of the first switching element 61. Here, the reference frequency FS is a predetermined constant frequency. The reference frequency FS can be any frequency in the range from 1kHz to 5kHz, for example. An example of a reference frequency FS is 2kHz. The pre-driver circuit 72 also inputs an ON signal as a steady-state signal to the gate 64G of the fourth switching element 64. As a result, the control unit 90 can drive the electric motor 20.

[0029] While the control unit 90 is driving the electric motor 20 in the first drive process, the overcurrent detection circuit 71 may detect that an overcurrent has flowed through the driver circuit 60. More specifically, under the above circumstances, the overcurrent detection circuit 71 may detect that an overcurrent has flowed through the driver circuit 60 due to a surge generated in conjunction with the first drive process, even if no overcurrent has actually flowed. In this case, the pre-driver circuit 72 of the control unit 90 stops driving the electric motor 20 by stopping the input of the first control signal S1 to the gate 61G of the first switching element 61. At this time, the pre-driver circuit 72 may also turn off the fourth switching element 64 by stopping the input of an ON signal to the gate 64G of the fourth switching element 64.

[0030] <Second drive process> Even if the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 during the execution of the first drive process, the control unit 90 will drive the electric motor 20 by a second drive process if there is a request to drive the electric motor 20. The second drive process is a process that drives the electric motor 20 by inputting a second control signal S2, which is different from the first control signal S1, to the gate 61G of the first switching element 61. More specifically, the second drive process drives the electric motor 20 by operating the first switching element 61 in a manner that is less likely to generate surges in the driver circuit 60 compared to when the electric motor 20 is driven by the first drive process.

[0031] Specifically, the processing circuit 80 of the control unit 90 inputs a command signal to the pre-driver circuit 72 for executing the second drive process. In response to the command signal, the pre-driver circuit 72 controls the first switching element 61 and the fourth switching element 64 to the ON state, while controlling the second switching element 62 and the third switching element 63 to the OFF state. At this time, the pre-driver circuit 72 inputs a second control signal S2 to the gate 61G of the first switching element 61. An example of the second control signal S2 is a steady signal, i.e., an ON signal. When a steady signal is input to the gate 61G, the first switching element 61 remains in the ON state. The pre-driver circuit 72 also inputs the ON signal, which is a steady signal, to the gate 64G of the fourth switching element 64.

[0032] <Decision Process> Even when the electric motor 20 is being driven by the second drive process, the overcurrent detection circuit 71 may detect that an overcurrent has flowed through the driver circuit 60. The fact that the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60, whether during the execution of the first drive process or the second drive process, indicates that there is a possibility that an abnormality such as a short circuit has actually occurred in the driver circuit 60.

[0033] Therefore, the control unit 90 performs a determination process to determine whether or not an abnormality has occurred in the driver circuit 60 during the execution of the second drive process. That is, if the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, the pre-driver circuit 72 of the control unit 90 stops inputting the second control signal S2 to the gate 61G of the first switching element 61. The pre-driver circuit 72 also stops inputting an ON signal to the gate 64G of the fourth switching element 64, turning off the fourth switching element 64. As a result, the control unit 90 stops driving the electric motor 20. When the pre-driver circuit 72 stops driving the electric motor 20 in this way, the processing circuit 80 of the control unit 90 determines in the determination process that an abnormality has occurred in the driver circuit 60. In other words, the control unit 90 determines that an abnormality has occurred in the driver circuit 60 if the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process.

[0034] <If the electric motor is requested to be stopped> When it is requested that the electric motor 20 be stopped, the processing circuit 80 inputs, for example, a command signal to stop the driving of the electric motor 20 to the pre-driver circuit 72. In response to the command signal, the pre-driver circuit 72 controls the first switching element 61, the second switching element 62, the third switching element 63, and the fourth switching element 64 to the off state.

[0035] <Decision Control> Next, with reference to Figures 2 and 3, the determination control performed by the driver circuit 60, the control circuit 70, and the processing circuit 80 will be described. This determination control is for determining whether or not there is an abnormality in the driver circuit 60.

[0036] First, referring to Figure 2, we will explain the determination control when the driver circuit 60 is functioning normally. As shown in Figure 2(a), assume that at timing t11, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 to execute the first drive process. In this case, the pre-driver circuit 72 inputs the first control signal S1, which is a pulse signal with a reference frequency FS, to the gate 61G of the first switching element 61. This starts the driving of the electric motor 20 by the first drive process. As a result, as shown in Figure 2(c), the electric motor 20 turns ON after timing t11.

[0037] At the subsequent timing t12, if the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60, as shown in Figure 2(d), the overcurrent detection circuit 71 turns on a temporary flag indicating the detection of an overcurrent. Then, as shown in Figure 2(c), at timing t12, the pre-driver circuit 72 turns off the first switching element 61 by stopping the input of the first control signal S1 to the gate 64G of the first switching element 61. As a result, the pre-driver circuit 72 stops driving the electric motor 20. In other words, the pre-driver circuit 72 terminates the driving of the electric motor 20 by the first driving process if the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 during the execution of the first driving process.

[0038] At the subsequent timing t13, when the processing circuit 80 confirms that the temporary flag is in the ON state, as shown in Figure 2(e), the processing circuit 80 turns on a confirmation flag indicating that the temporary flag has been confirmed. Then, as shown in Figure 2(d), the temporary flag turns OFF. Subsequently, as shown in Figure 2(a), at timing t14, which is a predetermined first period P1 after timing t13, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 to terminate the first drive process. An example of the first period P1 is several milliseconds to several tens of milliseconds.

[0039] Then, as shown in Figure 2(b), at timing t15, which is a predetermined second period P2 after timing t14, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 to execute the second drive process. An example of the second period P2 is several milliseconds to several tens of milliseconds. When the above command signal is input, the pre-driver circuit 72 drives the electric motor 20 by inputting a second control signal S2 to the gate 61G of the first switching element 61. This starts the driving of the electric motor 20 by the second drive process.

[0040] Here, the second control signal S2 is an ON signal as a steady-state signal. Therefore, the ON / OFF state of the first switching element 61 does not change during the second drive process. As a result, surges caused by changes in the ON / OFF state of the first switching element 61 do not occur in the driver circuit 60. Consequently, the terminal voltage of the first switching element 61 does not change due to surges. In other words, it is suppressed that the terminal voltage falls outside the voltage detection range of the overcurrent detection circuit 71. Therefore, it is possible to suppress the detection of overcurrent by the overcurrent detection circuit 71 due to surges during the execution of the second drive process. Accordingly, if the driver circuit 60 is functioning normally, as shown in the example in Figure 2, it will not be determined that there is an abnormality in the driver circuit 60 when the second drive process is being executed. In other words, as shown in Figure 2(f), the abnormality flag indicating that the driver circuit 60 is abnormal remains in the OFF state.

[0041] Then, if the overcurrent detection circuit 71 does not detect an overcurrent in the driver circuit 60 between timing t15 and timing t16 after a predetermined third period P3, then, as shown in Figure 2(b), at timing t16, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 to terminate the second drive process. The pre-driver circuit 72 then stops driving the electric motor 20 by turning off the first switching element 61. This terminates the second drive process. The third period P3 is approximately a few milliseconds to several tens of milliseconds.

[0042] Then, as shown in Figure 2(a), if the predetermined recovery condition is met at timing t17, which is later than timing t16, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 to execute the first drive process at timing t17. That is, if the overcurrent detection circuit 71 does not detect that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, the control unit 90 terminates the second drive process and executes the first drive process.

[0043] For example, the processing circuit 80 determines that the recovery condition is met if all of the following requirements (1) and (2) are met. Requirement (1): At least four predetermined periods P4 have elapsed since the completion of the second drive process.

[0044] Requirement (2): The required value of the current to be supplied to the electric motor 20 must be less than or equal to a predetermined specified value. Here, the fourth period P4 of requirement (1) is defined as follows, for example. As a premise, the power supplied to the electric motor 20 in the second drive process is greater than the power supplied to the electric motor 20 in the first drive process. Therefore, the temperature of the electric motor 20 may become relatively high after the execution of the second drive process. Thus, the fourth period P4 is predetermined as a period for cooling the electric motor 20 after the execution of the second drive process. The fourth period P4 is approximately a few milliseconds to several tens of milliseconds.

[0045] Furthermore, the specified value for requirement (2) is defined, for example, as follows. As a premise, in vehicle 100, the larger the current flowing through the electric motor 20, the more likely surges are to occur in the driver circuit 60 during the execution of the first drive process. In other words, in the motor control device 50, when the first drive process is executed while a relatively large current is flowing through the electric motor 20, a processing flow like the period from timing t11 to timing t16 shown in Figure 2 is likely to occur. Therefore, the specified value for requirement (2) is predetermined as a threshold that makes it less likely for a processing flow like the period from timing t11 to timing t16 shown in Figure 2 to occur. Note that requirement (2) is satisfied, for example, when the brake pedal is not pressed by the driver of vehicle 100, or when the amount of pressure applied to the brake pedal by the driver of vehicle 100 is relatively small.

[0046] Next, referring to Figure 3, we will explain the control mechanism for determining when an abnormality actually occurs in the driver circuit 60. Note that the situation at timings t21 to t25 shown in Figures 3(a) to 3(f) is the same as the situation at timings t11 to t15 shown in Figures 2(a) to 2(f). Therefore, we will omit the explanation of the situation at timings t21 to t25 shown in Figures 3(a) to 3(f).

[0047] In the example shown in Figure 3, the second drive process starts at timing t25. When the second drive process is being executed, the on / off state of the first switching element 61 does not change, so no surge caused by the on / off state change of the first switching element 61 occurs in the driver circuit 60. However, in the example shown in Figure 3, an abnormality actually occurs in the driver circuit 60, so even while the second drive process is being executed, at timing t26, the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60. Then, as shown in Figure 3(d), the overcurrent detection circuit 71 turns on the temporary flag, and the pre-driver circuit 72 stops inputting the second control signal S2 to the gate 64G of the first switching element 61. That is, as shown in Figure 3(c), at timing t26, the pre-driver circuit 72 stops driving the electric motor 20. At the subsequent timing t27, when the processing circuit 80 confirms that the temporary flag is on, as shown in Figure 3(e), the processing circuit 80 turns on the confirmation flag. As a result, the temporary flag is turned off, as shown in Figure 3(d).

[0048] In this case, the processing circuit 80 determines in the judgment process that an abnormality has occurred in the driver circuit 60. That is, as shown in Figure 3(f), at timing t27, the processing circuit 80 turns on an abnormality flag indicating that the driver circuit 60 is abnormal. Then, as shown in Figure 3(b), at timing t27, the processing circuit 80 inputs a command signal to the pre-driver circuit 72 to terminate the second drive process. This terminates the second drive process.

[0049] <Effects of this embodiment> The motor control device 50 of this embodiment can achieve the following effects. (1) As shown in Figure 3, if the overcurrent detection circuit 71 detects that an overcurrent has flowed during the execution of the first drive process, and if the overcurrent detection circuit 71 detects that an overcurrent has flowed during the execution of the second drive process, it is determined that an abnormality has occurred in the driver circuit 60. For example, as shown in Figure 2, even if the overcurrent detection circuit 71 detects that an overcurrent has flowed during the execution of the first drive process, if the overcurrent detection circuit 71 does not detect that an overcurrent has flowed during the execution of the second drive process, it is not determined that an abnormality has occurred in the driver circuit 60. This prevents the processing circuit 80 from mistakenly determining that an abnormality has occurred in the driver circuit 60, even if the overcurrent detection circuit 71 detects that an overcurrent has flowed in the driver circuit 60 because a surge occurred in the driver circuit 60 during the execution of the first drive process.

[0050] (2) When the electric motor 20 is driven in the first drive process, the operating voltage applied to the electric motor 20 is lower than the operating voltage applied to the electric motor 20 when the electric motor 20 is driven in the second drive process. Therefore, the first drive process is superior to the second drive process in terms of reducing power consumption and reducing heat generation of the electric motor 20.

[0051] Therefore, if the overcurrent detection circuit 71 does not detect that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, the processing circuit 80 terminates the second drive process and executes the first drive process. In other words, even if the system transitions from the first drive process to the second drive process, if it is determined that there is no abnormality in the driver circuit 60 afterward, it returns to the first drive process, which is normally used. This reduces the power consumption associated with driving the electric motor 20 and also reduces the heat generated by the electric motor 20, compared to the case where the electric motor 20 is driven continuously by the second drive process.

[0052] (3) If the overcurrent detection circuit 71 detects that an overcurrent has flowed to the driver circuit 60 during the execution of the first drive process, a stop period for the pump 10 will occur between the end of the drive of the electric motor 20 by the first drive process and the start of the drive of the electric motor 20 by the second drive process. However, when the pump 10 is operated by the electric motor 20 to draw brake fluid from the reservoir of the braking device BD, the stop period is relatively short, so the reservoir will not become full.

[0053] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0054] In the above embodiment, the determination control may be modified. For example, the first drive process may be modified. Specifically, the reference frequency FS in the first drive process may be lower than 2kHz or higher than 2kHz.

[0055] For example, the second drive process may be modified. Specifically, the pre-driver circuit 72 may drive the electric motor 20 by inputting a pulse signal with a frequency higher than the reference frequency FS as the second control signal S2 to the gate 61G of the first switching element 61 during the second drive process. With this configuration, since the frequency of the pulse signal in the second control signal S2 is higher than the frequency of the pulse signal in the first control signal S1, the period during which surges occur in the driver circuit 60 is shorter during the execution of the second drive process compared to the execution of the first drive process. Therefore, during the execution of the second drive process, for example, the voltage fluctuation due to a surge that occurred at the first time point and the voltage fluctuation due to a surge that occurred at the second time point, which is later than the first time point, interfere with each other, thereby suppressing changes in the terminal voltage of the first switching element 61 caused by surges. This makes it possible to suppress the detection of overcurrent caused by surges during the execution of the second drive process. An example of the frequency of the pulse signal in the second control signal S2 is 20 kHz.

[0056] For example, the recovery conditions may be changed. Specifically, the processing circuit 80 may determine that the recovery conditions are met if one or more of the above requirements (1) and (2) are met. Also, specifically, the processing circuit 80 may determine that the recovery conditions are met if all three requirements are met, which include the above requirements (1) and (2) plus a new requirement (3). In other words, the recovery conditions may be changed as appropriate, taking into account the characteristics of the electric motor 20, etc.

[0057] For example, the timing at which the control unit 90 determines the recovery condition may be changed. Specifically, the control unit 90 may determine that the recovery condition is met when the above requirement (2) is satisfied. In this case, the control unit 90 may determine the recovery condition while the second drive process is being executed. In this configuration, the control unit 90 continues the second drive process if the overcurrent detection circuit 71 does not detect that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, and the recovery condition is not met. On the other hand, the control unit 90 terminates the second drive process if the overcurrent detection circuit 71 does not detect that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, and the recovery condition is met. The control unit 90 then executes the first drive process after a predetermined fourth period P4 or longer has elapsed since the termination of the second drive process. With this configuration, for example, it is possible to prevent the period during which the electric motor 20 is stopped from becoming excessively long due to the failure to meet requirement (2) after the termination of the second drive process.

[0058] For example, the situation in which the processing circuit 80 completes the second drive process and executes the first drive process is not limited to the situation described above. Specifically, it is possible that, due to a cause other than a surge, the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 during the execution of the first drive process, and the overcurrent detection circuit 71 also detects that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, leading to the determination that an abnormality has occurred in the driver circuit 60. Considering such a situation, the processing circuit 80 can complete the second drive process and execute the first drive process even when the overcurrent detection circuit 71 detects that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process. In this case, it is preferable for the processing circuit 80 to execute the first drive process after a predetermined fifth period P5 has elapsed since the completion of the second drive process. This suppresses the heat generation of the electric motor 20 during the fifth period P5, thereby preventing the temperature of the electric motor 20 from becoming excessively high.

[0059] For example, if the processing circuit 80 has finished the first drive process and is executing the second drive process, it may continue to execute the second drive process. That is, even if the overcurrent detection circuit 71 does not detect that an overcurrent has flowed through the driver circuit 60 during the execution of the second drive process, the processing circuit 80 may not execute the first drive process and may continue to execute the second drive process.

[0060] For example, the switching element to be controlled in PWM control can be changed. As a specific example, in the first drive process, the pre-driver circuit 72 may drive the electric motor 20 by inputting the first control signal S1, which is a pulse signal of reference frequency FS, to the gate 64G of the fourth switching element 64 instead of the first switching element 61. In this case, the overcurrent detection circuit 71 may detect that an overcurrent has flowed through the driver circuit 60 based on the terminal voltage, which is the voltage between the drain 64D and the source 64S of the fourth switching element 64.

[0061] In the above embodiment, the configuration of the driver circuit 60 may be changed. For example, if the driver circuit 60 includes the first switching element 61, it does not need to include the other switching elements 62 to 64. Even with this configuration, the pre-driver circuit 72 can control the drive of the electric motor 20 by inputting the first control signal S1 or the like to the gate 61G of the first switching element 61.

[0062] In the above embodiment, the braking device BD may be configured to include an electric cylinder instead of the pump 10 as a source of brake fluid. In this case, the electric cylinder discharges an amount of brake fluid corresponding to the drive of the electric motor 20.

[0063] In the above embodiment, the electric motor 20 controlled by the motor control device 50 may be an electric motor 20 that functions as a power source for other on-board actuators other than the braking device BD.

[0064] <Other technical ideas> The technical concepts that can be understood from the above embodiments and modified examples are described below. (Note 1) The aforementioned electric motor is the power source for the pump that discharges brake fluid. Preferably, the control unit adjusts the discharge amount of brake fluid from the pump by controlling the drive of the electric motor.

[0065] (Note 2) In the second drive process, the control unit preferably inputs a signal to the switching element as the second control signal that operates the switching element in a manner that is less likely to generate surges in the driver circuit compared to when the electric motor is driven in the first drive process. [Explanation of symbols]

[0066] 10... Pump 20… Electric motor 30... Battery 50…Motor control device 60... Driver circuit 61…First switching element 62...Second switching element 63…Third switching element 64…Fourth switching element 70...Control circuit 71... Overcurrent detection circuit 72… Pre-driver circuit 80… Processing circuit 81…Execution device 82…Storage device 90... Control Unit 100...vehicles BD…Brake device

Claims

1. A vehicle motor control device for controlling the drive of an electric motor on board a vehicle, A driver circuit having a switching element arranged in a power supply line connecting the power source and the electric motor, which drives the electric motor by supplying power to the electric motor via the switching element, An overcurrent detection circuit that detects when an overcurrent flows through the driver circuit based on the terminal voltage of the switching element, The system includes a control unit that controls the drive of the electric motor by operating the driver circuit, The control unit, A first drive process that drives the electric motor by inputting a first control signal, which is a pulse signal of a reference frequency, to the switching element, If the overcurrent detection circuit detects that an overcurrent has flowed through the driver circuit during the execution of the first drive process, the first drive process is terminated, and a second drive process is performed to drive the electric motor by inputting a second control signal, which is different from the first control signal, to the switching element. If the overcurrent detection circuit detects that an overcurrent has flowed through the driver circuit during the execution of the second drive process, a determination process is performed to determine that an abnormality has occurred in the driver circuit. Execute Vehicle motor control device.

2. In the second drive process, the control unit drives the electric motor by inputting a steady-state signal as the second control signal to the switching element. The vehicle motor control device according to claim 1.

3. In the second drive process, the control unit drives the electric motor by inputting a pulse signal with a frequency higher than the reference frequency as the second control signal to the switching element. The vehicle motor control device according to claim 1.

4. If the control unit does not detect an overcurrent flowing through the driver circuit during the execution of the second drive process, as detected by the overcurrent detection circuit, it terminates the second drive process and executes the first drive process. A vehicle motor control device according to claim 2 or claim 3.

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