CN113864035A - Cooling system for internal combustion engine and method thereof - Google Patents

Abstract

A plurality of sensors (602,607,608) are used to acquire two-wheeled vehicle operation data. An axial fan (404) is mounted on the shroud and adapted to axially introduce air into an interior portion of the shroud (402) covering the cylinder head (201) and cylinder block (202) assembly. The axial fan is driven by a central hub mounted motor (406) controlled by a controller unit (601). The controller unit is configured to continuously receive two-wheeled hybrid vehicle operational data from the sensors to determine a thermal state of the internal combustion engine, a speed of the internal combustion engine, and a capacity of a battery for supplying controlled power to the electric motor (406). Therefore, the forced cooling system controls the operation of the cooling fan at the target position based on the IC engine cooling demand.

Description

Cooling system for internal combustion engine and method thereof

The invention is a divisional application of Chinese patent application with the priority date of 2017, 3 and 9 and the application number of 201810196595.0, wherein the invention name of the divisional application is 'a cooling system for an internal combustion engine and a method thereof' filed in 2018, 3 and 9.

Technical Field

The present invention generally relates to two-wheeled or three-wheeled seat vehicles. More particularly, the present invention relates to a forced air cooling system employed to cool an internal combustion engine of a vehicle of the saddle type.

Background

Vehicles utilize power from both an Internal Combustion (IC) engine and an electric motor to drive them. The chemical energy of the fuel is converted into mechanical energy by an engine that burns the fuel using an oxidant (air), and a battery powers the motor. One type of vehicle is a straddle-type two-wheeled vehicle. During operation of the IC engine, combustion of the fuel and oxidant occurs in the combustion chamber and transfers mechanical energy to the reciprocating piston. This operation generates a large amount of thermal energy in and around the cylinder head and the cylinder block. This heat energy can increase the temperature of the IC engine and the atmosphere surrounding it. Therefore, there is a need to cool the cylinder head, cylinder block, its associated components, and the ambient air. Two-wheeled straddle-type vehicles typically employ a body panel surrounding the IC engine such that the cylinder head and cylinder block are completely enclosed within the scooter body portion and vehicle components. Therefore, for such two-wheeled vehicles, an additional forced air cooling system needs to be employed for cooling the IC engine. Typically, such forced air cooling systems include a fan operatively connected to the crankshaft, and the fan forces air to flow through a shroud surrounding the IC engine. The fan may be of the centrifugal or axial type and may be located near the crankshaft or near the cylinder head and block. Axial fans are advantageous because they work on partial cooling and cool the internal combustion engine more efficiently. Conventionally, the axial fan is operatively coupled to the IC engine crankshaft, so that when the IC engine is in operation, the axial fan runs continuously, and the rotational speed is dependent on the speed on the crankshaft. Such cooling systems have serious drawbacks and impact on the styling of the vehicle, including improper cooling, more packaging space, extra parts count, and difficulty in servicing. In hybrid vehicles, additional cooling issues are faced due to changing operating modes due to the driver's operation in various modes during a single cycling cycle.

Drawings

The detailed description is illustrated by reference to the accompanying drawings. The same reference numbers are used throughout the drawings to reference like features and components.

Fig. 1a shows a side view of a two-wheeled vehicle employing an embodiment of the present invention.

FIG. 1b shows an isometric view of an internal combustion engine mounted on a frame assembly of a two-wheeled vehicle employing an embodiment of the present invention.

Fig. 2 shows a side view of an internal combustion engine employing an embodiment of the invention.

FIG. 3 illustrates a cross-sectional view (X-X) of an internal combustion engine showing an axial fan and shroud, according to an embodiment of the present invention.

FIG. 4 illustrates an exploded view of an axial fan and shroud according to an embodiment of the present invention.

Fig. 5a shows a cross-sectional view (Y-Y) of the cylinder block and the axial fan and shroud of the internal combustion engine according to an embodiment of the invention.

Fig. 5b shows an enlarged isometric view (Z) of the cylinder block and axial fan assembly and shroud of an internal combustion engine showing the exhaust system outlet in accordance with an embodiment of the present invention.

FIG. 6 shows a block diagram of an axial fan system according to an embodiment of the invention.

FIG. 7 illustrates a flow chart of a method of an axial fan system for determining a thermal condition of an internal combustion engine according to an embodiment of the present invention.

Fig. 7a shows the decision states for various conditions of the engine operating state and the ignition switch state.

Detailed Description

Various features and embodiments of the invention will be apparent from the further description that follows. According to one embodiment, an Internal Combustion (IC) engine as described herein operates in four cycles for a hybrid vehicle. Such an IC engine is mounted in a straddle-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 the present invention. Also, "front" and "rear" and "left" and "right" mentioned in the following description of the illustrated embodiments refer to forward and backward and left and right directions as viewed from the rear of the IC engine and viewed forward.

The IC engine includes a cylinder head, a reciprocating piston positioned within the cylinder block below the cylinder head, a combustion chamber formed between the cylinder block and the cylinder head, a rotatable crankshaft for transferring mechanical energy to a drive train, and a connecting rod that transfers energy applied to the reciprocating piston to the rotatable crankshaft. During operation of the IC engine, combustion of the air-fuel mixture occurs within the combustion chamber. This operation generates a large amount of thermal energy inside and around the cylinder head and the cylinder block, which increases its temperature and the temperature of the atmosphere surrounding it. Therefore, the cylinder head, the cylinder block and its associated components and the ambient air need to be cooled by a cooling system.

Although cooling of the cylinder head and cylinder block of the IC engine is necessary, excessive cooling is not desirable because it reduces the thermal efficiency of the IC engine. Therefore, the goal of any cooling system is to keep the engine operating at the most efficient operating temperature. It should be noted that the engine is very inefficient when cold and therefore the cooling system is designed in such a way that we need to maintain the actual overall operating temperature of the cylinder block. Therefore, the cooling system should ideally reduce the cooling effect when the IC engine is warmed up or operating slowly, and cool it when it is operating at a higher temperature. Thus, ideally, the cooling system should maintain the highest effective operating temperature.

There are two commonly used air cooling systems. Forced air cooling systems and natural air cooling systems. In the natural air cooling system, heat conducted to the outside of the cylinder block is radiated and conducted away by an air flow naturally obtained from the atmosphere during the running of the vehicle. For efficient cooling by atmospheric air, fins are provided around the cylinder head and the cylinder block, which increases the contact area exposed to the atmosphere. In forced air cooling systems, atmospheric air is drawn into the cooling system from the outside atmosphere through an inlet by using a cooling fan. The rotation of the cooling fan is integrated with the rotation of the rotatable crankshaft. The shroud surrounding the cylinder head, cylinder block and IC engine directs atmospheric air to cool it. Thus, heat generated due to combustion will be conducted to the fins as the air flows over the fins, and the heat will be dissipated to the air flow. The shroud may be made up of multiple parts and typically houses a cooling fan and may have a plurality of baffles to direct atmospheric air. The shield also has vent holes for hot gas to exit.

Typically, in a straddle-type vehicle, the IC engine is positioned under the seat, at the lower rear of the vehicle. There are two side hoods surrounding the IC engine on the left and right sides of the vehicle. The IC engine is swingably supported by the rear suspension system and attached to a frame of the vehicle. The cylinder block, cylinder head and other related components of such an internal combustion engine are closed and heated during operation thereof. Such internal combustion engines are typically cooled using a forced air cooling system due to lack of adequate air circulation around them.

Generally, in order to cool the cylinder block, a forced air cooling system is used in combination, in which a centrifugal fan is integrated with the rotation of the rotatable crankshaft. However, such centrifugal fan assemblies have many drawbacks, such as having more packaging space, utilizing a greater number of components, and resulting in high costs. In addition, centrifugal forced air cooling systems have shrouds and cooling fans that are exposed to the harsh external environment and, therefore, may be affected by incoming dust, water splash, and rocks. The presence of an external shroud enclosing the IC engine and cooling fan can also affect vehicle styling and appearance. Therefore, to avoid these drawbacks, an axial fan system may be used.

In the axial fan type forced air cooling system, an axial fan is disposed to face a side portion of the cylinder head and the cylinder block. A shroud surrounds the cylinder head and the cylinder block, and an axial fan is mounted on the shroud such that the air flow is directed axially within the shroud. The fan cover is used to extend in the axial direction of the cylinder block and is fixed to a shroud that covers the axial flow fan. The axial fan is typically operatively connected to the rotatable crankshaft by a transmission system such as a gear train connected to the crankshaft, a flexible belt and belt drive such as a V-belt drive, or even a drive transmission by means of an axial gear on the axial fan that meshes with a drive gear fixed to a magneto assembly driven by the rotatable crankshaft.

As highlighted above, an effective cooling system should maintain the temperature of the cylinder block at the optimum operating temperature. Too much heat removal reduces the thermal efficiency of the engine and ineffective removal results in overheating. However, typically in forced air cooling systems, the cooling fan is operatively connected to the crankshaft, and thus increases the suction force for the cooling air flow as the IC engine speed increases regardless of engine temperature. In many cases, if the cooling fan is coupled to the rotatable crankshaft, it is necessary to control the cooling speed, which is difficult. In traffic conditions where the vehicle is traveling through congested traffic, the IC engine and traction motors may be continuously switched and started and stopped. Also, under cold atmospheric conditions, it is undesirable to circulate cold air at a higher suction rate, as the operating temperature may not be maintained. The increased amount of cold air may cause a delay in warming up the IC engine even under the IC engine cold start condition. In addition, under these conditions, a relatively large amount of power is used to drive the cooling fan, and the cooling is also not uniform. Therefore, it is desirable to control the operation of the cooling fan based on the IC engine cooling requirements.

Axial fan forced air cooling systems are known in the art. In the axial fan type forced air cooling system, efficient cooling can be achieved and a compact structure can be formed and the drawbacks associated with the centrifugal type forced air cooling system can be alleviated. However, such axial fan forced air cooling systems also suffer from the drawback of not being able to control the cooling fan based on the IC engine cooling requirements. Axial fan forced air cooling systems also have other drawbacks associated with them. There is a transmission mechanism that transmits power to drive the axial flow fan. Such transmission systems add complexity and require frequent maintenance and additional lubrication. Moreover, transmission systems that use belts and pulleys to transmit power have drawbacks, including belt slip and loss of belt tension with frequent use. To prevent such slippage, a belt tensioning mechanism may be used, but this only adds cost and may result in component complexity. In addition, it is difficult to accommodate all of the transmission systems in small and limited layouts, such as scooters. Also, the operation of the axial flow fan sometimes causes noise, which is undesirable. Also, the axial fan type forced air cooling system may have many local portions of the cylinder block which have a high temperature but are inefficiently cooled.

The present invention aims to alleviate the above-mentioned drawbacks and proposes a new axial fan forced air cooling system for vehicles that can provide an independent and intermittent local forced air cooling system for the cylinder head and cylinder block of an IC engine. This is achieved by using an axial fan system that takes advantage of the benefits provided by using an axial fan system and controls the operation of the IC engine based on its thermal state and speed and the operating state of the electric traction motor. The axial fan system is implemented by eliminating any gearing mechanism that operably connects the axial fan system to the rotatable crankshaft. The present invention also aims to increase cooling system efficiency by enhancing internal shroud area, biasing air towards critical cooling areas in the cylinder head and block, and to improve hot gas emissions and optimize to reduce pressure losses.

By the above design change, the following advantages can be obtained: such as efficient cooling of critical areas, improved air circulation within the shroud, avoidance of mechanical connections and lubrication of those mechanical components, reduced airflow losses in the cooled space, improved heat dissipation, a more compact and durable structure, simplicity of construction, automated ease of operation, ease of removal for installation and maintenance, and added aesthetic value by avoiding exposure of the cooling system to the atmosphere to aid in vehicle styling.

The invention, as well as all the accompanying embodiments and other advantages thereof, will be described in more detail in connection with the accompanying drawings in the following paragraphs.

FIG. 1a shows a two-wheeled vehicle according to one embodiment of the present invention. The vehicle includes a generally U-shaped frame that provides a generally open central area to allow a rider to "step" on the vehicle. Typically, the frame includes 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 obliquely downward and rearward to form a flat "striding" section 117 extending toward the rear of the two-wheeled vehicle and connected to a pair of side tubes 109. The stride section includes two support brackets 120 at both ends (only the rear support bracket is shown). A pair of side tubes (109a and 109b) are attached to the stride section of the main tube on the support bracket 120 such that the pair of side tubes are arranged at both ends substantially parallel to each other as viewed from the front of the two-wheeled vehicle. The other end of the main pipe 107 has a head pipe 102, and the head pipe 102 is configured to rotatably support a steering pipe (not shown). Gusset 116 connects head pipe 102 with main pipe 107. The front suspension system 121 is connected to the lower end of a steering tube (not shown). A handlebar support member (not shown) is connected to an upper end of the steerer tube (not shown) and supports a handlebar assembly 106, which is rotatable on both sides. The upper portion of the upper bracket (not shown) includes a visor assembly 124 that surrounds the handlebar 106, the rearview mirror assembly 105, the headlamp 104 and the instrument cluster (not shown). Two telescoping front suspension systems 121 (only one shown) are attached to a bracket (not shown) on the lower portion of a steering tube (not shown) on which the front wheels 119 are supported. The upper portion of the front wheel 119 is covered by a front fender 103 mounted to the lower portion of a steering shaft (not shown). A pair of side tubes 109 is attached to the main tube 107 at one end and extends rearward in a substantially horizontal direction at the other end when viewed from the front of the two-wheeled vehicle. A plurality of cross braces including bridge mounting brackets 114 are secured between a pair of side tubes 109 to support vehicle accessories, including utility boxes (not shown), seats 108, and fuel tank assemblies (not shown).

The two-wheeled vehicle further includes rear wheels 113, a fuel tank (not shown), a rear armrest 118, and a seat 108. Left and right rear swing arm brackets (not shown) are pivotally mounted to the U-shaped frame at the rear of the stride structure 117 and support the swing arm assemblies. The swing arm assembly includes left and right swing arms 115 (only one shown) pivotally mounted to left and right rear swing arm brackets (not shown) and is vertically swingable about a pivot point and supported by two rear wheel suspensions 111 disposed at the rear of the swing arm assembly. In addition, the swing arm assembly includes a front engine mount cross tube (not shown) attached between the left and right swing arms 115, and a rear engine mount cross tube 125. The IC engine 101 is mounted between a front engine mounting cross tube (not shown) and a rear engine mounting cross tube 125 such that the IC engine 101 is swingably supported on a swing arm assembly. The rear wheel 113 is connected to the rear end of the swing arm assembly, and is configured to rotate by the driving force of the IC engine 101 transmitted via a belt driving device (not shown) from the IC engine 101. The rear fender 110 covers at least a portion of the rear wheel 113 and is located below a fuel tank (not shown). An electric traction motor 130 (see fig. 6) is connected to the rear wheel 113, forming a hub that can drive the rear wheel 113. Electric traction motors 130 draw electric power from batteries disposed in appropriate locations on the hybrid vehicle. The battery may be charged by the IC engine 101 and may also be charged from the outside. The two-wheeled vehicle also includes a plurality of electrical and electronic components including a headlight 104, a tail light 112, a Transistor Controlled Ignition (TCI) unit (not shown), and a starter motor (not shown).

FIG. 1b shows an isometric view of an IC engine mounted on a swing arm assembly attached to a U-shaped frame assembly of a vehicle. An axial forced air cooling system according to an embodiment of the present invention is shown arranged to cover a portion of an IC engine 101. A bridge mounting bracket 114 is shown secured between a pair of side tubes (109a and 109b) to support vehicle accessories, including utility boxes (not shown), seat 108, and fuel tank assemblies (not shown). The bridge mounting bracket 114 is mounted toward the front of the pair of side pipes 109 and is positioned next to the IC engine 101, and is designed such that it is U-shaped, and the cylinder head and cylinder block assembly 101 of the IC engine 101 substantially occupies the space below the bent U-shaped bridge mounting bracket 114. The axial forced air cooling system is mounted above the cylinder head and cylinder block 202 assembly (see fig. 3, 6); the bridge mounting bracket 114 is thus mounted above the axial forced air cooling system. For an axial forced air cooling system to work effectively, the system should have sufficient air gap available to draw air within the shroud. But the current arrangement prevents a sufficient air gap around the system. Thus, an opening 114a is provided in the bridge mounting bracket 114 to allow the system to access the air gap between the body panel of the vehicle and the pair of side tubes 109. In addition, due to low pressure generated in the air gap between the vehicle body panel and the pair of side pipes 109, atmospheric air from below the vehicle is drawn from the atmosphere and occupies its position.

Fig. 2 shows a side view of an IC engine 101 according to an embodiment of the invention. The IC engine 101 is composed of a cylinder head 201, a cylinder block 202 (see fig. 3 and 6), and a crankcase 203. The axial forced air cooling system is mounted above the cylinder head 201 and cylinder block 202 such that the axial fan 404 is positioned in alignment with a high heat zone such as spark plug 309 to manage spark plug temperature. This results in cooling air directly impinging on the spark plug once it is drawn inside by the axial fan 404. Thus, efficient cooling can be achieved.

Fig. 3 shows a sectional view taken along line X-X of the IC engine 101, showing the main parts. During operation, combustion of the fuel and oxidant occurs in the combustion chamber and mechanical energy is transferred to the reciprocating piston 306. After combustion, hot exhaust gas is produced that exits the cylinder block 202. The combustion of the air-fuel mixture in the cylinder block 202 generates a large amount of thermal energy, which increases the temperature of the air around the cylinder block and the cylinder block 202. The cylinder block 202 has an extended surface, called a fin, to increase the surface area for effective heat dissipation. The fins increase the heat transfer from the combustion chamber to the outside, which is then removed by forced air circulation. The combustion gas after combustion is also very hot and is discharged from the cylinder block 202 through the exhaust port on the cylinder head 201. An exhaust pipe (not shown) is connected to the cylinder head 201, and exhaust gas is discharged out of the cylinder head 201 through the exhaust pipe (not shown). Therefore, the area around the exhaust pipe connected to the cylinder head 201 is also at an elevated temperature and requires effective cooling.

FIG. 4 shows an exploded view of forced axial fan air cooling according to an embodiment of the present invention. In this embodiment, the system includes an axial fan assembly 400 mounted on a LH shroud 402. LH shroud 402 is modified to have a circular raised protruding area 402a around the outer periphery of which a plurality of protruding portions 402b are arranged. The circular raised area 402a makes a space formed at the inner periphery of the LH shroud 402 to accommodate the axial flow fan 404. In one embodiment of the present invention, there are three raised portions 402b that are equally spaced from each other on the outer periphery of the circular raised area 402 a. The protruding portion 402b has a hole with an internal thread at the center thereof. The fan cover 401 is installed to close the opening from the outside. The fan cover 401 is made of a plastic resin material and has a contour having a size similar to the outer peripheral size of the circular projection area 402 a. The fan housing 401 is adapted to abut the outer periphery of the circular raised area 402 a. The fan cover 401 also has a convex portion 401a axially protruding from the outer circumferential surface of the fan cover. The bulge portion 401a also has an internally threaded hole, and the bulge portion can perfectly abut against the protruding portion 402b of the LH shroud 402. The holes on the boss portion 401a and the protrusion portion 402b are perfectly matched so that they can be attached by using a connecting means such as nuts and bolts, fasteners 417, 418, and the like. The fan housing 401 also includes a grill 401b that closes the fan housing to protect the axial fan blades from external interference and to prevent the ingress of rocks and other particles.

The axial fan 404 includes a hub within which a motor 406 is received. A plurality of twisted guide blades project from the hub and project radially outward of the hub. A plurality of twisted guide vanes are connected to the outer cone. The outer cone is an annular band which surrounds a central hub, with the guide blades located inside the outer cone. The guide vanes are twisted so that when the motor 406 rotates, a pressure differential is created between the air behind the fan at low pressure and the air outside the fan at high pressure. This pressure difference causes air to be drawn inside the axial flow fan 404. The twisted shape of the guide vanes and the shape of the fan shroud grille twist, directing and drawing this air into the interior and then directing the air towards the interior portion of the shroud.

The hub of the axial fan comprises a downstream bushing portion. The hub sleeve fits within the raised portion of the fan mounting bracket 407. The fan mounting bracket 407 is a single metal bracket that includes a central annular portion 407 a. The inner circumferential surface of the central annular portion 407a has a protruding surface adapted to cooperate with a bushing portion of an axial fan hub. The central annular portion 407a has a plurality of arms projecting radially outward and positioned equidistant from each other, and has an upper hole at its end. The arms also have a lower bore with internal threads that is located immediately adjacent the base of each arm, near the central annular portion 407 a. The lower holes are used to securely fix the axial fan 404 and the fan mounting bracket 407 together by means of attachment means such as bolts, fasteners 411, and the like. The upper hole has an internal thread and the three arms are equally spaced such that the upper hole just abuts on the inner surface of the protruding portion on the inner surface of LH shroud 402. The arms also have cutouts that provide additional strength and rigidity, and also act as deflectors that deflect the airflow. Fan mounting bracket 407 is secured to LH shroud 402 by fasteners 410,412 inserted into the upper holes and bosses. The axial fan system including axial fan 404, fan case 401, and fan mounting bracket 407 is integrated with LH shroud 402 as a subsystem or assembled as a separate component. The lower bore also serves to mount spark plug deflector 405 within the interior portion of LH shroud 402.

The spark plug deflector 405 is used to divert the cooling air flow 315 to the critical portion of the cylinder block 202. These key portions include the area around the spark plug 309 and the hot zone area 505 around the portion where the exhaust pipe is connected to the cylinder block 202. The system in this embodiment includes a spark plug deflector 405 and an exhaust deflector 503. The spark plug deflector 405 includes a central body having a curved profile with an angle of curvature that is nearly vertical. One end of the center body has a curved profile to deflect the cooling air flow 315 toward the center of the cylinder block 202, and the other end has two arms with holes at their ends. The two arms are arranged parallel to each other and have cutouts to provide strength and rigidity. The holes in the arms are correspondingly mated with the lower holes provided in the engine mounting bracket 407. The exhaust deflector 503 further improves cooling efficiency by directing the cooling airflow toward the wall of the cylinder block 202.

Fig. 5a shows a top cross-sectional view of cylinder block 202. This figure illustrates a possible path taken by cooling air 315 flowing through the interior portion of the shroud. The axial fan 404 draws cooling air 315 into the shroud and the cooling air enters the inner portion of the shroud. In the inner portion of the shroud, the cooling air splits into two paths, a long path 506 around the cylinder head and block assembly, cooling both edges of the cylinder head and block assembly, and a short path 507 substantially cooling the exhaust hot zone 505 of the cylinder head 201. A long path 506 of cooling air flow is directed out of the shroud through the outlet vent 502. The outlet vent hole 502 is located in one corner of the lower edge of the RH shroud 403 surrounding the location 505 where the exhaust pipe connects to the cylinder head 201. The short path 507 of the cooling air flow cools the other remaining edge of the connection that is accommodated between the exhaust pipe and the cylinder head 201. Short air path 507 cools these areas and exits through exhaust vent 501. By having more space on fewer hot zones near the intake of the LH shroud and less space on more hot zones such as spark plug 309, the entire shroud is optimized with respect to the clearance of the IC engine between all sides. The shroud (402) includes a hot air outlet formed at one edge of the shroud (402) located proximate to the hot zone region (505), the hot air outlet having a first edge and a second edge, the first edge adapted to project outwardly from an outer surface of the shroud (402) such that a width of the first edge is greater than a width of the second edge to form an angularly sloped profile when viewed from a side view of the internal combustion engine (101).

Fig. 5b shows an 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 outlet according to an embodiment of the invention. Short air path 507 flows through hot zone 505 near the exhaust system outlet and hot air exits the shroud through exhaust vents 501. However, when the cooling air in the short air path 507 flows through the hot zone area 505 to extract heat, the temperature of the cooling air slowly rises and becomes hot, which is problematic at this location. The density of this hot air is lighter and, due to the short air path 507, the velocity of the air is significantly reduced and the density of the lighter hot air increases, whereby the hot air accumulates near the location of the hot zone region 505 and cannot exit the exhaust vent 501. To address this issue, the profile of the shroud curves under the outlet vent (see 403a), as seen from the interior portion of the RH shroud 403. This shape partially directs the cooling air flow from the long path 506 toward the exhaust vents 501. This flow of air directed toward the exhaust vents 501 occurs with increased velocity. This is primarily due to the more space provided during the cooling air flow over the long path 506 and due to the ridges 403b disposed near the outlets that streamline the flow, which help to expel the hot air that accumulates near the exhaust vents 505, helping to avoid airflow deviation and reduce pressure losses. Ridges (402a and 403b) are provided in the inlet and outlet regions for better heat transfer between the air flow and the engine and more streamlined motion of the air flow.

The outlet vent (502) is further disposed at a bottom corner edge of the cylinder block and cylinder head surface. This provides a desirable curved profile (403a) to increase the exit velocity from the long path 506 and also prevents hot air from the front of the IC engine from entering the outlet vent (502) and creating a blow back. The outlet vents 502 are designed with angled openings, projecting and sloping toward the front to avoid cooling air flow 315 from entering and hot air from exiting to avoid mixing, back flow and increasing pressure losses. This design ensures that the hot air outlet is substantially below the two-wheeled vehicle and helps to change the direction of the hot air outlet. The outlet vents 502 also remain flat to vent more heated air toward the bottom. This avoids the flow of hot air heating the utility box (not shown) towards the cabin area.

FIG. 6 illustrates a system block diagram of a system to determine the thermal state of the IC engine 101 and the operating state of the electric traction motors 130, according to an embodiment of the present invention. The operation of the system includes multiple stages of supplying and regulating power to the electric motor 406 to control forced air cooling based on the thermal state of the IC engine and the operating state of the electric traction motor 130.

The main elements of the system include the IC engine 101, the air unit 601, the ignition switch 603 serving as a control switch, the electric traction motor 130, and the battery 604. When the ignition switch is operated, a rider of the hybrid vehicle selects an operation mode of the hybrid vehicle on the drive mode selector. Based on this selection, the drive mode selector starts the IC engine 101 or the electric traction motor. The IC engine 101 drives the rear wheels 113 of the hybrid vehicle through an end transmission 606. The magneto assembly 301 is operably connected to a rotatable crankshaft 305 and is configured to generate an electric current that is sent to a battery 604 located at a suitable location in the vehicle to charge it. This power from the battery 604 is used to drive the cooling system controller unit 601, which further drives the electric motor 406 and the electric traction motor 130, the electric motor 406 forming part of the hub of the axial fan 404. Power from the battery 604 to the motor 406 is regulated by the controller unit 601. The battery 604 also drives the electric traction motor 130 and can be externally charged. The controller unit 601 includes a processor and a memory. The processor is configured to, among other capabilities, retrieve and execute computer readable instructions stored in the memory to indicate a method of operating the above-described system. The controller unit 601 is also supplied with electric power from a battery 604, and the entire system is turned on to operate only when a rider of the two-wheeled vehicle operates an ignition switch 603. IC engine 101 also includes one or more sensors configured to extract IC engine operating data to detect a thermal condition of the IC engine. The magneto assembly 301 includes a speed sensor 607 to detect the speed of the vehicle. Battery 604 also includes a battery voltage measurement device 608 to measure battery capacity. In the present embodiment, a temperature sensor 602 capable of continuously measuring the temperature of the lubricating oil is located in close proximity to the lubricating oil circulating device located in the cylinder block 202. It should be noted that the present embodiment is by no means a limitation or a measurement of any parameter with the help of a sensor or sensors located at any position of the IC engine and/or the two-wheeled vehicle, which enables a determination of the thermal state of the IC engine without departing from the scope of the invention.

The control of the cooling fan motor 406, which forms 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 are in turn dependent on the operating conditions of the two-wheeled vehicle and the external atmospheric conditions. These conditions occur, for example, during traffic congestion, movement over terraced surfaces, and slow movement under 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. Battery capacity is also continuously monitored while the hybrid vehicle is operating in the electric mode. These measurements are continuously transmitted to the controller unit 601. Based on these input signals, the controller unit 601 will disconnect the motor 406 by cutting off the power supply. The axial fan 404 will stop operating and cooling will not occur. This will have a positive effect on the IC engine and help to increase the operating temperature when heat rejection stops. The desired operating temperature is reached and the lube oil temperature is increased, which is monitored by the controller unit 601 via the temperature sensor 602. Once the optimum operating temperature is reached, the controller unit 601 switches on the electric motor 406, thereby switching on the axial fan 404 and starting the air cooling. Further, based on inputs from the speed sensor 607 and the battery capacity measurement device 608, the rotational speed of the axial fan 404 can also be controlled and monitored. Thus, under intermittent operation of the axial fan 404, IC engine cooling becomes efficient and performance is improved as compared to continuous operation.

FIG. 7 illustrates a method of measuring a thermal condition of an IC engine having an axial fan forced air cooling system. The method may be described in the general context of computer-executable instructions and communications that are transmitted to and received by other elements in a 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 an alternate method. In addition, individual blocks may be deleted from the method without departing from the spirit and scope of the invention described herein. Furthermore, the method can be implemented in any suitable hardware, software, firmware, or combination thereof, as will be explained in relation to another embodiment. Moreover, the method can be implemented in other similar systems, although with minor modifications, as can be best understood by those skilled in the art.

Fig. 7a shows determination states of various conditions of the engine operating state and the ignition switch state. Fig. 7a shows various conditions under which the axial fan is switched on. According to an embodiment of the present invention, the axial flow fan is turned on when the temperature is higher than a predetermined value or the engine is started.

In method block 701, the ignition switch is actuated by the driver of the two-wheeled vehicle, and the controller unit 601 is energized to control the operation of the axial fan 404. The method comprises two main steps that have to be taken, namely measuring conditions 702, 703 and checking condition 710. The measurement conditions include a number of method blocks, where in method block 702, controller unit 601 receives IC engine operation data, such as engine temperature data, engine speed data, and battery capacity data, from temperature sensor 602, speed sensor 607, and battery measurement device 608. The controller unit 601 then performs a check condition 710. The check condition 710 generally includes a number of steps represented as method blocks. In the check condition, the controller unit 601 compares the received temperature data with a first predetermined value, and second, the controller unit 601 determines the IC engine mode or the electric mode of the hybrid vehicle, and controls the speed of the axial flow fan 404 based on the speed data and the battery capacity. Based on the determined state, the controller unit 601 will send a suitable signal to switch the axial fan to the on state or the off state, and also to control its speed. The method represented by these two steps effectively controls the axial flow fan, thereby providing intermittent and independent localized cooling of the cylinder block (spot cooling).

The check condition 710 includes the following steps. In block 703, the controller unit 603 determines whether the temperature accepted in block 702 is greater than a first predetermined value. In one embodiment of the invention, the first predetermined value is 90 degrees celsius. It is theoretically known that the temperature generated under standard operation is in the range of 90 to 120 degrees celsius for a two-wheeled vehicle having a swingably supported single cylinder engine and having a cylinder block enclosed in a side cowl. Thus, if the cooling system is activated at the above temperature range, the IC engine is maintained at the operating temperature. If the answer is no for the determination in block 703, proceed to block 711. At block 711, the controller unit 601 transmits a first signal to turn off the axial fan. At block 712, the axial fan 404 receives the first signal and turns off. Subsequently, the checking condition is exited and the measuring condition is repeated at block 702. If the answer to the determination in block 703 is yes, the next step continues to block 704. At block 703, it should be noted that the conditional loop in block 703 is executed whenever the ignition is on, regardless of whether the IC engine is on or off or operating in electric mode. At block 704, the controller unit 601 determines whether the vehicle is in the IC engine mode or the electric mode by receiving the drive selector signal.

If it is determined that the vehicle is in electric mode, then the condition continues 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 a second predetermined range, the controller unit 601 will cause the speed of the axial fan to operate at maximum capacity. In one embodiment, the second predetermined range is between voltages V1 and V2, where V2 is greater than V1, and the maximum capacity of the fan is operating at "S" rpm. Thus, if the battery capacity exceeds V2, the fan will run at maximum capacity "S" rpm. If the battery capacity is between the second predetermined range, V1 and V2, then the axial fan is driven by the controller unit 601 less than its maximum capacity "S" "'d 1" ". Here, the fan speed is running at "S1" rpm. If the battery capacity is below the second predetermined range V1, the axial fan is driven by the controller unit 601 less than its maximum capacity "S" "'d 2" ". Here, when the battery capacity is lower than V1, the fan speed is operated at "S2" rpm. In embodiments of the present invention, the battery voltage can range from 12.5V to 48V. Accordingly, at block 708, the controller unit 601 responsively asserts a second signal to turn on the axial fan 404 and vary the speed of the axial fan 404. In another embodiment, the temperature input is analyzed if the temperature is too high (e.g., the temperature exceeds the value "T" degrees celsius), and the fan will operate at maximum capacity "S" rpm even if the battery capacity is between the second predetermined range, V1 and V2.

If the IC engine mode is determined in block 704, then proceed to block 705. 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", the controller unit 601 operates the speed of the axial fan at a minimum capacity (fan speed "S3" RPM). Here, the third predetermined range ranges from "U1" rpm to "U2" rpm (U2 is greater than U1). Thus, if the engine speed exceeds U2rpm, the fan will be running at its minimum capacity S3 rpm. If the vehicle speed is within the third predetermined range U3, the axial fan is driven by the controller unit 601 at less than its maximum capacity "S" d 3%. If the vehicle speed is below the third predetermined range U3, the axial fan is driven at its maximum capacity (fan speed of Srpm) by the controller unit 601. Accordingly, at block 706, the controller unit 601 responsively asserts the third signal to turn on the axial fan 404 and vary the speed of the axial fan 404. Subsequently, the checking condition is exited and the measuring condition is repeated at block 702. It is important to mention that the parameters d1, d2, and d3 may vary based on engine size, vehicle layout, and that the parameters d1, d2, and d3 may differ to control fan speed based on battery voltage, engine temperature, and engine speed.

It can be seen from the above method that under all conditions, in which the IC engine is in an elevated thermal state, the axial fan can be switched on and off, and its speed can be controlled. Control of the axial fan is completely dependent on engine thermal conditions and engine speed/battery capacity. Thus, during engine shutdown conditions (where the IC engine is shut down but the temperature is high), for example, or during engine submerged conditions (where the engine is turned off by operation of an ignition switch (not in an ignition-locked state) or a kill switch), the thermal state of the cylinder block can exceed the operating temperature and thus cooling may be required. The present invention also contemplates operation under these conditions, unlike the cooling systems proposed in the prior art, which depend on crankshaft rotation. Thus, intermittent and independent local cooling of the engine block may be achieved due to the continuous monitoring of the temperature data of the controller unit 601.

Many modifications and variations of the present subject matter are possible in light of the above disclosure. Therefore, within the scope of the claimed subject matter, the disclosure may be practiced other than as specifically described.

Claims (7)

1. A forced air cooling system for cooling a cylinder head (201) and cylinder block (202) assembly of an Internal Combustion (IC) engine (101) of a saddle-type vehicle, the 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;

the method is characterized in that:

the shroud (402) having an axial fan (404) mounted on the shroud (402), and the axial fan (404) being adapted to axially introduce air into an interior portion of the shroud (402) covering the cylinder head (201) and cylinder block (202) assembly; and

the axial fan (404) is mounted above the cylinder head (201) and cylinder block (202), and the axial fan (404) is positioned in alignment with a spark plug (309).

2. A forced air cooling system according to claim 1, wherein the shroud (402) directs forced air from the axial fan (404) towards the spark plug (309) side of the cylinder head.

3. A forced air cooling system according to claim 1, wherein the shroud (402) has an integral fan mounting bracket (407) to mount the axial fan (404), and the fan mounting bracket (407) is fixed to the shroud (402) with suitable fasteners (410, 412).

4. A forced air cooling system according to claim 1, wherein at least one deflecting member (405) is mounted on the inner part of the shroud (402) downstream of the axial fan (404), and said at least one deflecting member (405) is adapted to alter the path of the air in the inner part of the shroud (402).

5. A forced air cooling system according to claim 1, wherein the axial fan (404) comprises a hub and a bushing portion, the bushing portion being located downstream of the air flow and the bushing portion fitting within a boss portion of the fan mounting bracket (407).

6. A forced air cooling system according to claim 1, wherein the axial fan (404) comprising the fan housing (401) and the fan mounting bracket (407) is integrated as a subsystem with a part of the shroud (402).

7. A forced air cooling system according to claim 6, wherein the fan housing (401) is adapted to abut the outer periphery of the circular raised area (402a) of the shroud (402).

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