Claims:WE CLAIM:
1. An oil lubrication system (200) for an internal combustion engine (100), the oil lubrication system providing lubrication to a plurality of parts of the internal combustion engine (100), the oil lubrication system (200) comprising:
an oil reservoir (210) on a periphery of a camshaft bearing bracket (322) of the camshaft bearing (320) of the camshaft (310), the oil reservoir (210) providing lubrication oil to an outer racing (320o) of the camshaft bearing (320); and
an oil routing path (222) for channelling the lubrication oil from an oil gallery (220) of the internal combustion engine (100) to the oil reservoir (210), the oil gallery (220) being a network of plurality of oil paths for transferring lubrication oil within the internal combustion engine (100), the oil gallery (220) enabling transferring of lubrication oil from an oil sump (112) to various components of the internal combustion engine (100).

2. The oil lubrication system (200) as claimed in claim 1, wherein the oil reservoir (210) is formed as a circular groove on at least some portion of an inner surface (322a) of the camshaft bearing bracket (322).

3. The oil lubrication system (200) as claimed in claim 2, wherein the circular groove is formed as a ring around the complete periphery on the inner surface (320a) of the camshaft bearing bracket (322).

4. The oil lubrication system (200) as claimed in claim 1, wherein the oil reservoir (210) is formed as a circular groove on at least some portion of an inner surface of a cylinder head (103) of the internal combustion engine (100), the cylinder head (103) housing the camshaft bearing bracket (322).

5. The oil lubrication system (200) as claimed in claim 4, wherein the circular groove is formed as a ring around the complete periphery on the inner surface of the cylinder head (103).

6. The oil lubrication system (200) as claimed in claim 1, wherein the oil routing path (222) makes an angle of ten to fifteen degrees with a longitudinal axis (150) of the engine (100).

7. The oil lubrication system (200) as claimed in claim 1 includes at least one oil flow restrictor (240) for controlling the flow of lubrication oil towards the oil sump (112) of the oil lubrication system (200).

8. The oil lubrication system (200) as claimed in claim 7, wherein the one at least oil flow restrictor (240) is provided at the terminal ends of the oil gallery (220), the oil flow restrictors (240) being configured for partially restricting the exit flow of lubrication oil from the oil gallery (220) towards the oil sump (112).

9. The oil lubrication system (200) as claimed in claim 1, wherein the network of plurality of oil paths includes an oil path to supply lubrication oil to an inner race (320i) of the camshaft bearing (320).

10. The oil lubrication system (200) as claimed in claim 1 includes an oil reservoir inlet (212) for supplying lubrication oil to the oil reservoir (210), the oil routing path (222) connecting to the oil reservoir (210) through the oil reservoir inlet (212).

, Description:FIELD OF THE INVENTION
[001] The present invention relates to lubrication in an internal combustion engine and more particularly to active hydrodynamic lubrication for camshaft bearings of an internal combustion engine.

BACKGROUND OF THE INVENTION
[002] During the movement of various parts of a machine, it is desired that one metallic part should not come in direct contact with other metallic surfaces. A direct metal to metal contact leads to undesired friction and noise during the operation of the machine. Further, a direct metal to metal contact among the machine parts also increases the rate of wear and tear, thus reducing the life of the machine parts.
[003] An internal combustion engine is an assembly of numerous metallic parts. A cam shaft housed in a cylinder head of the internal combustion engine controls the timing of the valves/ports of a combustion chamber. The camshaft is mounted using a cam shaft ball bearing. The camshaft ball bearing has an outer race and an inner race. The outer race of the camshaft ball bearing is housed and press fitted in a ball bearing bracket. It is also known in the art to provide the ball bearing bracket as a drilled-out provision within the cylinder head. The provision within the cylinder head houses the camshaft ball bearing and the ball bearing is press fitted into this provision in the cylinder head.
[004] In relation to internal combustion engines, ball bearing bracket is basically a drilled-out portion in the cylinder head casting of the internal combustion engine. The camshaft ball bearing (ball bearing) is then press fitted inside this drilled out portion of the cylinder head wherein the outer race of the ball bearing is press fitted in the cylinder head. The bearing thus fitted in the cylinder head facilitates the motion of a camshaft of the internal combustion engine.
[005] Further, it is known in the art to use different material for the cylinder head and the bearings because the functionality desired from each of the cylinder head and bearings is different. The bearings are designed to minimize friction and bear loads, whereas the cylinder head is designed considering cost factors and thermal conductivity of the material. As a result, it is well known in the art to manufacture cylinder heads using cast iron and bearings are made of steel.
[006] Due to difference in the materials of cylinder head (cast iron) and the outer race (steel) of the bearings, the clearance between the two assembled parts – cylinder head provisioning as bracket and outer race of bearing - keeps varying with changing temperature due to heat generation as a result of friction. This is a consequence of the difference in the thermal expansion rate of different materials – steel and cast iron. As a result of such unequal expansion of the two assembled parts, metal to metal contact happens and friction is generated. This leads to unnecessary noise and vibrations of the bearing and hence engine.
[007] Conventionally, it is known in the art to use a retainer for restricting the axial vibrations in the camshaft. The retainer substantially takes care of the axial vibrations. However, the retainer and other solutions in the prior art fail to address the problem of the lateral vibrations of the camshaft especially during heated conditions when there is difference in expansion of the components.
[008] Besides, in the prior art, the ball bearing of the camshaft is provided only a single lubrication. Only an inner race of the camshaft ball bearing is provided lubrication. Even after the single lubrication of the inner race, metal to metal contact between the cylinder head and the outer race of the bearing is unavoidable.
[009] As mentioned earlier, metal-to-metal friction leads to durability issues because of greater wear and tear. Also, the valve timing which is managed by the camshaft is disturbed resulting in decrease in engine efficiency. The fuel consumption increases, and this adds to running cost.
[010] Thus, there is a need in the art for a lubrication system for an internal combustion engine, which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[011] In one aspect, the present invention is directed at an oil lubrication system for an internal combustion engine including a camshaft bearing of a camshaft of the internal combustion engine. The oil lubrication system includes an oil reservoir and an oil routing path. The oil reservoir is located on a periphery of a camshaft bearing bracket of the camshaft bearing of the camshaft. The oil reservoir stores and provides lubrication oil to an outer racing of the camshaft bearing. The oil routing path transfers and channels the lubrication oil from an oil gallery of the internal combustion engine to the oil reservoir. The oil gallery is a network of plurality of oil paths for transferring lubrication oil within the internal combustion engine. The oil gallery enabling transferring of lubrication oil from an oil sump to various components of the internal combustion engine.
[012] In one embodiment, the oil reservoir is formed as a circular groove on at least some portion of an inner surface of the camshaft bearing bracket. In one embodiment, the camshaft bearing bracket is formed as a drilled-out hole in the cylinder head. In another embodiment, the circular groove is formed as a complete ring around the complete periphery on the inner surface of the camshaft bearing bracket.
[013] In another embodiment, the oil routing path makes an angle of ten to fifteen degrees with a longitudinal engine axis.
[014] In another embodiment, the oil lubrication system includes at least one oil flow restrictor for controlling the flow of lubrication oil towards the oil sump of the oil lubrication system. The restrictor is provided at the terminal ends of the oil gallery and are configured for partially restricting the exit flow of lubrication oil from the oil gallery towards the oil sump.
[015] In a further embodiment, the network of plurality of oil paths includes an oil path to supply lubrication oil to an inner race of the camshaft bearing.
[016] In another embodiment, the oil lubrication system includes an oil reservoir inlet for supplying lubrication oil to the oil reservoir. The oil routing path connects to the oil reservoir through the oil reservoir inlet.

BRIEF DESCRIPTION OF THE DRAWINGS
[017] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figures 1A and 1B illustrate a schematic view of an internal combustion engine 100, wherein
Figure 1A illustrates the internal combustion engine in a perspective view with a crank case cover removed; and
Figure 1B illustrates a part of the internal combustion engine in another perspective view with the crank case cover removed; in accordance with an embodiment of the invention.
Figure 2A illustrates an oil lubrication system for the internal combustion engine, in accordance with an embodiment of the invention.
Figures 2B-D illustrate a cylinder head of the internal combustion engine in various sectional front views, in accordance with an embodiment of the invention.
Figures 3A-C illustrate the cylinder head in various perspective sectional views to elaborate more on the oil lubrication system, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[018] The present invention relates to an oil lubrication system for an internal combustion engine. More particularly, the present invention relates to an oil lubrication system for a camshaft bearing of the internal combustion engine.
[019] Figures 1A and 1B illustrate a schematic view of an internal combustion engine 100, in accordance with an embodiment of the present invention. Figure 1A illustrates the internal combustion engine 100 in a perspective view with a crank case cover removed. Figure 1B illustrates a part of the internal combustion engine 100 in another perspective view with the crank case removed. In accordance with an embodiment, the internal combustion engine 100 (engine 100) includes a cylinder block 102 supported by a crankcase assembly 101. The cylinder block 102 defines a cylinder portion at which a piston can perform reciprocating motion. A cylinder head 103 is mounted to the cylinder block 102 and the cylinder head 103 acts as one end of the cylinder portion. The cylinder block 102 is provided with cooling fins 106.
[020] The engine 100 includes a piston (not shown) performing a reciprocating motion in the cylinder portion due to force imparted to it by the combustion of air-fuel mixture. This reciprocating motion is converted and transferred to a rotary motion of a crankshaft 110 through a connecting rod (not shown). Further, a cylinder head-cover 104 is mounted to the cylinder head 103. The cylinder head 103 includes an intake port 105 and an exhaust port 108 that are provided on a first face and a second face of the cylinder head 103. In the present embodiment, the first face is an upward facing side and the second face is a downward facing side thereof. Further, the cylinder head 103 supports a camshaft assembly (not shown in Figures 1A and 1B) that is capable of operating intake valve(s) and exhaust valve(s) of the internal combustion engine 100.
[021] The internal combustion engine 100 includes a gear oil pump drive (not labelled) connected to the crankshaft 110 and rotates integrally with it. The gear oil pump drive includes a primary driving gear 113. The primary driving gear 113 acts a primary drive and is capable of transferring rotational force or torque to a primary driven gear (not shown). The primary driven gear is thus operably connected to the crankshaft 110. The cylinder head 103 comprises a valve train arrangement to control opening and closing of intake and exhaust valves present at the intake port 105 and one or more exhaust ports 108 thereby controlling intake of air-fuel mixture and outlet of exhaust gases. The camshaft assembly (not shown) is rotatably mounted to the cylinder head 103. A cam chain (not shown) operably connects the crankshaft 110 and camshaft assembly. A driven sprocket of the camshaft assembly is configured to be meshed with the primary driving gear 113 and the driven sprocket transfers the rotary motion of the crankshaft 110 to the camshaft assembly. During running of the vehicle, a large amount of heat is generated inside the internal combustion engine 100. For reducing the impact of the heat on the piston, the cylinder block 102 and other engine parts, an oil sump 112 is provided in the crankcase assembly 101 to store oil and collect the falling oil during normal operation to be cycled again through an oil drain plug 114. Usually, the oil sump 112 is provided at the bottom-side of the left-hand side of the crankcase assembly 101 for continuous lubrication using an oil lubrication system 200 (explained in greater detail with reference to Figures 2A-D) and cooling of a piston and a plurality of piston cylinder wall and other parts of the internal combustion engine 100.
[022] Figure 2A illustrates the oil lubrication system 200 for the engine 100 in accordance with an embodiment of the invention. Figures 2B-D illustrate the cylinder head 103 in various sectional front views, in accordance with an embodiment of the invention.
[023] The oil lubrication system 200 for the engine 100 provides lubrication to engine parts including to a camshaft bearing 320 of a camshaft 310 of the engine 100. The camshaft bearing 320 facilitates the motion of the camshaft 310. The oil lubrication system 200 includes an oil reservoir 210 and an oil routing path 222. The oil reservoir 210 is located on a periphery of a camshaft bearing bracket 322 of the camshaft bearing 320. The oil reservoir 210 stores and provides lubrication oil to an outer racing 320o of the camshaft bearing 320. The oil routing path 222 transfers and channelises the lubrication oil from an oil gallery 220 of the internal combustion engine 100 to the oil reservoir 210. The oil gallery 220 is a network of plurality of oil paths for transferring lubrication oil within the internal combustion engine 100. The oil gallery 220 enables transferring of lubrication oil from an oil sump 112 (shown in Figure 1B) to various components of the internal combustion engine 100.
[024] Initially or when replacing, lubricating oil is poured through an opening at the top of the engine 100, and it goes through the oil gallery 220 eventually arriving in the oil sump 112. The oil drain plug 114 at the bottom of the engine 100 is used to remove lubrication oil from the engine 100 when replacing old/used lubrication oil.
[025] A set of special gears act as the gear oil pump drive - oil pumps. The oil pumps take the lubrication oil under low pressure and squeeze the lubrication oil to a high pressure, where it then passes through a chamber with a spring-loaded valve. The valve allows the oil to leave only under a specified pressure which is approximately between one lbs per square inch and sixty lbs per square inch depending upon the specification and size of the engine 100. The excess lubrication oil over and above this predefined limit is vented back to the oil sump 112. This is desirable because high oil pressure can damage bearings.
[026] From the oil pumps, the lubrication oil goes to the outside of an oil filter, where it is forced through media of the oil filter to a center of the engine 100, from where it exits into the oil gallery 220 for distribution to various parts of the engine 100. The oil filter is also provided with a bypass valve to keep the pressure from dropping too low if the oil filter becomes clogged so that in any condition sufficient lubrication oil reaches the components of the engine 100.
[027] Figures 3A-C illustrate the cylinder head 103 in various perspective sectional views to elaborate more on the oil lubrication system 200, in accordance with an embodiment of the invention. The oil reservoir 210 is formed as a circular groove on at least some portion of an inner surface 322a of the camshaft bearing bracket 322. As illustrated in Figure 3A, in another embodiment, the circular groove forming the oil reservoir 210 is formed as a ring around the complete periphery on the inner surface 320a of the camshaft bearing bracket 322.
[028] In an embodiment, the camshaft bearing bracket 322 is drilled-out in the cylinder head 103 and the camshaft bearing bracket 322 is integral part of the cylinder head 103 to which the outer race 320o of the camshaft bearing bracket 322 is press fitted. The oil reservoir 210 is formed as a circular groove on at least some portion of an inner surface 322a of a cylinder head 103 of the internal combustion engine 100. In another embodiment, the circular groove is formed as a ring around the complete periphery on the inner surface 322a of the cylinder head 103.
[029] Referring to figure 2A, the oil routing path 222, while connecting the oil gallery 220 and providing path to the lubrication oil to reach the oil reservoir 210, makes an angle of ten to fifteen degrees with a longitudinal axis 150 of the engine 100, in accordance with an embodiment of the invention.
[030] In an embodiment, the oil lubrication system 200 includes at least one oil flow restrictor 240. The oil flow restrictors 240 control the flow of lubrication oil towards the oil sump 112. The oil flow restrictors 240 are provided at the terminal ends of the oil gallery 220. The oil flow restrictors 240 are configured for partially restricting the exit flow of lubrication oil from the oil gallery 220 towards the oil sump 112. The oil flow restrictors 240 are configured so that the flow of the lubrication oil flowing towards the oil sump 112 has a lower flowing rate. For example, 60% of lubrication oil may be restricted and 40% of the lubrication oil may be allowed to move towards the oil sump 112, or vice versa. As a result, a desired amount of pressure is maintained to allow the lubrication oil to move upwards on the oil routing path 222 to enable for hydro dynamic lubrication.
[031] In accordance with an embodiment, the network of plurality of oil paths includes an oil path to supply lubrication oil to an inner race 320i of the camshaft bearing 320.
[032] In an embodiment, the oil lubrication system 200 includes an oil reservoir inlet 212 for supplying lubrication oil to the oil reservoir 210. The oil routing path 222 connects to the oil reservoir 210 through the oil reservoir inlet 212.
[033] Advantageously, the oil lubrication system provided by the invention provides double hydrodynamic lubrication to the camshaft bearing by providing additional lubrication to the outer race also. As a result, the oil lubrication system of the invention takes care of the lateral vibrations of the camshaft which were previously unattended.
[034] Further, the invention is able to achieve very high stiffness in the normal direction of the camshaft axis of rotation which in turn means lesser vibration because of dampening of vibrations between the camshaft and the outer race bracket. This further ensures better valve timing and improves engine performance with respect to the fuel efficiency, noise, emission and the like. Less friction leads to less noise and adds to comfort as well.
[035] Further, the rate of wear and tear reduces because of the additional lubrication provided by the invention. This reduces noise and friction and in turn increases performance, durability, and efficiency of the engine.
[036] Also, the lubrication system of the invention is retrofittable as only an additional oil routing path and circular groove is to be provided in the existing engine.
[037] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.