JPH09175213A - Driving device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a sudden change in steering characteristics by providing a controlling means for controlling a right wheel clutch and a left wheel clutch such that the ratio of torque distributed to a right wheel and a left wheel is increased as the rate of change of a steering angle is increased. SOLUTION: The wheel speeds of a left front, a right front, a left rear and a right rear wheels, a steering angle of a steering wheel and a rate of change thereof, a vehicle speed and a traverse acceleration are input by the signals of the sensors 36 to 39, 41, 42 and an ABS operating signal for indicating if the vehicle is under the control of an ABS or not is input as the signal from an ABS controller 43. Hydraulic oil supply to right and left wheel clutches 27, 28 is controlled by opening/closing hydraulic control valves 33, 34 by the control signals (b), (c) output by a controller 35, thereby controlling the connection/disconnection of both wheel clutches 27, 28 or the transmitting torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for a vehicle. In particular, the present invention relates to a drive device for a vehicle including a torque distribution device capable of changing a torque distribution ratio between left and right wheels.

[0002]

2. Description of the Related Art Conventionally, in a vehicle drive device,
A differential mechanism is provided between the left and right driving wheels to allow the differential that occurs during turning, etc., but this differential mechanism allows one of the left and right wheels to float off the road surface. If the vehicle becomes idle and spins, a state occurs in which the driving force is not transmitted to the other wheel. In order to avoid such a state, an apparatus provided with a differential limiting device for limiting the differential state of the differential mechanism in a predetermined state is disclosed in, for example, Japanese Patent Application Laid-Open No.
It has been proposed in, for example, JP-A-101236.

In this prior art, in order to further improve turning performance and high-speed stability, a vehicle speed, a steering state of a steering wheel, and the like are detected, and a differential limiting force of a differential limiting device is controlled to control a differential mechanism. The movement state is restricted or released. However, in this differential limiting device, the torque distribution ratio between the left and right wheels is not limited unless the vehicle turns or the ground contact state of the left and right wheels changes and the left and right wheels are not in a differential state. Cannot be changed.
That is, the torque distribution ratio cannot be changed in a normal straight traveling state in which there is no difference in rotation speed between the wheels.

On the other hand, by providing a hydraulic clutch for varying the transmission torque between the left and right wheels, the torque distribution ratio can be changed even when the vehicle is in a straight traveling state. For example, Japanese Patent Laid-Open No. 62-94421. It is proposed in the bulletin. In this drive device, the vehicle speed is detected by the vehicle speed sensor, and the steering amount and the steering direction are detected by the steering angle sensor.
The left / right torque distribution ratio can be changed. Therefore, turning performance and traveling stability can be improved.

Further, Japanese Laid-Open Patent Publication No. 1-233124 discloses a technique in which a hydraulic clutch having a variable transmission torque is provided between the left and right wheels, and the transmission path is changed to an input path for inputting driving torque to the left and right wheels. It has been proposed to provide a speed increasing device capable of detecting the steering force of the steering wheel and its differential value and increase the drive torque by the speed increasing device when the value exceeds a threshold value. In this drive device, the turning state can be predicted in advance by detecting the steering force of the steering wheel and its differential value, so that the responsiveness of the control can be improved, and the turning performance that matches the driver's request can be obtained. Can be

[0006]

By the way, in order to satisfy the turning request of the driver, the turning control is performed by detecting the steering angle amount and the differential value (steering angle change rate) of the steering angle amount as described above. However, in the drive device that performs turning control by changing the torque distribution ratio of the left and right wheels as mentioned above, if a sudden torque change occurs between the left and right wheels, it is not related to the steering wheel operation. However, the behavior of the vehicle may change suddenly.

As described in Japanese Patent Laid-Open No. 1-2333124, whether the threshold value is larger or smaller than the threshold value is detected, and
When the drive torque is changed by N, OFF control, the steering characteristic of the vehicle is at the threshold value in a turning state in which the steering wheel operation is gradually performed to increase or decrease the steering angle change rate (speed). Due to the sudden change, the driver may be anxious and the behavior of the vehicle may become unstable.

Therefore, an object of the present invention is to provide a drive device capable of changing the torque distribution ratio of the left and right wheels by means of respective clutches provided between the left and right wheels, thereby satisfying the driver's turning request and abruptly changing the steering characteristics. It is to provide a drive device for a vehicle that prevents the above.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems and achieve the object, a vehicle drive device of the present invention has the following arrangement. That is, the vehicle drive device according to the first aspect of the invention is provided in the power transmission system that receives the output from the power plant and transmits the power to the right wheel and the left wheel, and the power transmission unit of the power transmission system. , The right wheel clutch and the left wheel clutch that change the transmission torque to the right wheel and the left wheel, and the right wheel clutch and the left wheel clutch based on a predetermined signal to change the torque distribution ratio to the right wheel and the left wheel. In a vehicle drive device including a control means for controlling the steering wheel, a steering angle state detecting means for detecting a steering angle change rate of a steering wheel and a signal from the steering angle state detecting means are received. And a control means for controlling the right wheel clutch and the left wheel clutch so that the torque distribution ratio for the left wheel increases.

According to a second aspect of the present invention, there is provided a vehicle drive device comprising:
A power transmission system that receives output from the power plant and transmits power to the right wheel and the left wheel, and a right wheel clutch that is provided in a power transmission portion of the power transmission system and that changes transmission torque to the right wheel and the left wheel, respectively. And a left wheel clutch and a control means for controlling the right wheel clutch and the left wheel clutch based on a predetermined signal to change the torque distribution ratio to the right wheel and the left wheel. A steering angle state detecting means for detecting the rate of change of the angle, and a signal from the steering angle state detecting means to increase the difference in the value of the torque transmitted to the right wheel and the left wheel as the rate of change of the steering angle increases. And a control means for controlling the right wheel clutch and the left wheel clutch.

[0011]

According to the first aspect of the present invention, the right wheel clutch and the left wheel clutch are controlled so that the torque distribution ratio to the right wheel and the left wheel increases as the steering angle change rate increases. Therefore, gradually operate the handle,
Even when the steering angle speed increases or decreases, the torque distribution ratio increases with the increase in the steering angle change rate. That is, the torque distribution ratio also changes according to the change in the steering angular velocity. Therefore, the steering characteristic of the vehicle does not suddenly change at the threshold value, and there is no fear that the driver feels uneasy or the behavior of the vehicle becomes unstable.

According to the second aspect of the present invention, the right wheel clutch and the left wheel clutch are controlled so that the difference between the values of the torques transmitted to the right wheel and the left wheel increases as the steering angle change rate increases. Therefore, when the driver performs a sudden steering wheel operation, a large torque difference is generated between the left and right wheels, and good turning performance of the vehicle is obtained. Also, when the driver performs a slow steering wheel operation, a torque difference that is not so large is generated, so that the turning performance of the drive device does not occur so much and a stable turning can be performed. Even when the steering angular velocity is gradually changed, the torque difference gradually changes, so that the steering characteristics of the vehicle do not suddenly change, which makes the driver uneasy and the behavior of the vehicle becomes unstable. There is no danger of

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a four-wheel drive vehicle according to this embodiment and a control system thereof. This four-wheel drive vehicle has a driving force generated by a power plant 3 including an engine 1 and a transmission 2. Is input via the pair of transmission gears 4 and 5,
It has a front wheel drive system 10 and a rear wheel drive system 20 that drive the left and right front wheels 6, 7 and the left and right rear wheels 8, 9, respectively.

The front wheel drive system 10 is arranged in the longitudinal direction of the vehicle body and is driven by the driving force from the power plant 3 via the gears 4 and 5, and the front wheel drive shaft 11 and the shaft 1.
Differential device 12 for dividing the power input from 1 into left and right
And left and right axles 13 and 14 for transmitting the power divided by the device 12 to the left and right front wheels 6 and 7, respectively, whereby the left and right front wheels 6 and 7 are constantly driven by the driving force from the power plant 3. It is designed to be driven.

The rear wheel drive system 20 is also disposed in the front and rear direction of the vehicle body, and is driven by the driving force from the power plant 3 via the gears 4 and 5 to form a rear wheel drive shaft 2.
1 and left and right axles 24 and 25 that are driven by the drive shaft 21 via a pair of bevel gears 22 and 23 and transmit power to the left and right rear wheels 8 and 9, respectively.

In the rear wheel drive system 20,
A cut-off clutch 26 is provided on the rear wheel drive shaft 21 for interrupting the transmission of power to the left and right axles 24, 25 or the rear wheels 8, 9, and the left and right axles 24, 25.
Are provided with left and right wheel clutches 27 and 28 for connecting and disconnecting the transmission of power from the rear wheel drive shaft 21 to the left and right rear wheels 8 and 9 and changing the transmission torque. Each of the wheel clutches 27 and 28 is a multi-plate type hydraulic clutch, and is connected to hydraulic supply passages 31 and 32 led from a hydraulic source (not shown). Hydraulic control valves 33 and 34 for controlling the supply and discharge of hydraulic pressure to and from 27 and 28 are provided, respectively.

Further, a controller 35 for controlling the operation of the cutoff clutch 26 and the hydraulic control valves 33 and 34 is provided.
The cut-off clutch 26 is connected and disconnected by a control signal a output from the controller 35, and the hydraulic control valves 33 and 34 are opened and closed by control signals b and c also output from the controller 35. Thus, the supply and discharge of the hydraulic pressure to the left and right wheel clutches 27, 28 are controlled, whereby the connection / disconnection of the two wheel clutches 27, 28 or the transmission torque thereof is controlled.

The controller 35 includes signals d, e, f, and g from wheel speed sensors 36 to 39 for detecting the rotational speeds of the front, rear, left, and right wheels 6 to 9, respectively, for each of the above-described controls. A signal h from a steering angle sensor 41 for detecting an operation amount of a steering wheel 40 provided in a driver's seat of the vehicle, that is, a steering angle amount, and a signal i from a lateral acceleration sensor 42 acting on the vehicle body at the time of turning. Further, a signal j indicating whether or not ABS control is being performed is input from an ABS controller 43 that controls the operation of an ABS (anti-lock braking system) provided in the vehicle. Based on the input signals d to j, the cutoff clutch 26 and the left and right wheel clutches 27, 2
8 is controlled.

Next, the operation of this embodiment will be described with reference to a flowchart showing the control operation of the controller 35. Figure 2 shows a main routine of the control operation of the controller 35, first in step S _1, the controller 3
5 various variables used in the following control, flags, performs other initialization, and then fastening of the left and right wheels clutch 27, 28 in step S _2, the torque distribution ratio right and left rear wheels 8 and 9 in other words decide. Then, in step S _3, as the fastening of the two wheel clutches 27 and 28 becomes a value determined in step S _2, and outputs a control signal b, c to the hydraulic control valve 33, 34 shown in FIG. 1, Further, a control signal a for disconnecting and connecting the cutoff clutch 26 is output to the cutoff clutch 26.

[0020] The wheel according to the above step S ₂ clutch 2
In this embodiment, the control for determining the degree of engagement of FIGS.
Is performed as follows by the subroutine shown in FIG. That is, in this control, first, in step S _11, the signal from each sensor 36～39,41,42 shown in FIG. 1, the left front wheel, right front wheel, left rear wheel, the wheel speeds of the right rear wheel omega _FL, ω _FR ,
ω _RL , ω _RR , steering angle amount θ of the steering wheel 40, its rate of change ψ,
The vehicle speed V and the lateral acceleration G are input, and AB
As the signal j from the S controller 43, an ABS operation signal F _ABS indicating whether or not the ABS control is being performed is input. Here, the change rate ψ is calculated based on a change in the steering angle amount θ,
As the vehicle speed V, the slowest one of the wheel speeds ω _FL , ω _FR , ω _RL , and ω _RR is adopted as the vehicle speed.

Next, the controller 35 proceeds to step S
_{At 12} , the value of the ABS operation signal F _ABS is determined, and
For, that is, when the ABS control is currently performed by the ABS controller 43, the torque distribution ratio T _RL of left and right rear wheels 8,9 in step S _13, sets the T _RR are both zero. Therefore, in this case, the left and right wheel clutches 27, 2
No hydraulic pressure is supplied to any of the wheels 8, the axles 24 and 25 are shut off, and the driving force is not transmitted to the left and right rear wheels 8 and 9. This is for accurately performing the ABS control with the left and right rear wheels 8 and 9 being freely rotatable.

On the other hand, when the ABS control is not being performed, F _ABS = 0, and the controller 35 executes the above steps S12 to S14, and the absolute value of the steering angle amount θ is smaller than the predetermined value θ _0. It is determined whether or not. This predetermined value θ ₀ is a very small value indicating the width of the dead zone, and |
If θ | <θ ₀ , it is determined that the steering wheel 40 has not been operated and the vehicle is in a straight-ahead state.

[0023] Then, when in the straight traveling state, the controller 35, the turning flag F _C and the timer flag F _TM used in the first control during turning later in Step S ₁₅ are both 0
After having set in, before according to the following equation at step S _16, to calculate the rotational speed difference [Delta] [omega ₁ between the rear wheels.

The _{Δω 1 = (ω FL + ω} FR) - (ω RL + ω RR) Further, the controller 35, the speed difference [Delta] [omega ₁ is applied to a preset map shown in FIG. 4 in step S _17,
A first rear wheel distribution ratio T ₁ used for determining the final torque distribution ratios T _RL and T _RR of the rear wheels 8 and 9 is obtained. The map of FIG. 4 in this case, when the speed difference [Delta] [omega ₁ is positive (when the rotational speed of the front wheels 6 and 7 is greater than the rotational speed of the rear wheels 8 and 9), the first rear wheel distribution greater the value Since the ratio T ₁ is set to be large, for example, when the driving force applied to the front wheels 6, 7 is excessive and a slip occurs, the torque distribution to the rear wheels 8, 9 according to the degree of the slip. The ratio is increased, and the slip of the front wheels 6, 7 is suppressed.

The controller 35 determines in step S ₁₈
Then, the rotational speed difference Δω ₂ between the left and right wheels is calculated according to the following equation. Δω ₂ = (ω _FL + ω _RL ) − (ω _FR + ω _RR ) In step S ₁₉ , the absolute value of the speed difference Δω ₂ is applied to the map shown in FIG.
The second rear wheel torque distribution ratio T ₂ used to determine _RL and T _RR
Ask for. In this case, the map of FIG. 5 is set such that the larger the | Δω ₂ | is, the larger the second rear wheel distribution ratio T ₂ is. Therefore, for example, the friction coefficient of the road surface with respect to the left and right wheels is different, If there is a speed difference between the wheels,
The torque distribution ratio to the rear wheels 8 and 9 is increased, and the running stability of the vehicle during running on such a road surface is ensured.

Further, the controller 35 determines in step S
_20, applied to a map showing the vehicle speed V in FIG. 6, also the final torque distribution ratio T _RL, obtaining the third rear wheel distribution ratio T ₃ for use in the determination of T _RR. In this case, the map of FIG. 6 is set so that the third torque distribution ratio T ₃ is increased in accordance with the increase of the vehicle speed V in the high vehicle speed range. Is increased, and the straight running stability is increased.

[0027] Then, the controller 35 then executes step S _21, selects the most significant ones of the first to third rear wheel distribution ratio T _1, T _2, T ₃ obtained as described above and, and sets this as the total torque distribution ratio T _R for the left and right rear wheels 8,9, in step S _22, the two minutes the rear wheel distribution ratio T _R total, the right and left rear wheels 8, 9 as the final torque distribution ratios T _RL and T _RR .

In this manner, the torque distribution ratios T _RL and T _RR for the left and right rear wheels 8 and 9 during straight _traveling are determined. In this case, as is apparent from the maps of FIGS. , No difference in rotation speed between the rear wheels and between the left and right wheels,
In addition, during normal traveling, such as when the vehicle speed is not particularly high, the first to third rear wheel distribution ratios T ₁ , T ₂ , and T ₃ are all 0, so that the driving force from the power plant 3 is , 7
, And when at least one of the distribution ratios T ₁ , T ₂ , T ₃ is not 0, the four wheels are also transmitted to the rear wheels 8, 9. It becomes a driving state. Then, in the four-wheel drive state during the straight traveling, the torque distribution ratio to the left and right rear wheels 8 and 9 is always set to be equal. Further, the above rear wheel distribution ratios T ₁ , T ₂ , T ₃
Is the maximum value (0.5), the driving force is evenly distributed to the front and rear wheels, and as a result, the output of the power plant is transmitted to all the wheels by 1/4. Become.

On the other hand, when the steering angle amount θ of the steering wheel 40 is a predetermined value θ
During pivoting the ₀ or more, the controller 35 executes step S ₂₃ from the step S _14, the turning flag F
_C is 0 when the steering angle amount θ is increasing at the time of a straight line and at the beginning of turning, and is 1 in a stable turning state in which the steering angle amount θ stops increasing during turning. Therefore, when the controller 35 shifts from the straight traveling state to the turning state, the controller 35 sets F _C =
Since 0 executes Step S ₂₄ from the step S _23,
It is determined whether or not the absolute value of the steering angle amount change rate よ り 大 き い is greater than 0, and since this value is greater than 0 at the start of turning,
Further executes step S _25, the maximum value max to date steering angle change rate [psi of ([psi) and the change rate [psi at that time (at the time of turning start, the rate of change of current [psi until that point Is the maximum value max (ψ).

[0030] Then, in step S _26, based on the map shown in FIG. 7, the right and left rear wheels corresponding to the change rate [psi 8, 9
_Are set as base distribution ratios T _RLB and T _RRB . In that case,
Assuming that the rate of change ψ becomes a positive value when the steering angle amount θ increases when the steering wheel is operated to the left, as shown in FIG. 7, when the steering wheel is operated in that direction, as shown in FIG. The distribution ratio T _RRB is set to a value larger than the base distribution ratio T _RLB of the left rear wheel 8. Conversely, when the steering wheel is operated to the right, the base distribution ratio T _RLB of the left rear wheel 8 is set to the base distribution ratio T of the right rear wheel 9. It is set to a value greater than _RRB, and these base distribution ratio T _RLB, T _RRB is set to a larger value as the steering angle is large change rate [psi. Then, in step S _27, this manner is set by the base distribution ratios T _RLB, final torque distribution ratio T _RL of the T _RRB left and right rear wheels 8 and 9, as it is replaced by T _RR.

As a result, as shown in FIG. 9, the period (a) during which the rate of change 舵 of the steering angle amount at the beginning of turning is increasing.
The final torque distribution ratios T _RL and T _RR also increase in accordance with the increase, the left and right rear wheels 8 and 9 are driven by the distribution ratios T _RL and T _RR , and the rate of change ψ is the maximum value ψ _MAX And then 0
While drops to, that is, the maximum allocation ratio increasing the steering angle quantity theta period to stabilize at a constant steering angle theta ₁ finished (b) is, corresponding to the maximum value [psi _MAX steering angle change rate [psi (T _RL ) _MAX ,
(T _RR ) _MAX will be held. As described above, until the vehicle turns to the stable turning state in which the steering angle is constant, the rear wheels 8 and 9 are given a large distribution ratio, and the rear wheels on the outside in the turning direction are larger than the rear wheels on the inside in the turning direction. By giving the distribution, a good turning performance at the beginning of turning of the vehicle can be obtained.

[0032] Thereafter, when the steering angle change rate ψ is shifted to a stable turning state becomes 0, since the turning flag F _C is set to 1 in step S _28, the controller 35, then step S ₂₃ step S ₂₉ is executed to determine the value of the timer flag F _TM. This flag F _TM is initially 0, so the controller 35 then, in step S ₃₀ ,
A constant C ₀ for reducing the torque distribution ratio for the rear wheels 8 and 9 is set. The constant C ₀ is set based on the map shown in FIG. 8, and is set to a smaller value as the absolute value of the constant steering angle amount θ ₁ during the stable turning becomes larger. Then, the timer flag F _TM is set to 1 in step S _31, and thereby clear the reduction amount C of the torque distribution ratio to zero, in step S _32, by using the reduction value C, the torque distribution according to the following equation The ratio reduction coefficient K is calculated.

K = (1000−C) / 1000 Here, the numerical value (1000) is an example value determined in relation to the control cycle period, and in this case, the constant C ₀ is 1000 or less. Value.

[0034] While the reduction coefficient K is initially a 1, the next and subsequent control cycles, the step S ₃₃ from step S ₂₉ is executed (F _TM = 1), the constant C ₀ to reduction value C
There with progressively decreasing from being sequentially added each cycle, when it was reduced in the step S ₉₄ below zero is found, is fixed to 0 in step S _35. Then, in step _S36 , the controller 35 sets the reduction coefficient K from 1 to 0 as described above to the base distribution ratio T _RLB (= (T
_RL ) _MAX ) and T _RRB (= (T _RR ) _MAX ) to calculate final torque distribution ratios T _RL and T _RR of the rear wheels 8 and 9.

Thus, the final torque distribution ratio T _RL ,
As shown in FIG. 9, T _RR is the maximum distribution ratio (T _RL ) _MAX in the period (B) in the stable turning period (C),
(T _RR ) will gradually decrease from _MAX to 0,
The vehicle gradually shifts from the four-wheel drive state to the front wheels 6 and 7, so that stable traveling performance in the middle stage of turning can be obtained. Then, in particular the constant C ₀ is because it is set to a smaller value the larger the constant steering angle quantity theta _1, when a large該舵angle amount theta _1, as shown by the chain line in FIG. 9, the rear wheel 8 , 9 of the torque distribution ratio T _RL, T _RR is made to be reduced to 0 over a long period of time than when the steering angle quantity theta ₁ is small, the shift to two-wheel drive state is always smoothly become.

As described above, when the final torque distribution ratios T _RL and T _RR of the left and right rear wheels 8 and 9 during straight running and turning are determined, the controller 35 proceeds to step S _{3 in} the flowchart of FIG. The control signals b and c are transmitted to the hydraulic control valves 33 and 34 shown in FIG. 1 so that the degree of engagement of the left and right wheel clutches 27 and 28 becomes the degree of engagement at which the distribution ratios T _RL and T _RR are obtained. In addition to the output, the disconnection / connection control of the cutoff clutch 26 is performed by the control signal a. This control is specifically performed by a subroutine shown in FIG. In this control, the controller 35 first determines the value of the failure flag F _TRB at step S _41. This flag F _TRB becomes 1 when both the left and right wheel clutches 27 and 28 are out of order. In this case, the controller 3
5, cutting a cut-off clutch in step S ₄₂ (OF
F). As a result, when the wheel clutches 27 and 28 fail, the driving force from the power plant 3 is not transmitted to the rear wheels 8 and 9 and a two-wheel drive state in which only the front wheels 6 and 7 are driven is established.

On the other hand, at least one wheel clutch 27, 28 is normal, when the failure flag F _TRB is 0, the controller 35 executes step S _43, and determines the value of the running initial flag F _INI . This flag _FINI is 0 during the initial stage of running after the engine is started until the vehicle runs 300 m, for example, and becomes 1 when the running distance from the start of running exceeds 300 m. Therefore, the the flag F _INI initially a 0, the controller 35 executes step S ₄₄ from the step S _43, with waiting for the start of the engine, running further step S ₄₅ if the start, the cut-off The clutch 26 is connected (ON). Then, the travel distance from the start of running time is at the time beyond the 300 meters, the step S ₄₇ performed at step S _46, is set to 1 the running initial flag F _INI. Therefore, the wheel clutches 27, 2
Regardless of the state 8, the cutoff clutch 26 is always connected.

Next, the initial stage of traveling is completed and the flag F
_{When the INI} becomes 1, the controller 35 _proceeds to step _S48.
To determine the values of the torque distribution ratios T _RL and T _RR of the left and right rear wheels 8 and 9 determined in the above-described wheel clutch engagement degree determination routine, and when these are both 0 (during two-wheel drive). Is
In step _S49 , the cutoff clutch 26 is disconnected. Therefore, the driving force from the power plant 3 is not transmitted downstream from the cutoff clutch 26.

Further, the torque distribution ratio T _RL, when at least one of T _RR is not 0, the controller 35 determines whether the cut-off clutch 26 is disconnected by performing the step S _50, the cutting If it is, connect it outputs a control signal a in step S _51, also when connected to maintained. Then, in step S _52, and outputs a control signal b, c to connect the wheel clutches 27, 28. In this way, the rear wheels 8, 9
When the wheel clutches 27 and 28 are connected to transmit the driving force, the cutoff clutch 26 is first connected, and then the predetermined torque distribution ratios T _RL and T _RL of the left and right rear wheels 8 and 9 are connected. Wheel clutches 27 and 28 to be _RR
Are connected, and a four-wheel drive state corresponding to the traveling state is established.

[0040] Then, the controller 35 executes the subsequent steps S _53, and determines whether the left and right wheels clutch 27, 28 has failed together, if faulty, step S _54, S ₅₅ Then, the cut-off clutch 26 is disengaged, and the failure flag F _TRB is set to 1. Thereafter, the control at the time of failure by the above-described steps S ₄₁ and S ₄₂ is performed.

As described above, the cut-off clutch 26 and the wheel clutches 27 and 28 are controlled according to the running state.
28 are both disconnected (T _RL , T _RR = 0)
Since the cutoff clutch 26 is also disengaged (step _S49 ), when the driving force is not transmitted to the rear wheels 8, 9, the downstream portion of the rear wheel drive shaft 21 shown in FIG. , 23, the upstream portions of the left and right axles 24, 25, and the drive-side members of the wheel clutches 27, 28 are not unnecessarily driven, and the drive loss is reduced accordingly.

When at least one of the wheel clutches 27 and 28 is connected, the cut-off clutch 26 is connected prior to the connection (step _S51 ). Clutch 27,
28, and then to the rear wheels 8, 9 in order, which is transmitted to the enemy in stages, thereby preventing a large shock from being transmitted to the wheels at once.

As described above, when the cut-off clutch 26 is disengaged in a state where the driving force is not transmitted to the rear wheels 8 and 9, if this state is continued for a long time, the downstream portion of the rear wheel drive shaft 21 is disengaged. , A pair of bevel gears 22, 23, the upstream portions of the left and right axles 24, 25, and the wheel clutch 27,
Since the drive-side members 28 do not rotate for a long period of time, the bearings and oil seals that support them may be rusted or deteriorated due to lack of lubricating oil. However, in this embodiment, as described above, in the initial stage of traveling until the traveling distance from the start of traveling exceeds 300 m, the cutoff clutch 26 is connected even when the wheel clutches 27 and 28 are disconnected. As a result (step S ₄₅ ), during this time, the downstream portion of the rear wheel drive shaft 21 or the drive-side members of the wheel clutches 27 and 28 rotate to supply lubricating oil to bearings and oil seals. Thus, the above-described problems are prevented.

The timing for connecting the cut-off clutch 26 with the wheel clutches 27 and 28 disconnected is not limited to the above-described initial stage of travel, and the cut-off clutch 26 may be used for low-speed travel at a predetermined vehicle speed or less. It may be set at another time when the shock due to connection is relatively small.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration and a control system of a four-wheel drive vehicle according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a main routine of a control operation.

FIG. 3 is a flowchart illustrating a subroutine of vehicle clutch engagement degree determination control.

4 is an explanatory view of a map first rear Request wheel distribution ratio T _1.

5 is an explanatory view of a map for obtaining the second rear wheel distribution ratio T _2.

6 is an explanatory view of a map for obtaining the third rear wheel distribution ratio T _3.

FIG. 7 is an explanatory diagram of a map for _obtaining a base distribution ratio T _RRB of a right rear wheel and a base distribution ratio T _RLB of a left rear wheel.

It is an explanatory view of a map for obtaining the constant C ₀ for decreasing the torque distribution ratio [8] rear wheel.

FIG. 9 is a time chart showing a specific operation of this control.

FIG. 10 is a flowchart illustrating a subroutine of clutch control.

[Explanation of symbols]

3 Power plant 6, 7 Front wheel 8, 9 Rear wheel (left rear wheel, right rear wheel) 10 Front wheel drive system 20 Rear wheel drive system 26 Cutoff clutch 27, 28 Wheel clutch (left wheel clutch) , Right wheel clutch) 35 ... control means (controller) 41 ... steering angle sensor (steering angle state detecting means)

Claims (2)

[Claims] 1. A power transmission system that receives an output from a power plant and transmits power to a right wheel and a left wheel, and a power transmission portion of the power transmission system for transmitting torque to the right wheel and the left wheel, respectively. A drive device for a vehicle that includes a right wheel clutch and a left wheel clutch that are changed, and control means that controls the right wheel clutch and the left wheel clutch based on a predetermined signal to change a torque distribution ratio to the right wheel and the left wheel. At the steering angle state detection means for detecting the steering angle change rate of the steering wheel, and a signal from the steering angle state detection means, the torque distribution ratio to the right wheel and the left wheel increases as the steering angle change rate increases. And a control unit for controlling the right wheel clutch and the left wheel clutch. 2. A power transmission system which receives an output from a power plant and transmits power to a right wheel and a left wheel, and a power transmission portion of the power transmission system for transmitting torque to the right wheel and the left wheel, respectively. A drive device for a vehicle that includes a right wheel clutch and a left wheel clutch that are changed, and control means that controls the right wheel clutch and the left wheel clutch based on a predetermined signal to change a torque distribution ratio to the right wheel and the left wheel. , The steering angle state detecting means for detecting the steering angle change rate of the steering wheel, and the signal transmitted from the steering angle state detecting means, the torque transmitted to the right wheel and the left wheel as the steering angle change rate increases. A drive device for a vehicle, comprising: a control unit that controls the right wheel clutch and the left wheel clutch so that the difference between the values increases.