TECHNICAL FIELD
[0001] The present invention relates generally to an internal combustion engine. More particularly, the present invention relates to a crankshaft employed in the internal combustion engine of the two wheeled vehicle.
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BACKGROUND
[0002] An internal combustion engine converts thermal energy obtained from burning of a fuel with an oxidizer (air) into mechanical energy, which can be used to do some kind of mechanical work. It is used in a wide range of applications
10 including providing motive force for movement of a vehicle. The main parts of
the engine include a cylinder head, a reciprocating piston on a cylinder block and
• --a connecting-rod-which connectsthe- piston to the reciprocating crankshaft. The
connecting rod in the engine transfers power generated by the reciprocating piston
in the cylinder block of the engine and converts it into rotary motion of the
15 crankshaft together forming a slider crank mechanism. In a two wheeled vehicle having a single cylinder, the crankshaft usually comprises of a crankshaft lefthand side and crankshaft righthand side assembled on either side of the connecting rod big end. A crankpin is inserted between the connecting rod big end and the crankpin is connected by the crankshaft righthand side and crankshaft lefthand
20 side together forming the crankshaft assembly. Generally, in two wheeled vehicles (including motorcycles and scooters) having single cylinder engine, the crankshaft assembly is of split type configured to be divided into righthand side and lefthand side. Further, generally, each of the righthand side and lefthand side of the crankshaft has a right crank web and a left crank web forming counterweights.
25 The crankwebs weights are used as reciprocating masses to improve crankshaft balance and counter the reaction force due to crankshaft rotation. Typically, crankwebs of a single cylinder two wheeled vehicle is of circular cross section. This is particularly true in scooter type step through vehicle. It is desirable to eliminate the circular cross section of the crankwebs to a more eccentric
30 counterweight design. But, this is difficult in view of piston and connecting rod
2

lubrication requirements. Thus, it is desirable to have an eccentric loaded counterweight crankshaft design which also enables lubrication of piston and connecting rod.
5 BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.
[0004] Fig. 1. illustrates the side view of a two wheeled vehicle employing an 10 embodiment of the present subject matter.
[0005] Fig. 2. illustrates the isometric view of the internal combustion engine employing the embodiment of the present subject matter.
[0006] Fig. 3. illustrates the cross sectional view of the internal combustion engine illustrating an oil cleaner assembly according to the embodiment of the 15 present subject matter.
[0007] Fig. 4. illustrates the isometric view of the crankshaft and connecting rod according to the embodiment of the present subject matter.
[0008] Fig. 5. illustrates the exploded view of the crankshaft illustrating the oil cleaner assembly according to the embodiment of the present subject matter.
20 [0009] Fig. 6a. illustrates the isometric view of the oil cleaner assembly secured on one side of the crankshaft according to the embodiment of the present subject matter.
[00010] Fig. 6b. and Fig. 6c. illustrates the front view and side view of the oil cleaner assembly according to the embodiment of the present subject matter.
25 [00011] Fig. 7. illustrates an enlarged cross sectional view of the internal combustion engine showing the oil lubrication path according to the embodiment of the present subject matter.

[00012] Fig. 8a. illustrates the enlarged cross sectional view of the crankshaft supported by the crankcase through the RH roller bearing according to the embodiment of the present invention.
[00013] Fig. 8b. illustrates the exploded view of the right half of the crankshaft 5 assembled within the RH casing with the oil cleaner assembly according to the embodiment of the present invention.
DETAILED DESCRIPTION
[00014] Various features and embodiments of the present invention here will be 10 discernible from the following further description thereof, set out hereunder. According to an embodiment, an internal combustion (IC) engine described here operates in four-cycles. The IC-engine is installed in a step through type two wheeled vehicle colloquially called as scooter. It is pertinent to note that the IC engine may be mounted in two wheeled vehicles in different arrangements such as 15 in transverse and longitudinal fashion. However, in the ensuing description, such engine is transversely mounted at a lower portion of the step through type two wheeled vehicle. It is contemplated that the concepts of the present invention may be applied to other types of vehicles such as straddle-type motorcycle within the spirit and scope of this invention. Further "front" and "rear", and "left" and "right" 20 referred to in the ensuing description of the illustrated embodiment refer to front and rear, and left and right directions as seen from a rear portion of the IC engine and looking forward. The detailed explanation of the constitution of parts other than the present invention which constitutes an essential part has been omitted at suitable places.
25 [00015] Typically, in a two wheeled vehicle such as a scooter, a swinging IC engine having single cylinder is located below the seat at a lower rear portion of the vehicle. The IC engine, among other components, has a cylinder block comprising a cylinder head atop or in front of the cylinder block and receiving a reciprocating piston from the bottom or the rear. On combustion of the air-fuel
4

mixture, the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft. In this way, the reciprocatory motion of the piston is converted to rotatory motion of the crankshaft. The crankshaft is housed inside a crankcase beneath or behind the
5 cylinder block. In order to set the vehicle into motion, the power supplied to the crankshaft of the internal combustion engine is carried to a wheel of the vehicle, in a controllable way; through a transmission system. The transmission system in the conventional vehicle employs a centrifugal clutch and a continuously variable. transmission system, comprising of a two pulleys connected by an endless belt. A
10 variator mechanism connecting the pulley on the driving side enables movement of the pulley altering the diameter due to centrifugal forces. The gear change is obtained due this variation in effective diameter of the pulley.
[00016] 'Conventionally, the TC engines is provided with an engine lubrication" channel that enables lubrication of the moving engine components during engine
15 operation. The lubrication channel involves transmission of oil through a particular channel for achieving the desired lubrication and cooling of the engine components. The lubrication oil functions as a lubricating agent and a cooling agent in an internal combustion engine. The oil used for this purpose may be stored in an oil sump, which also acts as a repository for the oil expelled from the
20 engine components as a result of their working. The oil pump is utilized to draw and deliver the lubrication oil to desired locations within the engine for lubrication and cooling purposes under low, medium or high engine speed conditions. The circulating lubrication oil reduces the wear and tear and friction of the engine components and also ensures that the engine is consistently maintained under
25 optimal temperatures and thereby enhancing engine performance, life of engine components, and the service intervals of the lubricants. Conventionally, the oil sump is formed within a crankcase assembly.
[00017] In many two wheeled vehicles piston lubrication (through splash
lubrication) occurs though circulation of oil within an oil bore in the crankshaft
30 which meets the big end bore of the connecting rod and splashes to the piston
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from the bottom. Such systems also have special oil filters in the lubrication circuit and oil to circulated to the crankpin through a bore through the crankshaft. But, in small single cylinder compact scooter engine, it is desirable to mount various engine components on either side of the crankshaft. Typically, the 5 magneto assembly is mounted on one end on the right side and the centrifugal clutch for a transmission system is mounted on the left end. Due mounting of engine components on either side, it is difficult to drill an oil bore through the crankshaft to circulate the oil. The cross sectional diameter of the crankshaft is small and cannot bear the axial loads on the crankshaft and it can fail. Hence, in
10 such small single cylinder compact scooter engines, the lubrication oil is carried from the oil sump to a right casing of the crankcase assembly through a left casing. One channel in the right casing from the main lubrication channel is used
to supply oil to lubricate-crankshaft bearing, the connecting rod andtothe piston.
inside the cylinder block through splash lubrication. The crankshaft is secured
15 within the crankcase with the help of two roller bearings on which the axial loads act. The crankshaft lubrication channel is disposed on the right casing and meets the rightside roller bearing of the crankshaft and penetrates through the crankshaft, and enters the crankpin. The connecting rod also has a small oil groove at one end of the stem towards the big end bore to permit flow of oil for
20 lubrication which lubricates the crankpin, the big end bore and permits oil to splash on the piston.
[00018] During the supply of lubricating oil from the crankcase to the crankpin through the crankweb righthand side, generally a oil cleaner assembly is disposed. The oil cleaner assembly functions to filter debris, burrs, dust and other heavier
25 particles before the oil is splashed on to the piston through the connecting rod. Generally, the crankweb is circular in shape, and a front plate member having an annular opening is disposed in the front of the crankweb. The front plate member forms the oil cleaner assembly through which by centrifugal action throws the burrs, dust and other heavier particles towards the edge, while filtered lubricating
30 oil penetrates through the crankshaft to the crankpin.
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[00019] Conventionally, the shape of the crankweb is circular in order to facilitate this filtering of lubricating oil. However, this shape of the crankweb also contributes to excess weight of the crankshaft, excess machining and excess material used. This ultimately adds up to the cost of the two wheeled vehicle.
5 Hence, in order to reduce costs and alleviate the above mentioned drawbacks, it is desirable to have an eccentrically constructed crankweb having only counter weights. The eccentric crankweb is bell shaped having a narrow end and a broad end. The counterweights are disposed on the broad end and the crankpin used to mount the connecting rod is mounted on the narrow end. This design has
10 advantages such as reducing raw material usage, reduced machining during manufacturing (forging weight reduction) and reduced cost. Further, the eccentric crankweb achieves carbon dioxide and other emission reductions by reducing the crankshaft inertia.-This.reduction is.achieved without compromising in balancing mass as compared to circular crankshaft. However, this proposed layout does not
15 provide the desired cross sectional support to accommodate the front plate member and further there is no provision to facilitate the entry of lubrication oil from the right casing to inside the crankpin. Hence,the present invention proposes a new oil cleaner assembly for an eccentric crankshaft and the means to attach it to the crankshaft securely.
20 [00020] The present invention provides an internal combustion engine comprising a crankshaft enclosed and supported within a crankcase. A pair of roller bearings supports said crankshaft on the crankcase. The crankshaft comprises a pair of non circular T shaped counterweights disposed on either side of the connecting rod and connected to each other by a crankpin, each of said pair of counterweights
25 comprising a connection neck portion secured to a connecting rod, and an enlarged portion having a circular outer periphery and having the mass concentrated on the enlarged portion. There is a lubrication oil path in the crankshaft for supplying oil to lubricate the piston though oil splash. An oil cleaner assembly is disposed on at least one side of the crankshaft, said oil cleaner
30 assembly is circular in shape and secured to at least one of pair of counterweights
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and said oil cleaner assembly forming part of the lubrication oil path to filter the oil before lubrication of the piston through oil splash.
[00021] Further, the oil cleaner assembly comprises of a circular back-plate and an annular front plate attached to said back-plate, said circular back-plate having a 5 circular outline corresponding to the shape of said T shaped counterweight.
[00022] Furthermore, the oil cleaner assembly is secured by a spacer disposed adjacent to the oil cleaner assembly and securing the oil cleaner assembly, said spacer held on the crankshaft through transition fit. The roller bearing having its inner diameter is secured to the crankshaft through interference fit, and the outer 10 surface of the roller bearing is secured to the crankcase through interference fit such that, said oil cleaner assembly is held securely due to the axial force exerted by the roller bearing on the spacer when the crankshaft is secured within the crankcase.
[00023] With the above proposed invention, the following advantages can be 15 obtained such as preventing entry of foreign matter such as debris within the crankpin to lubricate the reciprocating piston by providing secured support to the oil cleaner assembly. The proposed oil cleaner assembly by itself acts as an envelope for the lubrication oil path on the crankshaft with efficient filtration. The assembly of the oil cleaner assembly during manufacturing and assembly is 20 simple and can be performed by simple operations such as press fitting. Hence, with the functionality of filtration of lubrication oil taken care, the T-shaped crankweb has less weight and uses less material. This helps in reducing cost and weight significantly.
[00024] The present invention along with all the accompanying embodiments and 25 their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00025] Fig. 1 illustrates the two wheeled vehicle (100) in accordance with one embodiment of the present invention. The vehicle comprises of a frame which is conventionally an underbone chassis frame which provides a generally open
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central area to permit "step-through" mounting by a rider. Typically, the frame assembly comprises of a head tube (102), a main tube (107), and a pair of side tubes 109 (only one shown). The two wheeled vehicle extends from a front portion (F) to a rear portion (R) in a longitudinal axis. The head tube (102) is
5 disposed towards the front portion (F), and the main tube (107) extends downwardly and rearwardly from the head tube (102) forming a flat horizontal step-through portion (117). The pair of side-tubes (109) extends rearwardly from the other end of the main tube (107) and supports vehicular attachments such as a seat (108), fuel tank assembly (not shown), a utility box (not shown) and pillion
10 handrest (118). The head tube (102) supports a steering tube (104) and further connected to the front suspension system (121) at the lower end. A handlebar support member (124) is connected to an upper end of the steering tube (104) and
. - supports a handlebar assembly (106)-Two telescopic front suspension.system (121) (only one is shown) supports the front wheel (119). The upper portion of the
15 front wheel (119) is covered by a front fender (103) mounted to the lower portion of the steering tube (104). There is front brake (not shown) and rear brake (114) arranged on the front wheel (119) and a rear wheel (113) respectively. The rear wheel (113) is supported towards the rear side of the frame by the IC engine (101) which is horizontally coupled swingably to the rear of the frame assembly of the
20 two wheeled vehicle through a rear suspension system (115). The IC engine (101) transfers the drive directly to the rear wheel (113) as it is coupled directly to it. The IC engine (101) comprises a continuously variable transmission (CVT) system, said CVT system disposed leftward of the IC engine (101) in the vehicle width direction. The rear wheel (113) is enclosed by a rear fender (110) connected
25 to the frame assembly.
[00026] Fig. 2 illustrates the isometric view of the IC engine (101) in accordance with the embodiment of the present subject matter. The IC engine (101) is made up of a cylinder head cover (201), cylinder head (202), cylinder block (203), and a crankcase (204). The crankcase (204) is made of a righthand casing (RH casing 30 204a) and a lefthand casing (LH casing 204b) which encloses the crankshaft (300) within it. The RH casing (204a) supports the righthand side of the crankshaft
9

- (411) and the LH casing (204b) supports the lefthand side of the crankshaft (413). The crankshaft (300) is disposed transversely with respect to the longitudinal cylinder axis. The CVT mechanism is disposed on the left side of the LH casing (204b) and is enclosed by a CVT cover (205) enclosing the left most portion of 5 the IC engine (101). An opening (205a) on the CVT cover (205) permits air within the CVT cover to cool the CVT transmission components.
[00027] Fig. 3. illustrates the cross-sectional view of the IC engine (101) showing its main parts according to the embodiment of the present invention. IC engine comprises a reciprocating piston (303) enclosed in the cylinder block (203), a
10 connecting rod (304) connecting the reciprocating piston (303) to a rotatable crankshaft (300). The cylinder head (202) is disposed over a cylinder block (203) forming a combustion chamber (314) at the junction. During operation, the burning'of fuel and oxidizer ^occurs in the combustion chamber (314) and transferr mechanical energy to the reciprocating piston (303) which transfers the
15 mechanical energy to the crankshaft (300) which generates power due to the slider crank mechanism. The cylinder head (202) comprises of at least one inlet valve (not shown) and at least one outlet valve (not shown) which are operated by means of rocker arms (not shown) and a camshaft (301) which consists of at least one inlet cam lobe (not shown) and at least one outlet cam lobe (not shown) which
20 actuates the rocker arms (not shown) when required. A cam-chain (313) is meshed between the crankshaft (300) and camshaft (301) in order to drive the camshaft (301) in the cylinder head (202). The inlet air fuel mixture from a throttle body (not shown) is connected to an inlet port of the IC engine (101) in the cylinder head (202) and an exhaust system including a muffler (not shown) is connected to
25 the exhaust port of the cylinder head (202). The CVT system (311) is attached to one end of the crankshaft (300) and a magneto assembly (308) is disposed at the other end of the crankshaft (300). The CVT system (311) comprises a V-belt between two stationary pulleys and one of them comprising the variator mechanism. The CVT cover (205) forms the outer portion of the IC engine (101)
30 and encloses the CVT system. The CVT cover (150) comprises a kickstarter assembly including a kickstart lever (206), assembled on a return spring (309) and
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a ratchet mechanism (350) configured to engage with the crankshaft (300) on the front side of the IC engine (101).
[00028] Fig. 4. illustrates the isometric view of the crankshaft (300) and connecting rod (304) according to the embodiment of the present subject matter. 5 The crankshaft (300) is housed and rotatably supported by the crankcase (204) on either side. In particular, the crankshaft (300) is rotatably supported by a pair of RH and LH roller bearings (307, 312) disposed inside the crankcase (204). The crankshaft (300) includes a pair of laterally extending arms with corresponding counterweights (410, 412), the pair of laterally extending arms including a RH
10 arm (411) and a LH arm (413) and their corresponding RH counterweight (410) and LH counterweight (412) extending laterally from a big end of the connecting rod (304a). The pair of roller bearings (307, 312) is disposed on either side of the connecting ro"d~(304) to rotatably support the'pair of laterally extending arms" (411, 413). The crankshaft further defines a pair of non circular T shaped
15 counterweights (410, 412) disposed on either side of the big end of connecting rod (304a) and connected to each other by a crankpin (414). Each of said pair of counterweights (410, 412) comprises a long and narrow connection neck portion (450) secured to the big end of connecting rod (304a), and an enlarged portion (460) having a circular outer periphery and having the mass concentrated on the
20 enlarged portion (460). This modified eccentric shaped counterweight acts as a crank-web and is much more superior as compared circular shaped crank-web having counterweights as the excess material towards the right and left on top of the mass concentrated region is saved. This decreases the weight of the crankshaft and also its cost of manufacture.
25 [00029] Fig. 5. illustrates the exploded view of the crankshaft of the IC engine (101) employing the embodiment of the present invention and housed in the crankcase (204). The crankshaft being of split type design has the RH arm (411) being magneto side (308) and the LH arm (413) being the CVT side (311). The crankpin (414) is inserted through the big end (304a) of the connecting rod (304)
30 and frictionally engaged on both sides of the connection neck portion (450)
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through holes present in the counterweights (410 and 412). A needle bearing (304b) is disposed between the crankpin (414) and the big end (304a) of the connecting rod (304) and is assembled in such a way that the internally facing circumferential surface of the big end (304a) acts as a bearing running zone for 5 the needle bearing (304b).
[00030) Fig. 6a. illustrates the isometric view of the oil cleaner assembly (401) secured on one side of the crankshaft (300). Fig. 6b. and Fig. 6c. illustrates the front view and side view of the oil cleaner assembly (401) according to the embodiment of the present subject matter. According to the present invention, an
10 oil cleaner assembly (401) is disposed on at least one side of the crankshaft (300). In the present embodiment, the oil cleaner assembly (401) is disposed on the right side of the crankshaft (401) and secured to the RH arm (411) immediately adjacehTto the RH counterweight (410). The oil cleaner assembly is circular"in" shape and it forms part of the lubrication oil path to filter the oil to lubricate the
15 piston though oil splash. The oil cleaner assembly (401) comprises of a circular back-plate (401b) and a front plate (401a) slightly bowl shaped with a annular hole (401d) at its centre. Thefront plate (401a) is secured to the side surface of said back-plate (401b) to interiorly define, in cooperation with the side of the back-plate (401b), a centrifugal separating chamber (401e). The oil cleaner
20 assembly (401) is disposed between the lubricating oil path such that, the lubricating oil is forced under pressure to ingress into the centrifugal separating chamber (401 e) under pressure. Since, the oil cleaner assembly (401) is securely attached to the crankshaft (300), during operation the oil cleaner assembly (401) rotates along with the crankshaft (300). The centrifugal force of the oil cleaner
25 assembly (401) forces the foreign particles and suspended solids in the oil within centrifugal separating chamber (401e) to be thrown by centrifugal action to the outside lip of the back-plate (401b). Thus, the remaining filtered and cleaned oil is forced into a crankpin opening (401c) configured to communicate with the crankpin bore (414a) to supply filtered oil to the crankpin (414) for lubrication of
30 the reciprocating piston (303) within the cylinder block (203) by splash lubrication. The foreign particles and other suspended solids include dust, metal
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filings etc. The back-plate (401b) of the-oil cleaner assembly (401) is circular in shape and has a circular outline. When it is secured to the T- shaped counterweight (410), the circular outline of the back-plate (401b) matches with the circular contours of the T-shaped counterweight (410). This way, the necessity 5 of the counterweights to be circular in shape is avoided and the function of the oil filtering can be performed effectively by the oil cleaner assembly (401) proposed in the present invention. In an embodiment, the back-plate (401b) and the front plate (401a) are made of steel alloy material.
[00031] Fig. 7. illustrates the enlarged cross sectional view of the IC engine
10 showing the oil lubrication mechanism within the crankshaft according to the
embodiment of the present subject matter. In the present embodiment, the
lubricating oil is supplied from the RH casing (204a) to the oil cleaner assembly
"~ (401). The RH casing (204a)"comprises a oil gallery (701) through' which
lubricating oil under pressure flows to the crankshaft (300). There is a small notch
15 (703) on the contact surfaces between the RH crankshaft bearing (307) on which the oil gallery (701) meets. The notch (703) defines a lubrication oil path in the crankshaft supplying oil to lubricate thepiston though oil splash from the bottom of the connecting rod, for the lubricating oil (700) to flow from the oil gallery (701) to the oil cleaner assembly (401). The lubricating oil (700) further gets
20 filtered by the oil cleaner assembly (401) and ingresses towards a crankpin bore (414a) through the backplate opening (401c). Crankpin (414) comprises a crankpin oil passageway (414b) which permits the flow of lubricating oil from the crankpin bore (414a) to the connecting rod big end (304a). The connecting rod big end (304a) is so shaped to throw the lubricating oil (700) under pressure at
25 every revolution of the crankshaft (300) and the lubricating oil is splashed all over the interior of cylinder block (203) into the piston (303).
[00032] Fig. 8a. illustrates the enlarged cross sectional view of the crankshaft
supported by the RH casing through the RH roller bearing (307) according to the
embodiment of the present invention. The oil cleaner assembly (401) is secured
30 by a spacer (501) disposed adjacent to and securing the oil cleaner assembly
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(401), said spacer (501) held on the crankshaft (300) through transition fit. The RH roller bearing (307) is having its inner diameter secured to the RH crankshaft surface (411a) through interference fit, and the outer surface of the RH roller bearing (307) is secured to the RH casing (204a) through interference fit. When 5 RH casing (204a) is assembled to join with the LH casing (204b), the spacer (501) is subjected to axial force exerted by the roller bearing (307) to the spacer (501). This axial force (F) on the spacer (501) holds the oil cleaner assembly (401) securely in position on the crankshaft (300). The diameter of the spacer can vary based on the force of clamping exerted by the roller bearing. The spacer 10 (501) is made of steel alloy.
[00033] Fig. 8b. illustrates the exploded view of the right half of the crankshaft assembled within the RH casing with the oil cleaner assembly according to the embodiment of the"present invention. It is seen from the figure that, the oil cleaner assembly (401) is securely held on the RH crankshaft surface (411a) by assembly
15 of the spacer (501) on the RH crankshaft surface (411a) by transition fit. However, in order to ensure a tight and secured fit of the oil cleaner assembly (401) on the crankshaft (300), the inner diameter of the RH roller bearing (307) is secured to the RH crankshaft surface (411a) by interference fit and further the RH roller bearing is having an outer diameter secured to the RH casing (204a) by
20 interference fit and the RH casing (204a) and LH casing (204b) are clamped together during assembly. Hence, this provides the axial clamping force (F) on the spacer (501) and thus holding the oil cleaner assembly (401) securely in position.
[00034] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of 25 the present subject matter, the present disclosure may be practiced other than as specifically described.
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We Claim:
1. An internal combustion engine (101) comprising:
a crankcase (204);
5 a cylinder block (203) disposed above said crankcase (204);
a piston (303) reciprocating within the cylinder block (203); a crankshaft (300) enclosed and supported within the crankcase (204), said piston (303) and said crankshaft (300) connected by a connecting rod (304) such that, the reciprocating motion of the piston (303) is converted
10 to rotary motion of the crankshaft (300);
a pair of roller bearings (307, 312) for supporting said crankshaft (300) on
-the crankcase (204); ....... ■ ....
said crankshaft (300) comprising a pair of non circular T shaped counterweights (410, 412) disposed on either side of the connecting rod
15 (304) and connected to each other by a crankpin (414), each of said pair of
counterweights (410, 412) comprising a connection neck portion (450) secured to the connecting rod (304), and an enlarged portion (460) having a circular outer periphery and having the mass concentrated on the enlarged portion (460);
20 a lubrication oil path (701, 703, 414a) in the crankshaft (300) supplying oil
to lubricate the piston (303) though oil splash from the bottom of the connecting rod (304), said crankcase (204) configured to supply oil to the lubrication oil path (701, 703, 414a); wherein,
25 an oil cleaner assembly (401) is separately mounted on at least one side of
the crankshaft (300); said oil cleaner assembly (401) is circular in shape and secured to at least one of pair of counterweights (410); and said oil cleaner assembly (401) forming part of the lubrication oil path (701, 703, 414a) to filter the oil before lubrication of the piston (303) through oil
30 splash.
15

2. The internal combustion engine (101) as claimed in claim 1, wherein said oil cleaner assembly (401) comprising a circular back-plate (401b) and an annular front plate (401a) attached to said back-plate (401b), said circular back-plate (401b) having a circular outline corresponding to the shape of said T shaped counterweight (410).
3. The internal combustion engine (101) as claimed in claim 1, wherein the oil cleaner assembly (401) is secured by a spacer (501) disposed adjacent to the oil cleaner assembly (401) and securing the oil cleaner assembly (401), said spacer (501) held on the crankshaft (300) through transition fit.
4. The internal combustion engine (101) as claimed in claim 1, wherein the roller bearing (307) having its inner diameter secured to the crankshaft (300) through interference fit, said outer, surface of the roller bearing (307) secured to the crankcase (204a) through interference fit, said oil cleaner assembly (401) held securely due to the axial force exerted by the roller bearing (307) on the spacer (501) when the crankshaft (300) is secured within the crankcase (204).
5. The internal combustion engine (101) as claimed in claim 1, wherein the back-plate (401b) comprises a crankpin opening (401d) configured to communicate with a bore (414a) within the crankpin (414) forming part of the lubrication oil path (701, 703, 414a) to supply filtered oil to the crankpin (414) for lubrication of the piston (303) within the cylinder block (203).
6. The internal combustion engine (101) as claimed in claim 1 or claim 3, wherein the back-plate (414b) and the front plate (414a) are made of steel alloy, and the spacer (501) is made of steel alloy.
7. The internal combustion engine (101) as claimed in claim 1, wherein a CVT
system (311) is attached to one end of the crankshaft (300) and a magneto
assembly (308) is disposed at the other end of the crankshaft (300).
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8. The internal combustion engine (101) as claimed in claim 1, wherein the oil cleaner assembly (401) is disposed on the right hand side of the crankshaft (300) and the oil is supplied from the right hand crankcase (204a) to the oil cleaner assembly (401).
5 9. The internal combustion engine (101) as claimed in claim 2, wherein the diameter of the spacer (501) can vary based on the force of clamping exerted by the roller bearing (307).
10. A two wheeled scooter type vehicle (100) comprising the internal combustion engine (101) as claimed in any of the preceding claims.
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