JP2022094457A - Motor drive control device - Google Patents

Abstract

To mount a component of an active clamp circuit for protecting a motor relay on a circuit board with a simple configuration.SOLUTION: An ECU includes: an inverter for energizing a coil of a plurality of phases of a motor 10 having a neutral point; a motor relay arranged on either a first energization wire of each phase between the coil of the plurality of phases and a neutral point or a second energization wire of each phase between the inverter and the coil of the plurality of phases, and cutting off energization from the inverter to the neutral point under external control; and an active clamp circuit that holds potential difference at a predetermined voltage when the motor relay is disposed on the first energization wire and when potential difference between the first energization wire on a neutral point side of the motor relay and the ground rises up to a predetermined voltage, or when the motor relay is disposed on the second energization wire and when potential difference between the second energization wire on a coil side of the motor relay and the ground rises up to a predetermined voltage.SELECTED DRAWING: Figure 1

Description

The present invention relates to a motor drive control device.

In the motor drive control device, the semiconductor relay (motor relay) installed in each phase energizing line between the inverter and the neutral point of the motor is cut off when the inverter drive semiconductor relay is short-circuited, and an electric brake is generated. Those that suppress it are known (see, for example, Patent Document 1). This motor relay is provided with an active clamp circuit between its gate and drain, which makes the drain-source voltage of the motor relay unique even if a counter electromotive voltage is generated by an external force during non-drive control of the motor. The withstand voltage is not exceeded.

Japanese Unexamined Patent Publication No. 2015-3273

By the way, due to various factors, a motor relay installed in a three-phase energizing line can be packaged in one relay package, and this relay package can be mounted on a circuit board on which an inverter or the like is formed. Of such relay packages, the external terminals that are electrically connected to the motor coil are motors that do not go through the circuit board (away from the circuit board) in consideration of the thermal effects of joining such as welding. It is supposed to be joined to the coil.

However, when the motor relay is installed in each phase current line between the neutral point and the motor coil, the external terminal connected to the motor coil in the relay package is internally connected to the drain terminal of the built-in motor relay. Will be done. Therefore, since the drain terminal of the motor relay does not appear on the circuit board as a pattern (conductor) via the external terminal of the relay package, the constituent elements of the active clamp circuit provided between the gate and drain of the motor relay are placed on the circuit board. It will be difficult to implement.

On the other hand, as described in Patent Document 1, when the motor relay is installed in each phase energizing line between the inverter and the motor coil, the drain terminal of the motor relay is formed as a pattern via the external terminal of the relay package. Appears on the circuit board. Therefore, it is relatively easy to mount the constituent elements of the active clamp circuit on the circuit board. However, since one Zener diode and one diode are required for each motor relay as a component of the active clamp circuit, it is desirable to reduce the number of components of the active clamp circuit from the viewpoint of reducing the mounting area of the circuit board. ..

Therefore, in view of the above problems, it is an object of the present invention to provide a motor drive control device capable of mounting a component element of an active clamp circuit for protecting a motor relay on a circuit board with a simple configuration.

Therefore, in the motor drive control device according to the present invention, the inverter that energizes the multi-phase coil of the electric motor having a neutral point and the first energizing line of each phase between the multi-phase coil and the neutral point. Alternatively, a semiconductor relay, which is arranged on one of the second energizing lines of each phase between the inverter and the multi-phase coil and cuts off energization from the inverter to the neutral point by external control, and a semiconductor relay are the first. When it is arranged on the 1 energizing line, when the potential difference between the 1st energizing line on the neutral point side of the semiconductor relay and the ground rises to a predetermined voltage, or when the semiconductor relay is arranged on the 2nd energizing line. Is provided with an active clamp circuit that holds the potential difference at a predetermined voltage when the potential difference between the second current-carrying wire on the coil side of the semiconductor relay and the ground rises to a predetermined voltage.

According to the motor drive control device of the present invention, the constituent elements of the active clamp circuit that protects the motor relay can be mounted on the inverter board with a simple configuration.

It is a schematic diagram which shows the structural example of the electric power steering. It is a circuit diagram which shows an example of the motor drive control apparatus which concerns on 1st Embodiment. It is a circuit diagram which shows an example of the inverter of the motor drive control device. It is explanatory drawing which shows the packaging of the motor relay of the motor drive control device. It is a time chart which shows an example of the voltage waveform of the motor drive control device. It is a circuit diagram which shows an example of the motor drive control apparatus which concerns on 2nd Embodiment. It is a circuit diagram which shows an example of the motor drive control apparatus which concerns on 3rd Embodiment. It is a time chart which shows an example of the voltage waveform of the conventional motor drive control device.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 shows an electric power steering as an application example of the motor drive control device according to the first embodiment. The electric power steering 2 mounted on the vehicle 1 assists the steering torque when the driver of the vehicle 1 performs a steering operation and steers the pair of steering wheels 4 with the steering torque of the steering wheel 3. ..

The steering torque generated by the operation of the steering wheel 3 is applied to the pinion gear 7 provided at the tip of the pinion shaft 6 via the steering shaft 5 and the pinion shaft 6 connected to the steering shaft 5 via a universal joint or the like. Be transmitted. The rotational motion of the pinion gear 7 due to the transmitted steering torque is converted into a linear motion in the vehicle width direction by the rack gear 8 that meshes with the pinion gear 7. The pair of tie rods 9 connected to the rack gear 8 is operated by this linear motion, and the steering wheels 4 connected to the pair of tie rods 9 are steered. The electric power steering 2 is configured to add an assist torque that assists the steering torque to the steering torque transmission path from the steering wheel 3 to the tie rod 9.

In the illustrated example, the electric power steering 2 includes a motor 10 that generates an assist torque and an ECU 11 that is a motor drive control device that controls the drive of the motor 10. Further, the electric power steering 2 includes a speed reducer 12 that reduces the output of the motor 10 and transmits it to the rack gear 8. Further, the electric power steering 2 includes a torque sensor 13 for measuring the steering torque, a rotation angle sensor 14 for measuring the rotation angle of the motor 10, and a vehicle speed sensor 15 for measuring the vehicle speed. As the torque sensor 13, various detection methods such as a magnetostrictive type, a strain gauge type, and a piezoelectric type can be adopted. Further, as the rotation angle sensor 14, various detection methods such as a Hall element, a resolver, a rotary encoder, and the like can be adopted.

The ECU 11 is supplied with power from the vehicle-mounted battery 16, and has a torque signal ST which is an output signal of the torque sensor 13, a rotation angle signal Sθ which is an output signal of the rotation angle sensor 14, and a vehicle speed signal which is an output signal of the vehicle speed sensor 15. Enter SV and. Further, the ECU 11 has a current sensor 17 for measuring the current flowing through the motor 10 inside the ECU 11.

The ECU 11 controls the drive of the motor 10 so as to generate an assist torque according to the operating state of the vehicle 1 based on the torque signal ST, the vehicle speed signal SV, the rotation angle signal Sθ, and the output signal of the current sensor 17. .. The torque generated by the motor 10 is transmitted to the rack gear 8 via the speed reducer 12, whereby the steering torque is assisted according to the operating state of the vehicle 1.

FIG. 2 shows an example of a main part of the motor 10 and the ECU 11.

The motor 10 is a three-phase brushless motor having a U-phase coil 10U, a V-phase coil 10V, and a W-phase coil 10W as stator coils, which are wound around a stator (not shown) and connected at a neutral point N. Is. Further, the motor 10 includes a rotor (not shown) as a permanent magnet rotor, and the rotating shaft of the rotor is attached to a stator or the like so that the rotor rotates due to the interaction between the magnetic force of the rotor and the magnetic force generated by the stator coil. It is pivotally supported. The shaft output of the rotor is transmitted to the reducer 12 as the torque generated by the motor 10.

The ECU 11 includes a power supply circuit 101, a booster circuit 102, an inverter 103, an inverter drive circuit 104, a first power supply relay 105, a second power supply relay 106, a noise filter circuit 107, motor relays 108 to 110, a first driver 111, and a second driver. It includes 112, a third driver 113, a gate-source resistance 114, a gate overvoltage protection element 115, a microcomputer 116, and an active clamp circuit 117.

The power supply circuit 101 is connected to the vehicle-mounted battery 16 via the ignition switch IGN, and when the ignition switch IGN is in the ON state, the output voltage of the vehicle-mounted battery 16 is adjusted (lowered) to the operating voltage required for each part of the ECU 11. And supply.

The booster circuit 102 is connected to the positive electrode of the vehicle-mounted battery 16 via the positive electrode side power supply line 118, and the output voltage of the vehicle-mounted battery 16 is required by the first to third drivers 111 to 113, the inverter drive circuit 104, and the like. It is boosted to voltage and supplied.

The inverter 103 is provided between the positive electrode side power supply line 118 and the negative electrode side power supply line 119 connected to the negative electrode of the vehicle-mounted battery 16 via the body ground of the vehicle 1 (hereinafter, simply referred to as “ground”). The inverter 103 converts the DC output of the vehicle-mounted battery 16 into alternating current and supplies it to the U-phase coil 10U, the V-phase coil 10V, and the W-phase coil 10W. The inverter drive circuit 104 is a circuit that generates a drive signal for driving a switching element described later provided in the inverter 103, and uses the boost voltage output by the booster circuit 102 when generating the drive signal. There is. Here, the inverter 103 and the inverter drive circuit 104 will be described in detail with reference to FIG. 3, which shows their internal configurations.

As shown in FIG. 3, in the inverter 103, the U-phase arm and the V-phase arm are located between the positive electrode side bus 103P connected to the positive electrode side power supply line 118 and the negative electrode side bus 103N connected to the negative electrode side power supply line 119. And the W phase arm are connected in parallel. The U-phase arm is configured by connecting the upper switching element 103 _UH and the lower switching element 103 _UL in series. The V-phase arm is configured by connecting the upper switching element 103 _VH and the lower switching element 103 _VL in series. The W-phase arm is configured by connecting the upper switching element 103 _WH and the lower switching element 103 _WL in series. Then, the two switching elements in each phase arm of the inverter 103 are connected to the coil of the corresponding phase of the motor 10 to form a three-phase bridge circuit. Specifically, the two switching elements 103 _UH and 103 _UL of the U-phase arm are connected to the end of the U-phase coil 10U, and the two switching elements 103 _VH and 103 _VL of the V-phase arm are connected to the V-phase coil 10V. The two switching elements 103 _WH and 103 _WL of the W phase arm are connected to the end of the W phase coil 10 W.

Switching elements 103 _UH , 103 _UL , 103 _VH , 103 _VL , 103 _WH , 103 _WL (hereinafter abbreviated as "103 _UH to 103 _WL ") are semiconductor elements having control terminals that can be controlled from the outside, and are back electromotive forces. It has an antiparallel diode D to circulate power back to the vehicle-mounted battery 16. Examples of the switching elements 103 _UH to 103 _WL include MOSFETs (Metal Oxide Semiconductor Metal Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). Hereinafter, it is assumed that the switching elements 103 _UH to 103 _WL are N-channel MOSFETs, and the diode D is a parasitic diode formed between the drain and the source in the manufacturing process of the MOSFET.

Further, as shown in FIG. 3, the inverter drive circuit 104 is composed of a plurality of drivers that generate drive signals for each of the switching elements 103 _UH to 103 _WL . That is, the inverter drive circuit 104 uses the U-phase upper driver 104 _UH that generates the drive signal of the switching element 103 _UH , the U-phase lower driver 104 _UL that generates the drive signal of the switching element 103 _UL , and the drive signal of the switching element 103 _VH . Of the V-phase upper driver 104 _VH to be generated, the V-phase lower driver 104 _VL to generate the drive signal of the switching element 103 _VL , the W-phase upper driver 104 _WH to generate the drive signal of the switching element 103 _WH , and the switching element 103 _WL . It is composed of a W-phase lower stage driver 104 _WL that generates a drive signal. Each driver generates a drive signal for driving the switching elements 103 _UH to 103 _WL on or off based on the control signal output from the microcomputer 116. For this drive signal, a boost voltage output from the booster circuit 102 is used so that the switching elements 103 _UH to 103 _WL can be turned on.

Referring to FIG. 2 again, the first power supply relay 105 and the second power supply relay 106 are arranged on the positive electrode side power supply line 118. The first power supply relay 105 and the second power supply relay 106 are semiconductor elements having control terminals that can be controlled from the outside, the first power supply relay 105 has a diode D1, and the second power supply relay 106 has a diode D2. ing. Hereinafter, it is assumed that the first power supply relay 105 and the second power supply relay 106 are N-channel MOSFETs, and the diodes D1 and D2 are parasitic diodes.

The first power relay 105 cuts off the supply of the output voltage from the vehicle-mounted battery 16 to the inverter 103 when the motor drive control is stopped or the electric power steering is abnormal. The first power supply relay 105 causes current to flow from the inverter 103 to the vehicle-mounted battery 16 in the forward direction of the diode D1 so that the diode D1 functions as a reverse-parallel return diode for returning the back electromotive force to the vehicle-mounted battery 16. Arranged in the direction.

The second power supply relay 106 cuts off the short-circuit current when the vehicle-mounted battery 16 is reversely connected. Specifically, when the second power supply relay 106 is reversely connected, the positive electrode and the negative electrode of the vehicle-mounted battery 16 are connected to the ground, the diode D of the switching elements 103 _UH to 103 _WL , and the diode D1 of the first power supply relay 105. It cuts off the closed circuit that conducts through. Therefore, the second power supply relay 106 is arranged so that the diode D2 cuts off the current returning from the inverter 103 to the vehicle-mounted battery 16 so that the current flows in the forward direction of the diode D2 from the vehicle-mounted battery 16 to the inverter 103. To.

The noise filter circuit 107 is arranged on the positive electrode side power supply line 118 on the inverter 103 side of both the first power supply relay 105 and the second power supply relay 106, and removes the conductive noise in the positive electrode side power supply line 118. .. The noise filter circuit 107 is configured as, for example, a π-type LC circuit or the like in which a capacitor connected to the ground is connected to both ends of the coil.

The motor relays 108 to 110 are arranged on the first energizing line L1 between the stator coils 10U, 10V, 10W and the neutral point N. Specifically, the U-phase motor relay 108 is arranged on the first energizing line L1 between the U-phase coil 10U and the neutral point N, and the first energizing line between the V-phase coil 10V and the neutral point N. The V-phase motor relay 109 is arranged in L1, and the W-phase motor relay 110 is arranged in the first current-carrying wire L1 between the W-phase coil 10W and the neutral point N. The motor relays 108 to 110 are semiconductor elements having control terminals that can be controlled from the outside, and each has a diode D3. The motor relays 108 to 110 reduce the phase current in order to suppress the electric brake generated by the short circuit current flowing in the stator coils 10U, 10V, 10W when a short circuit failure occurs in the switching elements 103 _UH to 103 _WL of the inverter 103. It shuts off. Hereinafter, it is assumed that the motor relays 108 to 110 are N-channel MOSFETs and the diode D3 is a parasitic diode. The motor relays 108 to 110, which are N-channel MOSFETs, have their source terminals connected to the neutral point N so that the diode D3 cuts off the current flowing from the in-phase coil to the coil of another phase via the neutral point N. The drain terminal is connected to the in-phase coil and arranged.

The first driver 111 outputs a drive signal to the control terminal of the first power supply relay 105, and the second driver 112 outputs a drive signal to the control terminal of the second power supply relay 106. The third driver 113 is driven to the control terminals of the motor relays 108 to 110 via the signal line 120 and the U-phase signal line 120U, the V-phase signal line 120V, and the W-phase signal line 120W that branch toward each motor relay. Output a signal. Each driver drives the first power supply relay 105, the second power supply relay 106, and the motor relays 108 to 110 while using the booster voltage output from the booster circuit 102 based on the control signal output from the microcomputer 116. Generate a signal.

One gate-source resistance 114 is provided in common with the three motor relays 108 to 110, and is provided by connecting the signal line 120 and the neutral point N. Further, the gate overvoltage protection element 115 is provided as a Zener diode whose cathode is connected to the signal line 120 and whose anode is connected to the neutral point N.

The microcomputer 116 can communicate with a calculation means such as a CPU (Central Processing Unit), a storage means such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and an input / output interface such as an I / O port via an internal bus. It is connected and configured.

The microcomputer 116 measures the steering torque from the torque signal ST, measures the vehicle speed from the vehicle speed signal SV, and calculates the target value (target torque) of the assist torque based on these measured values. Further, the microcomputer 116 measures the rotation angle of the motor 10 from the rotation angle signal Sθ, and also measures the current flowing through the motor 10 from the current signal Si which is the output signal of the current sensor 17, and the motor 10 is measured from these measured values. The current component (q-axis current) that contributes to the generated torque of is calculated. Then, the microcomputer 116 performs current feedback control so that the current component contributing to the generated torque of the motor 10 approaches the current (target current) corresponding to the target torque. For example, the microcomputer 116 calculates the voltage value of the command signal for comparison with the carrier signal such as a triangular wave based on the deviation between the target current and the q-axis current by PID control or the like. Then, the microcomputer 116 compares the command signal for which the voltage value is calculated with the carrier signal to generate a PWM (Pulse Width Modulation) signal, and each driver constituting the inverter drive circuit 104 uses this PWM signal as a control signal. Output to.

Further, the microcomputer 116 outputs a control signal to the inverter drive circuit 104, the first driver 111, the second driver 112, and the third driver 113. When the microcomputer 116 is performing drive control of the motor 10, the first driver 111 and the second driver send a control signal for turning on the first power relay 105, the second power relay 106, and the motor relays 108 to 110. 112, output to the third driver 113. In this state, the microcomputer 116 outputs a control signal corresponding to the deviation between the target current and the q-axis current to the inverter drive circuit 104. On the other hand, when the drive control of the motor 10 is stopped, the microcomputer 116 sends a control signal for turning off the first power supply relay 105, the second power supply relay 106, and the motor relays 108 to 110 to the first driver 111. Output to the second driver 112 and the third driver 113.

The active clamp circuit 117 sets the motor relays 108 to 110 so that the drain-source voltage of the motor relays 108 to 110 does not exceed the drain-source withstand voltage peculiar to each relay due to the counter electromotive voltage generated in the motor 10. It protects. The counter electromotive voltage generated in the motor 10 is assumed to be as follows. For example, the reverse that occurs when the motor 10 is rotated by an external force, such as when the vehicle-mounted battery 16 is removed or when the tires are manually moved during maintenance while the first power supply relay 105 and the second power supply relay 106 are off. An electromotive voltage is assumed. Alternatively, for example, when the motor relays 108 to 110 are turned off in response to the detection of an abnormality in the circuit system of the ECU 11 while traveling on an uneven road, the motor relays 108 to 110 are turned off while the motor 10 is being driven at a high rotation speed. The counter electromotive voltage generated when this is done is assumed.

The active clamp circuit 117 is provided on the ground line 121 connecting the signal line 120 and the ground. Specifically, in the ground line 121, a Zener diode 122 having a forward direction in which a current flows from the signal line 120 to the ground is arranged. Further, in the ground line 121, a diode 123 having a forward direction in which a current flows from the ground to the signal line 120 is arranged. This diode 123 prevents current from flowing from the signal line 120 to the ground via the ground line 121 when a drive signal is output from the third driver 113 to the motor relays 108 to 110 via the signal line 120. There is.

By the way, instead of the active clamp circuit 117, it is possible to form another active clamp circuit between the gate and the drain of the motor relays 108 to 110 on the circuit diagram. However, as shown in FIG. 4, the motor relays 108 to 110 are packaged in one relay package 124, and the relay package 124 is used as a circuit board 125 such as a PCB (Printed Circuit Board) on which the inverter 103 of the ECU 11 is formed. When mounted above, it may be difficult to form another active clamp circuit as described above.

For example, in the relay package 124, the external terminal 126 electrically connected to the motor coils 10U, 10V, 10W is a circuit board in consideration of reducing the thermal influence due to welding or the like and suppressing the increase in the substrate area. It is conceivable that the motor coils 10U, 10V, and 10W are joined without going through 125 (away from the circuit board 125). In this case, the external terminal 126 of the relay package 124 connected to the circuit board 125 is internally connected to the source terminals s and the gate terminal g of the built-in motor relays 108 to 110. Therefore, the source terminals s and gate terminals g of the motor relays 108 to 110 appear as patterns (conductors) on the circuit board 125 via the external terminals 126. On the other hand, of the relay package 124, the external terminals 126 connected to the motor coils 10U, 10V, 10W are internally connected to the drain terminals d of the built-in motor relays 108 to 110. Therefore, since the drain terminal d of the motor relays 108 to 110 does not appear as a pattern on the circuit board 125 via the external terminal 126, the configuration of the other active clamp circuit provided between the gate and the drain of the motor relays 108 to 110 is configured. It becomes difficult to mount the element on the circuit board 125. As described above, in order to enable the components of the active clamp circuit 117 to be mounted on the circuit board 125 even when the drain terminals d of the motor relays 108 to 110 do not appear as a pattern on the circuit board 125, the active clamp circuit 117 is active. A clamp circuit 117 is provided on the ground wire 121. Here, in order to make it easier to understand the operation of the active clamp circuit 117, first, the operation of the conventional ECU, that is, the ECU 11 assuming that the active clamp circuit 117 is not provided will be described with reference to FIG.

FIG. 8 shows an example of voltage waveforms of each part when the motor 10 (rotor) is rotated at a constant rotation speed by an external force during non-drive control of the motor 10 in the ECU 11 assuming that the active clamp circuit 117 is not provided. There is. In the first embodiment, in a coil in which a positive counter electromotive voltage higher than the ground potential (for example, zero volt) is generated, a current flowing to the neutral point N can be generated, and a negative reverse lower than the ground potential can be generated. It is assumed that the coil in which the electromotive voltage is generated can generate the current flowing through the inverter 103. Further, in the following, when the motor 10 is not driven and controlled, as described above, the switching elements 103 _UH to 103 _WL , the first power supply relay 105, the second power supply relay 106, and the motor relays 108 to 110 are all turned off. It is assumed that each part of the ECU 11 is in a state and has a potential corresponding to the ground potential.

FIG. 8A shows the waveforms of the counter electromotive voltages Vu, Vv, Vw of the stator coils 10U, 10V, 10W, and the neutral point potential VN. In the stator coils 10U, 10V, and 10W, the rotation of the motor 10 generates substantially sinusoidal counter electromotive voltages Vu, Vv, and Vw having a phase difference of an electric angle of 120 ° from each other. The coil in which a positive counter electromotive voltage is generated does not conduct with the neutral point N due to the diode D3 of the motor relay in the same phase, but the coil in which a negative counter electromotive voltage is generated is in the motor relay in the same phase. It conducts with the neutral point N via the diode D3. Therefore, the neutral point potential VN, which is the potential of the neutral point N, is generally the smallest of the negative counter electromotive voltages generated by the stator coils 10U, 10V, and 10W by the diodes D3 of the motor relays 108 to 110. It becomes the potential corresponding to. In other words, as shown in FIG. 8A, the neutral point potential VN generally fluctuates along the negative peak of the counter electromotive forces generated in the stator coils 10U, 10V, and 10W.

FIG. 8B shows the waveform of the inverter input voltage Vin. A current may flow from the neutral point N through the diode D3 in the coil in which the negative counter electromotive voltage is generated, but the neutral point N has no current supply source. Therefore, no current flows from the coil in which the negative counter electromotive voltage is generated to the noise filter circuit 107 through the diode D of the upper switching element having the same phase in the inverter 103. Therefore, the inverter input voltage Vin does not rise due to the charging of the capacitor of the noise filter circuit 107, and has a potential corresponding to the ground potential.

FIG. 8C shows waveforms of the gate potential Vg and the gate-source voltage Vgs of the motor relays 108 to 110. As described above, since there is no current supply source at the neutral point N and no voltage drop occurs in the gate-source resistance 114, the gate potential Vg of the motor relays 108 to 110 and the neutral point potential VN are substantially the same. It becomes. Since the source potentials of the motor relays 108 to 110 correspond to the neutral point potential VN, the gate-source voltage Vgs becomes substantially zero, and the motor relays 108 to 110 remain in the off state.

FIG. 8D shows waveforms of the drain-source voltage Vdsu of the U-phase motor relay 108, the drain-source voltage Vdsv of the V-phase motor relay 109, and the drain-source voltage Vdsw of the W-phase motor relay 110.

The drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are potential differences between the neutral point potential VN corresponding to the source potential and the counter electromotive voltage Vu, Vv, Vw corresponding to the drain potential.
Vdsu = Vu-VN
Vdsv = Vv-VN
Vdsw = Vw-VN

As described above, the neutral point potential VN is a potential corresponding to the smallest value among the negative counter electromotive voltages generated by the stator coils 10U, 10V, and 10W. Therefore, in particular, in a motor relay having the same phase as the coil in which the counter electromotive voltage Vu, Vv, Vw is at or near the peak in the positive direction, the drain-source voltage Vdsu, Vdsv, Vdsw becomes excessive and the motor The drain-source withstand voltage voltage inherent in the relays 108 to 110 may be exceeded. Therefore, the ECU 11 uses the active clamp circuit 117 to prevent the drain-source voltages Vdsu, Vdsv, and Vdsw from exceeding the drain-source withstand voltage Vlim. Next, the operation of the ECU 11 including the active clamp circuit 117 will be described with reference to FIG.

FIG. 5 shows an example of voltage waveforms of each part when the motor 10 (rotor) is rotated at a constant rotation speed by an external force during non-drive control of the motor 10 in the ECU 11 provided with the active clamp circuit 117.

FIG. 5A shows the waveforms of the counter electromotive voltages Vu, Vv, Vw of the stator coils 10U, 10V, 10W, and the neutral point potential VN. In the stator coils 10U, 10V, and 10W, the rotation of the motor 10 basically generates substantially sinusoidal counter electromotive voltages Vu, Vv, and Vw having a phase difference of an electric angle of 120 ° from each other. However, it differs from FIG. 8A in that the negative peaks of the counter electromotive voltages Vu, Vv, and Vw are clamped. This is due to the action of the active clamp circuit 117 described below.

The neutral point potential VN, and thus the anode potential of the Zener diode 122 in the active clamp circuit 117, is the most negative counter electromotive voltage generated in the stator coils 10U, 10V, 10W as described with respect to FIG. 8A. The potential corresponds to a small value. However, when the anode potential of the Zener diode 122 further decreases due to the rotation of the motor 10 and the reverse voltage of the Zener diode 122 becomes equal to or higher than the breakdown voltage, the Zener diode 122 yields and the anode potential becomes the first potential V1. Is held in. As a result, as will be described later, the gate potential Vg of the motor relays 108 to 110 is also held at the potential corresponding to the first potential V1 (see FIG. 5C). The first potential V1 is a negative potential that is lower than the ground potential by a potential difference corresponding to the breakdown voltage. When the Zener diode 122 yields, the neutral point N conducts with the ground via the Zener diode 122 after the breakdown and the gate-source resistance 114. Therefore, a current flows through the coil in which a negative counter electromotive voltage is generated from the neutral point N whose current supply source is ground via the diode D3 of the motor coil having the same phase as the current. Then, as shown in FIG. 5A, the neutral point potential VN drops to the second potential V2, which is lower than the first potential V1, due to the voltage drop in the gate-source resistance 114, and the current flows into the coil. The countercurrent voltage does not drop to a potential lower than the second potential V2. In this way, the negative peaks of the counter electromotive voltages Vu, Vv, and Vw generated in the stator coils 10U, 10V, and 10W are the ground potentials of the breakdown voltage of the Zener diode 122 and the voltage drop of the gate-source resistance 114. It is clamped by the second potential V2 subtracted from.

FIG. 5C shows waveforms of the gate potential Vg and the gate-source voltage Vgs of the motor relays 108 to 110. As described with respect to FIG. 5A, the anode potential of the Zener diode 122 after yielding is held at a negative first potential V1 lower than the ground potential. At this time, the neutral point potential VN drops to the second potential V2, which is lower than the first potential V1, due to the voltage drop in the gate-source resistance 114. Since the anode potential of the Zener diode 122 corresponds to the gate potential Vg of the motor relays 108 to 110, the gate potential Vg of the motor relays 108 to 110 is held at the potential corresponding to the first potential V1. Further, since the neutral point potential VN corresponds to the source potential of the motor relays 108 to 110, the gate-source voltage Vgs of the motor relays 108 to 110 is the potential difference (V1-) between the first potential V1 and the second potential V2. Corresponds to V2). If the resistance value of the gate-source resistance 114 is set so that the gate-source voltage Vgs at this time exceeds the gate threshold voltage, the motor relays 108 to 110 are turned on.

FIG. 5B shows the waveform of the inverter input voltage Vin. When the motor relay in phase with the coil in which the positive counter electromotive voltage is generated is turned on, current flows from the ground to the neutral point N via the diode D of the lower switching element in phase with the coil. .. A current flows from the neutral point N to the coil in which a negative counter electromotive voltage is generated via a motor relay in phase with the coil, and this current passes through the diode D of the upper switching element in phase with the coil. Flows to the noise filter circuit 107. As a result, the capacitor of the noise filter circuit 107 is charged, and the inverter input voltage Vin becomes a value larger than the ground potential.

FIG. 5D shows waveforms of the drain-source voltage Vdsu of the U-phase motor relay 108, the drain-source voltage Vdsv of the V-phase motor relay 109, and the drain-source voltage Vdsw of the W-phase motor relay 110. As described above, the drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are potentials corresponding to the smallest of the negative counter electromotive voltages generated by the stator coils 10U, 10V, and 10W. It is a potential difference between the sex point potential VN and the counter electromotive voltage Vu, Vv, Vw generated by the stator coils 10U, 10V, 10W. However, as described above, the negative peaks of the counter electromotive voltages Vu, Vv, and Vw generated in the stator coils 10U, 10V, and 10W are clamped (see FIG. 5A), so that the neutral point potential VN is , The potential is higher than that of the conventional ECU's neutral point potential VN (see FIG. 8A). Therefore, the maximum values of the drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are significantly smaller than those without the active clamp circuit 117 (see FIG. 8D). Therefore, by setting the clamp amount of the negative peak of the counter electromotive voltage Vu, Vv, Vw to a certain value or more, the drain-source voltage Vdsu, Vdsv, Vdsw should not exceed the drain-source withstand voltage Vlim. Can be done.

As is clear from the description with respect to FIG. 5, even if the motor 10 is rotated by an external force during non-drive control of the motor 10 and a counter electromotive voltage Vu, Vv, Vw is generated, the motor relays 108 to 110 are generated by the active clamp circuit 117. The drain-source voltage Vdsu, Vdsv, Vdsw is reduced. As a result, the drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are less likely to exceed the drain-source withstand voltage Vlim peculiar to each relay, so that the failure of the motor relays 108 to 110 is suppressed.

Further, the motor relays 108 to 110 are turned on by the action of the active clamp circuit 117, so that current can flow from each phase coil through the neutral point N. That is, a current flows into the neutral point N from the coil in which a positive counter electromotive voltage is generated, and this current flows from the ground through the diode D of the lower switching element of the inverter 103 having the same phase as the coil. Will be supplied. Further, a current flows from the neutral point N to the coil in which a negative counter electromotive voltage is generated, and this current is passed through the diode D of the upper switching element of the inverter 103 having the same phase as the coil. It flows to 107 to charge the capacitor. Therefore, when the motor 10 is rotated by an external force during non-drive control of the motor 10, an electric brake is generated in the motor 10, and the rotation speed of the motor 10 and thus the counter electromotive voltage Vu, Vv, Vw are rapidly reduced. As a result, the drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are less likely to exceed the inherent drain-source withstand voltage Vlim, so that failures of the motor relays 108 to 110 are suppressed.

As described above, according to the ECU 11, in addition to being able to suppress the failure of the motor relays 108 to 110 due to the active clamp circuit 117, the drains of the motor relays 108 to 110 are drained on the circuit board 125 by packaging the motor relays 108 to 110 and the like. Even when the terminals do not appear as a pattern, it becomes easy to mount the constituent elements of the active clamp circuit 117 on the circuit board 125.

[Second Embodiment]
Next, the motor drive control device according to the second embodiment will be described with reference to FIG. Like the ECU 11, the ECU 11a, which is a motor drive control device according to the present embodiment, is applied to the electric power steering 2 and controls the drive of the motor 10 that generates an assist torque.

In this embodiment, the parts different from those of the first embodiment will be mainly described, and the description of the first embodiment will be applied to the other parts as long as there is no contradiction. Therefore, the same reference numerals are given to the configurations similar to those of the first embodiment, and the description thereof will be omitted or simplified. The same applies to the following embodiments.

In the ECU 11a, the motor relays 108 to 110 are arranged on the second energizing line L2 between the stator coils 10U, 10V, 10W and the inverter 103. That is, the U-phase motor relay 108 is arranged on the second energizing line L2 between the U-phase coil 10U and the inverter 103, and the V-phase motor relay 109 is the second energizing line L2 between the V-phase coil 10V and the inverter 103. The W-phase motor relay 110 is arranged on the second energizing line L2 between the W-phase coil 10W and the inverter 103. In other words, in any of the motor relays 108 to 110, the source terminal is connected to the coil having the same phase, and the drain terminal is connected to the inverter 103.

A signal line for outputting a drive signal from the third driver 113 to the motor relays 108 to 110 is provided for each motor relay. That is, a control signal is output to the U-phase motor relay 108 via the U-phase signal line 120U, a drive signal is output to the V-phase motor relay 109 via the V-phase signal line 120V, and W is output to the W-phase motor relay 110. A drive signal is output via the phase signal line 120W.

The gate-source resistance 114 and the gate overvoltage protection element 115 are provided for each motor relay. That is, the gate-source resistance 114 and the gate overvoltage protection element 115 are provided by connecting the gate terminals of the motor relays 108 to 110 and the source terminals in parallel.

The active clamp circuit 117a is provided in the ground line 121 extending from the ground of the ECU 11a and the branch ground lines 121U, 121V, 121W which are branched at the branch point Na and connected to the signal lines 120U, 120V, 120W. Specifically, a Zener is applied to each of the U-phase branch ground line 121U connected to the signal line 120U, the V-phase branch ground line 121V connected to the signal line 120V, and the W-phase branch ground line 121W connected to the signal line 120W. The diode 122 is arranged. These Zener diodes 122 have a forward direction in which a current flows from the motor relays 108 to 110 to the branch point Na. Further, on the ground wire 121, a diode 123 having a forward direction in which a current flows from the ground to the branch point Na is arranged.

Next, the operation of the ECU 11a when the motor 10 (rotor) is rotated at a constant rotation speed by an external force during non-drive control of the motor 10 will be described. In the second embodiment, the coil in which a positive counter electromotive force higher than the ground potential is generated can generate a current flowing through the inverter 103, and a negative counter electromotive voltage lower than the ground potential is generated. It is assumed that the coil can generate a current flowing to the neutral point N.

When the coil in which the negative counter electromotive voltage is generated has a current supply source, the positive counter electromotive voltage is generated from the coil in which the negative counter electromotive voltage is generated through the neutral point N. Current flows through the coil. This current flows to the noise filter circuit 107 through the diode D3 of the motor relay in phase with the coil in which the positive countercurrent voltage is generated and the diode D of the upper switching element in phase with the coil in the inverter 103. However, in the active clamp circuit 117a, when the Zener diode 122 having the same phase as the coil in which the negative back electromotive force is generated does not yield, the coil in which the negative back electromotive force is generated grounds. It cannot be used as a current supply source. Therefore, no current flows from the coil in which the negative counter electromotive voltage is generated to the noise filter circuit 107.

When the negative counter electromotive voltage generated in one of the coils due to the rotation of the motor 10 further decreases and the reverse voltage of the Zener diode 122 having the same phase as the coil becomes equal to or higher than the breakdown voltage, the Zener diode 122 yields and the anode potential is held at the first potential V1. The first potential V1 is a potential lower than the ground potential by a potential difference corresponding to the breakdown voltage. When the Zener diode 122 yields, the source terminal of the motor relay in phase with the coil in which a negative countercurrent voltage is generated conducts with the ground via the Zener diode 122 after the breakdown and the gate-source resistance 114, and grounds. Current flows from the source terminal to the source terminal. At this time, the source potential of the motor relay having the same phase as the coil in which the negative counter electromotive voltage is generated decreases from the first potential V1 to the negative second potential V2 due to the voltage drop in the gate-source resistance 114. As a result, the source potential of the motor relay in phase with the coil in which the negative counter electromotive voltage is generated is clamped at the second potential V2. Therefore, the drain-source voltage of the motor relay in phase with the coil in which the negative counter electromotive voltage is generated is reduced as compared with the case where it is not clamped by the Zener diode 122. As a result, the drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are less likely to exceed the drain-source withstand voltage Vlim peculiar to each relay, so that the failure of the motor relays 108 to 110 is suppressed.

Further, in a motor relay having the same phase as the coil in which a negative countercurrent voltage is generated, the gate potential corresponds to the first potential V1 and the source potential corresponds to the second potential V2. The inter-voltage corresponds to the potential difference (V1-V2) between the first potential V1 and the second potential V2. If the resistance value of the gate-source resistance 114 is set so that the gate-source voltage at this time exceeds the gate threshold voltage, the motor relay is turned on. When the motor relay in phase with the coil in which the negative countercurrent voltage is generated is turned on, the coil is connected to the diode of the lower switching element in phase with the coil in the inverter 103 with the ground as the current supply source. Current flows in through D and a motor relay in phase with the coil. This current flows into the coil in which a positive countercurrent voltage is generated via the neutral point N, and then the upper switching of the diode D3 and the inverter 103 of the motor relay having the same phase as the coil and having the same phase as the coil. It flows to the noise filter circuit 107 via the diode D of the element to charge the capacitor. Therefore, when the motor 10 is rotated by an external force during non-drive control of the motor 10, an electric brake is generated in the motor 10, and the rotation speed of the motor 10 and thus the counter electromotive voltage Vu, Vv, Vw are rapidly reduced. As a result, the drain-source voltages Vdsu, Vdsv, and Vdsw of the motor relays 108 to 110 are less likely to exceed the inherent drain-source withstand voltage Vlim, so that failures of the motor relays 108 to 110 are suppressed.

According to such an ECU 11a, in addition to being able to suppress failures of the motor relays 108 to 110 by the active clamp circuit 117, it is possible to combine the diodes 123 of the active clamp circuit 117 into one. Therefore, as compared with the case where the active clamp circuit is provided between the gate and the drain of the motor relays 108 to 110, the number of constituent elements of the active clamp circuit 117 can be reduced, and the substrate area can be reduced.

The signal lines 120U, 120V, and 120W may be connected to the third driver 113 via the signal line 120, as in the ECU 11. In this case, the active clamp circuit 117a is provided by arranging the Zener diode 122 and the diode 123 on the ground wire 121 connected to the signal line 120 like the ECU 11. However, the gate-source resistance 114 and the gate overvoltage protection element 115 are provided in each of the motor relays 108 to 110.

[Third Embodiment]
Next, the motor drive control device according to the third embodiment will be described with reference to FIG. 7. Like the ECU 11, the ECU 11b, which is a motor drive control device according to the present embodiment, is applied to the electric power steering 2 and controls the drive of the motor 10 that generates an assist torque.

The ECU 11b is different from the ECU 11 in that it has an active clamp circuit diagnosis function for diagnosing a failure of the active clamp circuit 117. The active clamp circuit diagnostic function is embodied by a constant voltage output circuit 127, a neutral point potential monitor line 128, and a cathode potential monitor line 129, in addition to the microcomputer 116.

The constant voltage output circuit 127 is a circuit that applies a constant voltage output from a constant voltage power source such as a power supply circuit 101 to the cathodes of the Zener diode 122 and the diode 123 in response to a command signal from the microcomputer 116. The constant voltage output from the constant voltage output circuit 127 is a voltage (> 0) lower than the breakdown voltage of the Zener diodes 122 and 115.

In the illustrated example, the constant voltage output circuit 127 is configured by using the NPN transistor 130 and the PNP transistor 131. Specifically, in the NPN transistor 130, the base terminal is connected to the output port of the microcomputer 116, the emitter terminal is connected to the ground, and the collector terminal is connected to the base terminal of the PNP transistor 131 via the resistor 132. In the PNP transistor 131, the emitter terminal is connected to the constant voltage power supply 133, and the collector terminal is connected to the ground wire 121 connecting the cathodes of the Zener diode 122 and the diode 123.

The neutral point potential monitor line 128 is a signal line that connects the neutral point N and the microcomputer 116 and transmits a signal regarding the neutral point potential VN to the microcomputer 116. Further, the cathode potential monitor line 129 is a signal line for transmitting a signal relating to the cathode potential, which is the potential of the ground line 121 connecting the Zener diode 122 and the cathodes of the diode 123, to the microcomputer 116.

The microcomputer 116 measures the neutral point potential VN and the cathode potential based on the signals (these A / D conversion values, etc.) input to the input port via the neutral point potential monitor line 128 and the cathode potential monitor line 129. do. Then, the microcomputer 116 diagnoses whether or not a failure has occurred in the active clamp circuit 117 based on the measured potential.

Here, a mode of failure occurring in the active clamp circuit 117 will be described. As the failure that occurs in the active clamp circuit 117, a short circuit failure and a disconnection failure in each of the Zener diode 122 and the diode 123 are assumed.

When a short-circuit failure occurs in the Zener diode 122 of the active clamp circuit 117, the negative reverse is caused by the rotation of the motor 10 via the ground wire 121, the neutral point N, and the diode D3 with the ground as the current supply source. A current flows into the coil in which the electromotive voltage is generated. Therefore, when the gate-source voltage of the motor relays 108 to 110 exceeds the gate threshold voltage due to the voltage drop in the gate-source resistance 114, the motor relays 108 to 110 are forcibly turned on.

If a short-circuit failure has occurred in the diode 123 of the active clamp circuit 117, even if a drive signal is output from the third driver 113, it will be absorbed by the ground and the motor relays 108 to 110 may be turned on. become unable.

If at least one of the Zener diode 122 and the diode 123 of the active clamp circuit 117 has a disconnection failure, the active clamp circuit 117 will not function. Therefore, due to the rotation of the motor 10, the drain-source voltage of the motor relays 108 to 110 may exceed the drain-source withstand voltage Vlim peculiar to the motor relay, and the motor relays 108 to 110 may fail.

Using the active clamp circuit diagnostic function configured as described above, the ECU 11b diagnoses the short-circuit failure and disconnection failure assumed in each of the Zener diode 122 and the diode 123 of the active clamp circuit 117 as follows. .. Such a diagnosis is performed when the drive control of the motor 10 is stopped.

The microcomputer 116 makes the following circuit settings in order to diagnose whether or not a short-circuit failure has occurred in the Zener diode 122. That is, the microcomputer 116 sends a control signal for turning off the first power supply relay 105, the second power supply relay 106, the switching elements 103 _UH to 103 _WL of the inverter 103, and the motor relays 108 to 110 to the first driver 111 and the first driver 111. 2 Outputs to the driver 112, the third driver 113, and the inverter drive circuit 104. Further, the microcomputer 116 outputs a control signal for turning on the NPN transistor 130 of the constant voltage output circuit 127. Under such a circuit setting, a voltage (> 0) lower than the breakdown voltage of the Zener diodes 122 and 115 can be applied to the cathodes of the Zener diode 122 and the diode 123 in the active clamp circuit 117 by the constant voltage output of the constant voltage output circuit 127. Will be done. The microcomputer 116 determines that the cathode potential acquired from the signal input via the cathode potential monitor line 129 is a potential (> 0) lower than the potential obtained by adding the breakdown voltage of the Zener diodes 122 and 115 to the ground potential. Make a diagnosis on the condition.

When the Zener diode 122 is normal, the Zener diode 122 does not yield, so that no current flows from the constant voltage output circuit 127 to the neutral point N. Therefore, both the anode potential of the Zener diode 122 and the neutral point potential VN become potentials corresponding to the ground potential, and the gate-source voltage of the motor relays 108 to 110 becomes substantially zero, so that the motor relay 108 to 110 is in the off state. On the other hand, when a short-circuit failure occurs in the Zener diode 122, a current flows from the constant voltage output circuit 127 to the neutral point N via the Zener diode 122 and the gate-source resistor 114. This current further flows to the noise filter circuit 107 via the diodes D3 of the motor relays 108 to 110 and the diodes D of the upper switching elements 103 _UH , 103 _VH , and 103 _WH of the inverter 103 to charge the capacitor. Therefore, the anode potential of the Zener diode 122 is held at the first potential V1, and the neutral point potential VN becomes the second potential V2 lower than the first potential V1 due to the voltage drop in the gate-source resistance 114. As a result, when the gate-source voltage of the motor relays 108 to 110, which is the potential difference (V1-V2) between the first potential V1 and the second potential V2, exceeds the gate threshold voltage, the motor relays 108 to 110 become the third. It remains on regardless of the drive signal output from the driver 113. Therefore, the neutral point potential VN (corresponding to the ground potential) when the Zener diode 122 is normal and the neutral point potential VN (corresponding to the second potential V2) when a short-circuit failure occurs in the Zener diode 122 are defined. By setting a predetermined value, it can be diagnosed that a short-circuit failure has occurred in the Zener diode 122 when the neutral point potential VN is equal to or higher than the predetermined value.

The microcomputer 116 makes the following circuit settings in order to diagnose whether or not a short-circuit failure has occurred in the diode 123. That is, the microcomputer 116 first sends a control signal for turning on the first power supply relay 105, the second power supply relay 106, the upper switching element 103 _UH , 103 _VH , 103 _WH of the inverter 103, and the motor relays 108 to 110. It outputs to the driver 111, the second driver 112, the third driver 113, and the inverter drive circuit 104. Under such a circuit setting, when the diode 123 is normal, the current path from the neutral point N to the ground via the resistors 114 and the Zener diodes 122 and 115 is cut off by the diode 123. Therefore, the neutral point potential VN becomes a value corresponding to the output voltage of the vehicle-mounted battery 16. On the other hand, when a short-circuit failure occurs in the diode 123, a current flows from the neutral point N to the ground via the resistors 114 and the Zener diodes 122 and 115, and the neutral point potential VN is the output voltage of the vehicle-mounted battery 16. Significantly decreases from. Therefore, by setting a predetermined value that defines the neutral point potential VN when the diode 123 is normal and the neutral point potential VN when a short-circuit failure occurs in the diode 123, the neutral point potential VN can be set. If it is less than a predetermined value, it can be diagnosed that a short circuit failure has occurred in the diode 123.

The microcomputer 116 indirectly diagnoses whether or not a disconnection failure has occurred in at least one of the Zener diode 122 and the diode 123 by the failure diagnosis of the motor relays 108 to 110. Specifically, the microcomputer 116 sends a control signal for turning on the first power supply relay 105, the second power supply relay 106, and the upper switching elements 103 _UH , 103 _VH , 103 _WH of the inverter 103 to the first driver 111, Output to the second driver 112 and the inverter drive circuit 104. Under such a circuit setting, when the microcomputer 116 outputs a control signal for turning on the motor relays 108 to 110 to the third driver 113, the neutral point potential VN is more significant than the output voltage of the vehicle-mounted battery 16. If it is too low, it can be diagnosed that the motor relays 108 to 110 are stuck off. On the other hand, when the microcomputer 116 outputs a control signal for turning off the motor relays 108 to 110 to the third driver 113 and the neutral point potential VN is significantly higher than the ground potential, the motor relays 108 to It can be diagnosed that on-sticking has occurred in 110. By the way, the failure of the motor relays 108 to 110 such as sticking on or sticking off may have occurred due to the fact that the active clamp circuit 117 is not functioning. Therefore, when the microcomputer 116 diagnoses that the motor relays 108 to 110 have a failure, it diagnoses that at least one of the Zener diode 122 and the diode 123 may have a disconnection failure. can.

According to such an ECU 11b, in addition to having the same effect as that of the ECU 11, it is possible to diagnose a failure of the active clamp circuit 117 when the drive control of the motor 10 is stopped. Therefore, according to the ECU 11b, when it is diagnosed that the active clamp circuit 117 is out of order, the drive control of the motor 10 can be stopped or limited to avoid the secondary failure of the motor 10 and the ECU 11b. It will be possible.

The electric power steering 2 may be configured to be redundant. In the redundant electric power steering 2, the motor 10 includes a plurality of electrically independent winding sets with the U-phase coil 10U, the V-phase coil 10V, and the W-phase coil 10W as one winding set. Any of 11a and 11b can be provided for each winding set. Each ECU can also include a torque sensor 13, a rotation angle sensor 14, a vehicle speed sensor 15, and an in-vehicle battery 16. In short, the redundant electric power steering 2 has a plurality of systems, with the ECU provided for one winding set of the motor 10 and the sensors associated therewith as one system. In the electrically redundant electric power steering 2 as described above, even if one system fails, the drive control of the motor 10 can be continued in the other system, and the reliability of the electric power steering 2 can be improved. .. The board area of the ECUs 11, 11a, and 11b increases due to the redundancy of the electric power steering 2, but in the ECU 11a in particular, the number of constituent elements of the active clamp circuit 117 can be reduced, so that the increase in the board area can be suppressed. It becomes valid.

In the ECU 11b, the active clamp circuit diagnostic function has been added to the configuration of the ECU 11, but the active clamp circuit diagnostic function can be added to the configuration of the ECU 11a. In this case, the voltage output from the constant voltage output circuit 127 is applied to the branch point Na (see FIG. 6).

In the first to third embodiments, the ECUs 11, 11a, and 11b that drive and control the motor 10 that generates the assist torque in the electric power steering 2 are exemplified as the motor drive control device, but the present invention is not limited thereto. For example, even if it is a motor drive control device that drives and controls the motor 10 used in a compression ratio variable mechanism that makes the compression ratio variable in an internal combustion engine, a variable valve timing mechanism that makes the opening / closing timing of an intake / exhaust valve variable, and the like. Anything that has a relay is applicable.

Although the contents of the present invention have been specifically described with reference to the preferred embodiments, the technical ideas described above can be appropriately combined and used as long as there is no contradiction. Further, it is obvious that those skilled in the art can adopt various modifications based on the basic technical idea and teaching of the present invention.

10 ... Motor, 10U, 10V, 10W ... Stator coil, 11, 11a, 11b ... ECU, 103 ... Inverter, 108, 109, 110 ... Motor relay, 116 ... Microcomputer, 117, 117a ... Active clamp circuit, 121 ... Ground Wire, 121U, 121V, 121W ... Branch ground wire, 122 ... Zener diode, 123 ... Diode, 127 ... Constant voltage output circuit, 128 ... Neutral point potential monitor wire, 129 ... Cathode potential monitor wire, L1 ... First energizing line , L2 ... 2nd energizing line, N ... neutral point, V2 ... 2nd potential

Claims (3)

An inverter that energizes the multi-phase coils of an electric motor with a neutral point,
It is arranged on either the first current-carrying wire of each phase between the multi-phase coil and the neutral point or the second current-carrying wire of each phase between the inverter and the multi-phase coil, and is external. A semiconductor relay that cuts off the energization from the inverter to the neutral point by control from
When the semiconductor relay is arranged on the first energizing line, the potential difference between the first energizing line on the neutral point side of the semiconductor relay and the ground rises to a predetermined voltage, or the semiconductor relay. Is arranged on the second energizing line, and when the potential difference between the second energizing line on the coil side of the semiconductor relay and the ground rises to a predetermined voltage, the potential difference is held at the predetermined voltage. With the active clamp circuit,
Equipped with a motor drive control device. When the semiconductor relay is arranged on the first energizing line, the first energizing line on the neutral point side of the semiconductor relay and the control terminal of the semiconductor relay are connected via a resistor, while the said. When the semiconductor relay is arranged on the second energizing line, the second energizing line on the coil side of the semiconductor relay and the control terminal of the semiconductor relay are connected via a resistor.
The motor drive control device according to claim 1, wherein the active clamp circuit is arranged on a ground line connecting the control terminal and the ground. The motor drive control device according to claim 1 or 2, further comprising a diagnostic function for diagnosing the active clamp circuit.

Images