WO2024075318A1 - Coil switching system for vehicle motor, control device, method for controlling vehicle motor, and computer program - Google Patents

Abstract

This coil switching system comprises a drive motor that drives a wheel of a vehicle, a control device that controls the drive motor, a power converter that converts DC power outputted from a battery to AC power and supplies the AC power to the drive motor, and a coil switching device that switches a connection state of a plurality coils in the drive motor between a first connection state and a second connection state, the control device including a torque control unit that changes the output torque of the drive motor by changing the alternating electric current outputted from the power converter at a prescribed speed change timing of the vehicle, and a switching control unit that causes the coil switching device to switch from the first connection state to the second connection state after the alternating electric current has changed.

Description

Winding switching system for vehicle motor, control device, control method for vehicle motor, and computer program

This disclosure relates to a winding switching system for a vehicle motor, a control device, a control method for a vehicle motor, and a computer program. This application claims priority to Japanese Application No. 2022-162243, filed on October 7, 2022, and incorporates by reference all of the contents of said Japanese application.

Patent Document 1 discloses that in vehicles that do not have stepped transmissions and in which the wheels are driven by a drive motor, such as electric vehicles and hybrid vehicles, a pseudo-shift change can be created by performing torque fluctuation control that reduces the torque of the drive motor by a set fluctuation amount and then increases it.

JP 2018-166386 A

A winding switching system for a vehicle motor according to one embodiment of the present disclosure includes a drive motor that drives the wheels of a vehicle, a control device that controls the drive motor, a power converter that converts DC power output from a battery into AC power and supplies the AC power to the drive motor, and a winding switching device that switches the connection state of a plurality of windings in the drive motor between a first connection state and a second connection state, and the control device includes a torque control unit that changes the output torque of the drive motor by changing the AC current output from the power converter at a predetermined shift timing of the vehicle, and a switching control unit that causes the winding switching device to switch from the first connection state to the second connection state after the AC current has changed.

The present disclosure can be realized not only as a winding switching system for a vehicle motor having the above-mentioned characteristic configuration, but also as a control device included in the winding switching system for a vehicle motor, or as a control method for a vehicle motor having steps corresponding to characteristic processes in the control device. The present disclosure can be realized as a computer program that causes a computer to function as a control device, or as a semiconductor integrated circuit as a part or all of the control device.

FIG. 1 is a diagram illustrating an example of the configuration of a winding switching system according to the first embodiment. FIG. 2 is a block diagram illustrating an example of a hardware configuration of the control device. FIG. 3 is a circuit diagram showing an example of the configuration of the winding switching device according to the first embodiment. FIG. 4 is a timing chart showing an example of timing for switching the windings of the motor in the winding switching system according to the first embodiment. FIG. 5 is a flowchart showing an example of an electrical up-shifting process performed by the control device according to the first embodiment. FIG. 6 is a flowchart showing an example of an electrical downshifting process performed by the control device according to the first embodiment. FIG. 7 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. FIG. 8 is a timing chart showing an example of timing for switching the windings of a motor in the winding switching system according to the third embodiment. FIG. 9 is a timing chart showing an example of timing for switching the windings of a motor in the winding switching system according to the fourth embodiment. FIG. 10 is a timing chart showing an example of a pseudo speed change control process in the winding switching system according to the fifth embodiment. FIG. 11 is a flowchart showing an example of a pseudo shifting process performed by the control device according to the fifth embodiment. FIG. 12 is a functional block diagram showing an example of functions of the control device according to the sixth embodiment. FIG. 13 is a flowchart showing an example of a forced up-shift determination process performed by the control device according to the sixth embodiment. FIG. 14 is a flowchart showing an example of a forced downshift determination process performed by the control device according to the sixth embodiment.

<Problems to be Solved by the Present Disclosure>
The pseudo-shift change in the vehicle disclosed in Patent Document 1 is not an actual gear change by a stepped transmission, but is realized at the expense of the running performance of the vehicle.

<Effects of the present disclosure>
According to the present disclosure, it is possible to efficiently utilize the performance of the drive motor of an electric vehicle while providing the driver with a gear shifting sensation similar to that of a stepped transmission.

Overview of the embodiments of the present disclosure
Below, an overview of the embodiments of the present disclosure will be listed and described.

(1) The winding switching system for a vehicle motor according to this embodiment includes a drive motor that drives the wheels of a vehicle, a control device that controls the drive motor, a power converter that converts DC power output from a battery into AC power and supplies the AC power to the drive motor, and a winding switching device that switches the connection state of a plurality of windings in the drive motor between a first connection state and a second connection state. The control device includes a torque control unit that changes the output torque of the drive motor by changing the AC current output from the power converter at a predetermined shift timing of the vehicle, and a switching control unit that causes the winding switching device to switch from the first connection state to the second connection state after the AC current has changed. This allows the performance of the drive motor to be efficiently used to achieve a shift equivalent to that achieved by a mechanical transmission (hereinafter also referred to as "electrical shifting"). Furthermore, by changing the output torque of the drive motor in response to the switching of the connection state of the windings of the drive motor, the driver can be given a shifting sensation similar to that of a mechanical transmission.

(2) In the above (1), the torque control unit may reduce the output torque of the drive motor by reducing the AC current output from the power converter at a first shift timing, and the switching control unit may switch the winding switching device from the first connection state to the second connection state after the AC current has decreased to a first target value or less. This makes it possible to realize an electrical shift similar to an upshift by a mechanical transmission while the vehicle is accelerating or maintaining its speed.

(3) In the above (2), the torque control unit may reduce the output torque of the drive motor by reducing the AC current output from the power converter at a second shift timing different from the first shift timing, and the switching control unit may switch the winding switching device from the second connection state to the first connection state after the AC current has decreased to or below the first target value. This makes it possible to realize an electrical shift similar to a downshift by a mechanical transmission while the vehicle is accelerating or maintaining its speed.

(4) In the above (1), the torque control unit may increase the output torque of the drive motor by increasing the AC current output from the power converter at the first shift timing, and the switching control unit may switch the winding switching device from the first connection state to the second connection state after the AC current has increased to or above a second target value. This makes it possible to realize an electrical shift similar to an upshift by a mechanical transmission while the drive motor is performing regenerative braking.

(5) In the above (4), the torque control unit may increase the output torque of the drive motor by increasing the AC current output from the power converter at a second shift timing different from the first shift timing, and the switching control unit may switch the winding switching device from the second connection state to the first connection state after the AC current has increased to or above a second target value. This makes it possible to realize an electrical shift similar to a downshift by a mechanical transmission while the drive motor is performing regenerative braking.

(6) In any one of (1) to (5) above, the second connection state may be a connection state in which the drive motor outputs a lower torque than the first connection state at the same rotation speed. This makes it possible to switch the connection state of the windings of the drive motor between the first connection state of a high-torque, low-speed type and the second connection state of a low-torque, high-speed type.

(7) In the above (6), the control device may further include a first determination unit that determines, when the connection state of the plurality of windings is the first connection state, a timing before the induced voltage generated in the windings exceeds the output voltage of the battery as a first forced shift timing, and the torque control unit changes the output torque of the drive motor by changing the AC current output from the power converter at the first forced shift timing determined by the first determination unit, and the switching control unit may cause the winding switching device to switch from the first connection state to the second connection state after the AC current has changed. When the induced voltage generated in the windings exceeds the output voltage of the battery, it is not possible to change the current flowing in the windings to zero. If the connection state of the windings is switched by the relay while a current is flowing in the windings, the relay may be damaged. With the above configuration, when the connection state of the windings is switched from the first connection state to the second connection state, the current flowing in the windings can be suppressed and the relay can be protected.

(8) In the above (7), the first determination unit may determine the timing at which the physical quantity related to the induced voltage exceeds a first threshold value corresponding to the output voltage of the battery as the first forced shift timing. This makes it possible to accurately determine the timing before the induced voltage exceeds the output voltage of the battery by using the physical quantity related to the induced voltage.

(9) In the above (8), the physical quantity may be one of the voltage in the winding, the rotation speed of the drive motor, the current flowing through the winding, and the output torque of the drive motor. This makes it possible to accurately determine the timing before the induced voltage exceeds the battery output voltage by one of the voltage in the winding, the rotation speed of the motor, the current flowing through the winding, and the output torque of the motor, which can be easily detected by a sensor.

(10) In any one of (7) to (9) above, the control device may further include a determination unit that, when the connection state of the plurality of windings is the second connection state, determines whether or not the induced voltage exceeds the output voltage of the battery after the connection state of the windings is switched from the second connection state to the first connection state, and a prohibition unit that prohibits the switching control unit from switching the connection state of the windings when the determination unit determines that the induced voltage exceeds the output voltage of the battery. This prevents the induced voltage of the windings from exceeding the output voltage of the battery after the connection state of the windings is switched from the second connection state to the first connection state. Therefore, the relay can be protected from damage.

(11) In any one of (7) to (10) above, the control device may further include a second determination unit that, when the connection state of the plurality of windings is the second connection state, determines the timing after the induced voltage becomes equal to or lower than the output voltage of the battery after the connection state of the windings is switched from the second connection state to the first connection state as the second forced shift timing, and the torque control unit changes the output torque of the drive motor by changing the AC current output from the power converter at the second forced shift timing determined by the second determination unit, and the switching control unit may cause the winding switching device to switch from the second connection state to the first connection state after the AC current has changed. This prevents the induced voltage of the winding from exceeding the output voltage of the battery after the connection state of the windings is switched from the second connection state to the first connection state. Thus, the relay can be protected from damage.

(12) In the above (11), the second determination unit may determine, as the second forced shift timing, the timing at which the physical quantity related to the induced voltage becomes equal to or lower than a second threshold value corresponding to the output voltage of the battery. This makes it possible to accurately determine the timing after the induced voltage becomes equal to or lower than the output voltage of the battery, using the physical quantity related to the induced voltage.

(13) In any one of (1) to (12) above, the winding switching system may further include an input device that receives a gear shift instruction from a driver, and the gear shift timing may be the timing at which the input device receives the gear shift instruction from the driver. This allows the drive motor to perform electrical gear shifting in accordance with the driver's gear shift instruction.

(14) In any one of (1) to (12) above, the shift timing may be determined based on the rotation speed of the drive motor, the output torque, the acceleration command amount for the vehicle, and the braking command amount for the vehicle. This allows the drive motor to perform electrical shifting according to the timing determined by the motor rotation speed, the output torque, the acceleration command amount (the amount of depression of the accelerator pedal), and the braking command amount (the amount of depression of the brake pedal).

(15) In any one of (1) to (14) above, the torque control unit may gradually decrease or increase the effective current of the AC current output from the power converter from the shift timing. This allows the torque to be changed smoothly, providing the driver with a natural shift feeling.

(16) In the above (15), the torque control unit may change the effective current in a ramp shape from the shift timing. This allows the driver to feel a smooth shift in torque.

(17) In any one of (1) to (14) above, the torque control unit may change the effective current of the AC current output from the power converter in a stepwise manner based on the shift timing. This allows the driver to feel a sudden change in torque when shifting.

(18) In any one of (1) to (17) above, the torque control unit may execute a pseudo-shift control process to decrease and then increase the AC current output from the power converter at a pseudo-shift timing different from the shift timing. This causes the drive motor to execute a pseudo-shift in addition to the electrical shift. This allows the driver to feel a multi-stage shift.

(19) The control device according to this embodiment is a control device for controlling a drive motor that drives the wheels of a vehicle, and includes a torque control unit that changes the output torque of the drive motor by converting DC power output from a battery into AC power and changing the AC current output from a power converter that supplies the AC power to the drive motor at a predetermined shift timing of the vehicle, and a switching control unit that switches the connection state of a plurality of windings in the drive motor from a first connection state to a second connection state after the AC current has changed. As a result, the connection state of the windings of the drive motor is switched from the first connection state to the second connection state, so that electrical shifting can be achieved by efficiently utilizing the performance of the drive motor. Furthermore, by changing the output torque of the drive motor in accordance with the switching of the connection state of the windings of the drive motor, the driver can be given a shifting sensation similar to that of a mechanical transmission.

(20) The method for controlling a vehicle motor according to this embodiment is a method for controlling a vehicle motor executed by a control device that controls a drive motor that drives the wheels of the vehicle, and includes the steps of: changing the output torque of the drive motor by converting DC power output from a battery into AC power and changing the AC current output from a power converter that supplies the AC power to the drive motor at a predetermined shift timing of the vehicle; and causing a winding switching device that switches the connection state of a plurality of windings in the drive motor to switch from a first connection state to a second connection state after the AC current has changed. This switches the connection state of the windings of the drive motor from the first connection state to the second connection state, making it possible to efficiently utilize the performance of the drive motor to realize an electrical shift. Furthermore, by changing the output torque of the drive motor in accordance with the switching of the connection state of the windings of the drive motor, it is possible to give the driver a shifting sensation similar to that of a mechanical transmission.

(21) The computer program according to this embodiment is a computer program used by a control device that controls a drive motor that drives the wheels of a vehicle, and causes a computer to execute the steps of: changing the output torque of the drive motor by converting DC power output from a battery into AC power and changing the AC current output from a power converter that supplies the AC power to the drive motor at a predetermined shift timing of the vehicle; and causing a winding switching device that switches the connection state of multiple windings in the drive motor to switch from a first connection state to a second connection state after the AC current has changed. This switches the connection state of the windings of the drive motor from the first connection state to the second connection state, making it possible to efficiently utilize the performance of the drive motor to achieve electrical shifting. Furthermore, by changing the output torque of the drive motor in accordance with the switching of the connection state of the windings of the drive motor, it is possible to give the driver a shifting sensation similar to that of a mechanical transmission.

<Details of the embodiment of the present disclosure>
Hereinafter, the details of the embodiments of the present invention will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any desired manner.

[1. First embodiment]
[1-1. Winding switching system]
FIG. 1 is a diagram illustrating an example of the configuration of a winding switching system according to the first embodiment.

The winding switching system 10 is mounted on a vehicle (hereinafter referred to as an "electric vehicle") that is propelled by a motor, such as an electric vehicle or a plug-in hybrid vehicle. The winding switching system 10 includes a motor 20, a power converter 30, a battery 40, a control device 50, and a winding switching device 100.

The motor 20 is a driving motor that generates the propulsive force for the electric vehicle. In other words, the motor 20 is connected to the wheels 60 and is a drive motor that drives the wheels 60. The motor 20 is driven by three-phase AC power. One example of the motor 20 is a permanent magnet synchronous motor.

The battery 40 is a battery that supplies power to drive the motor 20. The battery 40 is a secondary battery, for example a lithium ion battery.

The power converter 30 is an inverter that converts DC power supplied from the battery 40 into three-phase AC power. The power converter 30 may also have the function of converting the three-phase AC power output when the motor 20 functions as a generator into DC power and charging the battery 40.

The power converter 30 includes legs for the U, V, and W phases. The U-phase leg includes switches 31u and 32u, the V-phase leg includes switches 31v and 32v, and the W-phase leg includes switches 31w and 32w. The switches 31u, 32u, 31v, 32v, 31w, and 32w perform switching to convert DC power into three-phase AC power. The switches 31u, 32u, 31v, 32v, 31w, and 32w are, for example, IGBTs (Insulated Gate Bipolar Transistors) or power MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors).

Power line 35u corresponding to U phase extends from the U phase leg, power line 35v corresponding to V phase extends from the V phase leg, and power line 35w corresponding to W phase extends from the W phase leg. In power converter 30, current sensor 33u is provided on power line 35u, current sensor 33v is provided on power line 35v, and current sensor 33w is provided on power line 35w. Current sensor 33u detects the current value of current Iu of U phase. Current sensor 33v detects the current value of current Iv of V phase. Current sensor 33w detects the current value of current Iw of W phase. Current sensors 33u, 33v, 33w can detect the current values of currents Iu, Iv, Iw flowing through power lines 35u, 35v, 35w, including DC and AC components. The current sensors 33u, 33v, and 33w are, for example, DCCTs (direct current transformers) or shunt resistors.

The winding switching device 100 is disposed between the motor 20 and the power converter 30. However, the position of the winding switching device 100 is not limited to between the motor 20 and the power converter 30. The power converter 30 and the winding switching device 100 are connected by power lines 35u, 35v, and 35w, and the winding switching device 100 and the motor 20 are connected by a plurality of power lines 25. The winding switching device 100 switches the connection state of the multiple windings of the motor 20. The configuration of the winding switching device 100 will be described later. The three-phase AC currents Iu, Iv, and Iw output from the power converter 30 are supplied to the motor 20 via the winding switching device 100.

The control device 50 controls the motor 20. Specifically, the control device 50 controls the motor 20 by controlling the power converter 30 and the winding switching device 100. Signal lines extend from the control device 50 to each of the switches 31u, 32u, 31v, 32v, 31w, and 32w, and the control device 50 controls the on/off timing of the switches 31u, 32u, 31v, 32v, 31w, and 32w. A signal line extends from the control device 50 to the winding switching device 100, and the control device 50 outputs a switching command signal to the winding switching device 100 to command the switching of the winding connection state.

The control device 50 is connected to a sensor 71 that detects the amount of depression of the brake pedal 70, and receives a detection signal output from the sensor 71. The control device 50 is connected to a sensor 81 that detects the amount of depression of the accelerator pedal 80, and receives a detection signal output from the sensor 81.

A rotation sensor 201 that detects the rotation speed of the motor 20 and a torque sensor 202 that detects the output torque of the motor 20 are attached to the output shaft of the motor 20. The rotation sensor 201 and the torque sensor 202 are connected to the control device 50. The control device 50 receives the detection signal output from the rotation sensor 201 and receives the detection signal output from the torque sensor 202.

The control device 50 is connected to a gear shift indicator 90. The gear shift indicator 90 is an input device that allows the driver to input gear shift instructions. The gear shift indicator 90 is, for example, a shift lever. In another example, the gear shift indicator 90 is a switch that allows the driver to instruct shifting up or down. The gear shift indicator 90 outputs a gear shift instruction signal in response to the driver's operation. The control device 50 receives the gear shift instruction signal output from the gear shift indicator 90.

FIG. 2 is a block diagram showing an example of the hardware configuration of the control device. The control device 50 includes a processor 501, a non-volatile memory 502, a volatile memory 503, and an interface (I/F) 504.

The volatile memory 503 is, for example, a semiconductor memory such as SRAM (Static Random Access Memory) or DRAM (Dynamic Random Access Memory). The non-volatile memory 502 is, for example, a flash memory, a hard disk, or a ROM (Read Only Memory). The non-volatile memory 502 stores a motor control program 510, which is a computer program, and data used to execute the motor control program 510. Each function of the control device 50 is achieved by the motor control program 510 being executed by the processor 501. The motor control program 510 can be stored in a recording medium such as a flash memory, a ROM, or a CD-ROM. The processor 501 controls the power converter 30 and the winding switching device 100 using the motor control program 510.

The processor 501 is, for example, a CPU (Central Processing Unit). However, the processor 501 is not limited to a CPU. The processor 501 may be a GPU (Graphics Processing Unit). The processor 501 is, for example, a multi-core processor. The processor 501 may be a single-core processor. The processor 501 may be, for example, an ASIC (Application Specific Integrated Circuit), or a programmable logic device such as a gate array or an FPGA (Field Programmable Gate Array). In this case, the ASIC or the programmable logic device is configured to be capable of executing the same processing as the motor control program 510.

The I/F 504 is connected to the rotation sensor 201, the torque sensor 202, the sensor 71, the sensor 81, and the gear shift indicator 90. The I/F 504 is, for example, an input/output interface or a communication interface. The I/F 504 receives a detection signal of the rotation speed of the motor 20 output from the rotation sensor 201. The I/F 504 receives a detection signal of the output torque of the motor 20 output from the torque sensor 202. The I/F 504 receives a detection signal of the brake pedal depression amount output from the sensor 71. The I/F 504 receives a detection signal of the accelerator pedal depression amount output from the sensor 81. The I/F 504 receives a gear shift indicator signal output from the gear shift indicator 90.

[1-2. Configuration of the winding switching device]
3 is a circuit diagram showing an example of the configuration of the winding switching device according to the first embodiment. The motor 20 includes a plurality of windings 21u, 22u, 21v, 22v, 21w, and 22w. The windings 21u and 22u correspond to the U phase, the windings 21v and 22v correspond to the V phase, and the windings 21w and 22w correspond to the W phase. However, the number of windings for each phase is not limited to two, and may be three or more. The windings 22u, 22v, and 22w are connected at a neutral point 23.

The winding switching device 100 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w for each phase between a series connection state and a parallel connection state. The winding switching device 100 includes control circuits 103u, 103v, and 103w, and switching circuits 104u, 104v, and 104w.

The switching circuits 104u, 104v, and 104w switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w between a series connection state and a parallel connection state under control of the control device 50. The series connection state is an example of a first connection state, and the parallel connection state is an example of a second connection state.

Below, the connection relationship between the winding switching device 100, the power line 35u, and the motor 20 will be explained for the U phase. The same applies to the V and W phases, so the explanation will be omitted.

Power line 35u is connected to one end of winding 21u. Power line 212u extends from the other end of winding 21u. Power line 221u extends from one end of winding 22u, and power line 222u extends from the other end.

The switching circuit 104u includes semiconductor relays 111u, 112u, and 113u. The semiconductor relays 111u, 112u, and 113u are, for example, IGBTs or power MOSFETs.

The power line 35u is drawn into the winding switching device 100. Inside the winding switching device 100, the power line 35u branches at a midpoint and is connected to a first terminal of a semiconductor relay 111u. A second terminal of the semiconductor relay 111u is connected to a first terminal of a semiconductor relay 112u. A power line 221u extending from the winding 22u is connected to the connection point between the second terminal of the semiconductor relay 111u and the first terminal of the semiconductor relay 112u. The power lines 212u, 221u, and 222u extend from the motor 20 and are drawn into the winding switching device 100.

The second terminal of the semiconductor relay 112u is connected to the first terminal of the semiconductor relay 113u. A power line 212u extending from the winding 21u is connected to the connection point between the second terminal of the semiconductor relay 112u and the first terminal of the semiconductor relay 113u. A power line 222u extending from the winding 22u is connected to the second terminal of the semiconductor relay 113u.

When the semiconductor relays 111u and 113u are in the OFF state and the semiconductor relay 112u is in the ON state, the windings 21u and 22u are connected in series. When the semiconductor relays 111u and 113u are in the ON state and the semiconductor relay 112u is in the OFF state, the windings 21u and 22u are connected in parallel.

A signal line extending from the control circuit 103u is connected to each of the gate terminals of the semiconductor relays 111u, 112u, and 113u. A signal line extending from the control device 50 is connected to the control circuit 103u.

The control circuit 103u controls the semiconductor relays 111u, 112u, and 113u to be turned on and off by applying gate voltages to the gate terminals of the semiconductor relays 111u, 112u, and 113u individually. Specifically, when the control circuit 103u receives an instruction from the control device 50 to switch the connection state of the windings 21u and 22u from a series connection state to a parallel connection state, the control circuit 103u sets the semiconductor relays 111u and 113u to an on state and sets the semiconductor relay 112u to an off state. When the control circuit 103u receives an instruction from the control device 50 to switch the connection state of the windings 21u and 22u from a parallel connection state to a series connection state, the control circuit 103u sets the semiconductor relays 111u and 113u to an off state and sets the semiconductor relay 112u to an on state.

The control circuit 103u is, for example, configured with multiple logic circuits (AND circuits, NOT circuits, latch circuits, etc.). In another example, the control circuit 103u is configured with a processor. For example, the control circuit 103u is configured with a one-chip microcomputer. The control circuit 103u may also be configured with a programmable logic device such as an ASIC or FPGA.

[1-3. Functions of the control device]
Returning to Fig. 1, the following describes the functions of the control device 50. The control device 50 has the functions of a torque control unit 511 and a switching control unit 512. When the processor 501 executes the motor control program 510, the functions of the torque control unit 511 and the switching control unit 512 are realized.

The torque control unit 511 changes the output torque of the motor 20 by changing the AC current output from the power converter 30 at a predetermined gear shift timing of the electric vehicle. The switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 after the AC current output from the power converter 30 has changed.

The gear shift timing is, for example, the timing at which the control device 50 receives a gear shift command output from the gear shift indicator 90. That is, in a vehicle equipped with a gear shift indicator 90, when the driver uses the gear shift indicator 90 to instruct a gear shift, the control device 50 changes the AC current output from the power converter 30 from the timing at which the gear shift command is input to the control device 50.

In another example, the gear shift timing is determined based on the rotation speed of the motor 20, the output torque of the motor 20, the depression amount of the brake pedal 70 (braking command amount), and the depression amount of the accelerator pedal 80 (acceleration command amount). That is, an automatic gear shift control device (not shown) in the vehicle generates a gear shift command based on the rotation speed of the motor 20, the output torque of the motor 20, the depression amount of the brake pedal 70 (braking command amount), and the depression amount of the accelerator pedal 80 (acceleration command amount), and the generated gear shift command is input to the control device 50. When a gear shift command generated by such an automatic gear shift control device is input to the control device 50, the control device 50 changes the AC current output from the power converter 30 from the timing when the gear shift command was input to the control device 50.

When windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in series, motor 20 can output high torque. When windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in parallel, motor 20 outputs less torque than when connected in series at the same rotation speed. In other words, when windings 21u, 22u, 21v, 22v, 21w, and 22w are connected in series, motor 20 is in a low rotation, high torque state, and when windings 21u, 22u, 21v, 22v, 21w, and 22w are connected in parallel, motor 20 is in a high rotation, low torque state. Switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a series connection state to a parallel connection state corresponds to shifting up in a mechanical transmission, and switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a parallel connection state to a series connection state corresponds to shifting down in a mechanical transmission. Switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a series connection state to a parallel connection state is also called "electrical shift up," and switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a parallel connection state to a series connection state is also called "electrical shift down."

For example, the torque control unit 511 reduces the output torque of the motor 20 by reducing the AC current output from the power converter 30 at the first shift timing. After the AC current output from the power converter 30 has decreased to or below the first target value, the switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a series connection state to a parallel connection state. The first shift timing is the timing when an electrical upshift is instructed.

Figure 4 is a timing chart showing an example of the switching timing of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 in the winding switching system according to the first embodiment. Figure 4 shows an example of the timing of a speed change command, the current supplied to motor 20 (hereinafter also referred to as "motor current"), the output torque of motor 20 (hereinafter also referred to as "motor torque"), and the on/off switching of semiconductor relays 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, and 113w when the connection state of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 is switched from a series connection state to a parallel connection state. In the following, the semiconductor relays 111u, 111v, and 111w are collectively referred to as "relays 111," the semiconductor relays 112u, 112v, and 112w are collectively referred to as "relays 112," and the semiconductor relays 113u, 113v, and 113w are collectively referred to as "relays 113."

At time t11, a gear change command (electrical downshift command) is input to the control device 50. The torque control unit 511 reduces the motor current Iq from time t11. The motor current Iq is the effective current (Q-axis current) of the AC current provided to the motor 20. In the example shown in FIG. 4, the motor current Iq gradually decreases in a ramp shape. As the motor current Iq decreases, the motor torque also decreases.

At time t12, the motor current Iq reaches the first target value Th1. The torque control unit 511 stops the reduction of the motor current Iq from time t12 when the motor current Iq reaches the first target value Th1. In other words, from time t12 onwards, the motor current Iq is maintained at the first target value Th1. From time t12 onwards, the reduction of the motor torque also stops.

The switching control unit 512 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from a series connection state to a parallel connection state at a timing after time t12. In the example of FIG. 4, at time t01, which is after time t12, the relays 111 and 113 are switched from an on state to an off state, and at time t02, which is after time t01, the relay 112 is switched from an off state to an on state. During the period between time t01 and time t02, all of the relays 111, 112, and 113 are in the off state. This prevents all of the relays 111, 112, and 113 from being in the on state when switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w.

From time t21, which is after time t02, the torque control unit 511 increases the motor current Iq. The target value of the motor current Iq at this time is determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w. The target torque is determined based on the rotation speed of the motor 20, the output torque of the motor 20, the depression amount of the brake pedal 70 (braking command amount), and the depression amount of the accelerator pedal 80 (acceleration command amount). In the example shown in FIG. 4, the motor current Iq increases in a ramp shape. As the motor current Iq increases, the motor torque also increases.

At time t22, the motor current Iq reaches the target value. From time t22 when the motor current Iq reaches the target value, the torque control unit 511 stops increasing the motor current Iq. After time t22, the increase in the motor torque also stops.

As described above, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched from a series connection state to a parallel connection state, so the performance of the motor 20 can be efficiently utilized to electrically change speed from a low rotation, high torque state to a high rotation, low torque state. Furthermore, as the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched, the output torque of the motor 20 decreases, so the driver can be given the same feeling of shifting as with a mechanical transmission.

First target value Th1 is, for example, 0 A. If the connection state is switched while current is flowing through windings 21u, 22u, 21v, 22v, 21w, and 22w, a torque shock occurs due to a sudden change in current through windings 21u, 22u, 21v, 22v, 21w, and 22w, which are inductive loads. Furthermore, damage to relays 111, 112, and 113 due to a surge also occurs. By setting first target value Th1 to 0 A, the above-mentioned torque shock and damage to relays 111, 112, and 113 due to a surge can be suppressed.

For example, when the rotation speed of the motor 20 is increasing, i.e., when an electrical downshift is instructed while the vehicle is accelerating, the torque control unit 511 reduces the output torque of the motor 20 by reducing the AC current output from the power converter 30 at the second shift timing. After the AC current output from the power converter 30 has decreased to or below the first target value, the switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a parallel connection state to a series connection state. The second shift timing is the timing when an electrical downshift is instructed.

The connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched from a parallel connection state to a series connection state, so that the performance of the motor 20 can be efficiently utilized to electrically change the speed from a high rotation, low torque state to a low rotation, high torque state. Furthermore, as the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched, the output torque of the motor 20 increases, so that the driver can be given a shifting sensation similar to that of a mechanical transmission.

For example, when an electrical downshift is instructed while the motor 20 is performing regenerative braking, the torque control unit 511 increases the output torque of the motor 20 by increasing the AC current output from the power converter 30 at the second shift timing. During regenerative braking, a torque for braking the vehicle, i.e., a negative torque, is generated, and the braking force decreases as the output torque of the motor 20 increases (approaches zero). After the AC current output from the power converter 30 increases to or above the second target value, the switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a parallel connection state to a series connection state.

As described above, since the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched from a parallel connection state to a series connection state, the performance of the motor 20 can be efficiently utilized to electrically shift from a high rotation, low torque state to a low rotation, high torque state. The amount of regeneration by the motor 20 is higher in a low rotation, high torque state than in a high rotation, low torque state. Therefore, the regenerative braking force can be increased by electrical downshifting, and the driver can be given a deceleration sensation similar to that of engine braking. Furthermore, since the negative output torque of the motor 20 decreases (the absolute value of the output torque increases) as the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched, the driver can be given a shifting sensation similar to that of a mechanical transmission.

The torque control unit 511 can gradually increase the motor current Iq in a ramp-like manner during an electrical downshift. The motor current Iq gradually decreases in a ramp-like manner during an electrical upshift, and the motor current Iq gradually increases in a ramp-like manner during an electrical downshift, providing the driver with a natural feeling of gear shifting.

The second target value Th2 is, for example, 0 A. This makes it possible to suppress damage to relays 111, 112, and 113 due to torque shocks and surges caused by sudden changes in current in windings 21u, 22u, 21v, 22v, 21w, and 22w.

For example, when an electrical upshift is instructed while the motor 20 is performing regenerative braking, the torque control unit 511 increases the output torque of the motor 20 by increasing the AC current output from the power converter 30 at the first shift timing. After the AC current output from the power converter 30 increases to or above the second target value, the switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a series connection state to a parallel connection state.

The connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched from a series connection state to a parallel connection state, so that the performance of the motor 20 can be efficiently utilized to electrically shift from a low rotation, high torque state to a high rotation, low torque state. By electrically shifting up, the regenerative braking force can be reduced, and the driver can be given a deceleration sensation similar to that of engine braking. Furthermore, as the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched, the negative output torque of the motor 20 increases (the absolute value of the output torque decreases), so that the driver can be given a shifting sensation similar to that of a mechanical transmission.

[1-4. Operation of the Winding Switching System]
Next, a description will be given of the operation of the winding switching device 100. In the control device 50, the processor 501 executes the motor control program 510 to perform electrical up-shifting processing and electrical down-shifting processing.

FIG. 5 is a flowchart showing an example of an electrical upshift process performed by the control device according to the first embodiment. In this example, it is assumed that windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in series at the start of the electrical upshift process.

When the driver wishes to electrically upshift the vehicle, he or she operates the gear shift indicator 90 and inputs an instruction to electrically upshift the vehicle. The processor 501 receives the instruction to electrically upshift (step S101).

The processor 501 refers to the detection signal of the torque sensor 202 and determines whether the motor torque is positive, i.e., whether the motor 20 is generating torque for accelerating the vehicle or maintaining its speed (hereinafter referred to as "acceleration torque") (step S102).

If the motor torque is positive (YES in step S102), the processor 501 outputs an instruction to the power converter 30 to reduce the motor current Iq (step S103). This starts the reduction of the motor current Iq.

The processor 501 obtains the current value of the motor current Iq from the detection signals of the current sensors 33u, 33v, and 33w, and determines whether the motor current Iq is equal to or less than the first target value Th1 (step S104).

If the motor current Iq is greater than the first target value Th1 (NO in step S104), the processor 501 executes step S104 again. If the motor current Iq is equal to or less than the first target value Th1 (YES in step S104), the processor 501 outputs an instruction to the power converter 30 to stop the reduction of the motor current Iq (step S105). This stops the reduction of the motor current Iq.

The processor 501 outputs an instruction to the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a series connection state to a parallel connection state (step S106). As a result, while the motor current Iq is equal to or less than the first target value Th1, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w is switched from a series connection state to a parallel connection state, and an electrical upshift is performed.

After outputting an instruction to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20, the processor 501 outputs an instruction to increase the motor current Iq to the power converter 30 (step S107). This starts the increase in the motor current Iq.

When the motor current reaches the target value determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w, the processor 501 outputs an instruction to the power converter 30 to stop the increase in the motor current Iq (step S108). This stops the increase in the motor current Iq. This completes the electrical shift-up process when the motor torque is positive.

If the motor torque is negative (NO in step S102), the motor 20 is performing regenerative braking. The power converter 30 functions as a DC/AC converter and converts the AC current output from the motor 20 into a DC current. The converted DC current is output to the battery 40 and stored. In this case, the processor 501 outputs an instruction to the power converter 30 to increase the motor current Iq (step S109). This starts the increase in the motor current Iq.

The processor 501 obtains the current value of the motor current Iq from the detection signals of the current sensors 33u, 33v, and 33w, and determines whether the motor current Iq is greater than or equal to the second target value Th2 (step S110).

If the motor current Iq is smaller than the second target value Th2 (NO in step S110), the processor 501 executes step S110 again. If the motor current Iq is equal to or greater than the second target value Th2 (YES in step S110), the processor 501 outputs an instruction to the power converter 30 to stop the increase in the motor current Iq (step S111). This stops the increase in the motor current Iq.

The processor 501 outputs an instruction to the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a series connection state to a parallel connection state (step S112). As a result, while the motor current Iq is equal to or greater than the second target value Th2, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w is switched from a series connection state to a parallel connection state, and an electrical upshift is performed.

After outputting an instruction to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20, the processor 501 outputs an instruction to reduce the motor current Iq to the power converter 30 (step S112). This starts the reduction of the motor current Iq.

When the motor current reaches the target value determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w, the processor 501 outputs an instruction to the power converter 30 to stop the reduction in the motor current Iq (step S113). This stops the reduction in the motor current Iq. This completes the electrical shift-up process when the motor torque is negative.

FIG. 6 is a flowchart showing an example of an electrical downshifting process performed by the control device according to the first embodiment. In this example, it is assumed that windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in parallel at the start of the electrical downshifting process.

When the driver wishes to electrically downshift the vehicle, he or she operates the gear shift indicator 90 and inputs an instruction to electrically downshift the vehicle. The processor 501 accepts the instruction to electrically downshift (step S201).

The processor 501 refers to the detection signal of the torque sensor 202 and determines whether the motor torque is positive, i.e., whether the motor 20 is generating an acceleration torque (step S202).

If the motor torque is positive (YES in step S202), the processor 501 outputs an instruction to the power converter 30 to reduce the motor current Iq (step S203). This starts the reduction of the motor current Iq.

The processor 501 obtains the current value of the motor current Iq from the detection signals of the current sensors 33u, 33v, and 33w, and determines whether the motor current Iq is equal to or less than the first target value Th1 (step S204).

If the motor current Iq is greater than the first target value Th1 (NO in step S204), the processor 501 executes step S204 again. If the motor current Iq is equal to or less than the first target value Th1 (YES in step S204), the processor 501 outputs an instruction to the power converter 30 to stop the reduction of the motor current Iq (step S205). This stops the reduction of the motor current Iq.

The processor 501 outputs an instruction to the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a parallel connection state to a series connection state (step S206). As a result, while the motor current Iq is equal to or less than the first target value Th1, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w is switched from a parallel connection state to a series connection state, and an electrical downshift is performed.

After outputting an instruction to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20, the processor 501 outputs an instruction to increase the motor current Iq to the power converter 30 (step S207). This starts the increase in the motor current Iq.

When the motor current reaches the target value determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w, the processor 501 outputs an instruction to the power converter 30 to stop the increase in the motor current Iq (step S208). This stops the increase in the motor current Iq. This completes the electrical downshift process when the motor torque is positive.

If the motor torque is negative (NO in step S202), the motor 20 is performing regenerative braking. In this case, the processor 501 outputs an instruction to the power converter 30 to increase the motor current Iq (step S209). This starts the increase in the motor current Iq.

The processor 501 obtains the current value of the motor current Iq from the detection signals of the current sensors 33u, 33v, and 33w, and determines whether the motor current Iq is greater than or equal to the second target value Th2 (step S210).

If the motor current Iq is smaller than the second target value Th2 (NO in step S210), the processor 501 executes step S210 again. If the motor current Iq is equal to or greater than the second target value Th2 (YES in step S210), the processor 501 outputs an instruction to the power converter 30 to stop the increase in the motor current Iq (step S211). This stops the increase in the motor current Iq.

The processor 501 outputs an instruction to the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 from a parallel connection state to a series connection state (step S212). As a result, while the motor current Iq is equal to or greater than the second target value Th2, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w is switched from a parallel connection state to a series connection state, and an electrical downshift is performed.

After outputting an instruction to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20, the processor 501 outputs an instruction to reduce the motor current Iq to the power converter 30 (step S212). This starts the reduction of the motor current Iq.

When the motor current reaches the target value determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w, the processor 501 outputs an instruction to the power converter 30 to stop the reduction of the motor current Iq (step S213). This stops the reduction of the motor current Iq. This completes the electrical downshift process when the motor torque is negative.

[2. Second embodiment]
The winding switching device of the second embodiment switches the connection state of the multiple windings of a motor between a full connection state in which all of the multiple windings are connected, and a partial connection state in which some of the multiple windings are connected.

FIG. 7 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. Motor 20A includes a plurality of windings 24u, 25u, 24v, 25v, 24w, and 25w. Windings 24u and 25u correspond to the U phase, windings 24v and 25v correspond to the V phase, and windings 24w and 25w correspond to the W phase. However, the number of windings for each phase is not limited to two, and may be three or more.

The winding switching device 100A switches the connection state of the windings 24u, 25u, 24v, 25v, 24w, and 25w for each phase between a fully connected state and a partially connected state. The winding switching device 100A includes control circuits 103u, 103v, and 103w and switching circuits 140u, 140v, and 140w.

The switching circuits 140u, 140v, and 140w switch the connection state of the windings 24u, 25u, 24v, 25v, 24w, and 25w between a fully connected state and a partially connected state. The fully connected state is an example of a first connection state, and the partially connected state is an example of a second connection state.

Power line 35u is connected to one end of winding 24u. The other end of winding 24u and one end of winding 25u are connected to each other, and power line 241u extends from the midpoint between winding 24u and winding 25u. Power line 241u branches into power lines 242u and 243w. Power line 251u extends from the other end of winding 25u. Power line 251u branches into power lines 252u and 253w.

Power line 35v is connected to one end of winding 24v. The other end of winding 24v and one end of winding 25v are connected to each other, and power line 241v extends from the midpoint between winding 24v and winding 25v. Power line 241v branches into power lines 242v and 243u. Power line 251v extends from the other end of winding 25v. Power line 251v branches into power lines 252v and 253u.

Power line 35w is connected to one end of winding 24w. The other end of winding 24w and one end of winding 25w are connected to each other, and power line 241w extends from the midpoint between winding 24w and winding 25w. Power line 241w branches into power lines 242w and 243v. Power line 251w extends from the other end of winding 25w. Power line 251w branches into power lines 252w and 253v.

The switching circuit 140u includes semiconductor relays 141u and 142u. The switching circuit 140v includes semiconductor relays 141v and 142v. The switching circuit 140w includes semiconductor relays 141w and 142w. The semiconductor relays 141u, 142u, 141v, 142v, 141w, and 142w are, for example, IGBTs or power MOSFETs.

In the switching circuit 140u, the first terminal of the semiconductor relay 141u is connected to the power line 242u, and the second terminal is connected to the power line 243u. The first terminal of the semiconductor relay 142u is connected to the power line 252u, and the second terminal is connected to the power line 253u. The connection relationship between the switching circuits 140v and 140w is the same as that of the switching circuit 140u, so a description is omitted.

When semiconductor relays 141u, 141v, and 141w are in the off state and semiconductor relays 142u, 142v, and 142w are in the on state, a fully connected state is reached in which all of windings 24u, 25u, 24v, 25v, 24w, and 25w are connected. When semiconductor relays 141u, 141v, and 141w are in the on state and semiconductor relays 142u, 142v, and 142w are in the off state, a partially connected state is reached in which only windings 24u, 24v, and 24w are connected among windings 24u, 25u, 24v, 25v, 24w, and 25w.

The other configurations of the winding switching device 100A according to the second embodiment are similar to those of the winding switching device 100 according to the first embodiment, so the same components are given the same reference numerals and their description is omitted.

In the second embodiment, an electrical upshift is performed by switching the connection state of the windings 24u, 25u, 24v, 25v, 24w, and 25w of the motor 20 from a full connection state to a partial connection state. An electrical downshift is performed by switching the connection state of the windings 24u, 25u, 24v, 25v, 24w, and 25w of the motor 20 from a partial connection state to a full connection state.

[3. Third embodiment]
In the third embodiment, the torque control unit 511 changes the effective current of the AC current output from the power converter 30 in a stepwise manner based on the shift timing.

FIG. 8 is a timing chart showing an example of the switching timing of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 in the winding switching system according to the third embodiment. Note that the configuration of the winding switching system according to the third embodiment is the same as the configuration of winding switching system 10 according to the first embodiment, so the same components are given the same reference numerals and descriptions thereof are omitted.

FIG. 8 shows an example of the timing of the gear shift command, motor current, motor torque, and on/off switching of semiconductor relays 111, 112, and 113 when the connection state of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 is switched from a series connection state to a parallel connection state.

At time t1, a gear change command (electrical upshift command) is input to the control device 50. At time t1, the torque control unit 511 reduces the motor current Iq in a stepwise manner to a value equal to or less than the first target value Th1. As the motor current Iq decreases, the motor torque also decreases in a stepwise manner. After time t1, the motor current Iq is maintained at the first target value Th1.

The switching control unit 512 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from a series connection state to a parallel connection state at a timing after time t1. In the example of FIG. 8, at time t01, which is after time t1, the relays 111 and 113 are switched from an on state to an off state, and at time t02, which is after time t01, the relay 112 is switched from an off state to an on state. During the period between time t01 and time t02, all of the relays 111, 112, and 113 are in the off state. This prevents all of the relays 111, 112, and 113 from being in the on state when switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w.

At time t2, which is after time t02, the torque control unit 511 increases the motor current Iq in a stepwise manner. The target value of the motor current Iq at this time is determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w. The target torque is determined based on the rotation speed of the motor 20, the output torque of the motor 20, the depression amount of the brake pedal 70 (braking command amount), and the depression amount of the accelerator pedal 80 (acceleration command amount). As the motor current Iq increases, the motor torque also increases in a stepwise manner.

As the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched, the output torque of the motor 20 decreases in a step-like manner, giving the driver the same feeling of shifting as with a mechanical transmission.

[4. Fourth embodiment]
In the fourth embodiment, the torque control unit 511 changes the effective current of the AC current output from the power converter 30 in a curved manner based on the shift timing.

Fig. 9 is a timing chart showing an example of the switching timing of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 in the winding switching system according to the fourth embodiment. Fig. 9 shows an example of the timing of the speed change command, motor current, motor torque, and on/off switching of semiconductor relays 111, 112, and 113 when the connection state of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 is switched from a series connection state to a parallel connection state.

At time t11, a gear change command (electrical upshift command) is input to the control device 50. The torque control unit 511 reduces the motor current Iq in a curved manner from time t11. In the example shown in FIG. 9, the slope of the decrease in the motor current Iq gradually increases from time t11, and the slope becomes infinite at the midpoint between time t11 and time t12. Thereafter, the slope of the decrease in the motor current Iq gradually decreases, and at time t12 the slope becomes 0 (stops decreasing).

At time t12, the motor current Iq reaches the first target value Th1. The torque control unit 511 stops the reduction of the motor current Iq from time t12 when the motor current Iq reaches the first target value Th1. In other words, from time t12 onwards, the motor current Iq is maintained at the first target value Th1. From time t12 onwards, the reduction of the motor torque also stops.

The switching control unit 512 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from a series connection state to a parallel connection state at a timing after time t12. In the example of FIG. 9, at time t01, which is after time t12, the relays 111 and 113 are switched from an on state to an off state, and at time t02, which is after time t01, the relay 112 is switched from an off state to an on state. During the period between time t01 and time t02, all of the relays 111, 112, and 113 are in the off state. This prevents all of the relays 111, 112, and 113 from being in the on state when switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w.

From time t21, which is after time t02, the torque control unit 511 increases the motor current Iq. The target value of the motor current Iq at this time is determined based on the target torque in the parallel connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w. The target torque is determined based on the rotation speed of the motor 20, the output torque of the motor 20, the depression amount of the brake pedal 70 (braking command amount), and the depression amount of the accelerator pedal 80 (acceleration command amount). In the example shown in FIG. 9, the motor current Iq increases in a curved line. As the motor current Iq increases, the motor torque also increases.

In the example shown in FIG. 9, the slope of the increase in motor current Iq gradually increases from time t21, and the slope becomes infinite at the midpoint between time t21 and time t22. After that, the slope of the increase in motor current Iq gradually decreases, and at time t22 the slope becomes 0 (stops increasing).

At time t22, the motor current Iq reaches the target value. From time t22 when the motor current Iq reaches the target value, the torque control unit 511 stops increasing the motor current Iq. After time t22, the increase in the motor torque also stops.

As the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 is switched, the output torque of the motor 20 decreases in a curved manner. In the fourth embodiment, sharp changes in the motor torque are suppressed, so that the driver can be given a shifting sensation similar to that of a mechanical transmission.

[5. Fifth embodiment]
In the fifth embodiment, the torque control unit 511 executes a pseudo-shift control process to reduce and then increase the AC current output from the power converter 30 at a pseudo-shift timing different from the timing of the electrical up-shift and electrical down-shift (electrical shift timing).

FIG. 10 is a timing chart showing an example of pseudo-speed change control processing in the winding switching system according to the fifth embodiment. FIG. 10 shows an example of the timing of a speed change command, motor current, motor torque, and on/off switching of semiconductor relays 111, 112, and 113 when the connection state of windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 is switched from a series connection state to a parallel connection state.

At time t31, a gear shift command (pseudo gear shift command) is input to the control device 50. The torque control unit 511 reduces the motor current Iq from time t31. In the example shown in FIG. 10, the motor current Iq gradually decreases in a ramp shape. As the motor current Iq decreases, the motor torque also decreases.

At time t32, the motor current Iq reaches the third target value Th1. The torque control unit 511 stops the reduction of the motor current Iq from time t32 when the motor current Iq reaches the first target value Th1. In other words, from time t32 onwards, the motor current Iq is maintained at the first target value Th1. From time t32 onwards, the reduction of the motor torque also stops.

The torque control unit 511 maintains the motor current Iq at the first target value Th1 for a certain period of time. During this period, the switching control unit 512 does not switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w. In other words, the semiconductor relays 111 and 113 maintain the ON state, and the semiconductor relay 112 maintains the OFF state.

From time t41, which is after time t32, the torque control unit 511 increases the motor current Iq. That is, the torque control unit 511 increases the motor current Iq after maintaining it at the first target value Th1 for a certain period of time. Note that the torque control unit 511 may increase the motor current Iq without providing a stop period after the motor current Iq has decreased to the first target value Th1 or less.

The target value of the motor current Iq at this time is the same as the target value before the change in the motor current Iq. In the example shown in FIG. 10, the motor current Iq increases in a ramp shape. As the motor current Iq increases, the motor torque also increases.

At time t42, the motor current Iq reaches the target value. From time t42 when the motor current Iq reaches the target value, the torque control unit 511 stops increasing the motor current Iq. After time t42, the increase in the motor torque also stops.

FIG. 11 is a flowchart showing an example of pseudo-shift processing by the control device according to the fifth embodiment.

The driver operates the gear shift indicator 90 to input a gear shift instruction to the vehicle. The processor 501 accepts the gear shift instruction (step S301).

The processor 501 refers to the detection signal of the torque sensor 202 and determines whether the motor torque is positive, i.e., whether the motor 20 is generating an acceleration torque (step S302).

If the motor torque is positive (YES in step S302), the processor 501 outputs an instruction to the power converter 30 to reduce the motor current Iq (step S303). This starts the reduction of the motor current Iq.

The processor 501 obtains the current value of the motor current Iq from the detection signals of the current sensors 33u, 33v, and 33w, and determines whether the motor current Iq is equal to or less than the first target value Th1 (step S304).

If the motor current Iq is greater than the first target value Th1 (NO in step S304), the processor 501 executes step S304 again. If the motor current Iq is equal to or less than the first target value Th1 (YES in step S304), the processor 501 outputs an instruction to the power converter 30 to stop the reduction of the motor current Iq (step S305). This stops the reduction of the motor current Iq.

The processor 501 outputs an instruction to increase the motor current Iq to the power converter 30 without switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 (step S306). This starts the increase in the motor current Iq.

When the motor current Iq reaches the same target value as the target value before the change in the motor current Iq, the processor 501 outputs an instruction to the power converter 30 to stop the increase in the motor current Iq (step S307). This stops the increase in the motor current Iq. This completes the pseudo-speed change process when the motor torque is positive.

If the motor torque is negative (NO in step S302), the motor 20 is performing regenerative braking. In this case, the processor 501 outputs an instruction to the power converter 30 to increase the motor current Iq (step S308). This starts the increase in the motor current Iq.

The processor 501 obtains the current value of the motor current Iq from the detection signals of the current sensors 33u, 33v, and 33w, and determines whether the motor current Iq is greater than or equal to the second target value Th2 (step S309).

If the motor current Iq is smaller than the second target value Th2 (NO in step S309), the processor 501 executes step S309 again. If the motor current Iq is equal to or greater than the second target value Th2 (YES in step S309), the processor 501 outputs an instruction to the power converter 30 to stop the increase in the motor current Iq (step S310). This stops the increase in the motor current Iq.

The processor 501 outputs an instruction to the power converter 30 to reduce the motor current Iq without switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20 (step S311). This starts the reduction of the motor current Iq.

When the motor current Iq reaches the same target value as the target value before the change in the motor current Iq, the processor 501 outputs an instruction to the power converter 30 to stop the reduction in the motor current Iq (step S312). This stops the reduction in the motor current Iq. This completes the pseudo-speed change process when the motor torque is negative.

As described above, the output torque of the motor 20 changes in response to a gear shift command without switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w of the motor 20, so the driver can feel a pseudo gear shift even when no electrical gear shift is performed.

By combining the pseudo-shifting process described above with an electrical shifting, the driver can be made to feel a simulated sensation of multi-speed shifting. For example, by performing pseudo-shifting process when switching between 1st and 2nd gear, between 2nd and 3rd gear, between 4th and 5th gear, and between 5th and 6th gear, and performing electrical shifting process (electrical up-shifting process and electrical down-shifting process) when switching between 3rd and 4th gear, the driver can be made to feel a simulated sensation of six-speed shifting, while electrical shifting that efficiently utilizes the performance of the motor can be performed when switching between 3rd and 4th gear.

[6. Sixth embodiment]
The configuration of a winding switching system according to the sixth embodiment will be described with reference to FIG.

The winding switching device 100 has voltage sensors 34u, 34v, and 34w that detect the voltages in the windings 21u, 21v, and 21w. In a specific example, a voltage sensor 34u is arranged between the power lines 35u and 212u, a voltage sensor 34v is arranged between the power lines 35v and 212v, and a voltage sensor 34w is arranged between the power lines 35w and 212w. The voltage sensors 34u, 34v, and 34w are connected to the control device 50. The control device 50 can receive the detection values of the voltage sensors 34u, 34v, and 34w.

The other configurations of the winding switching system according to the sixth embodiment are similar to those of the winding switching system 10 according to the first embodiment, so the same components are given the same reference numerals and their description is omitted.

FIG. 12 is a functional block diagram showing an example of the functions of the control device according to the sixth embodiment. In addition to a torque control unit 511 and a switching control unit 512, the control device 50A includes the functions of a first determination unit 513, a judgment unit 514, a prohibition unit 515, and a second determination unit 516.

The functions of the torque control unit 511 and the switching control unit 512 are the same as those in the first embodiment, so detailed explanations will be omitted.

The first determination unit 513 determines the timing before the induced voltage generated in the windings 21u, 22u, 21v, 22v, 21w, 22w exceeds the output voltage of the battery 40 as the first forced shift timing when the connection state of the multiple windings 21u, 22u, 21v, 22v, 21w, 22w is a series connection state. The first forced shift timing is the timing for starting the forced switching of the connection state of the windings 21u, 22u, 21v, 22v, 21w, 22w from the series connection state to the parallel connection state, regardless of the presence or absence of a shift command from the shift indicator 90 or the automatic shift control device.

An induced voltage is generated in the windings 21u, 22u, 21v, 22v, 21w, and 22w according to the rotation speed of the motor 20. The power converter 30 can control the applied voltage of the windings 21u, 22u, 21v, 22v, 21w, and 22w within the range of the output voltage of the battery 40. Since the polarity of the induced voltage in the windings 21u, 22u, 21v, 22v, 21w, and 22w is opposite to the polarity of the applied voltage, if the induced voltage exceeds the output voltage of the battery 40, the current in the windings 21, 22u, 21v, 22v, 21w, and 22w cannot be reduced to zero. Therefore, if the first target value Th1 is 0A and the induced voltage exceeds the output voltage of the battery 40, the motor current Iq cannot be reduced to the first target value Th1 in the electrical shift-up process.

In the sixth embodiment, the first determination unit 513 monitors the induced voltages generated in the windings 21u, 22u, 21v, 22v, 21w, and 22w in the series connection state, and determines the timing before the induced voltage transitions from a range below the output voltage of the battery 40 to a range above the output voltage as the first forced shift timing.

The torque control unit 511 changes the output torque of the motor 20 by changing the AC current output from the power converter 30 at the first forced shift timing determined by the first determination unit 513. After the AC current has changed, the switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from a series connection state to a parallel connection state.

In one specific example, when the first determination unit 513 determines the first forced shift timing, it generates an electrical upshift command. This starts the electrical upshift process.

In one specific example, the first determination unit 513 can determine the timing at which the physical quantity related to the induced voltage exceeds a first threshold value corresponding to the output voltage of the battery 40 as the first forced gear shift timing. The physical quantity is, for example, the rotation speed of the motor 20. In this case, the first determination unit 513 can obtain a detection value from the rotation sensor 201. Another example of the physical quantity is the voltage in the windings 21u, 21v, and 21w. In this case, the detection value can be obtained from each of the voltage sensors 34u, 34v, and 34w. The physical quantity may be the current flowing through the windings 21u, 22u, 21v, 22v, 21w, and 22w, or the output torque of the motor 20. In the following description, the physical quantity is the rotation speed of the motor 20.

When the connection state of the multiple windings 21u, 22u, 21v, 22v, 21w, and 22w is a parallel connection state, the determination unit 514 determines whether or not the induced voltage exceeds the output voltage of the battery after the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w is switched from a parallel connection state to a series connection state.

In a specific example, the determination unit 514 can determine whether the physical quantity related to the induced voltage in the series connection state is equal to or less than the second threshold value corresponding to the output voltage of the battery 40. More specifically, the determination unit 514 acquires the rotation speed of the motor 20. From the rotation speed of the motor 20, the induced voltage when the windings 21u, 22u, 21v, 22v, 21w, and 22w are in a series connection state can be identified. The second threshold value is, for example, the rotation speed of the motor 20 when the induced voltage when the windings 21u, 22u, 21v, 22v, 21w, and 22w are in a series connection state becomes equal to the output voltage of the battery 40. However, the second threshold value is not limited to this. For example, the second threshold value may be the rotation speed of the motor 20 when the induced voltage when the windings 21u, 22u, 21v, 22v, 21w, and 22w are in a series connection state is lower than the output voltage of the battery 40 by a predetermined margin.

When the determination unit 514 determines that the induced voltage exceeds the output voltage of the battery 40, the prohibition unit 515 prohibits the switching control unit 512 from switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w. In a specific example, the prohibition unit 515 prohibits the switching control unit 512 from switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w while the rotation speed of the motor 20 exceeds the second threshold value. This switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from a parallel connection state to a series connection state, preventing the induced voltage from exceeding the output voltage of the battery 40.

When the rotation speed of the motor 20 becomes equal to or lower than the second threshold value, the prohibition unit 515 cancels the prohibition of the switching control unit 512 from switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w.

The second determination unit 516 determines the timing after the induced voltage becomes equal to or lower than the output voltage of the battery 40 after the connection state of the windings 21u, 22u, 21v, 22v, 21w, 22w is switched from the parallel connection state to the series connection state when the connection state of the multiple windings 21u, 22u, 21v, 22v, 21w, 22w is in the parallel connection state as the second forced shift timing. The second forced shift timing is the timing for starting the forced switching of the connection state of the windings 21u, 22u, 21v, 22v, 21w, 22w from the parallel connection state to the series connection state, regardless of the presence or absence of a shift command from the shift indicator 90 or the automatic shift control device.

In the series connection state, regenerative power can be recovered more efficiently than in the parallel connection state. Furthermore, in the series connection state, the higher the rotation speed of the motor 20, the greater the amount of regeneration. Therefore, for example, when the vehicle is decelerating in the parallel connection state, in order to efficiently recover regenerative power, it is preferable to perform an electrical downshift at a timing when the rotation speed of the motor 20 is as high as possible and the induced voltage after switching to the series connection state is within the range of the output voltage of the battery 40 or less.

The second determination unit 516 estimates the induced voltage generated in the windings 21u, 22u, 21v, 22v, 21w, and 22w in the series connection state, and determines the timing at which the induced voltage transitions from a range exceeding the output voltage of the battery 40 to a range below the output voltage of the battery 40 as the second forced shift timing.

The torque control unit 511 changes the output torque of the motor 20 by changing the AC current output from the power converter 30 at the second forced shift timing determined by the second determination unit 516. After the AC current has changed, the switching control unit 512 causes the winding switching device 100 to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from a parallel connection state to a series connection state.

In one specific example, when the second determination unit 516 determines the second forced shift timing, it generates an electrical downshift command. This starts the electrical downshift process.

In one specific example, the second determination unit 516 can determine, as the second forced shift timing, the timing at which the physical quantity related to the induced voltage becomes equal to or less than a second threshold value corresponding to the output voltage of the battery 40. For example, the second determination unit 516 determines, as the second forced shift timing, the timing at which the rotation speed of the motor 20 becomes equal to or less than the second threshold value.

The operation of the winding switching system according to the sixth embodiment will be described below. The control device 50A executes the following forced shift-up determination process and forced shift-down determination process.

FIG. 13 is a flowchart showing an example of a forced upshift determination process performed by the control device according to the sixth embodiment. In this example, it is assumed that windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in series.

The rotation sensor 201 detects the rotation speed of the output shaft of the motor 20 and outputs the detected rotation speed. For example, the rotation sensor 201 detects the rotation speed at a constant cycle and outputs the detection result. The control device 50A receives the detection value of the rotation speed output from the rotation sensor 201 (step S401).

The processor 501 compares the acquired rotation speed R with the first threshold value Th1_R and determines whether the rotation speed R exceeds the first threshold value Th1_R (step S402). The first threshold value Th1_R is a value that is a predetermined margin lower than the rotation speed of the motor 20 when the induced voltage generated in the windings 21u, 22u, 21v, 22v, 21w, and 22w in the series connection state matches the output voltage of the battery 40.

If the rotation speed R is equal to or less than the first threshold value Th1_R (NO in step S402), the processor 501 returns to step S401.

If the rotation speed R exceeds the first threshold value Th1_R (YES in step S402), the processor 501 determines that timing as the first forced shift timing. The processor 501 generates an electrical upshift command (step S403).

Then, the processor 501 starts the electrical upshift process (step S404). As a result, after the motor current Iq decreases, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w switches from a series connection state to a parallel connection state. This completes the forced upshift determination process.

FIG. 14 is a flowchart showing an example of a forced downshift determination process performed by the control device according to the sixth embodiment. In this example, it is assumed that windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in parallel.

The control device 50A receives the detected value of the rotation speed output from the rotation sensor 201 (step S501).

The processor 501 compares the acquired rotation speed R with the second threshold value Th2_R and determines whether the rotation speed R is equal to or lower than the second threshold value Th2_R (step S502). The second threshold value Th2_R is a value lower than the rotation speed of the motor 20 by a predetermined margin when the induced voltage generated in the windings 21u, 22u, 21v, 22v, 21w, and 22w in the series connection state matches the output voltage of the battery 40. The second threshold value Th2_R may be the same value as the first threshold value Th1_R, or may be a different value. For example, the second threshold value Th2_R is a value lower than the first threshold value Th1_R. This makes it possible to prevent the rotation speed R from exceeding the first threshold value Th1_R soon after the electrical downshift is completed, causing a forced upshift.

If the rotation speed R is greater than the second threshold value Th2_R (NO in step S502), the processor 501 prohibits an electrical downshift (step S503). As a result, even if an electrical downshift command is given by the driver, for example, an electrical downshift is not executed. With electrical downshifts prohibited, the processor 501 returns to step S501.

If the rotation speed R is equal to or lower than the second threshold value Th2_R (YES in step S502), the processor 501 determines that timing as the second forced shift timing. In this case, if electrical downshifting is prohibited, the processor 501 releases the prohibition of electrical downshifting. Once the processor 501 determines the second forced shift timing, it generates an electrical downshift instruction (step S504).

Then, the processor 501 starts the electrical downshift process (step S505). As a result, after the motor current Iq approaches zero, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w switches from a parallel connection state to a series connection state. This completes the forced downshift determination process.

[7. Supplementary Notes]
The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not the above-described embodiments, and includes the meaning equivalent to the claims and all modifications within the scope thereof.

10 Winding switching system 20 Motor (drive motor)
21u, 22u, 21v, 22v, 21w, 22w Winding 23 Neutral point 25 Power line 30 Power converter 31u, 32u, 31v, 32v, 31w, 32w Switch 33u, 33v, 33w Current sensor 34u, 34v, 34w Voltage sensor 35u, 35v, 35w Power line 40 Battery 50, 50A Control device 501 Processor 502 Non-volatile memory 503 Volatile memory 504 Interface (I/F)
DESCRIPTION OF SYMBOLS 510 Motor control program 511 Torque control unit 512 Switching control unit 513 First decision unit 514 Judgment unit 515 Prohibition unit 516 Second decision unit 60 Wheel 70 Brake pedal 71 Sensor 80 Accelerator pedal 81 Sensor 90 Gear shift indicator 100 Winding switching device 103u, 103v, 103w Control circuit 104u, 104v, 104w Switching circuit 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, 113w Semiconductor relay 201 Rotation sensor 202 Torque sensor 212u, 221u, 222u Power line 20A Motor 24u, 25u, 24v, 25v, 24w, 25w Winding 100A Winding switching device 140u, 140v, 140w Switching circuit 141u, 142u, 141v, 142v, 141w, 142w Semiconductor relay 241u, 242u, 243u, 251u, 252u, 253u, 241v, 242v, 243v, 251v, 252v, 253v, 241w, 242w, 243w, 251w, 252w, 253w Power line

Claims (21)

1. A drive motor that drives the wheels of the vehicle;
   A control device for controlling the drive motor;
   a power converter that converts DC power output from a battery into AC power and supplies the AC power to the drive motor;
   a winding switching device that switches a connection state of a plurality of windings in the driving motor between a first connection state and a second connection state;
   Equipped with
   The control device includes:
   a torque control unit that changes an output torque of the drive motor by changing an AC current output from the power converter at a predetermined shift timing of the vehicle;
   a switching control unit that causes the winding switching device to switch from the first connection state to the second connection state after the AC current has changed;
   including,
   Winding switching system for vehicle motors.
2. the torque control unit reduces the AC current output from the power converter at a first shift timing to reduce an output torque of the drive motor;
   the switching control unit causes the winding switching device to switch from the first connection state to the second connection state after the AC current has decreased to a first target value or less.
   The winding switching system for a vehicle motor according to claim 1 .
3. the torque control unit reduces the AC current output from the power converter at a second shift timing different from the first shift timing, thereby reducing the output torque of the drive motor;
   the switching control unit causes the winding switching device to switch from the second connection state to the first connection state after the AC current has decreased to or below the first target value.
   The winding switching system for a vehicle motor according to claim 2 .
4. the torque control unit increases the AC current output from the power converter at a first shift timing to increase an output torque of the drive motor;
   the switching control unit causes the winding switching device to switch from the first connection state to the second connection state after the AC current has increased to or above a second target value.
   The winding switching system for a vehicle motor according to claim 1 .
5. the torque control unit increases the AC current output from the power converter at a second shift timing different from the first shift timing to increase an output torque of the drive motor;
   the switching control unit causes the winding switching device to switch from the second connection state to the first connection state after the AC current has increased to or above a second target value.
   The winding switching system for a vehicle motor according to claim 4.
6. the second connection state is a connection state in which the drive motor outputs a torque lower than that in the first connection state at the same rotation speed;
   The winding switching system for a vehicle motor according to any one of claims 1 to 5.
7. the control device further includes a first determination unit that determines, when the connection state of the plurality of windings is the first connection state, a timing before an induced voltage generated in the windings exceeds an output voltage of the battery, as a first forced shift timing,
   the torque control unit changes an output torque of the drive motor by changing an AC current output from the power converter at the first forced shift timing determined by the first determination unit,
   the switching control unit causes the winding switching device to switch from the first connection state to the second connection state after the AC current has changed;
   7. The winding switching system for a vehicle motor according to claim 6.
8. The first determination unit determines, as the first forced shift timing, a timing at which a physical quantity related to the induced voltage exceeds a first threshold value corresponding to an output voltage of the battery.
   The winding switching system for a vehicle motor according to claim 7.
9. the physical quantity being one of a voltage in the winding, a rotational speed of the drive motor, a current flowing through the winding, and an output torque of the drive motor;
   The winding switching system for a vehicle motor according to claim 8.
10. The control device includes:
    a determination unit that determines, when the connection state of the plurality of windings is the second connection state, whether or not the induced voltage exceeds an output voltage of the battery after the connection state of the windings is switched from the second connection state to the first connection state;
    a prohibition unit that prohibits the switching control unit from switching the connection state of the winding when the determination unit determines that the induced voltage exceeds an output voltage of the battery;
    Further comprising:
    The winding switching system for a vehicle motor according to any one of claims 7 to 9.
11. the control device further includes a second determination unit that, when the connection state of the plurality of windings is the second connection state, determines a timing after the induced voltage becomes equal to or lower than an output voltage of the battery after the connection state of the plurality of windings is switched from the second connection state to the first connection state as a second forced shift timing,
    the torque control unit changes an output torque of the drive motor by changing an AC current output from the power converter at the second forced shift timing determined by the second determination unit,
    the switching control unit causes the winding switching device to switch from the second connection state to the first connection state after the AC current has changed.
    The winding switching system for a vehicle motor according to any one of claims 7 to 10.
12. The second determination unit determines, as the second forced shift timing, a timing at which the physical quantity related to the induced voltage becomes equal to or less than a second threshold value corresponding to an output voltage of the battery.
    The winding switching system for a vehicle motor according to claim 11.
13. The winding switching system further includes an input device that receives a gear shift instruction from a driver,
    The gear shift timing is a timing at which the input device receives the gear shift instruction from the driver.
    The winding switching system for a vehicle motor according to any one of claims 1 to 12.
14. the gear shift timing is determined based on a rotation speed of the drive motor, an output torque, an acceleration command amount of the vehicle, and a braking command amount of the vehicle.
    The winding switching system for a vehicle motor according to any one of claims 1 to 12.
15. The torque control unit gradually decreases or gradually increases an effective current of the AC current output from the power converter from the shift timing.
    The winding switching system for a vehicle motor according to any one of claims 1 to 14.
16. The torque control unit changes the effective current in a ramp shape from the shift timing.
    The winding switching system for a vehicle motor according to claim 15.
17. the torque control unit changes an effective current of the AC current output from the power converter in a stepwise manner based on the shift timing.
    The winding switching system for a vehicle motor according to any one of claims 1 to 14.
18. the torque control unit executes a pseudo-speed-change control process of decreasing and then increasing an AC current output from the power converter at a pseudo-speed-change timing different from the speed-change timing.
    The winding switching system for a vehicle motor according to any one of claims 1 to 17.
19. A control device for controlling a drive motor that drives wheels of a vehicle,
    a torque control unit that changes an output torque of the drive motor by changing an AC current output from a power converter that converts DC power output from a battery into AC power and supplies the AC power to the drive motor, at a predetermined shift timing of the vehicle;
    a switching control unit that causes a winding switching device that switches a connection state of a plurality of windings in the drive motor to switch from a first connection state to a second connection state after the AC current changes;
    Equipped with
    Control device.
20. A method for controlling a vehicle motor executed by a control device that controls a drive motor that drives wheels of a vehicle, comprising:
    a step of converting DC power output from a battery into AC power and changing an AC current output from a power converter that supplies the AC power to the drive motor, at a predetermined shift timing of the vehicle, thereby changing an output torque of the drive motor;
    causing a winding switching device, which switches a connection state of a plurality of windings in the driving motor, to switch from a first connection state to a second connection state after the AC current changes;
    including,
    A method for controlling a motor for a vehicle.
21. A computer program used by a control device that controls a drive motor that drives wheels of a vehicle,
    On the computer,
    a step of converting DC power output from a battery into AC power and changing an AC current output from a power converter that supplies the AC power to the drive motor, at a predetermined shift timing of the vehicle, thereby changing an output torque of the drive motor;
    causing a winding switching device, which switches a connection state of a plurality of windings in the driving motor, to switch from a first connection state to a second connection state after the AC current changes;
    In order to execute
    Computer program.
    

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