Torque multiplier system in motorcycles

Field of invention

The present invention relates to a "Torque multiplier system in motorcycles" and more particularly to an automatic transmission in which a worm and worm wheel gear mechanism is mounted on a drive shaft.

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 (G), gear-box (H), linkage (I) acting on the internal gearshift mechanism. Both the electric motors (A) & (G) 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 (G) in the gearshift system is responsible for up or down gearshift and electric motor's torque is amplified by another gearbox (H) and mechanical leverage, in linkage (I) and transferred to internal gearshift mechanism (J).

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 (G). This in turn rotates linkage (I) through gearbox (H). Linkage (I) rotates internal gearshift mechanism (J), which shifts gear by rotating the gearshift cam drum (K) 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). The gearbox (H) consists of predominantly spur gear train arranged in a housing over bearing supports. Also, there is an additional mechanical linkage connecting auxiliary gearbox to a gearshift pawl.

However, in the above system housing and bearing supports are more complicated, because the external gear nests within the internal gear. Moreover, fabrication is limited to the shaper generating process, and usually special tooling is required. Use of these spur gears doesn't provide a silent and vibration less operation. Another major drawback with the above system is requirement of large number of spur gears, thus increasing the part count. Moreover, the above said large number of gears and mechanical linkages have the angular displacement to a tune of 30-40 degrees while gear shifting.

This necessitates the present invention in light of above said lacunas. As a result, a need arises to address the above problems in light of better handling and maintenance of the motor vehicle.

Another objective of the present invention is to reduce the overall cost of the system by employing new gear train system.

Another objective of the present invention is to provide alternative and a much more simpler arrangement of the gear train for the system.

Brief description of the invention

The present invention relates to a system for automatically effecting speed change in power transmission from an internal combustion engine or the like by utilising the gear ratio change action of a worm and worm wheel gear arrangement for actuating the cam mechanism through mechanical linkages connecting auxiliary gearbox to the gearshift pawl.

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 actuating system

Figure 4 illustrates an existing torque actuator system

Figure 5a illustrates front view of a typical spur gear train

Figure 5b illustrates top view of a typical spur gear train arrangement

Figure 6a illustrates front view of worm and worm wheel arrangement according to the present invention

Figure 6b illustrates top view of worm and worm wheel arrangement 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 1,2,4a, 4b, 5a and 5b. 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. Usually spur gear arrangement (Figure 5a and 5b) is used in transmission system.

The output shaft (1) of gearshift electric motor (G) has a spur gear, which is in mesh with another gear (2). Gears (2), (3), (4), (5) and (6) form a spur gear train. The output from gearbox is taken from shaft (7).

The present invention (Figure 6a, 6b) relates to a system for automatically effecting speed change in power transmission from an internal combustion engine or the like by utilising the gear ratio change action of a worm and worm wheel gear arrangement (12) for actuating the cam mechanism through mechanical linkages connecting auxiliary gearbox to the gearshift pawl.

In the present invention (Figure 6a and 6b), the output shaft (9) from the electric motor (8) has a worm cut on to it, which in turn is in mesh with a worm wheel (10). The output from gearbox is taken from shaft (11) and actuates the gearshift cam drum (K).

When the rider of the motorcycle gives the trigger for gearshift, controller would provide signal to the electric motor (A). Electric motor is connected to the clutch release through a gear arrangement (B) wherein the torque produced by the electric motor (A) is effectively transferred to the gear box (B) which in turn build it around the hydraulic circuit (C &D) and finally to the clutch release (through E). Thereafter, once the controller senses clutch actuation, it directs the gear shift motor (8) to transfer the effective torque through worm gear arrangement (12) to shaft (11) to actuate the gearshift cam drum (K).

The above arrangement reduces the necessity of separate mechanical linkages. Apart from this, due to its compact nature, worm and worm wheel can be placed inside the engine (or gear box) crankcase. Use of the above arrangement has not only helped in saving cost of the system, but also has reduced the part numbers as well as the weight.

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 transmission system for two-wheelers characterised by a clutch actuation system and a gear actuation system, wherein the said gear actuation system comprises of an electric motor (8) having an output shaft (9) with a worm gear arrangement (12).

2. The transmission system as claimed in claim 1, wherein the said output shaft (9) is provided with a worm cut that meshes with a worm wheel (10) having an output shaft (11).

3. The transmission system as claimed in claim 1, wherein when the controller senses clutch actuation, it directs the said motor (8) to transfer the effective torque through the said worm gear arrangement (12) to the said shaft (11) to actuate a gearshift cam drum (K).

4. A motorcycle having a transmission system as claimed in claim 1.