JPS63101173A - Four-wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To make the steering ratio of rear wheel with respect to front wheel variable according to the vehicle speed, by converting the rotation of a rotary shaft interlocked with a front wheel steering mechanism through a steering ratio changing mechanism which is operated by means of an actuator being controlled corresponding to the vehicle speed. CONSTITUTION:In a rear wheel steering ratio changing mechanism 25, if an output shaft 16 is concentric with an input shaft 14, rotation of the input shaft 14 does not cause rotation of an yoke member 17 around the axis of its shaft 19, thereby a tierod 35 is not moved to the right/left and only the front wheel is steered. Upon variation of vehicle speed, a rear wheel steering controller 31 receives signals from a vehicle speed detecting means 32 and a position detecting means 33 to drive a motor 26. Consequently, a rolling member 22 rotates around a shaft 23 and inclines back and forth. Inclination of the rolling member 22 causes inclination of the output shaft together with the yoke member 17 so as to vary the steering angle of rear wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering system for a vehicle that changes the steering ratio of rear wheels to front wheels in accordance with vehicle speed.

(Prior art and object of the invention) In Japanese Patent Application Laid-open No. 55-91457 proposed by the present applicant,
2. Description of the Related Art A four-wheel steering system for a vehicle that changes the steering ratio of rear wheels to front wheels in accordance with vehicle speed is known.

The present invention relates to this type of four-wheel steering system.

The purpose of this is to create a new steering mechanism that follows the rotation taken from the front wheel steering mechanism that steers the front wheels in conjunction with the steering operation of the steered wheels. An object of the present invention is to provide a four-wheel steering system for a vehicle that can change the steering ratio of rear wheels to front wheels according to vehicle speed using a ratio changing mechanism.

(Structure of the Invention) In order to achieve such an object, the present invention provides a front wheel steering mechanism 8 that steers the front wheels 6, 6 in conjunction with the steering operation of the steered wheels 1, and a front wheel steering mechanism 8 that steers the rear wheels 36, 36. A rear wheel steering mechanism 38, a rotation shaft 12 that is linked to the front wheel steering mechanism 8 and transmits the front wheel steering direction and amount to the rear wheel steering mechanism 38, and a vehicle speed detection means 32 that detects vehicle speed. , an actuator 26 controlled in accordance with a signal from the vehicle speed detection means 32, and the actuator 26. A steering ratio changing mechanism 25 is provided between the rear wheel steering mechanism 8 and the rotating shaft 12 and changes the steering ratio of the rear wheels 36° 36 to the front wheels 6.6 according to the vehicle speed. The present invention is characterized in that it is configured as a four-wheel steering device for a vehicle.

Specifically, the steering ratio changing mechanism 25 has a rotating member 16 that is interlocked with the rotating shaft 12 and has a variable inclination angle.
The angle of inclination of the rotating member 16 is changed by an actuator 26 via worm gears 28 and 29.

More specifically, the rotating member 16 is rotatably supported by a yoke member 17, and the yoke member 17 is supported by a swinging member 22.
The swinging portion 22 is supported swingably around a support shaft 19 perpendicular to the rotating member 16, and the swinging portion 22 is supported around a support shaft 19 in a direction perpendicular to the rotating member 16.
A worm gear 28 is supported tiltably around a support shaft 23 in a direction perpendicular to the worm gear 28 .
゜29 is interposed.

(Function) First, the front wheel steering direction and the amount of steering are transmitted to the rear wheel steering mechanism 38 by the rotation shaft 12 that is interlocked with the front wheel steering mechanism 8 .

The rotation of the rotation shaft 12 is converted by a steering ratio changing mechanism 25 operated by an actuator 26 controlled in response to a signal from a vehicle speed detection means 32, and the rear wheels 6.
The steering ratio of 6.36 is variable depending on the vehicle speed.

In this way, while the rear wheel steering mechanism 38 follows the rotation extracted from the front wheel steering mechanism 8, the rear wheels 36, 36 relative to the front wheels 6, 6 are controlled by the steering ratio changing mechanism 25 that responds to the vehicle speed.
The steering ratio can be changed according to the vehicle speed.

Further, in the embodiment, a steering ratio changing mechanism 2 is provided which has a rotating member 16 that is linked to the rotating shaft 12 and whose inclination angle is variable via an actuator 26 and worm gears 28 and 29.
In particular, the presence of the worm gears 2B and 29 prevents the actuator (motor) 26 from being turned by an external force, that is, the steering ratio does not change due to an external force.

Furthermore, the four-wheel steering mechanism as a whole transmits the front wheel steering direction and steering amount through the rotation shaft 12, is controlled by the vehicle speed, and changes the inclination angle of the rotation member 16, so the mechanism itself is made smaller. can. In addition, since the steering ratio changing mechanism 25 does not have a sliding part that moves in the axial direction, the steering rigidity is high.

(Example) Examples will be described below based on the accompanying drawings.

In FIG. 1, a steering shaft 2 of a steering wheel 1 is meshed with a rack shaft 4 in a steering gear box 3 via a pinion, and a knuckle arm 7.7 supports left and right front wheels 6, 6.
are connected to both ends of the rack shaft 4 via tie rods 5.5, and the front wheels 6.6 are connected to the steered wheels 1 by the front wheel steering mechanism 8.
The steering force of the steered wheels 1 is reduced by a power assisting means (not shown) attached to the steering gear box 3.

Furthermore, a rotary take-off shaft 9 that meshes with the rack shaft 4 through a pinion is installed in the steering gear box 3 and protrudes rearward. An input shaft 14 shown in FIGS. 2 to 4 is connected to this rotation shaft 12 via a universal joint 13.

An output shaft 16 serving as a rotating member is connected to the input shaft 14 via a universal joint 15, and this output shaft 16 is connected to a yoke member 17.
It is rotatably fitted to the The front portion of the yoke member 17 is formed into upper and lower bifurcated portions 18.18.
The yoke member 17 is pivotally attached to the upper and lower sides of the swinging member 22, which has a hollow rectangular shape when viewed from the front, by the vertical support shafts 19.19, and thereby the yoke member 17 is pivoted in the horizontal direction around the upper and lower support shafts 19.19 relative to the swinging member 22. It is supported so that it can swing freely.

The swinging member 22 is pivotally connected to a housing 24 fixed to the vehicle body by horizontal support shafts 23.degree.23 that protrude outward from the left and right. 23 so as to be tiltable in the front and rear directions.

In this way, the steering ratio changing mechanism 25 is constructed, and furthermore, a motor 26 serving as an actuator is fixed to one outer surface of the housing 24, and a drive shaft 27 protruding downward from the motor 26 and a swinging member 22 are connected to each other. It is connected to one support shaft 23 via worm gears 2B and 29. That is, a ohm 28 is fixed to the drive shaft 27, and a pinion 29 that meshes with the ohm 28 is fixed to the support shaft 23.

Further, as shown in FIG. 4, there is a rear wheel steering control device 31 using an on-vehicle computer, a vehicle speed detection means 32 for detecting the vehicle speed, and a position detection means 33 for detecting the tilting state of the swinging member 22.
A rear wheel steering mechanism and 31 are vehicle speed detection means 3.
The motor 26 receives signals from the motor 2 and the position detection means 33, and sends appropriate control signals to the motor 26 to control its driving.

As shown in FIG. 1, knuckle arms 37.37 that support the left and right rear wheels 36.36 are connected to the rear of the yoke member 17 via tie rods 35.35, and the rear wheels 36 are controlled by the rear wheel steering mechanism 38.゜36 is the rear wheel steering control device 31
According to the operation of the steering ratio changing mechanism 25, the vehicle is steered as described later.

The functions of the above-mentioned four-wheel steering system, particularly the steering ratio changing mechanism 25 for the rear wheels 36 and 36, will be explained based on FIG. 5.

First, the output shaft 16 is located concentrically with the input shaft 14 as shown in FIG.
When the output shaft 16 coincides with the X-ray, the rotation shaft 12 transmits the front wheel steering direction and steering amount in conjunction with the front wheel steering mechanism 8.
Even if the output shaft 16 rotates via the input shaft 14 due to the rotation of
Since it does not rotate around the line, the tie rod 35 is not moved in the left-right direction, so only the front wheels 6,677) are steered, and the rear wheels 36, 36 are not steered at all.

When the vehicle speed changes from this state, the rear wheel steering control device 31
receives signals from the vehicle speed detection means 32 and position detection means 33, makes a judgment, and sends an appropriate control signal corresponding to the vehicle speed to the motor 26 to control its drive. The rotation of the drive shaft 27 due to the drive of the motor 26 is transmitted to the support shaft 23 of the swinging member 22 via the worm gears 28 and 29.
The pivoting member 22 moves along the axis of the support shaft 23, Z-
It rotates around the Z line and tilts forward and backward.

That is, when the vehicle speed decreases from the state shown in FIG. 5(a), for example, as shown in FIG. 5(b), due to the inclination of the swinging member 22, the output shaft 16 together with the yoke member 17 moves downward by an angle α with respect to the line X-X. As a result, the input shaft 14
The rotation is converted by the yoke member 17 into a rotation about the line Y'-Y' in which the support shaft 19 is tilted backward by an angle α.

Here, the relationship between the tilt angle α and the rotation angle φ of the yoke member 17 around the Y'-Y' line with respect to the rotation angle θ of the input shaft 12 is expressed as tanφm5ina tanO, that is, by changing the tilt angle α. Therefore, the relationship between the rotation angle 0 and the rotation angle φ is variable.

Therefore, in FIG. 5(b), the yoke member 17 is Y'
-Y' line, the tie rod 35 is moved in the left-right direction, for example, the rear wheel 35 is moved in the opposite direction to the front wheel 6.6.
6.36 The ship was steered.

If the vehicle speed increases from the state shown in Figure 5(a),
Due to the reverse rotation of the motor 26, the swinging member 22 is tilted as shown in FIG. The rotation of the shaft 14 is converted by the yoke member 17 into a rotation around the Y"-Y" line in which the support shaft 19 is tilted forward by an angle α, and this time the rear wheel 6.6 is rotated in the same direction as the front wheel 6.6. Be steered.

(Effects of the Invention) As described above, according to the present invention, the front wheel steering direction and steering amount are transmitted to the rear wheel steering mechanism by the rotating shaft interlocked with the front wheel steering mechanism, and the rotation of the rotating shaft is is converted by a steering ratio changing mechanism operated by an actuator controlled according to a signal from a vehicle speed detection means, and the steering ratio of the rear wheels to the front wheels is made variable according to the vehicle speed. While the rear wheel steering mechanism follows the extracted rotation, the steering ratio of the rear wheels relative to the front wheels can be changed in accordance with the vehicle speed using the steering ratio changing mechanism that responds to the vehicle speed.

In addition, in the embodiment, a steering ratio changing mechanism is adopted which has a rotating member that is linked to a rotating shaft and whose inclination angle can be varied from the actuator via a worm gear. motor) is not diverted, that is, the steering ratio is not changed by external force. Furthermore, the four-wheel steering mechanism as a whole transmits the front wheel steering direction and steering amount through a rotating shaft, and is controlled by the vehicle speed.
Since the mechanism changes the inclination angle of the rotating member, the mechanism itself can be made smaller. In addition, since the steering ratio changing mechanism does not have a sliding part that moves in the axial direction, the steering rigidity is high.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a four-wheel steering system according to the present invention, and FIG.
The figure is a perspective view of the housing portion that houses the steering ratio changing mechanism, Figure 3 is a sectional view taken along the line m-■ in Figure 2, Figure 4 is a perspective view of the main part including the steering ratio changing mechanism, and Figure 5 ( 7A to 7C are perspective views showing the operating principle of the steering ratio changing mechanism. In the drawings, 1 is a steering wheel, 3 is a steering gear box, 4 is a rack shaft, 6 is a front wheel, 8 is a front wheel steering mechanism, 9 is a rotation take-out shaft, 12 is a rotation shaft, 14 is an input shaft, 16 17 is a rotating member, 17 is a yoke member, 19 is a support shaft, 22 is a swinging member, 23 is a support shaft, 24 is a housing, 25 is a steering ratio changing mechanism, 26 is an actuator, 28.29 is a worm gear, 31 is a Rear wheel steering control device, 32, vehicle speed detection means, 33
36 is a rear wheel, and 38 is a rear wheel steering mechanism. Patent applicant: Agent for Honda Motor Co., Ltd.
Patent Attorney Part 2 1) Part 1 Patent Attorney
Kuni Ohashi Tokoma Patent Attorney Ko
Udo Yama Patent Attorney No 1)
Figure 5 ■

Claims (3)

[Claims] (1) A front wheel steering mechanism that steers the front wheels in conjunction with the steering operation of the steered wheels; a rear wheel steering mechanism that steers the rear wheels; and a front wheel steering mechanism that steers the front wheels in conjunction with the front wheel steering mechanism. a rotation shaft that transmits a steering amount to the rear wheel steering mechanism; a vehicle speed detection means that detects vehicle speed; an actuator that is controlled according to a signal from the vehicle speed detection means; the actuator, the rear wheel steering mechanism, and the A four-wheel steering system for a vehicle, comprising: a steering ratio changing mechanism that is interposed between rotating shafts and changes the steering ratio of rear wheels to front wheels according to vehicle speed. (2) In claim 1, the steering ratio changing mechanism has a rotating member that is interlocked with the rotating shaft and has a variable inclination angle, and the inclination angle of the rotating member is variable. A four-wheel steering system for a vehicle, characterized in that the change is made from the actuator via a worm gear. (3) In claim 2, the rotating member is rotatably supported by a yoke member, and the yoke member is configured to swing relative to the swinging member around a support axis perpendicular to the rotating member. The swinging member is supported to be movable, the swinging member is supported to be tiltable about a support shaft perpendicular to the support shaft with respect to the vehicle body, and the worm gear is interposed between the support shaft and the actuator. A four-wheel steering device for a vehicle characterized by the following.