JPH0649475B2 - Rear-wheel drive for motorcycles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel drive system for a motorcycle that supports a rear wheel by means of a cantilever type rear arm, and particularly, the rear wheel is driven by a chain. Related to the device.

[Conventional technology]

Conventionally, a technique of supporting a rear wheel of a motorcycle by a cantilever type rear arm is known (for example, Japanese Utility Model Publication No. 53-53237).
Issue). Such a cantilever type suspension device has a simple structure and is extremely effective in reducing the weight of the vehicle, but the rigidity of the rear arm decreases, so it is necessary to consider to reduce the external force acting on it as much as possible. There is.

[Problems to be solved by the invention]

In the case of chain driving the rear wheels supported by the cantilever type rear arm, if the axis of the rear arm is not aligned with the extension direction of the drive chain, a large bending force acts on the rear arm due to the tensile force of the chain. Proper reinforcement is required.

[Object of Invention, Structure for Solving Problems]

The object of the present invention is to reduce the bending force acting on the rear arm when driving the rear wheel supported by the cantilevered rear arm to chain drive, and to reduce the required strength to reduce the weight and structure. For the sake of simplification, a base end portion that is rotatably supported by a pivot bearing on a rear portion of a vehicle body frame, and a rear end that extends rearward from the base end portion and rotatably supports a rear wheel 1 In a rear wheel drive device of a motorcycle having a cantilevered rear arm having a book support arm portion, a rear end of the support arm portion of the rear arm is protruded to both sides in a vehicle width direction from the support arm portion, and a protruding end portion Both sides are provided with a cylinder portion in which a bearing for a rear wheel axle is mounted, the cylinder portion of the rear wheel is pierced through and supported by the cylinder portion, and flanges are provided at both ends of this axle portion so as to face the protruding end portion of the cylinder portion. On the flange on the rear wheel side of the rear arm of the flange The dynamic disk is positioned and mounted around the cylinder, and the rear wheel drive sprocket, which is connected to the output shaft of the engine through the drive chain, is positioned and mounted around the cylinder on the flange on the other side. The pivot bearing is positioned below the drive chain, and the rear wheel tire extends toward the position below the drive chain gradually outward in the vehicle width direction as the support arm portion of the rear arm goes rearward from the base end portion. It is characterized in that it is formed so as to extend inward at a position more rearward.

〔Example〕

The present invention will be described below with reference to the illustrated embodiments. In the figure, 1 is a motorcycle, and 2 is its body frame. A front wheel 4 is rotatably supported on the front portion of the body frame 2 via a front fork 3, and a rear wheel 6 is supported on the rear portion via a rear arm 5. Reference numeral 7 is a shock absorber that connects the free end of the rear arm 5 and the vehicle body frame 2. Reference numeral 8 is a power unit composed of an engine and a transmission, and drives a driven sprocket 10 mounted on the rear wheel 6 from its output shaft 8a via a chain 9. Reference numeral 11 is a fuel tank, and 12 is a passenger seat.

The rear arm 5 is a cast product of an aluminum alloy, is machined, and is supported by a pivot shaft 30 on the rear portion of the vehicle body frame 2 so as to be vertically swingable. The rear arm 5 is of a cantilever type, and as shown in FIG. 2, a base end portion 5a supported by a pivot bearing 35, which will be described later, so as to be vertically swingable with respect to the vehicle body frame 2, and from this base end portion 5a. It is formed of one supporting arm portion 5b extending rearward and an axle supporting cylinder portion 5c provided at a rear end of the supporting arm portion 5b. The supporting arm portion 5b gradually extends outward from the base end portion 5a toward the rear in the vehicle width direction to a position below the chain 9, and extends inward at a position rearward of the tire 6d of the rear wheel 6. Is formed. Further, the tubular portion 5c is formed so as to project from the rear end of the support arm portion 5b to both sides in the vehicle width direction, and the ball bearings 13, 13 are concentrically fitted and fitted to both of the projecting end portions. There is. A rear wheel support cylinder 14 and a support cylinder 15 of the driven sprocket 10 are fitted to the ball bearings 13, 13.
Each of the cylinders 14 and 15 is non-rotatably connected to each other by an inner spline formed on the inner side and an outer spline formed on the outer surface of the axle 16, and is further prevented from coming off by a nut 17. Reference numeral 16a is a cylindrical portion that supports the inner ends of the cylinders 14 and 15. In this embodiment, the outer spline formed on the outer surface of the axle 16 is composed of a large-diameter portion on the head 16b side and a small-diameter portion on the bolt 16c side, so that the axle 16 can be easily inserted and removed.

That is, the rear wheel support cylinder 14, the support cylinder 15, and the cylinder portion 5c of the axle 16 are rotatably supported via the ball bearing 13. The rear wheel support cylinder 14 and the support cylinder 15 are provided with mounting flanges 14a and 15a, respectively, which are opposed to the projecting ends of the cylinder portion 5c. The mounting flange 14a of the rear wheel support cylinder 14 is arranged on the rear wheel 6 side of the rear arm 5, and the mounting flange 15a of the support cylinder 15 is arranged on the side of the rear arm 5 opposite to the rear wheel 6.

The rear wheel and the braking disc 18 are supported by the mounting flange 14 a of the rear wheel support cylinder 14. The braking disk 18 is arranged at a position between the rear wheel 6 and the rear arm 5 and around the cylindrical portion 5c, and constitutes a disc brake that cooperates with the caliper 19 and the pad 20. Reference numerals 21 and 22 are bolts and nuts for fixing the braking disc 18 to the rear wheel support cylinder 14 together with the rear wheel 6 described later. The rear wheel 6 is a so-called casting wheel in which the spoke 6a, the rim 6b, and the hub 6c are integrally cast, and the spoke 6a is provided so as to be displaced from the widthwise center of the rim 6b in the direction opposite to the rear arm 5. A space is provided inside the rim 6b in which brakes such as the brake disk 18 and the caliper 19 are arranged. 6d is a tire.

The cushioning rubber 23 is attached to the mounting flange 15a of the support cylinder 15.
A mounting bolt 24 supported by the nut is provided, and the driven sprocket 10 is fastened by a nut 25. The driven sprocket 10 is also arranged at a position around the cylindrical portion 5c.

Reference numeral 26 is a decorative cover fitted to the inner peripheral surface of the hub 6c.

A rear end 5a of the rear arm 5 is supported by the vehicle body frame 2 so as to be movable in the front-rear direction and lockable. That is, the support ring 2a of the rear arm 5 is welded to the vehicle body frame 2, and the support members 31 supporting both ends of the pivot 30 are supported thereat slidably in the front-rear direction and welded to the support member 31. The bolt 32 and the two nuts 33 are arranged so that the front-rear position can be adjusted and locked. Reference numeral 34 is a spacer interposed between the left and right support members 31, and this spacer 34 is provided with the pivot bearings 35, 35, and the rear arm 5
Both ends of are rotatably supported. The pivot bearings 35, 35 are plain bearings in this embodiment, but the present invention is not limited to this, and needle bearings and other rolling bearings can be adopted without any trouble.

The pivot bearing 35 is arranged below the chain 9 (below the pulling side).

Since this embodiment has the above construction, the power unit 8
Is driven, and the driven sprocket 10 mounted on the rear wheel 6 is driven from the output shaft 8a through the chain 9,
Since the support cylinder 15 rotates and the axle 16 and the rear wheel support cylinder 14 rotate with it, the rear wheel 6 is driven and the motorcycle runs.

〔The invention's effect〕

As described above, in the rear wheel drive system for a motorcycle according to the present invention, the rear wheel axle shaft is provided at the rear end of the support arm portion of the rear arm so as to project from the support arm portion to both sides in the vehicle width direction. Is provided with a rear wheel axle through which the flange is provided, and flanges facing the projecting ends of the cylinder are provided at both ends of the axle. Install the braking disc on the side flange around the cylinder, and on the other side the rear-wheel drive sprocket connected to the engine output shaft via the drive chain around the cylinder. A position where the pivot bearing is positioned below the drive chain, and the support arm portion of the rear arm is gradually moved outward in the vehicle width direction below the drive chain as it goes rearward from the base end portion. The rear wheel drive sprocket can be brought as close as possible to the rear wheel because the rear wheel drive sprocket is extended as far as possible, and the rear wheel support sprocket is used for rear wheel drive. Since it extends rearward from the lower position of the drive chain that extends forward from the sprocket, in other words, the position near the rear wheel, even if strong tension that drives the rear wheel acts between the output shaft and the driven sprocket, the rear arm No large bending force is generated in No. 5. Therefore, there is an effect that the rear arm 5 is not required to have high strength.

Further, since the rear arm cylindrical portion is projected from the support arm portion on both sides in the vehicle width direction and the bearings for axle support are provided on both of the projecting end portions, the distance between these bearings can be widened. Support is stable. Moreover, since the support arm is located between the two bearings, the rear end of the support arm is less likely to be twisted when a force is applied to the support arm from the rear wheel via the axle. Therefore, in order to secure the rigidity of the rear arm, it is not necessary to increase the size or provide reinforcement, so that the weight of the rear arm can be reduced.

In addition, when flanges are positioned on both ends of the axle (both sides of the cylinder) and braking discs and rear wheel drive sprockets are attached to these flanges respectively, a braking disc and rear wheel drive sprockets are provided at one end of the axle. Compared with, it is possible to reduce the amount of protrusion of the axle with respect to the cylinder portion, and it is compact. When the braking disc and the rear wheel drive sprocket are arranged at positions around the cylinder portion, the circumference of the cylinder portion provided for stabilizing the axle support and reducing the twisting force as described above can be used without waste, The mounting density of parts is increased and the rear arm rear part becomes compact.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a side view of a motorcycle, and FIG. 2 is an enlarged cross-sectional view showing a II-II cross section thereof. 5 ... Rear arm, 8 ... Power unit, 8a ... Output shaft, 9 ... Chain, 10 ... Sprocket, 35 ...
Pivot bearing.

Claims (4)

[Claims] 1. A base end portion rotatably supported by a pivot bearing on a rear portion of a body frame, and a support arm extending rearward from the base end portion to rotatably support a rear wheel by a rear wheel. A rear-wheel drive device for a motorcycle having a cantilevered rear arm having a rear portion, a rear end of a support arm portion of the rear arm,
A cylinder portion is provided which projects from the support arm portion on both sides in the vehicle width direction and has rear wheel axle bearings mounted on both of the projecting end portions. A flange facing the protruding end of the cylinder is provided, and a braking disk is positioned around the cylinder and attached to the flange on the rear wheel side of the rear arm of these flanges, and on the other side of the flange to the output shaft of the engine. A rear-wheel drive sprocket connected through a drive chain is positioned and mounted around the cylinder, the pivot bearing is positioned below the drive chain, and the support arm of the rear arm is rearward from the base end. It is formed so as to gradually extend outward in the vehicle width direction to a position below the drive chain and extend inward at a position rearward of the tire of the rear wheel. Rear-wheel drive system of the motorcycle. 2. The rear wheel drive system for a motorcycle according to claim 1, wherein the pivot bearing is a plain bearing. 3. The rear wheel drive system for a motorcycle according to claim 1, wherein the pivot bearing is a needle bearing or another rolling bearing. 4. The rear-wheel drive system for a motorcycle according to claim 1, wherein the rear arm is made of light alloy and is hollow.