JP2017019427A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase of an energy loss in the entire vehicle when braking is requested.SOLUTION: When braking is requested, a target distribution ratio Dr* is set in such a way that a total loss Lt produced by adding a loss Lb in a hydraulic brake device to a drive-system loss Ld becomes a minimum value; a front wheel-drive motor and a rear wheel-drive motor are controlled in such a way that the two motors drive at a distribution ratio Dr within the respective minimum torque ranges; and the two motors and a hydraulic brake device are controlled so as to output required torque to a drive shaft. This makes it possible to minimize a loss in the entire vehicle when braking is requested, thus suppressing an increase of an energy loss in the entire vehicle.SELECTED DRAWING: Figure 2

Description

  More particularly, the present invention relates to a first motor capable of inputting / outputting power to / from front wheels, a second motor capable of inputting / outputting power to / from rear wheels, and hydraulic braking force to front wheels and rear wheels. And a hydraulic brake device.

  Conventionally, this type of electric vehicle includes an engine that outputs power to the front wheels, a motor generator that can input and output power to the rear wheels, and a wheel brake that applies braking force to the front and rear wheels. It has been proposed (see, for example, Patent Document 1). In this electric vehicle, the driving power distribution between the front wheels and the rear wheels is set so that the engine has a predetermined fuel consumption, and the engine and the motor generator are controlled according to the set driving power distribution, thereby The fuel consumption can be reduced.

JP 2005-53317 A

  However, in the above-described electric vehicle, when the braking request is made, if the target torque of the motor generator based on the set driving force distribution exceeds the regeneration upper limit torque of the motor generator, the torque output from the motor generator is reduced. Limit with the regenerative upper limit torque. In this case, the wheel brake is operated in order to supplement the braking torque that is insufficient with respect to the required braking torque required for the vehicle. Due to the operation of the wheel brake, energy loss may increase in the entire vehicle.

  The main object of the electric vehicle of the present invention is to suppress an increase in energy loss in the entire vehicle when a braking request is made.

  The electric vehicle of the present invention employs the following means in order to achieve the main object described above.

The electric vehicle of the present invention is
A first motor capable of inputting and outputting power to the front wheels;
A second motor capable of inputting and outputting power to the rear wheels;
A hydraulic brake device capable of applying a braking force by hydraulic pressure to the front wheels and the rear wheels;
The rear wheel torque with respect to the sum of the front wheel torque output to the front wheel and the rear wheel torque output to the rear wheel within the range of the regeneration upper limit torque of the first and second motors when a braking request is made. A control means for controlling the first and second motors and the hydraulic brake device so that the ratio of is a target distribution ratio and a required braking force is applied to the vehicle;
An electric vehicle comprising:
The control means is configured such that when the braking request is made, the front wheel and rear wheel torques are within the range of the regeneration upper limit torque of the first and second motors, and the loss of the first and second motors and the Setting the target distribution ratio so that the total loss, which is the sum of the hydraulic brake loss, falls within a predetermined range including the minimum value;
It is characterized by that.

  In the electric vehicle of the present invention, when a braking request is made, the sum of the front wheel torque output to the front wheels and the rear wheel torque output to the rear wheels within the range of the regeneration upper limit torque of the first and second motors. The first and second motors and the hydraulic brake device are controlled so that the ratio of the rear wheel torque to the target distribution ratio is obtained and the required braking force is applied to the vehicle. At this time, the front wheel and rear wheel torques are within the range of the regeneration upper limit torque of the first and second motors, and the total loss that is the sum of the loss of the first and second motors and the loss of the hydraulic brake includes a minimum value. Set the target distribution ratio to be within the range. Thereby, when a braking request is made, an increase in energy loss of the entire vehicle can be suppressed.

It is a block diagram which shows the outline of a structure of the electric vehicle 20 as one Example of this invention. It is a flowchart which shows an example of the target distribution ratio setting process routine performed by the electronic control unit 70 of an Example. It is explanatory drawing which shows an example of the relationship between distribution ratio Dr, loss Ld, and total loss Lt when requesting torque Td * is made constant when a braking request is made.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of a configuration of an electric vehicle 20 as an embodiment of the present invention. As shown in FIG. 1, the electric vehicle 20 of the embodiment includes motors 32 and 42, inverters 34 and 44, a battery 50, a hydraulic brake device 90, and an electronic control unit 70.

  The motor 32 is configured as, for example, a synchronous generator motor, and its rotor is connected to a drive shaft 36 that is coupled to front wheels 38 a and 38 b via a differential gear 37. The motor 42 is configured as, for example, a synchronous generator motor, and its rotor is connected to a drive shaft 46 that is connected to the rear wheels 48 a and 48 b via a differential gear 47. The inverters 34 and 44 are connected to the power line 54 together with the battery 50. The motors 32 and 42 are rotationally driven by switching control of a plurality of switching elements (not shown) of the inverters 34 and 44 by the electronic control unit 70.

  The battery 50 is configured as, for example, a lithium ion secondary battery or a nickel hydride secondary battery, and is connected to the power line 54.

  The hydraulic brake device 90 includes brake wheel cylinders 96a, 96b, 98a, 98b attached to the front wheels 38a, 38b and the rear wheels 48a, 48b, and a brake actuator 94. The brake actuator 94 is configured as an actuator for applying a braking force to the front wheels 38a and 38b and the rear wheels 48a and 48b. Specifically, the brake actuator 94 applies a braking force corresponding to the share of the brake to the front wheels 38a and 38b and the rear wheels 48a and 48b among the braking forces applied to the vehicle according to the brake pedal position BP and the vehicle speed V. Regardless of adjusting the hydraulic pressure of the brake wheel cylinders 96a, 96b, 98a, 98b so as to act, or braking the brake pedal 85, the brake is applied so that the braking force acts on the front wheels 38a, 38b and the rear wheels 48a, 48b. The hydraulic pressure to the wheel cylinders 96a, 96b, 98a, 98b can be adjusted. The brake actuator 94 is driven and controlled by the electronic control unit 70.

Although not shown, the electronic control unit 70 is configured as a microprocessor centered on a CPU. In addition to the CPU, a ROM that stores a processing program, a RAM that temporarily stores data, an input / output port, and a communication port Is provided. Signals from various sensors are input to the electronic control unit 70 via input ports. Examples of signals from various sensors include the following.
Rotation positions θmf and θmr from a rotation position detection sensor that detects the rotation positions of the rotors of the motors 32 and 42
-Phase currents Iuf, Ivf, Iur, Ivr from a current sensor attached to a power line connecting motors 32, 42 and inverters 34, 44
A battery voltage Vb from a voltage sensor attached between the terminals of the battery 50
A battery current Ib from a current sensor attached to the output terminal of the battery 50
-Battery temperature Tb from the temperature sensor attached to the battery 50
-Ignition signal from the ignition switch 80-Shift position SP from the shift position sensor 82 that detects the operation position of the shift lever 81
Accelerator opening degree Acc from the accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83
-Brake pedal position BP from the brake pedal position sensor 86 that detects the amount of depression of the brake pedal 85
・ Vehicle speed V from vehicle speed sensor 88
-Master cylinder pressure from pressure sensor attached to master cylinder 92-Wheel speeds Vwa-Vwd from wheel speed sensors attached to front wheels 38a, 38b and rear wheels 48a, 48b
・ Steering angle θst from steering angle sensor

Each control signal is output from the electronic control unit 70 via an output port. Examples of the various control signals include the following.
・ Switching control signals for a plurality of switching elements (not shown) of the inverters 34 and 44 ・ Drive control signals for the brake actuator 94

  The electronic control unit 70 calculates the rotational speeds Nmf and Nmr of the motors 32 and 42 based on the rotational positions of the rotors of the motors 32 and 42 from the rotational position detection sensor. Further, the electronic control unit 70 calculates the storage ratio SOC of the battery 50 based on the integrated value of the battery current Ib detected by the current sensor. Here, the storage ratio SOC is the ratio of the capacity of power that can be discharged from the battery 50 to the total capacity of the battery 50. Further, the electronic control unit 70 allows the driver to depress the brake pedal 85 based on the wheel speeds Vwa to Vwd of the front wheels 38a and 38b and the rear wheels 48a and 48b from the wheel speed sensor, the steering angle from the steering angle sensor, and the like. Anti-lock brake device function (ABS) for preventing any of the front wheels 38a, 38b and the rear wheels 48a, 48b from slipping due to locking, or the front wheels 38a, 38b when the driver depresses the accelerator pedal 83 And vehicle behavior stability control such as traction control (TRC) for preventing any one of the rear wheels 48a and 48b from slipping due to idling, and posture holding control (VSC) for holding the posture while the vehicle is turning. Do.

  In the electric vehicle 20 of the embodiment thus configured, the electronic control unit 70 sets the required torque Td * required for traveling based on the accelerator opening Acc and the vehicle speed V, and the torque of the front wheels 38a, 38b and the rear The torque commands Tmf * and Tmr * of the motors 32 and 42 are set so that the distribution ratio Dr, which is the ratio of the torque of the rear wheels 48a and 48b to the sum of the torque of the wheels 48a and 48b, becomes the target distribution ratio Dr *. Then, switching control of switching elements (not shown) of the inverters 34 and 44 is performed so that the motors 32 and 34 are driven by the torque commands Tmf * and Tmr *. By such control, the vehicle travels with the required torque Td * while setting the distribution ratio Dr to the target distribution ratio Dr *.

  In the electric vehicle 20 of the embodiment, when the brake pedal 85 is depressed, that is, when a braking request is made, the electronic control unit 70 determines the required torque Td * (negative value) based on the brake position BP and the vehicle speed V. ) And the temporary torques Tmftmp and Tmrtmp of the motors 32 and 42 are set so that the distribution ratio Dr becomes the target distribution ratio Dr *. Subsequently, the larger torque of the temporary torque Tmftmp and the minimum torque Tmfmin that can be output from the motor 32 (the absolute value of the minimum torque Tmfmin is the regeneration upper limit torque of the motor 32) is set as the torque command Tmf * of the motor 32. The larger torque between the torque command Tmrtmp and the minimum torque Tmrmin that can be output from the motor 42 (the absolute value of the minimum torque Tmrmin is the regeneration upper limit torque of the motor 42) is set in the torque command Tmr * of the motor 42. Then, switching control of switching elements (not shown) of the inverters 34 and 44 is performed so that the motors 32 and 42 are driven by the torque commands Tmf * and Tmr * so that the required torque Td * is output to the drive shaft 36. In response, the brake actuator 94 is operated. By such control, the brake actuator 94 is operated to output the required torque Td * to the drive shaft 36 while the motors 32 and 42 are driven to regenerate within the range of the minimum torques Tmfmin and Tmrmin (regeneration upper limit torque of the motors 32 and 42). To do.

  Next, the operation of the electric vehicle 20 of the embodiment configured as described above, particularly the operation when setting the target distribution ratio Dr * will be described. FIG. 2 is a flowchart illustrating an example of a target distribution ratio setting process routine executed by the electronic control unit 70 of the embodiment.

  When this routine is executed, the electronic control unit 70 sets a required torque Td * required for traveling based on the accelerator opening Acc, the brake position BP, and the vehicle speed V (step S100), and a braking request is made. It is determined whether or not (step S110). In the process of step S110, it is determined that a braking request is made when the required torque Tr * is a negative value.

  When the braking request is not made (step S110), the target distribution ratio Dr * is set so that the loss Ld of the drive system becomes the minimum value (step S120). When the regeneration request is made (step S110), the drive system The target distribution ratio Dr * is set so that the total loss Lt obtained by adding the loss Lb of the hydraulic brake device 90 to the loss Ld is the minimum value (step S130). Here, the drive system includes motors 32 and 42, inverters 34 and 44, and differential gears 37 and 47. Further, the total loss Ld of the drive system includes losses of the motors 32 and 42 (iron loss, copper loss, mechanical loss, etc.), losses of the inverters 34, 44 (switching loss of switching elements constituting the inverters 34, 44, etc.). , Losses of the differential gears 37 and 47 (gear engagement loss, etc.) are included. In the process of step S120, the relationship between the distribution ratio D1 at which the loss Ld becomes the minimum value and the required torque Td * is obtained in advance by experiment or analysis and stored in a ROM (not shown), and the required torque Td * is given. The corresponding distribution ratio D1 is derived and set to the target distribution ratio Dr *. Further, in the process of step S130, the relationship between the distribution ratio D2 and the required torque Td * at which the torque output from the motors 32 and 42 is greater than or equal to the minimum torque Tfmin and Trmin and the total loss Lt is the minimum value is tested in advance. Or obtained by analysis or the like and stored in a ROM (not shown). When the required torque Td * is given, the corresponding distribution ratio D2 is derived and set to the target distribution ratio Dr *.

  FIG. 3 is an explanatory diagram showing an example of the relationship between the distribution ratio Dr, the loss Ld, and the total loss Lt when the required torque Td * is constant when a braking request is made. In the figure, the broken line indicates the relationship between the distribution ratio Dr and the loss Ld, and the solid line indicates the relationship between the distribution ratio Dr and the total loss Lt. When a braking request is made, the torque output from the motors 32 and 42 is limited by the minimum torque Tmfmin, and the hydraulic brake device 90 may operate. When the hydraulic brake device 90 operates, a loss due to heat of the hydraulic brake device 90 occurs. Therefore, if the distribution ratio D1 at which the drive system loss Ld becomes the minimum value is the target distribution ratio Dr *, the total loss Lt including the loss Ld of the hydraulic brake device 90 may not be the minimum value as shown in the figure. Further, when the target distribution ratio Dr * is set, if the minimum torques Tfmin and Trmin are not considered, the temporary torques Tmftmp and Tmrtmp are limited to the minimum torques Tfmin and Trmin, and the torque commands Tmf * and Tmr * are set. Therefore, the actual distribution ratio deviates from the target distribution ratio Dr *, and the actual total loss Lt does not become the minimum value. In the embodiment, when a braking request is made, the torque output from the motors 32 and 42 is equal to or greater than the minimum torque Tfmin, Trmin, and the distribution ratio D2 at which the total loss Lt is the minimum value is set to the target distribution ratio Dr *. By setting, the loss of the entire vehicle can be reduced, and the increase of the energy loss of the entire vehicle can be suppressed.

  According to the electric vehicle 20 of the present embodiment described above, when a braking request is made, the total loss Lt obtained by adding the loss Lb of the hydraulic brake device 90 to the drive system loss Ld becomes the minimum value, and the motor 32, The target distribution ratio Dr * is set so that the torque output from 42 falls within the range of the minimum torques Tmfmin and Tmrmin (regeneration upper limit torque of the motors 32 and 42), and the distribution ratio Dr becomes the target distribution ratio Dr *. By controlling the hydraulic brake device 90 so that the motors 32 and 42 are driven and the required torque Tr * is output to the drive shaft 36, an increase in energy loss of the entire vehicle can be suppressed.

  In the electric vehicle 20 of the embodiment, the target distribution ratio Dr * is set so that the loss Ld and the total loss Lt become the minimum values in the processes of steps S120 and S130, but the loss Ld and the total loss Lt are the minimum values. The target distribution ratio Dr * is not limited to the one that sets the target distribution ratio Dr * so that, for example, the loss Ld and the total loss Lt, such as the distribution ratio near the minimum value of the loss Ld and the total loss Lt, are reduced. You only have to set it.

  In the embodiment, the present invention is applied to the electric vehicle 20 including the motor 32 capable of inputting / outputting power to the front wheels 38a, 38b and the motor 42 capable of inputting / outputting power to the rear wheels 48a, 48b. In addition to the hardware configuration of the electric auto 20, the present invention may be applied to a hybrid vehicle in which an engine and a generator are connected to the drive shaft 36 through a planetary gear.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the motor 32 corresponds to a “first motor”, the motor 42 corresponds to a “second motor”, the hydraulic brake device 90 corresponds to a “hydraulic brake device”, and the electronic control unit 70 “control means”. Is equivalent to.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of electric vehicles.

  20 electric vehicle, 32, 42 motor, 34, 44 inverter, 36, 46 drive shaft, 37, 47 differential gear, 38a, 38b front wheel, 48a, 48b rear wheel, 50 battery, 54 power line, 70 electronic control unit, 80 Ignition switch, 81 shift lever, 82 shift position sensor, 83 accelerator pedal, 84 accelerator pedal position sensor, 85 brake pedal, 86 brake pedal position sensor, 88 vehicle speed sensor, 90 hydraulic brake device, 92 master cylinder, 94 brake actuator, 96a , 96b, 98a, 98b Brake wheel cylinder.

Claims (1)

A first motor capable of inputting and outputting power to the front wheels;
A second motor capable of inputting and outputting power to the rear wheels;
A hydraulic brake device capable of applying a braking force by hydraulic pressure to the front wheels and the rear wheels;
The rear wheel torque with respect to the sum of the front wheel torque output to the front wheel and the rear wheel torque output to the rear wheel within the range of the regeneration upper limit torque of the first and second motors when a braking request is made. A control means for controlling the first and second motors and the hydraulic brake device so that the ratio of is a target distribution ratio and a required braking force is applied to the vehicle;
An electric vehicle comprising:
The control means is configured such that when the braking request is made, the front wheel and rear wheel torques are within the range of the regeneration upper limit torque of the first and second motors, and the loss of the first and second motors and the Setting the target distribution ratio so that the total loss, which is the sum of the hydraulic brake loss, falls within a predetermined range including the minimum value;
An electric vehicle characterized by that.

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