Cooling fan for an Internal Combustion Engine

Field of the Invention:

The present invention relates to "Cooling fan for Internal Combustion Engine". In particular this invention relates to cooling fan mounting method for internal combustion engine.

Background of the Invention:

Generally centrifugal fans are used for cooling engines in automotive industry. With demand of high power engines, cooling requirements of the engines are also increasing. Centrifugal fans are used to deliver high velocity air to cool the engines. Among many parameters like fan blade inlet - outlet angles, blade length, number of blades and blade thickness, the number of blades is an important parameter that affect the fan cooling performance. Higher number of blades increases the fan mass flow rates proportionally. In the known prior art the fan mounting system incorporating screws, leads to cutting of the blades, which in turn reduces the effective number of blades on the fan. This reduces the fan cooling efficiency and hence reduces heat-dissipating capacity. The cooling fan is generally mounted on the rotating magneto at three locations. The magneto is mounted on the crankshaft with a bolt, which rotates when engine runs. The above mounting system of the fan consists of three machine screws, three flat washers, three spring washer. Apart from these mounting accessories, three metal inserts are also used as an integral part of the fan at these three locations. With this system the fan is constraint in both rational and axial motions. Again due to stability reason these mounting locations are preferred near the periphery of the fan diameter, as a result, a few blades are cut to accommodate these mounting systems. Other disadvantages associated with the known prior art is assembly and disassembly of such fan mounting system which renders it inconvenient and time consuming. As mentioned above, to hold the cooling fan in place on the magneto, twelve hardware parts (three screws, six washers and three inserts) are required. As a consequence, use of these multiple parts requires more labour to install, align and tighten the machine screws on the holes provided on the magneto. Considering that automobile companies are producing the large numbers of vehicles fitted with the centrifugal fans, this process of fan mounting is undesirable, inconvenient and time consuming. In addition to this, mounting accessories also adds to the extra cost of the vehicle.

Hence the objective of the present invention is to overcome the above problems associated with the prior arts.

Summary of the invention:

The present invention has been devised in view of the above difficulties and it is therefore an object of the present invention to devise a new fan mounting system wherein the fan with uniform blades can be used.

Another object of the present invention is to provide a centrifugal fan with uniform blades that can be mounted on both magneto and crankshaft without multiple parts.

Another object of the present invention is to increase the mass flow rate and efficiency by providing uniform blades.

Yet another object of the present invention is to make the fan mounting method cost effective and this objective is achieved by reduction in number of mounting parts.

Further object of the present invention is to provide a fan mounting method which can be easily assembled.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Brief Description of the Drawings:

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein

FIG. 1 illustrates a conventional two wheeler.

FIG. 2 shows one of the preferred embodiment according to the present invention.

FIG. 3 shows the fan according to the present invention.

FIG. 4 shows the magneto according to the present invention.

FIG. 5 shows another embodiment of the present invention.

Detailed Description of the Drawings:

Embodiments of the present invention now be described with reference to the accompanying drawings. In the following description, "front", "rear", "upper", "lower", "right", "left" and "bottom" represent directions viewed from the perspective of the vehicle rider.

The present invention relates to cooling fan for a two wheeler or three wheeler. For the purpose of illustration a conventional motorcycle will be roughly described. Drawing reference to Figure.1 a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (103) of the vehicle frame, a front wheel (104) attached to these front forks (102), a handle bar (105) connected to the front forks (102), a fuel tank (106) attached so as to straddle an upper part of the vehicle frame, a seat (107) attached to the upper rear portion of the vehicle frame, an engine unit (108) attached to the lower front section of the vehicle frame, a swing arm (109) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown in the drawing) from the vehicle frame and a rear wheel (110) attached to a rear end of swing arm (109). The intake system of the engine comprises of a carburettor (117), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover (111) for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (112) for covering an upper part of the front wheel (104), and a rear fender (113) for covering an upper part of the rear wheel (110). The drive from the engine (108) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

Typically magneto is mounted on the crankshaft and the rotary motion of the crankshaft is transmitted to the magneto rotor through a key during normal operation of the engine. This magneto generates electricity required for operation of ignition, lightning and signalling systems of a vehicle driven by the engine.

In a vehicle particularly two wheeler and three wheeler having such an engine as above described, the said magneto is covered with a shroud. The magneto rotor is provided with a cooling fan which rotates as the engine runs. The cooling fan sucks air axially through openings provided in the shroud and forces it out in a radial direction to achieve forced air cooling. The shape of the shroud is such that the forced air flow is directed over the parts to be cooled like cylinder and cylinder head to cool them. Such cooling is assisted by provisions of fins on the cylinder and cylinder head. Effective cooling plays an important role in desired performance of an internal combustion engine. The effectiveness of air cooling depends on an unrestricted passage of air flow towards cylinder and cylinder head fins. The efficiency of the fan can be calculated from:

where, TJ is the fan efficiency, m is mass flow rate, P is the delivery pressure, p is
the air density, V is the outlet velocity, x is the fan torque and co is the fan angular velocity. The product TCO represents power input to the fan.

Clearly, when the fan with uniform blades is used there is a high mass flow rate thereby cooling efficiency increases. Hence it is necessary to devise a new fan mounting system such that without disturbing the profile of the blades the fan can be used.

It is an object of the present invention is to provide a fan mounting method which increases the mass flow rate. With this object in view, the present invention provides an internal combustion engine with centrifugal cooling fan (201) (shown in figure 2) located centrally on the magneto (202). The said fan includes a plurality of uniform blades (203) ( shown in figure 2 and 3) arranged around the central axis of the fan (201) with a hole at the centre. A metal insert (204) is moulded at the centre of the fan (201) as an integral part. The crankshaft (205), that used to mount with the magneto earlier, is now used to couple both the magneto (202) and the fan (201) in the present invention. The said crankshaft (205) is extended such that it passes through both the magneto (202) and the fan (201). A bolt (206) at the end of the crankshaft is used to tighten the said fan (201). This restricts the axial motion of the fan. The metal insert (204) at the centre of the said fan bears the tightening forces exerted by the bolt (206).

Referring to figure 3 the said fan preferably includes at least one mounded part (301) at the fan base that extends towards the magneto (202) as projection. These extended part(s) (301) are provided to mount the said centrifugal fan (201). The magneto (202) is provided with corresponding number of hole(s) (401) (shown in figure 4) to accommodate the above said projected part (301) of the fan base. The coupling between the fan (201) and the magneto (202) is male/female type without the need of the multiple parts like washers and screws. This restricts fan (201) from rotational motion. Since the projection(s) (301) on the fan is on the base, it does not cut the fan blades thereby allowing the fan to have uniform blades throughout.

In another embodiment of the present invention shown in figure 5, the male/female relationship between the said fan (201) and the magneto can be reversed i.e. the
projection(s) (501) is provided on the magneto (202) and corresponding hole(s) (502) are provided on the fan base. The depth of hole on the fan is such that it does not extend through the fan thickness in the axial direction. The length of the projection(s) on the magneto is such that it does not cut the fan blades.

A comparative study was made with the prior design & modified design. The table below shows the effect on the fan performance near idling RPM = 1500

Even though the characteristics and advantages of the present invention have been set forth in the foregoing description, those skilled in the art should understand that the disclosure is illustrative only, and they could make various design changes, permutations and adjustments herein, especially in matters of shape, size, arrangement and number of projections and the corresponding slots, without departing from the spirit and scope of the invention in its broadest from.

We Claim:

1. A cooling fan for an internal combustion engine comprising:

a magneto mounted to crankshaft of the engine;

a fan located centrally on the magneto

a plurality of uniform blades provided on the fan;

at least one metal insert provided at the centre of the fan as an integral part;

at least one bolt provided at the end of the fan;

at least one projection on fan base extending towards magneto; and

at least one hole provided on magneto to accommodate the said projection(s).

2. A cooling fan for an internal combustion engine comprising:

a magneto mounted to crankshaft of the engine;

a fan located centrally on the magneto

a plurality of uniform blades provided on the fan;

at least one metal insert provided at the centre of the fan as an integral part;

at least one bolt provided at the end of the fan;

at least one projection on magneto extending towards fan; and

at least one hole provided on fan to accommodate the said projection(s).

3. The cooling fan as claimed in claim 1 and claim 2, wherein the said bolt is provided to tighten the fan to the crankshaft.

4. The cooling fan as claimed in claim 1 and claim 2, wherein the said metal insert is provided to bear the tightening forces exerted by the bolt.

5. The cooling fan as claimed in claim 1 and claim 2, wherein the said projections are provided to mount the fan to the magneto.