JPH04287773A - Rear wheel steering device - Google Patents

Abstract

PURPOSE:To improve the action input transfer efficiency by rotating the first gear via an input shaft in response to the front wheel steering angle, rotating and swaying the second gear, and moving a rear wheel steering rack in the vehicle width direction by the rotation and sway in a rear wheel steering device for a vehicle. CONSTITUTION:When the first gear 40 is rotated in the direction of an arrow A1, for example, via an input shaft 9 in response to the front wheel steering angle, the second gear 45 engaged with it is rotated in the direction of an arrow B1. A rear wheel steering rack 12 engaged with the second gear 45 is moved in the direction of an arrow E1. While the front wheel steering angle is small, the second gear 45 is swayably supported on the input shaft 9 by a pair of the front and rear arms 46, 47, thus the second gear 45 is not rotated, and the rotation center 45A is swayed toward a position D1. The rear wheel steering rack 12 is moved in the direction E2 by this sway. The shift quantity in the direction E2 is set larger than the shift quantity in the direction E1.

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 device for a front and rear wheel steered vehicle in which the rear wheels are steered in accordance with the front wheel steering angle.

0002

2. Description of the Related Art In a steering angle sensitive front and rear wheel steered vehicle, the rear wheels are required to make complex movements in response to the front wheel steering angle. For example, the rear wheel steering device disclosed in Japanese Patent Publication No. 60-44186 includes a cam that moves according to the front wheel steering angle and a cam follower provided on the rear wheel steering shaft, and the movement of the cam is controlled by the cam follower. This movement of the rear wheel steering shaft in the vehicle width direction is used to steer the rear wheels.

[0003] Furthermore, the rear wheel steering device disclosed in Japanese Utility Model Publication No. 60-50078 uses a crank mechanism and a planetary gear mechanism to control the rotation of an input shaft according to the front wheel steering angle to a rear wheel steering rack. The rear wheels are steered by moving the rear wheel steering rack in the vehicle width direction.

0004

[Problems to be Solved by the Invention] In the conventional system that directly transmits steering input to the rear wheel steering shaft using a cam and a cam follower, the transmission resistance is large and the steering cannot be performed smoothly. .

[0005] In addition, there is a device that transmits steering operation input to a rear wheel steering rack using a crank mechanism and a planetary gear mechanism.
The structure is extremely complicated and impractical, and the transmission efficiency of steering input is also extremely low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rear wheel steering system that can solve the problems of the prior art described above.

[0007]

[Means for Solving the Problems] The present invention is characterized in that a front wheel steering vehicle in which the rear wheels are steered by moving a rear wheel steering rack in the vehicle width direction in accordance with the front wheel steering angle. A first gear that rotates around an axis in the longitudinal direction of the vehicle according to the angle, and a second gear that meshes with the first gear are provided, the first gear is supported by a fixed member, and the second gear rotates in the longitudinal direction of the vehicle. The second gear is rotatable around an axis and swingable around the rotation axis of the first gear, and is engaged with a fixed member via a cam so that the second gear rotates and swings as the first gear rotates. The second gear and the rear wheel steering rack are meshed with each other such that the rear wheel steering rack moves in the vehicle width direction in conjunction with the rotation and rocking of the second gear.

Further, it is preferable that the rear wheel steering rack is pressed against the second gear by an elastic member.

[0009]

[Operation] According to the structure of the present invention, when the first gear rotates due to a steering operation input, the second gear rotates and the first gear rotates.
It oscillates around the rotation axis of the gear. The rotation of the second gear moves the rear wheel steering rack in the vehicle width direction, and the swinging of the second gear also moves the rear wheel steering rack in the vehicle width direction.

[0010] Thereby, a steering operation input is transmitted from the first gear to the rear wheel steering rack via the second gear.

[0011] Furthermore, the direction and magnitude of the swing of the second gear with respect to rotation are determined depending on the shape of the cam. Thereby, the direction and magnitude of movement of the rear wheel steering rack in the vehicle width direction are determined according to the cam shape.

Furthermore, when the second gear swings, the amount of engagement between the second gear and the rear wheel steering rack tends to change. By pressing the rear wheel steering rack against the second gear by the elastic member, it is possible to eliminate changes in the amount of engagement thereof.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 shows a schematic configuration of a front and rear wheel steered vehicle that controls the rear wheel steering angle in accordance with 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 that meshes with the rack 4 is interlocked with a handle 6. As a result, when the handle 6 is operated, the front wheel steering member 2 moves in the vehicle width direction, and the front wheels 1 are steered.

Further, a rack (not shown) is formed on the front wheel steering member 2 in addition to the rack 4, and the front end of an input shaft 9 of a rear wheel steering device 8 is attached to a pinion 7 that meshes with this rack. . The input shaft 9 is rotatably supported by the vehicle body via a bearing 23 about an axis in the longitudinal direction of the vehicle. As a result, when the front wheel steering member 2 moves in the vehicle width direction due to a steering input, the pinion 7 rotates, and the input shaft 9 rotates by an amount corresponding to the front wheel steering angle.

The rear wheel steering device 8 includes a rear wheel steering rack 12.
A tie rod 1 is attached to each end of this rear wheel steering rack 12.
The vehicle is provided with left and right rear wheels 10 that are connected to each other via 1.

The rear wheel steering rack 12 is supported by the 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 movement of the rear wheel steering rack 12 in the vehicle width direction.

As shown in FIG. 2, the conversion mechanism 13 includes a housing (fixing member) 30 that is attached to the vehicle body. The rear end of the input shaft 9 is supported by the housing 30 via bearings 31 and 32. Note that a dust seal 33 is interposed between the input shaft 9 and the housing 30.

A first gear 40 is attached to the rear end of the input shaft 9. The rotation shaft 40A of the first gear 40 is coaxial with the rotation shaft of the input shaft 9.

A second gear 45 that meshes with the first gear 40 and the rear wheel steering rack 12 is provided inside the housing 30.
is provided. The rotation axis of the second gear 45 is parallel to the first gear 40. In this embodiment, the gears 40 and 45 and the rack 12 are helical.

The second gear 45 is supported by the input shaft 9 via a pair of front and rear arms 46 and 47. that arm 4
6 and 47 are attached to the input shaft 9 so as to be swingable about the axis of the input shaft 9. Further, the second gear 45 is connected to the arm 46
, 47 has a bush 48 rotatable about the longitudinal axis of the vehicle.
, 49. As a result, the second gear 45 is rotatable around the axis in the longitudinal direction of the vehicle, and the second gear 45 is rotatable around the axis in the vehicle longitudinal direction.
It is possible to swing around a rotation axis 40A.

The second gear 45 is rotated so that the rotation of the first gear 40 causes the second gear 45 to rotate and swing.
is engaged with the housing 30 via a cam 50. This cam 50 has a cam follower 51 as shown in FIG.
and a cam groove 52. The cam follower 51
has a cylindrical shape that protrudes rearward from a flange 45 a formed at the rear end of the second gear 45 . The cam groove 52 is
It is formed on a plate 53 fixed to the inner surface of the housing 30. The shape of the cam groove 52 is such that while the front wheel steering angle is small, the second gear 45 rotates and swings, and when the front wheel steering angle exceeds a certain angle, the second gear only rotates and does not swing. It is considered a thing.

That is, in FIG. 1, the cam follower 5
1 is at the position indicated by N in the figure when the front wheel steering angle is 0. When the handle 6 is operated left or right from this state, the first gear 40 rotates in the direction of arrow A1 in the figure, the second gear 45 rotates in the direction of arrow B1 in the figure, and the cam follower 51 rotates in the direction of arrow B1 in the figure.
is guided by the cam groove 52 and moves to the position indicated by C1 in the figure. By this movement of the cam follower 51, the second gear 4
The rotation center 45A of No. 5 moves to the position indicated by D1 in the figure. As a result, the second gear 45 rotates and swings. When the first gear 40 further rotates in the direction of arrow A1 from this state, the cam follower 51 moves from the C1 position to the F1 position. Between this C1 position and F1 position, the cam groove 5
2 is located on the circumference centered on the D1 position. Thereby, when the cam follower 51 moves from the C1 position to the F1 position, the second gear 45 only rotates.

Furthermore, when the handle 6 is operated to the left or right with the cam follower 51 in the N position, the first gear 40 rotates in the direction of arrow A2 in the figure, and the second gear 45 rotates in the direction of arrow B2 in the figure. However, the cam follower 51 is connected to the cam groove 5.
2 and moves to the position shown by C2 in the figure. Due to this movement of the cam follower 51, the rotation center 45A of the second gear 45 moves to the position indicated by D2 in the figure. As a result, the second gear 45 rotates and swings. When the first gear 40 further rotates in the direction of arrow A2 from this state, the cam follower 51 moves from the C2 position to the F2 position. Between the C2 position and the F2 position, the cam groove 52 is
It is assumed that it is located on the circumference centered on the 2nd position. Thereby, when the cam follower 51 moves from the C2 position to the F2 position, the second gear 45 only rotates.

The second gear 45 and the rear wheel steering rack 12 are engaged with each other so that the rear wheel steering rack 12 moves in the vehicle width direction in conjunction with the rotation and rocking of the second gear 45. . In this embodiment, the rear wheel steering rack passes through the housing 30 and is disposed below the second gear 45.

When the first gear 40 rotates in the A1 direction, the rear wheel steering rack 12 moves in the arrow E1 direction due to the rotation of the second gear 45 in the arrow B1 direction. Further, while the front wheel steering angle is small, the rotation center 45A of the second gear 45 swings toward the D1 position, and the swing of the second gear 45 causes the rear wheel steering rack 12 to move in the direction of the arrow E2. . E2 of the rear wheel steering rack 12 due to the swinging of the second gear 45
The amount of movement in the E1 direction is greater than the amount of movement of the rear wheel steering rack 12 in the E1 direction due to the rotation of the second gear 45. As a result, the rear wheel steering rack 12 moves in the E2 direction while the front wheel steering angle is small. Then, when the front wheel steering angle reaches a certain level or more, the second gear 45 does not swing but only rotates, so the rear wheel steering member 12 moves in the E1 direction.

When the first gear 40 rotates in the direction A2,
Contrary to the case of rotation in the A1 direction, the rear wheel steering rack 12 moves in the E1 direction while the front wheel steering angle is small, and when the front wheel steering angle becomes large, the rear wheel steering rack 12 moves in the E2 direction.

As a result, as shown in FIG. 4, while the front wheel steering angle is small, the front wheels 1 and the rear wheels 10 are in an in-phase state where they are steered in the same direction, and when the front wheel steering angle is large, the front wheels 1 and 10 are steered in the same direction.
and the rear wheels 10 are steered in opposite directions, resulting in a reverse phase state.

Furthermore, the rear wheel steering rack 12 is connected to the second gear 4.
A compression coil spring (elastic member) 60 is provided to press against the spring 5 . That is, the through hole 3 is formed in the lower part of the housing 30.
0a is formed, and a cylindrical support 61 is formed in this through hole 30a.
is inserted so that it can be moved up and down. The upper end of this support 61 is a recessed portion 61a that follows the shape of the rack 12. Then, the adjusting screw 6 is inserted into the through hole 30a of the housing 30.
2 is screwed in, and a compression coil spring 60 is interposed between the adjustment screw 62 and the support 61. As a result, when the rack 12 is pushed by the compression coil spring 60 via the support 61, the rack 12 is bent upward and pressed against the second gear 45. Furthermore, by adjusting the amount by which the adjusting screw 62 is screwed into the housing 30, the pressing force thereof can be adjusted. Note that a lock nut 63 is screwed onto the adjustment screw 62.

[0030] As a result, the second gear 45 becomes the first gear 40.
When the second gear 45 swings around the rotating shaft 40A, the second gear 45
This prevents the amount of engagement between the rear wheel steering rack 12 from changing and maintains smooth engagement.

According to the above configuration, since the steering operation input corresponding to the front wheel steering angle is transmitted from the first gear 40 to the rear wheel steering rack 12 via the second gear 45, the steering operation input is transmitted only via the cam. The transmission resistance is smaller than those that transmit directional operation input. Furthermore, the structure is simpler and more practical than a system that transmits steering input through a planetary gear mechanism and a crank mechanism, and the transmission efficiency can be improved.

Note that the present invention is not limited to the above embodiments.

For example, in the above embodiment, the cam follower of the cam 50 is provided on the second gear 45, and the cam groove 52 is formed on the plate 53 attached to the housing 30. Housing the follower 3
It may be set to 0.

Further, in the above embodiment, the second gear 45 is supported by the input shaft 9 via the arms 46 and 47, but it may also be supported by the housing 30. It is only necessary to swing the first gear 40 around the rotating shaft 40A.

Further, in the above embodiment, the first gear 40 is supported by the housing 30 attached to the vehicle body, but the first gear 40 is not limited to this, and may be supported by a fixed member. Further, the second gear 45 may also be engaged with the fixed member via the cam 50.

Further, the shape of the cam 50 is not limited to the above-mentioned embodiment, and may be any shape that corresponds to the required steering characteristics.

Further, as shown in FIG. 5, a pair of cam followers 51a and 51b are provided on the flange 45a of the second gear 45, and each cam follower 51a is provided on the plate 53.
, 51b may be provided with a pair of cam grooves 52a, 52b. In this case, when the front wheel 1 is steered left or right, the second gear 45 rotates and swings due to the engagement of one cam follower 51b and one cam groove 52a, and the front wheel 1 When the vehicle is steered to the left or right, the second gear 45 rotates and swings as the other cam follower 51b and the other cam groove 52b engage with each other. The rest is similar to the above embodiment, and the same parts are designated by the same reference numerals.

Further, in the above embodiment, the input shaft 9 and the first gear 40 are directly connected, but the rotation of the input shaft 9 is transmitted to the first gear 40 via the gear 70 as shown in FIG. The point is that the first gear 40 only needs to rotate around the axis in the longitudinal direction of the vehicle in accordance with the front wheel steering angle. The rest is the same as in the above embodiment, and the same parts are designated by the same reference numerals.

[0039]

According to the rear wheel steering device according to the present invention, a steering operation input according to the front wheel steering angle is transmitted from the first gear to the rear wheel steering rack via the second gear. Since the rear wheels are steered by moving the rack in the vehicle width direction, the transmission resistance of the steering input can be reduced compared to a system that transmits the steering input using only a cam. Further, since it is only necessary to provide a second gear between the first gear and the rear wheel steering rack and a cam between the second gear and the fixed member, it is possible to use a planetary gear mechanism and a cam mechanism. It has a simpler structure than the conventional one, is practical, and has good transmission efficiency of steering operation input.

Furthermore, since the rear wheel steering rack is pressed against the second gear by the elastic member, it is possible to achieve smooth engagement between the second gear and the rack.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of a rear wheel steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a rear wheel steering device according to an embodiment of the present invention.

[
FIG. 3 is an explanatory diagram of the configuration of a front and rear wheel steered vehicle according to an embodiment of the present invention

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

FIG. 5 is an explanatory diagram of a cam according to a different embodiment of the present invention.

[
FIG. 6 is a sectional view of a rear wheel steering device according to a different embodiment of the present invention.

[Explanation of symbols]

12 Rear wheel steering rack 30 Housing (fixed member) 40 1st gear 45 2nd gear 50 cam 60 Compression coil spring (elastic member)

Claims (2)

[Claims] Claim 1: In a front and rear wheel steered vehicle in which the rear wheels are steered by moving a rear wheel steering rack in the vehicle width direction in accordance with the front wheel steering angle, a front wheel steering rack that rotates about the longitudinal axis of the vehicle in accordance with the front wheel steering angle is provided. 1 gear and a 2nd gear that meshes with this 1st gear.
A gear is provided, the first gear of which is supported by a fixed member, the second gear of which is rotatable around an axis in the longitudinal direction of the vehicle and swingable around an axis of rotation of the first gear, The second gear is engaged with the fixed member via a cam so that the second gear rotates and swings.
A rear wheel steering device characterized in that a second gear and a rear wheel steering rack are engaged with each other so that the rear wheel steering rack moves in the vehicle width direction in conjunction with rotation and rocking of the gear. 2. The rear wheel steering device according to claim 1, wherein the rear wheel steering rack is pressed against the second gear by an elastic member.