JPH03276804A - Rear wheel suspension device for rear wheel-steered vehicle - Google Patents

Abstract

PURPOSE:To limit the load inputted to a rear wheel steering device to the minimum by arranging a specific control link, and generating the moment reaction opposite to the moment around a kingpin shaft. CONSTITUTION:A rear wheel suspension device has a wheel support 30 rotatably supporting rear wheels 3R, an upper arm 33 constituted of the first upper arm 31 and the second upper arm 32, a lower arm 36 constituted of the first lower arm 34 and the second lower arm 35, a stabilizer 37 suppressing the inclination of a vehicle body at the time of a turn, and a shock absorber 38 suppressing the vertical vibration of the vehicle body. A control link 49 provided to connect the end section of the stabilizer 37 to the wheel support 30 generates the moment reaction B opposite to the moment A around a kingpin shaft KP generated by the lateral force applied to the rear wheel on the turn outside when a vehicle is turned.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel suspension system for a rear wheel steered vehicle equipped with a rear wheel steering device for steering the rear wheels.

(Prior Art) Conventionally, in order to reduce the steering force of the rear wheels in a rear wheel steering vehicle, as shown in, for example, Japanese Unexamined Patent Publication No. 58-214463, the caster trail of the rear wheels is made negative, and
A device configured to have a negative kingpin offset is known. That is, as shown in FIG. 12, in a side view of the right rear wheel 3R, the intersection O between the kingpin axis KP and the road surface is located on the rear side of the vehicle body than the ground contact center G of the rear wheel 3R, and the intersection 0 and the By setting the caster trail 1, which is the distance in the longitudinal direction from the ground contact center G, to be negative, the restoring torque generated during turning, that is, the self-lining torque, is reduced, and the steering force of the rear wheels 3R is reduced. . Further, as shown in FIG. 13, when viewed from the rear of the rear wheel 3R, the intersection point 0 between the kingpin shaft P and the road surface is located outside of the vehicle body than the ground contact center G of the rear wheel 3R, and the intersection point O and the ground contact center By setting the kingpin offset m, which is the distance in the left-right direction from G, to a negative value, the road surface resistance that occurs when turning in a running state is reduced, and the turning force of the rear wheels 3R is reduced.

(Problem to be Solved by the Invention) When the caster trail 1 and king pin offset m of the rear wheel 3R are each negative as described above, the king pin offset m is negative as shown in FIG. Since the shaft KP is offset to the rear of the vehicle body relative to the ground contact center G of the rear wheels, when the vehicle is turning to the left, the lateral force acting on the right rear wheel 3R located on the outside of the turn is Accordingly, a moment A acts to steer the rear wheel 3R in the toe-in direction around the kingpin axis KP. Since such a moment acts, there has conventionally been a problem in that a large load is applied to the rear wheel steering device.

In other words, a rear wheel steering system is generally provided with a neutral position biasing means for keeping the rear wheels in the straight-ahead direction when an abnormality occurs in the rear wheel steering control system. The biasing means is configured to obtain a biasing force sufficient to overcome the moment about the kingpin shaft generated by the lateral force acting on the rear wheel by elastic deformation of a spring or the like. For this reason, it is necessary to form the springs etc. to a certain extent large size, which also increases the size of the nozzle that accommodates the springs etc. Furthermore, in normal rear wheel steering control, it is possible to reduce responsiveness and cause hunting. Become.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rear wheel suspension system for a rear wheel steering vehicle that can minimize the load input to the rear wheel steering system. That is.

(Means for Solving the Problems) The rear wheel suspension system for a rear wheel steered vehicle according to the present invention generates a moment reaction force in the opposite direction to the moment around the king pin axis by disposing a predetermined control link,
This is intended to achieve the above objective.

That is, in a rear wheel suspension system of a rear wheel steering vehicle equipped with a rear wheel steering device that steers the rear wheels, a stabilizer is rotatably supported on the vehicle body, and a control link connects the end of the stabilizer to a wheel support. and the control link is arranged so as to generate a moment reaction force in the opposite direction to a moment about the kingpin axis generated by a lateral force acting on the rear wheel on the outside of the turn when the vehicle turns. That is.

(Operations and Effects of the Invention) As shown in the above configuration, the control link provided to connect the end of the stabilizer to the wheel support is connected to the kingpin axis generated by the lateral force acting on the rear wheel on the outside of the turn when the vehicle turns. Since it is arranged so as to generate a moment reaction force in the opposite direction to the surrounding moment, the load input to the rear wheel steering device can be suppressed to a minimum due to the canceling effect of both moments. This results in
The biasing force of the neutral position biasing means can be reduced, and the rear wheel steering device can be configured compactly.

(Examples) Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram showing one embodiment of a rear wheel suspension system for a rear wheel steered vehicle according to the present invention.

This rear wheel steering vehicle includes a front wheel steering device 2 that steers left and right front wheels IL and IR, and a rear wheel steering bag L4 that steers left and right rear wheels 3L and 3R. The front wheel steering device 2 includes:
A steering shaft 6 that is rotatably driven by the steering wheel 5, and a rack and pinion mechanism 7 that converts the rotational motion of the steering shaft 6 into linear motion.
A front wheel steering rod 8 driven by this rack and pinion mechanism 7, and a pair of left and right knuckle arms 10L connected to both left and right ends of this front wheel steering rod 8 via tie rods 9L and 9R, respectively.

10R. The front wheel steering device 2 also assists the movement of the front wheel steering rod 8. (A power cylinder 11 and a control knob 12 for switching the oil passage according to the operation of the steering wheel 5 are provided.

The rear wheel steering device 4 has tie rods 13L, 13R and a knuckle arm 14L at both left and right ends, respectively.

A malfunction occurs in the rear wheel steering rod 15 connected to the left and right rear wheels 3L and 3R via the rear wheel 14R, the power cylinder 16 that assists the driving force of the rear wheel steering port 5, and the rear wheel steering device 4. A centering spring 17 serves as a neutral position biasing means for biasing the rear wheel steering port/socket 15 to a neutral position at certain times, and a centering spring 17 serves as a neutral position biasing means for biasing the rear wheel steering port 15 to a neutral position, and a centering spring 17 that biases the rear wheels 3L and 3R with respect to the front wheels IL and IR depending on the vehicle speed.
The steering ratio variable mechanism 18 is provided to change the steering ratio.

The structure of this variable steering ratio mechanism 18 is conventionally well known, so a detailed explanation thereof will be omitted, but it is driven by an input shaft 21 connected to the front wheel steering rod 8 via a rack and pinion mechanism 19 and a connecting shaft 20. The driving force is transmitted to the control valve 23 of the /(war cylinder 16) via the control rod 22, and the control valve 2
The rear wheel steering rod 15 is configured to be driven by a connecting member (not shown) provided on the valve casing of No. 3 in accordance with a preset steering ratio characteristic.

That is, the steering ratio variable mechanism 18
．． For example, the control unit 27 controls the operating state of the second
As shown in the figure, the rear wheels 3L and 3R are steered in the opposite phase direction to the front wheels IL and IR when the vehicle speed is in the range of 0 to less than 3 s&/h,
Hold the rear wheel 3R in the neutral position at a vehicle speed of 357 m/h,
Rear wheel 3L in the range exceeding 51Qa/h.

The steering wheel 3R is configured to be steered in the same phase direction as the front wheels IL and IR. The operating state of the variable steering ratio mechanism 18 and the steering ratio sensor 28 are detected, and the detection signal is input to the control section 27, which performs feedback control.

Further, a solenoid valve 29 is provided in the oil passage of the control valve 23, and this solenoid valve 29 is driven according to a control signal output from the control section 27 when a failure occurs in the rear wheel steering device 4, and the control valve 23, thereby eliminating the hydraulic pressure in the power cylinder 16 and returning the rear wheel steering rod 15 to the neutral position by the biasing force of the centering spring 17. ing.

Next, the rear wheel suspension system of this embodiment applied to the rear wheel steered vehicle will be described. 3.4 and 5 are a side view as seen from the center of the vehicle, a rear view as seen from the rear, and a plan view showing the suspension device provided on the right rear wheel 3R. As shown in these figures, the rear wheel suspension system includes a wheel support 30 that rotatably supports the rear wheel 3R, an upper arm 33 consisting of a first upper arm 31 and a second upper arm 32, a tenth upper arm 34, and a second upper arm 32. The vehicle includes a lower arm 36 consisting of an arm 35, a stabilizer 37 that suppresses the tilting of the vehicle body when turning, and a shock absorber 38 that suppresses vertical vibration of the vehicle body.

The wheel support 30 has an extension portion 39 extending above the rim portion along the inner surface of the rear wheel 3R, and a knuckle arm 14R extending from the lower end toward the rear side of the vehicle body. The side end of the rear wheel steering rod 5 is connected via a ball joint 40. The first upper arm 31 of the upper arm 33 is disposed so as to extend in the longitudinal direction of the vehicle body, and its rear end is connected to the wheel support 31 through a ball joint 41.
The front end portion is pivotally connected to the vehicle body via an elastic bushing 42. Further, the second upper arm 32 of the upper arm 33 is disposed below the first upper arm 31 so as to extend in the vehicle width direction, and its outer end is pivotally connected to the intermediate portion of the wheel support 30 via a ball joint 43. The inner end is pivotally connected to the vehicle body via an elastic bushing 44.

The tenth arm 34 of the lower arm 3B is disposed to extend in the longitudinal direction of the vehicle body, its rear end is pivotally connected to the lower end of the wheel support 30 via a ball joint 45, and its front end is attached to an elastic bush 46. It is pivotally connected to the vehicle body via. Also, the 20th arm 3 of the lower arm 36
5 is disposed behind the tenth arm 34 to extend in the vehicle width direction, its outer end is pivotally connected to the lower end of the wheel support 30 via a ball joint 47, and its inner end is elastic. It is pivotally connected to the vehicle body via a bush 48. And the above 1. 2nd upper arm 31.32
The center of the ball joints 41 and 43 and the 1st ball joint. 20th
A kingpin axis KP is formed by a line connecting the intersection of the center lines of the arm 34 and 35, and the wheel support 30 is configured to rotate around this kingpin axis KP to steer the rear wheel 3R.

The stabilizer 37 is disposed between the upper arm 33 and the lower arm 36 so as to extend in the vehicle width direction, and is rotatably supported by the vehicle body via a bracket 49. Further, the stabilizer 37 is provided with a side portion extending toward the front side of the vehicle body at the side end portion thereof, and the tip portion thereof is connected to the wheel support 30 via a control link 49. The shock absorber 38 includes a shock absorber 50 that is disposed on the rear side of the upper arm 33 and extends in the vertical direction, and a coil spring 51 that is disposed outside of the upper part of the shock absorber 50. The lower end of the shock absorber 50 is connected to the wheel support 30, and the upper end of the shock absorber 50 is attached to the vehicle body.

As shown in FIG. 6, the upper end of the king pin shaft KP is inclined toward the rear of the vehicle body when viewed from the side, and the intersection O between the king pin shaft KP and the road surface is lower than the ground contact center G of the rear wheel 3R. It is arranged so as to be located on the front side of the vehicle body, and the caster trail 1 is set to be positive. Further, as shown in FIG. 7, the king pin shaft KP has an upper end inclined inward of the vehicle body when viewed from the rear of the vehicle body, and the king pin shaft K
The intersection point O between P and the road surface is located inward of the vehicle body from the ground contact center G, and the kingpin offset m
is set correctly. Therefore, as shown in FIG. 8 when viewed from above, the kingpin axis KP intersects the road surface at point 0 in front of the ground contact center G of the rear wheel 3R, and extends toward the outside of the turn when the vehicle is turning left. When a lateral force acts on the rear wheel 3R, the rear wheel 3R responds to this lateral force.
A moment A acts around the king pin axis KP to steer the wheel in the toe-out direction.

However, in this embodiment, the stabilizer 37
The control link 49 that connects the side part of the wheel support 30 to the wheel support 30 is disposed with its lower end inclined inward on the front inner side of the kingpin shaft KP.
A tensile stress corresponding to the above-mentioned moment is generated in the control link 49, and this force causes a moment B to act on the rear wheel 3R to steer the rear wheel 3R in the toe-in direction around the king pin axis KP.

As described above, according to this embodiment, the control link 49 provided to connect the end of the stabilizer 37 to the wheel support 30 controls the kingpin axis generated by the lateral force acting on the rear wheel on the outside of the turn when the vehicle turns. Since it is arranged so as to generate a moment reaction force B in the opposite direction to the moment A around KP, the load input to the tie rod 13R of the rear wheel steering device 4 can be suppressed to a minimum. Thereby, the biasing force of the centering spring 17 can be reduced, and the rear wheel steering device 4 can be configured compactly. That is, the centering spring 17, which holds the rear wheels 3L and 3R in the neutral position when a failure occurs in the rear wheel steering device 4, handles a moment A due to a lateral force acting when the vehicle turns, and a moment B due to a reaction force of the control link 49. It is only necessary to set the biasing force so as to withstand a load corresponding to the difference between The load on the hydraulic system that drives the engine can be reduced.

Note that the arrangement of the king pin shaft KP is not limited to the above embodiment, and various changes can be made. For example, as shown in FIG. 9, the kingpin axis KP is inclined so that the upper end is located on the front side of the vehicle body when viewed from the side, and the intersection O between the kingpin axis KP and the road surface is the center of contact of the rear wheel 3R. Place the caster trail 1 on the rear side of the vehicle body than G.
By setting the above-mentioned intersection point O to be located inward of the vehicle body from the ground contact center G when viewed from the rear of the vehicle body and setting the king pin offset m to be positive, as shown in FIG. As shown in FIG. 11, the axis KP and the road surface may be configured to intersect at a point O located on the rear side of the ground contact center G when viewed from above. In this case, a force A is used to steer the rear wheel 3R on the outside of the turn in the toe-in direction in accordance with the lateral force that acts when the automobile turns.
acts around the kingpin axis KP. For this reason, the hunt roll link 49 is disposed on the rear inner side of the king pin shaft KP with its lower end inclined inward,
By configuring the moment reaction force B to act in the toe-out direction, the steering forces A and B can be made to act in a direction in which they cancel each other out.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of a rear wheel suspension system for a rear wheel steering vehicle according to the present invention, FIG. 2 is a graph showing the relationship between vehicle speed and steering ratio, and FIG. 3 is a graph showing the relationship between vehicle speed and steering ratio. FIG. 4 is a rear view of the embodiment as seen from the rear; FIG. 5 is a plan view of the embodiment; FIG. 6 is a king pin 7 is a rear view of the same, FIG. 8 is a plan view of the same, FIG. 9 is a side view of another example of the arrangement of the king pin shaft and the stabilizer, 10. 11 is a plan view of the same, FIG. 12 is a side view showing the arrangement of the king pin shaft in the conventional example, FIG. 13 is a rear view of the same, and FIG. 14 is a plan view of the same. It is. IL, IR...Front wheel 3L, 3R...Rear wheel 4...Rear wheel steering device 5...Steering wheel 15R...Tie rod 17...Centering spring (neutral position biasing means) 30...・Wheel support 37...Stabilizer 38...Buffer device 49...Control link KP...King pin shaft (Figure 2) Figure 9 Figure 0 Figure 1 Figure 2 Figure 3 Figure 4 Figure 2

Claims (1)

[Claims] A rear wheel suspension system for a rear wheel steering vehicle equipped with a rear wheel steering device for steering the rear wheels, comprising: a stabilizer rotatably supported on the vehicle body; and an end of the stabilizer used as a wheel support. and a connecting control link, the control link being arranged so as to generate a moment reaction force in the opposite direction to a moment about the kingpin axis generated by a lateral force acting on the rear wheel on the outside of the turning when the vehicle turns. A rear wheel suspension system for a rear wheel steering vehicle, characterized in that: