FIELD OF INVENTION
[0001] The present invention relates to a cooling system for a continuously
variable transmission (CVT) type engine and more particularly to an air inlet structure for a V-belt drive continuously variable transmission in a two-wheeled vehicle.
5 BACKGROUND OF INVENTION
[0002] In vehicles with V-belt Continuously Variable Transmission (CVT),
frictional heat is generated by frictional contact between the V-belt and the pulleys, namely the driving pulley and the.driven pulley. Due to generation of this frictional heat, temperature inside the transmission system increases which leads to expansion of the V-10 belt, which further leads to the desired gear change ratio not being obtained. Frictional heat also leads to deterioration of the V-belt. Therefore, effective cooling of a V-Belt CVT is necessary to obtain the desired gear ratio as well as to improve the durability of parts of the CVT especially the V-belt.
[0003] Cooling arrangement for CVT known in the art generally has its air inlet at
15 the side of the transmission case, towards the engine, near the cooling cowl of the engine. In such an arrangement, due to heat radiated from the engine, the cooling air entering the inlet of the CVT cooling arrangement gets heated, up leading to reduction in cooling efficiency. Further, in such an arrangement, dust and muddy water raised by the rear wheel can easily enter the air outlet.
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SUMMARY OF THE INVENTION
[0004] The objective of the present invention is aimed to obviate defects in the
prior art, and provide a CVT cooling arrangement that provides enhanced cooling efficiency of the CVT system and prevents entry of dust and muddy water into the air 5 outlet structure ("outlet" with respect to air filter & "inlet" with respect to the CVT cover variator), and this forms the main objective of the present invention. In the present invention, the air inlet of the CVT engine is secluded from the hot temperature and hot air coming from the cylinder head and cylinder block by hiding the CVT inlet in an enclosure.
10 [0005] The enclosure covers the CVT inlet but allows the fresh air to enter inside
the CVT. The enclosure that covers the CVT inlet is integrated with the air filter of the vehicle. According to the disclosed embodiment of the invention, the air filter is in vicinity of the cover variator and close to the CVT air inlet. Hence, a protrusion is made on the air filter outer body, which extends up to the CVT inlet and envelopes the same.
15 BRIEF DESCRIPTION OF DRAWINGS
Figure 1 illustrates a typical two-wheeler.
Figure 2 illustrates airflow inside a typical two-wheeler.
Figure 3 illustrates the sectional view of air inlet in a typical CVT type engine.
Figure 4 illustrates the proposed envelope for the CVT inlet.

DETAILED DESCRIPTION OF THE INVENTION
[0006] A V- belt drive continuously variable transmission (CVT) is structured
such that a V belt is put on a drive pulley mounted to the crankshaft and a driven pulley arranged at the rear end of the transmission case. The drive pulley includes a cylindrical 5 drive shaft member spline connected to the crankshaft to be rotated therewith. The driven pulley includes a cylindrical driven shaft member rotatable mounted to a rotating shaft rotatable supported by the transmission case. The drive pulley is provided with a fixed pulley half fixed to the crankshaft and a movable pulley half that can approach the fixed pulley half and can be separated from the fixed pulley half. Power for driving the 10 movable pulley half axially to vary the width of a belt groove formed between the fixed pulleys half and the movable pulley half for winding the V belt, is transmitted to the movable pulley half from an electric motor attached to the transmission case.
[0007] The driven pulley is provided with an inner cylinder coaxially encircling
the output shaft so that the output shaft can be relatively rotated on an outer cylinder with
15 which the inner cylinder is slid ably engaged so that relative turning around the axis and axial relative movement is possible. The driven pulley is also provided with a fixed pulley half fixed to the inner cylinder, a movable pulley half fixed to the outer cylinder opposite to the fixed pulley half. The V belt is wound onto a belt groove formed between the fixed pulley half and a movable pulley half of both the pulleys. The distance between
20 the centers of the pulleys to where the belt makes contact in the groove is known as the pitch radius.

[0008] When the pulleys are far apart, the belt rides lower and the pitch radius
decreases. When the pulleys are close together, the belt rides higher and the pitch radius increases. The ratio of the pitch radius on the driving pulley to the pitch radius on the driven pulley determines the gear. When one pulley increases its radius, the other 5 decreases its radius to keep the belt tight. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios, from low to high and everything in between; For example, when the pitch radius is small on the driving pulley and large on the driven pulley, the rotational speed of the driven pulley decreases, resulting in a lower gear. When the pitch radius is large on the driving pulley and small 10 on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher gear.
[0009] Since here in CVT type engine, such gear changing takes place with
constant movement of a belt on pulleys which are rotating in themselves, due to friction between the pulleys and the belt a large amount of heat is generated. Since lubricating the 15 CVT belt and pulleys cannot be an option as the belts would start slipping on the said pulleys and the effective gear ration wouldn't be achieved, the CVT engines are provided with air cooling from inside.
[00010] Figure 1 shows a typical two wheeler 1 with a CVT type engine. Figure 1
shows a rear wheel 2, CVT engine 3, an air filter 4, a front wheel 5, a floor board 6, an 20 utility box 7, a headlamp 8, a side cover 9, front shock absorber 10, rear shock absorber 11, pillion hand grab rail 12 and a tail lamp 13. The arrows on top shows the front and rear directions of the vehicle. The engine 3 is laid in the direction from front to rear with

the internal combustion engine's cylinder head and cylinder block in front portion and the transmission with the CVT belt on the rear with respect to the said cylinder head and cylinder block.
[00011] Figure 2 illustrates the cooling mechanism of a CVT engine with the air
5 flow depicting the air inlet point, air flow path and the air exit. Fresh air enters the CVT engine from air inlet 21, travels to cool down the CVT belt and the pulleys and finally exits the CVT engine from the exit point 22. As shown in the Figure 2, in case when the air inlet 21 is open from top, there is more chances of mud, water, stones entering the CVT engine which may reduce the life of the air filter and the cooling efficiency of the 10 CVT engine.
[00012] Figure 3 illustrates the cut section of air inlet 21. The air inlet 21
comprises of an air filter 31, ribs 21 and space 33 between two ribs. The cross section of the air inlet 21 across the axis. AA' is also shown in Figure 2. The ribs functions to support the said filter and streamline the filtered air which gets filtered through the filter 15 31 and to force the filtered air across the CVT engine. At the same time, the ribs also provide stiffness to the air filter 3land the air inlet 21.
[00013] Figure 4 illustrates the CVT engine with air inlet according to the
disclosed invention. The air inlet 21 is covered with a protrusion 21', the protrusion 21' being integrated with the air filter. Figure 4 shows the air filter 4, air inlet 21, air inlet 20 cover 21', and cylinder head 41, cover variator 42, exhaust muffler 43. The cylinder head 41 and the exhaust muffler body 43 are heat radiating parts due to their higher temperature during engine ON condition.

[00014] The air inlet 21 is located in-between these two heat radiating parts, the air
surrounding the air inlet may get heated which is not recommended as hot air going inside the CVT engine may damage the CVT belt and effective cooling of the cover variator can't be achieved. Providing a cover 21' on the air inlet 21 not only shields the 5 air inlet from the heat radiating parts, it also obstructs any mud or water entry inside the air filter 31 through the air inlet. The clearance between the air inlet 21 and the air inlet cover 21' is optimized to allow airflow and avoid the mud entry and water entry on to the air filter 3, hence by using the air inlet cover 21', the life of the air filter 31 is enhanced and water entry inside the CVT engine is inhibited.
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We claim:
1. A cooling system for an internal combustion engine (3) of a two wheeler
comprising:
5 an internal combustion engine (3) with a cylinder portion (41) and a CVT
transmission portion covered by a cover variator (42);
. an air filter (4) to induct air from the outside atmosphere and force the air into the internal combustion engine (3); the air filter (4) being equipped with an air inlet covering structure on its exterior body;
10 a cover variator (42) which covers the CVT portion of the said internal
combustion engine (4)and has an air inlet port (21);
characterized in that:
the said air inlet covering structure (21') provided on the said air filter
(4) externally covers and overlaps with the said air inlet port (21) on the
15 said cover variator (42) with a predetermined gap to allow entry of
atmospheric air inside the said cover variator.(42).
2. The cooling system for an internal combustion engine (3) as claimed in Claim 1
wherein the air inlet cover structure (21') is integrated with the air filter body.
3. The cooling system for an internal combustion engine (3) as claimed in Claim 1
20 wherein the said air inlet cover structure (21') envelopes the air inlet port (21) on
cover variator (42) from the top.