JPH0464913B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a four-wheel steering system for a vehicle that steers the rear wheels in accordance with the steering of the front wheels, and particularly to a suspension structure for the rear wheels. .

(Prior Art) Today, a four-wheel steering device for a vehicle is being developed that steers the rear wheels following the steering of the front wheels of the vehicle. In this four-wheel steering system, the rear wheels are normally steered in the same phase direction as the front wheels in a high vehicle speed range, so that lane changes can be made extremely smoothly, for example, on a highway with good driving stability. Furthermore, in a low vehicle speed range, the rear wheels are steered in the opposite phase to the front wheels, making it possible to reduce the turning radius, and this four-wheel steering device is known as an excellent steering system. (For example, see Japanese Patent Application Laid-Open No. 58-97566.) The actuator of the rear wheel steering device that steers the rear wheels is preferably installed forward of the vehicle body from the center of the rear wheels due to the layout. The front end of the rotatably supported wheel support member is connected to the actuator by the front suspension arm, the rear end of the wheel support member is attached to the vehicle body by the rear suspension arm, and vibrations from the rear wheels are transmitted to the vehicle body. In order to prevent this from happening, the rear suspension arm is attached to the vehicle body via a rubber bushing. When the vehicle turns and a lateral force is applied to the rear wheel, the rear wheel on the outside of the turn will rotate toward the toe-out side. Therefore, a problem arises in that good steering characteristics cannot be obtained. To explain in detail, when the actuator of the four-wheel steering system is configured to be located forward of the center of the rear wheels as described above, the compliance (lateral displacement) of the link mechanism on the front suspension side of the rear wheels becomes zero, The amount of compliance becomes forward < backward. Therefore, a serious problem arises when toe-out occurs due to lateral force. That is, in a steering system such as a four-wheel steering system, the front end of the wheel support member, the front suspension, and the connection with the actuator are configured via rigid joints such as ball joints, and the compliance (lateral displacement ) is eliminated so that the desired steering angle is accurately generated at the rear wheels. Afterwards,
When the actuator of a four-wheel steering system is placed forward of the center of the rear wheels, the above-mentioned problems arise.

(Object of the Invention) The object of the present invention is to provide a four-wheel steering system for a vehicle in which the actuator of the rear wheel steering system that steers the rear wheels is provided forward of the center of the rear wheels. To provide a four-wheel steering device for a vehicle that prevents a rear wheel on the outer wheel side of turning from turning in an out direction even if a lateral force is applied to the rear wheel.

(Structure of the Invention) A four-wheel steering device for a vehicle according to the present invention is a vehicle equipped with a steering device that steers the front wheels and a rear wheel steering device that steers the rear wheels according to predetermined conditions. A subframe is mounted on the vehicle body via a rubber member, and the actuator of the rear wheel steering device is mounted on this subframe at a position in front of the rear wheels, and the actuator and the front position of the rear wheels are rigid bodies. A suspension arm, which is connected via a joint and located at the rear of the actuator, is swingably supported by the subframe via an elastic body, and by the lateral force input to the rear wheel, The subframe is supported so as to be swingable so as to orient the rear wheel in a toe-in direction as the rubber member deforms. Therefore, when a force is applied to the rear wheel on the outer side of the turning center when the vehicle turns, the subframe is pressed via the rear suspension arm, and the subframe moves toward the turning center. When the subframe moves, the actuator of the rear wheel drive device fixed to the subframe also moves toward the turning center. Therefore, a rotational force in the toe-in direction is generated on the rear wheel on the outer side of the turn via the front suspension arm disposed between the front end of the wheel support member of the rear wheel and the actuator, causing the rear wheel on the outer side of the turn to toe out. rotation in the direction is prevented.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

The figure is a schematic diagram showing an embodiment of the four-wheel steering device of the present invention.

The front wheel steering device 2 that steers the front wheels 1L and 1R is
Steering wheel 3 and rotational movement of this steering wheel in the left and right direction of the vehicle body (vehicle width direction)
Gearbox 4 that converts and transmits the reciprocating motion of
A hydraulically actuated actuator 5 is installed in parallel with the gearbox 4, and a tie rod 6 is connected to the gearbox 4 and the actuator 5 to reciprocate the vehicle body in the left-right direction. consists of knuckle arms 7, 7' connected to the left and right front wheels 1L, 1R, and in response to the steering of the steering wheel 3, the tie rod 6 is reciprocated in the left-right direction of the vehicle body to steer the front wheels 1L, 1R left and right. It is composed of The tie rod 6 is provided with a rack 8 that moves as the tie rod 6 moves.
A shaft 9 extending in the longitudinal direction of the vehicle body transmits front wheel steering force to a rear wheel steering device 11 that steers rear wheels 10L and 10R. This rear wheel steering device 11 has a box 12 that converts the rotation of the shaft 9 into a reciprocating movement in the left and right direction of the vehicle body, and a hydraulic actuator 13 installed in parallel with this gear box 12. 10L,
It is mounted in front of the subframe 14 arranged between 10R and 10R. This subframe 14 is
The rear end is pivoted by a pivot 15, and the front end is attached to the vehicle body via rubber members 16, 16', so that when a force in the left and right direction of the vehicle body is applied to the subframe 14, the subframe 14 swings. It's getting old. On the other hand, the rear wheels 10L and 10R are rotatably supported by wheel support members 17 and 17' each having a T-shaped planar shape. Both ends of the tie rod 18, which is moved in the left-right direction of the vehicle body by the actuator 13, are connected by front suspension arms 19, 19'. a rear suspension arm 2 whose one end is connected to the rear end of the wheel support members 17, 17';
The other ends of 0 and 20' are pivotally connected to the subframe 14. Connection between the front ends of the wheel support members 17, 17' and the front suspensions 19, 19', and the front suspensions 19, 19' and the tie rod 18.
connection of both ends of the wheel support member 17,1
7' and the rear suspensions 20, 20' are connected by a rigid joint (pole joint) 24. Actuators 5 and 13
The oil is discharged from the oil pump 21, and the oil is discharged from the flow divider 22.
The oil diverted by is supplied, and the steering force of the steering wheel 3 is reduced. A speed change gear device 23 is provided at an intermediate portion of the shaft 9, and the ratio of the steering angle of the front wheels 1L, 1R to the steering angle of the rear wheels 10L, 10R is set to a predetermined value.

Next, in the embodiment configured as above,
The behavior of the rear wheel when a lateral force is applied to the rear wheel on the outer wheel side of the turn during a turn will be explained.

Now, when the vehicle turns to the right in the figure, a lateral force in the direction of the turning center is applied to the rear wheel 10L on the outer wheel side of the turn.
This lateral force is transmitted to the subframe 14 by the rear suspension arm 20, and
4 swings to the right around a pivot 15. Since the actuator 13 is mounted in front of the subframe 14, it is moved to the right in the figure as the subframe 14 swings. When the actuator 13 moves, the end of the tie rod 18 in the actuator 13 and the wheel support member 17
Front suspension arm 1 connected to the front end of
9 and 19', the rear wheel 10L receives a force to rotate in the toe-in direction, and as a result, the force in the toe-out direction and the force in the toe-in direction cancel each other out, causing the rear wheel 10L on the outer wheel side of the turn to rotate in the toe-out direction. Prevented from turning. In addition, rear wheel 10L, 1
The vibrations that 0R receives from the road surface are caused by subframe 1.
Rubber member 16,1 provided between 4 and the vehicle body
6'. Note that rubber members may also be provided at the pivot points of the rear suspension arms 20, 20' to the subframe 15 to better absorb vibrations.

In the above embodiment, the subframe was attached to the vehicle body by a pivot at the rear end and via a rubber member at the front, but without having a pivot, all parts were attached to the vehicle body via a rubber member. It may be attached. In this case, the subframe does not swing, but moves in parallel in the left-right direction of the vehicle body, thereby preventing the rear wheel on the outer turning wheel from rotating in the toe-out direction.

(Effects of the Invention) In the present invention, when the vehicle turns, the subframe moves toward the center of the turn via the rear suspension arm due to the lateral force generated in the rear wheel on the outer side of the turn toward the center of the turn. As a result, the actuator of the rear wheel drive device fixed to the subframe moves and moves the front suspension arm by almost the same amount of movement as the rear suspension arm. This prevents the wheels from turning in the toe-out direction, providing good steering characteristics, and since the subframe is attached to the vehicle body via a rubber member, vibrations from the rear wheels are prevented from being transmitted to the vehicle. .

[Brief explanation of the drawing]

The drawing is a schematic diagram showing an embodiment of a four-wheel steering system for a vehicle according to the present invention. 1L, 1R...Front wheel, 2...Front wheel steering device, 3
... Steering wheel, 4 ... Gearbox, 5 ... Actuator, 6 ... Tie rod,
7... Nutacle arm, 8... Rack, 9... Shaft, 10L, 10R... Rear wheel, 11... Rear wheel steering device, 12... Gearbox, 13... Actuator, 14... Subframe, 15... Pivot, 16, 16'...Rubber member, 17, 17'...
...Wheel support member, 18...Tie rod, 1
9,19'...Front suspension arm, 20,
20'... Rear suspension arm, 21...
Oil pump, 22... Flow divider.

Claims (1)

[Claims] 1. In a vehicle equipped with a steering device that steers the front wheels and a rear wheel steering device that steers the rear wheels according to predetermined conditions, a subframe is mounted on the vehicle body between the rear wheels via a rubber member, The actuator of the rear wheel steering device is mounted on this subframe at a position in front of the rear wheel, and the actuator and the front position of the rear wheel are connected via a rigid joint, and the actuator is located at the rear of the actuator. The suspension arm is swingably supported by the sub-frame via an elastic body, and due to the lateral force input to the rear wheel, the sub-frame is caused to rotate as the rubber member deforms. A four-wheel steering device for a vehicle, characterized in that the four-wheel steering device is supported so as to be swingable so as to direct the wheels in a toe-in direction.