Electric vehicles

Abstract

Even when the maximum power that can be input to the energy storage device is limited, the system avoids inputting excessive power to the device while outputting sufficient braking force through motor regenerative control. [Solution] The electric vehicle includes a first motor 22 connected to one of the front wheels 29a, 29b and rear wheels 39a, 39b, a second motor 32 connected to the other of the front wheels 29a, 29b and rear wheels 39a, 39b, a battery 40 capable of exchanging power with the first motor 22 and the second motor 32, a clutch CL for connecting and disconnecting the first motor 22 from one of the wheels, and an electronic control unit 60 that, when a braking force output is required while driving in a situation where the maximum power that can be input to the battery 40 is limited, turns off the clutch CL so that the first motor 22 is disconnected from one of the wheels, and then controls the first motor 22 for power and the second motor 32 for regenerative braking.

Description

Technical Field

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[0001] The present disclosure relates to an electric vehicle.

Background Art

[0002] Conventionally, as this type of electric vehicle, there has been proposed one that includes a motor as a drive source and a battery capable of supplying power to the motor and charging the power generated by the motor, and that switches between four-wheel drive running in which the front and rear wheels are driven and two-wheel drive running in which either the front wheel or the rear wheel is driven (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described electric vehicle, the vehicle can be braked while charging the battery by performing regenerative control of the motor. However, when the maximum power that can be charged into the battery is limited, sufficient braking force cannot be output from the motor. Instead of regenerative control of the motor, it is also conceivable to output the necessary braking force by a mechanical brake, but there may be a case where the usage frequency of the mechanical brake increases and its lifespan decreases.

[0005] The main object of the electric vehicle of the present disclosure is to output sufficient braking force by regenerative control of the motor while avoiding excessive power from being input into the power storage device.

Means for Solving the Problems

[0006] The electric vehicle of the present disclosure has adopted the following means in order to achieve the above main object.

[0007] The electric vehicle of the present disclosure is A first motor connected to one of the front or rear wheels, A second motor connected to the other wheel of the front wheel and the other of the rear wheels, A power storage device capable of exchanging power with the first motor and the second motor, A connection release mechanism for connecting and disconnecting the first motor and the one wheel, When braking force output is required during driving, the control unit controls the disconnection mechanism so that the first motor is disconnected from one of the wheels, and then controls the first motor for power and the second motor for regenerative braking. The gist of it is that it is equipped with the following features.

[0008] In the electric vehicle of this disclosure, when braking force output is required during driving, a first motor disconnected from one of the front or rear wheels is subjected to power control, while a second motor connected to the other of the front or rear wheels is subjected to regenerative control. This allows at least a portion of the power generated by the regenerative control of the second motor to be consumed by the power control of the first motor. As a result, sufficient braking force can be output by the regenerative control of the second motor while avoiding excessive power input to the energy storage device.

[0009] In the electric vehicle of this disclosure, the control unit may set the braking power required for the vehicle, regenerate control the second motor so that the braking power is output, and power control the first motor so that any surplus power generated by the regenerative control of the second motor that exceeds the maximum power that can be input to the energy storage device is consumed. In this way, the required braking power can be output while charging the energy storage device within a range that does not exceed the maximum input power by the regenerative control of the second motor.

[0010] Furthermore, in the electric vehicle of this disclosure, an engine connected to the rotating shaft of the first motor may be provided, and the control unit may power control the first motor so that the engine is motorized when a braking force output is required during driving. In this way, the power generated by the regenerative control of the second motor can be consumed by the engine's losses in addition to the losses of the first motor and the inverter driving the first motor. Therefore, any surplus power generated by the regenerative control of the second motor that exceeds the maximum power that can be input to the energy storage device can be consumed more reliably by power control of the first motor. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the electric vehicle of this disclosure. [Figure 2] This flowchart shows an example of deceleration processing when the accelerator is released. [Figure 3] This is an explanatory diagram showing an example of a map for setting the torque required for deceleration. [Figure 4] This is an explanatory diagram showing an example of a map for setting the target rotational speed. [Figure 5] This is a schematic diagram of the configuration of other electric vehicles. [Modes for carrying out the invention]

[0012] Next, we will describe the forms for implementing this disclosure.

[0013] Figure 1 is a schematic diagram of the electric vehicle 20 of the present disclosure. The electric vehicle 20 is configured as an electric vehicle and, as shown in Figure 1, comprises a first motor 22, a first inverter 24, a second motor 32, a second inverter 34, a battery 40, a clutch CL, and an electronic control unit 60.

[0014] The first motor 22 and the second motor 32 are configured, for example, as synchronous generator motors. The rotor of the first motor 22 (not shown) is connected via a clutch CL to a drive shaft 26 connected to the front wheels 29a and 29b via a differential gear 28. The rotor of the second motor 32 (not shown) is connected via a differential gear 38 to a drive shaft 36 connected to the rear wheels 39a and 39b. Alternatively, the rotor of the first motor 22 may be connected via a differential gear 28 to a drive shaft 26 connected to the front wheels 29a and 29b, and the rotor of the second motor 32 may be connected via a clutch CL to a drive shaft 36 connected to the rear wheels 39a and 39b via a differential gear 38. The first motor 22 and the second motor 32 are equipped with rotation position detection sensors 22a and 32a, respectively, for detecting the rotation position of the rotors.

[0015] The first inverter 24 and the second inverter 34 are configured as well-known inverter circuits having six transistors and six diodes. The first inverter 24 and the second inverter 34 are connected to the power line 42. The first inverter 24 converts DC power from the battery 40 into three-phase AC power by PWM control and applies it to the first motor 22 to drive the first motor 22. The second inverter 24, similar to the first inverter 24, converts DC power from the battery 40 into three-phase AC power by PWM control and applies it to the second motor 32 to drive the second motor 32.

[0016] The battery 40 is configured as, for example, a lithium-ion battery. The battery 40 is connected to the first inverter 24 and the second inverter 34 via a power line 42. A smoothing capacitor is attached to the power line 42. Voltage sensors 41a for detecting the battery voltage Vb are attached to both terminals of the battery 40. Current sensors 41b for detecting the battery current Ib are attached to the terminals of the battery 40. A temperature sensor 41c for detecting the battery temperature Tb is attached to the battery 40.

[0017] The electronic control unit 60 is configured as a microcomputer centered around the CPU 62. In addition to the CPU 62, the electronic control unit 60 includes a ROM 64, a RAM 66, an input port (not shown), an output port (not shown), and the like.

[0018] The electronic control unit 60 inputs the rotational positions θ1 and θ2 of the first motor 22 and the second motor 32 detected by the rotational position detection sensors 22a and 32a, the battery voltage Vb detected by the voltage sensor 41a, the battery current Ib detected by the current sensor 41b, the battery temperature Tb detected by the temperature sensor 41c, etc. via the input port. The electronic control unit 60 calculates the rotational speed N1 of the first motor 22 based on the rotational position θ1 of the first motor 22, and calculates the rotational speed N2 of the second motor 32 based on the rotational position θ2 of the second motor 32. The electronic control unit 60 calculates the state of charge SOC of the battery 40 based on the integrated value of the battery current Ib. The state of charge SOC is the ratio of the capacity of the electric power that can be discharged from the battery 40 to the total capacity of the battery 40. The electronic control unit 60 also sets the input limit Win (negative value) and the output limit Wout (positive value) based on the state of charge SOC of the battery 40 and the battery temperature Tb. The input limit Win is the maximum value of the input power allowed for the battery 40. The output limit Wout is the maximum value of the output power allowed for the battery 40. Note that the input limit Win and the output limit Wout can be set by multiplying a temperature-dependent value, which is a value based on the battery temperature Tb, by a correction coefficient based on the state of charge SOC of the battery 40.

[0019] The electronic control unit 60 also inputs the start signal ST from the start switch 70, the shift position SP detected by the shift lever position sensor 72 attached to the shift lever 71, the accelerator opening Acc detected by the accelerator pedal position sensor 74 attached to the accelerator pedal 73, and the brake pedal position BP detected by the brake pedal position sensor 76 attached to the brake pedal 75. The electronic control unit 60 also inputs the vehicle speed V detected by the vehicle speed sensor 78.

[0020] In the electric vehicle 20 configured in this way, as driving modes, it has a two-wheel driving mode and a four-wheel driving mode. The two-wheel driving mode is a mode in which the clutch CL is turned off to disconnect the first motor 22 from the front wheels 29a and 29b and the rear wheels 39a and 39b are driven by the second motor 32 to run. The four-wheel driving mode is a mode in which the clutch CL is turned on to connect the first motor 22 to the front wheels 29a and 29b and the front wheels 29a and 29b and the rear wheels 39a and 39b are driven by the first motor 22 and the second motor 32 to run.

[0021] In the two-wheel driving mode, the CPU 62 of the electronic control unit 60 sets a driving required torque Td* required for driving based on the accelerator opening Acc and the vehicle speed V. Subsequently, the CPU 62 multiplies the driving required torque Td* by the vehicle speed V to calculate a driving required power Pd*. Next, the CPU 62 sets an execution power P* so that the driving required power Pd* is output within the range of the input limit Win and the output limit Wout of the battery 40. Then, the CPU 62 divides the execution power P* by the rotational speed N2 of the second motor 32 to set a target torque T2* of the second motor 32. When the CPU 62 sets the target torque T2*, the CPU 62 performs switching control on the transistors of the second inverter 34 so that the target torque T2* is output from the second motor 32.

[0022] In four-wheel driving mode, the CPU 62 sets the effective power P*, similar to the two-wheel driving mode described above. Next, the CPU 62 distributes the effective power P* to the front and rear wheels according to the front-to-rear distribution ratio corresponding to the driving conditions to determine the front wheel effective power Pf* and the rear wheel effective power Pr*. Then, the CPU 62 divides the front wheel effective power Pf* by the rotational speed N1 of the first motor 22 to set the target torque T1* for the first motor 22, and divides the rear wheel effective power Pr* by the rotational speed N2 of the second motor 32 to set the target torque T2* for the second motor 32. Once the target torques T1* and T2* are set, the CPU 62 switches the transistors of the first inverter 24 so that the target torque T1* is output from the first motor 22, and switches the transistors of the second inverter 34 so that the target torque T2* is output from the second motor 32.

[0023] Next, we will explain the operation when the accelerator pedal 83 is released to decelerate while driving. Figure 2 is a flowchart showing an example of the deceleration process when the accelerator is released, which is performed by the electronic control unit 60. This process is repeatedly performed at predetermined intervals when the accelerator pedal 83 is released while driving.

[0024] When the deceleration process is executed when the accelerator is released, the CPU 62 of the electronic control unit 60 first inputs the rotational speed N1 of the first motor 22, the rotational speed N2 of the second motor 32, the vehicle speed V, the battery input limit Win, etc. (step S100). Next, the CPU 62 sets the deceleration request torque Td*, which is a negative driving request torque, based on the deceleration request torque setting map and the vehicle speed V (step S110). Figure 3 is an explanatory diagram showing an example of the deceleration request torque setting map. Note that if the electric vehicle 20 has a driving mode in which acceleration and deceleration are performed by operating only the accelerator pedal 83, the CPU 62 may set the deceleration request torque Td* based on the accelerator opening Acc in addition to the vehicle speed V.

[0025] Next, the CPU 62 calculates the deceleration request power Pd*, which is the negative driving request power, by multiplying the deceleration request torque Td* by the vehicle speed V (step S120). Then, it determines whether the deceleration request power Pd* is less than the input limit Win (step S130). This process determines whether power exceeding the input limit Win will be input to the battery 40 when the first motor 22 and the second motor 32 are regeneratively controlled to output the deceleration request power Pd*. Situations in which the deceleration request power Pd* is less than the input limit Win are likely to occur when the maximum power that can be input to the battery 40 (input limit Win) is limited, such as when the battery temperature Tb is not within the appropriate range or when the charge level SOC is close to full charge. Therefore, in step S130, the CPU 62 may also determine whether the battery temperature Tb is within the appropriate temperature range or whether the charge level SOC is less than a predetermined percentage close to full charge.

[0026] When the CPU 62 determines that the deceleration request power Pd* is not less than the input limit Win, it regenerates the first motor 22 and the second motor 32 so that the deceleration request power Pd* is output (step S140), and then terminates the accelerator-off control process. Specifically, if the current driving mode is the two-wheel driving mode, the CPU 62 divides the deceleration request power Pd* by the rotational speed N2 of the second motor 32 to set the target torque (regenerative torque) T2* of the second motor 32 and controls the second inverter 34. If the current driving mode is four-wheel driving mode, the CPU 62 determines the front wheel required power Pf* and the rear wheel required power Pr* based on the deceleration required power Pd* and the front-to-rear distribution ratio, sets the target torque T1* for the first motor 22 by dividing the front wheel actual power Pf* by the rotational speed N1 of the first motor 22, and sets the target torque T2* for the second motor 32 by dividing the rear wheel actual power Pr* by the rotational speed N2 of the second motor 32, and controls the first inverter 24 and the second inverter 34.

[0027] On the other hand, if the CPU 62 determines that the deceleration request power Pd* is less than the input limit Win, it determines whether or not the vehicle is in four-wheel driving mode (step S150). If the CPU 62 determines that the vehicle is in four-wheel driving mode, it switches to two-wheel driving mode by disengaging the first motor 22 from the front wheels 29a and 29b by turning off the clutch CL (step S160), and proceeds to step S170. If the CPU 62 determines that the vehicle is not in four-wheel driving mode but in two-wheel driving mode, it proceeds to step S170 while maintaining two-wheel driving mode.

[0028] Next, the CPU 62 subtracts the input limit Win from the deceleration request power Pd* to set the surplus power Ps (=Pd*-Win) (step S170). Subsequently, the CPU 62 determines whether the absolute value of the surplus power Ps (|Ps|) is less than or equal to the maximum power consumption Pmax (step S180). The maximum power consumption Pmax is the maximum power that can be consumed by controlling the first motor 22 to the maximum allowable rotational speed N1max when the first motor 22 is disconnected from the front wheels 29a and 29b (no-load state).

[0029] When the CPU 62 determines that the absolute value of the surplus power Ps is less than or equal to the maximum power consumption Pmax, it determines that the surplus power Ps can be consumed by the power control of the first motor 22, and sets the target rotational speed N1* of the first motor 22 based on the target rotational speed setting map and the absolute value of the surplus power Ps (step S190). The target rotational speed N1* is the rotational speed of the first motor 22 required to consume the surplus power Ps when the first motor 22 is power-controlled in an unloaded state with the first motor 22 disconnected from the front wheels 29a, 29b. Figure 4 is an explanatory diagram showing an example of the target rotational speed setting map. The target rotational speed N1* is set to be higher as the absolute value of the surplus power Ps increases. Next, the CPU 62 divides the deceleration request power Pd* by the rotational speed N2 of the second motor 32 to set the target torque (regenerative torque) T2* of the second motor 32 (step S200). Then, the CPU 62 controls the first inverter 24 so that the first motor 22 rotates at a target rotational speed N1* (step S230), and controls the second inverter 34 so that a target torque T2* is output from the second motor 32 (step S240), and then terminates the deceleration process when the accelerator is released.

[0030] By controlling the first motor 22, which is disconnected from the front wheels 29a and 29b, with power, and simultaneously controlling the second motor 32 connected to the rear wheels 39a and 39b with regenerative control, a portion of the power generated by the second motor 32 through regenerative control is consumed by the no-load loss of the first motor 22, the no-load loss of the drive force transmission mechanism on the first motor 22 side of the clutch CL, and the switching loss of the first inverter 24. This prevents excessive power exceeding the input limit Win of the battery 40 from being input to the battery 40, even when the input limit Win of the battery 40 is limited. Furthermore, the regenerative control of the second motor 32 outputs a deceleration request power Pd*, enabling deceleration driving.

[0031] In step S180, the CPU 62 determines that the absolute value of the surplus power Ps is greater than the maximum power consumption Pmax (the power consumed by rotating the first motor 22 at the maximum rotational speed N1max). If the CPU 62 determines that the surplus power Ps cannot be consumed by the power control of the first motor 22, it sets the target rotational speed N1* of the first motor 22 to the maximum rotational speed N1max (step S210). Next, the CPU 62 sets the target torque (regenerative torque) T2* of the second motor 32 by dividing the value obtained by subtracting the maximum power consumption Pmax from the input limit Win of the battery 40 (Win-Pmax) by the rotational speed N2 of the second motor 32 (step S220). Then, the CPU 62 controls the first inverter 24 so that the first motor 22 rotates at the target rotational speed N1* (step S230), and controls the second inverter 34 so that the target torque T2* is output from the second motor 32 (step S240), and ends the deceleration process when the accelerator is released. As a result, the second motor 32 is regeneratively controlled so as not to exceed the sum of the maximum power that can be input to the battery 40 (input limit Win) and the maximum power consumption Pmax consumed by the power control of the first motor 22. Therefore, it is possible to more reliably avoid inputting power exceeding the input limit Win to the battery 40.

[0032] In the embodiment described above, the electric vehicle 20 is in the form of an electric vehicle equipped with a first motor 22, a second motor 32, a battery 40, and a clutch CL. However, in addition to a hardware configuration similar to that of an electric vehicle, it may also be a hybrid vehicle (including a plug-in hybrid vehicle) equipped with an engine. Furthermore, the electric vehicle 20 may also be a fuel cell vehicle equipped with a fuel cell in addition to a hardware configuration similar to that of an electric vehicle. For example, as shown in the electric vehicle 120 illustrated in Figure 5, in addition to the first motor 22 and the second motor 32, it may be configured as a hybrid vehicle equipped with an engine 122 whose output shaft is connected to the rotor of the first motor 22, and an automatic transmission 130 whose input shaft is connected to the rotor of the first motor 22 and whose output shaft is connected to the drive shaft 26 via a clutch CL. In this case, by disengaging the clutch CL and controlling the first motor 22 which is disconnected from the front wheels 29a and 29b, while simultaneously controlling the regenerative braking of the second motor 32 connected to the rear wheels 39a and 39b, the power generated by the regenerative braking of the second motor 32 can be consumed by the losses of the engine 122, in addition to the losses of the first motor 22 and the first inverter 24. As a result, the surplus power Ps can be consumed more reliably by the power control of the first motor 22, and it is possible to more reliably avoid excessive power exceeding the input limit Win being input to the battery 40.

[0033] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on the main elements of the embodiment and the means for solving the problem will be explained. In this embodiment, the first motor 22 corresponds to the first motor of the present disclosure, the second motor 32 corresponds to the second motor, the battery 40 corresponds to the energy storage device, the clutch CL corresponds to the connection / disconnection mechanism, and the electronic control unit 60 corresponds to the control unit. Also, the engine 122 corresponds to the engine.

[0034] Furthermore, the correspondence between the main elements of the examples and the main elements of the invention described in the section on means for solving the problem is not intended to limit the elements of the invention described in the section on means for solving the problem, as the examples are merely one example to specifically illustrate a form for carrying out the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the examples are merely one specific example of the invention described in the section on means for solving the problem.

[0035] The above describes the forms for implementing this disclosure using examples, but this disclosure is not limited in any way to these examples, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0036] This disclosure is applicable to the electric vehicle manufacturing industry. [Explanation of Symbols]

[0037] 20,120 Electric vehicle, 22 First motor, 22a Rotation position detection sensor, 24 First inverter, 26 Drive shaft, 28 Differential gear, 29a,29b Front wheels, 32 Second motor, 32a Rotation position detection sensor, 34 Second inverter, 36 Drive shaft, 38 Differential gear, 39a,39b Rear wheels, 40 Battery, 41 Voltage sensor, 41b Current sensor, 41c Temperature sensor, 42 Power line, 60 Electronic control unit, 62 CPU, 64 ROM, 66 RAM, 70 Ignition switch, 71 Shift lever, 72 Shift position sensor, 73 Accelerator pedal, 74 Accelerator pedal position sensor, 75 Brake pedal, 76 Brake pedal position sensor, 78 Vehicle speed sensor, CL Clutch.

Claims

1. A first motor connected to one of the front or rear wheels, A second motor connected to the other wheel of the front wheel and the other of the rear wheels, A power storage device capable of exchanging power with the first motor and the second motor, A connection release mechanism for connecting and disconnecting the first motor and the one wheel, When braking force output is required during driving, the control unit controls the disconnection mechanism so that the first motor is disconnected from one of the wheels, and then controls the first motor for power and the second motor for regenerative braking. An electric vehicle equipped with [a specific feature / equipment].

2. The electric vehicle according to claim 1, The control unit, when a braking force output is required during driving, sets the required braking power for the vehicle, regenerates the second motor so that the braking power is output, and controls the first motor to operate so that any surplus power generated by the regenerative control of the second motor that exceeds the maximum power that can be input to the energy storage device is consumed. Electric vehicle.

3. An electric vehicle according to claim 1 or 2, The engine is connected to the rotating shaft of the first motor, The control unit controls the first motor to operate so that the engine is motorized when a braking force output is required during driving. Electric vehicle.

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