JP4730543B2 - Vehicle driving force distribution control device - Google Patents

Description

  The present invention relates to a driving force distribution control device that controls driving force distribution between front and rear wheels of a vehicle.

For example, in an electronically controlled on-demand four-wheel drive vehicle, the driving force from the engine is transmitted to one of the front wheels or the rear wheels, and a part of the transmitted driving force is transmitted to the front wheels or the rear via a driving force distribution device such as an electronically controlled coupling. A technique for distributing to the other of the rear wheels and realizing appropriate vehicle running characteristics by controlling driving force distribution has been put into practical use (for example, see Patent Document 1).
The technique disclosed in Patent Document 1 is intended to suppress understeer and oversteer during turning of the vehicle, and is applied to an FR vehicle-based four-wheel drive vehicle. A transfer limiting device is provided between the front and rear wheels of the vehicle as a driving force distribution device that distributes a part of the driving force of the rear wheel to the front wheel side, and generates a differential limiting force between the left and right wheels of the rear wheel. When the wheel speed of the outer turning wheel is higher than the wheel speed of the inner turning wheel and the inner wheel is estimated to be gripping, the driving force distributed to the front wheels is reduced by reducing the driving force distribution between the front and rear wheels by the transfer. And the differential limiting force between the left and right wheels by the differential limiting device is reduced, thereby suppressing understeer.
Japanese Patent No. 2527204

  The technique of Patent Document 1 focuses on the differential rotation between the left and right wheels, and controls the driving force distribution by the transfer and the differential limiting force by the differential limiting device. The differential rotation is only one of the indices indicating the turning state of the vehicle, and is insufficient for appropriately controlling the driving force distribution and the differential limiting force. For example, even if the differential rotation between the left and right wheels or the front and rear wheels is the same, the optimal driving force distribution and differential limiting force differ depending on whether the vehicle's steering characteristics are understeer or oversteer. Depending on the turning state of the vehicle, the driving force distribution of the transfer and the differential limiting force of the differential limiting device are improperly controlled, resulting in a problem that good steering characteristics cannot be realized.

  The present invention has been made to solve such problems, and the object of the present invention is to appropriately control the driving force distribution between the front and rear wheels based on an index that represents the turning state of the vehicle. Accordingly, it is an object of the present invention to provide a driving force distribution control device for a vehicle that can realize a good steering characteristic regardless of the turning state of the vehicle.

In order to achieve the above object, the invention of claim 1 is provided between the front and rear wheels of the vehicle , and driving force distribution means capable of variably distributing a part of the driving force transmitted from the driving source to the front wheels to the rear wheels. A control amount calculating means for calculating a control amount corresponding to turning as a correction amount for driving force distribution to be distributed to the rear wheel side based on a turning state of the vehicle, a steer characteristic determining means for determining a current steering characteristic of the vehicle, When it is determined that the wheel speed of the front wheel is higher than the wheel speed of the rear wheel based on the detection result by the wheel speed detecting means and the wheel speed detecting means for detecting the wheel speeds of the front and rear wheels respectively , the steer characteristic determined by the steer characteristic determining means When the characteristic is understeer, the driving force distribution between the front and rear wheels is increased and corrected based on the turning control amount. When the steering characteristic is oversteer, the driving force distribution between the front and rear wheels is reduced based on the turning control amount. Corrected, if the front wheel speed is determined to be lower than the wheel speed of the rear wheels, decrease corrected on the basis of the turning corresponding control variable the driving force distribution between the front and rear wheels regardless of the steering characteristic which is determined by the steering characteristic determination means And a driving force distribution control unit that controls the driving force distribution unit based on the corrected driving force distribution .

Therefore, the control amount calculation means calculates the turning correspondence control amount as a correction amount for the driving force distribution to be distributed to the rear wheels based on the turning state of the vehicle, and the steering characteristic determination means determines the current vehicle steering characteristic. The wheel speed of the front and rear wheels is detected and detected by the wheel speed detecting means. Torque movement by the driving force distribution between the front and rear wheels is performed from the high wheel speed side to the low wheel speed side. Therefore, when the front wheel speed is higher than the rear wheel speed, the rear wheel is moved from the front wheel through the driving force distributing means. If the torque is moving to the wheel and the driving force distribution is increased and corrected based on the turning control amount because it is understeering, the lateral force increases as the driving force of the front wheels decreases, and the yaw moment increases, causing the understeering. When the driving force distribution is corrected to decrease because the steering is oversteered, the lateral force increases as the driving force of the rear wheels decreases, and the oversteer is suppressed due to the decrease of the yaw moment.

Also, when the front wheel speed is lower than the rear wheel speed, the torque moves from the rear wheel to the front wheel via the driving force distributing means, the front wheel is reversely driven from the rear wheel side, and the rear wheel When braking force (negative driving force) is generated and the driving force distribution is corrected to decrease in the case of understeer, the lateral force increases as the driving force of the front wheels decreases, and understeer is suppressed by increasing the yaw moment. If the driving force distribution is corrected to decrease in the case of oversteering, the lateral force increases as the braking force of the rear wheels decreases, and the oversteer is suppressed due to the decrease in yaw moment. This controls the driving force distribution that should be distributed to the other side of the front and rear wheels in an integrated manner, reflecting not only the wheel speeds of the front and rear wheels, but also the vehicle's steering characteristics, realizing good steering characteristics regardless of the turning state of the vehicle Is done.

The invention of claim 2 is provided between the front and rear wheels of the vehicles, a part of the driving force transmitted to the rear wheel from a drive source and a variable dispensable driving force distributing means to the front wheel side, a turning state of the vehicle Control amount calculation means for calculating a control amount corresponding to turning as a correction amount for driving force distribution to be distributed to the front wheel based on, steer characteristic determination means for determining the current steering characteristic of the vehicle, and wheel speeds of the front and rear wheels respectively When it is determined that the wheel speed of the rear wheel is higher than the wheel speed of the front wheel based on the detection result by the wheel speed detecting means and the wheel speed detecting means, the front and rear wheels are determined when the steer characteristic determined by the steer characteristic determining means is understeer. While the steering force is oversteer, the driving force distribution between the front and rear wheels is increased and corrected based on the turning control amount. If it is determined to be lower than the wheel speed of the wheels, the steering characteristic determination means by reducing corrected on the basis of the turning corresponding control variable the driving force distribution between the front and rear wheels regardless of the steering characteristic is determined, based on the driving force distribution of the corrected Driving force distribution control means for controlling the driving force distribution means .

Accordingly, the control amount calculation means calculates the turning correspondence control amount as a correction amount for the driving force distribution to be distributed to the front wheels based on the turning state of the vehicle, and the steering characteristic determination means determines the current steering characteristic of the vehicle. The wheel speeds of the front and rear wheels are detected by the wheel speed detecting means. The torque movement by the driving force distribution between the front and rear wheels is performed from the high wheel speed side to the low wheel speed side. Therefore, when the wheel speed of the rear wheel is higher than the wheel speed of the front wheel, from the rear wheel through the driving force distribution means. If the torque is moving to the front wheel and the driving force distribution is corrected to be reduced based on the turning control amount because it is understeering, the lateral force increases as the driving force of the front wheel decreases and the yaw moment increases, causing the understeering. If the driving force distribution is corrected to increase due to the suppression of oversteering, the lateral force increases as the driving force of the rear wheels decreases, and the oversteer is suppressed due to the decrease in yaw moment.

Also, when the rear wheel speed is lower than the front wheel speed, the torque moves from the front wheel to the rear wheel via the driving force distribution means, the rear wheel is driven backward from the front wheel side, and the front wheel is controlled. When power (negative driving force) is generated and the driving force distribution is corrected to decrease in the case of understeer, the lateral force increases as the braking force of the front wheels decreases, and understeer is suppressed due to the increase in yaw moment. When the driving force distribution is corrected to decrease in the case of oversteer, the lateral force increases as the driving force of the rear wheels decreases, and the oversteer is suppressed due to the decrease in yaw moment. This controls the driving force distribution that should be distributed to the other side of the front and rear wheels in an integrated manner, reflecting not only the wheel speeds of the front and rear wheels, but also the vehicle's steering characteristics, realizing good steering characteristics regardless of the turning state of the vehicle Is done.
As a preferred embodiment, the control amount calculation means includes a control amount for differential rotation based on a difference in wheel speed between the front and rear wheels, an acceleration corresponding control amount based on an acceleration state of the vehicle accompanying an accelerator operation, and a brake It is configured to calculate at least one of the deceleration control amount based on the deceleration state of the vehicle accompanying the operation as the base control amount of the driving force distribution, and the driving force distribution control means controls the base control amount to turn. It is desirable to configure to increase or decrease based on the amount.
Accordingly, at least one of the control amount corresponding to the differential rotation, the control amount corresponding to the acceleration, and the control amount corresponding to the deceleration is calculated as the base control amount of the driving force distribution, and this base control amount is corrected to increase or decrease based on the turning control amount. It is corrected. That is, since the base control amount is corrected based on the turning control amount, not only the increase correction but also the reduction correction is always possible, and the driving force that should reliably distribute the turning control amount to the other side of the front and rear wheels. It can be reflected in the distribution.
According to a third aspect of the present invention, in the first or second aspect, the steer characteristic determining unit includes a target turning state index determining unit that determines a target turning state index based on a running state of the vehicle, and an actual turning state index of the vehicle. An actual turning state index detecting means for detecting, and determining the steering characteristic of the current vehicle based on the target turning state index and the actual turning state index, and the control amount calculating means is determined as the steer characteristic by the steer characteristic determining means Grip limit index estimating means for identifying the front and rear slip wheels based on the understeer and oversteer and estimating the grip limit index correlating with the grip limit from the driving force and lateral force of the slip wheel, and based on the turning state of the vehicle Calculates the required yaw moment to suppress understeer or oversteer and can achieve the required yaw moment Slip required to achieve the required lateral force calculated by the required lateral force calculating means on the premise of the required lateral force calculating means for calculating the required lateral force and the grip limit index calculated by the grip limit index calculating means Driving force reduction amount calculating means for calculating the driving force reduction amount of the wheel, and calculating a turning correspondence control amount according to the driving force reduction amount of the slip wheel calculated by the driving force reduction amount calculation means.
Accordingly, the steering characteristic of the vehicle is determined based on the target turning state index determined by the target turning state index determination unit and the actual turning state index detected by the actual turning state index detection unit. The occurrence of understeer during turning of the vehicle is caused by slip due to insufficient lateral force of the front wheel, and occurrence of oversteer is caused by slip due to insufficient lateral force of the rear wheel, so when the understeer is determined as the steer characteristic, the front wheel becomes a slip wheel. When the vehicle is oversteered, the rear wheel is specified as a slip wheel.
Then, a grip limit index correlating with the grip limit from the driving force and lateral force of the slip wheel, for example, a friction circle defining a grip limit for the driving force and the lateral force is estimated by the grip limit index estimating means. Further, after calculating the required yaw moment for suppressing understeer or oversteer by the required lateral force calculation means based on the turning state of the vehicle, the required lateral force of the slip wheel that can achieve the required yaw moment is calculated, and the grip The driving force decrease amount of the slip wheel for achieving the required lateral force on the assumption of the limit index is calculated by the driving force decrease amount calculating means, and the turning control amount is calculated by the control amount calculating means according to the driving force decrease amount. Is done.
That is, the vehicle steer characteristic is determined based on the specific target turning state index and the actual turning state index, and on the premise of the grip limit index that correlates with the grip limit of the slip wheel, Turning based on specific calculated values such as the required yaw moment to suppress oversteer, the required lateral force of the slip wheel that can achieve the required yaw moment, and the amount of decrease in the driving force of the slip wheel to achieve the required lateral force Since the corresponding control amount is calculated, it is possible to calculate the turn corresponding control amount that is more realistic compared to, for example, the case where the turn corresponding control amount is set based on past empirical rules and experimental results.
As a preferred aspect, the required lateral force calculating means calculates a required yaw moment for suppressing understeer or oversteer based on a deviation between the target yaw rate determined from the turning state of the vehicle and the actual yaw rate, and the required yaw moment It is desirable that the required lateral force of the slip wheel is calculated from the above.
With such a configuration, it is possible to calculate an appropriate required yaw moment and thus a more appropriate turning correspondence control amount based on a yaw rate that directly represents the turning state of the vehicle.

As described above, according to the vehicle driving force distribution control device of the first aspect of the present invention, in the vehicle that distributes a part of the driving force of the front wheels to the rear wheels, the current steering characteristic that directly represents the turning state of the vehicle. Since the driving force distribution between the front and rear wheels is corrected to increase or decrease according to the combination of the front and rear wheel speeds, the driving force distribution between the front and rear wheels can be controlled appropriately, thereby ensuring understeer and oversteer. Can be suppressed .
According to the vehicle driving force distribution control device of the second aspect of the present invention, in the vehicle that distributes a part of the driving force of the rear wheels to the front wheels, the current steering characteristic that directly represents the turning state of the vehicle and the wheels of the front and rear wheels Since the driving force distribution between the front and rear wheels is corrected to increase or decrease according to the combination with the magnitude relationship of the speed, the driving force distribution between the front and rear wheels can be controlled appropriately, thereby reliably suppressing understeer and oversteer. it can.
According to the driving force distribution control device for a vehicle of the invention of claim 3 , in addition to claim 1 or 2 , after determining the steering characteristic of the vehicle based on the specific target turning state index and the actual turning state index. Based on the grip limit index that correlates with the grip limit of the slip wheel, the specific yaw moment to suppress the understeer and oversteer determined as the steer characteristics, the required lateral force of the slip wheel, the amount of decrease in driving force, etc. Since the turning control amount applied to the driving force distribution means is calculated based on the calculated value, the driving force distribution between the front and rear wheels can be appropriately controlled based on the turning correspondence control amount that is more realistic, and the vehicle understeer and Oversteer can be reliably suppressed.

[First embodiment]
Hereinafter, a first embodiment in which the present invention is embodied in a driving force distribution control device that controls driving force distribution between front and rear wheels of an electronically controlled on-demand four-wheel drive vehicle based on an FF vehicle will be described.
FIG. 1 is an overall configuration diagram showing a vehicle driving force distribution control apparatus according to this embodiment. A front differential 1 (hereinafter referred to as a front differential) is provided at the front of the vehicle, and an engine driving force (not shown) is input to the ring gear 2 fixed to the front differential 1 via a transmission. The front differential 1 is connected to the left and right front wheels 4 via a drive shaft 3. The front differential 1 transmits the driving force of the engine input to the ring gear 2 to the left and right front wheels 4 while allowing a differential. The front differential 1 is provided with a front electronic control LSD5, and the front electronic control LSD5 applies a differential limiting force between the left and right front wheels 4 in accordance with an engagement state of an electromagnetic clutch (not shown) incorporated therein.

  The ring gear 2 of the front differential 1 meshes with a pinion gear 7 fixed to the front end of the front propeller shaft 6, and the rear end of the front propeller shaft 6 is connected to the rear propeller via an electronic control coupling 8 (driving force distribution means). It is connected to the front end of the shaft 9. A pinion gear 10 fixed to the rear end of the rear propeller shaft 9 meshes with a ring gear 12 of a rear differential 11 (hereinafter referred to as rear differential), and left and right rear wheels 14 are connected to the rear differential 11 via a drive shaft 13. Has been.

  A part of the driving force of the engine is distributed from the front differential 1 to the rear differential 11 side through the propeller shafts 6 and 9 and the electronic control coupling 8, and is transmitted to the left and right rear wheels 14 while allowing the differential differential. The The electronic control coupling 8 adjusts the driving force distributed from the front wheel 4 side to the rear wheel 14 side, that is, the driving force distribution between the front and rear wheels 4, 14 in accordance with the state of engagement of a built-in electromagnetic clutch (not shown). . The principle of adjusting the driving force distribution is not limited to this, and any change can be made as long as the driving force distribution can be adjusted using a control device such as a pump or a motor. The engagement state of the clutch may be adjusted by operating the hydraulic piston with the supplied hydraulic oil.

  On the other hand, a 4WD ECU 21 is installed in the interior of the vehicle. The 4WD ECU 21 includes an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, and a central processing unit ( CPU), a timer counter, and the like. On the input side of the 4WD ECU 21 are a steering angle sensor 22 that detects the steering angle θstr of the steering, a vehicle speed sensor 23 that detects the vehicle speed V, a yaw rate sensor 24 that detects the yaw rate YR of the vehicle, and the wheels 4 and 14 of the vehicle. Various sensors such as a wheel speed sensor 25 for detecting wheel speeds NFR, NFL, NRR, NRL and a lateral acceleration sensor 26 for detecting a lateral acceleration GY generated when the vehicle turns are connected, and on the output side of the ECU for 4WD, Various devices such as the electromagnetic clutch of the front electronic control LSD 5 and the electromagnetic clutch of the electronic control coupling 8 are connected.

  The 4WD ECU 21 controls the engagement state of the electromagnetic clutch of the front electronic control LSD 5 and the electronic control coupling 8 based on the detection information from the various sensors. In the present embodiment, for the purpose of suppressing understeer and oversteer during turning of the vehicle, based on a friction circle (grip limit index) correlated with the grip limit of the front and rear wheels 4, 14, the distance between the front and rear wheels 4, 14 by the electronically controlled coupling 8 is determined. The control of the driving force distribution is executed, and the procedure for setting the control amount of the electronic control coupling 8 will be described below.

  The setting of the control amount of the electronically controlled coupling 8 is executed according to a different procedure depending on whether the steering characteristic of the vehicle is understeer or oversteer, and will be described separately for each steering characteristic. In the present embodiment, the ECU 21 is currently based on a comparison result between an actual yaw rate YR (actual turning state index) detected by the yaw rate sensor 24 (actual turning state index detecting means) and a target yaw rate YT (target turning state index) described later. After determining the steering characteristic occurring in the vehicle (steer characteristic determination means), the control amount is set according to the steering characteristic. However, the steer characteristic determination method is not limited to this, and can be arbitrarily changed.

  FIG. 2 is a block diagram showing a procedure for setting the control amount of the electronic control coupling 8 that is executed by the ECU 21 when understeer occurs, and FIGS. 3 and 4 are schematic views showing a control state of driving force distribution based on the set control amount. First, the case where understeer occurs according to these figures will be described. 3 and 4 schematically show a two-wheel model by averaging the wheel speeds NFR and NFL of the left and right front wheels 4 and the wheel speeds NRR and NRL of the left and right rear wheels 14, and FIG. 3 shows the average front wheel speed NFave. FIG. 4 shows a case where the rear wheel average wheel speed NRave is lower than the rear wheel average wheel speed NRave.

  3 and 4, the length and direction of the vertical black solid arrows Adrv attached to the front and rear wheels 4 and 14 indicate the magnitude and direction of driving force (whether driving or braking). The length of the black solid straight arrow Acornering in the left direction attached to 14 represents the magnitude of the lateral force, while the white straight arrows Adrv and Acornering are control amounts corresponding to the steering characteristics (control rate Ty corresponding to yaw rate). The correction | amendment condition with respect to the driving force and lateral force based on is represented. The lengths of the white rotating arrows Arev attached to the front and rear wheels 4 and 14 represent the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave. The direction represents the torque movement amount and the movement direction by the driving force distribution according to the final control amount T of the electronic control coupling 8.

  Understeer of the vehicle is a phenomenon caused by slip due to insufficient lateral force of the front wheel 4, and it is assumed that the front wheel 4 at this time uses the driving force and the grip against the lateral force defined by its own friction circle to the limit. In other words, it can be interpreted that there is room for increasing the lateral force by reducing the driving force of the front wheels 4 and suppressing understeer. On the other hand, the driving force of the front wheel 4 changes according to the torque distributed from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8 or the torque transmitted from the rear wheel 14 to the front wheel 4. 4 and 14 can be adjusted according to the driving force distribution.

  Under the above viewpoint, the control amount of the electronic control coupling 8 at the time of understeer is set according to FIG. First, the front wheel driving force calculation unit 31 calculates the driving force FX generated by the front wheels 4 based on the engine torque and the driving force distribution between the front and rear wheels 4 and 14, and the front wheel lateral force calculation unit 32 calculates the driving force FX. A lateral force FCF generated by the front wheels 4 is calculated according to the following equation (1) from the detected lateral acceleration GY and the previously determined front wheel shared mass MF.

FCF = MF × | GY | ... (1)
The front wheel driving force FX from the front wheel driving force calculation unit 31 and the front wheel lateral force FCF from the front wheel lateral force calculation unit 32 are input to the front wheel friction circle calculation unit 33. Based on these information, the front wheel friction circle calculation unit 33 calculates the following equation: According to (2), the front wheel friction circle FFR is calculated as the radius of the friction circle FFR (grip limit index estimation means).

FFR = √ (FX ² + FCF ² ) (2)
The grip force exerted by the front wheels 4 is influenced by various factors such as the difference in tire wear, the difference in road surface friction coefficient according to the weather (clear weather and snowfall) and the road surface form (paved road and dirt), Since the friction circle FFR is estimated from the driving force FX and the lateral force FCF when the front wheel 4 reaches the grip limit and causes understeer, the estimated friction circle FFR has a magnitude that accurately correlates with the grip force of the front wheel 4. Become.

  The yaw moment calculation unit 34 calculates a target yaw rate YT based on the steering angle θstr from the steering angle sensor 22 and the vehicle speed V from the vehicle speed sensor 23 (target turning state index determination means), and the target yaw rate YT and the yaw rate sensor 24 Based on the detected deviation ΔY from the actual yaw rate YR, a required yaw moment YAWM required to suppress understeer is calculated. The required yaw moment YAWM is input to the front wheel required lateral force calculation unit 35, and the front wheel required lateral force calculation unit 35 calculates the required lateral force FCFT of the front wheel 4 necessary to achieve the required yaw moment YAWM according to the following equation (3). (Required lateral force calculation means).

FCFT = YAWM / LF (3)
Here, LF is the distance from the center of gravity to the front axis.
The front wheel friction circle FFR from the front wheel friction circle calculation unit 33, the front wheel lateral force FCF from the front wheel lateral force calculation unit 32, and the front wheel requested lateral force FCFT from the front wheel requested lateral force calculation unit 35 are supplied to the front wheel driving force decrease amount calculation unit 36. The front wheel driving force reduction amount calculation unit 36 receives the front wheel 4 driving force reduction amount FXT necessary to increase the lateral force FCF of the front wheel 4 by an amount corresponding to the required lateral force FCFT on the assumption of the front wheel friction circle FFR. It is calculated according to the following equation (4) (driving force reduction amount calculating means).

FXT = | FX | −√ (FFR ² − (FCF + FCFT) ² ) (4)
The calculated driving force decrease amount FXT of the front wheel 4 is input to the control amount calculation unit 37, and the control amount calculation unit 37 uses the yaw rate corresponding control amount Ty (turning correspondence) as a correction amount for the driving force distribution corresponding to the driving force decrease amount FXT. Control amount) is calculated according to the following equation (5) (control amount calculation means).
Ty = FXT × R / FHG ……… (5)
Here, R is a tire radius of the front wheel 4 and FHG is a gear ratio of the ring gear 2 and the pinion gear 7.

  On the other hand, the base control amount calculation unit 38 calculates a base control amount Tbase other than the yaw rate corresponding control amount Ty. For example, a differential rotation control amount is calculated based on the difference between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave when the vehicle is turning, and the initial slip is suppressed based on the accelerator operation amount during acceleration of the vehicle accompanying the accelerator operation. The acceleration-related control amount is calculated, and when the vehicle decelerates due to the braking operation, the deceleration-related control amount for stabilizing the vehicle posture is calculated based on the vehicle deceleration, etc., and the sum total of these control amounts is the base Set as control amount Tbase. The wheel speed determination unit 39 calculates the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave from the wheel speeds NFR, NFL, NRR, and NR, and the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave are calculated. A magnitude relationship is determined.

  The magnitude of the yaw rate corresponding control amount Ty from the control amount calculation unit 37, the base control amount Tbase from the base control amount calculation unit 38, and the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave from the wheel speed determination unit 39. The relationship is input to the final control amount calculation unit 40, and the final control amount calculation unit 40 calculates the final control amount T according to the conditions shown in FIG. The actual driving force distribution between the front and rear wheels 4 and 14 is controlled based on the final control amount T set in this way. That is, the duty ratio corresponding to the final control amount T is set from a map (not shown), and the engagement state is adjusted by the excitation of the electromagnetic clutch of the electronic control coupling 8 based on the duty ratio. The driving force distribution is adjusted to a value corresponding to the final control amount T (driving force distribution control means).

  Since the torque movement by the driving force distribution between the front and rear wheels 4 and 14 is performed from the high wheel speed side to the low wheel speed side, the front wheel average wheel speed NFave shown in FIG. 3 is higher than the rear wheel average wheel speed NRave (NFave). > N Rave), the torque moves from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8. That is, a part of the driving force of the front wheel 4 is distributed to the rear wheel 14, so that the rear wheel 14 generates a driving force corresponding to the torque movement and the driving force of the front wheel 4 is reduced. As shown in FIG. 2, in the final control amount calculation unit 40, the final control amount T is corrected to increase by the yaw rate corresponding control amount Ty, so that the actual driving force between the front and rear wheels 4 and 14 as the final control amount T increases. Distribution also increases. As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 increases, and the driving force of the rear wheel 14 increases while the driving force of the front wheel 4 decreases as shown by the white arrows Adrv and Acornering in FIG. The driving force of the front wheels 4 at this time decreases by the amount corresponding to the driving force decrease amount FXT calculated by the front wheel driving force decrease amount calculation unit 36, and the required lateral force calculated by the front wheel required lateral force calculation unit 35 accordingly. The lateral force of the front wheel 4 increases by the amount corresponding to FCFT, and the yaw moment of the vehicle increases by the amount corresponding to the requested yaw moment YAWM calculated by the yaw moment calculation unit 34 with the increase of the lateral force of the front wheel 4 and is generated in the vehicle. Understeer is suppressed.

  Further, in the traveling state where the average front wheel speed NFave shown in FIG. 4 is lower than the average rear wheel speed NRave (NFave <NRave), the torque is moved from the rear wheel 14 to the front wheel 4 via the electronic control coupling 8. . That is, the front wheel 4 is reversely driven from the rear wheel 14 side, the rear wheel 14 generates a braking force (negative driving force) corresponding to the torque movement, and the driving force of the front wheel 4 is increased. As shown in FIG. 2, in the final control amount calculation unit 40, the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty, so that the actual driving force between the front and rear wheels 4 and 14 as the final control amount T decreases. Distribution also declines. As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 decreases, and the braking force of the rear wheel 14 decreases as shown by the white arrows Adrv and Acornering in FIG. 4, while the driving force of the front wheel 4 decreases. Accordingly, as described above, the lateral force increases as the driving force of the front wheels 4 decreases, and understeer is suppressed as the yaw moment increases.

Although not shown in FIG. 2, the yaw rate control amount Ty is not reflected in the calculation of the final control amount T when the steering characteristic is neutral steer even when the vehicle is not turning or is turning, and the base control amount is not reflected. Since Tbase is set as the final control amount T as it is, the driving force distribution control for suppressing the understeer as described above is not executed.
On the other hand, a case where oversteer occurs in a turning vehicle will be described. FIG. 5 is a block diagram showing the procedure for setting the control amount of the electronic control coupling 8 executed by the ECU 21 when oversteer occurs, and FIGS. 6 and 7 are schematic views showing the control state of the driving force distribution based on the set control amount. FIG. 6 shows a case where the front wheel average wheel speed NFave is higher than the rear wheel average wheel speed NRave, and FIG. 7 shows a case where the front wheel average wheel speed NFave is lower than the rear wheel average wheel speed NRave.

  Oversteering of the vehicle is a phenomenon caused by slip due to insufficient lateral force of the rear wheel 14. At this time, the rear wheel 14 uses the driving force and the grip against the lateral force defined by its own friction circle to the limit. In other words, it can be interpreted that there is room for suppressing the oversteer by increasing the lateral force due to the decrease in the driving force of the rear wheel 14. On the other hand, the driving force of the rear wheel 14 changes according to the torque distributed from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8 or the torque transmitted from the rear wheel 14 to the front wheel. 4 and 14 can be adjusted according to the driving force distribution.

  Under the above viewpoint, the control amount of the electronic control coupling 8 during oversteering is set according to FIG. First, the rear wheel driving force calculation unit 31 ′ calculates the driving force RX generated by the rear wheel 14 based on the driving force distribution between the front and rear wheels 4 and 14, and the rear wheel lateral force calculation unit 32 ′ calculates the lateral acceleration sensor. A lateral force RCF generated by the rear wheel 14 is calculated according to the following equation (6) from the lateral acceleration GY detected by the vehicle 26 and the rear wheel shared mass MR that is known in advance.

RCF = MR × | GY |… (6)
The rear wheel driving force RX from the rear wheel driving force calculating unit 31 ′ and the rear wheel lateral force RCF from the rear wheel lateral force calculating unit 32 ′ are input to the rear wheel friction circle calculating unit 33 ′, and based on these information, the rear wheel driving force RX In the wheel friction circle calculation unit 33 ′, the rear wheel friction circle RFR is calculated as the radius of the friction circle RFR according to the following equation (7) (grip limit index estimation means).

RFR = √ (RX ² + RCF ² ) (7)
As with the front wheel 4, the friction circle RFR is also estimated for the rear wheel 14 from the driving force RX and lateral force RCF when the grip limit is reached and oversteer occurs, so the estimated friction circle RFR is the grip of the rear wheel 14. The magnitude correlates accurately with force.
The yaw moment calculation unit 34 ′ calculates a required yaw moment YAWM necessary for suppressing oversteer according to the same procedure as that for the understeer, and the rear wheel required lateral force calculation unit 35 ′ calculates the next required yaw moment YAWM. The required lateral force RCFT of the rear wheel 14 necessary for achieving the required yaw moment YAWM is calculated according to the equation (8) (required lateral force calculating means).

RCFT = YAWM / LR (8)
Here, LR is the distance from the center of gravity to the rear axis.
The rear wheel friction circle RFR from the rear wheel friction circle calculation unit 33 ′, the rear wheel lateral force RCF from the rear wheel lateral force calculation unit 32 ′, and the rear wheel requested lateral force RCFT from the rear wheel requested lateral force calculation unit 35 ′ are The rear wheel driving force decrease amount calculating unit 36 ′ inputs the rear wheel driving force decrease amount calculating unit 36 ′ to calculate the lateral force RCF of the rear wheel 14 corresponding to the required lateral force RCFT on the premise of the rear wheel friction circle RFR. The driving force reduction amount RXT of the rear wheel 14 necessary for the increase is calculated according to the following equation (9) (driving force reduction amount calculating means).

RXT = | RX | −√ (RFR ² − (RCF + RCFT) ² ) (9)
The calculated driving force reduction amount RXT of the rear wheel 14 is input to the control amount calculation unit 37 ′, and the control amount calculation unit 37 ′ controls the yaw rate as a correction amount corresponding to the driving force distribution corresponding to the driving force reduction amount RXT. An amount Ty (a turning control amount) is calculated according to the following equation (10) (control amount calculation means).

Ty = RXT × R / RHG (10)
Here, RHG is a gear ratio between the ring gear 12 and the pinion gear 10.
On the other hand, the processing of the base control amount calculation unit 38 ′ and the wheel speed determination unit 39 ′ is the same as that during the understeer, the base control amount calculation unit 38 ′ calculates the base control amount Tbase, and the wheel speed determination unit 39 ′ The magnitude relationship between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave is determined.

Based on the above information, the final control amount calculation unit 40 ′ calculates the final control amount T according to the conditions shown in FIG. 5, and the electronic control coupling 8 drives the front and rear wheels 4 and 14 based on the final control amount T. The force distribution is adjusted (driving force distribution control means).
In the driving situation (NFave> NRave) where the average front wheel speed NFave is higher than the average rear wheel speed NRave shown in FIG. 6, the torque moves from the front wheel 4 to the rear wheel 14 via the electronically controlled coupling 8 as in FIG. is doing. That is, a part of the driving force of the front wheel 4 is distributed to the rear wheel 14, so that the rear wheel 14 generates a driving force corresponding to the torque movement and the driving force of the front wheel 4 is reduced. As shown in FIG. 5, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty in the final control amount calculation unit 40 ′, the actual driving between the front and rear wheels 4 and 14 according to the decrease in the final control amount T. Power distribution also decreases. As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 is reduced, and the driving force of the rear wheel 14 is reduced while the driving force of the front wheel 4 is increased, as indicated by white arrows Adrv and Acornering in FIG. At this time, the driving force of the rear wheel 14 is reduced by an amount corresponding to the driving force reduction amount RXT calculated by the rear wheel driving force reduction amount calculation unit 36 ′, and is calculated by the rear wheel required lateral force calculation unit 35 ′ accordingly. The lateral force of the rear wheel 14 is increased by the amount corresponding to the requested lateral force RCFT, and the yaw moment of the vehicle is increased by the amount corresponding to the requested yaw moment YAWM calculated by the yaw moment calculating unit 34 ′ as the lateral force of the rear wheel 14 increases. And the oversteer occurring in the vehicle is suppressed.

  Further, in a traveling state where the average front wheel speed NFave shown in FIG. 7 is lower than the average rear wheel speed NRave (NFave <NRave), the torque from the rear wheel 14 to the front wheel 4 via the electronically controlled coupling 8 is the same as in FIG. Is moving. That is, the front wheel 4 is reversely driven from the rear wheel 14 side, and the rear wheel 14 generates a braking force corresponding to the torque movement. As shown in FIG. 5, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty in the final control amount calculation unit 40 ′, the actual driving between the front and rear wheels 4 and 14 according to the decrease in the final control amount T. Power distribution also decreases. As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 decreases, and the braking force of the rear wheel 14 decreases as shown by the white arrows Adrv and Acornering in FIG. 7, while the driving force of the front wheel 4 decreases. Accordingly, as described above, the lateral force increases as the driving force of the rear wheel 14 decreases, and oversteer is suppressed as the yaw moment increases.

  As described above, in the vehicle driving force distribution control apparatus according to the present embodiment, the vehicle steer characteristics are integrated in addition to the magnitude relationship between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave during the turning of the vehicle. Therefore, the driving force distribution between the front and rear wheels 4 and 14 is controlled. The steer characteristic of the vehicle indicates in which direction the yaw moment of the vehicle should be corrected, and the magnitude relationship between the front wheel average wheel speed NFave and the rear wheel average wheel speed NRave is the direction of torque movement between the front and rear wheels 4 and 14, and hence the drive Since the change direction of the yaw moment due to the increase / decrease of the force distribution is expressed, the optimum driving force distribution between the front and rear wheels 4 and 14 can be set for the turning state of the vehicle based on the combination of both conditions. Therefore, understeering and oversteering can be reliably suppressed by appropriately controlling the driving force distribution between the front and rear wheels 4, 14, so that a good steering characteristic can always be realized regardless of the turning state of the vehicle.

  Further, in this embodiment, after determining the vehicle steer characteristic based on the specific target yaw rate YT and the actual yaw rate YR, the slip wheels exceeding the grip limit based on the steer characteristic are the front and rear wheels 4, 14. Based on the friction circles FFR and RFR estimated from the slip wheel driving forces FX and RX and the lateral forces FCF and RCF, the required yaw moment YAWM and the required yaw moment for suppressing understeer and oversteer are specified. Yaw rate control amount based on specific calculated values such as slip wheel driving force reduction amounts FXT, RXT for achieving the required lateral force FCFT, RCFT of the slip wheel that can achieve YAWM, and the required lateral force FCFT, RCFT Ty is calculated. Therefore, compared with the case where the yaw rate corresponding control amount Ty is set based on, for example, past empirical rules and experimental results, the yaw rate corresponding control amount Ty more realistic can be calculated, and thus the front and rear wheels 4 can be more appropriately calculated. , 14 can be controlled.

  In addition, since the friction circles FFR and RFR that accurately correlate with the grip force of the slip wheel are estimated based on the driving forces FX and RX and the lateral forces FCF and RCF, for example, a difference in tire wear state, weather (clear weather or snowfall) ) And the road surface form (paved road or dirt), the appropriate yaw rate control amount Ty can be calculated without being affected by the difference in the road surface friction coefficient. In other words, there is an advantage that it is not necessary to detect the tire wear state and the road surface friction coefficient by the sensor and to perform the compensation process in order to eliminate the influence of these disturbance factors.

On the other hand, the actual yaw rate YR and the target yaw rate YT are applied to the determination process of the vehicle steering characteristic and the calculation process of the required yaw moment YAWM in the yaw moment calculation units 34 and 34 '. These yaw rates YR and YT are applied to the vehicle. It can be regarded as an index that directly represents the turning state of. Therefore, the determination of the steering characteristic and the calculation of the required yaw moment YAWM can be accurately executed based on these yaw rates YR and YT, and the driving force distribution between the front and rear wheels 4 and 14 can be further appropriately controlled.
[Second Embodiment]
Next, a second embodiment in which the present invention is embodied in a driving force distribution control device that controls the driving force distribution between the front and rear wheels 4 and 14 of the FR vehicle-based electronically controlled on-demand four-wheel drive vehicle will be described.

  The control of the driving force distribution between the front and rear wheels 4 and 14 performed in the present embodiment is executed under the same idea as the control in the first embodiment, and is based on the FF vehicle base 4 in the first embodiment. Considering that the torque movement between the front and rear wheels 4 and 14 is in the opposite direction with respect to the wheel drive vehicle, based on the yaw rate corresponding control amount Ty in the final control amount calculation units 40 and 40 ′ shown in FIGS. The difference is that the correction direction is changed. Therefore, the description which overlaps a common structure and the location of a processing content is abbreviate | omitted, and demonstrates a different point mainly.

8 and 9 are schematic views showing the control state of driving force distribution when understeer occurs. FIG. 8 shows the case where the average front wheel speed NFave is higher than the average rear wheel speed NRave, and FIG. 9 shows the average front wheel speed. A case where NFave is lower than the rear wheel average wheel speed NRave will be described. First, a control state of driving force distribution when understeer occurs will be described with reference to these drawings.
In an FR vehicle-based electronically controlled on-demand four-wheel drive vehicle, the driving force from the engine is transmitted to the rear wheel 14, and a part of the driving force of the rear wheel 14 is provided between the front and rear wheels 4, 14. 8, the driving force distributed to the front wheel 4 side from the rear wheel 14 side to the front wheel 4 side according to the engagement state of the electromagnetic clutch of the electronic control coupling 8, that is, between the front and rear wheels 4 and 14 Adjust the driving force distribution.

  Since the torque movement by the driving force distribution between the front and rear wheels 4 and 14 is performed from the high wheel speed side to the low wheel speed side, the front wheel average wheel speed NFave shown in FIG. 8 is higher than the rear wheel average wheel speed NRave (NFave). > N Rave), the torque moves from the front wheel 4 to the rear wheel 14 via the electronic control coupling 8. That is, the rear wheel 14 is reversely driven from the front wheel 4 side, the front wheel 4 generates a braking force (negative driving force) corresponding to the torque movement, and the driving force of the rear wheel 14 increases. At this time, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty (T = Tbase−Ty), the actual driving force distribution between the front and rear wheels 4 and 14 decreases as the final control amount T decreases. . As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 decreases, and the braking force of the front wheel 4 decreases as shown by the white arrows Adrv and Acornering in FIG. 8, while the driving force of the rear wheel 14 decreases. Accordingly, the lateral force increases as the driving force of the front wheels 4 decreases, and understeer is suppressed as the yaw moment increases.

  Further, in the traveling state (NFave <NRave) where the average front wheel speed NFave shown in FIG. 9 is lower than the average average wheel speed NRave, the torque is moved from the rear wheel 14 to the front wheel 4 via the electronic control coupling 8. . That is, a part of the driving force of the rear wheel 14 is distributed to the front wheel 4, so that the front wheel 4 generates the driving force corresponding to the torque movement and the driving force of the rear wheel 14 is reduced. At this time, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty (T = Tbase−Ty), the actual driving force distribution between the front and rear wheels 4 and 14 decreases as the final control amount T decreases. . As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 decreases, and the driving force of the rear wheel 14 increases while the driving force of the front wheel 4 decreases as shown by the white arrows Adrv and Acornering in FIG. Accordingly, the lateral force increases as the driving force of the front wheels 4 decreases, and understeer is suppressed as the yaw moment increases.

On the other hand, the control situation of the driving force distribution at the time of oversteer will be described. FIGS. 10 and 11 are schematic diagrams showing the control situation of the driving force distribution at the time of oversteer. FIG. 10 shows the average front wheel speed NFave as the average of the rear wheels. FIG. 11 shows a case where the front wheel average wheel speed NFave is lower than the rear wheel average wheel speed NRave.
In the driving situation (NFave> NRave) where the average front wheel speed NFave is higher than the average rear wheel speed NRave shown in FIG. 10, the torque moves from the front wheel 4 to the rear wheel 14 via the electronically controlled coupling 8 as in FIG. is doing. That is, the rear wheel 14 is reversely driven from the front wheel 4 side, and the front wheel 4 generates a braking force corresponding to the torque movement. At this time, since the final control amount T is corrected to decrease by the yaw rate corresponding control amount Ty (T = Tbase−Ty), the actual driving force distribution between the front and rear wheels 4 and 14 decreases as the final control amount T decreases. . As a result, the amount of torque movement from the front wheel 4 to the rear wheel 14 decreases, and the braking force of the front wheel 4 decreases while the driving force of the rear wheel 14 decreases as indicated by the white arrows Adrv and Acornering in FIG. Accordingly, the lateral force increases as the driving force of the rear wheel 14 decreases, and oversteer is suppressed as the yaw moment increases.

  Further, in the traveling state where the average front wheel speed NFave shown in FIG. 11 is lower than the average rear wheel speed NRave (NFave <NRave), the torque from the rear wheel 14 to the front wheel 4 via the electronically controlled coupling 8 is the same as in FIG. Is moving. That is, a part of the driving force of the rear wheel 14 is distributed to the front wheel 4, so that the front wheel 4 generates the driving force corresponding to the torque movement and the driving force of the rear wheel 14 is reduced. At this time, since the final control amount T is corrected to be increased by the yaw rate corresponding control amount Ty (T = Tbase + Ty), the actual driving force distribution between the front and rear wheels 4 and 14 increases as the final control amount T increases. As a result, the amount of torque movement from the rear wheel 14 to the front wheel 4 increases, and the driving force of the rear wheel 14 decreases while the driving force of the front wheel 4 increases as shown by the white arrows Adrv and Acornering in FIG. Accordingly, the lateral force increases as the driving force of the rear wheel 14 decreases, and oversteer is suppressed as the yaw moment increases.

The control of the driving force distribution between the front and rear wheels 4 and 14 at the time of understeer and oversteer is performed as described above. Although not redundantly described, according to the vehicle driving force distribution control device of the present embodiment, In the four-wheel drive vehicle, exactly the same functions and effects as those described in the first embodiment can be obtained.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the yaw rate YR is applied as the target turning state index. However, the present invention is not limited to this as long as the index correlates with the turning state of the vehicle. For example, the lateral acceleration detected by the lateral acceleration sensor 26 instead of the yaw rate is used. The acceleration GY may be applied.

1 is an overall configuration diagram showing a driving force distribution control device for a four-wheel drive vehicle based on an FF vehicle according to a first embodiment. It is a block diagram which shows the setting procedure of the control amount of the electronic control coupling performed by ECU at the time of understeer. It is a schematic diagram which shows the control condition of driving force distribution when front wheel average wheel speed is higher than rear wheel average wheel speed in understeer. It is a schematic diagram which shows the control condition of driving force distribution when a front-wheel average wheel speed is lower than a rear-wheel average wheel speed by understeer. It is a block diagram which shows the setting procedure of the control amount of the electronic control coupling performed by ECU at the time of oversteer. It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is higher than the rear wheel average wheel speed in oversteer. It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is lower than the rear wheel average wheel speed in oversteer. It is a schematic diagram which shows the control condition of driving force distribution when a front-wheel average wheel speed is higher than a rear-wheel average wheel speed by the understeer in 2nd Embodiment. It is a schematic diagram which shows the control condition of driving force distribution when a front-wheel average wheel speed is lower than a rear-wheel average wheel speed by understeer. It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is higher than the rear wheel average wheel speed in oversteer. It is a schematic diagram showing a control situation of driving force distribution when the front wheel average wheel speed is lower than the rear wheel average wheel speed in oversteer.

Explanation of symbols

4 Front wheel 8 Electronically controlled coupling (drive force distribution means)
14 rear wheel 21 4WD ECU (control amount calculation means, steering characteristic determination means, driving force distribution control means,
Target turning state index determining means, grip limit index estimating means, required lateral force calculating means,
Driving force reduction amount calculation means)
24 Yaw rate sensor (actual turning state index detection means)
25 Wheel speed sensor (wheel speed detection means)

Claims (3)

Driving force distribution means provided between the front and rear wheels of the vehicle and capable of variably distributing a part of the driving force transmitted from the driving source to the front wheels to the rear wheel side;
Control amount calculation means for calculating a turn corresponding control amount as a correction amount for the driving force distribution to be distributed to the rear wheel side based on the turning state of the vehicle;
Steer characteristic determining means for determining the current steering characteristic of the vehicle;
Wheel speed detecting means for detecting the wheel speeds of the front and rear wheels,
When it is determined that the wheel speed of the front wheel is higher than the wheel speed of the rear wheel based on the detection result by the wheel speed detection means , the driving force between the front and rear wheels is when the steering characteristic determined by the steering characteristic determination means is understeer. While the distribution is increased and corrected based on the turning control amount, when the steering characteristic is oversteer, the driving force distribution between the front and rear wheels is reduced and corrected based on the turning control amount so that the front wheel speed is If it is determined that the vehicle speed is lower than the wheel speed, the driving force distribution between the front and rear wheels is corrected to decrease based on the turning control amount regardless of the steering characteristic determined by the steering characteristic determination unit , and the corrected driving force distribution is obtained. Driving force distribution control means for controlling the driving force distribution means based on
Vehicles of the driving force distribution control device comprising the. Driving force distribution means provided between the front and rear wheels of the vehicle and capable of variably distributing a part of the driving force transmitted from the driving source to the rear wheel to the front wheel side;
Control amount calculation means for calculating a turn corresponding control amount as a correction amount for the driving force distribution to be distributed to the front wheel side based on the turning state of the vehicle;
Steer characteristic determining means for determining the current steering characteristic of the vehicle;
Wheel speed detecting means for detecting the wheel speeds of the front and rear wheels,
When it is determined that the wheel speed of the rear wheel is higher than the wheel speed of the front wheel based on the detection result by the wheel speed detecting means , the driving force between the front and rear wheels is when the steer characteristic determined by the steer characteristic determining means is understeer. While the distribution is reduced and corrected based on the turning control amount, when the steering characteristic is oversteer, the driving force distribution between the front and rear wheels is increased and corrected based on the turning control amount, and the wheel speed of the rear wheel is adjusted to that of the front wheel. If it is determined that the vehicle speed is lower than the wheel speed, the driving force distribution between the front and rear wheels is corrected to decrease based on the turning control amount regardless of the steering characteristic determined by the steering characteristic determination unit , and the corrected driving force distribution is obtained. Driving force distribution control means for controlling the driving force distribution means based on
Vehicles of the driving force distribution control device comprising the. The steer characteristic determining means includes
Target turning state index determining means for determining a target turning state index based on the running state of the vehicle;
An actual turning state index detecting means for detecting an actual turning state index of the vehicle,
A steering characteristic of the current vehicle is determined based on the target turning state index and the actual turning state index,
The control amount calculation means is
The grip limit for identifying the slip wheel of the front and rear wheels based on the understeer and oversteer determined as the steer characteristic by the steer characteristic determination means, and estimating a grip limit index correlated with the grip limit from the driving force and lateral force of the slip wheel Index estimation means;
A required lateral force calculating means for calculating a required yaw moment for suppressing the understeer or oversteer based on the turning state of the vehicle, and calculating a required lateral force of the slip wheel capable of achieving the required yaw moment;
Based on the grip limit index calculated by the grip limit index calculating means, the driving force decrease that calculates the slip wheel driving force reduction amount required to achieve the required lateral force calculated by the required lateral force calculating means. A quantity calculating means,
Driving force distribution control device for a vehicle according to claim 1 or 2, wherein in response to the driving force reduction amount of the slip ring which is calculated by the above SL driving force reduction amount calculating means, and calculates the turning corresponding control amount.

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