DESC: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 forced air cooling system employed to cool the internal combustion engine of the saddle type vehicle.

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.
[00011] Fig. 6. illustrates the block diagram of the axial fan system according to the embodiment of the present invention.
[00012] Fig. 7. illustrates the method flowchart of the axial fan system to determine the thermal state of the internal combustion engine according to the embodiment of the present invention.
[00013] Fig. 7a. illustrates the determinant status for various conditions of Engine running status & ignition switch status.

DETAILED DESCRIPTION
[00014] 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.
[00015] 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.
[00016] 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.
[00017] 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.
[00018] 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.
[00019] 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.
[00020] 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.
[00021] 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.
[00022] 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.
[00023] The present invention aims to alleviate the above mentioned drawbacks and proposes anew axial fan type forced air cooling system for the vehicle which can provide an independent and intermittent spot forced air cooling system for the cylinder head and cylinder block of the IC engine. This is achieved by using an axial fan system to utilize the advantages provided by using the axial fan system and controlling its operation based on the thermal state and speed of the IC engine and operating state of the electric traction motor. The axial fan system is implemented by eliminating any transmission mechanism operably connecting the axial fan system to the rotatable crankshaft. The present invention also aims to improve cooling system effectiveness by enhancing interior shroud area, deviate air towards critical cooling zones in cylinder head and cylinder block, and to improve hot air discharge and optimize to reduce pressure losses.
[00024] 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, automatic and convenient operation, 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.
[00025] 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.
[00026] 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 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 (not shown), a seat 108 and a fuel tank assembly (not shown).
[00027] 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).
[00028] 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 system according to the embodiment of the present invention is shown arranged to cover a part of the IC engine 101. 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 (not shown), 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.
[00029] 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.
[00030] 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.
[00031] 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.
[00032] The axial fan 404 comprises a hub which houses an electric motor 406 inside the hub. Plurality of twisted guide vanes project from the hub and project radially outside the hub. The plurality of twisted guide vanes joins an outer cone. The outer cone is circular strip which encloses the central hub with guide vanes inside. The guide vanes 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 and the shape of the fan cover grills twist, guide and draw this air inside which is then directed towards the interior portions of the shroud.
[00033] The hub of axial fan comprises of a bush portion located downstream. The hub bushing mates inside the boss portion 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 of the LH shroud 402.
[00034] 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.
[00035] 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 of the shroud. The axial fan 404 draws cooling air 315 inside the shroud and the cooling air enters the interior portions of the shroud. In the interior portion 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 and a second edge, said first edge adapted to project outwardly from the outer surface of the shroud (402) such that the first edge is greater in width than the second edge to form an angularly slanted profile as viewed from the side view of the internal combustion engine (101).

[00036] 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 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.
[00037] 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 angular 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).
[00038] Fig. 6 illustrates the system block diagram of a system to determine the thermal state of the IC engine 101 and operating state of the electric traction motor 130 according to the embodiment of the present invention. The operation of this system comprises of various stages to supply and regulate power to the electric motor 406 in order to control the forced air cooling based on the thermal state of the IC engine and operating state of the electric traction motor 130.
[00039] The major elements of the system comprise the IC engine 101, a controller unit 601, an ignition switch 603 which functions as a control switch, the electric traction motor 130 and a battery 604. On operating the ignition switch, the rider of the hybrid vehicle selects the operational mode of the hybrid vehicle on the drive mode selector. Based on the selection, the drive mode selector starts the IC engine 101 or the electric traction motor. The IC engine 101 drives the rear wheel 113 of the hybrid vehicle through an end transmission means 606. A magneto assembly 301 is operably connected to the rotatable crankshaft 305 and configured to generate electric current which is sent to the battery 604 located at a suitable location in the vehicle to recharge it. This power from the battery 604 is used to drive the cooling system controller unit 601 which further drives the electric motor 406 forming part of the hub of the axial fan 404 and the electric traction motor 130. The power from the battery 604 to the electric motor 406 is regulated by a controller unit 601. The battery 604 also drives the electric traction motor 130 and can be recharged externally. The controller unit 601 comprises of a processor and a memory. Among other capabilities the processor is configured to fetch and execute computer-readable instructions which denote the method to operate the above system stored in the memory. The controller unit 601 is also powered by the battery 604, and the entire system is switched on to be operated only on the operation of an ignition switch 603 by the rider of the two wheeled vehicle. The IC engine 101 also comprises of one or more sensors configured to extract IC engine operational data to detect the thermal state of the IC engine. The magneto assembly 301 comprises a speed sensor 607 to detect the speed of the vehicle. The battery 604 also comprises a battery voltage measurement device 608 to measure the battery capacity. In the present embodiment, there is a temperature sensor 602 located in close proximity to the lubricating oil recirculation located in the cylinder block 202 which can continuously measure the lubricating oil temperature. It is to be noted that, the present embodiment is by no means a limitation and measurement of any parameter with the aid of one sensor or plurality of sensors located at any of the locations of the IC engine and/or the two wheeled vehicle which is capable to determining the thermal state of the IC engine can be implemented without deviating from the scope of the present invention.
[00040] The control of the cooling fan electric motor 406 forming part of the hub of the axial fan 404 depends on the temperature of the cylinder head 201 and cylinder block 202, the speed of the vehicle and the battery capacity. The temperature of the cylinder block 202 and the speed of the vehicle in turn depends on the operating conditions of the two wheeled vehicle and the outside atmospheric conditions. Such conditions occur for example during slow movement during heavy traffic, movement on a gradient surface, and cold start conditions. This operating temperature state is continuously measured by the temperature sensor 602 by measuring the lubricating oil and the speed is continuously measured by the speed sensor 607. The battery capacity is also continuously monitored when the hybrid vehicle is operating in electric mode. These measurements are continuously transmitted to the controller unit 601. Based on these input signals, the controller unit 601 will switch-off the electric motor 406 by cutting off the power supply. The axial fan 404 will stop operating and the cooling does not take place. This will have a positive effect on the IC engine and help increase the operating temperature as heat removal is stopped. The required operating temperature is reached, the lubricating oil temperature increases which are monitored by the controller unit 601 through the temperature sensor 602. Once, the optimum operating temperature is reached, the controller unit 601 switches on the electric motor 406 thus switching on the axial fan 404 and begin the air cooling. Further, based on the input from speed sensor 607 and the battery capacity measurement device 608, the speed of rotation of the axial fan 404 can also be controlled and monitored. Thus, with this intermittent operation of the axial fan 404 as compared to continuous operation, the IC engine cooling is efficient and performance is improved.
[00041] Fig. 7 illustrates a methodology to measure the thermal state of the IC engine having the axial fan forced air cooling system. The method may be described in the general context of computer executable instructions, and communications sent and received to other elements in the system. Generally, computer executable instructions can include routines, methods, programs, objects, components, data structures, procedures, modules, functions, and the like that perform particular functions or implement particular abstract data types. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method, or alternate methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the present invention described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof as will be explained in another embodiment. Furthermore, the method can be implemented in other similar systems albeit with a few variations as will be best understood by a person skilled in the art.
[00042] Fig. 7a. illustrates the determinant status for various conditions of Engine running status & ignition switch status. Figure 7a illustrates various conditions under which the axial fan is switched ON. According to one embodiment of the present invention, the axial fan is switched ON when either the temperature is above a pre-determined value or the engine is ON.
[00043] The ignition switch is actuated by the driver of the two wheeled vehicle in method block 701, the controller unit 601 is powered on to control the operation of the axial fan 404. The method comprises of two major steps that must be taken, namely the measuring condition 702, 703 and check condition 710. The measuring condition comprises plurality of method blocks, wherein the controller unit 601 receives IC engine operational data such as engine temperature data, engine speed data, and battery capacity data in method block 702 from the temperature sensor 602, speed sensor 607 and battery measuring device 608. The controller unit 601 then executes the check condition 710. The check condition 710 collectively comprises of a plurality of steps represented as method blocks. In the check condition, the controller unit 601 compares the received temperature data to a first predetermined value, secondly the controller unit 601 determines the IC engine mode or electric mode of the hybrid vehicle and based on speed data and battery capacity controls the speed of the axial fan 404. Based on the state so determined, the controller unit 601 will send a suitable signal to switch the axial fan to ON state or OFF state and also control its speed. The method represented by the two steps effectively controls the axial fan, thus providing intermittent and independent spot cooling to the cylinder block.
[00044] The check condition 710 comprises the following steps. At block 703 the controller unit 601 determines whether the temperature so received at block 702 is greater than a first predetermined value. In one embodiment of the present invention the first predetermined value is 90 degrees centigrade. It is known in theory that for a two wheeled vehicle having a single cylinder engine swingably supported and having the cylinder block enclosed within side cowls, the temperature generated at normal operation is within a range of 90 degrees centigrade to 120 degrees centigrade. Hence, the IC engine is maintained at operating working temperature if the cooling system is actuated at the above range of temperature. If the answer to the determination in block 703 is no, block 711 is proceeded to. In block 711 the controller unit 601 transmits a first signal to switch OFF the axial fan. The axial fan 404 at block 712 receives the first signal and switches OFF. Subsequently, the check condition is exited, and the measuring condition at block 702 is repeated. If the answer to the determination at block 703 is yes, the next step to block 704 is proceeded to. At block 703 it is to be noted that irrespective of IC engine being switched off or switched on or running in electric mode, the condition loop in block 703 is executed as long as ignition switch is on. At block 704 the controller unit 601 determines by receiving the drive selector signal, whether the vehicle is in IC engine mode or electric mode.
[00045] If the determination is that the vehicle is in electric mode, then condition proceeds to block 709. Here, the controller unit 601 determines the battery capacity based on the battery capacity sensor. The battery capacity is compared to a second predetermined range. If the battery capacity exceeds the second predetermined range then, the speed of the axial fan is made to run in full capacity by the controller unit 601. In one embodiment, the second predetermined range is between voltage V1 to V2 where V2 is greater than V1, and the full capacity of the fan runs at “S” rpm. Hence, if the battery capacity exceeds V2, then the fan will run at full capacity of “S” rpm. If the battery capacity is within the second predetermined range in between V1 & V2, then the axial fan is driven at “d1” % less of its full capacity “S” by the controller unit 601. Here the fan speed is running at “S1” rpm. If battery capacity is below the second predetermined range V1, then the axial fan is driven at further “d2” % less of its full capacity by the controller unit 601. Here the fan speed is running at “S2” rpm when the battery capacity is below V1. In the embodiment of the present invention, the battery voltage can range from 12.5V to 48V. Hence, at block 708 the controller unit 601 accordingly sends a second signal to switch on and vary the speed of the axial fan 404. In an another embodiment, the temperature input is analyzed, and the fan will run at full capacity of “S” rpm even if the battery capacity is between the second predetermined range in-between V1 & V2, if the temperature is excessively higher such as for example temperatures exceed a value of “T” degrees centigrade.
[00046] If the determination at block 704 is IC engine mode, then block 705 is proceeded to. Here, the controller unit 601 determines the engine speed based on the engine speed sensor 607. The engine speed is compared to a third predetermined range “U3”. If the engine speed exceeds the third predetermined range “U3”, then, the speed of the axial fan is made to run in least capacity (fan speed RPM “S3”) by the controller unit 601. Here the third predetermined range is from “U1” rpm to “U2” rpm (U2 is greater than U1). Hence, if the engine speed exceeds U2 rpm, then the fan will run at its least capacity of S3 rpm. If the vehicle speed is within the third predetermined range U3, then the axial fan is driven at d3 % less of its full capacity “S” by the controller unit 601. If vehicle speed is below the third predetermined range U3, then the axial fan is driven at its full capacity (fan speed of S rpm) by the controller unit 601. Hence, at block 706 the controller unit 601 accordingly sends a third signal to switch on and vary the speed of the axial fan 404. Subsequently, the check condition is exited, and the measuring condition at block 702 is repeated. It is necessary to mention that the parameters d1, d2 & d3 may vary based on the engine size, vehicle layout and the parameters d1, d2 or d3 may be different for controlling the fan speed based on the battery voltage, engine temperature and engine speed.
[00047] With the above method, it can be seen that, at all conditions wherein the IC engine is at an increased thermal state the axial fan can be switched on and switched off and its speed can be controlled. The control of the axial fan is completely dependent on the engine thermal state and the engine speed/battery capacity. Hence, during conditions such as engine idling wherein the IC engine is at idling but the temperature is high, or during engine soaking condition wherein the engine is switched off by operation of ignition switch (not in ignition lock state) or kill switch the thermal state of the cylinder block can exceed above operating temperatures and hence may require cooling. The present invention envisages operating in those conditions as well unlike cooling systems proposed in prior arts which are dependent on crankshaft rotation. Hence, due to continuous monitoring of the temperature data by the controller unit 601, it is possible to have intermittent and independent spot cooling of the engine cylinder block.
[00048] 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. A forced air cooling system to perform cooling of a cylinder head (201) and a cylinder block (202) assembly of an internal combustion (IC) engine (101) of a saddle type vehicle, said forced air cooling system comprising:
a shroud (402) arranged to cover at least a portion of the internal combustion engine (101) including the cylinder head (201) and cylinder block (202) assembly;
one or more sensors (602, 607, 608) to acquire two wheeled vehicle operational data;
an axial fan (404) mounted on the shroud (402), and said axial fan (404) adapted to introduce air axially into the interior portion of the shroud (402) covering the cylinder head (201) and cylinder block (202) assembly;
characterized in that:
the axial fan (404) driven by a centrally hub mounted electric motor (406), said electric motor (406) is controlled by a controller unit (601), said controller unit (601) configured to continuously receive two wheeled vehicle operational data from said one or more sensors (602, 607, 608) to determine the thermal state of the internal combustion engine (101), speed of the internal combustion engine (101) and capacity of a battery supplying power to the electric motor (406), and the controller unit (601) selectively controlling the electric motor (406) based on said vehicle operational data received from said one or more sensors (602, 607, 608).
2. The forced air cooling system as claimed in claim 1 wherein the shroud (402) directs forced air coming from the axial fan (404) towards the spark plug (309) side of the cylinder head.
3. The forced air cooling system as claimed in claim 1, wherein the shroud (402) has an integrated fan mounting bracket (407) for mounting said axial fan (404) and the fan mounting bracket (407) secured to shroud (402) using suitable fasteners (410, 412).
4. The forced air cooling system as claimed in claim 1, wherein the controller unit (601) selectively controls at least one of an enabling and disabling of the axial fan (404).
5. The forced air cooling system as claimed in claim 1 or claim 2, wherein the controller unit (601) in addition to selectively controlling one of enabling and disabling of the axial fan (404) also controls the speed of rotation of the axial fan (404).
6. The forced air cooling system as claimed in claim 1 or 2, wherein said at least one of the sensor (602, 607, 608) is selected from a group comprising an engine speed sensor (607) disposed on a magneto assembly (301) of the IC engine (101), an engine oil temperature sensor (602) disposed within a crankcase (203) of the internal combustion engine (101), and a battery capacity sensor (608) disposed on the battery (604)
7. A forced air cooling system for a saddle type vehicle, wherein the saddle type vehicle comprises of:
an exhaust pipe connected to the cylinder head (201) and adapted to allow exhaust gases to be removed from the internal combustion engine (101) thereby creating a heat zone area around the junction of attachment of the exhaust pipe to the cylinder head (201);
a frame assembly comprising a main-tube (107) and a pair of side-tubes (109), each of the pair of side-tubes (109) parallel to each other and attached to one end of the main-tube (107) by a cross bar, and said internal combustion engine (101) swingably mounted on the pair of side-tubes (109);
a seat assembly (108);
a utility box; and
a bridge mounting bracket (114) disposed between each of said pair of side-tubes (109); the bridge mounting bracket (114) is disposed in proximity to the axial fan (404) mounted on the shroud (402), said bridge bracket (114) configured to support the utility box and the seat assembly 108;
characterized in that:

the bridge mounting bracket (114) comprises an air inlet opening (114a) to allow easy access of the air to enter the interior portion of the shroud (402) when the axial fan (404) is in operation.
8. The forced air cooling system as claimed in claim 1, wherein 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 and a second edge, said first edge adapted to project outwardly from the outer surface of the shroud (402) such that the first edge is greater in width than the second edge to form an angularly slanted profile as viewed from the side view of the internal combustion engine (101).
9. The forced air cooling system as claimed in claim 1 or claim 5, wherein the shroud (402) further comprises an exhaust opening to permit the passage and attachment of the exhaust pipe, said exhaust opening is made substantially larger than the heat zone area (505).
10. The forced air cooling system as claimed in claim 1, wherein at least one deflecting member (405) is mounted downstream of the axial fan (404) on the interior portion of the shroud (402), and said at least one deflecting member (405) adapted to change the path of air in the interior portion of the shroud (402).
11. A method for controlling an axial fan (404) of a forced air cooling system of a two wheeled vehicle, said method comprising steps of:
receiving of vehicle operational data from one or more sensors (602, 607, 608) on the internal combustion engine (101) by a controller unit (601),
receiving of an engine power signal; actuated by a drive mode selector; by the controller unit (601),
determining, by the controller unit (601) whether the temperature is greater than a first predetermined value, and if the temperature is not greater than a first predetermined value, then transmitting a first signal to switch “OFF” an axial fan (404);
determining, by the controller unit (601) if the temperature is greater than a first predetermined value, when at least one of the internal combustion engine (101) is powered “ON” and ignition switch is “ON” then the controller unit (601) transmitting the signal to switch “ON” and control the speed of the axial fan (404).
12. The method for controlling an axial fan (404) of a forced air cooling system of a two wheeled vehicle as claimed in claim 11 wherein the receiving of vehicle operational data and providing signal to the electric motor (406) is performed on a real time basis.
13. The method for controlling an axial fan (404) of a forced air cooling system of a two wheeled vehicle as claimed in claim 11 wherein the operator of the engine actuates drive mode selector to select the mode of driving of the vehicle.
14. The method for controlling an axial fan (404) of a forced air cooling system of a two wheeled vehicle as claimed in claim 11 or claim 12 wherein the controller unit (601) decides the amount of electric power to be sent to the electric motor based on the vehicle operational data.
15. The method for controlling an axial fan (404) of a forced air cooling system of a two wheeled vehicle as claimed in claim 11 wherein the controller unit (601) receives the temperature parameter through sensor mounted at at least one of the cylinder block and cylinder head (202, 202a), engine speed parameter through sensor mounted at the magneto (301) and the state of charge of battery through sensor mounted in a battery management system (608).
16. The forced air cooling system for a saddle type vehicle as claimed in claim 7 wherein the 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).

17. A forced air cooling system to perform cooling of a cylinder head (201) and a cylinder block (202) assembly of an internal combustion (IC) engine (101) of a saddle type vehicle, said forced air cooling system comprising:
a shroud (402) arranged to cover at least a portion of the internal combustion engine (101) including the cylinder head (201) and cylinder block (202) assembly;
characterized in that:
the shroud (402) has an axial fan (404) mounted on the shroud (402) and the axial fan (404) is adapted to introduce air axially into the interior portion of the shroud (402) covering the cylinder head (201) and cylinder block (202) assembly; and
the axial fan (404) is mounted over the cylinder head (201) and cylinder block (202) and the axial fan (404) is located in line to spark plug (309).
18. The forced air cooling system as claimed in claim 16 wherein axial fan (404) comprises of a hub and a bush portion, the bush portion located in downstream of air flow and the bush portion mating inside the boss portion of a fan mounting bracket (407).
19. The forced air cooling system as claimed in claim 16 wherein the axial fan (404) comprising a fan cover (401) and fan mounting bracket (407) integrated as a subsystem with a portion of shroud (402).
20. The forced air cooling system as claimed in claim 17 wherein the fan cover (401) is adapted to abut the outer periphery of the circular raised projected area (402a) of the shroud (402).