“A TILTING MOTOR CYCLE WITH THREE WHEELS AND A RIGID REAR AXLE”

FIELD OF APPLICATION

The present invention relates to a tilting motor cycle with at least three wheels and a rigid rear axle.

BACKGROUND

Tilting motor cycles are known with at least three wheels and a rigid rear axle, designed to carry loads placed at the rear end of the frame.

In particular, such vehicles comprise a rear end having an engine group and a rigid axle provided with a couple of rear wheels; the rear end is hinged to the frame in order to allow a rolling of the frame about a rolling axis and a pitching of the rear end about a pitching axis; the rear end is further connected to the frame by means of a suspension system.

The main connection between the rear end and the frame is carried out by means of the interposition of a joint, which allows both the rolling and the pitching between the frame and the rear end.

From a structural point of view, in this type of vehicles, it is attempted to limit the passage of loads through the joint to a maximum, hence the positioning of the suspension on the vertical of the axis of the rear wheels.

However, in this way, by connecting the engine to the frame by a damper during the rolling, instead of following a circular trajectory around the rolling axis, the upper fixing thereof tends to follow a smaller arc of a circle with the center in the lower fixing thereof.

This condition is shown, for example, in figure 1 , wherein the circular trajectory around the rolling axis is indicated with reference 2, while the effective trajectory with the center in the lower fixing is indicated with reference 3.

Since the damper cannot extend, if the load, which compresses it does not decrease (and indeed increases on the bend), the rear part of the vehicle will tend to lower, thus increasing the incidence and the front wheel trail of the front end of the motor cycle.

Such increases can be measured geometrically and have the effect of making the drive heavier and the vehicle less reactive to the rotation of the handlebars.

PRESENTATION OF THE INVENTION

Thus, the need is felt to overcome the drawbacks and limitations stated with reference to the prior art.

Such need is satisfied by a tilting motor cycle according to claim 1.

DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will become clearer from the description below of preferred, non-limiting embodiments thereof, wherein:

- figure 1 represents a schematic view of a tilting motor cycle of the prior art;

- figure 2 represents a perspective view of a tilting motor cycle according to one embodiment of the present invention;

- figure 3 represents a detailed perspective view of the enlarged detail III in figure 2;

- figure 4 represents a schematic side view of a tilting motor cycle according to one embodiment of the present invention;

- figures 5a, 5b, 5c represent constructional diagrams of possible embodiments of the present invention;

- figures 6-7 represent views of a possible embodiment of a motor cycle according to the present invention;

- figures 8-9 represent views of a further possible embodiment of a motor cycle according to the present invention;

- figure 10 represents a perspective view of a further embodiment of the present invention.

Elements or parts of elements in common between the embodiments described below will be indicated with the same numerical references.

DETAILED DESCRIPTION

With reference to the aforesaid figures, an overall schematic view of a tilting motor cycle according to the present invention is globally indicated with reference 4.

The tilting motor cycle 4 comprises at least three wheels, including at least one front wheel 8 and two rear wheels 12, 14.

The motor cycle 4 further comprises a frame 16, comprising a front end 18 and a rear end 20. The rear end 20 comprises an engine group 24 and said couple of rear wheels 12, 14.

The rear end 20 is typically a rear end with a rigid rear axle.

The rear end 20 is hinged to the frame 16 in order to allow a rolling of the frame 16 about a rolling axis R-R and a pitching of the rear end 20 about a pitching axis B-B. For example, as shown better in figure 3, the tilting motor cycle 4 comprises an articulated joint 22 arranged between the frame 16 and the rear end 20 to cause said rolling and pitching of the frame 16.

According to a possible embodiment, the articulated joint 22 comprises a Neidhart joint (figure 3).

Such Neidhart joint rotatably connects the two axes to each other, in this case integral with the frame 16 and the engine group 24 respectively, to allow not only a relative rotation but also slight misalignments between the axes themselves. These misalignments can be obtained by the elastic deformation of rollers (cylindrical or conical) made of elastic material, typically of rubber, which act as elastically yielding bearings.

The rear end 20 is further connected to the frame 16 by means of a suspension system, shown in different configurations in figures 5a, 5b e 5c, which comprise a couple of uprights 26, 28 connected at the bottom by means of two first hinges 32, to the engine group 24, at least one first crosspiece 36 hinged, at the distal ends 40, 42 thereof, to the uprights 26, 28.

In particular, the uprights 26,28 are arranged between opposite sides and the first crosspiece 36 extends between said pair of opposing uprights 26,28. The crosspiece 36 is rotatably connected at the distal ends 40, 42 to the uprights 26, 28

The center C of the first crosspiece 36 is connected to the frame 16 directly or indirectly by means of a transmission element 44.

The uprights 26, 28 or the transmission element 44 comprise a suspension 48 to dampen the rear end 20 with respect to the frame 16.

The suspension 48 comprises at least one spring and/or a damper yielding according to a longitudinal axis L-L of the suspension 48.

The type of spring and/or damper is irrelevant for the purposes of the present invention.

According to one embodiment, the first crosspiece 36 is shaped as a triangle so that the center C and the distal ends 40, 42 of the first crosspiece 36 are arranged in a triangle, and the apex of the triangle coincides with the center C of the first crosspiece 36 and is situated at a predetermined distance D from the baseline T, which joins the distal ends 40, 42.

The distance K between said rolling axis R-R and a line S, which joins said two first hinges 32 substantially coincides with said predetermined distance D.

Due to this correspondence between the distances D and K an overall neutral rolling suspension is obtained, wherein the kinematic variation in the rolling angle does not require a variation in the length of the suspension, which can be seen schematically in figure 5a.

In fact, from a geometric point of view, the correspondence between the distances D and K means that the kinematic rotation of the suspension is perfectly centered in the rolling axis; in this way, the simple rolling movement of the frame 16 neither involves nor requires a lengthening or shortening of the suspensions 48. Consequently, the simple rolling movement does not cause a lifting or a lowering of the vehicle at the rear end and nor does it require any geometrical variation in the angle of incidence and the front end.

In other words, due to the described kinematic mechanism, the suspension 48 is allowed to work as though it were fixed on a through point for the rolling axis (Fig.4) with all of the advantages described above.

Furthermore, the use of an articulated quadrilateral allows the load transfers to be balanced and consequently, the compressions and extensions of the suspensions of the uprights, which maintain the same length both in static conditions and dynamic conditions.

Figure 5a schematically illustrates the kinematic behavior of the articulated quadrilateral. In particular, the first lower hinges 32 stay still because they are associated with an engine group 24 with a rigid axle. A virtual crosspiece is sketched at the bottom of the figure whose center line advantageously passes through the rolling axis R-R. In the event of rolling, the virtual lower crosspiece stays still, while the first crosspiece 36 rotates (i.e. rolls) parallel to the virtual crosspiece, which remains still due to the mechanical connection given by the uprights 26, 28. In fact, the articulated quadrilateral allows the upper crosspiece, i.e. the first crosspiece 36, to rotate, always keeping the parallelism with the lower‘virtual’ crosspiece.

Preferably, the first hinges 32, the uprights 26,28, the center C of the first crosspiece 36 and the distal ends 40,42 of said first crosspiece 36 lie on a common suspension plane.

According to one embodiment, said common suspension plane is perpendicular to the rolling axis R-R. This condition facilitates the rolling movement of the frame and allows smaller misalignments between the movable elements and consequently, reduced friction during the compression of the suspensions and the rotations of the uprights 26, 28. There are also advantages in terms of overall size. In fact, the two suspensions incorporated in the uprights 26, 28 tilt by the same angle as the single suspension, but they remain displaced towards the center line; in the case of a narrow motor cycle lane this difference can be decisive.

In this regard, the difference in size between the solution in figures 6-7 and the solution in figures 8 and 10 is shown in figure 9.

According to a first embodiment (figures 5a, 8), the distal ends 40, 42 of the first crosspiece 36 are hinged to upper ends 50, 52 of the uprights 26, 28, and the center C of the first crosspiece 36 is directly hinged to the frame 16. Each of the uprights 26, 28 comprises a suspension 48 to dampen the rear end 20 with respect to the frame 16. This embodiment classically comprises the use of two equal suspensions, one at each upright 26, 28. It is also possible to arrange a spring at one of said uprights 26, 28 and a damper at the other upright 28, 26. This solution offers the advantage of considerably containing the overall size in a transverse direction, i.e. perpendicular to the rolling axis R-R. The containment of the size is schematized in figure 9, in which, with the same rolling angle, the transverse size of a quadrilateral provided with only one first crosspiece 32 and two uprights (each provided with suspensions 48) is compared to a quadrilateral having a couple of crosspieces 32, 56, which is described better below.

The advantage in terms of size lies in the fact that the two suspensions tilt by the same angle, but remain displaced towards the center or center line: in the case of a narrow lane, this can be decisive in terms of size.

In particular, in a second embodiment (figures 5b, 6, 7), the motor cycle 4 comprises a second crosspiece 56, besides the first crosspiece 36. Each of the uprights 26, 28 is hinged to the engine group 24 in a first lower end 60, 62.

The uprights 26, 28 are hinged to the first crosspiece 36 in an opposite upper end 50, 52 and to the second crosspiece 56 in an intermediate position 64 between the lower 60, 62 and upper ends 50, 52.

In other words, starting from the top, the uprights 26, 28 are hinged to the first crosspiece 36, to the second crosspiece 56 and to the engine group 24 respectively.

In turn, the second crosspiece 56 is hinged centrally to a lower end 68 of the transmission element 44. The transmission element 44 is hinged, in turn, in an intermediate position, to the first crosspiece 36 and at an upper end to the frame 16. Advantageously, the transmission element 44 further comprises a suspension 48 provided, for example, with a spring and a damper (fig. 10).

This solution allows the use of a single suspension 48, but it also requires the use of a second crosspiece 56. In terms of transverse size, as seen, this is increased with respect to the solution with two suspensions at the uprights 26, 28. However, this solution allows the exclusion of potential manufacturing flaws of the two suspensions in the first embodiment, which would result in the asymmetric working of the rolling system.

According to a third embodiment (figures 5c, 10), the transmission element 44 is hinged to the frame 16 to allow an oscillation of the transmission element about a transverse axis F-F parallel to the pitching axis B-B of the motor cycle 4.

Furthermore, the distal ends 40, 42 of the first crosspiece 36 are hinged to upper ends 50, 52 of said uprights 26, 28, and the center C of the first crosspiece 36 is hinged to the transmission element 44. In turn, the transmission element comprises a suspension 48 connected to the frame.

This solution allows the overall size of the suspension to be limited further: in particular, in the part comprised between the wheels, it is possible to replace the two suspensions with two struts and thus place a single suspension 48 at the top, which can consequently work under compression. In this case, too, the solution allows the exclusion of potential manufacturing flaws of the two suspensions in the first embodiment, which would result in the asymmetric working of the rolling system. According to one embodiment, the rotation axes of the lower hinges 32 of the first crosspiece 36 and the hinges of the uprights 26, 28 are parallel to the rolling axis R- R.

This condition facilitates the rolling movement of the frame and allows slighter misalignments between the movable elements and consequently reduced friction during the compressions of the suspensions and the rotations of the uprights 26, 28. As can be appreciated from the description, the present invention allows the drawbacks of the prior art to be overcome.

In particular, the present invention defines a neutral rolling suspension, wherein the simple geometric variation in the rolling angle does not require a variation in the length of the suspension.

In this way, the stability of the vehicle is improved significantly with respect to the solutions of the prior art since the rear part of the vehicle tends not to lower, thus increasing the incidence and consequently the front wheel trail of the front end of the motor cycle.

At the same time, the size of the suspension of the present invention is contained and therefore allows the rear end to bear caissons, also with considerable dimensions.

A person skilled in the art can make various modifications and changes to the motor cycles described above to satisfy specific and contingent needs, all of which are contained in the scope of the invention as defined by the following claims.