A COOLING FAN

FIELD OF THE INVENTION

[0001] The present invention relates generally to an internal combustion engine and more particularly, but not exclusively, to a cooling fan connected to a four cycle internal combustion engine.

BACKGROUND OF THE INVENTION

[0002] A conventional two wheeled vehicle is powered by an internal combustion engine (hereinafter "engine") generally disposed at a lower half of the vehicle. This engine converts chemical energy into mechanical energy by combustion of air-fuel mixture within a combustion chamber of the engine. The engine, among other components, has a cylinder block comprising a cylinder head over the cylinder block 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. In this way, the reciprocatory motion of the piston is converted to rotatory motion of the crankshaft. The crankshaft is housed inside a crankcase proximately to the cylinder block.

[0003] Several types of internal combustion engines are known in the prior art including a two cycle and a four cycle engine. In India, small cubic capacity engines are generally two cycle engines with single speed transmission. They have their own distinct advantages such as better manuverabilty in congested traffic with out the need for frequent shiting of gears thereby improving fuel economy. However, two cycle engines emit higher pollutants. A four cycle internal combustion engine, on the other hand, is advantageous in terms of meeting stringent emission norms and ensures better fuel efficiency.

[0004] Further, such engines with forwardly tilted cylinder block are heated up during their operation and hence are either natural air cooled, or forced air cooled by use of a cooling fan, or both. In such engine, usually the cooling fan is directly supported on a dry magneto assembly and the erankcase is sealed to allow dry operation of the magneto without use of a lubrication oil. However, this mounting of the cooling fan is undesirable if the internal combustion engine has a wet magneto configuration.

SUMMARY OF THE INVENTION

[0005] The present subject matter is directed to overcoming one or more problems as set forth above and thereby to obviate a lacunae in the prior art. It is therefore an object of the present subject matter to disclose a cooling fan for a four cycle internal combustion engine with a forwardly titled cylinder block and having a wet magneto configuration. Another object of the present subject matter is to propose an internal combustion engine unit having a wet magneto internal to, and a cooling fan external to, a erankcase wherein the cooling fan is not directly mounted on the magneto. Another object of the present subject matter is to use the kick start system provided in an internal combustion engine unit for mounting of a cooling fan.

[0006] To this end, the present invention discloses a four cycle internal combustion engine unit comprising a forwardly tilted cylinder block, a wet type magneto disposed within a crankcase, a crankshaft driving the magneto and rotatably supporting a coupling member, and a cooling fan disposed laterally to the magneto and external to the crankcase. According to an aspect of the present invention, the cooling fan is rotatably supported on a fan shaft through a supporting mechanism. The fan shaft is driven by the crankshaft and coupled to it through the coupling member.

[0007] According to another aspect, the supporting mechanism further comprises a supporting plate mounted on a one endportion of the fan shaft and secured to the cooling fan, a nut to tighten the supporting plate against the one endportion of the fan shaft and a plurality of fasteners securing the cooling fan to the supporting plate.

[0008] The foregoing objectives and summary is provided to introduce a selection of concepts in a simplified form, and is not limiting. 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 subject matter and the claims should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0009] 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:

FIG. 1 shows a sectional view of an internal combustion engine unit with a cooling fan according to the present invention.

FIG. 2 shows an exploded view of the portion of the engine of FIG. 1 with the cooling fan according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[00010] In order that those skilled in the art can understand the present invention, the invention is further described below so that various features of the invention thereof proposed here are discernible from the description thereof set out hereunder. However, the description and the appended drawings are only used by those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention.

[00011] According to an embodiment, the engine described here is a four cycle internal combustion engine. Such engine is installed in a two wheeled vehicle. It is pertinent to note that the such engine may be mounted in the two wheeled vehicle in different arrangements such as in transverse and longitudinal fashion. However, in the ensuing description, such engine is transversely mounted at a lower portion of the two wheeled vehicle. It is contemplated that the concepts of the present invention may be applied to other types of vehicles within the spirit and scope of this invention. Further "front" and "rear", and "left" and "right" referred to in the ensuing description of the illustrated embodiment refer to front and rear, and left and right directions as seen from a rear portion of the internal combustion engine and looking forward. Furthermore, a longitudinal axis unless otherwise mentioned, refers to a front to rear axis relative to the engine, while a lateral axis unless otherwise mentioned, refers generally to a side to side, or left to right axis relative to the engine.

[00012] FIG. 1 shows a sectional view of an internal combustion engine unit 100 according to the present invention. In a preferred embodiment, the engine unit has a small cubic capacity and is installed in a moped type motorcycle. In an embodiment, the engine has a cubic capacity of lOOcc or below depending upon the intended application and load. However, the concepts illustrated in the present subject matter are usable in higher cubic capacity engines also. The four cycle engine unit includes a crankcase 101, a cylinder block 102 coupled to the crankcase 101, a cylinder head 103 and a cylinder head cover 104. In an embodiment, the engine unit has a forwardly titled or horizontal cylinder block 102 disposed in such a way that the cylinder block axis is approximately parallel to the longitudinal axis of the engine unit. This type of mounting provides more floor space in the motorcycle which is used for load carrying applications. The cylinder head 103 is coupled to the front portion of the cylinder block 102 and the cylinder head cover 104 is coupled to the front portion of the cylinder head 103.

[00013] A reciprocating piston 107 slidably fitted in the cylinder block 102 is connected via a connecting rod 108 to a crankshaft 110. The crankshaft 110 is rotatably supported by the crankcase 101. An intake port and an exhaust port formed in the cylinder head 103 communicate with a combustion chamber 109 formed by being surrounded by the cylinder bore, the cylinder head 103 and the piston 107. An intake valve (not shown) is provided at the combustion chamber side opening of the intake port and an exhaust valve (not shown) is provided at the combustion chamber side opening of the exhaust port. A camshaft 106 is rotatably supported by the cylinder head 103 so as to open and close the intake valve and the exhaust valve. Rotational power is transmitted from the crankshaft 110 to the camshaft 106 by a timing transmission means. The timing transmission means includes a drive sprocket, a driven sprocket and an endless chain (not shown). The intake and exhaust valves are operated via rocker arms connected to the camshaft 106.

[00014] The crankshaft 110 delivers power to a rear wheel of the motorcycle by means of a transmission unit comprising a clutch (not shown) and chain drive. The clutch is preferably of centrifugal type and is located on one side of the longitudinal axis of the cylinder block 102. The engine unit 100 is provided with a single speed transmission for better fuel efficiency and riding convenience where the engagement and disengagement of clutch is based on crankshaft r.p.m. The size of the engine unit is thus small as a big transmission with a plurality of gears is not required. The clutch is mounted on one endportion of the crankshaft 110. To balance the engine unit, a magneto 113 is mounted on the opposite endportion of the crankshaft 110. In an embodiment of the engine unit, the clutch 112 is present on the left side of the engine whereas a magneto 113 is provided on the right side of the engine. The magneto has a wet type configuration and is disposed within the crankcase 101. External to the magneto 113, a cooling fan 116 is provided to force cool the engine.

[00015] In the engine unit constituted as above, an air fuel mixture is supplied to the combustion chamber 109 from the intake port compressed by the piston 107, ignited by a spark plug 111 and then burned. In that way, the air fuel mixture is converted to energy to rotate the crankshaft 110 via the piston 107. Thereafter exhaust gases generated are discharged from the exhaust port to the outside through an exhaust pipe. The exhaust pipe extends from the engine to the rear wheel, and is connected to an exhaust muffler (not shown) disposed laterally to the rear wheel.

[00016] According to an aspect of the present invention, the engine unit is provided with a kick start system to manually start the engine. The kick start system is operatively connected to the crankshaft 110. The kick start system 150 is accomodated in the crankcase 101 and comprises of a kick shaft 151, a kick start spring 152 housed in a kick start spring guide 152a, a ratchet 153, a kick drive gear 154, a kick idler gear 155, a coupling member 157 and a driveshaft 158. The crankshaft 110, driveshaft 158 and kick shaft 151 are parallel to each other. The ratchet 153 and the kick drive gear 154 are rotatably supported on the kick shaft 151 and disposed spaced apart from each other. According to an aspect, the ratchet 153 is rigidly mounted on the kick shaft 151 and located distal to the kick drive gear 154. In an embodiment, the ratchet 153 is disposed at one endportion of the kick shaft 151 and the kick drive gear 154 is disposed rightward to the ratchet 153.

[00017] The kick drive gear 154 is engaged with and drives the kick idler gear 155 mounted on the driveshaft 158. The kick idler gear 155 is engaged with and drives the coupling member 157 which in turn is in rigid connection with the crankshaft 110. The driveshaft 158 is positioned on the rear right side of the crankcase 101. Further, the kick shaft 151 is mechanically connected to a manually operable kick start lever (not shown) rigidly disposed at other endportion of the kick shaft 151 opposite to the one endportion housing the ratchet 153. It transmits the vehicle operator's pedal force to the crankshaft 110 and starts the engine. After the kick is over, the kick start lever spring 152 retracts the kick start lever back to its default position.

[00018] The kick drive gear 154 drives the kick idler gear 155 mounted on the driveshaft 158 which then drives the coupling member 157. In an embodiment, the coupling member 157 has a first lateral groove 157b which receives the endportion of the crankshaft 110 supporting the magneto 113. The coupling member 157 is in rigid connection with the crankshaft 110 through the first lateral groove 157b and drives the crankshaft 110. Through this kick start system 150, a user can kick start the motorcycle by applying manual force on the kick start lever 152 which is transmitted to the crankshaft 110 and the engine is cranked.

[00019] The ratchet 153 engages with the kick drive gear 154 to transfer the manual force to the crankshaft 110. The kick force acts laterally outward from left to right axis. On kicking, the ratchet 153 meshes with the kick drive gear 154 along the axis of the kick shaft 151 so that the torque and the r.p.m of the crankshaft 110 is reduced thereby eliminating kick slip. The kicking torque is stepped up by the overall gear ratio at the crankshaft. Further, the kick start system 150 is disposed towards the one side of the longitudinal axis of the cylinder block 102 and therefore frees up space for other components of the engine unit 100.

[00020] The engine is heated up during its operation and requires proper cooling for efficient function. This is achievable by better channelization of air for forced air cooling. In the present invention, the cylinder block 102 is cooled by forced air cooling whereas the crankcase 101 and cylinder head 103 are cooled by natural air cooling. For forced air cooling, the engine unit is provided with the cooling fan 116 disposed laterally to the magneto 113 and external to the crankcase 101. In an embodiment, the cooling fan 116 is of centrifugal type. The engine unit is externally covered with a fan cowl 118 for directing the forced air by the cooling fan 116 towards the cylinder block 102. The cooling fan 116 sucks the environmental air and directs the incoming air towards the fan cowl 118. The fan cowl 118 provides volute profile to the channelized air to maintain the velocity of the air. After cooling the cylinder block 102, hot air exits the fan cowl 118 laterally to the engine.

[00021] According to another aspect of the present invention, the cooling fan 116 is driven by a separate fan shaft 119 and is connected to it through a coupling mechanism. As shown in FIG. 1 and FIG. 2, the supporting mechanism further comprises a supporting plate 122 mounted on a one endportion of the fan shaft 119 and secured to the cooling fan 116, a nut 121 to tighten the supporting plate 122 against the one endportion of the fan shaft 119 and a plurality of fasteners 124 securing the cooling fan 116 to the supporting plate 122. The supporting plate 122 maintains a gap between the cooling fan 116 and the crankcase 101. In an embodiment, the supporting plate 122 is a star-shaped structure located outside the crankcase and is fabricated from metal, alloy or plastic resin. The nut 121 stops the axial movement of the cooling fan and the supporting plate 122. The fasteners 124 pass through the cooling fan surface and fasten the cooling fan 116 to the supporting plate 122 at least at three points.

[00022] Further, the fan shaft 119 itself is supported on the crankcase 101. The fan shaft 119 receives the drive from the crankshaft 110 and is coupled to the crankshaft through the coupling member 157. The one endportion of the fan shaft 119 protrudes out of the crankcase 101 and is connected to the cooling fan 116. A one other endportion opposite to the one endportion of the fan shaft 119 is within the crankcase 101 and is connected to the coupling member 157. The coupling member 157 separates the fan shaft 119 from the crankshaft 110 and hence they are not directly connected. The coupling member 157 is thus helpful during kick start as well as in cooling fan mounting. In a preferred embodiment, the coupling member 157 is a kick driven gear engaged with the kick start system 150.

[00023] According to another aspect, the one other endportion of the fan shaft 119 comprises a polygonal projection 120 and the coupling member 157 comprises a polygonal socket 157a. During assembly, the polygonal socket 157a of the coupling member 157 receives the polygonal projection 120 of the fan shaft 119 to rigidly connect the fan shaft 119 to the coupling member 157 and lock it therein. Therefore, the fan shaft 119 is in rigid connection to the coupling member 157 and further to the crankshaft 110. The fan shaft 119 receives the drive from the crankshaft and rotates with it. In a preferred embodiment, the polygonal projection 120 of the fan shaft 119 is hexagonal in shape and the polygonal socket 157a of the coupling member 157 is also hexagonal in shape.

[00024] An oil seal 125 is provided in the fan shaft 119 so that the lubricant remains within the crankcase 101 and does not leak towards the fan. This provision allows the magneto 113 to run wet with oil churning inside the crankcase 101 and enabling the cooling fan 116 to have a dry operation.

[00025] The present subject matter and its equivalent thereof offer many advantages, including those which have been described henceforth. The present invention provides a cooling fan mounting for an internal combustion engine unit with a wet type magneto configuration where the magneto is inside and cooling fan is outside the crankcase. In the present invention, the cooling fan 116, the magneto 113 and the coupling member 157 are disposed on one side of the longitudinal median plane of the cylinder block 102. Further, the coupling member serves multiple purposes. Firstly, it provides drive to the crankshaft to crank the engine as a part of the kick start system. Secondly the polygonal socket of the coupling member rigidly and partially houses the fan shaft on which the cooling fan is mounted. It is also used to tighten the magneto assembly against the crankshaft. Thirdly, the first lateral groove of the coupling member opposite to the polygonal socket receives one endportion of the crankshaft.

[00026] The present subject matter is thus described. The description is no intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above description. The forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.

We claim:

1. A four cycle internal combustion engine unit (100) comprising: a forwardly tilted cylinder block (102), a wet type magneto (113) disposed within a crankcase (101), a crankshaft (110) driving the magneto (113) and rotatably supporting a coupling member (157), a cooling fan (116) for cooling the internal combustion engine unit disposed laterally to the magneto (113) and external to the crankcase (101), wherein the cooling fan (116) is rotatably supported on a fan shaft (119) through a supporting mechanism, and wherein further the fan shaft (119) is driven by the crankshaft (110) and coupled to the crankshaft through the coupling member (157), the coupling member (157) being a component of, and engaged with, a kick start system (150).

2. The internal combustion engine unit as claimed in claim 1, wherein the supporting mechanism further comprises a supporting plate (122) mounted on a one endportion of the fan shaft (119) and secured to the cooling fan (116), a nut (121) to tighten the supporting plate (122) against the one endportion of the fan shaft (119) and a plurality of fasteners (124) securing the cooling fan (116) to the supporting plate (122).

3. The internal combustion engine unit as claimed in claim 2, wherein the supporting plate (122) is star-shaped structure and fabricated from metal, alloy or plastic resin.

4. The internal combustion engine unit as claimed in claim 1, wherein a one other endportion of the fan shaft (119) comprises a polygonal projection (120) and the coupling member (157) comprises a polygonal socket (157a), and wherein further the polygonal socket (157a) of the coupling member (157) receives the polygonal projection (120) of the fan shaft (119) to rigidly connect the fan shaft to the coupling member (157).

5. The internal combustion engine unit as claimed in claim 4, wherein the coupling member also comprises a first lateral groove (157b) opposite to the polygonal socket (157a) to receive one endportion of the crankshaft (110).

6. The internal combustion engine unit as claimed in claim 1, wherein the cooling fan (116), the wet type magneto (113) and the coupling member (157) are disposed on one side of the longitudinal median plane of the cylinder block (102).

7. A cooling fan (116) rotatably disposed on a fan shaft (119), the fan shaft comprising a one endportion and a one other endportion and driven by a crankshaft (110) of a four cycle internal combustion engine unit (100), the cooling fan (116) located laterally to a wet type magneto (113) outside of a crankcase (101) of the engine unit wherein a coupling member (157) rigidly couples the fan shaft (116) to the crankshaft (110), and wherein, the cooling fan (116) is disposed on the fan shaft (119) through a supporting mechanism comprising a supporting plate (122) mounted on the one endportion of the fan shaft (119) and secured to the cooling fan (116), a nut (121) to tighten the supporting plate (122) against the one endportion of the fan shaft (119) and a plurality of fasteners (124) securing the cooling fan (116) to the supporting plate (122).

8. The cooling fan as claimed in claim 7, wherein the one other endportion of the fan shaft (119) comprises a polygonal projection (120) and the coupling member (157) comprises a polygonal socket (157a) and a first lateral groove (157b), and wherein further the polygonal socket (157a) of the coupling member (157) receives the polygonal projection (120) of the fan shaft (119) to rigidly connect the fan shaft (119) to the coupling member (157).

9. The cooling fan as claimed in claim 7, wherein the coupling member (157) is a component of, and engaged with, a kick start system (150).

10. The internal combustion engine unit as claimed in any of the preceding claims, wherein the fan shaft (119) is supported on the crankcase (101) of the internal combustion engine unit.