Control device of electric vehicle

Abstract

To provide a control device of an electric vehicle that can avoid shock at the time of accelerating the vehicle.SOLUTION: A control device of an electric vehicle, which controls the electric vehicle equipped with an engine, a battery for storing electricity obtained by converting power of the engine and a driving motor that supplies driving force for running driving wheels using electricity of the battery, comprises a starting control part that starts the engine when required driving electricity based on required driving torque exceeds a threshold, and a threshold setting part that lowers the threshold, when rotation speed lowers by more than predetermined speed, when the rotation speed of the engine lowers during non-operation of the engine.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for an electric vehicle.

Background Art

[0002] A series hybrid system includes, for example, an engine, a power generation motor that generates electricity using the power of the engine, a drive motor that generates a driving force for traveling, and a battery that stores electric power supplied to the drive motor and the like.

[0003] A hybrid vehicle equipped with such a system travels either by EV (Electric Vehicle) driving or HV (Hybrid Vehicle) driving. In EV driving, the vehicle travels using only the electric power stored in the battery without generating electricity by the power generation motor. In HV driving, the vehicle travels using both the electric power generated by the power generation motor by the power of the engine and the electric power supplied from the battery.

[0004] For example, when the hybrid vehicle is accelerated during EV driving and the electric power required by the drive motor exceeds the maximum discharge amount of the battery, the engine is started and the vehicle switches to HV driving.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when starting the engine, a predetermined amount of electric power is required in the power generation motor. Therefore, when the engine is started when the electric power required for the drive motor exceeds the maximum discharge amount of the battery, as a result of supplying electric power to the power generation motor, the electric power supplied to the drive motor may be limited. This may cause a shock.

[0007] An object of the present invention is to avoid a shock during acceleration.

Means for Solving the Problems

[0008] To achieve the above object, a control device for an electric vehicle according to the present invention includes an engine, a battery that stores electric power obtained by converting the power of the engine, and a drive motor that supplies a driving force for driving wheels using the electric power of the battery. A control device for an electric vehicle, comprising: a start control unit that starts the engine when the drive required power based on the drive required torque exceeds a threshold value; and a threshold value setting unit that lowers the threshold value when the rotational speed of the engine is decreasing during non-operation of the engine and the amount of decrease in the rotational speed is a predetermined value or more.

[0009] In this way, by lowering the threshold value for starting the engine when the amount of decrease in the rotational speed of the engine is a predetermined value or more, the timing of starting the engine can be advanced. As a result, since the supply of electric power to the drive motor is not restricted, a shock during acceleration can be avoided.

[0010] Further, the amount of decrease in the threshold value corresponds to the output of the engine when the amount of decrease in the rotational speed of the engine is a predetermined value or more. Further, the output of the engine is calculated based on the rotational speed of the engine and the inherent inertia torque of the engine when the amount of decrease in the rotational speed of the engine is a predetermined value or more.

[0011] In this way, by determining the amount of decrease in the threshold value according to the output based on the rotational speed of the engine, the timing of starting the engine can be adjusted more precisely.

Advantages of the Invention

[0012] According to the present invention, shock during acceleration can be avoided.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0014] Hereinafter, a control device for an electric vehicle according to an embodiment will be described with reference to FIGS. 1 to 4.

[0015] (Embodiment) FIG. 1 is a block diagram showing an example of the schematic configuration of a hybrid vehicle 1 according to an embodiment. The hybrid vehicle 1 is an example of an electric vehicle.

[0016] The hybrid vehicle 1 is equipped with a series hybrid system 2. The hybrid system 2 includes an engine 11, a power generation motor 12 (MG1: motor for power generation), a drive motor 13 (MG2: motor for driving), a battery 14, and a PCU (Power Control Unit) 15.

[0017] The engine 11 is a power source of the hybrid vehicle 1. The engine 11 is, for example, a gasoline engine or a diesel engine.

[0018] The power generation motor 12 is, for example, a permanent magnet synchronous motor. The rotating shaft of the power generation motor 12 is mechanically connected to the crankshaft of the engine 11 via a gear (not shown). For example, an engine output gear is supported on the crankshaft of the engine 11 so as not to rotate relative to each other, and a motor gear is supported on the rotating shaft of the power generation motor 12 so as not to rotate relative to each other, and the engine output gear and the motor gear are meshed with each other.

[0019] The drive motor 13 is, for example, a permanent magnet synchronous motor larger than the power generation motor 12. The rotating shaft of the drive motor 13 is connected to a drive system 16 for rotationally driving the drive wheels 17. The drive system 16 includes a differential gear, and the power of the drive motor 13 is transmitted to the differential gear and distributed from the differential gear to the drive wheels 17 composed of the left and right front wheels or rear wheels and transmitted. As a result, the left and right drive wheels 17 rotate, and the hybrid vehicle 1 moves forward or backward.

[0020] The battery 14 is, for example, a battery pack combining a plurality of secondary batteries (for example, lithium ion batteries). The battery 14 outputs DC power of, for example, about 200 to 350 [V].

[0021] The PCU 15 is a unit for controlling the driving of the power generation motor 12 and the drive motor 13, and includes a first inverter 21, a second inverter 22, and a converter 23. Further, the PCU 15 manages data such as the current, voltage, temperature, battery remaining amount, and maximum battery discharge amount of the battery 14.

[0022] When the engine 11 is started, the DC power output from the battery 14 is boosted by the converter 23, and the boosted DC power is converted into AC power by the first inverter 21, and the AC power is supplied to the power generation motor 12. As a result, the power generation motor 12 is operated in power running, and the engine 11 is motored (cranked) by the power generation motor 12 (motoring operation). When the rotational speed of the crankshaft of the engine 11 has increased to the rotational speed required for starting by motoring and the spark plug of the engine 11 is sparked, the engine 11 starts.

[0023] When the hybrid vehicle 1 is running, the drive motor 13 is operated in power running, and the drive motor 13 generates power.

[0024] When the power required by the drive motor 13 is less than the threshold value for starting the engine 11, the hybrid vehicle 1 runs in EV mode. That is, the engine 11 is stopped, power generation by the power generation motor 12 is not performed, power is supplied from the battery 14 to the drive motor 13, and the drive motor 13 is driven by that power.

[0025] On the other hand, when the power required by the drive motor 13 exceeds the threshold value for starting the engine 11, the hybrid vehicle 1 runs in HV mode. That is, the engine 11 starts, and the power generation motor 12 is operated in power generation operation (regenerative operation), so that the power of the engine 11 is converted into AC power by the power generation motor 12. Then, the AC power from the power generation motor 12 is converted into DC power by the first inverter 21, and the DC power output from the first inverter 21 is converted into AC power by the second inverter 22, and the drive motor 13 is driven by supplying the AC power to the drive motor 13. Details of the threshold value will be described later.

[0026] The ECU device 31 is a control device that controls the hybrid system 2. For example, the ECU device 31 performs the above-described threshold setting operation and executes control to start the engine 11 when the power required by the drive motor 13 exceeds the threshold value. The ECU device 31 is an example of a control device.

[0027] An accelerator sensor 32 is connected to the ECU device 31. The accelerator sensor 32 outputs a detection signal corresponding to the operation amount (accelerator opening) of the accelerator pedal operated by the driver.

[0028] The ECU device 31 includes a microcomputer (microcontroller unit) not shown. The microcomputer includes, for example, an arithmetic device such as a CPU (Central Processing Unit) and a storage unit such as a ROM (Read Only Memory) not shown. The ECU device 31 communicates with other devices such as the accelerator sensor 32 according to a communication protocol such as CAN (Controller Area Network).

[0029] FIG. 2 is a block diagram showing an example of the functional configuration of the ECU device 31 according to the embodiment. Each function described with reference to FIG. 2 is realized by the CPU of the ECU device 31 reading and executing a program stored in a ROM or the like.

[0030] As shown in FIG. 2, the ECU device 31 includes an operation determination unit 311, an acquisition unit 312, a threshold setting unit 313, and a start control unit 314.

[0031] The operation determination unit 311 determines whether or not the engine 11 is in a non-operating state.

[0032] The acquisition unit 312 acquires the rotational speed of the engine 11 (hereinafter, may be referred to as the engine rotational speed) every time. The acquisition unit 312 also acquires the power required for the drive motor 13. Specifically, the acquisition unit 312 acquires a detection signal corresponding to the accelerator opening from the accelerator sensor 32 every time, and calculates a drive required torque based on the detection signal. The acquisition unit 312 also acquires the rotational speed of the drive motor 13. The acquisition unit 312 calculates the power required for the drive motor 13 (hereinafter, may be referred to as the drive required power) based on the drive required torque and the rotational speed of the drive motor 13.

[0033] The threshold setting unit 313 performs the setting operation of the threshold of the drive required power. In the setting operation of the threshold of the drive required power, the threshold setting unit 313 determines whether or not the engine speed is decreasing based on the engine speed acquired every time. When the threshold setting unit 313 determines that the engine speed is decreasing, it further determines whether or not the amount of decrease is equal to or more than a predetermined value. When the amount of decrease in the engine speed is equal to or more than a predetermined value, the threshold setting unit 313 executes the process of lowering the threshold.

[0034] At this time, the amount of decrease in the threshold corresponds to the output of the engine 11 when it is determined that the amount of decrease in the engine speed is equal to or more than a predetermined value. Specifically, the threshold setting unit 313 calculates the amount of decrease corresponding to the output of the engine 11 based on the engine speed of the engine 11 and the inherent inertia torque of the engine 11 when it is determined that the amount of decrease in the engine speed is equal to or more than a predetermined value.

[0035] The start control unit 314 executes the control to start the engine 11 when the drive required power exceeds the threshold.

[0036] Next, with reference to FIG. 3, the threshold setting operation in the ECU device 31 and the start control of the engine 11 will be described in more detail while comparing with the prior art. FIG. 3 is a graph showing the time transition of each parameter before and after starting the engine in the prior art and the embodiment.

[0037] FIG. 3(a) is a graph for explaining the prior art. In FIG. 3(a), graphs G1 to G4 are illustrated. On the other hand, FIG. 3(b) is a graph for explaining the embodiment. In FIG. 3(b), graphs G5 to G8 are illustrated. Graphs G1 and G5 show the time transition of the drive required power, graphs G2 and G6 show the time transition of the engine speed, graphs G3 and G7 show the time transition of the power supplied to the drive motor (MG2 power), and graphs G4 and G8 show the time transition of the power supplied to the power generation motor (MG1 power).

[0038] First, the engine start control in the prior art will be described. Graph G1 shows a state where the drive required power based on the drive required torque increases with the passage of time, that is, a state where the hybrid vehicle is accelerating. In the prior art hybrid vehicle, the maximum battery discharge amount Wout of the battery is set as the threshold value of the drive required power. That is, when the drive required power is equal to or less than the maximum battery discharge amount Wout (left side of the broken line in Graph G1), the hybrid vehicle 1 runs in EV mode and power generation by the power generation motor is not performed (see Graph G4). At this time, since no power is supplied from the power generation motor, the engine speed is decreasing (see Graph G2). Also, the drive motor performs power running only by the output from the battery (see Graph G3).

[0039] On the other hand, when the drive required power exceeds the maximum battery discharge amount Wout (right side of the broken line in Graph G1), the power generation motor starts the engine. Specifically, power for starting the engine is supplied from the battery to the power generation motor, the power generation motor performs power running (cranking), and the engine 11 starts. When the start of the engine is completed, the power generation motor starts regenerative operation (see Graph G4).

[0040] The power running of the drive motor contributes by the amount obtained by subtracting the power used for starting the engine from the output of the battery. As shown in Graph G1, when the start of the engine is started, since the drive required power exceeds the maximum battery discharge amount Wout, the power available for the drive motor is limited by the amount of power supplied to the power generation motor for starting the engine (see Graph G3). Also, since the engine speed is decreasing until immediately before the start of the engine is started (see Graph G2), the power required by the power generation motor increases as the amount of the decrease becomes steeper. Therefore, as the amount of the decrease in the engine speed becomes steeper, the power supply to the drive motor is restricted. As a result, in the prior art, there may be a case where a shock occurs such that the acceleration becomes dull at the start of the engine as the amount of the decrease in the engine speed becomes steeper.

[0041] On the other hand, when the threshold setting unit 313 of the ECU device 31 of the embodiment determines that the decrease amount of the engine speed is equal to or greater than a predetermined value, it executes a process of decreasing the threshold from the maximum battery discharge amount Wout (refer to the two-dot chain line in graph G5).

[0042] As a result of the threshold being decreased, in a state where the drive required power increases with the passage of time, the starting timing of the engine 11 is advanced compared to the prior art (refer to graph G5). That is, since the power generation motor 12 performs power running (cranking) before the drive required power exceeds the maximum battery discharge amount Wout, the peak of the power supplied to the power generation motor 12 is also advanced (refer to graph G8). When the engine 11 starts, since the drive required power does not exceed the maximum battery discharge amount Wout, it is possible to avoid the power available for the drive motor 13 from being limited (refer to graph G7). Thereby, it is possible to avoid a shock during acceleration.

[0043] Next, with reference to FIG. 4, the processing in the hybrid vehicle 1 will be described. FIG. 4 is a flowchart showing the flow of processing in the ECU device 31 of the embodiment.

[0044] The operation determination unit 311 determines whether the engine 11 is in a non-operating state (S101). If the operation determination unit 311 determines that the engine 11 is not in a non-operating state (S101: No), the process ends. If the operation determination unit 311 determines that the engine 11 is in a non-operating state (S101: Yes), the acquisition unit 312 acquires the drive required power based on the drive required torque and the rotation speed of the engine 11 (S102).

[0045] The threshold setting unit 313 determines whether the engine speed is decreasing (S103). If the threshold setting unit 313 determines that the engine speed is not decreasing (S103: No), the process ends.

[0046] On the one hand, when it is determined that the engine speed is decreasing (S103: Yes), the threshold setting unit 313 determines whether the decrease amount of the engine speed is equal to or greater than a predetermined value (S104). If the threshold setting unit 313 determines that the decrease amount of the engine speed is not equal to or greater than the predetermined value (S104: No), the process ends. On the other hand, when it is determined that the decrease amount of the engine speed is equal to or greater than the predetermined value (S104: Yes), the threshold setting unit 313 executes a process of lowering the threshold (S105).

[0047] The start control unit 314 determines whether the drive required power exceeds the threshold value (S106). If the start control unit 314 determines that the drive required power does not exceed the threshold value (S106: No), the process of this determination is repeated. When the start control unit 314 determines that the drive required power exceeds the threshold value (S106: Yes), it starts the engine 11 (S107), and the process ends.

[0048] (Summary) As described above, the ECU device 31 of the present embodiment includes a start control unit 314 that starts the engine 11 when the drive required power based on the drive required torque exceeds the threshold value, and a threshold setting unit 313 that lowers the threshold value when the engine speed of the engine 11 is decreasing during the non-operation of the engine 11 and the decrease amount of the engine speed is equal to or greater than a predetermined value.

[0049] Thereby, when the decrease amount of the engine speed of the engine 11 is equal to or greater than a predetermined value, by lowering the threshold value of the drive required power for starting the engine 11, the drive required power can be increased over time, that is, at the time of acceleration, the start of the engine 11 can be advanced. Thereby, since it is possible to prevent the power supply to the drive motor 13 from being restricted, it is possible to avoid shock.

[0050] The amount of decrease in the threshold value corresponds to the output of the engine 11 when the decrease amount of the engine speed of the engine 11 is equal to or greater than a predetermined value, and the output of the engine 11 is calculated based on the engine speed of the engine 11 when the decrease amount of the engine speed of the engine 11 is equal to or greater than a predetermined value and the inherent inertia torque of the engine 11.

[0051] As a result, the threshold value is lowered by an amount corresponding to the electric power required by the power generation motor 12 for starting the engine 11, so that the starting timing of the engine 11 is adjusted more precisely. As a result, for example, it is possible to avoid a situation in which the engine 11 is started earlier than necessary, narrowing the EV driving range (scenes where EV driving is performed).

[0052] In the above-described embodiment, the amount of decrease in the threshold value is determined based on the rotational speed of the engine 11 when it is determined that the amount of decrease in the engine rotational speed is equal to or greater than a predetermined value, but this is not the only case. The amount of decrease in the threshold value may be not only a variable value as described above but also a fixed value. Alternatively, the amount of decrease may be changed stepwise according to the change in the amount of decrease in the engine rotational speed.

[0053] The embodiments and modifications of the present invention have been described above. However, the above-described embodiments and modifications are presented as examples and are not intended to limit the scope of the present invention. This novel embodiment and modification can be implemented in various other forms. Also, various omissions, replacements, and changes can be made without departing from the gist of the invention. Further, this embodiment and modification are included in the scope and gist of the invention and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0054] 1... Hybrid vehicle, 11... Engine, 12... Power generation motor, 13... Drive motor, 14... Battery, 17... Drive wheels, 31... ECU device, 311... Operation determination unit, 312... Acquisition unit, 313... Threshold setting unit, 314... Starting control unit.

Claims

1. An engine, a battery that stores electric power obtained by converting the power of the engine, and a drive motor that supplies a driving force for driving wheels using the electric power of the battery, wherein the control device for an electric vehicle comprises: a start control unit that starts the engine when the drive required power based on the drive required torque exceeds a threshold value; a threshold value setting unit that lowers the threshold value when the amount of decrease in the rotational speed of the engine is equal to or greater than a predetermined value when the engine is not operating; The control device for an electric vehicle according to claim 1, comprising: a control device for an electric vehicle.

2. The amount by which the threshold value is lowered is: corresponding to the output of the engine when the amount of decrease in the rotational speed of the engine is equal to or greater than the predetermined value, The control device for an electric vehicle according to claim 1.

3. The output of the engine is: calculated based on the rotational speed of the engine and the inherent inertia torque of the engine when the amount of decrease in the rotational speed of the engine is equal to or greater than the predetermined value, The control device for an electric vehicle according to claim 2.

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