JPH0784141B2 - Four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel drive vehicle that enables adjustment of driving force distribution.

(Prior Art) Conventionally, as a four-wheel drive vehicle capable of adjusting the distribution of the driving force between the front and rear wheels, the one described in JP-A-60-135327 is known.

This is achieved by providing hydraulic clutches between the transmission and the final reduction gear for the rear wheels, and between the final reduction gear for the rear wheels and the left and right rear wheels, respectively, and controlling these three clutches in an integrated manner. It was to adjust the distribution of driving force between the front and rear wheels.

(Problems to be Solved by the Invention) However, in the conventional four-wheel drive vehicle described above, the output from the transmission is directly transmitted to the front wheel drive system.
It was impossible to obtain driving force distribution near the rear wheels.

In addition, even though the left and right clutches are provided on the rear wheel axles, each clutch was controlled in an integrated manner, so it is impossible to control the driving force distribution between the left and right wheels. However, in the four-wheel drive state, there is a drawback that it exhibits a strong understeer characteristic that is a characteristic peculiar to a four-wheel drive vehicle.

(Means for Solving the Problem) Means for solving the above-mentioned problems according to the present invention include a transmission and a front wheel differential device so that transmission of driving force from the transmission to the front wheel differential device can be connected and disconnected. Between the transmission and the left and right rear wheels so that the transmission of the drive force from the transmission to the left and right rear wheels can be independently connected and disconnected. And left and right rear clutches respectively interposed in the driving force transmission path between the two clutches, and the three clutches based on the traveling state detected by the traveling state detecting means and the traveling state detecting means. A four-wheel drive vehicle comprising: a controller that calculates each joining rate; and a clutch actuating means that actuates each of the three clutches based on a calculation result by the controller.

(Operation) According to the present invention, the front clutch interposed in the drive force transmission path between the transmission and the front wheel differential device, and the drive force transmission path interposed between the transmission and the left and right rear wheels, respectively. Since the engagement rates of the left and right rear clutches are independently controlled by the clutch operating means based on the running state, the driving force distribution to the front wheels is performed by the front clutch, and the driving force distribution to the rear wheels is performed at the left and right rear clutches. It is possible to control the distribution of the driving force between the front and rear wheels between the front and rear wheels by controlling the front and rear wheels so that the acceleration and turning performances are most improved in each running condition. The driving force distribution can be selected in a wide range.

Also, if these three clutches are simultaneously disengaged or made to have a low engagement rate, the driving force can be disengaged or reduced, and cornering force at the turning limit and interference with the anti-skid brake can be easily avoided. .

Further, the driving force distribution between the left and right rear wheels is adjusted by independently controlling the engagement ratio of the left and right rear clutches, and the steer characteristic can be controlled by the yaw moment generated by the difference in the driving force between the left and right rear wheels. It will be possible.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, the driving force output from a transmission (not shown) is transmitted to the casing 2 of the front clutch 1 as indicated by the white arrow in the figure. A rear wheel output shaft 3 is directly connected to the casing 2, and the output from the transmission is directly transmitted to the rear wheel output shaft 3. On the other hand, the front wheel output shaft 4 is connected to the casing 2 via the wet multi-plate clutch mechanism 5 of the front clutch 1 so as to be freely contactable and separable.

The front wheel output shaft 4 is drivingly connected to a casing of a front wheel differential gear 6, and the differential gear 6 is connected to the front wheel output shaft 4.
The driving force input from is distributed to the left and right front wheels 7 and 8 and transmitted. Further, the engagement rate of the front clutch 1 is controlled according to the magnitude of the supplied hydraulic pressure. Specifically, the hydraulic pressure supplied is adjusted by adjusting the valve opening rate of a front clutch electromagnetic valve described later. Is controlled, and the clutch engagement rate is controlled. Therefore, the driving force transmitted to the front wheels 7 and 8 is controlled depending on the operating state of the front clutch 1. If the front clutch 1 is completely disengaged, the driving force transmission to the front wheels 7 and 8 is cut off. It is also possible. Note that since the hydraulic pressure supply mechanism and the electromagnetic valve can use known ones, the description of the specific configuration will be omitted.

Further, the rear wheel output shaft is drive-connected via a propeller shaft 9 to a casing 12 into which left and right rear clutches 10 and 11 are integrated. The wet multi-plate clutch mechanism 13 of the rear left clutch 10 controls the connection between the casing 12 and the left rear wheel axle 15 connected to the left rear wheel 14, and similarly, the wet multi-plate clutch mechanism of the rear right clutch 11 is used. The plate clutch mechanism 16 controls the connection between the casing 12 and the left rear wheel axle 18 connected to the left rear wheel 17. These left and right rear clutches
Similar to the above-mentioned front clutch 1, 10 and 11 are those whose joint ratio is controlled according to the magnitude of the supplied hydraulic pressure, and adjust the valve opening ratio of the electromagnetic valve provided independently of each other. This allows the supplied hydraulic pressure to be controlled independently on the left and right. Therefore, the left and right rear clutch 1
The driving force transmitted to the rear wheels 14 and 17 is controlled independently according to the operating state of 0 and 11 to the rear clutch.
It is also possible to individually cut off the transmission of driving force to the rear wheels 14 and 17 if 10 and 11 are completely separated.

The front clutch 1 is of a type that is completely engaged in a state where hydraulic pressure is not supplied, and the engagement rate decreases as the supplied hydraulic pressure increases. The rear clutches 10 and 11 are different from the front clutch 1. On the contrary, a type is used in which the hydraulic pressure is completely cut off without being supplied, and the joining rate increases as the supplied hydraulic pressure increases.
Therefore, even if a failure occurs in the hydraulic pressure supply system, it is possible to prevent the vehicle from being unable to run, and also to secure the gear-shift parking function when the vehicle is stopped.

As described above, according to the configuration of the driving force transmission system shown in FIG. 1, the front wheels 7, 8,
The driving force transmission state to the left rear wheel 14 and the right rear wheel 17 is independently controlled, and the drive distribution state between the front and rear wheels and between the left and right rear wheels can be freely controlled.

FIG. 2 shows an outline of a control device for controlling the operation of the above three electromagnetic valves.

That is, the front clutch electromagnetic valve 21, the rear left clutch electromagnetic valve 22, the rear right clutch electromagnetic valve 23
The operation of 4W consists of a microcomputer, etc.
It is controlled by the D controller 24.
This controller 24 and each electromagnetic valve 21-23
Is a clutch operating means.

In addition, the longitudinal G that detects the longitudinal acceleration acting on the vehicle body
A sensor 25, a left and right G sensor 26 that detects a lateral acceleration acting on the vehicle body, wheel speed sensors 27 to 30 that detect the rotational speed of each wheel, a steering angle sensor 31 that detects the steering angle of the steering wheel, and a throttle opening of the engine. Provided with a throttle opening sensor 32 that detects the degree of rotation, an engine speed sensor 33 that detects the number of revolutions of the engine, a gear speed sensor 34 that detects the gear position of the transmission, and a gradient sensor 35 that detects the longitudinal inclination angle of the vehicle body. And these sensors
The information detected by 25-35 is the controller 24 respectively.
It is supposed to be input to. Further, a signal indicating that control is in progress is input from the controller 36 of the antiskid brake device when the antiskid is being executed.

The control operation executed in the controller 24 based on these input information is shown in the flow chart of FIG.

That is, when the control is started as shown in FIG. 3, first, in step S1, the detection signals from the respective sensors are read, and at the same time, the road surface μ and the turning limit index value are calculated based on the input information. Here, the road surface μ is the output of the front-rear G sensor 25, the output of each wheel speed sensor 27 to 30, and the gear position sensor.
It is calculated based on the drive output speed and the like calculated from the outputs of the engine speed sensor 33 and the engine speed sensor 33, and the turning limit index value is the left / right G sensor 26, the steering angle sensor 31, and the wheel speed sensors 27.
Calculated based on ~ 30 outputs.

After that, in step S2, it is determined whether or not the anti-skid brake is operating based on the output from the ABS controller 36, and if it is operating, priority is given to all other controls and the process proceeds to step S3. The front clutch 1 and the rear clutches 10 and 11 are completely disengaged. this is,
This is to prevent the state of restraint by the drive system between the wheels from interfering with the anti-skid control and preventing accurate skid control from being executed.

On the other hand, if it is determined that the skid control is not being executed in step S2, the process proceeds to step S4, it is determined whether or not the vehicle is turning based on the output of the steering angle sensor 31, and it is determined that the vehicle is not turning. If so, it is further determined in step S5 whether or not the vehicle is accelerating based on the outputs of the throttle opening sensor 31, the engine speed sensor 34, and the wheel speed sensors. If it is determined that the vehicle is accelerating, the process proceeds to step S6, and it is determined whether or not the vehicle is traveling at high speed based on the output of each wheel speed sensor. If the vehicle is traveling at high speed, the process proceeds to step S7. . In step S7, the front clutch 1 is controlled to the intermediate state and the rear clutches 10 and 11 are completely locked. This state is an accelerating state during high-speed straight traveling, and is a four-wheel drive state in which the driving force is distributed to the rear wheels, so that high acceleration performance is obtained and power circulation between the front and rear wheels is avoided.

When it is determined in step S6 that the vehicle is not traveling at high speed, the process proceeds to step S8 and the front clutch 1 and the rear clutches 10 and 11 are completely locked. This state is an accelerating state during low-speed straight-ahead traveling, and a direct-coupled four-wheel drive state provides high acceleration performance and improves running performance on rough roads and low μ roads.

On the other hand, if it is determined in step S5 that the vehicle is not accelerating, then the procedure proceeds to step S9, in which it is determined from the output of the gradient sensor 34 whether the vehicle is downhill, and if it is determined that the vehicle is traveling downhill, step S10 is performed. Reach In step S10, the front clutch 1 is disengaged and the rear clutches 10 and 11 are locked to drive the rear wheels. This state is when decelerating or going straight downhill in a steady state.Because the front wheels are disconnected from the drive system, the engine braking force is prevented from acting on the front wheels. Good steering initial response is ensured.

If it is determined in step S9 that the vehicle is not traveling downhill, the process proceeds to step S11, in which it is determined whether or not the road surface μ is low by comparing the road surface μ calculated in step S1 with the reference value. If it is determined that μ is low, step S12
Leading to. In step S12, the front clutch 1 is completely locked and the rear clutches 10 and 11 are controlled to the intermediate state. This state is a steady state or a deceleration state when traveling straight on a low μ road except when going downhill.It is a four-wheel drive state in which the driving force is distributed near the front wheels, and high stability and good straight running against changes in road surface μ are achieved. Stability is secured.

When it is determined in step S11 that the road surface μ is not low, the process proceeds to step S7, where the front clutch 1 is controlled to the intermediate state and the rear clutches 10 and 11 are completely locked. This state is a steady state or a deceleration state when traveling straight on a high μ road except when going downhill, and it is a four-wheel drive state in which the driving force is distributed near the rear wheels, and high acceleration / deceleration performance is obtained and high-speed traveling is performed. Power circulation is also avoided, and good steering initial responsiveness is ensured with a margin left for the grip of the front tires.

Furthermore, if it is determined in step S4 that the vehicle is turning,
In step S13, it is determined whether or not the turning limit index value calculated in step S1 is equal to or greater than a predetermined value. If it is determined that the turning limit index value is equal to or greater than the predetermined value,
At step S3, the front clutch 1 and the rear clutches 10 and 11 are completely disengaged. In this state, the turning state of the vehicle may exceed the grip limit of the tire. By disengaging each clutch, the driving force and engine braking force transmitted to the tire are cut off, so that the tire can exert its effect. The cornering force is increased, the turning limit is improved, and the occurrence of spin is avoided.

If it is determined in step S13 that the turning limit index value is not greater than or equal to the predetermined value, it is determined in step S14 whether or not the vehicle is accelerating, and if it is, the program proceeds to step S16 and the road surface μ is It is determined whether or not it is low. Step S16
When it is determined that the road surface μ is low, the process proceeds to step S17, where the front clutch 1 and the turning outer wheel side rear clutch are completely locked, and the turning inner wheel side rear clutch is controlled to an intermediate state. This state is a turning acceleration state on a low μ road, and it is a four-wheel drive state in which the driving force of the rear wheels on the turning inner wheel side is reduced, resulting in high driving performance and the yaw moment due to the driving force difference between the left and right rear wheels. Turnability is improved.

When it is determined in step S16 that the road surface μ is not low, the process proceeds to step S18. In step S18, the front clutch 1 and the rear clutch on the turning inner wheel side are controlled to an intermediate state, and the rear clutch on the turning outer wheel side is completely locked. This state is a turning acceleration state on a high μ road, and is a four-wheel driving state in which the driving forces of the front wheels and the rear wheels on the turning inner wheel side are reduced. In this state, the yaw moment due to the driving force difference between the left and right rear wheels improves the turning performance, and at the same time, the driving force of the front wheels is reduced to improve the cornering force of the front wheels, thereby improving the steer response. In addition, the rear clutch on the turning inner wheel side is controlled to an intermediate state to allow a differential between the left and right rear wheels, and the front clutch is controlled to an intermediate state to tight tight braking phenomenon and high-speed running. The power circulation phenomenon of is also avoided.

On the other hand, if it is determined in step S14 that the vehicle is not accelerating, the process proceeds to step S19, it is determined whether or not the vehicle is traveling downhill, and if it is determined that the vehicle is not traveling downhill, the above-described step S12 is performed.
Then, the front clutch 1 is completely locked and the rear clutches 10 and 11 are controlled to the intermediate state. This state is a steady state or deceleration state during turning other than downhill, and it becomes a four-wheel drive state of driving force distribution near the front wheels, improving stability against changes in road surface μ and at the same time a tuck-in phenomenon occurs. It becomes easier and the turning performance is improved. Further, by controlling the rear clutches 10 and 11 to the intermediate state, the differential between the left and right rear wheels is allowed, and the tight corner braking phenomenon and the power circulation phenomenon during high speed traveling are avoided.

On the other hand, when it is determined in step S19 that the vehicle is downhill, the process proceeds to step S20, and the front clutch 1 and the rear clutches 10 and 11 are controlled to the intermediate state. This state is a steady state or a decelerating state during turning when descending a hill, and the transmission of the engine braking force is reduced, but the cornering force is increased by that amount and the turning performance is improved. In addition, the left and right rear clutches are controlled to the intermediate state to allow the differential between the left and right rear wheels, and the front clutch is controlled to the intermediate state to control the tight corner braking phenomenon and the power during high speed running. Circulation phenomena are also avoided.

Then, after the processing of steps S3, S7, S8, S10, S12, S17, S18 and S20 is completed, the process returns to step S1 and the following determination processing is repeated.

According to the above-described embodiment, the clutches 1, 10 and 11 are independently controlled so that the acceleration performance and the turning performance are most improved in each traveling state, so that the driving force distribution between the front and rear wheels and the left and right rear wheels are controlled. Since the driving force distribution between the wheels is controlled in a wide range, the optimal driving force distribution according to the driving condition can be obtained, and the effect of further improving the acceleration performance and turning performance of the vehicle can be achieved, and at the same time, tight corner braking can be performed. Phenomena and power circulation phenomena are also effectively avoided.

It should be noted that the present invention is not limited to the above-described embodiment, and the clutch operating means may be configured to manually control the state of each clutch. The rate may be controlled in more steps or in a stepless manner. When controlling the clutch engagement rate in multiple stages or steplessly, the final engagement rate may be determined according to the wheel slip rate, lateral acceleration, steering angle, and the like. Needless to say, various other modifications are possible.

(Effects of the Invention) As specifically described above with the embodiments, according to the present invention, the driving force distribution between the front and rear wheels and the driving force distribution between the left and right rear wheels are controlled in a wide range with a simple configuration. It is possible,
The effect is to provide a four-wheel drive vehicle with significantly improved running performance.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a drive system showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of the control system, and FIG. 3 is a flow chart diagram showing control contents. 1 …… Front clutch 10,11 …… Rear clutch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-220930 (JP, A)

Claims (1)

[Claims] 1. A front clutch interposed in a drive force transmission path between a transmission and a front wheel differential device to enable connection and disconnection of transmission of a drive force from the transmission to the front wheel differential device; Left and right rear clutches respectively interposed in the drive force transmission path between the transmission and the left and right rear wheels so that the transmission of the drive force from the machine to the left and right rear wheels can be independently connected and disconnected. And a controller for calculating the engagement ratio of each of the three clutches based on the traveling state detected by the traveling state detecting means, and a traveling state detecting means for detecting the traveling state, and a calculation result by the controller. And a clutch actuation means for actuating each of the three clutches.