JPH05105108A - Rear wheel steering device for car - Google Patents

Abstract

PURPOSE:To make rear wheel steering stably and with good durability even with a truck, etc., in which double tires are adopted for the rear wheels by forming a rear axle housing with possibility of steering round a fulcrum of rotation supported at an upper radius rod in association with motion of a rear wheel steering actuator. CONSTITUTION:A rear axle housing 2 is suspended on a body frame 13 through an air spring 11, and at the two ends thereof rear wheels 18 are supported. An upper radius rod 3 is extended ahead from the fulcrum of rotation 2A furnished in the center of the rear axle housing 2 in such a way as spreading toward the head. A rear wheel steering actuator 4 is installed horizontally on the side wall surface of the body frame 13. A lower radius rod 5 is extended horizontally fore and aft in a plane vertical to the actuator 4 and is coupled by its one end with the rear axle housing 2 and by the other end with the actuator 4 through a revolving lever 6.

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 system for vehicles, particularly trucks.

[0002]

2. Description of the Related Art Various four-wheel steering systems have been proposed in which the rear wheels are steered in conjunction with the steering of the front wheels in order to improve the steering stability of the vehicle at high speeds. The four-wheel steering system relates to a vehicle in which front and rear wheels are independently suspended, and in a vehicle in which the rear wheels are supported by a rigid rear axle housing, particularly in a truck in which double tires are adopted for the rear wheels. Since the contact area applied to the tire is larger than that of a passenger car, the four-wheel steering system described above cannot be adopted.

For this reason, the applicant has previously proposed the four-wheel steering system shown in FIGS. 5 and 6. To specifically explain the device configuration, reference numeral 10 in the drawings is a chassis frame of a vehicle such as a truck, and includes a pair of left and right side members 12 extending in the vehicle front-rear direction and both ends extending in the vehicle width direction. A plurality of cross members 14 fixed to the left and right side members 12
It consists of and. Reference numeral 16 is a rigid rear axle housing supporting double tires 18 on both sides in the vehicle width direction, and 20 is a spring support member attached to the upper side surface of the rear axle housing 16 near both ends in the vehicle width direction by fasteners such as U bolts 22. , 24 are a pair of air springs, which are arranged in front of and behind the rear axle housing 16 with the end portion therebetween, and are interposed between the spring supporting member 20 and the side member 12 of the chassis frame 10, 26.
Is an upper radius rod which is arranged along the longitudinal center line of the chassis frame 10 and has a V-shaped planar shape, and the apex portion of the radius rod 26 is a center of the rear axle housing 16 via a ball joint 28. Differential casing 30 provided in the part
And the free ends of both legs of the rod 26 are respectively connected to the undercarriage frame 1 via ball joints 32.
It is pivotally attached to the 0 side member 12.

On the other hand, below the upper radius rod 26, a lower radius rod 34 having a V-shaped plan is disposed, and one end thereof is connected to a connecting member 36. The connecting member 36 is attached to the lower surface of the differential casing 30 via a rubber bush type flexible joint 42. The other end of the lower radius rod 34 is pivotally attached to the chassis frame 10 via a ball joint 44. Further, the upper radius rod 26 and the lower radius rod 34 are arranged so as to form a substantially parallel link mechanism in the vertical plane.

A bracket 46 is fastened together with the spring support member 20 by the U bolts 22 to the lower side surfaces of the rear axle housing 16 near both ends in the vehicle width direction, and a ball joint 48 is fixed to the bracket 46.
One end of a pair of left and right actuating rods 50 is pivotally attached via. The other end of each actuating rod 50 is connected to the side member 1 described above.
The lower end of an actuating lever 56 pivotally supported by a pin 54 on a bracket 52 fixed to the two webs or side walls is pivotally connected by a pin 58, respectively. Further, at the upper end of the operating lever 56, a piston shaft 62 of a hydraulic cylinder 60 forming a pair of left and right rear wheel steering actuators is provided with a pin 64.
Cylinder 6 of the same actuator
6 is pivotally supported on the web or side wall of the side member 12 by a pin 68.

[0006]

However, according to the above-mentioned prior art, since the rotation fulcrum 28 of the upper radius rod and the support portion at the top of the lower radius rod are arranged to be displaced forward and backward in the vehicle length direction, If it is attempted to steer around the rotation fulcrum 28, the lower radius rod may act in a direction to prevent the steer, and the steer may not be smoothly steered. For this reason, in the above-mentioned prior art, the connecting member 36 supporting the top of the lower radius rod is devised so that the rubber bush 84 is interposed in the rotation supporting portion thereof and the shaft supporting portion thereof extends in the vehicle width direction. Although it is configured to be freely rotatable relative to each other within a small turning angle range using the horizontal axis and slidable in the axial direction, such a configuration complicates the configuration of the connecting member and In particular, since the support portion at the top of the lower radius rod is the most loaded portion, wear due to sliding with the horizontal shaft, fatigue of the rubber bush portion, and the like are likely to occur, resulting in poor durability.

In view of the above-mentioned drawbacks of the prior art, the present invention provides a rear wheel steering device which is durable even in a truck or the like in which double tires are used for the rear wheels, and which is capable of reliably and stably steering the rear wheels. The purpose is to provide.

[0008]

According to the present invention, a rear axle housing 2 is suspended from an undercarriage frame 1 via an air spring 11 and supports a rear wheel 18 at both ends in the vehicle width direction.
A rotation fulcrum 2A provided at a central portion of the rear axle housing 2 in the vehicle width direction, and a divergent end extending toward the vehicle body front side from the rotation fulcrum 2A, the free end of which is supported by the frame 1.
A flat V-shaped or Y-shaped upper radius rod 3,
A rear wheel steering actuator 4 mounted substantially horizontally on the side wall surface of the chassis frame 1 and reciprocating in the longitudinal direction of the vehicle body.
And a lower radius rod 5 extending substantially horizontally in the vehicle front-rear direction in a plane substantially vertical to the actuator 4, one end of the lower radius rod 5 being on the rear axle housing 2 side and the other end being via a turning lever 6. By connecting to the rear wheel steering actuator 4, the rear wheel steering actuator 4 is actuated in response to steering during high speed running of the vehicle, so that the rear axle housing is centered on the rotation fulcrum 2A supported by the upper radius rod 3. It is characterized in that it can be steered.

[0009]

According to this technical means, since the operation fulcrums of the rear wheel steering actuator 4 are provided at both ends of the rear axle housing 2, the operation points of the actuator 4 are centered on the housing rotation fulcrum 2A. Since a large acting force can be obtained according to the principle of the child, and the driving distance (steering angle) is symmetrical, a large acting force is exerted on a rear wheel 18 having a double tire. Even in a device that requires force, the rear wheel 18 can be steered reliably and reliably. At this time, since the lower radius rod 5 that is displaced below the rotation fulcrum 2A of the upper radius rod 3 is not provided as in the prior art, there is no member that acts in the direction to prevent the steering. Therefore, it becomes possible to steer smoothly.

According to the present technical means, the actuator 4, the rotating lever 6, and the lower radius rod 5 operate in a substantially vertical plane, so that the acting force is not dispersed and the driving distance of the actuator 4 is accurate. Can be well transmitted to the rear axle housing 2 side. In this case, it is preferable that the turning distance from the turning lever shaft fulcrum 6A to the upper and lower ends is set to 1: 1 so that the turning distance can be set corresponding to the driving distance of the actuator 4. Further, the vertical movement of the rear axle housing 2 with respect to the chassis frame 1 that occurs during turning traveling during steering or the like due to unevenness of the ground surface is caused by the air spring 1.
However, in the present invention, since the rotation lever 6 and the lower radius rod 5 pivotally supported on the lower end of the rotation lever 1 operate in a substantially vertical plane, the other end of the rod 5 is Even if the rear axle housing 2 provided at the upper and lower sides moves up and down, the rod 5 merely swings in a vertical plane, and the suspension operation is not hindered.

Further, according to the present technical means, as shown in FIGS. 3 and 4, the lower radius rod 5, the rear axle housing 2 and the upper radius rod 3 are substantially disposed on both sides of the pivot fulcrum 2A of the rear axle housing 2 in a plane. Since the bilaterally symmetrical triangular shape is formed, it is possible to surely prevent the rear axle housing 2 from turning when the actuator 4 is in the non-driving state.
It is possible to stably steer and maintain its posture.

Further, since the present technical means uses not the leaf suspension but the air spring 11, not only the vertical swing, but also the chassis frame 1 and the forward / backward swing required for the steering can be permitted. No problem with the rudder.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail below as an example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Not too much. 1, FIG. 2 and FIG. 3 show a rear wheel steering device according to an embodiment of the present invention, and a description will be given focusing on differences from the embodiment. A chassis frame 1 of a vehicle such as a truck includes a pair of left and right side members 13 extending parallel to the front-rear direction of the vehicle body, and a plurality of cross members 15 extending in the vehicle width direction and having both ends fixed between the side members 13. It consists of The rear axle housing 2 is made of a rigid tubular body supporting double tires 18 at both ends in the vehicle width direction, and the housing 2 is fixed by a fastener 51 at a substantially central position on an upper surface of a support beam 17 extending substantially horizontally. After that, the housing 2
It is suspended on the left and right side members 13 through a pair of air springs 11 mounted on both sides of the beam 17 with the beam sandwiched therebetween.

An upper radius rod 3 having a stabilizer 19 attached to the rear end of the support beam 17 is also provided.
Is a V-shaped plane similar to the prior art, and its top is rotated in a plane direction to a rotation fulcrum 2A (pillar pin) which is erected upright on the center of the upper surface of the center of the rear axle housing 2 including the differential casing 21. While freely supporting the shaft, the legs of the rod 3 are extended symmetrically toward the front of the vehicle in a laterally divergent manner, and the free ends are attached to the chassis frame 1
Is pivotally attached to the side member 13 of.

On the other hand, on the side wall surface of each side member 13 corresponding to the projecting position of the shaft end of the rear axle housing 2, a hydraulic cylinder 4 is horizontally directed forward of the vehicle in parallel with the side wall surface of the member 13 via a web 23. The piston shaft 25 provided on the front side of the piston shaft 25 is axially supported by the upper end of the rotary lever 6. The rotation lever 6 is pivotally supported on the bracket 27 attached to the side member 13 so as to be swingable at a predetermined angle along a plane substantially perpendicular to the actuator 4, and the actuator 4 on the upper end side of the pivot fulcrum 6A. The distance between the connecting portions and the lower radius rod 5 connecting portion on the lower end side is set to 1: 1.

The lower radius rod 5 has a connecting portion 5 at both ends.
A bracket 29 which has a rod shape having a and 5b, extends horizontally along a plane substantially vertical to the actuator 4, and has one end attached to the lower end of the rotating lever 6 and the other end attached to the lower surface of the rear axle housing 2. Is connected to a mounting hole 29a formed on the vertical center line of the rotation fulcrum 2A. In addition, the hydraulic cylinder 4 forming the rear wheel steering actuator,
A stopper for limiting the expansion and contraction stroke of the piston shaft 25 is built in, and the stopper allows the hydraulic cylinder 4 to move.
When the hydraulic cylinder 4 is stopped, the rear axle housing 2 is set to be accurately steered in 1 degree increments within a preset small angle range of 1 to 5 degrees. By actuating the illustrated neutral spring or hydraulically locking the piston shaft 25
Can be fixed to the neutral position, whereby the rear wheels 18 connected to the rear axle housing 2 can be held in a straight traveling state with a steering angle of zero.

The operation of this embodiment will be briefly described below.
When the front wheels are steered while the vehicle is traveling at high speed, the control valve operates in response to a command from the controller, and as shown in FIG. 4, the pair of rear wheel steering actuators 4 operate in mutually opposite directions, so that Rotating levers 6 connected to one ends of the actuators 4 rotate in opposite directions along a vertical plane, and a right (left) side lower radius rod 5 connected to the other end of the rotating levers 6 is The lower radius rod 5 on the front side of the vehicle body and the left (right) side lower radius rod 5 are driven on the rear side of the vehicle body in a substantially horizontal direction. As a result, the bracket 27 and the support beam 17
The shaft end of the rear axle housing 2 pushes via
When the rear axle housing 2 is pulled, the rear axle housing 2 rotates around the rotation fulcrum 2A for a predetermined angle, and the rear wheel 18 follows the rotation.
Will be steered.

[0018]

As described above, according to the present invention, it is possible to obtain a rear wheel steering device which has good durability even in a truck or the like in which a rear tire has a double tire and which is capable of reliably and stably steering the rear wheels. I can do things. And so on.

[Brief description of drawings]

FIG. 1 is a perspective view showing a rear wheel steering device according to an embodiment of the present invention,

FIG. 2 is a front view of a main part of FIG.

FIG. 3 is a plan view of an essential part of FIG.

4 (A) is a plan view and FIG. 4 (B) is a front view.

FIG. 5 is a plan view showing a rear wheel steering device according to a prior application technique.

6 is a front view of FIG.

[Explanation of symbols]

 1 Chassis frame 2 Rear axle housing 2A Rotation fulcrum 3 Upper radius rod 4 Rear wheel steering actuator 5 Lower radius rod 6 Rotating lever 11 Air spring 18 Rear wheel

Claims (1)

[Claims] 1. A rear axle housing suspended on an undercarriage frame via an air spring and supporting rear wheels at both ends in the vehicle width direction, a rotation fulcrum provided at a center portion in the vehicle width direction of the rear axle housing, and the rotation. A flat V-shaped or Y-shaped upper radius rod that extends toward the front of the vehicle from the fulcrum toward the front of the vehicle and has its free end supported by the frame; A rear wheel steering actuator that reciprocates, and a lower radius rod that extends substantially horizontally in the vehicle front-rear direction in a plane that is substantially vertical to the actuator.One end of the lower radius rod is turned to the rear axle housing side and the other end is turned. By connecting to the rear wheel steering actuator via a lever, the rear wheel can be handled in response to steering while the vehicle is traveling at high speed. A rear wheel steering system for a vehicle, characterized in that a rear axle housing is configured to be steerable around a rotation fulcrum supported by the upper radius rod by operating a steering actuator.