WO2008087664A1

WO2008087664A1 - Clutch transmission assembly of a two wheeler

Info

Publication number: WO2008087664A1
Application number: PCT/IN2008/000033
Authority: WO
Inventors: Vinay Chandrakant Harne; Jaya Jothi Johnson Vethanayagam
Original assignee: Tvs Motor Company Limited
Priority date: 2007-01-19
Filing date: 2008-01-18
Publication date: 2008-07-24
Also published as: MY163905A; BRPI0806711A2

Abstract

This description relates to a clutch transmission assembly for a two-wheeler. The clutch transmission assembly includes a transmission casing having a primary drive gear mounted on a crankshaft and a primary driven gear mounted on a countershaft. A centrifugal clutch assembly is mounted on the crankshaft for engaging or disengaging the primary drive gear, while a multi-plate clutch assembly is mounted on the countershaft for engaging or disengaging the primary driven gear. A gearshift shaft mounted parallel to the countershaft has one end attached to a gearshift lever and other end attached to a clutch release arm. A clutch release rod is connected to a manual clutch lever at one end to manually engage or disengage the multi-plate clutch assembly and at other end is rotatably connected to a clutch release override. The clutch release rod is responsive to the manual clutch lever for providing a push force and disengages the multi-plate clutch assembly thereby overriding the clutch release arm.

Description

CLUTCH TRANSMISSION ASSEMBLY OF A TWO-WHEELER FIELD OF INVENTION

The present invention relates to a clutch transmission assembly of a two-wheeled vehicle. BACKGROUND

Power transmission from a crankshaft to a drive shaft is generally achieved through a clutch and a series of reduction gears. In a dual clutch mechanism, power is first transmitted from the crankshaft to an intermediate or a counter shaft and then to the drive shaft. A first, centrifugally operated clutch is mounted on the crankshaft and a second, manual clutch is mounted on the counter shaft or the intermediate shaft. The second clutch is normally a multi-plate type mounted on the intermediate shaft or the counter shaft and transmits power from the counter shaft to the drive shaft.

The first and the second clutches can either be locked together so that they rotate at the same speed. Alternatively, the first and the second clutches can be decoupled so that they rotate at different speeds.

Such a dual clutch mechanism is prevalent in many motorcycles, because the mechanism provides uninterrupted power transmission to the drive shaft and is easy to operate. However, the dual clutch mechanism also causes jerky movements when a vehicle is started. Also in this case, when a rider shifts from a lower gear ratio to a higher ratio, substantial power is needed to drive to the higher gear ratio, which is not usually achieved. As a result, the rider has to provide more force using his/her leg to shift the gear and simultaneously disengage the clutch since this is achieved simultaneously by a single lever operation. Therefore a need arises for a clutch actuation mechanism to overcome the above mentioned problems.

SUMMARY

The present disclosure relates to a clutch transmission assembly for a two-wheeler vehicle. The clutch transmission assembly includes a transmission casing, a crankshaft rotatably mounted in the transmission casing, and a primary drive gear mounted on the crankshaft. In addition, a centrifugal clutch assembly is mounted on the crankshaft for engaging or disengaging the primary drive gear. Further, the transmission casing includes a countershaft mounted parallel to the crank shaft and a primary driven gear mounted on the countershaft. A multi-plate clutch assembly is also mounted on the countershaft for engaging or disengaging the primary driven gear using a plurality of secondary gears.

A gearshift shaft is mounted parallel to the countershaft in the transmission casing. One end of the gearshift shaft is attached to a gearshift lever and the other end of the gearshift shaft is attached to a clutch release arm. The clutch release arm is operatively connected to a clutch release pin of the multi-plate clutch assembly. A driveshaft is mounted parallel to the gearshift shaft in the transmission casing. The driveshaft has a plurality of secondary driven gear(s) and a sprocket drive to transmit power to a rear wheel of the vehicle.

The clutch transmission assembly further includes a clutch release rod to manually engage or disengage the multi-plate clutch assembly. One end of the clutch release rod is connected to a manual clutch lever, whereas the other end is rotatably connected to a clutch release override. The clutch release rod of the clutch transmission assembly is responsive to the manual clutch lever for providing a push force that corresponds to disengagement of the multi-plate clutch assembly thereby overriding the clutch release arm.

These and other features, aspects, and advantages of the present subject matter will become better understood with reference to the following description and appended claims. This Summary is provided to introduce a selection of concepts in a simplified form. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig.l illustrates a sectional view of a clutch assembly without a manual clutch lever attached to the clutch assembly. Fig.2 illustrates a cross-sectional view of a gearbox assembly of a motorcycle in accordance with one embodiment of the present subject matter.

Fig.3 illustrates a sectional view of the multi-plate clutch assembly in accordance with one embodiment of the present subject matter depicting the auto clutch release arm in a disengaged position. Fig.4 illustrates a sectional view of the multi-plate clutch assembly in accordance with one embodiment of the present subject matter depicting the auto clutch release arm in an engaged position. Fig.5 illustrates a sectional view of the multi-plate clutch assembly in accordance with one embodiment of the present subject matter showing the clutch release rod in an actuated position.

Fig.6 illustrates a sectional view of the multi-plate clutch assembly in accordance with one embodiment of the present subject matter depicting the clutch release rod in a released position.

Fig.7 illustrates a cross-sectional view of a clutch transmission assembly with respect to one embodiment of the present subject matter showing the clutch release rod overriding the auto clutch release arm. Fig.8 illustrates a perspective top view of a two-wheeled vehicle with respect to one embodiment of the present subject matter.

DETAILED DESCRIPTION

The disclosure provides a clutch transmission assembly for a two-wheeled vehicle having a transmission casing. A primary drive gear is mounted on a crankshaft that is rotatably mounted on the transmission casing. A centrifugal clutch assembly is mounted on the crankshaft for engaging or disengaging the primary drive gear. A primary driven gear is mounted on a countershaft that is mounted parallel to the crankshaft in the transmission casing. Further, a multi-plate clutch assembly is mounted on the countershaft for engaging or disengaging of the primary driven gear with a plurality of secondary gears. A gearshift shaft is mounted parallel to the countershaft in the transmission casing. One end of the gearshift shaft is attached to a gearshift lever and the other end of the gearshift shaft is attached to a clutch release arm. The clutch release arm is operably connected to a clutch release pin of the multi-plate clutch assembly. A driveshaft is mounted parallel to the gearshift shaft in the transmission casing. The driveshaft comprises a plurality of secondary driven gear(s) and a sprocket drive to transmit power to a rear wheel. A clutch release rod manually engages or disengages the multi-plate clutch assembly. One end of the clutch release rod is connected to a manual clutch lever while the other end is rotatably connected to a clutch release override. The clutch release rod of the clutch transmission assembly is responsive to the manual clutch lever for providing a push force to disengage the multi-plate clutch assembly and to override the clutch release arm. The two-wheeled vehicle can be, for example, a step-through motorcycle. In an embodiment, relating to a clutch transmission assembly, a centrifugal clutch assembly includes a centrifugal clutch and a drum clutch. In another embodiment, the primary drive gear is attached to the drum clutch. In yet another embodiment, the centrifugal clutch engages the drum clutch at a predetermined speed to enable continuous power transmission.

Fig.l illustrates a sectional view of a clutch assembly without a manual clutch lever attached to the assembly in accordance with one embodiment of the present subject matter. The clutch assembly includes an auto clutch release arm 107 that disengages a clutch release pin 105 when the auto clutch release arm 107 is pushed by a gear shifting lever. The gear shifting lever, not shown in this figure, is operated by a rider.

Fig.l also shows a centrifugal clutch assembly, mounted on a crankshaft 103. The centrifugal clutch assembly includes a centrifugal clutch 112a and a drum clutch 112b. The centrifugal clutch 112a is mounted on the crankshaft 103 whereas the drum clutch 112b freely rotates on the crankshaft 103. The centrifugal clutch 112a starts rotating along with drum clutch 112b when the crankshaft 103 attains a high angular speed, such as about 3000 rpm.

The centrifugal clutch 112a is normally in a disengaged position and gets engaged on attaining high angular speed. On the other hand, the multi-plate clutch assembly 101 is normally in an engaged position and gets disengaged when the gearshift lever is operated by the rider. Thus, in such a dual clutch mechanism, power is continuously transmitted from the engine through the crankshaft 103 to the counter shaft 108 and finally to the drive shaft 109 in an uninterrupted manner.

Fig-2 illustrates a cross-sectional view of a gearbox assembly of the motorcycle in accordance with one embodiment of the present subject matter. In the present embodiment, the manual clutch actuation mechanism is coupled with a dual clutch mechanism inside a transmission casing 121. Fig.2 shows a clutch release rod 102 in the engaged position. The clutch release rod 102 is actuated during the manual depression of a lever provided on the handlebar of the motorcycle. The clutch release rod 102 forces a clutch release override 106 to press the clutch release pin 105 and disengage the multi- plate clutch assembly 101. During this process of disengaging the multi-plate assembly 101, the auto clutch release arm 107 is not used and becomes redundant.

The clutch release assembly thus allows the rider to manually disengage the clutch through a hand operated lever. This reduces rider fatigue substantially, since less force is exerted by the rider while shifting gears. Further, enough power gets exerted on the gear wheel with a higher gear ratio when the rider shifts the gear from a lower gear ratio to the higher gear ratio.

Fig.2 also shows the arrangement of the multi-plate clutch assembly 101 mounted on the counter shaft 108. When the primary drive gear 104 is engaged, a primary driven gear 111 rotates, which in turn rotates the counter shaft 108. When the manual clutch lever is operated, the manual clutch engages and disengages secondary drive gears that are attached to the counter shaft 108. This in turn transfers power to the corresponding secondary driven gears respectively, which are mounted on a drive shaft 109. Power is then transmitted from the drive shaft 109 to the wheels through a sprocket drive 110.

Fig.3 illustrates a sectional view of the multi-plate clutch assembly 101 in accordance with one embodiment of the present subject matter, showing the auto clutch release arm 107 in the disengaged position. In the disengaged position, steel plates 120 and a friction plate 119 in the multi-plate clutch assembly 101 are held together tightly to transfer torque to the drive gears mounted on the counter shaft 108. Friction plates 119 are placed side by side adjacent to each of the steel plate 120 in the multi-plate clutch assembly 101. No gap is present between the friction plates 119 in the disengaged position of the auto clutch release arm 107, as the multi-plate clutch assembly 101 is in the engaged position.

Fig.4 illustrates a sectional view of the multi-plate clutch assembly 101 in accordance with one embodiment of the present subject matter, showing the auto clutch release arm 107 in the engaged position. When the rider shifts gears by a foot operated lever, the gear shifting action simultaneously engages the auto clutch release arm 107, which in turn pushes the clutch release pin 105 into the counter shaft 108. This disengages the clutch and facilitates gear shifting. An operating gap 113 (measuring around 0.6mm) is present between the friction plates 119 in the engaged position of the auto clutch release arm 107, since the multi-plate clutch assembly 101 is in the disengaged position.

Referring to Fig. 5 and Fig. 8 that illustrate a sectional view of the multi-plate clutch assembly 101 and a perspective top view of a two wheeled vehicle respectively, the clutch release rod 102 is shown in the actuated position. When a manual (hand operated) clutch lever 118 (refer Fig 7) is depressed by the rider, the clutch release rod 102 is rotated to a predetermined angle clockwise. This pushes the clutch release override 106 against the clutch release pin 105 through auto clutch release arm 107, thereby disengaging the clutch and facilitating gear shifting. A substantial gap 113 is present between the friction plates 119 in the actuated position of the clutch release rod 102, since the multi-plate clutch assembly 101 is in the disengaged position.

Fig.6 illustrates a sectional view of the multi-plate clutch assembly 101 in accordance with one embodiment of the present subject matter, showing the clutch release rod 102 in the released position. In the released position, the steel plates 120 of the multi- plate clutch assembly 101 are held together tightly to transfer torque to the drive gears mounted on the counter shaft 108. Friction plates 119 are placed side by side adjacent to each of the steel plate 120 in the multi-plate clutch assembly 101. No gap is observed between the friction plates 119 in the engaged position of the clutch release rod 102, since the multi-plate clutch assembly 101 is also in the engaged position. Further, the clutch release rod 102 is brought back to the initial position by rotating it counter-clockwise to a predetermined angle. This occurs when the clutch release rod 102 is released once the rider releases the hand operated clutch lever. The multi-plate clutch assembly 101 comprises a plurality of steel plates 120 and a plurality of friction plates 119 that are stacked side by side. The friction plates 119 are connected to a plurality of slots 123 on the outer diameter of a clutch housing 130. The friction plates 119 are connected to the slots 123 through a plurality of lugs 122 that are provided on the outermost periphery of the friction plates 119.

Fig.7 illustrates a cross-sectional view of a clutch transmission assembly with respect to one embodiment of the present subject matter. The multi-plate clutch assembly 101 mounted on the counter shaft 108 is disengaged by the push force exerted on the clutch release pin 105 by the auto clutch release arm 107. The auto clutch release arm 107 is depressed when the rider operates a gearshift lever not shown in this figure. The gearshift lever is mounted at the outer end of a gearshift shaft 116 and the auto clutch release arm 107 is mounted with spring means at the inner end of the gearshift shaft 116. Each time the rider shifts the gearshift lever 117, the auto clutch release arm 107 is activated, thereby disengaging the multi-plate clutch assembly 101 and facilitating gear shifting. Disengaging the clutch release rod 102 engages the multi-plate clutch assembly 101 and thereby transmits uninterrupted power to the drive shaft 109 (not shown in Fig.7) through the set of driven gears mounted on it.

When the manual clutch lever is depressed, the clutch release rod 102 rotates clockwise thereby pushing the clutch release override 106 against the clutch release pin

105. During this operation, the auto clutch release arm 107 is rendered redundant. Thus, shifting of the gearshift shaft 116 by the rider does not activate the auto clutch release arm

107. Hence the operation of the manual clutch lever overrides the auto clutch release arm 107, reducing the effort required from the rider for shifting gears. The friction plates 119 of the multi-plate clutch assembly 101 are tightly held together by a series of springs 124 thereby exerting an axial pressure on the plurality of steel plates 120. The steel plates 120 when applied with an axial pressure, transfers maximum torque. Fig.8 illustrates a perspective top view of a two wheeler vehicle with respect to one embodiment of the present subject matter. The manual clutch lever 118 is projected through a lever opening (not seen in Fig.8) at the left end of the left handlebar. The gearshift lever 117 is attached to the exterior end of the gearshift shaft 116 (not seen in Fig.8) for use by the rider for shifting gears. Depression of the manual clutch lever 118 and simultaneous gear shifting enables overriding of the auto clutch release arm 107 present at the interior end of the gearshift shaft 116 (not seen in Fig.8).

Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.

Claims

' I/ we claim:

1. A clutch transmission assembly for a two-wheeler comprising: a transmission casing (121); a primary drive gear (104) mounted on a crankshaft (103), wherein said crankshaft is rotatably mounted in said transmission casing (121), and a centrifugal clutch assembly (112) mounted on said crankshaft (103) for engaging or disengaging of said primary drive gear (104); a primary driven gear (111) mounted on a countershaft (108), wherein said countershaft (108) is mounted parallel to said crankshaft (103) in said transmission casing (121), and a multi-plate clutch assembly (101) is mounted on said countershaft (108) for engaging or disengaging of said primary driven gear (111) with a plurality of secondary gears; a gearshift shaft (116) mounted parallel to said countershaft (108) in said transmission casing (121), wherein one end of said gearshift shaft (116) is attached to a gearshift lever (117) and other end of said gearshift shaft is attached to a clutch release arm (107), said clutch release arm is operably connected to a clutch release pin (105) of said multi-plate clutch assembly

(101); a driveshaft (109) mounted parallel to said gearshift shaft (116) in said transmission casing (121), wherein said driveshaft (109) comprises a plurality of secondary driven gear(s) and a sprocket drive (110) to transmit power to a rear wheel; and a clutch release rod (102), characterized in that said clutch release rod (102), manually engages or disengages said multi-plate clutch assembly (101), wherein one end of said clutch release rod (102) is connected to a manual clutch lever (118) and other end is rotatably connected to a clutch release override (106); wherein said clutch release rod (102) of said clutch transmission assembly is responsive to said manual clutch lever (118) for providing a push force to disengage said multi-plate clutch assembly (101) and to override said clutch release arm (107).

2. The clutch transmission assembly as claimed in claim 1, wherein the two-wheeler is a step-through motorcycle.

3. The clutch transmission assembly as claimed in claim 1 wherein said centrifugal clutch assembly (112) comprises a centrifugal clutch (112a) and a drum clutch (112b).

4. The clutch transmission assembly as claimed in claim 1 wherein said primary drive gear (104) is attached to said drum clutch (112b).

5. The clutch transmission assembly as claimed in claim 1, wherein said centrifugal clutch (112a) engages said drum clutch (112b) at a predetermined speed to enable continuous power transmission.

6. The clutch transmission assembly as claimed in claim 1, wherein said primary driven gear (111) is mounted to a clutch housing (130) of said multi-plate clutch assembly (101).

' 7. The clutch transmission assembly as claimed in claim 1, wherein said multi-plate clutch assembly (101) comprises a plurality of steel plates (120) and friction plates (119) placed side by side.

8. The clutch transmission assembly as claimed in claim 1 wherein said manual clutch lever (118) provides a push force more than the force achieved by said clutch release arm (107) for disengaging said multi-plate clutch assembly (101).

9. The clutch transmission assembly as claimed in claim 1 or claim 6 or claim 7, wherein said friction plates (119) are connected through a plurality of lugs (122) provided on the outermost periphery of said friction plates (119) to a plurality of slots (123) provided on the outer diameter of said clutch housing (130).

10. The clutch transmission assembly as claimed in claim 1 or claim 7, wherein said friction plates (119) are held together tightly by a series of springs (124) thereby exerting axial pressure on said steel plates (120).

11. The clutch transmission assembly as claimed in claim 1, wherein said clutch release rod ( 102) is provided with a dowel pin (114) and a return spring (115).

12. The clutch transmission assembly as claimed in claim 1, wherein said clutch release rod (102) rotates clockwise when said manual clutch lever (118) is pressed, thereby pushing said clutch release override (106) against said clutch release pin (105) and thereby disengaging said multi-plate clutch assembly (101).

13. The clutch transmission assembly as claimed in claim 1, wherein said clutch release rod (102) rotates counter-clockwise when said manual clutch lever (118) is depressed thereby engaging said multi-plate clutch assembly (101).

' 14. The clutch transmission assembly as claimed in claim 1 or claim 7, wherein the gap between said friction plates (119) when said multi-plate clutch assembly (101) is disengaged by said manual clutch lever (118) is substantially less than the gap between said friction plates (119) when the clutch is disengaged by said clutch release arm (107).

15. The clutch transmission assembly as claimed in claim 1 or claim 7, wherein said friction plates (119) of said multi-plate clutch assembly (101) are stacked without gap as observed in the engaged mode.