JP7331723B2 - motor drive - Google Patents

Description

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

2. Description of the Related Art Shift By Wire (hereinafter referred to as SBW) control is used as a motor driving device for controlling a shift mechanism of a vehicle. In the SBW control, the motor drive circuit included in the motor control unit drives and controls the SRM (switched reluctance motor), which is a three-phase motor. Drive the mechanism by a specific angle. Thereby, the shift positions such as parking (P), reverse (R), neutral (N), and drive (D) are switched.

A motor drive device that performs such drive control shortens the rise time of the current by, for example, maintaining the ON state of a switch in the energization path of the coil of the energized phase when the drive current rises, and High-speed motor drive is achieved by ensuring sufficient torque quickly. Further, when the drive current falls, by keeping the switch of the energized phase in the OFF state, the current disappears quickly and the torque becomes zero.

In this case, when an H-bridge circuit is used as a circuit for energizing the motor, a freewheeling diode is used in correspondence with the freewheeling of the motor drive current. As a result, the forward voltage Vf of the diode is generated even during freewheeling while the motor coil is energized, and heat is continuously generated in the diode due to the time integration of the power indicated by the drive current×forward voltage. For this reason, it is necessary to use a diode with high heat resistance for the freewheeling diode, which causes an increase in cost and size.

In response to this, the applicant proposes a configuration that reduces loss due to heat generation by replacing the freewheeling diode with a freewheeling switch such as a MOSFET and turning on the freewheeling switch at the timing when the return current flows. are doing.

JP 2012-125096 A Japanese Patent Application No. 2019-138795

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

SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor driving apparatus that can detect a state in which a return switch is fixed in an OFF state as a failure by detecting current. .

According to the motor drive device of claim 1, as a drive circuit for driving a multiphase motor, a series circuit of a freewheeling switch and a driving switch, each having a freewheeling diode, is connected to a driving power supply and a ground for each phase. and the common connection point of the series circuit is connected to each phase coil of the multiphase motor. The current detection unit is arranged in an energization path between the drive circuit and each phase coil, and detects each energized phase current. The controller controls ON/OFF of each switch constituting the drive circuit based on the current detected by the current detector. Further, when the drive switch is alternately turned ON/OFF while suppressing the rotation of the rotor of the polyphase motor, the control unit controls the return switch based on the current value detected when at least the return switch is turned on. OFF fixed failure is detected.

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

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

Further, according to the motor drive device of claim 3, the controller controls the current value detected in the first energization pattern for turning on the return switch and turning off the return switch 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 fixed OFF failure of the return switch is detected. In this case as well, fixed OFF faults can be detected from the difference in current value when the return switch is turned ON and OFF.

1 is a diagram showing an electrical configuration of a motor drive device according to a first embodiment; FIG. Schematic diagram of SBW system Flowchart showing the processing content of the control circuit A diagram showing a current waveform according to the first and second energization patterns and the presence or absence of fixed OFF failure. FIG. 11 is a second embodiment and shows current waveforms according to the presence or absence of fixed OFF failure; FIG. 11 is a third embodiment and shows current waveforms according to the first and second energization patterns and the presence or absence of fixed OFF failure; 4 is a flowchart showing the processing contents of the control circuit according to the fourth embodiment; Figure showing current waveforms according to presence/absence of fixed OFF failure FIG. 5 is a diagram showing an electrical configuration of a motor drive device according to a fifth embodiment;

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

The motor unit 20 includes a motor 21 and an encoder sensor 22 , and the rotational force of the motor 21 is reduced by a speed 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 pole portions. The motor 21 is provided with coils 21a, 21b, and 21c corresponding to three phases of U-phase, V-phase, and W-phase as a stator. . One ends of the coils 21a to 21c are commonly connected to the power supply line L1. The other ends of the coils 21a to 21c are selectively energized by the motor control unit 30, respectively.
The encoder sensor 22 detects the rotational position of the rotor of the motor 21 , and the rotational position signal output by the sensor 22 is read by the motor controller 30 .

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

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

The control circuit 40 has a microcomputer 41 and a control IC 42 . Hereinafter, the microcomputer 41 is called. A gate drive signal is applied from the control IC 42 to each gate of the switches 31 to 36 . The microcomputer 41 drives and controls the driving switches 31 to 33 and the freewheeling switches 34 to 36 via the control IC 42, and receives the terminal voltages of the current detection resistors 37U, 37V, and 37W to detect the motor drive currents Iu and Iv. , Iw. The current detection resistor 37 is an example of a current detection section.

A 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 . ON/OFF of the ignition relay 39 is controlled by the host ECU 50 according to ON/OFF of the ignition switch of the vehicle. Also, the ON/OFF of the motor power supply relay 38 is performed by the microcomputer 41 via the control IC 42 .

As shown in FIG. 2 , the motor section 20 is driven and controlled by a motor control section 30 and functions as a drive source for the switching mechanism 4 . The switching mechanism 4 includes a detent plate 5 fixed to the shaft 3, a detent spring 6, and the like. 8. The detent plate 5 is provided with a pin 5a projecting in the direction of the shaft 3 and engaged with a groove at the tip of the manual valve 7. As shown in FIG.

In the manual valve 7, the detent plate 5 is rotationally driven by the motor portion 20 so that the pin 5a is rotationally moved, and the manual valve 7 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. be. The manual valve 7 is provided in the valve body 9, and the shift range is changed by reciprocating the manual valve 7 in the axial direction.

Four recesses 5b for holding the manual valve 7 at positions corresponding to the respective ranges are provided at positions on the outer peripheral side of the detent plate 5 in contact with the detent springs 6 . The rotational position of the detent plate 5 is held at the position of one of the concave portions 5 b by the biasing force of the detent spring 6 .

The recesses 5b correspond to ranges 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 rotates most in the forward rotation direction is the D position, and the position where it rotates most in the reverse rotation direction is the P position.

The parking lock portion 8 has a parking rod 10 , a cone 11 , a parking lock pole 12 , a shaft portion 13 and a parking gear 14 . The parking rod 10 moves the cone 11 in the direction of arrow P 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 figure. 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, thereby locking the parking gear 14. As shown in FIG.

Next, the operation of this embodiment will be described. In this embodiment, the control circuit 40 performs processing for detecting a state in which the return switches 34 to 36 are fixed at OFF as a "fixed OFF failure". At that time, a current is applied to each of the phase coils 21a, 21b, and 21c of the motor 21 so that the rotor of the motor 21 is not rotated.

As shown in FIG. 3, the microcomputer 41 starts monitoring pulse signals output from the encoder sensor 22 as rotational position signals and drive currents Iu, Iv, and Iw of the motor 21 (S1). Then, calculation of the rotation speed of the motor 21 is started based on the output interval of the pulse signal (S2). Next, when the power supply to 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 stops (YES), the microcomputer 41 drives the driving switches 31 to 33 of each phase by PWM (Pulse Width Modulation) at a duty ratio of 30%, for example, in step S5, as shown in FIG. . As a result, a current of about 10 A, for example, flows through the coils 21a to 21c under the condition that the rotor is not rotated, but the return switches 34 to 36 are not PWM-driven and are maintained in the OFF state.

Then, the phase current flowing through each of 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). As for the current value I1, the crest value of the current waveform is detected. In step S<b>5 , for example, the return current when the driving switch 31 is turned off flows through the diode 34 a of the return switch 34 . The energization pattern here corresponds to the second energization pattern.

In subsequent steps S8 and S9, the same processing as in steps S3 and S4 is performed. Then, as in step S5, the driving switches 31 to 33 are PWM-driven with a duty ratio of 30%, but here, the freewheeling switches 34 to 36 are complementarily PWM-driven (S10). Then, the phase current flowing through each of the phase coils 21a to 21c is detected as I2 (S11). In step S<b>10 , for example, the return current when the drive switch 31 is turned off flows through the return switch 34 . The energization pattern here corresponds to the first energization pattern.

Then, when the power supply to 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 the obtained difference is equal to or greater than a predetermined value ΔI. It judges (S14). If the difference is greater than or equal to the predetermined value ΔI (YES), the return switches 34 to 36 are determined to be normal (S15), and if the difference is less than the predetermined value ΔI (NO), the return switches 34 to 36 are abnormal. "OFF fixed failure" (S16). Then, for example, a diagnosis notification is sent to the host ECU 50 (S17).

As shown in FIG. 4, in the second energization pattern in step S5, return current flows through, for example, the U-phase diode 34a, so a loss corresponding to the forward voltage Vf occurs. As a result, the slope of the current decrease becomes steeper. On the other hand, in the first energization pattern in step S10, since the return current flows through the return switch 34, the loss like the second energization pattern does not occur, and the slope of the decrease in the current becomes gentle accordingly.

Therefore, in the first energization pattern, the current value I2 becomes larger than the current value I1 if the return switch 34 is normally turned ON and OFF in accordance with the PWM drive. Then, if any one of the return switches 34 to 36 has a "fixed OFF 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, failure determination of the return switches 34 to 36 is performed.

As described above, according to the present embodiment, as the drive circuit 30D for driving the motor 21, the series circuits of the return switches 34 to 36 and the drive switches 31 to 33 are connected to the vehicle power supply 1 and the ground for each phase. , and the common connection points of the series circuit are connected to the phase coils 21a to 21c of the motor 21, respectively. Current detection resistors 37U, 37V, and 37W are arranged in the energization paths between the drive circuit 30D and the coils 21a to 21c of each phase, and these detect the phase currents that are energized. Based on the current detected by the current detection resistor 37, the control circuit 40 controls ON/OFF of each of the switches 31 to 36 forming the drive circuit 30D. In addition, the control circuit 40 controls the current value detected when at least the return switches 34 to 36 are turned on when the drive switches 31 to 33 are alternately turned on/off while suppressing the rotation of the rotor of the motor 21. Based on this, the fixed OFF failure of the return switches 34 to 36 is detected.

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

(Second embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are 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 by averaging a plurality of detected values. Then, in step S13, the average value of the current values I1 and the average value of the current values 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 peak values of current waveforms at specific times when the drive switches 31 to 33 are turned on. 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, it is desirable to capture the peak value of the current waveform 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 crest value according to the second and subsequent driving signal pulses. The number of peak values of the current value I1 and the number of peak values of the current value I2 may be different as long as the current value is within a relatively stable period.

(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 fixed OFF failures. 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 a preset reference value 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 return switches 34 to 36 are turned on, and compares the current value with the reference value. is detected, it is possible to detect fixed OFF failures by simpler control than in the first embodiment.

(Fifth embodiment)
5th Embodiment shows the structure which uses a current limiting resistance in order to suppress rotation of the rotor of the motor 21. FIG. As shown in FIG. 9, a switch 51 and a current limiting resistor 52 are connected between the power line L2 and the ground. One of the fixed terminals of the switch 51 is connected to the ground through the current limiting resistor 52, and the other is directly connected to the ground. Then, the microcomputer 41 controls switching of the switch 51 .

In normal control for driving the motor 21, the changeover switch 51 is switched to the ground side. For example, in the first embodiment, the changeover switch 51 is switched to the current limiting resistor 52 side immediately before steps S5 and S10 are executed. By controlling in this manner, the degree of freedom in setting the PWM duty ratio when turning ON/OFF the drive switches 31 to 33 can be increased.

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

An external diode may be used instead of the body diode as the diode forming the free-wheeling path.
The second and third embodiments may be applied to the fourth embodiment.
In the fifth embodiment, the switch and the current limiting resistor may be arranged on the power 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 cooperation between hardware and software.
The present invention is not limited to the SBW system, and may be applied to other systems.
Although the present disclosure has been described with reference to examples, it is understood that the present disclosure is not limited to such examples or structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and configurations, as well as other combinations and configurations, including single elements, more, or less, are within the scope and spirit of this disclosure.

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

Claims (11)

It drives a polyphase motor (21),
A series circuit of freewheeling switches (34-36) and driving switches (31-33), each having a freewheeling diode (34a-36a), is connected between the driving power source (1) and the ground corresponding to each phase. and a drive circuit (30D) connected to each of the phase coils (21a to 21c) of the multiphase motor at a common connection point of the series circuit, and
a current detection unit (37U to 37W) arranged in an energization path between the drive circuit and each of the phase coils for detecting each phase current to be energized;
a control unit (40) for controlling ON/OFF of each switch constituting the drive circuit based on the current detected by the current detection unit;
When the drive switch is alternately turned ON/OFF while suppressing the rotation of the rotor of the multiphase motor, the control unit, based on a current value detected when at least the return switch is turned ON, A motor drive device for detecting an OFF fixed failure of the return switch. 2. The motor driving device according to claim 1, wherein the controller compares a current value detected when the freewheeling switch is turned on with a predetermined reference value to detect a fixed OFF failure of the freewheeling switch. While the control unit turns off the drive switch,
Based on the result of comparison between the current value detected in the first energization pattern in which the return switch is turned on and the current value detected in the second energization pattern in which the return switch is turned off, the return current is determined. 2. The motor driving device according to claim 1, wherein a fixed off failure of the switch is detected. If a difference between a current value detected in the first energization pattern and a current value detected in the second energization pattern is less than a predetermined value, the controller detects a fixed OFF failure of the return switch. 4. The motor driving device according to claim 3. 5. The motor drive device according to claim 3, wherein the control unit compares an average value of currents detected in the first energization pattern with an average value of currents detected in the second energization pattern. The control unit detects a peak value of the current detected during a period in which the current is relatively stable in the first energization pattern and a peak value of the current detected in a period in which the current is relatively stable in the second energization pattern. 5. The motor drive device according to claim 3 or 4, wherein the comparison is made between . 7. The motor drive device according to claim 6, wherein the control unit compares peak values of currents detected when the drive switch is turned on a specific number of times in the first and second energization patterns. 8. The motor driving device according to claim 7, wherein the specific number of times is the second time or later. The motor drive device according to any one of claims 1 to 8, wherein the control section restricts the amount of current supplied to the coil to suppress the rotation of the rotor. The motor drive device according to any one of claims 1 to 8, wherein the control unit suppresses the rotation of the rotor by simultaneously energizing the phase coils according to the same energization pattern . 11. The polyphase motor according to any one of claims 1 to 10, wherein the polyphase motor is a switched reluctance motor (SRM), and one end side of coils of all phases is commonly connected to one terminal of a driving power source. motor drive.

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