(i) Field of the Invention
The present invention relates to an improvement in or relating to a saddle type vehicle employing a rear-wheel independent suspension system, and more particularly to an improved saddle type wheeled vehicle for off-road service which is designed to reduce changes in the camber aspect of its rear suspension system.
(ii) Description of the Prior Art
It is an essential requirement in the design of a vehicle for use on irregular and uneven ground that a driver of the vehicle may readily control the balance thereof while driving on the rough and uneven ground and also that the vehicle exhibits an excellent maneuverability. In this respect, there has been developed a four-wheeled vehicle of saddle-riding type, in which there are provided two wheels each on the front and rear axles.
It is generally known that a variety of vehicles of four-wheeled saddle-riding type have been developed which have a common basic construction as follows.
That is, the saddle-type four-wheeled vehicle of this type is designed with a main frame, on which a front pair of wheels and a rear pair of wheels are provided, each of these wheels having a tire of low internal pressure and with a relatively great area of contact upon the ground, which is so-called "a balloon tire". Also, this type of vehicle is generally equipped with a bar-handle for operating the front wheel steering mechanism, and it has a step structure upon which the driver may rest his feet on either side of the main frame.
While the rigid type suspension was once a common construction for this type of vehicle in the earlier designs, an improvement has been adopted in the meantime such that the front axle is equipped with the wishbone-type suspension, and the rear axle is provided with a rigid-axle unit suspension. One of the most recent type of suspension known, employs a rear suspension of independent type such as, for example, a diagonal swing axle type suspension.
However, when adopting an independent type suspension system for the rear wheels of a vehicle, it would be essential that a vehicle's frame has a substantial width, since an engine may take a substantial space in the middle thereof. Because of such a spatial restriction, when there is an equal distance across either pair of wheels, it is inevitable that the inclination of a tire with respect to the vertical line or the camber of a tire would become greater, particularly when running on irregular ground, owing to a relatively short extension of a suspension arm of the suspension system. This is an undesirable restriction in the conventional design of suspension for this type of vehicle.
In consideration of such an undesirable restriction in design which is particular to the conventional construction of a four-wheeled vehicle as noted above, it would be desirable to reduce such undesirable changes in the camber of a pair of wheels which may occurs particularly when running on irregular ground.
The present invention is essentially directed to the provision of an improved construction of a rear suspension for a wheeled vehicle of saddle riding type for use on irregular ground.