JPH0325077A - Rear wheel steering gear for four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To set a rear wheel steering characteristic against the front wheel steering quantity optionally and easily by constructing the title device in such way as to convert the rotation of an input shaft into the motion of a cam body and move a rear wheel steering rod axially by the motion of the cam body, thus performing rear wheel steering. CONSTITUTION:The rotation of an input shaft 22 is converted into the motion of a cam body 27 within the face intersecting the axial direction of a rear wheel steering rod 20 by a converting means 25. A cam follower 37 provided fixedly at the rear wheel steering rod 20 moves in the axial direction of the rear wheel steering rod 20 by the motion of the cam body 27. The axial movement of the rear wheel steering rod 20 is generated by the movement of the cam follower 37, thus performing rear wheel steering. A rear wheel steering characteristic against the front wheel steering quantity can be thereby set optionally and easily by changing the shape of the cam body 27.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a rear wheel steering device for a four-wheel steering vehicle.

In this specification, the left side of FIG. 11 will be referred to as the front, the right side of the same figure will be referred to as the rear, the lower side of the figure will be referred to as the left, and the upper side of the figure will be referred to as the right.

Prior Art and Problems of the Invention As a rear wheel steering device for a four-wheel steering vehicle, a rear wheel steering device is arranged so that it can move in the direction of an axis extending left and right as well as rotate around the axis, and steers the rear wheels by moving in the left and right direction. a means for adjusting the rotation angle of the rear wheel steering rod around its axis; and a means for adjusting the rotation angle of the rear wheel steering rod around its axis; A device is known in which the direction and amount of movement of the rear wheel steering rod in the left and right direction are controlled by adjusting the rotation angle of the rear wheel steering rod around its axis. (See Japanese Unexamined Patent Publication No. 163064/1983).

However, in the case of this rear wheel steering device, the left-right movement of the rear wheel steering rod is caused by a combination of circular motions of two rotating bodies, and the steering characteristic of the rear wheels with respect to the amount of steering of the front wheels becomes a constant sine curve. It is difficult to obtain arbitrary steering characteristics.

An object of the present invention is to solve the above problems and provide a rear wheel steering device for a four-wheel steering vehicle that has a high degree of freedom and can arbitrarily set the steering characteristics of the rear wheels relative to the amount of steering of the front wheels.

Means for Solving the Problems A rear wheel steering device in a four-wheel steering vehicle according to the present invention has rear wheels arranged so as to be movable in an axial direction extending left and right, and which steers the rear wheels by moving in the left and right direction. a steering rod; a cam body that moves in a plane intersecting the axial direction of the rear wheel steering rod; a means for converting rotation of the input shaft into the movement of the cam body; and a means fixedly provided on the rear wheel steering rod. , and a cam follower that moves in the axial direction of the rear wheel steering rod by the movement of the cam body.

The rotation of the operation input shaft is changed to the flI of the rear wheel steering rod by the conversion means.
This is converted into a movement of the cam body in a plane intersecting the I-line direction. Due to the above movement of the cam body, the cam follower fixedly provided on the rear wheel steering rod moves in the axial direction of the rear wheel steering rod,
This movement causes axial movement of the rear wheel steering rod,
The rear wheels are steered. Therefore, by changing the shape of the cam body, the steering characteristics of the rear wheels relative to the amount of steering of the front wheels can be arbitrarily and easily set.

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

The same parts and parts are denoted by the same reference numerals throughout the drawings, and their explanation will be omitted.

FIG. 11 shows a schematic configuration of a four-wheel steering vehicle equipped with a rear wheel steering device according to the present invention. The rear wheel steering device is connected to the front wheel steering device R (2) by a connecting shaft (1) extending in the front-rear direction. The connecting sleeve (1) is made up of a plurality of shafts connected by a universal joint, and includes a binion shaft (3) at the front end.
The binion (4) of the rack rod (5) of the front wheel steering system (2)
) are meshed with each other. Both ends of the rack rod (5) are the knuckle arms of the left and right front wheels (6). (7> Tie rod (
8). Then, by rotating the steering wheel (9), the rack rod (5)
moves in the left-right direction, and the front wheels (6) are steered. In addition, as the rack rod (5) moves in the left-right direction, the connecting shaft (l) rotates by a corresponding amount, and this rotation is transmitted to the input shaft of the rear wheel steering device, and the input shaft is connected to the front wheel (8). The rear wheel steering device is equipped with a rear wheel steering rod (20) corresponding to the rack rod (5) of the front wheel steering device (2). ) extends in the left-right direction and is supported by a housing (2l) fixed to the vehicle body so as to be movable in the axial direction (left-right direction).

Both ends of the rear wheel steering rod (20) are connected to the left and right rear wheels (11).
The rear wheel steering rod (20) is connected to the knuckle arm (12) of the vehicle via a tie rod (13), and the rear wheel (l1) is steered by moving the rear wheel steering rod (20) in the left and right direction.

Hereinafter, a plurality of embodiments of the rear wheel steering device will be described separately.

Example 1 This example is shown in FIGS. 1-3. In Figures 1 and 2, the input shaft (22) of the rear wheel steering system is
The axis is oriented in the left-right direction and is perpendicular to the connecting shaft (1), and a predetermined length from the left end is the housing (2l).
) and is supported by bearings (23>(24) provided at appropriate locations in the housing (21) so that it does not move in the axial direction but can rotate around the axis.

A worm (25) is installed between both bearings (23) and (24) on the input shaft (22).A worm (25) is installed in the housing (21) with an inclined surface that meshes with the teeth (25a) of the worm (25). (30a> and warm (25)
A rack (30) is disposed that moves in the front-back direction as the rack rotates.

Support shafts (28) extending in the front and back direction are fixed to both front and rear end surfaces of the rack (30), and these shafts (28)
8) is supported movably in the axial direction by bushes (29) provided at appropriate locations on the housing (2l). At the bottom of both left and right sides of the rack (30
) is made into a cam body (27). Rear wheel steering rod (20
) is supported via splines (31, 32) at appropriate locations on the housing (21) so that it can move axially but not rotate. The right side of the rear wheel steering rod (20>) is supported via a bush (33) at a suitable location in the housing (2l) so that it can move in the axial direction but not rotate. 20)
, there are two projecting upwards at a predetermined interval in the left and right direction.
Two shaft portions (34) are integrally provided. Both shaft portions (
84) includes rollers (3) that can each rotate around their axes.
5> is attached via a bearing (36).

These rollers (35>) are connected to the cam surface (
The cam follower (37) engages with the cam follower (26).

When the input shaft (22) rotates, the worm (25>) rotates, and the cam body (27) moves in either the front or back direction due to the meshing of the teeth (25a) of the worm (25) with the teeth (30a) of the rack (30). As a result, the cam follower (3
7) moves in either the left or right direction along the cam surface (26), and the rear wheel steering rod (20) also moves in the left or right direction to steer the rear wheel (ii).

The shape of the cam surface (26) of the cam body (27>) is similar to that of the front wheel (6).
The steering angle ratio of the rear wheel (11) and the rotation angle of the input shaft (22) are shaped so that the relationship is as shown by the solid line (A) in FIG. i.e. front wheel (6)
When the steering wheel (9) starts to turn from the neutral position shown in Fig. 1, where neither the front wheels nor the rear wheels (l1) are steered, the human power shaft (22) also starts to rotate. Both the front and rear wheels (8) and (11) are steered in the same phase so that the steering angle ratio between the rear wheels (6) and the rear wheels (11) is positive.

At this time, the steering angle of the rear wheel (1l) increases as the rotation angle increases until the rotation angle of the human power shaft (22) reaches a predetermined angle (X).
If it exceeds , it becomes smaller as the rotation angle of the input shaft (22) becomes larger. Further, when the rotation angle of the input shaft (22) reaches a predetermined angle (Y), the steering angle ratio becomes O, and the steering angle of the rear wheels (l1) becomes zero. The amount of rotation of the steering wheel <9> increases and the input ITo (22)
When the rotational angular force (angle (Y)) is exceeded, the steering angle ratio between the front wheels (6) and the rear wheels (it) becomes negative, and the front wheels (6) and rear wheels (11) are steered in opposite phase. , as the rotation angle force of the input shaft (22) increases, the steering angle of the rear wheels (l1) also increases.

Therefore, when changing lanes during high-speed driving, which requires a small rotation angle of the steering wheel (9), the front wheels (6) and rear wheels (11) are steered in the same phase, allowing lane changes to be made safely and smoothly. 1; is carried out.In the case of a low-speed car crash or U-turn where the rotation angle of the steering wheel (9) becomes large, the front wheels (6) and rear wheels (1l)
and force {The turning radius of the vehicle becomes smaller due to anti-phase steering,
One wheel is easily maneuvered.

The steering angle ratio of the front wheels (6) and rear wheels (11) and the human power axis (
The relationship with the rotation angle of 22) can be arbitrarily set by changing the J-cedar shape of the cam (26).

For example, the relationship shown by the chain line (B) in Figure 3 is such that only the front wheels (8) are steered until the rotation angle of the human power shaft (22) reaches a force (Y); In order to obtain a relationship in which the angular ratio is negative, the shape of the cam surface (2B) is such that the middle part of its length extends over a predetermined length in the front and rear direction, as shown by the chain line (C) in FIG. Just keep it straight. Then, while the cam follower (37) is engaged with the chain line (C), the cam follower (37)
37) does not move left or right, and the rear wheel (l1)
is not steered.

Example 2 This example is shown in FIGS. 4 and 5. In both figures, the support shaft (40) extending in the front-rear direction passes through the cam body (27>), and the cam body (27) is connected to the support shaft (40).
0) in the front-back direction.

Both ends of the support shaft (40) are fixed to the housing (2l).

Example 3 This example is shown in FIG. In the same figure,
A cam groove (4l) extending in the front-rear direction on the lower surface of the rack (30)
) is formed, and both side surfaces of the cam groove (41) serve as cam surfaces (26) that are displaced in the left-right direction. The rear wheel steering rod (20) is integrally provided with one shaft portion (42) that projects upward. A roller (43) that can rotate around the axis is attached to the shaft (42) via a bearing (44>.The roller (43) is attached to the cam follower (37).
), and is inserted into the cam plate (41) and engaged with the two cam surfaces (2B).

Example 4 This example is shown in FIGS. 7 and 8. In both figures, the input shaft (45) of the rear wheel steering device has an axis facing in the front-rear direction, and a predetermined length portion from the rear end is pushed into the housing (2l).
It is supported by bearings (46) and (47) provided at appropriate locations on the shaft so that it does not move in the axial direction but can rotate around the axis. A ball screw (48) and its nut (49) are provided between both bearings (4B) (47) on the input shaft (45>).Cams displacing in the left-right direction are mounted on both left and right sides of the nut (49). The surface (2B) is shaped, and this nut (49) is a cam body (27).The two left and right cam followers (37) fixedly provided on the rear wheel steering rod (20) are each a cam body. It engages with the cam surfaces (2B) on both left and right sides of the body (27).

Example 5 This embodiment is shown in FIGS. 9 and 10.

In both figures, the input shaft (22) of the rear wheel steering device is inserted a predetermined length from its left end into the front part of the housing (21), and is prevented from moving in the axial direction by the bearings (54) (24). It is supported so that it can rotate around an axis. In the center of the front and rear inside the housing (2l), there are teeth (5) that mesh with the il! (25a) of the worm (25) at the front end.
A sector gear (50) having 0a) is arranged. Support shafts (5l) extending in the left-right direction are integrally provided on both left and right side surfaces of the sector gear (50>).This support shaft (5l) is connected to a bearing provided at an appropriate location on the housing (2l>). (52) <58) so as to be rotatable around the axis.
A cam surface (2B) that is displaceable in the left and right direction is formed on the rear end of both left and right sides of the gear (50) on an arc centered on the sleeve (51) when viewed from the left or right. is the cam body (
27〉. Two left and right cam followers (37) fixedly provided on the rear wheel steering rod (20>) engage with cam surfaces (26) on both left and right sides of the cam body (27), respectively.

As the input shaft (22) rotates, the worm (25)
rotates, thereby causing the sector gear (50> to rotate around the axis of the support shaft (51). As a result, the cam follower (87>) moves in either the left or right direction along the cam surface (26), and the rear wheel The steering rod (2o) also moves left or right to steer the rear wheels (11).

EFFECTS OF THE INVENTION According to the rear wheel steering device of this invention, as described above, the rotation of the input shaft is converted into the movement of the cam body, and the movement of the cam body moves the rear wheel steering rod in the axial direction. The wheels are steered.

Therefore, by changing the shape of the cam body, the steering characteristics of the rear wheels relative to the amount of steering of the front wheels can be arbitrarily and easily set.

[Brief explanation of drawings]

Embodiment 1 of the present invention is shown in FIGS. 1 to 3. FIG. 1 is a horizontal sectional view of the rear wheel steering device, FIG. 2 is a sectional view along the line and a graph showing the relationship between the steering angle ratio of the rear wheels and the rotation angle of the input shaft. 4 and 5 show a second embodiment of the present invention, FIG. 4 is a horizontal sectional view of the rear wheel steering device, and FIG. 5 is a sectional view taken along the line v--v in FIG. 4. FIG. 6 is a diagram corresponding to FIG. 2 showing an implementation fs3 of the present invention. FIG. 7 and FIG. 8 are embodiment 4 of this invention.
FIG. 7 is a horizontal sectional view of the rear wheel steering device, and FIG. 8 is a sectional view taken along the line ■-■ in FIG. 7. Embodiment 5 of the present invention is shown in FIGS. 9 and 10, in which FIG. 9 is a horizontal sectional view of the rear wheel steering device, and FIG. 10 is a sectional view taken along the line X--X in FIG. 9. FIG. 11 is a schematic diagram of a four-wheel steering vehicle equipped with a rear wheel steering device according to the present invention. (2>...Front wheel steering device, (20)...Rear wheel steering rod, (22) (45)...Input shaft, (25)...Worm, (27)...Cam body, (30) ... rack,
(37)...Cam follower, (48)...Ball screw, (49>...Nut, (50)...Sector gear.

Claims (1)

[Scope of Claims] A rear wheel steering rod that is arranged to be movable in the axial direction extending left and right and that steers the rear wheels by moving in the left and right direction, and a surface that intersects with the axial direction of the rear wheel steering rod. a cam body that moves within the cam body; a means for converting the rotation of the input shaft into the movement of the cam body; A rear wheel steering device for a four-wheel steering vehicle, which is equipped with a cam follower that moves.