JPH02227375A - Rear-wheel steering system for vehicle - Google Patents

Abstract

PURPOSE:To make it excellent in durability as well as to prevent any dislocation from occurring in alignment of rear wheels by installing an output shaft, a cam member and a symmetrical pair of roller members, and interposing an elastic body between those of roller members and output shaft. CONSTITUTION:When a cam member 38 is rotated and driven according to each steering angle of front wheels, an output shaft 26 is driven in the car width direction via a pair of rollers 37L, 37R in contact with both sides of the outer circumferential surface and thereby rear wheels are steered in accordance with a cam characteristic of the cam member 38. In this case, a rubber bush 50 is interposed between the roller 37L on one side. Accordingly, even if elastic force of this rubber bush 50 is varied, a positional relationship between the cam member 38 and the output shaft 26 is constantly set at all times via the roller 37R on the other where this rubber bush is not installed, so that any dislocation is in no case produced in alignment of the rear wheels at time of the neutral state.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rear wheel steering device for a vehicle, for example, a rear wheel steering device that steers the rear wheels in an opposite phase to the front wheels when the steering angle of the front wheels is large. Regarding equipment.

[Prior art]

Conventionally, as a rear wheel steering device included in a vehicle's four-wheel steering device, a speed-sensitive system is used that steers the rear wheels in the opposite phase to the front wheels at low vehicle speeds, and steers the rear wheels in the same phase as the front wheels at high vehicle speeds. type, and a steering angle sensitive type that steers the rear wheels in the same phase as the front wheels when the steering angle of the front wheels is small, and steers the rear wheels in the opposite phase to the front wheels when the steering angle of the front wheels is large. (For example, see Japanese Patent Laid-Open No. 18572/1983).

In order to simplify the structure of the above-mentioned steering angle sensitive rear wheel steering device, a device employing a cam mechanism is described in Japanese Patent Laid-Open No. 63-97468.

In this rear wheel steering device, an input shaft linked to the steering handle extends between the left and right rear wheels, a cam plate is fixed to this input shaft, and spherical bushings as cam driven parts are attached to the left and right sides of the cam plate. A pair of driven joint levers are arranged, and the front end of each driven joint lever is pivotally connected to the vehicle body so as to be rotatable around a vertical pivot shaft, and the rear ends of the pair of driven joint levers are A pair of spherical bushes are held in contact with both sides of the outer peripheral surface of the cam plate by connecting them with a turnbuckle, and the middle part of each driven joint lever is connected to the knuckle arm of the rear wheel via a tie rod. .

The cam plate has a substantially triangular shape with a curved outer peripheral surface.

In the above rear wheel steering device, when the steering wheel is steered, the cam plate rotates via the input shaft, and the cam plate moves a pair of spherical bushes to the left or right, and a pair of driven joint levers and a pair of spherical bushings move to the left or right. The rear wheels are steered to the left or right turning direction via the tie rods.

[Problem to be solved by the invention]

In the rear wheel steering device described above, since a pair of driven joint levers that are long in the front and rear direction are provided, the device becomes large and difficult to arrange in relation to the rear wheel steering device and the rear wheel suspension device.

Since the left and right pair of spherical bushings and the input shaft are shifted in the vertical direction, a large external force is applied from one tie rod to one side of the cam plate via the driven joint lever and the spherical bushing when the car is cornering. As a result, a large rotational moment acts on the cam plate. Therefore, there is a fatal problem in that the operating force of the steering wheel becomes extremely heavy.

When a car is running, especially when cornering, hundreds of external forces act on the rear wheel steering system from the rear wheels via the tie rods, but the pair of spherical bushings is kept in contact with the cam plate. There is a need. Due to manufacturing errors in various parts such as tie rods and driven levers, it is difficult to maintain the above contact state.

Therefore, thick-walled spherical bushings that appear to be made of rubber are used as the pair of spherical bushings, but since the pair of spherical bushings is in direct sliding contact with the cam plate, durability is lacking due to wear of the spherical bushings. A turnbuckle is required to keep the bushing in contact with the cam plate under preload, which increases the number of parts and increases the size of the device.The spherical bushing deteriorates over long periods of use.
When the elastic force of the left and right spherical bushings is no longer uniform, the rear wheels will no longer be in a neutral state even if the cam plate is in a neutral state, causing a misalignment of the rear wheels and impeding driving stability. , and other problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steering angle sensitive cam type rear wheel steering device that has a simple structure, is excellent in durability, and does not cause misalignment of the rear wheels.

[Means to solve the problem]

The rear wheel steering device for a vehicle according to the present invention is a four-wheel steering device that steers the rear wheels in response to the steering of the front wheels, and includes a single output shaft that connects the left and right rear wheels via a tie rod, and a steering wheel for the front wheels. A cam member that rotates around an axis that intersects with the output shaft according to the steering angle, and a pair of left and right roller members that are rotatably provided on the output shaft and abut on both left and right sides of the outer peripheral surface of the cam member. and an elastic body is provided between the roller member and the output shaft.

[Effect]

In the rear wheel steering device according to the present invention, the cam member is rotationally driven according to the steering angle of the front wheels, and when the cam member rotates, the pair of rollers that are in contact with the left and right sides of the outer peripheral surface of the cam member are rotated. The output shaft is driven to move in the vehicle width direction via the member, and the rear wheels are steered according to the steering angle of the front wheels and the cam characteristics of the cam member.

Since the elastic body is interposed between the roller member and the output shaft,
The elastic body has excellent durability because it does not come into sliding contact with the cam member, and for example, by using an elastic body that is externally attached to the roller pivot shaft, the preload can be applied and inserted in a compressed state. The means for loading can be omitted.

It is possible to absorb manufacturing errors in various parts and hold the pair of roller members in contact with the cam member, and the elastic body can absorb vibrations transmitted from the rear wheel to the output shaft.

〔Effect of the invention〕

According to the rear wheel steering device according to the present invention, as explained in the above [Function] section, by interposing the elastic body between the roller member and the output shaft, the durability of the elastic body can be increased. , it is possible to absorb manufacturing errors in various parts and maintain the pair of rollers in contact with the cam member, and the elastic body can absorb vibrations transmitted from the rear wheel, and a preload is applied to the elastic body. It is possible to reduce the size of the device by omitting the means for doing so.

[Examples] Examples of the present invention will be described below with reference to the drawings.

This embodiment relates to a rear wheel steering device in a four-wheel steering device suitable for passenger cars, microbuses, buses, small trucks, trucks, etc. In particular, this embodiment is applicable to a steering angle sensitive rear wheel steering device of an automobile. This is an example of the case where the present invention is applied.

As shown in FIGS. 1 and 2, a four-wheel steering system for an automobile includes a front-wheel steering system 10 that steers left and right front wheels 1, and a front-wheel steering system 10 that is interlocked with the front-wheel steering system 10 via an intermediate shaft 23. and a rear wheel steering device 20 that steers the rear wheels 2 of the vehicle.

First, the front wheel steering system 0 will be explained.

A pair of left and right front wheels 1 extend in the vehicle width direction. Steering rod 13
The steering handle 1 is connected via a pair of tie rods 14 connected to both ends of the steering rod 13, respectively.
A pinion I5 is connected to the lower end of the steering shaft 12 extending from the steering shaft 1, and the pinion 15 meshes with a main rack 13a formed on the steering rod 13. Therefore, when the steering handle 11 is rotated to the left (counterclockwise) as shown by the arrow F in FIG.
5, the steering rod 13 is moved to the right, the left and right front wheels 1 are rotated counterclockwise around the king pin (as shown in the diagram), and steered in the left turning direction. When the vehicle is rotated to the right (clockwise), the left and right front ends 1 are rotated clockwise and steered in the right turning direction. Although not shown in the drawings, the steering force of the steering handle 11 is configured to be power assisted by a well-known hydraulic power steering mechanism.

Next, the rear wheel steering device 20 will be explained.

A sub-rack member 21 extending in the vehicle width direction is fixed to the steering rod 13, and a sub-rack is formed on the lower surface of the sub-rack member 21, extending from the sub-rack member 21 to the rear wheel steering device 20 in the longitudinal direction. An extending intermediate shaft 23 is provided;
The pinion 22 at the front end of the intermediate shaft 23 meshes with the sub rack on the lower surface of the sub rack member 21, and the rear end portion of the intermediate shaft 23 is connected to the input shaft 25 of the rear wheel steering device 20 by a coupling 24. Therefore, when the steering handle 11 is operated in the direction of arrow F, the force direction, the intermediate shaft 23
rotates clockwise as seen from the rear as indicated by an arrow F2, and the rotation angle of the intermediate shaft 23 is proportional to the turning angle of the front wheels 1, which is proportional to the rotation angle of the steering handle 11.

The rear wheel steering device 20 is disposed toward the vehicle width direction slightly behind and above the differential gear device 3 between the left and right rear wheels 2 and the left and right axle casings 4, and outputs an output of the rear wheel steering device 20. A pair of left and right tie rods 28 are connected to both ends of the shaft 26 (see FIGS. 4 and 5) via pole joints 27 (see FIGS. 4 and 5), and the outer side of each tie rod 28 is The end portion is rotatably connected to the bracket 6 on the rear side of the wheel support member 5 of the rear wheel 2 via a vertical pin 7, and the wheel support member 5 is connected to the outer end of the axle casing 4 in a substantially vertical direction. They are rotatably connected via a bottle member. Therefore, when the output shaft 26 of the rear wheel steering device 2o is driven to the left as shown by the arrow F3, the rear wheels 2 are steered clockwise in the left turning direction in FIG. When driven to the right, the left and right rear wheels 2 are steered counterclockwise in the right turning direction.

Here, the details of the structure of the rear wheel steering device 20 will be explained in the fourth section.
This will be explained with reference to FIGS.

Inside the hollow housing 29 consisting of the lower housing 30 and the upper housing 31, there is a housing 1 extending horizontally in the vehicle width direction.
A book output shaft 26 is disposed to be movable in the left and right direction, and the output shaft 26 has a pair of left and right rod portions 32L and 32R, and a pair of left and right rod portions integrally formed at the inner ends of each rod portion 32L and 32R. It consists of bifurcated roller pivot parts 33L and 33R, and a connecting shaft part 34 that connects the rear arm parts 35a of these roller pivot parts 33L and 33R and is integrally formed with the roller pivot parts 33L and 33R. Each of the roller pivots 33L and 33R has a pair of front and rear arms 35a and 35b, and the left roller pivot 33L that opens to the right in FIG. 4 has both ends supported by the front and rear arms 35a and 35b. A roller 37L is rotatably pivoted by a horizontal pivot shaft 36 facing in the front-rear direction.
Further, a roller 37R is rotatably attached to the right roller pivot portion 33R that opens to the left by a horizontal pivot shaft 36 oriented in the front-rear direction and supported at both ends by the front and rear arm portions 35a and 35b.

A vertical plate-shaped cam member 38 is disposed between the left and right rollers 37L and 37R, and the left and right sides of the outer peripheral surface of the cam member 38 correspond to the corresponding rollers 37L and 37R, respectively.
The pair of rod portions 32L and 32 of the output shaft 26
R, the pair of rollers 37L and 37R, and the cam member 38 are arranged on the same linear axis in plan view, and the pair of opening/end portions 32L and 32R of the output shaft 26 and the pair of roller 37L
- The center portions of 37R and the cam member 38 are arranged on the same linear axis when viewed from the front. A horizontal support shaft 39 facing in the front-rear direction is inserted into the center of the cam member 38 and pushed through.
The front end of the support shaft 39 is supported in the shaft hole of the lower housing 30 via a radial bearing 40, and the rear end of the support shaft 39 is supported in the shaft hole of the upper housing 31 via a radial bearing 41. A key 42 is interposed between 38 and the support shaft 39, and the cam member 38 can rotate together with the support shaft 39 around the support shaft 39. Small diameter shaft portion 3 at the front end of the support shaft 39
9a extends forward through a hole in the cap-shaped protrusion 30c of the lower housing 30, and thrust bearings 43 and 44 are mounted on the inside and outside of the protrusion 30c, and the outer thrust bearing 44 is attached to the small diameter shaft 39a. The inner thrust bearing 43 is held by a screwed nut 45 and a lock nut 46.
is in contact with the annular end surface of the support shaft 39. Therefore, the support shaft 3
9 is restricted from moving in the axial direction by a pair of thrust bearings 43 and 44. The rear end portion of the support shaft 39 is inserted into a guide hole 47 formed in the connecting shaft portion 34 and elongated in the left-right direction, and the support shaft 39 is in contact with both the upper and lower surfaces of the guide hole 47. Therefore, the output shaft 2 including the connecting shaft portion 34
6 is movable in the horizontal direction relative to the support shaft 39, but is not allowed to move relative to the vertical direction.

The outer peripheral surface of the cam member 38 and the pair of rollers 37L and 37
A pair of rollers 37 is used to prevent gaps from forming between R.
Either one of L or 37R (in this example, the left roller 3
7L) is attached to the roller pivot portion 33L via a pair of front and rear hard rubber bushes 50.

As shown in FIG. 7, the roller 37L is attached to the pivot shaft 36 via a sleeve 51 press-fitted into the pivot shaft 36 and a bearing metal 52 externally fitted on the sleeve 51, and is attached to both ends of the pivot shaft 36. A collar 5 for regulating the position of the sleeve 51 is provided in the part.
3 is fitted onto the outside, and an annular rubber bushing 50 is compressed and installed in an annular space between each collar 53 and the inner circumferential surface 54 of the pivot hole of the arm portions 35a and 35b. The rubber bushing 50 is, for example, as shown in FIG. 8, a hard rubber bushing main body 50b compressed by applying a preload is assembled and bonded between a metal inner cylinder 50a and a metal outer cylinder 50c. This rubber bushing 50 is for rear wheel 2
from the roller 37L via the tie rod 28 and output shaft 26.
・It is capable of withstanding the load that acts on 37R.

In order to rotate the cam member 38 according to the turning angle of the front wheel 1, a spur gear 55 is fixed to the support shaft 39 within the housing 29, and a small diameter pinion 56 is provided that meshes with the lower right side of the spur gear 55. The pinion 56 is fixed to the rear end of the input shaft 25, the input shaft 25 extends forward through the boss portion 30b of the lower housing 30, and the front end of the input shaft 25 is connected to the intermediate shaft 23 by the coupling 24. The human power shaft 25 is connected to the rear end portion so as to rotate integrally with the boss portion 3.
0b, and as shown in FIG. 6, the input shaft 25 is restricted from moving in the front-rear direction by engaging a restriction pin 58 in an annular groove 57 on the outer periphery of the input shaft 25. .

The intermediate shaft 23 is reduced in speed by a predetermined reduction ratio with respect to the rotation of the steering shaft 12 via the auxiliary rack and pinion 22, and the spur gear 55 is reduced in speed with respect to the rotation of the intermediate shaft 23 by (diameter of pinion 56)/( The speed is reduced by the reduction ratio of the spur gear 55 (diameter).

Therefore, the cam member 38 is attached to the steering handle 1.
The cam member 38 is rotated in proportion to the steering angle of the front wheels 1, which is proportional to the steering angle of the front wheels 1, and when the steering wheel 11 is operated in the direction of arrow F in FIG. (in the direction of arrow F4 in FIG. 5), and when the steering handle 11 is operated in the direction opposite to arrow F1, it is rotated in the opposite direction.

Here, the shape of the cam member 38 will be explained.

FIG. 10 shows a cam member 38 and a pair of rollers 37L and 37R.
This is a diagram showing the relative positional relationship between the two and the two, viewed from the rear.

The cam member 38 is symmetrical when viewed from the rear, and when the steering angle of the front wheels 1 is zero, the cam member 38 is in a neutral state as shown by the solid line in FIG. 10, and the left roller 37L is at the point P0.
The roller 37R on the right side is in contact with point Q0. On both left and right sides of the outer peripheral surface of the cam member 38, a first cam surface 61, a second cam surface 62 extending upward from the upper end of the first cam surface 61, and a third cam surface 62 extending downward from the lower end of the first cam surface 61 are provided. cam surfaces 63 are respectively formed, and the range of the first cam surface 61, the second cam surface 62, and the third cam surface 63 is the steering range.

The first cam surface 61 functions in cooperation with the first cam surface 61 on the opposite side, so that the steering wheel 11 can be rotated counterclockwise or clockwise by, for example, 200 degrees (this means that the steering angle θ of the front wheels 1, =
This is to maintain the rear wheels 2 in a neutral state in which they are not steered when the wheels are steered in the range below (corresponding to 15 degrees).

The first cam surface 61 has a radius R centered on the center 0 of the support shaft 39.
is a cylindrical surface (that is, a cylindrical surface consisting of circular arcs P, P), and this corresponds to a range in which the steering wheel 11 is steered, for example, by 200 degrees counterclockwise or clockwise, for a total of 400 degrees, and when the steering wheel 11 is turned counterclockwise. When the cam member 38 is steered by 200 degrees, the cam member 38 rotates in the direction of arrow F, and the left roller 37L moves to point P1, and the right roller 37R moves to point Q.
When the steering wheel 11 is rotated clockwise by 200 degrees, the cam member 38 rotates in the direction opposite to the arrow F5, and the left roller 37L moves to point P2, and the right roller 37R moves to point Q. come into contact with

The second cam surface 62 functions in cooperation with the third cam surface 63 on the opposite side, and the third cam surface 63 functions as the second cam surface 62 on the opposite side.
The second cam surface 62 and the third cam surface 63 function together to rotate the steering wheel 11 counterclockwise or clockwise by 200 degrees.
In other words, when the steering angle θ of the front wheels 1 becomes larger than 15 degrees, the rear wheels 2 are steered in the opposite phase to the front wheels 1 in proportion to the angle (θF 15). It is something.

The second cam surface 62 is a curved surface determined by a curve P + P 3, and the radius from the center 0 gradually increases from point P1 to point P.

The third cam surface 63 is a curved surface determined by curves P and P, and the radius from the center 0 gradually decreases from point P2 to point P4. And diameter PIQ2 - diameter P: l Q4
= 2R, and from the point between point P and point 23 to point Q2 and point 9
The diameter to the corresponding point between 4 is also 2R. This means that the third cam surface 63 between curves P2P4 and curves Q and Q
, the same applies to the relationship with the second cam surface 62 between.

When the left roller 37L abuts point P3, the right roller 37R abuts point Q, and when the left roller 37L abuts point P4, the right roller 37R abuts point Q3. Therefore, as long as the cam member 38 rotates within the steering range, the left roller 37L and right roller 37R always come into contact with the outer peripheral surface of the cam member 38. However, point P within the steering range.

The vicinity of point P4 and the vicinity of point P4 are ranges that are hardly used in practice.

FIG. 11 shows the characteristics of the rear wheel steering device 20 determined by the cam member 38, etc., with the steering angle θF of the front wheels 1 on the horizontal axis and the steering angle θ8 of the rear wheels 2 on the joint axis. Yes, θ, 0 is, for example, θ. =15 degrees.

In order to easily assemble the cam member 38 between the pair of left and right rollers 37L and 37R, the diameter of the cam member 38 is smaller than 2R in the portion of the outer peripheral surface of the cam member 38 that is outside the steering range. It is also formed short. Point P
, from point Q to the diameter P. It is formed linearly parallel to Qo and has a diameter P.

P, is formed significantly shorter than 2R, and points P3 and 23
The diameter from the point in between to the point between point Q4 and point 24 is also formed to be considerably shorter than 2R, and the total height of the cam member 38 in the neutral state shown in FIG. 10 is also formed to be significantly shorter than 2R. .

Next, the structure of the housing 29 will be explained with reference to FIG. 9.

In order to incorporate the output shaft 26, cam member 38, spur gear 55, pinion 56, etc. into the housing 29, the housing 29 is divided into a lower housing 30 and an upper housing 31 at a mating surface 60, and is formed into a hollow shape. In the housing 29 of the embodiment, the following measures have been taken regarding the direction of the mating surface 60.

When a car is running, especially when cornering, an axial force of several hundred kg acts from the rear wheels 2 to the tie rod 2 and acts from the tie rod 28 to the end of the output shaft 26, and the tie rod 28 acts against the output shaft 26. Since it is tilted forward and downward, the output shaft 2 is attached to the housing 29 fixed to the vehicle body.
A component force RF of the axial force from 6 acts in the direction shown in FIG.

On the other hand, a rotational moment acts on the cam member 38 via the rollers 37L and 37R due to the axial force transmitted from the tie rod 28 to the output shaft 26, and the pair of reaction forces MF are generated within the vertical plane 64 shown in FIG. It acts on the housing 29 from the output shaft 26. In order to assemble the above-mentioned parts into the housing 29, it is common to orient the mating surface 60 in the vertical direction, but this is not preferable in view of the above component force RF and reaction force MF. Therefore, the mating surface 60 of the housing 29 is connected to the output shaft 26.
The above component force RF and reaction force M acting on the housing 29 from
It is an inclined surface including the axis AC of the output shaft 26 so as to intersect with the direction F, and is formed as a forward upward inclined surface inclined at an angle of about 45 degrees with respect to the vertical plane. Along the mating surface 60, flange portions 30a and 31a are formed on the outer periphery of the lower housing 30 and the outer periphery of the upper housing 31, respectively;
These flange parts 30a and 31a are connected to each other by a plurality of bolts 6.
It is fixed at 5. With such a mating surface 60, the various parts mentioned above can be easily assembled, and the component force RF and force MF can be easily assembled using the relatively small flange portions 30a and 31a and the bolts 65.
It can be made sufficiently strong against. The outer end portions of the rod portions 32L and 32R and the inner portions of the ball joint 27 and tie rod 28 are covered with a bellows-like member 47 made of rubber.

The operation of the automobile rear wheel steering system configured as described above will be explained.

As mentioned above, when the steering wheel 11 is steered in the direction of the arrow F in FIG. 1, the cam member 38 rotates in the direction of the arrow FsO in FIG. When the handle 11 is steered in the opposite direction, the cam member 38 also rotates in the opposite direction.

When the steering angle of the front wheel 1 is within 15 degrees in the left turning direction or right turning direction, the rollers 37L and 37R move on the first cam surface 61 of the cam member 38 with the same radius, so the roller 37L
and 37R are located symmetrically with respect to the center Q, and the rear wheels 2 are not steered and maintain a neutral state.

When the front wheel 1 is steered by 15 degrees or more in the left turning direction, the roller 37L rolls on the second cam surface 62 on the left side, and the roller 37L rolls on the second cam surface 62 on the left side.
R rolls on the third cam surface 63 on the right side. As a result, the radius from center 0 to roller 37L is
Since the radius becomes larger than the radius up to 7R, the output shaft 26 moves to the left, and the pair of rear wheels 2 are steered in the left turning direction (clockwise in Fig. 1) via the pair of tie rods 28. be done.

When the front wheel 1 is steered by 15 degrees or more in the right turning direction, the roller 37L moves on the third cam surface 63 on the left side, and the roller 37L moves on the left third cam surface 63.
R moves on the second cam surface 62 on the right side. As a result, the radius from center 0 to roller 37L is
7R, the output shaft 26 moves to the right, and the pair of rear wheels 2 rotate to the right (counterclockwise in Figure 1) via the pair of tie rods 28. Be steered.

As described above, when the front wheels 1 are steered by 15 degrees or more by turning the steering wheel 11 counterclockwise or clockwise by 200 degrees or more, the rear wheels 2 are steered in a phase opposite to that of the front wheels 1. That will happen.

However, although the steering angle θ of the rear wheels 2 is proportional to (θF 15), the steering angle θ8 of the rear wheels 2 is about 10 degrees at most.

When the car is running, a large axial force is applied from the tie rod 28 to the output shaft 26 as described above, but a large axial force acts on the output shaft 26 between the pair of rod parts 32L and 32R and the pair of rollers 37L and 37R.
Since the cam member 38 and the cam member 38 are arranged on the same axis, the axial force is mainly transmitted as a compressive force between the members and the earthen floor, and no large bending moment is generated in any member.

Since the pivot shaft 36 is supported at both ends, no large bending moment is generated on the pivot shaft 36 either. Since the rollers 37L and 37R come into contact with the left and right sides of the cam member 38, the support shaft 3
9, the cam member 38 exerts almost no force on it.

Therefore, various members such as the output shaft 26, the cam member 38, and the support shaft 39 can be made as small as possible to realize the rear wheel steering device 20 that is small, lightweight, and has a simple structure. Moreover,
Since the output shaft 26 is a single member, the steering of the left and right rear wheels 2 is reliably synchronized.

The rubber bush 50 is interposed only between the roller 37L and the roller pivot 33L, and is not interposed between the roller 37R and the roller pivot 33R.

If rubber bushings 50 are provided on both rollers 37L and 37R, if the rubber bushings 50 deteriorate during long-term use, the elastic forces of both rubber bushings 50 will differ and the output to the cam member 38 will be different. The rear wheel 2 when the shaft 26 is slightly displaced to the left or right and is in a neutral state.
This will cause the alignment to go out of order.

In this embodiment, since the rubber bushing 50 is provided only on one roller 37L, even if the elastic force of the rubber bushing 50 changes, the positional relationship between the cam member 38 and the output shaft 26 is the same as that of the roller 37R on which the rubber bushing 50 is not provided. Since it is always set to a constant value via , there is no possibility of misalignment of the rear wheels 2 in the neutral state.

Since the rubber bush 50 is assembled with a preload applied, it is very difficult to assemble the cam member 38 between the left and right rollers 37L and 37R. In order to facilitate the assembly of the cam member 38, the diameter of the cam member 38 outside the steering range (for example, the diameter Ps in FIG. 10) is adjusted as described above.
Pb) is formed to be significantly shorter than 2R.

The cam member 38 on which the support shaft 39 is assembled is attached to the housing 2.
When assembling the cam member 3 to the output shaft 26 in advance outside of 9, as shown in FIGS. Insert the end into the guide hole 47. At this time, since the dimensions are sufficiently smaller than 2R, it can be easily assembled as shown in FIG. Next, when the cam member 38 is rotated clockwise in FIG. 13 together with the support shaft 39, the roller 37L rolls on the third cam surface 63 and the first cam surface 61.
Since the roller 37R rolls on the second cam surface 62 and the first cam surface 61, it can be assembled into the state shown in FIG. 14 very easily.

Next, the spur gear 55 and the bearings 4o, 41, 43, and 44 are assembled to the support shaft 39, and then these assemblies and the assembly of the pinion 56 and input shaft 25 are attached to the lower housing 30.
Then, the upper housing 31 is assembled to the lower housing 30. When assembling a car, front wheel 1
It is necessary to maintain the cam member 38 in the neutral state shown in FIGS. 5 and 10 until the alignment of the rear wheel 2 and the alignment of the rear wheel 2 are set. Therefore, when the unit of the rear wheel steering device 20 is assembled as described above, the vertical groove 66 at the rear end of the support shaft 39 is inserted into the upper housing 3 as shown in FIG.
The cam member 38 is set to a neutral state in alignment with the pair of upper and lower marks 67 of the lower housing 30, and the input shaft 25 is temporarily fixed with the bolt 68 of the boss portion 30b of the lower housing 30. However, after the assembly of the automobile is completed and the alignment of the front wheels 1 and the rear wheels 2 are set, the bolts 68 are removed.

A pair of thrust bearings 43 and 44 are provided at the front end of the support shaft 39 that supports the cam member 38, and since the support shaft 39 is supported in the axial direction by these thrust bearings 43 and 44, the output shaft 39 is The connecting shaft portion 34 is the roller pivot portion 33L
・Because it is asymmetrical in the front and back relative to 33R, even if an external force in the axial direction is applied to the support shaft 39, the support shaft 39 does not move in the axial direction, and there is a large rotational sliding resistance between the support shaft 39 and the housing 29. will not occur. However, thrust bearing 44
may be provided at the rear end of the support shaft 39.

Regarding the housing 29, since the mating surface 60 of the lower housing 30 and the upper housing 31 is formed as a front upward slope inclined at 45 degrees with respect to the vertical plane as described above, the lower housing 30 and the upper housing 31 This is advantageous in terms of bonding strength, and there is no problem when assembling various parts into the housing 29.

[Another example]

In place of the rear wheel steering device 20 of the embodiment described above, a rear wheel steering device 20A as shown in FIGS. 16 and 17 may be used. However, parts that are the same as or similar to those of the rear wheel steering device 20 are given the same reference numerals and explanations thereof will be omitted.

In this rear wheel steering device 2OA, a worm gear mechanism 70 is provided to transmit the rotation of the input shaft 25 to the support shaft 39.

That is, a worm wheel 71 is fixed to the front part of the support shaft 39 within the housing 39, and a small-diameter worm gear 72 that meshes with the lower part of the worm wheel 71 is disposed below the worm wheel 71 in the left-right direction. The vicinity of the left end and the right end of the worm gear 72 are supported by the pivot parts 73 and 74 of the lower housing 30 via bearing metal, and a small diameter bevel gear 74 is fixed to the left end of the worm gear 72.
A bevel gear 7 that meshes with a bevel gear 75 is provided at the rear end of the input shaft 25.
6 is fixed. The reduction ratio of this worm gear mechanism 70 is set to be the same as the reduction ratio of the reduction mechanism consisting of the spur gear 55 and pinion 56 of the previous embodiment.

The steering handle 11 is indicated by arrow F in FIG.

When the input shaft 25 is steered in this direction, the input shaft 25 rotates in the direction of arrow F, the cam member 38 rotates in the direction of arrow F1 in FIG. When the cam member 38 is steered in the direction opposite to the arrow F1, the cam member 38 rotates in the opposite direction.

Therefore, the operation of steering the rear wheels 2 is similar to that of the rear wheel steering device 20 of the embodiment described above, and detailed explanation thereof will be omitted.

The operation of this worm gear mechanism 70 will be explained as follows.
Tie rod 2 when driving a car, especially when cornering
8, a large external force acts on the output shaft 26 and the rollers 37L and 37R, and a rotational moment acts on the cam member 38, but the rotational moment is transferred to the worm gear mechanism 70.
Since the signal is cut off by the input signal and is not transmitted to the input shaft 25, no problems such as heavy steering of the steering wheel 11 occur.

It should be noted that the shapes and structures of the output shaft and the cam member are merely examples, and it goes without saying that appropriate changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of a four-wheel steering system for an automobile, FIG. 2 is a view in the direction of the arrow ■ in FIG.
Fig. 3 is a perspective view of the rear wheel steering device, Fig. 4 is a cross-sectional plan view of the rear wheel steering device, Fig. 5 is a sectional view taken along the line V-V in Fig. 4, and Fig. 6 is a sectional view taken along the line Vl-VI in Fig. 4. 7 is an enlarged sectional view of the roller pivot structure of the left roller pivot, FIG. 8 is an enlarged sectional view of the rubber bushing, FIG. 9 is a sectional view taken along the line IX-IX in FIG. 4, and FIG. 10 is the cam. Explanatory diagram of operation of members and rollers, 11th
The figure is a rear wheel steering characteristic diagram, Figures 12 to 14 are explanatory diagrams of each stage when assembling the cam member to the output shaft, Figure 15 is an end view of the support shaft facing the rear surface of the upper housing, and Figure 16 is an end view of the support shaft facing the rear surface of the upper housing. The figure is a cross-sectional plan view of a rear wheel steering device according to another embodiment, and FIG. 17 is a sectional view taken along the line X--X in FIG. 16. 1...Front wheel, 2...Rear wheel, '10...Front wheel steering device, 20.2OA...Rear wheel steering device, 23...Intermediate shaft, 26...Output shaft, 37L, 37R...Roller,
38...Cam member, 39...Spindle, 61...First
Cam surface, 62...second cam surface, 63...third cam surface.

Claims (1)

[Claims] (1) In a four-wheel steering system that steers the rear wheels according to the steering of the front wheels, there is one output shaft that connects the left and right rear wheels via a tie rod, and an output shaft that intersects with the output shaft according to the steering angle of the front wheels. a cam member that rotates about an axis to generate the output; and a pair of left and right roller members that are rotatably provided on the output shaft and abut on both left and right sides of the outer peripheral surface of the cam member, and the roller member and the output A rear wheel steering device for a vehicle, characterized in that an elastic body is interposed between shafts.