LUBRICATION CHANNEL FOR AN INTERNAL COMBUSTION
ENGINE

FIELD OF THE INVENTION

[0001] The subject matter as described herein, relates generally to an
internal combustion engine and more particularly, but not exclusively, to a lubrication channel for an internal combustion engine.

BACKGROUND OF THE INVENTION

[0002] A conventional two wheeled vehicle is powered by an internal combustion 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 said engine, among other components, has a cylinder comprising a cylinder head atop or in front of the cylinder and receiving a reciprocating piston from the bottom or the rear. 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 beneath or behind the cylinder block. In order to set the vehicle into motion, the power supplied to the crankshaft of the internal combustion engine is carried to a wheel of the vehicle, in a controllable way, through a transmission system. The transmission system in the conventional vehicle employs a clutch and a gearbox with plurality of gears, wherein gear shift is achieved manually which enables gears to be selected only in an ascending or descending sequence.

A gear less transmission system, called a continuously variable transmission system, is also known where the gearshift is achieved by centrifugal forces.

[0003] Conventionally, the internal combustion engines are provided with
an engine lubrication channel that enables lubrication of the moving engine components during engine operation. The lubrication channel involves transmission of oil through a particular channel for achieving the desired lubrication and cooling of the engine components. The lubrication oil functions as a lubricating agent and a cooling agent in an internal combustion engine. The oil used for this purpose.may be stored in an oil sump, which also acts as a repository for the oil expelled from the engine components as a result of their working. The oil pump is utilized to draw and deliver the lubrication oil to desired locations within the engine for lubrication and cooling purposes under low, medium or high engine speed conditions. The circulating lubrication oil reduces the wear and tear of the engine components and also ensures that the engine is consistently maintained under optimal temperatures and thereby enhancing engine performance, life of engine components, and the service intervals of the lubricants. The routing of lubrication oil plays an important role in
maintaining the lubrication oil volume.

[0004] Conventionally, the oil sump is formed . within a crankcase
assembly. The lubrication oil is carried from the oil sump to a right casing of the crankcase assembly through a left casing. The lubrication channel for transfering the lubrication oil from the left casing to the right casing involves a series of drill holes and takes long time to reach the crankshaft and cylinder head. Due to more number of oil channels and holes, the lubrication path is spread over a longer distance which increases the dead volume of the oil in the lubrication channel. Further, the crankcase assembly is heavy as it accomodates the several oil holes and chambers. More particularly, the series of drill holes and oil openings in the right casing and the left casing to route the oil to the crankshaft and the cylinder head increases the overall weight of the crankcase assembly. Still further, any change in the location of oil holes or oil path is subject to the machining of the crankcase assembly which is.practically difficult.

SUMMARY OF THE INVENTION

[0005] . Therefore, it is always advantageous to provide an optimal route
for the lubrication oil to reach the crankshaft and the cylinder head. It is also advantageous that the oil flow path is shortest possible to reduce the flow losses and ensure the lubrication oil reaching quickly to the engine parts, more particularly, the cylinder head and crankshaft. The present invention is aimed at overcoming the challenges associated with the lubrication channel of a conventional internal combustion engine, preferably a small engine and provide an optimal path for the lubrication oil to reach the crankshaft and the cylinder head.

[0006] It is an object of the present invention to reduce the time taken for
the lubrication oil to reach the crankshaft and cylinder head so that the durability of the engine is improved. It is another object of the present invention to reduce the dead volume in the lubrication channel. It is another object of the present invention to simplify the design of the crankcase assembly to achieve a reduction in its weight and hence cost.

[0007] To this end, the present invention proposes an internal combustion
engine comprising'a crankcase assembly including a left casing and a right casing, a crankshaft housed within said crankcase assembly and a lubrication channel for lubrication of said crankshaft. The lubrication channel further comprises an output oil channel and a crankshaft lubrication channel formed in the right casing of the crankcase assembly, and a crankcase exit opening is formed in a crankcase block seating surface in the crankcase assembly, wherein the output oil channel and the crankshaft lubrication channel are joined to each other at the crankcase exit opening. The output oil channel and the crankshaft lubrication channel are substantially planar and angularly disposed to each other.The present invention achieves a very compact and short oil flow path for the lubrication oil. It enables ease of machining within the crankcase assembly to achieve the lubrication according to the present invention.

[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 THE DRAWINGS

[0009] The above and other features, aspects, and advantages of the
subject matter will be better understood with regard to the following description and accompanying drawings where:

[00010]. FIG. 1 is a perspective view of a power unit in a motorcycle
according to the present invention.

[00011] FIG. 2 is an exploded view of a cylinder assembly and a crankcase
assembly of the power unit of FIG. 1.

[00012] FIG. 3 shows a front sectional view of the crankcase assembly
illustrating an oil sump.

[00013] FIG. 4 shows a symmetrical view of a left casing and a right casing
assembled to form the crankcase assembly.

[00014] FIG. 5(a) and 5(c) respectively show a right side view of the right
casing across the section E-E of the FIG. 5(b), and a left side view of the right casing across the section E-E of the FIG. 5(b).

[00015] FIG. 6 shows a schematic right' side view of the crankcase
assembly illustrating the lubrication channel of the engine.

[00016] FIG. 7(a) shows a perspective view of a block gasket according to
the present invention.

[00017] FIG. 7(b) shows a rear view of a cylinder block according to the
present invention.

DETAILED DESCRIPTION OF THE INVENTION

[00018] The present subject matter and its embodiments would now be
described in greater detail in conjunction with the figures in the following description. The following description provides a convenient illustration for implementing exemplary embodiments of the invention. It is to be noted that terms "front", "rear", "left", "right", and like terms are used herein based on the direction indicated in the drawings. Incidentally, in the drawings to be used in the following explanation including FIG. 1, the front of the engine is indicated by an arrow "Fr" and the rear of the engine is indicated by an arrow "Rr", and further the lateral right side of the engine is indicated by an arrow "R" and the lateral left side of the "engine" is indicated by an arrow "L" as necessary. Furthermore, a longitudinal axis refers to a front to rear axis relative to the engine, while a lateral axis refers to a side to side, or left to right axis relative to the engine. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The internal, combustion engine shown in ensuing drawings is a four stroke single cylinder swinging internal combustion engine with a forwardly titled cylinder head generally mounted on a scooter type motorcycle. However, the concepts disclosed in the present invention can be practiced in other engines like a vertical engine.
[00019] FIG. 1 shows a perspective view of an internal combustion engine
10 according to an embodiment of the present invention. The engine 10 is one made by unitizing a cylinder assembly 12 and a crankcase assembly 14, and rotatably supports a rear -wheel of the motorcycle. The rear portion of the .

crankcase assembly includes a power transmission system including a
continuously variable transmission made by using a belt and a pulley. The engine
10 has an air cleaner 22 mounted on the upper surface side of the crankcase
assembly 14 positioned on the rear side of the engine. The air cleaner 22 exhibits
a box shape generally, and has an air intake pipe 20 extending from the vicinity of
an upper portion thereof. It also comprises of an intake hose 24 extending from a
right side portion towards a carburettor which further carries an air-fuel mixture
for combustion through an intake pipe 26. Further, the crankcase assembly 14 is
covered from a left side by a variator cover 18 which seals the crankcase assembly
from the left side and supports the components of the continuously variable
transmission. During operation of the engine 10, the components of the power
transmission system become hot and hence are air cooled. The air enters the
crankcase assembly 14 from a front portion of the left side thereof through an inlet
tube 16. The variator cover 18 comprises of an opening (not shown) for receiving
the incoming air. ._
[00020] FIG. 2 shows an exploded view of the engine 10 illustrating the
components in detail. The cylinder assembly 12 is made in a manner that a cylinder head cover 12A, a cylinder head 12B and a cylinder 12C are sequentially joined in a front to rear direction. The cylinder head 12B comprises of a valve train assembly and is covered by the cylinder head cover 12A. The cylinder 12C receives a reciprocating piston (not shown) from the rear and generates the mechanical energy to drive the engine..The cylinder assembly 12 is disposed in a manner that the cylinder axis, falls along the longitudinal axis of the engine 10.

Further, the intake pipe 26 communicates with an intake port in the cylinder head 12B, and through an intake passage constituted by these members, the purified air is mixed with fuel is supplied to the intake port in the cylinder head 12B from the air cleaner 22. In the lower surface side of the cylinder assembly 12, an exhaust port is formed, and from the exhaust port, an exhaust pipe extends rearward while bending and is connected to a muffler at the rear of the motorcycle.
[00021] A head sealing member 13 is disposed between a rear surface of
the cylinder head 12B and a front surface of the cylinder 12C. A second sealing member called as a block sealing member 15 is disposed between a rear surface of -the cylinder 12C and the front surface of the crankcase assembly 14. The front surface is referred to as crankcase block seating surface (CBSF) 28 because the rear surface of the cylinder rests on the crankcase through CBSF 28. In the present embodiment, the CBSF 28 faces the front direction of the engine 10. The head sealing member 13 and the block sealing member 15 seal the respective mating surfaces against any oil or pressure leaks.
[00022] The crankcase assembly 14 is disposed rearwardly of the cylinder
assembly and comprises of a left casing 40 and a right casing 30 joined to each other to develop into the crankcase assembly 14. The left casing 40 is disposed toward the left side L of the crankcase assembly and the right casing 30 is disposed toward the right side R of the crankcase assembly. The left casing 40 is joined to the right casing 30 at a mating face 33. In an embodiment, a sealing member is provided between the left casing 40 and the right casing 30 to seal the two.

[00023] FIG. 3 shows a sectional view of a front portion of the crankcase
assembly 14. A crankshaft 56 is supported by the left casing 40 and the right casing 30 in the engine width direction from the left L to the right R direction. In an embodiment, the left casing 40 comprises of a left crankshaft opening 41a as shown in FIG. 2. A left bearing 42a is supported in the left crankshaft opening 41a. Similarly, the right casing 30 comprises of a right crankshaft opening 31^a. A right bearing 42a is supported in the right crankshaft opening 31a. The left crankshaft opening 41a is co-axial to the right crankshaft opening 31a. The left and right bearings 42a and 32a rotatably support the crankshaft 56 respectively in the left casing 40 and the right casing 30 in a manner that the long axis of the crankshaft 56 (referred in the description by 56L-56R) is parallel to the lateral axis L-R of the engine and perpendicular to the longitudinal axis Fr-Rr of the engine. The rotation of the crankshaft drives the valve train assembly in the cylinder head 12B through a cam chain.
[00024] As shown in FIG. 2, the left casing 40 is provided with an oil
chamber 46. The oil chamber comprises of an oil filter 44 at a lower front portion of a right face of the left casing 40. A drain plug 45 closes the oil filter 44 from the bottom and seals the crankcase assembly. Thus, as,shown in FIG. 3, in the lower most region of the crankcase assembly 14, an oil sump 51 is formed by the left casing 40 and the right casing 30. The oil sump 51 is spread from the left casing to the right casing and is positioned lower than all other engine components. When seen from a left direction, an oil pump 47 is disposed adjacent to the crankshaft 56 and receiving drive from the crankshaft 56. The oil chamber

46 is sealed towards a left face of the left casing 40 by an oil pump cover 50. As shown in FIG. 2, the oil pump cover 50 includes an oil seal 52 to seal the crankshaft 56 from the left direction. It also keeps the dry power transmission system disposed in the left casing 40 away from the lubrication oil An oil pump sealing member 48 is disposed between a mating surface 54 of oil chamber 46 and the oil pump cover 50. It further seals the oil chamber 46 from any undesirable oil or pressure leaks. The left casing 40 is covered from the left side by the variator cover 18. A rear portion of the left casing 40 rearwardly of the oil chamber 46 comprises of a clutch shaft opening 62, an intermediate shaft opening 64 and a wheel shaft opening 66 disposed adjacently of each other when seen in left side view to respectively support a clutch shaft, an intermediate shaft and a wheel shaft.
[00025] FIG. 4 shows a symmetrically exploded view of the left casing and
the right casing from a rear direction of the engine. An oil pump outlet pocket 71 is formed between a right face of the left casing 40 and a left face of the right casing 30. The oil pump outlet pocket 71' comprises of a right cavity 71-1 formed in the right face of the left casing 40 below the crankshaft axis and a left cavity 71-2 formed in the left face of the right casing 30 below the crankshaft axis. The left cavity 71-2 is a mirror image of the right cavity 71-2. When the left casing 40 and the right casing 30 join each other along the mating surface 33, an outer surface of the right cavity 71-1 is juxtaposed on an outer surface of the left cavity 71-2 and together they develop into the oil pump outlet pocket 71. The right cavity 71-1 further comprises of a transfer port opening 43 connected to at least

one of the transfer ports of the oil pump 47. The transfer port opening 43 is formed at a higher elevation than the rest of the right cavity 71-1 and introduces the lubrication oil into the oil pump outlet pocket 71. The left cavity 71-2 further comprises of a first exit hole 35 formed at a lower elevation than the rest of the left cavity 71-2. The first exit hole 35 transfers the lubrication oil from the oil pump outlet pocket 71 to a right face of the right casing 30. In an embodiment, the first exit hole 35 is formed in the right casing 30by way of drilling. According to . an aspect, the first exit hole 35 is parallel to the long axis 56L-56R of the crankshaft.
[00026] FIG, 5(b) shows a front sectional view of the right casing 30. FIG.
5(a) shows the right face of the right casing 30 and FIG. 5(c) shows the left face of the right casing 30 when the right casing 30 is sectioned along the axis E-E as shown in FIG. 5(b), The right casing 30 further comprises of an output oil channel 36 and a crankshaft lubrication channel 38. In an embodiment, the output oil channel 36 and a crankshaft lubrication channel 38 meet each other at the CBSF 28. A crankcase exit opening 58 is formed on the CBSF 28. One end of the output oil channel 36 is connected to the first exit hole 35 and the other end is connected to the crankcase exit opening 58. One end of the crankshaft lubrication channel 38 is connected to the crankcase exit opening 58 and the other end is connected to the right crankshaft opening 31a. In an embodiment, the crankcase exit opening 58 is a circular hole and is closed by a. plug with a metering orifice 59. In an embodiment, the metering orifice 59 is a nozzle. From the crankcase exit opening 58, the lubrication oil is channelled forwardly into the cylinder assembly 12.

[00027] According to an aspect of the present invention, the output oil
channel 36 and the crankshaft lubrication channel 38 are substantially planar and angularly disposed to each other. In an embodiment, the angle between the output oil channel 36 and the crankshaft lubrication channel 38 is an acute angle. More particularly in an embodiment, said angle is in a range between 35 to 45 degrees. Further, the crankshaft lubrication channel 38 leading to crankshaft 56 is parallel to a crankshaft central plane and lies substantially above the long axis of the crankshaft 56L-56R. The output oil channel 36 crosses the centre plane of the crankshaft when seen from a right view.Still further, the diameter of the crankshaft lubrication channel 38 is smaller than that of output oil channel 36.
[00028] The working of the lubrication channel is now explained with the
help of FIG. 5(a) to 7(b). The rotation of the crankshaft 56 operates the oil pump 47. As the oil pump 47 operates, the lubrication oil from the oil sump 51 is filtered by the oil filter 44 and is channelized into a first transfer port 68 of the oil pump 47. As shown in FIG. 6, due to rotation of the oil pump, the oil in the first transfer port 68 is moved to a second transfer port 69 having a transfer port channel 70. The oil after crossing the transfer port channel 70 is introduced into the oil pump outlet pocket 71 through the transfer port opening 43. The oil pump outlet pocket 71 is filled with the oil and thus the oil is also introduced to the right casing 30. In the oil pump outlet pocket 71, the oil flows downwards and exits the oil pump outlet pocket 71 through the first exit hole 35. The oil then flows parallel to the long axis of the crankshaft covering the width of the right casing 30 and enters the output oil channel 36. The oil flows upwardly and in the front direction towards

the crankcase exit opening 58 in the CBSF 28. The flow of oil in the output oil channel 36 is shown in FIG. 5(a). A portion of this oil reaching the crankcase exit' opening 58 enters the crankshaft lubrication channel 38. The oil in the crankshaft lubrication channel 58 is then introduced to the right crankshaft opening 31a through which it lubricates the crankshaft 56.
[00029] Another portion of the lubrication oil from the crankcase exit
opening 58 is introduced into the cylinder assembly. As shown in FIG. 7(a), the block sealing member 15 comprises of a first stud opening 15a and a second exit hole 15b. A rear portion of the cylinder 12C also comprises of a second stud opening 29a and a third exit hole 29b as shown in FIG. 7(b). A connecting groove 29c is formed on a rear surface 29 of the cylinder 12C mating the CBSF 28 (with block sealing member 15 disposed between the two). The crankcase exit opening 58, the second exit hole 15b and the third exit hole 29b are co-axial and the portion of the lubrication oil from the crankcase exit opening 58 is thus transferred to the third exit hole 29b. The oil then follows the connecting groove 29c and enters the second stud opening 29a through which it enters the valve train assembly.
. [00030] According to an aspect, the crankcase exit opening 58 is located
close to the stud opening on the CBSF of the right casing 30.
[00031] Thus, the lubrication oil reaches the crankshaft and the cylinder
head through the short path. The oil pump outlet pocket is directly connected to the CBSF through the output oil channel 36 formed in the right casing 30. From the CBSF, the crankshaft lubrication channel 38 carries the oil straight to the

crankshaft The short path reduces the flow volume hence ensuring quick reaching of lubrication oil to the engine parts particularly to crankshaft and cylinder head.
[00032] From CBSF, oil distribution is controlled through the metering
orifice 59. The hole in the plug controls the oil flow to cylinder head and crankshaft By altering hole dimension in the metering orifice, oil distribution to crankshaft and cylinder head can be changed.
[00033] The flow path machined in the crankcase assembly is parallel to
crankcase face which enables easy machining with less investment. Firstly, the crankshaft lubrication channel 38 is drilled in the right casing from the crankcase exit opening 58 in the CBSF followed by the output oil channel 36 subsequent to which the crankcase exit opening 58 is closed with the plug having metering orifice 59= Since drilling is from the CBSF parallel to the longitudinal axis of the engine, the machining is easy.
[00034] The present subject matter is thus described. The description is not
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 embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore 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. The internal combustion engine (10) comprising a crankcase assembly
(14) including a left casing (40) and a right casing (30), a crankshaft (56)
housed withinsaid crankcase assembly (14) and a lubrication channel for
lubrication of said crankshaft (56), characterized in that,
the lubrication channel further comprises an output oil channel (36) and a crankshaft lubrication channel (38) formed in the right casing (30) of the crankcase assembly, and
7 a crankcase exit opening (58) is formed in a crankcase block seating surface (28) in the crankcase assembly, wherein the output oil channel (36) and the crankshaft lubrication channel (38) are joined to each other at the crankcase exit opening (58).
2. The internal combustion engine as claimed in claim 1, wherein the output oil channel (36) and the crankshaft lubrication channel (38) are substantially planar and angularly disposed to each other.
3. The internal combustion engine as claimed in claim 1, wherein the crankcase exit opening (58) is closed by a plug with a metering orifice (59).
4. The internal combustion engine as claimed in claim 1, wherein the crankshaft lubrication channel (38) leading to crankshaft (56) is "parallel to a crankshaft central plane and lies substantially above a long axis of the crankshaft (56L-56R).

5. The internal combustion engine as claimed in claim 1, wherein the diameter of the crankshaft lubrication channel (38) is smaller than that of output oil channel (36).
6. The internal combustion engine as claimed in claim 1, wherein the output oil channel (36) is directly connected to an oil pump outlet pocket (71) formed by the mating of a right face of the left casing (40) and a left face of the right casing (30) through a first exit hole (35) fabricated parallel to the long axis of the crankshaft (56).
„ 7. The. internal.combustion engine as claimed in claim 1, wherein the oil .in the crankshaft lubrication channel (38) is introduced to the crankshaft (56) through a right crankshaft opening (31a) formed in the right casing (30).
8. The internal combustion engine as claimed in claim 1, whereinthe crankcase exit opening (58) is.located close to a stud opening on the crankcase block seating surface(28) of the right casing (30).