FIELD OF INVENTION

[0001] The present invention relates to an internal combustion engine and more particularly to an apparatus for reducing engine noise.

BACKGROUND OF INVENTION

[0002] Free and repeated rocking of rocker arm along the rocker shaft axis due to tappet clearance under the action of engine vibration, creates tappet noise. This noise can be reduced if free rocking of rocker arm is arrested.

[0003] A noise generated in the engine due to repeated knocking of tappet screw on the valve stem generates an irritating undesirable noise. Moreover, due to continuous hitting of tappet screw on the valve stem generates additional heat and wearing off the tappet screw and valve stem. Hence, there is a requirement of a mechanism, which can help in attenuating the free rocking of rocker arm due to hitting of tappet screw and valve stem.

SUMMARY OF THE INVENTION

[0004] The current invention relates to placing a "C" shaped elastic member having eyehole at both of the ends. One end of the "C" shaped elastic member is fastened between the nut tappet adjuster and the arm rocker such that this eyehole passes through the screw tappet adjuster. The other eyehole passes through the valve stem. This portion of the valve stem is the portion of valve projected out of the valve spring retainer at the upper portion of the spring. This mechanism pushes the rocker arm in the upward direction and the valve spring retainer upper portion in the downward direction in such a way that a positive clearance is formed during repetitive movement of the rocker arm. Such a mechanism is replicated and applied at both the sides i.e. the inlet side and the exhaust side rocker arm.

[0005] The novel aspect of this invention is that, unlike stand alone springs fastened elsewhere differing from what is explained here which require the spring to actuate completely through the valve lift, this concept requires that the spring actuate only by amount of pre-set tappet clearance. This enables lesser spring actuation, higher spring life due to less fatigue, to have low preload in the spring as actuation requirement is less, low wear and tear at all contact points, lower harm to other critical engine components during failure, no additional requirement of mounting structure; can be adapted to existing engines.

BRIEF DESCRIPTION OF DRAWINGS

Figure lillustrates a typical two-wheeler.

Figure 2illustratesan engine cut section depicting the cylinder head and the cylinder block.

Figure 3 illustrates the cylinder head and its components.

Figure 4A & 4B Shows the rocker arm& tappet clearance in inlet and exhaust side respectively.

Figure 5A & 5B shows the rocker arm and the leaf spring.

Figure 5C shows the first embodiment as assembly of first elastic member attached to the rocker arm.

Figure 6A &6B shows second embodiment of the leaf spring.

Figure 7shows the second embodiment as assembly of second elastic member on the rocker arm of the cylinder head.

Figure 8A & 8B shows third embodiment of the elastic member mechanism and fastening of elastic member in cylinder head.

DETAILED DESCRIPTION OF THE INVENTION

[0006] The engine noise reducing mechanism as disclosed and described in the current invention is applicable to all kinds of engines with rocker arm. Cylinder head noise can be generated due to different sources. Tappet noise is one of the significant sources. Valve seating impact, rocker arm to tappet screw impacts and rocker arm to camshaft impacts results in tappet noise. As engine operating temperature increases tappet clearance resulting in higher impact energy and noise.

[0007] The engine noise, which is originating from the tappet screw hitting repetitively on the valve stem, is reduced by using the elastic member mechanism. This elastic member mechanism is described as follows. Free rocking of arm rocker along the Shaft rocker axis due to tappet clearance under the action of engine vibration creates tappet noise. This noise can be reduced if free rocking of arm rocker is arrested. Prior art available with torsional spring (helical) and/or wave spring washer at arm rocker assembly to enforce positive contact/gap at the tappet zone. This ensures NO free rocking of arm rocker during dwell time thus reducing tappet noise.

[0008] The present invention uses a leaf spring: a thin "C" shaped elastic member having eye (hole) at both ends, an arm rocker assembly: an arm pivotally mounted on Shaft rocker and makes tangential contact with both cam profile and valve stem tip, which upon camshaft rotation actuates Intake or exhaust valve, a screw tappet adjuster: child component of arm rocker assembly, screwed through the tappet hole present at the tip of rocker arm to make contact with valve tip, a nut tappet adjuster: child component of arm rocker assembly, screwed onto screw tappet adjuster to lock screw tappet adjuster from loosening and to maintain tappet clearance throughout the operation of engine, a roller assembly rocker: child component of arm rocker assembly, pinned to the opposite end of rocker arm to that of screw tappet adjuster, which makes tangential contact with cam profile, a valve: a tappet valve used as intake and/or exhaust valve of an internal combustion engine, a retainer valve spring: cap that is located on valve stem with the help of cotters and preloads the helical spring that is coaxial with the valve, a cotter valve: cotters used to lock retainer valve spring with valve stem.

[0009] A thin "C" shaped elastic member having eye (hole) at both ends, one eye of which is fastened between nut tappet adjuster and arm rocker and located through screw tappet adjuster, whereas the other eye is located through valve stem projecting out of the retainer valve spring and resting on it, so as to push both arm rocker and retainer valve springs apart to enforce positively the pre-set tappet clearance while the roller on arm rocker assembly dwells over the base circle of the cam profile.

[00010] Arm rocker assembly enables engine intake/exhaust valves' actuation, arm rocker is pivoted on shaft rocker and it makes tangential contact with both cam-lobe and valve stem tip. Inherently there will be some pre-set gap maintained between screw tappet (part of arm rocker assembly) and tip of valve stem; this gap is termed as tappet clearance. Free rocking of arm rocker along the shaft rocker axis due to tappet clearance under the action of engine vibration creates tappet noise. This noise can be reduced if free rocking of arm rocker is arrested.

[00011] The spring when assembled will get preloaded because of angle bend change from that of free condition. The preload is such a way that it exerts separation force between arm rocker and Retainer valve spring. The separation distance will be equal to preset tappet clearance. During the time when roller is on the base circle part of cam profile, tappet clearance will be positively ensured between screw tappet and valve stem due to the action of leaf spring. As the camshaft begins to rotate with the engine start, lobe portion comes in contact periodically with the roller, the tappet clearance gradually starts reducing and eventually becomes zero; subsequently as the roller continues its travel on cam-lobe, and the valve is actuated by the rocker arm. As the roller alights off the cam-lobe portion, the valve actuation reverses to become eventually zero lift and tappet clearance gets created again as the roller is pressed against the cam lobe by the elastic member always. Because of this mechanism impact load between rocker arm to valve and rocker arm to camshaft is avoided. This improves life of valve train components and noise is reduced. In the description that follows, the intake side and exhaust side valves and other parts have been denoted by a suffix A and a suffix B in addition to the corresponding numerals for the corresponding parts.

[00012] Figure 1 shows a typical two wheeler with a rider seat 1, a rear wheel 2, an engine 3, an air intake box 4, a front wheel 5, a footboard 6, an utility box 7, a head lamp 8, a side cover 9, a pair of front suspension 10, a pair of rear suspension 12, a grab rail 12 and a tail lamp 13. The rider uses the rider seat 1 for sitting while the vehicle is in uses the engine 3 is placed between the front wheel 5 and rear wheel 2. The rider while being seated on the rider seat 1 places his foot on the footboard 6. The utility box 7 is used for storing various materials. The air intake box 4 provides induction air for the engine 3. The pair of front suspensions 10 and rear suspensions llprovides the rider with shock absorbing comfort while the vehicle is running on an uneven and not so smooth road.

[00013] Figure 2 shows the internal construction as shown in cut section view of engine 3. The engine 3 has a cylinder head 21, cylinder block 22, camshaft 33, rocker arm24, valve intake 25, valve exhaust 26, connecting rod smaller end 27, connecting rod bigger end 28, and crank web 29. The connecting rod smaller end 27 is connected to piston at one end and to the crank-web 29 at the other end through its bigger end. During combustion, piston is pushed downwards, the smaller end is pushed downwards, it provides a rotator motion to the crank web, and hence, the connecting rod bigger end along with the crank web rotates. The rotation of the crank web provides the synchronized rotation to the camshaft 33 through a cam chain (not shown in the figure). The camshaft 23 is equipped with two cam lobes (which will be described in coming figures), profile of which defines the opening and closing of the inlet and exhaust valves. The rocker arm 24 moves on its axis, and degree of movement is being decided by the profile of the cam of the camshaft 23. Depending upon the movement of the rocker arm 24, the intake valve stem 25's and exhaust valve 26's movement is controlled thus it may close or open the passage of inlet and exhaust.

[00014] Figure 3shows the cylinder head internal construction with screw tappet inlet side 31A, Screw tappet outlet side 31B, spring upper retainer inlet side 32A, Spring upper retainer outlet side 32B, Spring valve inlet side 33A, Spring outlet side 33B, spring lower retainer inlet side 34A, Spring lower retainer outlet side 34B, shaft rocker inlet 35A, Shaft rocker exhaust 35B, cam inlet 36A, cam exhaust 36B, inlet valve 37A, exhaust valve 37B. The two sides namely, inlet side and exhaust side have a very similar construction and constitute similar parts. For convenience, inlet side has been labeled with a suffix "A" and outlet side has been labeled with a suffix "B". In the cylinder head construction, the cam inlet 36A has a profile, which decides the movement of inlet rocker arm around the axis of shaft rocker arm35A. The shaft rocker inlet 35A on the other end is connected to the screw tappet inlet side 31A through the rocker arm body and it rests on the spring upper retainer inlet side. The spring valve inlet side avoids any jerk on the rocker arm and at the same time inhibits the pressure waves which would have been created which may have lead to noise generation.

[00015] In this cylinder head inlet side construction, the inlet valve 37A is at a time open and another time closed wherein the said opening and closing is decided by the movement of the inlet valve end 37A closer to valve lower retainer 39 or farther. When the inlet valve end 37A sits on the valve lower retainer, the valve is in the closed position and no gas comes inside the engine cylinder. Similarly, the exhaust side cylinder head is constructed wherein the profile of cam exhaust 36B defines the movement of the rocker arm exhaust side around the shaft rocker exhaust. Similar to the inlet side, on the exhaust side also, the other end of the rocker arm is connected to the screw tappet outlet side 31B, The spring valve outlet side has two retainers namely the spring valve outlet upper retainer 32B and the spring valve outlet lower retainer 34B which inhibits any shock arising out of the movement of the valve stem and the screw tappet outlet side 31B.

[00016] Figure 4A and 4B wherein the Figure 4A shows the valve in open condition and Figure 4B shows the valve in closed condition. Figure 4A and Figure 4B show first embodiment of the current invention with body rocker arm inlet 41A, screw tappet inlet side 42A, valve inlet stem upper portion 43A, and elastic member 45A and nut tappet inlet 44A. It is to be noticed that, the screw tappet inlet side 42A and valve inlet stem upper portion 43A are not touching each other. During engine operation, the repetitive striking of these two portions namely the screw tappet inlet side 42A and valve inlet stem upper portion 43A leads to undesirable noise generation. Hence, this is an objective of this invention to inhibit this noise by using a elastic member45A inbetween the screw tappet inlet side 42A and valve inlet stem upper portion 43A. A similar elastic member rocker arm exhaust spring 45B is placed between the screw tappet exhaust side 42A and valve exhaust stem upper portion 43B.

[00017] Figure, 5A, 5B and 5Cshow the rocker arm, spring leaf and assembly of elastic member on the rocker arm. Figure 5A shows the screw tappet 31, nut tappet 44, shaft rocker 52 and screw tappet groove 53. Figure 5B shows the elastic member 45's upper portion 54 and the screw tappet groove 55.It can be seen in the Figure 5C that the elastic member l's upper portion 54 is accommodated inbetween the rocker arm body by use of the nut tappet. The other portion of the elastic member 45, which is spring 1 space 55, is accommodated inside the upper spring retainer 32. It is to be noted that in this description, since the construction is same on both the sides, the use of prefixes "A" and "B" are not required and the discussed embodiment is applicable on both the sides i.e. the inlet side and the exhaust side.

[00018] Figure 6A and 6B shows another embodiment of the invention in which one end of the elastic member 60 instead of being fastened to the spring retainer is kept free and under tension inside the cylinder head cover and the other end is fastened to the screw tappet with help of the nut tappet. In Figure 6A, the elastic member 60 has two ends namely end 61 and end 62. The end 62 is fastened to the screw tappet with help of nut tappet 44 as shown in Figure 6B and the other end 61 is kept free under tension inside the cylinder head cover.

[00019] Figure 7 shows the second method of placing the elastic member 60 inside the cylinder head on the rocker arm body to inhibit the noise produced by tappet during the engine operation. In this second way of performing the invention, it can be seen in the current invention, that the elastic member 60A on the inlet side and the elastic member 60B on the exhaust side are placed on the rocker body and fastened by the respective tappet nut screws and the other end of the elastic member is freely and under tension retained by the cylinder head cover.

[00020] Figure 8A and 8B shows another embodiment and a way of performing the elastic member installation on the rocker arm wherein one end of the elastic member is retained by the rocker arm body by virtue of sliding mechanism and the other end of the elastic member is fixed on the horizontal bridge plate between two camshaft bearing housing on the cylinder head using a nut. As shown in Figure 8A, the elastic member 80 has two ends 81 and 83 and a bent 82. The bent 82 provides the spring effect and the upper holes of second elastic member 81 provides the fastening mechanism for fastening the elastic member to the horizontal bridge plate between two camshaft bearing housing on the cylinder head and restrict its motion. The end 83 is resting on the rocker body profile and this elastic member slides on the rocker body and simultaneously pushes the rocker body downside. Figure 8B shows the shaft rocker arm 74B, horizontal bridge plate between two camshaft bearing housing on the cylinder head 21 and the valve stem 26 with the second elastic member 80 fastened to the horizontal bridge plate between two camshaft bearing housing on the cylinder head with the fastener 84 and on the other end the elastic member is resting on the rocker arm body.

[00021] Blade/elastic member is used to bias the rocker arm during its entire oscillation. This reduces impact or oscillations of rocker arm during base circle or/and opening and closing of valve. Form of the spring is designed in such a way that spring accommodates larger deflection (within permissible stress) with least possible load in both installed and maximum position of the rocker arm. As described in the above description, all three methods can be used for inhibiting the noise caused due to tappet inside the cylinder head by dampening down the repetitive hitting of tappet screw and the valve stem.

We claim:

1. An internal combustion engine comprising: a plurality of valves (25, 26) with two ends namely a poppet end (37B) and a valve stem end (31B); wherein the position of the said poppet end (37B) controls the opening and closing of ports with valve (25, 26) either to allow or prohibit the charge entry or exit to or from the cylinder; the said valve stem (43A, 43B) being surrounded by a spring (33B); a spring upper retainer (32B) from top and a spring lower retainer (34B) from bottom; a rocker arm (24A, 24B); wherein the said rocker arm (24A, 24B) has a rocker body with two ends; to the first end a roller (56) is attached which follows a path as defined by a cam (36A) and to the second end a tappet screw (42A, 42B) is attached which actuates one of the said valve stem (25,26); the tappet screw (42A, 42B); wherein the said tappet screw (42A, 42B) has two ends and a middle portion in such a way that upper end is fastened to the said rocker arm (24A, 24B) by a nut tappet (44A, 44B); the said middle portion passes through the rocker arm (41A, 41B); and the said lower end rests on the one end of the said valve stem (43A, 43B); wherein a pre-stressed elastic member (45A, 45B) is attached between the said tappet screw upper end (31A, 31B) and the said spring upper retainer (32A,32B) to stop the free rocking motion of the said rocker arm tappet screw (42A, 42B) end to and forth the said valve stem upper end (43A, 43B).

2. An internal combustion engine comprising: a plurality of valves (25, 26) with two ends namely a poppet end (37B) and a valve stem end (31B); wherein the position of the said poppet end (37B) controls the opening and closing of ports with valve (25, 26) either to allow or prohibit the charge entry or exit to or from the cylinder; the said valve stem (43A, 43B) being surrounded by a spring (33B); a spring upper retainer (32B) from top and a spring lower retainer (34B) from bottom; a rocker arm (24A, 24B); wherein the said rocker arm (24A, 24B) has a rocker body with two ends; to the first end a roller (56) is attached which follows a path as defined by a cam (36A) and to the second end a tappet screw (42A, 42B) is attached which actuates one of the said valve stem (25,26); the tappet screw (42A, 42B); wherein the said tappet screw (42A, 42B) has two ends and a middle portion in such a way that upper end is fastened to the said rocker arm (24A, 24B) by a nut tappet (44A, 44B); the said middle portion passes through the rocker arm (41A, 41B); and the said lower end rests on the one end of the said valve stem (43A, 43B); wherein a pre-stressed elastic member (60A, 60B) is attached between the said tappet screw (42A, 42B) and upper end on the cylinder head cover inner side (71) to stop the free rocking motion of the rocker arm tappet screw end to and forth the valve stem upper end.

3. An internal combustion engine comprising: a plurality of valves (25, 26) with two ends namely a poppet end (37B) and a valve stem end (31B); wherein the position of the said poppet end (37B) controls the opening and closing of ports with valve (25, 26) either to allow or prohibit the charge entry or exit to or from the cylinder; the said valve stem (43A, 43B) being surrounded by a spring (33B); a spring upper retainer (32B) from top and a spring lower retainer (34B) from bottom; a rocker arm (24A, 24B); wherein the said rocker arm (24A, 24B) has a rocker body with two ends; to the first end a roller (56) is attached which follows a path as defined by a cam (36A) and to the second end a tappet screw (42A, 42B) is attached which actuates one of the said valve stem (25,26); the tappet screw (42A, 42B); wherein the said tappet screw (42A, 42B) has two ends and a middle portion in such a way that upper end is fastened to the said rocker arm (24A, 24B) by a nut tappet (44A, 44B); the said middle portion passes through the rocker arm (41A, 41B); and the said lower end rests on the one end of the said valve stem (43A, 43B); wherein a pre-stressed elastic member (80A, 80B) is placed between the cylinder head and the rocker arm body; the said elastic member (80A, 80B) pulls or pushes the said rocker arm body (82A, 82B) in the upward or downward direction to stop the free rocking motion of the rocker arm tappet screw end to and forth the valve stem upper end.

4. An internal combustion engine as claimed in Claim 1 or Claim 2 wherein the first end of the elastic member (60A, 60B) is attached to the said tappet screw (42A, 42B) by a nut tappet (44A, 44B).

5. An internal combustion engine as claimed in Claim 1 wherein the second end of the said elastic member (60A, 60B) is held inside the screw tappet groove 5.

6. An internal combustion engine as claimed in Claim 3 wherein the elastic member (80A, 80B) is mounted on the cylinder head at one end and other is freely resting on the rocker arm body (82A, 82B).