Clutch actuation system in motorcycles

Field of the invention

The present invention relates to "Clutch actuation system in motorcycles" and more particularly to the clutch actuation system using a lead screw.

Description of the prior art

A typical automated manual transmission (AMT) for a motorcycle involves separate systems for clutch actuation and gearshift in addition to a conventional wet multi-plate clutch and a constant mesh gearbox. The conventional clutch actuation (Figure 3) generally involves an electric motor (A), gearbox (B), hydraulic master cylinder (C), fluid container (D), hose (E) and hydraulic slave cylinder (F) acting on the clutch.

Similarly, the conventional gearshift system (Figure 4) involves electric motor (1), gear-box (2), linkage (3) acting on the internal gearshift mechanism. Both the electric motors (A) & (1) are controlled by a controller.

The electric motor (A) in clutch actuation system is responsible for clutch disengagement or engagement. The torque from the motor (A) is amplified in gearbox (B) and hydraulic circuit and transferred to clutch release bearing through hydraulic circuit.

The electric motor (1) in the gearshift system is responsible for up or down gearshift and electric motor's torque is amplified by another gearbox (2) and mechanical leverage, in linkage (3) and transferred to internal gearshift mechanism (4).

When the rider of the motorcycle gives trigger for gearshift, the said controller provides signal to the electric motor (A). The initial torque provided by this motor (A) is converted into displacement of the master cylinder's (C) piston through gearbox (B) and a crank mechanism. The force at the master cylinder (C) is amplified in the slave cylinder (F), which disengages the clutch by applying force on clutch release bearing. After sensing clutch disengagement through a sensor, controller provides signal to the electric motor (1). This in turn rotates linkage (3) through gearbox (2). Linkage (3) rotates internal gearshift mechanism (4), which shifts gear by rotating the gearshift cam drum (5) either up or down as per original trigger provided by the driver. Once the gearshift process is over, the electric motor (A) is signalled to rotate in reverse direction to engage the clutch. As this is done, force on the master cylinder (C) holding clutch in disengaged state is removed and the clutch springs displace master cylinder's (C) piston to original position through slave cylinder (F). Hence, the gearshift process is completed.

Presently, the clutch actuation is done using a hydraulic actuator that works on the hydraulic leverage principle. It involves an electromechanical actuator (electric motor + gearbox), mechanical linkage, hydraulic circuit consisting of primary cylinder, hoses, slave cylinder and fluid, and clutch apparatus. However the magnitude of multiplication is dependent on the cylinder size and hence is limited on the motor ratings and reducing gearbox settings. Another major drawback of the system is complex arrangement of the above said hydraulic actuator organization and thus leading to leakages, vibration, wear and tear and maintenance. As a result, a need arises to address the above problems in light of better handling, performance and maintenance of the motor vehicle.

Another objective of the present invention is to make the system a comprehensive sturdy one and having minimise the total part count and weight of the system.

Brief description of the invention

In the present invention the output shaft of the clutch actuating electric motor has a worm (helical screw) arrangement, which is in mesh with a worm wheel nut. This worm wheel nut has got internal square threads, which sit on external square thread cuts on the clutch disengaging power screw to move forward and apply force on clutch release bearing, thus disengaging the clutch and holding in the disengaged state. After completion of the gear shift process, reversing the current reverses the motor rotation and hence the clutch disengaging power screw moves back engaging the clutch again.

Brief description of the drawings

Figure 1 illustrates side view of a motorcycle

Figure 2 illustrates sectional view of a four-stroke internal combustion engine according to prior art

Figure 3 illustrates an existing clutch actuation system

Figure 4 illustrates an existing gear actuation system

Figure 5 illustrates the clutch actuation system according to the present
invention.

Detailed description of the invention

In general, a motorcycle has a body that is considerably small compared to a common passenger car or other such vehicle, and the space required for assembling necessary parts and devices is limited. In order to cope with the limitation upon available space, it is necessary to make the apparatus to be accommodated in such a space more compact. Further, this requirement may be applied not only to motorcycles, but also to common vehicles and other machines and apparatuses wherein a compact arrangement of a number of parts and devices is necessary to avoid excessive space consumption. A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 1,2,3 4 and 5. Figure 1 illustrates a typical motorcycle comprising a frame 101, front fork 102 attached to a pivot tube 103 of the vehicle frame 101, a front wheel 104 attached to these front forks 102, a handle bar 105 connected to the front forks 102, a fuel tank (not shown in the figure) attached so as to straddle an upper part of the vehicle frame 101, a seat 107 attached to the upper rear portion of the vehicle frame 101, an engine unit 108 attached to the lower front section of the vehicle frame 101, a swing arm 109 attached to a lower rear section of the vehicle frame 101, suspended by a rear shock absorber 110 from the vehicle frame 101 and a rear wheel 111 attached to a rear end of swing arm 109. The intake system of the engine (not shown in the figure) comprises of a carburettor, intake duct and an air cleaner. The exhaust system of the engine 106 comprises of exhaust pipe and a muffler The motorcycle is also provided with a side cover for covering a side section of the vehicle frame 101, a front fender 113 for covering an upper part of the front wheel 104, and a rear fender 114 for covering an upper part of the rear wheel 111.

Figure 2 illustrates a single-cylinder four-stroke internal combustion engine that is started by a starter motor, with its crankshaft extending in the lateral axis motorcycle. The engine is divided into right and left parts with respect to the longitudinal centre plane of the vehicle, and a multi-stage gear transmission and a multi-disk friction clutch that are integrally assembled in the crank case.

An engine starter includes a starting motor 215, and a gear train that transmits torque from the motor 215 to a crankshaft assembly 208 of the engine mounted on left 210 and right main 206 bearings.

The starter motor includes an electric motor 215, an output shaft, a pinion gear mounted on the output shaft, and an idler gear that is constantly meshed with a pinion gear, further, a starter gear 214 having gear teeth engaged with those of said idler gear and a one way clutch 238 mounted in continuous engagement with the starter gear 214 to engage and disengage the transmission of torque with the crank shaft 246.

The starter gear 214 is mounted on crankshaft, away from the crankshaft main bearing, which is fitted on the crankcase 244 provided with a boss to house the bearing. An axial clearance for starter gear 214 is maintained between magneto rotor 234 and the boss of the main bearing housing of the crankcase 244. A plurality of pillars is provided on crankcase 244 projecting beyond the bearing housing boss to arrest the movement of starter gear 214 and control the float. Occasional rubbing of starter gear due to float, the pillars 212 on crankcase 244 wear out over a period. This wear out of the pillars 212 on crankcase creates a space causing excessive float of starter gear 214 in axial direction. Further, this movement of starter gear 214 in axial direction results in increased vibration and noise associated with starting mechanism of engine.

In the aforementioned small motorcycles or similar vehicles, it is necessary to provide a construction that permits ready driving operation even by one who is not skilled in driving techniques, in addition to minimizing the number of parts so as to simplify construction. Because a construction in which a gear ratio change is effected by a pedalling operation requires much skill for expert handling, it is desirable to employ a semi automatic transmission in which the gear ratio of an output shaft for rotating the drive wheel is automatically changed as per the instruction of the user. This semi-automatic transmission usually has an assembly including a number of parts such as clutch means, and with an increase of the number of component parts, the space for assembling the parts is correspondingly increased, leading to a size increase for the entire system.

In the present invention (Figure 5), the output shaft (7) of the clutch actuating electric motor (6) has a worm (helical screw) arrangement, which is in mesh with a worm wheel nut (8). This worm wheel nut (8) has got internal square threads, which sit on external square thread (9) cuts on the clutch disengaging power screw (10) to move forward and apply force on clutch release bearing, thus disengaging the clutch and holding it in the disengaged state. After the completion of the gearshift process, reversing the current reverses the motor rotation and hence the clutch disengaging power screw (10) moves backward engaging the clutch again. This system can directly be assembled in the crankcase. Hence, robustness of the system is considerably increased.

As a result of this configuration, maintenance, wear & tear, oil leakage, etc are avoided. Moreover, vibrations as well as weight and part are reduced to a great extent due to firm and robust design as prescribed by the present invention.

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: We Claim:

1. A clutch actuation system for a four-stroke internal combustion engine comprising a clutch actuating electric motor (6), the output shaft (7) of which has a helical screw arrangement meshed with a worm wheel nut (8) having internal square threads, that lock with the external square threads (9) cuts on a clutch disengaging power screw (10).

2. A clutch actuation system as claimed in claim 1, wherein when the said clutch actuating electric motor (6) rotates, the said worm wheel nut (8) which sits on said clutch disengaging power screw (10) moves forwards and apply force on clutch release bearing disengaging the clutch.

3. A clutch actuation system as claimed in claim 1, wherein when the said clutch actuating electric motor (6) rotates in reverse direction, the said worm wheel nut (8) which sits on said clutch disengaging power screw (10) moves backwards and engages the clutch.

4. A motorcycle having a clutch actuation system for a four-stroke internal combustion engine comprising a clutch actuating electric motor (6), the output shaft (7) of which has a helical screw arrangement meshed with a worm wheel nut (8) having internal square threads, that lock with the external square threads (9) cuts on a clutch disengaging power screw (10).