JP6434832B2 - Motor control device and electric power steering device using the same - Google Patents

Description

  The present invention relates to a motor control device having a plurality of inverters and an electric power steering device using the same.

  Patent Document 1 discloses an electric motor drive device that has two inverters and prevents damage due to energization of a large current, and an electric power steering device using the same. In the technique of this Patent Document 1, a power supply relay or electronic component caused by energizing a large current is detected by detecting a short-circuit failure of a power supply relay in a control unit and simultaneously turning on a power supply relay in which no short-circuit failure has occurred. This prevents damage to the mounted substrate.

JP 2014-45578 A

  By the way, in a motor control device having a plurality of systems of inverters as in Patent Document 1, if a power relay fails, abnormal heat may be generated when a large current flows. For example, when a reverse connection protection relay composed of a MOSFET fails and turns off, a current flows through a parasitic diode between the source and drain of the MOSFET. In some cases, the power consumption at the time of failure of the reverse connection protection relay reaches 10 times or more of the normal value. For this reason, there is a problem that the amount of heat generation becomes large and the motor output decreases due to overheat protection.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device capable of suppressing a decrease in motor output due to overheat protection, and an electric power steering device using the same. It is in.

A motor control device according to the present invention includes a plurality of motor drive circuits that drive an electric motor, and a control device that controls the plurality of motor drive circuits, and the control device has a faster temperature rise than normal. A change in the current sharing ratio between the systems supplied from the motor drive circuits of the plurality of systems to the electric motor, detecting a failure based on a difference in temperature increase rate, and a current of the motor drive circuit of the failed system Is controlled to be smaller than the current of the motor drive circuit of the normal system, and the failure detection based on the difference in the temperature increase rate is performed by determining the failure of the motor drive circuit from the difference between the measured value and the estimated value of the temperature increase rate. The measured value of the temperature increase rate is obtained from the detected temperature and the actual measurement time required for increasing the predetermined temperature, and the estimated value of the temperature increase rate is the estimated time required for increasing the estimated temperature and the predetermined temperature. Obtained from a, characterized in that.
Further, the motor control device of the present invention each has a power relay circuit, a plurality of motor drive circuits for driving the electric motor, a temperature sensor for detecting a temperature rise due to heat generation of the power relay circuit, A control device for controlling the motor drive circuits of the plurality of systems, the control device based on a temperature detection signal input from the temperature sensor, when the temperature rise is faster than normal, the motors of the plurality of systems The current sharing ratio between each system supplied from the drive circuit to the electric motor is changed, a failure is detected based on the difference in temperature rise rate, and the current of the motor drive circuit of the failed system is converted to a normal system motor drive circuit. It is characterized by controlling so that it may become smaller than this electric current.

An electric power steering apparatus according to the present invention is an electric power steering apparatus that assists a steering force by an electric motor, and controls a plurality of motor drive circuits that drive the electric motor and the plurality of motor drive circuits. And the controller changes the current sharing ratio between the systems supplied to the electric motor from the motor drive circuits of the plurality of systems when the temperature rise is faster than normal, and the rate of temperature increase The failure is detected based on the difference in temperature rise rate, the motor drive circuit of the failed system is stopped, the electric motor is driven by the remaining motor drive circuit, and the assist is continued. The faulty motor drive circuit is identified from the difference between the measured value and the estimated value of the temperature rise rate, and the measured value of the temperature rise rate is the detected temperature and the predetermined temperature. Calculated from the measured time required for the rise, the estimated value of the temperature increase rate is determined from the estimated time required for increasing the estimated temperature and a predetermined temperature, characterized in that.
The electric power steering device of the present invention is an electric power steering device that assists the steering force by an electric motor, each of which has a power relay circuit, and a plurality of motor drive circuits for driving the electric motor, A temperature sensor for detecting a temperature rise due to heat generation of the power relay circuit; and a control device for controlling the motor drive circuits of the plurality of systems, the control device based on a temperature detection signal input from the temperature sensor When the temperature rises faster than normal, change the current sharing ratio between the systems supplied to the electric motor from the plurality of motor drive circuits, detect a failure based on the difference in temperature rise rate, The motor drive circuit of the faulty system is stopped and the electric motor is driven by the remaining motor drive circuit to continue the assist. To.

  In the present invention, the ambient temperature is monitored, and when the temperature rise is faster than normal, the current sharing ratio between each system supplied to the electric motor from the multiple motor drive circuits is changed, and the temperature rise rate difference A failure is detected based on And the output reduction of the electric motor by overheat protection can be suppressed by suppressing heat_generation | fever by stopping the motor drive circuit of the failure system | strain.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. 1 is a circuit diagram of a motor control device according to an embodiment of the present invention. It is a flowchart which shows the failure detection operation | movement of the motor control apparatus shown in FIG. It is a characteristic view which shows the time change of the electric current value of the initial state (normal time) in the motor control apparatus shown in FIG. It is a characteristic view which shows the example of the actual value and estimated value of a change of a substrate temperature when an electric motor is driven with the motor drive circuit of the 1st, 2nd system. It is a characteristic view which shows the example of the measured value and estimated value of a change of a substrate temperature when the motor drive circuit of the 1st system is stopped and the motor drive circuit of the 2nd system is operated. It is a characteristic view which shows the example of the actual value and the estimated value of the change of a substrate temperature when operation | movement is continued only by the motor drive circuit of a 2nd system | strain. It is a characteristic view which shows the example of the actual value and the estimated value of the change of a substrate temperature when operating the motor drive circuit of the 1st system and stopping the motor drive circuit of the 2nd system. It is a characteristic view which shows the example of the measured value and estimated value of a change of a substrate temperature when operation | movement is continued only by the motor drive circuit of a 1st system | strain. It is for demonstrating the modification 3 of this invention, Comprising: It is a characteristic figure which shows the time change of the system total energization current value when the energization current of the 1st system is increased and the energization current of the 2nd system is decreased. is there. This is for explaining the fourth modification of the present invention. When the first system is driven only by the energization current of the first system and then the second system is also used, the total system energization current value and the required output It is a characteristic view which shows a relationship.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic configuration of an EPS apparatus according to an embodiment of the present invention. This apparatus includes a steering wheel 10, a steering torque detection sensor 11, an assisting electric motor 12, a motor control device 13, and the like. Has been. A steering torque detection sensor 11 and a speed reducer 16 are provided in a steering column 15 that includes the steering shaft 14.

  When the driver performs the steering operation, the steering torque generated in the steering shaft 14 is detected by the steering torque detection sensor 11, and the electric motor is operated by the motor controller 13 based on the steering torque signal S1, the vehicle speed signal S2, and the like. By driving and controlling 12, a steering assist force corresponding to the traveling state of the vehicle is generated from the electric motor 12. As a result, when the pinion gear 17 provided at the tip of the steering shaft 14 rotates, the rack shaft 18 moves horizontally to the left and right in the traveling direction, so that the driver's steering operation is transmitted to the wheels (tires) 20 and the vehicle. Change direction.

  Next, the motor control apparatus according to the embodiment of the present invention used in the EPS apparatus shown in FIG. 1 will be described in detail with reference to FIG. The electric motor 12 is a three-phase motor and includes a U-phase coil, a V-phase coil, and a W-phase coil of a first system, and a U-phase coil, a V-phase coil, and a W-phase coil of a second system, each of which is a first. The motor drive circuit 21a of the system and the motor drive circuit 21b of the second system can be individually driven. The motor drive circuit 21a includes an inverter 22a, a driver 23a of the inverter 22a, a capacitor 24a, a power relay circuit 25a, a driver 26a of the power relay circuit 25a, and the like. Similarly, the motor drive circuit 21b includes an inverter 22b, a driver 23b of the inverter 22b, a capacitor 24b, a power supply relay circuit 25b, a driver 26b of the power supply relay circuit 25b, and the like. Both motor drive circuits 21a and 21b are controlled by a microcomputer (CPU) 27 that functions as a control device.

  The inverter 22a has a three-phase bridge circuit configuration including three sets of switching elements that drive the U phase, the V phase, and the W phase of the electric motor 12 for each phase via the drive lines 28U, 28V, and 28W. In this example, each switching element is composed of N-channel MOSFETs 31-36.

In the MOSFETs 31 and 32, the drain and the source are connected in series between one end of the power supply line 37a and the current detection resistor 38a, and one end of the drive line 28U is connected to a common connection point. In the MOSFETs 33 and 34, the drain and source are connected in series between one end of the power supply line 37a and the current detection resistor 38a, and one end of the drive line 28V is connected to a common connection point. In the MOSFETs 35 and 36, the drain and source are connected in series between one end of the power supply line 37a and the current detection resistor 38a, and one end of the drive line 28W is connected to the common connection point. The other end of the current detection resistor 38a is grounded, detects a current flowing through the inverter 22a, and supplies a detection signal S3 to the microcomputer 27.
Here, the diodes D1 to D6 connected in the forward direction between the source and drain in the MOSFETs 31 to 36 are parasitic diodes.

  Power supply line 37a is connected to battery BA through power supply relay circuit 25a. A capacitor 24a is connected between the power supply line 37a and the grounding point. Capacitor 24a assists power supply from battery BA to inverter 22a and removes noise components such as surge current. The power relay circuit 25a is configured by connecting the drains and sources of N-channel MOSFETs 39 and 40 that function as a power relay and a reverse connection protection relay in series. If the MOSFET 39 having the parasitic diode D13 is used for the power supply relay, the circuit may be destroyed when the polarity of the power supply (battery BA) is mistakenly connected. Therefore, in order to protect the circuit, a reverse connection protection relay (MOSFET 40) is provided so that the directions of the parasitic diodes D13 and D14 are opposite.

  The driver 23a corresponds to the H-side driver unit corresponding to the MOSFETs 31, 33, and 35 that are upstream drive elements (upper arms) and the MOSFET 32, 34, and 36 that are downstream drive elements (lower arms), respectively. An L-side driver unit is provided. The gates of MOSFETs 31, 33, and 35 are connected to the output terminals of the H-side driver units, respectively, and are selectively turned on / off by the microcomputer 27. The MOSFETs 32, The gates 34 and 36 are connected and selectively turned on / off by the microcomputer 27. Furthermore, the gates of the MOSFETs 39 and 40 in the power supply relay circuit 25a are connected to the output terminal of the driver 26a, and the microcomputer 27 selectively controls on / off.

  The inverter 22b has the same circuit configuration as the inverter 22a, and includes three sets of switching elements that drive the U phase, the V phase, and the W phase of the electric motor 12 for each phase via the drive lines 29U, 29V, and 29W. It is a three-phase bridge circuit configuration. In this example, each switching element is composed of N-channel MOSFETs 41 to 46.

In the MOSFETs 41 and 42, the drain and the source are connected in series between one end of the power supply line 37b and the current detection resistor 38b, and one end of the drive line 29U is connected to a common connection point. In the MOSFETs 43 and 44, the drain and the source are connected in series between one end of the power supply line 37b and the current detection resistor 38b, and one end of the drive line 29V is connected to a common connection point. In the MOSFETs 45 and 46, the drain and the source are connected in series between one end of the power supply line 37b and the current detection resistor 38b, and one end of the drive line 29W is connected to a common connection point. The other end of the current detection resistor 38b is grounded, detects a current flowing through the inverter 22b, and supplies a detection signal S4 to the microcomputer 27.
Here, the diodes D7 to D12 connected in the forward direction between the source and drain in the MOSFETs 41 to 46 are parasitic diodes.

  The power line 37b is connected to the battery BA through the power relay circuit 25b. A capacitor 24b is connected between the power supply line 37b and the grounding point. Capacitor 24b assists power supply from battery BA to inverter 22a and removes noise components such as surge current. The power relay circuit 25b is configured by connecting the drains and sources of N-channel MOSFETs 49 and 50 that function as a power relay and a reverse connection protection relay in series. If the MOSFET 49 having the parasitic diode D15 is used for the power relay, the circuit may be destroyed if the polarity of the power source (battery BA) is connected by mistake. Therefore, in order to protect the circuit, a reverse connection protection relay (MOSFET 50) is provided so that the directions of the parasitic diodes D15 and D16 are opposite.

  The driver 23b corresponds to the H-side driver unit corresponding to the MOSFETs 41, 43, and 45, which are upstream drive elements (upper arms), and the MOSFETs 42, 44, and 46, which are downstream drive elements (lower arms), respectively. An L-side driver unit is provided. The gates of the MOSFETs 41, 43, 45 are connected to the output terminals of the respective H side driver units and are selectively controlled to be turned on / off by the microcomputer 27. The MOSFETs 42, 43, 45 are respectively connected to the output terminals of the respective L side driver units. The gates 44 and 46 are connected and selectively turned on / off by the microcomputer 27. Furthermore, the gates of the MOSFETs 49 and 50 in the power supply relay circuit 25b are connected to the output terminal of the driver 26b, and the microcomputer 27 selectively controls on / off.

  The microcomputer 27 receives the steering torque signal S1, the vehicle speed signal S2, the detection signals S3 and S4 of the current detection resistors 38a and 38b, the temperature detection signal S5 from the temperature sensor (thermistor) 51, and the like, and the motor drive circuits 21a and 21b. Is controlled to drive the electric motor 12 to generate a steering assist force according to the traveling state of the vehicle from the electric motor 12. The temperature sensor 51 is provided on the same substrate as the substrate on which the MOSFETs 40 and 50 in the power supply relay circuits 25a and 25b are mounted, for example, and detects the substrate temperature.

Next, the failure detection operation of the motor control device shown in FIG. 2 will be described with reference to FIGS. The failure detection operation shown in the flowchart of FIG. 3 is activated and executed at predetermined time intervals (for example, in units of msec).
In the initial state (normal time), the electric motor 12 is supplied with a plurality of motor drive circuits, in this example, as shown in FIG. 4, from the first system motor drive circuit 21a and the second system motor drive circuit 21b. Supplied and driven with a total system energization current value obtained by adding these currents.

  In the normal assist state using the first and second motor drive circuits 21a and 21b, the microcomputer 27 outputs, for example, a pulse width modulation signal (PWM signal) to the drivers 23a and 23b. Further, a signal for turning on the power supply relay circuits 25a and 25b is output to the drivers 26a and 26b. Each of the H-side driver and the L-side driver in the drivers 23a and 23b supplies a drive signal based on the PWM signal to the gates of the MOSFETs 31 to 36 and 41 to 46 in the inverters 22a and 22b, respectively, based on the PWM signal. To selectively control on / off.

  The electric motor 12 is three-phase driven by the motor drive circuit 21a via the drive lines 28U, 28V and 28W, and is three-phase driven by the motor drive circuit 21b via the drive lines 29U, 29V and 29W. At this time, the assist force is changed by varying the duty of the PWM signal as necessary and controlling the output torque of the electric motor 12.

  The microcomputer 27 monitors the substrate temperature (or ambient temperature), and supplies the electric motor 12 from the first and second system motor drive circuits 21a and 21b when the temperature rises faster than normal. A fault is detected based on the difference in temperature rise rate by changing the current sharing ratio between the systems. At this time, the microcomputer 27 specifies the failed motor drive circuits 21a and 21b from the difference between the actually measured value and the estimated value of the temperature rise rate. The actually measured value of the temperature rise rate can be obtained from the detected temperature and the actually measured time required for increasing the predetermined temperature, and the estimated value of the temperature increase rate can be obtained from the estimated temperature and the estimated time required for increasing the predetermined temperature.

That is, based on the temperature detection signal S5 input from the temperature sensor 51, the microcomputer 27 determines whether the substrate temperature increase rate (actual value) ΔT is higher than the estimated value Δt by a predetermined value (X% or more). Determine (ST1). Here, the estimated value Δt is obtained, for example, by the following equation with respect to the past estimated value Δt ′ acquired last time.
Δt = KI ² −J (Δt′−T ₀ ) + Δt ′
In the above equation, K is a heat generation coefficient, I is an energization current, J is a heat dissipation coefficient, and T ₀ is a reference temperature (ambient temperature).

  If the operation is normal, the actual measurement value ΔT and the estimated value Δt gradually increase with an almost equal increase rate as time passes. However, if heat is generated due to a failure, as shown in FIG. 5, the substrate temperature increase rate (actually measured value) ΔT indicated by the solid line increases with respect to the temperature change of the estimated value Δt indicated by the broken line. If the increase rate is higher than the predetermined value X%, for example, if it exceeds the estimated value Δt + 10%, the operation of the first system motor drive circuit 21a is stopped under the control of the microcomputer 27 (ST2). If it is not higher than the predetermined value X%, it is determined that there is no failure since heat is not generated, and the detection operation is terminated.

Here, the base point of the temperature rise of the measured value ΔT and the estimated value Δt is any of the following (1) to (3).
(1) Increasing a predetermined value of the detection temperature (for example, the substrate temperature is increased by 5 ° C.)
(2) A predetermined time (for example, 10 seconds)
(3) Increase in a predetermined value of the estimated temperature (for example, the estimated value of the substrate temperature is increased by 2 ° C.)
The value is cleared every time any of the above (1) to (3) is established, and the rate of temperature increase from that time point is compared with the measured value ΔT and the estimated value Δt.

  In the next step ST3, it is determined again whether or not the rate of increase in substrate temperature (actually measured value) ΔT is higher than the estimated value Δt by a predetermined value (X% or more). As shown by a solid line in FIG. 6, when the actual measurement value ΔT rapidly increases and the rate of increase in the substrate temperature increases by X% or more, the power supply relay circuit 25b of the second system motor drive circuit 21b, for example, the reverse connection protection relay 50 May break down and generate heat. Therefore, the electric motor 12 is driven only by the first system motor drive circuit 21a, and the second system motor drive circuit 21b is stopped (ST4).

  On the other hand, when the increase rate is not higher than X%, as shown in FIG. 7, the actually measured value and the estimated value gradually increase at an approximately equal increase rate. In this case, it is determined that the power relay circuit 25a of the first system motor drive circuit 21a, for example, the reverse connection protection relay 40, has failed to generate heat, and the electric motor 12 is operated only by the second system motor drive circuit 21b. The driving operation is continued (ST5). As a result, the amount of generated heat is reduced, and overheat protection is not performed, so that a reduction in motor output can be suppressed.

  In step ST6, it is determined whether or not the substrate temperature increase rate (actual value) ΔT is higher than the estimated value Δt by a predetermined value (X%) or more. As shown in FIG. 8, when the rate of increase in the substrate temperature is high as in FIG. 6, it is estimated that the cause of the heat generation is other than the power relay circuit, and therefore the first system motor drive circuit 21a. And the second motor drive circuit 21b drive the electric motor 12 (ST7). Then, the cause of heat generation is examined by another failure detection method.

  On the other hand, when the substrate temperature increase rate (actual value) ΔT is not higher than the estimated value Δt by a predetermined value (X%) or more in step ST6, the electric motor 12 is driven only by the first system motor drive circuit 21a. The operation to continue is continued (ST8). In this case, as shown in FIG. 9, the actually measured value and the estimated value gradually increase at substantially the same rate of increase. It is determined that the power relay circuit 25b of the second system motor drive circuit 21b, for example, the reverse connection protection relay 50 has failed and is generating heat, and the electric motor 12 is driven only by the first system motor drive circuit 21a. Continue (ST8). As a result, the amount of generated heat is reduced, and overheat protection is not performed, so that a reduction in motor output can be suppressed.

  According to the configuration and operation as described above, in a motor drive device having two motor drive circuits and an EPS device using the same, when a power relay circuit in one motor drive circuit fails, an abnormality is detected. It is possible to detect and suppress an increase in ambient temperature due to a faulty part. As a result, it is possible to improve safety by suppressing an abnormal decrease in motor output due to overheat protection.

Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
[Modification 1]
For example, in the above-described embodiment, the case where the electric motor is driven by the two motor drive circuits has been described. However, the present invention can be applied to a motor control device that drives the electric motor by three or more motor drive circuits in the same manner. Of course.

[Modification 2]
The case where the motor control device is applied to the EPS device has been described as an example. However, the present invention is not limited to the EPS device, and can be used for various other devices and systems that drive an electric motor by a plurality of motor drive circuits.

[Modification 3]
Moreover, the motor drive circuits 21a and 21b of the first system and the second system were alternately stopped to detect a change in temperature rise. From the motor drive circuits 21a and 21b of the first system and the second system to the electric motor 12 You may make it change the sharing ratio of the electric current between each system | strain to supply. For example, as shown in FIG. 10, the energization current value (consumption current) of the first system motor drive circuit 21a is increased from a0 to a1, and the energization current value of the second system motor drive circuit 21b is decreased from a0 to a2. Then, the system total energization current value may be set to be the same as that shown in FIG. 9, and a faulty motor drive circuit may be detected from a change in the temperature increase rate.

[Modification 4]
Alternatively, as shown in FIG. 11, when the required output corresponding to the steering torque signal S1 is 50% or less, the electric motor 12 is driven only by the first system motor drive circuit 21a, and the required output exceeds 50%. If the output of the first system motor drive circuit 21a alone is insufficient, the electric motor 12 is driven by the motor drive circuit 21b of the second system by that amount, and the motor drive malfunctions due to the change in the temperature increase rate. A circuit may be detected.

  Thus, it is not always necessary to completely stop one of the motor drive circuits. When the assist is necessary, the electric motor 12 is changed by the motor drive circuits 21a and 21b of the first system and the second system by changing the current sharing ratio. Drive. Then, a failure may be detected based on the difference in temperature increase rate, and the motor drive circuit of the failed system may be stopped.

[Modification 5]
Further, the example in which the temperature sensor 51 is provided on the same substrate as the substrate on which the MOSFETs 40 and 50 are mounted has been described. However, the temperature sensor 51 may be provided at another position as long as the temperature rise due to heat generation of the MOSFETs 40 and 50 can be detected. Alternatively, a detection signal of a temperature sensor provided in advance may be used. The heat generation of the MOSFETs 40 and 50 can be estimated not only from the direct or indirect measurement of the temperature but also from the value of the current flowing through the power supply lines 37a and 37b.

[Modification 6]
Furthermore, the example in which the power supply relay circuits 25a and 25b are configured by the power supply relays 39 and 49 and the reverse connection protection relays 40 and 50 formed of MOSFETs having parasitic diodes has been described. It is applicable also to the structure of.

[Modification 7]
In addition, although each switching element is a field effect transistor as an example, other semiconductor switching elements such as an IGBT (Insulated Gate Bipolar Transistor) can be similarly applied.

  DESCRIPTION OF SYMBOLS 12 ... Electric motor, 13 ... Motor control device, 21a, 21b ... Motor drive circuit, 22a, 22b ... Inverter, 23a, 23b ... Driver, 27 ... Microcomputer (control device), 25a, 25b ... Power relay circuit, 31- 36, 41 to 46 ... MOSFET, 39, 49 ... power relay, 40, 50 ... reverse connection protection relay, 51 ... temperature sensor

Claims (8)

A plurality of motor drive circuits for driving the electric motor, and a controller for controlling the plurality of motor drive circuits;
When the temperature rises faster than normal, the control device changes the current sharing ratio between the systems supplied from the motor drive circuits of the multiple systems to the electric motor, and malfunctions based on the difference in temperature increase rate. And control the current of the motor drive circuit of the faulty system to be smaller than the current of the motor drive circuit of the normal system ,
The detection of the failure based on the difference in the temperature increase rate is to identify the failed motor drive circuit from the difference between the measured value and the estimated value of the temperature increase rate, and the measured value of the temperature increase rate is determined based on the detected temperature and a predetermined value. A motor control device characterized in that it is obtained from an actual measurement time required for temperature rise, and an estimated value of the temperature rise rate is obtained from an estimated temperature and an estimated time required for a predetermined temperature rise . The estimated value of the temperature rise rate is calculated by the control device from the consumption current of the motor drive circuit, and the heat release amount is calculated from the previous estimated temperature rise rate value and the ambient temperature. The motor control device according to claim 1 , wherein the motor control device is calculated based on a heat release amount and an estimated value of a previous temperature increase rate. The control device calculates an estimated value of the temperature increase rate every time one of an increase in a predetermined value of the detected temperature, an elapse of a predetermined time, and an increase in the predetermined value of the estimated temperature, The motor control device according to claim 1 or 2 . Each has a power relay circuit and controls a plurality of motor drive circuits for driving an electric motor , a temperature sensor for detecting a temperature rise due to heat generation of the power relay circuit, and the plurality of motor drive circuits. A control device,
The control device , based on a temperature detection signal input from the temperature sensor , shares current between the systems supplied to the electric motor from the plurality of motor drive circuits when the temperature rises faster than normal. A motor characterized by detecting a failure based on a difference in temperature rise rate by changing the ratio and controlling the current of the motor drive circuit of the failed system to be smaller than the current of the motor drive circuit of the normal system Control device. The said control apparatus drives the said electric motor with the motor drive circuit of the system | strain which increased the electric current, when the share ratio of the electric current between each system | strain was changed and the temperature increase rate fell. Item 5. The motor control device according to any one of Items 1 to 4 . The control device determines that the motor drive circuit of the system whose current has been increased is faulty when the increase in temperature increase rate when the current sharing ratio between the systems is changed is greater than a predetermined value. to, that the motor control device according to claim 1 to 5 any one of claims, characterized in. An electric power steering device that assists the steering force with an electric motor,
A plurality of motor drive circuits for driving the electric motor; and a control device for controlling the plurality of motor drive circuits;
When the temperature rises faster than normal, the control device changes the current sharing ratio between the systems supplied from the motor drive circuits of the multiple systems to the electric motor, and malfunctions based on the difference in temperature increase rate. , Stop the motor drive circuit of the faulty system, continue the assist by driving the electric motor with the remaining motor drive circuit ,
The detection of the failure based on the difference in the temperature increase rate is to identify the failed motor drive circuit from the difference between the measured value and the estimated value of the temperature increase rate, and the measured value of the temperature increase rate is determined based on the detected temperature and a predetermined value. An electric power steering apparatus characterized in that it is obtained from an actual measurement time required for temperature rise, and an estimated value of the temperature rise rate is obtained from an estimated temperature and an estimated time required for a predetermined temperature rise . An electric power steering device that assists the steering force with an electric motor,
Each has a power relay circuit and controls a plurality of motor drive circuits for driving an electric motor , a temperature sensor for detecting a temperature rise due to heat generation of the power relay circuit, and the plurality of motor drive circuits. A control device,
The control device , based on a temperature detection signal input from the temperature sensor , shares current between the systems supplied to the electric motor from the plurality of motor drive circuits when the temperature rises faster than normal. The ratio is changed, the failure is detected based on the difference in the temperature increase rate, the motor drive circuit of the failed system is stopped, and the assist is continued by driving the electric motor with the remaining motor drive circuit. Electric power steering device.