JP6306966B2 - Electric vehicle drive device - Google Patents

Description

  The present invention relates to a drive device for an electric vehicle that transmits the output of a motor to a plurality of drive wheels, and more particularly to a device that can eliminate the lock state of the motor and improve the start performance of the vehicle with a simple configuration.

For example, an AC motor such as a permanent magnet (PM) type synchronous motor is used as a driving power source for an electric vehicle.
If energization is continued when the motor is in a locked state, the current concentrates in a predetermined phase, and particularly the power element is likely to overheat. As a result of overheating, when the temperature becomes higher than a predetermined value, it is necessary to limit the output torque of the motor in order to protect the device.

  As conventional techniques for dealing with such motor locks of electric vehicles, for example, in Patent Documents 1 to 3, a motor is locked by providing a clutch in a part of a power transmission path from the motor to the drive wheels. Describes that the restarting of the motor is facilitated by weakening the engaging force of the clutch.

JP 2011-190854 A JP 2007-1573 A JP 2008-126867 A

However, in the case of the above-described prior art, it is necessary to newly add an unnecessary clutch device to the system when the motor is not locked, which complicates the configuration of the device and increases the weight and cost.
In addition, if the running resistance at the start of the vehicle is large, such as when the vehicle is stuck on a rough road or when starting at a steep climb, the motor starting torque will overcome the running resistance even if the vehicle is released from the locked state. There is a concern that the vehicle will not be able to start and become locked again.
In view of the above-described problems, an object of the present invention is to provide a drive device for an electric vehicle that can eliminate a locked state of the motor and improve the start performance of the vehicle with a simple configuration.

The present invention solves the above-described problems by the following means.
The invention according to claim 1 is a motor as a driving power source, a power transmission mechanism that transmits a driving force of the motor to the first driving wheel and the second driving wheel, the first driving wheel, and the An electric vehicle drive device comprising: a clutch that restrains a differential from the second drive wheel; and an engagement control unit that controls an engagement force of the clutch, wherein the lock state detection unit detects a lock state of the motor. The engagement control means reduces the engagement force of the clutch until the lock state is released when the lock state is detected when the vehicle is requested to start, and then the engagement force of the clutch is reduced. An electric vehicle drive device characterized by being increased.
According to this, when the locked state occurs, the torque required for starting the motor can be reduced and the locked state can be canceled by reducing the engagement force of the clutch and causing one of the drive wheels to idle.
After that, by increasing the clutch engagement force, the torque of the motor and the inertia of the idling drive wheel (kinetic energy accumulated in the idling drive wheel) are transmitted to the non-idling drive wheel. Therefore, it is possible to easily start the vehicle by applying a large torque.
Such clutches can be used for driving force distribution control, differential limiting, etc., which are generally mounted on a vehicle drive device, and a new device is added to support motor lock. There is no need.

The invention according to claim 2 is characterized in that the electric vehicle is a four-wheeled vehicle, the first driving wheel is a front wheel, and the second driving wheel is a rear wheel. It is a drive device of this electric vehicle.
The invention according to claim 3 is characterized in that the driving force of the motor is always transmitted to one of the front wheel or the rear wheel, and the driving force of the motor is transmitted only when the clutch is engaged, to the other. The drive device for an electric vehicle according to claim 2.
According to a fourth aspect of the present invention, the power transmission mechanism includes a center differential that allows a differential between the front wheel and the rear wheel, and the clutch is a differential limiting mechanism that limits the differential of the center differential. The drive device for an electric vehicle according to claim 2, wherein the drive device is provided.
According to each of these inventions, the present invention can be easily applied to existing vehicles using the differential limiting mechanism of the AWD system.

The invention according to claim 5 includes output control means for controlling the output of the motor, wherein the output control means controls the torque of the motor in response to a driver request, and detects the lock state and controls the fastening. The means for increasing the torque of the motor with respect to the torque set according to the driver request when the means reduces the engagement force of the clutch. 2. A drive device for an electric vehicle according to item 1.
According to this, when the torque for the motor to escape from the locked state is insufficient due to a shortage of the accelerator pedal depression amount of the driver, the actual torque is increased with respect to the torque set according to the driver request. By performing the control, the escape from the locked state can be speeded up to prevent the device from overheating.

According to a sixth aspect of the present invention, there is provided a temperature detecting means for detecting or estimating at least one of the temperature of the motor and the temperature of the motor control unit, and at least one of the temperature of the motor and the temperature of the motor control unit. Output restriction control means for restricting the output of the motor when the output restriction temperature exceeds a predetermined value, and the fastening control means, after detecting the locked state, the temperature of the motor and the motor control The drive of the electric vehicle according to any one of claims 1 to 5, wherein a fastening force of the clutch is reduced before at least one of the temperature of the unit reaches the output limit temperature. Device.
According to this, it is possible to prevent the vehicle from starting more difficult due to the output limitation by releasing the locked state by controlling the clutch engaging force before the motor output limitation is started.

The invention according to claim 7 comprises friction coefficient estimating means for estimating the friction coefficient of the road surface,
The said fastening control means increases the fastening force of the said clutch after a locked state is cancelled | released according to the increase in the said friction coefficient, The any one of Claim 1-6 characterized by the above-mentioned. It is a drive device of an electric vehicle.
According to this, it is possible to suppress the slip of the drive wheel on the side where rotation starts due to the increase in clutch engagement force, and to start the vehicle stably.

The invention according to claim 8 is characterized in that the fastening control means slows the increasing speed of the fastening force of the clutch after the locked state is released in accordance with the increase in the rotational speed of the motor. The drive device for an electric vehicle according to any one of claims 1 to 7.
According to this, when the rotation speed of the motor is high, it is possible to prevent the vehicle from suddenly starting by suddenly engaging the clutch.

The invention according to claim 9 is characterized in that the engagement control means increases the engagement force of the clutch after the number of rotations of the motor becomes equal to or greater than a predetermined value after the locked state is eliminated. An electric vehicle driving apparatus according to any one of claims 1 to 8.
According to this, it is possible to prevent the driving force from being insufficient at the time of clutch engagement and falling into the locked state again.

The invention according to claim 10 is provided with a rotation speed control means for controlling the rotation speed of the motor when starting to increase the engagement force of the clutch so as to approach a predetermined target rotation speed after the locked state is eliminated. The drive device for an electric vehicle according to any one of claims 1 to 7, wherein the drive device is an electric vehicle.
According to this, it is possible to prevent the differential rotation from becoming large when the clutch is engaged and adversely affecting the durability of the clutch or the like.

According to an eleventh aspect of the present invention, when the engagement control unit detects that the vehicle does not start even if the engagement force of the clutch is increased after the locked state is released, the engagement force of the clutch is again applied. The electric power according to any one of claims 1 to 10, wherein the electric power is reduced until the locked state is released, and then the engagement force of the clutch is increased more rapidly than the previous increase in the engagement force. It is a drive device of a vehicle.
According to this, a greater driving force can be applied when it is difficult to start due to a road surface gradient or a wheel getting stuck in a groove.

  As described above, according to the present invention, it is possible to provide a drive device for an electric vehicle capable of eliminating the motor lock state and improving the start performance of the vehicle with a simple configuration.

It is a figure which shows the structure of the power train which has the Example of the drive device of the electric vehicle to which this invention is applied. It is a flowchart which shows operation | movement of the drive device of the electric vehicle of an Example. It is a figure which shows an example of transition of each parameter in the power train which has the drive device of the electric vehicle of an Example. FIG.

  An object of the present invention is to provide a drive device for an electric vehicle that can eliminate the motor lock state and improve the start performance of the vehicle with a simple configuration, and the front wheels are directly connected to the motor and the rear wheels are driven via a clutch. In the AWD electric vehicle, when there is a start request and the motor is in a locked state, the clutch engaging force is reduced to cause the front wheels to idle to release the locked state, and then the clutch is re-engaged to rotate the front wheel side rotating part. The problem was solved by transmitting the torque due to the inertia to the rear wheels together with the motor output torque to start the vehicle.

Embodiments of a drive device for an electric vehicle to which the present invention is applied will be described below.
The drive device for an electric vehicle according to the embodiment is provided, for example, in a four-wheeled electric vehicle (EV).
FIG. 1 is a diagram illustrating a configuration of a power train having a drive device for an electric vehicle according to an embodiment.

  As shown in FIG. 1, the drive device 1 includes a motor 10, a power transmission mechanism 20, a front differential 30, a rear differential 40, a clutch 50, a battery 60, an inverter 70, a motor control unit 80, an AWD control unit 90, and the like. Configured.

The motor 10 is used as a driving power source for a vehicle, and is configured as a motor generator having a function of performing regenerative power generation.
As the motor 10, for example, a permanent magnet (PM type) three-phase induction AC motor or a synchronous motor is used.
The motor 10 is provided with a temperature sensor 11 that detects a device temperature such as a motor main body and a drive circuit, and a rotation sensor 12 that detects the rotational speed of the rotor.
Outputs from the temperature sensor 11 and the rotation sensor 12 are transmitted to the motor control unit 80.

The power transmission mechanism 20 transmits the output of the motor 10 to the front differential 30 and the rear differential 40, respectively.
The power transmission mechanism 20 is provided with a speed reducer, a transmission, a damper, and the like as necessary.

The front differential 30 is provided at the center of the left and right front wheels, and transmits the driving force transmitted from the power transmission mechanism 20 to the left and right front wheels.
The front differential 30 includes a final reduction gear, a differential device that absorbs differential rotation between the left and right front wheels, and the like.
The front differential 30 is provided with a front wheel rotation sensor 31 that detects the rotation speed of the front wheel (front shaft).
The output of the front wheel rotation sensor 31 is transmitted to the AWD control unit 90.

The rear differential 40 is provided at the center of the left and right rear wheels, and transmits the driving force transmitted from the power transmission mechanism 20 to the left and right rear wheels.
The rear differential 40 includes a final reduction device, a differential device that absorbs differential rotation between the left and right rear wheels, and the like.
The rear differential 40 is provided with a rear wheel rotation sensor 41 that detects the rotation speed of the rear wheel (rear shaft).
The output of the rear wheel rotation sensor 41 is transmitted to the AWD control unit 90.

The clutch 50 is provided in a part of the mechanism that transmits the driving force from the power transmission mechanism 20 to the rear differential 40, and can cut the power transmission therebetween or adjust the transmitted driving force.
As the clutch 50, for example, a wet multi-plate clutch capable of continuously adjusting the crimping force electromagnetically or by hydraulic control can be used.

The battery 60 supplies driving power for the motor 10.
The battery 60 includes a secondary battery such as a lithium ion battery or a nickel metal hydride battery.
The battery 60 is charged by, for example, an external power source or regenerative power generation of the motor 10, and supplies the accumulated power to the inverter 70.

The inverter 70 converts the DC power supplied from the battery 60 into three-phase AC and supplies it to the U, V, and W phase coils of the motor 10 to drive the motor 10.
Inverter 70 drives motor 10 in accordance with a torque command value transmitted from motor control unit 80.

The motor control unit 80 comprehensively controls the motor 10 and its auxiliary machines.
The motor control unit 80 includes, for example, information processing means such as a CPU, storage means such as RAM and ROM, an input / output interface, a bus connecting these, and the like.
The motor control unit 80 sets a target output torque of the motor 10 based on a driver request torque set based on a driver input from an accelerator pedal (not shown) and a command from a cruise control control device, and sequentially generates torque command values. Is transmitted to the inverter 70.

The motor control unit 80 includes a current sensor 81 that detects a current value.
The motor control unit 80 is a device that limits the torque command value when the temperature of the switching element (IGBT) estimated from the output value of the current sensor 81 or the sensor value of the temperature sensor 11 is a high temperature equal to or higher than a predetermined value. Perform protection control.
Further, the motor control unit 80 has a lock state determination function for determining the lock state of the motor 10 when the rotation sensor 12 does not detect rotation even though the torque command value is output.

The AWD control unit 90 controls the restraining force and torque distribution of the front and rear wheels by controlling the clutch 50 and its accessories.
During normal travel, the AWD control unit 90 sets various parameters relating to the travel state of the vehicle such as vehicle speed, motor torque, estimated friction coefficient of the road surface, steering angle, brake braking force, yaw rate, and rotation speed of each drive wheel. Accordingly, AWD control for setting the engagement force of the clutch 50 is performed.
The AWD control unit 90 communicates with the motor control unit 80 via an in-vehicle LAN such as a CAN communication system, and performs cooperative control described below when the vehicle starts.

Next, the operation at the start of the drive device for the electric vehicle according to the embodiment will be described.
FIG. 2 is a flowchart illustrating the operation of the drive device for the electric vehicle according to the embodiment.
FIG. 3 is a diagram illustrating an example of transition of each parameter in the power train having the drive device for the electric vehicle according to the embodiment.
In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the required driving force, motor command torque, front wheel shaft rotation speed (proportional to motor rotation speed), rear wheel shaft rotation speed, device temperature, and motor in order from the top. The torque limit rate and the clutch engagement amount are shown.
The horizontal axis in FIG. 3 shows the corresponding steps in FIG. 2 (up to S08).
Hereinafter, the steps will be described step by step in FIG.

<Step S01: Vehicle start request determination>
The motor control unit 80 determines the presence or absence of a vehicle start request (intention that the driver intends to start the vehicle) based on the operation amount of the accelerator pedal or a command from the cruise control control device.
If there is a vehicle start request, the process proceeds to step S02, and if not, the process proceeds to step S11.

<Step S02: Required Driving Force Determination>
The motor control unit 80 compares the current torque command value with a preset threshold value, and determines whether or not the required driving force is greater than the driving force that rotates (idls) the front wheels.
The threshold value can be set based on, for example, the estimated friction coefficient (estimated μ) of the road surface estimated by the previous traveling and the ground contact load of the front wheels.
Various known methods can be used for the estimation of the friction coefficient. For example, the friction coefficient can be estimated based on a self-aligning torque during turning.
If the requested driving force is greater than the driving force causing the front wheels to idle, the process proceeds to step S03, and otherwise the process proceeds to step S11.

<Step S03: Motor Lock State Determination>
Based on the torque command value transmitted to the inverter 70 and the output of the rotation sensor 12, the motor control unit 80 determines whether or not the motor 10 is in a locked state that is difficult to start.
The lock state is determined by overheating the device and the temperature of the switching element estimated from the sensor value of the temperature sensor 11 or the sensor value of the current sensor 81 reaches a predetermined output limit temperature, and the output limit is started. It is preferable to establish it before the start, and to start the engagement force control of the clutch 50 described below at an early stage (before the torque of the motor 10 is limited).
If the motor is locked, the process proceeds to step S04, and otherwise the process proceeds to step S11.

<Step S04: Decreasing clutch engagement force>
The AWD control unit 90 lowers the fastening force of the clutch 50 from the fastening force set based on the normal AWD control, and substantially puts the clutch 50 in the disconnected state (released state).
As a result, the torque of the motor 10 is substantially transmitted only to the front wheels, and the front wheels are likely to idle.
At this time, the motor control unit 80 may increase the torque command value with respect to the driver request torque set in accordance with, for example, the accelerator operation so that the front wheels are more likely to idle.
Thereafter, the process proceeds to step S05.

<Step S05: Determination of front wheel rotation start>
The AWD control unit 90 determines whether or not the front wheel has started rotating (idling) based on the output of the front wheel rotation sensor 31.
If the front wheel has started rotating, the process proceeds to step S05, and if the front wheel has stopped, the process proceeds to step S11.

<Step S06: Road surface μ estimation and storage>
The AWD control unit 90 acquires the torque command value when the rotation of the front wheel is detected from the motor control unit 80, and estimates and stores the current road surface friction coefficient (μ) based on the torque command value.
Thereafter, the process proceeds to step S07.

<Step S07: Determination of Front Wheel Rotation Speed>
The AWD control unit 90 calculates the rotation speed of the front wheel based on the output of the front wheel rotation sensor 31, and determines whether or not the rotation speed of the front wheel is equal to or greater than a predetermined value.
If the rotation speed of the front wheels is equal to or higher than the predetermined value, the process proceeds to step S08, and otherwise, the process proceeds to step S11.

<Step S08: Increasing clutch engagement force>
The AWD control unit 90 linearly increases (re-engages) the engagement force of the clutch 50 to a predetermined target engagement force.
At this time, the target fastening force is set to be larger as the road surface μ stored in step S06 is higher.
Further, the time until the clutch 50 increases the fastening force from the substantially disengaged state and reaches the target reaching force is longer as the rotational speed of the motor 10 at the start of the fastening force increase is higher in order to prevent the rear wheel from slipping. The lower the road surface μ stored in step S06, the longer it is set.
Thereafter, the process proceeds to step S09.

<Step S09: Rear wheel rotation start determination>
The AWD control unit 90 determines whether or not the rear wheel has started rotating based on the output of the rear wheel rotation sensor 41.
If the rear wheel has started to rotate, the process proceeds to step S10, and if the rear wheel has stopped, the process proceeds to step S11.

<Step S10: Clutch engagement force normal control return>
The AWD control unit 90 returns the engagement force control of the clutch 50 to the AWD control for normal traveling.
Then, it progresses to step S11.

<Step S11: Determination of rear wheel rotation in normal fastening control>
Based on the output of the rear wheel rotation sensor 41, the AWD control unit 90 determines whether the rear wheel continues to rotate in the AWD control for normal traveling.
When the rear wheel is rotating, the series of processing is ended (returned), and when the rear wheel is stopped, the process proceeds to step S12.

<Step S12: Decreasing clutch engagement force>
The AWD control unit 90 lowers the fastening force of the clutch 50 from the fastening force set based on normal AWD control, and substantially puts the clutch 50 in a disconnected state.
Thereafter, the process proceeds to step S13.

<Step S13: Front Wheel Rotation Determination>
Based on the output of the front wheel rotation sensor 31, the AWD control unit 90 determines whether or not the front wheel is rotating at a speed equal to or higher than a predetermined value.
If the front wheel is rotating at a speed equal to or higher than the predetermined value, the process proceeds to step S14. Otherwise, the process returns to step S12 to repeat the subsequent processes.

<Step S14: Rapid increase in clutch engagement force>
The AWD control unit 90 linearly increases the engagement force of the clutch 50 to a predetermined target engagement force.
At this time, the time until the clutch 50 reaches the target reaching force from the substantially disengaged state is set to be shorter (faster increasing speed of the engaging force) than the first re-engagement in step S08, and the rear wheel is set to be short To transmit a larger torque.
Thereafter, the series of processing is terminated (returned).

According to the present embodiment described above, the following effects can be obtained.
(1) When the locked state of the motor 10 occurs, the locked state can be eliminated by reducing the fastening force of the clutch 50 and causing the front wheels to idle.
Thereafter, by increasing the engagement force of the clutch 50, the torque of the motor 10 and the torque caused by the inertia of the front wheel, its drive system parts (front differential 40, drive shaft, etc.), brake rotor, etc. (accumulated in the front wheel side rotating part) Transmitted kinetic energy) to the rear wheels, a large torque can be applied to the rear wheels and the vehicle can be started easily.
Such a clutch 50 can use what is generally mounted on the AWD transfer for driving force distribution control, differential limitation, etc., and it is necessary to add a new device to support the motor lock. There is no.
(2) The torque command value is set with respect to the torque command value set based on the driver request torque when the torque at which the motor 10 escapes from the locked state is insufficient due to the driver's accelerator pedal depression amount being insufficient. By controlling to increase the speed, the escape from the locked state can be speeded up and the device can be prevented from overheating.
(3) By setting the engagement force at the time of re-engagement of the clutch 50 based on the road surface μ estimated at the start of idling of the front wheels, the slip of the rear wheel at the time of re-engagement on the low μ road is suppressed, and the vehicle It is possible to start stably.
(4) When the rotational speed during idling of the front wheels is high, it is possible to prevent the vehicle from suddenly starting due to sudden engagement of the clutch by reducing the engagement force increasing speed at the time of clutch re-engagement.
(5) By re-engaging the clutch after the rotational speed of the front wheel becomes equal to or higher than a predetermined value, it is possible to prevent the torque transmitted to the rear wheel from being insufficient and falling into the locked state again.
(6) When the vehicle cannot start due to initial clutch release and re-engagement, rapid re-engagement of the clutch can apply a large torque to the rear wheels and improve the start performance.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configuration of the drive device for the electric vehicle is not limited to the configuration of the above-described embodiment, and can be changed as appropriate.
For example, in the embodiment, the front wheel is AWD directly connected to the motor and the rear wheel is driven via a clutch. However, the rear wheel side may be directly connected to the motor and the front wheel may be driven via a clutch.
Further, in a full-time AWD system having a center differential such as a planetary gear type or a bevel gear type, a differential limiting clutch that restricts the differential between the front wheel side output portion and the rear wheel side output portion of the center differential is a clutch of the embodiment. By controlling in the same manner as described above, substantially the same effect can be obtained.
Further, in a two-wheel drive vehicle, even in a clutch that restricts the differential of the left and right drive wheels, it is possible to cope with motor lock and improve startability by performing the same control as in the embodiment.
(2) Although the vehicle of the embodiment is a so-called pure EV, the present invention is not limited to this, and can be applied to a fuel cell vehicle and an engine electric hybrid vehicle having an EV travel mode.
(3) In the embodiment, the fastening force and the fastening speed at the time of re-engagement are changed according to the motor rotational speed at the time of reducing the clutch fastening force, but instead, the motor rotational speed is set to the target speed. It is good also as a structure controlled to become. According to this, it is possible to prevent the differential rotation at the time of re-engagement from becoming large and adversely affecting the durability of the clutch.

DESCRIPTION OF SYMBOLS 1 Drive apparatus 10 Motor 11 Temperature sensor 12 Rotation sensor 20 Power transmission mechanism 30 Front differential 31 Front wheel rotation sensor 40 Rear differential 41 Rear wheel rotation sensor 50 Clutch 60 Battery 70 Inverter 80 Motor control unit 81 Current sensor 90 AWD control unit

Claims (11)

A motor that is a driving power source;
A power transmission mechanism for transmitting the driving force of the motor to the first driving wheel and the second driving wheel;
A clutch for restraining a differential between the first drive wheel and the second drive wheel;
An electric vehicle drive device comprising: an engagement control means for controlling an engagement force of the clutch;
A lock state detecting means for detecting a lock state of the motor;
The engagement control means reduces the engagement force of the clutch until the lock state is released, and then increases the engagement force of the clutch when there is a request to start the vehicle and the lock state is detected. An electric vehicle drive device characterized by the above. The electric vehicle is a four-wheeled vehicle,
The first drive wheel is a front wheel;
The drive device for an electric vehicle according to claim 1, wherein the second drive wheel is a rear wheel. The electric power according to claim 2, wherein the driving force of the motor is constantly transmitted to one of the front wheel or the rear wheel, and the driving force of the motor is transmitted only when the clutch is engaged to the other. Vehicle drive device. The power transmission mechanism includes a center differential that allows differential between the front wheels and the rear wheels,
The drive device for an electric vehicle according to claim 2, wherein the clutch is provided in a differential limiting mechanism that limits the differential of the center differential.
Characterized by Comprising output control means for controlling the output of the motor;
The output control means controls the torque of the motor in response to a driver request. When the lock state is detected and the fastening control means reduces the fastening force of the clutch, the output control means sends the torque of the motor to the driver. The drive device for an electric vehicle according to any one of claims 1 to 4, wherein the torque is increased according to a request. Temperature detecting means for detecting or estimating at least one of the temperature of the motor and the temperature of the motor control unit;
An output limit control means for limiting the output of the motor when at least one of the temperature of the motor and the temperature of the motor control unit is equal to or higher than an output limit temperature of a predetermined value;
The engagement control means reduces the engagement force of the clutch after at least one of the temperature of the motor and the temperature of the motor control unit reaches the output limit temperature after the locked state is detected. The drive device for an electric vehicle according to any one of claims 1 to 5, wherein the drive device is an electric vehicle. Friction coefficient estimation means for estimating the friction coefficient of the road surface is provided,
The said fastening control means increases the fastening force of the said clutch after a locked state is cancelled | released according to the increase in the said friction coefficient. The one of the Claims 1-6 characterized by the above-mentioned. Drive device for electric vehicle. The engagement control means slows the increase speed of the engagement force of the clutch after the locked state is released in accordance with an increase in the number of rotations of the motor. The driving device for an electric vehicle according to claim 1. The engagement control means increases the engagement force of the clutch after the rotation state of the motor becomes equal to or higher than a predetermined value after the locked state is eliminated. The driving device for an electric vehicle according to claim 1. 2. A rotation speed control means for controlling the rotation speed of the motor when starting to increase the engagement force of the clutch after the locked state is released to approach a predetermined target rotation speed. The drive device for an electric vehicle according to any one of claims 1 to 7. When the engagement control unit detects that the vehicle does not start even if the clutch engagement force is increased after the lock state is released, the engagement control unit reduces the clutch engagement force again until the lock state is released. Then, the driving force of the electric vehicle according to any one of claims 1 to 10, wherein the fastening force of the clutch is increased more rapidly than when the previous fastening force was increased.

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