JPH0725348B2 - Front and rear wheel steering system for motorcycles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a front wheel and a rear wheel of a two-wheeled vehicle such as a motorcycle and a bicycle, in which a front wheel and a rear wheel are steered in conjunction with front wheel steering operation of a handlebar. The present invention relates to a steering device.

(Prior Art) In recent years, a so-called four-wheel steering device of a type that simultaneously steers two front wheels and two rear wheels in an automobile has already been put into practical use.

On the other hand, even in a motorcycle such as a motorcycle, by steering the front and rear wheels at the same time, the movement of the rider (driver) required for steering (moving the weight in the steering direction) can be reduced, and the minimum turning radius can be reduced. Recently, based on the knowledge that the front wheel can be made smaller, a device for steering the front wheel and the rear wheel in cooperation with the front wheel steering is being developed.

By the way, a prior art of such a front and rear wheel steering device is disclosed in, for example, JP-A-61-160374.
That is, the front wheel is steered by arranging a front fork supporting the front wheel so as to be rotatable around the steering axis of the front end of the frame, and turning the handlebar at the upper end of the steering shaft. In addition, steering of the rear wheels,
The axle of the rear wheels is pivotally supported on a drive shaft orthogonal to the center line of the vehicle body, an offset lever is fixed to the lower end of the steering shaft of the front fork, and the other end of the push-pull cable with one end attached to the offset lever. Is attached to a rocker arm pivotally attached to a rear frame so as to be horizontally rotatable, and a rear steering arm arranged via a bearing on a rear wheel axle and the rocker arm are connected by a tie rod,
This is done by turning the rocker arm in conjunction with the turning operation of the handlebar.

(Problems to be Solved by the Invention) In the above-mentioned conventional front and rear wheel steering system, the upper ends of the front forks are inclined rearward of the vehicle body, and the front wheels are slanted along the front forks even if they are going to move vertically. Since the front wheels are moved up and down, the drag force when the front wheels are moved up and down is large, and the wheel base changes when the front wheels are moved up and down. Further, since the rear wheels are steered via the rocker arm that horizontally turns, the shape of the link member that constitutes the steering system becomes complicated, and it is not easy to attach the link member to the vehicle body. Moreover, since the fulcrum (rotation center) position of the tie rod connected to the rear steering arm is supported by the rocker arm, the rear wheels are symmetrically turned left and right in response to the left and right rotation of the handlebar. Is difficult to arrange.

The present invention has been made in view of the above points, and the wheel base is substantially constant even when the front and rear wheels are moved up and down, and the minimum turning radius is smaller than the wheel base length. The steering system for the front and rear wheels leading to the steering arm for the rear wheels is composed of a combination of relatively short members with a simple shape, is easy to manufacture, has a high durability, and can be used from the road surface that acts on the front and rear wheels. It is difficult for the reaction force of the vehicle and the vibrations of the front and rear wheels to directly affect the handlebars, and it is easy to arrange the front and rear wheels to turn symmetrically in response to the left and right rotation of the handlebars. Further, it is an object of the present invention to provide a front / rear wheel steering device for a two-wheeled vehicle, in which the front and rear wheels can be easily attached and detached.

(Means for Solving the Problems) The gist of the present invention for achieving the above-mentioned object is as follows: a) The frame is pivotally supported on the front portion of the frame and extends forward.
A front steering arm that rotatably supports the front wheels in a cantilever manner is pivotally mounted horizontally between the tips of a pair of upper and lower front swing arms that are curved to allow the front wheels to swing, which form a parallel link. A suspension unit is interposed between the front swing arm and the frame, and b) a rear wheel is pivotally supported on a vertical portion near a rear portion of the frame and extends rearward to form a parallel link. A rear steering arm that rotatably supports the rear wheel in a cantilever manner is pivotally mounted between the tips of a pair of upper and lower rear swing arms that are curved so as to horizontally swing, and the vertical portion near the rear portion of the frame and one of the above A suspension unit is interposed between the rear swing arm and c) a first steering shaft having a handlebar at an upper end is provided at a front end portion of the frame, and a second steering shaft is provided at the frame. The third steering shaft is rotatably supported by the rear portion of the frame in the intermediate portion so as to be rotatable about shafts in a substantially vertical direction, and d) the first steering shaft and the second steering shaft are provided on both shafts. The second steering shaft and the third steering shaft are connected to each other by offset first tie rods, and the second steering shaft and the third steering shaft are connected to each other by second tie rods offset from both shafts, and e) to the second steering shaft. One end of the third tie rod is offset and connected, the other end of the third tie rod is offset and connected to the front steering arm, and the third steering shaft is curved to allow the rear wheel to turn. One end of the fourth tie rod is offset and connected, and the other end of the fourth tie rod is off to the rear steering arm with respect to a pivot point of the rear swing arm. And f) the pivot point of the third tie rod with respect to the second steering shaft and each pivot point of the pair of front swing arms with respect to the frame are arranged on an extension line of the second steering shaft. , The fourth with respect to the third steering shaft
The pivotal fulcrum of the tie rod and the pivotal fulcrum of the pair of rear swing arms with respect to the rear portion of the frame are arranged on an extension line of the third steering shaft.

(Operation) According to the front and rear wheel steering system of the present invention, the first steering shaft rotates counterclockwise by turning the handlebar in the traveling direction (hereinafter, referred to as left direction), and the first steering shaft rotates in the first direction.
The rotation of the steering shaft causes the second steering shaft to rotate counterclockwise via the tie rod, and the rotation of the second steering shaft causes the third steering shaft to rotate counterclockwise via the tie rod. And
Due to the rotation of the second steering shaft, the front steering arm rotates to the left via the tie rod, and the front wheels turn to the left. At the same time, the rotation of the third steering shaft causes the rear steering arm to rotate leftward or rightward via the tie rod, and the rear wheels turn leftward or rightward. On the other hand, the reaction force from the road surface acting on the front wheels and the rear wheels and the vibrations of the front and rear wheels during traveling are
Most of them are absorbed by the steering shaft or the third steering shaft, and it becomes difficult to directly act on the first steering shaft (in other words, the handlebar). Further, in both steering systems from the handlebar to the front or rear steering arm, the first steering shaft, the second steering shaft, and the third steering shaft, which form a part of them, are fixed to the frame, respectively. The steering force from the handlebar is simultaneously transmitted to the front and rear steering arms, and the links that form the steering system for the front and rear wheels have a simple shape and are used for steering. Operation is standardized in the longitudinal direction of the vehicle body or around the vertical axis, and the first steering shaft, the second steering shaft, and the third steering shaft can be arranged on the center line of the vehicle body, so that the handlebar can be rotated left and right. Therefore, it is easy to dispose the front wheels and the rear wheels symmetrically to the left and right. Furthermore, both the front and rear wheels move up and down in a substantially vertical direction via a pair of upper and lower swing arms, and the wheel base is always substantially constant.

(Embodiment) FIG. 1 is a left side view of a motorcycle showing an embodiment of the present invention with a part thereof omitted, FIG. 2 is a view taken along the line II-II of FIG. 1, and FIG. Fig. 4 and Fig. 4 are rear views.

As shown in FIGS. 1 and 2, the frame 1 of the motorcycle X has a vehicle body center plane N (FIGS. 2, 3, and 4).
After being inclined downward from the front upper part 1a toward the rear intermediate part 1b, it is extended slightly downward to the rear end, and is divided into both sides at the rear end upper part 1c as shown in FIG. It is formed on the forked vertical portion 1d. Furthermore, each vertical part 1d
Is formed in a horizontal portion 1e that is bent at a lower end thereof at a right angle and extends forward, and a front end portion of each horizontal portion 1e is formed in a standing portion 1f that is inclined slightly rearward and upward.

The front wheel 5 is cantilevered by a front steering arm 10 pivotally mounted on a pair of leading swing arms 6, 7 extending forward from the standing portion 1f of the frame 1. That is, as shown in FIG. 1, a space is provided between the bifurcated upright portions 1f of the frame 1, and the base end portions of a pair of upper and lower swing arms 6 and 7 have pivot shafts 8 as shown in FIG. , 9 are pivotally mounted respectively. Each swing arm 6, 7 is curved in a C shape as shown in FIGS. 2 and 5 when viewed from above to allow the front wheel 5 to turn to the right, and each arm 6, 7 is The end portion is integrally formed with the pipe portion 6a, 7a into which the pivot shaft 8 or 9 is inserted.

As shown in FIG. 1, the lower end of the front steering arm 10 is provided with a pair of kingpins at the tips of the pair of swing arms 6 and 7 (vehicle body center plane N (FIG. 2, FIG. 3, and FIG. 4)). It is rotatably supported horizontally via 11. And at the lower end of this front steering arm 10,
As shown in FIG. 2, a bearing sleeve 10a is integrally formed orthogonal to the vehicle body center plane N.
The axle 5a of the front wheel 5 is rotatably and cantilevered through a bearing 5b. As shown in FIG. 3, the front steering arm 10 has its lower portion bent upward from the vehicle center plane N to one side (left side of the vehicle body, right side in FIG. 3).

On the other hand, the rear wheel 15 has a rear steering arm 2 pivotally attached to a pair of upper and lower trading-type rear swing arms 16 and 17 extending rearward from between the forked vertical portions 1d of the frame 1.
It is cantilevered at 0. That is, as shown in FIGS. 1 and 2, between the upper end and the lower end of the bifurcated vertical portion 1d, the base end portions of the pair of upper and lower rear swing arms 16 and 17 are arranged as shown in FIGS. ), The pivot shaft 18,1
9 are pivotally attached to each other. Further, each of the rear swing arms 16 and 17 is provided on one side of the vehicle body center plane N as shown in FIGS. 2, 7 (a) and 7 (b) so as to allow the rear wheel 15 to turn to the left. It is curved in a concave shape toward one side (left side), and the base end portions of the arms 16 and 17 are formed integrally with the pipe portions 16a and 17a into which the pivot shafts 18 or 19 are inserted.

At the ends of the pair of rear swing arms 16 and 17 (on the center plane N of the vehicle body), the upper and lower ends of the rear steering arm 20 (see FIG. 1) are rotatably supported by a pair of king pins 21 (see FIG. 1). Has been done. A bearing sleeve 20a is integrally formed at an intermediate portion of the rear steering arm 20 (FIG. 1) at right angles to the center plane N of the vehicle body. The bearing sleeve 20a penetrates through the bearing sleeve 20a and the axle 15a of the rear wheel 15a. Bearing 15
It is rotatably supported via b. And the rear wheel 15
Is fixed to one end of the axle 15a protruding from the bearing sleeve 20a and supported in a cantilever manner. In addition, the bearing sleeve
A driven sprocket 22 is integrally rotatably provided at the other end of the axle 15a protruding from the shaft 20a. As shown in FIG. 1, in the vicinity of the lower portion of the frame vertical portion 1d, a drive sprocket 23 is driven by an engine (not shown) mounted on the frame 1 in front of the frame 1d via a gear mechanism (not shown). The drive sprocket 23 and the driven sprocket 22 are connected by an endless chain 24 or an endless belt.

Then, the first steering shaft 2 is welded and fixed to the front end upper portion 1a of the frame 1 on the vehicle body center plane N (Figs. 2 and 3) with its upper end inclined slightly rearward with respect to the vertical direction. It penetrates through the head pipe 3 and is rotatably arranged by a bearing 3a. At the upper end of the first steering shaft 2,
The handlebars 4 projecting to both sides are integrally fixed.

An end pipe 26 in which the second steering shaft 25 is welded and fixed in a substantially vertical direction to the frame middle portion 1b on the vehicle body center plane N (Figs. 2 and 3) with its upper end side inclined slightly rearward.
And is rotatably arranged by a bearing 27.

Further, the third steering shaft 35 passes through an end pipe 36 welded and fixed to the frame rear end upper portion 1c in a substantially vertical direction on the vehicle body center plane N (FIG. 4), and is rotatably arranged by a bearing 37. It is set up.

At the lower end of the first steering shaft 2, a first offset lever 41
The base end of the vehicle is located on the front end side of the vehicle body center plane N (FIGS. 2 and 3).
From one side to the one side (here, the left side), and is fixed. Further, the upper end of the second steering shaft 25 and the upper end of the third steering shaft 35 respectively have second and third upper offset levers 42 and 4 respectively.
The base end of 3 has a tip end side on the vehicle body center plane N (see FIGS.
It sticks out by sticking out from the same side (here, left side) from the figure.

1 and 2, the lower surface of the front end portion of the first offset lever 41 and the second upper offset lever 42
The upper surface of the tip end of the first tie rod 28 having rod ends 28a, 28b, which are one of universal joints, attached at both ends so that the offset amounts are equal to the first steering shaft 2 and the second steering shaft 25. Are linked by. Further, the upper surface of the second upper offset lever 42 near the base end and the upper surface of the tip end of the third upper offset lever 43 have the same offset amount with respect to the second steering shaft 25 and the third steering shaft 35, respectively. Are connected to each other by second tie rods 29 having rod ends 29a and 29b, which are one type of universal joints, attached at both ends.

A second lower offset lever is provided at a lower end of the second steering shaft 25.
The base end of 44 is fixed by protruding the tip end side from the vehicle body center plane N (FIG. 3) to one side (left side), and the lower end of the tip end of the offset lever 44 and the upper end of the front steering arm 10 are freely movable. Rod end 30a, 30b which is a kind of joint
Are connected by a third tie rod 30 via. The offset amounts of the fulcrums A and D at both ends of the third tie rod 30 are set to be equal.

Further, at the lower end of the third steering shaft 35, the base end of the third lower offset lever 45 is provided so that the tip end side is the vehicle body center plane N (FIG. 4).
Is fixed by projecting to one side (left side) orthogonal to this from the tip lower surface of the offset lever 45 and the intermediate portion of the rear steering arm 20 via rod ends 31a and 31b which are a kind of universal joints. It is connected by four tie rods 31.

By the way, as shown in FIG. 1, the offset amount a (4th tie rod 31) of the pivotal fulcrum J on the base end rod end 31a side
(Fig.) Is set to be smaller than the offset amount b (Fig. 4) of the pivotal fulcrum G on the tip rod end 31b side. Therefore, the rotation angle of the rear steering arm 20 is smaller than the rotation angle of the third steering shaft 35. As shown in FIG. 2, the fourth tie rod 31 has a shape in which both end portions are bent to one side at a substantially right angle and then further bent at a substantially right angle so as to be parallel to the vehicle body center plane N. .
In other words, like the rear swing arms 16 and 17, the rear swing arms 16 and 17 are curved in a concave shape to allow the rear wheel 15 to turn to the right.

Furthermore, front wheel 5 side suspension unit such as shock absorber
A bracket 52 extends from the middle pipe 26 near the center curved portion of the upper swing arm 6 and extends leftward from the middle pipe 26.
(FIG. 3) is interposed. As described above, by disposing the suspension unit 51 near the central curved portion of the upper swing arm 6, it is possible to effectively use the space above and to store the suspension unit in a compact manner.
The number of parts required for mounting 51 is minimized, and there is no interference with the front wheels 5 during turning. Further, a suspension unit 61 on the rear wheel 15 side such as a shock absorber is interposed between a bracket 62 extending downward from the vicinity of the base end of the lower rear swing arm 17 and a bracket 63 extending rearward from the end pipe 36. It is equipped.

In FIG. 2, 5c is a front wheel, 5d is a front tire, 55 is a front brake disc, 56 is a front caliper, 15c is a rear wheel, 15d is a rear tire,
65 is a rear brake disc and 66 is a rear caliper.

By the way, in the case of the present embodiment, as shown in FIG. 1, a straight line connecting the axis of the drive sprocket 23 and the axis of the driven sprocket 22 is a pair of upper and lower rear swing arms 16,17.
Since the rear wheel 15 is located in the middle of the sprocket 23, the rear wheel 15 moves up and down about the axis of the drive sprocket 23 fixed to the frame 1 as a fulcrum. The distance between the axes of 22,23 hardly changes.

Further, in the present embodiment, as is apparent from FIG. 1, the tip side of the third tie rod 30 with respect to the front steering arm 10 and the pivot points A, B and C of the pair of front swing arms 6 and 7 are from the side. It is located on the same straight line (here, an extension line of the first steering shaft 2) P, and the third tie rod
The pivotal fulcrums D of 30 and the pivotal fulcrums E and F of the pair of front swing arms 6 and 7 with respect to the frame front end upright 1f are:
It is located on the same straight line (here, an extension line of the second steering shaft 25) Q when viewed from the side, and the straight lines P and Q are substantially parallel to each other, and the third tie rod 30 and the swing arms 6 and 7 are , Are parallel to each other when viewed from the side, and form a so-called parallel link. Therefore, even if the front wheels 5 move up and down during traveling, the upper end of the front steering arm 10 is not pushed or pulled by the third tie rod 30 in association with the up and down movement, and therefore the steering arm 10 ( The direction of the front wheels 5) does not change. Further, in the present embodiment, similarly to the front wheel 5 side described above, the tip end side of the fourth tie rod 31 with respect to the rear steering arm 20 and the pivot points G, H, I of the pair of rear swing arms 16, 17 are seen from the side. Are located on the same straight line (here, an extension line of the king pin 21) R, and the pivotal fulcrum J of the proximal end side of the fourth tie rod 31 and the pivotal fulcrums of the pair of rear swing arms 16 and 17 with respect to the frame vertical portion 1d. K and L are located on the same straight line (here, an extension line of the third steering shaft 35) S when viewed from the side, and further,
The straight lines R and S are parallel to each other, and the fourth tie rod 31 and the rear swing arms 16 and 17 are parallel to each other when viewed from the side, and form a so-called parallel link. Therefore, even if the rear wheel 15 moves up and down while traveling, the upper end of the rear steering arm 20 will move along with the up and down movement of the fourth tie rod 31.
It is not pushed or pulled by and therefore the direction of the rear steering arm 20 (rear wheel 15) does not change.

However, the present invention is not limited to the above-mentioned configuration, and the pair of swing arms 6, 7 and 16, with respect to the base end side pivot points D and J of the tie rods 30 and 31 and the frame 1.
If the 17 pivot points E, F and K, L are arranged on the same straight lines Q and S, for example, the lengths of the tie rods 30 and 31 can be changed,
Tie rods 30 and 31 for swing arms 6, 7 and 16, 17
Can be implemented even if the angle is slightly inclined.

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

In FIGS. 1 and 2, the handlebar 4 is moved in the direction in which the driver is going to proceed (hereinafter, referred to as the right side).
When is rotated, the first steering shaft 2 rotates clockwise and the first offset lever 41 rotates clockwise together with the first steering shaft 2. At the same time, the first tie rod 28 pulls it forward, the second upper offset lever 42 at the upper end of the second steering shaft 25 rotates clockwise together with the second steering shaft 25, and the second tie rod 29 pulls it forward. Third
The upper offset lever 43 rotates clockwise with the third steering shaft 35. At this time, the second steering shaft 25 and the third steering shaft
The rotation angle of 35 is the first steering shaft 2 and the second steering shaft 25 or the third steering shaft 2.
Since the offset amount at both ends of the first tie rod 28 and the offset amount at both ends of the second tie rod 29 with respect to the steering shaft 35 are equal to each other, they are equal to the rotation angle of the first steering shaft 2. At the same time, the second lower offset lever 44 at the lower end of the second steering shaft 25 and the third lower offset lever 45 at the lower end of the third steering shaft 35 are also clocked by the rotation of the second steering shaft 25 or the third steering shaft 35, respectively. Rotate in the direction.

Then, as the second lower offset lever 44 rotates, the third tie rod 30 is pushed forward so that the front steering arm 10 moves to the front swing arms 6 and 7.
Rotate clockwise around the fulcrums B and C of
Turns to the right. At this time, the rotation angle of the front steering arm 10 depends on the second steering shaft 25 and the third tie rod 30 with respect to the pivot points B and C of the front steering arm 10.
Since the offset amounts at both ends are equal, they are equal to the rotation angle of the second steering shaft 25 and also equal to the rotation angle of the first steering shaft 2. Even when the handlebar 4 is rotated in the opposite direction (left side), the front wheels 5 turn leftward in the same manner as described above.

Further, as the third lower offset lever 45 rotates, the fourth tie rod 31 is pulled forward and the rear steering arm 20 moves clockwise with the pivotal fulcrums H and I with the rear swing arms 16 and 17 as fulcrums. It rotates and the rear wheel 15 turns to the right. At this time, the rotation angle α of the rear steering arm 20 is the rotation angle α of the rear wheel 15 (Fig. 2).
Is the tip of the fourth tie rod 31 with respect to the pivot points H and I of the third steering shaft 35 and the rear steering arm 20 (rod end 3
1b side) offset amount b is the fourth relative to the third steering shaft 35
Since it is larger than the offset amount a of the tie rod 31 base end (rod end 31a side), the rotation angle of the third steering shaft 35 is smaller than the rotation angle β of the first steering shaft 2 (FIG. 2). Even when the handlebar 4 is rotated in the opposite direction (left side), the rear wheel 15 turns leftward in the same manner as described above.

Further, the vertical movement of the front wheels 5 during traveling or diving is performed by a pair of upper and lower front swing arms forming a parallel link.
Since the rocking action of 6, 7 is followed, the front wheel 5 smoothly moves up and down in a substantially vertical direction. Further, since the rear wheel 15 also moves vertically in a substantially vertical direction via the pair of upper and lower rear swing arms 16 and 17 forming a parallel link, the wheel base remains substantially constant even when the front and rear wheels 5 and 15 move vertically. There is.

8 to 11 show another embodiment of the present invention. The difference from the embodiment is that the upper rear swing arm 116 is pivotally mounted by a pivot shaft 118 between the middle portion of the forked vertical portion 1d of the frame and the middle portion of the rear steering arm 120. In addition, the third lower offset lever 145, which is provided at the lower end of the third steering shaft 135 having a shorter length than that in the above-mentioned embodiment, projects to the right side of the vehicle body center plane N, is offset to the right side of the vehicle body center plane N, and Four
While fixing the rod end 131a of the tie rod 131,
The rod end 131b of the fourth tie rod 131 is connected to the upper end of the rear steering arm 120.

Therefore, in the case of the present embodiment, when the driver rotates the handlebar 4 in the direction in which the driver is going to move (for example, to the right), the third lower offset lever 145 rotates clockwise together with the third steering shaft 135. , The pivot point (rod end 29b) of the second tie rod 29 with respect to the third upper offset lever 43 at the upper end of the third steering shaft 135 and the third at the lower end of the third steering shaft 135.
Since the pivot point (rod end 131a) of the fourth tie rod 131 with respect to the lower offset lever 145 is opposite to the vehicle body center plane N, the fourth tie rod 131 pushes the rear steering arm 120 to the rear, With the pivotal fulcrums H and I of the swing arms 116 and 17 as fulcrums, the rear wheels 15 rotate counterclockwise, and the rear wheel 15 turns to the left side in the opposite direction to the above embodiment. Further, since the fourth tie rod 131 is arranged above the upper side rear swing arm 116, the second steering shaft 135 (and the end pipe 136) can be made shorter and more compact than those of the above-mentioned embodiment. It should be noted that the other configurations are completely the same as those in the above-mentioned embodiment, and those common members are denoted by the same reference numerals as those in the above-mentioned embodiment.

By the way, in the front and rear wheel steering device of the present invention,
As is common to the two embodiments, the steering angle α of the rear wheels 15 during steering is considerably smaller than the steering angle β of the front wheels 5 (α = 2 to 3 when β = 40 to 45 °).
.Degree.), The offset amounts a and b at both ends of the fourth tie rods 31 and 131 are set to have a relationship of b> a (see FIGS. 4 and 11).

(Effects of the Invention) According to the front and rear 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 and the third steering shaft are provided in the middle of the steering system for the front and rear wheels from the first steering shaft having the handlebar to the steering arm, the tie rods and offsets that form the steering system for the front and rear wheels are provided. Each member such as a lever can be formed in a simple shape having a relatively short length, such as a straight rod shape or a straight plate shape, the members can be made common, and manufacturing becomes easy. Also,
Since the third steering shaft for steering the rear wheels is rotated via the second steering shaft for steering the front wheels, a long tie rod for transmitting rotation that connects the first steering shaft and the third steering shaft is provided. Displacement of each component when steering the front and rear wheels is unnecessary because the steering system is constructed by combining the components of relatively short and simple shape in the vertical direction and the horizontal direction by the joint. And the movable range of the joint between each component is reduced, there is less restriction on the arrangement of the steering system with respect to the vehicle body compared to the above-mentioned conventional device of this kind, and in addition, in correspondence to the left and right rotation of the handlebar, It is easy to arrange the steering system for turning the front and rear wheels symmetrically to the left and right respectively. Further, since each steering system is held by the frame at two or three positions of the first steering shaft and the second steering shaft or the second steering shaft and the third steering shaft, the structural strength is high.
(2) With the configuration of (1), most of the reaction force from the road surface acting on the front wheels and the rear wheels and the vibrations of the front wheels and the rear wheels during traveling are absorbed by the second steering shaft or the third steering shaft. , It is difficult to directly act on the handlebar.

(3) The wheel base is substantially constant even when the front wheels and the rear wheels move up and down. Further, the rear wheels can be steered in the forward (same) direction or the reverse direction in conjunction with the steering of the front wheels, and the front and rear wheels are cantilevered by the steering arm, so that they can be easily attached and detached. .

[Brief description of drawings]

1 to 7 show a first embodiment of a front and rear wheel steering system according to the present invention. FIG. 1 is a left side view with a part of a motorcycle omitted, and FIG. 2 is II-II of FIG. FIG. 3 is a front view, FIG. 4 is a rear view, FIG. 5 is a plan view showing the front swing arm and pivot portions thereof, and FIG.
FIG. 7 (a) is a perspective view showing the frame structure near the steering shaft.
Is a plan view showing the upper-side rear swing arm and its pivot portion, and FIG. 7 (b) is a plan view showing the lower-side rear swing arm and its pivot portion. Also, FIGS.
FIG. 8 shows a second embodiment of the front / rear wheel steering system of the present invention. FIG. 8 is a left side view with a part of the motorcycle omitted, and FIG. 9 is a view taken along the line IX-IX in FIG. FIG. 10 is a front view of the same, and FIG. 11 is a rear view of the same. 1 ... Frame, 2 ... First steering shaft, 4 ... Handlebar, 5 ... Front wheel, 6,7 ... Front swing arm, 10
...... Front steering arm, 15 …… Rear wheel, 16,17,
116 …… Rear swing arm, 20,120 …… Rear steering arm, 25 …… Second steering shaft, 28,29,30,31,131 ……
Tie rod, 35,135 …… Third steering shaft, 41,42,43,44,45,1
45 …… Offset lever, 51,61 …… Suspension unit.

Claims (4)

[Claims] 1. A front portion of the frame is pivotally supported and extends forward,
A front steering arm that rotatably supports the front wheels in a cantilever manner is pivotally mounted horizontally between the tips of a pair of upper and lower front swing arms that are curved to allow the front wheels to swing, which form a parallel link. A suspension unit is interposed between the front swing arm and the frame, and is pivotally supported on a vertical portion near a rear portion of the frame and extends rearward,
A rear steering arm that rotatably supports the rear wheel in a cantilever manner is pivotally mounted between the tips of a pair of upper and lower rear swing arms that are curved to allow the rear wheel to turn, and that form a parallel link. Then, a suspension unit is interposed between the vertical portion near the rear portion of the frame and one of the rear swing arms, the first steering shaft having a handlebar at the upper end is provided at the front end portion of the frame, and the second steering shaft is provided at the second steering shaft. A third steering shaft is rotatably supported by a rear portion of the frame at an intermediate portion of the frame so as to be rotatable about shafts in a substantially vertical direction, and the first steering shaft and the second steering shaft are provided on both shafts. The second steering shaft and the third steering shaft are connected to each other by the first tie rods that are offset from each other, and the second steering shaft and the third steering shaft are connected to each other by the second tie rods that are offset from both shafts. One end of the three tie rods is offset and connected, the other end of the third tie rod is offset and connected to the front steering arm, and the third steering shaft is curved so as to allow the rear wheels to turn. One end of the fourth tie rod is offset and connected, and the fourth tie rod is connected to the rear steering arm by the fourth tie rod.
The other end of the tie rod is offset and connected to the pivot point of the rear swing arm, and the pivot point of the third tie rod with respect to the second steering shaft and each pivot point of the pair of front swing arms with respect to the frame are It is arranged on the extension line of the second steering shaft, and the pivotal fulcrum of the fourth tie rod with respect to the third steering shaft and the pivotal fulcrum of the pair of rear swing arms with respect to the frame rear portion are arranged on the extension line of the third steering shaft. A front and rear wheel steering device for a two-wheeled vehicle characterized by being arranged. 2. An offset amount at both ends of the third tie rod with respect to each pivot of the second steering shaft and the front steering arm is equalized, and an offset amount at one end side of the fourth tie rod with respect to the third steering shaft is defined as follows. The front / rear wheel steering system for a two-wheeled vehicle according to claim 1, wherein an offset amount on the other end side of the fourth tie rod with respect to a rear steering arm is smaller. 3. The pair of front swing arms and the third tie rod form parallel links with each other, and the pair of rear swing arms and the fourth tie rod form parallel links with each other. Alternatively, the front and rear wheel steering device for the two-wheeled vehicle according to item 2. 4. A base end of a first offset lever is provided at a lower end of the first steering shaft so as to project to one side, and a base end of a second upper offset lever is provided at an upper end of the second steering shaft and the third steering shaft. The base end of the third upper offset lever is provided at the upper end of the shaft so as to project to one side, and the lower end of the first offset lever and the upper end of the second upper offset lever are respectively interposed by universal joints. The first tie rods are connected to each other, and the lower surface of the first offset lever near the base end portion and the upper surface of the tip end portion of the third upper offset lever are respectively interposed by a universal joint to form a second joint.
Connected by a tie rod, the base end of the second lower offset lever is provided at the lower end of the second steering shaft so as to project to one side, and the lower end of the tip of the second lower offset lever and the front steering arm,
The position of the front swing arm offset from the pivot point is connected by a third tie rod with a universal joint interposed therebetween, and the base end of the third lower offset lever is directed to one side at the lower end of the third steering shaft. 4. A tie rod which is provided so as to project, and a lower end surface of the offset lever and a position of the rear steering arm which is offset with respect to a pivotal fulcrum of a rear swing arm are connected by a fourth tie rod with a universal joint interposed therebetween. The front and rear wheel steering device for a motorcycle according to any one of 1.