Motor control device and electric power steering device

Abstract

The motor control device comprises: an abnormality determination unit (51) for determining whether a temperature detection circuit is abnormal; a first temperature estimation unit (52) for outputting a value obtained by gradually increasing the temperature detected by the temperature detection circuit at a constant increasing rate to a predetermined set value as a first temperature estimation value when the temperature detection circuit is determined to be abnormal; and a second temperature estimation unit (54) for calculating a value obtained by adding a temperature rise value estimated based on a motor current to the first temperature estimation value as a second temperature estimation value.

Description

Technical Field

[0001] The present invention relates to a motor control device and an electric power steering device. Background Art

[0002] Patent Documents 1 and 2 describe a technology in which the motor temperature is estimated by adding a detected temperature detected by a temperature detection circuit to a temperature rise value estimated based on a motor current flowing through the electric motor, and when the estimated motor temperature exceeds a threshold value, the motor current flowing through the electric motor is limited.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4135437

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2012-148629 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In a structure in which the motor temperature is estimated by adding the detected temperature of the temperature detection circuit to the increase value estimated based on the motor current, if an abnormality occurs in the temperature detection circuit, it is necessary to estimate the motor temperature by adding a relatively high set value to the increase value estimated based on the motor current instead of the detected temperature, thereby protecting the motor.

[0009] Therefore, when an abnormality occurs in the temperature detection circuit while the motor current is flowing, the estimated value of the motor temperature may immediately exceed the threshold value, and the motor current may be limited even though the actual motor temperature is lower than the threshold value.

[0010] The present invention has been completed with the above-mentioned problems in mind, and its purpose is to prevent the motor current from being excessively restricted immediately after an abnormality occurs in the temperature detection circuit, in a structure that estimates the motor temperature by adding the detected temperature detected by a temperature detection circuit to the rising value of the temperature estimated based on the motor current, and limits the motor current when the estimated value of the motor temperature becomes above a threshold temperature.

[0011] Means for solving problems

[0012] To achieve the above-mentioned object, a motor control device according to one embodiment of the present invention includes: a motor current control circuit for controlling a motor current flowing through an electric motor; a temperature detection circuit having a temperature detection element disposed near the motor current control circuit; a rise value estimating unit for estimating a rise value in the temperature of the electric motor caused by the motor current; an abnormality determination unit for determining whether the temperature detection circuit is abnormal; a first temperature estimating unit for outputting a detected temperature detected by the temperature detection circuit as a first temperature estimate value when the temperature detection circuit is determined to be normal, and for outputting a value gradually increasing at a constant rate from the detected temperature detected by the temperature detection circuit to a predetermined set value as the first temperature estimate value when the temperature detection circuit is determined to be abnormal; a second temperature estimating unit for calculating a value obtained by adding the rise value to the first temperature estimate value as a second temperature estimate value; and a current limiting unit for limiting the motor current such that the motor current gradually decreases as the second temperature estimate value increases when the second temperature estimate value exceeds a predetermined threshold value.

[0013] An electric power steering device according to another embodiment of the present invention includes the above-described motor control device and an electric motor controlled by the motor control device, and applies a steering assist force to a steering system of a vehicle via the electric motor.

[0014] Effects of the Invention

[0015] According to the present invention, in a structure in which the motor temperature is estimated by adding the detected temperature detected by a temperature detection circuit to the rising value of the temperature estimated based on the motor current, and the motor current is limited when the estimated value of the motor temperature becomes a temperature above a threshold, it is possible to prevent the motor current from being excessively limited immediately after an abnormality occurs in the temperature detection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic configuration diagram showing an example of an electric power steering device according to an embodiment.

[0017] Figure 2 This is a schematic configuration diagram showing an example of an electronic control unit (ECU) according to the first embodiment.

[0018] Figure 3 This is a circuit diagram of an example of a temperature detection circuit.

[0019] Figure 4 This is a block diagram showing an example of the functional configuration of the temperature measuring unit according to the first embodiment.

[0020] Figure 5 This is an explanatory diagram schematically showing changes in the ECU temperature estimate value when an abnormality occurs in the temperature detection circuit.

[0021] Figure 6 This is a block diagram showing an example of the functional configuration of the control arithmetic device according to the first embodiment.

[0022] Figure 7 This is a flowchart of an example of the motor control method according to the first embodiment.

[0023] Figure 8 It is a schematic configuration diagram showing an example of an electronic control unit according to the second embodiment and the third embodiment.

[0024] Figure 9 This is a block diagram showing an example of the functional configuration of the temperature measuring unit according to the second embodiment.

[0025] Figure 10 This is an explanatory diagram schematically showing changes in the ECU temperature estimate value when an abnormality occurs in the temperature detection circuit.

[0026] Figure 11 This is a block diagram showing an example of the functional configuration of the control arithmetic device according to the second embodiment.

[0027] Figure 12 This is a flowchart of an example of a motor control method according to the second embodiment.

[0028] Figure 13 This is a block diagram showing an example of the functional configuration of a temperature measuring unit according to a modification.

[0029] Figure 14 This diagram shows the relative positional relationship between the power conversion circuit and the temperature detection element mounted on the circuit board.

[0030] Figure 15 This is a schematic diagram of a heat dissipation structure that releases heat generated by the power conversion circuit.

[0031] Figure 16 This is a block diagram showing an example of the functional configuration of a temperature measuring unit according to the third embodiment.

[0032] Figure 17 This is an explanatory diagram schematically showing a method for calculating an estimated ECU temperature value when a temperature detection circuit is abnormal.

[0033] Figure 18 This is a schematic structural diagram showing a first modified example of the electric power steering device.

[0034] Figure 19 This is a schematic structural diagram showing a second modified example of the electric power steering device.

[0035] Figure 20 This is a schematic structural diagram showing a third modified example of the electric power steering device. DETAILED DESCRIPTION

[0036] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0037] The embodiments of the present invention described below illustrate devices and methods for embodying the technical concept of the present invention. However, the technical concept of the present invention is not limited to the structure and arrangement of the components to the following. The technical concept of the present invention can be modified in various ways within the technical scope defined by the technical solutions described in the claims.

[0038] (First embodiment)

[0039] (structure)

[0040] Figure 1 This is a schematic diagram showing an example of an electric power steering (EPS) system according to an embodiment. A steering shaft (steering shaft, handle shaft) 2 of a steering wheel (steering handle) 1 is connected to steered wheels 8L and 8R via a reduction gear (worm gear) 3 forming a reduction mechanism, universal joints 4a and 4b, a rack and pinion mechanism 5, tie rods 6a and 6b, and further via hub units 7a and 7b.

[0041] The rack and pinion mechanism 5 includes a pinion 5a connected to a pinion shaft receiving steering force from the universal joint 4b and a rack 5b meshing with the pinion 5a. The rack 5b converts rotational motion transmitted to the pinion 5a into linear motion in the vehicle width direction.

[0042] A torque sensor 10 for detecting a steering torque Th is provided on the steering shaft 2 . Also, a steering angle sensor 14 for detecting a steering angle θh of the steering wheel 1 is provided on the steering shaft 2 .

[0043] Furthermore, a motor 20 that assists the steering force of the steering wheel 1 is connected to the steering shaft 2 via a reduction gear 3. The motor 20 may be, for example, a multi-phase motor. The following description uses an example of a three-phase motor with dual windings, in which a first coil system and a second coil system are wound within the same motor housing, rotating a common rotor using the two coil systems. However, the motor 20 may be a motor other than a dual-winding motor, and the number of phases of the motor 20 may not be three. Multiple motors 20 that assist the steering force of the steering wheel 1 may also be connected to the same steering shaft 2.

[0044] An electronic control unit (ECU) 30 that controls the electric power steering device is supplied with electric power from a battery 13 , and an ignition key signal is inputted via an ignition switch 11 .

[0045] ECU 30 calculates the current command value for the assist control command based on the steering torque Th detected by torque sensor 10, the vehicle speed Vh detected by vehicle speed sensor 12, and the steering angle θh detected by steering angle sensor 14. ECU 30 controls the current supplied to motor 20 (A-phase current I1a, B-phase current I1b, and C-phase current I1c of the first system coil, and A-phase current I2a, B-phase current I2b, and C-phase current I2c of the second system coil) using a voltage control command value obtained by applying compensation to the current command value. ECU 30 is an example of the "motor control device" described in the technical claims.

[0046] The steering angle sensor 14 is not essential. The steering angle θh can be calculated by adding the torsion angle of the torsion bar of the torque sensor 10 to the product of the motor rotation angle θm obtained by the rotation angle sensor 23a, which detects the rotation angle of the motor 20's rotating shaft, and the gear ratio of the reduction gear 3. The rotation angle sensor 23a can be, for example, a resolver that detects the motor's rotational position or a magnetic sensor that detects the magnetic field of a magnet attached to the motor 20's rotating shaft. Alternatively, the steering angle of the steered wheels 8L and 8R can be used instead of the steering angle θh. For example, the steering angle can be detected by detecting the displacement of the rack 5b.

[0047] The ECU 30 includes, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0048] The storage device may include any of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include registers, cache memory, ROM (Read Only Memory) used as a main storage device, and RAM (Random Access Memory), etc.

[0049] The functions of the ECU 30 described below are realized by, for example, a processor of the ECU 30 executing a computer program stored in a storage device.

[0050] Alternatively, the ECU 30 may be formed of dedicated hardware for executing each information processing described below.

[0051] For example, the ECU 30 may include a functional logic circuit provided in a general-purpose semiconductor integrated circuit. For example, the ECU 30 may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0052] Figure 2 This is a schematic diagram showing an example of the configuration of the ECU 30 according to the first embodiment. The ECU 30 includes a motor rotation angle detection circuit 23, a control arithmetic unit 31, a first motor current cutoff circuit 33A, a second motor current cutoff circuit 33B, a first gate drive circuit 41A, a second gate drive circuit 41B, a first power conversion circuit (first inverter) 42A, a second power conversion circuit (second inverter) 42B, a first power supply cutoff circuit 44A, a second power supply cutoff circuit 44B, and a temperature detection circuit 45.

[0053] The ECU 30 is connected to a power wiring PW via a connector CNT, which transmits electric power from the battery 13. A positive-side line Lp of the power wiring PW is connected to the control arithmetic device 31 via a noise filter circuit formed by a choke coil L and ceramic capacitors C1 and C2. The positive-side line Lp of the power wiring PW branches at a branch point Pb into a first positive-side line LpA and a second positive-side line LpB.

[0054] The first positive-side line LpA and the second positive-side line LpB are power supply lines for supplying power to the first power conversion circuit 42A and the second power conversion circuit 42B, respectively, and are connected to the first power shutoff circuit 44A and the second power shutoff circuit 44B, respectively.

[0055] One end of the choke coil L is connected to the positive-side line Lp and one end of the ceramic capacitor C1. The other end of the choke coil L is connected to one end of the ceramic capacitor C2, the control arithmetic device 31, and the branch point Pb. The other ends of the ceramic capacitors C1 and C2 are grounded. Meanwhile, the negative-side line of the power wiring PW is connected to the ground line of the ECU 30.

[0056] Signals of the steering torque Th detected by the torque sensor 10 , the vehicle speed Vh detected by the vehicle speed sensor 12 , and the steering angle θh detected by the steering angle sensor 14 are transmitted to the control computing device 31 via the connector CNT.

[0057] The control arithmetic device 31 calculates a current command value, serving as a control target value for the drive current of the motor 20, based at least on the steering torque Th. The control arithmetic device 31 then applies compensation, etc. to the current command value to obtain voltage control command values V1a, V1b, V1c, V2a, V2b, and V2c, which are then output to the first gate drive circuit 41A and the second gate drive circuit 41B. The voltage control command values V1a, V1b, and V1c are the A-phase, B-phase, and C-phase voltage control command values, respectively, for the first system coil. The voltage control command values V2a, V2b, and V2c are the A-phase, B-phase, and C-phase voltage control command values, respectively, for the second system coil.

[0058] The first power supply cutoff circuit 44A has a series circuit structure in which the sources of two FETs QC1 and QC2 are connected to each other, with the parasitic diodes in reverse orientation. The drain of FET QC1 is connected to the first positive-side line LpA, and the drain of FET QC2 is connected to the drains of FETs Q1, Q3, and Q5 of the first power conversion circuit 42A. The control arithmetic device 31 outputs a control signal SpA to the first gate drive circuit 41A, which controls the energization and de-energization of the first power supply cutoff circuit 44A. The first gate drive circuit 41A outputs gate signals for FETs QC1 and QC2 based on the control signal SpA, thereby energizing or de-energizing the power supply current from the battery 13 to the first power conversion circuit 42A.

[0059] Furthermore, the second power supply cutoff circuit 44B has a series circuit structure in which the sources of two FETs QD1 and QD2 are connected to each other, with the parasitic diodes in opposite directions. The drain of FET QD1 is connected to the second positive-side line LpB, and the drain of FET QD2 is connected to the drains of FETs Q1, Q3, and Q5 of the second power conversion circuit 42B. The control arithmetic device 31 outputs a control signal SpB to the second gate drive circuit 41B, which controls the energization and de-energization of the second power supply cutoff circuit 44B. The second gate drive circuit 41B outputs gate signals for FETs QD1 and QD2 based on the control signal SpB, thereby energizing or de-energizing the power supply current from the battery 13 to the second power conversion circuit 42B.

[0060] When voltage control command values V1a, V1b, and V1c are input from the control arithmetic device 31, the first gate drive circuit 41A generates six gate signals by pulse-width modulating (PWM) these voltage control command values V1a, V1b, and V1c and a triangular wave carrier signal. These gate signals are then output to the first power conversion circuit 42A.

[0061] When voltage control command values V2a, V2b, and V2c are input from the control arithmetic device 31, the second gate drive circuit 41B generates six gate signals by pulse-width modulating (PWM) these voltage control command values V2a, V2b, and V2c and a triangular wave carrier signal. These gate signals are then output to the second power conversion circuit 42B.

[0062] The first power conversion circuit 42A includes three switching arms SWAa, SWAb, and SWAc each including FETs as switching elements, and an electrolytic capacitor CA.

[0063] The switching arms SWAa, SWAb, and SWAc are connected in parallel. The A-phase switching arm SWAa includes FETs Q1 and Q2 connected in series, the B-phase switching arm SWAb includes FETs Q3 and Q4 connected in series, and the C-phase switching arm SWAc includes FETs Q5 and Q6 connected in series. Gate signals output from the first gate drive circuit 41A are input to the gates of each of the FETs Q1-Q6. These gate signals cause the A-phase current I1a, B-phase current I1b, and C-phase current I1c to flow from the connection points between the FETs in the switching arms SWAa, SWAb, and SWAc via the first motor current interruption circuit 33A to the A-phase winding, B-phase winding, and C-phase winding of the first system coil of the motor 20.

[0064] The electrolytic capacitor CA has a noise removal function and a power supply assisting function for the first power conversion circuit 42A.

[0065] The second power conversion circuit 42B includes three switching arms SWBa, SWBb, and SWBc each including FETs as switching elements, and an electrolytic capacitor CB.

[0066] The switching arms SWBa, SWBb, and SWBc are connected in parallel. The A-phase switching arm SWBa includes FETs Q1 and Q2 connected in series, the B-phase switching arm SWBb includes FETs Q3 and Q4 connected in series, and the C-phase switching arm SWBc includes FETs Q5 and Q6 connected in series. A gate signal output from the second gate drive circuit 41B is input to the gates of each of the FETs Q1 to Q6. These gate signals cause the A-phase current I2a, B-phase current I2b, and C-phase current I2c to flow from the connection points between the FETs in the switching arms SWBa, SWBb, and SWBc via the second motor current interruption circuit 33B to the A-phase winding, B-phase winding, and C-phase winding of the second system coil of the motor 20.

[0067] The electrolytic capacitor CB has a noise removal function and a power supply assisting function for the second power conversion circuit 42B.

[0068] Alternatively, the first power conversion circuit 42A and the second power conversion circuit 42B may supply three-phase current to two different motors that generate steering assist forces for assisting steering of the steering wheel 1. The two different motors may be connected to the same steering shaft 2 via a reduction gear, for example.

[0069] Current detection circuits 39A1, 39B1, and 39C1 are provided on the source side of the FETs Q2, Q4, and Q6, which form the lower arms of the switching arms SWAa, SWAb, and SWAc of the first power conversion circuit 42A. Current detection circuits 39A1, 39B1, and 39C1 detect the downstream currents of the switching arms SWAa, SWAb, and SWAc, respectively, as the A-phase current, B-phase current, and C-phase current of the first system coil, and output their detected values I1ad, I1bd, and I1cd.

[0070] Current detection circuits 39A2, 39B2, and 39C2 are provided on the source side of the FETs Q2, Q4, and Q6, which form the lower arms of the switching arms SWBa, SWBb, and SWBc of the second power conversion circuit 42B. Current detection circuits 39A2, 39B2, and 39C2 detect the downstream currents of the switching arms SWBa, SWBb, and SWBc as the A-phase current, B-phase current, and C-phase current of the second system coil, respectively, and output their detected values I2ad, I2bd, and I2cd.

[0071] The first motor current cutoff circuit 33A includes three current cutoff FETs QA1, QA2, and QA3. The source of FET QA1 is connected to the connection point of FETs Q1 and Q2 in the switching arm SWAa of the first power conversion circuit 42A, and its drain is connected to the A-phase winding of the first system coil of the motor 20. The source of FET QA2 is connected to the connection point of FETs Q3 and Q4 in the switching arm SWAb, and its drain is connected to the B-phase winding of the first system coil. The source of FET QA3 is connected to the connection point of FETs Q5 and Q6 in the switching arm SWAc, and its drain is connected to the C-phase winding of the first system coil.

[0072] The control arithmetic device 31 outputs a control signal SmA to the first gate drive circuit 41A, which controls the energization and deenergization of the first motor current cutoff circuit 33A. The first gate drive circuit 41A outputs gate signals for the FETs QA1-QA3 based on the control signal SmA, thereby switching the A-phase current I1a, B-phase current I1b, and C-phase current I1c flowing from the first power conversion circuit 42A to the motor 20.

[0073] The second motor current cutoff circuit 33B includes three current cutoff FETs: QB1, QB2, and QB3. The source of FET QB1 is connected to the connection point of FETs Q1 and Q2 of the switching arm SWBa of the second power conversion circuit 42B, and its drain is connected to the A-phase winding of the second system coil of the motor 20. The source of FET QB2 is connected to the connection point of FETs Q3 and Q4 of the switching arm SWBb, and its drain is connected to the B-phase winding of the second system coil. The source of FET QB3 is connected to the connection point of FETs Q5 and Q6 of the switching arm SWBc, and its drain is connected to the C-phase winding of the second system coil.

[0074] The control arithmetic device 31 outputs a control signal SmB to the second gate drive circuit 41B, which controls the energization and deenergization of the second motor current cutoff circuit 33B. The second gate drive circuit 41B outputs gate signals to the FETs QB1-QB3 based on the control signal SmB, thereby switching the A-phase current I2a, B-phase current I2b, and C-phase current I2c flowing from the second power conversion circuit 42B to the motor 20.

[0075] The motor rotation angle detection circuit 23 obtains a detection value from the rotation angle sensor 23a and detects a motor rotation angle θm, which is the rotation angle of the rotation shaft of the motor 20. The motor rotation angle detection circuit 23 outputs the motor rotation angle θm to the control arithmetic device 31.

[0076] The temperature detection circuit 45 includes a temperature sensor 45a located near the first power conversion circuit 42A and the second power conversion circuit 42B. The temperature sensor 45a is an example of a "temperature detection element." Furthermore, the temperature sensor 45a does not need to be located near the first power conversion circuit 42A and the second power conversion circuit 42B. The temperature sensor 45a can be located in a location on the ECU 30 that is susceptible to heat generation.

[0077] The temperature detection circuit 45 detects the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B based on the output of the temperature sensor 45a and outputs a detection signal Sd1 indicating the detection result. In the following description, the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B detected by the temperature detection circuit 45 (the temperatures indicated by the detection signal Sd1) may be referred to as "ECU temperature detection value Te1."

[0078] For example, the temperature sensor 45a may be a thermistor, and the temperature detection circuit 45 may include a thermistor processing circuit that detects the temperature of the first power conversion circuit 42A and the second power conversion circuit 42B based on the resistance value of the thermistor.

[0079] Figure 3: This is a circuit diagram of an example of a temperature detection circuit 45. The temperature detection circuit 45 includes a voltage divider circuit formed by connecting a thermistor 45a, serving as a temperature sensor, and a fixed resistor R in series, and a capacitor Ct. The voltage divider circuit, consisting of the thermistor 45a and the fixed resistor R, divides a predetermined voltage Vcc by the ratio of the resistance value of the thermistor 45a to the resistance value of the fixed resistor R, and outputs the resulting voltage divider value as a detection signal Sd1 to the control arithmetic device 31.

[0080] Reference Figure 2 The control arithmetic device 31 obtains the detection values I1ad, I1bd, and I1cd of the A-phase current, B-phase current, and C-phase current of the first system coil, the detection values I2ad, I2bd, and I2cd of the A-phase current, B-phase current, and C-phase current of the second system coil, and the detection signal Sd1 from the temperature detection circuit 45 via the A / D conversion unit 31a.

[0081] The control arithmetic unit 31 includes a temperature measuring unit 31b that measures the ECU temperature, which is the temperature of the first power conversion circuit 42A and the second power conversion circuit 42B, and estimates the motor temperature, which is the temperature of the motor 20 (for example, the temperature of the coil windings of the motor 20). The temperature measuring unit 31b measures the ECU temperature based on the ECU temperature detection value Te1 indicated by the detection signal Sd1 from the temperature detection circuit 45. Furthermore, the temperature measuring unit 31b estimates the motor temperature based on the ECU temperature detection value Te1 and the motor current detection values I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd flowing through the motor 20.

[0082] Figure 4 This is a block diagram showing an example of the functional configuration of the temperature measuring unit 31 b according to the first embodiment. The temperature measuring unit 31 b includes an ECU temperature measuring unit 50 , a sensor abnormality determination unit 51 , an ECU temperature estimating unit 52 , an increase value estimating unit 53 , and an adder 54 .

[0083] The ECU temperature measuring unit 50 measures the ECU temperature Te, which is the temperature of the first power conversion circuit 42A and the second power conversion circuit 42B, based on the ECU temperature detection value Te1.

[0084] The sensor abnormality determination unit 51 determines whether or not there is an abnormality in the temperature detection circuit 45. The sensor abnormality determination unit 51 outputs an abnormality determination signal Sa indicating the determination result.

[0085] The ECU 30 of the first embodiment includes a single temperature detection circuit (temperature detection circuit 45). In the following description of the first embodiment, a case where the temperature detection circuit 45 is abnormal is referred to as "temperature detection circuit abnormality," and a case where the temperature detection circuit 45 is not abnormal is referred to as "temperature detection circuit normal."

[0086] On the other hand, the ECU 30 of the second and third embodiments described below includes multiple temperature detection circuits (a first temperature detection circuit 45 and a second temperature detection circuit 46). In the description of the second and third embodiments described below, a case where at least one of the first and second temperature detection circuits 45 and 46 is abnormal is described as "temperature detection circuit abnormality," and a case where neither the first and second temperature detection circuits 45 and 46 are abnormal (i.e., both the first and second temperature detection circuits 45 and 46 are normal) is described as "temperature detection circuit normal."

[0087] The sensor abnormality determination unit 51 can determine that the temperature detection circuit 45 is abnormal when the detection signal Sd1 is outside the predetermined range, and can determine that the temperature detection circuit is not abnormal (normal) when the detection signal Sd1 is within the predetermined range.

[0088] For example, in Figure 3 In the example of the temperature detection circuit 45 shown, if the thermistor 45a is disconnected due to an abnormality, the detection signal Sd1 rises and becomes greater than the upper limit of the predetermined range, thereby detecting an abnormality in the temperature detection circuit 45. Furthermore, if the thermistor 45a is short-circuited due to an abnormality, the detection signal Sd1 falls and becomes less than the lower limit of the predetermined range, thereby detecting an abnormality in the temperature detection circuit 45.

[0089] For example, even if the detection signal Sd1 reaches a value outside the specified range, the sensor abnormality determination unit 51 can determine that the temperature detection circuit is not abnormal until the detection signal Sd1 remains outside the specified range for a specified time TL. The sensor abnormality determination unit 51 can determine that the temperature detection circuit is abnormal if the detection signal Sd1 remains outside the specified range for a specified time TL or longer. The specified time TL can be, for example, 1 second. This prevents erroneous detection of an abnormality in the temperature detection circuit 45 due to temporary fluctuations in the detection signal Sd1, for example, caused by noise.

[0090] Furthermore, if the sensor abnormality determination unit 51 detects an abnormality in the temperature detection circuit, the sensor abnormality determination unit 51 maintains the state of detecting an abnormality in the temperature detection circuit until the ignition switch 11 is turned off. When the ignition switch 11 is turned off, the sensor abnormality determination unit 51 is reset to the normal state.

[0091] The ECU temperature estimation unit 52 estimates the temperatures of the first and second power conversion circuits 42A and 42B based on the ECU temperature detection value Te1 indicated by the detection signal Sd1 of the temperature detection circuit 45 and the abnormality determination signal Sa output from the sensor abnormality determination unit 51 .

[0092] Hereinafter, the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B estimated by the ECU temperature estimation unit 52 may be referred to as "ECU temperature estimate Tes." The ECU temperature estimation unit 52 is an example of a "first temperature estimation unit," and the ECU temperature estimate Tes is an example of a "first temperature estimate value."

[0093] When the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal, the ECU temperature estimation unit 52 may output the ECU temperature detection value Te1 indicated by the detection signal Sd1 as the ECU temperature estimation value Tes.

[0094] When the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the ECU temperature estimation unit 52 outputs a value obtained by gradually increasing the ECU temperature detection value Te1 detected by the temperature detection circuit 45 before the temperature detection circuit is determined to be abnormal at a constant increase rate ΔTr [°C / second] to a specified set value Ts as the ECU temperature estimation value Tes.

[0095] For example, when the detection signal Sd1 of the temperature detection circuit 45 is within a predetermined range, the ECU temperature estimation unit 52 may temporarily hold the ECU temperature detection value Te1 detected by the temperature detection circuit 45 as the held value Thd and sequentially update it.

[0096] At time t1, when detection signal Sd1 from temperature detection circuit 45 becomes a value outside the specified range, ECU temperature estimation unit 52 stops updating held value Thd. While detection signal Sd1 remains outside the specified range, held value Thd held immediately before time t1 is output as ECU temperature estimate value Tes until a specified time TL has elapsed.

[0097] That is, the ECU temperature detection value Te1 immediately before the output signal of the temperature detection element becomes a value outside the specified range is maintained as the held value Thd, and while the state in which the detection signal Sd1 is a value outside the specified range continues, the held value Thd is output as the ECU temperature estimation value Tes until the specified time TL has passed.

[0098] When the state in which the detection signal Sd1 is a value outside the specified range continues even at time t2 after the specified time TL from time t1, the ECU temperature estimation value 52 is output as the ECU temperature estimation value Tes, which is the value gradually increased from the held value Thd maintained immediately before time t1 at a constant increase rate ΔTr [°C / second] to the specified set value Ts.

[0099] When the detection signal Sd1 returns to a value within the predetermined range before time t2, the ECU temperature estimation unit 52 outputs the ECU temperature detection value Te1 indicated by the detection signal Sd1 received from the temperature detection circuit 45 as the ECU temperature estimation value Tes and restarts updating of the held value Thd.

[0100] Figure 5 This is an explanatory diagram schematically showing changes in the ECU temperature estimate value Tes when an abnormality occurs in the temperature detection circuit.

[0101] During the period before time t1, the detection signal Sd1 from the temperature detection circuit 45 is within a predetermined range. The ECU temperature estimation unit 52 outputs the ECU temperature detection value Te1 indicated by the detection signal Sd1 as the ECU temperature estimation value Tes. Furthermore, the ECU temperature detection value Te1 detected by the temperature detection circuit 45 is temporarily held as a held value Thd and is subsequently updated.

[0102] When the detection signal Sd1 of the temperature detection circuit 45 becomes a value outside the specified range at time t1, the updating of the held value Thd is stopped (i.e., the held value Thd just before the detection signal Sd1 becomes a value outside the specified range is held), and the held value Thd is output as the ECU temperature estimation value Tes.

[0103] If the detection signal Sd1 continues to be a value outside the prescribed range even at time t2 after a prescribed time TL from time t1, the ECU temperature estimation unit 52 outputs a value that gradually increases from the held value Thd at a constant increase rate ΔTr [°C / second] to the prescribed set value Ts as the ECU temperature estimation value Tes at time t2.

[0104] Reference Figure 4. The increase value estimation unit 53 estimates the increase value Rt of the motor temperature caused by the motor current flowing through the motor 20. For example, the increase value estimation unit 53 can estimate the increase value Rt by subtracting the heat dissipation of the motor 20 from the integral value of the sum of the squares of the detected values I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd of the motor current. The adder 54 calculates the value obtained by adding the increase value Rt to the ECU temperature estimation value Tes as the motor temperature estimation value Tm. The adder 54 is an example of the "second temperature estimation unit" described in the technical solution, and the motor temperature estimation value Tm is an example of the "second temperature estimation value" described in the technical solution.

[0105] Reference Figure 2 The control arithmetic device 31 limits the motor current flowing through the motor 20 when the ECU temperature Te exceeds a threshold value or when the motor temperature estimated value Tm exceeds a threshold value.

[0106] Figure 6 This is a block diagram of an example of the functional structure of the control operation device 31 of the first embodiment. Figure 6 Although only the functional structure of the first system coils for driving the motor 20 is described, the functional structure of the second system coils for driving the motor 20 also has the same structure.

[0107] The control operation device 31 includes a current command value operation unit 60, a first current limiting unit 61, subtractors 62 and 63, a second current limiting unit 64, a proportional-integral (PI) control unit 65, a two-phase / three-phase conversion unit 66, a three-phase / two-phase conversion unit 67, and an angular velocity conversion unit 68, and drives the motor 20 through vector control.

[0108] The current command value calculation unit 60 calculates a q-axis current command value Iq0 and a d-axis current command value Id0 to be passed to the motor 20 based on the steering torque Th, the vehicle speed Vh, the motor rotation angle θm of the motor 20 , and the rotational angular velocity ω of the motor 20 .

[0109] The first current limiting unit 61 limits the q-axis current command value Iq0 and the d-axis current command value Id0 based on the abnormality determination signal Sa output from the temperature measuring unit 31 b , the ECU temperature Te, and the motor temperature estimated value Tm, thereby calculating the limited q-axis current command value Iq1 and the d-axis current command value Id1 .

[0110] For example, when the ECU temperature Te exceeds a predetermined first threshold value Ta1, the first current limiting unit 61 limits the q-axis current command value Iq0 and the d-axis current command value Id0 as the ECU temperature Te increases, thereby calculating the q-axis current command value Iq1 and the d-axis current command value Id1. In other words, the q-axis current command value Iq1 and the d-axis current command value Id1 can be calculated so that they gradually decrease as the ECU temperature Te increases.

[0111] Alternatively, for example, when estimated motor temperature value Tm exceeds second threshold value Tb1, first current limiting unit 61 may further limit q-axis current command value Iq0 and d-axis current command value Id0 as estimated motor temperature value Tm increases, thereby calculating q-axis current command value Iq1 and d-axis current command value Id1. Specifically, q-axis current command value Iq1 and d-axis current command value Id1 may be calculated so that they gradually decrease as estimated motor temperature value Tm increases.

[0112] Furthermore, for example, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the first current limiting unit 61 may calculate q-axis current command value Iq1 and d-axis current command value Id1 that are smaller than q-axis current command value Iq0 and d-axis current command value Id0. For example, the q-axis current command value Iq1 and d-axis current command value Id1 may be calculated by limiting the q-axis current command value Iq0 and d-axis current command value Id0 to 50%.

[0113] For example, the first current limiting unit 61 may set a limiting gain K1 corresponding to the abnormality determination signal Sa, a limiting gain K2 corresponding to the ECU temperature Te, and a limiting gain K3 corresponding to the motor temperature estimated value Tm.

[0114] The first current limiting unit 61 may set the limit gain K1 to “1” when the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal, and may set the limit gain K1 to “0.5” when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal.

[0115] When the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal and the ECU temperature Te exceeds the first threshold value Ta1, the first current limiting unit 61 may gradually decrease the value of the limit gain K2 from "1" to "0" as the ECU temperature Te rises from the first threshold value Ta1 to the third threshold value Ta2. The value of the limit gain K2 may gradually decrease linearly from "1" to "0" as the ECU temperature Te rises from the first threshold value Ta1 to the third threshold value Ta2.

[0116] When the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the first current limiting unit 61 may set the value of the limit gain K2 to “1”.

[0117] The first current limiting unit 61 may also provide a hysteresis characteristic for the limiting gain K2. For example, if the ECU temperature Te exceeds the first threshold Ta1 while the limiting gain K2 is set to "1," the limiting gain K2 value is gradually reduced from "1" as the ECU temperature Te rises from the first threshold Ta1. As long as the ECU temperature Te does not reach the third threshold Ta2 (i.e., as long as the limiting gain K2 value does not reach "0"), the first current limiting unit 61 decreases or increases the limiting gain K2 value within the range of "1" to "0" as the ECU temperature Te fluctuates within the range of the first threshold Ta1 to the third threshold Ta2.

[0118] After the ECU temperature Te reaches the third threshold value Ta2 (i.e., the limit gain K2 value reaches "0"), the first current limiting unit 61 does not increase the limit gain K2 value from "0" even if the ECU temperature Te is lower than the third threshold value Ta2. When the ECU temperature Te drops below a fourth threshold value Ta3, which is lower than the third threshold value Ta2, the first current limiting unit 61 may begin increasing the limit gain K2. As the ECU temperature Te drops to a fifth threshold value Ta4, which is lower than the first threshold value Ta1, the limit gain K2 value may be gradually increased from "0" to "1." For example, the fourth threshold value Ta3 may be set to a value lower than the first threshold value Ta1 or a value higher than the first threshold value Ta1.

[0119] As long as the ECU temperature Te does not reach the fifth threshold value Ta4 (that is, as long as the value of the limiting gain K2 does not become "1"), the first current limiting unit 61 decreases or increases the value of the limiting gain K2 within the range of "0" to "1" in accordance with the fluctuation of the ECU temperature Te within the range of the fourth threshold value Ta3 to the fifth threshold value Ta4.

[0120] When estimated motor temperature Tm exceeds second threshold value Tb1, first current limiting unit 61 may gradually decrease the value of limit gain K3 from "1" to "0" as estimated motor temperature Tm increases from second threshold value Tb1 to sixth threshold value Tb2. For example, the value of limit gain K3 may be linearly decreased from "1" to "0" as estimated motor temperature Tm increases from second threshold value Tb1 to sixth threshold value Tb2.

[0121] Alternatively, the limit gain K3 may have the same hysteresis characteristic as that of the limit gain K2 described above.

[0122] The first current limiting unit 61 calculates a q-axis current command value Iq1 and a d-axis current command value Id1 by limiting the q-axis current command value Iq0 and the d-axis current command value Id0 based on the limit gains K1 , K2 , and K3 .

[0123] For example, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal (that is, when the limiting gain K1 = "1"), the first current limiting unit 61 can, for example, select any smaller gain K4 = min (K2, K3) between K2 and K3, and calculate the product of the q-axis current command value Iq0 and the d-axis current command value Id0 multiplied by the gain K4 as the q-axis current command value Iq1 = K4 × Iq0 and the d-axis current command value Id1 = K4 × Id0.

[0124] Furthermore, for example, the products of multiplying the q-axis current command value Iq0 and the d-axis current command value Id0 by the gains K2 and K3 can be calculated as q-axis current command value Iq1 = K2 × K3 × Iq0 and d-axis current command value Id1 = K2 × K3 × Id0 .

[0125] For example, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal (for example, when the limiting gain K1 = "0.5"), the first current limiting unit 61 can calculate the product of the q-axis current command value Iq0 and the d-axis current command value Id0 multiplied by the limiting gains K1 and K3 as the q-axis current command value Iq1 = K1×K3×Iq0 and the d-axis current command value Id1 = K1×K3×Id0.

[0126] On the other hand, the detection values I1ad, I1bd, and I1cd of the A-phase current, B-phase current, and C-phase current of the first system coil of the motor 20 detected by the current detection circuits 39A1, 39B1, and 39C1 are converted into currents id and iq of the d-q2 axis by the three-phase / two-phase conversion unit 67.

[0127] Subtractors 62 and 63 respectively subtract the fed-back currents iq and id from the limited q-axis current command value Iq1 and d-axis current command value Id1 to calculate q-axis deviation current Δq0 and d-axis deviation current Δd0 .

[0128] The second current limiting unit 64 limits the upper limit values of the q-axis deviation current Δq0 and the d-axis deviation current Δd0 . The limited q-axis deviation current Δq and d-axis deviation current Δd are input to the PI control unit 65 .

[0129] The PI control unit 65 calculates voltage command values vq and vd that set the q-axis deviation current Δq and the d-axis deviation current Δd to zero. The two-phase / three-phase conversion unit 66 converts the voltage command values vd and vq into A-phase voltage control command values V1a, B-phase voltage command values V1b, and C-phase voltage command values V1c, respectively, for the first system of the motor 20 and outputs them to the first gate drive circuit 41A.

[0130] The angular velocity converter 68 calculates the rotational angular velocity ω of the motor 20 based on the temporal change in the motor rotational angle θm. The motor rotational angle θm and the rotational angular velocity ω are input to the current command value calculation unit 60 and used for vector control.

[0131] Figure 7 This is a flowchart of an example of the motor control method according to the first embodiment.

[0132] In step S1 , the ECU temperature measuring unit 50 , the sensor abnormality determination unit 51 , and the ECU temperature estimating unit 52 obtain a detection signal Sd1 from the temperature detection circuit 45 .

[0133] In step S2 , the ECU temperature measuring unit 50 measures the ECU temperature Te based on the ECU temperature detection value Te1 .

[0134] In step S3, the first current limiting unit 61 determines whether the ECU temperature Te exceeds the first threshold value Ta1. If the ECU temperature Te exceeds the first threshold value Ta1 (step S3: Yes), the process proceeds to step S4. If the ECU temperature Te does not exceed the first threshold value Ta1 (step S3: No), the process proceeds to step S5.

[0135] In step S4 , the first current limiting unit 61 limits the q-axis current command value Iq0 and the d-axis current command value Id0 .

[0136] In step S5 , the current detection circuits 39A1 , 39B1 , 39C1 , 39A2 , 39B2 , and 39C2 detect the motor currents I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd, respectively.

[0137] In step S6 , the increase value estimating unit 53 estimates the increase value Rt of the motor temperature caused by the motor current based on the motor currents I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd.

[0138] In step S7, the sensor abnormality determination unit 51 determines whether the temperature detection circuit is abnormal. If the temperature detection circuit is abnormal (step S7: Yes), the process proceeds to step S9. If the temperature detection circuit is not abnormal (step S7: No), the process proceeds to step S8.

[0139] In step S8 , the ECU temperature estimation unit 52 sets the ECU temperature detection value Te1 as the ECU temperature estimation value Tes. Thereafter, the process proceeds to step S11 .

[0140] In step S9, the first current limiting unit 61 limits the q-axis current command value Iq0 and the d-axis current command value Id0. In step S10, the ECU temperature estimating unit 52r gradually increases the ECU temperature estimate Tes at a constant rate of increase ΔT to a predetermined set value Ts. For example, the ECU temperature estimate Tes is increased by a predetermined step amount per unit time. The process then proceeds to step S11.

[0141] In step S11 , the adder 54 calculates a value obtained by adding the increase value Rt to the ECU temperature estimate value Tes as the motor temperature estimate value Tm.

[0142] In step S12, the first current limiting unit 61 determines whether the estimated motor temperature value Tm exceeds the second threshold value Tb1. If the estimated motor temperature value Tm exceeds the second threshold value Tb1 (step S12: Yes), the process proceeds to step S13. If the estimated motor temperature value Tm does not exceed the second threshold value Tb1 (step S12: No), the process ends.

[0143] In step S13 , the first current limiting unit 61 limits the q-axis current command value Iq0 and the d-axis current command value Id0 , and then the process ends.

[0144] (Effects of the First Embodiment)

[0145] (1) The ECU 30 includes: a first power conversion circuit 42A and a second power conversion circuit 42B, which control the motor current flowing through the motor 20; a temperature detection circuit 45, which has a temperature sensor 45a arranged near the first power conversion circuit 42A and the second power conversion circuit 42B; a rise value estimation unit 53, which estimates the rise value Rt of the temperature of the motor 20 caused by the motor current; a sensor abnormality determination unit 51, which determines whether the temperature detection circuit 45 is abnormal; and an ECU temperature estimation unit 52, which uses the detected temperature of the temperature detection circuit 45 as the ECU temperature estimation unit when the sensor abnormality determination unit 51 determines that the temperature detection circuit 45 is normal. The temperature estimation value Tes is output. When the sensor abnormality determination unit 51 determines that the temperature detection circuit 45 is abnormal, the ECU temperature estimation unit 52 gradually increases the detected temperature detected by the temperature detection circuit 45 at a constant increasing rate to a predetermined set value Ts and outputs it as the ECU temperature estimation value Tes; the adder 54 calculates the value obtained by adding the ECU temperature estimation value Tes and the rise value Rt as the motor temperature estimation value Tm; and the first current limiting unit 61, when the motor temperature estimation value Tm exceeds a specified threshold value, the first current limiting unit 61 limits the motor current in a manner that the motor current gradually decreases as the motor temperature estimation value Tm increases.

[0146] The sensor abnormality determination unit 51 determines that the temperature detection circuit 45 is normal when the output signal of the temperature sensor 45a is within a predetermined range, and determines that the temperature detection circuit 45 is abnormal when the output signal of the temperature sensor 45a is outside the predetermined range.

[0147] This prevents the motor current from being excessively limited due to a sudden increase in the estimated motor temperature value Tm when an abnormality occurs in the temperature detection circuit 45. Furthermore, by limiting the motor current so that the motor current gradually decreases even when the estimated motor temperature value Tm exceeds a predetermined threshold, it is possible to suppress increases in the estimated motor temperature value Tm and prevent the motor current from being excessively limited.

[0148] (2) The ECU temperature estimation unit 52 can maintain the detected temperature detected by the temperature detection circuit 45 as a holding value. When it is determined that the temperature detection circuit 45 is abnormal, the value that gradually increases at a constant increasing rate from the holding value maintained before the temperature detection circuit 45 is determined to be abnormal to a prescribed set value Ts as the ECU temperature estimation value Tes is output.

[0149] Thus, when an abnormality occurs in the temperature detection circuit 45 , it is possible to prevent the ECU temperature estimate value Tes from being calculated based on the abnormal detection value.

[0150] (3) The sensor abnormality determination unit 51 may determine that the temperature detection circuit is abnormal if the output signal of the temperature detection element remains outside the specified range for a specified period of time or longer. The ECU temperature estimation unit 52 may maintain the temperature detected by the temperature detection circuit 45 as a hold value, and output a value that gradually increases at a constant rate over time from the hold value immediately before the output signal of the temperature sensor 45a becomes outside the specified range to a specified set value as the ECU temperature estimate value Tes.

[0151] This can prevent erroneous detection of an abnormality in the temperature detection circuit 45 due to a temporary change in the output signal of the temperature sensor 45 a caused by the influence of noise or the like.

[0152] (4) The electric power steering device includes an ECU 30 and a motor 20 controlled by the ECU 30, and the motor 20 applies steering assist force to the vehicle's steering system. The electric power steering device includes a torque sensor 10 for detecting the steering torque of the steering wheel 1, and the ECU 30 includes a current command value calculation unit 60 for setting a current command value for the motor current flowing through the motor 20 based on at least the steering torque. The current control of the motor current supplied to the electric motor can be made redundant by the first power conversion circuit 42A and the second power conversion circuit 42B. The first current limiting unit 61 can limit the motor current flowing through the motor 20 to a current smaller than the current command value when it is determined that the temperature detection circuit is abnormal. Thus, the electric power steering device can limit the motor current in such a way that the temperature of the motor current control circuit is below the allowable temperature.

[0153] (Second embodiment)

[0154] In the ECU 30 of the second embodiment, the temperature detection circuits for detecting the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B are made redundant.

[0155] Figure 8 1 is a schematic diagram showing an example of the configuration of the ECU 30 of the second embodiment. The ECU 30 of the second embodiment includes a first temperature detection circuit 45 and a second temperature detection circuit 46 as the temperature detection circuit 45 of the first embodiment. The other components of the ECU 30 of the second embodiment are the same as those of the first embodiment.

[0156] In addition, descriptions of components and functions common to the ECU 30 of the first embodiment are omitted. In the following description, the temperature sensor 45a of the first temperature detection circuit 45 is referred to as "first temperature sensor 45a".

[0157] The second temperature detection circuit 46 includes a second temperature sensor 46a disposed near the first power conversion circuit 42A and the second power conversion circuit 42B. The first temperature sensor 45a and the second temperature sensor 46a are examples of a "first temperature detection element" and a "second temperature detection element," respectively. Furthermore, the second temperature sensor 46a does not need to be disposed near the first power conversion circuit 42A and the second power conversion circuit 42B. The second temperature sensor 46a can be disposed in a location on the ECU 30 that is susceptible to heat generation.

[0158] The second temperature detection circuit 46 detects the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B based on the output of the second temperature sensor 46a, and outputs a detection signal Sd2 indicating the detection result. In the following description, the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B detected by the second temperature detection circuit 46 (the temperatures indicated by the detection signal Sd2) may be referred to as "ECU temperature detection value Te2."

[0159] The second temperature detection circuit 46 may have the same structure as the first temperature detection circuit 45. For example, the second temperature sensor 46a of the second temperature detection circuit 46 may be a thermistor with the same characteristics as the first temperature sensor 45a of the first temperature detection circuit 45, and the fixed resistors R of the first and second temperature detection circuits 45 and 46 may have the same resistance value.

[0160] The control arithmetic device 31 obtains the detection signal Sd2 from the second temperature detection circuit 46 via the A / D converter 31a. The temperature measuring unit 31b estimates the motor temperature based on the ECU temperature detection values Te1 and Te2 indicated by the detection signals Sd1 and Sd2 from the first and second temperature detection circuits 45 and 46, and the motor current detection values I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd flowing through the motor 20.

[0161] Figure 9 1 is a block diagram of an example of the functional configuration of the temperature measuring unit 31b of the second embodiment. The temperature measuring unit 31b includes a sensor abnormality determination unit 51, an ECU temperature estimation unit 52, an increase value estimation unit 53, and an adder 54. Figure 4 Description will be given of the components and functions common to the temperature measuring unit 31b of the first embodiment shown.

[0162] The sensor abnormality determination unit 51 determines whether or not at least one of the first temperature detection circuit 45 and the second temperature detection circuit 46 is abnormal, and outputs an abnormality determination signal Sa indicating the determination result.

[0163] In the descriptions related to the second embodiment and the third embodiment, the situation where at least one of the first temperature detection circuit 45 and the second temperature detection circuit 46 is abnormal is recorded as "temperature detection circuit abnormality", and the situation where both the first temperature detection circuit 45 and the second temperature detection circuit 46 are not abnormal (that is, the situation where both the first temperature detection circuit 45 and the second temperature detection circuit 46 are normal) is recorded as "temperature detection circuit non-abnormal".

[0164] For example, the sensor abnormality determination unit 51 may determine that the temperature detection circuit is abnormal if the difference ΔTe between the ECU temperature detection value Te1 indicated by the detection signal Sd1 of the first temperature detection circuit 45 and the ECU temperature detection value Te2 indicated by the detection signal Sd2 of the second temperature detection circuit 46 is greater than or equal to a predetermined value ΔTt. The sensor abnormality determination unit 51 may determine that the temperature detection circuit is not abnormal if the difference ΔTe is less than the predetermined value ΔTt.

[0165] For example, the predetermined value ΔTt may be 5° C. Thus, even if a certain degree of error exists between the ECU temperature detection value Te1 and the ECU temperature detection value Te2 due to variations in components constituting the first temperature detection circuit 45 and the second temperature detection circuit 46 , it is possible to prevent erroneous detection of an abnormality in the first temperature detection circuit 45 and the second temperature detection circuit 46 .

[0166] For example, even if the difference ΔTe exceeds the predetermined value ΔTt, the sensor abnormality determination unit 51 may determine that the temperature detection circuit is not abnormal until the difference ΔTe remains at or above the predetermined value ΔTt for a predetermined time TL. The sensor abnormality determination unit 51 may determine that the temperature detection circuit is abnormal if the difference ΔTe remains at or above the predetermined value ΔTt for a predetermined time TL or longer. For example, the predetermined time TL may be 1 second. This prevents, for example, a temporary increase in the difference ΔTe due to noise or the like from falsely detecting an abnormality in the first or second temperature detection circuit 45 or 46.

[0167] The ECU temperature estimation unit 52 estimates the temperatures of the first power conversion circuit 42A and the second power conversion circuit 42B based on the ECU temperature detection value Te1 represented by the detection signal Sd1 of the first temperature detection circuit 45, the ECU temperature detection value Te2 represented by the detection signal Sd2 of the second temperature detection circuit 46, and the abnormality determination signal Sa output from the sensor abnormality determination unit 51.

[0168] If the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal, the ECU temperature estimation unit 52 may select either the ECU temperature detection value Te1 or the ECU temperature detection value Te2 to output as the ECU temperature estimation value Tes. For example, the ECU temperature estimation unit 52 may output the higher of the ECU temperature detection values Te1 and Te2 as the ECU temperature estimation value Tes, or may output the lower of the two values as the ECU temperature estimation value Tes.

[0169] When the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the ECU temperature estimation unit 52 outputs the value obtained by gradually increasing the ECU temperature detection value Te1 detected by the first temperature detection circuit 45 or the ECU temperature detection value Te2 detected by the second temperature detection circuit 46 at a constant increase rate ΔTr [°C / second] to a specified set value Ts as the ECU temperature estimation value Tes.

[0170] For example, if the sensor abnormality determination unit 51 outputs the ECU temperature detection value Te1 as the ECU temperature estimate value Tes immediately before determining that the temperature detection circuit is abnormal, the ECU temperature estimation unit 52 outputs the ECU temperature detection value Te1 as the ECU temperature estimate value Tes at time t1 when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal. The ECU temperature estimation unit 52 begins increasing the ECU temperature estimate value Tes from time t1, and outputs the value gradually increasing at a constant rate of increase ΔTr from the ECU temperature detection value Te1 detected by the first temperature detection circuit 45 at time t1 to a predetermined set value Ts as the ECU temperature estimate value Tes.

[0171] Similarly, if the sensor abnormality determination unit 51 outputs the ECU temperature detection value Te2 as the ECU temperature estimate value Tes immediately before determining that the temperature detection circuit is abnormal, the ECU temperature estimation unit 52 outputs the ECU temperature detection value Te2 as the ECU temperature estimate value Tes at time t1 when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal. The ECU temperature estimation unit 52 begins increasing the ECU temperature estimate value Tes from time t1, and outputs the value obtained by gradually increasing the ECU temperature detection value Te2 detected by the second temperature detection circuit 46 at time t1 at a constant rate of increase ΔTr until it reaches a predetermined set value Ts as the ECU temperature estimate value Tes.

[0172] The ECU temperature estimation unit 52 may change the increase rate ΔTr according to the ECU temperature detection value Te1 detected by the first temperature detection circuit 45 or the ECU temperature detection value Te2 detected by the second temperature detection circuit 46 at time t1 when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal.

[0173] For example, when the ECU temperature detection value Te1 is output as the ECU temperature estimated value Tes until immediately before the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, a lower increase rate ΔTr may be set when the ECU temperature detection value Te1 is high, compared to when the ECU temperature detection value Te1 is low. For example, the higher the ECU temperature detection value Te1, the lower the increase rate ΔTr may be set.

[0174] When the ECU temperature detection value Te2 is output as the ECU temperature estimated value Tes until immediately before the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, a lower increase rate ΔTr may be set when the ECU temperature detection value Te2 is high, compared to when the ECU temperature detection value Te2 is low. For example, the higher the ECU temperature detection value Te2, the lower the increase rate ΔTr may be set.

[0175] Figure 10 This diagram schematically illustrates the change in the ECU temperature estimate Tes when a temperature detection circuit abnormality occurs. This diagram describes a case where the ECU temperature detection value Te1 is output as the ECU temperature estimate Tes immediately before the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal. If the ECU temperature detection value Te2 is output as the ECU temperature estimate Tes, the ECU temperature detection value Te1 is replaced with the ECU temperature detection value Te2.

[0176] The solid line L1 represents the time change of the ECU temperature estimation value Tes output from the ECU temperature estimation unit 52 when the ECU temperature detection value Te1 at time t1 when the sensor abnormality judgment unit 51 judges that the temperature detection circuit is abnormal is relatively high T1, and the single-dot chain line L2 represents the time change of the ECU temperature estimation value Tes output from the ECU temperature estimation unit 52 when the ECU temperature detection value Te1 at time t1 is relatively low T2.

[0177] exist Figure 10 In the example shown, even if the difference ΔTe exceeds the predetermined value ΔTt, the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal until the difference ΔTe remains at or above the predetermined value ΔTt for a predetermined time TL. Therefore, the ECU temperature estimation unit 52 outputs the ECU temperature detection value Te1 as the ECU temperature estimate value Tes until time t1, at which the difference ΔTe remains at or above the predetermined value ΔTt for the predetermined time TL. At time t1, the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal.

[0178] When the ECU temperature detection value Te1 at time t1 is temperature T1, the ECU temperature estimation unit 52 starts to increase the ECU temperature estimation value Tes from time t1 as shown by the solid line L1, gradually increases at a constant increase rate ΔTr1 [°C / second] from temperature T1, and outputs the ECU temperature estimation value Tes that reaches the specified set value Ts at time t2.

[0179] On the other hand, when the ECU temperature detection value Te1 at time t1 is temperature T2, as shown by the single-dotted chain line L2, the ECU temperature estimation unit 52 starts to increase the ECU temperature estimation value Tes from time t1, gradually increases at a constant increase rate ΔTr2 [°C / second] from temperature T2, and outputs the ECU temperature estimation value Tes that reaches the specified set value Ts at time t3.

[0180] The sensor abnormality determination unit 51 can be configured to reduce the rate of increase ΔTr1 when the ECU temperature detection value Te1 at time t1 is relatively high (T1) compared to the rate of increase ΔTr2 when the ECU temperature detection value Te1 at time t1 is relatively low (T2). Higher-temperature objects dissipate more heat, so the temperature rise slows down when the same amount of heat is applied. The higher the ECU temperature detection value Te1 at time t1, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the lower the rate of increase ΔTr of the ECU temperature estimate Tes. This prevents the ECU temperature estimate Tes from becoming excessively high.

[0181] Figure 11 This is a block diagram of an example of the functional structure of the control operation device 31 of the second embodiment. Figure 11 Only the functional structure of the coil of the first system driving the motor 20 is described in the figure, but the functional structure of the coil of the second system driving the motor 20 also has the same structure. Figure 6 Description will be given of the common components and functions of the control arithmetic device 31 of the first embodiment shown.

[0182] The first current limiting unit 61 limits the q-axis current command value Iq0 and the d-axis current command value Id0 based on the abnormality determination signal Sa output from the temperature measuring unit 31 b and the motor temperature estimated value Tm, thereby calculating the limited q-axis current command value Iq1 and the d-axis current command value Id1.

[0183] For example, when estimated motor temperature value Tm exceeds second threshold value Tb1, first current limiting unit 61 may calculate q-axis current command value Iq0 and d-axis current command value Id0 by limiting q-axis current command value Iq0 and d-axis current command value Id0 more gradually as estimated motor temperature value Tm increases. In other words, q-axis current command value Iq1 and d-axis current command value Id1 may be calculated so that they gradually decrease as estimated motor temperature value Tm increases.

[0184] Furthermore, for example, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the first current limiting unit 61 may calculate q-axis current command values Iq1 and d-axis current command values Id1 that are smaller than the q-axis current command value Iq0 and the d-axis current command value Id0. For example, the q-axis current command values Iq1 and d-axis current command values Id1 may be calculated by limiting the q-axis current command values Iq0 and Id0 to 50%.

[0185] Furthermore, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, even when the motor temperature estimate value Tm does not exceed the second threshold value Tb1, the first current limiting unit 61 can calculate the q-axis current command value Iq1 and the d-axis current command value Id1 that are smaller than the q-axis current command value Iq0 and the d-axis current command value Id0 (for example, the q-axis current command value Iq0 and the d-axis current command value Id0 are set to 50%, respectively).

[0186] For example, the first current limiting unit 61 may set the limit gain K1 corresponding to the abnormality determination signal Sa and the limit gain K3 corresponding to the motor temperature estimated value Tm.

[0187] For example, the first current limiting unit 61 may provide a hysteresis characteristic for the limiting gain K3. For example, when the limiting gain K3 reaches "1," if the estimated motor temperature Tm exceeds the second threshold Tb1, the limiting gain K3 is gradually decreased from "1" as the estimated motor temperature Tm rises from the second threshold Tb1. As long as the estimated motor temperature Tm does not reach the sixth threshold Tb2 (i.e., as long as the limiting gain K3 does not reach "0"), the first current limiting unit 61 decreases or increases the limiting gain K3 within the range of "1" to "0" as the estimated motor temperature Tm fluctuates within the range from the second threshold Tb1 to the sixth threshold Tb2.

[0188] After the estimated motor temperature value Tm reaches the sixth threshold value Tb2 (i.e., the value of the limit gain K3 becomes "0"), the first current limiting unit 61 does not increase the value of the limit gain K3 from "0" even if the estimated motor temperature value Tm remains below the sixth threshold value Tb2. When the estimated motor temperature value Tm decreases to below the seventh threshold value Tb3, which is lower than the sixth threshold value Tb2, the first current limiting unit 61 may begin increasing the limit gain K3, gradually increasing the value of the limit gain K3 from "0" to "1" as the estimated motor temperature value Tm decreases to the eighth threshold value Tb4, which is lower than the second threshold value Tb1. For example, the seventh threshold value Tb3 may be set to a value lower than or higher than the second threshold value Tb1.

[0189] As long as the motor temperature estimate Tm does not reach the eighth threshold value Tb4 (that is, as long as the value of the limiting gain K3 does not become "1"), the first current limiting unit 61 reduces or increases the value of the limiting gain K3 within the range of "0" to "1" in response to the upward and downward fluctuation of the motor temperature estimate Tm within the range of the seventh threshold value Tb3 to the eighth threshold value Tb4.

[0190] The first current limiting unit 61 calculates the products of multiplying the q-axis current command value Iq0 and the d-axis current command value Id0 by the limit gains K1 and K3 as q-axis current command value Iq1 = K1 × K3 × Iq0 and d-axis current command value Id1 = K1 × K3 × Id0 .

[0191] Furthermore, the temperature measuring unit 31 b of the second embodiment can output the ECU temperature Te in the same manner as the temperature measuring unit 31 b of the first embodiment.

[0192] In addition, the first current limiting unit 61 of the second embodiment can limit the q-axis current command value Iq0 and the d-axis current command value Id0 based on the abnormality determination signal Sa output from the temperature measuring unit 31b, the ECU temperature Te, and the motor temperature estimated value Tm, and calculate the limited q-axis current command value Iq1 and the d-axis current command value Id1, similar to the first current limiting unit 61 of the first embodiment.

[0193] Figure 12 This is a flowchart of an example of a motor control method according to the second embodiment.

[0194] The processing of step S20 is the same as Figure 7 The processing of steps S21 to S29 is the same as that of step S1. Figure 7 The processing of steps S5 to S13 is the same.

[0195] Figure 13 This is a block diagram of an example of the functional configuration of the temperature measuring unit 31b of the modified embodiment. The temperature measuring unit 31b of the modified embodiment has Figure 9 In addition to the structure of the temperature measuring unit 31 b of the second embodiment shown, an ECU temperature measuring unit 50 is further provided.

[0196] The ECU temperature measuring unit 50 measures the ECU temperature Te, which is the temperature of the first power conversion circuit 42A and the second power conversion circuit 42B, based on the ECU temperature detection value Te1 and the ECU temperature detection value Te2. The ECU temperature measuring unit 50 can select either the ECU temperature detection value Te1 or the ECU temperature detection value Te2 and output it as the ECU temperature Te. For example, the ECU temperature measuring unit 50 can output the higher of the ECU temperature detection values Te1 and Te2 as the ECU temperature Te, or it can output the lower value as the ECU temperature Te.

[0197] (Effects of the Second Embodiment)

[0198] (1) The ECU 30 includes: a first power conversion circuit 42A and a second power conversion circuit 42B, which control the motor current flowing through the motor 20; temperature detection circuits 45 and 46, which have temperature sensors 45a and 46a arranged near the first power conversion circuit 42A and the second power conversion circuit 42B; a rise value estimation unit 53, which estimates the rise value Rt of the temperature of the motor 20 caused by the motor current; a sensor abnormality determination unit 51, which determines whether the temperature detection circuit is abnormal; and an ECU temperature estimation unit 52, which, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal, calculates the temperature detected by the temperature detection circuits 45 and 46. The temperature is output as the ECU temperature estimate Tes. When the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the value gradually increases from the detection temperature detected by the temperature detection circuits 45 and 46 at a constant increase rate ΔTr to the specified set value Ts and is output as the ECU temperature estimate Tes; the adder 54 calculates the value obtained by adding the ECU temperature estimate Tes and the rise value Rt as the motor temperature estimate Tm; and the first current limiting unit 61 limits the motor current in a manner that gradually decreases as the motor temperature estimate Tm exceeds a specified threshold value.

[0199] This prevents the motor current from being excessively limited due to a sudden increase in the estimated motor temperature value Tm if an abnormality occurs in the temperature detection circuit. Furthermore, by limiting the motor current so that the motor current gradually decreases even when the estimated motor temperature value Tm exceeds a predetermined threshold, it is possible to suppress increases in the estimated motor temperature value Tm and prevent the motor current from being excessively limited.

[0200] (2) The temperature detection circuits 45 and 46 may include temperature sensors 45a and 46a, respectively, and may output a detection signal indicating an ECU temperature detection value Te1 corresponding to the output of the temperature sensor 45a and a detection signal indicating an ECU temperature detection value Te2 corresponding to the output of the temperature sensor 46a. The sensor abnormality determination unit 51 may determine that the temperature detection circuit is abnormal when the difference ΔTe between the higher first detected temperature and the lower second detected temperature of the ECU temperature detection values Te1 and Te2 is greater than a predetermined value ΔTt. The ECU temperature estimation unit 52 may output the first detected temperature as the ECU temperature estimation value Tes when it is determined that the temperature detection circuit is normal.

[0201] In this way, by determining whether the temperature detection circuit is abnormal based on the ECU temperature detection values Te1 and Te2 of the multiple temperature detection circuits 45 and 46, it is possible to determine abnormality of the temperature detection circuit more accurately and quickly than when a single temperature detection circuit is provided.

[0202] (3) The sensor abnormality determination unit 51 may determine that the temperature detection circuit is abnormal when the difference ΔTe between the first detected temperature and the second detected temperature is greater than or equal to a predetermined value ΔTt for a predetermined time TL or longer. The ECU temperature estimation unit 52 may output, as an ECU temperature estimation value Tes, a value that gradually increases at a constant rate of increase ΔTr from the first detected temperature output by the temperature detection circuit 45 or 46 at the time when the difference ΔTe is greater than or equal to the predetermined value ΔTt for the predetermined time TL, until it reaches a predetermined set value Ts.

[0203] This can prevent a temporary increase in the difference ΔTe due to the influence of noise or the like from being erroneously detected as an abnormality in the temperature detection circuit.

[0204] (4) When it is determined that the temperature detection circuit is abnormal, the ECU temperature estimation unit 52 may output an ECU temperature estimation value Tes that gradually increases at a lower increase rate ΔTr when the detected temperature detected by the temperature detection circuit 45 or 46 is high, compared to when the detected temperature detected by the temperature detection circuit 45 or 46 is low.

[0205] Thus, when the temperature detected by the temperature detection circuit 45 or 46 is high at the time when it is determined that the temperature detection circuit is abnormal, the ECU temperature estimate value Tes can be prevented from becoming excessively high.

[0206] (Third embodiment)

[0207] The structure of the ECU 30 of the third embodiment is similar to that of the reference Figure 8The structure of the control operation device 31 of the third embodiment is the same as that of the ECU 30 of the second embodiment described above. Figure 6 The control arithmetic device 31 of the first embodiment described above has the same structure as that of the ECU 30. In addition, descriptions of the components and functions common to the ECU 30 of the second embodiment and the control arithmetic device 31 of the first embodiment will be omitted.

[0208] Reference Figure 8 The first temperature sensor 45a of the first temperature detection circuit 45 and the second temperature sensor 46a of the second temperature detection circuit 46 are mounted on the same circuit board as the FETs Q1 to Q6 of the first power conversion circuit 42A and the FETs Q1 to Q6 of the second power conversion circuit 42B, which are heat generating components.

[0209] Figure 14 This diagram schematically illustrates the relative positional relationship between the power conversion circuits (first power conversion circuit 42A, second power conversion circuit 42B) and the temperature sensors (first temperature sensor 45a, second temperature sensor 46a) mounted on the circuit board 70. In the following description, two orthogonal axial directions parallel to the component mounting surface of the circuit board 70 are referred to as the first direction D1 and the second direction D2, respectively.

[0210] like Figure 14 As shown, the circuit board 70 has a semi-elliptical shape obtained by dividing an elongated shape along a minor axis in a plan view. One edge e1 of the two edges e1 and e2 in the first direction D1 is formed in an arc shape, and the other edge e2 is formed in a straight line.

[0211] The first power conversion circuit 42A and the second power conversion circuit 42B are arranged along the second direction D2, and the first temperature sensor 45a and the second temperature sensor 46a are disposed between the first power conversion circuit 42A and the second power conversion circuit 42B in the second direction D2. Thus, by disposing the first temperature sensor 45a and the second temperature sensor 46a between the first power conversion circuit 42A and the second power conversion circuit 42B, temperature anomalies in both the first power conversion circuit 42A and the second power conversion circuit 42B can be effectively detected without favoring either the first power conversion circuit 42A or the second power conversion circuit 42B.

[0212] For example, the first temperature sensor 45a and the second temperature sensor 46a may be arranged on the positive electrode side line Lp of the power wiring PW (see Figure 8) branches into a first positive-side line LpA and a second positive-side line LpB near a branch point Pb. For example, a first temperature sensor 45a and a second temperature sensor 46a may be disposed between the first positive-side line LpA and the second positive-side line LpB near the branch point Pb, on the side of the power conversion circuits 42A and 42B.

[0213] By arranging the first temperature sensor 45a and the second temperature sensor 46a near the branch point Pb where the first positive side line LpA and the second positive side line LpB, which are power supply lines toward the first power conversion circuit 42A and the second power conversion circuit 42B, branch off, it is easy to arrange the first temperature sensor 45a and the second temperature sensor 46a between the first power conversion circuit 42A and the second power conversion circuit 42B.

[0214] For example, the first temperature sensor 45a and the second temperature sensor 46a can be arranged on a center line CL that passes approximately through the center of the circuit board 70 in the second direction D2 (i.e., the center line CL along the first direction D1). By arranging the first temperature sensor 45a and the second temperature sensor 46a on the center line CL, it is easier to position the first temperature sensor 45a and the second temperature sensor 46a between the first power conversion circuit 42A and the second power conversion circuit 42B. Furthermore, since heat easily accumulates in the center of the circuit board 70, arranging the first temperature sensor 45a and the second temperature sensor 46a in a location prone to high temperatures facilitates detection of overheating of the ECU 30.

[0215] Furthermore, the first temperature sensor 45a and the second temperature sensor 46a can be arranged close to each other. By placing the first temperature sensor 45a and the second temperature sensor 46a close to each other, the thermal coupling between the first temperature sensor 45a and the second temperature sensor 46a can be strengthened. As a result, the temperature detected by the first temperature sensor 45a and the temperature detected by the second temperature sensor 46a can be brought close to each other.

[0216] Thus, an abnormality occurring in the first temperature detection circuit 45 and the second temperature detection circuit 46 can be detected based on the difference between the detected temperatures of the first temperature sensor 45 a and the second temperature sensor 46 a .

[0217] In addition, the first temperature sensor 45a and the second temperature sensor 46a may be mounted on the circuit board 70 so as to be oriented in different directions. Figure 14 In FIG. 4 , reference numerals 45 b and 45 c denote electrodes at both ends of a first temperature sensor 45 a serving as a thermistor, and reference numerals 46 b and 46 c denote electrodes at both ends of a second temperature sensor 46 a serving as a thermistor.

[0218] exist Figure 14In the example, the electrodes 45b and 45c at both ends of the first temperature sensor 45a are arranged along the second direction D2, and the electrodes 46b and 46c at both ends of the second temperature sensor 46a are arranged along the first direction D1. The orientation of the first temperature sensor 45a is orthogonal to the orientation of the second temperature sensor 46a.

[0219] By orienting the first temperature sensor 45 a and the second temperature sensor 46 a in different directions in this manner, it is possible to prevent the first temperature sensor 45 a and the second temperature sensor 46 a from being damaged simultaneously when stress is applied to the circuit board 70 .

[0220] As described above, when detecting an abnormality in the first temperature detection circuit 45 and the second temperature detection circuit 46 based on the difference in detected temperatures between the first temperature sensor 45a and the second temperature sensor 46a, if both sensors experience the same abnormality and the detected temperatures do not differ, the abnormality may not be detected. By preventing both sensors from being damaged simultaneously due to stress applied to the circuit board 70, the occurrence of the same abnormality in both sensors due to damage caused by stress can be suppressed.

[0221] The FETs Q1 to Q6 and temperature sensors (first temperature sensor 45a and second temperature sensor 46a) included in each of the first power conversion circuit 42A and the second power conversion circuit 42B can be thermally connected to the same heat dissipation component (heat sink). Since the heat dissipation component is made of a material with good thermal conductivity, thermally connecting the FETs Q1 to Q6, the first temperature sensor 45a, and the second temperature sensor 46a, which are heat-generating components, to the same heat dissipation component facilitates detection of temperature anomalies in the first power conversion circuit 42A and the second power conversion circuit 42B.

[0222] In addition, by thermally connecting the first temperature sensor 45a and the second temperature sensor 46a to the same heat dissipation component, the thermal coupling between the first temperature sensor 45a and the second temperature sensor 46a becomes tighter, and the detection temperature of the first temperature sensor 45a can be closer to the detection temperature of the second temperature sensor 46a.

[0223] Figure 15 Schematic diagram of a heat dissipation structure for dissipating heat generated by the first power conversion circuit 42A and the second power conversion circuit 42B. The heat dissipation member 72 may be a heat sink formed of a metal with good thermal conductivity, such as aluminum alloy.

[0224] The surfaces f1 of the FETs Q1 to Q6 included in the first power conversion circuit 42A and the second power conversion circuit 42B, which are located opposite the circuit substrate 70, and the surfaces f2 of the first temperature sensor 45a and the second temperature sensor 46a, which are located opposite the circuit substrate 70, are thermally connected to the same heat sink 72. For example, the surfaces f1 and f2 are in contact with the heat sink 72 via thermal interface materials (TIMs) 73 and 74, such as conductive paste (e.g., thermal paste), respectively.

[0225] FETs Q1-Q6 can be, for example, switching elements with a top surface (upper surface) heat dissipation structure. For example, FETs Q1-Q6 can be switching elements in which the thermally conductive pad connected to the source pad is exposed from the resin package (mold) that seals the chip on the surface (upper surface) opposite to the surface (bottom surface) provided with the drain pad. Furthermore, for example, FETs Q1-Q6 can be switching elements having a mold formed of a resin with high thermal conductivity, with the mold having a thinner wall on the surface opposite to the surface provided with the drain pad.

[0226] Figure 16 This is a block diagram showing an example of the functional configuration of the temperature measuring unit 31b of the third embodiment. The temperature measuring unit 31b includes a sensor abnormality determination unit 51, an ECU temperature measuring unit 50, and a motor temperature estimation unit 55. The functions of the sensor abnormality determination unit 51 of the third embodiment are the same as those of the sensor abnormality determination unit 51 of the second embodiment, and the functions of the ECU temperature measuring unit 50 of the third embodiment are the same as those of the modified example of the second embodiment, and therefore their description will be omitted.

[0227] The motor temperature estimating unit 55 estimates the motor temperature of the motor 20. Specifically, the motor temperature estimating unit 55 estimates the ECU temperature (i.e., calculates an estimated ECU temperature value Tes) based on the ECU temperature detection values Te1 and Te2 and the abnormality determination signal Sa output from the sensor abnormality determination unit 51. The motor temperature is also estimated based on the estimated ECU temperature value Tes and the motor current detection values I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd.

[0228] If the sensor abnormality determination unit 51 determines that the temperature detection circuit is not abnormal, the motor temperature estimation unit 55 selects either the ECU temperature detection value Te1 or the ECU temperature detection value Te2 as the ECU temperature estimation value Tes. For example, the motor temperature estimation unit 55 may select the higher of the ECU temperature detection values Te1 and Te2 as the ECU temperature estimation value Tes, or may select the lower of the two values as the ECU temperature estimation value Tes.

[0229] When the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the motor temperature estimation unit 55 calculates a value that gradually increases from the ECU temperature detection value Te1 or the ECU temperature detection value Te2 at a constant increase rate ΔTr [°C / second] to a predetermined set value Ts as the ECU temperature estimation value Tes.

[0230] Figure 17 This diagram schematically illustrates the method for calculating the ECU temperature estimate Tes when a temperature detection circuit abnormality occurs. For example, if the ECU temperature detection value Te1 is selected as the ECU temperature estimate Tes until immediately before time t1, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the motor temperature estimation unit 55 sets the ECU temperature detection value Te1 as the ECU temperature estimate Tes at time t1, when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal. The motor temperature estimation unit 55 then begins increasing the ECU temperature estimate Tes from time t1, calculating the value that gradually increases at a constant rate of increase ΔTr from the ECU temperature detection value Te1 detected by the first temperature detection circuit 45 at time t1 to a predetermined set value Ts as the ECU temperature estimate Tes.

[0231] On the other hand, if the ECU temperature detection value Te2 was selected as the ECU temperature estimate value Tes until immediately before time t1 when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal, the motor temperature estimation unit 55 sets the ECU temperature detection value Te2 as the ECU temperature estimate value Tes at time t1 when the sensor abnormality determination unit 51 determines that the temperature detection circuit is abnormal. The motor temperature estimation unit 55 begins increasing the ECU temperature estimate value Tes from time t1 and calculates a value that gradually increases at a constant rate of increase ΔTr from the ECU temperature detection value Te2 detected by the second temperature detection circuit 46 at time t1 until it reaches a predetermined set value Ts as the ECU temperature estimate value Tes.

[0232] Reference Figure 16 The motor temperature estimating unit 55 estimates a motor temperature increase value Rt caused by the motor current flowing through the motor 20. For example, the motor temperature estimating unit 55 can estimate the motor temperature increase value Rt by subtracting the amount of heat dissipated by the motor 20 from the integrated value of the sum of the squares of the motor current detection values I1ad, I1bd, I1cd, I2ad, I2bd, and I2cd.

[0233] The motor temperature estimating unit 55 calculates a value obtained by adding the increase value Rt to the ECU temperature estimated value Tes as the motor temperature estimated value Tm.

[0234] In addition, the motor control method of the third embodiment is similar to that of the reference Figure 7The motor control method is the same as the flowchart of FIG.

[0235] (Effects of the Third Embodiment)

[0236] (1) The ECU 30 includes: a circuit board 70; a first power conversion circuit 42A mounted on the circuit board 70 and supplying current to drive the motor 20; a second power conversion circuit 42B mounted on the circuit board 70 and supplying current to drive the same motor 20 as or a different motor 20 to which the first power conversion circuit 42A is supplied with current; temperature detection circuits 45 and 46 each having temperature sensors 45 a and 46 a; and a first current limiter 61 that limits the current supplied by the first power conversion circuit 42A and the current supplied by the second power conversion circuit 42B based on the temperatures detected by the temperature detection circuits 45 and 46. The temperature sensors 45 a and 46 a are mounted on the circuit board 70 on which the first power conversion circuit 42A and the second power conversion circuit 42B are mounted and are located between the first power conversion circuit 42A and the second power conversion circuit 42B.

[0237] This makes it possible to satisfactorily detect temperature abnormalities in both the first power conversion circuit 42A and the second power conversion circuit 42B without favoring either the first power conversion circuit 42A or the second power conversion circuit 42B.

[0238] (2) The surface of the switching element included in the first power conversion circuit 42A opposite to the circuit substrate 70, the surface of the switching element included in the second power conversion circuit 42B opposite to the circuit substrate 70, and the surfaces of the temperature sensors 45a and 46a opposite to the circuit substrate 70 can be thermally connected to the same heat dissipation component 72.

[0239] This makes it easier to detect temperature abnormalities in the first power conversion circuit 42A and the second power conversion circuit 42B.

[0240] (3) The temperature sensors 45 a and 46 a may be arranged substantially in the center of the circuit board 70 in the arrangement direction where the first power conversion circuit 42A and the second power conversion circuit 42B are arranged.

[0241] This makes it easier to dispose the first temperature sensor 45a and the second temperature sensor 46a between the first power conversion circuit 42A and the second power conversion circuit 42B. Furthermore, since heat easily accumulates in the center of the circuit board 70, disposing the first temperature sensor 45a and the second temperature sensor 46a in a location prone to high temperatures facilitates detection of overheating of the ECU 30.

[0242] (4) The sensor abnormality determination unit 51 can determine whether the temperature detection circuits 45 and 46 are abnormal based on the difference between the detected temperature corresponding to the output of the first temperature sensor 45a and the detected temperature corresponding to the output of the second temperature sensor 46a, and the first temperature sensor 45a and the second temperature sensor 46a are arranged close to each other.

[0243] This allows for a tight thermal coupling between the first temperature sensor 45a and the second temperature sensor 46a. Consequently, the temperature detected by the first temperature sensor 45a and the temperature detected by the second temperature sensor 46a can be brought close to each other, and an abnormality occurring in the temperature detection circuits 45 and 46 can be detected with high accuracy based on the difference between the temperatures detected by the first temperature sensor 45a and the second temperature sensor 46a.

[0244] (5) The sensor abnormality determination unit 51 can determine whether the temperature detection circuits 45 and 46 are abnormal based on the difference between the detection temperature corresponding to the output of the first temperature sensor 45a and the detection temperature corresponding to the output of the second temperature sensor 46a, and the surface of the first temperature detection element on the opposite side of the circuit substrate 70 and the surface of the second temperature detection element on the opposite side of the circuit substrate 70 are thermally connected to the same heat dissipation component 72.

[0245] As a result, the thermal coupling between the first temperature sensor 45 a and the second temperature sensor 46 a becomes closer, and the temperature detected by the first temperature sensor 45 a and the temperature detected by the second temperature sensor 46 a can be made closer.

[0246] (6) The first temperature sensor 45 a and the second temperature sensor 46 a may be temperature detection elements having the same structure, or the first temperature sensor 45 a and the second temperature sensor 46 a may be mounted on the circuit board 70 with the first temperature sensor 45 a and the second temperature sensor 46 a oriented in different directions.

[0247] This can prevent the first temperature sensor 45a and the second temperature sensor 46a from being damaged simultaneously when stress is applied to the circuit board 70. Therefore, it is possible to suppress the first temperature sensor 45a and the second temperature sensor 46a from failing simultaneously.

[0248] (Variation)

[0249] While the above description describes an example of the rotation angle detection device of the present invention being applied to a column-assisted electric power steering system, also known as an upstream-assisted system, the rotation angle detection device of the present invention can also be applied to a downstream-assisted electric power steering system. The following describes configurations of the rotation angle detection device of the present invention applied to single-pinion-assisted, rack-assisted, and dual-pinion-assisted electric power steering systems, as examples of downstream-assisted electric power steering systems.

[0250] In the case of the downstream assist mode, the motor 20, the rotation angle sensor 23a, and the ECU 30 may not be separate structures, but may be integrated as shown in FIG. Figures 18 to 20 The dotted line shows an integrated MCU (Motor Control Unit).

[0251] Figure 18 This figure shows an example of a configuration in which the rotation angle detection device of the present invention is applied to a single-pinion assist electric power steering system. A steering wheel 1 is connected to a universal joint 4a on one side of an intermediate shaft via a steering shaft 2. Furthermore, an input-side shaft 4c of a torsion bar (not shown) is connected to the other universal joint 4b.

[0252] The rack-and-pinion mechanism 5 includes a pinion (pinion gear) 5a, a rack bar (rack) 5b, and a pinion shaft 5c. The input-side shaft 4c and the rack-and-pinion mechanism 5 are connected via a torsion bar (not shown). This torsion bar is twisted by the deviation in the rotational angle between the input-side shaft 4c and the rack-and-pinion mechanism 5. The torque sensor 10 electromagnetically measures the torsion angle of the torsion bar as the steering torque Th of the steering wheel 1.

[0253] The motor 20 that assists the steering force of the steering wheel 1 is connected to the pinion shaft 5 c via the reduction gear 3 . The rotation angle sensor 23 a calculates the rotation angle information of the motor rotating shaft of the motor 20 similarly to the above embodiment.

[0254] Figure 19 This figure shows an example of a configuration in which the rotation angle detection device of the present invention is applied to a rack-assisted electric power steering system. A spiral groove (not shown) is formed on the outer circumference of the rack bar 5b, and a spiral groove (not shown) with the same lead is also formed on the inner circumference of the nut 81. A ball screw is formed by arranging multiple rolling elements in the rolling path formed by these spiral grooves.

[0255] A belt 84 is wound around a drive pulley 82 connected to the rotating shaft 20a of the motor 20 that assists the steering force of the steering wheel 1, and a driven pulley 83 connected to a nut 81. The rotational motion of the rotating shaft 20a is converted into linear motion of the rack bar 5b. Similar to the above-described embodiment, the rotation angle sensor 23a calculates the rotation angle information of the motor rotating shaft of the motor 20.

[0256] Figure 20The following figure shows an example configuration of a rotation angle detection device according to the present invention applied to a dual-pinion assist electric power steering system. The dual-pinion assist electric power steering system includes, in addition to the pinion shaft 5c and the pinion 5a, a second pinion shaft 85 and a second pinion 86. The rack bar 5b includes first rack teeth (not shown) that mesh with the pinion 5a and second rack teeth (not shown) that mesh with the second pinion 86.

[0257] The motor 20 that assists the steering force of the steering wheel 1 is connected to the second pinion shaft 85 via the reduction gear 3 . The rotation angle sensor 23 a calculates the rotation angle information of the motor rotation shaft of the motor 20 similarly to the above embodiment.

[0258] Description of Reference Numerals

[0259] 1…Steering wheel, 2…Steering shaft, 3…Reduction gear, 4a, 4b…Universal joint, 4c…Input shaft, 5…Rack and pinion mechanism, 5a…Pinion (counter gear), 5b…Rack bar (rack), 5c…Pinion shaft, 6a, 6b…Tie rods, 7a, 7b…Hub unit, 8L, 8R…Steering wheels, 10…Torque sensor, 11…Ignition switch, 12…Vehicle speed sensor, 13…Battery, 14…Steering angle sensor, 20…Motor, 23… Motor rotation angle detection circuit, 30... Electronic control unit, 31... Control calculation device, 31a... A / D converter, 31b... Temperature measurement unit, 33A... First motor current cutoff circuit, 33B... Second motor current cutoff circuit, 39A1, 39A2, 39B1, 39B2, 39C1, 39C2... Current detection circuit, 41A... First gate drive circuit, 41B... Second gate drive circuit, 42A... First power conversion circuit, 42B... Second power conversion circuit, 44A... First power cutoff circuit, 44B... Second power cutoff circuit, 45... Temperature detection circuit, First temperature detection circuit, 45a... Temperature sensor, First temperature sensor, 46... Second temperature detection circuit, 46a... Second temperature sensor, 50... ECU temperature measurement unit, 51... Sensor abnormality determination unit, 52... ECU temperature estimation unit, 53... Increased value estimation unit, 54... Adder, 55... Motor temperature estimation unit, 60... Current command value calculation unit, 61...first current limiting unit, 62, 63...subtractor, 64...second current limiting unit, 65...PI control unit, 66...two-phase / three-phase conversion unit, 67...three-phase / two-phase conversion unit, 68...angular velocity conversion unit, 70...circuit board, 72...heat dissipation component, 73, 74...thermal interface material (TIM), 81...nut, 82...drive pulley, 83...driven pulley, 84...belt, 85...second pinion shaft, 86...second pinion.

Claims

1. A motor control device, characterized in that: The motor control device comprises: a motor current control circuit that controls the motor current flowing through the electric motor; a temperature detection circuit having a temperature detection element disposed near the motor current control circuit; an increase value estimating unit that estimates an increase value of the temperature of the electric motor caused by the motor current; an abnormality determination unit configured to determine whether the temperature detection circuit is abnormal; a first temperature estimating unit that outputs a detected temperature detected by the temperature detection circuit as a first temperature estimated value when the temperature detection circuit is determined to be normal, and outputs a value obtained by gradually increasing at a constant rate from the detected temperature detected by the temperature detection circuit to a predetermined set value as the first temperature estimated value when the temperature detection circuit is determined to be abnormal; a second temperature estimating unit that calculates a value obtained by adding the first temperature estimated value to the increase value as a second temperature estimated value; as well as a current limiting unit that limits the motor current so that the motor current gradually decreases as the second estimated temperature value increases, when the second estimated temperature value exceeds a predetermined threshold value; The first temperature estimating unit sets the constant increase rate to a lower value when the temperature detected by the temperature detection circuit is high compared to when the temperature detected by the temperature detection circuit is low.

2. The motor control device according to claim 1, wherein: The temperature detection circuit includes a first temperature detection element and a second temperature detection element as the temperature detection elements, and outputs the detected temperature corresponding to the output of the first temperature detection element and the detected temperature corresponding to the output of the second temperature detection element. When the difference between a higher first detected temperature and a lower second detected temperature of the detected temperatures corresponding to the outputs of the first temperature detecting element and the second temperature detecting element is greater than a predetermined value, the abnormality determination unit determines that the temperature detection circuit is abnormal. When it is determined that the temperature detection circuit is normal, the first temperature estimating unit outputs the first detected temperature as the first temperature estimated value.

3. The motor control device according to claim 2, wherein: When the difference between the first detected temperature and the second detected temperature is greater than or equal to the predetermined value for a period of time exceeding a predetermined value, the abnormality determination unit determines that the temperature detection circuit is abnormal. When the difference between the first detected temperature and the second detected temperature remains greater than the specified value for the specified time, the first temperature estimation unit outputs as the first temperature estimation value a value that gradually increases at a constant rate of increase from the first detected temperature output by the temperature detection circuit to the specified set value over time.

4. The motor control device according to claim 1, wherein: The abnormality determination unit determines that the temperature detection circuit is normal when the output signal of the temperature detection element is a value within a predetermined range, and determines that the temperature detection circuit is abnormal when the output signal of the temperature detection element is a value outside the predetermined range.

5. The motor control device according to claim 4, wherein: The first temperature estimating unit holds the temperature detected by the temperature detection circuit as a held value. When the temperature detection circuit is determined to be abnormal, the first temperature estimating unit outputs, as the first temperature estimated value, a value that gradually increases at a constant increasing rate over time from the held value held before the temperature detection circuit is determined to be abnormal to the predetermined set value.

6. The motor control device according to claim 4, wherein: When the output signal of the temperature detection element continues to be a value outside the predetermined range for a predetermined time or longer, the abnormality determination unit determines that the temperature detection circuit is abnormal. The first temperature estimating unit holds the temperature detected by the temperature detection circuit as a held value. The first temperature estimating unit outputs, as the first temperature estimated value, a value that gradually increases at a constant increasing rate over time from the held value held immediately before the output signal of the temperature detection element becomes a value outside the predetermined range to the predetermined set value.

7. An electric power steering device, characterized in that: The electric power steering device comprises: The motor control device according to any one of claims 1 to 6; and an electric motor controlled by the motor control device, The electric power steering device applies a steering assist force to a steering system of a vehicle via the electric motor.

8. The electric power steering device according to claim 7, characterized in that The electric power steering device includes a torque sensor for detecting a steering torque of a steering wheel. The motor control device includes a current command value setting unit that sets a current command value of a motor current flowing through the electric motor based on at least the steering torque. The motor current control circuit includes a first system power converter and a second system power converter for respectively supplying a motor current flowing through the electric motor. When it is determined that the temperature detection circuit is abnormal, the current limiting unit limits the motor current flowing through the electric motor to a current having a value smaller than the current command value.

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