DESC:FIELD OF INVENTION
[0001] The present invention relates to an internal combustion engine and more particularly to transmission system of said engine.
BACKGROUND OF INVENTION
[0002] An internal combustion engines comprises of output shaft, which is connected to driven wheel through a transmission chain. The sprocket assembly is an important force-transmitting member, which bears extreme load changes resulting into unpleasant gear clash noise during gear shifting operation in sequential manual transmission gearboxes. These unpleasant gear noises are caused due to hitting of the sprocket hub with the drive sprocket also called as sleeve. Moreover, the hitting of the sprocket hub with the drive sprocket also results in uneven wearing off of the drive sprocket sleeve and the sprocket hub. This may result in a disturbed force transmission from the driven shaft to the rear wheel. Hence, there is a requirement to reduce the clashing of the drive sprocket sleeve and the sprocket hub.
[0003] In such a sequential manual transmission gearbox, the gears are typically engaged by sliding them on their shafts. For shifting gears, careful timing and throttle manipulation is required. This results in spinning the gears at roughly the same speed when engaged. These transmissions are also called sliding mesh transmissions, because of the difficulty in changing gears and the unpleasant gear clash noise that often is accompanied during gear shifting.
SUMMARY OF THE INVENTION
[0004] While retaining the existing sequential shift arrangement that is non-synchronized, the current invention discloses an additional incorporation of damper, which substantially reduces the unpleasant gear clash noise during gear shifting operation in a sequential manual transmission gearbox.
[0005] Synchronized transmissions can be used to obviate the above problem of gear clashing noises. Automobile and light truck transmissions are now almost universally synchronized. Manual transmissions gearboxes are usually of non-synchronized transmission type only. They are used because of simplicity of the mechanism, improved reliability due to the fewer parts and reduced cost. To obviate the problems associated with the existing drive sprocket sleeve and the sprocket hub design with noise, the current invention discloses incorporation of a dampening element in-between said drive sprocket sleeve and the sprocket hub.
BRIEF DESCRIPTION OF DRAWINGS
[0006] Figure 1illustrates a typical two-wheeler.
[0007] Figure 2 illustrates a typical engine and surrounding parts of a two-wheeler with the driving sprocket.
[0008] Figure 3 illustrates a typical engine and surrounding parts of a two-wheeler with the driving sprocket without a retainer plate.
[0009] Figure 4 illustrates the sprocket assembly.
[00010] Figure 5 illustrates a sectional view of the sprocket assembly.
[00011] Figure 6 illustrates projection of the drive sprocket along an axis AA.
[00012] Figure 7 illustrates projection of the retainer along an axis FF & SS.
DETAILED DESCRIPTION OF THE INVENTION
[00013] In order that those skilled in the art can understand the present invention, the invention is further described below in detail so that various features of the invention thereof proposed here are discernible from the description thereof set out hereunder. However, these descriptions and the appended drawings are only used for those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention.
[00014] First, the engine described here is a four-cycle, geared internal combustion engine. The engine is a multi-valve engine. In a preferred embodiment, said engine is mounted on a two-wheeled vehicle. However, the concepts described herein can also be used in the engine mounted on a three wheeled or a four-wheeled geared vehicle.
[00015] The following description describes the current invention. Typically in a geared transmission for an internal combustion engine, output from the gear box is taken from the drive sprocket mounted on the drive shaft. In the current invention, said drive sprocket is split into a two-part construction. The inner part is mounted on the drive shaft. This inner part has a provision to accommodate spring dampers which also guides the outer part. The inner profile of the outer part of said drive sprocket constructed such that to take the drive via the spring dampers and also guided on the inner part. The outer profile contains the sprocket profile which has been cut as per the number of teethes required for a rated output to the rear wheel. This damper mechanism also includes one retainer front plate which locates said inner part and also connects the rear retainer plate. The power output transmission is from the inner part of said sprocket mounted on the drive shaft and is transmitted to the outer part of said sprocket through the spring dampers. This arrangement enables to carry out additional dampening action to absorb the rotational shocks due to torque fluctuations. This additional dampening arrangement substantially helps in reducing the unpleasant gear clash noise during gear shifting.
[00016] Figure 1 shows a typical two-wheeled vehicle 10 with a fuel tank 1, rider seat 2, rear wheel 3, center stand 4, engine 5, front wheel 6, front fork 7 and head lamp 8. The transmission chain which connects the engine transmission to the rear wheel is not visible in the current view though present on the other side of the vehicle.
[00017] Figure 2 shows engine 5, cylinder block 21, cylinder head 22, magneto cover 23, carburetor 24 and sprocket 25. Sprocket 25 is further connected to the rear wheel 3 again through yet another sprocket. Figure 2 shows the internal combustion engine 5 with the sprocket 25 with a retaining cover (Figure 7) as per the current invention. The internal construction of the proposed sprocket 25 has been dealt in with more detail in Figure 5.
[00018] Figure 3 shows engine 5, cylinder block 21, cylinder head 22, magneto cover 23, carburetor 24 and sprocket 25. Figure 3 shows the internal combustion engine 5 with the sprocket 25 without a retaining cover (Figure 7) as per the current invention. Figure 3 shows the internal construction of spring members of the sprocket 25 which is explained further in Figure 4.
[00019] Figure 4 shows sprocket 25, spring dampener 41, spring dampener 42, spring dampener 43, spring dampener 44, sprocket hub 45,drive sprocket (sleeve) 46, retainer fastener 47, retainer fastener 48 and drive shaft 49. The drive sprocket 46 and sprocket hub 45 are provided with a plurality of male-female cut out portions on their inner radius and outer periphery respectively to accommodate the plurality of spring dampener 41, 42, 43, and 44 respectively. The plurality of female cut outs (61, 62) are provided in said sprocket hub 45 and said drive sprocket 46 to accommodate plurality of force transmitting spring dampeners (41, 42, 43 44). The cut out portions (61, 62) (Figure 4) are designed to hold the dampener spring (41, 42, 43, and 44) in such a way that, the force is transmitted from the driving shaft 49 to the sprocket hub 45, sprocket hub 45 transmits the force to spring dampener (41, 42, 43, and 44) and spring dampener (41, 42, 43, and 44) transmit force to said drive sprocket (sleeve) 46.
[00020] The main objective of the current invention is to inhibit the direct force transmission from driving shaft towards the drive sprocket 46 and from the drive sprocket 46 to the driving shaft. Hence, to achieve the dampening of force transmission in-between said drive sprocket 46 and sprocket hub 45, a plurality of spring dampener 41, 42, 43, and 44 are evenly placed in-between said drive sprocket 46 and sprocket hub 45. The springs dampeners 41, 42, 43, and 44, after being placed in the slots formed in the cut out (61, 62) are covered by a retainer plate 71. The retainer plate 71 is fastened to the sprocket hub 45 by using plurality of fasteners 48.
[00021] Figure 5 shows cross section of the sprocket assembly. Figure 5 further shows one of the plurality of spring dampeners 42, sprocket hub 45, drive sprocket (sleeve) 46, retainer fastener 48, spring locating pin 51 and drive sprocket teeth 52. The driving shaft is located at the location 49, which drives the sprocket hub 45. The sprocket hub 45 transmits the force to plurality of springs 41,42,43,44. The plurality of dampening springs 41,42,43,44 transmit the force to the drive sprocket 46. The drive sprocket 46 is further coupled to rear wheel sprocket on the rear wheel by help of a transmission chain.
[00022] Figure 6 shows drive sprocket (sleeve) 46 cut section view along the axis AA. Figure 7 shows front retainer 71 with cut section along FF & SS axis. A plurality of female cutouts 61 are made into said drive sprocket and a plurality of male cutouts 62 are made into said sprocket hub to accommodate plurality of spring dampeners in said male female cutouts (61, 62) between said drive sprocket and sprocket hub. The pluralities of spring dampeners (41, 42, 43, and 44) function as a force transmission member from said sprocket hub 45 to said drive sprocket.
,CLAIMS:We claim:
1. A transmission system for an internal combustion engine (5) comprising:
a crankshaft being powered from combustion of fuel inside a cylinder of said internal combustion engine (5);
a gear box connected to the crankshaft which performs various gear changing steps and drives a final driving shaft (49);
a sprocket assembly (25) comprising of a sprocket hub (45) rigidly coupled to said final driving shaft (49) and a drive sprocket (46) coupled to a rear wheel sprocket through a transmission chain;
wherein a plurality of female cut outs (61, 62) are provided in said sprocket hub (45) and said drive sprocket (46) to accommodate plurality of force transmitting spring dampeners (41, 42, 43 44).

2. The transmission system for an internal combustion engine as claimed in claim 1 wherein the female cutout (62) on drive sprocket (46) and female cut out (61) on the sprocket hub (45) face each other to accommodate plurality of spring dampeners (41, 42, 43 44).

3. The transmission system for an internal combustion engine as claimed in claim 1 wherein the force transmission takes place from said sprocket hub (45) to said drive sprocket (46) through said plurality of spring dampeners (41, 42, 43 44).