Electric vehicle

Abstract

The invention provides an electric vehicle capable of suppressing fluctuation of torque of an output shaft. An electric vehicle is provided with: wheels; a drive unit having a motor for driving the wheels and a clutch provided in a power transmission path between the wheels and the motor; the storage battery is connected with the motor; and a control device configured to control regenerative braking by the motor and to control connection and disconnection of the clutch. In a case where emergency braking or wheel locking is detected, the control device restricts regenerative braking by the motor and cuts off the clutch.

Description

Technical Field

[0001] The technology disclosed in this specification relates to electric vehicles. Background Technology

[0002] Patent document 1 discloses an electric vehicle comprising: wheels; a drive unit having a motor for driving the wheels and a clutch disposed in a power transmission path between the wheels and the motor; a battery connected to the motor; and a control device for controlling motor-based regenerative braking and controlling the engagement and disengagement of the clutch.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2015-134534

[0004] In the electric vehicle of Patent Document 1, motor-based regenerative braking is performed while the clutch is engaged during vehicle braking. Therefore, if the vehicle is subjected to emergency braking, motor-based regenerative braking is performed while the clutch is engaged. In this case, a torque generated by the drive unit of the electric vehicle is produced in the drive unit. The output shaft torque varies due to this torque. Summary of the Invention

[0005] This specification provides techniques for suppressing variations in output shaft torque.

[0006] The electric vehicle disclosed in this specification may include: wheels; a drive unit having a motor for driving the wheels and a clutch disposed in a power transmission path between the wheels and the motor; a battery connected to the motor; and a control device configured to control regenerative braking based on the motor and to control the engagement and disengagement of the clutch. In the event of emergency braking or wheel locking, the control device may also limit the regenerative braking based on the motor and disengage the clutch.

[0007] According to the above structure, in the event of emergency braking or wheel lock-up, motor-based regenerative braking is limited and the clutch is disengaged. In this case, since the power transmission path between the wheel and the motor is cut off, the torque generated in the drive unit is suppressed. Therefore, fluctuations in the output shaft torque caused by torque can be suppressed. Attached Figure Description

[0008] Figure 1 The structure of one embodiment of the electric vehicle 2 is schematically shown.

[0009] Figure 2 A flowchart showing the clutch processing performed by the control device 40 of the electric vehicle 2.

[0010] Figure 3 This is a time graph showing the motor speed, etc., of electric vehicle 2. Detailed Implementation

[0011] Reference Figure 1 The electric vehicle 2 will be described below. Electric vehicle 2 is a battery electric vehicle, a hybrid electric vehicle, a fuel cell electric vehicle, or a plug-in hybrid electric vehicle.

[0012] The electric vehicle 2 includes a body 10 and a pair of wheels 12r and 12l disposed on the body 10. In this embodiment, the wheels 12r and 12l are a pair of front wheels disposed at the front of the body 10, but they may also be a pair of rear wheels.

[0013] The electric vehicle 2 also includes a battery 20 and a drive unit 22. The battery 20 has multiple secondary battery cells configured for repeated charging and discharging. The secondary battery cells are not particularly limited and can be, for example, lithium-ion battery cells or nickel-metal hydride battery cells. The drive unit 22 includes a motor 24, a transmission mechanism 26, a differential gear 28, and a pair of clutches 30r and 30l. The motor 24 is connected to the battery 20. The motor 24 functions not only as a prime mover driven by electricity supplied from the battery 20, but also as a generator for regenerative braking of the wheels 12r and 12l. That is, when the electric vehicle 2 brakes, regenerative braking of the wheels 12r and 12l can be performed by making the motor 24 function as a generator. The differential gear 28 and the pair of clutches 30r and 30l are provided in the power transmission path 32 between the wheels 12r and 12l and the motor 24. Clutch 30r is positioned between differential gear 28 and wheel 12r, and clutch 30l is positioned between differential gear 28 and wheel 12l.

[0014] The electric vehicle 2 also includes a control unit 40 and a sensor class 42. The control unit 40 is a so-called ECU. The control unit 40 is constructed using a computer device and has a memory for storing various control programs and a processor for executing these control programs. The control unit 40 obtains sensor signals from the sensor class 42 installed in the electric vehicle 2 and controls the operation of various components of the electric vehicle 2. The sensor class 42 includes an accelerator pedal sensor, a brake pedal sensor, a brake hydraulic pressure sensor, a wheel speed sensor, a motor speed sensor, etc.

[0015] (Clutch handling;) Figure 2 )

[0016] Reference Figure 2 The clutch operation performed by the control device 40 of the electric vehicle 2 will be described. Furthermore, at the moment the clutch operation begins, clutches 30r and 30l are in the engaged state.

[0017] In S10, the control device 40 monitors the situation where the acceleration operation becomes "invalid" and the braking operation becomes "valid". If the acceleration operation becomes "invalid" and the braking operation becomes "valid", the control device 40 determines "yes" in S10 and proceeds to S20.

[0018] In S20, the control device 40 determines whether emergency braking has been detected. As an example, the control device 40 detects emergency braking using the rate of change of brake fluid pressure, the rate of change of brake pedal travel, etc. If emergency braking is detected (yes in S20), the control device 40 proceeds to S22. Conversely, if no emergency braking is detected (no in S20), the control device 40 proceeds to S30.

[0019] In S22, the control device 40 disables regenerative braking based on the motor 24.

[0020] In S24, the control device 40 performs a cutting-off process to switch the clutches 30r and 30l from the engaged state to the disengaged state.

[0021] In S26, the control device 40 monitors for situations where emergency braking becomes undetectable. If emergency braking is undetectable, the control device 40 determines "yes" in S26 and proceeds to S28.

[0022] In S28, the control device 40 performs an engagement process to switch the clutches 30r and 30l from the disengaged state to the engaged state. If S28 ends, the control device 40 returns to S10.

[0023] In addition, in S30, the control device 40 determines whether wheel lock is detected. As an example, the control device 40 detects wheel lock using the wheel slip ratio calculated based on the wheel's rotational speed. If wheel lock is detected ("yes" in S30), the control device 40 proceeds to S32. On the other hand, if wheel lock is not detected ("no" in S30), the control device 40 returns to S10.

[0024] S32 and S34 are the same as S22 and S24, respectively.

[0025] In S36, the control device 40 monitors the situation where wheel lock becomes undetectable. If wheel lock is not detected, the control device 40 determines "yes" in S36 and proceeds to S38.

[0026] S38 is the same as S28. If S38 ends, the control device 40 returns to S10.

[0027] (Specific circumstances)

[0028] Reference Figure 3 The timeline illustrates the actions of electric vehicle 2 under emergency braking and the actions of a comparative example electric vehicle under emergency braking. Figure 3 In the diagram, solid lines represent information about electric vehicle 2, and dashed lines represent information about the comparative electric vehicle. The comparative electric vehicle, however, lacks clutches 30r and 30l and does not perform [operations / functions]. Figure 2 Apart from the clutch handling, it has the same structure as electric vehicle 2. Furthermore, the electric vehicle in the comparative example may also be without clutches 30r and 30l.

[0029] First, the operation of the comparative example electric vehicle will be explained. At time T1, acceleration is "invalid," and at time T2, braking is "valid." In the comparative example electric vehicle, at time T3, the wheel speed changes due to emergency braking. For the comparative example electric vehicle, even under emergency braking, regenerative braking based on motor 24 is not prohibited, and clutches 30r and 30l remain engaged. In this case, the motor speed also changes according to the change in wheel speed, generating torque in drive unit 22. As a result, the output shaft torque exhibits a relatively large torque variation.

[0030] Next, the operation of electric vehicle 2 will be explained. Similar to the electric vehicle in the comparative example, at time T1, the acceleration operation becomes "invalid," and at time T2, the braking operation becomes "valid" (in...). Figure 2 (Yes in S10). At time T13, electric vehicle 2 determines that emergency braking has been detected (Yes in S20). In this case, electric vehicle 2 prohibits regenerative braking based on motor 24 (S22) and switches clutches 30r and 30l from the engaged state to the disengaged state (S24). As a result, wheels 12r and 12l are disconnected from motor 24, and at time T14, the motor speed becomes zero. In this case, the torque generated by drive unit 22 is suppressed, and as a result, torque fluctuations generated by the output shaft torque are also suppressed.

[0031] (Effects of this embodiment)

[0032] As described above, the electric vehicle 2 includes: wheels 12r and 12l; a drive unit 22 having a motor 24 for driving the wheels 12r and 12l and clutches 30r and 30l disposed in a power transmission path 32 between the wheels 12r and 12l and the motor 24; a battery 20 connected to the motor 24; and a control device 40 configured to control regenerative braking based on the motor 24 and to control the engagement and disengagement of the clutches 30r and 30l. In the event of emergency braking or wheel lock-up (in... Figure 2(Yes in S20, Yes in S30), the control device 40 restricts regenerative braking based on motor 24 (S24, S34) and disengages the clutch (S24, S34).

[0033] According to the above structure, in the event of emergency braking or wheel lock-up, regenerative braking based on motor 24 is limited, and clutches 30r and 30l are disengaged. In this case, since the power transmission path 32 between wheels 12r and 12l and motor 24 is cut off, the torque generated in drive unit 22 is suppressed. Therefore, fluctuations in output shaft torque caused by torque can be suppressed.

[0034] Explanation of reference numerals in the attached figures:

[0035] 2… Electric vehicle; 10… Body; 12l, 12r… Wheel; 20… Battery; 22… Drive unit; 24… Motor; 26… Transmission mechanism; 28… Differential gear; 30l, 30r… Clutch; 32… Power transmission path; 40… Control device; 42… Sensors.

Claims

1. An electric vehicle, wherein, include: wheel; The drive unit has a motor that drives the wheel and a clutch disposed in the power transmission path between the wheel and the motor; A storage battery is connected to the motor; as well as The control device is configured to control regenerative braking based on the motor, and to control the engagement and disengagement of the clutch. In the event of emergency braking or wheel locking, the control device limits the regenerative braking based on the motor and disengages the clutch.

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