JPH0577761A - Rear wheels steering device - Google Patents

Abstract

PURPOSE:To reduce the transmission resistance of the steering operational input by achieving steering of the rear wheels by the shifting in the vehicle width direction of a rack for steering the rear wheels on the basis of the rotation of a threaded shaft due to the rotation of an input shaft, and by the shifting of a rack for steering the rear wheels on the basis of the whiling of the threaded shaft due to the rotation of the input shaft. CONSTITUTION:A pinion provided to a shaft end of an input shaft 9 of a rear wheels steering device is engaged with a rack formed to a front wheels steering member, and a threaded shaft 34 is rotated due to the rotation of the input shaft 9 which is rotated by the quantity corresponding to the front wheels steering angle, and at the same time the threaded shaft is whirled. The pinion 37 is rotated due to the shifting of a nut 35 in the longitudinal direction of a vehicle caused by the rotation of the threaded shaft 34. And the rack 12 is shifted in the vehicle width direction due to the shifting of the nut 35 in the vehicle width direction caused by the whirling of the threaded shaft 34. The shifting of the rack 12 in the vehicle width direction is combined by the shifting on the basis of the rotation of the threaded shaft 34 and the shifting on the basis of the whirling of the threaded shaft 34, leading to reduction of the transmission resistance of the steering operational input.

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 in a front and rear wheel steering vehicle in which rear wheels are steered according to a front wheel steering angle.

[0002]

2. Description of the Related Art In a steering angle-sensitive type front and rear wheel steering vehicle, the rear wheels are required to make complicated movements according to the front wheel steering angle. For example, a rear wheel steering system disclosed in Japanese Patent Publication No. 60-44186 includes a cam that moves according to a front wheel steering angle and a cam follower provided on a rear wheel steering shaft. Is converted into movement of the rear wheel steering shaft in the vehicle width direction, and the rear wheel is steered by the movement of the rear wheel steering shaft in the vehicle width direction.

Further, a rear wheel steering system disclosed in Japanese Utility Model Laid-Open No. 60-50078 discloses a rack for steering a rear wheel, which rotates an input shaft according to a steering angle of a front wheel through a crank mechanism and a planetary gear mechanism. And the rear wheels are steered by the movement of the rear wheel steering rack in the vehicle width direction.

[0004]

However, in the case where the steering operation input is directly transmitted to the rear wheel steering shaft by the cam and the cam follower as in the prior art, the transmission resistance is large and the steering operation cannot be smoothly performed. ..

Further, a device for transmitting a steering operation input to a rear wheel steering rack by a crank mechanism and a planetary gear mechanism is as follows:
The structure is extremely complicated and not practical, and the transmission efficiency of steering operation input is extremely low.

An object of the present invention is to provide a rear wheel steering system that can solve the above-mentioned problems of the prior art.

[0007]

A feature of the present invention is to provide a front-wheel steering vehicle in which a rear wheel is steered by moving a rear-wheel steering rack in a vehicle width direction according to a front-wheel steering angle. An input shaft that rotates around the longitudinal axis of the vehicle depending on the angle, a screw shaft that is integrated with the input shaft and that is eccentric to the input shaft, a nut that is screwed to the screw shaft, and a nut that is formed on the nut. A rack and a pinion that meshes with the rack, the input shaft of which is rotatably supported by the vehicle body about the axis, and the pinion is movably supported by the vehicle body in the vehicle width direction. The pinion is meshed with the rear wheel steering rack so that the rear wheel steering rack moves in the vehicle width direction by the movement in the vehicle front-rear direction, and the vehicle width of the nut due to the whirling of the screw shaft. As the rear wheel steering rack moves in the vehicle width direction by the direction movement, lies in its pinion is connected to the nut.

[0008]

According to the structure of the present invention, when the input shaft rotates about the longitudinal axis of the vehicle in accordance with the front wheel steering angle, the screw shaft integrated with the input shaft rotates, so that the screw shaft is screwed onto the screw shaft. The nut moves in the front-rear direction of the vehicle. The movement of the nut rotates the pinion that meshes with the rack formed on the nut, and the rotation of the pinion moves the rear wheel steering rack in the vehicle width direction.

Further, since the screw shaft is eccentric with respect to the input shaft, the rotation of the input shaft causes the screw shaft to swirl around an axis extending in the longitudinal direction of the vehicle. By this whirling of the screw shaft, the nut moves in the vertical direction and the vehicle width direction. The movement of the nut in the vehicle width direction moves the pinion connected to the nut in the vehicle width direction, and the movement of the pinion in the vehicle width direction moves the rear wheel steering rack that meshes with the pinion in the vehicle width direction.

That is, the movement of the rear wheel steering rack in the vehicle width direction is a combination of movement based on rotation of the screw shaft and movement based on whirling of the screw shaft. The amount of movement of the rack based on the rotation of the screw shaft linearly changes according to the front wheel steering angle. The amount of movement of the rack based on the whirling of the screw shaft periodically changes according to the front wheel steering angle. Therefore, by adjusting the gear ratio between the pinion and the rack, the amount of eccentricity of the screw shaft with respect to the input shaft, and the like, the movement of the rear wheel steering rack according to the front wheel steering angle can be made desired.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a schematic structure of a front and rear wheel steering vehicle in which the rear wheel steering angle is controlled according to the front wheel steering angle. The left and right front wheels 1 are connected via a front wheel steering member 2 and a tie rod 3. A rack 4 is formed on the front wheel steering member 2, and a pinion 5 meshing with the rack 4 is interlocked with a handle 6. As a result, when the steering wheel 6 is operated, the front wheel steering member 2 moves in the vehicle width direction to steer the front wheels 1.

A rack (not shown) is formed separately from the rack 4 on the front wheel steering member 2, and a front end of an input shaft 9 of a rear wheel steering device 8 is attached to a pinion 7 that meshes with the rack. .. The input shaft 9 is supported by the vehicle body so as to be rotatable around the vehicle longitudinal axis. Accordingly, when the front wheel steering member 2 moves in the vehicle width direction by the steering operation input, the pinion 7 rotates, so that the input shaft 9 rotates by an amount corresponding to the front wheel steering angle.

The rear wheel steering device 8 is provided with a rear wheel steering rack 12, and the left and right rear wheels 10 are connected to each end of the rear wheel steering rack 12 via tie rods 11. The rear wheel steering rack 12 is supported by a vehicle body via a bearing 24 so as to be movable in the vehicle width direction. The rear wheel steering device 8 includes a conversion mechanism 13 that converts the rotation of the input shaft 9 into the movement of the rear wheel steering rack 12 in the vehicle width direction.

As shown in FIGS. 1 and 2, the conversion mechanism 13 includes a housing 32 which supports the input shaft 9 via bearings 30 and 31. The input shaft 9
A dust seal 28 is interposed between the housing 32 and the housing 32. The housing 32 is fixed to a component member 33 of the vehicle body. Inside the housing 32, the input shaft 9
A screw shaft 34 is integrally formed on the outer periphery of the. In this embodiment, the screw shaft 34 is a ball screw. The axis 34c of the screw shaft 34 is eccentric with respect to the axis 9c of the input shaft by an amount indicated by e in the figure.

A nut 35 is screwed onto the screw shaft 34. The nut 35 is a ball nut, and a ball (not shown) is interposed between the ball nut and the screw shaft 34, which is a ball screw. A rack 36 is formed around the nut 35. The axial direction of the rack 36 is along the vehicle front-rear direction.

A pinion 37 that meshes with the rack 36 is provided. The axis of the pinion 37 is along the vertical direction. The pinion 37 is supported by the housing 32 so as to be movable in the vehicle width direction.
In this embodiment, the pinion 37 includes a pair of upper and lower arms 38,
It is rotatably supported by the bearing 39 via bearings 40, 41. Each arm 38, 39 has a housing 32
The support shafts 42, 43 screwed into the
It is rotatably supported via 5. As a result, the arms 38 and 39 swing about the support shafts 42 and 43, whereby the pinion 37 moves in the vehicle width direction.

When the input shaft 9 rotates, the screw shaft 34 rotates, so that the nut 35 screwed onto the screw shaft 34 moves in the vehicle front-rear direction. The movement of the nut 35 causes the pinion 37 that meshes with the rack 36 formed on the nut 35 to rotate. The pinion 37 is meshed with the rear wheel steering rack 12 so that the rear wheel steering rack 12 moves in the vehicle width direction by the rotation of the pinion 37.

The shaft center 9c of the input shaft 9 and the shaft center 3 of the screw shaft 34
Since it is eccentric from 4c, the rotation of the input shaft 9 causes the screw shaft 34 to swing around an axis along the vehicle front-rear direction. Due to the whirling of the screw shaft 34, the nut 35
Moves in the vertical direction and the vehicle width direction. This nut 35
The pinion 37 and the nut 35 are connected so that the rear wheel steering rack 12 moves in the vehicle width direction by the movement in the vehicle width direction. In this embodiment, the pair of arms 38,
A roller 48 is rotatably supported by a bearing 39 via a bearing, and the nut 35 is sandwiched between the roller 48 and the pinion 37. As a result, when the nut 35 moves in the vehicle width direction due to the whirling of the screw shaft 34, the arms 38 and 39 swing around the support shafts 42 and 43, and the pinion 37 moves in the vehicle width direction. By the movement of the pinion 37 in the vehicle width direction, the rear wheel steering rack 12 meshing with the pinion 37 moves in the vehicle width direction.

The movement of the pinion 37 in the vehicle width direction is the movement of the pinion 37 and the rear wheel steering rack 1 on an arc centered on the support shafts 42 and 43 in this embodiment.
Measures are taken to prevent the amount of meshing with 2 from changing. That is, the support yoke 50 and the spring 51 are inserted into the insertion hole 32a formed in the housing 32, and the adjustment screw 52 is screwed into the insertion hole 32a. The support yoke 50 is movable in the front-rear direction of the vehicle, and the elastic force of the spring 51 presses the rear wheel steering rack 12 against the pinion 37 to prevent the meshing amount between the pinion 37 and the rear wheel steering rack 12 from changing. is doing.
In addition, by adjusting the screwing amount of the adjusting screw 52 into the insertion hole 32 a, the elastic force of the spring 51 is adjusted to adjust the pinion 3.
7 and the rack 12 can be smoothly meshed with each other.

According to the rear wheel steering system 8 having the above-described structure, the input shaft 9 rotates in accordance with the steering angle of the front wheels 1, whereby the screw shaft 34 rotates and whirls. The rotation of the screw shaft 34 moves the nut 35 in the vehicle front-rear direction to rotate the pinion 37, and the rotation of the pinion 37 moves the rear wheel steering rack 12 in the vehicle width direction. Further, the pinion 37 moves in the vehicle width direction by the movement of the nut 35 in the vehicle width direction due to the whirling motion of the screw shaft,
The movement of the pinion 37 causes the rear wheel steering rack 12 to move in the vehicle width direction. That is, the rear wheel steering rack 1
The vehicle width direction movement of 2 is a combination of movement based on rotation of the screw shaft 34 and movement based on whirling of the screw shaft 34. Therefore, by adjusting the gear ratio between the pinion 37 and the racks 36, 12 and the eccentric amount e of the screw shaft 34 with respect to the input shaft 9, the rear wheel steering rack 12 according to the front wheel steering angle.
The movement of can be desired.

In FIG. 4, an alternate long and short dash line 60 in the drawing shows the relationship between the front wheel steering angle and the rear wheel steering angle when the rear wheel steering rack 12 moves based on the rotation of the screw shaft 34. The rear-wheel steering angle changes linearly according to. In the figure, a chain double-dashed line 61 indicates the relationship between the front wheel steering angle and the rear wheel steering angle when the rear wheel steering rack 12 moves based on the whirling of the screw shaft 34, and the rear wheel steering according to the front wheel steering angle. The angle changes periodically. The solid line 62 in the figure is a composite of the relationship shown by the one-dot chain line 60 in the figure and the relationship shown by the two-dot chain line 61 in the figure. The front wheel steering angle and the rear wheel steering angle of the front and rear wheel steering vehicle according to the configuration of the present invention are shown. Shows the relationship with. That is, while the front wheel steering angle is small, the front wheels 1 and the rear wheels 10 are steered in the same direction, and when the front wheel steering angle is large, the front wheels 1 and the rear wheels 10 are steered in opposite directions. Then, the steering characteristic becomes favorable as a front and rear wheel steering vehicle.

The present invention is not limited to the above embodiment.

For example, in the above embodiment, a ball screw is used as the screw shaft 34, but an acme screw may be used, and the nut 35 may be an acme nut instead of a ball nut. In the above embodiment, the pinion 37 is configured to move in the vehicle width direction by swinging, but it may be configured to move linearly in the vehicle width direction.

[0025]

According to the rear wheel steering apparatus of the present invention, the rear wheel steering rack moves in the vehicle width direction based on the rotation of the screw shaft caused by the rotation of the input shaft and the whirling of the screw shaft caused by the rotation of the input shaft. Since the rear wheels are steered by the movement of the rear wheel steering rack based on the vehicle width, the transmission resistance of the steering operation input is smaller than that when the steering operation input is transmitted to the rear wheels using only the cam. In addition, the structure is simplified as compared with the structure using the planetary gear mechanism and the cam mechanism, and it is practical and can improve the transmission efficiency of the steering operation input.

[Brief description of drawings]

FIG. 1 is a sectional view of a rear wheel steering system according to an embodiment of the present invention.

FIG. 2 is a plan sectional view of a main part of a rear wheel steering system according to an embodiment of the present invention.

FIG. 3 is a structural explanatory view of a front and rear wheel steering vehicle according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a front wheel steering angle and a rear wheel steering angle of a front and rear wheel steering vehicle according to an embodiment of the present invention.

[Explanation of symbols]

 1 Front Wheel 9 Input Shaft 10 Rear Wheel 12 Rear Wheel Steering Rack 34 Screw Shaft 35 Nut 36 Rack 37 Pinion

Claims (1)

[Claims] 1. A front-rear wheel steering vehicle in which rear wheels are steered by movement of a rear-wheel steering rack in a vehicle width direction according to a front-wheel steering angle, an input rotating around a vehicle front-rear direction axis center according to a front-wheel steering angle. A shaft, a screw shaft that is integrated with the input shaft and is eccentric to the input shaft, a nut screwed to the screw shaft, a rack formed on the nut, and a pinion that meshes with the rack, The input shaft is rotatably supported by the vehicle body about its axis, the pinion is movably supported by the vehicle body in the vehicle width direction, and the rack for steering the rear wheels is mounted on the vehicle by the movement of the nut in the vehicle longitudinal direction by the rotation of the screw shaft. The pinion is engaged with the rear wheel steering rack so as to move in the width direction, and the rear wheel steering rack is moved in the vehicle width direction by the movement of the nut in the vehicle width direction due to the whirling of the screw shaft. A rear wheel steering device, wherein the pinion is connected to a nut so as to move.