Cooling Fan for Internal Combustion Engine

Field of the invention

The present invention relates generally to a cooling fan for an internal combustion engine and more particularly pertains to a cooling fan mounting for a continuously variable transmission engine.

Background of the invention

The present invention relates to a continuously variable transmission (CVT) engine normally used in scooter type motorcycle. A scooter type motorcycle needs a cooling system to effectively dissipate heat developed by the working engine. Apart from the engine lubrication system which absorbs this heat to some extent, majority of engine cooling is accomplished by air flowing over engine or introduced to it by a centrifugal fan located on the crankshaft.

CVT is a mechanical device in which the torque transmission ratio is infinitely variable over a certain working range. A CVT automatically changes torque transmission ratio depending on engine load and speed conditions. This contrasts with a conventional geared transmission which has a limited number of selectable torque transmission ratios. CVT comprises of a driving pulley connected to a first half of a crankshaft of the engine, a driven pulley connected to wheels and a drive belt transmitting torque from the driving pulley to the driven pulley. Typically a cooling system in a CVT involves a fan on the driving pulley assembly. The driving pulley assembly in turn is mounted on the crankshaft.

The said fan is either an integral part of one half of the driving pulley by casting or welded on one half of the driving pulley or separately mounted on the crankshaft with internal splines. These types of designs limit the use of fan designs for optimum performance. Moreover a separate ratchet and spacer is required for such construction. Additionally the spot welding of the fan with the drive pulley may damage the starter gear teeth and may negatively impact the strength properties of the gear once it engages with the bendix for starting the engine. The present invention is directed to overcoming one or more problems as set forth above.

Summary of the invention

It is an hence an object of the present invention to disclose a fan mounting system that provides a split fan made of plastic or the like designed for maximum air flow separately mounted on the crankshaft with no need of either casting with drive pulley or spot welding with drive pulley.

Therefore the present invention, in accordance with one embodiment thereof, discloses a continuously variable transmission system for a straddle type vehicle connecting between an engine crankshaft and a wheel comprising a driving pulley connectable to the engine crankshaft; a driven pulley connectable to said driving pulley; a belt member connected between said driving pulley and said driven pulley and operable to transmit rotary motion between them; a cooling fan placed on the crankshaft ahead of the driving pulley wherein said cooling fan is enmoulded with an extended steel ratchet. In another embodiment of the present invention, the said cooling fan is enmoulded with a steel bush.

Another object of the present invention is to provide fan mounting system eliminating separate ratchet and spacer.

Yet another object of the present invention is to provide a separate fan design with fan blades optimized for maximum air flow and providing ease of manufacturing.

The foregoing objectives and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention 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 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 those skilled in the art from this detailed description.

Brief description of the drawings

Figure 1 shows a schematic view of the concerned two wheeled scooter type motorcycle.

Figure 2 is a sectional view of an embodiment of the CVT comprising an enmoulded fan according to the present invention.

Figure 3 shows a sectional side view of a first embodiment of the enmoulded fan according to the present invention.

Figure 4 shows a sectional side view of a second embodiment of the enmoulded fan according to the present invention.

Detailed description of the invention

In the ensuing exemplary embodiments, the vehicle is a two wheeled scooter type motorcycle with a swinging power unit. However it is contemplated that the disclosure in the present invention may be applied to any like vehicle without defeating the spirit of the invention.

Further "front" and "rear", and "left" and "right" referred to 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 scooter type motorcycle and looking forward. Furthermore, a longitudinal axis refers to a front to rear axis relative to the scooter type motorcycle,

while a lateral axis refers generally to a side to side, or left to right axis relative to the scooter type motorcycle.

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 a concerned straddle ride type vehicle with a swinging power unit. 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.

As shown in Figure 2, the belt driven CVT includes a driving pulley assembly 206 provided on an input shaft 207 (crankshaft), connected to a source of rotary power such as the engine 102, and a driven pulley assembly 209 provided on an output shaft 212 connected to the driven wheel. A drive belt 208 connects the driving pulley with the driven pulley. The driven belt 208 is preferably V-shaped and can be made of variety of of suitable configuration and material. By changing the contact diameter of the drive belt, the rotation speed transmitted from the input shaft 207 to the output shaft 212 is changed continously and helps maintain variable gear ratos. The continously variable transmission unit has fan blades on the primary pulley extending radially outwards.

Fixed face of the driving pulley 206 is provided with gear teeth on its outer periphery, hence it serves as starter gear also. Fan 301 for cooling of variomatic transmission is positioned for mounting with driving pulley assembly. The said fan is a separate part with blades designed for maximum flow and made of plastic material, manufactured through moulding.

In one of the embodiment of the present invention as shown in Figure 3, fan 401 is en-moulded with steel bush 402. Steel bush 402 with enmoulded fan 401 is assembled on crankshaft 207 with clearance fit. The steel bush 402 serves as a spacer between driving pulley 206 and a nut 403. The ratchet is integrated with nut 402. Ratchet has threads on its inner diameter, hence clamps entire driving pulley assembly on crankshaft. Since the ratchet is integrated with nut, hence the requirment of a separate nut is eliminated.

During assembly the enmoulded fan with the steel bush is held and secured by ratchet and nut. Separate fan design gives optimum design of fan blades for maximum flow and also provides ease of manufacturing.

Another embodiment of the present invention as shown in Figure 4, the fan 301 is enmoulded with extended steel ratchet 303. This extended steel ratchet also serves as spacer between driving pulley 206 and nut 304. Extended steel ratchet 302 with en-moulded fan is provided with splines on inner diameter and is assembled on crankshaft through splines 305. The nut 304 is used with washer to clamp entire driving pulley assembly 206 on crankshaft 207. In this embodiment the need for separate ratchet and spacer is eliminated. The present invention with enmoulded fan provides the flexibility of designing the fan blades for optimum air flow.

The present invention is thus described. Although the expression "scooter type motorcycle" is used in this specification it is to be construed as including any other type of motor vehicle as well, to which this invention is applicable. 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 are also possible without departing from the scope and ambit of this Invention which will 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 continuously variable transmission system for a straddle type vehicle connecting between an engine crankshaft and a wheel comprising:

a driving pulley connectable to the engine crankshaft; a driven pulley connectable to said driving pulley; a belt member connected between said driving pulley and said driven pulley and operable to transmit rotary motion between them; a cooling fan placed on the crankshaft ahead of the driving pulley wherein said cooling fan is enmoulded with an extended steel ratchet.

2. A continuously variable transmission system as claimed in claim 1, wherein said extended steel ratchet with enmoulded fan is provided with splines on inner diameter and is assembled on the crankshaft through it.

3. A continuously variable transmission system for a straddle type vehicle connecting between an engine crankshaft and a wheel comprising:

a driving pulley connectable to the engine crankshaft; a driven pulley connectable to said driving pulley; a belt member connected between said driving pulley and said driven pulley and operable to transmit rotary motion between them; a cooling fan placed on the crankshaft ahead of the driving pulley wherein said cooling fan is enmoulded with a steel bush.

4. A continuously variable transmission system as claimed in claim 3, wherein said steel bush with enmoulded fan is assembled on crankshaft with clearance fit.

5. A continuously variable transmission system as claimed in claim 3, wherein a ratchet is integrated with a nut and has threads on its inner diameter clamping entire driving pulley on the crankshaft.

6. A continuously variable transmission system substantially as claimed in any of the preceding claims and illustrated with reference to the accompanying drawings.