JP2021129391A - Motor drive device - Google Patents

Abstract

To provide a motor drive device that can determine a failure by detecting a current when a reflux switch is fixed at OFF.SOLUTION: A drive circuit 30D connects series circuits of reflux switches 34 to 36 and drive switches 31 to 33 corresponding to respective phases between a vehicle power supply 1 and the ground, and connects common connection points of the series circuits to respective phase coils 21a to 21c of a motor 21 to drive the motor 21. Current detection resistors 37u, 37v, and 37w are arranged in an energization path between the drive circuit 30D and each of the phase coils 21a to 21c to detect respective phase currents to be energized. A control circuit 40 controls ON/OFF of each of the switches 31 to 36 constituting the drive circuit 30D on the basis of the current detected by the current detection resistor 37. Further, the control circuit 40 detects an OFF fixed failure of the reflux switches 34 to 36 on the basis of a current value to be detected when at least the reflux switches 34 to 36 are turned on in a case in which the drive switches 31 to 33 are alternately turned on and off while suppressing the rotation of the rotor of the motor 21.SELECTED DRAWING: Figure 1

Description

The present invention relates to a device for driving a polyphase motor.

As a device that controls the shift mechanism of the vehicle by a motor drive device, there is a device that controls shift by wire (hereinafter referred to as SBW). In SBW control, the shift range is switched by driving and controlling the three-phase motor SRM (switched reluctance motor) by the motor drive circuit included in the motor control unit and transmitting the motor rotation to the shaft via gears. Drive the mechanism by a specific angle. As a result, the shift position of parking (P), reverse (R), neutral (N), drive (D), etc. is switched.

A motor drive device that performs such drive control shortens the rise time of the current by keeping the switch in the energization path of the coil of the energization phase in the on state when the drive current starts up, and at the start of energization, for example. By securing sufficient torque quickly, high-speed motor drive is realized. Further, when the drive current is turned off, the current disappears quickly and the torque becomes zero by keeping the switch of the energizing phase in the off state.

In this case, in the case where the H-bridge circuit is used as the energizing circuit for the motor, a diode for reflux is used corresponding to the reflux of the motor drive current. As a result, the forward voltage Vf of the diode is generated even when the motor coil is energized while the motor coil is energized, and heat is continuously generated in the diode due to the time integration of the electric power represented by the drive current × the forward voltage. For this reason, it is necessary to use a diode for reflux having high heat resistance, which has led to an increase in cost and size.

On the other hand, the applicant proposes a configuration in which the reflux diode is replaced with a reflux switch such as a MOSFET and the reflux switch is turned on at the timing when the reflux current flows to reduce the loss due to heat generation. doing.

Japanese Unexamined Patent Publication No. 2012-12509 Japanese Patent Application No. 2019-138795

In the above configuration, it is assumed that the state in which the reflux switch is fixed at OFF is determined as a failure by detecting the current. In this case, since the current flowing through the coil fluctuates during the period in which the rotation of the motor is controlled, there is a problem that the detected current cannot be compared with a predetermined value for determination.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a motor drive device capable of determining a failure by detecting a current when the reflux switch is fixed at OFF. ..

According to the motor drive device according to the first aspect, as a drive circuit for driving the multi-phase motor, a drive power supply and a ground are provided as a drive circuit having a return diode and a series circuit of the drive switch corresponding to each phase. Connect to and connect the common connection point of the series circuit to each phase coil of the multi-phase motor. The current detection unit is arranged in the energization path between the drive circuit and each phase coil, and detects each phase current to be energized. The control unit controls ON / OFF of each switch constituting the drive circuit based on the current detected by the current detection unit. Further, the control unit is a reflux switch based on the current value detected at least when the reflux switch is turned ON when the drive switch is alternately turned ON / OFF while suppressing the rotation of the rotor of the multi-phase motor. OFF Fixed failure is detected.

With this configuration, a stable current at a level that can suppress the rotation of the rotor is alternately turned on and off of the drive switch to energize the coil of the motor. Then, at least by monitoring the current value detected when the reflux switch is turned on, it is possible to determine whether or not the reflux switch is in the OFF-fixed state, so that it is possible to detect an OFF-fixed failure. ..

Specifically, as in the motor drive device according to claim 2, the control unit compares the current value detected when the reflux switch is turned on with the reference value to detect an OFF fixed failure of the reflux switch. do. That is, when comparing the current flowing through the reflux switch when the reflux switch is turned on and the current flowing through the reflux diode when the reflux switch is turned off, the latter case is consumed by the diode. The larger the power, the faster the current falls. As a result, the current value becomes smaller than the current flowing in the former case. On the other hand, when the reflux switch is fixed at OFF, there is no difference in the current values between the two, so that an OFF fixing failure can be detected.

Further, according to the motor drive device according to claim 3, the control unit turns off the current value detected in the first energization pattern in which the reflux switch is turned on and the reflux switch is turned off while the drive switch is turned off. Based on the result of comparison with the current value detected in the second energization pattern in the case of the above, the OFF fixed failure of the reflux switch is detected. Also in this case, as described in claim 2, the OFF fixed failure can be detected by the difference in the current values when the reflux switch is turned ON and OFF.

The figure which shows 1st Embodiment and shows the electric structure of the motor drive device. Schematic configuration of SBW system Flowchart showing the processing contents of the control circuit The figure which shows the 1st and 2nd energization pattern and the current waveform according to the presence or absence of OFF fixed failure. FIG. 2 is a diagram showing a current waveform according to the presence or absence of an OFF fixed failure in the second embodiment. FIG. 3 is a diagram showing current waveforms according to the presence / absence of the first and second energization patterns and OFF fixed failure in the third embodiment. A flowchart showing the processing contents of the control circuit according to the fourth embodiment. OFF fixed diagram showing the current waveform according to the presence or absence of failure FIG. 5 is a diagram showing an electrical configuration of a motor drive device according to a fifth embodiment.

(First Embodiment)
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 4. In FIG. 1, the motor drive device 100 includes a motor unit 20 and a motor control unit 30, and receives power from a vehicle power supply 1 via power supply lines L1 and L2 to drive and control the motor 21 of the motor unit 20 to transmit driving force. The SBW system is driven and controlled via the unit 2. The driving force transmission unit 2 transmits the driving force transmitted from the motor 21 to the shift range switching mechanism 4 via the shaft 3 which is the output shaft, that is, the rotational force. Hereinafter, it is simply referred to as "switching mechanism 4". The motor 21 is an example of a multi-phase motor.

The motor unit 20 includes a motor 21 and an encoder sensor 22, and the rotational force of the motor 21 is decelerated by a reduction mechanism 23 combined with gears and transmitted to the shaft 3. The motor 21 is a three-phase SRM, and the rotor is composed of a magnetic material having a predetermined number of salient poles. The motor 21 is provided with coils 21a, 21b, and 21c corresponding to three phases of U phase, V phase, and W phase as stators, and the rotor rotates by the suction force generated by direct current energization to these coils 21a to 21c. .. One end side of the coils 21a to 21c is commonly connected to the power supply line L1. The motor control unit 30 selectively energizes the other ends of the coils 21a to 21c.
The encoder sensor 22 detects the rotation position of the rotor of the motor 21, and the rotation position signal output by the sensor 22 is read by the motor control unit 30.

The motor control unit 30 includes six switches 31 to 36 composed of n-channel type MOS transistors and also includes a control circuit 40. The six switches 31 to 36 have body diodes 31a to 36a, respectively. Hereinafter, these are simply referred to as diodes 31a to 36a. Further, the switches 31 to 36 include drive switches 31 to 33 connected to the low side of the power supply line L2 side and reflux switches 34 to 36 connected to the high side of the power supply line L1 side. The drive switch 31, the reflux switch 34, the drive switch 32 and the reflux switch 35, the drive switch 33, and the reflux switch 36 are connected in series, respectively. That is, the six switches 31 to 36 are connected by a three-phase bridge, and these constitute the drive circuit 30D.

The positive terminal of the vehicle power supply 1 is connected to the power supply line L1 via the motor power relay 38, and the power supply line L2 is connected to the ground in common with the negative terminal of the vehicle power supply 1. As a result, the DC voltage of the vehicle power supply 1 corresponding to the driving power supply is supplied to the motor control unit 30. The power supply line L1 is connected to one end side common to the coils 21a to 21c of the motor 21. The common connection points of the return switches 34 to 36 and the drive switches 31 to 33 are connected to the other end side of the coils 21a to 21c via the current detection resistors 37U, 37V and 37W.

The control circuit 40 includes a microcomputer 41 and a control IC 42. Hereinafter, it is referred to as a microcomputer 41. A gate drive signal is given to each gate of the switches 31 to 36 from the control IC 42. The microcomputer 41 drives and controls the drive switches 31 to 33 and the reflux switches 34 to 36 via the control IC 42, and takes in the terminal voltages of the current detection resistors 37U, 37V, and 37W, respectively, to drive the motor drive currents Iu, Iv. , Iw is detected. The current detection resistor 37 is an example of a current detection unit.

Further, the positive terminal of the vehicle power supply 1 is connected to the power supply terminal of the control IC 42 via the ignition relay 39. The ON / OFF of the ignition relay 39 is controlled by the upper ECU 50 according to the ON / OFF of the ignition switch of the vehicle. Further, the motor power relay 38 is turned ON / OFF by the microcomputer 41 via the control IC 42.

As shown in FIG. 2, the motor unit 20 is driven and controlled by the motor control unit 30, and functions as a drive source for the switching mechanism 4. The switching mechanism 4 includes a detent plate 5 and a detent spring 6 fixed to the shaft 3, and transfers the rotational driving force of the shaft 3 output from the deceleration mechanism 23 to the manual valve 7 of the driving force transmission unit 2 and the parking lock unit. Communicate to 8. The detent plate 5 is provided with a pin 5a projecting in the direction of the shaft 3 and is engaged with a groove portion at the tip of the manual valve 7.

The pin 5a of the manual valve 7 is rotationally moved by the rotational drive of the detent plate 5 by the motor unit 20, and is reciprocated in the axial direction by the driving force transmitted through the portion of the manual valve 7 that engages with the pin 5a. NS. The manual valve 7 is provided on the valve body 9, and the shift range is changed by the manual valve 7 reciprocating in the axial direction.

At a position in contact with the detent spring 6 on the outer peripheral side of the detent plate 5, four recesses 5b for holding the manual valve 7 at a position corresponding to each range are provided. The rotational position of the detent plate 5 is held at the position of any recess 5b by the urging force of the detent spring 6.

The recess 5b corresponds to each range of D (drive), N (neutral), R (rear), and P (parking) from the base side of the detent spring 6. That is, the position where the detent plate 5 is rotated most in the forward rotation direction is the D position, and the position where the detent plate 5 is rotated most in the reverse rotation direction is the P position.

The parking lock portion 8 includes a parking rod 10, a cone 11, a parking lock pole 12, a shaft portion 13, and a parking gear 14. When the detent plate 5 swings in the reverse rotation direction, that is, in the rotation direction opposite to the "forward rotation direction" in the drawing, the parking rod 10 moves the cone 11 in the direction of the arrow P. As a result, the parking lock pole 12 is pushed up in the direction of the arrow L, and the convex portion 12a and the parking gear 14 are engaged with each other to lock the parking gear 14.

Next, the operation of this embodiment will be described. In the present embodiment, the control circuit 40 performs a process for detecting a state in which the reflux switches 34 to 36 are fixed at OFF as an “OFF fixed failure”. At that time, a current that is a condition for not rotating the rotor of the motor 21 is applied to the phase coils 21a, 21b, and 21c of the motor 21.

As shown in FIG. 3, the microcomputer 41 starts monitoring the pulse signal output by the encoder sensor 22 as the rotation position signal and the drive currents Iu, Iv, and Iw of the motor 21 (S1). Then, the calculation of the rotation speed of the motor 21 is started based on the output interval of the pulse signal (S2). Next, when the energization of the motor 21 is stopped (S3), it is determined whether or not the rotation of the motor 21 has stopped (S4).

When the rotation of the motor 21 is stopped (YES), the microcomputer 41 drives the drive switches 31 to 33 of each phase in step S5 by PWM (Pulse Width Modulation), for example, at a duty ratio of 30%, as shown in FIG. .. As a result, a current of, for example, about 10 A is passed through the coils 21a to 21c under the condition that the rotor is not rotated, but the reflux switches 34 to 36 are not PWM driven and are maintained in the OFF state.

Then, the phase current flowing through the phase coils 21a to 21c is detected as I1 (S6), and the current value I1 is recorded in the memory or the like inside the microcomputer 41 (S7). The current value I1 detects the peak value of the current waveform. In step S5, for example, the reflux current when the drive switch 31 is turned off flows through the diode 34a of the reflux switch 34. The energization pattern here corresponds to the second energization pattern.

In the following steps S8 and S9, the same processing as in steps S3 and S4 is performed. Then, similarly to step S5, the drive switches 31 to 33 are PWM-driven at a duty ratio of 30%, but here, the reflux switches 34 to 36 are PWM-driven in a complementary manner (S10). Then, the phase current flowing through each of the phase coils 21a to 21c is detected as I2 (S11). In step S10, for example, the reflux current when the drive switch 31 is turned off flows through the reflux switch 34. The energization pattern here corresponds to the first energization pattern.

Then, when the energization of the motor 21 is stopped (S12), the microcomputer 41 calculates the difference between the current value I2 and the current value I1 of each phase (S13), and determines whether or not the obtained difference is equal to or greater than the predetermined value ΔI. Judgment (S14). If the difference is greater than or equal to the predetermined value ΔI (YES), the reflux switches 34 to 36 are determined to be normal (S15), and if the difference is less than the predetermined value ΔI (NO), the reflux switches 34 to 36 are abnormal, that is, “ It is determined that "OFF fixed failure" (S16). Then, for example, a diagnostic notification is sent to the upper ECU 50 (S17).

As shown in FIG. 4, in the second energization pattern in step S5, the reflux current flows through, for example, the U-phase diode 34a, so that a loss corresponding to the forward voltage Vf occurs. As a result, the slope at which the current decreases becomes steep. On the other hand, in the first energization pattern in step S10, since the recirculation current flows through the recirculation switch 34, the loss unlike the second energization pattern does not occur, and the inclination of the current decrease is gentled accordingly.

Therefore, in the first energization pattern, if the return switch 34 is normally turned ON and OFF with the PWM drive, the current value I2 becomes larger than the current value I1. Then, if any of the reflux switches 34 to 36 is "OFF fixed failure", the first energization pattern becomes equal to the second energization pattern, and the current value I2 becomes substantially the same value as the current value I1. As a result, the failure determination of the reflux switches 34 to 36 is performed.

As described above, according to the present embodiment, as the drive circuit 30D for driving the motor 21, a series circuit of the return switches 34 to 36 and the drive switches 31 to 33 is provided with the vehicle power supply 1 and the ground corresponding to each phase. The common connection point of the series circuit is connected to each of the phase coils 21a to 21c of the motor 21. Current detection resistors 37U, 37V, 37W are arranged in the energization path between the drive circuit 30D and the phase coils 21a to 21c, and each phase current energized by these is detected. The control circuit 40 controls ON / OFF of each of the switches 31 to 36 constituting the drive circuit 30D based on the current detected by the current detection resistor 37. Further, the control circuit 40 is a current value detected when at least the reflux switches 34 to 36 are turned on when the drive switches 31 to 33 are alternately turned on and off while suppressing the rotation of the rotor of the motor 21. The OFF fixed failure of the reflux switches 34 to 36 is detected based on the above.

Specifically, the current value I1 detected in the first energization pattern in which the recirculation switches 34 to 36 are turned on while the drive switches 31 to 33 are turned off, and the second energization when the recirculation switch is turned off. The OFF fixed failure can be detected based on the result of comparison with the current value I2 detected in the pattern, that is, the difference between the current values I2 and I1.
Further, the control circuit 40 simultaneously energizes the phase coils 21a to 21c of the motor 21 according to the same energization pattern, so that the current energized in the phase coils 21a to 21c is applied under the condition that the rotor is not rotated. It can be detected in a substantially steady state.

(Second Embodiment)
Hereinafter, the same parts as those in the first embodiment are designated by the same reference numerals, description thereof will be omitted, and different parts will be described. In the second embodiment, as shown in FIG. 5, the current values I1 and I2 detected in steps S6 and S11 are obtained as values obtained by averaging a plurality of detected values. Then, in step S13, the average value of the current value I1 and the average value of the current value I2 are compared.

(Third Embodiment)
In the third embodiment, as shown in FIG. 6, the current values I1 and I2 detected in steps S6 and S11 are captured by the peak value of the current waveform at a specific number of times when the drive switches 31 to 33 are turned on, respectively. Then, in step S13, the peak value of the current value I1 and the peak value of the current value I2 are compared. In this way, when capturing the peak value of the current waveform, it is desirable to perform it within a period in which there is a difference between the peak values of the current values I1 and I2. Specifically, it is preferable to set the peak value according to the second and subsequent drive signal pulses. As long as the current value is within a relatively stable period, the number of peak values of the current value I1 and the number of peak values of the current value I2 may be different.

(Fourth Embodiment)
In the fourth embodiment, as shown in FIGS. 7 and 8, only the first energization pattern in step S10 is executed to detect the OFF fixed failure. As shown in FIG. 7, steps S10 to S12 are executed following steps S1 to S4. Then, the difference between the current value (I2) of each phase detected in step S11 and the predetermined reference value set in advance is calculated (S21). After that, steps S14 to S17 are executed in the same manner as in the first embodiment.

As described above, according to the fourth embodiment, the microcomputer 41 compares the current value detected when the first energization pattern is executed and the reflux switches 34 to 36 are turned on with the reference value, and is fixed to OFF. Is detected, so that the OFF fixed failure can be detected by a simpler control than in the first embodiment or the like.

(Fifth Embodiment)
The fifth embodiment shows a configuration in which a current limiting resistor is used to suppress the rotation of the rotor of the motor 21. As shown in FIG. 9, a changeover switch 51 and a current limiting resistor 52 are connected between the power supply line L2 and the ground. One of the fixed terminals of the changeover switch 51 is connected to the ground via the current limiting resistor 52, and the other is directly connected to the ground. Then, the microcomputer 41 controls the switching of the changeover switch 51.

In normal control for driving the motor 21, the changeover switch 51 is switched to the ground side, and for example, in the first embodiment, the changeover switch 51 is switched to the current limiting resistor 52 side immediately before executing steps S5 and S10. With this control, the degree of freedom in setting the PWM duty ratio when turning on / off the drive switches 31 to 33 can be further increased.

(Other embodiments)
Although a three-phase motor 21 is used, it can also be applied to a multi-phase motor having four or more phases.
The drive switch can be placed on the high side and the reflux switch can be placed on the low side. In this case, the coils 21a to 21c may be connected to the ground side at one end side which is commonly connected.
In addition to the MOS transistor, a switching element such as an IGBT can be used for the drive switch and the reflux switch.

As the diode forming the reflux path, an external diode may be used instead of the body diode.
The second and third embodiments may be applied to the fourth embodiment.
In the fifth embodiment, the changeover switch and the current limiting resistor may be arranged on the power supply line L1 side.
The functions realized by the microcomputer 41 and the control IC 42 may be realized by either hardware or software, or by collaboration between the hardware and the software.
Not limited to the SBW system, it may be applied to other systems and the like.
Although the present disclosure has been described in accordance with the examples, it is understood that the present disclosure is not limited to the examples and structures. The present disclosure also includes various modifications and modifications within a uniform range. In addition, various combinations and forms, as well as other combinations and forms that include only one element, more, or less, are also within the scope of the present disclosure.

In the drawing, 1 is the vehicle power supply, 2 is the driving force transmission unit, 4 is the shift range switching mechanism, 5 detent plate, 7 is the manual valve, 20 is the motor unit, 21 is the motor, 21a to 21c are the coils, and 23 is the deceleration mechanism. , 30, 50, 60, 70 are motor control units, 30D is a drive circuit, 31 to 33 are drive switches, 34 to 36 are recirculation switches, 40 is a control circuit, 41 is a microcomputer, and 42 is a control IC. ..

Claims (11)

It drives a multi-phase motor (21).
A series circuit of the recirculation switch (34 to 36) and the drive switch (31 to 33) each having a recirculation diode (34a to 36a) is provided between the drive power supply (1) and the ground corresponding to each phase. A drive circuit (30D) connected to the series circuit and a common connection point of the series circuit connected to each phase coil (21a to 21c) of the multi-phase motor.
A current detection unit (37U to 37W) arranged in the energization path between the drive circuit and each of the phase coils and detecting each phase current to be energized, and
A control unit (40) for controlling ON / OFF of each switch constituting the drive circuit is provided based on the current detected by the current detection unit.
The control unit alternately turns on / off the drive switch while suppressing the rotation of the rotor of the multi-phase motor, and at least based on the current value detected when the reflux switch is turned on. A motor drive device that detects an OFF fixed failure of the reflux switch. The motor drive device according to claim 1, wherein the control unit compares a current value detected when the reflux switch is turned on with a predetermined reference value to detect an OFF fixed failure of the reflux switch. While the control unit turns off the drive switch,
Based on the result of comparing the current value detected in the first energization pattern in which the reflux switch is turned on with the current value detected in the second energization pattern when the reflux switch is turned off, the reflux switch is used. The motor drive device according to claim 1, wherein a switch OFF fixed failure is detected. If the difference between the current value detected in the first energization pattern and the current value detected in the second energization pattern is less than a predetermined value, the control unit detects the OFF fixed failure of the reflux switch. 3. The motor drive device according to claim 3. The motor drive device according to claim 3 or 4, wherein the control unit compares the average value of the currents detected in the first energization pattern with the average value of the currents detected in the second energization pattern. The control unit has a peak value of the current detected during the period when the current is relatively stable in the first energization pattern and a peak value of the current detected during the period when the current is relatively stable in the second energization pattern. The motor driving device according to claim 3 or 4. The motor drive device according to claim 6, wherein the control unit compares the peak values of the currents detected when the drive switch is turned on a specific number of times in the first and second energization patterns. The motor driving device according to claim 7, wherein the specific number of times is the second and subsequent times. The motor drive device according to any one of claims 1 to 8, wherein the control unit limits the amount of current energized in the coil to suppress rotation of the rotor. The motor drive device according to any one of claims 1 to 8, wherein the control unit suppresses rotation of the rotor by energizing each phase coil at the same time. The multi-phase motor is a switched reluctance motor (SRM), according to any one of claims 1 to 10, wherein one end of a coil of all phases is commonly connected to one terminal of a drive power supply. Motor drive.

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