Claims:1. A mechanical valve lash adjuster characterized by
a torsion spring;
a rocker support shaft cap; and
an eye bolt;
wherein one arm of the closed wound torsion spring is fixed to the cylinder head using eye bolt and the other end is fixed to the rocker arm.

2. The mechanical valve lash adjuster as claimed in claim 1 wherein, the closed wound torsion spring is assembled with a pre-tension.

3. The mechanical valve lash adjuster as claimed in claim 1 wherein, the valve lash is set using feeler gauge and the torsion spring with pre-tension is then fitted.

4. The mechanical valve lash adjuster as claimed in claim 2 wherein, the pre-tension value is just enough to overcome the valve lash clearance.

5. The mechanical valve lash adjuster as claimed in claim 2 wherein, the torsion spring moves with the rocker arm maintaining a continuous contact of rocker arm tip with valve stem.

6. The mechanical valve lash adjuster as claimed in claim 1 wherein, the rocker support shaft cap is fitted on the existing rocker support shaft and circlip.

7. The mechanical valve lash adjuster as claimed in claim 6 wherein, the diameter of the cap is such that the torsion spring doesn’t buckle under high deflection.

8. The mechanical valve lash adjuster as claimed in claim 6 wherein, the reduced body diameter of the torsion spring during deflection does not touches the rocker support shaft cap.

9. The mechanical valve lash adjuster as claimed in claim 1 wherein, the eye bolt fitted on the cylinder head acts as a part to hinge one arm of the torsion spring.

10. The mechanical valve lash adjuster as claimed in claim 9 wherein, the eye bolt is screwed into cylinder head.

11. The mechanical valve lash adjuster as claimed in claim 1 wherein, the torsion spring in assembled condition creates a small space between adjusting screw and push rod.

12. The mechanical valve lash adjuster as claimed in claim 11 wherein, the clearance is inversely proportional to rocker arm ratio filled with pressurized oil.

13. The mechanical valve lash adjuster as claimed in claim 11 wherein, the valve stem expands at higher temperatures that is accommodated in the space between adjusting screw and push rod.

14. The mechanical valve lash adjuster as claimed in claim 2 wherein, the pre-tension force of the torsion spring is not high enough to overcome pre-compressed forces of the valve spring, thereby the valve remains closed.
, Description:FIELD OF THE INVENTION
[001] The subject matter of the present invention, in general, pertains to valve operating apparatus of an internal combustion engine, and more particularly to maintaining the valve lash clearance.

BACKGROUND OF INVENTION
[002] A valve (especially Poppet or Mushroom valve) is typically used to control the timing and quantity of gas or vapour flow into an engine. The valve is usually a flat disk of metal with a long rod known as the 'valve stem' attached to one side. The stem is used to push down on the valve and open it, with a spring generally used to return it to the closed position when the stem is not being depressed. The engine normally operates the valves by pushing on the stems with cams and cam followers. The shape and position of the cam determines the valve lift and when and how quickly (or slowly) the valve is opened. The cams are normally placed on a fixed camshaft that is then geared to the crankshaft, running at half crankshaft speed in a four-stroke engine. As the valve stem extends into lubrication in the cam chamber, it must be sealed against blow-by to prevent cylinder gases from escaping into the crankcase, even though the stem to valve clearance is very small, typically 0.04-0.06 mm, a rubber lip-type seal ensures that excessive amounts of oil are not drawn in from the crankcase on the induction stroke and that exhaust gas does not enter the crankcase on the exhaust stroke. Worn valve guides or defective oil seals are characterised by a puff of blue smoke from the exhaust when releasing the accelerator pedal after allowing the engine to overrun and there is high manifold vacuum, such as when changing gears. In multi-valve engines more than one intake valve and one exhaust valve per cylinder is used to improve engine performance.

[003] Valve Lash or Valve Clearance is the gap between the rocker arms and the valve tappet. This clearance needs to be tightly controlled as if it is too little, the valves may not be seated properly and if it is too much, it will lead to valve train noise, and excess load on the valves and valve train components. The valve lash basically cuts off the lower portion of the cam profile. The lower section is where the cam profile is designed to gently open and close the valve. Too much valve lash eliminates the more "gentle" sections and basically leads to "slamming" the valve while opening and closing.

[004] Owing to manufacturing tolerances, engine wear, and because different parts of the valve train and engine "grow" as the engine heats up, the clearance may change and must be set correctly. Camshafts are ground assuming a certain amount of valve lash. If changed, there comes a risk of changing the performance and durability of the cam grinder designed into their lobes.

[005] On overhead cam engines the pushrods are eliminated and sometimes the rocker is not included so the valve is operated directly from the Cam Lobe. But there is still valve lash. Over Head Cam engines are presumed to be higher performance engines and usually have dual overhead cams for 4 or 5 valve engines but some experts argue that they are more complex and pushrod engines are simpler, cheaper, more compact, and have less engine friction.

[006] A tappet, also termed a lifter, is a part that runs on the camshaft and made to move vertically by the action of the rotating cam. In an overhead valve engine, tappet is fitted low down in the engine block. From there it drives a long thin pushrod, up to the top of the engine, above the cylinder head. The rockers, arranged on a rocker shaft beneath the rocker cover, reverse the direction of the valve movement to press the valves downwards to open them. Early tappets had rollers to reduce wear from the rotating camshaft, but it was found that the roller pivots wore even faster and also that the small radius of the rollers also tended to accelerate wear on the expensive camshaft. Tappets then developed plain flat ends, although these were slightly shaped as 'mushroom' tappets as a perfectly flat end led to 'slamming' against a steep camshaft face. To reduce wear from the rotating camshaft, the tappets were usually circular and allowed, or even encouraged, rotating. This avoided grooves developing from the same point always running on the same point of the camshaft.

[007] Conventionally, engine arrangement was adjusted by turning a screw set in the end of the rocker that pressed on the end of the pushrod. This adjustment was done by rotating the engine until the cam was at its lowest point, giving the widest gap, then adjusting the rocker until this gap was at the correct spacing, as measured with the use of a feeler gauge. Misadjusted tappets give rise to an audible 'tappet rattle' from the rocker cover, in case the valve clearances are excessive. Over-tight clearances may, even worse, lead to bent pushrods. The adjusting screw was locked by a locknut. If the screw became loose, the adjustment would also work loose and may even lead to engine fires, as practically observed.

[008] Reference is made to US 2,962,011 B2 wherein a mechanical valve lash adjuster is disclosed. The self-adjusting rocker mounting for use in a poppet valve or like operating linkage, a rocker having an opening extending therethrough in the thrust direction, a bearing support extending through said opening, bearing means slidable on said support and journaling the thrust side of the rocker adjacent said opening, a nut on the support oppositely of the bearing means from the rocker, said nut and support being inter-threaded with non-locking threads, and resilient means reacting operatively between the support and nut in opposing movement of the nut in the direction of rocker thrust, said nut and bearing means having coating surfaces accommodating rotation of the nut under rocker thrust loads transmitted thereto by the bearing means.

[009] Reference is also made to US 3,818,879 B2 wherein a mechanical valve lash adjuster is disclosed. The mechanical valve lash adjuster comprising a body member having a generally planar face thereon and a bore therein, said bore being located at an acute angle with respect to the plane of said face, a wedge slidably located within said bore of the body member and having a planar surface thereon, the included angle of wedge being the same as said acute angle whereby said planar surface may be parallel to said face on said body member and opposite therefrom, driving means engaging the wedge and cooperating with the body member to selectively position the wedge in said bore with respect to the body member, said driving means including means engaging the wedge for normally resisting rotary movement of the driving means with respect to the wedge, and a spring operatively associated with the body member and the wedge to maintain the wedge in engagement with the driving means.

[0010] A hydraulic valve lifter, also known as a hydraulic tappet or a hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. Conventional solid valve lifters require regular adjusting to maintain a small clearance between the valve and its rocker or cam follower. This space prevents the parts from binding as they expand with the engine's heat, but may lead to noisy operation and increased wear as the parts rattle against one another until they reach operating temperature. The hydraulic lifter was designed to compensate for this small tolerance, allowing the valve train to operate with zero clearance that would lead to quieter operation, longer engine life, and eliminating the need for periodic adjustment of valve clearance. A hydraulic lifter, situated between the camshaft and each engine's valve, is a hollow steel cylinder encasing an internal piston. This piston is held at the outer limit of its travel with a strong spring. The lobed camshaft rhythmically presses against the lifter, which transmits the motion to the engine valve one of two ways, i.e., either through a pushrod which actuates the valve via a rocker mechanism or in the case of overhead camshafts, via direct contact with the valve stem or rocker arm. The oil under constant pressure is supplied to the lifter via an oil channel, through a small hole in the lifter body. When the engine valve is closed (lifter in a neutral position), the lifter is free to fill with oil. As the camshaft lobe enters the lift phase of its travel, it compresses the lifter piston, and a valve shuts the oil inlet. Oil is nearly incompressible, so this greater pressure renders the lifter effectively solid during the lift phase. As the camshaft lobe travels through its apex, the load is reduced on the lifter piston, and the internal spring returns the piston to its neutral state so the lifter can refill with oil. This small range of travel in the lifter's piston is enough to allow the elimination of the constant lash adjustment.

[0011] Hydraulic lifters were introduced in the 1950's as a way to make mass produced engines quieter, and not require the maintenance of periodic valve lash adjustment. They use oil pressure to pump up a "plunger" when the valve is on its seat to eliminate any clearance, basically eliminate valve lash. This plunger has a small amount of leakage, so oil may slowly leak out so the plunger does not hold the valve off its seat when the valve ought to be closed. But in the short amount of time that the valve is open, very little oil may leak out so it acts as a solid lifter then. Actually, oil does leak out when the valve is open, and the oil is not incompressible, therefore, a hydraulic lifter is assumed to have about .006" of effective lash. Hydraulics lifters are typically not used on racing motors as at higher RPMs they "pump up", meaning there is so little time for bleed down that they start to hold the valve off its seat. This causes loss in performance and drastically cause valve temps to go up as the valves are cooled by transferring heat to the seat. Hydraulics lifters are typically heavier and "springier" thereby adding additional problems of keeping the valve train under control at high RPMs.

[0012] Reference is made to US 6,039,017 B2 wherein a hydraulic lash adjuster having a piston capable of forming a pivot for a member of an engine valve train connecting a cam and a valve is disclosed. It includes a hydraulic lash adjusting element of varying length for acting in the valve train, an expansion spring for extending the length of the lash adjuster to take up lash in the valve train between valve opening events and a lash spring which biases the adjuster element away from the piston a small amount to maintain a sufficient amount of lash in the valve train between valve opening events to prevent holding open of the valve during cold engine operation. During steady state operation, the lash spring introduces a fixed amount of mechanical lash into the valve train. In non-steady state transient operations, such as during cold engine start up, the amount of mechanical lash may be reduced when growth of the valve train components exceeds the leak down rate of the hydraulic lash adjusting element. However, as long as the amount of mechanical lash is adequate to offset the excessive growth of the valve train components, opening of the valve due to thermal pump up is prevented. As the engine warms up and a normal leak-down rate of the hydraulic lash adjusting element is reached, operation with a fixed amount of mechanical lash returns.

[0013] The advantages of conventional Hydraulic tappets being a) no need for service or adjustment as the whole process is actuated by hydraulic pressure at engine start; b) cheaper operation, as there is no need for service and charges associated with tappet clearance setting maintenance; c) minimum amount of maintenance is required once the proper preload is set d) hydraulic tappets usually survive through the whole of the engine life without any service requirements; e) fully adjustable for any changes in block and cylinder head sizes; and f) less valve train noise. While the disadvantages of conventional Hydraulic Tappets being a) require more complex and more expensive cylinder head design; b) less stiff at higher engine speeds due to hydraulic valve pumping up with high pushrod forces forcing oil to squeeze out; c) effective RPM range being limited; d) more sensitive to engine oil quality and frequency of oil changes, as carbon sludge and residues may easily lock up the tappets or block oil channels, making the clearance setting ineffective, this has negative impact especially on the engine camshaft and valves due to excessive wear if the clearance setting is not working correctly.

[0014] Electronic valve control systems manipulate the valve timing using a computer controlled actuator attached to the camshaft. Usually two camshafts are utilized, one to control the intake valves and the other to control the exhaust valves. The camshaft may contain two sets of lobes wherein one set is for low and the other for high RPMs. As the camshaft rotates, the lobes push open the spring-loaded valves that are then closed by the force of springs. The ECU selects which set of lobes to use based on the engine speed. Another approach to variable valve timing employs a cam phasing mechanism to monitor and adjust the rotation of the camshaft relative to the rotation of the crankshaft.

[0015] There are other mechanical/electrical methods that come one step closer to eliminating the camshaft altogether. Three of these methods are Electro-Pneumatic Valves (EPV), Electro-Hydraulic Valves (EHV), and Electromagnetic Valves (EMV). EPV and EHV involve electric solenoids to control the flow of compressed air or hydraulic fluid to the valves at the appropriate time. Existing EPV and EHV systems generally eliminate the spring mechanism but still employ the cam. Electromagnetic valves control the valve opening directly with a solenoid, eliminating camshafts and many other related components such as lifters, timing chains etc. Engines of this design are currently undergoing development and have not made it past the prototype stage.

[0016] Reference is made to US 8,468,985 B2 wherein an electro-hydraulic variable valve lift apparatus is disclosed that includes a housing, a master portion that is slidably disposed to the housing and contacts a cam, a first oil supply portion which supplies hydraulic pressure, a slave piston that is slidably disposed within the housing and defines an oil chamber with the master portion, a latching portion that is supplied the hydraulic pressure from the first oil supply portion and selectively connects the slave piston and the master portion, a second oil supply portion which selectively supplies hydraulic pressure to the oil chamber so as to control relative distances between the master portion and the slave piston when the slave piston is disengaged with the master portion, and a stepped portion formed to the housing between the master portion and the slave piston to elastically support the master portion.

[0017] Reference is also made to US 7,509,933 B2 wherein a Type 2 engine, a valve deactivation hydraulic lash adjuster (DHLA) is disclosed that replaces the conventional hydraulic lash adjuster in the train of a gas-exchange valve in a compression-ignited engine. In a Type 3 engine, a similar DHLA is disposed within an articulated rocker arm which is made selectively competent (valve activating) or incompetent (valve deactivating) thereby. A solenoid valve within the assembly diverts hydraulic fluid between support and non-support of a piston slidably disposed in housing and terminating in a ball head. The valve is force-balanced. The preferred hydraulic fluid is diesel fuel, allowing for smaller diameter passages and cleaner operation than in prior art systems, eliminating the need for an accumulator chamber and accumulator piston as in the prior art.

[0018] The proposed invention will reduce the noise generated by valve hitting at lower loads by keeping the rocker arm tip in continuous contact with the valve stem and yet maintaining the desired clearance required for expansion. It would further reduce wear due to hitting which would lead the engine to run for longer hours without re-setting tappet clearance.

SUMMARY OF THE INVENTION
[0019] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0020] An object of the present invention is to provide a torsion spring operated mechanical valve lash adjuster.

[0021] Another object of the present invention is to provide an eye bolt to hinge one arm of the torsion spring to the cylinder head.

[0022] Another object of the present invention is to provide a rocker support shaft cap for the torsion spring.

[0023] Yet another object of the present invention is a torsion spring to keep the rocker arm tip in continuous contact with valve stem while accommodating clearance required for valve stem expansion.

[0024] Yet another object of the present invention is a torsion spring assembled with pre-tension with one end fixed on the eye bolt and the other end on the rocker arm.

[0025] Yet another object of the present invention is the pre-tension value is just more than enough to overcome the valve lash clearance.

[0026] Yet another object of the present invention is the eye bolt that in turn is screwed into cylinder head.

[0027] Yet another object of the present invention is the valve lash being set using feeler gauge (not illustrated) and then the torsion spring with pre-tension is fitted.

[0028] Yet another object of the present invention is the torsion spring in assembled condition creates a small space between adjusting screw and push rod that would be filled with pressurized oil.

[0029] Yet another object of the present invention is when the valve stem expands at higher temperature, the effect of such expansion would be accommodated in space between adjusting screw and push rod.

[0030] Yet another object of the present invention is torsion spring moving with the rocker arm and the high stiffness avoids failure.

[0031] Yet another object of the present invention is that the pre-tension force provided by the torsion spring not being high enough to overcome the pre-compressed forces of the valve spring and thus the valve remains closed.

[0032] Yet another object of the present invention is the rocker support shaft ensures that the torsion spring does not buckle under high deflection nor does the reduced body diameter of the spring during deflection touches the shaft.

[0033] Accordingly, in one aspect the present invention, a torsion spring with one end fixed to the cylinder head with the help of an eye bolt while the other end is fixed to the rocker arm is disclosed. The torsion spring is closed wound, assembled with a pre-tension and is the primary component of the mechanism. It moves with the rocker arm hence, helps maintaining a continuous contact of rocker arm tip with valve stem.

[0034] In another aspect, the rocker support shaft cap is fitted on the existing rocker support shaft and circlip. The diameter of the cap is such that the torsion spring doesn’t buckle under high deflection nor does the reduced body diameter of the spring during deflection touches the rocker support shaft cap.

[0035] In another aspect, the eye bolt is fitted on the cylinder head. The said eye bolt acts as a part to hinge one arm of the torsion spring.

[0036] Briefly, there is a provided a torsion spring to keep the rocker arm tip in continuous contact with valve stem while accommodating clearance required for valve stem expansion. The torsion spring is assembled with pre-tension where one end is fixed on the eye bolt that in turn is screwed into cylinder head and the other end on the rocker arm with the pre-tension value being just more than enough to overcome the valve lash clearance. A valve lash is set using feeler gauge (not illustrated) and then the torsion spring with pre-tension is fitted. The torsion spring in assembled condition creates a small space between adjusting screw and push rod, such clearance is inversely proportional to rocker arm ratio that would be filled with pressurized oil. When the valve stem expands at higher temperature then effect of such expansion would be accommodated in the given space. The torsion spring moves with the rocker arm and hence the stiffness is kept high to avoid failure. The rocker support shaft is designed in a manner that the torsion spring does not buckle under high deflection nor does the reduced body diameter of the spring during deflection touches the shaft.

[0037] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0038] Figure 1 illustrates the side view of the valve lash adjustment through torsion spring arrangement.

[0039] Figure 2 illustrates the distance perspective view of valve lash arrangement.

[0040] Figure 3 illustrates the perspective view of the arrangement when the rocker support shaft cap removed for illustration of circlip and shaft.

[0041] Figure 4 illustrates the torsion spring for mechanical valve lash adjustment.

[0042] Figure 5 illustrates the rocker support shaft cap that is fitted on the existing rocker support shaft and circlip.

[0043] Figure 6 illustrates the eye bolt that acts as a part to hinge one arm of the torsion spring.

[0044] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0045] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0046] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0047] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0048] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0049] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0050] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0051] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0052] The subject invention lies in providing a torsion spring operated mechanical valve lash adjuster.

[0053] In the present invention, a torsion spring (6) that stores mechanical energy when it is twisted is used for valve lash adjustment. The torsion spring (6) in twisted condition exerts a force (actually a torque) in the opposite direction; proportional to the amount of angle it is twisted. This ability of torsion spring (6) to provide a torque has been used to maintain the valve lash clearance. It solves the problem of rocker arm tip (9) hitting the valve stem (10) as the said tip continues to remain in contact with the said stem due to torque exerted by torsion spring (6).

[0054] In one implementation, a torsion spring (6) operated mechanical valve lash adjuster is provided for.

[0055] In one implementation, an eye bolt (8) to hinge one arm of the torsion spring (6) to the cylinder head (1) is provided for.

[0056] In one implementation, a rocker support shaft cap (7) for the torsion spring (6) is provided for.

[0057] In one implementation, the torsion spring (6) is used to keep the rocker arm tip (9) in continuous contact with valve stem (10) while accommodating clearance required for valve stem expansion.

[0058] In one implementation, the torsion spring (6) is assembled with pre-tension where one end is fixed on the eye bolt (8) which in turn is screwed into cylinder head (1) and the other end on the rocker arm (5). The pre-tension value is just more than enough to overcome the valve lash clearance.

[0059] In one implementation, the valve lash is set using feeler gauge (not illustrated) and then the torsion spring (6) with pre-tension is fitted. Since cylinder head (1) is fixed on crankcase (not illustrated) with the help of bolt(s) (2), the rocker arm (5) moves down with the torsion spring (6), to the torsion spring’s original/assembled position, about its axis along the rocker support shaft cap (7).

[0060] In one implementation, the torsion spring (6) in assembled condition creates a small space between adjusting screw (4) and push rod (3), such clearance is inversely proportional to rocker arm ratio, that which would be filled with pressurized oil. When the valve stem (10) expands at higher temperature then effect of such expansion would be accommodated in the given space.

[0061] In one implementation, the torsion spring (6) moves with the rocker arm (5) with the stiffness kept high to avoid failure.

[0062] In one implementation, the pre-tension force provided by the torsion spring (6) is not high enough to overcome the pre-compressed forces of the valve spring and thus the valve remains closed.

[0063] In one implementation, the rocker support shaft cap (7) is designed in such a way that the torsion spring (6) does not buckle under high deflection nor does the reduced body diameter of the spring (6) during deflection touches the shaft cap (7).

[0064] The concept of the mechanism, as shown in Figure 1, is developed to have a continuous contact between rocker arm tip (9) and the valve stem (10) end while accommodating valve expansion. The design was made to reduce valve hitting noise at lower loads and reduce the wear due to impact. By considering forces acting on the rocker arm, fatigue factor of safety, pre-tension forces of the spring and its effect on valve spring forces a suitable torsion spring (6) was designed.

[0065] The torsion spring (6) keeps the rocker arm tip (9) in continuous contact with valve stem (10) while accommodating clearance required for valve stem expansion, as can be seen from Figure 2. The torsion spring (6) is closed wound and assembled with pre-tension where one end is fixed on the eye bolt (8) that in turn is screwed into cylinder head (1) and the other end on the rocker arm (5) with the pre-tension value being just more than enough to overcome the valve lash clearance. A valve lash is set using feeler gauge (not illustrated) and then the torsion spring (6) with pre-tension is fitted. As the cylinder head (1) is fixed on crankcase (also not illustrated) with the help of bolts (2), the rocker arm (5) moves down with the torsion spring (6), to the torsion spring’s original/assembled position, about its axis along the rocker support shaft cap (7). The torsion spring (6) in assembled condition creates a small space between adjusting screw (4) and push rod (3), such clearance is inversely proportional to rocker arm ratio that would be filled with pressurized oil. When the valve stem expands at higher temperature then effect of such expansion would be accommodated in the given space. The torsion spring (6) moves with the rocker arm (5) and hence the stiffness is kept high to avoid failure. The pre-tension force provided by the torsion spring (6) is not high enough to overcome the pre-compressed forces of the valve spring and thus the valve remains closed. The rocker support shaft cap (7) is designed in a manner that the torsion spring (6) does not buckle under high deflection nor does the reduced body diameter of the spring (6) during deflection touches the shaft cap (7).

[0066] The proposed mechanism uses few components in the valve train system and inculcates the ease of assembly and replacement. This is cost effective as compared to electric, hydraulic systems and bearing and nut arrangement with torsion spring.

[0067] In Figure 3, the rocker support shaft cap removed for illustration of circlip and shaft. The torsion spring (6) with one of its end being fixed to the cylinder head (1) using Eye bolt (8) while the other end is fixed to the rocker arm (5). The torsion spring (6) is assembled with a pre-tension and is the primary component of the mechanism and it moves with the rocker arm (5) thereby maintaining a continuous contact of rocker arm tip (9) with valve stem (10). The rocker support shaft cap (7) is fitted on the existing rocker support shaft (11) and circlip (10). The diameter of the cap is such that the torsion spring (6) doesn’t buckle under high deflection nor does the reduced body diameter of the spring (6) during deflection touches the rocker support shaft cap (7). The eye bolt (8) being fitted on the cylinder head (1) acts as a part to hinge one arm of the torsion spring (6).

[0068] Some of the important features of the present invention, considered to be noteworthy are mentioned below:

1. The present invention employs a simple mechanism for mechanical valve lash adjustment.
2. The present invention is easy to assemble.
3. The present invention is economic and cost effective.
4. Replacement of the torsion spring, rocker support shaft cap and eye bolt.

[0069] Although a hassle free, economic and cost effective way to maintain valve lash clearance has been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the torsion spring operated mechanical valve lash adjuster.