Electric vehicle control device

Abstract

To control a SOC of each battery to an appropriate value in a vehicle of which front wheels and rear wheels are independently driven by a motor.SOLUTION: A control device of an electric vehicle comprises a front wheel drive device for driving front wheels and a rear wheel drive device for driving rear wheels, and independently drives the front wheels and the rear wheels by a motor. The device comprises a SOC control part which controls a SOC of a battery for the front wheels and a SOC of a battery for the rear wheels. The SOC control part sets a target SOC of the battery for the rear wheels to be larger than a target SOC of the battery for the front wheels if it is determined that a travel route of the electric vehicle up to a destination has a lot of slopes on a road surface.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Patent Document 1 discloses that a front-wheel drive unit for driving the front wheels and a rear-wheel drive unit for driving the rear wheels each include a motor, a battery, and a fuel cell, and the required drive torque is distributed to the front and rear wheels at an arbitrary distribution ratio. In the configuration described in Patent Document 1, when the required drive power is less than a predetermined value, it is determined that charging the battery is possible, and the battery is charged using surplus power from the fuel cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-333707 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an electric vehicle in which the front and rear wheels are driven independently by motors, the power consumption differs between the front wheel battery and the rear wheel battery depending on the driving state. This results in a difference in the amount of charge required for each battery. However, the configuration described in Patent Document 1 only charges the battery so that the SOC (State of Charge) falls within a predetermined range when the SOC of the battery is below a predetermined value, and does not consider setting the SOC of each battery to an appropriate value. Therefore, it is desirable to control the SOC of each battery to an appropriate value, taking into account the difference in the amount of charge required for each battery.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a control device for an electric vehicle that can control the SOC of each battery to an appropriate value in a vehicle in which the front wheels and rear wheels are driven independently by a motor. [Means for solving the problem]

[0006] The present invention is a control device for an electric vehicle comprising a front-wheel drive unit for driving the front wheels and a rear-wheel drive unit for driving the rear wheels, and in which the front wheels and the rear wheels are driven independently by motors, wherein the front-wheel drive unit has a front-wheel motor for driving the front wheels and a front-wheel battery for supplying power to the front-wheel motor, and the rear-wheel drive unit has a rear-wheel motor for driving the rear wheels and a rear-wheel battery for supplying power to the rear-wheel motor, and is provided with a SOC control unit for controlling the SOC of the front-wheel battery and the SOC of the rear-wheel battery, and when the SOC control unit determines that the driving route to a destination in the electric vehicle has a road surface with a steep gradient, it sets a target SOC for the rear-wheel battery higher than the target SOC for the front-wheel battery. Effect of the Invention

[0007] In this invention, based on the fact that a greater load is placed on the rear wheels than on the front wheels on a sloped road surface, regardless of whether it is uphill or downhill, the target SOC of the rear wheel battery is set to be higher than the target SOC of the front wheel battery when the driving route is a route with a steep slope. This makes it possible to efficiently charge and discharge each battery according to the slope of the road surface, enabling efficient driving and controlling the SOC of each battery to an appropriate value. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a skeleton diagram that illustrates an electric vehicle according to an embodiment. [Diagram 2] FIG. 2 is a diagram for explaining a case where an electric vehicle travels on an uphill road. [Diagram 3] FIG. 3 is a diagram for explaining a case where an electric vehicle runs on a flat road. [Figure 4] FIG. 4 is a diagram for explaining a case where an electric vehicle travels on a downhill road. [Diagram 5] FIG. 5 is a graph showing the relationship between the target SOC of each battery and the gradient of the road surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for an electric vehicle according to an embodiment of the present invention will be specifically described below with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

[0010] Fig. 1 is a skeleton diagram showing a schematic diagram of an electric vehicle according to an embodiment. The electric vehicle 1 is a vehicle capable of independently driving front wheels 2 and rear wheels 3 by a motor. The electric vehicle 1 is equipped with a motor for driving each of the front, rear, left and right wheels. The electric vehicle 1 is equipped with a front-wheel drive unit 10 that drives the front wheels 2, a rear-wheel drive unit 20 that drives the rear wheels 3, and a control device 30 that controls the front-wheel drive unit 10 and the rear-wheel drive unit 20.

[0011] The front-wheel drive device 10 uses a motor to independently drive a left front wheel 2A and a right front wheel 2B. The front-wheel drive device 10 includes a front-wheel battery 11, a power controller (hereinafter referred to as PCU) 12, a front-wheel motor (MG) 13, and a transaxle (T / A) 14.

[0012] The front wheel battery 11 is a battery that supplies power to the front wheel motor 13. The front wheel battery 11 is composed of a secondary battery such as a lithium ion battery. Of the multiple batteries (on-board batteries) mounted on the electric vehicle 1, the front wheel battery 11 is the first battery.

[0013] The PCU 12 is a power conversion device that converts the power of the front wheel battery 11 and supplies it to the front wheel motor 13 to drive the front wheel motor 13. The PCU 12 includes a DCDC converter 15 and an inverter 16. The inverter 16 includes a left front wheel inverter 16A and a right front wheel inverter 16B. The left front wheel inverter 16A is electrically connected to the front wheel battery 11 via the DCDC converter 15. The right front wheel inverter 16B is electrically connected to the front wheel battery 11 via the DCDC converter 15. Furthermore, the left front wheel inverter 16A and the right front wheel inverter 16B are electrically connected.

[0014] The front wheel motor 13 is a power source of the electric vehicle 1 and drives the front wheels 2. Power output from the front wheel motor 13 is transmitted to the front wheels 2 via a transaxle 14. The transaxle 14 is a power transmission mechanism that connects the front wheel motor 13 and the front wheels 2 so that power can be transmitted. The front wheel motor 13 is electrically connected to the front wheel battery 11 via the PCU 12.

[0015] The front wheel motor 13 includes a left front wheel motor 13A that drives the left front wheel 2A, and a right front wheel motor 13B that drives the right front wheel 2B. The left front wheel motor 13A is connected to the left front wheel 2A via a left front wheel transaxle 14A so as to be capable of transmitting power, and is electrically connected to the front wheel battery 11 via a left front wheel inverter 16A. The right front wheel motor 13B is connected to the right front wheel 2B via a right front wheel transaxle 14B so as to be capable of transmitting power, and is electrically connected to the front wheel battery 11 via a right front wheel inverter 16B.

[0016] The rear wheel drive device 20 uses a motor to independently drive a left rear wheel 3A and a right rear wheel 3B. The rear wheel drive device 20 includes a rear wheel battery 21, a PCU 22, a rear wheel motor (MG) 23, and a transaxle (T / A) 24.

[0017] The rear wheel battery 21 is a battery that supplies power to the rear wheel motor 23. The rear wheel battery 21 is configured by a secondary battery such as a lithium ion battery. Of the multiple batteries (on-board batteries) mounted on the electric vehicle 1, the rear wheel battery 21 is the second battery.

[0018] The PCU 22 is a power conversion device that converts the power of the rear wheel battery 21 and supplies it to the rear wheel motor 23 to drive the rear wheel motor 23. The PCU 22 includes a DCDC converter 25 and an inverter 26. The inverter 26 includes a left rear wheel inverter 26A and a right rear wheel inverter 26B. The left rear wheel inverter 26A is electrically connected to the rear wheel battery 21 via the DCDC converter 25. The right rear wheel inverter 26B is electrically connected to the rear wheel battery 21 via the DCDC converter 25. Furthermore, the left rear wheel inverter 26A and the right rear wheel inverter 26B are electrically connected.

[0019] The rear wheel motor 23 is a power source for the electric vehicle 1 and drives the rear wheels 3. Power output from the rear wheel motor 23 is transmitted to the rear wheels 3 via a transaxle 24. The transaxle 24 is a power transmission mechanism that connects the rear wheel motor 23 and the rear wheels 3 so that power can be transmitted. The rear wheel motor 23 is electrically connected to the rear wheel battery 21 via the PCU 22.

[0020] The rear wheel motor 23 includes a left rear wheel motor 23A that drives the left rear wheel 3A, and a right rear wheel motor 23B that drives the right rear wheel 3B. The left rear wheel motor 23A is connected to the left rear wheel 3A via a left rear wheel transaxle 24A so as to be capable of transmitting power, and is electrically connected to the rear wheel battery 21 via a left rear wheel inverter 26A. The right rear wheel motor 23B is connected to the right rear wheel 3B via a right rear wheel transaxle 24B so as to be capable of transmitting power, and is electrically connected to the rear wheel battery 21 via a right rear wheel inverter 26B.

[0021] Furthermore, the electric vehicle 1 is capable of charging the on-board battery with power supplied from an external power source, and is also capable of charging the on-board battery with power generated by the solar panel 51. The electric vehicle 1 is equipped with a charging device 40, a solar charging device 50, and a relay device 60.

[0022] Charging device 40 is a device that charges an on-board battery with power supplied from an external power source. Charging device 40 includes a charging port 41 to which a charging plug of an external charger is connected, and a relay 42. Charging port 41 includes a positive terminal and a negative terminal, and is electrically connected to relay device 60 via relay 42. Relay 42 is provided between charging port 41 and relay device 60, and selectively cuts off the electrical connection between charging port 41 and relay device 60.

[0023] For example, when a charging plug is connected to charging port 41 to charge the on-board battery with power supplied from an external power source (during external charging), relay 42 is closed to electrically connect charging port 41 and relay device 60. On the other hand, when external charging is not being performed, relay 42 is opened to cut off electrical connection between charging port 41 and relay device 60. The opening and closing of relay 42 is controlled by control device 30. Control device 30 controls charging device 40.

[0024] The solar charging device 50 includes a solar panel 51 and a switch (SW) 52. The solar panel 51 is a solar cell module that generates power when exposed to sunlight. For example, the solar panel 51 is installed on the roof of the electric vehicle 1. The power generated by the solar panel 51 can be charged into an on-board battery. The switch 52 is provided between the solar panel 51 and the relay device 60, and selectively cuts off the electrical connection between the solar panel 51 and the relay device 60.

[0025] For example, when the power generated by the solar panel 51 is charged to the vehicle battery (solar charging), the switch 52 is closed to electrically connect the solar panel 51 and the relay device 60. In this case, the power generated by the solar panel 51 is output to the relay device 60 via the switch 52. On the other hand, when solar charging is not being performed, the switch 52 is opened to cut off electrical continuity between the solar panel 51 and the relay device 60. The opening and closing of the switch 52 is controlled by the control device 30. The control device 30 controls the solar charging device 50.

[0026] The relay device 60 switches an internal relay so as to charge any one of the multiple vehicle batteries when performing external charging or solar charging. The relay device 60 includes a first relay 61, a second relay 62, and a third relay 63.

[0027] The first relay 61 is a relay for connecting so that electricity can flow when charging the front wheel battery 11 during external charging or solar charging. When the rear wheel battery 21 is to be charged, the first relay 61 opens to cut off the current path to the front wheel battery 11.

[0028] The second relay 62 is a relay for connecting so that electricity can flow when charging the rear wheel battery 21 during external charging or solar charging. When the front wheel battery 11 is to be charged, the second relay 62 opens to cut off the current path to the rear wheel battery 21.

[0029] The third relay 63 is a relay for connecting so as to be conductive when charging the third battery 80 to drive electronic devices 70 such as an air conditioner during external charging or solar charging. When the front wheel battery 11 or rear wheel battery 21 is to be charged, the third relay 63 opens to cut off the conductive path to the third battery 80.

[0030] The third battery 80 is electrically connected to the electronic device 70 without going through the relay device 60. Therefore, the third battery 80 can be used to drive the electronic device 70 regardless of whether the relay device 60 is open or closed.

[0031] It is also possible to use the front wheel battery 11 and the rear wheel battery 21 to drive the electronic device 70. The electronic device 70 can be electrically connected to the front wheel battery 11, and can also be electrically connected to the rear wheel battery 21. The front wheel battery 11 and the rear wheel battery 21 are electrically connected to the electronic device 70 without going through the relay device 60.

[0032] Furthermore, the electric vehicle 1 includes a fourth battery 90 as an on-board battery. The fourth battery 90 supplies power to the other three batteries. The front wheel battery 11, the rear wheel battery 21, and the third battery 80 can each be electrically connected to the fourth battery 90.

[0033] The control device 30 is an electronic control device that controls the electric vehicle 1. This electronic control device includes a microcontroller equipped with a CPU, RAM, ROM, and an input / output interface. The control device 30 performs signal processing according to a program pre-stored in the ROM. Signals from various sensors mounted on the electric vehicle 1 are input to the control device 30.

[0034] For example, signals from an accelerator opening sensor that detects the accelerator opening, which is the amount of accelerator pedal operation, a signal from a vehicle speed sensor that detects the vehicle speed, a signal from a current sensor that detects the current of the front wheel battery 11, a signal from a voltage sensor that detects the voltage of the front wheel battery 11, a signal from a current sensor that detects the current of the rear wheel battery 21, and a signal from a voltage sensor that detects the voltage of the rear wheel battery 21 are input to the control device 30. The control device 30 then executes various types of control based on the signals input from the various sensors.

[0035] Specifically, the control device 30 calculates the SOC of the front wheel battery 11 based on signals input from the current sensor and voltage sensor of the front wheel battery 11. The control device 30 sets a target SOC for the front wheel battery 11. Then, the control device 30 controls the SOC of the front wheel battery 11 so that the current SOC becomes the target SOC. Similarly, the control device 30 calculates the SOC of the rear wheel battery 21 based on signals input from the current sensor and voltage sensor of the rear wheel battery 21. The control device 30 sets a target SOC for the rear wheel battery 21. Then, the control device 30 controls the SOC of the rear wheel battery 21 so that the current SOC becomes the target SOC. In this way, the control device 30 is provided with an SOC control unit that controls the SOC of the front wheel battery 11 and the SOC of the rear wheel battery 21.

[0036] The control device 30 also acquires information about the travel route of the electric vehicle 1 from the navigation device. The navigation device sets a travel route to the destination based on the current position of the electric vehicle 1 and information about the destination set by an operation by a passenger of the electric vehicle 1. In other words, the navigation device has future route information for the electric vehicle 1 as information about the travel route to the destination. The navigation device outputs information about the travel route of the electric vehicle 1 to the destination to the control device 30.

[0037] The control device 30 also executes driving force control to control the driving force of the electric vehicle 1. In the driving force control, the control device 30 calculates the required driving force based on the accelerator opening and the vehicle speed. Furthermore, the control device 30 controls the distribution of driving force between the front wheels 2 and the rear wheels 3, thereby making it possible to arbitrarily control the driving force realized by the motors for the required driving force at the front and rear wheels. In other words, the control device 30 controls the distribution of the driving force between the front wheels 2 and the rear wheels 3 for the required driving force, thereby controlling the driving forces of the front and rear wheels to an arbitrary distribution ratio to realize the required driving force.

[0038] At this time, the driving force distribution ratio is determined according to the gradient (flatness) of the road surface on which the electric vehicle 1 runs. That is, the driving force distribution ratio that optimizes the energy efficiency of the electric vehicle 1 differs according to the gradient of the road surface, as shown in Figures 2 to 4. Specifically, the optimal value of the driving force distribution ratio differs depending on the front / rear load ratio of the electric vehicle 1, the road surface conditions, the gradient angle, etc.

[0039] 2, when the electric vehicle 1 travels on a flat road 101, it is efficient to distribute the driving force equally between the front wheels 2 and the rear wheels 3 because it is energy efficient to distribute the driving force according to the static load distribution of the electric vehicle 1. Therefore, when the electric vehicle 1 travels on the flat road 101, the control device 30 controls the distribution of driving force between the front wheels 2 and the rear wheels 3 to be equal. In this case, the power consumption of the front wheel battery 11 and the power consumption of the rear wheel battery 21 are equal.

[0040] As shown in Fig. 3, when the electric vehicle 1 travels on an uphill road 102, the upward gradient places a large load on the rear side of the electric vehicle 1, and since it is more energy efficient to distribute the driving force so that the ratio of the driving force to the rear side is increased, it is efficient to distribute the driving force so that the driving force to the rear wheels 3 is greater than the driving force to the front wheels 2. Therefore, when the electric vehicle 1 travels on an uphill road 102, the control device 30 controls the distribution of driving force between the front wheels 2 and the rear wheels 3 so that the ratio to the rear wheels 3 is greater. In this case, the power consumption of the rear wheel battery 21 is greater than the power consumption of the front wheel battery 11.

[0041] As shown in FIG. 4, when the electric vehicle 1 travels on a downhill road 103, a large load is applied to the front side of the electric vehicle 1 because of the downward gradient. In this state, if the electric vehicle 1 travels while maintaining a certain vehicle speed, it is necessary to perform regeneration by the motor, and the regeneration ratio on the front side becomes large. In other words, since energy efficiency is better when the driving force distribution is such that the amount of regeneration on the front side is large, it is efficient to distribute the driving force so that the amount of regeneration on the front wheels 2 is larger than the amount of regeneration on the rear wheels 3. Therefore, when the electric vehicle 1 travels on the downhill road 103, the control device 30 controls the distribution of driving force between the front wheels 2 and the rear wheels 3 so that the amount of regeneration on the front wheel 2 side is larger than the amount of regeneration on the rear wheel 3 side. In this case, the amount of regeneration (charge amount) of the rear wheel battery 21 becomes smaller than the amount of regeneration (charge amount) of the front wheel battery 11.

[0042] Thus, the greater the gradient of the road surface, regardless of whether it is uphill or downhill, and the less flat the surface, the more the electric vehicle 1 needs to make the SOC of the rear wheel battery 21 greater than the SOC of the front wheel battery 11. Therefore, the control device 30 calculates and sets the target SOC of the front wheel battery 11 and the target SOC of the rear wheel battery 21 based on the gradient of the planned travel route (the ratio of uphill and downhill slopes and the angle of the slope) from future route information.

[0043] As shown in Fig. 5, the control device 30 sets the target SOC for each battery for the driving route to the destination of the electric vehicle 1 such that the greater the gradient of the road surface, regardless of whether it is uphill or downhill, the greater the target SOC for the rear wheel battery 21 than the target SOC for the front wheel battery 11. The target SOC for the rear wheel battery 21 gradually increases as the gradient increases from the flat side. On the other hand, the target SOC for the front wheel battery 11 gradually decreases as the gradient increases from the flat side. The control device 30 sets the target SOC for the front wheel battery 11 smaller than the target SOC for the rear wheel battery 21, and the greater the proportion of flatness, the smaller the difference between the target SOCs, and the greater the proportion of gradient, the greater the difference between the target SOCs.

[0044] As described above, according to the embodiment, in an electric vehicle 1 equipped with multiple batteries, in a vehicle system in which each battery is used to drive a different wheel or operate electronic device 70, the target SOC (remaining battery capacity) of the battery used to drive the wheels can be changed according to the gradient and flatness of the route to be traveled in the future. When the route on which the electric vehicle 1 is travelling has a steep gradient, the control device 30 sets the target SOC of the rear wheel battery to be higher than the target SOC of the front wheel battery. This makes it possible to efficiently charge and discharge each battery according to the gradient of the road surface, enabling efficient travel and controlling the SOC of each battery to an appropriate value.

[0045] Furthermore, when a flat route is expected, the control device 30 sets the target SOC of the front wheel battery 11 to be approximately the same as the target SOC of the rear wheel battery 21. This makes it possible to control the front wheel battery 11 and the rear wheel battery 21 to their appropriate SOCs according to the driving route to the destination.

[0046] In addition, by setting the target SOC for the front and rear wheels according to the travel route, it is possible to maximize the travel distance relative to the battery charging time. The control device 30 can execute charging control using external charging or solar charging.

[0047] For example, the control device 30 sets the target SOC of each battery to a value that matches the route as shown in Figure 5, and during external charging or solar charging, prioritizes charging of either the front wheel battery 11 or the rear wheel battery 21, whichever battery has a greater deviation from the target SOC. This makes it possible to maximize the driving distance after charging within the limited charging time. Note that if sufficient charging time is available, it is desirable to charge the batteries to full charge without relying on the target SOC.

[0048] Also, the control device 30 can determine the route gradient before starting to travel on the travel route, and charge based on the target SOC calculated from that. Alternatively, the control device 30 can use the route gradient determination result to determine the charging priority when charging using the solar panel 51 while traveling. Furthermore, the control device 30 can determine the route gradient each time charging is performed while traveling, and charge according to the latest target SOC.

[0049] It should be noted that the above-described embodiment is merely an example, and the number of batteries mounted on the electric vehicle 1 and the relationship between the batteries and the corresponding drive wheels are not limited to this embodiment.

[0050] In addition, the charging method after the target SOC is set is not limited to the above-mentioned method, and may be any method capable of charging any battery. For example, an engine may be used as a power generation method. Specifically, the electric vehicle 1 may be a range extender vehicle equipped with a power generation engine.

[0051] Furthermore, the setting of the target SOC according to the gradient of the route, the target SOC before and after the flat road and the rate at which the target SOC changes as the gradient increases are not limited to those shown in FIG. [Explanation of symbols]

[0052] 1 Electric vehicles 2 Front wheels 2A Left front wheel 2B Right front wheel 3 Rear wheel 3A Left rear wheel 3B Right rear wheel 10 Front wheel drive 11 Front wheel battery 13 Front wheel motor 13A Left front wheel motor 13B Right front wheel motor 20 Rear wheel drive 21 Rear wheel battery 23 Rear wheel motor 23A Left rear wheel motor 23B Right rear wheel motor 30 Control device

Claims

[Claim 1] a front-wheel drive device including a front-wheel motor that drives the front wheels and a front-wheel battery that supplies power to the front-wheel motor; a rear wheel drive device including a rear wheel motor that drives the rear wheels and a rear wheel battery that supplies power to the rear wheel motor; an accelerator opening sensor that detects an accelerator opening, which is an amount of operation of an accelerator pedal; A vehicle speed sensor for detecting a vehicle speed; A control device for an electric vehicle in which the front wheels and the rear wheels are driven independently by a motor, setting a target SOC for the front wheel battery; calculating an SOC of the front wheel battery based on a signal input from a current sensor that detects a current of the front wheel battery and a signal input from a voltage sensor that detects a voltage of the front wheel battery; controlling the front wheel drive device so that the SOC of the front wheel battery becomes a target SOC of the front wheel battery; setting a target SOC for the rear wheel battery; calculating an SOC of the rear wheel battery based on a signal input from a current sensor that detects a current of the rear wheel battery and a signal input from a voltage sensor that detects a voltage of the rear wheel battery; controlling the rear wheel drive device so that the SOC of the rear wheel battery becomes a target SOC of the rear wheel battery; Calculating a required driving force based on a signal input from the accelerator opening sensor and a signal input from the vehicle speed sensor; controlling a distribution of the driving force of the front wheels and the driving force of the rear wheels with respect to the required driving force; When the electric vehicle travels on an uphill road, a drive force distribution between the front wheels and the rear wheels is controlled so that the drive force of the rear wheels is greater than the drive force of the front wheels; When the electric vehicle travels downhill, a drive force distribution between the front wheels and the rear wheels is controlled so that a regenerative amount by the front wheel motor is greater than a regenerative amount by the rear wheel motor; When it is determined that a driving route to a destination of the electric vehicle has a steep gradient of a road surface, a target SOC of the rear wheel battery is set to be higher than a target SOC of the front wheel battery. A control device for an electric vehicle.

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