JPS63232091A - Rear-wheel suspension for motorcycle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a motorcycle equipped with a unit swing type engine.

[Conventional technology]

A unit swing engine integrates the engine body, power transmission mechanism, and rear wheel shaft into one transmission case, and because it reduces the number of parts and reduces manufacturing costs, it is widely used in various types of motorcycles. Widely used.

As disclosed in Japanese Unexamined Patent Publication No. 58-131322, a motorcycle equipped with this type of unit swing type engine has a bracket protruding from the upper surface of the rear part of the transmission case of the unit swing type engine. It is common to install a shock absorber between the vehicle body frame and the vehicle body frame.

[Problem that the invention seeks to solve]

However, in such a structure, since the position supporting the rear part of the transmission case is largely shifted laterally from the center of the vehicle body, the rear part of the transmission case is twisted by the torsional moment generated by the reaction force from the ground, and the rear part of the transmission case is twisted. There was a problem where the wheels tended to tilt left and right. Furthermore, in order to suppress this, it is necessary to increase the rigidity of the transmission case, which causes the problem of increased weight. This problem becomes especially noticeable when wide tires are installed.

[Means for solving problems]

Therefore, the applicant analyzed the relationship between the support of the unit swing type engine and the torsion at the rear of the transmission case, and
Based on the results, we conducted an experiment and found that when the front part of a unit swing type engine is supported, the entire transmission case is elastically deformed, absorbing the twisting of the rear part of the transmission case.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a rear wheel suspension system for a motorcycle that can prevent the rear wheel from tilting to the left or right without increasing the rigidity of the transmission case more than necessary. be. The rear wheel suspension system according to the present invention is provided with a bracket that protrudes upward substantially along the direction of this surface on the rear surface of the engine body of a unit swing type engine, and a load is applied between the bracket and the vehicle body frame on the rear surface of the engine body. A shock absorber is inserted so as to act in the plane direction of the surface.

[Effect]

In the present invention, the entire transmission case is elastically deformed to bend vertically, and this elastic deformation absorbs twisting of the rear portion of the transmission case.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view showing a rear wheel suspension system for a motorcycle according to the present invention, FIG. 2 is a plan view of the same, and FIG. 3 is a side view showing a scooter type motorcycle equipped with a rear wheel suspension system. In FIG. 3, the reference numeral 1 indicates a motorcycle having a footrest 2. As shown in FIG.

Reference numeral 3 denotes a body frame extending in the longitudinal direction of the motorcycle 1, which includes a handling coaxial pipe 3a' and a footrest plate 2 from the steering shaft pipe 3a.
A down tube 3b consisting of a single tube whose lower side faces rearward, and a pair of left and right tubes that branch from the rear of the down tube 3b to left and right, bend upward at the rear of the footrest 2, and then head rearward again. It is composed of a rear frame 3c made of a tubular body. Steering shaft tube 3 at the front of the vehicle body
A front wheel 5 is suspended via a front fork 4 rotatably supported by a, and a wide rear wheel 7 is suspended at the rear via a unit swing type engine 6 pivotally connected to a rear frame 3C. The front and rear wheels are equipped with ultra-low pressure wide tires.

In order to function as a component of the suspension system for the rear wheel 7, the unit swing type engine 6 is pivoted to a support bracket 8 fixed to the rear frame 3c by a pivot shaft 9 so as to be able to swing up and down. Similar to the conventional one,
By integrally holding the engine body 11, the power transmission mechanism equipped with a belt or chain that transmits the power of the engine body 11 rearward, and the rear wheel shaft 12 that supports the rear wheels 7 with the transmission case 13, It has a substantially inverted shape when viewed from above. Specifically, the engine main body 11 is a forced air-cooled engine having a crankshaft disposed in the vehicle width direction, and has a cylinder supported substantially vertically.

On the right side of the cylinder, a cooling fan for cooling the cylinder and a generator are arranged in the shroud, and on the left side, a power transmission mechanism connected to the crankshaft and a transmission case 13 covering this mechanism are arranged. There is.

15 is an air cleaner disposed above the transmission case 13, and 16 is a carburetor interposed between the air cleaner 15 and the engine body 11. This carburetor 16 is disposed at a corner formed by the transmission case 13 and the engine body 11.

Reference numeral 17 denotes an exhaust pipe extending obliquely downward from the front surface of the engine body 11. This exhaust pipe 17 extends rearward under the engine body 11, and is connected to the rear wheel 7 at the engine body 11.
The exhaust muffler 18 is connected to the exhaust muffler 18 supported on the right side of the exhaust muffler 18.

Reference numeral 21 denotes a bracket that is integrally provided on the rear surface 22 of the engine main body 11 and protrudes upward substantially along the surface direction of the rear surface 22. In the embodiment, it is protruded from the rear surface of the crankcase at a position shifted to the right from the center of the vehicle body. The reason for this shift to the right is to bring the rear wheel 7 as close to the crankcase as possible. Reference numeral 23 denotes a shock absorber that buffers the vertical swinging of the unit swing type engine 6, and is housed in a triangular space in side view formed between the rear frame 3c, the rear wheel 7, and the engine body 11. There is. The lower part of this shock absorber 23 is pivotally connected to the bracket 21 with a pivot 24, and the upper part is connected to the rear frame 3C.
It is pivotally connected by a pivot 26 to a mounting bracket 25 fixed to the. Here, the fixing position of the mounting bracket 25 is set so that a line connecting the center of the pivot shaft 26 and the center of the pivot shaft 24 is substantially parallel to the surface direction of the rear surface 22.

In the embodiment, since the surface direction of the rear surface 22 of the engine body 11 is inclined upward, the mounting bracket 25
It is positioned further forward than Braqueso) 21. That is, the shock absorber 23 is interposed between the bracket 21 and the rear frame 3c so that the load acts in the direction of the rear surface 22.

In the rear wheel suspension system for a motorcycle configured in this manner, the unit swing type engine 6 is pivotally connected to the rear frame 3C by the pivot 9, and is also supported by the rear frame 3C via the shock absorber 23. , the rear wheel 7 can be suspended vertically movably with respect to the rear frame 3C.

Furthermore, since the entire transmission case 13 is elastically deformed to bend vertically, this elastic deformation can absorb twisting occurring at the rear of the transmission case. Therefore, it is possible to suppress the rear wheel shaft 12 from swinging from side to side.

FIG. 4 is a schematic diagram seen from the rear for explaining the state in which tear stains are absorbed at the rear of the transmission case.

The solid line indicates a state assuming that the transmission case I3 is not elastically deformed in the vertical direction, that is, a state in which the rear part of the transmission case is supported as in the conventional case. In this state, the rear portion of the transmission case is twisted about the support portion, so the elevation angle θ of the rear wheel shaft 12 becomes large. The two-dot chain line shows the state of the device of the present invention in which the support at the rear of the transmission case is released, and in this state, the entire transmission case 13 is elastically deformed upward. As a result, the rear part of the transmission case moves upward relative to the rear wheel shaft 12, so that the twist occurring in the rear part of the transmission case is absorbed, and the elevation angle θ of the rear wheel shaft 12 becomes smaller.

At this time, the rear wheel shaft 12 is displaced upward by a displacement amount δ due to the elastic deformation of the transmission case 13.

Here, since the bracket 21 is made to protrude upward substantially along the surface direction of the rear surface 22 and the shock absorber 23 is interposed so that the load acts in the surface direction of the rear surface 22, the load is transferred to the rear surface 22.
can be made to act in a stronger direction. Therefore, there is no need to provide special reinforcement to the rear surface 22 to increase its rigidity.

In addition, in the embodiment, the carburetor 16 is connected to the transmission case 13.
and the engine main body 11,
Since the shock absorber 23 is arranged on the opposite side, the corner space that must be formed between the tread of the rear wheel 7, which has an arcuate cross section, and the unit swing type engine 6 can be effectively utilized. Can be done.

Furthermore, there is an advantage that interference between the shock absorber 23 and the air cleaner 15 can be suppressed, and the volume of the air cleaner 15 can be increased.

〔Effect of the invention〕

As explained above, according to the present invention, a bracket is provided on the rear surface of the engine body of a unit swing type engine and protrudes upward substantially along the surface direction, and the load is applied between the bracket and the vehicle body frame. Since the shock absorber is inserted so as to act in the direction of the rear surface, the entire transmission case is elastically deformed to bend vertically, and this elastic deformation absorbs the twisting of the rear part of the transmission case.

Therefore, since it is possible to suppress the rear wheel shaft from swinging, it is possible to suppress the rear wheel from tilting to the left or right. Further, since the transmission case, which has a large cross-sectional area as a whole, elastically deforms to absorb twisting of the rear part of the transmission case, there is no need to make the rigidity of the transmission case itself higher than necessary.

[Brief explanation of drawings]

FIG. 1 is a side view showing a rear wheel suspension system for a motorcycle according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a side view showing a scooter type motorcycle equipped with a rear wheel suspension system. FIG. 4 is a schematic diagram seen from the rear for explaining the state in which tear stains are absorbed at the rear of the transmission case. 3°°, Body frame - 6... Unit swing type engine, 7... Rear wheel, 11... Engine body, 13... Transmission case, 21... Bracket, 22 ... Rear surface, 23 ... Shock absorber. Figure 2 Figure 4

Claims (1)

[Claims] In a motorcycle in which a unit swing type engine, in which an engine body, a power transmission mechanism, and a rear wheel shaft supporting a rear wheel are integrally held by a transmission case, is pivoted to a body frame, approximately this A rear wheel suspension system for a motorcycle, comprising a bracket that protrudes upward along the surface direction, and a shock absorber interposed between the bracket and the body frame so that the load acts in the surface direction of the rear surface. .