DESC:TECHNICAL FIELD
[0001] The present invention relates generally to a two wheeled vehicle. More particularly, the present invention relates to a cooling system employed to cool the internal combustion engine of the two wheeled vehicle.

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 employed to do a wide variety of mechanical work. It is used in a wide range of applications including providing motive force for movement of an automobile. One such type of automobile powered by an internal combustion engine is a step-through type two wheeled vehicle, colloquially called scooter. The main parts of the internal combustion engine include a cylinder head, a reciprocating piston on a cylinder block and a connecting rod which connects the piston to the reciprocating crankshaft. During operation of the internal combustion engine, the burning of fuel and oxidizer occurs in the cylinder block and transfers mechanical energy to the reciprocating piston. This operation generates lot of thermal energy in and around the cylinder block. This thermal energy increases the temperature of the cylinder block and the atmospheric air surrounding it. Hence, it is necessary to cool the cylinder block, its associated components and the surrounding air. The IC engines of step-through type two wheeled vehicle such as scooter, usually employ a centrifugal fan which is operably connected to the crankshaft, and the fan forces air flow through a shroud surrounding the internal combustion engine. During circulation of the air through the shroud, less amount of air flows through many critical hot zones around the internal combustion engine. This is undesirable as targeted critical hot zones are not cooled and this reduces engine performance and decreases cooling efficiency of the internal combustion engine. Thus to improve internal combustion engine performance and to address above discussed problems, a new forced air cooling system is proposed.
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 side view of a two wheeled vehicle employing an embodiment of the present subject matter.
[0005] Fig. 2 illustrates an internal combustion engine which is swingably mounted below the side tube of the two wheeled vehicle according to the embodiment of the present subject matter.
[0006] Fig. 3 illustrates the side view of the internal combustion engine in accordance with the embodiment of the present subject matter.
[0007] Fig. 4 illustrates the cross sectional view (X-X) of the internal combustion engine and the working of the forced air cooling system employing the embodiment of the present subject matter.
[0008] Fig. 5a illustrates the isometric view of a shroud in a prior art.
[0009] Fig. 5b illustrates the isometric view of the shroud according to the embodiment of the present subject matter.
[00010] Fig. 5c illustrates the top view of the shroud according to the embodiment of the present subject matter.
[00011] Fig. 5d illustrates the front view of the shroud according to the embodiment of the present subject matter.
[00012] Fig. 6 depicts curves for heat transfer rate plotted against flow rate, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
[00013] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. According to an embodiment, the internal combustion engine described here operates in four cycles. Such an internal combustion engine is installed in a step through type two wheeled vehicle. It is pertinent to note that the internal combustion engine may be mounted in two wheeled vehicles in different arrangements such as in transverse, inclined or 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 within the spirit and scope of this invention. Further "front" and "rear", and "left" and "right" 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 internal combustion 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.
[00014] During operation of the internal combustion engine, the burning of air fuel mixture occurs in a combustion chamber formed between a cylinder head and cylinder block. This operation generates lot of heat and thermal energy in and around the cylinder head and cylinder block and increases the temperature of the space and parts surrounding it. If this thermal energy is not dissipated, it may result in the failure of the cylinder head and cylinder block. Also, large temperature differences may lead to a distortion of the internal combustion engine components due to the thermal stresses set up thereby. It is also seen that higher temperatures also lower the volumetric efficiency of the internal combustion engine. Hence, it is necessary to cool the cylinder block, its associated components and the surrounding air. Generally, a cooling system is required to cool the internal combustion engine components.
[00015] Typically, in a step-through type vehicle such as a scooter, a swinging internal combustion engine is located below the seat at a lower rear portion of the vehicle. There are two side cowls surrounding the internal combustion engine on right and left side of the vehicle. The internal combustion engine is swingably supported by rear suspension system and attached to the frame of the vehicle. Cylinder block of such internal combustion engines are enclosed and are heated up during their operation. Since, proper air circulation is lacking and inadequate around the enclosed cylinder block, such internal combustion engines are typically cooled by employing forced air cooling system. In a forced cooling system, atmospheric air is drawn inside the cooling system from the outer atmosphere through an inlet by using a centrifugal fan. The rotation of the centrifugal fan is integrated to the rotation of the engine crankshaft. A shroud surrounding the cylinder block and the internal combustion engine guides the atmospheric air thereby cooling the cylinder block. Hence, the heat generated due to combustion in the cylinder block will be conducted to fins on it. Fins are provided around the cylinder block which increases the contact area exposed to the circulating air. When the air flows over the fins, heat will be dissipated to the cooling air. The shroud can be made up of multiple parts and usually houses with the internal combustion engine for providing the cooling to the cylinder block and other parts. The shroud will also have a cutout for shroud exit.
[00016] Although cooling of the cylinder block of the internal combustion engine is necessary, in conventional forced cooling systems the air does not flow through many critical hot zones around the IC engine. The main critical hot zones required to be cooled are the zone around the spark plug on the cylinder head and the zone around the connection of the exhaust pipe to the cylinder head. The forced cooling system should supply adequate air flow around the critical zones, but it should also supply to other zones of the IC engine. As described above, the cylinder block and cylinder head have fins which radiate the heat generated by the combustion chamber capable of being radiated by fins and that heat is then further carried away by the flowing air. To optimize cooling around the spark plug, the shroud is designed to direct air towards the spark plug. Further, the shroud exit area of the shroud is disposed around the exhaust pipe connection zone. In small capacity IC engines, generally the spark plug zone and the exhaust connection zone are disposed on adjacent faces of the cylinder head. Hence in conventional shroud assembly the flowing air is directed towards the spark plug and further made to exit through the shroud exit area around the exhaust pipe connection zone, the flowing air takes a shorter path to exit the shroud assembly and very less air is circulated through the longer path around the cylinder block and cylinder head. This reduces the overall heat extracting capacity of the IC engine and may get overheated leading to undesirable results.
[00017] The present invention aims to address the above drawbacks by providing a forced cooling system that can reliably divert the cooling air flow by proportionally splitting the flowing air stream into two parts (first air stream passage and the second air stream passage) downstream of the centrifugal fan. The first air path takes a shorter path being directed towards the spark plug zone and further being directed adjacent to the spark plug to the exhaust connection zone and flowing out of the shroud assembly. The second air path is diverted to take a longer path around the cylinder head and cylinder block far away from the spark plug zone before exiting from the shroud exit from the opposite side. To achieve this, the shroud assembly comprises at least one rib disposed on the inner surface of the shroud assembly downstream of the centrifugal fan, said rib having its longer edge disposed parallel along the flowing air and extending from the bottom of the shroud assembly uptil the spark plug area. Further, the rib has a profile so shaped that its cross section reduces as from bottom to top to match the contours of the shape of the outer surface of the cylinder head and cylinder block and prevent leakage of air after diversion. This solution is simple to manufacture, and effective in operation. Such a device can result better heat extraction and improved cooling efficiency of the cooling system. The device proposed also ensures a smooth flow of air, smooth diversion of air, reduces air resistance, which will enhance the flow of cooling air around the internal combustion engine parts.
[00018] With the above proposed invention, the following advantages can be obtained such as simple in manufacturing, less turbulent air flow even after diversion, better heat dissipating effect, compact structure, no change in capacity of centrifugal fan, improved thermal efficiency of internal combustion engine, prevents leakage of flowing air after diversion, no decrease in velocity of air after diversion and improvement of overall mechanical efficiency of the vehicle.
[00019] The present invention along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00020] Fig. 1 illustrates side view of a two wheeled vehicle (100) in accordance with one embodiment of the present invention. The vehicle (100) comprises of a frame which is conventionally a U-shaped frame which provides a generally open central area to permit “step-through” mounting by a rider. Typically, the frame comprises of a head tube (102), a main tube (107), and a pair of side-tubes (109) (only one shown). One end of the main tube (107) extends downwardly and rearwardly in a horizontal direction to form a step-through portion (117) which then connects with the pair of side-tubes (109). At the other end of the main tube (107) there is the head tube (102) configured to rotatably support a steering tube (111) and further connected to a front suspension system (121) at the lower end. A handlebar support member (not shown) is connected to an upper end of the steering tube (111) and supports a handlebar assembly (106). Two telescopic front suspension systems (121) (only one is shown) are attached to a bracket (not shown) on the lower part of the steering tube (111) on which is supported a front wheel (119). The upper portion of the front wheel (119) is covered by a front fender (103) mounted to the lower portion of the steering shaft (111). The pair of side-tubes (109) includes a down frame section inclined downwards and connected to the main tube (107) at one end of the step-through portion (117). A plurality of cross pipes (not shown) is secured in between the pair of side-tubes (109) to support vehicular attachments including a utility box (not shown), a seat assembly (108) and a fuel tank assembly (not shown). The vehicle (100) is supported by a side stand (110). Further, the present invention is also being applicable for a three-wheeled vehicle (100).
[00021] The frame is covered by plurality of body panels, mounted and covering it. A floorboard (105) is provided at the step-through space provided above the step-through portion (117). A rear fender (115) is covering at least a portion of a rear wheel (116) towards the rear of the vehicle (100). The vehicle (100) comprises of plurality of electrical and electronic components including a headlight (128), a taillight (113), a transistor controlled ignition (TCI) unit (not shown), and a starter motor (not shown). Further a hub (118) is mounted on the rear wheel (116).
[00022] Fig. 2 illustrates an internal combustion (IC) engine (101) which is swingably mounted below the side-tube (109). The IC engine (101) is mounted on a swing arm (209), which is swingably connected to the step-through type frame using a toggle link. The IC engine (101) is connected to a rear wheel (116) through a transmitting means (not shown), such as a belt drive or a chain drive connecting the output of the IC engine (101) and the rear wheel (116). The rear wheel (116) is mounted to the end of the swing arm (209) and mounted to the frame through one or more rear suspension(s) (129) provided in the rear portion of the vehicle (100) for comfortable ride. In an embodiment of the present invention, the vehicle (100) is a hybrid vehicle (100) comprising an electric traction motor along with the IC engine (101). In the present embodiment, the electric traction motor is disposed at the hub (118) which is mounted on the rear wheel (116). Hence, the electric traction motor is directly connected to the rear wheel (116). A battery system (not shown) is disposed at convenient location in the vehicle (100) which supplies power the drive the electric motor (202). There is front brake (not shown) and rear brake (not shown) arranged on the front wheel (119) and rear wheel (116) respectively.
[00023] Fig. 3 illustrates the side 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 (202), cylinder block (203), a cylinder head cover (201) and crankcase (204). A centrifugal fan (303) is mounted on a crankshaft (401) on any one end of the IC engine (101) in its width direction. In the present embodiment the centrifugal fan (303) is mounted on the rightward side of the IC engine and the shroud assembly is configured to cover the right part of the crankcase (204), the cylinder head (202) and the cylinder block (203). The cylinder head cover (201) for the IC engine (101) is mounted on the crankcase (204), and the assembly of the cylinder head (202) and cylinder block (203). The forced air cooling system (200) comprises the centrifugal fan (303), and a shroud assembly (301) for directing and circulating air inside the IC engine (101). The shroud assembly is made up by assembling two parts, namely attaching the RH shroud (301) with the LH shroud (not shown) enclosing the IC engine (101). The LH shroud covers a left part of the portion of the cylinder block (203) and cylinder head (202). The RH shroud (301) comprises two portion, one portion is a crankcase portion (301a) having a grilled circular opening (301c) and the cylinder portion (301b) enclosing the cylinder head (202) and cylinder block (203). When the RH shroud (301) is assembled to enclose the right side of the IC engine (101), the centrifugal fan (303) is enclosed by the grilled circular opening (301c). The grilled circular opening (301c) is exposed to the atmosphere through the lower half of the vehicle (100) such that during operation of the centrifugal fan (303) the atmospheric air gets drawn through the grilled circular opening (301c) to be guided by the shroud assembly. The other cylinder portion (301b) encloses the other half portion of the cylinder block (203) and cylinder head (202) and connects to the LH shroud by means of bosses. The zone of connection between the RH shroud (301) and the LH shroud on the bottom direction of the IC engine (101) forms a shroud exit (502) which permits the exit of the hot air after circulation around the IC engine (101). Further, the cylinder head (202) comprises an exhaust connection zone (202a) on which the exhaust pipe (114a) is attached to the cylinder head (202). The shroud exit (502) surrounds the exhaust connection zone (202a). The RH shroud (301) has a circular opening (302) through which surrounds a spark plug (410) is mounted on the cylinder head (202). The circular opening (302) facilitates the removal and attachment of the spark plug (410) without the need for removal of the RH shroud (301).
[00024] Fig. 4 illustrates the cross-sectional view taken along the line X-X of the IC engine (101) showing its main parts and the working of the forced air cooling system according to the embodiment of the present invention. The internal combustion engine comprises a reciprocating piston (402) enclosed in the cylinder block (203), a connecting rod (403) connecting the reciprocating piston (402) to a rotatable crankshaft (401). During operation, the burning of fuel and oxidizer occurs in the cylinder block (203) and transfers mechanical energy to the reciprocating piston (402) which transfers the mechanical energy to the rotatable crankshaft (401) which generates power due to the slider crank mechanism. The centrifugal fan (303) is attached to the rotatable crankshaft (401) on the right side of the IC engine (101) and the RH shroud (301) encloses the IC engine (101) on the right side over the centrifugal fan (303) such that, during rotation of the rotatable crankshaft (401), the centrifugal fan (303) which is integrally mounted on it rotates along with it drawing cooling air inside the RH shroud (301). The IC engine (101) further comprises other ancillary systems which include starting system (not shown), transmission system (405), lubrication system (not shown) and magneto assembly (411) all housed in the crankcase (204).
[00025] The cylinder head (202) comprises of a valve train mechanism (407) which controls at least one inlet valve (not shown) and at least one outlet valve (not shown). The valve train mechanism (407) is driven by the rotatable crankshaft (401) through a cam-chain (412). The inlet air fuel mixture from the throttle body (not shown) is connected to an inlet portion in the cylinder head (202) and an exhaust pipe including a muffler (114) is connected to the outer portion of the cylinder head (202). After combustion, the hot exhaust gases are generated which are expelled out of the cylinder head (202) around the exhaust port. The combustion of air-fuel mixture in the cylinder block (205) generates a lot thermal energy which increases the temperature of the cylinder head (202) and cylinder block (203) and the air surrounding it. The cylinder head (202) and the cylinder block (203) have extended surfaces (fins) to increase the surface area for effective heat dissipation. Hence, the zone around the cylinder head (202) and cylinder block (203) is under increased temperature and requires efficient cooling. But, due to the proximity of the exhaust connection zone (202a) and a spark plug zone (410a) (being on adjacent sides of the cylinder head surface) there is area of low pressure and hence the flowing air takes the shorter path to flow over the spark plug zone (410a), the exhaust pipe zone and exits from the shroud exit (502). The embodiment of the present invention has at least one rib (501) disposed in downstream of the centrifugal fan (303) in the cylinder portion (301b) of the RH shroud (301) to divert the incoming air flow stream (510) into a first air passage (510a) and a second air passage (510b). This way, we can ensure the circulation of the incoming air flow stream (510) throughout the shroud assembly or the shroud (301) for effective cooling. In present embodiment, the RH shroud (301) is interchangeably termed as the shroud (301).
[00026] Fig. 5a illustrates the isometric view of a prior art wherein the RH shroud is illustrated. Here the representative air flow is shown after it is drawn inside the shroud assembly by the centrifugal fan. The shroud exit (502) and spark plug zone (410a) are disposed in close proximity to the incoming air flow stream (510) as the air flow meets the cylinder head (202) and cylinder block (203) assembly on the right side of the IC engine (101). Due to pressure difference and close proximity of the shroud exit (502), most of the air flow flows over the spark plug zone (410a), the exhaust connection pipe zone and exits through the shroud exit of the shroud as shown in figure. Adequate flow of air around the longer path of the air flow through the shroud (301) around the cylinder head (202) and cylinder block (203) is not obtained. This non uniform cooling of the cylinder head (202) and cylinder block (203) is extremely undesirable as it reduces the thermal efficiency of the IC engine (101) and reduces effectiveness of the forced air cooling system. To alleviate this and other drawbacks in existing state of art, the rib (501) is introduced to divide the incoming air flow stream (510) into the first air passage (510a) and the second air passage (510b), wherein the second air passage (510b) diverts the flowing air around the cylinder head and cylinder block before the air exits through the shroud exit. The air flow in the first air path performs the function of cooling the spark plug zone (410a) and the exhaust connection zone (202a).
[00027] Fig. 5b illustrates the isometric view of the RH shroud (301) according to the embodiment of the present subject matter. The RH shroud (301) comprises the rib (501) disposed on the inner surface of the RH shroud (301) downstream of the centrifugal fan (303) having its longer edge oriented parallel to the flowing direction of air. The rib (501) has a cross sectional profile to match the contours of the cylinder head (202) and cylinder block (203) on which the RH shroud (301) is assembled. As shown in Fig. 4, the upper portion of the longer edge of the rib (501) has contours which match exactly with the surface contours of the cylinder head (202) and cylinder block (203). This profile ensures that there is minimum leakage of air after the flow of air has been diverted and the air remains diverted till the air flow reaches the end of RH shroud (301) and bifurcates to cool different hot zones of the cylinder head (202) and cylinder block (203). The term incoming air flow stream (510) is also interchangeably used as the air stream (510).
[00028] The atmospheric air is drawn inside when the centrifugal fan (303) is in operation. The air flow downstream of the RH shroud (301) when it is flowing across from the centrifugal fan (303) to the cylinder head (202) and cylinder block (203) is intercepted by the rib (501) at the zone of division (P) which divides the air stream (510) to flow through two air paths, namely the first air stream passage (510a) and the second air stream passage (510b). The first air stream passage (510a) is the path formed towards the lower part of the rib (501) which directs the air flow to the spark plug zone (410a) disposed towards the top of the RH shroud (301) before the air is flown through the shroud exit (502) around the exhaust connection zone (202a) located on the face adjacent of the spark plug (410) on the cylinder head (202) face. The second air stream passage (510b) is formed towards the upper part of the rib (501) which is directed away from the centre of the RH shroud (301) due to the gentle curved shape of the rib (501) away from the spark plug zone (410a) towards the upper side of the RH shroud. This facilitates the air to flow around the cylinder head (202) and cylinder block (203) through the LH shroud before exiting from the shroud exit (502) from the other side of the shroud.
[00029] Fig. 5c illustrates the top view of the RH shroud (301) according to the embodiment of the present subject matter. The rib (501) having its longer edge is slightly curved away from the spark plug (410). This slight curvature of the rib directs the flowing air in the second air stream passage (510b) away from the spark plug zone (410a) and towards the upper edge of the cylinder head (202) and cylinder block (203) to be recirculated around the cylinder head (202) and cylinder block (203). The curvature of the rib (501) has a radius (r) in the order of between 150 millimeters to 200 millimeters. The longer edge of the rib (501) has a length (L) in the range 60 millimeters to 100 millimeters. This ensures the right profile of the rib (501) to divide the flowing air stream. Further, the distance at the point of division of air stream is such that, the flowing air is divided in a proportion of 2:3 (L1:L2) along the length (L) of the longer edge of the rib (501), such that 40% of the total flowing air drawn inside by the centrifugal fan (303) is directed towards first air stream passage (510a), while 60% of the total flowing air is directed to the second air stream passage (510b). Furthermore, the rib (501) is disposed above a centre line (Z-Z) drawn parallel to the horizontal axis and passing through the centre of the crankcase portion (301a). The crankcase portion (301a) of the RH shroud (301) is circular in the shape.
[00030] Fig. 5d illustrates the side view of the RH shroud (301) according to the embodiment of the present subject matter. The shroud exit (502) and the spark plug zone (410a) (shown in Fig. 5b and Fig. 5c) are illustrated. The arms projections are illustrated when they are configured to be assembled with the LH shroud to form the shroud exit (502). Different modifications are feasible to be conceived by person skilled in the art. Further, in an embodiment more than one rib (501) are disposed in a predetermined array on the shroud (301) for forming multiple duct or passages (510a,510b) to distribute the incoming air stream (510) to the different critical parts of the internal combustion (IC) engine (101) and the exhaust connection zone (202a) as required by respective design of the system.
[00031] Fig. 6 depicts curves (400a, 400b, 400c) for heat transfer rate of the circulated air flow stream (510) plotted against flow rate of the circulated air flow stream (510), in accordance with an embodiment of the present subject matter where a curve (400a) depicts that without the presence of the rib (501) heat transfer rate is low in comparison with the presence of the rib (501) as shown by the curves (400b, 400c). Further, the thermal efficiency of the internal combustion engine (101) is improved as heat transfer rate is improved due to the presence of at least one rib (501) disposed in downstream of the centrifugal fan (303) in the cylinder portion (301b) of the shroud (301) to divert the incoming air flow stream (510) into a first air passage (510a) and a second air passage (510b). Hence, the present subject matter ensures that the circulation of the incoming air flow stream (510) throughout the shroud (301) performs the action of cooling effectively.
[00032] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.
,CLAIMS:We Claim:
1. An internal combustion (IC) engine (101) for a vehicle (100) comprising:
a crankcase (204);
a centrifugal fan (303) operably attached to the crankcase (204) on any one side of the internal combustion (IC) engine (101) in the width direction;
a cylinder block (203) disposed above the crankcase (204);
a cylinder head (202) disposed above the cylinder block (203), the cylinder head (202) comprising:
a spark plug (410) disposed on the same side of the internal combustion (IC) engine (101) as that of the centrifugal fan (303); and
an exhaust connection zone (202a) disposed on the cylinder head (202) face adjacent to the cylinder head (202) face on which the spark plug (410) is disposed, the exhaust connection zone (202a) configured to permit the attachment of an exhaust pipe (114a);
a shroud (301) enclosing the cylinder head (202), the cylinder block (203), the crankcase (204) of the internal combustion (IC) engine (101) including the centrifugal fan (303);
the centrifugal fan (303) configured to direct air inside the shroud (301); and
the shroud (301) comprising of a crankcase portion (301a) having a grilled circular opening (301c) and a cylinder portion (301b) enclosing the cylinder head (202) and cylinder block (203),
wherein the shroud (301) comprises at least one rib (501) is disposed in downstream of the centrifugal fan (303) in the cylinder portion (301b) of the shroud (301).

2. The internal combustion (IC) engine (101) as claimed in claim 1, wherein the rib (501) has a longer edge oriented parallel to the direction of flow of air, wherein length (L) of the longer edge lies in the range 60 millimeters to 100 millimeters.
3. The internal combustion (IC) engine (101) as claimed in claim 1, wherein the shroud (301) has a circular opening (302) to facilitate the removal and attachment of the spark plug (410) without the need for removal of the shroud (301).
4. The internal combustion (IC) engine (101) as claimed in claim 1, wherein curvature of the rib (501) has a radius (r) in the order of between 150 millimeters to 200 millimeters.
5. The internal combustion (IC) engine (101) as claimed in claim 1, wherein the rib (501) proportionally divides the air stream (510) into at least two separate air stream passages (510a, 510b) including a first air stream passage (510a) and a second air stream passage (510b).
6. The internal combustion (IC) engine (101) as claimed in claim 1, wherein the longer edge of the rib (501) has a profile which is straight at the lower end and gently curved away from the spark plug (410).
7. The internal combustion (IC) engine (101) as claimed in claim 1 or claim 5, wherein the first air stream passage (510a) directs the air flow to the spark plug (410) and shroud exit (502) disposed adjacent to the spark plug (410), and the second air stream passage (510b) directs the air flow around the cylinder head (202) and cylinder block (203) assembly.
8. The internal combustion (IC) engine (101) as claimed in claim 1, wherein the rib (501) is disposed such that the flowing air stream (501) is divided in a proportion of 2:3 (L1:L2) along the longer edge of the rib (501).
9. The internal combustion (IC) engine (101) as claimed in claim 1, wherein the cross section of the rib (501) has a profile complementing the corresponding contours of the cylinder head (202) and cylinder block (203) to prevent any interference during assembly and prevent leakage of air.
10. A two wheeled vehicle (100) or a three wheeled vehicle (100) comprising an internal combustion (IC) engine (101) as claimed in claim 1 to claim 9.