Claims:We claim:
1. A saddle type vehicle with a forced-air cooling for an internal combustion (IC) engine (101), said saddle type vehicle comprising:
wherein, said IC engine (101) includes a cylinder head (201) and a cylinder block (202), said cylinder head (201) and cylinder block (202) being forwardly inclined when assembled in said vehicle and said IC engine (101) having a crankshaft axis of said IC engine (101) being disposed in a vehicle lateral direction;
an exhaust pipe being attached to a cylinder head (201) forming a heat zone area (505) at a junction of said attachment;
an axial fan (404), said axial fan (404) being disposed with a rotary axis of said axial fan (404) being in said vehicle lateral direction;
a frame assembly comprising a main-tube (107) and a pair of side-tubes (109), each of said pair of side-tubes (109) being parallel to each other and attached to one end of said main-tube (107) by a cross bar (107a), and said internal combustion engine (101) being swingably mounted on said frame assembly; said IC engine (101) being forced cooled through an axial fan (404),
a seat assembly (108);
a utility box (100a); and
a bridge mounting bracket (114), said bridge mounting bracket (114) being disposed between each of said pair of side-tubes (109);
wherein said bridge mounting bracket (114) being disposed in proximity to said axial fan (404), said axial fan (404) being covered by a shroud (402); and
wherein said bridge mounting bracket (114) includes an air inlet opening (114a) for enabling entry of cool air into an interior portion (402c) of said shroud (402), said cool air entry occurs when said axial fan (404) being in operation for cooling of said IC engine (101).
2. The saddle type vehicle with forced air cooling of an IC engine (101) as claimed in claim 1, wherein said bridge mounting bracket (114) being configured to support said utility box and said seat assembly (108).
3. The saddle type vehicle with forced air cooling IC engine (101) as claimed in claim 1, wherein said shroud (402) being configured with one or more opening (501, 502) for hot air to exit, said (502) being formed at one circumferential edge of said shroud (402) and said opening (502) being located in close proximity to said heat zone area (505).
4. The saddle type vehicle with forced air cooling IC engine (101) as claimed in claim 3, wherein said opening (502) includes a first edge (502a) and a second edge (502b), said first edge (502a) being configured to project outwardly from an outer surface (422) of said shroud (402).
5. The saddle type vehicle with forced air cooling IC engine (101) as claimed in claim 3, wherein said first edge (502a) being greater in dimension than said second edge (502b), and said first edge forms (502a) an angularly slanted profile as viewed from a side view of said internal combustion engine (101).
6. The saddle type vehicle with forced air cooling IC engine (101) as claimed in claim 1, wherein said shroud (402) includes an exhaust opening (501) for passage and attachment of said exhaust pipe, said exhaust opening (501) being substantially larger than said heat zone area (505).
7. The saddle type vehicle with forced air cooling IC engine (101) for a saddle type vehicle as claimed in claim 1, wherein said air inlet opening (114a) being provided in said bridge mounting bracket (114) for accessing air space between a body panel of said saddle type vehicle and said pair of side tubes (109).
, Description:TECHNICAL FIELD
[0001] The present invention relates generally to a two wheeled or three wheeled saddle type vehicle. More particularly, the present invention relates to a mounting arrangement of a forced air cooling system employed to cool the internal combustion engine of the saddle type vehicle. The present application is a divisional from the patent application number 201741008243 dated 09th March 2017 and relates to a cooling system for an internal combustion engine and a method thereof.

BACKGROUND
[0002] A vehicle utilizes motive force both from an internal combustion (IC) engine and an electric motor to drive it. The engine by way of combustion of a fuel with an oxidizer (air), converts chemical energy of the fuel into mechanical energy, and the battery powers the electric motor. One type of vehicle is a step-through type two wheeled vehicle. During operation of the IC engine, the combustion of fuel and oxidizer occurs in a combustion chamber and transfers mechanical energy to a reciprocating piston. This operation generates lot of thermal energy in and around a cylinder head and cylinder block. This thermal energy increases the temperature of the IC engine and the atmospheric air surrounding it. Hence, it is necessary to cool the cylinder head, cylinder block, its associated components and the surrounding air. Step-through type two wheeled vehicle, usually employ a body panel surrounding the IC engine, such that the cylinder head and the cylinder block is completely enclosed within scooter body parts and vehicular components. Hence, for such two wheeled vehicles, it is necessary to employ additional forced air cooling system for cooling the IC engine. Normally, such forced air cooling systems comprises of a fan which is operably connected to a crankshaft, and the fan forces air flow through a shroud surrounding the IC engine. The fan maybe of centrifugal type or axial flow type and can be located either near the crankshaft or close to the cylinder head and cylinder block. Axial flow type fans are advantageous as they work on spot cooling and cool the IC engine more effectively. Conventionally, the axial flow type fan is operably coupled to the IC engine crankshaft, hence operates continuously when the IC engine is in operation and speed of rotation depends on the speed on the crankshaft. This, system of cooling has severe drawbacks, which include improper cooling, more packaging space, additional number of parts, difficulty in serviceability and affects the automobile styling. In hybrid vehicles, an additional problem of cooling due to changing operating modes is faced, due to operation of various modes during a single ride cycle by the rider.

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 refer like features and components.
[0004] Fig. 1a. illustrates the side view of a two wheeled vehicle employing an embodiment of the present invention.
[0005] Fig. 1b. illustrates the isometric view of the internal combustion engine mounted on a frame assembly of the two wheeled vehicle employing the embodiment of the present invention.
[0006] Fig. 2. illustrates the side view of the internal combustion engine employing the embodiment of the present invention.
[0007] Fig. 3. illustrates the cross-sectional view (X-X) of the internal combustion engine showing the axial fan and shroud according to the embodiment of the present invention.
[0008] Fig. 4. illustrates the exploded view of the axial fan and shroud according to the embodiment of the present invention.
[0009] Fig. 5a. illustrates the cross sectional view (Y-Y) of the cylinder block of the internal combustion engine along with the axial fan and shroud according to the embodiment of the present invention.
[00010] Fig. 5b. illustrates the enlarged isometric view (Z) of the cylinder block of the internal combustion engine along with the axial fan assembly and shroud showing the exhaust system exit according to the embodiment of the present invention.

DETAILED DESCRIPTION
[00011] 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 (IC) engine described here operates in four cycles for a hybrid vehicle. Such an IC engine is installed in a 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 IC engine and looking forward.
[00012] The IC engine comprises of a cylinder head, a reciprocating piston inside a cylinder block located below the cylinder head, a combustion chamber formed between the cylinder block and cylinder head, a rotatable crankshaft to transfer mechanical energy to the transmission system and a connecting rod to transfer energy imparted to the reciprocating piston to the rotatable crankshaft. During operation of the IC engine, the burning of air fuel mixture occurs in the combustion chamber. This operation generates lot of thermal energy in and around the cylinder head and cylinder block which increases their temperature and atmospheric air surrounding it. Hence, it is necessary to cool the cylinder head, cylinder block, its associated components and the surrounding air through a cooling system.
[00013] Although cooling of the cylinder head and cylinder block of the IC engine is necessary, too much cooling is also not desirable since it reduces the thermal efficiency of the IC engine. So, the object of any cooling system is to keep the engine running at its most efficient operating temperature. It is to be noted that the engine is quite inefficient when it is cold and hence the cooling system is designed in such a way that we need to maintain a practical overall working temperature of the cylinder block. Hence, the cooling system should ideally reduce cooling effect when the IC engine is warming up or running slowly and cool it when it is operating at higher temperatures. Hence, ideally a cooling system should maintain a maximum efficient operating temperature.
[00014] There are two types of air cooling systems which are commonly used. Forced air cooling systems and natural air cooling systems. In natural air cooling system, the heat, which is conducted to the outer parts of the cylinder block, is radiated and conducted away by the stream of air, which is obtained from the atmosphere naturally during running of the vehicle. In order to have efficient cooling by means of atmospheric air, fins are provided around the cylinder head and cylinder block which increases the contact area exposed to the atmosphere. In forced air cooling systems, atmospheric air is drawn inside the cooling system from the outer atmosphere through an inlet by using a cooling fan. The rotation of the cooling fan is integrated to the rotation of the rotatable crankshaft. A shroud surrounding the cylinder head, cylinder block and the IC engine guides the atmospheric air thereby cooling it. Hence, the heat generated due to combustion will be conducted to the fins when the air flows over it and the heat will be dissipated to the air flow. The shroud can be made up of multiple parts and usually houses the cooling fan and may have plurality of deflectors to guide the atmospheric air. The shroud will also have vent holes for hot air exit.
[00015] Typically, in a step-through type vehicle, the IC engine is located below the seat at a lower rear portion of the vehicle. There are two side cowls surrounding the IC engine on right and left side of the vehicle. The IC engine is swingably supported by rear suspension system and attached to the frame of the vehicle. Cylinder block, cylinder head and other associated components of such IC engines are enclosed and are heated up during their operation. Since, proper air circulation is lacking around, such IC engines are typically cooled by employing forced air cooling system.
[00016] Generally, to cool the cylinder block, forced air cooling system is used, wherein a centrifugal fan is integrated to the rotation of the rotatable crankshaft. But, this centrifugal fan assembly has many drawbacks such a having more packaging space, utilizing more number of parts which result in high cost. Additionally, the centrifugal type forced air cooling system has the shroud and the cooling fan exposed to harsh outside environment, hence may be subjected to dust, water splash and stone entry. The presence of an external shroud enclosing the IC engine and the cooling fan also affects vehicle styling and looks. Hence, to avoid these drawbacks an axial fan system can be used.
[00017] In axial fan type forced air cooling system, an axial fan is arranged to face the side of the cylinder head and cylinder block. A shroud surrounds the cylinder head and cylinder block and the axial fan is mounted on the shroud such that, the air flow is directed axially inside the shroud. A fan cover is used extending in the axial direction of the cylinder block, and is fixed on the shroud covering the axial fan. The axial fan is usually operably connected to the rotatable crankshaft by means of transmission systems such as gear trains connecting to the crankshaft, flexible belt and pulley drive such as V-belt drives, or even drive transmission with the aid of axial gear on the axial fan meshed with a driving gear affixed to the magneto assembly which is driven by the rotatable crankshaft.
[00018] As highlighted above, an efficient cooling system should maintain the temperature of the cylinder block to optimum working temperature. Too much removal of heat lowers the thermal efficiency of the engine and ineffective removal causes overheating. But, usually in forced air cooling system, the cooling fan is operably connected to the crankshaft and hence this increases the suction of air flow for cooling as the IC engine speed increases irrespective of the engine temperature. In many conditions, rate of cooling needs to be controlled which is difficult if the cooling fan is coupled to the rotatable crankshaft. In traffic conditions where the vehicle is moving through heavy traffic, the IC engine and traction motor may be continuously switched and started and stopped. Also, during cold atmospheric conditions, it is not desirable to circulate cold air at a higher rate of suction as operating temperature may not be maintained. Even during IC engine cold start conditions, the increased volume of cold air can cause delay in IC engine warm up. Additionally, at these conditions relatively large amount of power is used to drive the cooling fan and also cooling is not uniform. Hence, it is desirable to control the operation of the cooling fan based on IC engine cooling requirements.
[00019] The axial fan type forced air cooling systems in state of art is known. In axial fan type forced air cooling systems, effective cooling can be achieved and one can form a compact structure and alleviate drawbacks associated with centrifugal type forced air cooling systems. Yet, such axial fan type forced air cooling systems also face the drawbacks of no control of the cooling fan based on IC engine cooling requirements. The axial fan type forced air cooling systems also have other drawbacks associated with it. There are transmission mechanisms which transmit power to drive the axial fan. Such transmission systems increase complexity and require frequent servicing and additional lubrications. Also, transmission systems that use belt and pulley to transmit power have drawbacks which include belt slippage and loss of belt tension over frequent usage. In order to prevent such slippage, belt tensioner mechanisms can be used, but that will only increase costs and contribute to complexity of parts. Additionally, accommodating all the transmission systems in a small and constrained layout such as a scooter is difficult. Also, the operation of axial fans may sometimes result in noise which is undesirable. Also, axial fan type forced air cooling systems may have many localized portions of the cylinder block which have higher temperature but are cooled ineffectively.
[00020] The present invention aims to alleviate the above mentioned drawbacks and proposes a new axial fan type forced air cooling system for the vehicle, the forced air cooling system being mounted on a bridge mounting bracket disposed between each of a pair of side-tubes of a frame assembly. The bridge mounting bracket is disposed in proximity to an axial fan which is covered by a shroud and the bridge mounting bracket comprising an air inlet opening for entering air in an interior portion of the shroud when the axial fan is in operation.
[00021] With the above design changes, the following advantages can be obtained such as efficient cooling of critical zones, improved air circulation within the shroud, avoiding use of mechanical linkages and avoid lubrication of those mechanical parts, reduced airflow losses within the cooling space, improved heat-dissipating effect, more compact and durable structure, simple in structure, is easy to remove the mounting and maintenance, and adds aesthetic value to contribute to vehicle styling by avoiding the exposure of cooling system to the atmosphere.
[00022] 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.
[00023] Fig. 1 illustrates the two wheeled vehicle in accordance with one embodiment of the present invention. The vehicle 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 slantingly downwards and rearwardly to form a flat “step-through” section 117 extending towards the rear of the two wheeled vehicle and connecting with the pair of side-tubes 109. The step-through section comprises of two support brackets 120 (only rear support bracket shown) at either end. The pair of side-tubes (109a & 109b) are attached to the step-through section of the main tube 107 through a cross bar 107a on the support bracket 120 such that the pair of side-tubes are disposed at either end substantially parallel to each other as viewed from the front of the two wheeled vehicle. The other end of the main tube 107 there is a head tube 102 which is configured to rotatably support a steering tube (not shown). A gusset plate 116 connects the head tube 102 with the main tube 107. A front suspension system 121 is connected at the lower end of the steering tube (not shown). A handlebar support member (not shown) is connected to an upper end of the steering tube (not shown) and supports a handlebar assembly 106 which can rotate both sides. The upper portion of the upper bracket (not shown) comprises of a visor assembly 124 which encloses the handlebar 106, mirror assembly 105, front head light 104 and instrument cluster (not shown). Two telescopic front suspension system 121 (only one is shown) is attached to a bracket (not shown) on the lower part of the steering tube (not shown) on which is supported the 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 (not shown). The pair of side-tubes 109 is attached to the main tube 107 at one end extends rearward in a substantially horizontal direction at the other end as viewed from the front of the two wheeled vehicle. A plurality of cross brackets including a bridge mounting bracket 114 is secured in between the pair of side-tubes 109 to support vehicular attachments including a utility box (100a), a seat 108 and a fuel tank assembly (not shown).
[00024] The two wheeled vehicle further includes a rear wheel 113, a fuel tank (not shown), a pillion hand-rest 118 and seat 108. A left and right rear swing arm bracket (not shown) is pivoted on the U-shaped frame assembly at the rear of the step-through structure 117, and supports a swing arm assembly. The swing arm assembly comprises of the left and right swing arms 115 (only one shown) pivoted to the left and right rear swing arm brackets (not shown), and is capable of swinging vertically about the pivot and supported through two rear wheel suspensions 111 arranged of the rear of the swing arm assembly. Additionally, the swing arm assembly comprises of a front engine mounting cross tube (not shown) attached between the left and right swing arm 115, and a rear engine mounting cross tube 125. The IC engine 101 is mounted between the front engine mounting cross tube (not shown) and the rear engine mounting cross tube 125 such that the IC engine 101 is swingably supported on the swing arm assembly. The rear wheel 113 is connected to rear end of the swing arm assembly and configured to rotate by the driving force of the IC engine 101 transmitted through a belt drive (not shown) from the IC engine 101. A rear fender 110 is covering at least a portion of the rear wheel 113 and it is positioned below the fuel tank (not shown). The electric motor 130 (See Fig. 6) is connected to the rear wheel 113 forming the hub of the rear wheel 113 which can drive it. The electric traction motor 130 draws power from a battery disposed in a suitable location on the hybrid vehicle. The battery can be charged by the IC engine 101 and also be externally charged. The two wheeled vehicle also comprises of plurality of electrical and electronic components including a headlight 104, a taillight 112, a transistor controlled ignition (TCI) unit (not shown), a starter motor (not shown).
[00025] Fig. 1b. illustrates the isometric view of the IC engine mounted on the swing arm assembly attached to the U-shaped frame assembly of the vehicle. The axial type forced air cooling in the IC engine (101) according to the embodiment of the present invention is shown. The bridge mounting bracket 114 is shown, which is secured in between the pair of side-tubes (109a & 109b) to support vehicular attachments including a utility box (100a), a seat 108 and a fuel tank assembly (not shown). The bridge mounting bracket 114 is mounted towards the front of the pair of side tubes 109 and is located in close proximity to the IC engine 101 and is designed such that it is U-shaped and the cylinder head and cylinder block assembly of the IC engine 101 substantially occupies the space below the curved U-shaped bridge mounting bracket 114. The axial type forced air cooling system is mounted over the cylinder head and cylinder block 202 assembly (See Fig. 3, 6); hence the bridge mounting bracket 114 is mounted over the axial type forced air cooling system. In order for the axial type forced air cooling system to work effectively, sufficient air space should be available for the system to draw the air inside the shroud. But the current arrangement prevents sufficient air space around the system. Hence, an opening 114a is provided in the bridge mounting bracket 114 to allow the system to access the air space between the body panel of the vehicle and the pair of side tubes 109. Additionally, due to the low pressure created in the air space between the body panel and the pair of side tube 109, atmospheric air from below the vehicle is drawn in from the atmosphere and occupies its place.
[00026] Fig. 2 illustrates the side view of the IC engine 101 in accordance with the embodiment of the present invention. The IC engine 101 is made up of a cylinder head 201, cylinder block 202 (See Fig. 3 & Fig. 6) and crankcase 203. The axial type forced air cooling system is mounted over the cylinder head 201 and cylinder block 202 such that the axial fan 404 is located in line to high heat zones like spark plug 309 to manage spark plug temperature. This results in cooling air directly impinging the spark plug as soon as it is drawn inside by the axial fan 404. Hence, effective cooling can be obtained. The cylinder head (201) and the cylinder block (202) being forwardly inclined when assembled in the vehicle and a crankshaft axis (Y-Y) of the IC engine (101) is disposed in a vehicle lateral direction (X-X). Further, the axial fan (404) is mounted on the shroud (402) such that a rotary axis of the axial fan (404) is in the vehicle lateral direction (X-X).
[00027] Fig. 3 illustrates the cross-sectional view taken along the line X-X of the IC engine 101 showing the main parts. During operation, the burning of fuel and oxidizer occurs in the combustion chamber and transfers mechanical energy to the reciprocating piston 306. After combustion hot exhaust gases are generated which are expelled out of the cylinder block 202. The combustion of air-fuel mixture in the cylinder block 202 generates a lot thermal energy which increases the temperature of the cylinder block and the air surrounding the cylinder block 202. The cylinder block 202 has extended surfaces to increase the surface area for effective heat dissipation called fins. The fins increase the heat transfer from combustion chamber to outside which is then removed by forced air circulation. The burnt gases after combustion are also very hot and are expelled from the cylinder block 202 through an exhaust port on the cylinder head 201. An exhaust pipe (not shown) is connected to the cylinder head 201, and the exhaust gases are expelled outside the cylinder head 201 through the exhaust pipe (not shown). Hence, the zone around the exhaust pipe connection to the cylinder head 201 is also under increased temperature and requires efficient cooling.
[00028] Fig. 4 illustrates the exploded view of the forced axial fan air cooling according to the embodiment of the present invention. In this embodiment the system comprises the axial fan assembly 400 mounted on the LH shroud 402. The LH shroud 402 is modified to have a circular raised projected area 402a with a plurality of boss portions 402b disposed around its outer periphery. The circular raised projected area 402a is such that, there is space formed at the inner periphery of the LH shroud 402 so as to accommodate an axial fan 404. In one embodiment of the present invention there are three boss portions 402b distributed equidistant to each other on the outer periphery of the circular raised projected area 402a. The boss portion 402b has a hole located at its center with internal threading. A fan cover 401 is mounted externally enclosing the opening. The fan cover 401 is made up of plastic resin material and having a profile similar in dimensions to that of the outer periphery of the circular projected area 402a. The fan cover 401 is adapted to abut the outer periphery of the circular raised projected area 402a. The fan cover 401 also has raised portions 401a projecting axially from the outer circumferential surface of the fan cover. The raised portions 401a also have holes with internal threading and the raised portions are capable of perfectly abutting the boss portions 402b of the LH shroud 402. The hole on the raised portions 401a and the boss portion 402b perfectly match such that they can be attached by using binding means such as nuts and bolts, fasteners 417, 418 etc. The fan cover 401 also comprises of grills 401b enclosing the fan cover to protect the axial fan blades from outside interference and prevent entry of stones and other particles.
[00029] The axial fan 404 comprises a hub 404b which houses an electric motor 406 inside the hub 404b. Plurality of twisted guide vanes 404a project from the hub 404b and project radially outside the hub 404b. The plurality of twisted guide vanes 404a joins an outer cone. The outer cone is circular strip which encloses the central hub with guide vanes inside. The guide vanes 404a twisted such that, when the electric motor 406 rotates, there is pressure difference created between the air behind the fan being at low pressure and air outside the fan being at high pressure. This pressure difference causes the air to get drawn inside the axial fan 404. The twisted shape of the guide vanes 404a and the shape of the fan cover grills twist, guide and draw this air inside which is then directed towards the interior portions (402c) of the shroud 402.
[00030] The hub of axial fan comprises of a bush portion located downstream. The hub bushing mates inside the boss portion 402b of a fan mounting bracket 407. The fan mounting bracket 407 is a single metal bracket which comprises a central annular portion 407a. The inner circumferential surface of the central annular portion 407a has a boss surface which is adapted to mate with the bush portion of the axial fan hub. The central annular portion 407a has a plurality of arms radially projecting outwards and is located equidistant to each other, with a upper-hole located at its end. The arms also have a lower-hole with internal threading located in close proximity to the base of each of the arm close to the central annular portion 407a. The lower-holes are used to secure the axial fan 404 securely with the fan mounting bracket 407 through binding means such as bolts, fasteners 411 etc. The upper-hole has internal threading and the three arms are so equidistantly distributed such that the upper-hole abuts exactly on the internal surface of the boss portions on the internal surface of the LH shroud 402. The arms also have cut-outs which provide additional strength and stiffness, and also act as deflectors to deviate the airflow. The fan mounting bracket 407 is secured to the LH shroud 402 by fasteners 410,412 inserted in the upper-hole and the boss portion. The axial fan system comprising of axial fan 404, fan cover 401 and fan mounting bracket 407 is integrated as a subsystem with the LH shroud 402 or assembled as separate parts. The lower-hole is also additionally used to mount the spark plug deflector 405 within the interior portion (402c) of the LH shroud 402.
[00031] The spark plug deflector 405 is used to divert the cooling air flow 315 to the critical portions of the cylinder block 202. Such critical portions include the area around the spark plug 309 and the heat zone area 505 around the portion wherein the exhaust pipe connects the cylinder block 202. The system in the present embodiment comprises the spark plug deflector 405 and an exhaust deflector 503. The spark plug deflector 405 comprises a central body with a curved profile, with the angle of curvature being almost perpendicular. One end of the central body has a curved profile to deflect the cooling air flow 315 towards the centre of the cylinder block 202 and the other end has two arms with a hole at its end. The two arms are disposed parallel to each other and has cut outs to provide strength and stiffness. The holes on the arms correspondingly mate with the lower-holes provided on the engine mounting bracket 407. The exhaust deflector 503 further improves efficiency of cooling by directing cooling air flow towards the cylinder block 202 walls.
[00032] Fig. 5a illustrates the top cross-sectional view of the cylinder block 202. The figure illustrates the possible path taken by the cooling air 315 flowing through the interior portion (402c) of the shroud. The axial fan 404 draws cooling air 315 inside the shroud and the cooling air enters the interior portions (402c) of the shroud. In the interior portion (402c) of the shroud, the cooling air divides and takes two paths, namely long path 506 around the cylinder head and block assembly cooling the two edges of the cylinder head and block assembly and the short path 507 cooling the substantially the exhaust heat zone 505 of the cylinder head 201. The long path 506 cooling air flow is directed out of the shroud through the exit-vent hole 502. The exit-vent hole 502 is located in one corner of that edge of the RH shroud 403 which encloses the location 505 where the exhaust pipe connects the cylinder head 201. The short path 507 cooling air flow cools the other remaining edge housing the connection between the exhaust pipe and cylinder head 201. The short air path 507 cools the areas and exits through the exhaust-vent hole 501. The entire shroud is optimized with respect to the clearance between the IC engine in all the sides by having more space on less heat zones near the intake of the LH shroud and less space on more heat zones like spark plug 309. The more space zones are further optimized by creating humps (402a and 403b) to have better contact of the air flow with heat zones by avoiding flow reversals. The shroud (402) comprises a hot air exit formed at one edge of the shroud (402) located in close proximity to the heat zone area (505), said hot air exit has a first edge (502a) and a second edge (502b), said first edge (502a) adapted to project outwardly from the outer surface of the shroud (402) such that the first edge (502a) is greater in dimension than the second edge (502b) to form an angularly slanted profile as viewed from the side view of the internal combustion engine (101).
[00033] Fig. 5b. illustrates the enlarged isometric view of the cylinder head 201 and cylinder block 202 of the IC engine 101 along with the axial fan 404 and shroud showing the exhaust system exit according to the embodiment of the present invention. The short air path 507 flows over the heat zone 505 near the exhaust system exit and the hot air exits from the shroud through the exhaust-vent hole 501. However, the problem arises at this location, when the cooling air in short air path 507 flows over the heat zone area 505 to extract heat, the cooling air slowly increases in temperature and becomes hot. The density of this hot air being lighter, and due to the short air path 507 taken, the velocity of the air reduces significantly and the density of the hot air being lighter rises, hence hot air accumulates around the region of the heat zone area 505 and does not exit the exhaust-vent hole 501. To address this problem, the profile of the shroud is curved below the exit-vent hole (see 403a) as seen from the interior portion (402c) of the RH shroud 403. This shape partly directs the cooling air flow from the long path 506 towards the exhaust-vent hole 501. This air flow directed towards the exhaust-vent hole 506 is coming with increased velocity. This is mainly due to more space provided during the cooling air flow long path 506 and due the humps 403b provided near the exit which streamlines the flow, which helps in expelling the hot air accumulation near the exhaust-vent hole 505 helps in airflow deviation & reducing pressure losses. The humps (402a and 403b) are provided in the intake and exit area for better heat transfer between the air flow and engine, and more streamlined motion of the air flow.
[00034] The exit-vent hole (502) is further disposed at the bottom corner edge of the cylinder block and cylinder head surface. The provides the desired curved profile (403a) to increase velocity from the long path 506 and also prevents hot air from the front of the IC engine from entering the exit-vent hole (502) and creating flow reversals. The exit-vent hole 502 is designed to have a circumferential opening, projecting and slanted towards the front to avoid intake cooling air flow 315 and hot air exit to avoid mixing, flowing backwards and increase pressure losses. The design ensures hot air exit is substantially below the two wheeled vehicle and helps change the direction of hot air exit. The exit-vent hole 502 is also maintained flat to vent out more hot air towards the bottom. This avoids hot air flow towards the cabin area heating up the utility box (not shown).
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.