Electric vehicle

Abstract

The invention provides a technology capable of more reliably suppressing torsional resonance generated in a drive unit. An electric vehicle is provided with: wheels; a drive unit having a motor that drives the wheels and a disconnection mechanism provided in a torque transmission path between the motor and the wheels; and a control device that controls the disconnection mechanism. The disconnection mechanism is capable of selectively implementing a connected state in which the torque transmission path is connected, a disconnected state in which the torque transmission path is disconnected, and a standby state which is a state between the connected state and the disconnected state. The control device switches the disconnect mechanism from the connected state to the standby state when the electric vehicle travels on the wavy road, and switches the disconnect mechanism from the standby state to the disconnected state when the electric vehicle is emergently braked after switching the disconnect mechanism to the standby state.

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 disconnection mechanism for a torque transmission path disposed between the motor and the wheels; and a control device that controls the disconnection mechanism. The disconnection mechanism can selectively achieve a connected state connecting the torque transmission path and a disconnected state cutting off the torque transmission path. When the electric vehicle is traveling on a wavy road and undergoes emergency braking, the control device switches the disconnection mechanism from the connected state to the disconnected state.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-151325

[0006] In electric vehicles, when emergency braking is performed while traveling on a wavy road, torsional resonance may occur in the drive system from the motor to the wheels due to repeated wheel spin and ground contact. To avoid or suppress such torsional resonance, the electric vehicle in Patent Document 1 is configured to switch the disconnection mechanism from an engaged state to an unengaged state when emergency braking is performed while traveling on a wavy road. However, torsional resonance may still occur in the drive system during the period from the time the emergency braking of the electric vehicle is performed until the disconnection mechanism switches from the engaged state to the unengaged state. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] This specification provides a technique that can more reliably suppress torsional resonance generated in a drive system.

[0009] Methods for solving problems

[0010] The electric vehicle disclosed in this specification may include: wheels; a drive unit having a motor driving the wheels and a disconnection mechanism for a torque transmission path disposed between the motor and the wheels; and a control device that controls the disconnection mechanism. The disconnection mechanism can selectively achieve a connected state connecting the torque transmission path, a disconnected state cutting off the torque transmission path, and a standby state as a state between the connected state and the disconnected state. The control device can switch the disconnection mechanism from the connected state to the standby state when the electric vehicle is traveling on a wavy road, and after switching the disconnection mechanism to the standby state, switch the disconnection mechanism from the standby state to the disconnected state when the electric vehicle performs emergency braking.

[0011] According to the above structure, when the electric vehicle is traveling on a wavy road, the disconnection mechanism switches from the connected state to the standby state. Therefore, when the electric vehicle subsequently undergoes emergency braking, the disconnection mechanism switches back to the disconnected state relatively quickly. As a result, torsional resonance generated in the drive system can be suppressed more reliably. Attached Figure Description

[0012] Figure 1 The structure of one embodiment of the electric vehicle 2 is schematically shown.

[0013] Figure 2 This is a flowchart illustrating the disconnection process.

[0014] Explanation of reference numerals in the attached figures

[0015] 2: Electric vehicle; 10: Vehicle body; 12l, 12r: Wheels; 20: Battery; 22: Drive unit; 24: Motor; 26: Transmission mechanism; 28: Disconnection mechanism; 30: Differential mechanism; 32: Torque transmission path; 40: Control device; 42: Sensors. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] The electric vehicle 2 also includes a battery 20 and a drive unit 22. The battery 20 has multiple secondary battery cells configured to be repeatedly charged and discharged. The secondary battery cells are not particularly limited here; for example, they can be lithium-ion battery cells or nickel-metal hydride battery cells. The drive unit 22 includes a motor 24, a transmission mechanism 26, a disconnection mechanism 28, and a differential mechanism 30. 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. The transmission mechanism 26, the disconnection mechanism 28, and the differential mechanism 30 are disposed in the torque transmission path 32 between the wheels 12r and 12l and the motor 24. The transmission mechanism 26 is connected to the motor 24. The differential mechanism 30 is connected to the wheels 12r and 12l. The disconnection mechanism 28 is disposed between the transmission mechanism 26 and the differential mechanism 30.

[0019] In addition, the drive unit 22 can be a single-axis planetary eAxle that utilizes a planetary gear mechanism, or it can be a three-axis eAxle.

[0020] The disconnecting mechanism 28 includes a clutch and an actuator for operating the clutch. For example, the clutch is a friction clutch or a jaw clutch. The actuator is an electric motor, an electromagnetic actuator, or a hydraulic actuator. The disconnecting mechanism 28 can selectively achieve a connected state of the torque transmission path 32, a disconnected state of the torque transmission path 32, and a standby state as a state between the connected and disconnected states. When a friction clutch is used as the clutch, the semi-engaged state is an example of the "standby state." Furthermore, when a jaw clutch is used as the clutch, the state before switching from the connected state to the disconnected state is an example of the "standby state."

[0021] 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, an image sensor, a gyroscope sensor, etc.

[0022] (Disconnect process;) Figure 2 )

[0023] Reference Figure 2 The disconnection process performed by the control device 40 of the electric vehicle 2 will be described. Furthermore, at the start of the disconnection process, the disconnection mechanism 28 is in a connected state.

[0024] In S10, the control device 40 determines whether the electric vehicle 2 is traveling on the wavy road. For example, the control device 40 can use an image sensor or a gyroscope sensor to determine whether the electric vehicle 2 is traveling on the wavy road. If the control device 40 determines that the electric vehicle 2 is traveling on the wavy road (S10: Yes), it proceeds to S12. On the other hand, if the control device 40 determines that the electric vehicle 2 is not traveling on the wavy road (S10: No), it remains in standby mode in S10.

[0025] In S12, the control device 40 switches the disconnection mechanism 28 from the connected state to the standby state.

[0026] The processing content of S20 is the same as that of S10. If the control device 40 determines "no" in S20, it proceeds to S22; if it determines "yes" in S20, it proceeds to S30.

[0027] In S22, the control device 40 switches the disconnection mechanism 28 from the standby state to the connected state.

[0028] In S30, the control device 40 determines whether the electric vehicle 2 is performing emergency braking. For example, the control device 40 uses the rate of change in brake fluid pressure and the rate of change in brake pedal travel to determine whether the electric vehicle 2 is performing emergency braking. If the control device 40 determines that the electric vehicle 2 is performing emergency braking (S30: Yes), it proceeds to S32. On the other hand, if the control device 40 determines that the electric vehicle 2 is not performing emergency braking (S30: No), it returns to S20.

[0029] In S32, the control device 40 switches the disconnecting mechanism 28 from the standby state to the disconnected state. As a result, the torque transmission path 32 between the wheels 12r, 12l and the motor 24 is cut off.

[0030] The processing content of S34 is the same as that of S30. If the control device 40 determines "no" in S34, it proceeds to S36; if it determines "yes" in S34, it remains in standby mode in S34. Alternatively, the control device 40 may determine "yes" in S34 if a predetermined time has elapsed since it determined that the electric vehicle 2 has not performed emergency braking.

[0031] In step S36, the control device 40 switches the disconnection mechanism 28 from the disconnected state to the connected state. When step S36 ends, the control device 40 returns to step S10.

[0032] (Effect of this embodiment)

[0033] As described above, the electric vehicle 2 includes: wheels 12r and 12l; a drive unit 22, which has a motor 24 for driving the wheels 12r and 12l and a disconnection mechanism 28 for a torque transmission path 32 disposed between the motor 24 and the wheels 12r and 12l; and a control device 40 that controls the disconnection mechanism 28. The disconnection mechanism 28 can selectively realize a connected state of connecting the torque transmission path 32, a disconnected state of cutting off the torque transmission path 32, and a standby state as a state between the connected state and the disconnected state. The control device 40 controls the disconnection mechanism 28 when the electric vehicle 2 is traveling on a wavy road. Figure 2 (S10) The disconnection mechanism 28 is switched from the connected state to the standby state. After the disconnection mechanism 28 is switched to the standby state, when the electric vehicle 2 performs emergency braking (S30: Yes), the disconnection mechanism 28 is switched from the standby state to the disconnection state.

[0034] According to the above structure, when the electric vehicle 2 is traveling on a wavy road, the disconnection mechanism 28 switches from the connected state to the standby state. Therefore, when the electric vehicle 2 is subsequently subjected to emergency braking, the disconnection mechanism 28 switches back to the disconnected state relatively quickly. As a result, torsional resonance generated in the drive unit 22 can be suppressed more reliably.

Claims

1. An electric vehicle, wherein, The electric vehicle has the following features: wheel; A drive unit having a motor that drives the wheel and a disconnection mechanism disposed in the torque transmission path between the motor and the wheel; as well as A control device that controls the disconnection mechanism. The disconnection mechanism can selectively realize a connected state that connects the torque transmission path, a disconnected state that cuts off the torque transmission path, and a standby state that serves as a state between the connected state and the disconnected state. When the electric vehicle is traveling on a wavy road, the control device switches the disconnection mechanism from the connected state to the standby state. After switching the disconnection mechanism to the standby state, when the electric vehicle performs emergency braking, the control device switches the disconnection mechanism from the standby state to the disconnection state.

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