JP7474181B2 - Motor control device and motor control method - Google Patents

Description

The present invention relates to a motor control device and a motor control method.

In an EV (Electric Vehicle) system, as shown in Patent Document 1, for example, a contactor is inserted between the battery and the motor drive circuit. When the motor is in regenerative operation, the contactor is in a closed state (on state), and the battery is charged by the regenerative current of the motor.

Figures 9A and 9B are block diagrams showing an overview of an EV motor control device. In Figures 9A and 9B, a contactor 503 is inserted between a battery 501 and a drive circuit 502. The drive circuit 502 is an inverter that basically has a bridge circuit configuration, and drives a motor 505 with a drive current. The capacitor 504 is a smoothing capacitor.

When the motor 505 is operated in regenerative mode, the motor 505 functions as a generator. In this case, the contactor 503 is normally in a closed state, as shown in FIG. 9A. Therefore, the regenerative current from the motor 505 is sent to the battery 501, and the battery 501 is charged.

However, due to fluctuations in the contactor coil drive voltage, poor contact in the contactor coil drive harness, mechanical shock, etc., contactor 503 may open (off) while the motor is operating. If contactor 503 opens during regenerative operation, as shown in FIG. 9B, the path that sends the regenerative current from motor 505 to battery 501 is cut off, and battery 501 is no longer charged. Furthermore, if contactor 503 opens during regenerative operation, the voltage of capacitor 504 increases due to the regenerative current from motor 505.

Patent No. 6296169

If contactor 503 opens during regenerative operation, the voltage of capacitor 504 rises, making an overvoltage protection function necessary to protect electronic components. In an EV system, if such a situation occurs, the regenerative brake will fail, so it is desirable for functionality to be restored as soon as possible. However, if contactor 503 is closed (turned on) in an overvoltage state, an inrush current will flow from capacitor 504 to battery 501, which may damage the contactor contacts and battery. In addition, if the charge of the capacitor is used to power the contactor coil, there is a risk that the maximum allowable voltage of the contactor coil will be exceeded.

In view of the above problems, the present invention aims to provide a motor control device and a motor control method that can quickly discharge the capacitor charge and restore regenerative operation when the contactor opens during regenerative operation.

A motor control device according to one aspect of the present invention is a motor control device having a gate drive output unit that applies a gate signal to a bridge circuit connected to a brushless motor, and a capacitor that smoothes the power supplied from a power source to the bridge circuit, and has a contactor connected between the power source and the bridge circuit, a contactor open detection unit that detects when the contactor is turned off, a memory unit that stores the rotor rotation angle for each phase at which the inductance change of the coil provided in the brushless motor is within a reference value, a rotor position detection unit that detects the rotor rotation angle, a command output unit that, when it is detected that the contactor is turned off during regenerative operation, refers to the memory unit and outputs a command to the gate drive output unit to discharge the capacitor to the coil of the phase at which the inductance change is within a reference value based on the detected rotation angle, and a contactor control unit that turns on the contactor when the period for discharging the capacitor ends.

According to the present invention, when the contactor opens during regenerative operation and the capacitor voltage rises, the charge in the capacitor is discharged using the motor coil of the phase with the smallest change in inductance, thereby quickly discharging the charge in the capacitor and restoring regenerative operation. This makes it possible to minimize the failure of the regenerative brake function.

1 is a configuration diagram of a motor control device according to a first embodiment of the present invention. 3 is an explanatory diagram of capacitor discharge control in the motor control device according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram of capacitor discharge control in the motor control device according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram of capacitor discharge control in the motor control device according to the first embodiment of the present invention. FIG. 11 is a graph showing an example of a change in inductance of an SR motor. 4 is a flowchart showing regenerative drive control in the motor control device according to the first embodiment of the present invention. 5 is a graph showing changes over time in a capacitor voltage and a power supply current in the motor control device according to the first embodiment of the present invention. FIG. 11 is a configuration diagram of a motor control device according to a second embodiment of the present invention. 10 is a flowchart of overvoltage detection in a second embodiment of the present invention. FIG. 11 is an explanatory diagram of overvoltage detection in a second embodiment of the present invention. FIG. 1 is a block diagram showing an overview of a motor control device for an EV. FIG. 1 is a block diagram showing an overview of a motor control device for an EV.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First Embodiment
Fig. 1 is a configuration diagram of a motor control device 1 according to a first embodiment of the present invention. In Fig. 1, a motor 10 is a motor that drives an EV (electric vehicle). An SR (switched reluctance) motor is used as the motor 10. The SR motor is brushless and includes a salient pole rotor and three-phase motor coils 11u, 11v, and 11w.

The motor coils 11u, 11v, and 11w of each phase of the motor 10 are supplied with PWM (Pulse Width Modulation) drive signals from the half-bridge circuit that constitutes the drive circuit 30. The currents flowing through the motor coils 11u, 11v, and 11w of each phase are detected by current sensors 13u, 13v, and 13w. In addition, the motor 10 is equipped with a rotation sensor 12 for detecting the rotational position of the rotor.

The battery 20 is a power source for driving the motor 10. The battery 20 may be a rechargeable secondary battery such as a lead-acid battery, a nickel-cadmium battery, a nickel-metal hydride battery, or a lithium-ion battery.

The drive circuit 30 is an inverter that generates three-phase drive currents, U-phase, V-phase, and W-phase, from the DC power source sent from the battery 20, and supplies them to the motor coils 11u, 11v, and 11w of each phase of the motor 10 to drive the motor 10. The drive circuit 30 is composed of MOS transistors 31u, 31v, and 31w, MOS transistors 32u, 32v, and 32w, diodes 33u, 33v, and 33w, and diodes 34u, 34v, and 34w.

The MOS transistors 31u and 32u and the diodes 33u and 34u form a half-bridge circuit that supplies a drive signal to the U-phase motor coil 11u. The MOS transistors 31v and 32v and the diodes 33v and 34v form a half-bridge circuit that supplies a drive signal to the V-phase motor coil 11v. The MOS transistors 31w and 32w and the diodes 33w and 34w form a half-bridge circuit that supplies a drive signal to the W-phase motor coil 11w.

A contactor 23 is inserted into the high-side power supply lines 21a and 21b that supply power from the positive electrode of the battery 20 to the drive circuit 30. A voltage sensor 61 detects the battery voltage between the high-side power supply line 21a on the battery 20 side and the low-side power supply line 22. A voltage sensor 62 detects the capacitor voltage between the high-side power supply line 21b on the drive circuit 30 side and the low-side power supply line 22. A current sensor 63 detects the power supply current flowing through the high-side power supply line 21b.

A capacitor 25 is connected between the high-side power supply line 21b and the low-side power supply line 22. The capacitor 25 smoothes the power supplied from the battery 20 to the drive circuit 30.

In addition, MOS transistors 27 and 28 are connected in series between the high-side power supply line 21a and the low-side power supply line 22. The connection point of MOS transistors 27 and 28 is connected to the high-side power supply line 21b via resistor 29. MOS transistors 27 and 28 precharge and discharge capacitor 25.

The control circuit 40 is made up of a CPU (Central Processing Unit), MPU (Micro Processor Unit), memory, etc., and controls each part. The control circuit 40 is made up of a voltage detection part 401, a current detection part 402, a rotor position detection part 403, a coil current detection part for each phase 404, a motor drive control part 405, a gate drive output part 406, a start/stop recognition processing part 407, a precharge/discharge control part 408, a contactor open detection part 409, a contactor control part 410, a discharge command output part 411, and a discharge timing memory part 412.

The voltage detection unit 401 detects the battery voltage and the capacitor voltage from the detection signals of the voltage sensors 61 and 62. The current detection unit 402 detects the power supply current from the detection signal of the current sensor 63. The rotor position detection unit 403 detects the rotation angle of the rotor of the motor 10 from the detection signal of the rotation sensor 12. The coil current detection unit 404 for each phase detects the current flowing through the motor coils 11u, 11v, and 11w for each phase from the detection signals of the current sensors 13u, 13v, and 13w.

The motor drive control unit 405 receives a drive command, a stop command, and a regeneration command. When the motor drive control unit 405 receives a drive command, it generates a control signal for driving the motor 10 and outputs it to the gate drive output unit 406. At this time, the motor 10 operates in power running mode. When the motor drive control unit 405 receives a stop command, it generates a control signal for stopping the motor 10 and outputs it to the gate drive output unit 406. At this time, the motor 10 rotates by inertia and then stops. When the motor drive control unit 405 receives a regeneration command, it generates a control signal for causing the motor 10 to perform a regenerative operation and outputs it to the gate drive output unit 406. In this case, the motor 10 operates in regenerative mode.

The gate drive output unit 406 generates gate signals for the MOS transistors 31u, 31v, and 31w and the MOS transistors 32u, 32v, and 32w of the drive circuit 30 from the control signal from the motor drive control unit 405. This causes a drive current to be supplied to the motor coils 11u, 11v, and 11w of each phase of the motor 10, causing the motor 10 to rotate.

The start/stop recognition processing unit 407 recognizes start and stop from the state of the start switch. When the start/stop recognition processing unit 407 recognizes start and stop, it outputs a control signal to the precharge/discharge control unit 408, which controls the MOS transistors 27 and 28 to precharge and discharge the capacitor 25.

The precharge/discharge control unit 408 supplies gate signals to the gates of the MOS transistors 27 and 28 to control the charging and discharging of the capacitor 25. When the contactor 23 is open, the MOS transistor 27 is on and the MOS transistor 28 is off, the capacitor 25 is precharged via the resistor 29. When the MOS transistor 28 is on and the MOS transistor 27 is off, the charge in the capacitor 25 is discharged via the resistor 29.

The contactor open detection unit 409 detects whether the contactor 23 is in an open (off) state or a closed (on) state based on the detection output of the voltage detection unit 401 and the detection output of the current detection unit 402. More specifically, the contactor open detection unit 409 detects that the contactor 23 is in an open state when the power supply current acquired from the current sensor 63 is a reference current (0 A) and the voltage of the capacitor 25 acquired from the voltage sensor 62 is equal to or higher than the reference voltage. That is, when a regenerative operation is performed with the contactor 23 in a closed state, the regenerative current flows to the battery 20, so the power supply current becomes negative. At this time, the voltage of the capacitor 25 becomes equal to or lower than the reference voltage. When a regenerative operation is performed with the contactor 23 in an open state, the regenerative current does not flow to the battery 20, so the power supply current becomes the reference current (0 A). Also, the regenerative current flows into the capacitor 25, so the voltage of the capacitor 25 becomes equal to or higher than the reference voltage.

The contactor control unit 410 controls the opening and closing of the contactor 23 based on the detection output of the voltage detection unit 401, the detection outputs of the precharge/discharge control unit 408, and the contactor open detection unit 409.

When the contactor 23 is detected to be open while the motor 10 is in a regenerative operation, the discharge command output unit 411 controls the motor coils 11u, 11v, and 11w to discharge the charge of the capacitor 25. As will be described later, in this embodiment, the discharge command output unit 411 forms a discharge path in the coil of the phase that has the smallest torque among the motor coils 11u, 11v, and 11w of each phase in response to the rotation angle of the rotor, and controls the MOS transistors 31u, 31v, and 31w and the MOS transistors 32u, 32v, and 32w of each phase so that the charge of the capacitor 25 is discharged.

The discharge timing memory unit 412 stores timing data for the phase with the smallest torque among the motor coils 11u, 11v, and 11w of each phase, corresponding to the rotation angle of the rotor. When controlling the discharge of the charge in the capacitor 25, the discharge command output unit 411 uses the timing data stored in the discharge timing memory unit 412 to form a discharge path in the coil of the phase with the smallest torque among the motor coils 11u, 11v, and 11w of each phase.

Next, the operation of the motor control device 1 according to the first embodiment of the present invention will be described. The motor control device 1 according to the first embodiment of the present invention is used to drive an EV vehicle. The motor 10 of the EV performs a power running operation in which power is supplied from the battery 20 to the motor 10 to rotate the rotor, and a regenerative operation in which the battery 20 is charged by the regenerative current of the motor 10 generated by the rotation of the rotor.

If the contactor 23 is open while the motor 10 is performing regenerative operation, the regenerative current of the motor 10 is no longer sent to the battery 20. In this case, the regenerative current of the motor 10 is sent from the high side power supply line 21b to the capacitor 25, and becomes the charging current for the capacitor 25. This causes the voltage of the capacitor 25 to rise. If the voltage of the capacitor 25 rises, regenerative control is stopped to prevent an overvoltage state, and the regenerative function is lost.

If the contactor 23 is immediately closed to restore the regenerative brake function, a voltage difference occurs between the high-side power supply line 21a and the high-side power supply line 21b, causing an inrush current to flow from the capacitor 25 to the battery 20. This may destroy the contacts of the contactor 23 and the battery 20.

In addition, when the voltage of capacitor 25 rises, it is possible to turn on MOS transistor 28 to discharge the charge of capacitor 25. However, in this case, since the charge of capacitor 25 is discharged via resistor 29, depending on the setting of the resistance value of resistor 29, it may take some time for the discharge to occur, and the voltage of capacitor 25 may not be reduced quickly.

Therefore, in this embodiment, when the contactor 23 is detected to be open during regenerative operation of the motor 10, a discharge path is formed in the coil of the phase of the motor coils 11u, 11v, 11w that has the smallest torque according to the rotation angle of the rotor, and the MOS transistors 31u, 31v, 31w and MOS transistors 32u, 32v, 32w of each phase are controlled so that the charge of the capacitor 25 is discharged. This will be explained below.

Figures 2A, 2B, and 2C are explanatory diagrams of capacitor discharge control in a motor control device according to a first embodiment of the present invention.

As shown in Figures 2A to 2C, each of the motor coils 11u, 11v, and 11w is connected to a half-bridge circuit that constitutes the drive circuit 30. That is, the MOS transistors 31u and 32u and the diodes 33u and 34u constitute a half-bridge circuit that supplies a drive signal to the U-phase motor coil 11u. The u-phase motor coil 11u is connected between the connection point between the MOS transistor 31u and the diode 34u and the connection point between the diode 33u and the MOS transistor 32u.

MOS transistors 31v and 32v and diodes 33v and 34v form a half-bridge circuit that supplies a drive signal to the V-phase motor coil 11v. The V-phase motor coil 11v is connected between the connection point between MOS transistor 31v and diode 34v and the connection point between diode 33v and MOS transistor 32v.

MOS transistors 31w and 32w and diodes 33w and 34w form a half-bridge circuit that supplies a drive signal to the W-phase motor coil 11w. The W-phase motor coil 11w is connected between the connection point between MOS transistor 31w and diode 34w and the connection point between diode 33w and MOS transistor 32w.

Now, as shown in FIG. 2A, when the MOS transistor 31u and the MOS transistor 32u of the U phase are turned on, the charge of the capacitor 25 flows through the MOS transistor 31u, the motor coil 11u, and the MOS transistor 32u, and the charge of the capacitor 25 can be discharged. Also, as shown in FIG. 2B, when the MOS transistor 31v and the MOS transistor 32v of the V phase are turned on, the charge of the capacitor 25 flows through the MOS transistor 31v, the motor coil 11v, and the MOS transistor 32v, and the charge of the capacitor 25 can be discharged. Also, as shown in FIG. 2C, when the MOS transistor 31w and the MOS transistor 32w of the W phase are turned on, the charge of the capacitor 25 flows through the MOS transistor 31w, the motor coil 11w, and the MOS transistor 32w, and the charge of the capacitor 25 can be discharged.

Which of the motor coils 11u, 11v, and 11w will form the discharge path for the capacitor 25 is determined taking into consideration the effect on the rotation of the motor. In this embodiment, the MOS transistors of each phase are driven so that the coil of the phase with the smallest torque among the motor coils 11u, 11v, and 11w of each phase corresponds to the rotation angle of the rotor and becomes the discharge path for the capacitor 25.

In other words, the torque of an SR motor can be calculated using the following formula:

From the above formula, the phase in which the inductance change (dL/dθ) is the smallest is the coil phase in which the torque is the smallest.

Figure 3 is a graph showing an example of the change in inductance of an SR motor. In Figure 3, the horizontal axis shows the rotation angle of the rotor, and the vertical axis shows the inductance.

In Figure 3, Lu indicates the change in inductance of the U phase, Lv indicates the change in inductance of the V phase, and Lw indicates the change in inductance of the W phase. Since the torque of an SR motor is expressed by the above formula, the torque is smallest in the phase where the amount of change in inductance of each of the U, V, and W phases is the smallest.

According to the graph in FIG. 3, the slope of the curve Lu, which indicates the change in inductance of the U-phase, is the smallest during period T1. Therefore, during period T1, the motor coil 11u of the U-phase has the smallest torque among the motor coils 11u, 11b, and 11w of each phase. In this case, as shown in FIG. 2A, the MOS transistor 31u and the MOS transistor 32u of the U-phase are turned on, and the charge of the capacitor 25 is discharged through the motor coil 11u.

In period T2, the slope of curve Lv, which indicates the change in inductance of V-phase, is the smallest. Therefore, at the timing of period T2, the coil of the phase with the smallest torque among the motor coils 11u, 11v, and 11w of each phase is the V-phase motor coil 11v. In this case, as shown in FIG. 2B, the MOS transistor 31v and the MOS transistor 32v of V-phase are turned on, and the charge of the capacitor 25 is discharged through the motor coil 11v.

In period T3, the slope of curve Lw, which indicates the change in inductance of the W phase, is the smallest. Therefore, at the timing of period T3, the motor coil 11w of the W phase is the coil with the smallest torque among the motor coils 11u, 11v, and 11w of each phase. In this case, as shown in FIG. 2C, the MOS transistor 31w and the MOS transistor 32w of the W phase are turned on, and the charge of the capacitor 25 is discharged through the motor coil 11w.

The discharge timing memory unit 412 stores timing data indicating the phase coil with the minimum torque corresponding to the rotor rotation angle based on the graph shown in FIG. 3. The discharge command output unit 411 determines the phase coil with the minimum torque at that timing among the motor coils 11u, 11v, 11w of each phase based on the data in the discharge timing memory unit 412. The gate drive output unit 406 outputs gate signals to the MOS transistors 31u, 31v, 31w and the MOS transistors 32u, 32v, 32w so that the coil of the determined phase among the motor coils 11u, 11v, 11w becomes the discharge path of the capacitor 25.

Figure 4 is a flowchart showing regenerative drive control in the motor control device according to the first embodiment of the present invention.

(Step S1) The contactor open detection unit 409 determines whether the contactor 23 is open or not, and if the contactor 23 is not open (Step S1: No), the process proceeds to Step S2. As described above, the contactor open detection unit 409 determines that the contactor 23 is open when the power supply current acquired from the current sensor 63 is the reference current (0 A) and the voltage of the capacitor 25 acquired from the voltage sensor 62 is equal to or higher than the reference voltage.

(Step S2) The motor drive control unit 405 generates electricity by rotating the motor 10 and performs regenerative operation.

(Step S3) The motor drive control unit 405 stops regenerative driving and proceeds to step S4.

(Step S4) The contactor open detection unit 409 outputs a command to the discharge command output unit 411 to perform discharge using the motor coil. As described above, the discharge process using the motor coil is a process in which the coil of the phase with the smallest torque is determined from the data in the discharge timing storage unit 412 among the motor coils 11u, 11v, and 11w of each phase, and the capacitor 25 is discharged using the motor coils 11u, 11v, and 11w of each phase.

(Step S5) The discharge command output unit 411 performs a discharge process using the motor coil until the voltage of the capacitor 25 becomes approximately the same as the power supply voltage. During this time, the contactor control unit 410 detects the voltage of the capacitor 25 and the voltage of the battery 20, and determines whether the voltage of the capacitor 25 has become approximately the same as the voltage of the battery 20 and the power supply voltage. If the voltage of the capacitor 25 has become approximately the same as the voltage of the battery 20, the process proceeds to step S6.

(Step S6) When the discharge command output unit 411 determines that the voltage of the capacitor 25 has become approximately the same as the voltage of the battery 20, it stops discharging the capacitor 25 by the motor coil and proceeds to step S7.

(Step S7) When the contactor control unit 410 determines that the voltage of the capacitor 25 has become approximately the same as the voltage of the battery 20, it closes the contactor 23 and proceeds to step S8. When the contactor 23 is closed, the regenerative current from the motor 10 flows through the high-side power supply line 21b, the contactor 23, and the high-side power supply line 21b to the battery 20, and the battery 20 becomes chargeable.

(Step S8) The motor drive control unit 405 resumes regenerative operation and sends regenerative current from the motor 10 to the battery 20 through the contactor 23, thereby charging the battery 20.

Figure 5 is a graph showing the change over time in capacitor voltage and power supply current in the motor control device 1 according to the first embodiment of the present invention.

In FIG. 5, before time t10, the contactor 23 is in a closed state and regenerative operation is performed. When the contactor 23 is in a closed state, the high side power supply line 21a and the high side power supply line 21b are connected via the contactor 23, so the voltage of the capacitor 25 is equal to the power supply voltage. In addition, since regenerative operation is performed with the contactor 23 in a closed state, the regenerative current flows to the battery 20 and the power supply current becomes a negative current of 0 A or less.

When the contactor 23 is open at time t10 and regenerative operation begins, the high side power supply line 21a and the high side power supply line 21b are disconnected, and the voltage of the capacitor 25 increases over time. Also, while the contactor 23 is open, no regenerative current flows to the battery 20, so the power supply current is 0 A.

When the voltage of capacitor 25 is recognized as an overvoltage at time t11, the charge of capacitor 25 is discharged using the motor coils 11u, 11v, and 11w of each phase until the voltage of capacitor 25 becomes equal to the power supply voltage. This causes the voltage of capacitor 25 to decrease.

When the voltage of capacitor 25 becomes equal to the power supply voltage at time t12, contactor 23 is closed. Because contactor 23 is closed, high side power supply line 21a and high side power supply line 21b are connected, and the voltage of capacitor 25 is maintained at the power supply voltage. When contactor 23 is closed and regenerative control resumes, line current flows to battery 20, and the power supply current becomes a negative current of 0 A or less.

As described above, in this embodiment, if the contactor 23 is in the open state and an overvoltage occurs while the motor 10 is performing a regenerative operation, the charge on the capacitor 25 is discharged through the motor coils 11u, 11v, and 11w of each phase. When the charge on the capacitor 25 is discharged through the motor coils 11u, 11v, and 11w of each phase, the charge on the capacitor 25 can be quickly discharged. Furthermore, in this embodiment, the charge on the capacitor 25 is discharged using the coil of the phase among the motor coils 11u, 11v, and 11w that has the smallest torque. Therefore, the charge on the capacitor 25 can be discharged without affecting the rotation of the motor 10.

Second Embodiment
In the first embodiment described above, the contactor open detection unit 409 detects that the contactor 23 is open when the power supply current is 0 A and an increase in the voltage of the capacitor 25 is detected, but instead of referring to the power supply current, the contactor open detection unit 409 may refer to the voltage of the battery 20 or the voltage of the capacitor 25. Furthermore, the contactor open detection unit 409 may detect that the contactor 23 is in an open state and an overvoltage has occurred by using the voltage difference between the voltage of the battery 20 and the voltage of the capacitor 25.

In general, the period for detecting the voltage of the capacitor 25 is often not short, and there may be cases where a filter circuit or other components are passed through on the path to obtain the detection result. In such cases, a certain amount of time may be required until detection. When using the voltage difference between the voltage of the battery 20 and the voltage of the capacitor 25, even if the voltage of the capacitor 25 has not risen to or above the overvoltage threshold at the time the voltage difference is detected, if it is detected that there is a certain degree of difference between the voltage of the battery 20 and the voltage of the capacitor 25, it can be determined that the contactor 23 is in the open state and an overvoltage has occurred. Therefore, the open state of the contactor 23 can be detected at a timing before the time required to detect that the voltage of the capacitor 25 has risen to or above the overvoltage threshold.

Figure 6 is a configuration diagram of a motor control device 1a according to a second embodiment of the present invention. In this second embodiment, a voltage difference determination unit 450 is provided. The voltage difference determination unit 450 detects the voltage difference between the voltage of the battery 20 and the voltage of the capacitor 25. The contactor open detection unit 409 uses the voltage difference between the voltage of the battery 20 and the voltage of the capacitor 25 to detect that the contactor 23 is in an open state and an overvoltage has occurred.

In addition, in this second embodiment, the power supplied to the coil of the contactor 23 is supplied from a control power supply 50 that is separate from the high-side power supply line, thereby preventing the coil of the contactor 23 from exceeding the maximum allowable voltage.

FIG. 7 is a flowchart showing a detection process in the third embodiment of the present invention.
(Step S<b>101 ) The voltage difference determination unit 450 obtains the voltage Vbat of the battery 20 and the voltage Vcap of the capacitor 25 from the detection outputs of the voltage sensors 61 and 62 .

(Step S102) The voltage difference determination unit 450 determines whether the voltage difference (Vcap-Vbat) between the voltage Vcap of the capacitor 25 and the voltage Vbat of the battery 20 is greater than a predetermined judgment reference voltage Va. If the voltage difference (Vcap-Vbat) is greater than the predetermined judgment reference voltage Va (Step S102: Yes), it outputs a command to the discharge command output unit 411 to discharge the motor coil, and proceeds to step S104. If the voltage difference (Vcap-Vbat) is not greater than the predetermined judgment reference voltage Va (Step S102: No), it proceeds to step S103.

(Step S103) If the voltage difference (Vcap-Vbat) is not greater than the predetermined reference voltage Va, normal operation is performed.

(Step S104) If the voltage difference (Vcap-Vbat) is greater than a predetermined judgment reference voltage Va, the discharge command output unit 411 performs a discharge process using the motor coil. The discharge process using the motor coil is a process in which the coil of the phase that produces the smallest torque is determined from the data in the discharge timing memory unit 412 among the motor coils 11u, 11v, and 11w of each phase, and the charge of the capacitor 25 is discharged using the motor coils 11u, 11v, and 11w of each phase until the voltage of the capacitor 25 becomes equal to the power supply voltage.

Figure 8 is an explanatory diagram of overvoltage detection in the third embodiment of the present invention. In Figure 8, the overvoltage threshold is Vth. When an overvoltage is detected from the voltage of capacitor 25, the timing of overvoltage detection is the time T102 when the voltage Vcap of capacitor 25 exceeds the overvoltage threshold by Vth. In contrast, in this embodiment, the timing of overvoltage detection is the time T101 when the voltage difference (Vcap-Vbat) between the voltage Vcap of capacitor 25 and the voltage Vbat of battery 20 becomes greater than a predetermined judgment reference voltage Va.

In this way, by detecting the voltage difference (Vcap-Vbat) between the voltage Vcap of the capacitor 25 and the voltage Vbat of the battery 20, the timing of overvoltage detection can be accelerated.

If the voltage difference (Vcap-Vbat) is greater than a predetermined reference voltage Va, the operation of the drive circuit 30 may be stopped and an error may be displayed.

The motor control device 1 in the above-mentioned embodiment may be realized in whole or in part by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to realize the function. Note that the term "computer system" here includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may include a medium that dynamically holds a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in such a case. Furthermore, the above-mentioned program may be a program for realizing a part of the above-mentioned function, or may be a program that can realize the above-mentioned function in combination with a program already recorded in the computer system, or may be a program that is realized using a programmable logic device such as an FPGA.

The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes designs that do not deviate from the gist of the present invention.

10...motor, 11u, 11v, 11w...motor coil, 20...battery, 23...contactor, 25...capacitor, 30...drive circuit, 40...control circuit, 403...rotor position detection unit, 405...motor drive control unit, 406...gate drive output unit, 407...start/stop recognition processing unit, 408...precharge/discharge control unit, 409...contactor open detection unit, 410...contactor control unit, 411...discharge command output unit, 412...discharge timing memory unit

Claims (5)

a gate drive output section that applies a gate signal to a bridge circuit that is connected to the brushless motor;
a capacitor for smoothing the power supplied from a power source to the bridge circuit;
A motor control device having
a contactor connected between the power supply and the bridge circuit;
a contactor open detection unit that detects that the contactor is turned off;
a storage unit that stores, for each phase, a rotation angle of a rotor at which a change in inductance of a coil provided in the brushless motor is within a reference value;
a rotor position detection unit that detects a rotation angle of the rotor;
a command output unit that, when it is detected that the contactor has been turned off during a regenerative operation, refers to the storage unit and outputs to the gate drive output unit a command to discharge the capacitor with respect to a coil of a phase in which a change in inductance is within a reference value based on the detected rotation angle;
and a contactor control unit that turns on the contactor when a period for discharging the capacitor ends. The contactor open detection unit is
2. The motor control device according to claim 1, wherein when the power supply current is a reference current value and the voltage of the capacitor is equal to or higher than the reference voltage, it is detected that the contactor has been turned off. The contactor control unit is
determining whether the voltage of the capacitor has decreased to the voltage of the power supply;
3. The motor control device according to claim 1, further comprising: a control circuit for controlling a motor that controls a current flowing from the capacitor to a voltage of the power source; a control circuit for controlling a current flowing from the capacitor to a voltage of the power source; The motor control device according to claim 1 , wherein the contactor open detection unit detects that the contactor has been turned off when a voltage difference between the capacitor voltage and the power supply voltage is greater than a predetermined determination reference voltage. A motor control method for driving a brushless motor by supplying power to a bridge circuit, comprising the steps of:
a contactor is inserted between the power supply and the bridge circuit, and a capacitor is provided to smooth the power supplied from the power supply to the bridge circuit;
detecting when the contactor is off;
detecting a rotation angle of a rotor of the brushless motor;
when it is detected that the contactor has been turned off during a regenerative operation, discharging the charge of the capacitor to a coil of a phase whose inductance change is within a reference value based on the detected rotation angle of the rotor;
turning on the contactor when a period of time for discharging the capacitor is completed;
A motor control method comprising:

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