JPS63301181A - Vehicle rear wheel steering device - Google Patents

Abstract

PURPOSE:To enable the right and left rear wheels to be simultaneously brought into toe-in by means of one driving means by supporting the right and left rear wheels so as to be capable of steering at least in the toe-in direction, and by interlocking respective connecting members extending from the right and left rear wheels via a cam member. CONSTITUTION:In a rear wheel steering mechanism B, a connecting mechanism D which interlocks mechanically the right and left wheels so as to be simultaneously brought into toe-in is provided. The connecting mechanism D is constituted by a cam member 21 having been rotatably supported on a vehicle body in the intermediate part of the right and left rear wheels, and in the right and left positions thereof, divided relay rods 23R, 23L being connected to the right and left tie rods 11R, 11L constituting connecting members are slidably held in the direction of the vehicle width. At the inner end parts of respective relay rods 23R, 23L, disklike cam followers 22R, 22L are provided so as to be abutted on the outer circumferential surface of the cam member 21 under the energization of respective springs 25R, 25L. The cam member 21 is made in an elliptic shape, and is turned by a driving means 5 including a step motor 35.

Description

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

(Prior art) There is a four-wheel steering type iI vehicle in which both the front wheels and the rear wheels are steered. There is one that allows the steering to be turned to In other words, a cylinder device is installed between the left and right suspension arms that support the rear wheels and the vehicle body, and these left and right cylinder devices provide a range of compliance (elastic deformation of the elastic bushing in the suspension). A vehicle has been proposed in which both the left and right rear wheels are toe-in when the front wheels are steered.

In this way, in a vehicle in which both the left and right rear wheels are toe-in, the rear wheel that is the inner wheel during a turn can be toe-in in advance in preparation for the next turn in the opposite direction. As a result, even on driving roads where left and right curves exist continuously, toe-in of the rear wheels, especially the outer wheels when turning, can be obtained in a responsive manner, which is desirable in terms of ensuring vehicle stability. .

(Problem to be Solved by the Invention) However, in order to steer the left and right rear wheels in the toe-in direction, as described in the above-mentioned publication, driving means for steering each of the left and right rear wheels (the cylinder in the above-mentioned publication) Providing each device separately for exclusive use is not desirable in terms of cost h, h or simplification of control.

The present invention was made in consideration of the following circumstances, and is based on the premise that the outer rear wheel of the left and right rear wheels is toed-in without causing the inner rear wheel to toe out. An object of the present invention is to propose a rear wheel steering device for a vehicle in which means for applying an external force for steering the rear wheels can be shared between the left and right rear wheels.

(Means and operations for solving the problem) In order to achieve the above-mentioned object, in the present invention, the left and right rear wheels are connected to each other by a linkage mechanism using a cam, so that the inner rear wheel is placed in a neutral position. It is mechanically linked so that the rear wheel, which is the outer wheel, is in toe-in position or toe-in. Specifically, the configuration is as follows. Namely.

The left and right rear wheels are respectively steerable at least in the toe-in direction, and the cam member is attached to the vehicle body, and the cam member and the left rear wheel are linked via the left connecting member. , the force member and the right rear wheel are linked via the right connecting member, and the cam member is driven in accordance with the left and right movement of the handle to connect one of the left and right rear wheels to the inner rear wheel. The structure is such that when the rear wheel is in a neutral position or in a toe-in state, the other rear wheel, which is the outer wheel, is toe-in.

With such a configuration, by driving the cam member, it is possible to bring the inner wheel of the left and right rear wheels to the middle position or toe-in, and toe-in the outer rear wheel.

(Examples) Examples of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, IR is the right front wheel, IL is the left front wheel, 2R is the right rear wheel, and 2L is the right rear wheel.The left and right front wheels IR1IL are linked by a front wheel steering mechanism A, and the left and right rear wheels 2R1
2L is linked by rear wheel steering a mechanism B.

In the embodiment, the front wheel steering mechanism A includes a pair of left and right knuckle arms 3R13R and a tie rod 4R54L, and a relay rod 5 that connects the pair of left and right tie rods 4R14L. A steering mechanism C is linked to the front wheel steering mechanism A, and the steering mechanism C is of a rack and pinion type in this embodiment. In other words, relay rack I.5 is connected to rack 6.
is formed, while the pinion 7 that meshes with the rack 6 is
It is connected to a handle 9 via a shaft 8. As a result, when the handle 9 is operated to the right, the relay rod 5 is displaced to the left in FIG. The steering wheel is steered to the right by an amount corresponding to the operational displacement φ of 9, that is, the steering angle of the steering wheel. Similarly, handle 9
When an operation is performed to turn the vehicle to the left, the left and right front wheels IR1IL are steered to the left in accordance with this operational displacement jj.

Similarly to the front wheel steering mechanism A, the rear wheel steering mechanism B also has a pair of left and right knuckle arms 10R110L and tie rods 11R, 11L, as well as the tie rods 11R,
It has a connecting mechanism that connects the 11Ls. As will be described later, this coupling mechanism mechanically links the left and right rear wheels 2R12L so that they are toe-in at the same time. In other words, when the right knuckle arm IOR rotates in the counterclockwise direction 91 in FIG. It moves clockwise in Figure 1 with 10L' as the center (left rear wheel 2L is toe-in).

The above connection mechanism will be explained in detail with reference to FIG. 4. This coupling mechanism has a +1 (cam member 2 rotatably attached to the body)
1 is on the right, and its center of rotation is indicated by reference numeral 21'. Further, the left and right positions of this cam member 21 are η;
1 left and right glue "23 R123L",
It slides in the vehicle width direction and is held on the vehicle body. The outer end of this relay rod 23R (23L) is connected to the tie rod 11R (IIL), and the inner end thereof is integrated with a disk-shaped cam follower 22R (22L). Each relay rod 23R123L is connected to the cam frame lower 2 by a spring 25R or 25L.
2R122L is always in contact with the outer peripheral surface of the cam member 21.

The cam member 21 has an elliptical shape, and its rotation center 2
1' and the cam follower 22R122L increases as the cam follower 22R122L rotates from the illustrated state, and this distance becomes maximum when the cam follower 22R122L is rotated by 90 degrees. Therefore, as the cam member 21 is rotationally driven from the illustrated state, (
90" rotation range), the right relay rod 23R is suppressed and displaced to the right in the figure, resulting in toe-in of the right rear wheel 2R, and the left relay rod 23L is suppressed and displaced to the left in the figure, resulting in left rear wheel 2R. The wheel 2L has toe-in by the same amount as the right rear wheel 2R.Then, the rotation center 21' and the cam follower 2
The illustrated state in which the distance to the left and right rear wheels 2R12L) is the minimum is the center)γ position of the left and right rear wheels 2R12L)p.

Spring 25R125L is for cam follower 22R.
, 22L are always in contact with the cam member 21, and when an abnormality occurs in the drive means (described later) for driving the cam member 21, the rear wheel 2R12L is forcibly moved to the middle position.
It has the function of returning to and maintaining. Therefore, the biasing force of the spring 25R125L is set to be large enough to hold the rear wheel 2R12L in a neutral position against the external force acting on the rear wheel 2R12L while driving (fail-safe function).
Furthermore, as is already clear from the description above, the cam member 21 also functions as a toe-out stopper that prevents the rear wheel 2R12L from being steered in the toe-out direction.

Next, a description will be given of the means for driving the cam member 21, that is, the driving means E for toe-in the left and right rear wheels 2R12L. This driving means E includes a shaft 31 rotatably held by the vehicle body and fixed to the cam member 21;
A step motor 35 that rotates the shaft 31 is provided.

Further, the driving of the step motor 35 is assisted (boosted) by a hydraulic power assist mechanism F via the pole screw 34. L pole screw 3
4 is provided with a large number of poles 34c interposed between a central shaft 31 and an outer cylinder 34b. Such a pole screw 34 is connected to the shaft 3 in a known manner.
The pole 34c is transferred to the outer periphery of 1 and the inner periphery of the outer cylinder 35b.
A threaded groove is formed, and by reciprocating the outer cylinder 34b (the outer cylinder 34b is attached to the 1V body so as not to rotate), the shaft 31 can be rotated in forward and reverse directions.

Note that the cam member 21 is actually set so that its rotation center 21' is in the rearward direction of the vehicle body +ii7.

A cylinder 41 fixed to a heavy body is disposed on the outer periphery of the outer cylinder 34b of the pole screw 34, and the inside of the cylinder 41 is defined into two oil chambers 43a and 43b by a piston 42 integrated with the outer periphery of the outer cylinder 34b. has been done. This oil chamber 4
3a and 43b are connected to a rotary control valve 46 attached to the shaft 31 via piping 44 or 45. Further, pipes 48 and 49 that are connected to a reservoir 47 are connected to the control knob 46, and one pipe 48 is connected to a motor 50.
A pump 51 driven by is connected. In addition,
Since the operation of such a power cylinder mechanism F itself is well known, its explanation will be omitted.

Furthermore, both pipes 44 and 45 (oil chambers 43a and 43b) can be brought into communication with each other by a solenoid valve 52.

61 in FIGS. 1 and 4 is a control unit composed of a microcomputer, which basically includes a CPU, ROM,
, is equipped with RAM. The control unit 61 receives signals from the sensors 62 to 64) and voltage from the battery 15. The sensor 62 detects the amount of operation of the steering wheel 9, that is, the steering angle of the steering wheel. The sensor 63 detects +lj speed. The sensor 64 is
This detects the rotational position of the shaft, that is, the actual turning angle of the rear wheels 2R12L. And control unit 6
1 is outputted to the step motor 35 and the solenoid valve 52.

The control unit 61 determines the ratio of the steering angle of the rear wheels 2R12L to the front wheels IR1IL (steering ratio) based on the steering angle and the vehicle speed, for example, as shown in FIG.
Feedback control is performed while monitoring the output from. Note that the second Jj is rewritten in terms of the relationship between the steering angles of the front wheels and the rear wheels and is shown in FIG. Of course, this 2! Peeling (Figure 3) is
Position example of steering characteristics of rear wheels 2R12L (11 (quick response type)
In addition to this, various other steering characteristics can be used as appropriate, such as a steering wheel angle responsive type.

Further, if any abnormality occurs, the control unit 61 operates the electromagnetic valve 52 to connect the two pipes 44 and 45. As a result, the rear wheels 2R12L are forcibly held at the neutral position 1'6 by the springs 25R and 25L.

FIGS. 5 and 6 each show another embodiment of the present invention, and the same components as those in the previous embodiment are given the same reference numerals and the explanation thereof will be omitted.

First, in the one shown in FIG. 5, the cam is a so-called positive cam. That is, a pair of left and right cam grooves 26R126L are formed on the plate surface of the cam member 21, and the inner end of the relay rod 23R (23L) is connected to the cam groove 26R (26L).
It is rotatably and slidably engaged with. The shape of the cam groove 26R126L itself corresponds to the outer peripheral shape of the cam member 21 shown in FIG.

In the vehicle shown in FIG. 6, only the outer rear wheel is towed in while the inner rear wheel is in the neutral position. That is, the cam member 21 is formed so that the portion on the L side of the rotation center 21' is a semi-ellipse, and the lower portion is formed as a semicircle. Therefore, when the cam member 21 is now rotated clockwise in the figure, the right relay rod 23R is displaced to the right in the figure and the right rear wheel 2R is towed in, but the left relay rod 23L is not displaced. , the left rear wheel 21 remains in the neutral position. Also,
When the cam member 21 is rotated counterclockwise in the figure,
Only the left rear wheel 2L is towed in, and the right rear wheel 2R remains in the neutral position. Of course, the steering direction of the handle 9 and the rotation direction of the cam member 21 are associated with each other so that the rear wheel on the toe-in side becomes the outer wheel when turning. In this way, by setting the rear wheel that is on the inside wheel side when turning, it is possible to prevent the dragging phenomenon of the rear wheel that is on the inside wheel side.
While turning, it is possible to obtain toe-in of the rear wheel, which will be the next outer wheel, in response to the next turn in the opposite direction. Of course, from the viewpoint of preventing the drag phenomenon of the inner rear wheel, the shape of the cam member 21 is designed to cause the inner rear wheel to toe-in within a smaller range than the toe-in of the outer rear wheel. It's okay. On the other hand, if this drag phenomenon is to be ignored, the toe-in of the inner rear wheel is greater than the 21 toe-in of the outer rear wheel, and the inner rear wheel is used more actively. Car 11 when turning
The q stability can also be expressed as (j).

Although the E embodiment has been described above, the compliance of a p-type bushing incorporated in the suspension may be used to steer the rear wheels. Further, the cam member 21 may be driven by mechanically linking it with the handle 9 without using a separate actuator such as the step motor 35.

(Effects of the Invention) As is clear from the above description, the present invention provides a dedicated rear wheel steering system for left and right rear wheels independently in order to toe in at least the outer rear wheels without causing the left and right rear wheels to toe out. This drive means can be shared between the left and right sides without sacrificing the drive means.

Furthermore, since the left and right rear wheels are mechanically linked to each other via the cam member as described above, this cam member can function as a toe-out stopper that prevents the left and right rear wheels from toe-out. It is also unnecessary to separately provide a toe-out stopper.

Furthermore, by setting the shape of the cam member, the toe-in width of the inner rear wheel and the outer rear wheel are made different from each other, and toe control is performed by actively utilizing this difference between the inner and outer wheels. You can also do it.

[Brief explanation of drawings]

Figure 51 is an overall system diagram showing one embodiment of the present invention. FIG. 2 and FIG. 3 are diagrams showing an example of the steering characteristics of the rear wheels. FIG. 4 is a detailed system diagram showing the main parts of FIG. 1. FIGS. 5 and 6 are front views of essential parts showing other embodiments of the present invention, respectively. B: Rear wheel steering a structure D = Connection mechanism E - Drive step 2R12L: Rear wheel 10R110L: Knuckle arm 11R111L: Tie rod 21: Cam member 22R, 22L: Cam follower 23R123L: Relay rod 31: Shaft 35 Step motor

Claims (1)

[Claims] (1) The left and right rear wheels are each supported by the vehicle body so as to be steerable at least in the toe-in direction, a cam member is attached to the vehicle body, and the cam member and the left rear wheel are linked via a left connecting member, The cam member and the right rear wheel are linked via the right connecting member, and the cam member is driven according to the left and right movement of the handle, so that one of the left and right rear wheels, which is the inner wheel, is in a neutral position. Alternatively, a rear wheel steering device for a vehicle is characterized in that in a toe-in state, the other rear wheel on the outer wheel side is toe-in.