JPS62238170A - Front and rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To reduce the driving force required for adjustment of a steering angle and improve the responsibility by providing a drive for moving a slide member at right angles to an output member, and controlling actuation of the driven in response to vehicle speed. CONSTITUTION:A rear wheel steering mechanism 21 is composed of a rotary input shaft 22, a main shaft 24, a slide member 31 and a drive 41, and the input shaft 22 is formed at the rear end thereof with a pinion 23, and the main shaft 24 is provided directly above the pinion 23, and an internal gear 25 is erected at the rear portion of the main shaft 24, and an arm 26 is formed integrally with the rear surface of the gear 25. The output member 27 is rearwardly spaced from the arm 26, and the slide member 31 is provided between a guide 28 and the arm 26. Actuation of the drive 41 causes a center piece 34 to be moved at right angles to the output member 27 and the slide member 31 to be moved at right angles thereto, so that the steering angle ratio of the rear wheel to the front wheel may be controlled in response to vehicle speed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a front and rear wheel steering system for a vehicle.

(Conventional technology) Front and rear wheel steering in which the rear wheels are steered together with the front wheels (hereinafter referred to as 4WS)
(abbreviated as ) system, λ and t, special public service 1980-4
As is well known from No. 4185, steering the rear wheels in the same direction as the front wheels at high speeds improves steering response, and steering the rear wheels in the opposite direction to the front wheels at low speeds improves the turning radius. It can be made smaller to improve maneuverability.

In this way, 4W changes the front and rear wheel steering angle ratio as a function of vehicle speed.
The S system uses an independent drive source such as an electric motor or hydraulic system separate from the front wheel steering mechanism to steer the rear wheels based on the front wheel steering angle and vehicle speed information, and the other uses the front wheel steering mechanism and rear wheel steering. In addition to mechanically connecting the rear wheel steering mechanism to the rear wheel steering mechanism, a drive device for adjusting the rear wheel steering angle according to the vehicle speed is further attached to the rear wheel steering mechanism (for example, Japanese Patent Application Laid-open Nos. 59-211383 and 59-211364). etc.).

(Problem to be solved by the invention) By the way, the former 4WS system requires an independent drive source to steer the rear wheels, which increases the weight and space, and also increases the steering angle and vehicle speed of the front and rear wheels. It is difficult to say that this method is the best in terms of responsiveness because it requires momentary detection of the steering angle ratio and vehicle speed.

On the other hand, in the latter 4WS system, the front and rear wheel steering mechanisms are mechanically connected, so the increase in steering force associated with steering the rear wheels is due to an increase in the capacity of the power assist device used in the front wheel steering mechanism. It is lighter than the former,
It takes up less space, and since the rear wheel steering angle is adjusted according to the vehicle speed in response to the front wheel steering angle, it also has excellent responsiveness. However, in the past, the output member of the rear wheel steering mechanism itself was moved up and down to adjust the rear wheel steering angle, which required a relatively large driving force.

(Means for solving the problem) In order to solve the problem, the present invention rotates the input shaft (22) of the rear wheel steering am with the rotation extracted from the front wheel steering mechanism, and the input shaft (22) 4WS of a vehicle that converts the rotation of the projecting member (27) into left-right movement to steer the rear wheels as well.
In the device, a main shaft (2) connected to the input shaft (22) is provided.
0 and a diametrical arm (2B) on the main shaft (24).
is integrally provided, while a guide (28) in the orthogonal direction is integrally provided with the output member (27), and between the arm (28) and the guide (2B), the main shaft (20) is provided with respect to the arm (28). Slidable in the diametrical direction and guided (2 days)
a drive device (41) for assembling a slide member (31) slidable in a direction perpendicular to the output member (27) and moving the slide member (31) in a direction perpendicular to the output member (27); and further includes the drive device (41)
The vehicle is characterized by being equipped with a control device (51) that controls the operation of the vehicle according to the vehicle speed.

Specifically, the slide member (31) includes a first slide piece (32) that is slidable in the diametrical direction of the main shaft (20) with respect to the arm (26), and a first slide piece (32) that is slidable in the diametrical direction of the main shaft (20) with respect to the arm (26), and a first slide piece (32) that is slidable in the diametrical direction of the main shaft (20) with respect to the arm (26); A second member that is slidable in a direction orthogonal to the member (27).
a slide piece (33) and the first slide piece (
32) and the second slide piece (33),
and a center piece (34) fitted to at least the first slide piece (32) so as to be rotatable relative to the first slide piece (32), and the center piece (34) is connected to the drive device (4).
1) moves in a direction perpendicular to the output member (27).

(Function) When the slide member (31) moves in the direction perpendicular to the projecting member (27), the slide member (3) moves against the input shaft (22).
1) changes the amount of deviation of the main shaft (24) and the arm (
26) functions as a crank arm, and its crank rotation is converted into the left and right direction of the output member (27) integrated with the guide (2B) via the slide member (31), and the front wheel
The steering angle ratio of the rear wheels to that of the vehicle is controlled according to the vehicle speed.

In particular, in order to adjust the rear wheel steering angle, the output member (27)
Since the slide member (31) is only moved up and down without moving itself up and down, only a small driving force is required for adjusting the steering angle.

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

FIG. 1 is a schematic perspective view of the 4WS system, in which (1) is a front wheel steering mechanism, (21) is a rear wheel steering mechanism, (51) is an EC1J which is a control device, and (53) is a vehicle speed sensor.

The front wheel steering mechanism (1) includes a handle (2), a steering shaft (3), a rotation input binion shaft (4), and a rack shaft (5).
), left and right tie rods for the front wheels, (8), knuckle arms (7), (7), etc., (8) is the front steering gear box, (9), (9) are the left and right front wheels. Yes, front steering gear box (8)
has a rotating pinion shaft (5) that meshes with the rack shaft (5).
11) is incorporated so as to protrude rearward.

The rotation extraction pinion shaft (11) is for extracting the rotation for rear wheel steering within a range of approximately ±270°, and the linkage shaft (13) is connected to this pinion shaft (11) via a joint (12). ) are connected, and the linkage shaft (
13) is equipped with a rear wheel steering mechanism (2) through India (10).
The rotation input shaft (22) of 1) is connected.

The main parts of the rear wheel steering mechanism (21) are as shown in Fig. 2.
Rotation input shaft (22), main shaft (20, output member (27),
It consists of a slide member (31) and a drive device (41), and in Fig. 1, (5B) and (5B) are the left and right tie rods for the rear wheels, (57) and (57) are the same knuckle arms, and (5B) are the left and right tie rods for the rear wheels.
8) Beam steering gear box, (59), (
59) are the left and right rear wheels.

As shown in FIG. 2, a binion (23) is formed at the rear end of the rotational input shaft (22), and a main shaft (24) is arranged directly above the input shaft (22). There is a fan-shaped internal gear (
25) is integrally installed vertically, and an internal gear (25
) is the diametrical arm (2B) of the main shaft (24).
are integrally formed. These internal gears (25)
The arm (26) is maintained in a vertical state when the rear wheels (5e) and (59) are in a neutral state of steering.

An output member (27) is arranged at a distance behind the arm (26). The output member (27) is a ring-shaped member arranged horizontally with the axis in the left-right direction, and a vertical guide (2B) perpendicular to the axis is integrally formed in the center of the output member (27). A slide member (31) is interposed between the arms (26).

The slide member (31) fits into the arm (26) from the rear, and includes a first slide piece (32) slidable in the diametrical direction of the main shaft (20), and the guide (2B).
It fits from the front and goes vertically w! It consists of a second movable slide piece (33) and a center piece (34) interposed between the first and second slide pieces (32) and (33). This centerpiece (3
The front and rear parts of 4) are fitted to be able to rotate concentrically relative to the centers of both slide pieces (32) and (33), and (35),
(38) are front and rear rolling elements for allowing relative rotation. A horizontal support shaft (37) whose axis is in the left-right direction is slidably fitted into the centerpiece (34), and the centerpiece (30) can be moved up and down in the vertical direction via this support shaft (37). A driving device!! (41) is provided.

The drive device (41) includes a motor (42) with an encoder that monitors the rotation speed and rotation angle, and four gears (43) in the left and right directions.
), (44), (44), (45), 2 wood feed screws on the left and right (48).

(46), two left and right nuts (47), (47), and a driven gear (44
) and (44) are fixedly installed, one driven gear (44) meshes with the driving gear (43) of the motor (42), and an intermediate gear (45) is connected between both driven gears (44) and (44). is intervened. The support shaft (37) is installed between the left and right oaks (47) and (47).

The basic principle of the main parts of the above-mentioned rear wheel steering mechanism (21) is as shown in FIG. 3, and the slide member (31) can be represented as - number of spheres.

Here, the rotation a and rotation angle information of the encoder-equipped motor (42) are input to the ECU (51) and compared with vehicle speed information from the vehicle speed sensor (53), and the optimal front and rear wheels are set according to the vehicle speed. The steering angle ratio is determined and the operation of the motor (42) is constantly verified.

Although the vehicle speed information may be obtained from a speedometer, responsiveness can be further improved by using pulses from wheels, vehicle speed information from radar, etc. The front and rear wheel steering angle ratio is also monitored by a motor with an encoder (42), but the movement of internal parts of the rear wheel steering mechanism (21), such as the rear wheel steering angle ratio (47), is monitored by a differential transformer, and sliding resistance. ,
Alternatively, direct monitoring using optical means can further improve responsiveness.

Next, the operation will be explained. Here, since the operation of the front wheel steering mechanism (1) is known, only the operation of the main part of the rear wheel steering mechanism (21) will be described.

First, the rotation taken out from the front wheel steering mechanism (1) is transmitted to the rotation input shaft (22), and is reduced by the reduction ratio of the binion (23) and internal gear (25), and then rotated to the main shaft (24).
) rotation is transmitted to

On the other hand, the rotation of the motor (42) according to the vehicle speed information is controlled by the gear (
43), (44), (44), and (45) to the left and right feed screws (4B) and (4G), the rotation of the feed screws (4B) and (441) causes the left and right nuts) (
47), (47) move up and down, and a supporting shaft (37) integrated with this moves up and down.
), the center piece (34) moves vertically in parallel, the first slide piece (32) slides along the arm (2B) in the diametrical direction of the main shaft (24), and the second slide piece (33 ) slides vertically along the guide (28).

Since the arm (2B) rotates together with the main shaft (20), the first slide piece (32) fitted to this arm (26) rotates as a crank relative to the main shaft (24), and this crank rotation causes the center piece to rotate. (34) and rolling element (3
5) is allowed by the interposed fitting, and at the same time is converted into left-right movement of the center piece (34). The second slide piece (33) also moves in the left-right direction integrally with this center piece (34), and the output member (27) integrated with the guide (28) fitted to this second slide piece (33) also moves in the left-right direction. do.

In this way, the rear wheels (59), (
The steering angle ratio of 59) is adjusted to an optimum value according to the vehicle speed.

Therefore, in this 4WS system, if h is changed as a function of vehicle speed, ycctan(θ/k
), and in a small range (θ/k), it can be considered as yoeθ, so it is possible to control the steering angle ratio of the front and rear wheels to be almost constant. At this time, since the speed of change in vehicle speed is generally smaller than the steering angle speed, it is not necessary to change h very rapidly, and therefore the driving force required for this change can also be small.

In the above description, let us assume that the input angle of the rotation input shaft (22) is θ and the rotation angle of the arm (2θ) is ψ, as shown in FIG.

ψ=θ/, and the center position of the slide member (31) represented as a sphere is h with respect to the axial center position of the main shaft (24),
If the amount of horizontal movement of the output member (27) is y, then y=ht
anψ=htan(θ/k).

Here, for example, let the maximum swing width of θ be 270°, and k==
6.5. If the range of h is ±18mm, y is approximately ±16mm.
The steering angle of the rear wheels (59) and (511) can be freely adjusted within the range of 1,000 mm.

(Effects of the Invention) As described above, according to the present invention, since the front and rear wheel steering mechanisms are mechanically connected, the increase in steering force caused by steering the rear wheels is applied to the front wheel steering mechanism. This can be achieved by increasing the capacity of the power assist device, and the rear wheel steering angle, which responds to the front wheel steering angle, is further adjusted according to the vehicle speed, resulting in excellent responsiveness. Since the slide member is only moved up and down without being moved, a small driving force is sufficient for adjusting the steering angle. In addition, it is only necessary to monitor the position of one part of the rear wheel steering mechanism and compare that value with the vehicle speed.
It also has the advantage of making it easier to monitor functions.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of the 4WS device, FIG. 2 is a transparent perspective view of the main parts of the rear wheel steering mechanism, and FIG. 3 is a diagram of its basic principle. In the drawing, (1) is the front wheel steering 4m structure, (11) is the pinion shaft for rotation extraction, (13) is the linkage shaft, (21) is
is the rear wheel steering mechanism, (22) is the input shaft, (23) is the binion, (20 is the main shaft, (25) is the internal gear,
(2B) is the arm, (27) is the output member, (28) is the guide, (31) is the slide member, (32) is the first slide piece, (33) is the second slide piece, (34) is the center piece , (35), (18) are rolling elements, (37
) is the spindle, (41) is the drive device, (42) is the motor, (
43), (44), (45) are gears, (4B) is a feed screw, (47) is a nut, (51) is a control device, (53)
is the vehicle speed sensor.

Claims (2)

[Claims] (1) Front and rear of a vehicle in which the input shaft of the rear wheel steering mechanism is rotated by the rotation extracted from the front wheel steering mechanism, and the rotation of the input shaft is converted into left-right movement of the output member to steer the rear wheels as well. In the wheel steering device, a main shaft connected to the input shaft is provided, a diametrical arm is integrally provided to the main shaft, a guide in an orthogonal direction is integrally provided to the output member, and between the arm and the guide, Assembling a slide member that is slidable on the arm in a diametrical direction of the main shaft and slidable on the guide in a direction orthogonal to the output member, and driving the slide member to move the slide member in a direction orthogonal to the output member. 1. A front and rear wheel steering device for a vehicle, comprising: a control device for controlling the operation of the drive device according to vehicle speed; (2) The slide member includes a first slide member that is slidable in a diametrical direction of the main shaft with respect to the arm.
a slide piece; a second slide piece that is slidable relative to the guide in a direction perpendicular to the output member; and a second slide piece that is interposed between the first slide piece and the second slide piece and that is at least connected to the first slide piece. 2. The front and rear wheel steering device for a vehicle according to claim 1, further comprising a center piece that is fitted in a relatively rotatable manner, and wherein the center piece moves in a direction perpendicular to the output member by the operation of the drive device.