Dual Centrifugal Fan

FIELD OF THE INVENTION

The present invention relates to a cooling system for an internal combustion engine and more particularly to a cooling system employing centrifugal fan(s) in an air-cooled internal combustion engine.

BACKGROUND OF THE INVENTION

The most common type of an internal combustion engine during the present times is an air-cooled engine, comprising a lightweight aluminium engine block, converting chemical energy into mechanical energy by combustion of air-fuel mixture within a combustion chamber of the engine. The said engine, among other components, generally has a cylinder comprising a cylinder head atop the cylinder and receiving a reciprocating piston from the bottom. On combustion of the air-fuel mixture, the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft and setting the vehicle into motion. In this way, the reciprocatory motion of the piston is converted to rotatory motion of the crankshaft which ultimately powers the vehicle.
Such an internal combustion engine produces significant amount of heat during the course of its operation. It is thus important to keep the engine temperature within the operable limit. So an engine is provided with cooling fins integrated around engine cylinder to dissipate accumulated heat generated from combustion and component friction within the engine. These cooling fins increase the surface area coming in contact with the air and hence help in engine cooling.

Sometimes the location of such an internal combustion engine in a two wheeler or a three wheeler is such that it requires forced air cooling to keep the engine temperature within the operable limit. To this end, the engine is generally provided with a single fan, mounted directly on an extension of the crankshaft, externally of the crankcase, for routing cool atmospheric air towards the engine surface as natural air is not directed properly towards the engine in sufficient volume to adequately cool the engine. The fan rotates at the same speed as that of crankshaft. External to this fan, a shroud or cover is provided to cover the engine and containing an opening which allows the cool atmospheric air into the shroud. The walls of the shroud direct the flow of air towards the hot engine surface(s) including cylinder head.

Usually in the aforementioned forced air cooling system, the cool atmospheric air is drawn axially inside the shroud opening through the centrifugal fan, and forced in radial direction towards the hot engine surface. As a result, the proximate surface(s) of the engine nearer to the fan is sufficiently cooled while the remote surface(s) of the engine farther from the fan is starved of the cool air.

Such cooling systems have various drawbacks when overall uniform cooling of the complete engine is desired. Firstly, in the entire process the direction of the incoming air changes from axial at the fan inlet to radial at the fan outlet. The proximate engine surface(s) nearer to the fan, which sees the incoming air from the fan, is cooled properly whereas the engine remote surface(s) far from the fan is scarcely cooled due to pressure drop and reduced air velocity at this surface. The uneven cooling of the engine from the front to the rear results in a high temperature gradient thereby reducing the cooling efficiency. A high temperature gradient may also result in failure of engine components and affects engine performance.
Secondly the scope for improvement in air flow rate is limited by fan design. At a given engine speed, the fan has a given air flow rate. When high flow rates are required the aforementioned cooling system fails to deliver the desired cooling output. Thirdly only a single fan can be used at a time in this type of cooling system thereby limiting the cooling capacity enhancement and fourthly surface area of cooling fins is generally higher in the single fan cooling system. The present invention is directed to overcoming one or more problems as set forth above.

SUMMARY OF THE INVENTION

It is hence an object of the present invention to provide an improved, efficient and uniform cooling system for uniform cooling of an internal combustion engine from two sides directly from the air flow of the fan, in a two wheeler or a three wheeler. To this end, the subject matter described herein, in accordance with an embodiment of the present subject matter thereof, relates to a dual centrifugal fan cooling system to minimize the temperature gradient along the engine surface which involves at least two fans, preferably of centrifugal type, mounted on the either side of the crankshaft of the engine.

Another aspect of the present invention is to provide a dual centrifugal fan cooling system for uniform cooling of an internal combustion engine where the said system is customizable for employing fans with different blade types. Yet another aspect of the present invention is to provide a fan cooled engine including a means for directing air toward the engine head as well as other engine components, the invention resulting in a light weight engine thereby resulting in incidental cost advantage.

The foregoing objectives and summary provide only a brief introduction to the present subject matter. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. However, it should be understood that the detailed description while indicating preferred embodiment(s) of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features, aspects, and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:

Figure 1 shows a side view of a typical two wheeler capable of accommodating the present invention.

Figure 2 shows a schematic diagram of prior art engine cooling system for an internal combustion engine showing shroud with single centrifugal fan.

Figure 3 depicts a dual centrifugal fan cooling system enclosed in the shroud mounted on the engine crankshaft according to an embodiment of the present invention.

Figure 4 shows the dual centrifugal fan system mounted on the crankshaft without the shroud.

Figure 5 shows an isometric view of the dual centrifugal cooling fan system wherein the shroud and other components are not shown.

Figure 6 illustrates heat transfer coefficient variation on the front and back side of the engine surfaces in prior art and in this invention.

Detailed description of the invention

The subject matter described herein relates to a cooling system for cooling an internal combustion engine wherein at least two centrifugal fans are mounted on either side of the crankshaft of the engine. Various other features of the cooling system according to the present invention here will be discernible from the following further description thereof set out hereunder.

In the ensuing exemplary embodiments, the vehicle is a scooter type motorcycle. However it is contemplated that the disclosure in the present invention may be applied to any automobile capable to hosting the dual centrifugal fan cooling system without defeating the spirit of the invention. Further "front" and "rear", and "left" and "right" wherever used in the ensuing description for the illustrated embodiment refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the vehicle and looking forward. Furthermore, a longitudinal axis refers to a front to rear axis relative to the vehicle, while a lateral axis refers generally to a side to side, or left to right axis relative to the vehicle.

The present invention is now described in detail in connection with the rendered drawings. It should be noted that like elements are denoted by the same reference numerals throughout the description. The detailed explanation of the constitution of parts other than the invention which constitutes an essential part has been omitted at opportune places.

Figure 1 illustrates the side view of the scooter type motorcycle with a swinging engine. Typically such a vehicle includes a body frame assembly made up of several tubes welded together which usually supports the body of the said vehicle. The vehicle has a steerable anterior wheel 110 and a driven rear wheel 111 driven by driving force generated by a power unit. The frame assembly 101 of the straddle ride type vehicle with the swinging power unit is an elongated structure, which typically extends from a forward end to a rearward end of the vehicle. It is generally convex in shape, as viewed from a side elevational view. The said frame assembly 101 includes a main frame and may also have a sub-frame. The sub-frame is attached to the main frame using appropriate joining mechanism. The frame assembly 101 includes a head tube and a down tube that extends downward from head tube. The frame assembly is covered by a plurality of vehicle body covers including a front panel 115, a leg shield 116, an under seat cover 117 and a side panel 112.

A handlebar assembly 105 and a seat assembly 106 are supported at opposing ends of the frame assembly and a generally open area is defined there between known as floorboard 107 which functions as a step through space. A fuel tank that stores fuel that is supplied to the engine is disposed at the rear end of the vehicle above the rear wheel. It is present on the upper side of the power unit along with a fuel tank cap. The seat for a driver and a pillion is placed forward to the fuel tank (not shown) and rearwardly of the floorboard 107. A muffler is provided to the right side of the rear wheel, and connects to the engine. A side stand fixed to the left side of the body frame supports the vehicle such that vehicle inclines to the left side. Typically, front 103 and rear 114 suspension assemblies are operatively positioned between the front 110 and rear 111 wheels and the frame assembly. The front suspension assembly 103 commonly is a telescopic fork arrangement while the rear suspension assembly 114 is a hydraulic damped arrangement.

In the said vehicle, the rear suspension swing arm typically supports the power unit which is configured to drive the rear wheel 111 of the vehicle. The power unit is structured such that an engine 102 and a swing case 108, which are well known for this form of straddle type vehicle, are integrally constructed. In an embodiment of the present invention, the engine is a four stroke single cylinder engine and the swing case 108 is connected to a left side surface of a crankcase of the engine 102 so as to extend forward.

It is disposed on the vehicle frame with one end of the swing case 108 attached to the rear wheel hub in such a way that the power unit is substantially angularly disposed to the ground. The engine 102 is arranged horizontally, that is, its crankshaft is placed at right angles to the longitudinal direction of the vehicle body. Since the basic construction of an engine is known to those versed in the art, the details have been omitted. The said power unit is surrounded by a shroud or a covering with a fan to enhance forced cooling of the power unit. This covering present over the power unit is known as cooling cowl (not shown) and may be made of plastic resin or the likes.

Figure 2 indicates a cooling system according to the prior art. A centrifugal fan 201 is mounted directly on the crankshaft (not shown) externally of the crankcase which runs along with the engine 102. The said fan 201 is surrounded by a shroud 202. The fan 201 is positioned relatively to the shroud 202 such that it may bring cool atmospheric air from the external environment into the shroud or through a grated opening 205 in the shroud 202. The fan 201 is mounted on a crankshaft by conventional means and is operative when the engine 102 is on, the fan running at engine speed.

When in operation, the fan 201 sucks cool atmospheric air axially from one end of the opening 205 of the shroud 202 and forces it in radial direction i.e. the fan blades rotate causing the air to enter the fan near the crankshaft and move perpendicularly from the said shaft. In the entire process, the direction of the flowing air changes from axial at the fan inlet to radial at the outlet 206. Furthermore, the shape of the shroud 202 is such that the sucked air from the fan is forced to move around the engine surfaces including the engine cylinder head 204 and the engine cylinder block 203 to increase the cooling and hence the engine is cooled by forced air flow.

However, the incoming air mainly cools a proximate engine surface 207 (front surface) near to the fan 201 and facing towards it. The air velocity reduces and pressure drops by the time air travels the length of the engine and reaches a remote engine surface 208 present on the opposite side of the proximate engine surface 207. Therefore the remote engine surface 208 is not sufficiently cooled leading to a high temperature gradient which is undesirable. To this end, in the present invention, a dual centrifugal fan cooling system is mounted on the crankshaft is described that would facilitate the cooling of engine surfaces from both the sides.

Figure 3 shows an embodiment of the present invention illustrating the present subject matter which is capable to be accommodated in the scooter type motorcycle described above. At least two centrifugal fans 301, 302 are mounted on the extended section of a crankshaft 303 of the engine 102. The shroud 202 is mounted on the engine substantially enclosing the engine 102 and the centrifugal fans. The shroud 202 has at least two grated openings (or air inlets), 205a and 205b respectively to enable entry of air into the shroud 202 from both sides. Upon engine operation, the rotation of the each fan is such that they suck cool atmospheric air from the external environment through the respective grated opening and force it towards the engine cylinder head 204 and cylinder block 203. Additionally the mounting of the fans is such that they are located internal to the shroud but external to a crankcase (not shown) of the engine 102.

In an aspect of the present invention, one centrifugal fan 301 sucks the air through the opening 205a in the shroud 202 and forces it towards the proximate surface(s) 207 housing the engine cylinder 203 whereas the other centrifugal fan 302 sucks the air simultaneously through the opening 205b in the shroud 202 and forces it towards the remote surface(s) 208 so that both the surfaces of the engine get uniform cooling. Both the fans 301, 302 rotate at the same speeds and simultaneously. The speed of rotation of the fans is directly proportional to the speed of the crankshaft 303.

The laterally sucked air traverses the engine length on either side and cools the proximate surface as well as the remote surface of the engine and exits the shroud 202 from the outlet 206. There can be various outlet positions at different locations on the shroud depending on the need. The outlet, in this embodiment thereof, is positioned along the longitudinal axis of the vehicle near to the engine cylinder head 204 so as to enable faster exit of the amalgamating air reaching from both the openings. The said outlet 206 can also be positioned on top of the cylinder head 204 behind the vehicle seat 106. In another embodiment of the present invention devoid of the outlet 206, one fan can be used to suck air and other fan can be used like an exhaust fan i.e. throwing out the air from the shroud.

It is to be noted that out of the two, one centrifugal fan (for e.g., 301) is mounted on the magneto which is the dry side of the crankcase of the engine. The crankshaft coming out from this side has no problem related to oil leakages from the crankcase. However, when a fan is provided on other side of the crankshaft (for e.g., 302) which is the oil side, oil leakage problem can be avoided by providing proper design of oil seals.

Figure 4 shows front view of the dual centrifugal fan mounted on the crankshaft. Other components are not shown. Different combination of fan types can be used to suite the cooling needs. For example, both the fans can have forward curved blades if higher air flow rates are desired. However, combination of backward and forward curved blades can also be used for better efficiency depending upon the system requirements.

Figure 5 shows the isometric view of the present invention according to an embodiment. The two fans mounted on the extension of the crankshaft force air towards engine from both the sides resulting in uniform temperature distribution with substantial reduction in average engine operating temperature.
Figure 6 illustrates a graph showing the temperature variation on the proximate and remote engine surfaces plotted against the position on the engine. Data points on the proximate and remote surface of the engine were marked and the temperatures were recorded. It is noticed that proximate surface 207 is having higher temperature compared to the remote surface 208 in prior art i.e. engine with single fan. When dual centrifugal fan cooling system as per the present invention is used, temperature drop on the remote surface increased significantly and it matches the temperature drop of proximate surface. Further, there is significant decrease in the overall engine temperature with dual fan when compared to single fan.

This results in significant drop in temperature gradients when dual fan cooling system is used.

It will be appreciated that the present subject matter and its equivalent thereof offers many advantages, including those which are described henceforth. The advantage of using dual centrifugal fan based cooling system is that the effective mass flow rate of the cooling air increases manifold. Hence, fans with less capacity can also be used to reduce engine power consumption.

Another major advantage of this invention is that the heat transfer coefficient can be enhanced significantly on the engine surfaces. In other words, temperature gradient along the respective engine surfaces can be reduced significantly. Furthermore a significant reduction in absolute temperature of the engine is achieved due to which thermal efficiency of the engine can be improved significantly which is not possible in the prior art. Consequent to the present invention, the surface area of the cooling fins can be reduced substantially to meet the same cooling requirements. This will result in significant reduction in engine mass and hence a light weight engine can be designed.

The present invention is thus described. The terms and expressions in this specification are of description and not of limitation and do not exclude any equivalents of the features illustrated and described, but it is understood that various other embodiments, modifications, substitutions, changes and equivalents are also possible without departing from the scope and ambit of the present invention which will now become apparent to those skilled in the art from this detailed description. Accordingly, the description is to be
understood as an exemplary embodiment and reading of the invention is not intended to be taken restrictively.

We claim:

1. A cooling system for uniform cooling of an air cooled internal combustion engine comprising:

a shroud for substantially covering the said internal combustion engine further comprising of at least two openings, preferably in the lateral direction, to allow the atmospheric air into the shroud, and at least two fans, preferably of centrifugal type, mounted on an extension of a crankshaft of the said engine on either side of the crankshaft, the said fans being external to a crankcase and internal to the said shroud in such a way that the fans are placed immediately behind the respective openings in the shroud, wherein one fan cools a proximate surface of the said engine whereas the other fan cools a remote surface of the said engine, both fans working simultaneously to suck in the atmospheric air into the shroud and rotating proportional to the rotating speed of the crankshaft.

2. The cooling system as claimed in claim 1, wherein the blades of both the said fans are adapted to suck cool atmospheric air from the external environment and direct it to the respective proximate and remote surfaces of the engine.

3. The cooling system as claimed in claim 1, wherein the said cooling system also comprises at least one outlet in the shroud for allowing the hot air leave the shroud, the said outlet preferably located on top of the shroud portion covering cylinder head of the said engine.

4. A dual centrifugal fan cooling system for cooling an air cooled internal combustion engine comprising:

a shroud for substantially covering the said internal combustion engine further comprising of at least two openings, preferably in the lateral direction to allow the atmospheric air into the shroud, and at least two fans mounted on an extension of a crankshaft of the said engine on either side of the crankshaft, the said fans being external to a crankcase and internal to the said shroud in such a way that the fans are placed immediately behind the respective openings in the shroud,

wherein one of the said fans suck the cool atmospheric air from the external environment into the shroud for cooling the engine surfaces and the other fan capable to act as an exhaust fan for throwing the hot air from the shroud, depending upon their blade types, both fans working simultaneously and rotating proportional to the rotating speed of the crankshaft.

5. A motorcycle having a cooling system as claimed in any of the preceding claims.

6. A cooling system for cooling an air cooled internal combustion engine substantially as claimed in any of the preceding claims and illustrated with reference to the accompanying drawings.