HK1069155B - Rear axle for motorcycles having a transmission cardan shaft - Google Patents

Description

Motorcycle rear axle with universal joint transmission shaft

Technical Field

The present invention relates to a rear axle of a motorcycle using a cardan drive shaft for transmitting power from an engine to a rear drive wheel.

Background

Although far less common than chain drive systems, cardan shaft drives for transmitting power in motorcycles are the subject of the covering of many patent publications, however, many of these documents describe the use of two swing arms connecting the rear wheel to the motorcycle frame, although with only a single damping unit, as described in DE-a-698258, CH-a-318696 and DE-a-1055981 for example.

Many further examples of motorcycle rear axles are known in the prior art, in which a cardan drive shaft is coupled with a single swing arm, although the two patent publications, which will be analyzed in detail below, represent the level of art considered to be the most relevant for the purposes of the present invention.

In both said patents, the housing containing the bevel gears for transmitting the motion to the driving wheels is not rigidly connected to the oscillating arm, but is articulated to the latter in a mobile (floating) manner. Furthermore, the housing is guided by a torque rod connected to the frame, so that the torque produced by the contact force of the rear wheel contacting the ground is opposed, i.e. compensated, by said torque rod portion. This also results in less extension of the suspension during acceleration of the motorcycle and less compression of the suspension during braking, i.e. deceleration, of the motorcycle. Thus, the motorcycle can be made to operate in a more appropriate manner.

In particular, patent publication US-A-4434868 discloses A rear axle formed by A four-bar linkage whose main components are an oscillating suspension arm comprising A cardan drive shaft with two universal joints, and A torque or connecting arm which supports all the weight of the motorcycle due to its end portions hinged to the frame and to the downwardly extending appendages of the housing containing the bevel gears, respectively. The main drawback of this construction is that when the torque arm and/or pin connecting the torque or connecting arm to the housing breaks down, the motorcycle becomes unusable because it is no longer able to support itself or even collapses.

In US-A-5067580, the swing arm of the rear axle carries the rear end portion of the shock absorber and is connected to the frame by A pivot whose axis does not coincide with the axis of rotation of the rear wheel; also, a torque or connecting arm is disposed above and extends parallel to the swing arm and is coplanar with the universal joint drive shaft. This construction, in addition to being naturally more expensive due to the more parts involved, has the obvious risk of the fact that the drive shaft is entirely unprotected (i.e. includes its two universal joints) and is therefore liable to hit obstacles that may be encountered during movement. Also, the lower edge of a coat (trousers or skirt) worn by a person using a motorcycle may be brought into the propeller shaft.

Disclosure of Invention

It is therefore desirable, and indeed as a main object of the present invention, to provide a motorcycle having all the advantages of the rear wheel or rear axle described above, without the technical drawbacks described above, which is characterized by a cardan drive shaft, a single suspension arm and a torque or connecting arm.

Another object of the invention is to provide a rear axle that can be produced on an industrial scale at a reasonably low cost.

These and other objects are achieved according to the invention in a rear axle having the features described below.

The present invention provides a rear axle of a motorcycle provided with a cardan shaft having a first universal joint for connection with an engine supported by a frame and a second universal joint for connection with a hub of a pinion constituting a pair of bevel gears together with a ring gear solidly connected to a rear driving wheel, wherein said rear axle comprises:

-a tubular body portion pivotally connected to the frame and housing said cardan drive shaft and said cardan joint;

-a housing connected to said tubular body and housing said pair of bevel gears;

-elastic damping means for suspending said tubular body to the vehicle frame;

-a non-deformable torque rod extending between two pivots, wherein a first pivot has an axis parallel to the axis of the pivot fixing said tubular body to the frame and is located at a higher level than the pivot;

characterized in that the second of said two pivots provided at the end of said torque rod has an axis parallel to the axis of rotation of the rear wheel and connects the torque rod with a mobile part supported in said housing by the other pivot solidly connected to the hub of the wheel and itself supporting said hub of the pinion.

Drawings

In summary, the features and advantages of the invention will be better understood by describing an embodiment thereof, given below by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 is a side view of one rear axle of a motorcycle, with the frame portion engaged with the rear axle schematically illustrated;

FIG. 2 is a cross-sectional view according to the horizontal line X-X of FIG. 1, including only the rear axle;

fig. 3 is a sectional view taken along line Y-Y of fig. 2, in which the portion of the frame that engages the rear axle is also schematically shown.

Detailed description of the preferred embodiments

In the preferred embodiment illustrated herein, the elements that connect together the main components of the rear axle, i.e. the hub 52 of the rear wheel 50 of the motorcycle and the frame 100 of the motorcycle (which, for the sake of clarity, is only schematically illustrated in the figures, as fully indicated above) are:

a hollow fork 10 with two parallel arms 15 and 17, connected to a casing 14 consisting of a pair of cooperating shells by a set of screws (not shown for greater clarity) corresponding to the respective projections 11 and 13. The yoke 10 and housing 14 may be made of any material at a cost that is tolerable by any industrial technique or method that ensures the desired level of mechanical strength. In this regard, they may be made of, for example, cast aluminum alloys. At the free ends of the two parallel arms 15 and 17, there are provided two supports 15A and 17A for housing a pivot 18 by means of which the fork 10 is suspended in a conventional manner to the frame 100 along an axis indicated with a in figures 1 and 2 so that it can oscillate in a vertical plane perpendicular to the axis of rotation R of the wheel 50;

a mobile element 20, which constitutes an essential feature of the invention, is made of a material of high strength, for example an aluminium alloy which preferably offers the additional advantage of a low weight, due to its important role in structure and function. When viewed from the side, as is actually shown in fig. 3, the mobile element 20 has an "L" shape with a median region 25 from which are visible a first arm 24 and a second arm 26, respectively, extending along axes H and V, both perpendicular to the rotation axis R of the wheel 50-see fig. 3. Said intermediate region 25 of the mobile element 20 is supported by means of a bearing 39 by a pivot 27 connected to a hub 52 of the rear wheel 50 by screws (generally indicated with 21, only the axis of which is shown in figure 2), and which is itself supported by the casing 14 by means of a bearing 29. The mobile element 20 is therefore enclosed in the above-mentioned housing 14, except for the free end of the second arm 26 which projects therefrom through the notch 19 provided on the top of the housing.

A torque rod 40, whose linear axis is indicated by C in figure 3, which extends above the fork 10 and is obviously also made of a high-strength material. The proximal portion 42 of the lever 40 is connected to the frame 100 by a first pivot 43, the axis Z of the first pivot 43 being parallel to the axis a of the pivot 18 by which the fork 10 is suspended to the frame, and the distal portion 44, the axis F of which is parallel to the axis of rotation R of the rear wheel 50, is connected to said free end of the second arm 26 of the mobile element 20 by a second pivot 45.

A spring-damper unit 60 connecting together the connection 62 of the frame 100 located above the pivots 43 and 45 provided at the ends of the torque rod 40 and the small holes 64 on the upper and outer sides of the arms 17 of the fork 10-see figures 1 and 3.

The longer arm 17 of the fork 10 surrounds a cardan drive shaft 30 extending along an axis indicated with B between a first universal joint 32 for connection with an output shaft 34 of an engine (not shown, but most known to be supported by the frame 100) and a second universal joint 36, said second universal joint 36 being described in further detail and being arranged more or less in correspondence with the flanges 11 and 13-see fig. 2. The axis B of the cardan drive shaft 30 and the axis C of the torque rod 40 define a vertical plane perpendicular to the axis of rotation R of the rear wheel 50. While the shorter arm 15 of the fork 10 is located on the opposite side of the rear wheel 50.

Further, the housing 14 accommodates a pair of bevel gears (bevel gear pair). The first gear is a pinion 22 shrink-fitted on a hub 33, which hub 33 is connected to said second universal joint 36 and is supported by the first arm 24 of said movable part 20 through a bearing 38. The second gear is a ring gear (ring gear) 23 shrink-fitted onto the aforementioned pivot 27 connected to the hub 52 of the rear wheel 50-see fig. 2 and 3. Inside said housing 14, said bevel gear is immersed in a lubricating oil bath defined by a first bellows washer 35 and a second bellows washer 28, wherein the first bellows washer 35 is held between the flanges 11, 13 of the fork 10 and the first arm 24 of the movable part 20, and the second bellows washer 28 is held between the free end portion of the second arm 26 of the movable part 20 and the edge of the hole 19 provided on the top of the housing 14-see fig. 3.

Due to the above-mentioned special construction, it is the movable part 20 that ensures the connection between the transmission shaft 30 and the torque rod 40. In this way, the rear axle according to the invention not only allows the fork 10 to oscillate conventionally about the axis a of the pivot 18 by which it is suspended to the frame 100, and therefore the rear wheel 50, in a vertical plane perpendicular to the rotation axis R of this wheel, but also allows the hub 33 of the pinion 22 to oscillate about this rotation axis R within the limits allowed by the width of the notch 19 on top of the casing 14 and by the clearance between the free end portions of the second arms 26 of the movable part 20.

This is a particularly advantageous feature of the present invention which is not, or is not, practically available in the prior art.

Another advantage of the present invention comes from the fact that: even in the case where the torque rod 40 and/or the pivots 43, 45 provided at the ends thereof are damaged or destroyed, the motorcycle does not collapse due to the movable member 20 functioning as the connecting means for connecting the propeller shaft 30 and the torque rod 40.

It will be appreciated that whilst the above description relates to a preferred embodiment of the present invention, many modifications and embodiments may be developed without departing from the scope of the present invention as defined in the appended claims.

In particular, it should be realised that it is even possible to arrange the torque rod differently with respect to the tubular body and the propeller shaft housed therein, and that different devices and methods can also be used for elastically suspending the fork to the frame of the motorcycle.

Claims (7)

1. A rear axle of a motorcycle provided with a cardan drive shaft (30) having a first universal joint (32) for connection with an engine supported by a frame (100) and a second universal joint (36) for connection with a hub (33) of a pinion (22) constituting a pair of bevel gears together with a ring gear (23) solidly connected to a rear driving wheel (50), wherein said rear axle comprises:

-a tubular body (10) connected to the frame (100) by means of a pivot (18) and housing said cardan drive shaft (30) and said cardan joint (32, 36);

-a housing (14) connected to said tubular body (10) and housing said pair of bevel gears (22, 23);

-elastic damping means (60) for suspending said tubular body (10) to the vehicle frame (100);

-a non-deformable torque rod (40) extending between two pivots (43, 45), wherein a first pivot (43) has an axis (Z) parallel to the axis (a) of the pivot (18) fixing said tubular body (10) to the frame (100) and is located higher than the pivot (18);

characterized in that the second pivot (45) of said two pivots provided at the end of said torque lever (40) has an axis (F) parallel to the rotation axis (R) of the rear wheel (50) and connects the torque lever (40) with the mobile part (20), which mobile part (20) is supported in said housing (14) by another pivot (27) solidly connected to the hub (52) of the wheel (50) and in turn supports said hub (33) of the pinion (22).

2. Motorcycle rear axle provided with a cardan drive shaft (30) according to claim 1, characterized in that said torque rod (40) extends above said tubular body (10) and therefore above said cardan drive shaft (30).

3. Motorcycle rear axle provided with a cardan drive shaft (30) according to claim 1 or 2, characterised in that the connection point (62) fixing said elastic damping means (60) for suspending said tubular body (10) to the frame (100) is located above the pivots (43, 45) provided at the ends of said torque rod (40).

4. Motorcycle rear axle provided with a cardan drive shaft (30) according to claim 1 or 2, characterised in that said tubular body (10) is fork-shaped with two parallel arms (15, 17), of which the longer arm (17) surrounds said cardan drive shaft (30) and has a projecting end portion (11) for connection with the flange (13) of the corresponding housing (14) for the bevel gears (22, 23), while the shorter arm (15) is located on the opposite side of the wheel (50).

5. Motorcycle rear axle provided with a cardan drive shaft (30) according to claim 1 or 2, characterized in that said movable part (20) comprises:

-a central zone (25) which is part of the mobile element and is supported by said pivot (27) solidly connected to the hub (52) of the wheel (50);

-a first arm (24) extending from said intermediate region (25) along an axis (H) perpendicular to the rotation axis (R) of the wheel (50), and which first arm (24) is part of a hub (33) supporting the pinion (22) through a jointed bearing (38);

-a second arm (26) extending from said intermediate region (25) along a further axis (V) perpendicular to the rotation axis (R) of the wheel (50) and to the axis (H) of said first arm (24), and which second arm (26) has a free end portion passing through and projecting from a hole (19) in said housing (14), this free end portion also being the portion of said second pivot (45) connecting said mobile part (20) with the torque rod (40).

6. Motorcycle rear axle provided with a cardan drive shaft (30) according to claim 5, characterized in that between the free end portion of said second arm (26) of said mobile part (20) and said hole (19) of the casing (14) there is retained a bellows gasket (28) suitable for preventing the leakage of lubricating oil from the casing (14).

7. Motorcycle rear axle provided with a cardan drive shaft (30) according to claim 6, characterised in that another bellows washer (35) performing the same function as said bellows washer (28) is held between said connecting portion (11, 13) of said shell (14) and said tubular body (10) and said first arm (24) of the mobile element (20).