Drive system for an internal combustion engine

Field of the invention

The present invention relates to "Drive system for an internal combustion engine" and more particularly to torque control mechanism for a single speed transmission system of an internal combustion engine.

Description of the prior art

Normally for a single speed transmission system includes an engine, a centrifugal clutch, a gearbox and a wheel. The transmission system is provided on the left side of the engine. A clutch arrangement is mounted on the crankshaft, which consists of shoes, which are pivoted on a plate, which rotates positively along with the crankshaft. A housing connected to the drive gear is freely mounted on the crankshaft. As the plate is rotated by the crankshaft at a speed more than a pre-determined value, due to centrifugal action, the shoes fly off and catch the housing inner surface and in turn rotate the housing and the gear along the crankshaft axis. The gear in turn drives a driven gear, which is mounted on a shaft in an axis parallel to the crankshaft axis. This shaft is mounted on crankcase L and cover clutch using bearings. On the outer side of the shaft, a drive sprocket is attached using splines. A chain drive is connected between the drive sprocket and driven sprocket.

The driven sprocket is attached on a shaft and which in turn is mounted on the extended portion of the crankcase L and a cover using bearings. On the right side of the shaft, the rear wheel is attached using splines and a central nut.

Normally in this type of arrangement higher torque generation is not possible in case more power is required. For example, driving in up-gradient scenario necessitates more torque, the scope of which is limited in single speed transmission system. When the clutch shoes engages with the housing there is small dip in RPM of the engine during which there will be an instantaneous loss of torque. This is perceived by the rider as a loss of power or loss of torque. Hence the objective of the invention is to overcome the above customer perceived momentary loss of torque by providing a torque multiplier system.

Second objective of the present invention is to provide a compact layout in the vehicle axial direction and better space utilisation in the engine layout. Brief description of the invention

Torque control mechanism for a single speed transmission system of an internal combustion engine comprises a crankshaft and a flywheel for storing energy. A first centrifugal clutch having a first centrifugal clutch hub is provided with pivotally mounted clutch shoes and a first centrifugal clutch housing. The first centrifugal clutch hub is coupled to the crankshaft and the first centrifugal clutch housing, having a flywheel attached to it, floats on the crankshaft along with a first sprocket. The second centrifugal clutch comprises a second centrifugal clutch hub provided with pivotally mounted clutch shoes and a second sprocket and second centrifugal clutch housing. The said second centrifugal clutch hub is connected to a first drive gear and the second clutch housing floats on a secondary shaft supported by bearing means on either side. The first drive gear, through an idler gear, drives the second drive gear. The idler gear is supported by bearings on both the sides. Both first drive and first driven gears have almost equal gear ratio.

Brief description of the drawings

Figure 1 illustrates side view of a motorcycle having single speed transmission.
Figure 2 illustrates a typical four stroke internal combustion engine.
Figure 3 illustrates transmission system according to the present invention.

Detailed description of the invention

A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 1, 2 and 3.

A motorcycle body frame 100 comprises a head pipe 101, at least a tube extending downwardly and then extends almost horizontally (not shown in the figure) and then at the posterior position extends upwards (not shown in the figure) and further backwardly and horizontally. The rear most part of the said tube is opened to the atmosphere. A front wheel 102 is carried through the intermediary of a front fork 103 that is rotatably mounted within the head pipe 101. A rear wheel 104 is carried on the rear end of a rear fork 105 that is swingably pivoted on the rearward lower position of the vehicle body frame 100. A seat 106 is disposed above the shock absorber 105. Forwardly of the seat, a fuel tank 107 is mounted over the mono pipe 101. Behind the fuel tank 107, a step through space 108 is provided between the fuel tank 107 and the seat 106. A four-stroke cycle engine 200 is mounted under a footboard 110 and behind the front wheel 102. The exhaust pipe 111 extends from the engine 109 to the rear portion of the vehicle.

The core part of a normal four stroke engine 200 is illustrated in figure 2. It is characterised by a cylinder 201 with the piston 202 moving up and down inside the cylinder 201. Some of the key engine parts along with their functions are spark plug (nor shown in the figure) which supplies the spark which ignites the air/fuel mixture so that combustion could occur; valves 203 wherein the intake and exhaust valves open at the proper time to let in air and fuel to let out exhaust; a piston 202 which is a cylindrical piece of metal that moves up and down inside the cylinder 201; piston rings 204 that provide a sliding seal between the outer edge of the piston 202 and the inner edge of the cylinder 201; connecting rod 205 which connects the piston 202 to the crankshaft 206; crankshaft 206 which turns the piston's up and down motion into circular motion; a sump 207 which surrounds the crankshaft 206 and contains oil which collects in the bottom of the sump 207; etc.

Torque control mechanism for a single speed transmission system 300 of an internal combustion engine 200 comprises a crankshaft 206 and a flywheel 306 for storing energy. A first centrifugal clutch 302 having a first centrifugal clutch hub 304 is provided with pivotally mounted clutch shoes and a first centrifugal clutch housing 305. The first centrifugal clutch hub 304 is coupled to the crankshaft 206 and the first centrifugal clutch housing 305, having a flywheel 306 attached to it, floats on the crankshaft 206 along with a first sprocket 313. The second centrifugal clutch 307 comprises a second centrifugal clutch hub 308 provided with pivotally mounted clutch shoes and a second sprocket 314 and second centrifugal clutch housing 309. The said second centrifugal clutch hub 308 is connected to a first drive gear 303 and the second clutch housing 309 floats on a secondary shaft supported by bearing means on either side. The first drive gear 303, through an idler gear 312, drives the second drive gear 311. The idler gear 312 is supported by bearings on both the sides.

When the crankshaft 206 rotates more than a certain RPM, the first centrifugal clutch hub 304 is engaged with the housing 305 present on the flywheel 306 and after that flywheel 306 rotates at the same RPM as that of crankshaft 206. The rotation of the said first centrifugal clutch 302 is more than the idle RPM (or RPM with no load condition) of the crankshaft 206 and this is to make sure such that the flywheel 306 doesn't act as a load to the crankshaft 206 when the engine 200 is started or cranked. The second centrifugal clutch hub 308 does not get engaged to the housing 309 until the crankshaft 206 rotates more than the prescribed second centrifugal clutch rotation. The flywheel 306 is coupled with second centrifugal clutch hub 308 by a chain drive 315 and it is subsequently connected to an idler gear 312 through a first drive gear 303. This idler gear 312 drives a second drive gear 311 which is connected to the final wheel shaft 310. The rotation of second centrifugal clutch 307 is higher than that of the first centrifugal clutch 302 and hence both the centrifugal clutch hubs are not engaged simultaneously. The flywheel 306 stores the energy when the engine 200 rotates higher than first centrifugal clutch 302 but lower than the second centrifugal clutch 307. As soon as the crankshaft 206 rotates more than minimum RPM that of second centrifugal clutch 307, then the second centrifugal clutch hub 308 is engaged with the housing 309 and to the gear and thus flywheel 306 discharges the stored energy subsequently to the rear wheel 104 through first drive gear 303, idler gear 312, second drive gear 31 land final wheel shaft 310. The torque control mechanism for a single speed transmission system controls initial or starting torque of the vehicle by discharging the stored energy in the flywheel for a predetermined duration and after the predetermined duration it works similar to the conventional system. Therefore the perceived momentary loss experienced by the user is avoided. Hence during the predetermined duration, the torque at the wheel of the vehicle is more than the conventional system

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 a single speed internal combustion engine comprising:

a. an engine having a crankshaft,

b. a first centrifugal clutch assembly having a hub rigidly fixed to the crankshaft along with a housing, a first sprocket and a flywheel floating on the crankshaft,

c. a second centrifugal clutch assembly having a hub and a housing and a second sprocket, the housing floating on a secondary co-axial shaft supported by bearing means and the said housing is coupled to a first drive gear,

d. a drive gear arrangement.

2. The transmission system as claimed in claim 1, wherein the said crankshaft is coupled to the said first centrifugal clutch hub and a first centrifugal clutch housing floats on it.

3. The transmission system as claimed in claim 1, wherein the said first centrifugal clutch housing is coupled to the said flywheel.

4. The transmission system as claimed in claim 1, wherein the said flywheel is coupled to the hub of said second centrifugal clutch assembly by a chain drive.

5. The transmission system as claimed in claim 1, wherein the said secondary clutch housing is connected to said drive gear arrangement.

6.The transmission system as claimed in claim 1, wherein the said drive gear arrangement comprises a first drive gear, idler gear, a second drive gear, and a final wheel shaft.

7. The transmission system as claimed in claim 1, wherein the first centrifugal clutch hub is engaged with the housing connected to said flywheel which in turn is connected to the said second centrifugal clutch hub through a chain drive and subsequently to said gear arrangement and as soon as the crankshaft rotates more than minimum RPM that of second centrifugal clutch, then the second centrifugal clutch housing is engaged with the second clutch hub connected to the said flywheel and to the drive gear of the system and thus flywheel discharges the stored energy to the drive gear through said idler gears and subsequent to the rear wheel.

8. A motorcycle characterised by a single speed transmission having a"single cylinder engine comprising

a. a crankshaft

b. a first centrifugal clutch

c. a second centrifugal clutch

d. a flywheel

e. a gear arrangement.