JPH05305830A - Driving force distribution controller of four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To promote an improvement in fuel consumption after securing the extent of fundamental performance by judging whether 4WD control is necessary or not, and when it is unnecessary, selecting a control transfer torque, and when it is necessary, selecting the maximum value between the control transfer torque and an environment corresponding transfer torque, and performing a job for clutch clamping force control. CONSTITUTION:This controller is provided with a control transfer torque calculating means (c) calcualting a control transfer torque for getting an optimum tuning characteristic on the basis of information by a front-rear-wheel speed detecting means (b) as a transfer torque to be trandsferred via a torque distributing clutch (a). In addition, torque conformed to a specified traveling ambience is calcualted by an ambience corresponding transfer torque calculating means (d). Then the controller is also provided with a 4WD requiredness judging means (e) which judges whether 4WD control is necessary or not, and when it is judged as disuse, a control transfer torque alone is selected, but when it is judged to be necessary, a transfer torque selecting means (f) selects the maximum value between the control transfer torque and the ambience corresponding transfer torque, and a clutch clamping force control means (g) controls the clamping force of a clutch (a).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive force distribution control device for a four-wheel drive vehicle in which direct drive is applied to one of the front and rear wheels and drive force is transmitted to the other through a torque distributing clutch.

[0002]

2. Description of the Related Art Conventionally, as a driving force distribution control device for a four-wheel drive vehicle of this type, for example, one disclosed in Japanese Patent Application Laid-Open No. 2-270640 is known.

According to the above-mentioned conventional source, in a four-wheel drive vehicle in which the transmission torque to the front wheel side is given by the rear wheel drive base by the clutch engagement force control, the front wheel side transmission torque is controlled in proportion to the front and rear wheel rotation speed difference. There is disclosed a control technique for calculating a transmission torque T ₁ , a starting torque T ₂ proportional to a throttle opening at the time of starting, and an initial torque T ₃ proportional to a vehicle speed, and outputting the maximum value as a front wheel side transmission torque.

Here, the starting torque T ₂ is a torque for obtaining sufficient traction without causing the rear wheels to spin when starting on a low friction coefficient road. Further, initial torque T ₃ is a torque for transmitting the control transmission torque T ₁ on the front wheel side without receiving the response delay effect of the hydraulic even at a low temperature (e.g. -25 ° C.), very weak torque clutch torque distribution By connecting with, the idle time for filling the gap of the multi-plate clutch is reduced.

[0005]

However, the above-mentioned conventional drive force distribution control device for a four-wheel drive vehicle is preferable because the starting performance on a low friction coefficient road and the hydraulic response at a low temperature can be obtained. However, even in a general driving environment such as a high friction coefficient road or normal temperature, the starting torque T ₂ and the initial torque T ₃ which are not originally required are constantly applied, so that the fuel consumption peculiar to a four-wheel drive vehicle deteriorates. There was a problem.

The present invention has been made in view of the above problems, and is a four-wheel drive vehicle in which the driving force is directly transmitted to one of the front and rear wheels and the driving force is transmitted to the other through a torque distribution clutch. It is an object of the present invention to improve fuel efficiency while ensuring proper basic performance of four-wheel drive control.

[0007]

In order to solve the above problems, the drive force distribution control device for a four-wheel drive vehicle according to the present invention determines whether or not the traveling environment of the vehicle requires proper four-wheel drive control. The control transmission torque is selected when it is unnecessary, and the maximum value is selected from the control transmission torque and the environment-friendly transmission torque when the control torque is required to perform clutch engagement force control.

That is, as shown in the claim correspondence diagram of FIG. 1, a torque distribution clutch a is provided in the middle of the drive system to the other of the rear wheels or front wheels with respect to the drive system directly connected to the engine to one of the front wheels or rear wheels. An optimum turning characteristic based on the front-rear wheel rotation speed difference information as a transmission torque transmitted through the front-rear wheel rotation speed difference detection means b for detecting the front-rear wheel rotation speed difference and the torque distribution clutch a. Control transmission torque calculating means c for calculating the obtained control transmission torque,
At least one environment-friendly transmission torque calculating means d for calculating environment-friendly transmission torque corresponding to a specific traveling environment as the transmission torque transmitted through the torque distribution clutch a, separately from the control transmission torque, and a vehicle. 4 wheel drive necessity determination means e for determining whether or not the traveling environment of 4 requires appropriate 4 wheel drive control, and 4 wheel drive for which the vehicle traveling environment is appropriate by the 4 wheel drive necessity determination means e. When it is determined that control is not required, select only control transmission torque,
When the four-wheel drive necessity determining means e determines that the traveling environment of the vehicle requires an appropriate four-wheel drive control, a transfer torque selecting means f for selecting the maximum value of the control transfer torque and the environment-compatible transfer torque. And a clutch engagement force control means g for controlling the engagement force of the torque distribution clutch a so that the transmission torque selected by the transmission torque selection means f is obtained.

[0009]

When the four-wheel drive necessity determining means e determines that the traveling environment of the vehicle does not require proper four-wheel drive control, the transmission torque selecting means f transmits the torque via the torque distribution clutch a. As the transmission torque to be transmitted, the control transmission torque that obtains the optimum turning characteristic is selected based on the front-rear wheel rotation speed difference information, and the clutch engagement force control means g changes the engagement force of the torque distribution clutch a so as to obtain this torque. Controlled.

Therefore, during traveling such as when traveling on a high friction coefficient road, where it is determined that proper four-wheel drive control is not required, the torque distribution clutch a is used unless the front-rear wheel rotational speed difference occurs. The released two-wheel drive state is achieved, and fuel efficiency is improved. Even when this is unnecessary, the turning performance improving performance by the control transmission torque is ensured to the minimum.

When it is determined by the four-wheel drive necessity determining means e that the vehicle traveling environment requires proper four-wheel drive control, the transmission torque selecting means g transmits the torque via the torque distribution clutch a. As the transmission torque, the maximum value is selected from the control transmission torque and the environmentally compatible transmission torque according to the specific traveling environment, and the clutch engaging force control means g causes the torque distribution clutch a to obtain the selected torque. The fastening force of is controlled.

Therefore, during traveling such as traveling on a road having a low coefficient of friction or traveling at the limit, it is determined that the proper four-wheel drive control is required, and the environment-friendly transmission torque is utilized.
Appropriate basic performance of four-wheel drive control such as low μ traction performance is secured.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) The configuration will be described.

FIG. 2 is an overall system diagram including a drive system of a four-wheel drive vehicle to which the torque split control system (corresponding to a drive force distribution control device) of the first embodiment of the present invention is applied.

The vehicle to which the torque split control system of the first embodiment is applied is a rear wheel-based four-wheel drive vehicle, and its drive system includes an engine 1, a transmission 2, a transfer input shaft 3, a rear propeller. Shaft 4,
The rear differential 5, the rear wheels 6, the transfer output shaft 7, the front propeller shaft 8, the front differential 9, and the front wheels 10 are provided, and the engine torque that has passed through the transmission 2 is directly transmitted to the rear wheels 6 and the front wheels 10. Is transmitted via a transfer clutch device 12 having a wet multi-plate friction clutch 11 (corresponding to a torque distribution clutch) provided between the transfer input / output shafts 3 and 7 which is a front wheel drive system.

A torque split control system for optimally controlling the distribution of the driving forces of the front and rear wheels while achieving both the driving performance and the steering performance is a transfer clutch device 12 (for example, a front end) having a wet multi-plate friction clutch 11 built therein. (See the specification and drawings of Japanese Patent Application No. 63-325379), the control oil pressure generator 20 that generates the control oil pressure Pc that is the clutch engagement force, and the solenoid valve 28 provided in the control oil pressure generator 20. A torque split controller 40 that outputs a predetermined dither current i * based on information from various input sensors 30.

The hydraulic control device 20 includes a motor 22 which is driven or stopped by a relief switch 21, a hydraulic pump 24 which is actuated by the motor 22 to suck up from a reservoir tank 23, and a pump discharge pressure (primary pressure) from the hydraulic pump 24. Accumulator 26 for accumulating the pressure) via the check valve 25, and the line pressure (secondary pressure) from the accumulator 26 is controlled to a predetermined control hydraulic pressure by the solenoid driven dither current i * from the torque split control unit 40.
With a solenoid valve 28 for adjusting to Pc, control hydraulic pressure
The hydraulic oil of Pc passes through the control hydraulic pipe 29 and is supplied to the clutch port.

As the various input sensors 30, as shown in the block diagram of the system electronic control system of FIG. 3, the left front wheel rotation sensor 30a, the right front wheel rotation sensor 30b, the left rear wheel rotation sensor 30c, the right rear wheel rotation sensor. 30d, a lateral acceleration sensor 30e, a longitudinal acceleration sensor 30f, and a throttle opening sensor 30g.

The torque split control unit 40 is shown in FIG.
As shown in the block diagram of the system electronic control system, the left front wheel speed calculation circuit 40a, right front wheel speed calculation circuit 40b, left rear wheel speed calculation circuit 40c, right rear wheel speed calculation circuit 40d, front wheel speed calculation circuit 40e, rear Wheel speed calculation circuit 40f, rotation speed difference calculation circuit 40g, gain calculation circuit 40h, control transmission torque calculation circuit 40i, starting torque calculation circuit 40j, initial torque calculation circuit 40k, 4WD necessity determination circuit 40m, transmission torque selection circuit 40n, It has a Ti conversion circuit 40p and a dither current output circuit 40q.

In the figure, A / D is an A / D converter and D / A is
It is a D / A converter.

The operation will be described.

(A) Front and rear wheel drive force distribution control processing operation FIG. 4 is a flowchart showing the flow of front and rear wheel drive force distribution control processing operation performed by the torque split controller 40 at a control cycle of 10 msec. explain.

In step 80, the left front wheel speed V _WFL , the right front wheel speed V _WFR , the left rear wheel speed V _WRL , and the right rear wheel speed are used as control information.
V _WRR , lateral acceleration Y _G , longitudinal acceleration X _G , and throttle opening θ are input.

In step 81, the front wheel speed V _WF is calculated from the average value of the left front wheel speed V _WFL and the right front wheel speed V _WFR, and the average value of the left rear wheel speed V _WRL and the right rear wheel speed V _WRR is calculated. By rear wheel speed
V _WR is calculated.

In step 82, the front wheel speed V _WF and the rear wheel speed V _WF
Front-rear wheel rotation speed difference detection value from _WR ΔV _W (= V _WR −V _WF ;
However, ΔV _W ≧ 0) is calculated (corresponding to front and rear wheel rotation speed difference detection means).

At step 83, the front and rear wheel rotation speed difference ΔV _W
The control gain K _h of the control transmission torque T ₁ with respect to
It is calculated by the following formula based on the reciprocal of Y _G.

K _h = α _h / Y _G (where K _h ≤β _h ) For example, when α _h = 1 and β _h = 10, the characteristic shown in FIG. K _h is selected so that it always has a linear neutral steer characteristic at all road friction coefficients.

In step 84, the control transmission torque T ₁ is calculated from the control gain K _h and the front and rear wheel rotation speed difference ΔV _W (corresponding to control transmission torque calculating means). This is shown in a torque characteristic map as shown in FIG. 5 (B).

In step 85, the starting torque T ₂ is calculated by the following equation based on the vehicle speed V _CAR and the throttle opening θ obtained by the function of the front wheel speed V _WF and the longitudinal acceleration X _G (environmentally friendly transfer torque). Equivalent to one of the computing means).

V _CAR = f ₁ (V _WF , X _G ) and T ₂ = f ₂ (V _CAR , θ).

Note that T ₂ = 0 ... V _CAR > 20 km / h T ₂ = K ′ · θ + T ₀ ... V _CAR ≦ 20 km / h (K ′, T ₀ are constants) For example, K ′ = 0.5 (kgm / deg), T ₀ = 4 (kgm)
When it is set to, the torque characteristic map is shown in FIG.

Here, T ₂ = 0 ... V _CAR > 20 km / h T ₂ = K ′ · (θ−θ ₀ ) + T ₀ so that the starting torque T ₂ is generated when the throttle opening θ is equal to or greater than a predetermined value. V _CAR ≦ 20 km / h For example, θ ₀ = 30 deg may be set.

In step 86, the initial torque T ₃ is calculated according to the lateral acceleration Y _G (corresponding to one of environment-friendly transmission torque calculating means).

This initial torque T ₃ is set such that the torque level becomes lower as the lateral acceleration increases so as to allow slippage between the clutch plates at the time of turning when lateral acceleration occurs. ₀ 'to T ₀ ' =
When 2 (kgm), Y _G0 = 0.45 (G), and Y _G1 = 0.6 (G), it is shown in a torque characteristic map as shown in FIG. 7.

At step 87, within the traveling distance L ₀ , T
_It is determined whether ₁ > max (T ₂ ', T ₀ ') has been experienced more than once.

Here, the traveling distance L ₀ monitored by integrating the vehicle speed and time is set to L ₀ = 1000 km, for example.

Further, the starting torque T ₂ 'used for the judgment
Is given by T ₂ '= 0 ... V _CAR > 20 km T ₂ ' = T ₀ ... V _CAR ≤ 20 km.

Further, the initial torque T ₃ used for the judgment
Is given by the initial torque T ₀ 'during straight travel.

Then, if YES at step 87, the routine proceeds to step 88, where the 4WD flag is set to 4WD.
When the flag is set to 1 and it is determined NO in step 87, the process proceeds to step 89 and the 4WD flag is set to 4WD.
Flag = 0 is set. The above steps 87 to 89 correspond to the four-wheel drive necessity determining means.

At step 90, 4WD at step 89
When the flag = 0 is set, the control transmission torque T ₁ is selected as the final transmission torque T, and 4WD is set in step 88.
When the flag is set to ₁ , the maximum value of the control transmission torque T ₁ , the starting torque T ₂ , and the initial torque T ₃ is selected as the final transmission torque T (corresponding to the transmission torque selection means).

In steps 91 and 92, the engagement force of the wet multi-plate friction clutch 11 is controlled (corresponding to clutch engagement force control means) to obtain the final transmission torque T set in step 90.

In step 91, the final transmission torque T set in step 90 is converted into the solenoid drive current i by the T-i characteristic table given in advance.

At step 92, the solenoid drive current i
Is converted to dither current i * (for example, i ± 0.1 A 100
Hz), and the dither current i * is output to the solenoid valve 28.

(B) When traveling without requiring proper four-wheel drive control During normal traveling on a high friction coefficient road, etc., when NO is determined in step 87 which is a four-wheel drive necessity determining step. , Step 80 to Step 86 → Step 87 →
The flow proceeds in the order of step 89 → step 90 → step 91 → step 92. At step 90, the control transmission torque T ₁ is selected as the final transmission torque T, and the wet multi-plate is obtained so as to obtain this control transmission torque T _1. The engagement force of the friction clutch 11 is controlled.

Here, in step 87, the traveling distance L ₀
It is judged within a time period whether T ₁ > max (T ₂ ', T ₀ ') has been experienced more than once. This judgment means that the road surface friction coefficient is estimated by long-term road surface learning. That is, when the vehicle runs on a low μ road, delicate accelerator work is required. For example, even if the accelerator is slightly depressed, the drive wheel slip will occur, and the control transmission torque T ₁ proportional to the front-rear wheel rotation speed difference will be generated. The level of will increase and will inevitably satisfy step 87. In addition, this road surface friction coefficient estimation showed a judgment mainly on low μ roads,
It may be possible to estimate the road surface friction coefficient by making a determination mainly on the high μ road, for example, starting and stopping 50 times repeatedly and whether T ₁ = Tmin continues for a predetermined time or more during that time.

Therefore, during traveling such as when traveling on a high friction coefficient road, where it is determined that proper four-wheel drive control is not required, unless there is a difference in front and rear wheel rotation speed, the wet multi-plate friction clutch 11 is used. Thus, the fuel economy is improved compared to the case where the initial torque T ₂ is continuously applied or the high starting torque T ₂ is applied at the time of starting. Even when this is unnecessary, the turning performance improving performance by the control transmission torque T ₁ is ensured to the minimum.

(C) When traveling that requires proper four-wheel drive control When traveling on a low friction coefficient road or on a limit traveling on a high friction coefficient road, the four-wheel drive necessity determining step is performed.
When YES is determined in step 7, step 80 to step 86 → step 87 → step 88 → step 90 →
The flow proceeds from step 91 to step 92, and in step 90, the maximum value of the control transmission torque T ₁ , the starting torque T ₂ , and the initial torque T ₃ is selected as the final transmission torque T, and this final transmission torque T is selected. The fastening force of the wet multi-plate friction clutch 11 is controlled so as to be obtained.

Therefore, when the vehicle is determined to require appropriate four-wheel drive control, such as when traveling on a low friction coefficient road or at the time of limit traveling, as described below, the starting torque T ₂ and the initial torque are set. The environment-friendly transmission torque due to the torque T ₃ is utilized to ensure proper basic performance of four-wheel drive control such as low μ traction performance.

1) The starting torque T ₂ ensures starting traction even when the vehicle starts on a low μ road.

2) The initial torque T ₃ eliminates the hydraulic response delay at low temperatures. As a result, to butt swing is prevented by applying a good response high torque during starting acceleration of imparting starting torque T _2, the response may control the transmission torque T ₁ is given when the control by the control transmission torque T ₁ Therefore, the turning performance aimed at at the time of turning on a low μ road or at the time of the limit turning is always secured, and the maneuverability is enhanced.

3) The initial torque T ₃ enhances the stability and the running performance during high-speed straight running.

As described above, in the drive force distribution control device for the four-wheel drive vehicle of the first embodiment, the following effects can be obtained.

[0054] (1) determines whether the running environment of the vehicle requires an appropriate four-wheel drive control, when not required to select a control transmission torque T _1, the time required, control the transmission torque T ₁
Since a device for controlling the clutch engagement force by selecting the maximum value among the starting torque T ₂ and the initial torque T ₃ is provided, it is possible to improve fuel efficiency while ensuring the basic performance of appropriate four-wheel drive control. it can.

(2) Since the starting torque T ₂ and the initial torque T ₃ are provided separately from the control transmission torque T ₁ as the environment-friendly transmission torque, the vehicle traveling environment is appropriate.
When it is judged that wheel drive control is required, the above 1), 2), 3)
The low μ traction performance of is demonstrated.

(Second Embodiment) Next, a second embodiment will be described.

The hardware structure of the second embodiment is exactly the same as that of the first embodiment, and therefore its explanation is omitted.

The operation will be described.

FIG. 8 is a flow chart showing the flow of the front and rear wheel drive force distribution control processing operation performed by the torque split controller 40 of the second embodiment.

The only difference from the flowchart of the first embodiment shown in FIG. 4 is step 93 for determining the necessity of four-wheel drive. In this step 93, it is judged whether or not T ₁ > max (T ₂ ', T ₀ ') has been experienced at least once while repeating start and stop 5 times. That is, while the step 87 of the first embodiment estimates the road surface friction coefficient by long-term road surface learning, the determination in step 93 estimates the road surface friction coefficient by short-term road surface learning. As a result, the road surface friction coefficient is estimated during one run from turning on the ignition to turning off the ignition, and estimation of the road surface friction coefficient is restarted at the next running. It should be noted that this road surface friction coefficient estimation showed a judgment that the low μ road is the main, but a judgment that the high μ road is the main, for example, T ₁ = Tmin continues for a predetermined time or more during the period from ON to OFF of the ignition. The road surface friction coefficient may be estimated based on whether or not it is done.

As described above, in the driving force distribution control device for the four-wheel drive vehicle of the second embodiment, the following effects are added to the effects of the first embodiment.

(3) Since it is a device for estimating the road surface friction coefficient by short-term road surface learning when determining the necessity of four-wheel drive, it can be adopted in the torque split controller 40 having no battery backup circuit. ..

(Third Embodiment) Next, a third embodiment will be described.

The hardware structure of the third embodiment is exactly the same as that of the first embodiment, and therefore its explanation is omitted.

The operation will be described.

FIG. 9 is a flow chart showing the flow of the front and rear wheel drive force distribution control processing operation performed by the torque split controller 40 of the second embodiment.

The difference from the flow chart of the first embodiment shown in FIG. 4 is that in determining the necessity of four-wheel drive, a minimum torque T _MIN that depends on the vehicle speed V _CAR is set (step 94). The limit torque T _MIN is used to determine the necessity of four-wheel drive (steps 95 and 96). The initial value of the 4WD flag is 4WD flag = 1.

At step 93, the minimum torque T _MIN is calculated from the vehicle speed V _CAR .

This minimum torque T _MIN is _calculated in step 93.
T _MIN = 4 (V _CAR ≤20 km / h) T _MIN = 8 (V _CAR > 20 km / h), as shown in the frame of the above, and as shown in FIG.
_MIN may be given as a variable value proportional to the vehicle speed V _CAR .

In step 94, once the 4WD flag =
If the state in which the control transmission torque T ₁ satisfies T ₁ ≧ T _MIN for 250 msec or more continuously occurs at least once after 0, it is determined to be a low μ road, and the routine proceeds to step 88, The 4WD flag = 1 indicating that four-wheel drive is required until the ignition is turned off is set.

At step 95, after the self-check is completed with the ignition turned on, the vehicle is completely stopped to start at 20 km / h or more.
If the condition that T ₁ ≧ T _MIN is satisfied for 250 msec or more does not occur once during two stops, it is judged to be a high μ road, and the process proceeds to step 89 and 4-wheel drive is unnecessary. 4WD = 0 is set.

As described above, in the four-wheel drive vehicle drive force distribution control device of the third embodiment, the following effects are added to the effects of the first embodiment.

(4) The minimum torque T _MIN (large on the high speed side) which depends on the vehicle speed V _CAR is set, and this minimum torque T _MIN is set.
_{Since the} necessity of four-wheel drive is determined using _MIN , if there is a tire diameter difference, it is prevented from being mistakenly judged to be a low μ road during high-speed driving on a high μ road, and the road surface is surely You can judge the friction coefficient.

That is, in the first and second embodiments, a threshold value that does not depend on the vehicle speed V _CAR is used to distinguish between the low μ road and the high μ road. If it is (particularly when V _WR > V _WF is severe), the threshold value may be exceeded during high-speed driving on a high μ road, and it may be mistakenly judged to be a low μ road.

Although the embodiment has been described above with reference to the drawings, the specific configuration and control contents are not limited to this embodiment.

For example, in the embodiment, an example in which the starting torque T ₂ and the initial torque T ₃ are applied as environment-friendly transmission torque is shown. However, hunting countermeasure torque, clutch protection torque, ABS operating torque, limit torque, front / rear torque Including acceleration sensitive torque, deceleration torque, fail safe torque, etc.
One or a combination of these may be used as the environment-friendly transmission torque.

[0077]

As described above, according to the present invention, the drive of a four-wheel drive vehicle is such that one of the front and rear wheels is directly connected and the other is supplied with the driving force through a torque distribution clutch. In the force distribution control device, as described in claim 1, it is determined whether or not the traveling environment of the vehicle requires appropriate four-wheel drive control, the control transmission torque is selected when unnecessary, and when necessary, Since it is a device that controls the clutch engagement force by selecting the maximum value from the control transmission torque and the environment-friendly transmission torque, it is possible to improve fuel efficiency while ensuring proper basic performance of four-wheel drive control. The effect is obtained.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a driving force distribution control device for a four-wheel drive vehicle according to the present invention.

FIG. 2 is an overall system diagram showing a drive system and a control system of a four-wheel drive vehicle to which the torque split control device (driving force distribution control device) of the first embodiment is applied.

FIG. 3 is a block diagram showing an electronic control system used in the torque split control device of the first embodiment.

FIG. 4 is a flowchart showing a flow of front and rear wheel driving force distribution control processing operations performed by the torque split controller of the first embodiment.

FIG. 5 (A) is a control gain characteristic diagram of a control transmission torque characteristic in the torque split control of the first embodiment,
FIG. 5B is a control transmission torque characteristic diagram.

FIG. 6 is a starting torque characteristic in the torque split control of the first embodiment.

FIG. 7 is an initial torque characteristic in the torque split control of the first embodiment.

FIG. 8 is a flowchart showing a flow of front and rear wheel driving force distribution control processing operations performed by the torque split controller of the second embodiment.

FIG. 9 is a flowchart showing a flow of front and rear wheel driving force distribution control processing operations performed by the torque split controller of the third embodiment.

FIG. 10 is a minimum torque characteristic diagram used for determining a road surface μ road in the device of the third embodiment.

[Explanation of symbols]

 a torque distribution clutch b front and rear wheel rotation speed difference detection means c control transmission torque calculation means d environment-friendly transmission torque calculation means e four-wheel drive necessity determination means f transmission torque selection means g clutch engagement force control means

Claims (1)

[Claims] 1. A torque distribution clutch provided in the middle of a drive system to the other of the rear wheels or front wheels for a drive system directly connected to the engine to one of the front wheels or the rear wheels, and front and rear wheels for detecting a difference in rotational speed between the front and rear wheels. Rotational speed difference detection means, and controllable transmission torque calculation means for calculating controllable transmission torque for obtaining optimum turning characteristics based on front and rear wheel rotational speed difference information, as transmission torque transmitted through the torque distribution clutch, At least one environment-friendly transmission torque calculating means for calculating, as the transmission torque transmitted through the torque distribution clutch, an environment-friendly transmission torque according to a specific traveling environment separately from the control transmission torque; A four-wheel drive necessity determining means for determining whether or not the environment requires appropriate four-wheel drive control, and a traveling ring of the vehicle by the four-wheel drive necessity determining means. Is determined not to require proper four-wheel drive control, only the control transmission torque is selected, and the four-wheel drive necessity determining means determines that the traveling environment of the vehicle requires appropriate four-wheel drive control. The transmission torque selecting means for selecting the maximum value of the control transmission torque and the environment-friendly transmission torque, and controlling the engagement force of the torque distribution clutch so that the transmission torque selected by the transmission torque selection means is obtained. A driving force distribution control device for a four-wheel drive vehicle, comprising: