JPH0794230B2 - Rear wheel steering mechanism - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering mechanism for a four-wheel steering vehicle, and more particularly to a rear wheel steering mechanism in which a rear wheel steering hydraulic actuator is disposed on the rear side of a rear wheel axle case.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Laid-Open No. 55-91458 and the like, in a four-wheel steering vehicle, steering the rear wheels in the opposite direction to the front wheels facilitates the direction change on a narrow road.
In the rear wheel steering mechanism of a four-wheel steering vehicle, the arms of the left and right rear wheels are connected by a tie rod parallel to the rear wheel axle case, and the tie rod is axially driven by a rear wheel steering hydraulic actuator. If the tire wheel that steers the rear wheels is arranged below the axle case, it may come into contact with an obstacle on the road, and if it is arranged above the tire case, the vehicle height becomes high and running stability is impaired.

Therefore, in general, the tie rod is arranged on the front side or the rear side of the axle case. If the tie rod is installed on the front side of the axle case, the tie rod may be bent in an inverted U-shape so that the middle portion straddles the propulsion shaft so that the tie rod does not interfere with the propulsion shaft that transmits power to the final reduction gear. Of the rear wheel is weakened, and the holding force for holding the rear wheel in the straight traveling position at low speed is weakened. The above problem can be solved by providing a neutral lock mechanism for each of the left and right rear wheels separately to hold the rear wheels in a straight-ahead position, but the configuration of the neutral lock mechanism becomes complicated and it is difficult to control activation / release. .

As shown in FIG. 3, when the tie rod 23 is disposed on the rear side of the axle case 5, the arm 9 which is supported by the king pin 6 on the axle case 5 and which projects rearward from the rear wheel knuckle is arranged in the vehicle width direction. The arm 9 is connected to the tie rod 23 by the pin 12 by projecting outwardly at an angle α. The tie rod 23 is integrally formed with a rod protruding from the piston of the hydraulic actuator 8. By tilting the arm 9 by an angle α, for example, when the vehicle is turning right and the tie rod 23 is driven to the right by the stroke s by the hydraulic actuator A, the steering angle βL of the left rear wheel is changed to the steering angle β of the right rear wheel.
It is deflected to the left more than R, and the rear wheel tires have less slip and less effort is required for cornering. If the arm 9 is tilted toward the center of the vehicle width, the Atkaman ratio (ratio of the steering angles of the left and right rear wheels) is reversed, which hinders smooth turning.
Even when the tie rod 23 is arranged on the rear side of the axle case 5, since the final reduction gear protrudes to the rear side of the axle case 5, the tie rod 23 is parallel to the axle case 5 to the rear side of the final reduction gear. When installed, the distance between the tie rod 23 and the axle case 5 becomes wider, and it becomes necessary to lengthen the arm protruding rearward from the rear wheel knuckle.

As described above, in order to obtain an appropriate Atkamann ratio, it is necessary to make the length of the tie rod 23 longer than the distance between the steering centers of the left and right rear wheels (interval between the king pins 6). In order to reduce the steering resistance of the rear wheels, it is necessary to bring them closer to the center of the width of the rear wheels. Therefore, the rear end of the arm 9 of the rear wheel knuckle projects into the rear wheel rim. When the arm 9 of the rear wheel knuckle projects into the rear wheel rim, the length of the arm 9 is limited by the radius of the rear wheel rim. If the inner diameter of the rear wheel rim is expanded in order to lengthen the arm 9 of the rear wheel knuckle, the vehicle height becomes high and the stability of the vehicle body deteriorates.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a tie rod driven by a rear wheel steering hydraulic actuator in parallel with the axle case on the rear side of the axle case. Thus, it is an object of the present invention to provide a rear wheel steering mechanism capable of setting an appropriate Atkaman ratio without being restricted by the direction and length of the arms of the rear wheel knuckle.

[0007]

In order to achieve the above object, the structure of the present invention is such that a hydraulic actuator having a rod parallel to the axle case is fixed to the rear side of the axle case of the rear wheel, and relayed at both ends of the rod. The middle part of the lever is axially supported, the support rod is connected to the rear end of each relay lever and the wall of the hydraulic actuator, and the tie rod is connected to the front end of each relay lever and the arm extending rearward from each rear wheel knuckle. It is a thing.

[0008]

The hydraulic actuator is arranged on the rear side of the axle case. A relay lever is supported at both ends of a rod protruding from the hydraulic actuator, and a front end of the relay lever and an arm protruding rearward from the rear wheel knuckle are connected by a tie rod substantially parallel to the axle case. Therefore,
Even if the arm of the rear wheel knuckle is shortened and the direction of the arm is deflected toward the vehicle width center side, there is no problem and an appropriate Atsukerman ratio can be obtained.

[0009]

1 is a plan sectional view of a rear wheel steering mechanism according to the present invention. The axle case 5 that supports the rear wheels 10 is provided with a final reduction gear 4 at the center, and an input shaft projecting forward from the final reduction gear 4 is connected to the rear end of the propulsion shaft 2 by a universal joint 3. Therefore, the rotation of the engine is transmitted to the axle 8 integral with the rear wheel knuckle 7 via the propulsion shaft 2, the final reduction gear 4, the axle inside the axle case 5, and a universal joint (not shown). The axle 8 is connected to a known rear wheel rim 10a and supports the tire of the rear wheel 10 on the rear wheel rim 10a. The rear wheel knuckle 7 is steerably supported by an end portion of the axle case 5 by a vertical kingpin 6. The rear wheel 10 is steered by rotating the arm 9 projecting rearward from the rear wheel knuckle 7 around the kingpin 6.

A hydraulic actuator 2 for steering the rear wheels 10.
0 is fixed to the rear side of the axle case 5 by a support plate 24. In the hydraulic actuator 20, a piston 22 is fitted in a cylinder 21, and both ends of a rod 23 connected to the piston 22 are projected from an end wall of the cylinder 21. Both ends of the rod 23, which are parallel to the axle case 5, rotatably support the intermediate portion of the relay lever 15 by pins 16. The rear end of the relay lever 15 and the wall portion of the cylinder 21 are connected by a support rod 18 and pins 17 and 19. The front end of the relay lever 15 and the arm 9 are connected by a tie rod 13 and pins 12 and 14 which are substantially parallel to the axle case 5.

In order to reduce the steering resistance of the rear wheels 10,
It is preferable that the position of the king pin 6 has a small deviation s from the width center of the rear wheel 10. The arm 9 may be shorter than the inner diameter of the rear wheel rim 10a, or the direction of the arm 9 may be inclined toward the vehicle width center side.

The posture of the rear wheel 10 during straight running is fixed by a neutral holding mechanism such as a spring that holds the piston 22 of the hydraulic actuator 20 in a neutral position. However, such a neutral holding mechanism is publicly known and is not directly related to the gist of the present invention, and therefore its explanation is omitted.

Next, the operation of the rear wheel steering mechanism according to the present invention will be described. For example, if pressure oil is supplied to the left chamber of the hydraulic actuator 20 and the oil in the right chamber is returned to the oil tank,
The rod 18 moves to the right, the relay lever 15 on the left side rotates clockwise about the pin 17, and the relay lever 15 on the right side also rotates clockwise. Therefore, the left and right tie rods 13 move to the right, and the respective rear wheel knuckles 7 rotate counterclockwise about the kingpin 6 to reach the right turn of the vehicle.

According to the present invention, the hydraulic actuator 20
By supporting the relay lever 15 on the end portion of the rod 23, the length of the arm 9 of the rear wheel knuckle 7 can be shortened. Since the hydraulic actuator 20 is arranged on the rear side of the axle case 5 and maintains a ground clearance substantially the same as that of the axle case 5, interference with road obstacles can be avoided.

As shown for the relay lever 15 on the left side in FIG. 2, the longitudinal distance L1 between the pin 16 and the pin 14 and the pin 1
By properly selecting the front-rear spacing L2 between the pin 6 and the pin 17, the inclination γ1 of the front half of the relay lever 15 and the inclination γ2 of the rear half of the relay lever 15, the Atkaman ratio (the left and right rear wheels in FIG. The ratio of the steering angles βL and βR) can be set.

[0016]

As described above, according to the present invention, a hydraulic actuator having a rod parallel to the axle case is fixed to the rear side of the axle case of the rear wheel, and the intermediate portion of the relay lever is axially supported at both ends of the rod. A support rod is connected to the rear end of each relay lever and the wall of the hydraulic actuator, and a tie rod is connected to the front end of each relay lever and an arm extending rearward from each rear wheel knuckle. Since the hydraulic actuator is arranged on the rear side of the axle case, the hydraulic actuator is at an appropriate height and it is possible to avoid interference with obstacles on the road surface.

By supporting the relay lever on the rod of the hydraulic actuator and connecting the relay lever and the arm of the rear wheel knuckle with the tie rod, the length of the arm can be shortened and the direction of the arm can be deflected to the vehicle width center side. However, it is possible to obtain an appropriate Azkerman ratio.

Since the rod of the hydraulic actuator can be arranged straight in parallel with the axle case, and the other components are also almost straight, the rigidity of the entire mechanism is high and the stability of the rear wheel posture during straight running is high. high.

By supporting the relay lever at the end of the hydraulic actuator, a large steering angle can be imparted to the arm of the rear wheel knuckle with a slight amount of movement of the hydraulic actuator, thus making the overall shape of the hydraulic actuator small. it can.

[Brief description of drawings]

FIG. 1 is a plan sectional view of a rear wheel steering mechanism according to the present invention.

FIG. 2 is a plan view of a relay lever in a copper rear wheel steering mechanism.

FIG. 3 is a plan view showing a schematic configuration of a conventional rear wheel steering mechanism.

[Explanation of symbols]

2: Propulsion shaft 3: Universal joint 4: Final reducer 5: Axle case 6: King pin 7: Rear wheel knuckle 8: Axle 9: Arm 10: Rear wheel 10a: Rim 12: Pin
13: Tyrod 14: Pin 15: Relay lever 1
6: Pin 17: Pin 18: Support rod 19: Pin 20: Hydraulic actuator 21: Cylinder 22:
Piston 23: Rod 24: Support plate

Claims (1)

[Claims] 1. A hydraulic actuator having a rod parallel to the axle case is fixed to the rear side of the axle case of the rear wheel, and an intermediate portion of a relay lever is axially supported at both ends of the rod.
A rear wheel steering mechanism characterized in that a support rod is connected to a rear end of each relay lever and a wall portion of the hydraulic actuator, and a tie rod is connected to a front end of each relay lever and an arm extending rearward from each rear wheel knuckle. .