Vehicle with at least two wheels and with swing arm having adjustable lateral stiffness

Abstract

To provide means for constraining a swing arm to the chassis of a vehicle so that the stiffness of the swing arm optimally absorbs the stresses during driving.SOLUTION: Provided is a two- or three-wheeled vehicle having at least one front wheel and one rear wheel connected to a chassis thanks to a suspension system, in which a rear-wheel suspension system comprises a swing arm connected to the chassis. The swing arm is swingably fixed to the chassis around an axis (Y) and is swingable around the axis (Y) perpendicular to a median plane (W) of the vehicle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The subject of the invention is a two- or three-wheeled vehicle, such as a bicycle or a motorcycle, as defined in the preamble of the independent claim. [Background technology]

[0002] As is known, a vehicle of the above type, such as a normal motorcycle, comprises a chassis coupled to at least one front wheel and at least one rear wheel, the latter of which is illustrated in the following description. This chassis supports at least one prime mover, which serves as a chassis function and also as a drive means. Such a prime mover may be an internal combustion engine, or an electric or hybrid engine. In this specification, the engine or part of the engine, which serves as a chassis function, is also considered as the chassis.

[0003] The engine drives a chain which meshes with a pinion or gear which is integrally connected to the hub of the rear wheel.

[0004] The rear wheel is mated with a swingarm (with one arm or two arms commonly referred to as bi-arm) that is connected at its first end to the chassis, and the second end of the swingarm (with one arm, there is one second end) is integrally connected to the hub of the rear wheel by means of a common pin of the rear wheel.

[0005] The first end of the swingarm has two arms at its free end with a through hole in the "little hub" that usually receives a pin or shaft provided in a hole formed in the chassis having a longitudinal axis perpendicular to and transverse to the longitudinal median plane of the motorcycle.

[0006] Plates and / or brackets may be provided that also serve a "chassis" function.

[0007] Regarding the method of connecting the swing arm to the frame, the shaft or pin that connects with the arm at the first end of the swing arm is usually inserted into a mechanical decoupling member, which is a combination of ball bearings, rollers, and / or needle rollers and a cage. This connection not only fixes the arm to the chassis, but also allows the arm to swing freely around the longitudinal axis of the shaft or pin.

[0008] The known solutions are superior to conventional suspension means in that they allow the necessary oscillating movements in the longitudinal plane between the swingarm and the chassis, but they do not allow the swingarm to move with some stiffness along the axis of the shaft that attaches it to the chassis. For this reason, the stiffness along the axis of the shaft cannot be calibrated (i.e. adjusted) without replacing the swingarm or parts of it. This stiffness becomes extremely critical when the motorcycle is turning in curves, especially when the motorcycle is intended for racing. In fact, the swingarm suspension means serves its purpose well as long as the stresses transmitted to it are in the longitudinal plane. If these stresses include a component perpendicular to the longitudinal plane, such as (but not limited to) when the motorcycle is turning, the suspension means may not always function properly.

[0009] There is therefore a need to provide a solution for restraining the swingarm to the vehicle chassis in a way that ensures that the stiffness of the swingarm can best absorb the stresses encountered during riding. Summary of the Invention [Problem to be solved by the invention]

[0010] Thus, the object of the present invention is to provide a two or three wheeled vehicle, such as a bicycle or motorcycle, with a swingarm that is attached to a chassis so that the lateral stiffness of the entire rear axle of the vehicle (with swingarm and wheels) can be appropriately calibrated to maximize the overall performance of the motorcycle, whether it is a racing motorcycle (so, for example, it is important to maximise the speed at which the vehicle turns) or a motorcycle for everyday use (so, for example, it is important to maximise ride comfort).

[0011] The object of the invention is therefore to enable the swing arm to move more or less along said axis or pin to adjust the stiffness of the rear axle as required, for example as a function of on-road travel, by acting at the point where the swing arm is attached to the vehicle body. [Means for solving the problem]

[0012] Another object is to provide a vehicle of the above type in which the above mentioned adjustments are obtained simply and quickly.

[0013] These objects, as well as other objects which will be apparent to those skilled in the art, are achieved by the vehicle defined in the appended claims. [Brief description of the drawings]

[0014] In order that the invention may be better understood, the following drawings are attached, given purely as non-limiting examples: [Figure 1] 1 is an exemplary cross-sectional view of a part of a motorcycle to which a rear wheel swingarm is fixed. [Diagram 2] FIG. 2 is a diagram showing a detail of FIG. [Diagram 3] 1 is a perspective view of a motorcycle according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] With reference to the accompanying drawings, a motorcycle 100 comprises a common chassis 110, a front wheel 120, a rear wheel 130 and an engine 140 mounted to the chassis and a rear wheel swingarm to functionally restrain the rear wheel. The term "functionally" is used to mean that the swingarm is fixed to a part of the motorcycle, i.e. a part of the motorcycle, fixed to the chassis. In particular, the swingarm comprises one or two arms that are restrained to the hub of the rear wheel. At a first end, the swingarm comprises two arms 1 and 2, which are shaped to accommodate between them the part of the vehicle to which they are fixed.

[0016] The swingarm 150 may be mounted on the crankcase 4 of the engine, so as to cooperate with and become part of the chassis. This is shown in figure 1, where the "little hubs" 3 at the ends of the two arms 1 and 2 are mounted on the crankcase 4 via corresponding threaded pins 5 received in each of the threaded holes 8 of said crankcase.

[0017] The pins may be supported on plates 10, 11 (and therefore form part of the chassis) which are restrained to the chassis and integrally connected thereto in known manner, as for example shown in the accompanying drawings.

[0018] The swingarm or its hub 3 is free to oscillate about pin 5 (as shown, coaxial with a Y axis perpendicular to the median plane W of the motorcycle) while the motorcycle is moving over the ground or road. This oscillating movement occurs in a known manner against a common suspension means (not shown) which is constrained to the swingarm and the chassis of the motorcycle.

[0019] According to the invention, a solution is provided for improving the lateral stiffness of the motorbike fork 150, and therefore of the entire rear axle, which is suitable to be achieved along the above-mentioned Y axis, the swing arm being free to move along the Y axis against dedicated elastic means.

[0020] Before describing the invention in detail, it is noted that the rocking of each hub 3 about each pin 5 is usually achieved by providing mechanical decoupling elements, i.e. ball and / or roller bearings, axial and / or radial and / or angular ball bearings, interposed between the swing arm, the chassis and the pins. According to the invention, said bearings may be replaced by mechanical decoupling elements 12 and 13 allowing both rocking about the Y axis and movement of each hub 3 and thus of the entire swing arm along the Y axis. However, the suspension means are not sensitive to small lateral movements, since they are provided with balancing means. The swing arm is always free to move laterally along the Y axis in addition to the longitudinal plane W.

[0021] Each of the mechanical decoupling members 12 and 13 can have various shapes, so long as it is possible to reliably guarantee a suitable coefficient of friction. For example, the mechanical decoupling members are low-friction sliding bushes or linear bushes with hydraulic support means, balls, etc.

[0022] An embodiment of such a mechanical decoupling member is shown in the accompanying drawings. In the embodiment shown in the accompanying drawings, the bore 14 of each hub 3 is provided with a cage 16 which accommodates a number of balls 18 at two locations 16A, 16B. At each location 16A, 16B, the balls 18 are held on each side by elastic rings 19 and 20 (O-rings) on which the balls strike during their respective movements along a direction parallel to the Y axis, for example caused by lateral forces resulting from a descent experienced by the vehicle when going around a bend.

[0023] At least one of the mechanical decoupling elements (the one on the left 11 in FIG. 1) cooperates with elastic or viscoelastic elements, such as Belleville washers 21, provided at both ends of the cage 16 (and thus of the mechanical decoupling elements 12), for example. Such Belleville washers 21 allow for centralized calibration or adjustment of the lateral stiffness of the swing arm.

[0024] Thus, according to the present invention, the swing arm is not only free to pivot about the Y axis, but also free to slide along the Y axis. Such movements are countered with a calibrated stiffness by the Belleville washer 21.

[0025] Movement along the Y axis is achieved by lateral movement of the balls in each cage and by the presence of expandable rings 19 and 20, allowing for low friction between the balls 18 and corresponding pins 5.

[0026] The lateral movement of the swing arm is small (a few millimeters) and is still sufficient to absorb the stresses well.

[0027] The preferred embodiment of the invention has been described with reference to a motorcycle. However, the invention can also be applied to bicycles. In light of the above description, other embodiments are possible. For example, Belleville washers may be provided on the mechanical decoupling members 12 and 13 provided on both hubs 3, the Belleville washers may be non-metallic members, and the mechanical decoupling members may not comprise balls but may be other prior art low friction moving decoupling members. In another embodiment, each pin 5 may be replaced by a shaft connecting the plates 10 and 11.

[0028] Such embodiments also fall within the scope of protection of the invention as defined in the claims set forth below.

Claims

1. a chassis (110) supported by at least one front wheel (120) and at least one rear wheel (130), the chassis (110) supporting at least one drive means, such as an internal combustion engine (100) and / or an electric and / or hybrid engine; A two or three wheeled motorcycle comprising: a swing arm (150) operatively connecting said chassis to said at least one rear wheel, said swing arm (150) having two arms (1, 2) at a first end, The two arms (1, 2) are operatively connected to the chassis via at least one pin (5) connected to their ends (3); The end (3) is connected to the pin (5) via a mechanical decoupling member (12, 13); The mechanical decoupling member is inserted into a corresponding hole (14) in the end (3) in which the pin (5) is received, the pin has a longitudinal axis (Y), the end (3) being free to pivot about the longitudinal axis while the motorcycle is in motion; The longitudinal axis is perpendicular to a median plane (W) of the motorcycle, A two- or three-wheeled motorcycle, characterized in that the ends (3) of the arms (1, 2) of the swing arm are also movable along the longitudinal axis (Y) of the pin.

2. 2. The motorcycle according to claim 1, characterized in that each of said mechanical decoupling members (12, 13) is a low-friction sliding decoupling member.

3. 3. A motorcycle according to claim 2, characterized in that the mechanical decoupling member is either a low-friction sliding bush or a linear bush, equipped with hydraulic support means or the like.

4. 3. The motorcycle according to claim 2, characterized in that the mechanical decoupling member comprises a cage (16) having at least one set of a plurality of balls (18) interposed between telescopic annular members (19, 20) provided in the cage (16) at both ends of the set of balls (18).

5. 5. The motorcycle according to claim 4, characterized in that the cage (16) comprises two parts (16A, 16B), each of which houses within itself a number of balls (18) interposed between telescopic annular members.

6. 3. The motorcycle according to claim 2, characterized in that at least one (12) of said mechanical decoupling members (12, 13) cooperates with elastic members (21) provided on both ends of said mechanical decoupling member (12).

7. Motorcycle according to claim 6, characterized in that said elastic member (21) has a predetermined but variable stiffness.

8. 7. The motorcycle according to claim 6, wherein the elastic member is a disc spring.

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