JP7545944B2 - Electric vehicle control device - Google Patents

Description

The present invention relates to a control device for an electric vehicle.

In recent years, hybrid vehicles (hereinafter also referred to as HEV vehicles) equipped with two types of power sources, an electric motor and an internal combustion engine, have become widely used. For example, HEV vehicles equipped with a series type hybrid system are known.

When such a hybrid system detects a system start request from the user, it controls the system main relay (hereinafter also referred to as SMR), connects the high-voltage battery and the PCU (Power Control Unit), and makes the HEV vehicle ready to run. In addition, when the hybrid system detects a system stop request from the user while the HEV vehicle is running or in a runnable state, it controls the SMR and cuts off the high-voltage circuit connecting the high-voltage battery and the PCU (see, for example, Patent Document 1).

JP 2020-99104 A

In the above-mentioned HEV vehicle, if the SMR is controlled and the high-voltage circuit is shut off while the HEV vehicle is running (the motor is driving), the back electromotive force generated in the drive motor may place a load on the capacitor inside the PCU. Conventionally, such back electromotive force has been dealt with by using a capacitor with high voltage resistance that can withstand the load. However, such capacitors are large and very expensive.

The present invention was made in consideration of the above-mentioned problems, and aims to suppress the generation of back electromotive force and reduce the cost of parts for HEV vehicles.

In order to achieve the above-mentioned object, the control device for an electric vehicle of the present invention is a control device for an electric vehicle having a high-voltage battery that supplies power to a traction motor, a power control unit that controls the supply of power from the high-voltage battery to the traction motor, and a relay unit that connects the high-voltage battery and the power control unit or cuts off the connection between the high-voltage battery and the power control unit, and is provided with a control unit that controls the relay unit when a system stop request is detected, thereby maintaining the connection between the high-voltage battery and the power control unit when the vehicle speed of the electric vehicle is equal to or greater than a predetermined threshold, and cutting off the connection between the high-voltage battery and the power control unit when the vehicle speed of the electric vehicle is less than the threshold. In addition, when the control unit detects an overcharged state of the high-voltage battery, it controls the relay unit to disconnect the high-voltage battery from the power control unit regardless of the vehicle speed of the electric vehicle, and when the control unit does not detect an overcharged state of the high-voltage battery and the capacity of the high-voltage battery exceeds a threshold value, it controls the power control unit to keep the absolute value of the torque of the traction motor below a predetermined threshold value until the vehicle speed of the electric vehicle becomes below the threshold value .

This invention makes it possible to suppress the generation of back electromotive force and reduce the cost of parts for HEV vehicles.

FIG. 1 is a block diagram showing an example of the configuration of a main part of a vehicle equipped with a control device for an electric vehicle according to an embodiment of the present invention. FIG. 2 is a flowchart showing an example of the SMR control process.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

<Hybrid system configuration>
1 is a block diagram showing an example of the configuration of a hybrid system 1. The hybrid system 1 is a series hybrid system and is mounted on an HEV (not shown).

As shown in FIG. 1, the hybrid system 1 includes an HEV-ECU 10, a PCU 11, a BMS (Battery Management System) 12, a high-voltage battery 13, an SMR 14, a generator motor (MG1) 15, and a drive motor (MG2) 16. An engine (not shown) is also connected to the hybrid system 1. The engine is, for example, a gasoline engine.

The HEV-ECU 10 is an example of a control unit. The HEV-ECU 10 is an ECU (Electronic Control Unit) that performs overall control of the entire hybrid system 1. The HEV-ECU 10 is equipped with a microcontroller (microcontroller unit), which includes, for example, a CPU, a non-volatile memory such as a flash memory, and a volatile memory such as a DRAM (Dynamic Random Access Memory).

The HEV-ECU 10 is connected to the PCU 11 and the BMS 12 via the CAN (Controller Area Network) communication protocol to enable two-way communication. The HEV-ECU 10 inputs to the PCU 11 information required for controlling the generator motor 15 and the drive motor 16, in addition to detection signals input from various sensors connected to the PCU 11.

In addition to the detection signals input from the various sensors connected to the BMS 12, the HEV-ECU 10 also inputs information required for controlling the high-voltage battery 13 to the BMS 12. The HEV-ECU 10 also controls the connection and disconnection between the PCU 11 and the high-voltage battery 13 by controlling the ON/OFF state of the SMR 14. The control of the SMR 14 will be described later.

The PCU 11 is an example of a power control unit. The PCU 11 is a unit for controlling the driving of the generator motor 15 and the drive motor 16. The PCU 11 includes an MG-ECU 111, a generator inverter 112, and a drive inverter 113. The MG-ECU 111 is an ECU that performs overall control of the PCU 11. The MG-ECU 111 includes a microcomputer, similar to the HEV-ECU 10.

The MG-ECU 111 is connected to various sensors necessary for controlling the operation of the generator motor 15 and the drive motor 16. Detection signals from these sensors are input to the MG-ECU 111. In addition to the detection signals from the various sensors, the MG-ECU 111 also receives information necessary for controlling the generator motor 15 and the drive motor 16 from the HEV-ECU 10.

The MG-ECU 111 controls the operation of the generator motor 15 and the drive motor 16 based on various detection signals and information input from the HEV-ECU 10.

The power generation inverter 112 converts the AC power from the power generation motor 15 into DC power. The power generation inverter 112 also inputs the converted DC power to the drive inverter 113. The drive inverter 113 converts the DC power input from the power generation inverter 112 into AC power and supplies it to the drive motor 16.

The BMS 12 is an ECU that controls the high-voltage battery 13. For example, the BMS 12 detects the voltage, current, temperature, etc. of the high-voltage battery 13, and performs control to protect the high-voltage battery 13 from overcharging, over-discharging, etc.

The BMS 12, like the HEV-ECU 10, is equipped with a microcomputer. Various sensors necessary for controlling the high-voltage battery 13 are connected to the BMS 12. Detection signals from the sensors are input to the BMS 12. In addition to the detection signals from the various sensors, information necessary for controlling the high-voltage battery 13 is also input to the BMS 12 from the HEV-ECU 10.

The BMS 12 controls the high-voltage battery 13 based on various detection signals and information input from the HEV-ECU 10. The BMS 12 can also detect when the high-voltage battery 13 is in an overcharged or over-discharged state. When the BMS 12 detects that the high-voltage battery 13 is in an overcharged or over-discharged state, it inputs a signal indicating this to the HEV-ECU 10.

The high-voltage battery 13 is a battery pack made up of multiple secondary batteries. The secondary batteries are, for example, lithium-ion batteries. The high-voltage battery 13 outputs, for example, DC power of approximately 200 to 350 V (volts).

The SMR 14 is an example of a relay unit. The SMR 14 connects or disconnects the PCU 11 and the high-voltage battery 13 by turning it ON/OFF. The SMR 14 is composed of a positive side SMR 141 and a negative side SMR 142. The positive side power supply path L1 is connected to the positive side power supply terminal of the high-voltage battery 13. Similarly, the negative side power supply path L2 is connected to the negative side power supply terminal of the high-voltage battery 13.

A positive SMR 141 is provided in the positive power supply path L1. A negative SMR 142 is provided in the negative power supply path L2. The SMR 14 is turned on/off according to the control of the HEV-ECU 10, and switches between connection and disconnection between the PCU 11 and the high-voltage battery 13.

The generator motor 15 is, for example, a permanent magnet synchronous motor. The rotating shaft of the generator motor 15 is mechanically connected to the engine crankshaft via a gear (not shown). For example, an engine output gear is supported on the engine crankshaft so as not to rotate relative to the generator motor, and a motor gear is supported on the rotating shaft of the generator motor 15 so as not to rotate relative to the generator motor, and the engine output gear and the motor gear are meshed.

The drive motor 16 is an example of a driving motor. The drive motor 16 is, for example, a permanent magnet synchronous motor that is larger than the generator motor 15. The rotating shaft of the drive motor 16 is connected to the drive system (not shown) of the HEV vehicle. The drive system includes a differential gear, and the power of the drive motor 16 is transmitted to the differential gear, and distributed and transmitted from the differential gear to drive wheels (not shown) consisting of the left and right front wheels or rear wheels. This causes the left and right drive wheels to rotate, and the HEV vehicle moves forward or backward.

The operation of the HEV vehicle will be briefly described below. When starting the engine, the DC power output from the high-voltage battery 13 is converted to AC power by the generator inverter 112, and the AC power is supplied to the generator motor 15. This causes the generator motor 15 to operate in powered running mode, and the engine is motored (cranked) by the generator motor 15.

When the engine crankshaft speed has increased to the required speed for starting due to motoring, the engine starts when the engine's spark plug is fired. When the HEV vehicle is running, the drive motor 16 is powered and generates power.

When the output required for the drive motor 16 is smaller than the output of the high-voltage battery 13, the HEV vehicle runs in EV mode. That is, the engine is stopped, no power is generated by the generator motor 15, and power is supplied from the high-voltage battery 13 to the drive motor 16, which drives the drive motor 16.

On the other hand, when the output required for the drive motor 16 exceeds the output of the high-voltage battery 13, the HEV vehicle runs in HV mode. That is, the engine is operated and the generator motor 15 operates to generate electricity (regenerative operation), so that the engine power is converted to AC power by the generator motor 15.

The AC power from the power generation motor 15 is then output to the power generation inverter 112. The power generation inverter 112 converts the AC power from the power generation motor 15 into DC power. The power generation inverter 112 then inputs the converted DC power to the drive inverter 113. The drive inverter 113 converts the input DC power into AC power and supplies it to the drive motor 16. This drives the drive motor 16.

In addition, when the remaining capacity of the high-voltage battery 13 falls below a predetermined level, the generator motor 15 operates to generate electricity while the engine is running, regardless of whether the drive motor 16 is running or stopped. At this time, the generator inverter 112 converts the AC power from the generator motor 15 into DC power. The converted DC power is supplied to the high-voltage battery 13, thereby charging the high-voltage battery 13.

When the HEV decelerates, the drive motor 16 operates in regenerative mode, and the power transmitted from the drive wheels to the drive motor 16 is converted into AC power. At this time, the drive motor 16 acts as a resistance to the driving drive system, and this resistance acts as a braking force (regenerative braking force) that brakes the HEV vehicle.

At this time, in the PCU 11, the AC power supplied from the drive motor 16 to the drive inverter 113 is input to the power generation inverter 112 and converted to DC power. The converted DC power is supplied to the high-voltage battery 13, thereby charging the high-voltage battery 13.

<SMR Control>
Next, a description will be given of the SMR control executed by the HEV-ECU 10 of the hybrid system 1. Fig. 2 is a flowchart showing an example of the SMR control.

SMR control is a process that controls the ON/OFF state of the SMR 14 and connects or disconnects the PCU 11 and the high-voltage battery 13. The HEV-ECU 10 executes SMR control when there is a system start request for the hybrid system 1, and when there is a system stop request.

First, the HEV-ECU 10 checks whether or not there is a system startup request from the user (step S1). Specifically, the HEV-ECU 10 checks whether or not there is an operation input from the user to start the system. If there is no system startup request (step S1: No), the process of step S1 is repeated. On the other hand, if there is a system startup request (step S1: Yes), the HEV-ECU 10 turns on the SMR 14 and connects the PCU 11 and the high-voltage battery 13 (step S2).

Then, the HEV-ECU 10 checks whether there is a system stop request (step S3). Specifically, the HEV-ECU 10 checks whether there is an operation input from the user to stop the system. Note that the HEV-ECU 10 may determine that there is a system stop request when, for example, it detects from the sensing results of an acceleration sensor or the like that the HEV vehicle has received an impact exceeding a threshold value.

If there is no system stop request (step S3: No), the process of step S3 is repeated. On the other hand, if there is a system stop request (step S3: Yes), the HEV-ECU 10 checks whether the high-voltage battery 13 is in an overcharged state (step S4). Specifically, the HEV-ECU 10 checks whether the BMS 12 has detected an overcharged state of the high-voltage battery 13.

If the battery is overcharged (step S4: Yes), the HEV-ECU 10 turns off the SMR 14, disconnects the PCU 11 from the high-voltage battery 13, and ends this process (step S8).

On the other hand, if the battery is not overcharged (step S4: No), the HEV-ECU 10 checks whether the capacity of the high-voltage battery 13 exceeds the threshold (step S5). If the capacity does not exceed the threshold (step S5: No), the process proceeds to step S7, which will be described later.

On the other hand, if the capacity exceeds the threshold value (step S5: Yes), the HEV-ECU 10 executes zero torque control (step S6). Here, zero torque control is a process that controls the output of the high voltage battery 13, etc., to adjust the magnitude of the three-phase current flowing through the drive motor 16, and controls the absolute value of the torque generated by the drive motor 16 to be 0 Nm.

In this embodiment, in step S6, control is performed so that the absolute value of the torque generated in the drive motor 16 becomes 0 Nm, but this is not limited thereto, and the absolute value of the torque generated in the drive motor 16 may be controlled so that it becomes less than a predetermined threshold value (e.g., 5 Nm, etc.).

Then, the HEV-ECU 10 checks whether the HEV vehicle has stopped (step S7). Specifically, the HEV-ECU 10 checks the vehicle speed of the HEV vehicle, and determines that the HEV vehicle has stopped when the vehicle speed becomes 0 km/h. Note that in this embodiment, the HEV-ECU 10 checks whether the HEV vehicle has stopped in step S7, but this is not limiting, and it may also be possible to check that the vehicle speed of the HEV vehicle has become less than a threshold value (e.g., 5 km/h).

If the HEV vehicle is not stopped (step S7: No), the process proceeds to step S5. On the other hand, if the HEV vehicle is stopped (step S7: Yes), the process proceeds to step S8 and ends.

<Action and effect>
As described above, according to the hybrid system 1 of this embodiment, even if a system stop request is detected, the connection between the PCU 11 and the high-voltage battery 13 can be maintained until the vehicle speed of the HEV drops below the threshold. Therefore, the hybrid system 1 of this embodiment can suppress the generation of a back electromotive force that occurs when the connection between the PCU 11 and the high-voltage battery 13 is cut off while the drive motor 16 is running.

Furthermore, in the hybrid system 1 according to this embodiment, by maintaining the connection between the PCU 11 and the high-voltage battery 13, the circulating current generated by the back electromotive force can be absorbed by the high-voltage battery 13. This reduces the load on the capacitor inside the PCU 11 caused by the circulating current. As a result, in the hybrid system 1 according to this embodiment, even if the capacitor is made smaller and its voltage resistance performance is reduced, the frequency of capacitor failure due to insufficient voltage resistance is reduced. In other words, by making the capacitor smaller, the component costs of the PCU can be reduced.

Furthermore, according to the hybrid system 1 of this embodiment, when a system stop request is detected, the output of the high-voltage battery 13 can be controlled so that the absolute value of the torque of the drive motor 16 is less than the threshold value, in addition to the control to maintain the connection between the PCU 11 and the high-voltage battery 13 until the vehicle speed of the HEV drops below the threshold value. As a result, the hybrid system 1 of this embodiment can suppress the deceleration caused by stopping the system. Therefore, the discomfort felt by the user due to the occurrence of deceleration can be reduced.

Furthermore, according to the hybrid system 1 of this embodiment, if the high-voltage battery 13 is in an overcharged state, the PCU 11 and the high-voltage battery 13 can be immediately disconnected. If the high-voltage battery 13 is in an overcharged state and the connection between the PCU 11 and the high-voltage battery 13 is maintained, an unexpected load may be placed on the high-voltage battery 13. Therefore, by immediately disconnecting the PCU 11 and the high-voltage battery 13, such a situation can be prevented.

In addition, various design modifications may be made to the above-mentioned configuration within the scope of the claims.

1: Hybrid system 10: HEV-ECU
11: PCU
111:MG-ECU
112: Power generation inverter 113: Drive inverter 12: BMS
13: High voltage battery 14: SMR
141: Positive electrode side SMR
142: Negative electrode side SMR
15: Generator motor 16: Drive motor

Claims (3)

A high-voltage battery that supplies power to the driving motor;
a power control unit that controls the supply of power from the high-voltage battery to the driving motor;
a relay unit that connects or disconnects the high voltage battery and the power control unit;
A control device for an electric vehicle having
a control unit that, when a system stop request is detected, controls the relay unit to maintain a connection between the high-voltage battery and the power control unit when the vehicle speed of the electric vehicle is equal to or higher than a predetermined threshold, and to cut off the connection between the high-voltage battery and the power control unit when the vehicle speed of the electric vehicle is less than the threshold;
Equipped with
The control unit is
When an overcharged state of the high-voltage battery is detected, the relay unit is controlled to cut off the high-voltage battery and the power control unit regardless of the vehicle speed of the electric vehicle.
When an overcharged state of the high-voltage battery is not detected and the capacity of the high-voltage battery exceeds a threshold, the power control unit is controlled to keep an absolute value of the torque of the driving motor below a predetermined threshold until a vehicle speed of the electric vehicle becomes below the threshold .
A control device for an electric vehicle. The control unit is
When the system stop request is detected, the relay unit is controlled to maintain a connection between the high-voltage battery and the power control unit when the electric vehicle is not stopped, and to cut off the connection between the high-voltage battery and the power control unit when the electric vehicle is stopped.
The control device for an electric vehicle according to claim 1. The control unit is
By controlling the power control unit, the absolute value of the torque of the driving motor is set to 0.
The control device for an electric vehicle according to claim 1.

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