Title of Invention

COMPRESSION RING

Abstract

A surface coated Compression Ring for use in piston compression ring grooves of piston ring assembly in internal combustion engine comprising of an outside and inside circumferential surfaces to form a wall having a top face and bottom face, with radially extending circumferential cross-sectional cut out portion on top edge of inside surface, with inwardly keystone tapering on the bottom face and wherein the cut out portion formed by chamfering or by under cut.

Full Text

BACKQROPHD OF IlfVEHTIOg :- Kalon ling is a metidlic circular spring with a high relative outward expanding strain. It fits into an anmilar groove that fits its section. The main ftinction of piston ring assembly is to seal the pressurized gas flow to crankcase and to meter the lube oil film thickness. Piston rings undergo considerable wear because of their sliding movement on cylinder wall and piston groove. In order to withstand this wear> tlie rings should have surface coating on tlie outer periphery and the portions where tliey are sulyjected to heavy sliding motion- The Compression Rings in autom.otive engines play a m^'or role in controlling excess lubricating oil consumption and so too control of blow by gas. Piston rings seive moi*e than one purpose; to contain and maintain cylinder and combustion pressure, to prevent oil from getting into the combustion chamber with the help of vahre guides and seals and to aid in heat transfer and thereby control of thermal changes in the engine. The top ring in general is for sealing against pressure losses from combustion process; is for maintaining a liigh buildup of pressure as piston arrives at tlie top of stroke when at a predetermined location the combustible mixture is ignited building up pressure to force the piston downward. The ability of piston ring to maintain this pressure is dependent on Ring gap and obviously hot gases do flow through this gap. The Ring gap or compressed g^p i.e., the end ^p measured when tlie ring is installed is critical. Further this ring gap is critical as burning gases do flow through this gap. Further too this ring is a barrier and transfers a large portion of the heat through its contact with the cylinder wall. The second ring is conventionally similar to top ring. It also has a ring gap which allows hot gases to fiirtlier penetrate down the cylinder wall into the crankcase oil. This is known as blow-by and has deleterious effects on the engine. Blow-by getting into tlie oil contaminates the oil with carbon particles from the combustion process, raises the acid level, heats up the oil and speeds up oxidation process. This efiectively begins the process of slowly diminishing the lubrication ability of the oil and allows the carbon particles to wear out all the parts which it is expected to lubricate. The second ring also serves as an oil scraper ring to help minimize the oil above the second ring and as such complements both as Compression Ring and the oil ring. PRIOR ART :- Originally piston rings were simple. Most engpbies had pistons with 3 or 4 ring grooves which were all commonly called **Compression Ring^. The common width and depth was about the same size and so rings had a nearly oquare cross secuon, several Holes were drilled in tKe piston just below the bottom groove to allow the oil to be scraped from the cylinder walls to inside of pistons as the oil control rings were unknown then; in that situation the entire wide fece of the ring had to seat to tihe cylinder before a good seal could occur. The purpose of the piston rings was to seal the pressures above the piston so that combustion could occur. Tlie rings did not control tlie upward movement of the oil films in the cylinders. Thereafter slotted lower groove in tlie piston and the vented or slotted oil ring was developed and oil economy improved. The new angled ring also become popular. These oil rings were quite simple rings and had no special constructional features to enhance the seal against the side of the groove to prevent oil from passing around the rings. Over the years, automotive engines have undergone lot of changes in the piston ring assembly, including the number of rings per cylinder which were 6 rings earlier and have come down to the level of the ciurent tln*ee i*ings version {3RV). Uiis 3RV assembly pack consists of two Compression Rings and one oil control ring. The Compression Rings are fiulher divided into Top Compression Rings and Second Compression Rings. The main role of tlie top rin^ is to seal the combustion chamber at radial and axial directions inside the piston groove. The second ring has to scrape the hibe oil by maintaining an optim-om oil film thickness ajbove the ring. The secondary function is to maintain em inter ring pressure between Compression Sings hy providing a seal fat gases that have escaped through the top ring gap. The role of the oil ring assembly is to ensure uniform oil film thickness on the entire inner periphery of the cylinder wall, by scraping the excess oil in one location and distributing it evenly to other locations on the cylinder wall. Also the practice of chrome plating on top groove Compression Ring^ was developed. Thereafter cylinder surface finishes liave improved and it was thought that a good supply of oil on the cylinders was necessary to prevent piston and ring scuffing. Previously fair amount of roughness was left to seat the crude rings, so oil consumption was even higher during the break-in process. Tapered face designs then cam.e about which maxjmiaed the sealing ability of the ring. Then torsional twist, more specifically reverse torsional twist ring, was developed- This design allowed the second gi'oove ring to seal against the sides of the groove to prevent high vacuum forces to pull oil past the rings. Secoxid ring's main function being considered for oil control, tlie tapered face design allowe and keeping the top ring seated against its groove. Without this escape path, trapped presumre will unseat the top ring, causing ring flirtter and reduced cylinder sealing at high RPM. Additionally a fluttering ring cannot transfer heat away from the piston to cylinder wall; causing piston overheating; top ring groove pound out, ring side wear and scuffing. Most of tlie oil consumption reduction exercises have been performed in the past decades by use of outer peripheral configurations of the second Compression Rings* Initially the outer periphery was perpendicular to the width side face and it was later changed to outer periphei-y provided with 1* taper to vertical* This tapei' is used to prevent upward scraping of oil during the piston ring movement towards the combustion chamber. This taper is given either by turning or by grinding the outer periphery of the ring. A few decades ago, a step called Napier step was provided with taper periphery. This step prevents oil flow into the piston ring groove by providing a bottom side face seal. Fig. 1 gives a clear picture of revolutionary changes that have taken place in development of second Compression Rings. The Tapered Ring ciirrently has a desu*ed taper on its outside face. The Tapered Ring lias a taper on its outside face of an amount, wliich is calculated depending on the size and usage of the riag, as its ability to seat in rapidly is well appreciated. Tliis makes it especially applicable to hai'dened or chromium plated cylinders. In slightly out-of round or distorted cylinders, its ability to seat-in quickly helps to prevent blow-by* Tlie development was further introdudng torsional twist in rings. A torsional twist is an inbuilt imbalance between the way the upper and lower sides of the ring compress that causes a twist in the ring when compressed. This torsional twist is utilized for better sealing effect. Ring flutter was oixe of the major })Toblems encountered ai>ove 5500 r|>m and the result is excessive blow-by. To overcome tliia, furtlier improy/ements began to be made on Compression Ring. Tlie positive twist was developed. A chamfer cut into ring's topside inside edge will cause it to ilex down in response to the introduction of cylinder gas pressiire and further leading to better sealing at hi^er rpm. By changii^ cross-sectional area on that inside and with properties associated with it^ if end gap of the ring comes together, the ring actually takes on a slight positive twist. It is no longer perpendicular to the bare. Bnt when the cyiindei^ gas preaaxu-e is introduced the ring flexes down and seals better against the bore. When a ring that's flat is flexed, only line seal was achieved. But with positive twist ling, sealing across a broader area was acliieved, as the special saucer shaped curvature leads to peripheral and side sealing when fitted into the cylinder. These twist Rings are of two types> one has small groove snd other has a bevel called ** Grooved Back Ring ** and ** Beveled Back Ring " respectively d the upper inside edge. The positive twist ring was good in blow-by control but had limitations in control of lube oil consumption because of entry of the scraped oil into the piston gi'oove. A new ring was again developed known as negative twist ring. Beside the positive twist taper-faced rings wherein lube oil control is important however negative (or reverse ) twist taper-faced rings are also used in the 2"^ groove. These rings have the cross-sectional cutout at the bottom side inner fece of the ring instead of at top side inner face of ring like in positive twist* So this twist and contact conditions in the groove are exactly reversed. With such rings it is important for the taper angle to be sufficiently large to prevent oil being pushed up by the top running surface edge. The negative twist ring was deCnitefy an impro\mment from positive twist as far as oil consumption was concerned but definitely liad a disadvantages of non-uniform coating thickness as it is finished with outer periphery taper ground. With regard to better oil sealing ability, the negative twist ring is said to liave better oil sealing action. Tliis is attributed to the fact tliat with the negative twist ring, the sealing point on tlie bottom side is at tlie outer edge-The purpose of this is to prevent oil scraped from the wall by the ring from I getting into the groove and then on the upstroke being conveyed around the back of the ring (Fig 2). As previously described, twist in Compression Rings is normally brought about by incorporating a cross-sectional cutout at the ring back - i,e,, positive twist (Fig. 2) or a negatives twist (Fig, 3)is generated in the ring depending on whethei* the cutout is on the top or bottom side of the ring inner. Keystone type of Ring lias its sides ta{>eted inwardly towards tlie back. The piston groove on which it is used must have its sides tapered with angle similar to that used on tlie ring. A "saucer*^ or Teller** ring can also be fabricated^ for instance^ by grinding the sides of a rectangular-section rii^ in a similar manner to fiill Keystone rings. •Teller*' rings have been successfully used in a case where conventional negative twist rings had caused excessive wear of the ring and groove around tlae gap due to lack of ring rotation (lai-ge oveilap). In such an instance, ^Teller" rings may be expected to yield axial wear advantages. In order to improve wear resistance, tlie outer periphery of the torsion ring is coated with different surface coatings. These coatings are filled on the periphery of the ring either as inlay or overlay. In positive torsion rings> since the outer taper is made by out oxit on the inner top edge, the coating thickness remains uniform throughout the axial direction. But in oil consumption reducing exercise, positive torsion ring has limitattmis in tliat it cannot prevent tlie scraped oil reaching the combustion chamber through the sides and back of the ring during upstroke. With regard to sealing against blow by, however this ring is superior to the negative torsion ring. hi negative torsion ring^, the coating material removal oix outer periphery in order to provide sufficient taper on periphery will result in non-uniform coating thickness. This in turn leads to peel-off of surface coating. So a great care has to be taken while designing and processing of negative torsion rings. Due to this the manufacturing cost is also high because of wastage of coating. See Fig. 4. DIBADVAITTAQEa OF PRIOR ART :- Recent piston and ring technology have developed thin, lower tension rings which highly reduce friction and improve fuel economy. They weigh less and reduce the reciprocating mass that pounds against the piston grooves with every stroke of tlie ;|riston. Howesrer low tension rings cannot tolerate much distortion in the cylinder bore and the thinner cross section of the rings doesnt conduct heat as efficiently, because with thicker rings pistons are partially cooled by heat conduction through the rings to the cylinder walls, by oU splash from underneath and by incoming air/fiiel charge. As such, rings were designed primarily focusing on one of two controls i,e., good lubricating oil consumption or good blow-by control, whichever was more essential. As per the prior art, the top ring had to have good blowby control and the second ring had to have good lube oH controls. Each one was defined and limited in its ftuiction and was desugned differently from each other. OBJECT OF UnTEHTIOlff :- The use of iK>sitive torsion or ut^ative torsion rings is laiown in the prior art. The prior art allows only one of the two controls i.e., good lube oil control or blowby controL In tliis re»i>ect, the Cotix]>res8ion Ring according to this invention substantially departs from the conventional concepts and designs of the prior art,, and in so doing provides a Compression Ring primarily developed for the purpose of provi Therefore it. can be appi^eciated that tliei-e existsi a need foi' new and improved surface coated Compression Ring wiiich can control botli lube oil atid blowby and this invention substantially frdfills this need. 4 This invention relates to a Compression Ring of an internal combustion engine, particularly a Compression Ring having a positive twist and tapered bottom side face such as to have good hibe oil control and also good blow-by control. Two types of twists ai*e in use conventionaUy because of having cross sectional cutout either at top or bottom side face of the ring. The material removal at the inner periphery of the Compression Rings as internal bevel or internal step cutouts, gives a saucer shaped curvature that leads to peripheral and side sealing when fitted into the cylinder. The location of the cutout determines whether the twist effect is positive or negative torsion. The cutout at topside inner face of ring will twist it and make the peripheral bottom running edge to extend outwardly. The side faces are then slanted^ so that the bottom side face inner edge as well as the bottom side running periphery will have sealing points against piston groove bottom side and cylinder waU respectively. This is familiarly known as * Positive torsion *, Fig 2 illustrates the effect of positive torsion ring. As the ring axial width reduces and the radial wall thickness incjreases, the effect, of this twist increases. The advantage of this ring is good conti'ol cfver blow by. Fig.2 shows positive twist ring as per the known art which gives good blow-by control. The arrows in tlie fig.2 indicate the points which axe the sealing points for both ^ gas * and * oH * flows. If the material cut out is placed in the bottom side face of the ring» the twist effect win be the exact nevisrse of Hie above. The outer periphery has to be sufficiently tapered to avoid top edge upward scraping. The contact points are bottom side groove outer side and cylinder wall periphery. See Fig, 3 for details. The negative torsion ring is said to liave better oil sealing than positive torsion ring because of its bottom side outer edge groove contact. Fig* 3 illustrates a negative twist ring as per tlie known art, which gives good lube oil control. The arrows in Fig.3 imlicate pomts wliicli me tlie sealing points for both * gas * and * oil * flows. The first dtgect of the }>reseiit invention is to incorporate both controls i.e., good lube oil control and good blowby control in a single Compression Ring such that it fulfills the requirement of top ling and second ring. It is another object of the present invention to provide a new and improved surface coated Compression Ring which has the advantages of prior art and also overcomes the disadvantages known in the prior art. It is another object of the present, invention to provide a new and improved surface coated Compression Ring which can be easily and efficientiy manufactured. It is another object of tlie ixresent invention to provide a new eaid improved surface coated Compression Ring which is of durable and reliable construction. ft is another object of the present invention to provide a new and iraproved surface coated Compression Ring which is economically available in the market. SUMMARY OF UnTKHYIOg :^ In view of the foregoing disach^antages inlierent in tlie known types of Compression Rings now present in the prior art, the present invention provides an improved Compression Ring, which will be described subsequently in greatm* details^ and which Compression Ring will have all the advantages of prior art and none of tlie disadvantages. As per the inihistiy practice foiloweciy the second ring w^as mainly treated not as a Compression Ring but an oil control and vacuum ring. As such, some of the second rings had the negative twist to achieve lube oil control. Some of the Second rings are of a negative twist, taper face design as illustrated in fig» 3 which allows the ring to glide over the cylinder wall during the piston upstroke. When the piston revei-ses direction, the sharp edge of the ring is forced out against tlie wall and acts like a squeezer to wipe off the excess oil. At the same time the second ring seals against the wall so the piston can pull as much vaccum as possible on the down stroke. Some Second rings have a taper faced corner groove, positive twist design as illustrated in fig, 2. The lower outside diameter of second compression ring may have scraper groove that coUects oil and also acts like an accumulator to reduce the interring pressure. The ring having a shallow groove along the lower outside diameter is called * NAPIER * or * TNC * type as illustrated in fig. 1. hi tliis invtstition, the novelty resides in sliifting tlie sealing i>oints to desired positions to achieve liigli lube oil control and high blowby control, together taking into consideration the different characteristics always associated with positive twist and negative twist independently in the prior art. Accordingly the novelty of the present invention is to utilise the positive twist characteristic in a conventional positive twist Compression Ring which gives good hlowby control and by modifying the configuration of the bottom side face of said ring into a tapered bottom side face to improve tlie lube oil control and so tliereby, to achieve a new Compression Ring witli a new shape. The invention resides essentially in the following ;- i) Preparing a surface coated Compression Ring with a positive twist - as per known art. ii) Tapering the bottom side face of the above ring. Thia iiicvention relates to maniifactiiie of a aiirfaoe coatfsd Compression Ring> more specifically received in second groove of piston but equally suitable to be used as the top ring. Novelty is felt to reside in the provision of tapered bottom side face of the ring with positive twist. More particularly with the Compression Ring having both good blow-by control like in a conventional positive twist ring along with good control of lube oil consumption like in a con^f'entional negath/e twist ring. IMPROVEBtEHT OVER PRIOR ART :- Tlie invention involves using the configuration of both positive twist ring and negative twist ring and creating the new configuration of the Compression Ring as per invention; By shifting tlie bottom side face sealing point of the positive tivist ring fi-om tlie point A as illustrated in Fig. 2, to point B in tlie improved design ring illustrated in Fig.S below, tlie limitatioii of control of lube oil consumption of positive twist ring is overcorae. This is made possible by tapering the bottom aide face of the ring as illustrated in Fig.5. The invention is to achieve all the following advantages in tlie invention :- Retain high blow-by control Achieve lidg^ lube oil control Reduced wear on side faces Longer life (due to uniform coating thickness) Reduced emission levels (due to lower oil consumption) Highly amenable for consistent mass production of periphery siirface coated piston rings PESCRIPTIOy OF PRAWIITQS :■ The invention will be better understood and objects than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the drawir^s enclosed herewith wherein the present invention will hereby be illustrated froza the following description of the accompanying drawings in which the preferred embodiment is illustrated :- Fig 1 : illustrates the periphery taper and the napier step of a Comjiression Ring. Pig 2 : is a ring with a positive twist having the sealing point A, at bottom side face. Pig 3 ; is a ring with a negative twist having sealing point at C, Fig 4 : ilhistratea the ring section and areas of material removed in a tapered negative twist ring. Fig 5 ; is a ring as per the invention wherein the sealing point is B on the bottom side face and further the bottom side face is tapered. Fig 6 : illnstratea the ring section and ai-eas of material removed in a positive twist compression as per tlie present invention. ft is to be noted that in studying fig 2 > fig 3 and fig 5 combinedly, by tapering the bottom side face of tlie ring in fig 2, we have shifted the sealing point *A' in fig 2 to point B' in fig 5, This means fig 5 is a modified version of fig 2 and additionally incorporating the characteristic noted in fig 3. According to the invention, the foregoing object is achieved by modifying the shape of bottom aide face of the ring into a tapered face. The Compi'esaion Ring as above exjalained will represent both better values of blow-by control along witli better values of lube oil control. As many different embodiments of the taper of the present invention can be made without departing irom the spirit and scope thereof, this invention is not limited to the si>ecific embodiments thereof mentioned here. DESCRIPTIOy OF HfyBHTION > A new and improved surface coated Compression Ring embodying the principles and concepts of the present invention will now be described. The present invention^ the new and ixap!*oved »nj-face coated Coinpieaaion Ring, in it« broadest context inchidea a positive torsion Compression Ring of known art but configured suitably at the bottom side, so MS to attain the desired objective of the invention. More parttcularly tlie present invention is concerned with a modification on the bottom side face of a Compression Ring having a positive twist such that the new version of the ring shall retain good blow-by control and additionally ac qiiiie goo Tiie salient feature of a conventional negative twist is that it establishes tw(^ line sealing contacts, one of wliich is with the Bottom groove and one with tht^ cylinder bore. The sharp inlay bottom edge provides efficient oil scraping. The outer edge contact established with tlie bottom flaiik of the groove pres/ents tlie oil from entering the groove avoiding tlie oil loss by side clearance^ back clearance, aide clearance route^ thereby reducing the oil consiimption passing the piston Assembly. The protective coating on the periphery aids in reducing the wear. The disadvantages of a conventional negative twist is that its peripheral taper has to be machined for an angle of at least 2 degrees. This requires increased surface ti'eatment tliickness and thereby increase in the cost of the ring. The uneven coating layei' depth across the width of the ring affects the adhesion. Tlie advantages of a conventional positive twist is tliat peripheral taper is induced by the positive twist; hence there is no need for taper grinding. The coating cost per ring tliereby is reduced. The outer edge periphery contact xvith groove is established similar to the reverse twist design enabling oil control which is achieved by its saucer shaped curvature (twist effect), inside the piston groove when fitted into the cylinder bore. Now keeping in mind the salient features and the disadvantages of the positive twist and negative twist, tlie Compression Ring as per the invention is configured suitably to reinforce the ad\^ntage of lube oil control and blowby control in a single ring itself, such that it is used as second Compression ring in iriston ring assembly and also capable of being used as top ring in the piston ring assembly. The compression ring as per the invention is a new and improved surface coated Compression Ring cojoiprising :- a, - an outside circumferential surface; eaOi inside circumferential surface; said outside circumferential surface and inside circumferential surface defining a wall; said outside surface and inside surface defining a top face at the top end of the W€ill; said outside surface and inside surface defining a bottom face at the bottom end of the wall; said inside surface and top face formed to have an inner top periphery; said inside surface and bottom face formed to have an inner bottom periphery; said outer surface and top face formed to have an outer top periphery; said outer sui-face axid bottom face formed to have an oiitei* bottom peripheiy; said inner top pei-ipheiy formed to liave a radially extending circumferential cross-sectional cutout portion; said bottom face formed to have an inwai'd taper extending from outside circumferential surface towards inside circumferential surface. The Compression rings as per the invention means either the first top rir^ or the second ring in the triple and multiple rings piston ring assembly. The cut out portion is formed in the said compression rings by chamferic^ means or by under cut. The taper formed in tlie said compression rings is by keystone taper* One of tiie embodiments of tlie present itivention will now be described witli reference to drawings : Fig 5 illustrates the shape and configuration of the Compression Ring according to the present invention with the new sealing points. Thus in accordance with the present invention as described above, the invention relates to a Compression Ring^ more specifically to second Compression Ring located in the second Campi*esauan Ring gi-oove, the second Compression Ring being of a cross-sectioned shape having an inside surface and top and bottom faces, a sealing means tlie said second Compression Ring being such that :- a. Cross-sectional cutout portion between the inside surface and top face of the second Compression Ring. b. Improvement comprising an inwai'dly tapered bottom face of the second Com-pression Ring. Fig 5 illustrates the shape of the positive twist rin« with bottom side keystone as per the invention, wherein by reshaping i.e., tapering the bottom side face, the sealing points are shifted to desired points of the Compression Ring to Acdiieve tlie desued higli lube oil control and desired liigh blowby conti'ol with the Compression Ring. As many vast number of cHffereiit embodiments of tlie present ms^entimi can be made without departing from the spirit and scope thereof, the present invention sliaH not be limited to specific embodiments tliereof except as defined in the claims. With respect to the above description then, it is to be reali2:ed that the optimum dimensional relationships for the taper at bottom side, to include vai*iations are deemed readily appai ent and obvious to those skilled in the art, and all equivalents to tliose illustrated in the diawings and described in specification are intended to be encompassed by the piesent invention. Furtlier all modifications axid clianges tliat will readily occur to tliose skilled in the art, is not de&iie WE CLAIM:- 1. A nefw and iauproved surface coated Compression Ring comprising :- an outside circumferential surface; an inside ciiciimferential surface; said outside circumferential surface and inside circumferential surface defining a wall; said outside surface and inside surface defining a top face at the top end of the wall; said outside surface and inside surface defining a bottom face at the bottom end of the wall; said inside surface and top face formed to have an inner top periphery; said inside surface and bottom face form.ed to have an inner bottom periphery; said outer stuface and top face formed to have an outer top periphery; said outei- sin^face and bottom face formed to have an enter bottom periphery; said inner top periphery formed to liave a radially extending circumferential cross-sectional cutout portion; said bottom face formed to have an inward taper extending from outside circumferential surface towards inside circumferential surface. 2. A new and improved surface coated Compression Ring as claimed in Claim 1, wherein Compressuon Ring means the second Compression Ring in triple-ring and multiple-ring piston ring assembly. 3. A new and improved surface coated Compression Ring as claimed in Claim 1, wherein Compression Ring means tlie JSrst top ring in triple-ring and multiple-ring piston ring assembly. 4. A nei^ and improved siarface coated Compression Ring as claimed in claha 1» wherein said cut-out portion is formed by chamfering. 5. A new and improved surface coated Compression Ring as claimed in claim 1, wherein said cut-out portion is formed by undercut, 6. A new and improved surface coated Compression Ring as claimed in claim 1, wherein inwardly tapered bottom face is formed by keystone taper. 7, A new and improved surface coated Compression Ring as claimed in claim 1 and as described in complete specification and as illustrated in. Fig 5 & 6 of accompanying di'awings.

Documents:

0034-che-2003-abstract.pdf

0034-che-2003-claims duplicate.pdf

0034-che-2003-claims original.pdf

0034-che-2003-correspondnece-others.pdf

0034-che-2003-correspondnece-po.pdf

0034-che-2003-description(complete) duplicate.pdf

0034-che-2003-description(complete) original.pdf

0034-che-2003-drawings.pdf

0034-che-2003-form 1.pdf

0034-che-2003-form 19.pdf

0034-che-2003-form 26.pdf

0034-che-2003-form 5.pdf