JP2008132919A - Electric power steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering control device capable of preventing a driver from feeling uncomfortable and uneasy even when a motor drive circuit is failed without increasing the size or cost. <P>SOLUTION: The electric power steering control device comprises a main motor drive circuit 20 which has switches S21-S24 between a power source 5 and itself and between a motor 4 and itself, and generates the motor driving current based on the current control value E to be output from an MCU 10, and a sub motor drive circuit 31 which has switches S31-S34 between the power source 5 and itself and between the motor 4 and itself, and generates the motor driving current smaller than that of the main motor drive circuit 20. The motor current detected by a main current detection circuit 22 is monitored by the MCU 10, and if it is determined from an abnormal value of the motor current that the main motor drive circuit 20 is failed, the switches S21-S24 are opened, the switches S31-S34 are closed and the motor 4 is driven by the sub motor drive circuit 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric power steering control device that applies a steering assist force to a steering handle by a motor, and more particularly to an electric power steering control device that can continue the steering assist force even when a motor drive circuit fails. .

  As a steering assist device for a steering handle in a vehicle such as an automobile, an electric power steering device using the rotational force of a motor is widely used. FIG. 7 is a diagram illustrating a schematic configuration of a general electric power steering apparatus. In the figure, a torque sensor 83 for detecting the operation torque of the shaft 82 directly connected to the steering handle 81, a vehicle speed sensor 84 for detecting the traveling speed of the vehicle, and a steering assist force are calculated based on detection signals from these sensors. A control device (hereinafter also referred to as an ECU) 85 of the electric power steering device, a motor 86 that generates rotational torque based on a signal output from the ECU 85, a reduction gear 87 that transmits the generated rotational torque to the steering mechanism, A battery power supply 89 that supplies current to the ECU 85 by turning on the ignition key 88, universal joints 90a and 90b that transmit the rotational movement of the steering handle 81 to the wheels, a rack and pinion 91, and a tie rod 92 are configured. ing.

  FIG. 8 is a block diagram showing a schematic configuration of the ECU 85. The ECU 85 includes a microcomputer unit (hereinafter also referred to as MCU) 851, a motor drive circuit 852, and a motor current detection circuit 853, and is detected by the torque sensor 83 by executing a program stored in the internal memory of the MCU 851. Based on the steering torque signal T and the vehicle speed signal V detected by the vehicle speed sensor 84, a current control value E for driving the motor 86 is generated, and the current control value E and the motor detected by the motor current detection circuit 853 are generated. Assist control is realized by performing feedback control so that the difference from the current i is small.

  Conventionally, the electric power steering apparatus configured as described above has been mounted mainly on light vehicles, but in recent years, the application range has been expanded to large vehicles such as ordinary passenger cars and RV cars. Large vehicles require a larger steering assist force than passenger cars because the vehicle weight is large. For this reason, for example, when a short circuit failure occurs in the above-described transistor (FET) constituting the motor drive circuit 852 during driving of the vehicle, the motor 86 is stopped and the operation of the steering handle 81 becomes suddenly heavy. Will give the person discomfort and anxiety.

  As a countermeasure against this, as a conventional example, when two motor drive circuits are provided, a motor is driven by one motor drive circuit (main motor drive circuit), and a failure occurs in the operating motor drive circuit, There is an electric power steering control device that switches to the other motor drive circuit (sub motor drive circuit) and continues to drive the motor (see, for example, Patent Documents 1 and 2).

  On the other hand, when it is necessary to generate a large steering assist force, such as when steering a large vehicle, the capacity of the motor drive circuit for flowing a large current and the accompanying increase in the heat dissipation structure for heat generation countermeasures Inevitably, these occupation ratios in the ECU are high.

Japanese Patent Laid-Open No. 11-91605 Japanese Patent No. 3696384

  Here, in the electric power steering control device described in Patent Documents 1 and 2 described above, in order to prevent interference between the two drive circuits, the motor drive circuit and each phase of the motor are connected between the motor drive circuit and the power source. It was necessary to provide an open / close switch in the middle of all connection lines to be connected. In an electric power steering apparatus applied to a large vehicle, the open / close switch must be capable of opening and closing a large current as the capacity of the motor drive circuit increases.

  In addition, the motor drive circuit is composed of a plurality of power elements such as FETs, and these power elements are expensive among the components of the ECU, and the price varies greatly depending on the capacity. It was sought after.

  Furthermore, in the motor drive circuit, heat generation increases when a large current flows. In order to solve this problem, a metal substrate is used to promote heat dissipation. For this reason, when the heat dissipation is large, it is necessary to increase the surface area of the metal substrate.

  Therefore, when the main motor drive circuit and the sub motor drive circuit have the same capacity as in the examples shown in Patent Documents 1 and 2, the sub motor drive circuit increases the cost of the electric power steering control device. It was not only a factor that caused an increase in size.

  The present invention has been made in view of the above-described circumstances, and its object is to provide two sets of motor drive circuits, when a motor is driven by one motor drive circuit, and a failure occurs in one drive circuit. Another object of the present invention is to provide an electric power steering control device that can be switched to the other motor drive circuit and continue to drive the motor, and that can suppress an increase in size and cost.

  In order to achieve the above-described object, an electric power steering control device according to the present invention is characterized by the following (1) to (5).

(1) Two sets of motor drive circuits that generate a motor drive current based on a current control value are provided, and when the motor is driven by one motor drive circuit, a failure occurs in the one motor drive circuit. An electric power steering control device that switches to the other motor drive circuit and continues to drive the motor, wherein the motor drive current generated by the other motor drive circuit is generated by the one motor drive circuit. It is smaller than the driving current of the motor.
(2) The electric power steering control device described in (1) above, which is generated by control means for generating a current control value based on a sensor signal for detecting a state of the vehicle and the one motor drive circuit. A motor current detection circuit for detecting a motor drive current, and the control means is generated by the other motor drive circuit when an abnormal value is detected in the motor drive current by the motor current detection circuit. The motor driving current is limited to be smaller than the motor driving current generated by the one motor driving circuit.
(3) In the electric power steering control device described in the above (2), each of the motor drive circuit and the power source, and the motor drive circuit and each phase of the motor. An open / close switch to be connected; an open / close switch connected between the other motor drive circuit and a power source; and an open / close switch connected between the other motor drive circuit and each phase of the motor. When the open / close switch connected to the motor drive circuit is closed, the open / close switch connected to the other motor drive circuit is opened, and an abnormal value is detected in the motor drive current by the motor current detection circuit Further, the open / close switch connected to the one motor drive circuit is opened, and the open / close switch connected to the other motor drive circuit is closed.
(4) In the electric power steering control device described in the above item (2), each of the motor drive circuit and the power source, and the motor drive circuit and each phase of the motor. An open / close switch to be connected; an open / close switch connected between the other motor drive circuit and the power supply; and an open / close switch connected between the other motor drive circuit and the ground. When the open / close switch connected to the other motor drive circuit is closed and the open / close switch connected to the other motor drive circuit is opened, and the motor current detection circuit detects an abnormal value in the motor drive current, The open / close switch connected to the motor drive circuit is opened, and the open / close switch connected to the other motor drive circuit is closed.
(5) The electric power steering control device according to any one of (1) to (4), wherein the one motor driving circuit is mounted on a metal substrate and generates a driving current for the motor. The other motor drive circuit includes a switching element that is mounted on a resin base plate and generates a drive current for the motor.

  According to the electric power steering control device described in (1) above, when a failure occurs in one motor drive circuit, the motor drive current of the other motor drive circuit is greater than the motor drive current of the one motor drive circuit. Since it is small, it is not necessary to use high-power components for the switching elements, power elements and the like constituting the other drive circuit, and the increase in size and cost of the apparatus can be suppressed.

  Further, according to the electric power steering control device described in (2) above, the control means determines the failure of one drive circuit from the detected abnormal value of the motor drive current of one motor drive circuit, and the other motor Since the drive circuit limits the motor current and drives the motor, it is not necessary to use high-power components for the switching elements, power elements, etc. that make up the other motor drive circuit. Costing can be efficiently suppressed.

  Furthermore, according to the electric power steering control device described in (3) above, it is possible to prevent interference between one motor drive circuit and the other motor drive circuit and to detect the motor drive current of one motor drive circuit. Since the failure of one drive circuit is determined from the abnormal value and the motor current is limited by the other motor drive circuit, the motor is driven. It is not necessary to use a component for high power, and the increase in size and cost of the apparatus can be efficiently suppressed.

  Further, according to the electric power steering control device described in (4) above, interference between one motor drive circuit and the other motor drive circuit can be prevented, and the motor drive current of one motor drive circuit is detected and controlled. Since the means determines the failure of one drive circuit from the abnormal value and limits the motor current with the other motor drive circuit to drive the motor, it is used as a component such as a switching element constituting the other motor drive circuit. It is not necessary to use a high-power one, and the open / close switch that connects the other motor drive circuit and each phase of the motor can be eliminated, further reducing the size and cost of the device. It becomes.

  Furthermore, according to the electric power steering control device described in (5) above, it is possible to effectively dissipate heat by mounting the switching element used in one drive circuit on the metal substrate, and drive one motor. When a failure occurs in the circuit, the motor drive current of the other motor drive circuit is smaller than the motor drive current of the one motor drive circuit, so the switching element used for the other drive circuit must be mounted on the resin base plate. This can further suppress the increase in size and cost of the apparatus.

  According to the present invention, two sets of motor drive circuits are provided, the motor is driven by one motor drive circuit, and when a failure occurs in one drive circuit, the motor is driven by switching to the other motor drive circuit. It is possible to provide an electric power steering control device that can be continued and can be suppressed in size and cost.

  In the embodiment of the electric power steering control device according to the present invention, two sets of motor drive circuits for generating a drive current of a three-phase brushless motor based on a current control value are provided, and the motor is usually driven by one motor drive circuit. However, an example of switching to the other motor drive circuit when a failure occurs in the motor drive circuit and continuing to drive the motor while limiting the drive current will be described with reference to the drawings.

(First embodiment)
Hereinafter, a first embodiment of an electric power steering control device according to the present invention will be described. FIG. 1 is a block diagram showing a schematic configuration of the electric power steering control device according to the first embodiment of the present invention.

  In FIG. 1, an electric power steering control device 1 includes a microcomputer unit (hereinafter referred to as MCU) 10, a main motor drive circuit 20, a sub motor drive circuit 31, a main drive circuit switcher 40, a sub drive circuit switcher 50, a motor. An angle detector 60 is included.

  A steering torque signal T is input to the MCU 10 from the torque sensor 3, and a three-phase brushless motor 4 for generating a steering assist force is connected in parallel to the main motor drive circuit 20 and the sub motor drive circuit 31 as a load. Moreover, the battery power source 5 is connected via open / close switches S21 and S31, which will be described later. The motor 4 is provided with a rotation angle sensor 6 such as a resolver for detecting the rotation angle, and transmits a rotation angle signal to the motor angle detector 60.

  The MCU 10 includes a CPU (not shown) and an internal memory. By executing a program stored in the internal memory, the MCU 10 receives a steering torque signal T input from the torque sensor 3 and a motor rotation angle sent from the motor angle detector 6. Based on the signal, a current control value E to be supplied to the main motor drive circuit 20 and the sub motor drive circuit 31 is generated so that the motor 4 generates an appropriate steering assist force according to the steering torque.

  The main motor drive circuit 20 is turned on / off by a PWM (pulse width modulation) signal, and is sent from six field effect transistors (hereinafter referred to as FETs) Q21 to Q26 and an MCU10 having a bridge configuration for passing a drive current to the motor 4. An FET gate drive circuit 21 that drives each of the gates of Q21 to 26 with a duty PWM signal determined based on the current control value E, a main current detection circuit 22 that detects a motor current to feedback control the motor 4, and an FET Q21 Are configured from an on / off switch S21 for controlling current supply from the battery power supply 5 to 26 and on / off switches S22 to 24 for controlling connection between the FETs Q21 to 26 and each phase of the motor 4.

  The FETs Q21 to 26 are composed of a high-current, high-voltage power MOSFET and effectively dissipate heat generated by the switching operation. For example, a metal substrate made of an aluminum alloy or the like as shown in FIG. The metal substrate 71 is mounted on the metal housing 72 and is in close contact with the metal housing 72. Since the metal substrate 71 has a smaller thermal resistance than a conventional resin substrate, the metal substrate 71 is excellent in a heat dissipation effect and can be suitably used in the electric power steering control device of the present embodiment.

  The sub motor drive circuit 31 has the same configuration as that of the main motor drive circuit 20, and is turned on / off by a PWM (pulse width modulation) signal, and has six FETs Q 31 to 36 and MCU 10 having a bridge configuration in which a drive current is supplied to the motor 4. FET gate drive circuit 33 that drives each of the gates of Q31 to 36 with a PWM signal with a duty determined based on the current control value E sent from the sub-current detection circuit that detects the motor current for feedback control of the motor 4 34, an open / close switch S31 for controlling current supply from the power source 5 to the FETs Q31 to 36, and open / close switches S32 to S34 for controlling connection between the FETs Q31 to 36 and each phase of the motor 4.

  The FETs Q31 to 36 are composed of power MOSFETs having a maximum drain current smaller than those of the FETs Q21 to 26 used in the main motor drive circuit 20 in consideration of downsizing of the electric power steering control device 1 main body and improvement of mountability. It is mounted on a resin substrate made of glass epoxy resin or the like. Considering miniaturization and improvement in mountability, it is desirable that the FETs Q31 to 36 be mounted without any heat dissipation structure. However, depending on the current capacity expected when the sub motor drive circuit 31 is used, as shown in FIG. It may be mounted on a resin substrate 73 made of glass epoxy resin or the like, and the heat dissipation plate constituting the FETs Q31 to 36 may be brought into close contact with the heat sink or the metal casing 72 to enhance the heat dissipation effect. The capacity of the sub motor drive circuit 31 is preferably 40% to 70% compared to the main motor drive circuit 20. Since the heat generation amount is proportional to the square of the current value, the heat generation amount can be reduced to half or less by setting the capacity to 70% or less. Further, considering the friction loss of the steering mechanism, the loss of viscosity, and the provision of a sustainable steering assist force, the capacity is preferably set to 40% or more.

  Next, the operation of the electric power steering control apparatus according to the present embodiment configured as described above will be described according to FIG. FIG. 4 is a flowchart for explaining an operation procedure of the electric power steering control device according to the present embodiment.

  First, when the ignition switch is turned on, the main drive circuit switch 40 controlled by the MCU 10 closes the open / close switches S21 to S24 (step S101), and the sub drive circuit switch 50 sets the open / close switches S31 to S34. Open (step S102).

  Next, the motor 4 is driven by the main motor drive circuit 20 that operates based on the current control value E output from the MCU 10 (step S103).

  In step S104, the motor current is detected by the main current detection circuit 20, and in the subsequent step S105, it is monitored whether or not the motor current detected by the MCU 10 shows an abnormal value, and whether or not the main motor drive circuit 20 has failed. Determine whether.

  As a result, when it is determined that the main motor drive circuit 20 has not failed, the process returns to step S104 and the same processing is repeated.

  On the other hand, if it is determined in step S105 that the main motor drive circuit 20 is out of order, the main drive circuit switcher 40 opens the open / close switches S21 to S24 (step S106) and the sub drive circuit switcher. 50 closes the open / close switches S31 to S34 (step S107).

  Then, the motor 4 is driven by the sub motor drive circuit 31 that operates based on the current control value E output from the MCU 10 and outputs a motor current smaller than the main motor drive circuit 20 (step S108).

  As a result, even if a failure occurs in the main motor drive circuit 20 during operation of the vehicle, the drive of the motor 4 can be continued by the sub motor drive circuit 31, so that the operation of the steering handle suddenly becomes heavy. This avoids discomfort and anxiety for the driver.

  In the above description, only the failure of the main motor drive circuit 20 has been described. However, during the operation of the main motor drive circuit 20, the motor 4 is temporarily opened and closed when the motor 4 is stopped by not performing the steering handle operation. The sub motor drive circuit 31 is opened by opening the switches S21 to S24 and closing the open / close switches S31 to S34 to operate the sub motor drive circuit 31 and detecting the motor current at that time by the sub current detection circuit 34. The presence or absence of a failure can be confirmed. And when there is a failure in the sub motor drive circuit 31, it is reported to the driver that the driver feels discomfort and anxiety due to suddenly heavy steering handle operation. Can be prevented.

  As described above, according to the electric power steering control apparatus of the first embodiment according to the present invention, the open / close switches S21 to S24 are provided between the power supply 5 and the motor 4, respectively. Open / close switches S31 to S34 are provided between the main motor drive circuit 20 that generates the drive current of the motor based on the current control value E output from the MCU 10, the power supply 5, and the motor 4, respectively. A sub-motor drive circuit 31 that generates a motor drive current smaller than the main motor drive circuit 20 is provided, and the open / close switches S21 to S24 are closed and the open / close switches S31 to S34 are opened. Drive.

  Then, the motor current detected by the main current detection circuit 22 is monitored by the MCU 10, and when it is determined from the abnormal value of the motor current that the main motor drive circuit 20 has failed, the open / close switches S21 to S24 are opened, and the open / close switch S31. S34 is closed and the motor 4 is driven by the sub motor drive circuit 31.

  As a result, even if a failure occurs in the main motor drive circuit 20 during the driving of the vehicle, it is possible to avoid the operation of the steering handle from becoming suddenly heavy and to make the driver feel uncomfortable and anxious. Never give.

  Further, by restricting the motor drive current of the sub motor drive circuit 31 to be smaller than the motor drive current of the main motor drive circuit 20 under the control of the MCU 10, the FETs Q31 to Q36 constituting the sub motor drive circuit 31 are provided with high power. Since it is not necessary to use a switch, a switch having a small current capacity that can be opened and closed can be used for the open / close switches S31 to S34 attached to the sub-motor drive circuit 31, thereby suppressing an increase in size and cost of the apparatus. be able to.

  Further, when performing the current control when the sub motor drive circuit 31 is used, the limit value is calculated based on the capacity of the sub motor drive circuit 31 in advance, the capacity of the sub motor drive circuit 31 or a smaller value, and a fixed value. It can be easily realized by multiplying the eigenvalue by the current control value E when the auxiliary motor drive circuit 31 is used.

  Further, as a means for further suppressing the increase in size and cost of the electric power steering control device 1, a method of using an element smaller than a required capacity and flowing a current exceeding the capacity of the auxiliary motor drive circuit 31 is conceivable. In that case, a temperature sensor such as a thermistor is attached in the vicinity of the sub motor drive circuit 31, and the current limit value when the sub motor drive circuit 31 is used is set according to the temperature of the sub motor drive circuit 31. This can be realized by decreasing the current value as the value increases.

(Second Embodiment)
Hereinafter, a second embodiment of the electric power steering control device according to the present invention will be described. FIG. 5 is a block diagram showing a schematic configuration of the electric power steering control device according to the second embodiment of the present invention. In addition, about the same structure as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In FIG. 5, the electric power steering control device 2 includes an MCU 10, a main motor drive circuit 20, a sub motor drive circuit 32, a main drive circuit switcher 40, a subdrive circuit switcher 50, and a motor angle detector 60.

  The sub motor drive circuit 32 includes FETs Q31 to 36, an FET gate drive circuit 33, a subcurrent detection circuit 34, an open / close switch S31, and an open / close switch S35 for controlling connection between the FETs Q31 to 36 and the ground.

  Next, the operation of the electric power steering control device of the present embodiment configured as described above will be explained. FIG. 6 is a flowchart for explaining an operation procedure of the electric power steering control device of the present embodiment.

  First, when an ignition switch (not shown) is turned ON, the main drive circuit switch 40 controlled by the MCU 10 closes the open / close switches S21 to S25 (step S201), and the sub drive circuit switch 50 uses the open / close switch S31, S35 is released (step S202).

  Next, the motor 4 is driven by the main motor drive circuit 20 that operates based on the current control value E output from the MCU 10 (step S203).

  In step S204, the motor current is detected by the main current detection circuit 20, and in the subsequent step S205, it is monitored whether or not the motor current detected by the MCU 10 shows an abnormal value, and whether or not the main motor drive circuit 20 has failed. Determine whether.

  As a result, when it is determined that the main motor drive circuit 20 has not failed, the process returns to step S204 and the same processing is repeated.

  On the other hand, if it is determined in step S205 that the main motor drive circuit 20 has failed, the main drive circuit switcher 40 opens the open / close switches S21 to S24 (step S206) and the sub drive circuit switchover. The open / close switches S31 and S35 are closed by the device 50 (step S207).

  Then, the motor 4 is driven by the sub motor drive circuit 32 that operates based on the current control value E output from the MCU 10 and outputs a motor current smaller than the main motor drive circuit 20 (step S108).

  As a result, even if a failure occurs in the main motor drive circuit 20 during operation of the vehicle, the drive of the motor 4 can be continued by the sub motor drive circuit 32, so that the operation of the steering handle suddenly becomes heavy. This avoids discomfort and anxiety for the driver.

  As described above, according to the electric power steering control device of the second embodiment according to the present invention, the open / close switches S21 to S24 are provided between the power source 5 and the motor 4, respectively. Open / close switches S31 and S35 are provided between the main motor drive circuit 20 that generates the drive current of the motor based on the current control value E output from the MCU 10, the power supply 5, and the ground, respectively. The motor drive circuit 20 includes a sub motor drive circuit 32 that generates a smaller motor drive current, closes the open / close switches S21 to S24 attached to the main motor drive circuit 20, and the open / close switch attached to the sub motor drive circuit 32. S31 and S35 are opened, and the motor 4 is driven by the main motor drive circuit 20.

  When the motor current detected by the main current detection circuit 22 is monitored by the MCU 10 and it is determined from the abnormal value of the motor current that the main motor drive circuit 20 has failed, the on / off switches S21 to S21 attached to the main motor drive circuit 20 S24 is opened, the open / close switches S31 and S35 attached to the sub motor drive circuit 31 are closed, and the motor 4 is driven by the sub motor drive circuit 32.

  As a result, in addition to the effects of the present invention in the first embodiment, the number of open / close switches attached to the sub motor drive circuit can be reduced from four to two, thereby further increasing the size and cost of the apparatus. It becomes possible to suppress effectively.

  The description of the specific embodiments is finished above, but the aspect of the present invention is not limited to these embodiments, and modifications, improvements, and the like can be made as appropriate. For example, in this embodiment, most of the processing is performed by software, but part or all of the processing may be realized by hardware such as FPGA (Field Programmable Gate Array), and various control methods may be used. Is also applicable. Furthermore, the present invention can be applied to all electric power steering devices regardless of the type (column type, pinion type, rack type) of the electric power steering device and the type of motor (with brush, brushless, etc.).

  The present invention includes two sets of motor drive circuits, and the motor is driven by one motor drive circuit. When a failure occurs in one drive circuit, the motor is driven by switching to the other motor drive circuit. This is effective for providing an electric power steering control device that can be continued and does not increase in size and cost, and is suitable not only for ordinary passenger cars such as light cars but also for large vehicles such as buses and trucks. .

1 is a block diagram showing a schematic configuration of an electric power steering control device according to a first embodiment of the present invention. It is a figure which shows the mounting state to the metal substrate of FET which comprises the main motor drive circuit of the electric power steering control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the mounting state to the resin substrate of FET which comprises the submotor drive circuit of the electric power steering control apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart for demonstrating the operation | movement procedure of the electric power steering control apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows schematic structure of the electric power steering control apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating the operation | movement procedure of the electric power steering control apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows schematic structure of a general electric power steering apparatus. It is a figure which shows schematic structure of the conventional electric power steering control apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Electric power steering control apparatus 3 Torque sensor 4 Motor 5 Battery power supply 10 MCU
20 Main motor drive circuit 21 Main current detection circuit 31, 32 Sub motor drive circuit Q21-Q26, Q31-Q36 FET
S21-S24, S31-S35 Open / close switch

Claims (5)

Two sets of motor drive circuits for generating a motor drive current based on the current control value are provided. When the motor is driven by one motor drive circuit and a failure occurs in the one motor drive circuit, the other An electric power steering control device that switches to a motor drive circuit and continues to drive the motor,
The drive current of the motor generated by the other motor drive circuit is
An electric power steering control device, wherein the electric power steering control device is smaller than a drive current of the motor generated by the one motor drive circuit. Control means for generating a current control value based on a sensor signal for detecting a state of the vehicle;
A motor current detection circuit for detecting a drive current of the motor generated by the one motor drive circuit,
The control means includes
When the motor current detection circuit detects an abnormal value in the motor drive current, the motor drive current generated by the one motor drive circuit is generated by the other motor drive circuit. The electric power steering control device according to claim 1, wherein the electric power steering control device is limited to be smaller than an electric current. Open / close switches connected between the one motor drive circuit and the power source and between the one motor drive circuit and each phase of the motor;
Open / close switches connected between the other motor drive circuit and the power source, and between the other motor drive circuit and each phase of the motor,
With
Closing the open / close switch connected to the one motor drive circuit;
Open the open / close switch connected to the other motor drive circuit,
When the motor current detection circuit detects an abnormal value in the motor drive current, the open / close switch connected to the one motor drive circuit is opened and the open / close switch connected to the other motor drive circuit The electric power steering control device according to claim 2, wherein: Open / close switches connected between the one motor drive circuit and the power source and between the one motor drive circuit and each phase of the motor;
An open / close switch connected between the other motor drive circuit and the power source and between the other motor drive circuit and the ground;
With
Closing the open / close switch connected to the one motor drive circuit;
Open the open / close switch connected to the other motor drive circuit,
When the motor current detection circuit detects an abnormal value in the motor drive current, the open / close switch connected to the one motor drive circuit is opened and the open / close switch connected to the other motor drive circuit The electric power steering control device according to claim 2, wherein: The one motor drive circuit includes a switching element that is mounted on a metal substrate and generates a drive current for the motor,
5. The electric power steering control device according to claim 1, wherein the other motor driving circuit includes a switching element that is mounted on a resin base plate and generates a driving current for the motor. 6. .

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