FIELD OF INVENTION

The invention generally relates to a swinging power unit type motorcycle and more particularly to mounting arrangement of the swinging power unit by the swing arm and is made swing-able with respect to a frame along with the swing arm.

BACKGROUND

In the power system of a motorcycle, generally a power unit is mounted on a body. A rear fork formed of pipe members is pivoted at one end to the intermediate rear part of the body. A rear wheel is borne at the other end, and is connected at said other end with the body side through cushion units to be swing-able including the rear wheel. The rear wheel and power unit are connected with each other through a chain or the like.

In the above power system, because the power unit and the rear fork supporting the rear wheel are separated from each other, and the rear wheel including the rear fork swings, a chain tensioner for the chain (or a belt tensioner in case a belt is used) will be required and the mechanism including its supporting means will be complicated.

Therefore, such system is adopted in a somewhat large motorcycle. In case of a small and light motorcycle, a simplified system in which the power system moves integrally is desirable.

Where the power system moves integrally, the power unit is formed by integrally connecting a power unit, rear wheel, and power-transmitting member, and is made swing-able with respect to a frame. A cushion unit is provided in between the power unit and the frame. In this case the power unit acts as a load-bearing member and thus requires adequate physical stiffness parameters that add to design complexities increased weight and cost.

Further the serviceability of rear wheel becomes difficult as the rear wheel is secured to the integral transmission case of the power unit.

Therefore it is necessary to lighten and simplify the power system including the rear wheel serviceability, and a sufficient strength must be retained while attaining the above.

SUMMARY

The present invention provides a swinging power unit type motorcycle, including a body frame, having a swing arm attached to the rear portion of the body frame a rear wheel secured rotatable to the swing arm and a cushion unit provided between the swing arm and the body frame.

The swing arm is adapted in such a way that a space to accommodate a power unit hung and secured from the swing arm is provided. In such a case the swing is constructed to bear the load and the power unit secured from the swing arm does not act as a load-bearing member.

Further as the power unit and the rear wheel are secured from the swing arm there is no relative motion between the two enabling a simple and required transmission system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawing which is incorporated in and constitute embodiments of the invention, illustrate several aspects of the invention and together with a description of the embodiments serve to explain the principles of the invention and thus, are not limited of the present invention and a brief description of the drawing is as follows:

Figure 1 is the side view of a swinging power unit mounted on the motorcycle according to an embodiment of the invention.

Figure 2 is an exemplary arrangement of the embodiments of the invention.

DETAILED DESCRIPTION

The embodiments disclosed below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. The invention may have application to all types of two wheeled vehicles.

Reference is made to Figure 1, which illustrates a step through type, motorcycle having a swing-able power unit (105) in accordance with the preferred embodiment of the invention. While the illustrated motorcycle comprises a step through motorcycle, certain features, aspects and advantages of the present invention may also find utility with other swinging power unit type motorcycles.

Said motorcycle is having a body frame (112) which extends firstly, obliquely downwards from the head pipe (not shown in figure) secondly, rearwards parallel to the ground defining first horizontal structure (113) and thirdly, obliquely upwards (109), and finally, rearwards substantially parallel to the ground defining second horizontal structure (114), said body frame (112) is formed of two horizontal members (113, 114) running parallel to each other spaced in transverse direction of the motorcycle.

Further, a swing arm (104) is pivotally connected to the obliquely upwards extending section (109)
wherein, the swing arm (104) extends firstly, rearwards parallel to the ground defining upper horizontal section (115), secondly, vertically downwards (117) and thirdly rearwards parallel to the ground defining lower horizontal structure (116), swing arm (104) is formed of two members (115,116) spaced from each other in transverse direction of the motorcycle.

Furthermore, a rear wheel (101) is secured to the body frame (112) through the rear suspension system. Wherein, the rear suspension system comprises of a swing arm (104) and a damper element (102) adapted to allow jounce and rebound of the rear wheel (101) with respect to the body frame (112).
The illustrated power unit (105) mounted in a swing-able manner below the swing arm (104) and from said power unit (105) power is transferred through the chain drive mechanism (107) to the rear wheel (101). The rear wheel (101) has an axle shaft (110), which is rotatable supported by the rear end of the lower horizontal structure (116) of the swing arm (104). The rear wheel (101) swings with the power unit (105) and its motion is damped by damper (102) thereby providing suspension for the rider. As the power unit (105) is swing-able there is no relative motion between the power unit drive shaft (106) and the wheel axle (110).

The power unit (105) is interposed in the space provided by an inverted L structure formed by the upper horizontal section (115) and the vertically downwards extending portion (117) of the swing arm (104). The power unit (105) can be bolted through appropriate brackets provided on the surface of power unit (105) casing and corresponding bosses provided on the swing arm (104).

Further, referring to figure 2 and comparing the fixing arrangement of the damper unit (102) over the swing arm (104) with figure 1, two of the possible exemplary arrangements are explained. In figure 1, damper unit (102) is fixed over the lower horizontal section (116), wherein figure 2 is providing another possible arrangement for the damper unit (102) mounting over the vertically downwards extending portion (117) of the swing arm such that the damper unit (102) is secured at the centre position of the motorcycle.

WHAT IS CLAIMED IS

1) A power unit swing type motorcycle comprising:

a body frame attached with a head pipe in front side of the motorcycle such that said body frame extending firstly, obliquely downwards from the head pipe secondly, rearwards parallel to the ground defining first horizontal structure and thirdly, obliquely upwards, and finally, rearwards substantially parallel to the ground defining second horizontal structure;

a swing arm pivotally connected to the obliquely upwards extending section of the frame, such that the swing arm extends firstly, rearwards parallel to the ground defining upper horizontal section, secondly, vertically downwards and thirdly rearwards parallel to the ground defining lower horizontal structure and atleast one damper unit is interposed between said body frame and the swing arm;

a power unit is interposed in a space neighbouring said swing arm and fixed with said swing arm through at least one fastening means; and

a rear wheel supported by said lower horizontal structure of the swing arm such that it can be driven by said power unit.

2) The power unit swing type motorcycle, as claimed in claim 1, wherein the space for the power unit is provided by an inverted L structure formed by the upper horizontal section and the vertically downwards extending portion.

3) The power unit swing type motorcycle, as claimed in claim 2, wherein the power unit is supported by the frame and the vertically downwards extending portion of the swing arm.

4) The power unit swing type motorcycle, as claimed in claim 1, wherein the damper unit is fixed with the frame and the vertically downwards extending portion.