JPH03186480A - Rear wheel steering device for four-wheel-steered vehicle - Google Patents

Abstract

PURPOSE:To simplify and miniaturize a structure at a low cost by converting the rotation of an input shaft into the rotation of an operation member around the axis of a gear, and transferring the rotation of the operation member to a rear wheel steering bar via a spherical bush and a control rod. CONSTITUTION:A rear wheel steering device 10 has a bevel gear 28 fixed at the rear end section of an input shaft 20 transferred with the steering force of front wheels and a ring gear 33 rotatably supported around the axis of a vertical shaft in a housing 22 and having the tooth face engaged with the bevel gear 28 on the lower face. A ball screw 35 is provided on the ring gear 33 via a support member 37, and it is connected to the motor shaft of an electric motor 38 for controlling the vehicle speed control. A control rod 41 protruded forward perpendicularly to the axial direction of a rear wheel steering bar 21 is inserted into a ball nut 39 screwed to the ball screw 35 via a spherical bush 42, and both ends of the steering bar 21 are connected to knuckle arms of rear wheels via tie rods.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a rear wheel steering device in a four-wheel steering vehicle, and more particularly, to a rear wheel steering device that can control the steering direction and amount of rear wheels for the same amount of front wheel steering. This invention relates to a rear wheel steering device.

In this specification, the left side of FIG. 4 will be referred to as the front, the right side will be referred to as the rear, the lower side will be referred to as the left, and the upper side will be referred to as the right.

Conventional technology As a rear wheel steering device in a four-wheel steering vehicle that can control the steering direction and amount of rear wheels relative to the same amount of front wheel steering, it can move in the direction of an axis extending left and right and can also rotate around the axis. a rear wheel steering rod that steers the rear wheels by moving left and right; a means for adjusting the rotation angle of the rear wheel steering rod around its axis; means for converting the rotation of the connecting shaft that rotates in accordance with the rotation into left and right movement of the rear wheel steering rod,
It is known that the direction and amount of movement of the rear wheel steering rod in the left and right direction is controlled by adjusting the rotation angle of the rear wheel steering rod around the axis (A) (Japanese Unexamined Patent Application Publication No. 1983-1991).
(Refer to Publication No.-163064).

Problem to be Solved by the Invention However, in the case of this rear wheel steering device, the movement of the rear wheel steering rod in the left and right direction is caused by the combination of the circular motions of the two rotating bodies. Moreover, the overall structure is complicated, and the device becomes large and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a rear wheel steering device for a four-wheel steering vehicle that has a simple structure and can be made smaller and less expensive.

Means for Solving the Problems A rear wheel steering device according to the present invention includes an input shaft that is rotated when steering the front wheels, a gear that is connected to the input shaft and that can rotate around a vertical axis, and an axial direction that extends left and right. a rear wheel steering rod that is arranged so as to be movable in the horizontal direction and that steers the rear wheels by moving in the left-right direction; an actuating member having a spherical through hole in the diametrical direction; a means for adjusting the diametrical position of the actuating member; A control rod fixedly provided on the wheel steering rod, and a control rod fitted into the control rod so as to be movable in the axial direction thereof, and fitted into a through hole of the actuating member so as to be rotatable and tiltable in a convenient direction. It consists of a spherical bushing.

Rotation of the working input shaft is converted by the gear into rotation of the actuating member about the axis of the gear. Then, the above rotation of the actuating member is
The signal is transmitted to the rear wheel steering rod via the ball bushing and the control rod, thereby causing the rear wheel steering rod to move in the left and right direction, thereby steering the rear wheels. In addition, by adjusting the position of the gear of the actuating part key by one diameter, the direction and amount of movement of the rear wheel steering rod in the left and right direction can be controlled for the same rotation angle of the car. , the steering direction and steering amount of the rear wheels are controlled in accordance with the same amount of steering of the front wheels.

Embodiment Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 4 shows a schematic configuration of a four-wheel steering vehicle equipped with a rear wheel steering device (10) according to the present invention.

The rear wheel steering device (10) has a connecting shaft (1
1) is connected to the front wheel steering device 02). The connecting shaft (11) is made up of a plurality of shafts connected by a universal joint.
4) is engaged with the rack rod (15) of the front wheel steering device (12). The front wheel steering device (I2) itself is a known one, and both ends of the rack rod (15) are connected to the left and right front wheels.
) via a tie rod (18). And the steering wheel (
By rotating the rack rod (19), the rack rod (15) moves in the left-right direction, and the front wheels (16) are steered. Further, as the rack rod (15) moves in the left-right direction, the connecting shaft 01 rotates by a corresponding amount, and this rotation is transmitted to the input shaft (20) of the rear wheel steering device (1 (1)).

The rear wheel steering device (10) includes a rear wheel steering rod (21) corresponding to the rack rod (<15) of the front wheel steering device (12). This steering rod (21) extends in the left and right direction, and extends in the axial direction (
It is supported by a housing (22) fixed to the vehicle body so as to be movable in the left and right directions.

Both ends of the steering rod (21) are connected to the knuckle arms (24) of the left and right rear wheels (23) via tie rods (25), and the steering rod (21) moves in the left-right direction as described later. As a result, the rear wheels (23) are steered.

As shown in Figures 1 and 2, the rear wheel steering device (10
)'s input shaft (20) extends in the front-rear direction, and rotates and moves in the front-rear direction. It is supported by the housing (22>) by a bearing (27) so that it does not move.

A bevel gear (28) is fixed to the rear end of the input shaft (20>.The rear wheel steering rod (21) is fixed to the rear end of the input shaft (20>).
It is supported so as to be movable in the axial direction by a bush (29) provided at an appropriate location.

Inside the housing (22) are ring teeth mounted via bearings (31) (32) for rotation around a vertical axis!
(33) is supported. Below the ring gear (33)]
A vertical shaft portion (33a) is provided at the center of fIj in a downwardly protruding manner, and a vertical shaft portion (33a) is provided at the center of the upper surface at the upper end.
The supporting body (34) on which 34a) is provided protrudes upward.
2, and both vertical shaft portions (33a) and (34a) are supported by the housing (22) via bearings (31) and (32). The teeth (33b) formed on the lower surface of the ring gear (33>) mesh with the teeth (28a) of the bevel gear (28), and the rotation of the input shaft (20) is controlled by the bevel gear (28).
) to the ring gear (33), and the ring gear (33) rotates by an amount corresponding to the rotation of the input shaft (20) during front wheel steering. Hence the rack of the front wheel steering system (12)! + (15) moves in the left-right direction, the ring gear (33) changes the amount of movement of the rack rod (15) and the front wheel (1
G) rotates by an amount corresponding to the amount of steering. Ring gear (3
Slightly above the ring gear (3), a diametrically extending ball screw (35) on the upper surface of the ring gear (33) is connected to the ring gear (33) via a bearing (36) so that it can rotate around its axis. 33) is supported by a support member (37) fixed to the upper surface. The ball screw (35) has a ring gear (
33) and J: are connected to the motor shaft of an electric motor (38) for vehicle speed response control via a speed reduction device (not shown). Although not shown, the motor (38) is connected to a control device using a microcomputer, and a switch for switching between four-wheel steering and two-wheel steering is connected to the control device. The ball nut (actuating member) (39) of the ball screw (35) is formed with a through hole (40) in the diametrical direction of the ring gear (33), the inner peripheral surface of which is a concave spherical surface. At the appropriate location on the rear wheel steering rod (21),
A control rod (41) having a circular cross section and protruding forward perpendicular to the axial direction ε is integrally provided. A spherical bushing (42) is fitted into the control rod (41) so as to slide in the axial direction of the control rod (41).
is fitted into the through hole (40) of the pole nut (39) so that it can rotate and tilt in any direction. The rotation of the motor shaft of the motor (38) is controlled by a ball screw (35).
), the ball screw (35) rotates, and the pole nut (39) moves along the ball screw (35).

When the motor (38) is in the neutral position, the ball nut I- (39) is in the neutral position on the rotation axis of the ring gear (33), as shown by the chain line (A) in FIG.
38) rotates in the predetermined same phase direction, the ball nut l-
(39) moves to the same phase position shown by the solid line (B) in the same figure, and when the motor (38) rotates to the opposite anti-phase position, the pole nut (39>) moves to the opposite phase position shown by the chain line (C) in the same figure. Move to.

As mentioned above, the input 1dl (20) rotates by an amount corresponding to the amount of steering of the front wheels (16>, that is, the amount of left-right movement of the rack rod (15>).The rotation of the input shaft (20) is caused by the bevel gear ( 28) to the ring gear (33), and the ring tooth! (33) rotates by an amount corresponding to the rotation of the input shaft (20).Therefore, the rack rod (15) of the front wheel steering device (12) rotates from side to side. When moving in the direction, the ball screw (35
) also rotates integrally with the ring gear (33) about a vertical axis. When the rack rod (15) is in the neutral position, the ball screw (35) is in the neutral position extending in the front-rear direction as shown in Figure 2, and when the rack rod (15) moves to the left, the input shaft (20) is indicated by the arrow (X) in Figures 1 and 2.
), the ring gear (35) and ball screw (35) simultaneously rotate clockwise when viewed from the top as shown by arrow (S) in Figure 2, and the rack rod (15) rotates. Conversely, when moving to the left, the input shaft (20)
Rotate the ring gear (3) in the direction shown by the arrow (Y) in the figure.
5) and the ball neck 35) rotate in one direction, counterclockwise when viewed from a plane, as shown by the arrow (T) in FIG. By controlling the position of the pole nut (39) with respect to the ball screw (35) with the motor (38), the direction and amount of movement of the steering rod (21), that is, the movement of the rear wheel (23), is controlled as described below. The steering direction and amount of steering are controlled.

When the ball nut (39) is stopped at the neutral position (A), the axis of the pole nut (39) is aligned with the ring gear (33).
), and even if the ball screw (35) rotates, the steering rod (21) does not move at all.

At this time, the steering rod (21) is in the neutral position, and even if the rack rod (15) moves to the right and the front wheels (16) are steered, the rear wheels (23) are not steered at all. That is,
It becomes a state of two-wheel steering.

When the pole nut (39) moves to the same phase position (B) as shown in Fig. 1, the steering rod (21) moves to the rack rod (15).
), and in-phase steering is performed in which the rear wheels (23) are steered in the same direction as the front wheels (16). With the pole nut (39) in the same phase position (B), the rack rod (15) moves to the left and the ring gear (33) and ball screw (35) become flat as shown in Figure 3 (a). When rotated clockwise when viewed from above, the pole nut (39) receives a leftward force from the ball screw (35), so
The steering rod (21) moves to the left. When the rack rod (15) moves to the right, the steering rod (21>) moves to the right.

When the pole nut (39) rotates to the opposite phase position (C) as shown in Figure 3(b), the steering rod (21> moves in the opposite direction to the rack rod (15>), and the rear wheels (23) Front wheel (i
6) is performed in the opposite direction.

With the pole nut (39) in the opposite phase position (C), the rack rod (15) moves to the left and the ring gear (33) and ball screw (35) become flat as shown in Figure 3(b). When viewed from above and rotated clockwise, the pole nut (3
9) receives a rightward force by the ball screw (35), so the steering rod (21) moves to the right. Rack rod (15
) moves to the right, conversely, the steering rod (21) moves to the left.

If the distance from the neutral position of the pole nut (39) with respect to the ball screw (35) is constant, the amount of steering of the front wheel (16>, that is, the ring gear (33>) and the ball screw (35)
) The greater the rotation angle of the steering rod (21>), the greater the amount of movement of the steering rod (21>.Also, even if the amount of steering of the front wheels (16), that is, the rotation angle of the ring gear (33) and ball screw (35) is the same, the rotation angle of the steering rod ( 21), that is, the amount of movement of the rear wheel (2
3) The amount of steering is determined when the pole nut <39> is at the neutral position (A
), the smaller it is, and it becomes larger as the distance from the neutral position of the pole nut (39) with respect to the ball screw (35>) increases.

The control of the steering direction and amount of steering of the rear wheels as described above is automatically performed by the control device based on various conditions of the vehicle. For example, at low speeds and when reversing, anti-phase steering is performed, and at high speeds, in-phase steering is performed. During cornering, anti-phase steering is performed at the entrance, and in-phase steering is performed from the middle. When changing driving lanes, anti-phase steering is suddenly changed to in-phase steering. In addition, the rear wheel (23) is used for steering the front wheel (I6).
It is also possible to slightly delay the steering of the vehicle.

Furthermore, if the changeover switch of the control device is switched to the two-wheel steering side, the pole nut (39) is fixed at the neutral position (A), and the rear wheels are not steered.

In the case of the above device, the steering wheel (19) and the steering rod (21) of the rear wheel steering device (10) are mechanically connected, so safety is high.

Effects of the Invention According to the rear wheel steering device of the present invention, as described above, the steering direction and amount of rear wheel steering can be controlled for the same amount of front wheel steering, and the structure is simple, compact, and inexpensive. It is possible to In particular, rotation of the input shaft is translated by a gear rotatable about a vertical axis into a rotation about the axis of the gear of an actuating member, which is movable over one diameter of the gear, and said rotation of the actuating member is caused by a control rod is transmitted to the rear wheel steering rod via
This causes the rear wheel steering rod to move in the left-right direction and the rear wheels are steered, so that the vertical dimension of the space required for installing the rear wheel steering device can be reduced.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view of the main parts of a rear wheel steering device showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view along the line ■-■ in Fig. 1 with a part omitted, and Fig. 3 is the same. A diagram equivalent to Figure 2 showing the phase steering state and anti-phase steering state, respectively, and Figure 4 is 4.
FIG. 1 is a schematic configuration diagram of a wheel-steering vehicle. (lO)...Rear wheel steering device, (1B>...Front wheel, (
20>...Input shaft, (21)...Rear wheel steering rod, (2
3)...Rear wheel, (33)...Ring gear, (39)
... Pole nut (operating member), (40) ... Through hole, (41> ... Control rod, (42> ... Spherical bushing.)

Claims (1)

[Scope of Claims] An input shaft that is rotated when front wheels are steered; a gear that is connected to the input shaft and that can rotate around a vertical axis; a rear wheel steering rod that steers the rear wheels by moving in the direction; and a diametrical through hole provided in the gear so as to be able to move one diameter above the rod and having a concave spherical inner circumferential surface. means for adjusting the diametrical position of the operating member; and a control fixedly provided on the rear wheel steering rod so as to project forward at right angles to the rear wheel steering rod. A four-wheel steering vehicle comprising: a rod; and a spherical bushing fitted into the control rod so as to be movable in its axial direction and fitted into a through hole of an actuating member so as to be rotatable and tiltable in any direction. Rear wheel steering device.