Electric vehicle control device

Abstract

To provide a four-wheel-drive electric-vehicular control apparatus capable of increasing an electric bill and an EV travel range.SOLUTION: A control apparatus 10 includes a distribution ratio computation part 13 for making a distribution ratio in a coordination amount of regenerative brake force between a front motor 25 and a rear motor 28 variable, and calculating the distribution ratio on the basis of a brake request quantity of a user when an eco mode is selected by the user and a brake request is present. Therefore, it is possible to determine a distribution ratio in a coordination amount of regenerative brake force between the front motor 25 and rear motor 28 at a distribution ratio with which a maximum (an optimal) regenerative power amount can be obtained on the basis of respective generative efficiencies of the front motor 25 and rear motor 28. As a result, it is possible to increase the sum total of the regenerative power amount obtainable from the front motor 25 and rear motor 28.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a control device for a four-wheel drive electric vehicle that is capable of independently controlling a front motor and a rear motor. [Background technology]

[0002] Japanese Patent Application Publication No. 2018-011488 discloses a control device for a four-wheel drive electric vehicle that is capable of independently controlling a front motor and a rear motor.

[0003] Four-wheel drive vehicles (4WD) are generally required to have performance such as high driving stability, strong torque, etc. Therefore, when obtaining regenerative power in a four-wheel drive electric vehicle such as that disclosed in the above publication, the distribution ratio of the coordinated amount of regenerative braking force of the front motor and the rear motor is set to a predetermined distribution ratio that prioritizes drivability.

[0004] Incidentally, even in a four-wheel drive vehicle, when an eco mode (which may be an EV priority mode) that improves the EV range (the distance that an electric vehicle can travel using the power stored in the battery) is manually selected by the user (passenger), it is desirable to improve electricity consumption and the EV range in response to the user's request.

[0005] However, in conventional technology, the distribution rate of the coordinated regenerative braking force between the front motor and rear motor is a predetermined distribution rate that prioritizes drivability, and is not determined based on the efficiency of the front motor and rear motor, so there is room for improvement in terms of electricity consumption and EV range. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-011488 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a control device for a four-wheel drive electric vehicle that can improve electricity consumption and EV cruising range. [Means for solving the problem]

[0008] The present invention which achieves the above object is as follows. (1) A control device for a four-wheel drive electric vehicle capable of independently controlling at least a front motor or a rear motor, a driving mode determination unit that determines whether a normal mode or an eco mode that increases an EV driving range compared to the normal mode is selected; a brake request determination unit that determines whether or not a brake request is made by a user; a distribution ratio calculation unit that, when the eco mode is selected and there is a brake request, makes a distribution ratio of a coordinated amount of regenerative braking forces of the front motor and the rear motor variable and calculates it according to a brake request amount of a user; a regenerative control execution unit that executes regenerative control of the front motor and the rear motor in accordance with the distribution ratio calculated by the distribution ratio calculation unit; A control device for an electric vehicle having the above-mentioned. (2) The control device for an electric vehicle according to (1), wherein the distribution ratio calculation unit calculates the distribution ratio so as to obtain a maximum amount of regenerative power based on the regenerative efficiency of the front motor and the rear motor in accordance with the brake request amount. (3) The regenerative efficiency of the front motor is set to be greater than the regenerative efficiency of the rear motor, The control device for an electric vehicle according to (1) or (2), wherein the distribution ratio calculation unit is configured to increase a ratio of the front motor compared to the distribution ratio when the normal mode is selected. Effect of the Invention

[0009] According to the control device for an electric vehicle of (1) or (2) above, when the eco mode is selected by the user and there is a brake request, the distribution ratio of the coordinated amount of regenerative braking force of the front motor and the rear motor is variable and has a distribution ratio calculation unit that calculates it according to the user's brake request amount. Therefore, the distribution ratio of the coordinated amount of regenerative braking force of the front motor and the rear motor can be set to a distribution ratio that obtains the maximum (optimum) amount of regenerative power based on the regenerative efficiency of each of the front motor and the rear motor. As a result, the total amount of regenerative power obtained by the front motor and the rear motor can be increased, improving electricity consumption and EV cruising range.

[0010] According to the control device for an electric vehicle of (3) above, the regenerative efficiency of the front motor is made greater than the regenerative efficiency of the rear motor, and the distribution ratio calculation unit is configured to increase the proportion of the front motor compared to when the normal mode is selected. As a result, the amount of regenerative power obtained can be increased compared to when the distribution ratio calculation unit is configured to increase the proportion of the rear motor. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a vehicle equipped with a control device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram of a control device according to an embodiment of the present invention. [Diagram 3] 3 is a control flowchart of the control device according to the embodiment of the present invention. [Figure 4] 5 is a graph showing a distribution rate of the coordinated amount of regenerative braking force between the front motor and the rear motor in a normal mode in the control device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device 10 for a four-wheel drive electric vehicle according to an embodiment of the present invention will now be described with reference to the drawings.

[0013] [Vehicle equipped with the control device] Fig. 1 shows an example of a vehicle 20 equipped with a control device 10 according to an embodiment of the present invention. Note that Fig. 1 shows a case where the vehicle 20 equipped with the control device 10 is an EV (Electric Vehicle), but the vehicle 20 may be a PHV (Plug-in Hybrid Vehicle), a HV (Hybrid Vehicle), or a FCV (Fuel Cell Vehicle) as long as it has a front motor 25 and a rear motor 28, which will be described later.

[0014] 1, vehicle 20 is a four-wheel drive electric vehicle and includes a battery 21, a converter 22, a front inverter 23, a front motor 25 housed in a front transaxle 24, a rear inverter 26, and a rear motor 28 housed in a rear transaxle 27. Vehicle 20 also includes front wheels 29, rear wheels 30, a brake sensor 31, and an eco mode switch 32.

[0015] The battery 21 is a secondary battery such as a lithium ion battery, a nickel metal hydride battery, etc. The battery 21 can be charged by power supplied from outside the vehicle 20 or by power generated by the front motor 25 and the rear motor 28.

[0016] The converter 22 boosts the DC power supplied from the battery 21 and supplies the boosted DC power to the front inverter 23 and the rear inverter 26. The converter 22 also reduces the DC power supplied from the front inverter 23 and the rear inverter 26 and supplies the reduced DC power to the battery 21.

[0017] The front inverter 23 converts the DC power supplied from the battery 21 and boosted by the converter 22 into three-phase AC power, and supplies the converted AC power to the front motor 25. The front inverter 23 also converts the AC power supplied from the front motor 25 into DC power, and supplies the converted DC power to the converter 22.

[0018] The rear inverter 26 converts the DC power supplied from the battery 21 and boosted by the converter 22 into three-phase AC power, and supplies the converted AC power to the rear motor 28. The rear inverter 26 also converts the AC power supplied from the rear motor 28 into DC power, and supplies the converted DC power to the converter 22.

[0019] The front motor 25 is configured by a three-phase synchronous motor. The front motor 25 is electrically connected to the front inverter 23. The front motor 25 is driven by the front inverter 23 and transmits power to front wheels (drive wheels) 29 of the vehicle. When a user (passenger) releases the accelerator operation or depresses a brake pedal (not shown), the front motor 25 is driven by the rotational force of the front wheels 29 to generate power. The regenerative power generated by the front motor 25 can be charged to the battery 21 via the front inverter 23 and the converter 22.

[0020] The rear motor 28 is configured by a three-phase synchronous motor. The rear motor 28 is electrically connected to the rear inverter 26. The rear motor 28 is driven by the rear inverter 26 and transmits power to rear wheels (drive wheels) 30 of the vehicle. When the user releases the accelerator operation or depresses a brake pedal (not shown), the rear motor 28 is driven by the rotational force of the rear wheels 30 to generate power. The regenerative power generated by the rear motor 28 can be charged into the battery 21 via the rear inverter 26 and the converter 22.

[0021] The front motor 25 and the rear motor 28 have different motor efficiency characteristics. Specifically, the front motor 25 has a higher efficiency (less motor loss) characteristic than the rear motor 28. Therefore, the regenerative efficiency (amount of regenerative power obtained) of the front motor 25 is greater than the regenerative efficiency (amount of regenerative power obtained) of the rear motor 28.

[0022] The brake sensor 31 detects the amount of depression of a brake pedal (not shown) by a user. A signal (information) from the brake sensor 31 is input to the control device 10.

[0023] The eco mode switch (which may be an EV priority mode switch) 32 is a switch that, when manually turned on by the user, sets the eco mode (a mode that prioritizes and increases the EV cruising distance) to on, and when manually turned off by the user, turns off the eco mode and sets to a normal mode (a mode that prioritizes drivability) that is not the eco mode. An on / off signal (information) of the eco mode switch 32 is input to the control device 10.

[0024] In a four-wheel drive vehicle as shown in FIG. 1, performance such as high driving stability and strong torque is required. Therefore, when obtaining regenerative power in a normal mode in which the eco mode is not selected, as shown in FIG. 4, the distribution ratio (hereinafter, simply referred to as the distribution ratio) in the cooperative amount of the regenerative braking force of the front motor 25 and the rear motor 28 is set to a predetermined (constant) distribution ratio (for example, front motor:rear motor=7:3) that prioritizes drivability. However, even in a four-wheel drive vehicle, when the eco mode is manually selected by the user, it is desirable to improve the electricity consumption and EV cruising distance according to the user's request. Therefore, in the embodiment of the present invention, the control device 10 is configured as follows.

[0025] [Control device] As shown in FIG. 2, the control device 10 includes a driving mode determination unit 11, a brake request determination unit 12, a distribution rate calculation unit 13, and a regenerative control execution unit .

[0026] The driving mode determination unit 11 determines whether the normal mode or the eco mode has been selected by the user based on information from the eco mode switch 32. Specifically, the driving mode determination unit 11 determines that the eco mode is selected when the eco mode switch 32 is turned on, and determines that the normal mode is selected rather than the eco mode when the eco mode switch 32 is not turned on (when the eco mode switch 32 is turned off).

[0027] The brake request determination unit 12 determines whether or not there is a brake request from the user based on information from the brake sensor 31. Note that the brake request determination unit 12 determines whether or not there is a brake request based on a signal from the brake sensor 31 that detects the amount of depression of a brake pedal (not shown), and therefore determines that there is no brake request during deceleration when the brake pedal is not depressed, such as when the user releases the accelerator operation.

[0028] When the eco mode is selected and there is a user's brake request, the distribution ratio calculation unit 13 varies the distribution ratio between the front motor 25 and the rear motor 28. Then, the amount of brake request is calculated, and the distribution ratio between the front motor 25 and the rear motor 28 is calculated according to the amount of brake request. The distribution ratio calculation unit 13 calculates the distribution ratio so that the maximum amount of regenerative power is obtained (so that the total motor loss is minimized) based on the regenerative efficiency of the front motor 25 and the rear motor 28 according to the amount of brake request. Since the regenerative efficiency of the front motor 25 is greater than that of the rear motor 28 as described above, the distribution ratio calculation unit 13 increases the ratio of the front motor 25 to, for example, 8:2, 9:1, or 10:0 compared to a predetermined distribution ratio (7:3) when the normal mode is selected.

[0029] The distribution ratio calculation unit 13 calculates the distribution ratio using a map (not shown) (distribution ratio map that minimizes the total loss) that is created in advance and stored in the control device 10. This map is created from motor loss maps created for the front motor 25 and the rear motor 28, and is created by calculating the distribution ratio so that the total motor loss of the front motor 25 and the rear motor 28 is minimized for any desired amount of coordination of regenerative braking forces of the front motor 25 and the rear motor 28 required.

[0030] The regenerative control execution unit 14 controls the front inverter 23 and the rear inverter 26 in accordance with the distribution ratio calculated by the distribution ratio calculation unit 13 to execute regenerative control of the front motor 25 and the rear motor 28 .

[0031] 3 is a flowchart showing a control routine of the control device 10. This control routine is executed at predetermined time intervals. First, in step S1, the driving mode determination unit 11 determines whether or not the eco mode has been manually selected by the user. If it is determined in step S1 that the eco mode has not been selected, the process proceeds to step S5, where the distribution ratio between the front motor 25 and the rear motor 28 remains at a predetermined distribution ratio that prioritizes drivability, and the process proceeds to the end step. On the other hand, if it is determined in step S1 that the eco mode has been selected, the process proceeds to step S2.

[0032] In step S2, the brake request determination unit 12 determines whether or not there is a brake request from the user. If it is determined in step S2 that there is no brake request, the process proceeds to step S5, where the distribution ratio between the front motor 25 and the rear motor 28 remains at a predetermined distribution ratio that prioritizes drivability, and the process proceeds to the end step. On the other hand, if it is determined in step S2 that there is a brake request, the process proceeds to step S3.

[0033] In step S3, the distribution ratio calculation unit 13 varies the distribution ratio between the front motor 25 and the rear motor 28. Then, the brake request amount by the user is calculated, and the distribution ratio of the coordinated amount of regenerative braking force of the front motor 25 and the rear motor 28 is calculated according to the brake request amount. Next, the process proceeds to step S4, where the front inverter 23 and the rear inverter 26 are controlled according to the calculated distribution ratio to execute regenerative control of the front motor 25 and the rear motor 28. Then, the process proceeds to the end step.

[0034] Next, the operation and effects of the embodiment of the present invention will be described. (A) When the eco mode is selected by the user and there is a braking request, the distribution ratio of the coordinated amount of regenerative braking force of the front motor 25 and the rear motor 28 is variable and is calculated according to the user's braking request amount, and a distribution ratio calculation unit 13 is provided. Therefore, the distribution ratio of the coordinated amount of regenerative braking force of the front motor 25 and the rear motor 28 can be set to a distribution ratio that obtains the maximum (optimum) amount of regenerative power based on the regenerative efficiency of each of the front motor 25 and the rear motor 28. As a result, the total amount of regenerative power obtained by the front motor 25 and the rear motor 28 can be increased, improving electricity consumption and EV cruising range.

[0035] (B) The regenerative efficiency of the front motor 25 is greater than that of the rear motor 28, and the distribution ratio calculation unit 13 is configured to increase the proportion of the front motor 25 compared to when the normal mode is selected. As a result, the amount of regenerative power obtained can be increased compared to when the distribution ratio calculation unit 13 is configured to increase the proportion of the rear motor 28.

[0036] (C) The brake request determination unit 12 determines whether or not there is a brake request based on a signal from the brake sensor 31 that detects the amount of depression of the brake pedal, and determines that there is no brake request during deceleration when the brake pedal is not depressed, such as when the user releases the accelerator. Therefore, it is possible to efficiently increase the amount of regenerative power specifically during deceleration when the brake pedal is depressed (during deceleration when the amount of regenerative power is relatively large), and to prioritize drivability of the four-wheel drive vehicle during deceleration when the brake pedal is not depressed (during deceleration when the amount of regenerative power is relatively small). [Explanation of symbols]

[0037] 10 Control device 11. Driving mode determination unit 12 Brake request determination unit 13 Distribution ratio calculation section 14 Regenerative control execution unit 20 Vehicles 21 Battery 22 Converter 23 Front inverter 26 Rear inverter 25 Front motor 28 Rear motor 31 Brake sensor 32 Eco mode switch

Claims

1. A control device for a four-wheel drive electric vehicle capable of independently controlling at least a front motor or a rear motor, a driving mode determination unit that determines whether a normal mode or an eco mode that increases an EV driving range compared to the normal mode is selected; a brake request determination unit that determines whether or not a brake request is made by a user; a distribution ratio calculation unit that, when the eco mode is selected and there is a brake request, makes a distribution ratio of a coordinated amount of regenerative braking forces of the front motor and the rear motor variable and calculates it according to a brake request amount of a user; a regenerative control execution unit that executes regenerative control of the front motor and the rear motor in accordance with the distribution ratio calculated by the distribution ratio calculation unit; having The distribution ratio calculation unit calculates the distribution ratio using a distribution ratio map created by calculating a distribution ratio from motor loss maps created for the front motor and the rear motor so that the sum of the motor losses of the front motor and the rear motor is minimized for any required coordinated amount of regenerative braking force of the front motor and the rear motor.

2. The control device for an electric vehicle according to claim 1 , wherein the distribution ratio calculation unit calculates the distribution ratio so as to obtain a maximum amount of regenerative power based on regenerative efficiencies of the front motor and the rear motor in accordance with the required braking amount.

3. The regenerative efficiency of the front motor is set to be greater than the regenerative efficiency of the rear motor, 3. The control device for an electric vehicle according to claim 1, wherein the distribution ratio calculation unit is configured to increase a ratio of the front motor compared to the distribution ratio when the normal mode is selected.

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