Front and rear wheel drive motorcycle

Abstract: A front and rear wheel drive motorcycle includes an engine unit (1) including a cylinder assembly (10) and a crank shaft (2) and first and second speed change belt mechanisms (3, 4) mounted to one end of the crank shaft (2) for driving the front and rear wheels (22, 17), respectively. The first and second speed change belt mechanisms (3, 4) are operatively connected to first and second speed change gear mechanisms (15, 20) through first and second driven pulleys (13, 18) respectively provided to the first and second speed change belt mechanisms (3, 4). To one end of the crank shaft (2) is mounted a driving pulley means (5, 6, 7) operated commonly with respect to the first and second speed change belt mechanisms (15, 20). The driving pulley means comprises a stationary driving pulley (5) mounted to one end of the crank shaft (2) and operated commonly with respect to the first and second speed change belt mechansims (15, 20) and a pair of movable driving pulleys (6, 7) mounted to one end of the crank shaft (2) with the stationary drinving pulley (5) interposed therebetween.

Description: BACKGROUND OF THE INVENTION The present invention relates to a front and rear wheel drive motorcycle adapted to be driven on a sandy ground or a road having a soft road surface condition and more particularly to a front and rear wheel drive motorcycle provided with non-stage speed change belt mechanism. Generally, a motorcycle is provided with an engine to which a multi-stage gear transmission mechanism is connected through a manual clutch and the engine is operatively connected to a rear wheel through a chain to drive the rear wheel. Namely, the motorcycle of this type is run by driving the rear wheel and is sterred by the front wheel. The speed change gears of the multi-stage gear transmission mechanism are selectively switched in accordance with a running speed of the motorcycle. The output of a power transmission shaft is branched through a differential clutch to drive the front wheel as disclosed in the Japanese Patent Laid-open Publication No. 58-206477, for example. The Japanese Laid-open Publication No. 61-181789, for example, discloses a three-wheeled vehicle in which the differential mechanism is eliminated between the front and rear wheels to drive only the front wheel. For the motorcycle in which only the rear wheel is driven by the engine, it may become impossible to be smoothly driven when the rear wheel is slipped particularly at a time of running on a sandy ground or soft road. On the other hand, for a motorcycle in which front and rear wheels are driven, it becomes necessary to be equipped with a differential clutch or a differential mechanism for absorbing rotation difference between the front and rear wheels due to the steering operation of the front wheel (WO 88/09739). In addition, for the diffential mechanism, it is necessary to provide a slip preventing mechanism capable of running the motorcycle by the transmission of the driving force to one wheel when another wheel is slipped. This complicates the structure of the mechanisms and, hence, the motorcycle itself, resulting in the increasing of the manufacturing cost. Moreover, during the running on the sandy ground or soft road, the wheels of the motorcycle receive large friction resistance from the road. Accordingly, the running speed of the motorcycle is extremely decreased during the changing operation of the speed change gear mechanism in the multi-stage gear transmission mechanism, thus being inconvenient for the smooth driving of the motorcycle. The object of the present invention is to provide a front and rear wheel drive motorcycle capable of smoothly running on a sandy road or soft road, for example, under the non-stage speed change operation without being provided with a differential mechanism and capable of making compact an engine unit and a driving mechanism of the motorcycle. The objects can be achieved according to the present invention by providing a front and rear wheel drive motorcycle having the features of claim 1. In preferred embodiments, the driving pulley means comprises a stationary driving pulley mounted to one end of the crank shaft and operated commonly with respect to the first and second speed change belt mechansims and a pair of movable driving pulleys mounted to one end of the crank shaft with the stationary driving pulley interposed therebetween. The stationary pulley is provided with an inner hollow portion in which a plurality of fans are located, the inner hollow portion being communicated with an axial bore of the crank shaft. Thereby, the belt mechanisms are effectively cooled. The cylinder assembly is directed forwardly with respect to the front wheel and the first driven pulley of the first speed change belt mechanism and the first speed change gear mechanism on the side of the front wheel are disposed at an upper side of the cylinder assembly of the engine unit. The cylinder assembly is directed forwardly with respect to the front wheel and the first driven pulley of the first speed change belt mechanism on the side of the front wheel and the first speed change gear mechanism on the side of the front wheel has an output shaft disposed at substantially holizontally in front of the first driven pulley. The first and second speed change belt mechanisms are operatively connected to first and second speed change gear mechanisms further through first and second centrifugal clutch means. The crank shaft has another end to which a magnet to which a cooling fan is secured is mounted. In another aspect of the present invention, the cylinder assembly is directed rearwardly with respect to the rear wheel, wherein the first speed change belt mechanism is operatively connected to first speed change gear mechanism disposed at a front upper portion of the engine unit, and the second speed change belt mechanism is disposed on a side of the cylinder assembly and operatively connected to second speed change gear mechanism disposed on a rear side of the cylinder assembly. According to the characters of the front and rear wheel drive motorcycle described above, the driving pulleys of two non-stage speed change belt mechanisms are mounted side by side on one end portion of the crank shaft to be accommodated in compact. The rotation difference between the front and rear wheels can be absorbed by the non-stage speed change belt mechanisms, so that there is no need for the provision of the differential cluch means, for example, thus making compact the mechanism and being manufacured with reduced cost. In addition, since the non-stage speed change belt mechanisms are automatically speed-changed, the motorcycle can run smoothly on a sandy road or soft road, for example. Even in a case where one wheel is slipped, the driving force is transmitted to the other wheel to thereby smoothly drive the motorcycle. Since the cylinder assembly of the engine unit is disposed horizontally forwardly, the driven pulleys and speed change mechanisms can be arranged on the upper side of the cylinder assembly, thus making compact the structure and reducing the height of the motorcycle body. In addition, the cylinder assembly of the engine unit is also disposed horizontally rearwardly to be positioned in a space in front of the rear side speed change gear mechanism, thus also making compact and reducing the height of the motorcycle body. The driven pulley on the front wheel side of the non-staged speed change belt mechanism is located at an upper portion in front of the crank shaft of the engine and the output shaft of the speed change gear mechanism is disposed on substantially the horizontal front side thereof, so that the speed change gear mechanism can be accommodated in a lower portion of the front portion of the motorcycle body. One stationary pulley mounted to one end of the crank shaft is commonly utilized for two non-stage speed change belt mechanisms, so that the total length of the crank shaft can be reduced, thus making compact the structure of the engine. The location of the fans in the inner hollow portion of the stationary pulley can effectively cool the belt, thus improving the durability thereof. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a front and rear wheel drive motocycle equipped with a speed change system according to the present invention; Fig. 2 is brief top plan view of the motorcycle shown in Fig. 1; Fig. 3 is a sectional view of one embodiment of a speed change system of the motorcycle shown in Fig. 1; Fig. 4 is a side view of the speed change mechanism shown in Fig. 3 with a side case removed; Fig. 5 is an enlarged sectional view of one end of the crank shaft shown in Fig. 3; Fig. 6 is a brief sectional view of a stationary pulley mounted to the crank shaft shown in Fig. 5; and Figs. 7, 8 and 9 are views corresponding to Figs. 1, 2 and 3, respectively and representing another embodiment according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a brief side view of a motorcycle of a front and rear wheel drive type according to the present invention, in which the motorcycle is equipped with a front wheel 22 and a rear wheel 17 which are driven by the operation of an engine 1 through chains 21 and 16, respectively. The front wheel 22 is steered by a handle member 24 through a front fork 23. Fig. 2 is a brief illustration of a plan view of the motorcycle shown in Fig. 1. Fig. 3 is a sectional view of a main body of the motorcycle shown in Fig. 1. Referring to Fig. 3, in which an engine 1 is provided with a cylinder assembly 1a directed substantially horizontally forwardly, two non-stage speed change belt mechanisms 3 and 4 are connected to one end of a crank shaft 2 of the engine 1. A stationary driving pulley 5 having conical surfaces on both sides thereof is mounted on the crank shaft 2 and two movable driving pulleys 6 and 7 are arranged on both conical surface sides of the stationary driving pulley 5 in contact therewith. As shown in Fig. 5, centrifugal weights 8 and 9 are incorporated in the movable driving pulleys 6 and 7, respectively to be outwardly displaceable along the inclined surfaces, so as to slide the movable driving pulleys 6 and 7 to approach the stationary driving pulley 5 when the rotation of the engine, i.e. the crank shaft 2, is increased, thus enlarging a belt stretched around the pulley 5 and, hence, increasing the running speed of the motorcycle. In a preferred embodiment of the present invention, the stationary driving pulley 5 may be provided with an inner hollow portion 10 in which a plurality of fans 11 are radially accommodated and the inner side of the hollow portion 10 is communicated with an axial hole 12 (Fig. 6) formed in the crank shaft 2 so as to forcibly cool the engine. The movable pulleys 6 and 7 and the stationary pulley 5 constitute, in a pair, a drive side pulley means. Reference numeral 33 in Fig. 3 designates a magnet which is mounted on the outer end of the crank shaft 2 and to which the fans 35 are secured. The fans 35 and the cylinder assembly 1a of the engine 1 is covered by a fan cover 34. As shown in Fig. 4, a driven pulley 13 of the non-stage speed change belt mechanism 3 is disposed behind the crank shaft 2 and connected to a speed change gear mechanism 15 through a centrifugal clutch 14, which in turn is connected to the rear wheel 17 through the chain 16. A driven pulley 18 of the non-stage speed change belt mechanism 4 is disposed on a front upper side of the crank shaft 2 and connected to a speed change gear mechanism 20 through a centrifugal clutch 19, which in turn is connected to the front wheel 22 through the chain 21. Accordingly, the driven pully 18 and the speed change gear mechanism 20 can be arranged to the upper portion of the cylinder assembly 1a of the engine, whereby the heights of the engine 1 and the driving portion, i.e. the whole height of the motorcycle body, can be made small and light. An output shaft 30 of the speed change gear mechanism 20 is disposed on the front side of the driven pulley 18 in substantially the horizontal direction. To the output shaft 30 is connected the chain 21 which is operatively connected to the front wheel 22. The driving unit including two non-stage speed change belt mechanisms 3 and 4 is arranged in a unit case 31 integrally formed with the case of the engine 1. The unit case 31 is mounted at the front lower portion of the motorcycle body to the front end of which a head pipe 28 (Fig. 1) is arranged. The engine 1 is arranged in the unit case 31 including an engine case half 32 so that the cylinder assembly 1a is directed horizontally forwardly. The driven pulley 18 for driving the front wheel 22 is disposed on the front side, but the front portion of the motorcycle body is made high, so that the driven pully 18 of the non-stage speed change belt mechanism can be effectively accommodated in the engine case half 32. The output shaft 30 is disposed on the front side thereof near the front fork 23 to thereby make short the length of the chain 21, thus making compact the unit case 31 and reducing vibration of the unit case and, hence, the motorcycle body. The front wheel 22 is secured to the front fork 23 which is bilaterally steered by the operation of the handle 24. A uniform speed ball joint 26 is mounted to an intermediate shaft 25 (Fig. 5) for the chain 21. The front portion of the cylinder assembly 1a may be inclined to the extent such that the front portion thereof does not abut against a case portion in which the driven pulley 18 is accommodated. When the engine 1 is idly driven, two non-stage speed change belt mechanisms 3 and 4 are rotated. Next, when the rotation speed of the engine 1 is slightly increased, the centrifugal clutches 14 and 15 are operatively connected to thereby drive the front and rear wheels 22 and 17, thus starting the running of the motorcycle. When the rotation speed of the engine 1 is further increased, the non-satge speed change belt mechanisms 3 and 4 are increased in speed to thereby incrase the running speed of the motorcycle. According to the structure of the motorcycle described above, the two non-stage speed change belt mechainsms 3 and 4 is opeartively associated with one stationary driving pulley 5, so that the crank shaft 2 is made short in length and since the stationary driving pulley 5 can be cooled by the rotation of the crank shaft 2, the temperature increasing thereof due to the friction between the pulley 5 and the non-stage speed change belt mechanisms 3 and 4 can be effectively prevented, thus improving the durability of the belt. Figs. 7, 8 and 9 represent another embodiment according to the present invention in which an engine 1 is provided with a cylinder assembly 1a which is directed horizontally forwardly and the arrangement of the other constructional elements are substantially the same as the arrangement shown in Figs. 1 to 3 and the details thereof are now omitted. According to this embodiment, there is provided a front and rear wheel drive motorcycle in which front and rear wheels are driven by an operation of an engine, comprising an engine unit including a cylinder assembly and a crank shaft, the cylinder assembly being directed forwardly with respect to the rear wheel, first and second speed change belt mechanisms mounted to one end of the crank shaft for driving the front and rear wheels, respectively, the first speed change belt mechanism being operatively connected to first speed change gear mechanism disposed at a front upper portion of the engine unit, the second speed change belt mechanism being disposed on a side of the cylinder assembly and operatively connected to second speed change gear mechanism disposed on a rear side of the cylinder assembly, and a driving pulley means mounted on one end of the crank shaft and operated commonly with respect to the first and second speed change belt mechanisms. According to the arrangement of this embodiment, the cylinder assembly 1a of the engine 1 is positioned between the location of the crank shaft 2 and the rear side non-stage speed change gear mechanism 15, thus effectively utilizing the space of the motorcycle body. It is to be understood that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.

Claims: A front and rear wheel drive motorcycle in which the front and rear wheels (22, 17) are driven by an operation of an engine (1) comprising: an engine unit (1) including a cylinder assembly (1a) and a crank shaft (2); means coupled to the crank shaft (2) for driving the front and rear wheels (22, 17), characterized in that said driving means comprise first and second speed change belt mechanisms (4, 3) mounted to one end of the crank shaft (2) for driving the front and rear wheels (22, 17), respectively, said first and second speed change belt mechanisms (4, 3) being operatively connected to first and second speed change gear mechanisms (20, 15) through first and second driven pulleys (18, 13) respectively provided to the first and second speed change belt mechanisms (4, 3); and that a driving pulley means (5, 6, 7) is mounted to one end of the crank shaft (2) and operated commonly with respect to the first and second speed change belt mechanisms (4, 3). A motorcycle according to claim 1, wherein said driving pulley means comprises a stationary driving pulley (5) mounted to one end of the crank shaft (2) and operated commonly with respect to the first and second speed change belt mechanisms (4, 3) and a pair of movable driving pulleys (7, 6) mounted to one end of the crank shaft (2) with the stationary driving pulley (5) interposed therebetween. A motorcycle according to claim 1 or 2, wherein said stationary pulley (5) is provided with an inner hollow portion (10) in which a plurality of fans (11) are located, said inner hollow portion (10) being comunicated with an axial bore (12) of said crank shaft (2). A motorcycle according to any of claims 1 - 3, wherein said cylinder assembly (1a) is directed substantially horizontally forwardly with respect to the front wheel (22) and the first driven pulley (18) of the first speed change belt mechanism (4) and the first speed change gear mechanism (20) on the side of the front wheel (22) are disposed at an upper side of the cylinder assembly of the engine unit (1). A motorcycle according to anyone of claims 1 - 4, wherein said cylinder assembly (1a) is directed substantially horizontally forwardly with respect to the front wheel (22) and the first driven pulley (18) of the first belt speed changing mechanism (4) on the side of the front wheel (22) and the first speed change gear mechanism (20) on the side of the front wheel (22) has an output shaft (30) disposed at substantially horizontally in front of the first driven pulley (18). A motorcycle according to anyone of claims 1-5, wherein said first and second speed change belt mechanisms ( 4, 3) is operatively connected to first and second speed change gear mechanisms (20, 15) further through first and second centrifugal clutch means (19, 14). A motorcycle according to anyone of claims 1-6, wherein said crank shaft (2) has another end to which a magnet (33) to which a cooling fan (35) is secured is mounted. A motorcycle according to claim 1, wherein said cylinder assembly (1a) is directed substantially horizontally forwardly with respect to the rear wheel, said first speed change belt mechanism (4) being operatively connected to said first speed change gear mechanism (20) disposed at a front upper portion of the engine unit (1), said second speed change belt mechanism (3) being disposed on a side of said cylinder assembly (1a) and operatively connected to said second speed change gear mechanism (15) disposed on a rear side of said cylinder assembly (1a).

Inventors: YAMAUCHI KOSAKU, YAMAUCHI, KOSAKU
Applicants: SUZUKI CO LTD, SUZUKI KABUSHIKI KAISHA
Application year: 1990
Main classification: B62M7
IPC codes: B62M7, B62M23, B62M9