TECHNICAL FIELD

The subject matter described herein, in general, relates to a clutch actuation assembly and in particular, relates to a clutch actuation assembly for two wheeled vehicles.

BACKGROUND

Typically, a clutch assembly is provided between a power source, such as an engine or a motor, of a vehicle and a transmission system of the vehicle to provide a smooth shift between gears and to facilitate transfer of power from the power source to the transmission system. The clutch assembly generally includes clutch plates, a clutch release pin, a clutch shaft, and clutch springs. The clutch assembly can be actuated by a clutch actuation assembly, for example, a cable clutch actuation assembly or a hydraulic clutch actuation assembly.

The cable clutch actuation assembly includes a clutch lever and a clutch cable. When a driver of the vehicle manually imparts a force on the clutch lever, the clutch cable gets drawn. The clutch cable actuates the clutch assembly by separating the clutch plates from each other, which results in disengagement of the clutch assembly. Accordingly, when the rider releases the clutch lever, the clutch springs bring the clutch plates back to their normal position, thereby re-engaging the clutch assembly. In the engaged state, the clutch assembly facilitates the transfer of power from the power source to the transmission whereas, in the disengaged state, the clutch assembly facilitates gear shifting.

In vehicles having a high torque output, a high frictional force is required to maintain engagement of the clutch. This high frictional force is generated by combining clutch plates, having a high coefficient of friction and large contact areas, with relatively high stiffness clutch springs. The high stiffness clutch springs are used for applying a necessary load on the clutch plates. Due to high friction and high load, a large manual force is required to actuate the clutch assembly and to separate the clutch plates. The force required to disengage the clutch increases with the separation of clutch plates due to increasing relative compression or extension of the clutch springs. The manual force required also increases as the size of the clutch plates increases, for example due to use of engines with high power output. However, the force that can be applied by the rider is limited. Additionally, the clutch cable has parasitic drag, is prone to degradation especially when exposed to high load applications, and its operation requires frequent adjustment of wear.

Therefore, usually, for high torque/high power output, a hydraulic clutch actuation assembly is used. The hydraulic clutch actuation assembly includes a manual clutch lever, a master cylinder, a slave cylinder, and an expandable hose adapted to transfer hydraulic fluid between the master and slave cylinders. When the clutch lever is retracted, the fluid inside the two cylinders gets pressurized and acts upon the clutch plates, thereby disengaging the engine from the transmission. As a result, better leverage ratio, and better clutch lever feel are obtained, but by making the overall assembly more expensive than the cable clutch actuation assembly. Additionally, the response of the hydraulic clutch gets affected because of the use of expandable hose and resultant transmission losses.

SUMMARY

The subject matter described herein is directed to a clutch actuation assembly for two- wheeled vehicles.

According to one embodiment, the clutch actuation assembly includes a cable clutch actuation assembly, an arm lever, and a hydraulic clutch actuation assembly. The cable clutch actuation assembly includes a clutch lever, and a clutch cable. The hydraulic clutch actuation assembly includes a master cylinder enclosing a first piston, a slave cylinder enclosing a second piston, and a pair of conduits connecting the master cylinder to the slave cylinder. Further, the clutch cable is connected to the master cylinder through the arm lever to provide axial motion to the first piston.

In operation, the cable clutch actuation assembly can be actuated by retracting the clutch lever. As a result, the clutch cable gets pulled. The clutch cable in turn pulls the arm lever, which further moves the first piston inside the master cylinder. The movement of the first piston provides motion to the second piston within the slave cylinder. Such motion is facilitated through the hydraulic pressure within the conduits connecting the master cylinder to the slave cylinder. The movement of the second piston is transferred to clutch plates of a clutch assembly by means of a clutch actuating member, thus disengaging the clutch assembly.

The integrated use of the cable clutch actuation assembly and the hydraulic clutch actuation assembly ensures reduced force on the clutch cable and reduced force required to operate the clutch assembly. Additionally, a higher leverage ratio is achieved by providing three leverages, i.e., at the clutch lever, the arm lever, and the hydraulic master cylinder, thus combining both the typical mechanical and hydraulic advantages, and 'having an additional mechanical advantage due to the arm lever. The clutch actuation assembly of the present subject matter is compact, efficient, and economical. Moreover, manual force required to shift gears is low, thus reducing driver fatigue.

These and other features, aspects, and advantages of the present subject matter will be 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 it is intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

Fig. Ia illustrates a side view of a two-wheeled vehicle depicting an exemplary clutch actuation assembly.

Fig. Ib illustrates a top view of the two-wheeled vehicle of Fig. Ia depicting the exemplary clutch actuation assembly.

Fig. 2a illustrates an exemplary arrangement of a master cylinder in the clutch actuation assembly.

Fig. 2b illustrates the isometric view of the master cylinder and the arm lever in the clutch actuation assembly, in accordance with one embodiment of the present subject matter. Fig. 2c illustrates another isometric view of the master cylinder and the arm lever in the clutch actuation assembly, in accordance with one embodiment of the present subject matter.

Fig. 3 illustrates a sectional view of an engine housing as viewed from a rear side of the two-wheeled vehicle.

Fig. 4 illustrates another sectional view of the engine housing as viewed from a rear side of the two-wheeled vehicle.

DETAILED DESCRIPTION

The subject matter disclosed herein relates to a clutch actuation assembly for a two- wheeled vehicle. For example and by no way limiting the scope of the subject matter, the two- wheeled vehicle is a motorcycle. The present subject matter integrates cable and hydraulic clutch actuation assemblies in order to provide a compact, efficient and a low cost clutch actuation assembly.

According to one embodiment, the clutch actuation assembly includes a cable clutch actuation assembly, an arm lever, and a hydraulic clutch actuation assembly. The cable clutch actuation assembly is actuated by retraction of a clutch lever provided on a handlebar of the motorcycle. To shift gears, a rider of the motorcycle retracts the clutch lever towards the handlebar. The retraction of the clutch lever actuates the cable clutch assembly that includes a clutch cable, and a cable sheath to cover the clutch cable. The clutch cable connects the clutch lever to the arm lever such that when the clutch is retracted, the clutch cable gets pulled in the direction of the clutch lever. The clutch cable in turn pulls the arm lever, thus transferring the motion of the clutch lever to the arm lever.

The arm lever further actuates the hydraulic clutch actuation assembly. The hydraulic clutch actuation assembly includes a main or master cylinder mounted on a bracket, a slave cylinder, and a pair of conduits connecting the master and the slave cylinder. The master cylinder includes a first piston and the slave cylinder includes a second piston. The first piston is connected to the arm lever such that the arm lever transfers motion of the clutch cable to the first piston and moves the first piston. The movement of the first piston increases fluid pressure inside the pair of conduits between the master cylinder and the slave cylinder. The pressure is transmitted to the second piston inside the slave cylinder through the conduits. The movement of the second piston actuates a clutch assembly of the motorcycle. In one embodiment, the clutch assembly includes clutch plates, a pair of springs, a clutch actuating member, a clutch bearing for supporting the clutch actuating member, and a spherical ball for transferring the motion of the second piston to the clutch actuating member. The clutch actuating member is pushed by the spherical ball to separate the clutch plates in the clutch assembly, thereby ensuring disengagement of the clutch assembly.

As the clutch assembly is in a disengaged state, the rider can make the required shift in the gears. Once the required gear ratio is achieved, the rider can release the clutch lever, thus releasing the tension in the clutch cable. Accordingly, the clutch cable and in turn the arm lever are released, thereby returning to a normal condition. This reduces the hydraulic pressure in the master cylinder and the slave cylinder. Due to pressure release, the clutch actuating member and the spherical ball get pushed towards the second piston by the action of the pair of springs present near the clutch plates. This brings the clutch plates together, thereby re-engaging the clutch assembly.

Fig. Ia illustrates a side view of a. motorcycle 100, depicting an implementation of a clutch actuation assembly 102.

Fig. Ib illustrates a top view of the motorcycle 100 depicting various components of the clutch actuation assembly 102. The clutch actuation assembly 102 includes a cable clutch actuation assembly 104 hereinafter referred to as cable assembly 104, a hydraulic clutch actuation assembly (not shown in the figure) hereinafter referred to as hydraulic assembly respectively, and an arm lever 106.

The cable assembly 104 includes a clutch cable 108 and a clutch lever 110. A cable sheath 112 covers the clutch cable 108. The cable sheath 112 protects the clutch cable 108 from any damage due to outside environment. The clutch lever 110 is provided on a handlebar 114 of the motorcycle 100, adjacent to a handle grip 116, for actuating the cable assembly 104 of the motorcycle 100. The clutch cable 108 transmits motion from the clutch lever 110 to the arm lever 106. In operation, the clutch lever 110 is retracted towards the handle grip 116 by a rider of the motorcycle 100, for example to shift gears. The retraction of the clutch lever 110 facilitates the transmission of motion from the clutch lever 110 to a clutch assembly (not shown in Figs. Ia and Ib) through the cable assembly 104, the arm lever 106 and the hydraulic assembly. The clutch lever also helps in force multiplication by transferring a small force applied by the rider into a relatively larger force at the arm lever as a result of known principles of leverage.

Though the current description has been provided with reference to a push-type clutch actuation, it will be easily understood by a person skilled in the art that the disclosed embodiments can be used for pull-type clutch actuation by suitably orienting the arm lever 106.

Fig. 2a illustrates an exemplary arrangement of a master cylinder 200 in the clutch actuation assembly 102. As mentioned above, the clutch actuation assembly 102 includes the hydraulic assembly, the cable assembly 104, and the arm lever 106. The hydraulic assembly includes the master cylinder 200, a slave cylinder (explained in detail later with reference to Fig. 3), and a pair of conduits such as a first conduit 202 and a second conduit (not shown in Fig. 2a) connecting the master cylinder 200 to the slave cylinder. In one embodiment, the slave cylinder is housed within an engine housing 204. Additionally, the master cylinder 200 is mounted on a bracket 206 and encloses a first piston (not shown in Fig. 2a).

In one embodiment, the first piston is capable of sliding within the master cylinder 200 and is set in motion by the clutch lever 110 through the cable assembly 104 and the arm lever 106. The clutch cable 108 and the arm lever 106 connect the clutch lever 110 to the first piston. In said embodiment, the arm lever 106 is mounted on the master cylinder housing and is hinged to the first piston at one end and to the clutch cable 108 at the other end. Further, the cable assembly 104 is guided on a frame 208 of the motorcycle 100 using a clip guide 210. Also, the cable assembly 104 includes a threaded end 212 mounted on the bracket 206 by means of a first fastener 214. The first fastener 214 may be a nut, a screw, a bolt or any other fastener known in the art.

In said embodiment, one end of the first conduit 202 is connected to the output of the master cylinder 200 by a fastening means such as a second fastener 216. The other end of the first conduit 202 is connected to the second conduit disposed in the engine housing 204. The second conduit can be connected to the first conduit 202 by another fastening means such as a third fastener 218. The second fastener 216 and the third fastener 218 may be a nut, a screw, a bolt or any other fastener known in the art. In one embodiment, the second and third fasteners 216 and 218 are benjo bolts..

A hydraulic fluid is present within and between the master cylinder 200 and the slave cylinder. In one embodiment, the hydraulic fluid used between the master cylinder 200 and the slave cylinder is high viscosity oil. For example, the hydraulic fluid used may be an engine oil so that any intermixing between the engine oil and the hydraulic fluid does not affect the functioning of the engine.

In one implementation, upon actuation of the clutch lever 110, the clutch cable 108 gets pulled towards the clutch lever 110, which in turn pulls the arm lever 106. The arm lever 106 transfers the motion of the clutch cable 108 to the first piston such that the first piston moves inside the master cylinder 200. The movement of the first piston creates pressure inside the master cylinder 200 containing the hydraulic fluid.

The quantity of the hydraulic fluid in the hydraulic assembly, i.e. the master cylinder 200, the slave cylinder and the two conduits, is maintained such that a motion of the first piston results in a motion of a second piston (not shown in Fig. 2) provided inside the slave cylinder. For this purpose, a fluid level sensor 220 is provided to periodically check a predetermined level of the hydraulic fluid in the cylinders and the conduits.

The transfer of motion from the first piston in the master cylinder 200 to the second piston in the slave cylinder is possible due to the movement of the hydraulic fluid from the master cylinder 200 to the slave cylinder through the pair of conduits. The pressure applied on the first piston is transmitted unchanged to the second piston. Since the force exerted is equal to a product of pressure and area of the piston, a small force exerted on the first piston is capable of providing a large force at the second piston (with a relatively larger area than the first piston). Such a force multiplication in the hydraulic assembly helps in disengaging a clutch assembly from an engine. Figs. 2b and Fig. 2c illustrate isometric views of the exemplary arrangement of the master cylinder 200 and the arm lever 106. In one implementation, the arm lever 106 is operably connected to the master cylinder 200. The arm lever 106 actuates the first piston disposed in the master cylinder 200. The first piston, in turn, actuates the second piston disposed in the slave cylinder as discussed in the explanation of Fig 2a.

In one embodiment, the engine housing 204 has the bracket 206 mounted on it. Further, the master cylinder 200 is mounted on the bracket 206 and the arm lever 106 is mounted in a housing of the master cylinder 200. The bracket 206 can be a sheet metal bracket and is also capable of receiving the clutch cable 108 through the cable guide 222.

As discussed above, the clutch cable 108 is connected to the clutch lever 110 on one end and the arm lever 106 at the other end. This other end is shown as an effort end 224 of the arm lever 106 in the figure 2c. The first piston of the master cylinder is operably connected to a load end 226 of the arm lever 106. The arm lever 106 is pivoted about a fulcrum pin 228 provided as fulcrum between the effort end 224 and the load end 226 of the arm lever 106. Further, the second fastener 216 connects the first end 230 of the first conduit 202 to the output of the master cylinder 200 while the third fastener 218 connects the second end 232 of, the first conduit 202 to the second conduit (within the engine housing 204).

In operation, when the rider of the motorcycle retracts the clutch lever in order to disengage a clutch assembly from an engine, the clutch cable 108 gets pulled towards the clutch lever 110. The clutch cable 108, which is connected to the arm lever 106, actuates the arm lever 106. To actuate the first piston of the master cylinder 200, force is applied at the effort end 224 of the arm lever 106. Since the effort end 224, in comparison to the load end 226, is placed farther from the fulcrum pin 228, a mechanical advantage is obtained. With this a multiplied force is obtained at the load end 226 of the arm lever 106. This multiplied force, due to the arm lever 106, is capable of actuating the first piston of the master cylinder 200. The mechanical advantage (MA) of a lever can be represented as:

M _A = £L ₌ °L ₍₁₎

F ₁ D, thus, ^ ₂ = — ...(2)

where Fi is the force applied at the effort end;

F ₂ is the force obtained at the load end;

D) is the distance from the effort end to the fulcrum pin; and

D ₂ is the distance from the load end to the fulcrum pin.

Therefore, when Di is greater than D ₂ , the force F ₂ obtained at the load end is greater than the applied force Fi and hence, a force multiplication is achieved.

Fig. 3 illustrates a first sectional view of the engine housing 204 as viewed from a rear side of the motorcycle 100, when seen through the path of the hydraulic fluid from the master cylinder 200 to the slave cylinder. Fig. 3 shows the clutch assembly 300 and the slave cylinder 302 of the hydraulic assembly connected to each other, according to an embodiment of the present subject matter. In said embodiment, the clutch assembly 300 is a multi-plate clutch assembly. The clutch assembly 300 includes a plurality of inside plates 304-1 and outside plates 304-2, which can be collectively referred to as clutch plates 304, and a pair of springs 306 and 308. The pair of springs 306 and 308 is provided to keep the clutch plates 304 of the clutch assembly 300 in an engaged state with a flywheel of an engine(not shown in the figure). In one embodiment, the springs 306 and 308 are compression springs and are attached to the outside plates 304-2.

As shown in Fig. 3, the slave cylinder 302 is housed within the engine housing 204 and includes a second piston 310, wherein the second piston 310 is capable of reciprocating inside the slave cylinder 302. The slave cylinder 302 is hydraulically connected to the master cylinder 200 through the first conduit 202 and a second conduit 312. Due to this, when the first piston within the master cylinder 200 is displaced by the arm lever 106, the hydraulic fluid between the master cylinder 200 and the slave cylinder 302 transfers pressure to the second piston 310, thereby transferring motion as well.

Fig. 4 illustrates a second sectional view of the engine housing 204 as viewed from the rear side of the motorcycle 100, when seen through the centre of the second piston 310. As explained in the illustration of Fig. 3, the second piston 310 is connected to a second conduit 312. On actuation of the master cylinder 200, the displacement of hydraulic fluid between the master cylinder 200 and the slave cylinder 302 leads to an axial motion of the second piston 310. Fig. 4 further depicts a clutch actuating member 400 for transferring the axial motion from the second piston 310 to the clutch assembly 300. In one embodiment, the clutch actuating member 400 is a pin. One end of the clutch actuating member 400 is disposed in the clutch assembly 300 and the other end is guided in the second piston 310 disposed within the slave cylinder 302. The clutch actuating member 400 is further supported by a clutch bearing 402. The clutch bearing 402 is seated inside the clutch assembly 300 and facilitates transfer of axial motion from the second piston 310 to the clutch assembly 300 in a frictionless manner.

The second piston 310 transfers the axial motion to the clutch actuating member 400 through a spherical ball 404. A pair of O-rings 406 is provided on the periphery of the second piston 310 to prevent any leakage of the hydraulic fluid from the other side of the second piston 310 inside the slave cylinder 302.

Based on all the illustrations including Fig. 4, the overall working of the clutch actuation assembly 102 of the motorcycle 100 can be understood as follows. While riding a two-wheeler, a rider presses the clutch lever 104 to disengage the clutch assembly 300, which is normally in an engaged condition, from an engine for example, to change gears, to start or to stop the motorcycle. When the clutch lever 110 is pressed, the clutch cable 108 gets pulled towards the clutch lever 110 and in turn pulls the arm lever 106, thereby transferring the motion of the clutch lever to the arm lever 106. The arm lever 106 then moves the first piston of the master cylinder 200. This results in an increase in the hydraulic pressure inside the master cylinder 200, due to which the fluid inside the first conduit 202 and the second conduit 312 is pushed.

The pressurized fluid further pushes the second piston 310 inside the slave cylinder 302 towards the clutch actuating member 400..The second piston 310 moves axially and contacts the clutch actuating member 400 through the spherical ball 404, thus pushing the clutch actuating member 400 in a forward direction. The forward movement of the clutch actuating member 400 compresses the pair of springs 306 and 308. The compressed springs 306 and 308 pushes the outside plates 304-2 away from the inside plates 304-1, thus separating the clutch plates 304 of the clutch assembly 300 and disengaging the clutch assembly 300. At this point of time, the rider can change the gears and increase or decrease the speed of the motorcycle 100.

As can be understood, by using the hydraulic assembly described above, unidirectional transfer of force can be achieved from the slave cylinder to the pin clutch release. However, it will be understood that the design of the hydraulic system can be suitably altered to use a pull type clutch assembly as well.

The rider can then release the clutch lever 110 to let the motorcycle operate in normal condition. As the clutch lever 110 is now released, the tension in the clutch cable 108 gets released and the clutch cable 108 returns to its normal condition, i.e., a, no tension state. Due to the release of tension in the clutch cable 108, the arm lever 106 too comes back to its original position, thus causing the first piston to also return to its normal position. Also, the hydraulic pressure inside the master cylinder 200 gets released and the fluid starts flowing towards the master cylinder 200.

This reverse flow of the fluid releases the pressure on the second piston 310 in the slave cylinder 302, and therefore the pressure on the clutch bearing 402, the clutch actuating member 400, and the pair of springs 306 and 308, which were at a compressed stage, is also released. As a result, the compressed springs 306 and 308 return to their normal relaxed condition, thereby moving the clutch actuating member 400 and the clutch bearing 402 towards the second piston 310 and pushing the second piston 310 back to its original position. This causes the clutch plates 304, and therefore the clutch assembly 300, to come back to their normal engaged state.

The previously described versions of the subject matter and its equivalent thereof have many advantages, including those which are described below. The combined use of the cable assembly 104 and the hydraulic assembly ensures reduction in the force acting on the clutch cable 108. Further, due to three leverages, i.e., the clutch lever 110, the arm lever 106, and the hydraulic assembly, the force required to operate the clutch assembly 300 is very low as the mechanical advantage is multiplied with the hydraulic advantage. Additionally, as the force on the clutch cable 108 is low, it does not degrade as fast as clutch cables in conventional cable clutch actuation assemblies do, and minimum maintenance is required for the clutch cable 108.

Further, the clutch actuation assembly 102 provides immediate response, unchanged clutch lever feel, and eliminates the need to adjust the manual force required for actuating the clutch lever. In comparison to typical hydraulic clutch actuation assemblies, the response time is less as the usage of hose is minimized or even eliminated. For vehicles having high torque output, the clutch actuation assembly 102 provides high clutch spring force and correspondingly high clutch disengagement force due to its high lever ratio. Also, manually imparted force to the clutch lever 110 in a disengaged position is low, which reduces fatigue experienced by the rider.

Moreover, the clutch actuation assembly 102 of the present subject matter is compact, efficient, and economical. Further, the clutch actuation assembly 102 as described herein can be retrofitted on current two wheelers, thereby providing benefits of the integrated clutch actuation to conventional two wheelers as well.

While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter.