DESC:TECHNICAL FIELD
[0001] The present subject matter relates generally to an internal combustion engine of a two-wheeled vehicle, and more particularly, but not exclusively, to an oil sealing assembly for the internal combustion engine of the two-wheeled vehicle.
BACKGROUND
[0002] An internal combustion engine converts thermal energy obtained from burning of a fuel with an oxidizer (air) into mechanical energy, which can be used to do some kind of mechanical work. It is used in a wide range of applications including providing motive force for movement of a vehicle. The main parts of the engine include a cylinder head, a reciprocating piston on a cylinder block and a connecting rod which connects the piston to the reciprocating crankshaft.

[0003] Typically, internal combustion engines, especially of horizontally disposed CVT based scooter-type two-wheelers, include a crankshaft, whose main bearings and lubricating circuits are linked because of the open lubrication system with the help of a cover filter assembly in the crankshaft RH side. Bearing layouts of such internal combustion engines often becomes a constraint whenever load or capacity of the engine increases. This is because of the higher size requirement of the bearing layout. Typically, bearing layout of such engines includes plurality of ball bearings provided with a metal or rubber based shielding for effecting oil sealing.

BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.
[0005] Fig. 1 illustrates a side view of a scooter-type two-wheeled vehicle as an example, in accordance with an embodiment of the present subject matter.

[0006] Fig. 2 (a) illustrates a side view of an engine assembly of the two-wheeled vehicle shown in Fig. 1, in accordance with an embodiment of the present subject matter.

[0007] Fig. 2 (b) illustrates a sectional top view of the engine assembly shown in Fig. 2 (a), in accordance with an embodiment of the present subject matter.

[0008] Fig. 3 (a) illustrates an enlarged sectional view of a lubrication system of the engine assembly shown in Fig. 2 (b), in accordance with an embodiment of the present subject matter.

[0009] Fig. 3 (b) illustrates an enlarged sectional view of a lubrication sub-system of the lubrication system shown in Fig. 3 (a), in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION
[00010] Generally, lubrication paths of horizontally disposed engines such as that of scooter-type two-wheeled vehicles, involves an entry path from crankcase RH side to crankpin on the crankshaft of the engine through a cover filter assembly. However, since the above mentioned lubrication path is not fully concealed, bearing assembly, for example, a ball bearing assembly disposed on the crankshaft RH side is usually made to have a shielding on the outer side in order to minimize the leakage for the oil entering the cover filter assembly and the crankpin.
[00011] However, internal combustion engines with such ball bearing assemblies are often bulkier and heavier, which makes the use of such ball bearing assemblies on the crankshaft RH side extremely cumbersome, more particularly, in case of scooter-type vehicles with lower engine capacity, for example, in the range of 100~125cc. The Ball bearings use hardened spherical balls, and hence the load is transmitted from the outer race to the balls and then from the balls to the inner race. Since there is very small area of contact of the spherical balls with the load, their load bearing capacity is less. The ball bearing fatigue life is also lowered.
[00012] Thus, conventional internal combustion engines of scooter-type two-wheelers started utilizing roller bearings on the crankshaft RH side instead of the generally used ball bearing assemblies. In roller bearings cylindrical rollers are used and the contact between the outer and inner race is not a point but a straight line. Hence, the roller bearing has increased load bearing capacity. It also controls noise, and vibrations improving NVH characteristics, more particularly, in case of engine having capacity in the range of 100~125cc or more.
[00013] However, use of roller bearings on the crankshaft RH side involves its own limitations. The roller bearings generate high amounts of friction and hence, typical metal or rubber shielding as used in case of ball bearing assemblies cannot be utilized in case of roller bearing assemblies for the purpose of preventing oil leakage, due to various manufacturing constraints. Thus, use of roller bearing assemblies carries with itself increased oil leakage from the lubrication circuit of the engine. In most cases, such increased leakage may lead to failure of engine crankshaft. Further, increase in the lubrication oil leakage leads to faster draining of lubrication oil inside the engine chamber leading to malfunctioning of many engine parts.
[00014] Thus, it is a challenge to provide internal combustion engine for scooter-type two-wheeled vehicles with reduced size of the bearing assembly and at the same time with optimal lubrication circuit which controls the oil leakage without compromising on the load carrying capacity of the engine.
[00015] The present subject matter provides an oil sealing assembly for an internal combustion engine of a two-wheeled vehicle, more particularly, for a scooter-type two-wheeled vehicle. In an embodiment, the internal combustion engine of the present subject matter includes a lubrication system, which has a centrally disposed connecting rod rotatably coupled with a crankshaft. In an embodiment, the crankshaft is provided with a ball bearing assembly on its LH side, and a roller bearing assembly on its RH side. Further, in an embodiment, the lubrication system of the present subject matter involves a lubrication path carrying lubrication oil through a RH side of the crankcase and crankpin to a bigger end of the connecting rod. In an embodiment, the roller bearing assembly of the present subject matter has an inner race that is press fitted against an outer diameter of the crankshaft RH side, and an outer race that is press fitted against the crankcase RH side, such that the inner race of the roller bearing rotates along with the rotating crankshaft RH side, and the outer race of the roller bearing remains stationary as a result of being press fitted with the crankcase RH side. The lubrication path supplies lubrication oil to the roller bearing assembly.
[00016] In an embodiment, the internal combustion engine is provided with an oil seal sub-assembly adjoining the roller bearing assembly on the RH side of the crankshaft. For instance, the oil seal sub-assembly of the present subject matter has an inner diameter that establishes a line contact with the outer diameter of the crankshaft RH. In an embodiment, the inner diameter of the oil seal sub-assembly is held tightly against the rotating crankshaft by means of a spring member, which ensures that the inner diameter of the oil seal sub-assembly is spring loaded and do not wobble or jump as a result of rotation of the crankshaft. Further, in an embodiment, the oil seal sub-assembly has an outer diameter that is press fitted against the crankcase RH side. Further, in an embodiment, the oil seal sub-assembly of the oil sealing assembly of the present subject matter ensures that any lubrication oil that passes through the inner race of the roller bearing and a clearance formed by the crankcase RH between the roller bearing assembly and the oil seal sub-assembly, is prevented from leaking.
[00017] In an embodiment, the oil sealing assembly of the present subject matter includes a controlled clearance formed between the crankshaft RH side and the crankcase RH side juxtaposing the oil seal sub-assembly, which controls oil leakage even when the oil seal sub-assembly fails. For instance, the oil seal sub-assembly may fail due to entry of dust or other foreign particles. In an embodiment, the controlled clearance of the oil sealing assembly that is formed between the crankshaft RH side and the crankcase RH side is of the order of 40~(100) microns, more particularly, in the range of 50~70 microns. The oil sealing assembly of the present subject matter ensures that the required oil pressure and oil flow to the bigger end of the connecting rod through the crankpin is optimally achieved.
[00018] Further, in an embodiment, the present subject matter, in order to counter the limitations of using the roller bearing assembly on the crankshaft RH side, involves mounting the oil seal sub-assembly, in close proximity to the right side of the roller bearing assembly, thereby forming a cavity between the oil seal sub-assembly, the roller bearing assembly, and the crankcase RH side, which enables controlling the leakage of the lubrication oil from the crankcase RH side. Further, in an embodiment, the spring loading of the inner diameter of the oil seal sub-assembly against the crankshaft RH side additionally ensures that leakage of lubrication oil flowing to the crankshaft is prevented. Further, in an embodiment, the controlled clearance between the crankshaft RH and the crankcase RH prevents any sudden failure of the engine.
[00019] In an embodiment, the press fitting of the inner and outer races of the roller bearing assembly against the crankshaft RH and the crankcase RH respectively ensures that the overall construction of the engine assembly is simplified, more particularly, due to elimination of additional clamping arrangement. Furthermore, the compact layout achieved as a result of the roller bearing assembly of the present subject matter and the lubrication system containing the oil sealing assembly of the present subjet matter ensures optimal downsizing of the engine of the scooter-type two-wheeled vehicle.
[00020] Further, in one embodiment, the present subject matter ensures the overall stiffness of the crankshaft assembly is increased, which further results in better and optimal NVH of the scooter-type two-wheeled vehicle. Further, in an embodiment, the increased load carrying capacity of the roller bearing assembly of the present subject matter ensures enhanced engine durability, as the roller bearing assembly of the present subject matter is capable of withstanding increased axial load. Moreover, reduction in the size of the bearing assembly of the internal combustion engine of the present subject matter helps in reducing the overall size of the engine, especially by reducing the crank radius as well as the crankshaft web diameter. Thus, allowing operation with lesser connecting rod centre distance, which further ensures reduction in overall engine centre distance without any compromise on the engine durability and performance.
[00021] The oil sealing assembly of the present subject matter has various advantages including better NVH aspects because of the rollers running inside the oil gallery. Further, enhanced bearing durability is achieved due to running in oil gallery. It also enables enhanced crankshaft stiffness, and better crankshaft dynamics at higher engine rpm. This is mainly achieved due to less crankshaft breathing / deflection. Furthermore, the present subject matter ensures engine compactness and crankshaft weight reduction, in addition to higher bearing load carrying capacity. Thus enabling commonisation of bottom portion of the internal combustion engine for two-wheeled vehicles of a particular range of engine capacity. The present subject matter ensures internal combustion engine with an oil gallery volume of approximately 5~12cc, more particularly operating at abour 7cc.
[00022] These and other advantages of the present subject matter would be described in greater detail in conjunction with the figures in the following description.
[00023] Fig. 1 illustrates a side view of a scooter-type two-wheeled vehicle (100) as an example, in accordance with an embodiment of the present subject matter. In an embodiment, the scooter-type two-wheeled vehicle (100) includes a body frame assembly (not shown), for example an underbone body frame assembly and covered by various covers. The body frame assembly supports a steering assembly including a steering shaft (not shown) and a handle bar assembly (111) in a front portion thereof. A front fork assembly (110) also provided in the front portion of the body frame assembly is rotatably supported on the steering shaft. The handlebar assembly (111) provided above the front fork assembly (110) allows steering of a front wheel. A headlamp assembly (116) is also supported on the handlebar assembly (111). Further, the front portion of the body frame assembly is provided with a front cover (103) to cover a forward facing side of the body frame assembly of the scooter-type vehicle (100). A front fender (109) is provided to cover an upper portion of a front wheel (101) of the vehicle (100). Left and right side covers (105) and (108) are disposed on the body frame assembly to cover left and right side surfaces of a rear portion thereof. Further, the vehicle (100) is provided with a floorboard (113) to enable resting of the rider’s feet during riding. A seat (107) is disposed above a side panel LH and RH (106). In an embodiment, a fuel tank assembly (not shown) is disposed underneath the seat (107). In an embodiment, a rear suspension member (115) for ensuring ride comfort is disposed rearwardly of the body frame assembly. The rear suspension assembly (115) comprises at least one rear suspension preferably on a left hand side of the scooter type vehicle (100). The rear suspension is mounted between a rear wheel (102) and the rear portion of the body frame assembly. However, in a scooter type vehicle (100) with two rear suspensions, the same may be disposed on the left side and the right side respectively thereof. An internal combustion engine assembly (120) capable of swinging is disposed downwardly and is at least partially covered by the left and right side covers.
[00024] Fig. 2 (a) illustrates a side view of the engine assembly (120) of the two-wheeled vehicle (100) shown in Fig. 1, in accordance with an embodiment of the present subject matter. In an embodiment, the engine assembly (120) includes a crankcase (not shown), a gear casing (not shown), a cover variator (203), cylinder head assembly including cylinder head (202) and cylinder head cover (208), and cylinder block (204). The crankcase houses the crankshaft (not shown), magneto assembly and CDI unit. In an embodiment, lubrication system and cooling system of the internal combustion engine is housed between the crankcase LH and RH. The combustion happens in the cylinder block (204) and the power is transmitted to the piston (not shown). The connecting rod (not shown) projects out of the body and is connected to the piston assembly (not shown), which is housed in the cylinder block (204), which is placed horizontally in relation to the axis of the engine assembly (120). Combustion gases generated are let out as exhaust from a muffler (not shown) extending along a right hand side of the vehicle (100).
[00025] The long hollow section towards the left side of the crankcase houses a CVT unit including a primary driver pulley unit, a secondary driven pulley unit and a V-belt drive, transmitting power between the two units. The left part of the crankcase that houses the CVT system is covered by the cover variator (203), which also houses a kickstarter assembly (206). The driven pulley unit contains a centrifugal clutch and the clutch shaft of which is connected to the rear wheel through a reducing gear shaft by meshing with an intermediate gear. When the engine assembly (120) is started and the crankshaft is rotated, the driver pulley unit of the rear wheel rotates and this rotation is transferred to the driven pulley unit by the belt drive. The different gear ratios are obtained by the continuous variation of the effective diameters of the V-belt pulleys.
[00026] In an embodiment, the crankcase is generally provided to have a plurality of mounting bosses on top and bottom of the engine assembly (120) to enable it to be swingably mounted on the rear portion of the body frame assembly of the vehicle (100). In an embodiment, the kickstarter assembly is generally disposed towards the left of the vehicle (100). There is also an oil sump inlet disposed towards the right portion in order to enable filling and refilling of lubricating oil whenever the oil quantity reduces.
[00027] Fig. 2 (b) illustrates a sectional top view of the engine assembly (120) shown in Fig. 2 (a), in accordance with an embodiment of the present subject matter. In an embodiment, the engine assembly (120) includes a crankshaft assembly (218) that is centrally coupled to a rotating connecting rod (224). In an embodiment, a ball bearing assembly (226) is disposed on one side of the crankshaft assembly (218), while a roller bearing assembly (216) is disposed on another side of the crankshaft assembly (218). The ball bearing and the roller bearing assemblies (226), (216) are separated by a centrally disposed crankpin (230). In an embodiment, a lubrication system (210) of the engine assembly (120) involves a lubrication path (222) entering from a right hand side of a crankcase (220) towards the crankpin (230). In an embodiment, the lubrication system (210) further includes an oil seal sub-assembly (214) disposed in close proximity to the roller bearing assembly (216). In an embodiment, the engine assembly (120) further includes a magneto assembly (212) disposed on a right hand side end of the crankshaft assembly (218). In an embodiment, the engine assembly (120) of the scooter-type two-wheeled vehicle (100) includes a CVT assembly (228) for effecting transmission of power to the driven means connecting the rear wheel (102) of the vehicle (100).
[00028] Fig. 3 (a) illustrates an enlarged sectional view of a lubrication system (210) of the engine assembly (120) shown in Fig. 2 (b), in accordance with an embodiment of the present subject matter. In an embodiment, the lubrication system (210) includes the lubrication path (222) carrying the lubrication oil enters the crankcase (220) from a crankcase RH (304) and passes through the crankpin (230) to the connecting rod (224). In an embodiment, the roller bearing assembly (216) is mounted juxtaposing the crankcase RH (304) allowing the lubrication path (222) to pass through the roller bearing assembly (216). In an embodiment, the roller bearing assembly (216) is mounted on a crankshaft RH side (308), while the ball bearing assembly (226) is mounted on a crankcase LH (350) supporting the crankshaft LH side (306). In an embodiment, a lubrication sub-system (302) includes the connecting rod (224) end allowing the passage of lubrication oil through the crankpin (230) and the roller bearing assembly (216) along with the adjoining oil seal sub-assembly (214) mounted on the crankcase RH (304).
[00029] Fig. 3 (b) illustrates an enlarged sectional view of a lubrication sub-system (302) of the lubrication system (210) shown in Fig. 3 (a), in accordance with an embodiment of the present subject matter. In an embodiment, the lubrication sub-system (302) includes an oil sealing assembly (320). In an embodiment, the oil sealing assembly (320) includes the roller bearing assembly (216) having a roller bearing inner race (312) press-fitted against an outer diameter of the crankshaft RH side (308), and a roller bearing outer race (310) press-fitted against the crankcase RH (304). In an embodiment, the oil sealing assembly (320) further includes the oil seal sub-assembly (214) having an oil seal outer diameter (318) press-fitted against the crankcase RH (304), and an oil seal inner diameter (316) spring-loaded against the outer diameter of the crankshaft RH side (308). In an embodiment, the inner diameter (316) of the oil seal sub-assembly (214) is held tightly against the rotating crankshaft RH side (308) by means of a ring shaped spring member (not shown), which ensures that the inner diameter (316) of the oil seal sub-assembly (214) is spring loaded and do not wobble or jump as a result of rotation of the crankshaft. The oil seal sub-assembly (214) is made up of elastomeric material and the spring member (not shown) is made of metal.
[00030] Further, in an embodiment, the oil sealing assembly (320) includes a first crankcase clearance (314) formed between the roller bearing assembly (216) and the oil seal sub-assembly (214). In an embodiment, the lubrication oil entering the crankcase RH (304) via the lubrication path (222) towards a bigger end (324) of the connecting rod (224), passes through the roller bearing inner race (312), which due to the rotation of the crankshaft RH side (308) may pass through the first crankcase clearance (314). The presence of oil seal sub-assembly (214) helps in preventing the further passage of the lubrication oil. However, due to extreme workload and constant rotation of the crankshaft, and due to entry of dust particles, and in the extreme case of a failure of the oil seal sub-assembly (214), there is a likelihood of the oil leaking out of the crankcase RH (304). The oil sealing assembly (320) of the present subject matter includes a controlled clearance (322) formed adjoining the oil seal sub-assembly (214) between the crankcase RH (304) and the crankshaft RH side (308) enables controlling the oil leakage from the crankcase RH (304) due to capillary forces generated by the leaking lubrication oil in such circumstances. In an embodiment, the controlled clearance formed between the crankcase RH (304) and the crankshaft RH side (308) is of the order of 40~100 microns, and most preferably, in a range of 50~70 microns.

[00031] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.
,CLAIMS:
We Claim:
1. An internal combustion engine assembly (120) for a two-wheeled vehicle (100), said internal combustion engine assembly (120) comprising:
a crankcase (220) including a crankcase RH (304) and a crankcase LH (350);
a crankshaft assembly (218) enclosed by said crankcase (220), said crankshaft assembly (218) comprising:
a crankshaft LH side (306) extending towards the crankcase LH (); and
a crankshaft RH side (308) extending towards the crankcase RH (304);
a connecting rod (224) coupled to said crankshaft assembly (218); and
a lubrication path (222) allowing passage of lubrication oil entering said connecting rod (224) through the crankcase RH (304);
wherein,
said internal combustion engine assembly (120) further comprising:
a roller bearing assembly (216) disposed on said crankshaft RH side (308), said roller bearing assembly (216) having an inner race (312) coupled to said crankshaft RH side (308), and an outer race (310) coupled to said crankcase RH (304);
said lubrication path (222) configured to permit ingress of lubrication oil to the roller bearing assembly (216);
an oil sealing assembly (320), said oil sealing assembly (320) comprising:
an oil seal sub-assembly (214) disposed adjoining said roller bearing assembly (216), said oil seal sub-assembly (214) having an outer diameter (318) coupled to said crankcase RH (304), and an inner diameter (316) spring-loaded against said crankshaft RH side (308); and
a controlled clearance (322) formed juxtaposing said oil seal sub-assembly (214) between said crankcase RH (304) and said crankshaft RH side (308).

2. The internal combustion engine assembly (120) as claimed in claim 1, wherein said crankshaft LH side (306) is mounted with a ball bearing assembly (226).
3. The internal combustion engine assembly (120) as claimed in claim 1, wherein the oil sealing assembly (320) includes a first crankcase clearance (314) formed between the roller bearing assembly (216) and the oil seal sub-assembly (214).
4. The internal combustion engine assembly (120) as claimed in claim 1, wherein said controlled clearance (322) formed between said crankcase RH (304) and said crankshaft RH side (308) is in a range of 40~100 microns.
5. The internal combustion engine assembly (120) as claimed in claim 3, wherein said controlled clearance (322) is preferably in a range of 50~70 microns.
6. The internal combustion engine assembly (120) as claimed in claim 1, wherein the connecting rod (224) coupled to said crankshaft assembly (218) through a crankpin (230), and said roller bearing assembly (216) is disposed in close proximity to the crankpin (230) on said crankshaft RH side (308).
7. The internal combustion engine assembly (120) as claimed in claim 6, wherein the lubrication path (222) enters the connecting rod (224) through the crankpin (230).
8. The internal combustion engine assembly (120) as claimed in claim 8, wherein the oil seal sub-assembly (214) is made up of elastomeric material.
9. The internal combustion engine assembly (120) as claimed in claim 1, wherein said a two-wheeled vehicle (100) is a scooter type vehicle.
10. The internal combustion engine assembly (120) as claimed in claim 9, wherein said internal combustion engine assembly (120) is swingably supported to a body frame assembly of said scooter type vehicle.