阅读说明：本技术 四轮驱动电动车辆的牵引控制装置和方法 (Traction control apparatus and method for four-wheel drive electric vehicle ) 是由 金贵哲 于 2020-09-29 设计创作，主要内容包括：本申请公开一种四轮驱动电动车辆的牵引控制装置和方法。当驱动轮打转时,控制驱动力以遏制驱动轮打转并确保启动性能和加速性能。该装置包括：第一马达,将驱动扭矩供应到四轮驱动电动车辆的主驱动轮；第二马达,将驱动扭矩供应到四轮驱动电动车辆的辅助驱动轮；分离器,设置在辅助驱动轮的车轴上,分离器选择性地将辅助驱动轮连接到第二马达,以控制辅助驱动轮和第二马达之间的动力传递；以及牵引控制器,控制第一马达和第二马达,其中在辅助驱动轮和第二马达通过分离器彼此连接的状态下,当在四轮驱动电动车辆行驶期间主驱动轮打转时,牵引控制器减小主驱动轮的驱动扭矩,并且与主驱动轮的驱动扭矩的减小量成比例地增加辅助驱动轮的驱动扭矩。(The application discloses a traction control device and method for a four-wheel drive electric vehicle. When the drive wheels spin, the drive force is controlled to suppress the spin of the drive wheels and ensure startability and acceleration performance. The device includes: a first motor supplying a driving torque to a main driving wheel of a four-wheel drive electric vehicle; a second motor supplying a driving torque to an auxiliary driving wheel of the four-wheel drive electric vehicle; a decoupler, disposed on the axle of the auxiliary drive wheel, selectively coupling the auxiliary drive wheel to the second motor to control power transfer between the auxiliary drive wheel and the second motor; and a traction controller controlling the first motor and the second motor, wherein the traction controller reduces a driving torque of the main driving wheels when the main driving wheels spin during running of the four-wheel drive electric vehicle in a state where the auxiliary driving wheels and the second motor are connected to each other through the decoupler, and increases the driving torque of the auxiliary driving wheels in proportion to an amount of reduction of the driving torque of the main driving wheels.)

1. A traction control device of a four-wheel drive electric vehicle, comprising:

a first motor that supplies a driving torque to main driving wheels of the four-wheel drive electric vehicle;

a second motor that supplies a driving torque to auxiliary driving wheels of the four-wheel drive electric vehicle;

a decoupler disposed on the axle of the auxiliary drive wheel, the decoupler selectively connecting the auxiliary drive wheel to the second motor to control power transfer between the auxiliary drive wheel and the second motor; and

a traction controller that controls the first motor and the second motor,

wherein the traction controller reduces the driving torque of the main driving wheels and increases the driving torque of the auxiliary driving wheels in proportion to an amount of reduction of the driving torque of the main driving wheels when the main driving wheels spin during running of the four-wheel drive electric vehicle in a state where the auxiliary driving wheels and the second motor are connected to each other through the separator.

2. The traction control device of claim 1,

in a state where the decoupler is disengaged, when the main drive wheels spin during running of the four-wheel drive electric vehicle, the traction controller reduces the drive torque of the main drive wheels and engages the decoupler so that the drive torque is supplied to the auxiliary drive wheels.

3. The traction control device of claim 2,

the traction controller controls the first motor to reduce the driving torque of the main driving wheel and controls the second motor to reduce the driving torque of the auxiliary driving wheel when the amount of spin of the main driving wheel after the engagement of the decoupler is equal to or greater than a predetermined first threshold level and the amount of spin of the auxiliary driving wheel is equal to or greater than a predetermined second threshold level.

4. The traction control device of claim 3,

the traction controller includes:

a brake controller that determines a first required torque of the first motor and a second required torque of the second motor; and

a motor controller that controls a torque of the first motor to achieve the first required torque and controls a torque of the second motor to achieve the second required torque.

5. The traction control device of claim 4,

when the amount of spin of the main drive wheels is less than the predetermined first threshold level and the amount of spin of the auxiliary drive wheels is less than the predetermined second threshold level after the decoupler is engaged, the brake controller notifies the motor controller that a command including information about the first required torque and the second required torque will not be sent to the motor controller.

6. The traction control device of claim 4,

when the brake controller detects that the main driving wheel is rotated, the motor controller controls the release to be switched to an engaged state.

7. The traction control device of claim 1,

the amount of increase in the drive torque of the auxiliary drive wheels is equal to or smaller than the amount of decrease in the drive torque of the main drive wheels.

8. The traction control device of claim 1,

the main drive wheel is a rear wheel and the auxiliary drive wheel is a front wheel.

9. A traction control method of a four-wheel drive electric vehicle, comprising:

determining, by a brake controller, whether a main driving wheel driven by a first motor is spun during running of the four-wheel drive electric vehicle;

reducing, by the brake controller, a torque of the first motor when it is determined that the main driving wheels spin, and determining whether the four-wheel drive electric vehicle is running in a two-wheel drive mode;

engaging a decoupler provided on an axle of auxiliary drive wheels so that the auxiliary drive wheels of the four-wheel drive electric vehicle are connected to a second motor to receive torque from the second motor when it is determined that the four-wheel drive electric vehicle is traveling in the two-wheel drive mode; and

when it is judged that the main driving wheel is spinning, the torque of the first motor is reduced by the brake controller, and the torque of the second motor is increased in proportion to the amount of reduction of the torque of the first motor.

10. The traction control method according to claim 9, further comprising:

controlling, by the brake controller, the first motor to reduce the torque of the main driving wheel and controlling the second motor to reduce the torque of the auxiliary driving wheel when it is determined that the amount of spin of the main driving wheel is equal to or greater than a predetermined first threshold level and the amount of spin of the auxiliary driving wheel is equal to or greater than a predetermined second threshold level after the engagement of the decoupler.

11. The traction control method according to claim 10,

a motor controller controls the first motor to achieve a first desired torque determined by the brake controller, and

the motor controller controls the second motor to achieve a second desired torque determined by the brake controller.

12. The traction control method according to claim 11, further comprising:

notifying, by the brake controller, the motor controller that a command including information on the first required torque and the second required torque will not be sent to the motor controller when the amount of spin of the main drive wheels is less than the predetermined first threshold level and the amount of spin of the auxiliary drive wheels is less than the predetermined second threshold level after the determination that the decoupler is engaged.

13. The traction control method according to claim 9,

an amount of increase in the torque of the second motor is equal to or less than an amount of decrease in the torque of the first motor.

14. The traction control method according to claim 9,

the main drive wheel is a rear wheel and the auxiliary drive wheel is a front wheel.

Technical Field

The present disclosure relates to a traction control apparatus and method of a four-wheel drive electric vehicle. More particularly, the present disclosure relates to a traction control apparatus and method for controlling driving force of driving wheels of a vehicle.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Generally, as one of systems for improving stability when a vehicle travels, there is a Traction Control System (TCS) that controls driving force when the vehicle rushes or suddenly accelerates, thereby preventing wheels of the vehicle from slipping or spinning.

Specifically, the TCS is a system for preventing a drive wheel from slipping or spinning when a vehicle is started or accelerated, thereby preventing poor traction of the vehicle and improving the starting performance and acceleration performance of the vehicle.

When the drive wheels of the vehicle slip or spin due to an excessive driving force of the vehicle at the time of vehicle startup or acceleration, the conventional TCS controls the speed of the drive wheels by reducing the driving force (driving torque) of the vehicle.

However, it has been found that when the TCS is operated during running of the vehicle, the driving force of the vehicle may be reduced, and thus the starting performance and the acceleration performance of the vehicle may be deteriorated. In particular, when the vehicle is running on an uphill slope, a reduction in the vehicle driving force due to the operation of the TCS and the resulting deterioration in the starting performance and the accelerating performance of the vehicle may cause serious problems, such as an accident.

Disclosure of Invention

The present disclosure provides a traction control apparatus and method of a four-wheel drive electric vehicle, which controls driving force in the case where driving wheels of the vehicle spin, thereby suppressing the driving wheels from spinning and ensuring starting performance and acceleration performance of the vehicle.

In one aspect of the present disclosure, a traction control apparatus of a four-wheel drive electric vehicle includes: a first motor configured to supply a driving torque to a main driving wheel of a four-wheel drive electric vehicle; a second motor configured to supply a driving torque to an auxiliary driving wheel of the electric vehicle; a decoupler (disconnect) provided on the axle of the auxiliary driving wheel, the decoupler being configured to connect the auxiliary driving wheel and the second motor to each other to allow power transmission between the auxiliary driving wheel and the second motor or disconnect the auxiliary driving wheel and the second motor from each other to interrupt power transmission between the auxiliary driving wheel and the second motor; and a traction controller configured to control the first motor and the second motor. In particular, when the main driving wheel is spun during the running of the electric vehicle in a state where the auxiliary driving wheel and the second motor are connected to each other through the decoupler, the traction controller reduces the driving torque of the main driving wheel and increases the driving torque of the auxiliary driving wheel in proportion to the amount of reduction of the driving torque of the main driving wheel.

In one form, in a disengaged state of the decoupler, the traction controller may reduce a drive torque of the main drive wheel when the main drive wheel is spun up during travel of the electric vehicle, and may engage the decoupler such that the drive torque is supplied to the auxiliary drive wheel.

In another form, the traction controller may control the first motor to reduce the driving torque of the main driving wheel and may control the second motor to reduce the driving torque of the auxiliary driving wheel when a revolution amount of the main driving wheel after the engagement of the decoupler is equal to or greater than a predetermined first threshold level and a revolution amount of the auxiliary driving wheel is equal to or greater than a predetermined second threshold level.

In another form, the traction controller may include: a brake controller configured to determine a required torque of the first motor (first required torque) and a required torque of the second motor (second required torque); and a motor controller configured to control a torque of the first motor to achieve the first required torque and to control a torque of the second motor to achieve the second required torque.

In another form, when the amount of spin of the main drive wheels is less than a first threshold level and the amount of spin of the auxiliary drive wheels is less than a second threshold level after the decoupler is engaged, the brake controller may notify the motor controller that a command including information about the first required torque and the second required torque will not be sent to the motor controller.

In another aspect of the present disclosure, a traction control method of a four-wheel drive electric vehicle includes: determining, by a brake controller, whether a main driving wheel driven by a first motor is spun during running of the four-wheel drive electric vehicle; reducing a torque of the first motor by the brake controller when it is judged that the main driving wheel is spun, and judging whether the electric vehicle is running in the two-wheel drive mode; engaging a decoupler provided on an axle of the auxiliary drive wheel so that the auxiliary drive wheel is connected to the second motor to receive torque from the second motor when it is determined that the electric vehicle is traveling in the two-wheel drive mode; and reducing, by the brake controller, the torque of the first motor and increasing the torque of the second motor in proportion to the reduction amount of the torque of the first motor when it is judged that the main driving wheel of the main driving wheel and the auxiliary driving wheel is spun.

In one form, the traction control method may further comprise: when it is determined that the amount of spin of the main drive wheels is equal to or greater than a predetermined first threshold level and the amount of spin of the auxiliary drive wheels is equal to or greater than a predetermined second threshold level after the engagement of the decoupler, the first motor is controlled by the brake controller to reduce the drive torque of the main drive wheels, and the second motor is controlled to reduce the drive torque of the auxiliary drive wheels. In this case, the motor controller may control the first motor to achieve the first required torque determined by the brake controller, and the motor controller may control the second motor to achieve the second required torque determined by the brake controller.

It is understood that the term "vehicle" or "vehicular" or other similar terms as used herein generally includes motor vehicles, such as passenger vehicles including Sport Utility Vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including various boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles, and other alternative fuel (e.g., derived fuel from resources other than petroleum) vehicles. As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as a gasoline and electric hybrid vehicle.

The following discusses the above and other features of the present disclosure.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

In order that the disclosure may be well understood, various forms thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 is a diagram showing a decoupler of a four wheel drive electric vehicle;

fig. 2 is a diagram showing a four-wheel drive electric vehicle based on rear-wheel drive;

fig. 3 is a diagram showing a four-wheel drive electric vehicle based on rear-wheel drive when a front decoupler is in an engaged state;

fig. 4 is a diagram showing a traction control apparatus;

fig. 5 is a view showing a connection structure between the rear motor and the rear wheel; and

fig. 6 is a flowchart illustrating a traction control method.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

In the following, reference will now be made in detail to exemplary forms of the present disclosure, examples of which are illustrated in the accompanying drawings.

It should be understood that the drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the disclosure. The specific design features of the present disclosure, including specific dimensions, orientations, locations, and shapes for example, as disclosed herein will be determined in part by the particular intended application and use environment.

In general, when a four-wheel drive electric vehicle travels in a two-wheel drive mode in which main drive wheels are driven and auxiliary drive wheels are not driven, reverse drive force is transmitted to a speed reducer through the auxiliary drive wheels, and thus a loss of resistance occurs.

Referring to fig. 1 and 2, the four-wheel drive electric vehicle is configured such that a decoupler 7 is provided on a front axle 82 to prevent reverse driving force from being transmitted to a front speed reducer 52 through front wheels 2, thereby suppressing or preventing resistance loss from occurring.

The separator 7 may be a dog clutch type separator. Front retarder 52 may be connected to front axle 82 through front differential gear 62.

As shown in fig. 2, the four-wheel drive electric vehicle may include a front motor 4 for driving the front wheels 2 and a rear motor 3 for driving the rear wheels 1. When the four-wheel drive electric vehicle employs a four-wheel drive system based on rear-wheel drive, the decoupler 7 may be mounted on the front axle 82.

When the decoupler 7 is in the engaged state, the vehicle travels in the four-wheel drive mode, and when the decoupler 7 is in the disengaged state, the vehicle travels in the two-wheel drive mode. The engaged state of the decoupler 7 is a state in which power transmission is permitted, and the disengaged state of the decoupler 7 is a state in which power transmission is interrupted.

In one form of the present disclosure, when the drive wheels spin while a four-wheel drive electric vehicle based on rear-wheel drive is running, the traction control device controls the drive torque of the drive wheels so as to restrain the drive wheels from spinning, thus ensuring the starting performance and the acceleration performance of the vehicle.

To this end, during operation of a Traction Control System (TCS) for suppressing spin-up of wheels, a traction control device performs traction control without causing a reduction in total driving torque, which is the sum of driving torque of front wheels and driving torque of rear wheels, or while minimizing the reduction in total driving torque.

The operations of a method or algorithm described in connection with the forms disclosed herein may be embodied directly in hardware (e.g., a processor) or in a software module executed by a processor, or in a combination of hardware and software modules. A software module may reside on a storage medium (i.e., memory and/or storage device) such as RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disk, a removable disk, a CD-ROM.

During operation of the TCS, traction control may be performed to control the driving force (driving torque) of the vehicle at the time of vehicle take-off or acceleration, thereby suppressing or preventing the driving wheels from slipping or spinning.

As shown in fig. 2 and 3, in the case of a four-wheel drive electric vehicle based on rear-wheel drive, the rear wheels 1 are main drive wheels, and the front wheels 2 are auxiliary drive wheels.

The four-wheel drive electric vehicle includes a front motor 4 for driving the front wheels 2 and a rear motor 3 for driving the rear wheels 1. The rear motor 3 may be referred to as a first motor, and the front motor 4 may be referred to as a second motor.

Referring to fig. 4, under the command of the brake controller 91, the front motor 4 and the rear motor 3 operate to achieve a required torque. When the drive wheels spin during running of the vehicle, the brake controller 91 calculates and determines an optimum required torque for suppressing the spin of the wheels, and sends a command including information on the required torque to the motor controller 92.

The brake controller 91 may determine the required torque of the front motor 4 and the required torque of the rear motor 3, respectively, and may send a command including information on the required torque of the front motor 4 and a command including information on the required torque of the rear motor 3 to the motor controller 92.

The Brake controller 91 is a controller that controls the overall operation of an Integrated Electric Brake (IEB) provided in the vehicle, and the IEB is a braking device configured to generate braking force to Brake the drive wheels.

The motor controller 92 is a controller that controls the overall operation of the front motor 4 and the rear motor 3. The motor controller 92 may be referred to as a Vehicle Control Unit (VCU) that controls a driving source of the vehicle.

The motor controller 92 controls the front motor 4 and the rear motor 3 to achieve the respective required torques of the front motor 4 and the rear motor 3.

The front motor 4 is configured to generate a driving torque supplied to the front wheels 2. That is, the front motor 4 generates torque for driving the front wheels 2 and supplies the torque to the front wheels 2. To this end, the front motor 4 is connected to the front axle 82 through the front reduction gear 52 and the front differential gear 62, and is connected to the front wheels 2 through the front axle 81.

As shown in fig. 1 to 3, the decoupler 7 is mounted on the front axle 82 to control the power transmission between the front motor 4 and the front wheel 2. When the decoupler 7 is in the engaged state, the torque of the front motor 4 is transmitted to the front wheels 2, but when the decoupler 7 is in the disengaged state, the transmission of the torque of the front motor 4 to the front wheels 2 is interrupted. In other words, the decoupler 7 may connect the front wheel 2 and the front motor 4 to each other to allow power transmission between the front wheel 2 and the front motor 4, or may disconnect the front wheel 2 and the front motor 4 from each other to interrupt power transmission between the front wheel 2 and the front motor 4.

As shown in fig. 3 and 5, the rear motor 3 is configured to generate a driving torque supplied to the rear wheel 1. That is, the rear motor 3 generates torque for driving the rear wheels 1 and supplies the torque to the rear wheels 1. For this purpose, the rear motor 3 is connected to the rear axle 81 through the rear speed reducer 51 and the rear differential gear 61, and is connected to the rear wheels 1 through the rear axle 81. No decoupler is mounted on the rear axle 81.

When the wheel spin occurs, the driving torque of the rear wheels 1 and the driving torque of the front wheels 2 can be controlled according to the command of the brake controller 91.

For example, the brake controller 91 may request a decrease in the drive torque supplied from the rear motor 3 to the rear wheels 1 based on the amount of turning of the rear wheels 1, and may request an increase in the drive torque supplied from the front motor 4 to the front wheels 2 based on the amount of decrease in the drive torque of the rear motor 3. In addition, the brake controller 91 may request a reduction in the drive torque supplied from the front motor 4 to the front wheels 2 based on the amount of rotation of the front wheels 2.

The brake controller 91 can control the torque of the front motor 4 and the torque of the rear motor 3 through the motor controller 92. In other words, the brake controller 91 may request the motor controller 92 to control the torque of the front motor 4 and the torque of the rear motor 3.

When only the rear wheel 1 of the front and rear wheels 2 and 1 is spun at a predetermined threshold speed or a speed higher than the predetermined threshold speed during running of the vehicle, the brake controller 91 requests the motor controller 92 to reduce the driving torque of the rear wheel 1 and increase the driving torque of the front wheel 2 in proportion to the reduction amount of the driving torque of the rear wheel 1. The threshold speed may be preset by experiment.

In other words, when only the rear wheels 1 are spinning at the threshold speed or higher, the motor controller 92 decreases the current torque of the rear motor 3 according to the request of the brake controller 91 and increases the current torque of the front motor 4 in proportion to the amount of decrease in the torque of the rear motor 3. In this case, the amount of reduction in the torque of the rear motor 3 may be determined based on the amount of revolution of the rear wheels 1.

In this way, since the driving torque of the front wheels 2 is increased in proportion to the amount of reduction in the driving torque of the rear wheels 1, it is possible to prevent or minimize the reduction in the total driving torque, which is the sum of the driving torque of the rear wheels 1 and the driving torque of the front wheels 2. Therefore, in the case where the drive wheels slip or spin, it is possible to ensure the running stability of the vehicle and prevent or minimize the deterioration of the starting performance and the accelerating performance of the vehicle.

The amount of increase in the drive torque of the front wheels 2 may be set equal to the amount of decrease in the drive torque of the rear wheels 1, or may be set smaller than the amount of decrease in the drive torque of the rear wheels 1. That is, the amount of increase in the drive torque of the front wheels 2 may be equal to or less than the amount of decrease in the drive torque of the rear wheels 1.

The amount of increase in the driving torque of the front wheels 2 may have a predetermined ratio with respect to the amount of decrease in the driving torque of the rear wheels 1. In this case, the ratio of the amount of increase in the driving torque of the front wheels 2 to the amount of decrease in the driving torque of the rear wheels 1 may be set in advance through experiments.

The brake controller 91 may determine the amount of reduction in the drive torque of the rear wheels 1 based on the amount of cranking of the rear wheels 1. That is, the brake controller 91 may determine the required torque of the rear motor 3 based on the amount of rotation of the rear wheels 1, the vehicle speed, and the like. The brake controller 91 may determine the required torque of the rear motor 3 as a value obtained by subtracting the reduction amount of the driving torque of the rear wheels 1 from the current driving torque of the rear wheels 1. That is, when the rear wheels 1 spin, the required torque of the rear motor 3 may be determined as a value obtained by subtracting a reduction amount of the driving torque of the rear wheels 1, which is determined based on the spin amount of the rear wheels 1, from the current driving torque of the rear wheels 1. The current driving torque may be determined based on the current vehicle speed, or the like.

The motor controller 92 controls the output torque of the rear motor 3 to achieve the required torque. The motor controller 92 may control the output torque of the rear motor 3 in a feedback control manner.

When the driving wheel spin is detected during the vehicle running in the two-wheel drive mode, the brake controller 91 requests the motor controller 92 to engage the decoupler 7.

The brake controller 91 determines that the drive wheels spin when the wheel speed of the drive wheels, which is calculated based on the wheel speed of the front wheels 2 and the wheel speed of the rear wheels 1, is greater than the vehicle speed by a predetermined level or more. The amount of rotation of the drive wheels may be calculated based on a difference between the vehicle speed and the wheel speed of the drive wheels. The wheel speed of each wheel may be detected by the wheel speed sensor 10.

The motor controller 92 controls the release 7 to be switched to the engaged state according to a request of the brake controller 91, and then sends a signal including information on the engaged state of the release 7 to the brake controller 91. When the engagement of the decoupler 7 is completed, the drive mode of the vehicle is switched from the two-wheel drive mode to the four-wheel drive mode.

When the engagement of the decoupler 7 is completed, the brake controller 91 calculates the required torque of the front motor 4 and the required torque of the rear motor 3 separately, and requests the motor controller 92 to achieve the required torques. In this case, the required torque of the rear motor 3 may be referred to as a first required torque, and the required torque of the front motor 4 may be referred to as a second required torque.

In addition, upon determining that both the front wheels 2 and the rear wheels 1 are spinning, the brake controller 91 may request the motor controller 92 to reduce the torque of the front motor 4 and the torque of the rear motor 3 individually.

In other words, when the amount of revolution of the front wheels 2 is equal to or greater than the front wheel threshold level and the amount of revolution of the rear wheels 1 is equal to or greater than the rear wheel threshold level, the brake controller 91 may request the motor controller 92 to achieve the required torque of the front motor 4 and the required torque of the rear motor 3 separately. The motor controller 92 controls the output torque of the front motor 4 and the output torque of the rear motor 3 in accordance with the request of the brake controller 91 to achieve the required torque of the front motor 4 and the required torque of the rear motor 3.

Here, the rear wheel threshold level and the front wheel threshold level may be set in advance by experiment or the like. The rear wheel threshold level and the front wheel threshold level may be set different from each other. The rear wheel threshold level may be referred to as a first threshold level and the front wheel threshold level may be referred to as a second threshold level.

The required torque of the front motor 4 and the required torque of the rear motor 3 may be set differently from each other. The amount of reduction in the torque of the front motor 4 and the amount of reduction in the torque of the rear motor 3 can be optimized by independently controlling the output torque of the front motor 4 and the output torque of the rear motor 3, respectively, and therefore, deterioration of the starting performance and the accelerating performance of the vehicle can be minimized.

After the engagement of the decoupler 7, when the amount of racing of the rear wheels 1 becomes smaller than the rear wheel threshold level and the amount of racing of the front wheels 2 becomes smaller than the front wheel threshold level, the brake controller 91 terminates the traction control for restraining the drive wheels from racing.

When the traction control is executed, the motor controller 92 controls the torque of the front motor 4 and the torque of the rear motor 3 in accordance with the request of the brake controller 91. When the traction control is ended, the motor controller 92 controls the front motor 4 and the rear motor 3 based on vehicle running state information including vehicle speed information. That is, when the traction control is ended, the vehicle runs in the normal drive mode.

When the traction control is terminated, the brake controller 91 sends a signal indicating termination of the traction control to the motor controller 92. That is, when the traction control is terminated, the brake controller 91 notifies the motor controller 92 that a command including information on the required torque of the motor will not be sent to the motor controller 92. Upon sensing that a command including information on the required torque is no longer sent from the brake controller 91, the motor controller 92 controls the front motor 4 and the rear motor 3 based on the vehicle running state information.

Here, the brake controller 91 and the motor controller 92 may constitute a traction controller 9 for performing traction control. In other words, the traction controller 9 may include a brake controller 91 and a motor controller 92. When the drive wheels spin during running of the vehicle, the traction controller 9 performs traction control for suppressing the spin of the wheels by controlling the operation of the front motor 4 and the operation of the rear motor 3.

Hereinafter, a traction control process for suppressing the spin of the wheels of the four-wheel drive electric vehicle will be described with reference to fig. 6.

Referring to fig. 6, during normal running of the vehicle, it is determined whether the rear wheel 1 is spinning through real-time monitoring. The brake controller 91 judges that the rear wheel 1 is spun when the spin amount of the rear wheel 1 is equal to or greater than a predetermined rear wheel threshold level "X", and the brake controller 91 judges that the rear wheel 1 is not spun when the spin amount of the rear wheel 1 is less than the rear wheel threshold level "X". During normal running of the vehicle, the traction control is not executed.

Upon determining that the rear wheel 1 is spinning, the brake controller 91 requests the motor controller 92 to reduce the torque of the rear motor 3. That is, upon determining that the amount of spin of the rear wheels 1 is equal to or greater than the rear wheel threshold level "X", the brake controller 91 sends a command including information on the required torque of the rear motor 3 and traction control start information to the motor controller 92 to first reduce the driving torque of the rear wheels 1.

Subsequently, the brake controller 91 determines whether the vehicle is running in the two-wheel drive mode. The brake controller 91 may determine the driving mode of the vehicle based on the information on the state of the separator 7 received from the motor controller 92. When the release 7 is in the release state, the brake controller 91 determines that the drive mode of the vehicle is the two-wheel drive mode. When the vehicle is running in the two-wheel drive mode, the brake controller 91 requests the motor controller 92 to engage the decoupler 7.

The motor controller 92 controls the release 7 to be switched to the engaged state according to the request of the brake controller 91. When the engagement of the separator 7 is completed, the motor controller 92 sends a signal including information on the engagement state of the separator 7 to the brake controller 91. When the engagement of the decoupler 7 is completed, the drive mode of the vehicle is switched from the two-wheel drive mode to the four-wheel drive mode.

When the engagement of the decoupler 7 is completed, the brake controller 91 requests the motor controller 92 to control the front motor 4 and the rear motor 3 individually based on the amount of revolution of the rear wheels 1 and the amount of revolution of the front wheels 2.

When the amount of rotation of the rear wheels 1 is still equal to or greater than the rear wheel threshold level "X" after the engagement of the decoupler 7, the brake controller 91 reduces the driving torque of the rear wheels 1 again through the motor controller 92. In this case, when the amount of spin of the front wheels 2 is less than the predetermined front wheel threshold level "Y", the brake controller 91 increases the driving torque of the front wheels 2 based on the amount of decrease in the driving torque of the rear wheels 1.

In other words, after the decoupler 7 is engaged, when the amount of spin of the rear wheels 1 is equal to or greater than the rear wheel threshold level "X" and the amount of spin of the front wheels 2 is less than the front wheel threshold level "Y", the brake controller 91 requests the motor controller 92 to reduce the driving torque of the rear wheels 1 and increase the driving torque of the front wheels 2. For this purpose, the brake controller 91 sends a command including information on the required torque of the front motor 4 and the required torque of the rear motor 3 to the motor controller 92.

In this case, the amount of increase in the driving torque of the front wheels 2 may be set in proportion to the amount of decrease in the driving torque of the rear wheels 1. That is, the amount of increase in the driving torque of the front wheels 2 may have a predetermined ratio with respect to the amount of decrease in the driving torque of the rear wheels 1. The amount of increase in the drive torque of the front wheels 2 may be set to a level equal to or less than the amount of decrease in the drive torque of the rear wheels 1.

In addition, after the decoupler 7 is engaged, when the amount of spin of the rear wheels 1 is equal to or greater than the rear wheel threshold level "X" and the amount of spin of the front wheels 2 is equal to or greater than the front wheel threshold level "Y", the brake controller 91 requests the motor controller 92 to reduce the driving torque of the rear wheels 1 and the driving torque of the front wheels 2.

In this case, the amount of reduction in the drive torque of the rear wheels 1 and the amount of reduction in the drive torque of the front wheels 2 may be individually determined based on the amount of spin of the rear wheels 1 and the amount of spin of the front wheels 2.

In addition, after the decoupler 7 is engaged, when the amount of spin of the rear wheels 1 is less than the rear wheel threshold level "X" and the amount of spin of the front wheels 2 is less than the front wheel threshold level "Y", the brake controller 91 terminates the traction control and sends a signal including traction control termination information to the motor controller 92.

When the traction control is terminated, the vehicle runs in the normal drive mode.

As is apparent from the above description, the traction control apparatus according to the exemplary form of the present disclosure has the following effects.

First, when wheel spin occurs during vehicle travel, the torque of the front motor and the torque of the rear motor are separately controlled, thereby ensuring the starting performance and the acceleration performance of the vehicle on a low-friction road or slope.

Second, when only the main driving wheels are spun up, the driving torque of the auxiliary driving wheels is increased in proportion to the amount of reduction in the driving torque of the main driving wheels, thereby preventing or minimizing the reduction in the total driving torque of the vehicle and thus ensuring the starting performance and the accelerating performance of the vehicle.

Third, when the main driving wheels spin in the two-wheel drive mode, the decoupler is engaged so that the drive mode of the vehicle is converted into the four-wheel drive mode, thereby restraining the main driving wheels from spinning and improving the running stability of the vehicle.

The present disclosure has been described in detail with reference to exemplary forms thereof. However, it will be appreciated by those skilled in the art that changes could be made in these forms without departing from the principles and concepts of the disclosure.