Electric vehicle

Abstract

To provide a technique capable of suppressing fluctuation of output shaft torque.SOLUTION: An electric vehicle includes a drive unit including wheels, a motor configured to drive the wheels, and a clutch provided 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 by the motor and to control connection and disconnection of the clutch. The control device restricts regenerative braking by the motor and disconnects the clutch when sudden braking or locking of the wheel is detected.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle that includes a drive unit having wheels, a motor that drives the wheels, and a clutch provided in a power transmission path between the wheels and the motor, a battery connected to the motor, and a control device that is configured to control regenerative braking by the motor and to control engagement and disengagement of the clutch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-134534 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electric vehicle of Patent Document 1, when braking the vehicle, regenerative braking is performed by the motor with the clutch engaged. Therefore, when the vehicle is suddenly braked, regenerative braking is performed by the motor with the clutch engaged. In this case, torsional torque is generated in the drive unit of the electric vehicle. This torsional torque causes fluctuations in the output shaft torque.

[0005] This specification provides a technique that can suppress fluctuations in output shaft torque. [Means for solving the problem]

[0006] The electric vehicle disclosed in this specification may include a drive unit having wheels, a motor that drives the wheels, and a clutch provided 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 by the motor and to control engagement and disengagement of the clutch. The control device may limit the regenerative braking by the motor and disengage the clutch when sudden braking or locking of the wheels is detected.

[0007] According to the above configuration, when sudden braking or wheel lock is detected, regenerative braking by the motor is limited and the clutch is disengaged. In this case, the power transmission path between the wheel and the motor is cut off, thereby suppressing torsional torque generated in the drive unit. Therefore, fluctuations in output shaft torque due to torsional torque can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 2 shows a schematic configuration of an embodiment of an electric vehicle 2. [Figure 2] 1 shows a flowchart of clutch processing executed by the control device 40 of the electric vehicle 2. FIG. [Figure 3] 4 is a time chart of the motor rotation speed etc. of the electric vehicle 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] An electric vehicle 2 will be described with reference to Fig. 1. The electric vehicle 2 is a battery electric vehicle, a hybrid electric vehicle, a fuel cell electric vehicle, or a plug-in hybrid electric vehicle.

[0010] The electric vehicle 2 includes a vehicle body 10 and a pair of wheels 12r, 12l provided on the vehicle body 10. In this embodiment, the wheels 12r, 12l are a pair of front wheels provided on the front part of the vehicle body 10, but may be a pair of rear wheels.

[0011] The electric vehicle 2 further includes a battery 20 and a drive unit 22. The battery 20 has a plurality of secondary battery cells and is configured to be repeatedly chargeable and dischargeable. The secondary battery cells are not particularly limited and may 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 power 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, the motor 24 can function as a generator to perform regenerative braking of the wheels 12r and 12l. The differential gear 28 and the pair of clutches 30r and 30l are provided in a power transmission path 32 between the wheels 12r and 12l and the motor 24. The clutch 30r is disposed between the differential gear 28 and the wheels 12r, and the clutch 30l is disposed between the differential gear 28 and the wheels 12l.

[0012] The electric vehicle 2 further includes a control device 40 and sensors 42. The control device 40 is a so-called ECU. The control device 40 is configured using a computer device and has a memory that stores various control programs, a processor that executes those control programs, and the like. The control device 40 acquires sensor signals from sensors 42 attached to the electric vehicle 2 and controls the operation of each component of the electric vehicle 2. The sensors 42 include an accelerator pedal sensor, a brake pedal sensor, a brake oil pressure sensor, a wheel speed sensor, a motor rotation speed sensor, and the like.

[0013] (Clutch processing; Figure 2) The clutch processing executed by the control device 40 of the electric vehicle 2 will be described with reference to Fig. 2. When the clutch processing is started, the clutches 30r and 30l are in an engaged state.

[0014] In S10, the control device 40 monitors whether the accelerator operation is turned "OFF" and the brake operation is turned "ON." If the accelerator operation is turned "OFF" and the brake operation is turned "ON," the control device 40 determines YES in S10 and proceeds to S20.

[0015] In S20, the control device 40 determines whether sudden braking has been detected. As an example, the control device 40 detects sudden braking by using the rate of change of brake oil pressure, the rate of change of brake pedal stroke, etc. If sudden braking is detected (YES in S20), the control device 40 proceeds to S22. On the other hand, if sudden braking is not detected (NO in S20), the control device 40 proceeds to S30.

[0016] In S22, the control device 40 prohibits the motor 24 from performing regenerative braking.

[0017] In S24, the control device 40 executes a disengagement process to switch the clutches 30r, 30l from the engaged state to the disengaged state.

[0018] In S26, the control device 40 monitors whether sudden braking is no longer detected. If sudden braking is not detected, the control device 40 determines YES in S26 and proceeds to S28.

[0019] In S28, the control device 40 executes an engagement process to switch the clutches 30r, 30l from a disengaged state to an engaged state. After S28 ends, the control device 40 returns to S10.

[0020] Furthermore, in S30, the control device 40 determines whether a wheel lock has been detected. As an example, the control device 40 detects a wheel lock using a wheel slip rate calculated from the number of rotations of the wheel. If a wheel lock is detected (YES in S30), the control device 40 proceeds to S32. On the other hand, if a wheel lock is not detected (NO in S30), the control device 40 returns to S10.

[0021] S32 and S34 are the same as S22 and S24, respectively.

[0022] In S36, the control device 40 monitors whether wheel lock is no longer detected. If wheel lock is not detected, the control device 40 determines YES in S36 and proceeds to S38.

[0023] S38 is the same as S28. When S38 ends, the control device 40 returns to S10.

[0024] (Specific case) The operation of the electric vehicle 2 when sudden braking occurs and the operation of the electric vehicle of the comparative example when sudden braking occurs will be described with reference to the time chart of Fig. 3. In Fig. 3, information related to the electric vehicle 2 is indicated by a solid line, and information related to the electric vehicle of the comparative example is indicated by a dashed line. The electric vehicle of the comparative example has the same configuration as the electric vehicle 2, except that it does not have the clutches 30r, 30l and does not execute the clutch processing of Fig. 2. Note that the electric vehicle of the comparative example does not necessarily have to have the clutches 30r, 30l.

[0025] First, the operation of the electric vehicle of the comparative example will be described. At time T1, the accelerator operation is turned "OFF," and at time T2, the brake operation is turned "ON." In the electric vehicle of the comparative example, fluctuations in wheel speed occur in response to sudden braking at time T3. Even when sudden braking occurs, the electric vehicle of the comparative example does not prohibit regenerative braking by the motor 24, and the clutches 30r, 30l are maintained in an engaged state. In this case, fluctuations in wheel speed also cause fluctuations in the motor rotation speed, generating torsional torque in the drive unit 22. As a result, relatively large torque fluctuations occur in the output shaft torque.

[0026] Next, the operation of the electric vehicle 2 will be described. As in the case of the electric vehicle of the comparative example, at time T1, the accelerator operation is turned "OFF," and at time T2, the brake operation is turned "ON" (YES in S10 of FIG. 2). At time T13, the electric vehicle 2 determines that sudden braking has been detected (YES in S20). In this case, the electric vehicle 2 prohibits regenerative braking by the motor 24 (S22), and switches the clutches 30r, 30l from an engaged state to a disengaged state (S24). This separates the wheels 12r, 12l from the motor 24, and the motor rotation speed becomes zero at time T14. In this case, the torsional torque generated in the drive unit 22 is suppressed, and as a result, torque fluctuations generated in the output shaft torque are also suppressed.

[0027] (Effects of this embodiment) As described above, the electric vehicle 2 includes the wheels 12r, 12l, the drive unit 22 having the motor 24 that drives the wheels 12r, 12l and the clutches 30r, 30l provided in the power transmission path 32 between the wheels 12r, 12l and the motor 24, the battery 20 connected to the motor 24, and the control device 40 configured to control regenerative braking by the motor 24 and to control engagement and disengagement of the clutches 30r, 30l. When sudden braking or wheel lock is detected (YES in S20 and YES in S30 in FIG. 2), the control device 40 limits regenerative braking by the motor 24 (S24, S34) and disengages the clutch (S24, S34).

[0028] According to the above configuration, when sudden braking or wheel lock is detected, regenerative braking by the motor 24 is limited and the clutches 30r, 30l are disengaged. In this case, the power transmission path 32 between the wheels 12r, 12l and the motor 24 is disconnected, thereby suppressing torsional torque generated in the drive unit 22. Therefore, fluctuations in output shaft torque caused by torsional torque can be suppressed. [Explanation of symbols]

[0029] 2: electric vehicle, 10: vehicle body, 12l, 12r: wheels, 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

[Claim 1] An electric vehicle, Wheels and a drive unit including a motor that drives the wheels and a clutch provided in a power transmission path between the wheels and the motor; a battery connected to the motor; a control device configured to control regenerative braking by the motor and to control engagement and disengagement of the clutch, When sudden braking or locking of the wheels is detected, the control device limits the regenerative braking by the motor and disengages the clutch. Electric vehicle.

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