Control device of four-wheel independent drive vehicle

Abstract

To achieve both improvement of traveling stability and improvement or maintenance of energy efficiency in turning travel of a four-wheel independent drive vehicle.SOLUTION: A controller 35 includes: a driving determination part 35a for determining whether a driving state is four-wheel driving or two-wheel driving; a turning determination part 35b for determining whether a vehicle travels for turning; a four-wheel turning control part 35c for exerting control such that each motor of four wheels becomes output torque suitable for turning travel, when it is determined by the driving determination part 35a that the driving state is the four-wheel driving and it is determined by the turning determination part 35b that the vehicle travels for turning; and a two-wheel turning control part 35d for exerting control such that the motor provided corresponding to driving wheels driven for two-wheel driving becomes the output torque suitable for turning travel when the two-wheel driving is determined and the turning travel is determined, and exerting control such that brake force by a brake mechanism of non-driving wheels or a steering angle by a steering mechanism are suitable for turning travel.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a vehicle control device that can control the drive torque of each of the four wheels independently, and in particular to a vehicle control device that can selectively set a four-wheel drive state in which all four wheels are driven, and a two-wheel drive state in which either the front or rear wheels are driven. [Background technology]

[0002] Patent Document 1 describes a vehicle in which each of the four wheels can be controlled independently. The independently driven wheel electric vehicle described in Patent Document 1 is configured such that each of the four wheels is provided with a motor, and the motors are individually controlled to allow the drive torque of each wheel to be individually and appropriately controlled. In this type of vehicle, yawing occurs in the vehicle body by providing a difference in drive torque between the left and right wheels, or between the front and rear wheels, so that the drive torque of each wheel can be controlled so that the vehicle travels along the turning path intended by the driver, thereby improving the turning performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-184911 A Summary of the Invention [Problem to be solved by the invention]

[0004] Appropriate control of the torque (driving torque and braking torque) of all four wheels of a vehicle can improve driving stability and running performance on rough roads, and can also improve braking performance by engine braking (driving force source brake). In an independently driven wheel vehicle as described in Patent Document 1, such characteristics are effectively utilized to independently control the torque of all four wheels during cornering to improve turning performance or running stability. However, since the motors that are the driving force sources for each wheel and the transmission mechanisms that transmit torque from the motors to the wheels have unavoidable losses due to friction and inertia, if the torque of all four wheels is constantly controlled during cornering, energy loss will increase, and there is a high possibility that the electric fuel consumption will worsen in, for example, an electric vehicle (BEV) or a hybrid vehicle (HEV or PHEV).

[0005] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide a control device that can achieve both improved driving stability during cornering of a four-wheel independent drive vehicle and improved or maintained energy efficiency. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a control device for a four-wheel independently drive vehicle, in which a driving force source is provided corresponding to each of a total of four wheels, two front wheels and two rear wheels, and the torque of each of the four wheels is controlled independently from one another by the driving force sources, thereby enabling four-wheel drive in which driving torque is generated by all four wheels and two-wheel drive in which driving torque is generated by any two wheels, either the front or rear, and which can be selected and set based on a required running state, and further provided with a braking mechanism for braking or a steering mechanism for steering at least non-driven wheels that are not driven by the driving force source in the two-wheel drive state, the control device comprising: a controller for controlling the driving force sources and the braking mechanism or the steering mechanism, and the controller is configured to control the selected and set drive state to be set by the four wheels. The vehicle is characterized in that it comprises a drive determination unit which determines whether the vehicle is in drive or two-wheel drive mode; a turning determination unit which determines whether the four-wheel independent drive vehicle is making a turn; a four-wheel turning control unit which, when the drive determination unit determines the four-wheel drive mode and the turning determination unit determines the turning mode, controls the drive power sources provided corresponding to each of the four wheels to have an output torque suitable for the turning mode; and, when the drive determination unit determines the two-wheel drive mode and the turning determination unit determines the turning mode, controls the drive power sources provided corresponding to the drive wheels driven for the two-wheel drive mode to have an output torque suitable for the turning mode, and controls the braking force by the brake mechanism or the steering angle by the steering mechanism of the non-driven wheels to be suitable for the turning mode. Effect of the Invention

[0007] According to the present invention, when a turning motion is determined while the vehicle is traveling in two-wheel drive, the torque of the two driven wheels (drive wheels) is controlled to a torque suitable for turning motion, and the braking force or steering angle of the non-driven wheels is controlled to be suitable for turning motion. In this case, the torque control of the drive wheels and the braking or steering control of the non-driven wheels are executed in coordination. Therefore, the number of wheels to be driven or the number of power sources to output the drive torque are limited to two, so that unavoidable losses are reduced and energy efficiency or electricity consumption is improved, and at least deterioration of energy efficiency or electricity consumption can be avoided, suppressed, or maintained. In this case, the torque or steering angle of the non-driven wheels is controlled by the brake mechanism or steering mechanism to be suitable for turning motion, so that turning performance is maintained, or deterioration is suppressed or avoided. On the other hand, when a turning motion is determined while the vehicle is traveling in four-wheel drive, the drive force source for each wheel is controlled so that the torque of each of the four wheels becomes a torque suitable for turning motion. In this case, the vehicle turns using all four wheels, improving driving stability during turning. In this case, the brake mechanism and steering mechanism do not function (operate) specifically for turning. Therefore, according to the present invention, it is possible to improve driving stability during turning and improve or maintain energy efficiency at the same time. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a schematic diagram of a drive system of a four-wheel independent drive vehicle according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a skeleton diagram showing an example of a rear wheel side drive unit. [Diagram 3] FIG. 2 is a skeleton diagram showing an example of a front wheel side drive unit. [Figure 4] 2 is a schematic diagram for explaining various mechanisms for driving, stopping, and turning a vehicle. FIG. [Diagram 5] FIG. 4 is a block diagram illustrating input and output signals of a controller. [Figure 6] FIG. 2 is a block diagram showing a functional configuration of a controller. [Figure 7] 4 is a flowchart illustrating an example of control executed in the embodiment of the present invention. [Figure 8] 4 is a diagram showing an example of a map in which the rotation speed of the oil pump for each driving mode is determined. FIG. [Figure 9] 6 is a flowchart for explaining a control example in which a drive state during cornering is determined based on a drive state at the start of cornering. [Figure 10] FIG. 4 is a diagram illustrating a required driving torque map used in a D range. [Figure 11] FIG. 10 is a diagram that illustrates a required drive torque map when the accelerator opening is 50% in the D range or L range. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0010] The vehicle targeted by the present invention is a four-wheel independent drive vehicle having a total of four wheels, two front wheels and two rear wheels, and a driving force source is provided corresponding to each wheel so that all four wheels can be driven independently of each other. An example of such a vehicle is shown in FIG. 1. The vehicle Ve shown here has left and right front wheels 1r, 1l and left and right rear wheels 2r, 2l, and drive units Pfr, Pfl, Prr, Prl are provided as driving force sources corresponding to these wheels 1r, 1l, 2r, 2l, respectively. Each of these drive units Pfr, Pfl, Prr, Prl is mainly composed of a motor and a gear reduction mechanism (transmission mechanism).

[0011] FIG. 2 shows a skeleton diagram of an example of the drive units Prr, Prl on the rear wheels 2r, 2l side. These drive units Prr, Prl are symmetrical, so they will be described together without being specifically designated as "right" or "left". Motors Mrr, Mrl are mounted with their central axis of rotation oriented in the front-rear direction of the vehicle Ve, and drive gears 4rr, 4rl are attached to their rotor shafts, which mesh with counter driven gears 5rr, 5rl. The counter driven gears 4rr, 4rl have a larger diameter than the drive gears 4rr, 4rl, and therefore these gear pairs form a reduction mechanism. Counter driven gears 6rr, 6rl, which are bevel gears, are provided on the same axis as the counter driven gears 5rr, 5rl so as to rotate integrally with them, and the counter drive gears 6rr, 6rl mesh with driven gears 8rr, 8rl, which are bevel gears integral with drive shafts 7rr, 7rl connected to the rear wheels 2r, 2l. By making the driven gears 8rr, 8rl larger in diameter than the counter drive gears 6rr, 6rl, these gear pairs can be used as a reduction mechanism.

[0012] These motors Mrr, Mrl, the reduction mechanism, and each bevel gear are accommodated in a liquid-tight state inside the casing 9. Electric oil pumps OPrr, OPrl are provided to supply oil mainly for cooling to the motors Mrr, Mrl inside the casing 9. These oil pumps OPrr, OPrl are provided at appropriate locations on the vehicle Ve outside the casing 9, and are configured to pump oil 11 from an oil reservoir 10 and supply the oil 11 to the motors Mrr, Mrl via cooling oil passages 12rr, 12rl. Although not shown in particular, the oil 11 is configured to flow back from inside the casing 9 to the oil reservoir 10. An oil cooler may be provided midway through the cooling oil passages 12rr, 12rl.

[0013] FIG. 3 shows a skeleton diagram of an example of the drive units Pfr, Pfl on the front wheels 1r, 1l side. These drive units Pfr, Pfl are symmetrical, so they will be described together without being specifically designated as "right" or "left". The motors Mfr, Mfl are mounted with their rotational center axis oriented in the width direction (lateral direction) of the vehicle Ve, and drive gears 13fr, 13fl are attached to the rotor shafts, and these drive gears 13fr, 13fl mesh with the idle gears 14r, 14l. Countershafts 15r, 15l are provided parallel to the rotational center axis of the idle gears 14r, 14l, and the idle gears 14r, 14l mesh with counter driven gears 16fr, 16rl attached to the countershafts 15r, 15l. The counter driven gears 16fr, 16fl have a larger diameter than the drive gears 13fr, 13fl attached to the motors Mfr, Mrl, and these gear pairs form a reduction mechanism. The counter drive gears 17fr, 17fl are attached to the counter shafts 15r, 15l, and these counter drive gears 17fr, 17fl mesh with the driven gears 19fr, 19fl that are integral with the drive shafts 18fr, 18fl that are connected to the front wheels 1r, 1l. The driven gears 19fr, 19fl have a larger diameter than the counter drive gears 17fr, 17fl, and these gear pairs form a reduction mechanism.

[0014] The motors Mfr, Mfl on the front wheels 1r, 1l are configured to be cooled by the oil 11, similarly to the motors Mrr, Mrl on the rear wheels 2r, 2l. That is, electric oil pumps OPfr, OPrl are provided corresponding to the motors Mfr, Mfl on the front wheels 1r, 1l, and these oil pumps OPfr, OPfl are configured to pump up the oil 11 from the oil reservoir 10 and supply the oil 11 to the motors Mfr, Mfl via the cooling oil passages 20fr, 20fl. Although not shown in particular, the oil that has cooled the motors Mfr, Mfl is configured to return to the oil reservoir 10. An oil cooler may be provided in the middle of the cooling oil passages 20fr, 20fl. Furthermore, the oil reservoir 10 and the oil 11 may be provided separately on the front wheels 1r, 1l and the rear wheels 2r, 2l.

[0015] An oil pump OPm is provided to pump up oil for lubrication. This oil pump OPm is a mechanical pump, and in the example shown in Fig. 3, is connected to the countershaft 15l on the left front wheel 1l side. Therefore, this oil pump OPm is driven while the vehicle Ve is running, and is configured to pump up the oil 11 from the oil reservoir 10 and supply the oil 11 to predetermined lubrication points.

[0016] An electric storage device (Bat) 21 is provided to exchange electric power between the motors Mfr, Mfl, Mrr, Mrl and the oil pumps OPfr, OPrl. The electric storage device 21 is mainly composed of secondary batteries such as lithium ion batteries and solid-state batteries. The motors Mfr, Mfl, Mrr, Mrl are, for example, permanent magnet synchronous motors, and are connected to the electric storage device 21 via power controllers PCfr, PCfl, PCrr, PCrl mainly composed of inverters. Therefore, the output torques and braking torques during energy regeneration of the motors Mfr, Mfl, Mrr, Mrl are individually controlled independently of each other. Note that the power controllers PCfr, PCfl, PCrr, PCrl only need to be independent of each other in function, and may be configured as an integrated unit as a whole.

[0017] The vehicle Ve is equipped with various mechanisms for running, stopping, and turning, just like a normal vehicle. The main components are shown in FIG. 4. The wheels 1r, 1l, 2r, and 2l are provided with brake mechanisms Bfr, ​​Bfl, Brr, and Brl. These brake mechanisms Bfr, ​​Bfl, Brr, and Brl are configured to generate braking forces by operating a brake pedal (not shown) and to generate braking forces by being electrically controlled. A vehicle stability system (VSC) 22 is provided as a system for electrically controlling the braking forces. The VSC 22 may have a configuration similar to that known in the art, and is, for example, a system that integrates a traction control system (TCS) 23 that operates the brake mechanisms Bfr, ​​Bfl, Brr, and Brl to limit the driving force of each wheel, and an antilock brake system (ABS) 24 that reduces or releases the braking force of the brake mechanisms Bfr, ​​Bfl, Brr, and Brl to avoid locking of each wheel.

[0018] The vehicle Ve shown in Fig. 4 has front wheels 1r, 1l as steerable wheels, and is provided with a power steering mechanism (PS or EPS) including a steering wheel 25, a steering linkage 26, and an actuator 27 for assisting steering force. Also, a mechanism for steering the rear wheels 2r, 2l in cooperation with the steering of the front wheels 1r, 1l is provided. That is, the vehicle Ve shown in Fig. 4 is a so-called four-wheel steering (4WS) vehicle, and is provided with a steering mechanism including a linkage 28 for steering the rear wheels 2r, 2l and an actuator 29 for operating the linkage 28. Also, a four-wheel steering (4WS) controller 30 is provided for controlling the actuator 27 for the front wheels 1r, 1l and the actuator 29 for the rear wheels 2r, 2l.

[0019] The vehicle Ve is further provided with an accelerator pedal 31 for accelerating and decelerating, a shift device 32 for selecting a gear stage or a driving range, a mode selection switch 33 for selecting a driving mode, etc. The shift device 32 and the mode selection switch 33 may be configured to select a gear stage (gear ratio) by a lever provided on the floor or center console, or to select a shift range, or may be configured to switch gear stages one by one by operating an up or down operation in a manual position, or may be configured to switch shift ranges in sequence or switch gear stages (gear ratios) one by one by operating a button switch provided on an instrument panel, a steering wheel, a steering column, etc. The vehicle Ve is also provided with a navigation system (NAVI) 34 that detects the position of the vehicle Ve, map data of the surrounding area, planned driving route, and other data and provides the driver with the data.

[0020] The driving modes are mainly control modes that control the drive torque based on a predetermined standard, such as a track mode that controls the drive torque and regenerative torque (braking torque) of each motor Mfr, Mfl, Mrr, Mrl and the braking force of each brake mechanism Bfr, ​​Bfl, Brr, Brl to improve cornering performance, a drift mode that individually controls the torque of each of the four wheels to eliminate understeer or to control to optimal traction and further improve agility and driving accuracy during cornering, and a manual sports mode that controls the gear stage (gear ratio) and steering angle to ensure a large drive torque up to high vehicle speeds to enable agile driving, etc. The mode selection switch 33 is configured to select one of these driving modes, or to cancel the selection and select the normal mode.

[0021] Various operating conditions of the vehicle Ve, including the vehicle speed, are detected by sensors, such as a vehicle speed sensor, an accelerator opening sensor, an oil temperature sensor, a steering angle sensor, a shift position sensor, a brake sensor, a driving mode sensor, a motor rotation speed sensor, and a motor temperature sensor, though not shown in the figure.

[0022] A controller 35 is provided that controls the drive torque and steering angle of the front and rear four wheels based on the operating state and the driving request state detected by these sensors. The controller 35 is mainly configured as a microcomputer, and is configured to perform calculations according to a predetermined program using input data and pre-stored data, and to output the results of the calculations as control command signals to the above-mentioned power controllers PCfr, PCfl, PCrr, PCrl, the electric oil pumps OPfr, OPrl, or the VSC 22 and the four-wheel steering controller 30. In particular, the controller 35 is configured to control the torque of each of the front and rear four wheels so as to perform cornering suitable for the driver's request, and in the case of a two-wheel drive state, to control the steering angle of either the front or rear two wheels (non-driven wheels) that are not generating drive torque.

[0023] Examples of input signals and output signals for performing such control are shown in Fig. 5. Examples of input signals are a vehicle speed signal, an accelerator opening signal, a shift position signal, a steering angle signal, an economy switch signal, a brake signal, a shift up (+) signal, a shift down (-) signal, a neutral signal, a track mode signal, a drift mode signal, etc. Examples of output command signals are the torque of the motor Mrl for the left rear wheel 2l, the torque of the motor Mrr for the right rear wheel 2r, a control signal for the oil pump OPrl for the left rear wheel 2l, a control signal for the oil pump OPrr for the right rear wheel 2r, the torque of the motor Mfl for the left front wheel 1l, the torque of the motor Mfr for the right front wheel 1r, a control signal for the oil pump OPfl for the left front wheel 1l, a control signal for the oil pump OPfr for the right front wheel 1r, a non-driven wheel steering angle signal, etc.

[0024] The control by these input signals and output signals is essentially a control of the drive torque of the four wheels and the steering angle of the non-driven wheels to perform cornering more accurately, and therefore the functional configuration of the controller 35 is as shown in FIG. 6. Since different controls are performed in four-wheel drive and two-wheel drive, the controller 35 needs to determine the requested drive state and the associated running state or the drive state or running state that is actually selected and set, and is provided with a drive determination unit 35a for this determination. This determination can be made based on, for example, the presence or absence of the track mode signal, the presence or absence of the drift mode signal, and the presence or absence of the selection of the manual sports mode. In addition, the controller 35 is provided with a turn determination unit 35b for determining whether the vehicle Ve is turning or will turn. This determination can be made based on the steering angle, or based on the position signal from the NAVI 34 or the signal of the planned route.

[0025] In the four-wheel drive state, the vehicle Ve can be caused to yaw by appropriately controlling the torque of the four wheels, so a four-wheel turning control unit 35c is provided to control the torque of each of the four wheels (specifically, the drive torque and regenerative torque of the motors Mfr, Mfl, Mrr, and Mrl described above). Furthermore, in the two-wheel drive state, the yaw of the vehicle Ve can be appropriately controlled by the torque of the two driven wheels (drive wheels) and the steering of the non-drive wheels, so a two-wheel turning control unit 35d is provided to control the torque of the drive wheels and the steering angle of the non-drive wheels.

[0026] An example of the control by the controller 35 will be described with reference to the flowchart shown in FIG. 7. The routine shown in FIG. 7 is executed repeatedly at predetermined short intervals when the vehicle Ve is turning or is about to turn. First, input data is acquired in step S1. The input data acquired here include the accelerator opening, vehicle speed, motor temperature, oil temperature, shift range, and driving mode. Next, the selected or set driving mode is determined. The driving mode determined here is whether the above-mentioned track mode is selected or set (step S2), whether the drift mode is selected or set (step S3), or whether the manual sports mode is selected or set (step S4). The order of these determinations is not particularly limited and may be any appropriate order.

[0027] If the result of any of the judgments in steps S2 to S4 is "Yes," four-wheel drive is required or the vehicle is traveling in two-wheel drive mode, so the oil pumps OPfr, OPfl, OPrr, and OPrl of the electric motors provided corresponding to the front and rear wheels are driven to actively supply oil to the motors Mfr, Mfl, Mrr, and Mrl to promote their cooling (step S5). In this state, turning control is performed using the driving torque of the front and rear four wheels (step S6). Then, the process returns. Here, "turning control using the driving torque of the front and rear four wheels" refers to control for turning the vehicle Ve by individually controlling the motors Mfr, Mfl, Mrr, and Mrl provided corresponding to the front and rear wheels 1r, 1l, 2r, and 2l, respectively, and individually controlling the driving torque of each wheel 1r, 1l, 2r, and 2l or the braking torque due to energy regeneration. In addition, this control controls each wheel 1r, 1l, 2r, and 2l so that the vehicle travels along a target driving path or target yaw determined based on the steering angle of the front wheels 1r and 1l and the vehicle speed, so that the vehicle can accurately turn as intended by the driver and achieve good driving stability.

[0028] On the other hand, if the result of the judgment in step S2 or step S4 is "NO", two-wheel drive is required or the vehicle is traveling in a two-wheel drive state, so that the oil pumps OPrr, OPrl provided corresponding to the rear wheels 2r, 2l as the drive wheels are driven to actively supply oil to the motors Mrr, Mrl for the rear wheels 2r, 2l to promote their cooling (step S7). In this state, turning control is executed using the drive torque of the left and right rear wheels 2r, 2l and the braking torque of the front wheels 1r, 1l as the non-drive wheels (step S8). Then, the process returns. Here, "using the drive torque of the left and right rear wheels 2r, 2l" means that the drive torque of the rear wheels 2r, 2l or the braking torque due to energy regeneration is controlled by the motors Mrr, Mrl provided corresponding to the rear wheels 2r, 2l. Also, "using the braking torque of the front wheels 1r, 1l" means that the braking torque of the front wheels 1r, 1l is controlled by the VSC 22 described above to generate a predetermined yaw. In this case, the energy consumption for running is only generated on the rear wheels 2r, 2l, so that the energy loss can be suppressed, or the energy efficiency (electricity cost) is improved. Also, in this case, even if the front wheels 1r, 1l do not generate a driving torque, they generate a braking torque, so that the turning of the vehicle Ve is substantially controlled by all four wheels, and therefore, although not as much as in a four-wheel drive state, the driver's intended turning can be accurately performed, and the running stability is improved.

[0029] When turning in a two-wheel drive state, the steering angle may be controlled in addition to or instead of controlling the braking torque of the non-driven wheels by the VSC 22. For example, when the front wheels 1r, 1l, which are steered wheels, are driven wheels, the rear wheels 2r, 2l, which are non-driven wheels, may be controlled by the four-wheel steering controller 30.

[0030] As described above, when the driving torque is controlled by the motors Mfr, Mfl, Mrr, Mrl, the oil pumps OPfr, OPfl, OPrr, OPrl are also driven to cool the motors Mfr, Mfl, Mrr, Mrl. However, since the load of each motor Mfr, Mfl, Mrr, Mrl and the amount of heat generated by the load vary depending on the driving mode, it is preferable to set the rotation speed (or oil discharge amount) of the oil pumps OPfr, OPfl, OPrr, OPrl according to the driving mode. FIG. 8 shows the rotation speed of the oil pumps OPfr, OPfl, OPrr, OPrl for each driving mode. The example shown here is a rotation speed map for a vehicle Ve that can set a manual range mode, which is a mode for manually selecting a range, a manual sports mode, which is a mode for manually selecting a gear stage (or gear ratio), a drift mode, and a track mode, and the rotation speed of the oil pumps OPfr, OPfl, OPrr, OPrl is set to be higher in the order of the modes listed here. Note that the rotation speed is increased as the motor temperature increases, which is the same for all modes.

[0031] As described above, when the vehicle Ve turns, the turning performance is improved by controlling each of the four wheels by an individual motor in the four-wheel drive state. On the other hand, the energy (electricity) consumption increases and the energy efficiency (electricity cost) deteriorates. On the other hand, in the two-wheel drive state, the energy efficiency (electricity cost) is improved, but the turning performance is lower than that in the four-wheel drive state. Therefore, whether the four-wheel drive or the two-wheel drive is selected during turning can be determined based on the driving mode selected or set as described above, but the driving state during turning may also be determined based on the driving state at the time when turning is started.

[0032] FIG. 9 is a flowchart for explaining a control example for determining a driving state during cornering based on a driving state at the start of cornering. The routine shown in FIG. 9 is repeatedly executed at predetermined short intervals while the vehicle Ve is traveling. First, input data is acquired in step S11. This is the same control as step S1 shown in FIG. 7 described above. Next, it is determined whether or not the economy switch is on (step S12). The economy switch is a switch for selecting a driving control that prioritizes energy efficiency (electricity consumption or fuel consumption), and although not shown, is provided on the instrument panel or steering wheel 25 of the vehicle Ve. If the determination result in step S2 is "yes", the process returns without performing any particular control. On the other hand, if the determination result in step S2 is "no", it is determined whether or not cornering has started (step S13). This determination can be made based on the steering angle, the lateral acceleration of the vehicle Ve, and the like. If the result of the determination in step S13 is "NO" because cornering has not started, the process returns without carrying out any particular control. On the other hand, if the result of the determination in step S13 is "YES", a determination is made as to whether the drive state at that time is two-wheel drive or not (step S14).

[0033] If the drive state at the start of cornering is two-wheel drive and the result of the determination in step S14 is "Yes," turning control is performed with any two wheels (drive wheels) driven by the motors (step S15). Then, the process returns. That is, the motors provided corresponding to the drive wheels are controlled so that the vehicle Ve runs along the target turning path or target yaw by actively controlling the drive torque of the drive wheels or the braking torque associated with energy regeneration. On the other hand, if the drive state at the start of cornering is not two-wheel drive and the result of the determination in step S14 is "No," turning control is performed with four wheels (step S16). Then, the process returns. That is, the motors provided corresponding to the wheels are controlled so that the vehicle Ve runs along the target turning path or target yaw by individually and actively controlling the drive torque of all four wheels, front and rear, or the braking torque associated with energy regeneration.

[0034] 9, if the vehicle is in four-wheel drive when cornering starts, the drive state is maintained during cornering and torque control for turning is performed on all four wheels, so that the vehicle can accurately turn as intended by the driver and driving stability is improved. Also, when the vehicle enters a corner in two-wheel drive mode, only two drive wheels are used and the other two wheels are not newly driven, so that deterioration of energy efficiency (electricity consumption) can be avoided or suppressed, or energy efficiency (electricity consumption) can be improved.

[0035] Here, the control of switching the driving range will be described. Each of the motors Mfr, Mfl, Mrr, and Mrl is controlled to achieve the required driving torque calculated from the accelerator opening and the vehicle speed. The required driving torque is preset so that the vehicle Ve runs smoothly and accelerates and decelerates without excess or deficiency. Depending on how the required driving torque is set, the acceleration and deceleration becomes large or small. On the other hand, the driving range includes a drive (D) range suitable for normal driving, a 3 range, a 2 range, and an L range which have a larger acceleration and deceleration than the drive (D) range, and these 3 range, 2 range, and L range are selected in order by operating the up (+) switch or the down (-) switch while the manual operation switch is on. The required driving torque is usually increased in the order listed here. FIG. 10 shows a schematic representation of the required driving torque map used in the D range, and FIG. 11 shows a schematic representation of the required driving torque map when the accelerator opening is 50% in the D range or the L range. [Explanation of symbols]

[0036] 1r,1l front wheel 2r,2l rear wheel 10 Oil Sump 11. Oil 12rr,12rl cooling oil path 20fr,20fl cooling oil path 21 Energy storage device 22 Vehicle Stability Controller (VSC) 23 Traction Control System (TCS) 24 Anti-lock Braking System (ABS) 25 Steering Wheel 26 Steering linkage 27 Actuator 28 Linkage 29 Actuator 30 Four-wheel steering controller 31 Accelerator pedal 32 Shifting device 33 Mode selection switch 34 Navigation system (NAVI) 35 Controller 35a Drive determination unit 35b Turning judgment section 35c Four-wheel turning control unit 35d Two-wheel turning control unit Bfr, Bfl, Brr, Brl Brake mechanism Mfr, Mfl, Mrr, Mrl Motor OPfr, OPfl, OPrr, OPrl Oil pump Pfr, Pfl, Prr, Prl drive unit PCfr, PCfl, PCrr, PCrl Power Controller Vehicle

Claims

[Claim 1] A control device for a four-wheel independent drive vehicle, in which a drive force source is provided corresponding to each of a total of four wheels, two front wheels and two rear wheels, and the torque of each of the four wheels is controlled independently from one another by the drive force sources, thereby enabling four-wheel drive in which drive torque is generated by all four wheels and two-wheel drive in which drive torque is generated by either the front or rear wheels, and which can be selected and set based on a required driving state, and further in which a braking mechanism is provided for braking or a steering mechanism is provided for steering at least non-driven wheels that are not driven by the drive force sources in the two-wheel drive state, a controller for controlling the driving force source and the braking mechanism or the steering mechanism, The controller: a drive determination unit that determines whether the selected and set drive state is the four-wheel drive or the two-wheel drive; A turning determination unit that determines whether the four-wheel independent drive vehicle is turning; a four-wheel turning control unit that controls the drive power sources provided corresponding to the four wheels, respectively, to output torques suitable for the turning motion when the drive determination unit determines that the vehicle is in four-wheel drive and the turning determination unit determines that the vehicle is in turning motion; a two-wheel turning control unit that, when the two-wheel drive is determined by the drive determination unit and the turning travel is determined by the turning determination unit, controls the drive force source provided corresponding to the driving wheels driven for the two-wheel drive so as to produce an output torque suitable for the turning travel, and controls the braking force by the brake mechanism of the non-driven wheels or the steering angle by the steering mechanism so as to be suitable for the turning travel. A control device for a four-wheel independent drive vehicle.

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