Spring suspension device

TECHNICAL FIELD

The present invention relates to a spring suspension device between frame part or chassis part and wheel- bearing part of a vehicle, for example a motorcycle. In this connection, a vehicle is intended, in which the suspension of the bearing part relative to the frame/chassis is dependent upon the loading of the wheel or wheels which are arranged in the bearing part. The invention relates inter alia to a spring suspension device in a motorcycle or similar vehicle, which com¬ prises a frame, relative to which a rear fork bearing a rear wheel is rotatably mounted.

STATE OF THE ART

Spring suspension devices of said type have been in existence for a long time in a great number of variants, usually in combination with some form of shock absorp- tion. Helical springs made of metal with hydraulic shock absorbers can be considered as standard in this con¬ nection, but torsion suspension has also been proposed.

DESCRIPTION OF THE INVENTION

TECHNICAL PROBLEM

Said constructions in general function well under ordinary conditions of use, that is to say driving on normal roads. If greater demands are made, however, for

- example in competitions over country terrain with a motorcycle, there are such great demands for suspension characteristics adapted to the weight and driving style of the rider and the nature of the terrain that the abovementioned constructions do not meet the demands.

The object of the invention is therefore to bring about a suspension of the type mentioned in the introduction, which results in a low centre of gravity on the vehicle, especially the motorcycle. Moreover, the suspension is also to be able to exhibit low weight and simple construction and permit simple adjustability of a wide range of suspension characteristics.

The invention is also to be able to operate effectively in interaction with the shock absorption function so that space-saving arrangements can be designed. It is especially important in the case of motorcycles that the space behind the frame and in front of the rear wheel can be divided for accessory equipment (tank, battery etc.).

The suspension and shock absorber device is also to be able to contribute to easier and more adaptable frame construction since it is possible to reduce the material in the frame.

SOLUTION

The invention solves these problems inter alia and proposes the arrangement of an elongated plate spring connected to the frame part and chassis part and the wheel-bearing part. Moreover, one or more members, so- called deflecting members, are arranged on the parts and these members enter respectively into interaction with the spring at different degrees of loading of the rear wheel and an interaction between the respective member and the spring results in the latter coming to work with a spring constant corresponding to the interaction. The spring thus comes to work with a number of spring con- stants corresponding to the number of members. The shorter the spring excursion between deflecting member and the wheel-bearing part, the higher the spring con¬ stant, and vice-versa.

In embodiments of the inventive idea, different designs

are proposed for the respective deflecting member which can be made with a spherical shape or other curved shape which can interact with the spring part in question and on which, during the suspension function, the spring rolls and gives different spring constants.

According to one embodiment of the invention, a spring suspension device is characterised by an elongated composite spring, flexibly mounted at a front end on a first guide shaft fastened to the lower, front part of the frame, further flexibly mounted at a rear end on a second guide shaft in one end of a link member, the link member being at its other end flexibly mounted on said rear fork on a third guide shaft, and the frame is provided on its underside with at least a first deflect- ing member which is arranged at a distance from the first guide shaft in such a manner that it bears against the composite spring upon a first relatively low loading of the rear fork relative to the frame. The low loading can, for example, be caused by the dead weight of the vehicle.

In addition to the first deflecting member, a second deflecting member can also be arranged on the underside of the frame at a distance from the first deflecting member in such a manner that it bears against the com¬ posite spring only upon a loading of the rear fork relative to the frame, which is considerably greater than said first loading.

There can even be a number of deflecting members, according to the suspension characteristics desired. In one embodiment, the deflecting members consist of rollers which are rotatable about shafts which are directed horizontally transversely to the longitudinal direction of the composite spring. In order to bring about increased adaptation according to demands for individual suspension, the fastening of the deflecting members can be designed in such a manner that the height position and longitudinal displacement position of the deflecting

members relative to the frame are adjustable. In an alternative embodiment of the suspension according to the invention, the first deflecting member is designed with such a surface, turned towards the composite spring, that upon increasing loading of the rear axle relative to the frame, an ever greater part of the surface bears against the composite spring. In a further embodiment, elastic material is included in the respective deflecting member in order to make possible a smooth transition from one spring constant to another. The spring constant is thus changed continuously or discontinuously by means of the interaction with the deflecting member(s).

The spring can be flexibly fastened at its one end and loosely (longitudinally displaceably) mounted at its other end. The spring can also in principle be mounted oh two wheel-bearing parts via its respective ends. The spring is arranged in the longitudinal direction of the vehicle in a motorcycle or two-wheeled vehicle and preferably in the transverse direction in a car (four- wheeled vehicle) . In the case of fastening to two wheel- bearing parts, for example front and rear wheel of a motorcycle, there is one deflecting member or two symmetrically arranged groups of deflecting members (one group for each wheel) . Each group can comprise one or more deflecting members and the groups can share the central deflecting member. In one embodiment, the spring can be fastened directly in the wheel-bearing part.

The damping arrangement to be used in combination with this suspension can be of different types and be mounted in different positions, so that the relative movement between frame and rear axle is damped. Conventional hydraulic dampers mounted between the frame and the rear fork are a possible construction. A damper of the type which is referred to in US patent 4,773,514 has proved to be especially suitable in this connection. This, damper comprises a sector-shaped oil-filled housing, in which a vane is rotatable about a shaft projecting out from the

housing. Channels are arranged for overflow of oil from one part of the housing to the other part of the same upon rotation of the shaft in relation to the housing, the vane driving oil through these channels. The vane is fixed via a link in an articulation point to the bearing part. The vane works in the essentially vertical plane of the vehicle and is situated under the wheel-bearing part.

ADVANTAGES

By means of the invention, a simple and effective sus- pension function is made possible, which can in an advantageous manner be built together with a damping function so that said space-saving and dimension reduc¬ tion (in the frame) can be brought about in, for example, motorcycles. This is achieved by virtue of the fact that a force-absorbing arrangement can be installed on the lower parts of the vehicle and makes it possible that the space (U) directly under the saddle becomes free for accessory equipment. The change in the suspension for different degrees of loading on the wheel in question can be made stepless. The device can be made with low weight if so desired by means of the use of a composite spring.

LIST OF FIGURES

A presently proposed embodiment which has the parts which are characteristic of the invention will be described below with simultaneous reference to

the figure which shows parts of a motorcycle from the side.

DETAILED EMBODIMENT

In the figure, the frame of a motorcycle is indicated by 1. In this, a rear fork 2 is rotatably mounted in a bearing 3 and bears a rear wheel 4 which is subject to a load F.

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An elongated composite spring 5 (can in certain cases consist of a steel spring or a spring made of another material) is flexibly mounted at a front end on a first guide shaft 6 which is fixed to the lower part of the frame in a stay 7 which is arranged vertically adjustably in relation to the frame. At its rear end, the composite spring is flexibly mounted on a second guide shaft δ in one end of a link member 9. This link member 9 is at its other end flexibly mounted on a third guide shaft 10 on the rear fork 2. On the underside of the frame, at a distance from the first guide shaft 6, a first deflecting member 11 in the form of a roller is arranged, which is rotatable about a shaft directed horizontally trans¬ versely to the longitudinal direction of the composite spring. This shaft and its bearing can be fixed ver¬ tically in relation to the frame 1, but can also be vertically adjustable. A second deflecting member 12, also in the form of a roller, rotatable about a shaft and mounted in the same manner as is the case for the first deflecting member, is arranged on the underside of the frame at a still greater distance from the first guide shaft 6, so that the composite spring only bears against this roller upon considerably greater loading than that which brings the first deflecting member to bear against the composite spring.

As indicated above, the damping can be arranged in different ways and is here shown diagrammatically as a damper of the type which is described in US 4,773,514, working between the frame 1 and the rear fork 2. It is indicated by.13.

The spring characteristics can be varied by adjustment of the height positions of the deflecting members 11, 12 in relation to the frame 1. As already mentioned, the front bearing of the composite spring 5 on a first guide shaft 6 can also be vertically adjustable.

The deflecting members can be made of elastic material

and can, for example, consist of polyurethane, rubber etc. Fastening to the frame can be carried out by means - of nuts and screws and longitudinal slots which make possible adjustability in the longitudinal direction of the frame. The height-adjustability can in this case be effected by means of selection of different heights of the members.

The extension of the spring 5 can vary and, for example, run inside or at the side of the frame 1. In one exemplary embodiment, the spring can be associated with the mounting 15 of the front wheel 14. This association is symbolised by 16, the extension above the lower parts of the frame 1 being clear.

Either of the bearing points 6 and 8 can be replaced by a sliding bearing, universal bearing etc., possibly supplemented by a sliding bearing on the central parts of the frame, for example in the position for the deflecting member 11 which can then be displaced. In the case of wheel-bearing parts on a car, the" spring extends in the transverse direction of the car and is mounted via its ends on the wheel-bearing parts/swinging brackets via links. A shock absorber 13 is in this connection arranged on each bearing part. The deflecting members are preferably arranged in the chassis in two symmetrical groups which each serve their bearing part. The deflect¬ ing members interact with the spring from its central part and outwards. The spring in the case shown functions only in the suspension function (not the mounting func¬ tion) . The spring can alternatively consist of a steel spring.

In the figure, the engine block, gearbox etc. have been indicated by 17, a saddle by 18, a tank by 19 and handle¬ bars by 20. A distance which symbolises the distance between the lower part of the frame and the centre of the mounting of the rear wheel 4 has been shown by A. M indicates a ground support. A space above the damper 13

and the swinging bracket fastening 3 is indicated by U.

In the figure, the length of the spring has been indicated by L and the distances between the ends of the spring and each deflecting point by tl and (.3 respect- ively. A distance between the deflecting points has been indicated by *2. A spring constant Kl on account of the spring bearing via the part 5a against the member 11 = L/L-'tl. A spring constant K2 on account of the spring bearing via the part 5b against the member 12 =

The invention is not limited to the embodiment shown above but can be subjected to modifications within the scope of the inventive idea and following claims.