JP2528893Y2 - Rear wheel steering mechanism - Google Patents

Description

[Detailed description of the invention] [Industrial applications]

The present invention relates to a rear wheel steering mechanism provided in a four-wheel steering vehicle.

[Prior art]

Four-wheel steering vehicles configured to steer the rear wheels in addition to the front wheels for the purpose of improving steering performance are widely used, and the four-wheel steering vehicles should be equipped with such four-wheel steering vehicles. A wheel steering mechanism employing a cam mechanism has been proposed, for example, in Japanese Patent Laid-Open No. 2-189273. The rear wheel steering mechanism disclosed in the publication includes a cam body rotated in response to the rotation of a steering wheel and a pair of left and right cam followers located at a predetermined interval in the vehicle width direction with the cam body interposed therebetween. And a moving rod supported in a manner capable of being slid in the vehicle width direction, and a rear wheel turning mechanism comprising a rear wheel turning member connected to both ends of the moving rod via a knuckle arm. There is at least one of the pair of cam followers,
A rubber bush is interposed between the roller and a support shaft inserted in the roller and perpendicular to the vehicle width direction. In the rear wheel turning mechanism having the above configuration, even when the contact pressure between the cam body and the roller increases, the roller is relatively moved away from the cam body with respect to the support shaft of the cam follower due to the elastic deformation of the rubber bush. Since it becomes movable, it is possible to avoid occurrence of a twist between the cam body and the roller. In addition, since it is possible to apply a preload between the cam body and the cam follower, even when the rollers of the cam body or the cam follower are worn, the rollers can be reliably brought into contact with the cam body, and the cam mechanism can be used. It can be operated smoothly. That is, the positional relationship between the cam body and the two support shafts of the cam follower is determined in advance so that the rubber bush is elastically deformed and the roller is brought into contact with the cam body with its elasticity.
The error caused by the manufacturing error of the profile of the cam body or the wear of the cam body and the rollers can be absorbed by the relative movement of the rollers in the direction of approach to the cam body due to the elastic deformation of the rubber bush, and the cam follower is always secured to the cam body. Can be contacted.

[Problems to be solved by the invention]

However, in the case where the rear wheel steering mechanism is constituted by a cam mechanism employing a cam follower structure in which a roller is elastically supported by a rubber bush as described above,
The problems described below have been found. That is, in the rear wheel steering mechanism, for example, when the rear wheel rides on a convex portion during high-speed running, a large force exceeding the elastic limit of the rubber bush acts between the cam body and the cam follower. When this occurs, the rubber bush may be deformed beyond the elastic limit, and the rubber bush may be crushed or broken. As a means for preventing such a problem, it is usually employed in a general mechanical field to increase the spring constant of a rubber bush to increase its strength. However, when the spring constant of the rubber bush is set to be high, the preload applied to the cam follower should be increased to secure smooth operation of the cam mechanism by absorbing irregularities due to manufacturing errors of the cam surface or rattling due to wear. You need to set it. Then, another problem arises in that the rotation resistance of the cam body becomes extremely large and the cam body cannot be rotated smoothly. In addition, when the preload is increased as described above, abrasion of the contact surfaces of the cam body and the cam follower is also doubled, and a problem that durability is reduced also arises. Further, since the preload must be set large, the assembling work of the cam mechanism becomes difficult, and there is a problem that productivity is reduced. The present invention was devised in view of the above-mentioned circumstances, and a rear wheel steering system employing a cam mechanism having a cam follower structure for elastically supporting a rotatable roller via a rubber bush. It is an object of a mechanism to solve the above-described conventional problem with a simple configuration.

[Means for Solving the Problems]

In order to solve the above problem, the present invention employs the following technical means. That is, the invention of the present application supports a cam body rotated in response to the rotation of a steering wheel, and a pair of left and right cam followers located at a predetermined interval in the vehicle width direction with the cam body interposed therebetween at an intermediate portion, and a vehicle width. A driving rod supported so as to be slidable in the direction, and a rear wheel turning mechanism comprising a rear wheel turning member connected to both ends of the driving rod via a knuckle arm. A roller rotatably fitted to the support shaft via a bearing, the roller being supported by an outer ring of the bearing via a rubber bush, and a predetermined force or more acting on the cam follower. In this case, a stopper is provided to restrict relative movement between the central axis of the roller and the central axis of the support shaft.

[Action and effect]

In the cam follower in the rear wheel steering mechanism having the above configuration, first, a roller that is brought into contact with the peripheral surface of the cam body is supported via a rubber bush on an outer ring of a bearing provided on the outer periphery of the support shaft. Therefore, even when a large contact pressure acts between the cam body and the roller during rotation of the cam body, the roller of the cam follower elastically deforms the rubber bush and moves away from the cam body with respect to the support shaft. Can move relatively.
For this reason, there is no occurrence of twisting between the peripheral surface of the cam body and the roller. Further, a preload can be applied between the cam body and the cam follower by utilizing the elastic deformation of the rubber bush. This makes it possible to absorb the unevenness of the outer peripheral surface caused by a manufacturing error of the cam body and the like by the elastic deformation of the rubber bush, so that the cam mechanism can be operated smoothly. Also, even if the contact surface of the cam body and the roller is worn, the abrasion generated by the abrasion is absorbed by the relative movement of the roller in the direction of approach to the cam body due to the elastic return deformation of the rubber bush, and the cam follower is cammed. It can be surely brought into contact with the body. Next, in the cam follower in the rear wheel steering mechanism having the above configuration, when a predetermined force or more acts on the cam follower, a stopper that regulates a relative movement between a center axis of the roller and a center axis of the support shaft is provided. Is provided. Due to the stopper, even if the contact pressure between the roller and the cam body is increased, the relative movement between the center axis of the roller and the center axis of the support shaft due to the elastic deformation of the rubber bush is not less than a certain value. It will not be. Therefore, the rubber bush is not deformed more than the deformation amount regulated by the stopper. In a four-wheel steering vehicle equipped with the rear wheel steering mechanism, an unexpected pressing force may act on the cam follower when the rear wheel runs on a road surface protrusion during high-speed running. Even in such a case, according to the present invention, the rubber bush can be prevented from being deformed beyond the elastic limit, and the rubber bush is not excessively compressed, crushed or broken. Further, since the strength of the rubber bush need not be increased more than necessary, the spring constant of the rubber bush can be set low. As a result, the preload applied to the cam follower does not need to be increased to a predetermined value or more, and the contact pressure between the roller and the cam body can be set low. As a result, the wear of the cam body and the cam follower is significantly reduced, and the durability of the rear wheel steering mechanism, particularly the cam mechanism, is remarkably improved. Further, since the above preload can be suppressed low,
The assembling of the cam mechanism becomes easy, and the productivity is greatly improved. In addition, since the amount of deformation of the rubber bush can be regulated, the maximum input acting on the rubber bush is
The setting can be made by the stopper. Therefore, the manufacture of the rubber bush is facilitated, and the reliability of the cam follower is also improved.

[Explanation of the embodiment]

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6. In this embodiment, the present invention is applied to a rear-wheel steering mechanism of a four-wheel steering device for an automobile as shown in FIG. The four-wheel steering system includes a front wheel steering mechanism 1 and a rear wheel steering mechanism 2, and mechanically transmits the rotation of the steering wheel 3 to the rear wheel steering mechanism 2 via a transmission shaft 4, and Is configured to be steered. The front wheel steering mechanism 1 is equipped with a general rack and pinion type steering gear. When the steering wheel 3 is turned, a rack rod (not shown) arranged in the gear box 7 moves in the vehicle width direction. At the same time, the movement is transmitted to the knuckle arms 9, 9 via tie rods 8, 8 connected to both ends of the rack rail, and the front wheel 5 is steered by the rotation of the knuckle arm 9 around the axis 10. Is done. On the other hand, a pinion (not shown) that is engaged with the rack rod is attached to the front end of the transmission shaft 4 so that movement of the rack rod can be taken out as rotation of the transmission shaft 4 via the pinion. Therefore, when the steering wheel 3 is rotated,
The rotation is transmitted to the transmission shaft 4. The rear wheel steering mechanism 2 includes a plate-like cam body 11 that is driven to rotate around an axis in the vehicle front-rear direction, a pair of left and right cam followers 12a and 12b arranged on both sides of the cam body 11, and the cam followers 12a and 12b. And the fixed housing 14
And a slide bar 15 slidably supported in the vehicle width direction. The cam body 11 is connected to the rear end of the transmission shaft 4, and is thus rotated in accordance with the rotation operation of the steering wheel 3. As shown in FIG. 5, a first cam surface 16 and a second cam surface 17 are provided on the outer peripheral surface of the cam body 11 symmetrically with respect to a central axis passing through the rotation axis O as a symmetric axis. The above cam surface
16 and 17, the distance from the rotation axis O is the reference circle A (the center of the rotation axis O and the cam followers 12a, 12b in the neutral state as shown in FIG. 5A). It is formed so as to be larger than the radius length of a circle whose diameter is the distance between the contact points with the body 11). Further, in the cam body 11, a portion opposed to each of the cam surfaces 16 and 17 with the rotation axis O interposed therebetween is:
Concave portions 18 and 19 are provided at a distance from the rotation axis O that is smaller than the radius of the reference circle A. On the other hand, as shown in FIG. 1, the cam followers 12a and 12b are connected to rollers 24a and 24b via bearings 23a and 23b on support shafts 13a and 13b fixed to the cam follower support 15a of the slide bar 15, respectively. It is configured to be rotatably supported. Further, as shown in FIG. 6, the slide bar 15
At both ends of the cam follower support portion 15a, a connecting shaft portion 15b is provided, and the connecting shaft portion 15b is connected to the tie rod 20 and the knuckle arm 2.
It is connected to the rear wheel 6 via 1. The cam body 11 according to the rotation operation of the steering wheel 3
Is rotated by a predetermined angle, and as shown in FIG. 5B or FIG. 5C, one of the cam followers 12a (or 1
When the cam surface 16 (or 17) faces the 2b), the other cam follower 12b (or 12a) has the concave portion 18 (or 1).
9) face each other. At this time, the one cam follower 1
2a (or 12b) is pushed outward in the vehicle width direction by the cam body 11, and the other cam follower 12b (or 12a) is connected to the one cam follower 12a (or 12b).
The same direction of movement is allowed. Therefore, the slide bar 15 supporting these cam followers 12a and 12b is
It is moved in the same direction as the cam followers 12a and 12b pushed by 1. The movement of the slide bar 15 in the vehicle width direction is transmitted to the knuckle arms 21 and 21 via the tie rods 20 and 20, and the rotation of the knuckle arms 21 and 21 causes the rear wheel 6 to rotate.
Is steered. FIG. 5 (b) shows a state where the rotation angles of the steering wheel 3 and the cam body 11 are small, and FIG. 5 (c) shows the state of the steering wheel 3 from the state of FIG. 5 (b). 3 is rotated further,
This shows a state where the cam body 11 has been largely rotated. In the state of FIG. 5B and the state of FIG. 5C,
The moving directions of the two cam followers 12a and 12b and the slide bar 15 are reversed, and therefore, the steering direction of the rear wheels is also reversed. Now, in this embodiment, the left and right cam followers
The present invention is applied to the right cam follower 12a in FIG. 1 among 12a and 12b. The cam follower 12a according to the present embodiment includes a collar 22a that is fitted and fixed on a support shaft 13a supported in a bridging manner on the cam follower support portion 15a of the slide bar 15, and a collar 22a.
a roller 23a rotatably supported by the bearing 23a and brought into contact with the outer periphery of the cam body 11, an inner periphery of the roller 24a, and an outer ring of the bearing 23a 25 and a rubber bush 26 interposed therebetween. As shown in FIGS. 2 and 3, the collar 22a has an eccentric shaft hole 27a inserted into the support shaft 13a. Therefore, when rotating the collar 22a around the support shaft 13a, a color 22a and roller 24a is caused to pivot about axis O ₁ around the support shaft 13a, thereby, the roller 24a
The vehicle width direction position of the center axis O ₂ becomes possible to deflection relative to the support shaft 13 of the. As a result, the position of the cam follower 12a in the vehicle width direction or the left and right cam followers 12a, 12b
The interval between them can be adjusted. In FIG. 1, reference numeral 28a denotes a ring-shaped operation plate which is fitted on the collar 22a so as to be relatively non-rotatable, and the collar 22a is rotated by rotating the operation plate 28a. be able to. In the present embodiment, the bearing 23a employs a needle bearing, and is fitted on a rod-shaped rolling element 23c that rolls on the outer peripheral surface of the collar 22a and an outer peripheral portion of a rolling track of the rolling element 23c. An outer ring 29 is provided. The roller 24a has a substantially U-shaped cross section having annular convex portions 31a and 31b whose inner peripheral side portions are extended radially inward in a flange shape, and is intermediate between the annular convex portions 31a and 31b. An outer peripheral portion of the rubber bush 26 is fitted in an annular concave portion 31 formed in the portion. The outer peripheral portion of the roller 24a is formed in a substantially spherical shape, and is brought into contact with the cam surface of the cam body 11. The one annular convex portion 31a is
4a is formed by screwing an annular ring on the inner periphery of the main body, and the outer peripheral portion of the rubber bush 26 is
It is configured so that it can be easily fitted and fixed inside. The rubber bush 26 has an outer cylinder 30 and an inner cylinder 32 formed of metal, and is constituted by interposing a cylindrical rubber body 33 having a predetermined spring constant therebetween. The outer cylinder 30 has an axial length corresponding to the annular concave portion 31,
The inner cylinder 32 has a length corresponding to the axial width of the roller 24a, and is fitted and fixed to the outer ring 29 of the bearing 23a while being fitted into the annular recess 31. Further, the rubber body 33 is formed such that its radial thickness is greater than the depth of the annular concave portion 31, and in a mounted state, a part of the rubber body 33 is extended from the annular concave portion 31. The roller 24a is configured to allow relative movement with respect to the support shaft 13a. With the above configuration, the roller 24a
Are elastically supported by the support shaft 13a via the rubber bush 26. Since the roller 24a is elastically supported, when the cam body 11 rotates, the roller 24a can move relative to the support shaft 13a of the cam follower 12a in a direction away from the cam body 11. Therefore, it is possible to reliably prevent the occurrence of a twist or the like between the cam body 11 and the roller 24a of the cam follower 12a rolling on the peripheral surface. For example, the processing accuracy of the cam body 11 varies, and a certain rotation angle position (for example, FIG. 5B or FIG. 5C) on the cam body 11
5), the cross-sectional length connecting the contacts of the rollers 24a, 24b of the left and right cam followers 12a, 12b is larger than the above-described cross-sectional length at the neutral position as shown in FIG. 5 (a). In such a case, in the conventional apparatus, there is a possibility that the roller 24a, 24b and the cam body 11 are twisted, and the apparatus cannot be operated smoothly. However, in the present embodiment, the distance between the left and right rollers 24a, 24b can be increased within a range in which the rubber bush 26 can be elastically deformed, so that the twisting can be avoided. Also,
Even if there is some variation in the processing accuracy of the cam body 11, the cam mechanism can be operated smoothly. Therefore, it is not necessary to increase the machining accuracy of the cam body 11 so much. In addition, if the device is used for a long period of time, the surfaces of the cam body 11 and the rollers 24a and 24b that are brought into contact with the cam body 11 will be worn and play will occur between them, and the cam mechanism will not operate smoothly. There is fear. However, in this embodiment, since the preload can be applied between the cam body 11 and the cam followers 12a and 12b by utilizing the elastic repulsion of the rubber bush 26, the play can be absorbed. That is, the interval between the contact surfaces of the rollers 24a, 24b of the cam followers 12a, 12b in the neutral state is initially set so that the rubber bush 26 is slightly elastically deformed, and the rollers 24a, 24b are provided with a certain elasticity. Can be pressed against the cam body 11. As a result, the surface of the cam body 11 and the rollers 24a, 24
The backlash between the roller b and the surface of the roller b can be absorbed by reducing the distance between the rollers 24a and 24b due to the elastic return deformation of the rubber bush 26. As a result, the positional relationship between the cam body 11 and the cam followers 12a and 12b can always be appropriately maintained, and the device can be operated smoothly for a long period of time. Further, in the rubber bush 26 according to the present embodiment, as described above, the axial length of the inner cylinder 32 corresponds to the axial width of the roller 24a. For this reason,
The outer peripheral side portions 34a, 34a of the inner cylinder 32 are spaced from the annular convex portions 31a, 31b of the inner peripheral side portions of the roller 24a by a gap h according to the amount of extension of the rubber body 33 from the annular concave portion 31. Open and facing. This gap h is equal to the cam follower 12a.
When an external force greater than a predetermined force acts on the inner cylinder 32, the rubber body 33 is elastically deformed, and the outer peripheral side parts 34a, 34a of the inner cylinder 32 and the inner peripheral surfaces 34b, 34b of the annular convex parts 31a, 31b are brought into contact. The inner cylinder 32 has outer peripheral side portions 34a, 34a.
An annular protrusion 31a, the inner peripheral surface 34b of 31b, and a 34b, to regulate the amount of deformation of the rubber bush 26, between the center axis O ₁ of the central axis O ₂ and the support shaft 13 of the roller 24a relative It constitutes a stopper 34 for restricting the movement. That is, when a large external force acts on the cam follower 12a, as shown in FIG. 4, both outer peripheral side portions 34a and 34a of the inner cylinder 32 constituting the stopper 34 and inner peripheral surfaces 34b and 34b of the annular convex portions 31a and 31b. 34b is brought into contact therewith. Therefore, the center axis O _{2 of the} roller 24a due to the elastic deformation of the rubber bush 26
A relative movement between the center axis O ₁ of the shaft 13a does not become a predetermined value or more. Therefore, the rubber bush 26
The deformation is not more than the deformation amount regulated by the stopper 34. This prevents the rubber bush 26 from being deformed beyond the elastic limit, and prevents the rubber bush 26 from being excessively compressed and the rubber body 33 from being crushed or broken. Note that the axial width of the rubber body 33 is set to
Is desirably set slightly smaller than the axial width of the rubber member 33 so that the rubber body 33 can be sufficiently deformed when an external force is applied. Further, since it is not necessary to increase the strength of the rubber bush 26, the spring constant of the rubber bush 26 can be set low. Therefore, it is not necessary to increase the preload applied to the cam follower 12a, and the rollers 24a and 24b and the cam body 1
It is possible to set the contact pressure of 1 low. As a result, the wear of the contact surface between the cam body 11 and the rollers 24a, 24b is greatly reduced, and the durability of the cam mechanism is remarkably improved. Further, since the preload can be suppressed to a low level, the assembling of the cam mechanism becomes easy, and the productivity is greatly improved. In addition, since the maximum input acting on the rubber bush 26 can be set by adjusting the gap h of the stopper 34, the manufacture of the rubber bush 26 is facilitated, and the reliability of the cam followers 12a and 12b is improved. The scope of the present invention is not limited to the above embodiments. In the embodiment, both outer peripheral side portions 34a, 34a of the inner cylinder 32 of the rubber bush 26 and inner peripheral surfaces 34 of the annular convex portions 31a, 31b of the roller 24a are provided.
By providing a gap h between the stopper 34
However, without providing the inner tube 32 in the rubber bush 26, the outer peripheral both sides of the outer ring 25 of the bearing 23a,
A stopper can be formed by directly contacting the inner peripheral surfaces 34b, 34b of the annular convex portions 31a, 31b. In addition, a stopper is formed by forming an annular convex portion on the outer peripheral surface side of the inner cylinder 32 of the rubber bush 26 and contacting the outer peripheral surface with the inner peripheral both sides of the roller 24a or the outer cylinder 30 of the bush 26. It can also be configured. Further, in the present embodiment, the present invention is applied to one of the cam followers 12a and 12b provided on both sides of the cam body 11, but the present invention may be applied to both of the cam followers 12a and 12b.

[Brief description of the drawings]

FIG. 1 is a plan view of a rear wheel steering mechanism according to a four-wheel steering system according to an embodiment, FIG. 2 is an enlarged sectional view of a cam follower in FIG. 1, and FIG. 3 is a line III-III in FIG. FIG. 4 is a cross-sectional view for explaining the operation of the cam follower according to the present invention, FIG. 5 is a schematic view of the cam mechanism according to the embodiment viewed from the direction of arrow V in FIG. FIG. 6 is a schematic diagram of a four-wheel steering device according to the embodiment. 11 cam body, 12a cam follower, 13a support shaft, 23a bearing, 24a roller, 26 rubber bush, 34 stopper.

Claims (1)

(57) [Scope of request for utility model registration] A cam body which is rotated in response to the rotation of a steering wheel, and a pair of left and right cam followers positioned at a predetermined interval in the vehicle width direction with the cam body interposed therebetween are supported at an intermediate portion, and the vehicle body is supported in a vehicle width direction. A rear wheel steering mechanism comprising a moving rod supported slidably, and a rear wheel steering member connected to both ends of the moving rod via a knuckle arm to a rear wheel, wherein the cam follower includes: The support shaft has a roller rotatably fitted and supported via a bearing, the roller is supported on the outer ring of the bearing via a rubber bush, and a predetermined force or more acts on the cam follower. A rear wheel steering mechanism, wherein a stopper for restricting relative movement between the center axis of the roller and the center axis of the support shaft is provided.