阅读说明：本技术 用于控制电动四轮驱动车辆的驱动的装置和方法 (Apparatus and method for controlling drive of electric four-wheel drive vehicle ) 是由 许志旭 于 2020-08-19 设计创作，主要内容包括：一种用于控制车辆的电动四轮驱动E-4WD的装置,包括：用于前轮的第一动力传动系,其中第一动力传动系包括发动机和前轮电动机；以及用于后轮的第二动力传动系,其中第二动力传动系包括后轮电动机。该装置根据车辆的驾驶员需求功率,提供后轮电动机驱动模式、前轮电动机驱动模式、驱动前轮电动机和后轮电动机这两者的组合驱动模式以及发动机-开启模式,从而提高车辆的燃料效率。(An apparatus for controlling an electric four-wheel drive (E-4WD) of a vehicle, comprising: a first power train for front wheels, wherein the first power train includes an engine and a front wheel motor; and a second power train for the rear wheels, wherein the second power train includes a rear wheel motor. The apparatus provides a rear wheel motor driving mode, a front wheel motor driving mode, a combined driving mode for driving both a front wheel motor and a rear wheel motor, and an engine-on mode according to power required by a driver of a vehicle, thereby improving fuel efficiency of the vehicle.)

1. An apparatus for controlling electric four-wheel drive of a vehicle, the apparatus comprising:

a first drive train for the front wheels,

wherein the first power train includes:

an engine, a front wheel motor, an engine clutch disposed between the engine and the front wheel motor and configured to selectively transmit power of the engine, an

A transmission configured to shift power of the engine and power of the front wheel motor and output the shifted power to the front wheels;

a second power train for the rear wheels,

wherein the second power train includes:

a rear wheel motor, and

a decelerator configured to decelerate power of the rear wheel motor and output the decelerated power to the rear wheel;

a battery connected to the front wheel motor and the rear wheel motor; and

a controller configured to:

selectively operating the front wheel motor or the rear wheel motor when a driver-demanded power of the vehicle is less than a sum of an available power from the front wheel motor and an available power from the rear wheel motor,

additionally operating the rear wheel motor or the front wheel motor when a driver-demanded power of the vehicle is greater than an available power of the front wheel motor or an available power of the rear wheel motor during operation of the front wheel motor or the rear wheel motor, and

operating the engine when the driver-demanded power is greater than a sum of available power from the front wheel motor and the rear wheel motor.

2. The apparatus of claim 1, wherein when the driver demanded power is less than a difference between a sum of the available power and a factor of each state of charge of the battery, the controller is configured to selectively operate the rear wheel motor or the front wheel motor to operate the vehicle in an electric vehicle mode.

3. The apparatus of claim 1, wherein,

the controller is configured to determine whether to operate the front wheel motor or the rear wheel motor based on power transmission efficiency of the front wheel motor and the rear wheel motor when the front wheel motor or the rear wheel motor is selectively operated;

the power transmission efficiency of the front wheel motor is the power transmission efficiency when the power of the front wheel motor is output to the front wheels through the transmission, and is determined by the operating efficiency of the transmission; and

the power transmission efficiency of the rear wheel motor is the power transmission efficiency when the power of the rear wheel motor is output to the rear wheels through the reduction gear, and is determined by the operating efficiency of the reduction gear.

4. The apparatus of claim 3, wherein:

comparing the available power of the front wheel motor multiplied by the operation efficiency of the transmission with the available power of the rear wheel motor multiplied by the operation efficiency of the decelerator, when determining whether to operate the front wheel motor or the rear wheel motor; and is

When the available power of the rear wheel motor multiplied by the operating efficiency of the speed reducer is larger than the available power of the front wheel motor multiplied by the operating efficiency of the transmission, the controller is configured to operate only the rear wheel motor so that the vehicle operates in an electric vehicle mode.

5. The apparatus of claim 3, wherein,

comparing the available power of the front wheel motor multiplied by the operation efficiency of the transmission with the available power of the rear wheel motor multiplied by the operation efficiency of the decelerator, when determining whether to operate the front wheel motor or the rear wheel motor; and is

When the available power of the front wheel motor multiplied by the operating efficiency of the transmission is greater than the available power of the rear wheel motor multiplied by the operating efficiency of the reduction gear, the controller is configured to operate only the front wheel motor to operate the vehicle in an electric vehicle mode.

6. The apparatus of claim 1, wherein, when the initial acceleration of the vehicle is performed only by the rear wheel motor, the controller is configured to:

driving the front wheel motor when a difference between the speed of the rear wheels and the speed of the front wheels is greater than a maximum reference value a, and

increasing the driving ratio of the front wheel motor to the rear wheel motor by a predetermined unit value for a predetermined interval until a difference between the speed of the rear wheel and the speed of the front wheel is reduced to be less than a minimum reference value β, and

when the difference between the speed of the rear wheels and the speed of the front wheels is determined to be less than the minimum reference value β, the controller is configured to increase the driving ratio of the rear wheel motor to the front wheel motor by a predetermined unit value for a predetermined interval.

7. The apparatus of claim 1, wherein:

when the difference between the speed of the rear wheels driven only by the rear wheel motor and the speed of the front wheels is less than a maximum reference value a, and the driver-demanded power is greater than the available power of the rear wheel motor, the controller is further configured to operate the front wheel motor together with the rear wheel motor; and is

The controller is further configured to operate the rear wheel motor together with the front wheel motor when the driver-demanded power is greater than the available power of the front wheel motor during driving of only the front wheel motor.

8. The apparatus of claim 1, wherein when the driver demanded power of the vehicle is greater than a difference between the sum of the available power and a factor of each state of charge of the battery, the controller is configured to operate the engine and operate the vehicle in a hybrid electric vehicle mode.

9. The apparatus of claim 8, wherein,

the controller is configured to compare the driver-demanded power with an optimum engine power at which the engine is driven at an optimum engine operating point;

when the driver-demanded power is less than the optimum engine power, the front-wheel motor is configured to generate power to charge the battery;

the controller is configured to compare the driver-demanded power with the optimum engine power at the time of driving the engine at the optimum engine operating point; and is

When the driver-demanded power is larger than the optimum engine power, the rear-wheel motor is driven as an auxiliary power source.

10. The apparatus according to claim 8, wherein when the driver-demanded power is larger than a sum of the optimum engine power and an available power of the rear wheel motor, the controller is configured to drive the front wheel motor such that the front wheel motor is used as a travel power source in addition to the rear wheel motor.

11. A method of controlling electric four-wheel drive of a vehicle having a first driveline for front wheels, a second driveline for rear wheels and a battery, wherein the first driveline comprises: an engine, a front wheel motor, an engine clutch disposed between the engine and the front wheel motor, and a transmission that shifts power of the engine and power of the front wheel motor and outputs the shifted power to the front wheels, and the second power train includes: a rear wheel motor and a speed reducer that decelerates power of the rear wheels and outputs the decelerated power to the rear wheels, the method including:

selectively driving, by a controller, the front wheel motor or the rear wheel motor based on power transmission efficiency of the front wheel motor and the rear wheel motor when a driver-demanded power of the vehicle is less than a sum of an available power from the front wheel motor and an available power from the rear wheel motor;

driving the front wheel motor and the rear wheel motor together by the controller when a driver-demanded power is greater than an available power of the front wheel motor or an available power of the rear wheel motor during driving of the front wheel motor or the rear wheel motor; and

driving the engine by the controller when the driver-demanded power is greater than the sum of the available powers.

12. The method according to claim 11, wherein, in selectively driving the front wheel motor or the rear wheel motor, when the driver required power is smaller than a difference between a sum of the available electric powers and a factor of each state of charge of the battery, the rear wheel motor or the front wheel motor is selectively driven to cause the vehicle to run in an electric vehicle mode.

13. The method of claim 11, wherein,

the power transmission efficiency of the front wheel motor is the power transmission efficiency when the power of the front wheel motor is output to the front wheels through the transmission, and is determined by the operating efficiency of the transmission; and is

The power transmission efficiency of the rear wheel motor is the power transmission efficiency when the power of the rear wheel motor is output to the rear wheels through the reduction gear, and is determined by the operating efficiency of the reduction gear.

14. The method according to claim 13, wherein in determining whether to operate the front wheel motor or the rear wheel motor, the available power of the front wheel motor multiplied by the operating efficiency of the transmission is compared with the available power of the rear wheel motor multiplied by the operating efficiency of the reduction gear; and is

Wherein when the available power of the rear wheel motor multiplied by the operating efficiency of the speed reducer is greater than the available power of the front wheel motor multiplied by the operating efficiency of the transmission, only the rear wheel motor is driven to operate the vehicle in an electric vehicle mode.

15. The method according to claim 13, wherein in determining whether to operate the front wheel motor or the rear wheel motor, the available power of the front wheel motor multiplied by the operation efficiency of the transmission is compared with the available power of the rear wheel motor multiplied by the operation efficiency of the reduction gear; and is

Wherein when the available power of the front wheel motor multiplied by the operating efficiency of the transmission is greater than the available power of the rear wheel motor multiplied by the operating efficiency of the reduction gear, only the front wheel motor is driven to operate the vehicle in an electric vehicle mode.

16. The method of claim 11, wherein:

driving the front wheel motor when a difference between a speed of the rear wheel and a speed of the front wheel is greater than a maximum reference value a when initial acceleration of the vehicle is performed by the rear wheel motor, and increasing a driving ratio of the front wheel motor to the rear wheel motor by a predetermined unit value for a predetermined interval until the difference between the speed of the rear wheel and the speed of the front wheel decreases to be less than a minimum reference value β; and is

Reversely increasing the driving ratio of the rear wheel motor to the front wheel motor by a predetermined unit value for a predetermined period of time when the difference between the speed of the rear wheel and the speed of the front wheel is less than a minimum reference value β.

17. The method of claim 11, wherein,

driving the front wheel motor together with the rear wheel motor when a difference between the speed of the rear wheel and the speed of the front wheel is less than a maximum reference value a due to driving only the rear wheel motor and when the driver-demanded power is greater than an available power of the rear wheel motor; and is

Driving the rear wheel motor together with the front wheel motor when the driver's required power is greater than the available power of the front wheel motor.

18. The method of claim 11, wherein the engine is driven to operate the vehicle in a hybrid electric vehicle mode when a driver demand power of the vehicle is greater than a difference between a sum of the available power and a factor of each state of charge of the battery.

19. The method according to claim 18, wherein in driving the engine, a driver-demanded power of the vehicle is compared with an optimum engine power at which the engine is driven at an optimum engine operating point,

when the driver-demanded power is less than the optimum engine power, the front-wheel motor generates power for charging the battery;

comparing the driver-demanded power with an optimum engine power at a time of driving the engine at an optimum engine operating point, and

when the driver-demanded power is larger than the optimum engine power, the rear-wheel motor is driven as an auxiliary power source.

20. The method according to claim 18, wherein, when the driver-demanded power is larger than the sum of the optimum engine power and the available power of the rear wheel motor while driving the engine, the front wheel motor is driven to be used as a running power source in addition to the rear wheel motor.

Technical Field

The present invention relates to an apparatus and method for controlling an electric four-wheel drive (E-4WD) vehicle. More particularly, the present invention relates to an apparatus and method for controlling the drive of an E-4WD vehicle, in which an engine and a front wheel motor are connected to front wheels, and a rear wheel motor is connected to rear wheels.

Background

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

As is well known, an electric motor as a running drive source is provided in a hybrid vehicle, an electric vehicle, a hydrogen fuel cell vehicle, or the like, and these vehicles are referred to as electric vehicles.

As an example of a four-wheel drive (4WD) power train of an electric vehicle, the electric vehicle employs a power train in which an engine and/or a front wheel motor is connected to front wheels and a rear wheel motor smaller than the front wheel motor is connected to rear wheels.

In one form, the 4WD powertrain may provide a primary drive source of the vehicle through an engine and a front wheel motor connected to the front wheels, and an auxiliary drive source through a rear wheel motor connected to the rear wheels. Since an optimized drive control method for vehicle running has not been established yet and the rear wheel motor maintains a limited level of drive in terms of drive assist, it is desirable to apply a more efficient drive control method.

In another form, the 4WD powertrain uses an engine connected to front wheels as a primary drive source for vehicle travel and a rear wheel motor connected to rear wheels as a secondary drive source when a loss of drive force occurs during shifting of the transmission during travel due to operation of the engine. The rear wheel motor operates to compensate for the loss of driving force.

Disclosure of Invention

In one aspect, the present invention provides an apparatus and method for controlling the drive of an electric four-wheel drive (E-4WD) vehicle, which achieves an improvement in fuel efficiency by driving-controlling a 4WD powertrain, in which an engine and a front-wheel motor are connected to front wheels and a rear-wheel motor is connected to rear wheels, by applying a rear-wheel motor drive control mode, a front-wheel motor drive control mode, a four-wheel motor drive control mode, and an engine-on control mode, respectively.

Objects of the present invention are not limited to the above objects, and other objects of the present invention not mentioned may be understood by the following description, and will also be clearly understood by the form of the present invention. Further, the objects of the present invention can be achieved by the means described in the appended claims and combinations thereof.

In an exemplary form, the present invention provides an apparatus for controlling drive of an E-4WD vehicle, comprising: a first powertrain for a front wheel, comprising: an engine, a front wheel motor, an engine clutch disposed between the engine and the front wheel motor and configured to selectively transmit power of the engine, and a transmission configured to shift the power of the engine and the power of the front wheel motor and output the shifted power to the front wheels; a second powertrain for a rear wheel, comprising: a rear wheel motor, and a speed reducer configured to decelerate power of the rear wheel motor and output the decelerated power to the rear wheel; a battery connected to the front wheel motor and the rear wheel motor for being chargeable and dischargeable; and a controller configured to: the controller performs control to selectively drive the front wheel motor and the rear wheel motor according to power transmission efficiency of the front wheel motor and the rear wheel motor when the driver-demanded power is less than a sum of the available power of the front wheel motor and the available power of the rear wheel motor, drives the front wheel motor and the rear wheel motor together when the driver-demanded power is greater than the available power of the front wheel motor or the available power of the rear wheel motor during driving of the front wheel motor or the rear wheel motor, and controls to drive the engine according to engine-on when the driver-demanded power is greater than the total available power.

In another exemplary form, the present invention provides a method of controlling drive of an electric four-wheel drive (E-4WD) vehicle, the vehicle including: powertrain for front wheels, comprising: an engine, a front wheel motor, an engine clutch disposed between the engine and the front wheel motor and configured to transmit or interrupt power of the engine, and a transmission configured to shift the power of the engine and the power of the front wheel motor to output the shifted power to the front wheels; and a powertrain for a rear wheel, comprising: a rear wheel motor and a decelerator configured to decelerate power of rear wheels and output the decelerated power to the rear wheels, and a battery connected to the front wheel motor and the rear wheel motor for charging and dischargeable, the method comprising: selectively driving the front wheel motor or the rear wheel motor based on power transmission efficiency of the front wheel motor and the rear wheel motor when the driver-demanded power is less than the total available power; driving the front wheel motor and the rear wheel motor together when the driver-demanded power is greater than the available power of the front wheel motor or the available power of the rear wheel motor during driving of the front wheel motor or the rear wheel motor; and driving the engine when the driver demand power is greater than the total available power.

Other aspects and exemplary forms of the invention are discussed below.

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

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 invention may be better understood, various forms thereof will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating power transmission of an electric four-wheel drive (E-4WD) vehicle;

FIG. 2 is a control configuration diagram illustrating a drive control method of an E-4WD vehicle according to one form of the present invention;

FIGS. 3 and 4 are flow charts illustrating a drive control method of an E-4WD vehicle according to one form of the present invention;

FIG. 5 is a power transmission block diagram illustrating a power transmission process in a rear wheel motor drive control mode in a drive control method of an E-4WD vehicle according to one form of the present invention;

FIG. 6 is a power transmission block diagram illustrating a power transmission process in a front wheel motor drive control mode in a drive control method of an E-4WD vehicle according to one form of the present invention;

FIG. 7 is a power transmission block diagram illustrating a power transmission process in a front wheel motor and rear wheel motor drive control mode in a drive control method of an E-4WD vehicle according to one form of the present invention; and

fig. 8 to 10 are power transmission blocks illustrating a power transmission process in an engine-on control mode in a driving control method of an E-4WD vehicle according to the present invention.

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.

Hereinafter, forms of the present invention will be described in detail with reference to 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 invention. The specific design features of the invention herein disclosed, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular design application and use environment.

Fig. 1 is a block diagram showing power transmission of an electric four-wheel drive (E-4WD) vehicle in which a power train for front wheels having an engine and a front wheel motor is combined with a power train diagram for rear wheels having a rear wheel motor, and fig. 2 is a control configuration diagram showing a drive control method of the E-4WD vehicle according to one form of the present invention.

As shown in fig. 1, the power train for the front wheels includes: an engine 100; a front wheel motor 120; an engine clutch 110 disposed between the engine 100 and the front wheel motor 120, and configured to transmit or disconnect power of the engine 100; a transmission 130 configured to shift power from the engine 100 and the front wheel motor 120 and output the shifted power to the front wheels 140; a Hybrid Starter Generator (HSG)150 connected to a crank pulley of the engine 100 and configured to perform starting of the engine 100 and generate electric power; and a battery 160 connected to the front wheel motor 120 and the HSG150 for being chargeable and dischargeable.

The transmission 130 may employ an Automatic Transmission (AT) or a Dual Clutch Transmission (DCT).

A power train for rear wheels includes: a rear wheel motor 170 connected to the battery 160 for charging and discharging; and a decelerator 180 configured to decelerate the power of the rear wheel motor 170 and output the decelerated power to the rear wheels 190.

As described above, the present disclosure focuses on: drive control for traveling of the E-4WD vehicle in which a power train for the front wheels is combined with a power train for the rear wheels is performed in a rear wheel motor drive control mode, a front wheel motor and rear wheel motor (four-wheel motor) drive control mode, and an engine-on control mode, respectively, in accordance with the driver's required power, whereby an improvement in fuel efficiency can be achieved, and marketability of the E-4WD vehicle can be improved.

As shown in fig. 2, the control device (control subject during drive control of E-4WD vehicle travel) may include: a high-level controller 10; an engine controller 20 configured to receive an instruction of the advanced controller 10 and control the overall driving and operating point of the engine 100; and a motor controller 30 configured to receive a torque command from the advanced controller 10 and control the overall driving of the front wheel motor 120 and the rear wheel motor 170.

Here, the drive control method of the E-4WD vehicle according to the present invention will be described below for various control modes.

Fig. 3 and 4 are flowcharts illustrating a driving control method of the E-4WD vehicle according to the present invention.

Rear wheel motor drive control mode

When the driver-demanded power is smaller than the sum of the available power of the front wheel motor 120 and the available power of the rear wheel motor 170 (available power of the front wheel motor 120 + available power of the rear wheel motor 170), control for selectively driving the front wheel motor 120 and the rear wheel motor 170 is performed in advance in accordance with the power transmission efficiency of the front wheel motor 120 and the rear wheel motor 170.

That is, the driver-required power, which varies according to the amount by which the driver steps on the accelerator pedal, is compared with the total available power (the sum of the available power of the front wheel motor 120 and the available power of the rear wheel motor 170). As a result of the comparison, when the driver-demanded power is less than the total available power (the sum of the available power of the front wheel motor 120 and the available power of the rear wheel motor 170), the front wheel motor 120 and the rear wheel motor 170 may be selectively driven to travel in an Electric Vehicle (EV) mode.

In this case, when the level of the state of charge (SOC) of the battery 160 is reduced to be equal to or less than a predetermined level, since the discharge of the battery 160 should be reduced or minimized, it is desirable to restrict the travel in the EV mode. Therefore, it is desirable to determine either only the front wheel motor 120 or only the rear wheel motor 170 is driven, or the engine-on time, using the factor of each SOC of the battery 160.

For reference, it is noted that the factor of each SOC of the battery 160 is a mappable variable term (a mappable variable item).

Therefore, the difference between the driver-required power and the total available power and the factor of each SOC of the battery 160 ((available power of the front wheel motor 120 + available power of the rear wheel motor 170) -the factor of each SOC of the battery 160) is compared (S101). As a result of the comparison, when the driver-required power is smaller than the difference between the total available power and the factors of the respective SOCs of the battery 160, only the front wheel motor 120 or only the rear wheel motor 170 may be driven to travel in the EV mode.

Otherwise, when the driver-demanded power is larger than the difference between the total available power and the factor of each SOC of the battery 160 ((available power of the front wheel motor 120 + available power of the rear wheel motor 170) -factor of each SOC of the battery 160), it is desirable to limit traveling in the EV mode in order to reduce or minimize discharge of the battery 160, and therefore, as described below, the engine 100 is driven according to the engine-on control mode in which the battery 160 is chargeable.

In one form, the control of selectively driving the front wheel motors 120 and the rear wheel motors 170 includes: whether to drive the front wheel motor 120 or the rear wheel motor 170 is determined based on the power transmission efficiency of the front wheel motor 120 and the rear wheel motor 170.

For this reason, as a result of the comparison in S101, when the driver required power is smaller than the difference between the total available power and the factor of each SOC of battery 160 ((available power of front wheel motor 120 + available power of rear wheel motor 170) -factor of each SOC of battery 160), it is desirable to perform determination of whether to drive front wheel motor 120 or rear wheel motor 170 for traveling in the EV mode. The reason why the front wheel motor 120 or the rear wheel motor 170 is used is that which motor has better power transmission efficiency with respect to each wheel.

In this case, when the power of the front wheel motor 120 is output to the front wheels 140 through the transmission 130, the power transmission efficiency of the front wheel motor 120 is the power transmission efficiency when the power of the front wheel motor 120 is output to the front wheels 140 through the transmission 130 and may be determined by the operating efficiency of the transmission 130, and when the power of the rear wheel motor 170 is output to the rear wheels 190 through the reduction gear 180, the power transmission efficiency of the rear wheel motor 170 is the power transmission efficiency and may be determined by the operating efficiency of the reduction gear 180.

Therefore, in order to determine whether to drive front wheel motor 120 or rear wheel motor 170 for running in the EV mode, the product of the available power of front wheel motor 120 and the operating efficiency of transmission 130 (available power of front wheel motor 120 × operating efficiency of transmission 130) and the product of the available power of rear wheel motor 170 and the operating efficiency of reduction gear 180 (available power of rear wheel motor 170 × operating efficiency of reduction gear 180) are compared (S102). As a result of the comparison, when the product of the available power of rear wheel motor 170 and the operating efficiency of reduction gear 180 (available power of rear wheel motor 170 × operating efficiency of reduction gear 180) is large, only rear wheel motor 170 is driven to travel in the EV mode (S103).

For example, the advanced controller 10 compares the product of the available power of the front wheel motor 120 and the operating efficiency of the transmission 130 (available power of the front wheel motor 120 × operating efficiency of the transmission 130) with the product of the available power of the rear wheel motor 170 and the operating efficiency of the reduction gear 180 (available power of the rear wheel motor 170 × operating efficiency of the reduction gear 180). When the product of the available power of the rear wheel motor 170 and the operating efficiency of the reduction gear 180 (available power of the rear wheel motor 170 x operating efficiency of the reduction gear 180) is determined to be large, the advanced controller 10 commands the motor controller 30 to execute the EV mode so that only the rear wheel motor 170 can be driven due to the current control of the motor controller 30.

Therefore, as shown in fig. 5, when only the rear wheel motor 170 is driven using the power of the battery 160, the rotational force of the rear wheel motor 170 is transmitted to the rear wheels 190 through the decelerator 180, so that the initial acceleration running of the vehicle can be performed and the driver required power can be satisfied by the available power of the rear wheel motor 170.

Meanwhile, during driving of the rear wheels 190 using the power of the rear wheel motor 170, when the running road surface is a low friction road surface, the rear wheels 190 slip and the speed of the rear wheels 190 suddenly increases compared to the speed of the front wheels 140, so that acceleration running of the vehicle may not be smoothly performed, and thus the running stability of the vehicle may be reduced.

In order to solve the above problem, the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (speed of the rear wheels 190 — speed of the front wheels 140) is compared with the maximum reference value α (S104). As a result of the comparison, when the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 is greater than the maximum reference value α, the front wheel motor 120 is driven by increasing the driving ratio of the front wheel motor 120 to the rear wheel motor 170 by a unit of up to 1% for a predetermined period of time (e.g., 10ms) (S105).

For example, when the advanced controller 10 compares the speed of the rear wheels 190 with the speed of the front wheels 140, and determines that the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (speed of the rear wheels 190-speed of the front wheels 140) is greater than the maximum reference value α, the advanced controller 10 commands the motor controller 30 to drive the front wheel motor 120 so that the front wheel motor 120 can be driven according to the current control of the motor controller 30 to increase the drive ratio by a unit of up to 1% within a predetermined period of time.

In one form, the driving of the front wheel motor 120 is performed by increasing the driving ratio of the front wheel motor 120 by a unit of up to 1% for a predetermined period of time (S105) until the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (speed of the rear wheels 190 — speed of the front wheels 140) is reduced to be less than the minimum reference value β.

In this case, the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (speed of the rear wheels 190-speed of the front wheels 140) is compared with the minimum reference value β (S106). As a result of the comparison, when the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 is determined to be less than the minimum reference value β, the driving ratio of the rear wheel motor 170 to the front wheel motor 120 is inversely increased by up to a predetermined unit for the stability of the accelerated running of the vehicle (S107).

As described above, since only the rear wheel motor 170 is driven while the driver required power is satisfied, acceleration running of the vehicle can be performed. In particular, since the rear wheel motor 170 is driven on a low-friction road surface, the driving ratios of the front wheel motor 120 and the rear wheel motor 170 are changed, so that stable vehicle acceleration can be performed.

In addition, a small rear wheel motor 170 having a capacity smaller than that of the front wheel motor 120 is used, thereby performing traveling in the EV mode for initial acceleration of the vehicle. Therefore, an improvement in fuel efficiency can be achieved.

Front wheel motor drive control mode

As described above, the driver-required power, which varies according to the amount by which the driver steps on the accelerator pedal, is compared with the total available power (the sum of the available power of the front wheel motor 120 and the available power of the rear wheel motor 170). As a result of the comparison, when the driver-demanded power is less than the total available power (the sum of the available power of the front wheel motor 120 and the available power of the rear wheel motor 170), the front wheel motor 120 and the rear wheel motor 170 may be selectively driven to travel in the EV mode.

In this case, when the SOC level of the battery 160 is reduced to be equal to or less than a predetermined level, since the discharge of the battery 160 should be reduced or minimized, it is desirable to limit the travel in the EV mode. Therefore, it is desirable to use the factor of each SOC of the battery 160 to determine whether only the rear wheel motor 170 is driven or only the front wheel motor 120 is driven, or the engine-on time.

Therefore, the difference between the driver-required power and the total available power and the factor of each SOC of the battery 160 ((available power of the front wheel motor 120 + available power of the rear wheel motor 170) -the factor of each SOC of the battery 160) is compared (S101). As a result of the comparison, when the driver-required power is smaller than the difference between the total available power and the factors of the respective SOCs of the battery 160, only the rear wheel motor 170 or only the front wheel motor 120 may be driven to travel in the EV mode.

Subsequently, as a result of the comparison in S101, when the driver required power is smaller than the difference between the total available power and the factor of each SOC of battery 160 ((available power of front wheel motor 120 + available power of rear wheel motor 170) -factor of each SOC of battery 160), it is desirable to perform the determination of whether to drive front wheel motor 120 or rear wheel motor 170 for running in the EV mode as described above. The reason why the front wheel motor 120 or the rear wheel motor 170 is used is that which motor has better power transmission efficiency with respect to each wheel.

Therefore, in order to determine whether to drive front wheel motor 120 or rear wheel motor 170 for running in the EV mode, the product of the available power of front wheel motor 120 and the operating efficiency of transmission 130 (available power of front wheel motor 120 × operating efficiency of transmission 130) and the product of the available power of rear wheel motor 170 and the operating efficiency of reduction gear 180 (available power of rear wheel motor 170 × operating efficiency of reduction gear 180) are compared (S102). As a result of the comparison, when the product of the available power of rear wheel motor 170 and the operating efficiency of reduction gear 180 (available power of rear wheel motor 170 × operating efficiency of reduction gear 180) is small, that is, the product of the available power of front wheel motor 120 and the operating efficiency of transmission 130 (available power of front wheel motor 120 × operating efficiency of transmission 130) is large, only front wheel motor 120 is driven to travel in the EV mode (S108).

For example, the advanced controller 10 compares the product of the available power of the front wheel motor 120 and the operating efficiency of the transmission 130 (available power of the front wheel motor 120 × operating efficiency of the transmission 130) with the product of the available power of the rear wheel motor 170 and the operating efficiency of the reduction gear 180 (available power of the rear wheel motor 170 × operating efficiency of the reduction gear 180). When the product of the available power of the front wheel motor 120 and the operating efficiency of the transmission 130 (available power of the front wheel motor 120 x operating efficiency of the transmission 130) is determined to be large, the advanced controller 10 commands the motor controller 30 to execute the EV mode so that only the front wheel motor 120 can be driven due to the current control of the motor controller 30.

Therefore, as shown in fig. 6, when only the front wheel motor 120 is driven using the power of the battery 160, the rotational force of the front wheel motor 120 is transmitted to the front wheels 140 through the transmission 130, so that initial acceleration running of the vehicle can be performed and the driver required power can be satisfied by the available power of the front wheel motor 120.

Front wheel motor and rear wheel motor drive control mode

The front wheel motor and rear wheel motor drive control mode refers to a mode in which the front wheel motor 120 and the rear wheel motor 170 are driven together when the available power of the front wheel motor 120 or the available power of the rear wheel motor 170 may not satisfy the driver's required power.

In other words, when the available power of the front wheel motor 120 or the available power of the rear wheel motor 170 does not satisfy the driver's required power, the front wheel motor and rear wheel motor drive control mode refers to: a mode in which the front wheel motors 120 are driven together while the rear wheel motors 170 are driven, and the rear wheel motors 170 are driven together while the front wheel motors 120 are driven.

When stable vehicle acceleration is performed due to driving only the rear wheel motor 170, that is, when the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (speed of the rear wheels 190-speed of the front wheels 140) is compared with the maximum reference value α (S104), and as a result of the comparison, when the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (speed of the rear wheels 190-speed of the front wheels 140) remains less than the maximum reference value α, the front wheel motor 120 may be driven together with the rear wheel motor 170 in accordance with the driver' S required power.

Therefore, the driver required power is compared with the available power of the rear wheel motor 170 (S112) in a state where the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (the speed of the rear wheels 190 — the speed of the front wheels 140) remains less than the maximum reference value α due to the driving of only the rear wheel motor 170, and, as a result of the comparison, when the driver required power is large, the front wheel motor 120 is driven together with the rear wheel motor 170 (S113) because the driver required power cannot be satisfied only by the available power of the rear wheel motor 170.

For example, in a state where the difference between the speed of the rear wheels 190 and the speed of the front wheels 140 (the speed of the rear wheels 190 — the speed of the front wheels 140) remains less than the maximum reference value α, when the driver-required power is large as a result of comparison of the driver-required power with the available power of the rear wheel motors 170, the advanced controller 10 commands the motor controller 30 to execute the EV mode so that the driving of the front wheel motors 120 can be further executed due to the current control of the motor controller 30 (S113).

In this case, when the front wheel motors 120 are driven together while the rear wheel motors 170 are driven, the power output of the rear wheel motors 170 is the maximum available power, and the power of the front wheel motors 120 is output at a level where the power of the rear wheel motors 170 is subtracted from the driver-required power (driver-required power — power of the rear wheel motors 170).

In contrast, when stable vehicle acceleration is performed because only the front wheel motor 120 is driven, the rear wheel motor 170 may be driven together in accordance with the driver's required power.

Therefore, the driver required power is compared with the available power of the front wheel motor 120 (S109), and, as a result of the comparison, when the driver required power is large, the rear wheel motor 170 is driven together with the front wheel motor 120 (S110) because the driver required power cannot be satisfied by the available power of the front wheel motor 120 alone.

For example, as a result of comparison of the driver-required power with the available power of the front wheel motor 120, when the driver-required power is large, the advanced controller 10 commands the motor controller 30 to execute the EV mode so that driving of the rear wheel motor 170 can be further performed due to current control of the motor controller 30 (S110).

In this case, when the rear wheel motor 170 is driven together while the front wheel motor 120 is driven, the power output of the front wheel motor 120 is the maximum available power, and the power of the rear wheel motor 170 is output at a level where the power of the front wheel motor 120 is subtracted from the driver required power (driver required power — power of the front wheel motor 120).

As described above, when the driver required power cannot be satisfied by the available power of only the front wheel motor 120 or the available power of only the rear wheel motor 170, the front wheel motor 120 is driven together while the rear wheel motor 170 is driven, and the rear wheel motor 170 is driven together while the front wheel motor 120 is driven, so that the driver required power can be satisfied. As shown in fig. 7, 4WD traveling in which the power of front wheel motor 120 is output to front wheels 140 and the power of rear wheel motor 170 is output to rear wheels 190 at the same time can be performed.

Engine onControl mode

When the driver-demanded power is greater than (available power for front wheel motor 120 + available power for rear wheel motor 170), the engine-on control mode refers to: a mode in which travel in the EV mode is restricted to reduce or minimize discharge of battery 160, and engine 100 is simultaneously turned on to meet the driver's required power.

As described above, when the level of SOC of the battery 160 is reduced to be equal to or less than the predetermined level during driving of the front wheel motor 120 and/or the rear wheel motor 170, it is desirable to limit traveling in the EV mode to reduce or minimize discharge of the battery 160, and thus the engine-on time can be determined using the factor of each SOC of the battery 160.

Therefore, as a result of comparison between the driver-required power and the difference between the total available power and the factor for each SOC of battery 160 ((available power of front wheel motor 120 + available power of rear wheel motor 170) -factor for each SOC of battery 160) in S101, when the driver-required power is greater than the difference between the total available power and the factor for each SOC of battery 160 ((available power of front wheel motor 120 + available power of rear wheel motor 170) -factor for each SOC of battery 160), engine 100 is turned on (S201).

Further, after S110 (driving of rear wheel motor 170 together with front wheel motor 120), or after S113 (driving of front wheel motor 120 together with rear wheel motor 170), when the driver required power is determined to be greater than the difference between the total available power and the factors of the respective SOCs of battery 160 ((available power of front wheel motor 120 + available power of rear wheel motor 170) -factors of the respective SOCs of battery 160), engine 100 is turned on (S201).

For example, when the advanced controller 10 determines that the driver-demanded power is larger than the difference between the total available power and the factor of each SOC of the battery 160 ((available power of the front wheel motor 120 + available power of the rear wheel motor 170) -factor of each SOC of the battery 160), the engine controller 20 controls the engine to be on according to the command of the advanced controller 10.

In one form, the engine controller 20 controls the driving of the engine 100 at a preset optimum engine operating point for improving fuel efficiency according to a command of the advanced controller 10 (S202).

Accordingly, in a state where engine 100 is driven, a Hybrid Electric Vehicle (HEV) running mode may be realized in which front wheel motor 120 or rear wheel motor 170 are driven together, or front wheel motor 120 and rear wheel motor 170 are driven simultaneously.

In this case, when engine 100 is driven at the preset optimum engine operating point, the driver-demanded power is compared with the optimum engine power at the time of driving engine 100 at the preset optimum engine operating point (S203). As a result of the comparison, when the driver required power is less than the optimum engine power, that is, the optimum engine power is greater than the driver required power, the front wheel motor 120 performs power generation for charging the battery 160 (S204).

In other words, when the optimum engine power is greater than the driver required power, it indicates that the driver required power can be satisfied by the optimum engine power. Therefore, as shown in fig. 8, the power of the engine 100 is output to the front wheels 140, and at the same time, the front wheel motor 120 is driven as a generator, so that the battery 160 can be charged.

Otherwise, as a result of comparison of the driver required power with the optimum engine power when the engine 100 is driven at the preset optimum engine operating point in S203, when the driver required power is greater than the optimum engine power, that is, the optimum engine power is less than the driver required power, the rear wheel motor 170 may be used as an auxiliary drive source to meet the driver required power because it indicates that the optimum engine power cannot meet the driver required power.

For this reason, as a result of the comparison of the driver required power with the optimum engine power, when the engine 100 is driven at the preset optimum engine operating point and the driver required power is greater than the optimum engine power, that is, the optimum engine power is less than the driver required power in S203, the rear wheel motor 170 may be used as the auxiliary drive source under the control of the motor controller 30 according to the command of the advanced controller 10 (S205).

In another form, the auxiliary driving force of the rear wheel motor 170 may be determined as a value obtained by subtracting the optimum engine power from the driver required power (driver required power — optimum engine power).

In this case, the reason why the rear wheel motor 170 is driven as the auxiliary power source is that the power transmission path for transmitting power from the rear wheel motor 170 to the rear wheels 190 through the speed reducer 180 is shorter in length and more efficient than the power transmission path for transmitting power from the front wheel motor 120 to the front wheels 140 through the transmission 130.

Therefore, as shown in fig. 9, the power of engine 100 is output to front wheels 140, and at the same time, the power of rear wheel motor 170 is output to rear wheels 190, so that the HEV mode (in which the vehicle travels using both the power of engine 100 and the power of rear wheel motor 170) can be realized while the 4WD travel can be performed.

Next, the driver required power is compared with the sum of the optimum engine power and the available power of the rear wheel motor 170 (optimum engine power + available power of the rear wheel motor 170) (S206). As a result of the comparison, when the driver required power is large, it indicates that the driver required power cannot be satisfied by the sum of the optimum engine power and the available power of the rear wheel motor 170. Therefore, in order to satisfy the driver' S required power, the front wheel motor 120 is further driven under the control of the motor controller 30 to serve as a travel power source in accordance with the command of the advanced controller 10 in addition to the rear wheel motor 170 (S207).

In some forms of the invention, the drive power of the front wheel motor 120 may be determined as a value obtained by subtracting the sum of the optimum engine power and the available power of the rear wheel motor 170 (driver required power- (optimum engine power + available power of the rear wheel motor 170)) from the driver required power.

Therefore, as shown in fig. 10, the power of engine 100 and the power of front wheel motor 120 are output to front wheels 140, while the power of rear wheel motor 170 is output to rear wheels 190, so that the HEV mode of high-load running can be realized using both the powers of front wheel motor 120 and rear wheel motor 170 in addition to the power of engine 100, while the 4WD running can be performed.

The present invention provides the following effects by the above problem solving means.

First, according to the present invention, it is possible to individually perform travel drive control of an E-4WD vehicle (in which a power train including an engine and a front wheel motor for front wheels is combined with a power train including a rear wheel motor for rear wheels) in a rear wheel motor drive control mode, a front wheel motor and rear wheel motor drive control mode, and an engine-on control mode according to driver required power, whereby an improvement in fuel efficiency can be achieved, and marketability of the E-4WD vehicle can be improved.

Second, vehicle travel that meets the driver's required power can be achieved throughout the entire load area of the E-4WD vehicle.

Third, the drive ratios of the front wheel motors and the rear wheel motors are adjusted so that stable vehicle acceleration can be performed on a low-friction road surface.

Although the forms of the present invention have been described in detail, the scope of the present invention is not limited to these forms, and various modifications and improvements devised by those skilled in the art using the basic concept of the present invention defined by the appended claims may further fall within the scope of the present invention.