INTERNAL COMBUSTION ENGINE

FIELD OF THE INVENTION

The present invention relates to an internal combustion engine and more particularly to a rocker arm with lash noise clamping in a four stroke internal combustion engine.

BACKGROUND OF THE INVENTION

An internal combustion engine is usually provided with a cylinder head assembly containing valves to control the in and out movements of charge and exhaust gases in the cylinder relative to the piston. As shown in Figure 1, the engine body includes a crankcase 2, a cylinder block 1 coupled to the crankcase 2, a cylinder head 3 coupled to the upper part of the cylinder block 1 and a head cover 4 coupled to the upper part of the cylinder head 3. A piston slidably 5 fitted in the cylinder block 1 is connected via a connecting rod 6 with a crankshaft 7. The crankshaft 7 is rotatably supported by the crankcase 2. The crankcase 2 is constructed by connecting a left crankcase and a right crankcase together.

The induction and exhaust processes in such engine are controlled by a mechanical system known as a valve train responsible for operation of the valves. Typically such valve train has at least two valves, an intake valve 16 and an exhaust valve 17 generally inclined relative to the cylinder axis. An intake port 13 and an exhaust port 14 formed in the cylinder head 3 communicate with the combustion chamber 12 formed by being surrounded by the cylinder bore, the cylinder head 3 and the piston 5. The intake valve 16 is provided at the combustion chamber side opening of the intake port 13 and the exhaust valve 17 is provided at the combustion chamber side opening of the exhaust port 14. A camshaft 22 is rotatably supported by the cylinder head 3 so as to open/close the intake valve 16 and the exhaust valve 17.

Rotational power is transmitted from the crankshaft 7 to the camshaft 22 by the valve train. The intake 16 and exhaust valves 17 are operated via rocker arms (25 & 26) connected to the camshaft 22. A rocker arm is swingably supported on a rocker shaft, fixedly supported on the cylinder head. The rocker arm comprises of two ends. One end of the rocker arm is in contact with an overhead cam, integral with the camshaft. As shown in Figure 2, the other end of the rocker arm is connected with the end portion of a valve stem of the intake or exhaust valve through an adjustment screw (tappet screw) for adjusting the valve clearance, so that the lift of the said cam is transmitted to the intake or exhaust valve. Valve clearance (or valve lash) is provided for greatest amount of valve opening on the high point of the camshaft lobe and assures that the valve is tightly closed on the low segment of the camshaft lobe. Additionally, an oil passage is usually provided inside rocker shaft and filled with engine lubricating oil which is supplied through an oil hole between the rocker shaft and the rocker arm to lubricate them.

In such a valve operating system, a forceful impact occurs between the tappet screw and the valve stem, attributable to valve lash, before the valve opening and after valve closing event. The impact generates unfavourable rocker noise mainly due to forceful contact between tappet screw and valve stem as well as between valve and valve seat. However the prior art shows that valve lash increases with increase in temperature of the system and also due to wear and tear of valve train components including the valve stem or the tappet screw. Consequently the rocker noise is intensified due to increased impact caused by increased valve lash.

In order to prevent the generation of rocker noise, a zero valve lash mechanism for maintaining zero valve clearance using hydraulic valve lifters or the likes has been already proposed. However, this mechanism complicates the configuration of the valve operating system and contributes to an increase in cost accompanied by an inertial weight increase which is disadvantageous overall for the valve operating system. The present invention is directed to overcoming one or more problems as set forth above.

SUMMARY OF THE INVENTION

It is therefore one of the object of the present invention to provide a novel rocker arm encompassing a lash noise damping system.

It is also an object of the present invention to dampen the increased rocker noise caused during high temperature operating conditions as well as during wear and tear of the valve train components including a valve stem and a tapper screw. To this end, the present invention discloses a lash noise damping system provided in a valve train for reducing the noise produced from a rocker arm during the operation of the said valve train comprising of at least one rocker arm supported on a rocker shaft, a holding structure supported at a valve end of the rocker arm, the holding structure being spread on both sides of a longitudinal axis of the rocker arm, the holding structure with provisions for at least one groove at a valve facing surface.

At least one sliding member capable of sliding movement within the said groove is provided, the said sliding member further comprising of a head and a base. A spring member is located inside the said groove, the spring member facing the head of the said sliding member and capable of compression, wherein the load on the tappet screw is partially absorbed by a working combination of the sliding member and the spring member thereby reducing the impact of the tappet screw on the valve stem.

Yet another object of the present invention is to improve the performance of an internal combustion engine and efficiency by employing a lash noise damping system in a rocker arm of a valve train of the engine.

The foregoing objectives and summary provide only a brief introduction to the present subject matter. 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 invention and the claims should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 shows a typical sectional view of an internal combustion engine comprising a valve train.

Figure 2 shows a typical rocker arm operating a valve according to prior art.

Figure 3 shows a partial assembly view of a rocker arm incorporating a lash noise damping system according to the present invention.

Figure 4 shows a sectional view of a holding structure of a rocker arm according to the present invention.

Figure 5 shows a perspective view of the holding structure of Figure 3 according to the present invention.

Figure 6 depicts a front view of the rocker arm with the lash noise damping system.

Figure 7 shows a sectional view of lash noise damping system according to the present invention.

Figure 8 shows a side view of lash noise damping system according to the present invention.

Figure 9 illustrates a sectional view of a cylinder head incorporating the lash noise damping system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter described herein relates to a novel rocker arm construction with lash noise damping system and its interaction with the valve stem of a valve.

Various other features and embodiments of the lash noise damping system according to the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the engine wherever cited is a four stroke overhead cam type single cylinder internal combustion engine. However it is contemplated that the disclosure in the present invention may be applied to any engine capable of accommodating the present subject matter without defeating the spirit of the invention. It is also to be noted that the present invention is not dependent on the type of a valve and therefore is equally workable with an intake or an exhaust valve.

The valve lash noise damping system is now described in detail in connection with the rendered figures 3-9. The detailed explanation of the constitution of parts other than the invention which constitutes an essential part has been omitted at suitable places.

The novelty of the present invention lies in the construction of a valve end of a rocker arm and its interface with a valve using spring force to dampen the excess impact load produced due to increased valve lash during high temperature operating conditions. Further, the same lash noise damping system may also be useful to reduce noise generated during normal working conditions.

Figure 3 depicts a partial assembly view of the valve lash noise damping system 100 according to the present invention. It comprises of a rocker arm supported on a rocker shaft 107 having two ends, a cam end 102 cooperative with an operating cam 108 through a roller 105 and a valve end 101 co-operative with a valve stem 301 of a valve through a tappet screw 103. The rocker shaft 107 is rotatably secured to a rocker shaft groove 106. The tappet screw 103 is secured to the rocker arm through a tappet nut 104 and passes through an opening 209 in the rocker arm in order to contact the valve stem 301.

The valve end 101 of the rocker arm is provided with a holding structure 201 spread on both sides of a longitudinal axis of the said rocker arm. It has provisions for at least one groove 206 towards a valve facing surface of the holding structure 201. In one of the embodiment of the present invention, the holding structure 201 encompasses two identical grooves facing the valve, one each on either side of the longitudinal axis of the said rocker arm as shown in the sectional view of the holding structure in Figure 4. The grooves are open on the side facing the valve and closed on side facing the valve end of the rocker arm. Since both the grooves are identical, hence the specification further explains the lash noise damping system through one groove. Figure 4 shows a perspective view of the holding structure 201.

Further, the lash noise damping system includes at least one sliding member 204 which is capable of sliding within the groove 206. The sideways movement of the sliding member is restricted by the walls, referred by the numeral 207, of the groove 206. The groove 206 receives the sliding member from the bottom. The sliding member 204 further comprises of a head 203 and a base 202. The base 202 is in continuous contact with a valve retainer 303 whereas the head 203 is in contact with a spring member 205.

Furthermore, the spring member 205 is provided inside the groove 206 facing the head 203 of the sliding member 204 and is capable of compression. According to an embodiment of the present invention, the spring member 205 is a helical coil spring compressed to a certain extent. The spring member is not fully compressed as well as not fully free. As the spring member 205 is surrounded on all sides, it is not secured to the groove or the sliding member.

As shown in Figure 4 and 6, a gap 208 is provided between the valve facing surface of the said holding structure 201 and the said sliding member 204. The gap 208 is not rigid and enables the sliding member 204 to properly slide in the groove 206. The range of the gap 208 varies based on the compression of the spring on receiving the load from the cam end 102 of the rocker arm. Figure 6 further shows a partial front view of the rocker arm with the lash noise damping system.

Figure 7 shows a sectional view of lash noise damping system 100 according to the present invention. It shows the interaction of the present system with the valve comprising of a valve stem 301, valve head, valve spring 302 and the valve retainer 303. The base 202 of the sliding member 204 is supported on the circumference of the valve retainer 303 and is in continuous contact with the said valve retainer 303. The surface of the base 202 in contact with the valve retainer 303 may, preferably, be a spherical surface enabling the contact with the valve retainer at only one point. The tappet screw 103 will be in contact with the valve stem 301 just before valve opening and after valve closing event. According to an embodiment of the present invention, the lash noise damping system has two sliding members on either side of the longitudinal axis of the rocker arm capable of sliding between two grooves provided in the holding structure. The bases of both the sliding members are supported and balanced on the circumference of the valve retainer 303 so as to work in tandem as shown in Figure 8.

The working of the lash noise damping system is now explained with the help of Figure 9. The valve lash of the valve train increases during high temperature operating conditions or during wear and tear of the valve train components including valve stem and tappet screw. As such the present invention is preferably suited for these conditions. When the cam lobe 108 transfers the load for opening of the valve to the rocker arm through the roller 105, the load effectively is transferred to the valve end 101 of the rocker arm rotatably supported on the rocker shaft 107. As the cam lobe lifts the roller, the tappet screw 103 goes down at the valve end 101 to make contact with the valve stem 301.

Since the valve lash is more, the impact load on contact between the tappet screw and the valve stem would be more. However, in the present invention, a part of this load is first absorbed by the working combination of the sliding member 204 and the spring member 205 thereby subsequently reducing the impact of the tappet screw on the valve stem 301. The sliding member 204 which is in contact with the valve retainer 303 pushes against the spring member 205 which compresses and partially absorbs the load on the tappet screw. The tappet screw then transfers the reduced load to the valve stem thereby opening the valve. Thus the said lash noise damping system reduces the noise produced from the rocker arm during the operation of the said valve train. It is to be noted that the present system works before valve opening and after the valve closing event.

The present subject matter and its equivalent thereof offer many advantages, including those which have been described henceforth. The present invention improves the dampening of increased rocker noise caused during high temperature operating conditions and during wear and tear of the valve train components including a valve stem and a tapper screw. Preferably the present invention works best with an increased valve lash but it can also be used under normal conditions. It also leads to improvement in the performance and efficiency of the internal combustion engine. Further the invention fulfils the need for simple, mechanical setup for dampening the noise produced due to increased valve lash. It is to be noted that the present invention can also be incorporated in case of 2 intake and 2 exhaust valves, thereby needing to be accommodated on four rocker arms that would be required in that case. The valve end of the four rocker arms would carry the invention.

The present invention 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. A lash noise damping system incorporated in a valve train comprising of:

at least one rocker arm with a cam end co-operative with an operating cam and a valve end co-operative with a valve stem of a valve through a tappet screw, the said rocker arm supported on a rocker shaft,

a holding structure supported at the said valve end of the said rocker arm, the said holding structure being spread on both sides of a longitudinal axis of the said rocker arm, the said holding structure with provisions for at least one groove at a valve facing surface, at least one sliding member capable of sliding movement within the said groove, the said sliding member further comprising of a head and a base,

a spring member located inside the said groove, the spring member facing the head of the said sliding member and capable of compression,

wherein the load on the tappet screw is partially absorbed by a working combination of the sliding member and the spring member thereby reducing the impact of the tappet screw on the valve stem, and wherein further, the said lash noise damping system reduces the noise produced from the said rocker arm during the operation of the said valve train due to increased valve lash during "nigh temperature operating conditions and also during wear and tear of the valve train components.

2. The lash noise damping system as claimed in claim 1, wherein a gap is provided between the valve facing surface of the said holding structure and the said sliding member and the said gap can vary in the event of the sliding movement of the said sliding member.

3. The lash noise damping system as claimed in claim 1, wherein the said base of the sliding member is supported on a valve retainer and in continuous contact with the said valve retainer.

4. The lash noise damping system as claimed in claim 1, wherein the surface of the base of the sliding member facing towards the said valve retainer is preferably spherical.

5. The lash noise damping system as claimed in claim 1, wherein the said valve may be an intake or an exhaust valve.

6. The lash noise damping system as claimed in claim 1, wherein the said spring member includes a helical coil spring.

7. The lash noise damping system as claimed in claim 1, wherein the said system becomes operational before a valve opening and after a valve closing event.

8. An internal combustion engine comprising said lash noise damping system as claimed in all or any of the preceding claims.

9. A valve train comprising of at least one rocker arm responsible for opening and closing of at least one valve with a valve stem, the said rocker arm comprising of a valve end facing the said valve and a cam end facing a cam lobe supported on a camshaft, the rocker arm further comprising of

a holding structure supported at the valve end and perpendicular to the longitudinal axis of the rocker arm, the holding structure further comprising of at least two grooves, each capable to accommodate a spring member and a sliding member wherein a variable gap is provided between a valve facing surface of the holding structure and the sliding member, the sliding member being supported on a valve retainer in such a way that in the event of transfer of load on the valve end by the cam lobe, the said load is partially absorbed by a working combination of the sliding member and the spring member thereby reducing the impact of the valve end of the rocker arm on the valve stem. 10. A lash noise damping system and a valve train for an internal combustion engine substantially as herein described and illustrated with reference to the accompanying drawings.