Device for controlling the drive of an electric four-wheel drive vehicle when changing gear

Abstract

The present invention provides an apparatus for controlling driving of an electric four-wheel drive vehicle at the time of gear shift. The apparatus controls the driving of the electric four-wheel drive vehicle so that energy loss occurring on a power transmission path during gear shift is minimized, thereby improving fuel efficiency.

Description

Technical Field

[0001] The present invention relates to a device for controlling the drive of an electric four-wheel drive vehicle during gear shifting, and more specifically, to a device for controlling the drive of an electric four-wheel drive vehicle such that energy loss occurring in the power transmission path during gear shifting is minimized, thereby improving fuel efficiency. Background Technology

[0002] As is well known, hybrid vehicles, electric vehicles, or hydrogen fuel cell vehicles are equipped with electric motors as their driving force; such vehicles are called electrified vehicles. An example of a four-wheel drive powertrain for an electrified vehicle is a powertrain system with an engine and / or a front-wheel motor connected to the front wheels and a rear-wheel motor (smaller than the front-wheel motor) connected to the rear wheels.

[0003] In a four-wheel drive powertrain with an engine and front wheel motor connected to the front wheels (which serve as the primary driving source for the vehicle) and a rear wheel motor connected to the rear wheels (which serves as an auxiliary driving source), the transmission is connected to the front wheel motor, while only the reducer is connected to the rear wheel motor, and there is no transmission connected to the rear wheel motor.

[0004] In a four-wheel drive powertrain, gear changes are unavoidable due to the presence of a transmission. When gear changes are performed during driving using a front-wheel motor and / or engine connected to the transmission, shift losses occur due to the differences in gear ratios between the shift gears. These shift losses contribute to decreased fuel efficiency.

[0005] The information disclosed in this section is provided only to enhance the understanding of the background of the invention, and therefore may contain information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0006] The present invention provides a device for controlling the drive of an electric four-wheel drive vehicle, which can minimize energy loss occurring in the power transmission path during gear shifting, thereby improving fuel efficiency.

[0007] The purpose of this invention is not limited to the above-described purpose. Other unmentioned purposes of this invention will be clearly understood by those skilled in the art (hereinafter referred to as "skilled persons") through the following description.

[0008] To achieve the aforementioned objective, in one aspect, the present invention provides an apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, the apparatus comprising: a front-wheel power system having an engine, a front-wheel motor, and a transmission configured to shift the power of the engine and the front-wheel motor and output the shifted power to the front wheels; a rear-wheel power system having a rear-wheel motor and a reducer configured to reduce the power of the rear-wheel motor and output the reduced power to the rear wheels; and a controller configured to, when gear shifting begins during engine-driven driving, instruct the rear-wheel motor to output a portion of the driver-demanded power corresponding to the power that can be output by the rear-wheel motor, and instruct the front-wheel motor to output a power obtained by subtracting the output power indicated to the rear-wheel motor (i.e., the rear-wheel motor output power) and the engine output power (driver-demanded power - rear-wheel motor output power - engine output power) from the driver-demanded power.

[0009] According to an exemplary embodiment of the present invention, the device has the following features.

[0010] First, when the sum of the maximum power that can be output by the front wheel motor and the maximum power that can be output by the rear wheel motor during driving is less than the power required by the driver, the controller can be configured to drive the engine and instruct the engine to output power determined according to the running line mapping.

[0011] Second, when the driver requests more power than the maximum power that the rear wheel motor can output during gear shifting, the controller can be configured to instruct the rear wheel motor to output the maximum power. In this case, the engine output power, corresponding to the power obtained by subtracting the maximum rear wheel motor power from the driver's requested power, can be output to the front wheels.

[0012] Furthermore, when the sum of the maximum rear wheel motor power and the engine output power exceeds the driver's required power during gear shifting, the controller can be configured to instruct the front wheel motors to generate electricity to charge the battery. The front wheel motors can also be configured to generate electricity to charge the battery using the power obtained by subtracting the maximum rear wheel motor power and the engine output power from the driver's required power. The battery can be connected to both the front and rear wheel motors for charging and discharging.

[0013] When the driver requests power equal to or less than the maximum power of the rear wheel motor during gear shifting, the controller can be configured to instruct the rear wheel motor to output the requested power and instruct the front wheel motor to generate electricity to charge the battery. In this case, the front wheel motor can be configured to use engine output power to generate electricity to charge the battery.

[0014] Third, when the transmission is not shifting gears during engine-driven driving, the controller can be configured to instruct the front wheel motor to output power obtained by subtracting the engine output power from the driver's requested power.

[0015] At this time, when the driver requests less power than the engine output, the controller can be configured to instruct the front wheel motor to generate electricity to charge the battery, and the front wheel motor can be configured to generate electricity using the power obtained by subtracting the engine output from the driver's requested power to charge the battery. Furthermore, when the driver requests more power than the engine output, the controller can be configured to instruct the front wheel motor to output the power obtained by subtracting the engine output from the driver's requested power.

[0016] Fourth, when the transmission begins to shift gears during driving using only the power of the front wheel motor, the controller can be configured to instruct the rear wheel motor to output the portion of the power requested by the driver that corresponds to the power that can be output by the rear wheel motor, and can instruct the front wheel motor to output the power obtained by subtracting the power output by the rear wheel motor from the power requested by the driver.

[0017] Specifically, when the maximum rear wheel motor power is equal to or greater than the driver's required power during gear shifting, the controller can be configured to instruct the rear wheel motor to output the driver's required power and to instruct the front wheel motor to output zero power. Furthermore, when the maximum rear wheel motor power is less than the driver's required power during gear shifting, the controller can be configured to: instruct the rear wheel motor to output the maximum power it can output, and instruct the front wheel motor to output the power obtained by subtracting the maximum rear wheel motor power from the driver's required power.

[0018] Fifth, when the sum of the maximum front wheel motor power and the maximum rear wheel motor power is equal to or greater than the power required by the driver, and the value obtained by multiplying the maximum rear wheel motor power by the reduction gear's operating efficiency is less than the value obtained by multiplying the maximum front wheel motor power by the transmission's operating efficiency, the controller can be configured to drive only the front wheel motors during driving.

[0019] In another aspect, the present invention provides an apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, the apparatus comprising: a front-wheel power system having an engine and a transmission configured to shift the power of the engine and output the shifted power to the front wheels; a rear-wheel power system having a rear-wheel motor and a reducer configured to reduce the power of the rear-wheel motor and output the reduced power to the rear wheels; and a controller configured to, when gear shifting begins during engine-driven driving, instruct the rear-wheel motor to output a portion of the power requested by the driver corresponding to the power that can be output by the rear-wheel motor, and instruct the engine to output power obtained by subtracting the power output by the rear-wheel motor from the power requested by the driver.

[0020] Specifically, when the maximum power output from the rear wheel motor during gear shifting is equal to or greater than the power required by the driver, the controller can be configured to instruct the rear wheel motor to output the power required by the driver and to stop the engine. When the maximum rear wheel motor power during gear shifting is less than the power required by the driver, the controller can be configured to instruct the rear wheel motor to output the maximum power and can also instruct the engine to output the power obtained by subtracting the maximum rear wheel motor power from the power required by the driver. Attached Figure Description

[0021] The above-mentioned and other features of the invention will now be described in detail with reference to exemplary embodiments shown in the accompanying drawings, which are given hereinafter by way of example only and are therefore not restrictive of the invention, wherein:

[0022] Figure 1 This is a schematic diagram illustrating an implementation scheme of the power transmission system for an electric four-wheel drive vehicle;

[0023] Figure 2 This is a schematic diagram illustrating the configuration for drive control during gear shifting in an electric four-wheel drive vehicle according to the present invention;

[0024] Figure 3 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention when driving the front wheel motor;

[0025] Figure 4 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention when changing speeds during the driving of the front wheel motor;

[0026] Figure 5 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention when it is running in engine operating mode;

[0027] Figure 6This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention when changing gears during operation in engine mode;

[0028] Figure 7A and Figure 7B This is a flowchart illustrating the drive control process of an electric four-wheel drive vehicle during gear shifting according to the present invention;

[0029] Figure 8 and Figure 9 This is a schematic diagram illustrating another embodiment of the power transmission system of an electric four-wheel drive vehicle.

[0030] It should be understood that the accompanying drawings are not necessarily drawn to scale, and illustrate various features illustrating the basic principles of the invention in a simplified manner. Specific design features of the invention disclosed herein (including, for example, specific dimensions, orientations, positions, and shapes) will be determined in part by the specific target application and environment of use. Throughout the various figures, reference numerals refer to the same or equivalent parts of the invention. Detailed Implementation

[0031] It should be understood that, as used herein, the terms “vehicle” or “of a vehicle” or other similar terms generally include motor vehicles, such as passenger vehicles including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, vessels including various boats and ships, aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., vehicles derived from non-petroleum fuels). As mentioned herein, a hybrid vehicle is a vehicle with two or more power sources, such as a vehicle that combines gasoline and electric power.

[0032] While exemplary embodiments are described as using multiple units to perform exemplary processes, it should be understood that exemplary processes can also be performed by one or more modules. Furthermore, it should be understood that the term controller / control unit refers to a hardware device including a memory and a processor, specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute said modules to perform one or more processes further described below.

[0033] Furthermore, the control logic of the present invention can be implemented as a non-volatile computer-readable medium on a computer-readable medium, comprising executable program instructions that are executed by a processor, controller / control unit, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage devices. The computer-readable recording medium can also be distributed across a network-connected computer system, thereby enabling the computer-readable medium to be stored and executed in a distributed manner via, for example, a telematics server or a controller area network (CAN).

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” are intended to include the plural forms as well. It will be further understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the described features, values, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated enumerations.

[0035] Unless otherwise stated or obvious from the context, the term "approximately" as used herein is understood to mean within the normal tolerance range in the field, such as within two standard deviations of the mean. "Approximately" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context clearly indicates otherwise, all numerical values ​​provided herein are modified by the term "approximately".

[0036] Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings. The details shown in the drawings are illustrative and may differ from actual implementations.

[0037] Figure 1 This is a schematic diagram illustrating the power transmission system of an electric four-wheel drive (E-4WD) vehicle, consisting of a front-wheel powertrain including an engine and a front-wheel motor, and a rear-wheel powertrain including a rear-wheel motor. Figure 2 This is a schematic diagram illustrating the configuration for drive control during gear shifting in an electric four-wheel drive vehicle according to the present invention.

[0038] As in Figure 1As shown, the front-wheel powertrain 100 may include an engine 110, a front-wheel motor 120, a transmission 130, and an engine clutch 140. The engine 110 and the front-wheel motor 120 may be configured to output the power required for vehicle operation. The transmission 130 may be connected to the rear end (output end) of the front-wheel motor 120 to shift the power between the engine 110 and the front-wheel motor 120 and to output the shifted power to the front wheels 150. The engine clutch 140 may be arranged between the engine 110 and the front-wheel motor 120 to perform engagement or disengagement operations.

[0039] More specifically, when the engine clutch 140 is engaged, engine power is transmitted to the transmission 130, and when the engine clutch 140 is disengaged, engine power is interrupted, and therefore no engine power is transmitted to the transmission 130. The transmission 130 can shift the power generated by the engine 110 and the front wheel motor 120 according to the gear position, and can transmit the shifted power to the front wheels 150. For example, an automatic transmission (AT) or a dual-clutch transmission (DCT) can be used as the transmission 130. Reference numeral 170 indicates a hybrid starter generator (HSG) 170, which is connected to the crankshaft pulley of the engine 110 to start the engine and generate electricity.

[0040] The front wheel motor 120 and the hybrid starter-generator 170 are electrically connected to the battery 160. The battery 160 can be connected to the front wheel motor 120 and the hybrid starter-generator 170 for charging and discharging. More specifically, the battery 160 can be configured to discharge to the front wheel motor 120 and the hybrid starter-generator 170, or can be charged by the front wheel motor 120 and the hybrid starter-generator 170. The rear wheel powertrain 200 may include a rear wheel motor 210 and a reduction gear 220, the rear wheel motor 210 being connected to the battery 160 for charging and discharging, and the reduction gear 220 being configured to reduce the power of the rear wheel motor 210 and output the reduced power to the rear wheels 230. The rear wheel motor 210 can be driven to output the power required for vehicle movement.

[0041] In this invention, when the transmission 130 is engaged during operation of an electric four-wheel drive vehicle comprised of a combination of a front-wheel power system 100 and a rear-wheel power system 200, the output power of the engine 110 and motors 120, 210 configured to drive the vehicle is controlled to minimize shift losses. Specifically, when shifting begins during operation using the engine 110 and / or the front-wheel motor 120 connected to the transmission 130, the power of the rear-wheel motor 210, which is not connected to the transmission 130, can be utilized to the maximum extent, thereby minimizing energy losses in the power transmission system during shifting and thus improving fuel efficiency.

[0042] As in Figure 2 As shown, the upper-level controller 11, the engine controller 12 configured to perform overall operation of the engine 110 according to the instructions of the upper-level controller 11, and the motor controller 13 configured to perform overall operation of the front wheel motor 120 and the rear wheel motor 210 according to the instructions of the upper-level controller 11 can be used as controller 10, which is the control mechanism for the engine 110 and motors 120 and 210 when the electric four-wheel drive vehicle changes gears.

[0043] Furthermore, the upper-level controller 11 can be configured to issue commands to the transmission controller 14 or receive information such as shift phase from the transmission controller 14. The transmission controller 14 can be configured to execute the operation of the transmission 130 according to the commands of the upper-level controller 11. The electric four-wheel drive vehicle can be set to a driving mode, such as an electric vehicle (EV) mode in which driving is performed using only the front wheel motor 120 and / or the rear wheel motor 210, and an engine operating mode in which driving is performed using the power of the engine 110.

[0044] The EV mode may include a front-wheel motor drive mode that uses only the power of the front-wheel motor 120 for driving. The engine operating modes may include: an engine-only drive mode that uses only the power of the engine 110 for driving, and a hybrid electric vehicle (HEV) mode that uses the front-wheel motor 120 and / or the rear-wheel motor 210 as auxiliary power sources while using the engine 110 as the primary power source.

[0045] In this invention, when a gear shift begins during driving using the power of the front-wheel power system 100 (which is equipped with a transmission 130) in the aforementioned driving mode, energy loss occurring in the power transmission path can be reduced. In other words, when a gear shift begins during driving in both front-wheel motor drive mode and engine operating mode, the power of the rear-wheel motor 210 is utilized to the maximum extent, thereby minimizing gear shift losses.

[0046] Figure 3 and Figure 4 This is a schematic diagram illustrating the power transmission path during operation in front-wheel motor drive mode. Specifically, Figure 3 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention before gear shifting. Figure 4 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention during gear shifting.

[0047] When the vehicle is being driven by the front wheel motor 120, such as in Figure 3 As shown, power from the front wheel motor 120 is transmitted to the front wheels 150 via the transmission 130, and the front wheel motor 120 is driven by power from the battery 160. When the driver's demand for power varies depending on the amount of accelerator pedal depressed (i.e., accelerator pedal travel), and is less than the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor, the front wheel motor 120 and / or the rear wheel motor 210 can be driven to perform driving in EV mode.

[0048] The maximum power output of the front wheel motor 120 is the maximum power that can be output by the front wheel motor 120, and the maximum power output of the rear wheel motor 210 is the maximum power that can be output by the rear wheel motor 210. Whether to drive only the front wheel motor 120 or the rear wheel motor 210 during EV mode operation can be determined based on power transmission efficiency. In other words, the power transmission efficiency of the front wheel motor 120 and the rear wheel motor 210 can be used to select and drive only one of them.

[0049] 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 wheel 150 through the gearbox 130, and can be determined based on the working efficiency of the gearbox 130. The power transmission efficiency of the rear wheel motor 210 is the power transmission efficiency when the power of the rear wheel motor 210 is output to the rear wheel 230 through the reducer 220, and can be determined based on the working efficiency of the reducer 220.

[0050] Accordingly, a first value A, obtained by multiplying the maximum power of the front wheel motor 120 by the working efficiency of the transmission 130, is compared with a second value B, obtained by multiplying the maximum power of the rear wheel motor 210 by the working efficiency of the reducer 220. When the first value A is greater than the second value B, only the front wheel motor 120 can be driven when driving in EV mode, which is preferred in terms of power transmission efficiency.

[0051] Furthermore, when the first value A is greater than the second value B, the power transmission efficiency of the front wheel power system 100 is improved, thereby allowing the driver's power requirements to be met by driving only the front wheel motor 120. In other words, when the first value A is greater than the second value B, the maximum power of the front wheel motor can be equal to or greater than the driver's power requirements.

[0052] Therefore, when the maximum front wheel motor power + maximum rear wheel motor power ≥ driver-required power and the maximum rear wheel motor power × reducer efficiency < maximum front wheel motor power × transmission efficiency, controller 10 can be configured to drive only the front wheel motor 120 in the vehicle's drive source. For example, in response to determining that the sum of the maximum front wheel motor power and the maximum rear wheel motor power (maximum front wheel motor power + maximum rear wheel motor power) is equal to or greater than the driver-required power, and in response to determining that the value obtained by multiplying the maximum front wheel motor power by the transmission efficiency (maximum front wheel motor power × transmission efficiency) is greater than the value obtained by multiplying the maximum rear wheel motor power by the reducer efficiency (maximum rear wheel motor power × reducer efficiency), the upper-level controller 11 can be configured to request the motor controller 13 to drive only the front wheel motor 120, and the motor controller 13 can be configured to drive only the front wheel motor 120.

[0053] When the transmission 130 begins shifting during operation using only the engine 110, the front wheel motor 120, and the rear wheel motor 210, the controller 10 can be configured to instruct the rear wheel motor 210 to output a portion of the power requested by the driver that can be output by the rear wheel motor 210. At this time, the request is for the rear wheel motor 210 to output power equal to or less than the maximum rear wheel motor power.

[0054] Whether the transmission 130 has started shifting can be determined based on shift synchronization. When the shift synchronization of the transmission 130 is equal to or greater than a predetermined first phase α during driving by only the front wheel motor 120, the controller 10 can be configured to determine that the transmission 130 has started shifting. For example, when the shift synchronization value received from the transmission controller 14 is equal to or greater than the first phase α, the upper-level controller 11 can be configured to determine that the transmission 130 has started shifting.

[0055] The first synchronization α can be set to the commonly used value of 1, but it can also be set to a value other than 1 depending on the rate at which the torque of the front wheel motor 120 decreases during gear shifting. For example, when the torque of the front wheel motor 120 can decrease relatively quickly during gear shifting, the first synchronization α can be set to a value other than 1.

[0056] In response to determining the start of a shift based on the shift synchronization information of the transmission 130, the controller 10 can be configured to compare the maximum rear wheel motor power with the driver's requested power. When the maximum rear wheel motor power is equal to or greater than the driver's requested power, the rear wheel motor 210 can operate to output the driver's requested power because it can output power that meets the driver's requested power. In other words, when the maximum rear wheel motor power is equal to or greater than the driver's requested power, a command requesting the output of power with the same value as the driver's requested power can be transmitted to the rear wheel motor 210, and a command requesting the output of zero power can be transmitted to the front wheel motor 120.

[0057] When the maximum power of the rear wheel motor is less than the power required by the driver, the rear wheel motor 210 can be operated to output the maximum power because it cannot output all the power required by the driver. The front wheel motor 120 can be operated to output the power obtained by subtracting the maximum power of the rear wheel motor from the power required by the driver (power required by the driver - power required by the rear wheel motor).

[0058] In other words, when the maximum rear wheel motor power is less than the driver's required power, the controller 10 can operate the rear wheel motor 210 to output the maximum rear wheel motor power, and the front wheel motor 120 can operate to output the power obtained by subtracting the maximum rear wheel motor power from the driver's required power. The result is, as in... Figure 4 As shown, the maximum power output of the rear wheel motor can be output to the rear wheel 230 via the reducer 220, and the power output of the front wheel motor can be output to the front wheel 150 via the gearbox 130.

[0059] As mentioned above, during gear shifting, the output power of the front wheel motor can be adjusted to 0 or to a value lower than the power value before gear shifting, thereby minimizing gear shifting losses.

[0060] Figure 5 and Figure 6 This is a schematic diagram illustrating the power transmission path when driving in engine operating mode. Specifically, Figure 5 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention before gear shifting. Figure 6 This is a schematic diagram illustrating the power transmission path of an electric four-wheel drive vehicle according to the present invention during gear shifting.

[0061] When the driver requests power greater than the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor (maximum front wheel motor power + maximum rear wheel motor power), the controller 10 can be configured to operate the engine 110 to meet the driver's power request. For example, when the driver requests power greater than the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor, the upper-level controller 11 can be configured to request the engine controller 12 to drive the engine 110, and the engine controller 12 can be configured to operate the engine 110 according to a predetermined optimal operating line (OOL) condition.

[0062] In response to receiving an instruction, engine 110 can be configured to output power determined according to optimal operating line conditions, and front wheel motor 120 can be requested to output power obtained by subtracting the power output by engine 110 (i.e., engine output power) from the driver's requested power (driver's requested power - engine output power).

[0063] At this time, when the power requested by the front wheel motor 120 is a positive (+) value, the front wheel motor 120 can be driven to output power to the front wheel 150 while the battery 160 is discharging. When the power requested by the front wheel motor 120 is a negative (-) value, the front wheel motor 120 can operate in generator mode to charge the battery 160.

[0064] The optimal operating line (as a value used to improve fuel efficiency) can be preset and stored in the engine controller 12. For example, an operating line map configured to determine the optimal engine torque that maximizes engine efficiency based on engine speed (RPM) can be stored in the engine controller 12. The engine controller 12 can be configured to adjust the drive of the engine 110 according to instructions from the higher-level controller 11 to the optimal operating line (i.e., the optimal torque value) determined by the operating line map.

[0065] When driving the vehicle in engine operating mode using the power of engine 110, such as in Figure 5 As shown, power from engine 110 is transmitted to the front wheels 150 via transmission 130. Transmission 130 begins shifting gears when driving in engine operating mode using power from engine 110 or engine 110 and front wheel motor 120, or when driving in engine operating mode using power from engine 110, front wheel motor 120, and rear wheel motor 210, as in... Figure 5As shown, the controller 10 can be configured to instruct the rear wheel motor 210 to output power that can be output by the rear wheel motor 210, and the battery 160 is charged using engine power, thereby minimizing the torque input to the transmission 130.

[0066] As previously mentioned, whether the transmission 130 has started shifting can be determined based on shift synchronization. When the shift synchronization of the transmission 130 is equal to or greater than a predetermined second phase β during operation in engine operating mode, the controller 10 can be configured to determine that the transmission 130 has started shifting. For example, when the shift synchronization value received from the transmission controller 14 is equal to or greater than the second phase β, the upper-level controller 11 can be configured to determine that the transmission 130 has started shifting.

[0067] The second synchronization β can be set to the commonly used value of 1, but it can also be set to a value other than 1 depending on the rate at which the torque of the engine 110 decreases during gear shifting. For example, when the torque of the engine 110 can decrease relatively quickly during gear shifting, the second synchronization β can be set to a value other than 1.

[0068] When the transmission 130 begins shifting gears while driving in engine operating mode, the controller 10 can be configured to request the rear wheel motor 210 to output a predetermined amount of power based on a comparison between the maximum rear wheel motor power and the driver's requested power. Specifically, when the maximum rear wheel motor power is equal to or greater than the driver's requested power, the controller 10 can be configured to request the driver's requested power from the rear wheel motor 210 and operate the rear wheel motor 210 to output power corresponding to the driver's requested power. When the maximum rear wheel motor power is less than the driver's requested power, the controller 10 can be configured to request maximum power from the rear wheel motor 210 and operate the rear wheel motor 210 to output maximum power.

[0069] When the rear wheel motor 210 requests power from the driver, the engine 110 can be configured to receive instructions on outputting the optimal power determined based on the optimal operating line conditions, and the front wheel motor 120 receives instructions on outputting the power obtained by subtracting the power output by the rear wheel motor and the power output by the engine from the driver's requested power (driver's requested power - rear wheel motor output power - engine output power).

[0070] At this time, since the rear wheel motor outputs power with the same value as the driver's required power (rear wheel motor output power = driver's required power), the front wheel motor 120 can be requested to output power with the same value as the engine output power, which has a negative (-) value. Therefore, the front wheel motor 120 can be configured to charge the battery 160 using the engine output power. In other words, the front wheel motor 120 can operate as a generator to charge the battery 160 using the engine output power.

[0071] For example, when the maximum rear wheel motor power is equal to or greater than the power required by the driver, the upper-level controller 11 can be configured to instruct the motor controller 13 to request the rear wheel motor 210 to output the power required by the driver and to request the front wheel motor 120 to output engine output power with a negative (-) value. The motor controller 13 can be configured to instruct the rear wheel motor 210 to output the power required by the driver and to instruct the front wheel motor 120 to use the engine output power to generate electricity to charge the battery 160.

[0072] Therefore, when the rear wheel motor 210 outputs all the power required by the driver, the power output from the engine 110 (i.e., the engine output power) is not output to the front wheels 150 but is applied to the front wheel motor 120, and the front wheel motor 120 uses the engine output power to charge the battery 160. In addition, the power output from the rear wheel motor can be transmitted to the rear wheels 230 via the reducer 220.

[0073] Additionally, when the shift begins and the rear wheel motor 210 is requested to output maximum power, the engine 110 can be requested to output power determined according to the operating line mapping, and the front wheel motor 120 can be requested to output power obtained by subtracting the maximum rear wheel motor power and the engine output power from the driver's requested power (driver's requested power - maximum rear wheel motor power - engine output power).

[0074] When the rear wheel motor 210 cannot output all the power requested by the driver during gear shifting, the power that cannot be output by the rear wheel motor 210 (i.e., the difference between the driver's requested power and the maximum rear wheel motor power) is compensated by the engine output power. In other words, when the maximum rear wheel motor power is less than the driver's requested power, at least a portion of the engine output power can be transmitted to the front wheels 150 via the transmission 130. At this time, the power transmitted to the front wheels 150 can be determined as the power obtained by subtracting the maximum rear wheel motor power from the driver's requested power (driver's requested power - maximum rear wheel motor power).

[0075] Therefore, the front wheel motor 120 can request power obtained by subtracting the engine output power (front wheel power - engine output power) from the power transmitted to the front wheel 150 (hereinafter referred to as "front wheel power"). When the power obtained by subtracting the engine output power from the front wheel power has a negative (-) value, that is, when the sum of the maximum rear wheel motor power and the engine output power is greater than the power requested by the driver, the front wheel motor 120 can be configured to charge the battery 160 using the power obtained by subtracting the front wheel power from the engine output power (engine output power - front wheel power).

[0076] More specifically, when the sum of the power requested from the rear wheel motor 210 and the engine 110 (maximum rear wheel motor power + engine output power) during gear shifting at transmission 130 exceeds the driver's required power, controller 10 can be configured to instruct front wheel motor 120 to generate power to charge battery 160. In this case, front wheel motor 120 can be configured to generate power to charge battery 160 using the power obtained by subtracting the maximum rear wheel motor power and engine output power from the driver's required power (driver's required power - maximum rear wheel motor power - engine output power).

[0077] For example, when the maximum power of the rear wheel motor is less than the power required by the driver, the upper-level controller 11 can be configured to instruct the motor controller 13 to request the rear wheel motor 210 to output maximum power and to request the front wheel motor 120 to output power obtained by subtracting the engine output power from the power transmitted to the front wheels (front wheel power - engine output power). The motor controller 13 can be configured to instruct the rear wheel motor 210 to output maximum power and to instruct the front wheel motor 120 to use the power obtained by subtracting the front wheel power from the engine output power (engine output power - front wheel power) to charge the battery 160.

[0078] Therefore, when the rear wheel motor 210 outputs maximum power, such as in Figure 6 As shown, a portion of the power output from engine 110 (i.e., front-wheel drive power) can be transmitted to front wheel 150, and the remaining power (engine output power - front-wheel drive power) can be used by front wheel motor 120 to charge battery 160. At this time, maximum rear wheel motor power can be output to rear wheel 230 via reduction gear 220. When gear shifting begins during engine operation, as described above, rear wheel motor 210 can be configured to output as much driving power as possible, and rear wheel motor 210 can be configured to provide increased driving power compared to the engine 110 output.

[0079] In the following text, reference will be made to Figure 7A and Figure 7BA drive control method for an electric four-wheel drive vehicle during gear shifting is described according to the present invention. Figure 7A and Figure 7B This is a flowchart illustrating a drive control method for an electric four-wheel drive vehicle during gear shifting according to the present invention. However, the drive control method during gear shifting according to the present invention is not limited to... Figure 7A and Figure 7B The order shown.

[0080] refer to Figure 7A First, the driver's requested power can be compared with the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor (maximum front wheel motor power + maximum rear wheel motor power) (S100). When the driver's requested power is greater than the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor, the engine 110 can be driven (S210).

[0081] When the driver requests power equal to or less than the sum of the maximum front wheel motor power and the maximum rear wheel motor power, a first value obtained by multiplying the maximum front wheel motor power by the transmission efficiency (maximum front wheel motor power × transmission efficiency) can be compared with a second value obtained by multiplying the maximum rear wheel motor power by the reducer efficiency (maximum rear wheel motor power × reducer efficiency) (S110).

[0082] When the first value is greater than the second value, driving in EV mode can be performed by driving only the front wheel motor 120 in the vehicle's drive source (S120). It can be determined whether the transmission 130 starts to shift gears while only driving the front wheel motor 120 (S130). When the transmission 130 starts to shift gears, the maximum rear wheel motor power can be compared with the power requested by the driver (S140).

[0083] When the maximum rear wheel motor power is equal to or greater than the driver's required power, the rear wheel motor 210 can be configured to output power with the same value as the driver's required power until the shift is completed (S150), and the front wheel motor 120 can be configured to output zero power to minimize shift loss. When the maximum rear wheel motor power is less than the driver's required power, the rear wheel motor 210 can be configured to output maximum power, and the front wheel motor 120 can be configured to output power obtained by subtracting the maximum rear wheel motor power from the driver's required power (driver's required power - maximum rear wheel motor power) until the shift is completed (S160), to reduce energy loss occurring in the transmission 130.

[0084] When the transmission 130 completes a gear shift, the vehicle drive mode can be switched back to the front wheel motor drive mode (S170), and the driver's requested power and the maximum front wheel motor power can be compared (S180). When the driver's requested power is equal to or less than the maximum front wheel motor power, the front wheel motor drive mode can be maintained. When the driver's requested power is greater than the maximum front wheel motor power, the rear wheel motor 210 can be driven (S190).

[0085] When the rear wheel motor 210 is started, the driver's requested power can be compared with the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor (S200). When the driver's requested power is greater than the sum of the maximum power of the front wheel motor and the maximum power of the rear wheel motor, the engine 110 can be driven (S210), because the driver's requested power cannot be output by driving only motors 120 and 210.

[0086] refer to Figure 7B The engine 110 can be driven to output power that maximizes engine efficiency based on optimal operating line control (S220). When driving the engine 110, it can be determined whether the transmission 130 has started to shift gears (S230). When the transmission 130 has not started to shift gears, the driver's requested power can be compared with the engine's output power based on optimal operating line control (S240).

[0087] When the transmission 130 is not shifting gears, the front wheel motor 120 can be configured to output power obtained by subtracting the engine output power from the driver's requested power. When the driver's requested power is less than the engine output power, the front wheel motor 120 can be configured to charge the battery 160 electrically connected to the front wheel motor 120 according to the instruction of the controller 10 (S250). At this time, the front wheel motor 120 can be configured to generate electricity using the power obtained by subtracting the driver's requested power from the engine output power. When the driver's requested power is greater than the engine output power, the front wheel motor 120 can be configured to output power obtained by subtracting the engine output power from the driver's requested power according to the instruction of the controller 10. At this time, the power from the battery 160 can be used to drive the front wheel motor 120, and the power output of the front wheel motor can be transmitted to the front wheels 150 via the transmission 130.

[0088] In response to determining the start of gear shifting in transmission 130 based on the comparison result in step S230, the maximum rear wheel motor power can be compared with the power requested by the driver (S260). When the maximum rear wheel motor power is equal to or greater than the power requested by the driver, since rear wheel motor 210 is capable of outputting the power requested by the driver, rear wheel motor 210 can be configured to output the power requested by the driver, and front wheel motor 120 can be configured to output power obtained by subtracting the power output by the rear wheel motor and the power output by the engine from the power requested by the driver (S270). At this time, since the power output by the rear wheel motor has the same power value as the power requested by the driver, front wheel motor 120 can be configured to charge battery 160 using engine power.

[0089] Until the transmission 130 completes the gear shift, the rear wheel motor 210 can be configured to output the power required by the driver, and the front wheel motor 120 can be configured to charge the battery 160 using the engine output power. When the maximum rear wheel motor power is less than the driver's required power, since the rear wheel motor 210 cannot fully output the driver's required power, the rear wheel motor 210 can be requested to output maximum power, and at least a portion of the engine output power can be transmitted to the front wheels 150 (S280). At this time, the engine power transmitted to the front wheels 150 (i.e., the power transmitted to the front wheels) can be determined as the power obtained by subtracting the maximum rear wheel motor power from the driver's required power (driver's required power - maximum rear wheel motor power).

[0090] At this time, the front wheel motor 120 can be requested to output power obtained by subtracting the maximum rear wheel motor power and the engine output power from the driver's requested power (driver's requested power - maximum rear wheel motor power - engine output power) (S280). Therefore, the front wheel motor 120 uses the power obtained by subtracting the power transmitted to the front wheel 150 from the engine output power (engine output power - front wheel transmitted power) to charge the battery.

[0091] For example, the motor controller 13 can be configured to control the battery charging operation of the front wheel motor 120 according to instructions from the upper controller 11. In this case, the engine power used by the front wheel motor 120 to charge the battery can be adjusted so that at least a portion of the engine output power is transmitted to the front wheels 150. Until the transmission 130 completes shifting, the rear wheel motor 210 can be configured to output maximum power, and the front wheel motor 120 uses the power obtained by subtracting the front wheel transmitted power from the engine output power (engine output power - front wheel transmitted power) to charge the battery 160.

[0092] on the other hand, Figure 8 and Figure 9This is a schematic diagram illustrating another embodiment of the power transmission system of an electric four-wheel drive vehicle. Figure 8 The arrows shown indicate the power transmission path before gear shifting while driving in engine operating mode. Figure 9 The arrows shown indicate the power transmission path during gear changes. (Reference) Figure 8 An electric four-wheel drive vehicle may include a power transmission system that is formed by a combination of a front-wheel power system 101 including an engine 111 and a rear-wheel power system 201 including a rear-wheel motor 211.

[0093] Specifically, the front-wheel powertrain 101 may include an engine 111 and a transmission 131, but not a front-wheel motor. The transmission 131 is configured to shift the power of the engine 111 and output the shifted power to the front wheels 151. The rear-wheel powertrain 201 may include a rear-wheel motor 211 and a reducer 221. The reducer 221 is configured to reduce the power of the rear-wheel motor 211 and output the reduced power to the rear wheels 231.

[0094] Even when the vehicle includes a front-wheel powertrain 101 and a rear-wheel powertrain 201, the rear-wheel motor 211 can be instructed to output maximum power during gear shifting while driving, thereby minimizing shifting losses. In other words, when shifting begins during driving using an engine 111 connected to the transmission 131, driving force can be maximized through the rear-wheel motor 211, which is not connected to the transmission 131, thereby minimizing energy losses in the power transmission system during gear shifting and improving fuel efficiency.

[0095] When the front wheel power system 101 does not include the front wheel motor, such as in Figure 8 As shown, it is not possible to charge the battery using the front wheel motor, but the engine power transmitted to the front wheels 151 via the transmission 131 is reduced, thereby reducing transmission loss. When the transmission 141 is not shifting gears in the vehicle, the driver's power demand can be requested from the engine 111 based on the driver's power demand, which varies according to the amount of pressure applied to the accelerator pedal, or the engine 111 can request power determined according to the optimal engine operating line.

[0096] At this time, when the engine cannot output all the power requested by the driver, it can request power from the rear wheel motor 211 by subtracting the engine output power from the driver's requested power (driver's requested power - engine output power). When the transmission 131 starts shifting during driving using the power of the engine 110 and / or the power of the engine 111 and the rear wheel motor 211 (as described above, i.e., during driving in engine operating mode), the controller 10 can be configured to compare the maximum rear wheel motor power with the driver's requested power, and request power that can be output by the rear wheel motor 211 based on the comparison result.

[0097] When the maximum rear wheel motor power is equal to or greater than the driver's required power, the rear wheel motor 211 can output power corresponding to the driver's required power, such as in... Figure 9 As shown, controller 10 can be configured to instruct rear wheel motor 211 to output power requested by the driver and request engine 111 to output zero power to stop engine 111.

[0098] When the maximum rear wheel motor power is less than the driver's required power, since the rear wheel motor 211 cannot output all the driver's required power, the controller 10 can be configured to: instruct the rear wheel motor 211 to output the maximum power, and instruct the engine 111 to output the power obtained by subtracting the maximum rear wheel motor power from the driver's required power (driver's required power - maximum rear wheel motor power).

[0099] As described above, the power transmitted to the front wheel 151 via the transmission 131 can be minimized during gear shifting, thereby reducing energy loss in the power transmission system during gear shifting. It is evident from the foregoing that, according to the present invention, energy loss in the power transmission path during gear shifting can be minimized, thereby improving fuel efficiency. Furthermore, most of the shift shock caused by torque intervention during gear shifting is eliminated, thereby improving marketability.

[0100] The effects of this invention are not limited to those described above, and those skilled in the art will clearly understand other unmentioned effects through the above description. It will be apparent to those skilled in the art that the invention described above is not limited to the above embodiments and drawings, and various substitutions, modifications, and variations can be made without departing from the technical concept of the invention.

Claims

1. A device for controlling the drive of an electric four-wheel drive vehicle during gear shifting, comprising: A front-wheel powertrain system includes an engine, a front-wheel motor, and a transmission, the transmission being configured to shift power between the engine and the front-wheel motor and to output the shifted power to the front wheels; A rear-wheel power system, comprising a rear-wheel motor and a reducer, the reducer being configured to reduce the power of the rear-wheel motor and output the reduced power to the rear wheels; as well as The controller is configured to, when the transmission shifts during engine-driven driving, instruct the rear wheel motors to output the portion of the power requested by the driver corresponding to the power that can be output by the rear wheel motors, and instruct the front wheel motors to output the power obtained by subtracting the power instructed to the rear wheel motors and the engine output power from the power requested by the driver. Specifically, in response to determining that the sum of the maximum power that can be output by the front wheel motor and the maximum power that can be output by the rear wheel motor is less than the power required by the driver, the controller is configured to drive the engine and instruct the engine to output power determined according to the operating line mapping. In response to determining that the driver requires more power than the maximum power that can be output by the rear wheel motor during gear shifting, the controller is configured to instruct the rear wheel motor to output the maximum power. The engine output power, which corresponds to the power obtained by subtracting the maximum power of the rear wheel motor from the power requested by the driver, is output to the front wheels.

2. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting according to claim 1, further comprising: The battery is connected to the front and rear wheel motors for charging and discharging. Specifically, in response to determining that the sum of the maximum rear wheel motor power and the engine output power during gear shifting exceeds the driver's required power, the controller is configured to instruct the front wheel motor to generate electricity to charge the battery. The front wheel motor is configured to generate electricity to charge the battery by subtracting the maximum power of the rear wheel motor and the engine output power from the driver's required power.

3. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 1, wherein: In response to determining that the driver's power demand during gear shifting is equal to or less than the maximum rear wheel motor power, the controller is configured to instruct the rear wheel motor to output the driver's power demand and instruct the front wheel motor to generate electricity to charge the battery. The front wheel motor is configured to use engine output power to generate electricity to charge the battery.

4. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 2, wherein, In response to determining that the transmission did not perform a gear shift during engine-driven driving, the controller is configured to instruct the front wheel motor to output power obtained by subtracting the engine output power from the driver's requested power.

5. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 4, wherein, In response to determining that the driver's power demand is less than the engine's output power, the controller is configured to instruct the front wheel motor to generate electricity to charge the battery, and the front wheel motor is configured to generate electricity to charge the battery using the power obtained by subtracting the engine's output power from the driver's power demand.

6. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 4, wherein, In response to determining that the driver's power demand is greater than the engine's output power, the controller is configured to instruct the front wheel motor to output power obtained by subtracting the engine's output power from the driver's power demand.

7. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 1, wherein, When the transmission begins to shift gears during driving using only the power of the front wheel motor, the controller is configured to: instruct the rear wheel motor to output the portion of the power requested by the driver that corresponds to the power that can be output by the rear wheel motor, and instruct the front wheel motor to output the power obtained by subtracting the power output by the rear wheel motor from the power requested by the driver.

8. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 7, wherein, In response to determining that the maximum rear wheel motor power during gear shifting is equal to or greater than the power required by the driver, the controller is configured to instruct the rear wheel motor to output the power required by the driver.

9. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 8, wherein, In response to determining that the maximum rear wheel motor power during gear shifting is equal to or greater than the power required by the driver, the controller is configured to instruct the front wheel motor to output zero power.

10. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 7, wherein, In response to determining that the maximum rear wheel motor power is less than the driver's required power during gear shifting, the controller is configured to: instruct the rear wheel motor to output the maximum power it can output, and instruct the front wheel motor to output the power obtained by subtracting the maximum rear wheel motor power from the driver's required power.

11. The apparatus for controlling the drive of an electric four-wheel drive vehicle during gear shifting, according to claim 7, wherein, In response to determining that the sum of the maximum front wheel motor power and the maximum rear wheel motor power is equal to or greater than the driver's required power, and that the value obtained by multiplying the maximum rear wheel motor power by the reduction gear's operating efficiency is less than the value obtained by multiplying the maximum front wheel motor power by the transmission's operating efficiency, the controller is configured to drive only the front wheel motors during driving.

12. A device for controlling the drive of an electric four-wheel drive vehicle during gear shifting, comprising: A front-wheel powertrain system, comprising an engine and a transmission, the transmission being configured to shift the power of the engine and output the shifted power to the front wheels; A rear-wheel power system, comprising a rear-wheel motor and a reducer, the reducer being configured to reduce the power of the rear-wheel motor and output the reduced power to the rear wheels; as well as The controller is configured to, when the transmission shifts during engine-driven driving, instruct the rear wheel motor to output the portion of the power requested by the driver corresponding to the power that can be output by the rear wheel motor, and instruct the engine to output the power obtained by subtracting the power output by the rear wheel motor from the power requested by the driver. In response to determining that the maximum power output by the rear wheel motor during gear shifting is equal to or greater than the power requested by the driver, the controller is configured to instruct the rear wheel motor to output the power requested by the driver and to stop the engine; in response to determining that the maximum power output by the rear wheel motor during gear shifting is less than the power requested by the driver, the controller is configured to: instruct the rear wheel motor to output the maximum power and instruct the engine to output the power obtained by subtracting the maximum rear wheel motor power from the power requested by the driver.

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