JPH0725345B2 - Front wheel steering system for motorcycles - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a front wheel steering system for a motorcycle such as a motorcycle or a bicycle.

(Prior Art) As a front wheel steering device for a motorcycle, most generally, a telescopic front wheel fork is disposed on a frame so as to be rotatable around its steering axis and fixed integrally to the upper end of the front wheel fork. A device having a structure in which a front wheel is steered by operating a handlebar is used.

Also, for motorcycles for racers, a pair of left and right swing arms extending forward from the frame support both front and rear axles of the axle so that they can move up and down in a substantially vertical direction, and a spherical bush formed in the center of the axle. On the other hand, the hub hole of the front wheel is press-fitted so that it can be horizontally swung, and one end of the hub hole and the steering shaft with the handlebar fixed to the upper end are connected by a link member having a structure in which a plurality of tie rods are connected by a joint, A device having a structure in which front wheels are steered by operating a handle bar has been proposed (Japanese Patent Laid-Open No. 57-15087).

Furthermore, recently, a steering arm that cantileverly supports the front wheels is supported by a pair of upper and lower swing arms extending forward from the frame so as to be vertically movable in a substantially vertical direction, and a steering shaft having a handlebar fixed to the upper end and the steering wheel. A device having a structure in which a plurality of tie rods are connected to each other by a link member having a structure in which a joint is connected and a front wheel is steered by operating a handle bar has been proposed (Japanese Patent Laid-Open No. 60-139583). issue).

(Problems to be Solved by the Invention) In the case of the first device described above, the structure is simple, but the front wheel fork (steering axis) is inclined rearward, and even if the front wheel tries to move vertically in the vertical direction, Since it can be moved up and down diagonally along the steering axis, there is a large drag when the front wheels move up and down, and the wheelbase (the axial distance between the front and rear wheels) also changes as the front wheels move up and down. . Furthermore, the work of attaching and detaching the front wheels is difficult and time-consuming.

In the second device described above, the wheel base hardly changes even when the front wheels move up and down, but like the first device, the work of attaching and detaching the front wheels is difficult and time-consuming. In addition, the steerable range of the front wheels is small, and the reaction force when steering the front wheels and the vibration of the front wheels during traveling are transmitted to the steering shaft via the link member, so the steering wheel directly connected to the steering shaft is used. Vibration is easily transmitted to the bar. Further, in terms of strength, since the steering shaft receives the reaction force from the front wheels, it is necessary to thicken the steering shaft and reinforce the frame of the steering shaft mounting portion.

In the third device described above, the wheel base does not change even when the front wheels move up and down, and the front wheels can be easily attached and detached. However, like the second device, the reaction force from the road surface when steering the front wheels, the vibration of the front wheels during traveling, and the like are transmitted to the steering shaft via the link member, and thus are directly connected to the steering shaft. Vibration is easily transmitted to the handlebar. Further, since the rocker arm below the steering shaft is pivotally mounted on the cylinder head of the engine so as to be horizontally rotatable, the steering system (the steering shaft and the link member) is maintained at the localization value. Is complicated and requires a stronger member. Moreover, since the fulcrum (rotation center) position of the tie rod connected to the steering arm is supported by the rocker arm, the handlebar rotates left and right (rotation angle).
Therefore, it is difficult to dispose the front wheels symmetrically (same rotation angle) to the left and right.

The present invention has been made in view of the above points, the wheel base is substantially constant even when the front wheels move up and down, the front wheels can be easily attached and detached, the reaction force from the road surface acting on the front wheels and the front wheels during traveling It is an object of the present invention to provide a front wheel steering system for a two-wheeled vehicle, in which vibrations or the like are less likely to directly act on the handlebars, and the steering system is composed of simple shaped members.

(Means for Solving the Problems) The gist of the front wheel steering system of the present invention for achieving the above-mentioned object is as follows: a) It is pivotally supported on the lower part of the frame and extends forward to form a parallel link. A steering arm rotatably supporting the front wheel in a cantilever manner is pivotally mounted between the ends of a pair of upper and lower swing arms that are curved to allow the front wheel to rotate, and a suspension unit is provided on one side. The first steering shaft, which is provided between the swing arm and the frame and has a handle bar at the upper end, is located above the front end of the frame, and the second steering shaft is located behind the first steering shaft in the frame. , And each of which is rotatably supported about an axis in a substantially vertical direction, and c) a first steering shaft and a second steering shaft which are offset from each other.
The second steering shaft is coupled to the steering shaft by offsetting one end of the second tie rod to the second steering shaft, and the steering arm is offset from the other end of the second tie rod to a pivot point of the swing arm. D) The pivotal fulcrum of the second tie rod with respect to the second steering shaft and the pivotal fulcrums of the pair of swing arms with respect to the frame are arranged on an extension line of the second steering shaft.

(Operation) According to the front wheel steering system of the present invention, since the front wheels move up and down in the substantially vertical direction via the swing arm, the wheel base is substantially constant, and the reaction force from the front wheels and the driving force during running are maintained. Most of the vibrations of the front wheels are absorbed by the second steering shaft supported by the frame, and rarely directly act on the first steering shaft. Furthermore, since the steering system from the handle bar to the steering arm is fixed to the frame at two locations, the first steering shaft and the second steering shaft, which form part of the steering system,
The structural strength is improved, and the steering force from the handlebar is transmitted to the steering arm.

(Embodiment) FIG. 1 is a left side view of a front portion of a motorcycle, FIG. 2 is a top view of the first steering axis of FIG. 1, and FIG. 3 is a front view of the same.

As shown in FIG. 1, the first steering shaft 2 has a vehicle body center plane N.
(FIGS. 2 and 3) Above the front end of the frame 1
It is rotatably arranged by a bearing 3 penetrating a head pipe 22 that is welded and fixed to 1a with a slight inclination to the rear with respect to the vertical direction. A handlebar 4 that extends to both sides is integrally fixed to the upper end of the first steering shaft 2.

A middle pipe 23 in which the second steering shaft 5 is welded and fixed in parallel to the head pipe 22 to the frame middle portion 1b behind and below the frame front end upper portion 1a on the vehicle body center plane N.
And is rotatably arranged by a bearing 6. As shown in FIG. 3, at the lower end of the first steering shaft 2 and the upper end of the second steering shaft 5, the base ends of offset levers 7 and 8 having the same length are provided on the front end side of the vehicle body center plane N. It sticks out by sticking out to the same side (here, the left side). The lower surface of the tip of the offset lever 7 and the upper surface of the tip of the offset lever 8 are connected by a first tie rod 9 via rod ends 9a and 9b, which are one type of universal joint. The first steering shaft 2 and the second steering shaft 5
The offset amounts a at both ends of the first tie rod 9 are set to be equal to each other.

As shown in FIG. 1, the front wheel 11 is cantilevered by a pair of upper and lower leading type swing arms 12 and 13 extending forward from a lower front end 1c of the frame 1. The swing arms 12 and 13 are curved in a C shape as shown in FIG. 2 when viewed from above to allow the front wheel 11 to turn to the right, and the base ends of the arms 12 and 13 are It is integrally formed with the pipe portions 12a, 13a into which the pivot shafts 14 or 15 are inserted. The pair of upper and lower swing arms 12 and 13 are
As shown in the drawing, a space is provided between the frame lower front ends 1c having a fork shape, and the base end pipe portions 12a and 13a thereof are pivotally attached by pivot shafts 14 and 15, respectively. As shown in FIG. 1, the pair of swing arms 1
A lower portion of the steering arm 16 is supported by a pair of kingpins 17 so as to be horizontally rotatable at the tips of the reference numerals 2 and 13 (on the center plane N of the vehicle body in FIG. 2). Then, as shown in FIG. 2, the lower end portion of the steering arm 16 is a bearing sleeve.
16a and penetrates through the bearing sleeve 16a of the front wheel 11
The axle 11a is rotatably cantilevered via a bearing 11b. Further, as shown in FIG. 3, a suspension unit 18 such as a shock absorber is interposed near the central curved portion of the upper swing arm 12 and a bracket 19 extending leftward from the middle pipe 23. . In this way, suspend the suspension unit 18 on the upper swing arm.
By arranging in the vicinity of the central curved portion of 12, it is possible to effectively use the space above it and store it compactly,
Further, the number of parts required for mounting the suspension unit 18 is minimized, and interference with the front wheel 11 during turning does not occur.

As shown in FIG. 3, the steering arm 16 has its lower portion bent upward from the vehicle body center plane N to one side (left side). Then, the base end of the offset lever 10 is fixed to the lower end of the second steering shaft 5 by protruding the tip end side to one side (left side) from the vehicle body center plane N, and as shown in FIG. The lower end of the tip of the steering wheel 10 and the upper end of the steering arm 16 are connected by a second tie rod 20 via rod ends 20a and 20b which are a kind of universal joints. The offset amounts b (FIG. 3) of the fulcrums A and D at both ends of the tie rod 20 are set to be equal.

By the way, in this embodiment, as is clear from FIG.
The tip side of the second tie rod 20 with respect to the steering arm 16 and the pivot points A, B, C of the pair of swing arms 12, 13
Is located on the same straight line (here, the extension line P of the first steering shaft 2) when viewed from the side, and also, a pair of swings with respect to the proximal end pivotal support point D of the second tie rod 20 and the frame lower front end 1c. The pivot points E and F of the arms 12 and 13 are located on the extension line Q of the second steering shaft 5, and the second tie rod 20 and the swing arms 12 and 13 are parallel to each other when viewed from the side. And constitutes a so-called parallel link. Therefore, even if the front wheel 11 moves up and down during traveling, the upper end of the steering arm 16 is not pushed or pulled by the second tie rod 20 due to the vertical movement, and therefore the steering arm 16 (front wheel The direction of 11) does not change. However, the present invention is not limited to this configuration, and the base end side pivotal support point D of the tie rod 20 and the pivotal support points E and F of the pair of swing arms 12 and 13 with respect to the frame lower front end 1c are connected to the second steering shaft. If you place it on the extension line Q of 5,
For example, if the length of the second tie rod 20 is changed or the tie rod 20 is slightly inclined with respect to the swing arms 12 and 13,
It is feasible. In FIG. 2, 11c is a wheel of the front wheel 11, 11d is a tire, 31 in FIG. 1 is a brake disc, and 32 is a caliper.

Next, an operation mode of the above-described embodiment will be described.

In FIG. 1 and FIG. 2, if the handlebar 4 is rotated in the direction in which the driver is going to move (for example, to the right), the first steering shaft 2 rotates clockwise and the first steering shaft 2 rotates. The offset lever 7 rotates clockwise as a fulcrum. At the same time, the first tie rod 9 pulls it forward, and the offset lever 8 at the upper end of the second steering shaft 5 rotates clockwise with the second steering shaft 5. At this time, the rotation angle of the second steering shaft 5 is determined by the offset amount a (the third
) Are equal to each other, and are equal to the rotation angle of the first steering shaft 2. At the same time, the offset lever 10 at the lower end of the second steering shaft 5 also rotates clockwise around the second steering shaft 5 as a fulcrum. With the rotation of the offset lever 10, the second
Tie rod 20 is pushed forward and steering arm 16
Rotates clockwise around pivots B and C with swing arms 12 and 13 as fulcrums, and front wheel 11 turns to the right. At this time, the rotation angle of the steering arm 16 is equal to that of the second steering shaft 5.
And second with respect to the pivot points B and C of the steering arm 16
Since the offset amounts b (FIG. 3) at both ends of the tie rod 20 are equal, they become equal to the rotation angle of the second steering shaft 5,
The rotation angle of the first steering shaft 2 is also equal. Even when the handlebar 4 is rotated in the opposite direction (left side), the front wheels 11 turn leftward in the same manner as described above. Further, the vertical movement of the front wheel 11 during running or diving follows the swinging action of the pair of upper and lower swing arms 12 and 13 forming a parallel link, so that the front wheel 11 smoothly moves up and down in a substantially vertical direction. Then, the shock when the front wheel 11 moves up and down is buffered by the expansion and contraction of the suspension unit 18.

(Effects of the Invention) According to the front wheel steering system for a two-wheeled vehicle of the present invention configured as described above, the following effects are achieved.

(1) Since the second steering shaft is provided in the middle of the steering system from the first steering shaft having the handlebar to the steering arm, each member such as a tie rod and an offset lever that constitutes the steering system is connected to a straight rod or a straight plate. Can be formed in a simple shape, the members can be shared, and the manufacturing becomes easy. Also,
Since the steering system is configured by combining the components of simple shapes with the joint in the substantially vertical direction and the substantially horizontal direction,
The displacement of each component when steering the front wheels and the movable range of the joint between each component are reduced, so that the arrangement of the steering system with respect to the vehicle body is less restricted as compared with the above-described conventional device. Furthermore, since the steering system is held by the frame at two locations, the first steering shaft and the second steering shaft, the structural strength is high.

(2) With the configuration of (1) above, most of the reaction force from the road surface acting on the front wheels and the vibration of the front wheels during traveling are absorbed by the second steering shaft, and it is difficult to directly act on the handlebar.

(3) The wheel base is almost constant even if the front wheels move up and down. Further, since the front wheels are supported by the steering arm in a cantilever manner, the front wheels can be easily attached and detached.

[Brief description of drawings]

1 to 4 show an embodiment of a front wheel steering system of the present invention. FIG. 1 is a left side view of the front part of a motorcycle, and FIG. 2 is a top view of the first steering axis of FIG. 3, FIG. 3 is a front view of the same, and FIG. 4 is a IV-IV of FIG. 1 showing a swing arm and a pivot.
FIG. 1 ... Frame, 2 ... First steering shaft, 4 ... Handlebar, 5 ... Second steering shaft, 7,8,10 ... Offset lever,
9,20 …… Tie rod, 11 …… Front wheel, 12,13 …… Swing arm, 16 …… Steering arm, 18 …… Suspension unit.

Claims (3)

[Claims] 1. A front wheel is rotatable between a pair of upper and lower swing arms that are pivotally supported by a lower portion of a frame and extend forward to form a parallel link, which are curved to allow the front wheel to turn. A steering arm supported in a cantilever manner is pivotally mounted so as to be horizontally rotatable, a suspension unit is interposed between one of the swing arms and the frame, and a first steering shaft having a handlebar at the upper end is provided above the front end of the frame. And a second steering shaft is rotatably supported at a rear position of the first steering shaft in the frame about a shaft in a substantially vertical direction, and the first steering shaft and the second steering shaft are supported. The first tie rods are respectively offset from both shafts, and one end of the second tie rod is offset from and connected to the second steering shaft, and the steering arm is connected to the first tie rod. The other end of the tie rod is offset and connected to a pivot point with respect to the swing arm, and the pivot point of the second tie rod with respect to the second steering shaft and each pivot point of the pair of swing arms with respect to the frame are set to the first pivot point. A front wheel steering device for a two-wheeled vehicle, wherein the front wheel steering device is arranged on an extension line of two steering shafts. 2. The second for the steering arm
The front wheel steering system for a two-wheeled vehicle according to claim 1, wherein the tip end side of the tie rod and each pivot point of the pair of swing arms are arranged on an extension line of the first steering shaft. 3. The front wheel steering system for a two-wheeled vehicle according to claim 1, wherein the offset amounts at both ends of the first tie rod and the offset amounts at both ends of the second tie rod are all equal.