Control device for electric vehicle

Abstract

To provide a control device of an electric vehicle capable of suppressing a load on a battery even when uphill traveling continues for a long period of time.SOLUTION: The electric vehicle includes a generator motor (3), a drive motor (4), a battery (9) that can be charged with electric power generated by the generator motor (3) and can supply electric power to the drive motor (4), a gradient sensor (93) that acquires gradient information of a road on which the electric vehicle (1) is traveling, and a ECU10 that limits a maximum speed by limiting power of the drive motor (4) when the electric vehicle (1) is traveling on an uphill road and an angle of a gradient of the uphill road is equal to or greater than a determination value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent document 1 describes a series hybrid vehicle that includes an engine, a generator motor driven by the engine, a storage battery that is charged with the power generated by the generator motor, and a drive motor that drives the drive wheels with the power generated by the generator motor or the discharged power of the storage battery.

[0003] In a series hybrid vehicle, the power for driving the drive motor is supplied by generating electricity using a generator motor when the engine is running, and any shortfall is made up for by electricity drawn from the battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-129313 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when the vehicle is traveling uphill for a long period of time, the amount of power taken out of the battery increases, which raises concerns about a decrease in the battery's SOC (State Of Charge) and an increase in battery temperature.

[0006] If the SOC drops too low or the battery temperature exceeds a set limit, severe output restrictions may be imposed on the vehicle's drive, making it impossible to operate the vehicle as desired for an extended period of time.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device for an electric vehicle that can reduce the load on the battery even when the vehicle is traveling uphill for a long period of time. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a control device for an electric vehicle that includes a generator motor, a drive motor, and a battery that can be charged with power generated by the generator motor and that can supply power to the drive motor, and that also includes a gradient sensor that acquires gradient information of the road on which the electric vehicle is traveling, and a control unit that, when the electric vehicle is traveling on an uphill road and the gradient angle of the uphill road is equal to or greater than a judgment threshold, limits the output of the drive motor and restricts the maximum speed. [Effects of the Invention]

[0009] In this way, according to the present invention, the load on the battery can be reduced even when the vehicle is traveling uphill for a long period of time. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an electric vehicle equipped with a control device for an electric vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of changing the maximum speed limit in accordance with the gradient of the road in a control device for an electric vehicle according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the procedure of the drive output limiting process of the control device for an electric vehicle according to one embodiment of the present invention. [Figure 4] FIG. 4 is a time chart showing changes in power consumption of the battery due to the drive output limiting process of the control device for an electric vehicle according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A control device for an electric vehicle according to one embodiment of the present invention is a control device for an electric vehicle that includes a generator motor, a drive motor, and a battery that can be charged with power generated by the generator motor and that can supply power to the drive motor, and is configured to include a gradient sensor that acquires gradient information of the road on which the electric vehicle is traveling, and a control unit that, when the electric vehicle is traveling on an uphill road and the gradient angle of the uphill road is equal to or greater than a judgment threshold, limits the output of the drive motor and restricts the maximum speed.

[0012] As a result, the control device for an electric vehicle according to one embodiment of the present invention can reduce the load on the battery even when the vehicle is traveling uphill for a long period of time. [Example]

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for an electric vehicle according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0014] In FIG. 1, an electric vehicle 1 equipped with an electric vehicle control device according to one embodiment of the present invention includes an engine 2, a generator motor 3, a drive motor 4, a differential 5, drive wheels 6, a generator motor inverter 7, a drive motor inverter 8, a battery 9, and an ECU (Electronic Control Unit) 10 as a control unit.

[0015] The engine 2 is formed with a plurality of cylinders. In this embodiment, the engine 2 is configured so that each cylinder undergoes a series of four strokes, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0016] The generator motor 3 has a rotating shaft connected to the output shaft of the engine 2. As a result, the generator motor 3 generates electric power using the driving force of the engine 2. The generator motor 3 supplies the generated electric power to the drive motor 4 and the battery 9.

[0017] The drive motor 4 has a rotating shaft connected to left and right drive wheels 6 via a differential 5. As a result, the drive motor 4 functions as an electric motor that drives the drive wheels 6 using power supplied from the generator motor 3 or power supplied from a battery 9 via a drive motor inverter 8, and also functions as a generator that generates electricity using the reverse drive force input from the differential 5.

[0018] The generator motor inverter 7 converts the three-phase AC power generated by the generator motor 3 into DC power, supplies it to the drive motor 4, and charges the battery 9 under the control of the ECU 10.

[0019] Under the control of the ECU 10, the drive motor inverter 8 converts DC power supplied from the drive motor 4 or the battery 9 into three-phase AC power and supplies it to the drive motor 4. Under the control of the ECU 10, the drive motor inverter 8 converts the three-phase AC power generated by the drive motor 4 into DC power and charges the battery 9.

[0020] The battery 9 is configured by a secondary battery such as a lithium ion battery. The battery 9 is connected to the generator motor 3 and the drive motor 4, and is charged by the power generated by the generator motor 3 or the power generated by the drive motor 4 (regenerative power).

[0021] The electric vehicle 1 is equipped with an accelerator pedal 90 that is operated by the driver. The amount of depression of the accelerator pedal 90 is detected by an accelerator opening sensor 91. The accelerator opening sensor 91 is connected to the ECU 10, detects the amount of depression of the accelerator pedal 90 as an accelerator opening, and transmits a signal corresponding to the accelerator opening to the ECU 10.

[0022] The ECU 10 is composed of a computer unit having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, etc., input ports, and output ports.

[0023] The ROM of the computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the ECU 10. That is, the CPU executes the program stored in the ROM using the RAM as a work area, causing the computer unit to function as the ECU 10 in this embodiment.

[0024] To the input port of the ECU 10, various sensors including the accelerator opening sensor 91 described above, a vehicle speed sensor 92, and a gradient sensor 93 are connected.

[0025] The vehicle speed sensor 92 detects the speed of the electric vehicle 1. The gradient sensor 93 is configured with, for example, a gyroscope, an acceleration sensor, etc., and outputs sensor information (voltage signal) corresponding to the angle, which is the angle of the traveling direction of the electric vehicle 1 with respect to the horizontal plane, as the gradient.

[0026] In this embodiment, the ECU 10 limits the maximum speed of the electric vehicle 1 in accordance with the accelerator opening. For example, the ECU 10 increases the limit value of the maximum speed as the accelerator opening increases until the accelerator opening reaches a predetermined opening, and when the accelerator opening reaches or exceeds the predetermined opening, the ECU 10 limits the maximum speed to a constant speed.

[0027] When the electric vehicle 1 is traveling on an uphill road and the angle of the gradient of the uphill road is equal to or greater than a determination threshold, the ECU 10 restricts the output of the drive motor 4 and limits the maximum speed.

[0028] The ECU 10 limits the torque required by the driver and the maximum speed, for example, by limiting the drive power of the drive motor 4.

[0029] The determination threshold is the lower limit of the gradient angle of an uphill road at which there is a possibility of an extreme drop in SOC or an increase in battery temperature, and is determined and set by experiment or the like.

[0030] When the electric vehicle 1 is traveling on an uphill road and the gradient angle of the uphill road remains equal to or greater than the judgment threshold for a time threshold or longer, the ECU 10 limits the output of the drive motor 4 and restricts the maximum speed.

[0031] The time threshold is the lower limit of the continuous driving time on an uphill road with a gradient angle equal to or greater than the judgment threshold, at which there is a possibility of a significant drop in SOC or an increase in battery temperature, and is determined and set by experiment or the like.

[0032] The ECU 10 sets the maximum speed, which is limited in accordance with the output limit of the drive motor 4, in accordance with the angle of the gradient of the uphill road on which the electric vehicle 1 is traveling.

[0033] For example, as shown in FIG. 2, the ECU 10 changes the limit value of the maximum speed, which is determined according to the accelerator opening, according to the angle of the gradient of the uphill road on which the electric vehicle 1 is traveling.

[0034] In Figure 2, when traveling on a road with a gentler gradient than a flat road, the maximum speed limit is lower than when traveling on a flat road with a smaller gradient, and when traveling on a road with a steeper gradient than a gentler road, the maximum speed limit is even lower than when traveling on a gentler road.

[0035] The driving output limiting process performed by the control device for an electric vehicle according to this embodiment configured as described above will be described with reference to Fig. 3. The driving output limiting process described below starts when the EUC 10 starts to operate, and is executed at preset time intervals.

[0036] In step S1, the ECU 10 acquires gradient information of the road on which the electric vehicle 1 is traveling from the gradient sensor 93. After executing the process of step S1, the ECU 10 executes the process of step S2.

[0037] In step S2, the ECU 10 determines whether the road surface angle is equal to or greater than a determination threshold value.

[0038] If it is determined that the road surface angle is equal to or greater than the determination threshold, the ECU 10 executes the process of step S3. If it is determined that the road surface angle is not equal to or greater than the determination threshold, the ECU 10 executes the process of step S6.

[0039] In step S3, the ECU 10 increments the duration determination counter by adding 1. After executing the process of step S3, the ECU 10 executes the process of step S4.

[0040] In step S4, the ECU 10 determines whether the duration determination counter is equal to or greater than a counter threshold value. The counter threshold value is a count value at which the elapsed time counted by the duration determination counter becomes a time threshold value.

[0041] If it is determined that the duration determination counter is equal to or greater than the counter threshold value, the ECU 10 executes the process of step S5. If it is determined that the duration determination counter is not equal to or greater than the counter threshold value, the ECU 10 ends the drive output limiting process.

[0042] In step S5, the ECU 10 limits the maximum speed by limiting the output of the drive motor 4. After executing the process of step S5, the ECU 10 ends the drive output limiting process.

[0043] In step S6, the ECU 10 clears the duration determination counter to 0. After executing the process of step S6, the ECU 10 ends the drive output limiting process.

[0044] Such operation of the drive output limiting process will be described with reference to FIG. At time t1, when the gradient angle becomes equal to or greater than the judgment threshold, the duration is measured, and at time t2, the duration for which the gradient angle of the uphill road is equal to or greater than the judgment threshold continues for more than the time threshold, so the maximum speed limit judgment is turned on and the output of the drive motor 4 is limited.

[0045] At the same time t2, when the accelerator pedal 90 is depressed and the accelerator opening increases, the power generated by the generator motor 3 increases as the power to drive the drive motor 4, but since this alone is insufficient, power from the battery 9 is also consumed.

[0046] If the output of the drive motor 4 is not limited, the vehicle speed will increase, as shown by the dotted line, and the power consumption of the drive motor 4 will also increase, causing the battery 9 to consume power continuously.

[0047] In this embodiment, the output of the drive motor 4 is limited, the power consumption is limited to the extent that the power generated by the generator motor 3 is sufficient, the maximum speed is limited, and the power consumption of the battery 9 is reduced.

[0048] As described above, in this embodiment, when the electric vehicle 1 is traveling on an uphill road and the gradient angle of the uphill road is equal to or greater than the determination threshold, the ECU 10 limits the output of the drive motor 4 and restricts the maximum speed.

[0049] This limits the output of the drive motor 4 when traveling uphill where the gradient angle is equal to or greater than the judgment threshold, thereby reducing the power consumed by the drive motor 4 from the battery 9 and preventing a sudden drop in the SOC of the battery 9 or a sudden rise in battery temperature in a short period of time.

[0050] Furthermore, when the electric vehicle 1 is traveling on an uphill road and the gradient angle of the uphill road remains equal to or greater than the judgment threshold for a period of time equal to or greater than the threshold, the ECU 10 limits the output of the drive motor 4 and restricts the maximum speed.

[0051] As a result, when the vehicle is traveling continuously on an uphill road with a gradient angle equal to or greater than the judgment threshold for a time threshold or longer, there is a greater concern that the SOC of the battery 9 may drop suddenly in a short period of time or that the battery temperature may rise suddenly. Therefore, by limiting the output of the drive motor 4, the above concerns can be alleviated.

[0052] Furthermore, the ECU 10 sets the maximum speed, which is limited in accordance with the output limit of the drive motor 4, in accordance with the angle of the gradient of the uphill road on which the electric vehicle 1 is traveling.

[0053] This allows for more efficient SOC management by adjusting the maximum speed according to the angle of the gradient of the uphill road, while minimizing the impact on drivability.

[0054] It is also possible to determine whether or not to limit the output of the drive motor 4 depending on the state of the SOC of the battery 9.

[0055] Furthermore, the gradient sensor 93 may acquire gradient information of the current location of the electric vehicle 1 from map information of a navigation system, or may acquire gradient information (which may be map information) of the current location of the electric vehicle 1 from a server device outside the vehicle.

[0056] In this embodiment, an example has been described in which the ECU 10 performs various determinations and calculations based on information from various sensors. However, the present invention is not limited to this. The electric vehicle 1 may be provided with a communication unit capable of communicating with an external device such as an external server, and the external device may perform various determinations and calculations based on detection information from various sensors transmitted from the communication unit. The communication unit may receive the determination results and calculation results, and the received determination results and calculation results may be used to perform various controls.

[0057] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0058] 1 Electric vehicles 2 engines 3. Generator motor 4 Drive motor 9 Battery 10 ECU (control unit) 90 Accelerator pedal 91 Accelerator opening sensor 92 Vehicle speed sensor 93 Gradient Sensor

Claims

1. A control device for an electric vehicle including a power generation motor, a drive motor, and a battery that can be charged with electric power generated by the power generation motor and can supply electric power to the drive motor, a gradient sensor that acquires gradient information of a road on which the electric vehicle is traveling; and a control unit that, when the electric vehicle is traveling on an uphill road and the gradient angle of the uphill road is equal to or greater than a judgment threshold, limits the output of the drive motor and restricts the maximum speed.

2. 2. The control device for an electric vehicle according to claim 1, wherein the control unit limits the output of the drive motor and restricts a maximum speed when the electric vehicle is traveling on an uphill road and a state in which an angle of the gradient of the uphill road is equal to or greater than a determination threshold continues for a time threshold or longer.

3. 3. The control device for an electric vehicle according to claim 1, wherein the control unit sets the maximum speed limited by limiting the output of the drive motor in accordance with the angle of the gradient of an uphill road on which the electric vehicle is traveling.

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