JPH01306371A - Rear wheel steering mechanism - Google Patents

Abstract

PURPOSE:To enable the rear wheel steering suited to the load distribution and suspension characteristic of a vehicle by using a cam mechanism so that the change of the rear wheel steering pattern can be easily conducted. CONSTITUTION:A rear wheel steering mechanism 1 extends in the longitudinal direction of a vehicle within a case 7 fixed and supported by body members such as an axle beam and the like, and it is provided with an input shaft 8 connected to the rear wheel part of a transmission shaft 5 so that it can not be relatively rotated, a pair of arm members 10 disposed with a cam body 9 between, and an arm connecting body 11 the both ends of which are connected to the arm members 10. The arm connecting body 11 is constituted utilizing a turn buckle 11a, and each of right and left bolt members 11a, 11b spirally fitted to the turn buckle 11a is provided with a pillow ball housing 11c and a pillow ball 11d rotatably installed therein. The regulation of the gap between the arm members 10 is made possible, whereby the position relation between the cam body 9 and a rotating roller 12 can be properly and appropriately determined.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a rear wheel steering mechanism applied to a four-wheel steering vehicle. [Conventional technology]

It is well known that optimal steering performance in accordance with various situations can be achieved by steering the rear wheels in addition to the front wheels under predetermined conditions. For example, when steering the rear wheels by mechanically transmitting the rotation of the steering wheel to the rear wheel steering mechanism,
Usually, when the front wheels have a small turning angle, the rear wheels are steered in the same phase by a predetermined angle, and when the front wheels have a large turning angle, the rear wheels are steered in the opposite phase by a predetermined angle. When the front wheels are steered significantly, this is usually done at extremely low speeds.
This is based on the fact that when making turns, such as lane changes at high speeds, the amount of steering of the front wheels becomes small. In this way, when the rear wheels are steered in the opposite phase, that is, when the rear wheels are steered in the same direction as the front wheels, the turning center of the vehicle shifts forward, and the turning radius is changed so that only the front wheels are steered. This makes it easier to maneuver the vehicle than when steering the vehicle. In addition, when changing lanes at high speeds, the rear wheels are steered in the same phase, that is, the rear wheels are steered in the same direction as the front wheels, thereby reducing sideslip caused by lateral G. 1 direction is suppressed and driving stability is improved. By the way, various rear wheel steering mechanisms for steering the rear wheels in this manner have been proposed in the past. For example, in the case of the rear wheel steering mechanism disclosed in Japanese Patent Application Laid-Open No. 58-21)968, an eccentric pin is provided on a rotating body that moves in conjunction with the rotation of the steering wheel, and the rotating body moves in conjunction with the rotation of the steering wheel. The movement of the eccentric bin in the vehicle width direction is transmitted to the rear wheel steering tie rod to steer the rear wheels.

[Problem to be solved by the invention]

However, in the rear wheel steering mechanism shown in the above publication,
By changing the eccentricity of the eccentric pin mentioned above, it is possible to increase or decrease the amount of steering of the rear wheels, but the amount of steering in the same phase direction is independent of the amount of steering in the opposite phase direction. It is not easy to steer the vehicle. Another problem is that it is not possible to easily change the turning point at a steering angle of 0 that is passed when changing from the same phase to the opposite phase as shown in FIG. The optimal rear wheel steering pattern varies depending on the vehicle's load distribution, suspension characteristics, etc.
Conventional rear wheel steering mechanisms cannot easily accommodate various rear wheel steering patterns. The present invention was devised under the above circumstances, and is applied to a four-wheel steering vehicle that has a simple structure and is configured to easily change the rear wheel steering pattern. The purpose of this invention is to provide a rear wheel steering mechanism that allows

[Means to solve the problem]

In order to solve the above problems, the rear wheel steering mechanism of the present invention includes: an input shaft extending in the longitudinal direction or the vertical direction of the vehicle; and a cam connected to the input shaft and rotated about its axis by rotation of the input shaft. and front and rear parts of the vehicle that support a cam follower that faces the input shaft and the cam body in the vehicle width direction, is supported so as to be swingable in the vehicle width direction, and comes into contact with the cam face of the cam body at an intermediate portion. a pair of arm members extending in the direction or up and down direction, both ends of which are respectively connected to the pair of arm members at positions apart from the center of swing;
and an arm connection body extending in the vehicle width direction between the pair of arm members, the cam face of the cam body being a cam face that pushes the cam follower outward in the vehicle width direction when rotated from a neutral rotation position. and a cam follower movement permitting surface portion that allows the cam follower to move inward in the vehicle width direction at a portion facing this cam surface and the rotation axis, and a rear wheel steering portion is provided at both ends of the arm connection body. The vehicle is characterized in that the members are connected to each other so as to be lined up on substantially the same axis in the vehicle width direction.

[Action and effect]

Each cam follower supported by a pair of arm members faces each other in the vehicle width direction with the cam body in between, so the cam body is rotated from the neutral rotation position by the rotation of the input shaft, and the cam surface comes into contact with one of the cam followers. Then, the cam follower movement permitting surface portion, which faces the cam surface with the rotation axis in between, faces the other cam follower. In this case, one of the cam followers is pushed outward in the vehicle width direction by the cam surface, and accordingly, the arm member supporting the cam follower is also swung in the vehicle width direction. On the other hand, the other force l causes the follower to be allowed to move inward in the vehicle width direction (in a direction that matches the outward direction in the vehicle width direction of the one cam follower), and each arm member is They are connected via an arm connector. Therefore, when the one arm member swings, the other arm member supporting the other cam holder 2a is also moved in the same direction. That is, when the cam body rotates from the neutral rotation position and the cam surface pushes one cam follower, each arm member is swung in a predetermined direction. At this time, the arm connecting body connecting each of the 7-arm members is moved in the vehicle width direction, thereby imparting vehicle width direction movement to the rear wheel steering member connected to the arm connecting body. The rear wheels are then steered. Also, depending on which cam follower is pushed behind the cam followers on both sides of the cam body, these cam followers,
The direction of the arm part (O) and the arm connection body change without moving, and the direction of the movement of the rear wheel steering member in the vehicle width direction also changes.The steering direction of the rear wheel also changes.Therefore, the cam body
The cam surface that first pushes one cam follower when rotated from the neutral rotation position (herein referred to as the first cam surface), and the cam surface that pushes the other cam follower when further rotated. (herein referred to as the second cam surface) are provided at predetermined rotational angle positions, and by changing the amount of rotation of the cam body, the steering direction of the rear wheels can be changed and the The wheels can be steered in the same phase direction and in the opposite phase direction. Now, in this way, the cam body can steer the rear wheels by pushing the cam follower with the cam surface and not moving it, but the amount of steering of the rear wheels depends on the rear wheel rotation. As the distance that the rudder member moves in the vehicle width direction, that is, the distance that the cam surface pushes the cam follower increases, the distance increases accordingly. The distance that the cam surface pushes the cam follower increases or decreases accordingly if the distance of the cam surface from the rotation axis changes, and the distance between the cam surface and the rotation axis changes accordingly. It can be changed by changing the shape (size) of the surface. Of course, the amount of steering of the rear wheels can be changed by simply changing the shape of the cam body. Furthermore, when the first cam surface and the first cam surface are provided, by changing the shapes of these cam surfaces, it is possible to independently increase or decrease the steering in the same phase direction and the opposite phase direction. can also be easily done. Furthermore, the steering timing of the rear wheels can also be changed by changing the rotation angle position forming the cam surface, that is, by changing the shape of the cam body. Furthermore, the turning point of the steering angle 0, which is passed when changing from the same phase to the opposite phase, can be easily changed by changing the rotational angle positions of the -L and Td first cam surfaces and second cam surfaces. . As described above, since the rear wheel steering mechanism of the present invention has a high degree of freedom in setting the rear wheel steering pattern, it can easily accommodate various rear wheel steering patterns. In addition, since the rear wheel steering member and the arm connection body are arranged approximately on the same axis in the vehicle width direction, these members are subject to bending due to the force transmitted between them in the vehicle width direction. No moments act. That is, since these members do not require great strength, they can be made smaller. This leads to miniaturization of the rear wheel steering mechanism itself and contributes to cost reduction.

[Explanation of Examples]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 5 schematically shows the overall configuration of a four-wheel steering vehicle equipped with the rear wheel steering mechanism 1 of the present invention. In this example, a configuration is shown in which 240 rotations of the steering wheel are mechanically transmitted to the rear wheel steering mechanism 1 to steer the rear wheels 17. In this example, the well-known rank-binion 2〇 steering mechanism is adopted as the front wheel steering mechanism 2. And front wheel steering a
The movement of the transverse 2nd rank j-T-3 in the vehicle width direction is extracted as rotational motion by a driven gear (not shown) disposed in the gear box 4, and the rotation of the driven gear is transferred to the vehicle body via the transmission shaft 5. The signal is inputted to a rear wheel steering mechanism 1 located at the rear. On the other hand, as shown in FIGS. 1 and 2, the rear end steering mechanism 1 extends in the vehicle n'q 2& direction within a case 7 that is fixedly supported by a vehicle body member such as the axle beam 6, and is connected to the transmission shaft. 5, an input shaft 8 connected to the rear wheel portion of the input shaft 8 so as not to rotate relative to each other; a cam body mounted to the rear end of the input shaft 8 through spline fitting so as not to rotate relative to each other; and the input shaft 8 and the cam body. A pair of arm members 10.10 are disposed on both sides of 9 so as to face each other in the vehicle width direction, and extend in the longitudinal direction of the vehicle. 10.1
An arm connection body +1 extending between 0 and 0 in the vehicle width direction. Further, the arm member 10 rotatably supports a rotating roller 12 provided as a cam follower that comes into contact with the cam face of the cam body 7 at its intermediate portion. The input shaft 8 is rotatably supported by a boss portion 13a of a support 13 fixed to the case 7 via a hair ring 14, and - the support 13 is rotated in the vertical direction. A pair of shaft supports 1 facing each other at a predetermined interval.
3b and 13b are respectively provided on both sides of the boss portion +3a. The arm member 10 has its front end rotatably supported by a pivot shaft 15 whose upper and lower ends are respectively supported by the shaft supports 13b, 13b.
On the other hand, the above-mentioned arm connection body 1 (which is capable of swinging in the vehicle width direction about the shaft 15) is constructed using a turnbuckle lla in this example. The left and right bolt members 1)b, 1)b that are screwed into this turnbuckle Ila have a pillow ball housing Il
c and a pillow ball li rotatably installed therein.
d is provided. and each arm member 10.10
By inserting the pillow balls 1) d, Ild of each bolt member 1) b, llb into the rear end and fixing them in the axial direction, the two arm members 10, 10 are connected to the arm connecting body 1). The rear ends are connected to each other via. Moreover, the arm connection body 1) is arm part +A' IO. The function is to maintain the distance between the axes of the rear end of the shaft 15 to the distance between the axes of the axes 15 and 15, and in the case of this example, as described above, this is done by using the turnbuckle lla. By utilizing this structure, the distance between the axes can be easily adjusted. That is, the distance between the axes indicated by -F can be adjusted by simply changing the amount of screwing of the bolt members 1)b and llb relative to the turnbuckle Ila. In this example, the arm member 10. 10lil
By making the interval adjustable, the positional relationship between the cam body 9 and the rotating roller 12 can be appropriately set. Then, a quirod 19 is connected to both ends of this arm connection body 1) via a knuckle arm 18 to the rear end 17.
are respectively connected as rear wheel steering members and aligned with the arm coupling body 1) on the road-to-axis line in the vehicle width direction. The tie rod 19 and the arm connection body 1) are connected by the screw shaft 19 of the tie rod end 19a.
b is carried out by tightening the cap into the screw hole lie provided at the end of the pillow ball housing IIc. Further, in the case of this example, as shown in FIG. 3, the cam body 9 is provided with neutral rotation as shown in FIG. The rotating roller 1 is located above the point of contact with the rotating roller 12 at the position where the rotation angle position is small.
The first four-sided portion 2 serves as a cam follower movement permitting surface portion that allows movement of the cam follower in the vehicle width direction inward (direction toward the rotation axis O) of the cam follower.
0, the distance from the rotation axis 0 at a portion with a larger rotational angular position is the distance between the point of contact with the rotating roller 12 at the neutral rotation position of the body 9 and the rotation axis O (hereinafter referred to as , which is referred to as a roller distance of 1). Further, at a portion facing the first concave surface portion 20 across the rotational axis 0, a first cam 22 whose distance from the rotational axis 0 is larger than the roller distance is provided, and the second cam 1fjj2] A second concave surface portion 23, which functions as the cam floss lower movement permitting surface portion, is provided at a portion facing each other with the rotation axis O interposed therebetween. The third concave surface portion 20 corresponds to the rotation roller 1 at the neutral rotation position.
After the distance bait 1 from the rotation axis 0 decreases smoothly from the point of contact with 2, the distance from the rotation axis ○ increases at a rate of change such as during heating, and at the end, the distance from the rotation axis ○ increases. It is formed into a substantially cylindrical inner surface shape where the distance is equal to the roller distance. Then, the second cam 21 shown in - rotates continuously from the end of the -th concave surface part 20, and the distance h+ from the 1st center O increases gradually and smoothly as the rotational angular position increases. It is formed like this. Also, No.
The first cam 2 faces the concave portion 20 across the rotation axis 0.
2, contrary to the first concave portion 20, during rotation from the contact position 1) After the distance from the center O gradually increases as the rotational angular position becomes larger than the roller distance, The distance from the rotation axis O gradually decreases at a rate of change such that the distance from the rotation axis O at the end thereof becomes equal to the roller distance. Then, the second concave surface portion 23 is connected to the first cam surface 22.2.
It is formed by casting at the end of 2. In addition, the first cam and 2
The weight of the first cam 21 is smaller than that of the first cam 21. Next, the operation of the four-wheel steering vehicle of this example including the rear wheel steering mechanism 1 configured as described above will be described. Here, when the front wheel 1G is turned to the right by steering the steering wheel 24, for example, the rotation direction of the transmission shaft 5 and the input shaft 6, which are rotated by the movement of the lever 3 in the vehicle width direction, is set to the first direction. In the figure and FIG. 5, the direction is indicated by arrow P. When the cam body 9 is rotated from the neutral rotation position as shown in 3171ta+ by starting to turn the steering wheel 24 to the right, at the beginning of the rotation, the rotation roller 12 on the right side in the figure is rotated as shown in FIG. The first cam surface 22 of the cam body 9 comes into contact with the first cam surface 22, whereby the right rotating roller I2 is pushed outward in the vehicle width direction (in a direction away from the rotation axis O) by the first cam body 22. Further, in conjunction with this, the right arm member 10 that supports the right rotating roller 12 is swung in the right direction of the arrow in the figure about the recording/rejection shaft 15. On the other hand, on the left rotating roller 12, the first cuff 1 surface 22 and the first concave surface portion 20 facing each other with the rotation axis 0 in between face each other. It is in a state where it is allowed to move inward (in a direction that matches the outward direction in the vehicle width direction of the rotating roller 12 on the right side), and also supports the rotating roller 12 on the left side. - The arm portion 4A1o is connected to the right arm member IO via the arm connection body 1). Therefore, the left arm member [0 is also caused to follow the J:l movement of the right arm member IO, and is swung M in the same direction (in the right direction of the arrow in the figure) as the right arm member IO. 1) is moved to the right in the vehicle width direction in FIG. Due to the movement of the arm coupling body 1) in the narrow width direction, the tie rods 9 and 19 connected thereto are moved in the vehicle width direction in the direction of the arrow in FIG. It begins to be steered to the right in the same phase as jtLt216. The amount of steering of the steering wheel 24 and the amount of rotation of the cam body 9 gradually increase, and when the end of the first cam surface 22 approaches the rotating roller 12, the amount of swinging of the arm member 10.10 from the neutral position increases. In other words, the amount of steering of the rear wheels 17 gradually decreases after passing through a constant value as shown in FIG. The steering angle becomes 0. When the amount of steering of the steering wheel 24 becomes even larger, the cam body 9 is further rotated from the above-mentioned rotational position and comes into contact with the terminal end of the first cam surface 22, as shown in FIG. The right rotating roller 12 that was in contact with it now has a second concave portion 23.
At the same time, the second cam 21 starts to come into contact with the left roller 12. As a result, the left rotary roller 12 is pushed by the cam body 9, the left arm member lO is swung in the direction of arrow (5) in the figure, and the right rotary roller 12 facing the second concave portion 23 is moved Since movement inward in the width direction is allowed, the right arm member 10 also moves the left arm member 1.
0-1) It is forced to follow the command and is made to swing in the same direction (the direction indicated by the arrow). And this arm member 10.1
In the direction of the arrow 0 (according to the description, the arm connecting body 1) is
This time, it is moved to the left side in the vehicle width direction in Fig. 1, and the tie opening, 19.19, is moved to the left side in the vehicle width direction in Fig. 5.
Since the rear wheels 17 are moved in the vehicle width direction, the rear wheels 17 are steered to the left in the opposite direction to the front wheels 16 from the above-described zero steering angle state. In other words, the rear wheels 17 pass through a turning point at a steering angle of 0, which is a turning point from the same phase to an opposite phase, as shown in FIG. As the amount of steering of the steering wheel 24 and the amount of rotation of the steering body 9 increase, the distance k from the rotational axis 0 of the portion of the second cam 21 that contacts the rotating roller 12 increases. As shown in the steering wheel 24Q)
As the 1 m steering amount increases, the amount of steering of the rear wheels 17 in the opposite phase also gradually increases. In addition, although the case where the front wheel 16 was steered fb to the right side was shown above, when the front wheel 16 was steered to the left side, -
Similarly to the above, when the amount of steering of the steering wheel 24 is small, the rear wheels 17 are steered in the same phase, and the steering wheel 24 is steered in the same phase.
When the amount of steering is large, the rear wheels 17 are steered in the opposite phase. By the way, in this example, changing the turning point is
This can be done by changing the rotational angular position of the terminal end of the first cam 22 (the rotational angular position of the boundary point between the first concave surface portion 20 and the second cam 21). Further, by changing the distances of the first cam surface 22 and the second cam surface 21 from the rotation axis O, it is possible to increase or decrease the amount of steering of the rear wheels 17 in the same phase and in the opposite phase. That is, by simply changing the shape of the cam body 9, various rear wheel steering patterns can be set. Further, as shown in FIG. 1, the tie rod 19 and the arm coupling body 1), which are members for steering the rear wheels, are arranged so as to be aligned on the road-axis line in the vehicle width direction. therefore,
In the case of the present invention, one arm member 10 is a tie rod 19
When the force (F) received from
As shown in the figure, the tie rod 19 is smaller than the case where the tie rod 19 is connected to the arm member 10 at a position spaced apart in the axial direction from the connection portion between the arm member 10 and the arm coupling body 1). In other words, since the arm member 10 and the like are not required to have great strength, they can be made smaller. Thereby, the rear wheel steering mechanism itself can be downsized, and costs can also be reduced. Note that the shape of the cam body can be modified in various ways other than the one shown in the above example. For example, the set number of cam surfaces and cam follower movable surface parts may be set to one each, and the rear wheels may be set only in the same phase. It is also possible to steer the vehicle. In addition, various design changes can be made to the structure of the arm connecting body, and it is also possible to change the input shaft to four-wheel drive using an electric motor.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a rear wheel steering mechanism according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line nn of FIG. 1, and FIG. 3 is a cam body and rotation according to an embodiment. Move the roller to ■- in Figure 1.
■A schematic diagram illustrating the action of the cam mechanism as seen from the direction of the line arrow; FIG. 4 is a graph showing an example of a rear wheel turning pattern showing the relationship between the rear wheel turning angle and the steering angle in the embodiment; FIG. 5 is a diagram schematically showing the overall configuration of a four-wheel steering vehicle in which the rear wheel steering mechanism according to the embodiment is adopted, and FIG. 6 is another aspect of the arm connection body and the arm member of the rear wheel steering member. FIG. 8... Power shaft, 9... Cam body, ) 0... Arm member, l[... Arm connection body, 12... Camfo+17 (rotating roller), 19... Rear wheel steering mechanism Shrine (
Quirod), 20...Cam follower movement allowable surface (
-th concave surface part), 21... cam surface (second cam surface), 22
... cam surface (first cam surface), 23... cam roll lower f hyperactivity allowing surface portion (second concave surface portion). 191 people Daihatsu Motor Co., Ltd. Figure 2

Claims (1)

[Claims] (1) An input shaft extending in the longitudinal direction or vertical direction of the vehicle; A cam body connected to the input shaft and rotated around its axis by rotation of the input shaft; a pair of arm members facing in the width direction, supported so as to be swingable in the vehicle width direction, and extending in the longitudinal direction or the vertical direction of the vehicle, supporting a cam follower that abuts the cam face of the cam body at an intermediate portion; an arm connecting body that is connected to a pair of arm members at both ends thereof at a position away from the center of swing thereof and extends in the vehicle width direction between the pair of arm members, the cam face of the cam body being capable of neutral rotation; A cam surface that pushes the cam follower outward in the vehicle width direction when rotated from the position, and a cam follower that allows the cam follower to move inward in the vehicle width direction at a portion opposite to the cam surface across the rotation axis. It has a movement permitting surface portion, and
Rear wheel steering members are arranged at both ends of the arm connection body so as to be aligned substantially on the same axis in the vehicle width direction,
A rear wheel steering mechanism characterized by being connected to each other.