Motor control device, motor device, and steering system

Abstract

A motor control device, a motor device, and a steering system of the present invention are provided with: a third inverter that is connected to a first branch point between a first multi-phase winding set and a first inverter and also to a second branch point between a second multi-phase winding set and a second inverter, and that is able to supply alternating-current power to the first multi-phase winding set or to the second multi-phase winding set; switching relays comprising a first switching relay arranged between the first branch point and the third inverter, and a second switching relay arranged between the second branch point and the third inverter; and a cutoff relay arranged between the first branch point / the second branch point and ground. The first switching relay and the second switching relay have a diode for conducting current in the direction going from a motor toward the third inverter. The cutoff relay has a diode for conducting current in the direction going from ground toward the motor.

Description

[Technical Field]

[0001] The present invention relates to a motor control device, a motor device, and a steering system. [Background technology]

[0002] The motor control device in Patent Document 1 comprises a main motor drive circuit that drives and controls a polyphase motor, a backup motor drive circuit that drives and controls the polyphase motor when an abnormality occurs in the main motor drive circuit, and an abnormality diagnosis unit that diagnoses abnormalities in the main motor drive circuit and the backup motor drive circuit.The motor control device has a normal drive state in which the polyphase motor is driven by only the main motor drive circuit, and a backup drive state in which, when the diagnosis result of the abnormality diagnosis unit of the main motor drive circuit in the normal drive state is abnormal, the motor current of the abnormal phase output unit is cut off and the cut-off phase output unit is switched to the phase output unit of the backup motor drive circuit of the same phase to drive the polyphase motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 129271 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when a motor has a first polyphase winding set and a second polyphase winding set, in addition to a first inverter that supplies AC power to the first polyphase winding set and a second inverter that supplies AC power to the second polyphase winding set, it is conceivable to provide a third inverter as a backup for the first and second inverters, so that when the first inverter or the second inverter fails, the third inverter can continue to control the motor. In addition, switching of the motor's drive path has traditionally been performed by switching the drive path between energized and cutoff using semiconductor switching elements such as FETs (Field Effect Transistors) placed in the drive path.

[0005] However, even in an OFF-control state, a current flows through a parasitic diode (or body diode) that is an internal diode in a semiconductor switching element such as an FET. Therefore, if the drive path is switched using a semiconductor switching element such as an FET, the inverter's output current may flow into the normal system via a parasitic diode, or a ground fault may be formed when a switching element in the inverter's lower arm shorts out, which could prevent normal current control of the first or second multi-phase winding set.

[0006] The present invention has been made in consideration of the current situation, and its purpose is to provide a motor control device, a motor device, and a steering system that can normally control the energization of the first polyphase winding set and the second polyphase winding set even if any of the first inverter, second inverter, and third inverter fails. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a power supply circuit including: a first inverter that supplies AC power to a first polyphase winding set of a motor; a second inverter that supplies AC power to a second polyphase winding set of the motor; a third inverter that is connected to a first branch point between the first polyphase winding set and the first inverter and to a second branch point between the second polyphase winding set and the second inverter, and that is capable of supplying AC power to the first polyphase winding set or the second polyphase winding set; and a first switching relay that is arranged between the first branch point and the third inverter, and a second switching relay that is arranged between the second branch point and the third inverter, wherein the first switching relay and the second switching relay conduct a current in a direction from the motor to the third inverter.A semiconductor switching element having a parasitic diode. The switching relay and the cutoff relay, a first system cutoff relay arranged between the first branch point and the ground of the first inverter, and composed of a semiconductor switching element having a parasitic diode that conducts a current in a direction from the ground of the first inverter toward the motor; a second system cutoff relay arranged between the second branch point and the ground of the second inverter, and composed of a semiconductor switching element having a parasitic diode that conducts a current in a direction from the ground of the second inverter toward the motor; and a third system cutoff relay arranged between the first branch point, the second branch point, and the ground of the third inverter, and composed of a semiconductor switching element having a parasitic diode that conducts a current in a direction from the ground of the third inverter toward the motor. The cutoff relay. [Effects of the Invention]

[0008] According to the present invention, even if any of the first inverter, second inverter, and third inverter fails, the energization control of the first polyphase winding set and the second polyphase winding set can be performed normally. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a configuration diagram of a steering system. [Figure 2] FIG. 2 is a block diagram showing the configuration of a motor control device. [Figure 3] 1 is a block diagram showing a detailed configuration of a motor control device according to a first embodiment. [Figure 4] FIG. 2 is a circuit diagram showing details of an inverter and a relay according to the first embodiment. [Figure 5] FIG. 4 is a circuit diagram showing a control state when a first inverter fails in the first embodiment. [Figure 6] FIG. 4 is a circuit diagram showing a control state when a first inverter fails in the first embodiment. [Figure 7] FIG. 10 is a block diagram showing a detailed configuration of a motor control device according to a second embodiment. [Figure 8] FIG. 10 is a circuit diagram showing details of an inverter and a relay according to a second embodiment. [Figure 9] FIG. 10 is a circuit diagram showing a control state when a first inverter fails in the second embodiment. [Figure 10] FIG. 10 is a circuit diagram showing a control state when a first inverter fails in the second embodiment. [Figure 11] FIG. 10 is a circuit diagram showing a control state when a third inverter fails in the second embodiment. [Figure 12] FIG. 10 is a circuit diagram showing a control state when a first inverter and a second inverter fail in the second embodiment. [Figure 13] FIG. 10 is a circuit diagram showing a control state when a first inverter and a fifth relay fail in the second embodiment. [Figure 14] FIG. 10 is a circuit diagram showing a control state when a third inverter and a fourth relay fail in the second embodiment. [Figure 15] FIG. 10 is a circuit diagram showing a control state when a third relay and a fourth relay fail in the second embodiment. [Figure 16] FIG. 10 is a block diagram showing a detailed configuration of a motor control device according to a third embodiment. [Figure 17] FIG. 10 is a circuit diagram showing details of an inverter and a relay according to a third embodiment. [Figure 18] FIG. 11 is a circuit diagram showing a control state when a first inverter fails in the third embodiment. [Figure 19] FIG. 11 is a circuit diagram showing a control state when a third inverter fails in the third embodiment. [Figure 20] FIG. 10 is a block diagram showing a detailed configuration of a motor control device according to a fourth embodiment. [Figure 21] FIG. 11 is a circuit diagram showing a control state when a third inverter fails in the fourth embodiment. [Figure 22] 4 is a flowchart showing a control procedure performed by the first control device and the second control device. [Figure 23] 4 is a flowchart showing a control procedure performed by the first control device and the second control device. [Figure 24] 10 is a flowchart showing a drive switching determination process based on an accumulated drive time, which is performed by the first control device and the second control device. [Figure 25] 10 is a flowchart showing a drive switching determination process based on an estimated FET temperature, which is performed by the first control device and the second control device. [Figure 26] 10 is a flowchart showing a control procedure performed by a third control device. [Figure 27] 10 is a flowchart showing a control procedure performed by a third control device. [Figure 28]10 is a flowchart showing a drive switching determination process based on an accumulated drive time, which is performed by the third control device. [Figure 29] 10 is a flowchart showing a drive switching determination process based on an estimated FET temperature, which is performed by a third control device. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a motor control device, a motor device, and a steering system according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of a steering system 1000 provided in a vehicle 1 such as an automobile.

[0011] The steering system 1000 includes a steering device 2000 and a reaction force generating device 3000. The steering device 2000 is a device that can steer the front wheels 2L, 2R, which are steerable wheels, by the operation of a motor 100, which is a steering actuator. The reaction force generating device 3000 is a device capable of applying a reaction torque to the steering wheel 500 by the operation of a motor 600 serving as a reaction force actuator.

[0012] Here, the steering device 2000 and the reaction force generating device 3000 are mechanically separated. In other words, the steering system 1000 is a steer-by-wire type steering system in which the steering wheel 500 and the front wheels 2L, 2R, which are the steered wheels, are mechanically separated. In addition, the steering system 1000 can be equipped with a mechanism that can mechanically connect the steering device 2000 and the reaction force generating device 3000, in other words, the front wheels 2L, 2R and the steering wheel 500, when an abnormality occurs within the system.

[0013] The steering device 2000 includes a motor 100 that generates a steering force to be applied to the front wheels 2L, 2R, a motor control device 200 that controls the motor 100, a steering mechanism 300, and a steering angle detection device 400 that detects the steering angle of the front wheels 2L, 2R, in other words, the position of the steering mechanism 300. The motor 100 is a brushless motor, and includes a motor rotation angle sensor 101 that detects the rotor position, in other words, the rotation angle of the output shaft.

[0014] The steering mechanism 300 is a mechanism that converts the rotational motion of the output shaft of the motor 100 into the linear motion of a steering rod 310, and in this embodiment uses a rack and pinion. The rotational driving force of the motor 100 is transmitted to the pinion shaft 330 via the reducer 320 .

[0015] On the other hand, the steering rod 310 is provided with a rack 311 that meshes with a pinion 331 provided on a pinion shaft 330, and when the pinion 331 rotates, the steering rod 310 moves horizontally in the left-right direction of the vehicle 1, thereby changing the steering angle of the front wheels 2L, 2R. The steering mechanism 300 is not limited to a rack and pinion, but may be a mechanism using a ball screw, for example.

[0016] The reaction force generating device 3000 includes a steering wheel 500 operated by the driver of the vehicle 1, a steering shaft 510 connected to the steering wheel 500 and rotating in accordance with the rotation of the steering wheel 500, a motor 600 that generates a steering reaction force, a motor control device 700 that controls the motor 600, and a steering angle detection device 800 that detects the steering angle, which is the operating angle of the steering wheel 500. Then, the motor control device 200 of the steering device 2000 (in other words, the steering control device) compares information on the target steering angle corresponding to the steering angle of the steering wheel 500 detected by the steering angle detection device 800 with information on the actual steering angle detected by the steering angle detection device 400, and controls the motor 100, which is the steering actuator.

[0017] Furthermore, the motor control device 700 of the reaction force generating device 3000 (in other words, a reaction force control device) determines a target reaction force torque based on information on the steering angle of the steering wheel 500, information on the speed of the vehicle 1, and the like. Then, the motor control device 700 controls the motor 600, which is a reaction force actuator, in accordance with the target reaction force torque to generate a steering reaction force.

[0018] The motor 600 is a brushless motor, and includes a motor rotation angle sensor 601 that detects the rotor position, in other words, the rotation angle of the output shaft. The motor control device 200 of the steering device 2000 and the motor control device 700 of the reaction force generating device 3000 are configured to be able to communicate with each other.

[0019] FIG. 2 is a block diagram showing a schematic configuration of the motor control device 200 of the steering device 2000 and the motor control device 700 of the reaction force generating device 3000. As shown in FIG. The steering device 2000 is a device that can steer the front wheels 2L, 2R by the output of a motor 100 that is a steering actuator. Here, the motor 100 is a three-phase brushless motor and has two multi-phase winding sets (three-phase winding sets) consisting of a U-phase coil, a V-phase coil, and a W-phase coil: a first winding set 100a and a second winding set 100b.

[0020] In other words, the motor 100 includes a first motor 100A having a first winding set 100a which is a stator with three-phase windings, and a second motor 100B having a second winding set 100b which is a stator with three-phase windings. In the steering device 2000, the first motor 100A and the second motor 100B act in parallel to steer the front wheels 2L, 2R.

[0021] The motor control device 200 has, as its control unit, a first control device 200A connected to the first winding group 100a and capable of controlling the flow of current through the first winding group 100a, a second control device 200B connected to the second winding group 100b and capable of controlling the flow of current through the second winding group 100b, and a backup third control device 200C that can switch between connection and disconnection with the first winding group 100a and between connection and disconnection with the second winding group 100b. The motor control device 200 and the motor 100 constitute a motor device.

[0022] The first control device 200A is an ECU (Electronic Control Unit) including a first MCU (Micro Controller Unit) 200A1, a first drive circuit 200A2, and a first relay 200A3. The second control device 200B is an ECU including a second MCU 200B1, a second drive circuit 200B2, and a second relay 200B3. The third control device 200C is an ECU including a third MCU 200C1, a third drive circuit 200C2, a third relay 200C3, and a fourth relay 200C4.

[0023] Here, among the MCUs 200A1, 200B1, and 200C1, for example, the MCUs 200A1 and 200B1 may be multi-core processors having multiple processor cores. For example, if a dual core is used as a multi-core, when an abnormality occurs in the first processor core that makes up the dual core, the second processor core can continue to control the motor, and the second processor core can also continue to monitor the pre-driver, inverter, power supply, etc. The MCU can also be referred to as a microcomputer, processor, processing unit, arithmetic unit, etc.

[0024] The MCUs 200A1, 200B1, and 200C1 output control signals for controlling the AC power supplied to the first motor 100A or the second motor 100B to the drive circuits 200A2, 200B2, and 200C2. The drive circuits 200A2, 200B2, and 200C2 include a pre-driver, an inverter, and the like, and supply AC power to the first winding set 100a or the second winding set 100b.

[0025] The first relay 200A3 is controlled to be turned on and off by the first MCU 200A1 of the first control device 200A, and switches between connection and disconnection of the first drive circuit 200A2 and the first winding set 100a. The second relay 200B3 is controlled to be turned on and off by the second MCU 200B1 of the second control device 200B, and switches between connection and disconnection of the second drive circuit 200B2 and the second winding set 100b.

[0026] The first relay 200A3 and the second relay 200B3 described above are phase relays that are configured by semiconductor switching elements that are respectively arranged on three-phase drive lines between the drive circuits and the winding sets in the first control device 200A and the second control device 200B, and that switch between connection and disconnection between the drive circuits and the winding sets.

[0027] The third relay 200C3 is controlled to be turned on and off by the third MCU 200C1 of the third control device 200C, and switches between connection and disconnection of the third drive circuit 200C2 and the first winding set 100a. The fourth relay 200C4 is controlled to be turned on and off by the third MCU 200C1 of the third control device 200C, and switches between connecting and disconnecting the third drive circuit 200C2 and the second winding set 100b.

[0028] The third relay 200C3 is a first switching relay for switching the circuit that drives the first winding group 100a from the first drive circuit 200A2 to the third drive circuit 200C2, and the fourth relay 200C4 is a second switching relay for switching the circuit that drives the second winding group 100b from the second drive circuit 200B2 to the third drive circuit 200C2.

[0029] The first relay 200A3 can be configured so that it can be controlled to be turned off (shutoff state) by the third MCU 200C1 of the third control device 200C. Furthermore, the first MCU 200A1 of the first control device 200A and / or the third MCU 200C1 of the third control device 200C can be configured to be turned off when an off command is output.

[0030] Similarly, the second relay 200B3 can be configured so that it can be controlled to be turned off by the second MCU 200B1 of the second control device 200B. Also, the second MCU 200B1 of the second control device 200B and / or the third MCU 200C1 of the third control device 200C can be configured to be turned off when an off command is output.

[0031] The first control device 200A monitors whether or not there is a failure in the first drive circuit 200A2 or the like. The second control device 200B also monitors whether or not there is a failure in the second drive circuit 200B2 or the like. Furthermore, the third control device 200C monitors whether or not there is a failure in the third drive circuit 200C2 or the like.

[0032] When a failure occurs in the first drive circuit 200A2 of the first control device 200A, the connection between the first drive circuit 200A2 and the first winding group 100a is interrupted by turning off the first relay 200A3, and instead the third drive circuit 200C2 and the first winding group 100a are connected by turning on the third relay 200C3. That is, if a failure occurs in the first control device 200A that controls the first winding group 100a, the third control device 200C can control the energization of the first winding group 100a instead of the first control device 200A.

[0033] Furthermore, when a failure occurs in the second drive circuit 200B2 of the second control device 200B, the connection between the second drive circuit 200B2 and the second winding set 100b is interrupted by turning off the second relay 200B3, and instead the third drive circuit 200C2 and the second winding set 100b are connected by turning on the fourth relay 200C4. That is, if the second control device 200B that drives and controls the second winding set 100b fails, the third control device 200C can control the energization of the second winding set 100b instead of the second control device 200B.

[0034] Furthermore, when a failure occurs in the third drive circuit 200C2 of the third control device 200C, the first drive circuit 200A2 and the first winding set 100a are connected, and the second drive circuit 200B2 and the second winding set 100b are connected, i.e., the normal state is maintained. Therefore, even if a failure occurs in any one of the first control device 200A, the second control device 200B, and the third control device 200C, the steering device 2000 can continue to control the first motor 100A and the second motor 100B, and can continue to steer the front wheels 2L and 2R by the steering device 2000 without degrading performance. Furthermore, even if a failure occurs in the first control device 200A and the second control device 200B, the third control device 200C can control the first motor 100A and the second motor 100B, allowing the steering device 2000 to continue steering the front wheels 2L, 2R.

[0035] On the other hand, the reaction force generating device 3000 is a device that can apply a reaction torque to the steering wheel 500 by the output of a motor 600 that is an actuator for reaction force. Here, the motor 600 is a three-phase brushless motor and has two multi-phase winding sets, a first winding set 600a and a second winding set 600b, each consisting of a U-phase coil, a V-phase coil and a W-phase coil.

[0036] In other words, the motor 600 includes a first motor 600A having a first winding set 600a which is a stator with three-phase windings, and a second motor 600B having a second winding set 600b which is a stator with three-phase windings. The reaction force generating device 3000 applies a reaction torque to the steering wheel 500 by the first motor 600A and the second motor 600B acting in parallel.

[0037] The motor control device 700 has a first control device 700A connected to the first winding set 600a and capable of controlling the supply of current to the first winding set 600a, and a second control device 700B connected to the second winding set 600b and capable of controlling the supply of current to the second winding set 600b. The first control device 700A includes a first MCU 700A1, a first drive circuit 700A2, and a first relay 700A3. The second control device 700B includes a second MCU 700B1, a second drive circuit 700B2, and a second relay 700B3.

[0038] The MCUs 700A1 and 700B1 output control signals to the drive circuits 700A2 and 700B2 to control the AC power supplied to the first motor 600A or the second motor 600B. The drive circuits 700A2 and 700B2 include a pre-driver, an inverter, and the like, and supply AC power to the first motor 600A or the second motor 600B.

[0039] The first relay 700A3 is controlled to be turned on and off by the first MCU 700A1, and switches between connection and disconnection between the first drive circuit 700A2 and the first winding set 600a. The second relay 700B3 is controlled to be turned on and off by the second MCU 700B1, and switches between connection and disconnection of the second drive circuit 700B2 and the second winding set 600b.

[0040] Like the motor control device 200, the motor control device 700 can include a third control device in addition to the first control device 700A and the second control device 700B. The motor control device 700 equipped with the third control device is configured so that when the first control device 700A fails, the third control device controls the energization of the first winding set 600a, and when the second control device 700B fails, the third control device controls the energization of the second winding set 600b.

[0041] "First embodiment" FIG. 3 is a block diagram showing a detailed configuration of a motor control device 200 according to a first embodiment. In FIG. 3, the same elements as those in FIG. 2 are denoted by the same reference numerals.

[0042] The first drive circuit 200A2 of the first control device 200A includes a first pre-driver 200A21 and a first inverter 200A22. The second drive circuit 200B2 of the second control device 200B includes a second pre-driver 200B21 and a second inverter 200B22. The third drive circuit 200C2 of the third control device 200C includes a third pre-driver 200C21 and a third inverter 200C22.

[0043] The motor 100 has a first motor rotation angle sensor 101A and a second motor rotation angle sensor 101B as motor rotation angle sensors 101 that detect the rotation angle of the output shaft of the motor 100. The first motor rotation angle sensor 101A and the second motor rotation angle sensor 101B are, for example, magnetic angle sensors that convert a change in a magnetic field caused by a magnet 102 provided on the output shaft of the motor 100 into an electric resistance. The first MCU 200A1 and the third MCU 200C1 acquire the output signal of the first motor rotation angle sensor 101A, and the second MCU 200B1 and the third MCU 200C1 acquire the output signal of the second motor rotation angle sensor 101B.

[0044] The vehicle 1 includes a first battery 11 as a first power source and a second battery 12 as a second power source. The first inverter 200A22 receives power supply from the first battery 11 via the power supply relay 13.

[0045] The second inverter 200B22 receives power supply from the second battery 12 via the power supply relay 14. The third inverter 200C22 receives power supply from the first battery 11 via a power supply relay 15, and also receives power supply from the second battery 12 via a power supply relay 16.

[0046] The MCUs 200A1, 200B1, and 200C1 are connected to a communication line 20 and configured to be able to communicate with each other. Furthermore, the first control device 200A has a diagnostic circuit 201 that monitors the operation of the first MCU 200A1, and the second control device 200B has a diagnostic circuit 202 that monitors the operation of the second MCU 200B1.

[0047] On the other hand, the wake-up circuit 203 included in the third control device 200C acquires a signal indicating the diagnosis result of the first MCU 200A1 output from the diagnostic circuit 201 and a signal indicating the diagnosis result of the second MCU 200B1 output from the diagnostic circuit 202. When the wakeup circuit 203 detects an abnormality in the first MCU 200A1 or the second MCU 200B1, it outputs a wakeup signal to the third MCU 200C1 to start up the third MCU 200C1.

[0048] The first control device 200A also includes a main voltage regulator 210 and a sensor voltage regulator 211. The main voltage regulator 210 converts the voltage of the first battery 11 into an operating voltage for the first MCU 200A1 and the like, and supplies the converted voltage to the first MCU 200A1, the first pre-driver 200A21, the diagnostic circuit 201, and the like.

[0049] Sensor voltage regulator 211 converts the output voltage of main voltage regulator 210 into an operating voltage for first turning angle sensor 400A that constitutes turning angle detection device 400, and supplies the converted voltage to first turning angle sensor 400A. The steering angle detection device 400 has a first steering angle sensor 400A and a second steering angle sensor 400B for redundancy.

[0050] The second control device 200B includes a main voltage regulator 220 and a sensor voltage regulator 221 . The main voltage regulator 220 converts the voltage of the second battery 12 into an operating voltage for the second MCU 200B1 and the like, and supplies the converted voltage to the second MCU 200B1, the second pre-driver 200B21, the diagnostic circuit 202, and the like. Sensor voltage regulator 221 converts the output voltage of main voltage regulator 220 into an operating voltage for second turning angle sensor 400B that constitutes turning angle detection device 400, and outputs the converted voltage to second turning angle sensor 400B.

[0051] The third control device 200C includes a main voltage regulator 230 and a sensor voltage regulator 231 . The main voltage regulator 230 converts the voltage of the first battery 11 or the second battery 12 into an operating voltage for the third MCU 200C1 and the like, and supplies the converted voltage to the third MCU 200C1, the third pre-driver 200C21 and the like. Sensor voltage regulator 231 converts the output voltage of main voltage regulator 230 into an operating voltage for first steering angle sensor 400A and second steering angle sensor 400B that constitute steering angle detection device 400, and supplies the converted voltage to first steering angle sensor 400A or second steering angle sensor 400B.

[0052] That is, first turning angle sensor 400A operates using the output voltage of sensor voltage regulator 211 or sensor voltage regulator 231 as a power supply voltage. Second turning angle sensor 400B operates using the output voltage of sensor voltage regulator 221 or sensor voltage regulator 231 as a power supply voltage.

[0053] On the other hand, first motor rotation angle sensor 101A operates using the output voltage of main voltage regulator 210 or main voltage regulator 230 as a power supply voltage. Second motor rotation angle sensor 101B operates using the output voltage of main voltage regulator 220 or main voltage regulator 230 as a power supply voltage.

[0054] The first MCU 200A1 acquires the output signal of the first turning angle sensor 400A via the sensor interface 261. The second MCU 200B1 acquires the output signal of the second turning angle sensor 400B via the sensor interface 262. The third MCU 200C1 acquires the output signal of the first turning angle sensor 400A and the output signal of the second turning angle sensor 400B via the sensor interface 263.

[0055] Furthermore, the first MCU 200A1 is connected via a CAN interface 241 to a CAN bus 251 that constitutes an in-vehicle network. The second MCU 200B1 is connected to the CAN bus 251 via the CAN interface 242.

[0056] The third MCU 200C1 is connected to the CAN bus 251 via the CAN interface 243. The first MCU 200A1, the second MCU 200B1, and the third MCU 200C1 communicate with other MCUs connected to the CAN bus 251. Furthermore, main voltage regulator 210 , main voltage regulator 220 , and main voltage regulator 230 operate based on a signal from ignition switch 260 .

[0057] FIG. 4 is a circuit diagram showing detailed configurations of inverters 200A22, 200B22, and 200C22 and relays 200A3, 200B3, 200C3, and 200C4 shown in FIG. The first inverter 200A22 is a three-phase bridge circuit including three sets of semiconductor switching elements. Each of the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL that constitute the first inverter 200A22 is composed of an N-channel MOS-FET (Metal Oxide Semiconductor Field Effect Transistor) in which parasitic diodes D11, D12, D13, D14, D15, and D16 are formed between the source terminal and the drain terminal.

[0058] In other words, the first inverter 200A22 is composed of semiconductor switching elements 1UH, 1VH, 1WH for each phase that constitute an upper arm, and semiconductor switching elements 1UL, 1VL, 1WL for each phase that constitute a lower arm. In the parasitic diode of an N-channel MOS-FET, the drain terminal side is the cathode and the source terminal side is the anode.

[0059] Similarly, the second inverter 200B22 is a three-phase bridge circuit including three sets of semiconductor switching elements. The semiconductor switching elements 2UH, 2UL, 2VH, 2VL, 2WH, and 2WL that make up the second inverter 200B22 are each composed of an N-channel MOS-FET with parasitic diodes D21, D22, D23, D24, D25, and D26 formed between the source terminal and the drain terminal.

[0060] Similarly, the third inverter 200C22 is a three-phase bridge circuit including three sets of semiconductor switching elements. Each of the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL that make up the third inverter 200C22 is composed of an N-channel MOS-FET in which parasitic diodes D31, D32, D33, D34, D35, and D36 are formed between the source terminal and the drain terminal.

[0061] The first relay 200A3 is composed of semiconductor switching elements 1RU, 1RV, 1RW arranged on the first drive lines 1DU, 1DV, 1DW for each phase, which connect the first inverter 200A22 and the first winding set 100a, respectively. Here, the semiconductor switching elements 1RU, 1RV, 1RW are N-channel MOS-FETs, and are connected to the first drive lines 1DU, 1DV, 1DW, respectively, so that the drain terminals are on the first winding group 100a side and the source terminals are on the first inverter 200A22 side.

[0062] The parasitic diodes DR11, DR12, and DR13 of the semiconductor switching elements 1RU, 1RV, and 1RW are oriented such that the cathodes are on the first winding set 100a side and the anodes are on the first inverter 200A22 side. That is, the semiconductor switching elements 1RU, 1RV, 1RW constituting the first relay 200A3 have parasitic diodes DR11, DR12, DR13 that conduct current in the direction from the first inverter 200A22 toward the first winding set 100a.

[0063] Similarly, the second relay 200B3 is composed of semiconductor switching elements 2RU, 2RV, 2RW arranged on second drive lines 2DU, 2DV, 2DW for each phase, which connect the second inverter 200B22 and the second winding set 100b, respectively. Here, semiconductor switching elements 2RU, 2RV, 2RW are N-channel MOS-FETs, and are connected so that their drain terminals are on the second winding set 100b side and their source terminals are on the second inverter 200B22 side.

[0064] The parasitic diodes DR21, DR22, DR23 of the semiconductor switching elements 2RU, 2RV, 2RW are oriented such that the cathodes are on the second winding set 100b side and the anodes are on the second inverter 200B22 side. That is, the semiconductor switching elements 2RU, 2RV, 2RW constituting the second relay 200B3 have parasitic diodes DR21, DR22, DR23 that conduct current in the direction from the second inverter 200B22 toward the second winding set 100b.

[0065] First branch points 1BU, 1BV, and 1BW are provided in the first drive lines 1DU, 1DV, and 1DW between the first relay 200A3 and the first winding set 100a. Further, second branch points 2BU, 2BV, and 2BW are provided on second drive lines 2DU, 2DV, and 2DW between the second relay 200B3 and the second winding set 100b. Furthermore, third branch points 3BU, 3BV, 3BW are provided on third drive lines 3DU, 3DV, 3DW that connect the third inverter 200C22 and the first branch points 1BU, 1BV, 1BW.

[0066] A third relay 200C3 is disposed in the third drive lines 3DU, 3DV, 3DW between the first branch points 1BU, 1BV, 1BW and the third branch points 3BU, 3BV, 3BW. Further, a fourth relay 200C4 is arranged in fourth drive lines 4DU, 4DV, 4DW for each phase that connect the third branch points 3BU, 3BV, 3BW and the second branch points 2BU, 2BV, 2BW.

[0067] The third relay 200C3 is configured by arranging a pair of semiconductor switching elements connected in series so that the parasitic diodes are oriented in opposite directions on each of the third drive lines 3DU, 3DV, and 3DW. More specifically, semiconductor switching element 3RU1 and semiconductor switching element 3RU2 are connected in series to third drive line 3DU between first branch point 1BU and third branch point 3BU.

[0068] Here, semiconductor switching element 3RU1 is arranged so that the drain terminal is on the third inverter 200C22 side (third branch point 3BU side) and the source terminal is on the first winding set 100a side (first branch point 1BU side). As a result, the anode of parasitic diode DR311 of semiconductor switching element 3RU1 is on the first winding set 100a side (first branch point 1BU side) and the cathode is on the third inverter 200C22 side (third branch point 3BU side). That is, semiconductor switching element 3RU1 has a parasitic diode DR311 that conducts current in a direction from first winding set 100a (first branch point 1BU) to third inverter 200C22 (third branch point 3BU).

[0069] On the other hand, semiconductor switching element 3RU2, which is paired with semiconductor switching element 3RU1, is arranged so that its source terminal is on the third inverter 200C22 side (third branch point 3BU side) and its drain terminal is on the first winding set 100a side (first branch point 1BU side). As a result, the cathode of parasitic diode DR312 of semiconductor switching element 3RU2 is on the first winding set 100a side (first branch point 1BU side) and the anode is on the third inverter 200C22 side (third branch point 3BU side).

[0070] That is, semiconductor switching element 3RU2 has a parasitic diode DR312 that conducts current in a direction from third inverter 200C22 (third branch point 3BU) to first winding set 100a (first branch point 1BU). In this way, semiconductor switching element 3RU1 and semiconductor switching element 3RU2 are connected in series so that the directions of parasitic diodes DR311 and DR312 are opposite to each other.

[0071] Similarly, in the third drive line 3DV between the first branch point 1BV and the third branch point 3BV, the semiconductor switching element 3RV1 and the semiconductor switching element 3RV2 are connected in series so that the orientations of the parasitic diodes DR321 and DR322 are opposite to each other. Furthermore, in the third drive line 3DW between the first branch point 1BW and the third branch point 3BW, the semiconductor switching element 3RW1 and the semiconductor switching element 3RW2 are connected in series so that the orientations of the parasitic diodes DR331 and DR332 are opposite to each other.

[0072] The fourth relay 200C4, like the third relay 200C3, is configured by arranging a pair of semiconductor switching elements connected in series so that the parasitic diodes are oriented in opposite directions on each of the fourth drive lines 4DU, 4DV, and 4DW. In detail, the semiconductor switching element 4RU1 and the semiconductor switching element 4RU2 are connected in series to the fourth drive line 4DU between the second branch point 2BU and the third branch point 3BU so that the directions of the parasitic diodes DR411 and DR412 are opposite to each other.

[0073] In addition, in the fourth drive line 4DV between the second branch point 2BV and the third branch point 3BV, a semiconductor switching element 4RV1 and a semiconductor switching element 4RV2 are connected in series so that the orientations of the parasitic diodes DR421 and DR422 are opposite to each other. Furthermore, in the fourth drive line 4DW between the second branch point 2BW and the third branch point 3BW, the semiconductor switching element 4RW1 and the semiconductor switching element 4RW2 are connected in series so that the orientations of the parasitic diodes DR431 and DR432 are opposite to each other.

[0074] Here, the first relay 200A3 is arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22, and is a relay having a parasitic diode that conducts current in the direction from the ground GND of the first inverter 200A22 toward the first winding group 100a (first motor 100A). In addition, the second relay 200B3 is arranged between the second branch points 2BU, 2BV, 2BW and the ground GND of the second inverter 200B22, and is a relay having a parasitic diode that conducts current in a direction from the ground GND of the second inverter 200B22 toward the second winding group 100b (second motor 100B).

[0075] Furthermore, the semiconductor switching elements 3RU2, 3RV2, and 3RW2 that configure the third relay 200C3 are arranged between the first branch points 1BU, 1BV, and 1BW and the ground GND of the first inverter 200A22. The semiconductor switching elements 3RU2, 3RV2, and 3RW2 that constitute the third relay 200C3 have parasitic diodes that conduct current in a direction from the ground GND of the third inverter 200C22 toward the first winding set 100a (first branch points 1BU, 1BV, and 1BW).

[0076] Furthermore, the semiconductor switching elements 4RU2, 4RV2, and 4RW2 that constitute the fourth relay 200C4 are arranged between the second branch points 2BU, 2BV, and 2BW and the ground GND of the third inverter 200C22. The semiconductor switching elements 4RU2, 4RV2, and 4RW2 that constitute the fourth relay 200C4 are relays having parasitic diodes that conduct current in a direction from the ground GND of the third inverter 200C22 toward the second winding group 100b (second branch points 2BU, 2BV, and 2BW).

[0077] The control states of the semiconductor switching elements constituting inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4 shown in FIG. 4 are when first inverter 200A22 (first drive circuit A2) and second inverter 200B22 (second drive circuit B2) are normal. Therefore, in the control state shown in FIG. 4, AC power is supplied from the first inverter 200A22 to the first winding set 100a, and AC power is supplied from the second inverter 200B22 to the second winding set 100b.

[0078] At this time, the on / off of each semiconductor switching element 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 and each semiconductor switching element 2UH, 2UL, 2VH, 2VL, 2WH, 2WL of the second inverter 200B22 is PWM (Pulse Width Modulation) controlled based on a steering angle command or a steering force command. Furthermore, the semiconductor switching elements 1RU, 1RV, and 1RW of the first relay 200A3 and the semiconductor switching elements 2RU, 2RV, and 2RW of the second relay 200B3 are maintained in the ON state.

[0079] On the other hand, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in the OFF state. Furthermore, the semiconductor switching elements 3RU1, 3RU2, 3RV1, 3RV2, 3RW1, and 3RW2 of the third relay 200C3 are maintained in the OFF state. Furthermore, the semiconductor switching elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, and 4RW2 of the fourth relay 200C4 are maintained in the OFF state.

[0080] Here, the third relay 200C3 and the fourth relay 200C4 are configured by connecting two semiconductor switching elements in series, with the parasitic diodes oriented in opposite directions, so that when each semiconductor switching element is in the off state, current is prevented from flowing through the parasitic diode. In other words, when the third relay 200C3 and the fourth relay 200C4 are in the off state, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 do not pass through the third relay 200C3 or the fourth relay 200C4 and flow into the third inverter 200C22 side.

[0081] In detail, the semiconductor switching elements 3RU2, 3RV2, and 3RW2 constituting the third relay 200C3 function as a cutoff relay that prevents the output current of the first inverter 200A22 from flowing into the third inverter 200C22 side. Furthermore, the semiconductor switching elements 4RU2, 4RV2, and 4RW2 constituting the fourth relay 200C4 function as a cutoff relay that prevents the output current of the second inverter 200B22 from flowing into the third inverter 200C22 side.

[0082] Therefore, even if a short circuit failure occurs in the semiconductor switching elements 3UL, 3VL, 3WL of the lower arm of the third inverter 200C22, the current is interrupted by the third relay 200C3 and the fourth relay 200C4. This prevents the formation of a ground fault circuit passing through the semiconductor switching elements 1UL, 3VL, 3WL that have short-circuited, and allows normal control of the energization of the first winding set 100a and the second winding set 100b.

[0083] In addition, the output current of the first inverter 200A22 is prevented from flowing into the second winding group 100b via the third relay 200C3 and the fourth relay 200C4, and the output current of the second inverter 200B22 is prevented from flowing into the first winding group 100a via the fourth relay 200C4 and the third relay 200C3. Therefore, the current supply control of the first winding group 100a and the second winding group 100b is performed normally.

[0084] FIG. 5 shows a control state when a short circuit failure occurs in the lower arm semiconductor switching element 1UL among the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL that constitute the first inverter 200A22. Here, since the first inverter 200A22 has failed, AC power is supplied to the first winding set 100a from the third inverter 200C22 for backup in place of the first inverter 200A22.

[0085] At this time, each semiconductor switching element 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 is switched from a PWM control state to an OFF state, and the semiconductor switching elements 1RU, 1RV, 1RW of the first relay 200A3 are switched from an ON state to an OFF state. Then, in order to supply AC power from the third inverter 200C22 to the first winding group 100a, PWM control of each semiconductor switching element 3UH, 3UL, 3VH, 3VL, 3WH, 3WL of the third inverter 200C22 is started, and the semiconductor switching elements 3RU1, 3RU2, 3RV1, 3RV2, 3RW1, 3RW2 of the third relay 200C3 are switched from the OFF state to the ON state.

[0086] As a result, AC power is supplied from the third inverter 200C22 to the first winding group 100a, and even if the first inverter 200A22 fails, AC power can be continuously supplied to the first winding group 100a. Here, the first relay 200A3 prevents the AC power supplied from the third inverter 200C22 to the first winding set 100a from being grounded via the semiconductor switching element 1UL that has short-circuited.

[0087] The first relay 200A3 is arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22, and is a relay having a parasitic diode that conducts current in a direction from the ground GND of the first inverter 200A22 toward the first winding set 100a (first branch points 1BU, 1BV, 1BW). Therefore, when the first inverter 200A22 fails, the first relay 200A3 is switched to the off state, and the first relay 200A3 functions as a cut-off relay that cuts off the flow of AC power supplied from the third inverter 200C22 to the first winding group 100a into the first inverter 200A22.

[0088] On the other hand, since the second inverter 200B22 is normal, PWM control of the semiconductor switching elements 2UH, 2UL, 2VH, 2VL, 2WH, and 2WL of the second inverter 200B22 continues, and the on state of the semiconductor switching elements 2RU, 2RV, and 2RW of the second relay 200B3 also continues. Furthermore, the semiconductor switching elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, and 4RW2 of the fourth relay 200C4 continue to be in the off state.

[0089] As a result, even if the first inverter 200A22 fails, AC power is supplied to the second winding set 100b from the second inverter 200B22. Furthermore, the semiconductor switching elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, and 4RW2 of the fourth relay 200C4 are maintained in the off state, and the fourth relay 200C4 is configured by combining two semiconductor switching elements such that the orientations of the parasitic diodes are opposite to each other.

[0090] This prevents the output current of third inverter 200C22 from flowing into second drive lines 2DU, 2DV, and 2DW of second winding set 100b via the parasitic diodes of semiconductor switching elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, and 4RW2. Furthermore, the semiconductor switching elements 4RU2, 4RV2, and 4RW2 constituting the fourth relay 200C4 function as a cutoff relay that prevents the output current of the second inverter 200B22 from flowing into the third inverter 200C22 side. Therefore, even if the first inverter 200A22 fails, the first winding set 100a and the second winding set 100b can be controlled normally.

[0091] As in the case of Figure 5, Figure 6 shows another aspect of the control state when a short circuit failure occurs in semiconductor switching element 1UL, one of the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, and 1WL that constitute the first inverter 200A22. In the control mode shown in FIG. 6, AC power is supplied to the first winding set 100a from the second inverter 200B22 in place of the failed first inverter 200A22.

[0092] That is, when the first inverter 200A22 fails, the backup third inverter 200C22 is not operated, and AC power is supplied to the first winding set 100a and the second winding set 100b from the normal second inverter 200B22. At this time, each semiconductor switching element 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 is switched from a PWM control state to an OFF state, and the semiconductor switching elements 1RU, 1RV, 1RW of the first relay 200A3 are switched from an ON state to an OFF state.

[0093] Furthermore, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in the OFF state without transitioning to the PWM control state. On the other hand, the semiconductor switching elements 3RU1, 3RU2, 3RV1, 3RV2, 3RW1, and 3RW2 of the third relay 200C3 and the semiconductor switching elements 4RU1, 4RU2, 4RV1, 4RV2, 4RW1, and 4RW2 of the fourth relay 200C4 are switched from the OFF state to the ON state. As a result, the output current of the second inverter 200B22 is supplied to the first winding set 100a via the second branch points 2BU, 2BV, 2BW, the fourth relay 200C4, the third branch points 3BU, 3BV, 3BW, the third relay 200C3, and the first branch points 1BU, 1BV, 1BW.

[0094] Here, the semiconductor switching elements 1RU, 1RV, and 1RW of the first relay 200A3 are in the off state, and the parasitic diodes DR11, DR12, and DR13 conduct current in the direction from the first inverter 200A22 to the first winding group 100a, but do not conduct current in the direction from the first winding group 100a to the first inverter 200A22. Therefore, the AC power output by the second inverter 200B22 that flows through the first drive lines 1DU, 1DV, and 1DW via the first branch points 1BU, 1BV, and 1BW is supplied to the first winding set 100a without flowing into the first inverter 200A22 side. That is, first relay 200A3 functions as a cutoff relay that prevents the current output by second inverter 200B22 from flowing into first inverter 200A22.

[0095] "Second embodiment" FIG. 7 is a block diagram showing a detailed configuration of a motor control device 200 according to a second embodiment. In FIG. 7, the same elements as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0096] The motor control device 200 in Figure 7 differs from the motor control device 200 in Figure 3 in that a fifth relay 200C5 whose on / off is controlled by the third MCU 200C1 of the third control device 200C is arranged between the third inverter 200C22 and ground GND. Also, the motor control device 200 of FIG. 7 has a third relay 200C3 and a fourth relay 200C4, similar to the motor control device 200 of FIG. 3, but differs in that the semiconductor switching elements 3RU2, 3RV2, 3RW2, 4RU2, 4RV2, and 4RW2 are omitted, as will be explained in detail later.

[0097] FIG. 8 is a circuit diagram showing a detailed configuration of inverters 200A22, 200B22, and 200C22 and relays 200A3, 200B3, 200C3, 200C4, and 200C5 shown in FIG. In FIG. 8, the same elements as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0098] The fifth relay 200C5 is configured with a semiconductor switching element 5R arranged between the third inverter 200C22 and the ground GND. Here, the semiconductor switching element 5R constituting the fifth relay 200C5 is an N-channel MOS-FET, and is connected so that the drain terminal is on the third inverter 200C22 side and the source terminal is on the ground GND side.

[0099] The parasitic diode DR5 of the semiconductor switching element 5R is oriented such that the cathode faces the third inverter 200C22 and the anode faces the ground GND. That is, the semiconductor switching element 5R constituting the fifth relay 200C5 has a parasitic diode DR5 that conducts a current in a direction from the ground GND toward the third inverter 200C22.

[0100] In other words, the fifth relay 200C5 is arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the third inverter 200C22, and is also arranged between the second branch points 2BU, 2BV, 2BW and the ground GND of the third inverter 200C22. The fifth relay 200C5 has a parasitic diode that conducts current in a direction from the ground GND of the third inverter 200C22 toward the motor 100, and functions as an interruption relay that interrupts the ground fault path to the ground GND of the third inverter 200C22.

[0101] A third relay 200C3 of the second embodiment shown in FIG. 8 is configured by omitting semiconductor switching elements 3RU2, 3RV2, and 3RW2 from the third relay 200C3 of the first embodiment shown in FIG. 4 and by semiconductor switching elements 3RU1, 3RV1, and 3RW1. Here, the parasitic diodes DR311, DR321, and DR331 of the semiconductor switching elements 3RU1, 3RV1, and 3RW1 have their anodes on the first winding group 100a side (the first branch points 1BU, 1BV, and 1BW side) and their cathodes on the third inverter 200C22 side (the third branch points 3BU, 3BV, and 3BW side).

[0102] That is, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 of the second embodiment shown in FIG. 8 have parasitic diodes DR311, DR321, and DR331 that conduct current in a direction from the first winding group 100a (first branch points 1BU, 1BV, and 1BW) to the third inverter 200C22 (third branch points 3BU, 3BV, and 3BW).

[0103] A fourth relay 200C4 of the second embodiment shown in FIG. 8 is configured by omitting the semiconductor switching elements 4RU2, 4RV2, and 4RW2 from the fourth relay 200C4 of the first embodiment shown in FIG. 4 and by using semiconductor switching elements 4RU1, 4RV1, and 4RW1. Here, the parasitic diodes DR411, DR421, and DR431 of the semiconductor switching elements 4RU1, 4RV1, and 4RW1 have their anodes on the second winding group 100b side (the second branch points 2BU, 2BV, and 2BW side) and their cathodes on the third inverter 200C22 side (the third branch points 3BU, 3BV, and 3BW side).

[0104] That is, the semiconductor switching elements 4RU1, 4RV1, and 4RW1 constituting the fourth relay 200C4 of the second embodiment shown in FIG. 8 have parasitic diodes DR411, DR421, and DR431 that conduct current in a direction from the second winding group 100b (second branch points 2BU, 2BV, and 2BW) to the third inverter 200C22 (third branch points 3BU, 3BV, and 3BW).

[0105] In the second embodiment, although a semiconductor switching element 5R constituting the fifth relay 200C5 is added, the number of semiconductor switching elements constituting the third relay 200C3 and the fourth relay 200C4 is reduced to half compared to the first embodiment. As a result, the motor control device 200 of the second embodiment can reduce the total number of semiconductor switching elements by five compared to the motor control device 200 of the first embodiment.

[0106] The control states of the semiconductor switching elements constituting inverters 200A22, 200B22, and 200C22 and relays 200A3, 200B3, 200C3, 200C4, and 200C5 shown in FIG. 8 indicate a control state in which first inverter 200A22 and second inverter 200B22 are normal, AC power is supplied from first inverter 200A22 to first winding group 100a, and AC power is supplied from second inverter 200B22 to second winding group 100b. At this time, the on / off of each semiconductor switching element 1UH, 1UL, 1VH, 1VL, 1WH, 1WL of the first inverter 200A22 and each semiconductor switching element 2UH, 2UL, 2VH, 2VL, 2WH, 2WL of the second inverter 200B22 is PWM (Pulse Width Modulation) controlled based on a steering angle command or a steering force command.

[0107] Furthermore, the semiconductor switching elements 1RU, 1RV, and 1RW of the first relay 200A3 and the semiconductor switching elements 2RU, 2RV, and 2RW of the second relay 200B3 are maintained in the ON state. On the other hand, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in the OFF state.

[0108] Furthermore, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 of the third relay 200C3 are maintained in the OFF state. Furthermore, the semiconductor switching elements 4RU1, 4RV1, and 4RW1 of the fourth relay 200C4 are maintained in the OFF state. Furthermore, the semiconductor switching element 5R of the fifth relay 200C5 is maintained in the OFF state.

[0109] Here, the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431 of each semiconductor switching element 3RU1, 3RV1, 3RW1, 4RU1, 4RV1, and 4RW1 that constitute the third relay 200C3 and the fourth relay 200C4 conduct current in a direction from the first winding group 100a or the second winding group 100b toward the third inverter 200C22. However, each of the semiconductor switching elements 3UL, 3VL, and 3WL that constitute the lower arm of the third inverter 200C22 is off, and the parasitic diodes D32, D34, and D36 of each of the semiconductor switching elements 3UL, 3VL, and 3WL do not pass current from the third relay 200C3 and the fourth relay 200C4 side to the ground GND side.

[0110] Furthermore, the semiconductor switching element 5R of the fifth relay 200C5 is also off, and the parasitic diode DR5 of the semiconductor switching element 5R does not allow current to flow from the third relay 200C3 and fourth relay 200C4 side to the ground GND side. Therefore, no ground fault circuit is formed via the semiconductor switching elements 3UL, 3VL, 3WL configuring the lower arm of the third inverter 200C22 and the semiconductor switching element 5R of the fifth relay 200C5. Therefore, the current supply control of the first winding group 100a and the second winding group 100b is performed normally.

[0111] Figure 9 shows the control state of each semiconductor switching element constituting inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C5 when a short circuit failure occurs in the lower arm semiconductor switching element 1UL of the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, 1WL constituting the first inverter 200A22 in the second embodiment. Here, instead of the failed first inverter 200A22, AC power is supplied from the second inverter 200B22 to the first winding set 100a, and the second inverter 200B22 supplies AC power to the second winding set 100b and the first winding set 100a.

[0112] Since the first inverter 200A22 has failed, the PWM control of the first inverter 200A22 is stopped. Furthermore, the semiconductor switching elements 1RU, 1RV, and 1RW that constitute the first relay 200A3 are switched from the on state to the off state.

[0113] On the other hand, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are maintained in the OFF state. Furthermore, the semiconductor switching element 5R of the fifth relay 200C5 is also maintained in the OFF state. Furthermore, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 and the semiconductor switching elements 4RU1, 4RV1, and 4RW1 constituting the fourth relay 200C4 are switched from the OFF state to the ON state.

[0114] In this case, the output current of the second inverter 200B22 flows from the second branch points 2BU, 2BV, 2BW to the third branch points 3BU, 3BV, 3BW through the semiconductor switching elements 4RU1, 4RV1, 4RW1 that constitute the fourth relay 200C4. Here, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 are in the OFF state, while the semiconductor switching elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 are in the ON state. Therefore, the output current of the second inverter 200B22 passes through the third branch points 3BU, 3BV, 3BW and the third relay 200C3 and reaches the first branch points 1BU, 1BV, 1BW.

[0115] In addition, the semiconductor switching elements 1RU, 1RV, and 1RW that make up the first relay 200A3 are off, and the parasitic diodes DR11, DR12, and DR13 of the semiconductor switching elements 1RU, 1RV, and 1RW are oriented such that the cathodes are on the first winding group 100a side and the anodes are on the first inverter 200A22 side. Therefore, the output current of the second inverter 200B22 that reaches the first branch points 1BU, 1BV, 1BW does not flow to the first inverter 200A22 side through the semiconductor switching elements 1RU, 1RV, 1RW that make up the first relay 200A3, but is supplied from the first branch points 1BU, 1BV, 1BW to the first winding group 100a.

[0116] In other words, when the first inverter 200A22 fails (when a short circuit failure occurs in the semiconductor switching element of the lower arm), the first relay 200A3 functions as an interrupter relay to prevent the formation of a ground fault circuit, and the second inverter 200B22 can normally control the first winding group 100a and the second winding group 100b.

[0117] In the first embodiment, as shown in FIGS. 5 and 6, even when the first inverter 200A22 fails, the first winding set 100a and the second winding set 100b can be controlled normally. However, in the second embodiment, the number of semiconductor switching elements constituting the relay is reduced compared to the first embodiment, and when the first inverter 200A22 fails, the first winding set 100a and the second winding set 100b can be controlled normally.

[0118] FIG. 10 shows the control state of each semiconductor switching element when a short-circuit failure occurs in the semiconductor switching element 1UL of the first inverter 200A22 in the second embodiment, similar to the failure mode in FIG. Here, when the first inverter 200A22 fails in a normal state in which the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, the state is switched to one in which the third inverter 200C22 supplies AC power to the first winding group 100a and the second winding group 100b.

[0119] In particular, when the first inverter 200A22 fails, the PWM control of the first inverter 200A22 and the second inverter 200B22 is stopped. Furthermore, the semiconductor switching elements 1RU, 1RV, 1RW constituting the first relay 200A3 are switched from the on state to the off state, and furthermore, the semiconductor switching elements 2RU, 2RV, 2RW of the second relay 200B3 are also switched from the on state to the off state.

[0120] Meanwhile, PWM control of the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 is started. Furthermore, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 and the semiconductor switching elements 4RU1, 4RV1, and 4RW1 constituting the fourth relay 200C4 are switched from the OFF state to the ON state.

[0121] In this control state, the output current of the third inverter 200C22 is supplied to the first winding group 100a via the third relay 200C3 and the first branch points 1BU, 1BV, and 1BW, and the output current of the third inverter 200C22 is supplied to the second winding group 100b via the fourth relay 200C4 and the second branch points 2BU, 2BV, and 2BW.

[0122] Here, a short circuit failure occurs in the semiconductor switching element 1UL of the first inverter 200A22. However, the semiconductor switching elements 1RU, 1RV, and 1RW that make up the first relay 200A3 are off, and the parasitic diodes DR11, DR12, and DR13 of the semiconductor switching elements 1RU, 1RV, and 1RW are oriented such that the cathodes are on the first winding group 100a side and the anodes are on the first inverter 200A22 side.

[0123] As a result, the output current of the third inverter 200C22 is prevented from flowing into the first inverter 200A22 by the first relay 200A3, which functions as a cut-off relay, thereby preventing the formation of a ground fault circuit via the semiconductor switching element 1UL, which has a short circuit fault. Therefore, even if the first inverter 200A22 fails, AC power can be normally supplied from the third inverter 200C22 to the first winding set 100a and the second winding set 100b.

[0124] FIG. 11 shows that in the second embodiment, when the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, even if a short circuit occurs in the semiconductor switching element 3UL of the lower arm of the third inverter 200C22, no ground fault circuit is formed via the semiconductor switching element 3UL.

[0125] In a state where the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 that constitute the third relay 200C3 and the semiconductor switching elements 4RU1, 4RV1, and 4RW1 that constitute the fourth relay 200C4 are held in the off state.

[0126] However, the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431 included in the semiconductor switching elements 3RU1, 3RV1, 3RW1, 4RU1, 4RV1, and 4RW1 have cathodes on the third inverter 200C22 side and anodes on the motor 100 side. Therefore, the current supplied to the first winding set 100a and the second winding set 100b can flow into the third inverter 200C22 through the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431.

[0127] However, the semiconductor switching element 5R constituting the fifth relay 200C5 is maintained in the OFF state, and the orientation of the parasitic diode DR5 of the semiconductor switching element 5R is set so that the cathode is on the third inverter 200C22 side and the anode is on the ground GND side. Therefore, the semiconductor switching element 5R (and the parasitic diode DR5) cuts off the ground fault path, and a ground fault circuit passing through the semiconductor switching element 3UL that has short-circuited is not formed.

[0128] That is, the fifth relay 200C5 functions as a cutoff relay that cuts off the ground fault path via the semiconductor switching element 3UL that has experienced a short circuit failure. Therefore, even if the semiconductor switching element 3UL of the lower arm of the third inverter 200C22 experiences a short circuit failure, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 are prevented from being grounded, and the first winding group 100a and the second winding group 100b are controlled normally.

[0129] Figure 12 shows the control state of each semiconductor switching element when a short circuit failure occurs in the semiconductor switching element 1UL of the lower arm of the first inverter 200A22 in the second embodiment, and further when a short circuit failure occurs in the semiconductor switching element 2UL of the lower arm of the second inverter 200B22. Here, AC power is supplied to the first winding group 100a from the third inverter 200C22 in place of the failed first inverter 200A22, and the supply of AC power to the second winding group 100b is stopped.

[0130] Specifically, each semiconductor switching element is controlled as follows. When the first inverter 200A22 enters a fault state due to a short-circuit failure of the semiconductor switching element 1UL and the second inverter 200B22 enters a fault state due to a short-circuit failure of the semiconductor switching element 2UL, the PWM control of the first inverter 200A22 and the second inverter 200B22 is stopped.

[0131] Furthermore, the semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 are switched from the on state to the off state, and the semiconductor switching elements 2RU, 2RV, and 2RW constituting the second relay 200B3 are also switched from the on state to the off state. Furthermore, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 that configure the third relay 200C3 are switched from the OFF state to the ON state.

[0132] On the other hand, the semiconductor switching elements 4RU1, 4RV1, and 4RW1 constituting the fourth relay 200C4 are maintained in the OFF state. Furthermore, the semiconductor switching element 5R constituting the fifth relay 200C5 is switched from the OFF state to the ON state.

[0133] Then, PWM control of the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL of the third inverter 200C22 is started. When each semiconductor switching element is controlled in this manner, even if the first inverter 200A22 fails, the AC power output by the third inverter 200C22 is supplied to the first winding group 100a, and current continues to flow to the first winding group 100a.

[0134] Furthermore, the semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 and the semiconductor switching elements 2RU, 2RV, and 2RW constituting the second relay 200B3 are switched to the OFF state. Moreover, the cathodes of the parasitic diodes DR11, DR12, DR13, DR21, DR22, and DR23 are on the first winding set 100a or second winding set 100b side, and the anodes are on the first inverter 200A22 or second inverter 200B22 side.

[0135] Furthermore, the semiconductor switching elements 4RU1, 4RV1, and 4RW1 constituting the fourth relay 200C4 are held in the off state, and the cathodes of the parasitic diodes DR411, DR421, and DR431 are on the third inverter 200C22 side and the anodes are on the second winding set 100b side. Therefore, it is possible to avoid the formation of a ground fault circuit passing through the semiconductor switching element 1UL that has short-circuited, and a ground fault circuit passing through the semiconductor switching element 2UL that has short-circuited, and the first winding set 100a can be controlled normally.

[0136] In other words, the first relay 200A3 functions as a cut-off relay that cuts off the ground fault circuit that passes through the semiconductor switching element 1UL that has experienced a short circuit failure, and the second relay 200B3 functions as a cut-off relay that cuts off the ground fault circuit that passes through the semiconductor switching element 2UL that has experienced a short circuit failure. Furthermore, the fourth relay 200C4 prevents the output current of the third inverter 200C22 from flowing to the second winding set 100b side.

[0137] Figure 13 shows an embodiment in which the fifth relay 200C5, which serves as an interruption relay for interrupting the ground fault path flowing into the ground GND of the third inverter 200C22, is composed of a first semiconductor switching element 5R1 (first interruption relay) and a second semiconductor switching element 5R2 (second interruption relay) connected in series to the first semiconductor switching element 5R1. Here, the orientation of the parasitic diode DR51 of the first semiconductor switching element 5R1 and the orientation of the parasitic diode DR52 of the second semiconductor switching element 5R2 are set so that the cathode is on the third inverter 200C22 side and the anode is on the ground GND side.

[0138] That is, the first semiconductor switching element 5R1 constituting the fifth relay 200C5 has a parasitic diode DR51 that conducts a current in a direction from the ground GND toward the third inverter 200C22. Similarly, the second semiconductor switching element 5R2 constituting the fifth relay 200C5 has a parasitic diode DR52 that conducts a current in a direction from the ground GND toward the third inverter 200C22. The first semiconductor switching element 5R1 and the second semiconductor switching element 5R2 are connected in series.

[0139] Here, FIG. 13 shows a state in which, when AC power is supplied from the first inverter 200A22 to the first winding group 100a and AC power is supplied from the second inverter 200B22 to the second winding group 100b, the semiconductor switching element 3UL of the lower arm of the third inverter 200C22 experiences a short-circuit fault, and further, the first semiconductor switching element 5R1 constituting the fifth relay 200C5 experiences a short-circuit fault. At this time, the second semiconductor switching element 5R2 prevents the formation of a ground fault circuit passing through the semiconductor switching element 3UL and the first semiconductor switching element 5R1.

[0140] In other words, even if a short circuit occurs in one of the semiconductor switching elements constituting the lower arm of the third inverter 200C22, and further, even if a short circuit occurs in one of the two semiconductor switching elements, the first semiconductor switching element 5R1 and the second semiconductor switching element 5R2 constituting the fifth relay 200C5, the drive current of the first winding group 100a and the second winding group 100b is prevented from faulting to ground. Therefore, even if the third inverter 200C22 fails and further, even if one of the two semiconductor switching elements constituting the fifth relay 200C5 fails, the first winding group 100a and the second winding group 100b can be controlled normally, and higher fail-safe performance can be exhibited than when the fifth relay 200C5 is composed of a single semiconductor switching element.

[0141] Figure 14 shows the control state of each semiconductor switching element when the fifth relay 200C5 is composed of the first semiconductor switching element 5R1 and the second semiconductor switching element 5R2, and the semiconductor switching element 3UL of the lower arm of the third inverter 200C22 suffers a short-circuit failure, and further the semiconductor switching element 4RV1 of the fourth relay 200C4 suffers a short-circuit failure. Here, the supply of AC power from the first inverter 200A22 to the first winding group 100a continues, while the supply of AC power to the second winding group 100b is stopped.

[0142] Specifically, the PWM control of the second inverter 200B22 is stopped, and the PWM control of the third inverter 200C22 is also kept stopped. Further, the second relay 200B3, the third relay 200C3, the fourth relay 200C4, and the fifth relay 200C5 are controlled to be in the OFF state. Then, AC power is supplied from the first inverter 200A22 to the first winding set 100a.

[0143] Here, the output current of the first inverter 200A22 is prevented from causing a ground fault via the semiconductor switching element 3UL that has experienced a short circuit by the fifth relay 200C5 that functions as a breaker relay. Furthermore, since the second inverter 200B22 and the second relay 200B3 are turned off and the supply of AC power to the second winding group 100b is stopped, the output current of the first inverter 200A22 does not flow to the second winding group 100b or cause a ground fault via the semiconductor switching element 4RV1 that has shorted out. Therefore, even if a short circuit fault occurs in the lower arm of the third inverter 200C22 and further in the fourth relay 200C4, the first winding set 100a can be controlled normally.

[0144] FIG. 15 shows the control states of the semiconductor switching elements when the semiconductor switching element 3RU1 of the third relay 200C3 and the semiconductor switching element 4RV1 of the fourth relay 200C4 suffer a short-circuit failure. In this case, the supply of AC power from the first inverter 200A22 to the first winding group 100a continues, while the supply of AC power to the second winding group 100b is stopped.

[0145] Specifically, the PWM control of the second inverter 200B22 is stopped, and the PWM control of the third inverter 200C22 is kept stopped. Further, the second relay 200B3, the third relay 200C3, the fourth relay 200C4, and the fifth relay 200C5 are controlled to be in the OFF state. On the other hand, by continuing the PWM control of the first inverter 200A22 and keeping the first relay 200A3 in the on state, the supply of AC power from the first inverter 200A22 to the first winding set 100a continues.

[0146] Here, the second inverter 200B22 and the second relay 200B3 are turned off, and the supply of AC power to the second winding set 100b is stopped. Therefore, the output current of the first inverter 200A22 does not flow to the second winding set 100b or cause a ground fault via the semiconductor switching element 3RU1 that has shorted out or the semiconductor switching element 4RV1 that has shorted out. Therefore, even if a short circuit occurs in the third relay 200C3 and the fourth relay 200C4, the first winding set 100a can be controlled normally.

[0147] "Third embodiment" FIG. 16 is a block diagram showing a detailed configuration of a motor control device 200 according to a third embodiment. In the motor control device 200 of FIG. 16, a sixth relay 200A6 is arranged between the first inverter 200A22 and the ground GND. The sixth relay 200A6 is controlled to be turned on or off by the first MCU 200A1 of the first control device 200A.

[0148] In addition, a seventh relay 200B7 is disposed between the second inverter 200B22 and the ground GND. The seventh relay 200B7 is controlled to be turned on or off by the second MCU 200B1 of the second control device 200B.

[0149] The motor control device 200 shown in FIG. 16 has the same configuration as the motor control device 200 of the second embodiment shown in FIG. 7, except that the sixth relay 200A6 and seventh relay 200B7 are added. Therefore, in FIG. 16, the same elements as those in FIG. 7 are given the same reference numerals, and detailed explanations thereof will be omitted.

[0150] FIG. 17 is a circuit diagram showing detailed configurations of inverters 200A22, 200B22, and 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C5, 200A6, and 200B7 shown in FIG. In FIG. 17, the same elements as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0151] The sixth relay 200A6 is configured with a semiconductor switching element 6R arranged between the first inverter 200A22 and the ground GND. Here, the semiconductor switching element 6R constituting the sixth relay 200A6 is an N-channel MOS-FET, and is connected so that its drain terminal is on the first inverter 200A22 side and its source terminal is on the ground GND side.

[0152] The orientation of the parasitic diode DR6 of the semiconductor switching element 6R is such that the cathode faces the first inverter 200A22 and the anode faces the ground GND. That is, the semiconductor switching element 6R constituting the sixth relay 200A6 has a parasitic diode DR6 that conducts a current in a direction from the ground GND toward the first inverter 200A22.

[0153] The seventh relay 200B7 is formed of a semiconductor switching element 7R arranged between the second inverter 200B22 and the ground GND. Here, the semiconductor switching element 7R constituting the seventh relay 200B7 is an N-channel MOS-FET, and is connected so that the drain terminal is on the second inverter 200B22 side and the source terminal is on the ground GND side.

[0154] The parasitic diode DR7 of the semiconductor switching element 7R is oriented such that the cathode faces the second inverter 200B22 and the anode faces the ground GND. That is, the semiconductor switching element 7R constituting the seventh relay 200B7 has a parasitic diode DR7 that conducts a current in a direction from the ground GND toward the second inverter 200B22.

[0155] The sixth relay 200A6 is arranged between the first branch points 1BU, 1BV, 1BW and the ground GND of the first inverter 200A22, and has a parasitic diode DR6 that conducts current in a direction from the ground GND of the first inverter 200A22 toward the first winding set 100a, and functions as an interruption relay that interrupts the path leading to a ground fault to the ground GND of the first inverter 200A22.

[0156] Similarly, the seventh relay 200B7 is arranged between the second branch points 2BU, 2BV, 2BW and the ground GND of the second inverter 200B22, and has a parasitic diode DR7 that conducts current in a direction from the ground GND of the second inverter 200B22 toward the second winding set 100b, and functions as an interruption relay that interrupts the path leading to a ground fault to the ground GND of the second inverter 200B22.

[0157] The sixth relay 200A6 can be configured by connecting two semiconductor switching elements 6R in series, and similarly, the seventh relay 200B7 can be configured by connecting two semiconductor switching elements 7R in series. Here, the two semiconductor switching elements 6R constituting the sixth relay 200A6 are each arranged to have a parasitic diode DR6 that conducts current in a direction from the ground GND of the first inverter 200A22 toward the first winding set 100a.

[0158] Similarly, each of the two semiconductor switching elements 7R constituting the seventh relay 200B7 is arranged to have a parasitic diode DR7 that conducts current in a direction from the ground GND of the second inverter 200B22 toward the second winding set 100b. In other words, the sixth relay 200A6 and the seventh relay 200B7 may include a first cutoff relay and a second cutoff relay connected in series.

[0159] In addition, the parasitic diodes DR11, DR12, and DR13 of the semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 shown in FIG. 17 are set in the opposite direction to those in the first embodiment shown in FIG. 4 and the second embodiment shown in FIG. 8. That is, the semiconductor switching elements 1RU, 1RV, and 1RW constituting the first relay 200A3 in FIG. 17 are arranged so that their drains are on the first inverter 200A22 side and their sources are on the first winding group 100a side, and the parasitic diodes DR11, DR12, and DR13 are oriented so that their anodes are on the first winding group 100a side and their cathodes are on the first inverter 200A22 side.

[0160] In other words, in the third embodiment, the semiconductor switching elements 1RU, 1RV, and 1RW that constitute the first relay 200A3 have parasitic diodes DR11, DR12, and DR13 that conduct current in a direction from the first winding group 100a toward the first inverter 200A22. Similarly, the parasitic diodes DR21, DR22, and DR23 of the semiconductor switching elements 2RU, 2RV, and 2RW constituting the second relay 200B3 shown in FIG. 17 are set in the opposite direction to those in the first embodiment shown in FIG. 4 and the second embodiment shown in FIG. 8.

[0161] That is, the semiconductor switching elements 2RU, 2RV, and 2RW constituting the second relay 200B3 in FIG. 17 are arranged so that their drains are on the second inverter 200B22 side and their sources are on the second winding group 100b side, and the parasitic diodes DR21, DR22, and DR23 are oriented so that their anodes are on the second winding group 100b side and their cathodes are on the second inverter 200B22 side. In other words, in the third embodiment, the semiconductor switching elements 2RU, 2RV, and 2RW that constitute the second relay 200B3 have parasitic diodes DR21, DR22, and DR23 that conduct current in a direction from the second winding group 100b toward the second inverter 200B22.

[0162] As will be described in detail later, the sixth relay 200A6 and the seventh relay 200B7 in Figure 17 function as cut-off relays that cut off the ground fault path to ground GND of the first inverter 200A22 and the ground fault path to ground GND of the second inverter 200B22, instead of the first relay 200A3 and the second relay 200B3. FIG. 17 shows a normal control state in which AC power is supplied from the first inverter 200A22 to the first winding set 100a, and AC power is supplied from the second inverter 200B22 to the second winding set 100b. In a normal control state, the first inverter 200A22 and the second inverter 200B22 are PWM controlled, so that the sixth relay 200A6 and the seventh relay 200B7 are maintained in the on state.

[0163] Figure 18 shows the control state of each semiconductor switching element constituting inverters 200A22, 200B22, 200C22 and relays 200A3, 200B3, 200C3, 200C4, 200C5, 200A6, 200B7 when a short circuit failure occurs in the lower arm semiconductor switching element 1UL of the semiconductor switching elements 1UH, 1UL, 1VH, 1VL, 1WH, 1WL constituting the first inverter 200A22 in the third embodiment. Here, in place of the failed first inverter 200A22, the third inverter 200C22 supplies AC power to the first winding set 100a, and the second inverter 200B22 normally supplies AC power to the second winding set 100b.

[0164] In detail, since the first inverter 200A22 has failed, the PWM control of the first inverter 200A22 is stopped, and the semiconductor switching elements 1RU, 1RV, 1RW constituting the first relay 200A3 are switched from the on state to the off state. Furthermore, the semiconductor switching element 6R constituting the sixth relay 200A6 is switched from the on state to the off state.

[0165] On the other hand, in order to supply AC power from the third inverter 200C22 to the first winding set 100a, the semiconductor switching elements 3UH, 3UL, 3VH, 3VL, 3WH, and 3WL constituting the third inverter 200C22 are PWM controlled. Furthermore, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 constituting the third relay 200C3 are switched from the OFF state to the ON state, and the semiconductor switching element 5R constituting the fifth relay 200C5 is also switched from the OFF state to the ON state.

[0166] On the other hand, the semiconductor switching elements 4RU1, 4RV1, and 4RW1 constituting the fourth relay 200C4 are maintained in the OFF state. In this control state, AC current is supplied to the first winding set 100a from the third inverter 200C22 in place of the failed first inverter 200A22.

[0167] Here, even if the semiconductor switching elements 1RU, 1RV, and 1RW that constitute the first relay 200A3 are switched to the off state, the parasitic diodes DR11, DR12, and DR13 allow current to pass from the first winding set 100a toward the first inverter 200A22. However, the semiconductor switching element 6R constituting the sixth relay 200A6 is controlled to be in the OFF state, and the orientation of the parasitic diode DR6 of the semiconductor switching element 6R is set so that the cathode is on the first inverter 200A22 side and the anode is on the ground GND side.

[0168] That is, when the sixth relay 200A6 is controlled to be turned off, it functions as an interruption relay that interrupts the ground fault path that flows from the first inverter 200A22 to the ground GND. Therefore, even if a short circuit occurs in the semiconductor switching element 1UL constituting the first inverter 200A22, a ground fault circuit passing through the semiconductor switching element 1UL is not formed. Therefore, even if a short circuit occurs in the lower arm of the first inverter 200A22, the first winding group 100a and the second winding group 100b can be controlled normally.

[0169] FIG. 19 shows that in the third embodiment, when the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, even if a short circuit occurs in the semiconductor switching element 3UL of the lower arm of the third inverter 200C22, no ground fault circuit is formed via the semiconductor switching element 3UL.

[0170] In a state where the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, the semiconductor switching elements 3RU1, 3RV1, and 3RW1 that constitute the third relay 200C3 and the semiconductor switching elements 4RU1, 4RV1, and 4RW1 that constitute the fourth relay 200C4 are held in the off state.

[0171] However, the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431 included in the semiconductor switching elements 3RU1, 3RV1, 3RW1, 4RU1, 4RV1, and 4RW1 have cathodes on the third inverter 200C22 side and anodes on the motor 100 side. Therefore, the current supplied to the first winding set 100a and the second winding set 100b can flow into the third inverter 200C22 through the parasitic diodes DR311, DR321, DR331, DR411, DR421, and DR431.

[0172] However, the semiconductor switching element 5R constituting the fifth relay 200C5 is maintained in the OFF state, and the orientation of the parasitic diode DR5 of the semiconductor switching element 5R is set so that the cathode is on the third inverter 200C22 side and the anode is on the ground GND side. Therefore, the semiconductor switching element 5R (and the parasitic diode DR5) functions as a breaker relay that breaks the ground fault path, and a ground fault circuit passing through the semiconductor switching element 3UL that has short-circuited is not formed.

[0173] Therefore, even if a semiconductor switching element in the lower arm of the third inverter 200C22 experiences a short-circuit failure, the output current of the first inverter 200A22 and the output current of the second inverter 200B22 are prevented from being grounded via the short-circuited semiconductor switching element. Therefore, even if a semiconductor switching element in the lower arm of the third inverter 200C22 experiences a short-circuit failure, the first winding group 100a and the second winding group 100b can continue to be controlled normally.

[0174] "Fourth embodiment" FIG. 20 is a block diagram showing a detailed configuration of a motor control device 200 according to a fourth embodiment. The motor control device 200 in FIG. 20 differs from the motor control device 200 shown in FIG. 7 only in that the fifth relay 200C5 is omitted and an eighth relay 200C8 is provided instead.

[0175] Therefore, in FIG. 20, the same elements as those in FIG. 7 are given the same reference numerals, and detailed explanations thereof will be omitted. The eighth relay 200C8 is arranged between the third branch points 3BU, 3BV, 3BW and the third inverter 200C22, and is on / off controlled by the third MCU 200C1 of the third control device 200C.

[0176] FIG. 21 is a circuit diagram showing a detailed configuration of inverters 200A22, 200B22, and 200C22 and relays 200A3, 200B3, 200C3, 200C4, and 200C8 shown in FIG. In FIG. 21, the same elements as those in FIG. 8 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0177] The eighth relay 200C8 is composed of semiconductor switching elements 8RU, 8RV, 8RW arranged on the third drive lines 3DU, 3DV, 3DW between the first inverter 200A22 and the third branch points 3BU, 3BV, 3BW, respectively. Semiconductor switching elements 8RU, 8RV, 8RW are arranged so that their drains are on the third branch points 3BU, 3BV, 3BW side (motor 100 side) and their sources are on the third inverter 200C22 side.

[0178] The parasitic diodes DR81, DR82, and DR83 of the semiconductor switching elements 8RU, 8RV, and 8RW are oriented such that the cathodes are on the third branch points 3BU, 3BV, and 3BW side, and the anodes are on the third inverter 200C22 side. That is, the semiconductor switching elements 8RU, 8RV, 8RW constituting the eighth relay 200C8 have parasitic diodes DR81, DR82, DR83 that conduct current in the direction from the third inverter 200C22 toward the third branch points 3BU, 3BV, 3BW.

[0179] The eighth relay 200C8 is provided as a cutoff relay in place of the fifth relay 200C5 arranged between the third inverter 200C22 and the ground GND in the second embodiment. The eighth relay 200C8 has parasitic diodes DR81, DR82, and DR83 that conduct current in a direction from the ground GND of the third inverter 200C22 toward the first winding group 100a and the second winding group 100b.

[0180] According to this configuration, when the first inverter 200A22 supplies AC power to the first winding group 100a and the second inverter 200B22 supplies AC power to the second winding group 100b, when a short circuit occurs in the semiconductor switching element 3UL of the lower arm of the third inverter 200C22, it is possible to avoid the formation of a ground fault circuit that passes through the semiconductor switching element 3UL.

[0181] As shown in FIG. 21, when the PWM control of the third inverter 200C22 is stopped, the semiconductor switching elements 3RU1, 3RV1, 3RW1 constituting the third relay 200C3, the semiconductor switching elements 4RU1, 4RV1, 4RW1 constituting the fourth relay 200C4, and the semiconductor switching elements 8RU, 8RV, 8RW constituting the eighth relay 200C8 are all held in the off state.

[0182] Here, the parasitic diodes of the semiconductor switching elements 3RU1, 3RV1, and 3RW1 that constitute the third relay 200C3 and the semiconductor switching elements 4RU1, 4RV1, and 4RW1 that constitute the fourth relay 200C4 can conduct current in a direction toward the third branch points 3BU, 3BV, and 3BW. However, the parasitic diodes DR81, DR82, and DR83 of the semiconductor switching elements 8RU, 8RV, and 8RW that configure the eighth relay 200C8 cut off the current flowing from the third branch points 3BU, 3BV, and 3BW to the third inverter 200C22.

[0183] Therefore, even if the semiconductor switching element 3UL of the lower arm of the third inverter 200C22 experiences a short-circuit failure, the eighth relay 200C8 prevents the output current of the first inverter 200A22 and the output current of the second inverter 200B22 from passing through the semiconductor switching element 3UL and causing a ground fault. Therefore, even if the semiconductor switching element 3UL in the lower arm of the third inverter 200C22 experiences a short-circuit failure, the first winding set 100a and the second winding set 100b can be controlled normally.

[0184] "Motor control procedure" An example of a control procedure for the motor 100 by the motor control device 200 will be described below. The flowcharts in Figures 22-25 show the control procedures performed by the first control device 200A (first MCU 200A1) and the second control device 200B (second MCU 200B1), and the flowcharts in Figures 26-29 show the control procedures performed by the third control device 200C (third MCU 200C1).

[0185] The control procedures shown in the flowcharts of Figures 22 to 29 include a process (hereinafter also referred to as a failure-time driving process) in which, when the first drive circuit 200A2 or the second drive circuit 200B2 fails, AC power is supplied to the first winding group 100a and the second winding group 100b by one of the normal drive circuits. Furthermore, in the failure driving process, a process of switching the driving circuit that supplies AC power to the first winding group 100a and the second winding group 100b (hereinafter also referred to as a drive switching process) is performed. The above drive switching process makes it possible to prevent the temperature rise of the semiconductor switching elements that constitute the inverter and to protect the semiconductor switching elements while continuing to drive the motor 100.

[0186] The control procedures shown in the flowcharts of FIGS. 22 to 25 are common to the first control device 200A and the second control device 200B. Therefore, in the following, the control procedure performed by the first control device 200A will be described as a representative example, and a description of the control procedure performed by the second control device 200B will be omitted.

[0187] The flowcharts in FIGS. 22 and 23 show the main routine of the control procedure by the first control device 200A. In step S801, the first control device 200A (first MCU 200A1) is started by turning on the ignition switch 260, which is the main switch for driving and stopping the vehicle 1, and then in the next step S802, acquires information on the target steering angles of the front wheels 2L, 2R.

[0188] In addition, in step S803, the first control device 200A acquires the output signal of the motor rotation angle sensor 101, and calculates the rotation angle of the motor 100 based on the acquired output signal. Furthermore, in step S804, the first control device 200A obtains the drive current of the motor 100 based on the output of a current sensor (not shown).

[0189] Next, in step S805, the first control device 200A diagnoses whether or not there is a failure in the drive system of the first winding set 100a, which includes the first drive circuit 200A2. The failure mode includes a short circuit failure of a semiconductor switching element that constitutes the first inverter 200A22. Then, in step S806, the first control device 200A determines whether or not the occurrence of a failure has been detected.

[0190] Here, if the first control device 200A detects the occurrence of a failure, the process proceeds from step S806 to step S807. In step S807, the first control device 200A transmits information to the other systems (the second control device 200A and the third control device 200C) indicating that the supply of AC power from the first inverter 200A22 to the first winding group 100a will be stopped due to the occurrence of a fault.

[0191] Then, first control device 200A stops the PWM control of first inverter 200A22 in step S808. In addition, in step S809, first control device 200A controls all of semiconductor switching elements 1RU, 1RV, 1RW that constitute first relay 200A3 (in other words, the phase relay of first winding set 100a) to be OFF.

[0192] In the case of the motor control device 200 of the third embodiment in which the sixth relay 200A6 and the seventh relay 200B7 are provided, the first control device 200A also controls the sixth relay 200A6 to be off when controlling the first relay 200A3 to be off in step S809. After controlling the first relay 200A3 to be turned off in step S809, the first control device 200A controls the power supply relay 13, which cuts off and connects the power supply path from the first battery 11 to the first inverter 200A22, to be turned off in step S810.

[0193] On the other hand, if the drive system of the first winding set 100a is normal, the first control device 200A proceeds from step S806 to step S811. In step S811, the first control device 200A determines whether or not there is a request to switch the drive circuit for the drive switching process.

[0194] As will be explained in detail later, first control device 200A determines whether or not there is a request to switch the drive circuit based on the accumulated drive time of first inverter 200A22, the estimated temperature of the semiconductor switching elements that make up first inverter 200A22, and the like. When the first control device 200A determines that a drive circuit switching request has been issued, it sets the drive switching determination flag FDS to 1 and stores information about the request to implement drive switching processing.

[0195] Next, in step S812, the first control device 200A transmits drive stop information based on the drive circuit switching request (in other words, information related to drive switching determination) to the other system. In addition, in step S813, the first control device 200A determines whether or not the system is being driven by the third inverter 200C22 for backup.

[0196] If the inverter is being driven by third inverter 200C22, first control device 200A proceeds to step S815 and stops the PWM control of first inverter 200A22. Furthermore, in step S816, first control device 200A controls semiconductor switching elements 1RU, 1RV, 1RW constituting first relay 200A3, which is a phase relay of first winding set 100a, to be all turned off.

[0197] On the other hand, if the inverter 200C is not being driven by the third inverter 200C22, the first control device 200A proceeds from step S813 to step S814 and determines whether the drive switching determination flag FDS is set to zero. The drive switching determination flag FDS is a flag that indicates whether an inverter switching command has been set, and the drive switching determination flag FDS=1 indicates that a command has been issued to switch the inverter that supplies AC power to the motor 100, in other words, that a drive switching request has been set.

[0198] Here, if the drive switching determination flag is set to 1 and a command to switch the inverter that supplies AC power to the motor 100 has been issued, the first control device 200A proceeds to step S815. Then, first control device 200A stops the PWM control of first inverter 200A22 in step S815, and further controls semiconductor switching elements 1RU, 1RV, 1RW constituting first relay 200A3 to turn off all of them in step S816.

[0199] On the other hand, when the motor 100 is not being driven by the third inverter 200C22, and the drive switching determination flag is set to zero and no inverter switching request has been set, the first control device 200A proceeds to step S817 and beyond, and PWM controls the first inverter 200A22 to supply AC power from the first inverter 200A22 to the motor 100.

[0200] In step S817, the first control device 200A determines the steering angle of the front wheels 2L, 2R based on the output signal of the steering angle detection device 400. Next, in step S818, the first control device 200A compares the actual turning angle with the target turning angle by feeding back the turning angle of the front wheels 2L, 2R obtained based on the output signal of the turning angle detection device 400 to the target value side.

[0201] Furthermore, in step S819, first control device 200A calculates a target motor torque for bringing the actual turning angle closer to the target turning angle, based on the control deviation, which is the difference between the actual turning angle and the target turning angle. In addition, in step S820, the first control device 200A determines a d-axis current command value and a q-axis current command value according to the target motor torque.

[0202] Then, the first control device 200A performs vector control in step S821. In detail, the first control device 200A performs a three-phase to two-phase conversion to convert the actual currents Iu, Iv, and Iw for each of the three phases into a d-axis actual current and a q-axis actual current, and further determines a d-axis voltage command value Vd and a q-axis voltage command value Vq based on the deviation between the d-axis actual current and the q-axis actual current and the d-axis current command value corresponding to the target motor torque.

[0203] Next, in step S822, the first control device 200A converts the d-axis voltage command value Vd and the q-axis voltage command value Vq into three-phase command voltages Vu, Vv, and Vw based on the rotation angle of the motor 100, and calculates the duty ratio of the PWM control based on the three-phase command voltages Vu, Vv, and Vw. Next, the first control device 200A turns on the power supply relay 13 in step S823.

[0204] Furthermore, in step S824, first control device 200A controls semiconductor switching elements 1RU, 1RV, 1RW constituting first relay 200A3, which is a phase relay, to be all ON. Then, in step S825, the first control device 200A outputs control pulses to the first pre-driver 200A21 to control the on / off of each semiconductor switching element of the first inverter 200A22 by PWM based on the three-phase command voltages Vu, Vv, and Vw.

[0205] After the processes in steps S810, S816, and S825, the first control device 200A proceeds to step S826 and determines whether the ignition switch 260 has been switched from on to off. If the ignition switch 260 is kept in the on state, the first control device 200A returns to step S802 and repeats the control processing of steps S802 to S825. On the other hand, when the ignition switch 260 is switched from on to off, the first control device 200A ends the control process of steps S802 to S825 described above.

[0206] FIG. 24 is a flowchart showing the details of the processing content in step S811, that is, a subroutine of the processing for determining whether or not there is a request to switch the drive circuit. The determination process shown in the flowchart of FIG. 24 shows, as one aspect, a drive switching determination based on the accumulated drive time.

[0207] First, in step S851, first control device 200A determines whether or not the output current of first inverter 200A22 is equal to or greater than predetermined value CTH. In other words, in step S851, the first control device 200A determines whether or not the semiconductor switching elements of the first inverter 200A22 are in a state where AC power is being supplied from the first inverter 200A22 to the first winding group 100a and whether or not the conditions are such that heat will be generated.

[0208] Here, when the first control device 200A determines that the output current of the first inverter 200A22 is greater than or equal to the predetermined value CTH, it proceeds to step S852 and performs an update process to increase the measurement counter MC, which measures the cumulative driving time of the first inverter 200A22, by 1 from the current value. On the other hand, when first control device 200A determines that the output current of first inverter 200A22 is less than predetermined value CTH, the process proceeds to step S853, where it determines whether measurement counter MC is equal to or less than zero.

[0209] If the measurement counter MC is equal to or less than zero, the first control device 200A resets the measurement counter MC to zero in step S854. On the other hand, if the measurement counter MC is greater than zero, the first control device 200A performs an update process in step S855 to subtract 1 from the current value of the measurement counter MC.

[0210] That is, if the output current of the first inverter 200A22 is equal to or greater than the predetermined value CTH, the measurement counter MC is incremented by 1 for each execution cycle of this subroutine. On the other hand, when the output current of the first inverter 200A22 is less than the predetermined value CTH, the measurement counter MC is decremented by 1 for each execution cycle of this subroutine, with zero as the lower limit. Therefore, the value of the measurement counter MC indicates the accumulated time during which the output current of the first inverter 200A22 is equal to or greater than the predetermined value CTH, in other words, the accumulated drive time which is the sum of the drive times of the first inverter 200A22.

[0211] In step S852, the first control device 200A performs an update process to increase the measurement counter MC by 1 from the current value, and then proceeds to step S856. In step S856, the first control device 200A determines whether a failure has been detected in the second control device 200B or the third control device 200C, which are the other systems, based on the failure information acquired from the second control device 200B or the third control device 200C.

[0212] If no failure is detected in the second control device 200B or the third control device 200C, the first control device 200A proceeds to step S857 and resets the drive switching determination flag FDS to zero, thereby saving information indicating that no request for switching the inverter (drive circuit) has occurred. In other words, when the first control device 200A, the second control device 200B, and the third control device 200C are all normal, a state is maintained in which AC power is supplied from the first inverter 200A22 to the first winding group 100a, and AC power is supplied from the second inverter 200B22 to the second winding group 100b.

[0213] Furthermore, after resetting the measurement counter MC to zero in step S854, the first control device 200A also proceeds to step S857 to reset the drive switching determination flag FDS to zero. In other words, when the first control device 200A resets the measurement counter MC to zero, it determines that the cumulative driving time of the first inverter 200A22 is short and there is currently no need to switch the inverter (drive circuit), and resets the drive switching determination flag FDS to zero.

[0214] On the other hand, if the first control device 200A determines in step S856 that a failure has been detected in the second control device 200B or the third control device 200C, it proceeds to step S858 and determines whether the measurement counter MC is greater than or equal to a predetermined value MCH. Then, if the measurement counter MC is equal to or greater than a predetermined value MCH (in other words, if the cumulative driving time of the first inverter 200A22 is equal to or greater than the set time), the first control device 200A proceeds to step S859 and sets the drive switching determination flag FDS to 1, thereby saving information indicating that a request to switch the inverter (drive circuit) has occurred.

[0215] The flowchart in FIG. 25 shows another example of the process for determining whether or not there is a request to switch the drive circuit. Here, first control device 200A estimates the temperature of the semiconductor switching element (MOS-FET) that constitutes first inverter 200A22, and performs drive switching determination based on the estimated temperature value of the semiconductor switching element.

[0216] In step S871, first control device 200A detects the temperature of first control device 200A (specifically, the temperature of the board on which first control device 200A is mounted) based on the output signal of a temperature sensor (not shown). Next, in step S872, first control device 200A performs a process of integrating the current value of the drive current output by first inverter 200A22. Then, in step S873, first control device 200A estimates the temperature rise of the semiconductor switching elements (MOS-FETs) that constitute first inverter 200A22 based on the integrated current value.

[0217] In the next step S874, first control device 200A obtains the temperatures of the semiconductor switching elements (estimated temperatures of the FETs) that constitute first inverter 200A22. In detail, the first control device 200A adds the estimated temperature rise value obtained in step S873 to the temperature of the first control device 200A detected in step S871 to estimate the temperature of the semiconductor switching elements that constitute the first inverter 200A22.

[0218] Next, in step S875, first control device 200A determines whether or not the estimated temperature of the semiconductor switching elements that constitute first inverter 200A22 is equal to or higher than predetermined value TSH. If the estimated temperature of the semiconductor switching elements constituting first inverter 200A22 is less than predetermined value TSH, first control device 200A proceeds to step S876 to determine whether the value of measurement counter MC is equal to or less than zero.

[0219] If the value of the measurement counter MC is equal to or less than zero, the first control device 200A resets the measurement counter MC to zero in step S877. On the other hand, if the value of the measurement counter MC is greater than zero, the first control device 200A performs an update process in step S878 to subtract 1 from the current value of the measurement counter MC.

[0220] Furthermore, if the estimated temperature of the semiconductor switching elements constituting the first inverter 200A22 is equal to or higher than a predetermined value TSH, the first control device 200A determines in step S879 whether a fault has been detected in the second control device 200B or the third control device 200C, which are the other systems, based on the fault information acquired from the second control device 200B and the third control device 200C. If no failure is detected in the other system, the first control device 200A proceeds to step S880 and resets the drive switching determination flag FDS to zero. Furthermore, after resetting the measurement counter MC to zero in step S877, the first control device 200A also proceeds to step S880 to reset the drive switching determination flag FDS to zero.

[0221] On the other hand, if the first control device 200A determines in step S879 that a failure has been detected in the other system, the process proceeds to step S881, where it performs an update process of incrementing the measurement counter MC by 1 from the current value. Next, in step S882, the first control device 200A determines whether the measurement counter MC is equal to or greater than a predetermined value MCH.

[0222] Then, if the measurement counter MC is equal to or greater than the predetermined value MCH, the first control device 200A proceeds to step S883 and sets the drive switching determination flag FDS to 1, thereby saving information indicating that a request to switch the inverter (drive circuit) has occurred. Moreover, if the measurement counter MC is less than the predetermined value MCH, the first control device 200A ends this subroutine immediately.

[0223] FIG. 26 is a flowchart showing a main routine of the control procedure by the third control device 200C (third MCU 200C1). The processing contents in each step from step S901 to step S906 in the flowchart of FIG. 26 are the same as those in step S801 to step S806 in the flowchart of FIG. 22, and therefore detailed description thereof will be omitted.

[0224] When the third control device 200C detects a failure in step S906, it proceeds to step S907 and transmits information indicating that a failure has occurred in the third control device 200C and that the supply of AC power from the third inverter 200C22 will be stopped to the first control device 200A and the second control device 200B, which are in the other system. Next, in step S908, third control device 200C stops the PWM control of third inverter 200C22.

[0225] Furthermore, in the next step S909, the third control device 200C controls the third relay 200C3 (first switching relay) and the fourth relay 200C4 (second switching relay) to be turned off. Furthermore, in step S910, the third control device 200C controls the cutoff relay for cutting off the ground fault path and the inflow of the drive current to turn off.

[0226] For example, in the first embodiment, the cut-off relays that the third control device 200C turns off in step S910 are the semiconductor switching elements 3RU2, 3RV2, and 3RW2 that constitute the third relay 200C3, and the semiconductor switching elements 4RU2, 4RV2, and 4RW2 that constitute the fourth relay 200C4. That is, in the first embodiment, the third relay 200C3 and the fourth relay 200C4 have a function as a switching relay as well as a function as a cutoff relay.

[0227] In the second and third embodiments, the cutoff relay that the third control device 200C turns off in step S910 is the fifth relay 200C5 (semiconductor switching element 5R). In the fourth embodiment, the cutoff relay that the third control device 200C turns off in step S910 is the eighth relay 200C8 (semiconductor switching elements 8RU, 8RV, 8RW).

[0228] After performing the control to turn off the cutoff relay in step S910, the third control device 200C controls the power supply relay 15 and the power supply relay 16 to turn off in step S911. On the other hand, if it is determined in step S906 that there is no malfunction, the third control device 200C proceeds to step S912 to make a drive switching determination. The drive switching determination performed in step S912 above will be described in detail later.

[0229] Next, in step S913, the third control device 200C transmits information regarding the driving and stopping of the third drive circuit 200C2 (third inverter 200C22) to the first control device 200A and the second control device 200B. Furthermore, in step S914, the third control device 200C determines whether or not the first drive circuit 200A2 (first inverter 200A22) is being driven, based on the information transmitted from the first control device 200A.

[0230] Here, if the first drive circuit 200A2 (first inverter 200A22) is not being driven, the third control device 200C proceeds to step S915 and determines whether the second drive circuit 200B2 (second inverter 200B22) is being driven based on the information transmitted from the second control device 200B. Then, if at least one of the first driving circuit 200A2 and the second driving circuit 200B2 is driving, the third control device 200C stops driving the third driving circuit 200C2 by performing processing similar to steps S908-S910 in steps S917-S919.

[0231] On the other hand, if the first drive circuit 200A2 and the second drive circuit 200B2 are not driving, the third control device 200C proceeds to step S916 to determine whether the drive switching determination flag FDS is zero. Here, when the drive switching determination flag FDS is 1 and a request has been made to switch from drive by the third drive circuit 200C2 (third inverter 200C22) to drive by another system, the third control device 200C stops drive by the third drive circuit 200C2 (third inverter 200C22) by performing the processing of steps S917 to S919.

[0232] Furthermore, if the drive switching determination flag FDS is zero and there is no request to switch from drive by the third drive circuit 200C2 (third inverter 200C22) to drive by another system, the third control device 200C performs the processes of steps S920 to S929. In addition, the third control device 200C executes the same processing as steps S817 to S823 in the flowchart of FIG. 23 described above in steps S920 to S926 of steps S920 to S929, and therefore detailed explanations thereof will be omitted here.

[0233] In step S927, the third control device 200C controls the third relay 200C3 and the fourth relay 200C4, which correspond to the phase relays in the drive by the third inverter 200C22, to be turned on. Furthermore, in the next step S928, the third control device 200C controls to turn on the cutoff relay that was the target of the off control in the above-mentioned step S910. Then, in the next step S929, the third control device 200C outputs control pulses to the third pre-driver 200C21 to control the on / off of each semiconductor switching element of the third inverter 200C22 by PWM based on the three-phase command voltages Vu, Vv, and Vw.

[0234] After the processes in steps S911, S919, and S929, the third control device 200C proceeds to step S930 and determines whether the ignition switch 260 has been switched from on to off. If the ignition switch 260 is held in the on state, the third control device 200C returns to step S902 and repeats the control processing of steps S902 to S929. On the other hand, when the ignition switch 260 is switched from on to off, the third control device 200C ends the control processing of steps S902 to S929 described above.

[0235] FIG. 28 is a flowchart showing the details of the processing content in step S912 of the flowchart in FIG. 26, that is, the subroutine for determining drive switching. The flowchart in FIG. 28 shows drive switching determination based on the accumulated drive time as one mode of drive switching determination.

[0236] First, in step S951, third control device 200C determines whether the output current of third inverter 200C22 is equal to or greater than predetermined value CTH. Here, when the third control device 200C determines that the output current of the third inverter 200C22 is greater than or equal to the predetermined value CTH, it proceeds to step S952 and performs an update process to increase the measurement counter MC, which measures the cumulative driving time of the third inverter 200C22, by 1 from the current value.

[0237] On the other hand, when third control device 200C determines that the output current of third inverter 200C22 is less than predetermined value CTH, the process proceeds to step S953, where it is determined whether measurement counter MC is equal to or less than zero. If the measurement counter MC is equal to or less than zero, the third control device 200C resets the measurement counter MC to zero in step S954, and then resets the drive switching determination flag FDS to zero in step S956. Furthermore, if the measurement counter MC is greater than zero, the third control device 200C performs an update process in step S955 to subtract 1 from the current value of the measurement counter MC.

[0238] In step S952, the third control device 200C performs an update process of increasing the measurement counter MC by 1 from the current value, and then proceeds to step S957. In step S957, the third control device 200C determines whether a failure has been detected in either the first drive circuit 200A2 or the second drive circuit 200B2.

[0239] If the third control device 200C detects a failure in either the first drive circuit 200A2 or the second drive circuit 200B2, that is, if there are two normal drive systems including the third drive circuit 200C2 and it is possible to switch the drive system that supplies AC power to the first winding group 100a and the second winding group 100b, the third control device 200C proceeds to step S958. In step S958, the third control device 200C determines whether the measurement counter MC is equal to or greater than a predetermined value MCH.

[0240] Then, if the measurement counter MC is equal to or greater than the predetermined value MCH, the third control device 200C proceeds to step S959 and sets the drive switching determination flag FDS to 1, thereby saving information indicating that a request to switch the inverter (drive circuit) has occurred. On the other hand, if the measurement counter MC is less than the predetermined value MCH, the third control device 200C ends this subroutine without setting the drive switch determination flag FDS.

[0241] Furthermore, if the third control device 200C determines in step S957 that neither the first drive circuit 200A2 nor the second drive circuit 200B2 is in a faulty state, that is, that both the first drive circuit 200A2 and the second drive circuit 200B2 are normal, or that both the first drive circuit 200A2 and the second drive circuit 200B2 are faulty, it proceeds to step S959 and sets the drive switching determination flag FDS to 1.

[0242] As a result, when the first drive circuit 200A2 and the second drive circuit 200B2 are faulty and in a drive-stopped state, even if a request to switch from drive by the third drive circuit 200C2 occurs, there is no normal drive circuit to drive the motor 100 in place of the third drive circuit 200C2, so the drive switch determination flag FDS is immediately set to 1. Furthermore, if the first drive circuit 200A2 and the second drive circuit 200B2 are normal, the drive switching determination flag FDS is immediately set to 1, since the drive switching determination flag FDS is immediately set to 1 because the drive switching determination flag FDS is returned to the standard state in which the first drive circuit 200A2 drives the first inverter 200A22 and the second drive circuit 200B2 drives the second inverter 200B22.

[0243] The flowchart in FIG. 29 shows another aspect of the drive switching determination in step S912 of the flowchart in FIG. Here, the third control device 200C estimates the temperature of the semiconductor switching element (MOS-FET) that constitutes the third inverter 200C22, and performs drive switching determination based on the estimated temperature value of the semiconductor switching element.

[0244] Note that the processing at each step S971 to step S979 in Figure 29 differs from steps S871 to step S878 and step S880 in Figure 25 in that it is processing by the third control device 200C and the target of temperature estimation is the semiconductor switching element that constitutes the third inverter 200C22, but the processing content is the same. Therefore, detailed description of the processing content in each step from step S971 to step S979 will be omitted.

[0245] If third control device 200C determines in step S975 that the estimated temperature of the semiconductor switching elements constituting third inverter 200C22 is equal to or higher than predetermined value TSH, third control device 200C proceeds to step S980. In step S980, the third control device 200C determines whether a failure has been detected in either the first drive circuit 200A2 or the second drive circuit 200B2.

[0246] If the third control device 200C detects a failure in either the first drive circuit 200A2 or the second drive circuit 200B2, that is, if there are two normal drive systems including the third drive circuit 200C2 and it is possible to switch the drive system that supplies AC power to the first winding group 100a and the second winding group 100b, the third control device 200C proceeds to step S981. In step S981, the third control device 200C performs an update process of incrementing the measurement counter MC by one from the current value.

[0247] Thereafter, the third control device 200C proceeds to step S982 and determines whether the measurement counter MC is equal to or greater than a predetermined value MCH. Then, if the measurement counter MC is equal to or greater than the predetermined value MCH, the third control device 200C proceeds to step S983 and sets the drive switching determination flag FDS to 1, thereby saving information indicating that a request to switch the inverter (drive circuit) has occurred.

[0248] On the other hand, if the measurement counter MC is less than the predetermined value MCH, the third control device 200C ends this subroutine without setting the drive switch determination flag FDS. Furthermore, if the third control device 200C determines in step S980 that neither the first drive circuit 200A2 nor the second drive circuit 200B2 is in a faulty state, that is, that both the first drive circuit 200A2 and the second drive circuit 200B2 are normal, or that both the first drive circuit 200A2 and the second drive circuit 200B2 are faulty, it proceeds to step S983 and sets the drive switching determination flag FDS to 1.

[0249] The control states of the relays and inverters when the control procedures shown in the flowcharts of FIGS. 22 to 29 are executed will be described below for the motor control devices 200 of the first to fourth embodiments, respectively. For example, in the motor control device 200 of the second embodiment, as shown in FIG. 9, if the first inverter 200A22 fails and AC power is supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b, and if the accumulated drive time of the second inverter 200B22 exceeds the set time or the estimated temperature of the FET of the second inverter 200B22 continues to exceed the set temperature, the second control device 200B sets the drive switching determination flag FDS to 1.

[0250] Then, when the second control device 200B sets the drive switching determination flag FDS to 1, it proceeds to steps S815 and S816 of the flowchart in FIG. 23, thereby stopping the supply of AC power from the second inverter 200B22 to the first winding group 100a and the second winding group 100b. When the supply of AC power from the second inverter 200B22 to the first winding group 100a and the second winding group 100b is stopped, the third control device 200C performs the processing from step S920 onwards in the flowchart of FIG. 27, thereby switching to a state in which AC power is supplied from the third inverter 200C22 to the first winding group 100a and the second winding group 100b (see FIG. 10).

[0251] In other words, the third control device 200C controls the third relay 200C3 and the fourth relay 200C4 to be all on and starts PWM control of the third inverter 200C22, thereby supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b. Then, when the third control device 200C continues to drive the third inverter 200C22 and sets the drive switching determination flag FDS to 1, the drive of the third inverter 200C22 is stopped and instead the state is switched to supplying AC power from the second inverter 200B22 to the first winding group 100a and the second winding group 100b (see Figure 9). As a result, even if the first inverter 200A22 fails, the supply of AC power to the first winding group 100a and the second winding group 100b continues, and the temperature rise of the semiconductor switching elements that make up the inverter that drives the motor 100 can be prevented.

[0252] Similarly, a case where the first inverter 200A22 fails as shown in FIG. 6 in the motor control device 200 of the first embodiment will be described. Here, when AC power is being supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b, if the cumulative drive time of the second inverter 200B22 exceeds the set time or the estimated temperature of the FET of the second inverter 200B22 continues to exceed the set temperature, the second control device 200B sets the drive switching determination flag FDS to 1, stops PWM control of the second inverter 200B22, and controls the second relay 200B3 to be turned off.

[0253] At this time, the third control device 200C controls the third relay 200C3 and the fourth relay 200C4 to be all on and starts PWM control of the third inverter 200C22, thereby supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b. That is, in the first embodiment, when the first inverter 200A22 fails, the state alternates between supplying AC power from the second inverter 200B22 to the first winding group 100a and the second winding group 100b and supplying AC power from the third inverter 200C22 to the first winding group 100a and the second winding group 100b.

[0254] Furthermore, in the motor control device 200 of the third embodiment shown in FIG. 17, for example, when the first inverter 200A22 fails, the second relay 200B3 is controlled to be on and the second inverter 200B22 is PWM controlled, while the third relay 200C3 and the fourth relay 200C4 are all controlled to be on, so that AC power can be supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b.

[0255] In this state, if the cumulative driving time of the second inverter 200B22 exceeds the set time or the estimated temperature of the FET of the second inverter 200B22 continues to exceed the set temperature, the second control device 200B sets the drive switching determination flag FDS to 1, stops PWM control of the second inverter 200B22, and controls the second relay 200B3 to off. Here, the third control device 200C maintains a state in which the third relay 200C3 and the fourth relay 200C4 are all controlled to be on, and starts PWM control of the third inverter 200C22, thereby supplying AC power to the first winding group 100a and the second winding group 100b from the third inverter 200C22 instead of the second inverter 200B22.

[0256] Furthermore, in the motor control device of the fourth embodiment shown in FIG. 21, for example, when the first inverter 200A22 fails, if the second relay 200B3 is controlled to be on and the second inverter 200B22 is PWM controlled, while the third relay 200C3 and the fourth relay 200C4 are all controlled to be on, AC power can be supplied from the second inverter 200B22 to the first winding group 100a and the second winding group 100b.

[0257] In this state, if the cumulative driving time of the second inverter 200B22 exceeds the set time or the estimated temperature of the FET of the second inverter 200B22 continues to exceed the set temperature, the second control device 200B sets the drive switching determination flag FDS to 1, stops PWM control of the second inverter 200B22, and controls the second relay 200B3 to off. Here, the third control device 200C maintains a state in which the third relay 200C3 and the fourth relay 200C4 are all controlled to be on, controls the eighth relay 200C8 to be on, and starts PWM control of the third inverter 200C22, thereby supplying AC power to the first winding group 100a and the second winding group 100b from the third inverter 200C22 instead of the second inverter 200B22.

[0258] In this way, when either the first drive circuit 200A2 or the second drive circuit 200B2 fails, the motor control device 200 alternately switches between a state in which the motor 100 is driven only by the normal drive circuit of the first drive circuit 200A2 or the second drive circuit 200B2, and a state in which the motor 100 is driven only by the third drive circuit 200C2. This allows the motor 100 to continue to be driven while suppressing the temperature rise of the semiconductor switching elements (FETs) that constitute the inverter that drives the motor 100, even if either the first drive circuit 200A2 or the second drive circuit 200B2 fails.

[0259] The technical ideas explained in the above embodiments can be used in appropriate combinations as long as no contradiction occurs. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical idea and teachings of the present invention.

[0260] For example, the steer-by-wire system may be a system equipped with a backup mechanism that mechanically couples the steering wheel 500 and the front wheels 2L, 2R with a clutch or the like. Furthermore, the steering device is not limited to a steer-by-wire system, but can be an electric power steering device in which the steering wheel and steered wheels (front wheels) are mechanically connected and which is equipped with a motor that generates steering force.

[0261] Furthermore, the semiconductor switching elements that make up the relay are not limited to MOSFETs, and IGBTs (Insulated Gate Bipolar Transistors) or the like can also be used. Furthermore, the motor control device 200 can include four or more control devices (four systems) each including an MCU, a drive circuit, and a relay.

[0262] Furthermore, if the MCU constituting the control device is multi-core, the multiple processor cores can monitor each other's operations. For example, when an abnormality occurs in the first processor core of the first and second processor cores that make up the dual core, the second processor core can continue to control the drive of the motor (actuator), and the second processor core can also continue to monitor the pre-driver, inverter, and power supply. [Explanation of symbols]

[0263] 100...motor, 100a...first winding set (first polyphase winding set), 100b...second winding set (second polyphase winding set), 200...motor control device, 200A...first control device (control unit), 200A22...first inverter, 200A6...sixth relay (shutoff relay), 200B...second control device (control unit), 200B22...second inverter, 200B7...seventh relay (shutoff relay), 200C...third control device (control unit), 200C22...third inverter, 200C5...fifth relay (shutoff relay), 2 00A3...first relay (phase relay, cut-off relay), 200B3...second relay (phase relay, cut-off relay), 200C3...third relay, 200C4...fourth relay, 1000...steering system, 2000...steering device, 3RU2, 3RV2, 3RW2...semiconductor switching elements (cut-off relays), 4RU2, 4RV2, 4RW2...semiconductor switching elements (cut-off relays), 1BU, 1BV, 1BW...first branch point, 2BU, 2BV, 2BW...second branch point, 3BU, 3BV, 3BW...third branch point

Claims

1. A motor control device that controls a motor including a first multi-phase winding set and a second multi-phase winding set, a first inverter connected to the first multi-phase winding set and configured to supply AC power to the first multi-phase winding set; a second inverter connected to the second multi-phase winding set and configured to supply AC power to the second multi-phase winding set; a third inverter connected to a first branch point between the first polyphase winding set and the first inverter and to a second branch point between the second polyphase winding set and the second inverter, the third inverter being capable of supplying AC power to the first polyphase winding set or the second polyphase winding set; A switching relay that can be switched between energization and cutoff, a first switching relay disposed between the first branch point and the third inverter; a second switching relay disposed between the second branch point and the third inverter; Equipped with the first switching relay and the second switching relay are configured by semiconductor switching elements having parasitic diodes that conduct current in a direction from the motor toward the third inverter. The switching relay; A cutoff relay that can be switched between energization and cutoff, a first system cutoff relay arranged between the first branch point and the ground of the first inverter, the first system cutoff relay being configured with a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the first inverter toward the motor; a second system cutoff relay arranged between the second branch point and the ground of the second inverter, the second system cutoff relay being configured with a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the second inverter toward the motor; a third system cutoff relay arranged between the first branch point, the second branch point, and the ground of the third inverter, and configured by a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the third inverter toward the motor; the interrupt relay, a control unit that controls the first inverter, the second inverter, the third inverter, the switching relay, and the cutoff relay; A motor control device comprising:

2. 2. The motor control device according to claim 1, a third branch point branching from between the third inverter and the first branch point toward the second branch point; The third system cutoff relay is disposed between the first branch point and the third branch point, and between the second branch point and the third branch point; Motor control device.

3. 2. The motor control device according to claim 1, the third system cutoff relay is disposed between the third inverter and ground; Motor control device.

4. 4. The motor control device according to claim 3, The third system cutoff relay includes a first cutoff relay and a second cutoff relay connected in series. Motor control device.

5. 4. The motor control device according to claim 3, When the control unit detects a failure of the first inverter, it turns on all of the switching relays to drive the motor using either the second inverter or the third inverter. Motor control device.

6. 6. The motor control device according to claim 5, the control unit switches between driving the motor by the second inverter and driving the motor by the third inverter in accordance with the temperature of the second inverter and the temperature of the third inverter. Motor control device.

7. 6. The motor control device according to claim 5, the control unit switches between driving the motor by the second inverter and driving the motor by the third inverter, depending on a driving time of the motor by the second inverter and a driving time of the motor by the third inverter. Motor control device.

8. 2. The motor control device according to claim 1, the first system cutoff relay is disposed between the first inverter and ground; the second system cutoff relay is disposed between the second inverter and ground; Motor control device.

9. 9. The motor control device according to claim 8, The first system cutoff relay and the second system cutoff relay each include a first cutoff relay and a second cutoff relay connected in series. Motor control device.

10. 2. The motor control device according to claim 1, the first system interruption relay is disposed between the first inverter and the first branch point; the second system cutoff relay is disposed between the second inverter and the second branch point; Motor control device.

11. 2. The motor control device according to claim 1, when the control unit detects a failure of the first inverter, it turns off the first system cutoff relay and turns on the first switching relay to supply AC power from the third inverter to the first polyphase winding set. Motor control device.

12. 2. The motor control device according to claim 1, When the control unit detects a failure in a switching element of a lower arm of the third inverter, the control unit turns off the third system cutoff relay and the switching relay. Motor control device.

13. 2. The motor control device according to claim 1, When the control unit detects a failure of a switching element of a lower arm of the third inverter and a failure of the first switching relay, the control unit turns off the third system cutoff relay and the switching relay, and further stops operation of either the first inverter or the second inverter. Motor control device.

14. 2. The motor control device according to claim 1, the control unit stops operation of either the first inverter or the second inverter when detecting a failure of the first switching relay and a failure of the second switching relay. Motor control device.

15. a motor including a first multiphase winding set and a second multiphase winding set; A motor control device for controlling the motor, a first inverter connected to the first multi-phase winding set and configured to supply AC power to the first multi-phase winding set; a second inverter connected to the second multi-phase winding set and configured to supply AC power to the second multi-phase winding set; a third inverter connected to a first branch point between the first polyphase winding set and the first inverter and to a second branch point between the second polyphase winding set and the second inverter, the third inverter being capable of supplying AC power to the first polyphase winding set or the second polyphase winding set; A switching relay that can be switched between energization and cutoff, a first switching relay disposed between the first branch point and the third inverter; a second switching relay disposed between the second branch point and the third inverter; Equipped with the first switching relay and the second switching relay are configured by semiconductor switching elements having parasitic diodes that conduct current in a direction from the motor toward the third inverter. The switching relay; A cutoff relay that can be switched between energization and cutoff, a first system cutoff relay arranged between the first branch point and the ground of the first inverter, the first system cutoff relay being configured with a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the first inverter toward the motor; a second system cutoff relay arranged between the second branch point and the ground of the second inverter, the second system cutoff relay being configured with a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the second inverter toward the motor; a third system cutoff relay arranged between the first branch point, the second branch point, and the ground of the third inverter, and configured by a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the third inverter toward the motor; the interrupt relay, a control unit that controls the first inverter, the second inverter, the third inverter, the switching relay, and the cutoff relay; the motor control device, A motor device comprising:

16. a steering device having a motor including a first polyphase winding set and a second polyphase winding set, and capable of steering the steered wheels of a vehicle by an output of the motor; A motor control device for controlling the motor, a first inverter connected to the first multi-phase winding set and configured to supply AC power to the first multi-phase winding set; a second inverter connected to the second multi-phase winding set and configured to supply AC power to the second multi-phase winding set; a third inverter connected to a first branch point between the first polyphase winding set and the first inverter and to a second branch point between the second polyphase winding set and the second inverter, the third inverter being capable of supplying AC power to the first polyphase winding set or the second polyphase winding set; A switching relay that can be switched between energization and cutoff, a first switching relay disposed between the first branch point and the third inverter; a second switching relay disposed between the second branch point and the third inverter; Equipped with the first switching relay and the second switching relay are configured by semiconductor switching elements having parasitic diodes that conduct current in a direction from the motor toward the third inverter. The switching relay; A cutoff relay that can be switched between energization and cutoff, a first system cutoff relay arranged between the first branch point and the ground of the first inverter, the first system cutoff relay being configured with a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the first inverter toward the motor; a second system cutoff relay arranged between the second branch point and the ground of the second inverter, the second system cutoff relay being configured with a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the second inverter toward the motor; a third system cutoff relay arranged between the first branch point, the second branch point, and the ground of the third inverter, and configured by a semiconductor switching element having a parasitic diode that conducts current in a direction from the ground of the third inverter toward the motor; the interrupt relay, a control unit that controls the first inverter, the second inverter, the third inverter, the switching relay, and the cutoff relay; the motor control device, A steering system equipped with

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