Rear wheel suspension mechanism for motorcycles and the like vehicles

Abstract: A rear wheel suspension mechanism for motor­ cycles and the like vehicles, of the kind used in motor­ cycles having a rear-wheel drive constituted of a sprocket (11) located at the output of the gearbox (13) and con­ nected by a transmission roller chain (10) to a sprocket or gear wheel (9) integral with the driving rear wheel (8a), or connected to the said gear wheel through an in­ termediate gear, the ensemble of gearing and wheel being supported by an oscillating ensemble or unit. According to the invention, the mechanism com­ prises an oscillating support (1;101;215;314;410) articu­ lated to the ends of at least two oscillating arms (4,4a; 201,202;301,302;401,402) placed longitudinally as regards the motorcycle traveling direction; an axle (8;108;218317; 411) for the rear driving wheel mounted in the oscillating support and having secured at one of their ends the sprocket or gear wheel (9;109;213;318;420) receiving the motion from the transmission roller chain (10;212;415); the opposite ends of the oscillating arms being articulated to respective points (5,6;105,106;203,204;404,405) of the motorcycle frame (205;305;406) placed above, under or coinciding with the center line (12;207;416) of the gear­ box output sprocket. The arrangement is such that the oscillating arms constitute, together with the rear wheel axle oscil­ lating support, an oscillating ensemble in the shape of at least an articulated polygon.

Description: The present invention relates to improvements in the rear wheel suspension mechanism for motorcycles and the like vehicles, to advantage for such motorcycles comprising a driving sprocket at the output of the gearbox, connected by means of a roller transmission chain to a sprocket or gear wheel which is integral with the axle of the rear driving wheel, the said axle being journaled in a support related with the oscillating system of the rear wheel. As it will be seen in the course of the present specification, the improvements are applicable, as well, to motorcycles provided with a transmission made of a shaft and toothed gearings. BACKGROUND OF THE INVENTION When a motorcycle is made to effect a sudden acceleration, the conventional transmission arrangement from the gearbox output sprocket to the sprocket mounted on the rear wheel axle supported by the oscillating ensemble, a force resolution takes place which tends to raise the vehicle rear wheel, with a corresponding loss of stability during the acceleration. With the aim of overcoming the above problem, the applicant devised two kinds of transmissions for motorcycles making the subject of the Spanish utility models Nº 293 283 and Nº 293 573 (basis for 2-part form of Claim 1) relating to respective motorcycle transmissions incorporating mechanism intended to obtain, upon a sudden acceleration arising, a force moment on the swing axle of the oscillating ensemble articulated to the motorcycle frame, tending to move the said frame towards the floor over which the motorcycle runs. It has been observed, in practice, that the force moment obtained with the transmission arrangements making the subject of the above utility models is excessive and sometimes even of a negative effect. In fact, when the motorcycle runs over an irregular floor, a stiffness effect of the rear driving wheel suspension arises which can lead to a chain rupture. Documents DE-A-2 457 291 and DE-A-2 615 083 disclose a motorcycle suspension system comprising two oscillating arms that provide a long pivotal radius for the rear wheel so as to permit increased suspension travel. The latter relates specially to the case of two rear wheels. FR-A- 2 495 093 discloses a rear suspension for motorcycles comprising also two oscillating arms and where the oscillation geometric axis of the rear wheel is located in the same plane of the rear wheel axle and of the drive sprocket axle, in front of this axle. This patent intends to minimize the lack of roadholding when acceleration takes place. US-A-4 058 181 discloses a motorcycle suspension systems comprising two oscillating arms on each side of the frame; an oscillating axle support for the rear wheel articulated the rear ends of the oscillating arms; the front ends of the oscillating arms being articulated to the motorcycle frame; and the joints forming an articulated polygon. This patent intends to resolve the problems of the long-travel suspensions specially in case of increased speed and cornering forces on paved surfaces. The suspension provides a rising rate of both springing and dampening which allows the wheel to have soft shock absorbing characteristics over minor surface irregularities, and a progressively greater rate as larger bumps are traversed. The aim of this patent is how to place the shock absorber in order to have the best position. However none of the references allows completely reduce the effect of accelerations and decelerations on the rear wheel. All references intend to improve the suspension system but are not interested in the suspension-transmission relationship. DESCRIPTION OF THE INVENTION The improvements making the subject of the present invention provide for a neutralization of the force moments arising with the sudden accelerations in a motorcycle, with a rather neutral than upward directed force moment, and with an ability for adjusting on the oscillating ensemble of the rear driving wheel, a force moment tending to apply it onto the floor in a regulable manner. The improvements subject of the invention essentially consist of an oscillating support articulated to the ends of at least two oscillating arms placed in longitudinal direction as regards the motorcycle traveling direction; an axle for the rear driving wheel mounted in the oscillating support and having secured thereto at one of their ends the sprocket or gear wheel receiving the motion from the transmission roller chain meshing with the gearbox output sprocket; the opposite ends of the oscillating arms being articulated to respective points of the motorcycle frame placed above, under or coinciding with the center line of the gearbox output sprocket; such that the oscillating arms constitute, together with the rear wheel axle oscillating support, an oscillating ensemble in the shape of at least an articulated polygon. In an advantageous embodiment all of the jointing points of the articulated polygon are of movable location in order to provide for adjustment of all of the distances between the said points. It has been foreseen that the articulated polygon is an articulated parallelogram the oscillating arms of which are parallel to the virtual line passing through the center lines of the sprockets or gearwheels over which the transmission roller chain meshes; it is possible for the said arms being located under, over or coinciding with the said center lines. According to another aspect of the instant improvements, the transfer of the rotation motion of the gearbox output sprocket to the driving rear wheel is performed by means of a rigid shaft, with no intermediate universal joint, connected at its ends to the gearbox output sprocket and the gear wheel integral with the driving rear wheel axle by respective gearwheel sets, preferably bevel gear sets. To advantage, all of the jointing points of the articulated polygon members are of variable location such as to provide for adjustment of the distances between the said points. In a specific embodiment, the rear wheel axle is mounted on an oscillating support articulated to the ends of at least two oscillating arms located in longitudinal direction as regards the motion direction of the motorcycle, whereas the opposite ends of the said oscillating arms are jointed to respective points of the motorcycle frame, placed over and(or under the center line of the gearbox output sprocket. Optionally, the articulated polygon is an articulated paralellogram the oscillating arms of which are parallel to the transmission shaft and located under, over or at the same height of the transmission shaft. They may, even, be substituted by this latter. In a further specific embodiment, the jointing points of the articulated paralellogram to the support carrying the rear driving wheel axle may form like triangles at both ends. At least the oscillating arms of the articulated polygon constituting the oscillating ensemble, are formed of at lest two mutually extensible and adjustable sections with means for adjusting and securing the desired mutual position. Preferably, the rear end of the oscillating arms are jointed to a smaller, cranked arm associated with the rear driving wheel axle, whereas the forward ends of the said arms are jointed to points of the motorcycle frame over and\or under the gearbox output shaft, such that the said jointing points and axles are not aligned and located at the apices of virtual like front and rear triangles with like or different sides. The rear cranked arm carrying the motorcycle rear wheel carries the shoe or block of the brake for the said wheel. At at least one end of the oscillating arms is connected within respective bushings having screws which are operable from the outside to regulate the extension of the respective arms and secure the assumed position, with the cooperation of safety nuts. In an advantageous embodiment, the front ends of the oscillating arms have respective extensions from the jointing points to the frame, the extension of one arm being connected to the extension of the opposite arm by means of respective cross-arranged shock absorbers of combined actions. The invention contemplates also the case in which the motion transmission is formed of roller chain and sprockets, and in such instance the axle of the driving wheel is mounted adjustable in the longitudinal direction as regards the motion direction of the motorcycle. According to the improvements making the subject of the present invention, a secondary transmission is inserted between at least one of the sprockets connected to the motorcycle transmission, either chain or rigid shaft, and the axle of the driving wheel or the gearbox output axle, such that the center lines of the sprockets connected to the transmission constitute one of the apices of respective virtual and like triangles, the other apices being formed by the jointing points of the oscillating ensemble arms. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present specification, the enclosed exemplary drawings show a practical embodiment of the suspension for motorcycles incorporating the improvements of the invention. In the said drawings: Figure 1 is an schematic lateral elevation of the suspension and transmission mechanism for motorcycles making the subject of the invention, with chain-and-gear transmission; Figures 2 and 3 are respective schematic elevation views corresponding to respective examples of embodiment of the invention, with shaft and sprocket transmission; Figure 4 is a schematic view in side elevation of a rear suspension ensemble with extensible and adjustable longitudinal oscillating or swinging arms; Figure 5 is a detail in longitudinal section at larger scale of one end of swinging arm fitted within a bushing with means for adjusting and securing the more or less extended position of the arm; Figure 6 is a view in side elevation of an embodiment of the invention incorporating sprocket gearings at both ends of a roller chain transmission for a motorcycle having a swinging ensemble formed of an articulated paralellogram, and Figure 7 is a similar view, though with a rigid shaft transmission. DESCRIPTION OF A PREFERRED EMBODIMENT A rear wheel suspension for motorcycles and the like vehicles comprises, according to the invention, in the version including a roller chain transmission shown in Figure 1, a support denoted with the reference numeral 1 in the shape of a brake drum, or whatever other shape, such as an arm, having articulated at points 2 and 3 one of the ends of at least two arms 4,4a. The opposite ends of these arms are jointed at points 5,6 of a section of the motorcycle frame, diagrammatic shown in the drawings by a part 7 that may have the more suitable shape according to the specific features of the motorcycle. Thus, it may be assumed that the jointing points of the arms are just those defining the formation of the articulated paralellogram regardless of the shape of the arms and the parts associated thereto for affixing their positions. The ensemble of the hitherto described parts constitute an articulated polygon that may be formed of an articulated parallelogram, as in the example shown, yet it may assume whatever other shape, for example trapezial or trapezoid-shaped, according to the distances of between the pairs of jointing points 2,3; 5,6; 2,5; and 3,6, for a purpose to be explained later on. On the other hand, axle 8 of the rear wheel 8a and the sprocket 9 may be, optionally, mounted more or less apart from the jointing point 3 by means of a conventional stretching device. This feasibility may be carried out by means of an oblong aperture extending in the longitudinal direction as regards the support 1. Like in the case of points 2 and 3, optional means may be arranged on the axle 8 for placing and securing it at the desired location as regards the longitudinal aperture. Although the Figures show an ensemble of articulated parallelogram placed at one side of the motorcycle, this ensemble could be doubled, one at either side of the same. From the above and looking to the drawings, it is inferred that the improvements according to the invention are based on obtaining at least one articulated polygon. This articulated parallelogram or polygon makes up the swinging ensemble of the rear wheel and the corresponding transmission sprocket, with the purpose of keeping constant the distance between the axles 8 and 12 and neutralizing the effects of sudden accelerations or decelerations of the engine, thus holding constant the length of the chain 10 and getting the associated shock absorber free to perform its function. When the swinging ensemble is to be applied to motorcycles intended to be run on uneven grounds, such as trial- or cross-motorcycles, the articulated polygon is located over the axles 8,12. When the swinging ensemble is devoted to motorcycles intended to be run on scarcely uneven grounds, the articulated polygon is located under the said axles. The ability of changing the positions of points 2, 3 and 8 allows the articulated polygon to be given different shapes (trapezial, trapezoidal) with different inclines of its sides, in order to adapt the swinging ensemble to specific applications. By changing the shape of the articulated polygon, it is possible to obtain a variation of the force component generated by the accelerations or decelerations of the engine, which is thoroughly regulable and controllable, either as regards the direction or the intensity of this component. In the version of Figures 2 and 3 the transmission comprises a support 101 in the shape of an arm or whatever other shape, such as the brake drum 101b (Fig. 2), bearing articulated at points 102,103 one end of at least two arms 104,104a. The opposite ends of these arms are articulated to points 105,106 of a section of the motorcycle frame which, in the drawings, is schematically shown by a part 107 that may have the more suitable form according to the specific features of the motorcycle. An axle 108 for the driving wheel 108a is mounted on the support 101 and carries a toothed crown, advantageously a bevel crown, as in the embodiments shown in Figures 2 and 3, receiving the rotation motion from a rigid transmission shaft 110 which requires no universal joint and has at one end a bevel sprocket 110a meshing with the bevel sprocket 111 mounted on the output shaft 112 of the gearbox 113. The opposite end of the transmission shaft 110 carries a further bevel sprocket 110b directly meshing with the toothed bevel crown 109, or else with an intermediate sprocket 109a in turn meshing with the crown 109, as in the case shown in Figure 3. In Figure 2 these points are located at the apices of respective like triangles the sides of which may be equal or different. It is thus assumed that the jointing points 102,103 and 105,106 of the arms 104,104a, just those which define the articulated paralellogram regardless of the shape of the arms and of the associated parts to secure the positions therefor. The ensemble of components describe until now constitute an articulated polygon that may be formed of an articulated paralellogram as in the example shown. The support 101 extends from one of its articulation points 102 or 103, to point 103 in the example shown, in a section 101a upon which the axle 108 for the driving wheel 108a is mounted (Fig. 3). The axle 108 may coincide with the jointing point 103 (Fig. 3). Although the drawings show an ensemble of articulated parallelogram placed at one side of the motorcycle, this ensemble may be doubled by placing one such ensemble at either side of the motorcycle. In Figure 3 the sprocket 110b of the transmission shaft 110 meshes with a sprocket 109a which meshes in turn with the crown 109, thereby to show several non restrictive examples of the use of an intermediate gear between the transmission shaft sprocket and the crown secured to the driving wheel axle. From the above described and Figures 2 and 3 of the drawings, it will be seen that the invention provides for incorporating to the motorcycle a rigid transmission shaft without the need for mounting an universal or articulated joint (such as a Cardan joint), owing to the adoption of the kind of swinging suspension with articulated parallelogram as described. This articulated parallelogram or polygon, which makes up the swinging suspension for the rear wheel, keeps constant the distance between the axles 108 and 112 regardless of the position of the suspension ensemble, so that the sprockets 110a and 110b keep always in mesh with the respective sprocket 111 and sprocket or crown 109 while they move about them according to the movements of the parallelogram and dispensing with the use of articulated joints. It is obvious that the absence of any articulated joint, besides of simplifying the transmission, reduces the breakdown risk and makes sturdier the transmission, together with the possibility of closing the ensemble within a protecting box that prevents entrance of dust and dirt and optimizes the lubrication condition, such that a motorcycle provided with the said improvements becomes ideal to be run over rough grounds. Furthermore, the swinging suspension ensemble neutralizes the effects of sudden accelerations or decelerations at the driving wheel, and at the same time sets the associated shock absorber free for performing its action. When the swinging ensemble is applied to motorcycles intended to be run over rough grounds, such as trial- and cross-motorcycles, the articulated polygon may be located over the axles 108,112, as in the example shown. When the swinging ensemble is to be used in motorcycles which are to be run over rather even grounds, the articulated polygon may be placed under the said axle. Figures 4 and 5 of the drawings show a version of the invention in which the articulated polygon constituting the swinging ensemble is formed of two longitudinal arms 201,202 with their forward ends articulated to respective points 203,204 of the motorcycle frame 205, over and under the gearbox output sprocket 206 mounted on a shaft 207, thus forming a virtual triangle of apices 203,204,207 the sides of which may be like or different. The rear ends 208 of arms 201,202 are mounted in adjustable position within respective bushings 209. The ends 208 have an internal nut 210 (Fig.3) into which a coaxial screw 211 is threadedly engaged and has a head which is operable from outside to extend more or less the corresponding longitudinal arm, and adapt the same to the specific needs of either side and provide for stretching the transmission chain 212 going from the gearbox output sprocket to the rear sprocket 213. The assumed position is locked by means of a safety nut 211a. The bushings 209 have lugs 214 articulated to the end of a cranked arm 215 about axles 216,217 located respectively over and under the axle 218 of the motorcycle rear wheel, thus forming a virtual triangle the apices of which correspond to the axles 216, 217 and 218. The cranked arm 215 carries secured thereon the shoe or block 219 of the motorcycle rear wheel brake. The front end of arm 201 has an extension 201a carrying articulated one end of a shock absorber 220, the opposite end of which is articulated on the arm 202, at a point located somewhat rearward (Fig.4). As it appears from the above description and the drawings (Fig. 4 and 5), owing to the extensible configuration of the longitudinal arms 201,202 it is feasible to accurately adjust the length of these arms by operation of the screws 211, according to the specific needs of either case and to the desired stretching of the chain, without a need for complicate setting operations. Another advantage derived from the described embodiment, is the possibility of giving the chain 212 and the transmission in general, an integral protection becoming very suitable for motorcycles intended to be run on dusty or muddy tracks. It is to be emphasized the action of the shock absorbers 220 which are extremely active in absorbing the sudden accelerations and brakings, thus cooperating to obtain a greater fit of the rear wheel onto the floor, thus improving the stability of the motorcycle. It is important that the lines passing through the points 216 and 203 on the one hand and 217 and 204 on the other, are parallel with one another and with the line joining the 218 and 207, as well as of the same length. The length of the sides of the virtual and like triangles with their apices at the points 216,217; 218,203; 204,207 is, however, optional. It should be underlined the fact that the jointing points of arms 201,202 are not aligned with the axes 207 or 208, according to which front or rear jointing point is considered, thus giving a greater versatility to the swinging ensemble structure. The improvements according to the version shown in Figures 6 and 7 of the drawings comprise a swinging ensemble in the shape of an articulated parallelogram consisting of two longitudinal arms 401,402 formed with conventional devices, generally denoted with 403, for adjusting the length of the arms. These arms, straight and provided with the adjusting devices 403 in the instant example, may have whatever other shape, for example elbowed or curved shape, to match, in every case, the features of the motorcycle. The arms 401,402 have an end which is jointed at points 404,405 to the motorcycle frame 406. The opposite ends of these arms are formed with lugs 407 to be jointed at points 408,409 to a support 410 upon which the axle 411 of the motorcycle driving wheel is mounted. The output shaft 412 of the gearbox 413 is connected to a conventional sprocket transmission 414 which imparts rotation to a sprocket 415, of center line 416, placed at the end of the motorcycle transmission, either chain 417 (Fig. 6) or rigid shaft 418 with terminal sprockets 419 (Fig. 7). The other terminal sprocket 420 of transmission 417 or 418, which revolves about a center line 421, is connected to a conventional transmission 422 imparting rotation to the crown 423 mounted on the axle 411 of the driving wheel. Looking to the drawings, it will be appreciated that, either in the version of Figure 21 or in the version of Figure 22, the jointing points 404,405 of arms 401,402 to the frame 406, and the center line 416 of the sprocket 415 located at one end of the transmission 417 or 418, constitute the apices of a virtual triangle which is identical to the triangle as defined by the jointing points 408,409 of arms 401,402 to the support 410, and the center line 421 of the sprocket 420 placed at the rear part of the transmission 417 or 418. This is so whichever the composition of the transmissions 414 and 422 may be. What is important is the identity of the triangles and the constant distance between the center lines 416 and 421 and the points 404 and 405 on the one hand and the points 408 and 409 on the other. Accordingly, the movements of the swinging ensemble do not alter the distance between the fundamental points of the motorcycle transmission, such as the center lines 416,421. It may be emphasized that, as in the preceding embodiments, the jointing points 404,405 and 408,409 define an articulated parallelogram regardless of the shape of the arms 401,402 and of the embodying of lugs 407 or complementary parts thereto. Also, the above improvements are likewise applicable to the swinging ensembles comprising more than one articulated parallelogram, regardless of the position in which the arms 401,402 are placed as regards the transmission 418 or 418. The improvements are also applicable to those swinging ensembles in which the arms 401,402 are connected with one another by means of transverse struts in turn connected to the piece supporting the driving wheel axle.

Claims: A rear wheel suspension and transmission mechanism for motorcycles and like vehicles having a rearwheel drive including a first sprocket (9;213;420) coupled to the rear drive wheel axle (8a) for rotation about a first axis (8;218;421), a second sprocket (11;206;415) coupled to a gear box output axle for rotation about a second axis (12;207;416), and transmission means for coupling said first (9;213;420) and second (11;206;415) sprocket, the second sprocket being the last element which transmits the power to the transmission means and the first sprocket being the first element which receives the power from the transmission means, said rear wheel suspension and transmission mechanism comprising: at least two oscillating arms (4,4a;201,202;401,402) extending substantially longitudinally relative to the motorcycle travelling direction; an oscillating axle support (1;215;410) articulated to a first end of each of said oscillating arms (4,4a; 201,202;410,402) at respective first joints (2,3;216,217; 408,409); an axle (8;218;411) for the rear driving wheel (8a) mounted in the oscillating support and coupled to the first sprocket (9;213;420); second ends of the oscillating arms (4,4a;201,202; 401,402) opposite the first ends thereof being articulated to respective points of a motorcycle frame at respective second joints (5,6;203,204;404,405); such that the oscillating arms (4,4a;201,202;401,402) constitute, together with the rear wheel axle oscillating support (1;215;410) an oscillating ensemble, said first (2,3;216,217;408,409) and second joints (5,6;203,204; 404,405) defining an articulated polygon, characterized in that said first joints (216,217;408,409) and said first sprocket axis (218;421) constitute apices of a first virtual triangle (216,217,218;408,409,421), and said second joints (203,204;404,405) and said second sprocket axis (207;416) constitute apices of a second virtual triangle (203,204,207;404,405,416), and in that said first and second virtual triangles are susbtantially congruent and have orientations which are substantially the same. A rear wheel suspension and transmission mechanism, according to claim 1 charaterized in that said first (2,3;216,217; 408,409) and second joints (5,6;203,204;404,405) are movable in order to provide for adjustment of all of the distances between said points. A rear wheel suspension and transmision mechanism, according to claims 1 and 2, characterized in that the articulated polygon (2,3,5,6) is an articulated parallelogram the oscillating arms (4,4a) of which are parallel to the virtual line passing through the centers (8,12) of the sprockets over which the transmission roller chain meshes. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that the oscillating arms (4,4a) are located under the virtual line passing through the centers (8,12) of the sprockets over which the transmission roller chain meshes. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that the oscillating arms (4,4a) are located over the virtual line passing through the centers (8,12) of the sprockets over which the transmission roller chain meshes. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that the oscillating arms (4,4a) are located coincident the virtual line passing through the centers of the sprockets (8,12) over which the transmission roller chain meshes. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that the transmission means comprises a rigid shaft (110;418), with no intermediate universal joint, connected at its ends to the first (109a;420) and second (111;415) sprockets by respective gearwheel sets (110a,110b;419). A rear wheel suspension and transmission mechanism, according to claim 9, characterized in that the gearwheels (110a,110b;419) which are integral with the transmission shaft ends are bevel sprockets and are connected to respective beveled gearwheels. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that the end of one said oscillating arm (201), jointed to the motorcycle frame, extends forwards (201a) and carries, jointed directly through cams, one end of a shock-absorber (220) the opposite end of which is articulated to the other oscillating arm (202) at a point located rearward of the second joint (204) of said arm to the motorcycle frame. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that the oscillating axle support (215) carries the shoe or block (219) of the brake for the rear wheel. A rear wheel suspension and transmission mechanism, according to claims 1 and 2, characterized in that at least one end of the oscillating arms (201,202; 401,402) is connected within respective bushings (209;403) having screws (211) which are operable from the outside to regulate the extension of the respective arms and secure the assumed position, with the cooperation of safety nuts (211a).

Inventors: BELIL CREIXELL JOSE LUIS, BELIL CREIXELL, JOSE LUIS, Belil Creixell, José Luis
Applicants: BELIL CREIXELL JOSE LUIS, BELIL CREIXELL, JOSE LUIS
Application year: 1988
Main classification: B62K25
IPC codes: B62K25