HEAD GASKET WITH BEAM-FUNCTIONING FIRE RING

Abstract: A head gasket (10) having a beam functioning fire ring (30) in the combustion opening (18) and having a bead (34) overlying a recess (36), the recess (36) having a width at least twice as great as the width of the bead (34), the height of the bead (34) being no greater than the height of the recess (36) and preferably no more than 60% of the height of the recess (36). The fire ring (30) may be a separate annulus disposed in the combustion opening (18) and have a pair of spaced feet (33) straddling and defining the recess (36).

Description: This invention is related to a gasket assembly comprising an expansive main gasket body having upper and lower main surfaces adapted to be disposed between the head and block of an internal combustion engine, and defining a plurality of openings, including at least one combustion opening, fluid openings and bolt holes, and a fire ring comprising an annulus positioned and disposed in each combustion opening, said fire ring comprising, in radial cross-section, an annular beam, an annular bead projecting from the beam in a first vertical direction and annular support feet projecting from the beam in the opposite vertical direction and said feet defining an annular recess therebetween, said bead lying above said recess and between said feet, said annular beam having upper and lower parallel surfaces, said annular bead projecting from one surface of the beam in the first vertical direction and said annular support feet projecting from the other surface of the beam, said annular recess being defined between said feet being rectangular in cross-section. A gasket assembly of this type is known from DE-A1-206 656. This reference discloses an elastic gasket having a U-shaped cross-section, wherein the U-legs rest on a compression bead whilst the engaging surface of a collar of said U-shaped cross-section is narrower than the total width of the cross-section in the middle between said two legs. This known structure aims to avoid formation of cracks on the supporting shoulder of the cylinder sleeve. The main portion of the gasket comprising a massive steel plate receiving the main portion of the compression. This steel plate guarantees that the fire ring can only be deformed elastically. FR-A-1 497 446 discloses a gasket comprising a fire ring having an upper concave surface and a lower convex surface. The upper concave surface forms two annular concentric sealing zones. The convex surface of the fire ring has an annular rib resting on an annular shoulder of a cylinder sleeve concentricly positioned to said two sealing zones. The diameter of the annular sealing zone formed between the sealing rib and the supporting shoulder of the cylinder sleeve is larger than the smallest one of that sealing zones and smaller than the greatest one of said sealing zones. The fire ring retains its elasticity under load and resumes substantially its initial concave-convex shape if the gasket is removed from block and cylinder. DE-A-1 425 524 discloses a gasket made from a metal sheet having said offset grooves. Said offset of the grooves assists a bending of the metal when the gasket is under load so that occluding and pressurizing of plastic material is achieved. It is an object of the present invention to improve the loading of a fire ring and its structure so that the gasket will properly seal at all thermal and mechanical load conditions. The present invention achieves this object by an improvement characterized in that said bead being offset radially from the vertical projection of the recess facing surface of each foot by a distance equal to at least one half of the radial width of said bead, and said bead height is no more than the height of the recess, said recess radial width is at least three times the width of the bead, said fire ring, in use, defining a loading curve which progressively first functions under load as a beam, next is elastically loaded under a relative low load, and thereafter is plastically deformed under a higher load. To achieve the object of the invention, an improvement of a method of sealing the cylinders of an internal combustion engine by a head gasket position between the head and block thereof is also provided, comprising the steps of providing a gasket assembly according to claim 1 between the head and block, then loading the gasket body such that the fire ring is compressed between the head and the block to cause the fire ring to function as a beam under that load, further loading and compressing that fire ring so that it functions under load elastically, and finally loading and compressing that fire ring so that it functions plastically under load. In use, the beam functioning fire ring defines a loading curve which progressively first functions under load as a beam, next is elastically loaded under a relative low load and thereafter is plastically deformed under a higher load. Further objects, features and advantages of the present invention will become apparent from the following description and drawings. Brief Description of The Drawings Fig. 1 is a plan view of a head gasket assembly in accordance with the present invention; Fig. 2 is an enlarged cross-sectional view of the fire ring portion of the gasket of Fig. 1 taken substantially alone line 2-2 of Fig. 1, and showing same juxtaposed with an internal combustion engine; Fig. 3 is a view like Fig. 2, but of the fire ring under low load; Fig. 4 is a view like Fig. 3, but of the fire ring under a higher load; Fig. 5 is a view like Fig. 4, but of the fire ring under a still higher load; and Fig. 6 is a curve showing the loading characteristics of a fire ring in accordance with the present invention. Description of A Presently Preferred Embodiment Referring now to the drawings, Fig. 1 illustrates a typical head gasket assembly with which the beam functioning embossed fire ring of the present invention may be employed. Thus head gasket 10 comprises a main gasket body 12 having two main surfaces, upper and lower main surfaces 14, 16, and a plurality of combustion openings 18 which are armored in accordance with the present invention. Main gasket body 12 is formed of a plurality of laminated layers, such as a metallic central core 20 and a pair of outer fiber-elastomer facing layers 22 which provide the upper and lower main surfaces 14, 16. Fiber-elastomer facing layers may comprise asbestos or glass fibers or other fibrous material and may utilize nitrile, neoprene, or polyacrylic elastomers as a binder. Fillers and other ingredients may also be present. Other flat gasket bodies may be used as well, such as, for example, cold rolled steel, among others. The dimensions and materials of the main gasket body may vary, as may be the adjuncts and sealing aids used therewith. The metallic core 20 may be unperforated and of cold rolled steel and the facings 22 are preferably moisture, water and oil resistant. The core and facings are preferably laminated to each other in a known manner, as with a conventional adhesive. Gasket 10 defines a plurality of suitable openings, such as fluid (oil and water) openings 24, as well as a plurality of bolt holes 26 for the purposes described in U.S. Patent 3,565,449. The water and oil openings 24 extend through the main gasket body and are intended to provide passageways through the gasket assembly 10. However, they are to be sealed so that water and/or oil will not spread beyond the openings 24. To that end, sealing means are conventionally provided around openings 24. In current practice, an elastomeric bead, such a silicone bead, is frequently desposited therearound, as by a silk-screening process, to form a sealing bead, usually one on each main surface 14, 16 in vertical alignment. In accordance with a preferred embodiment of the present invention the beam functioning fire ring may be an annulus 30 positioned and disposed in the gasket combustion opening and in vertical transverse cross-section comprises a beam section 31, a pair of perimetric inside and outside support rims 32, 32′ having feet 33, 33′ projecting from one side of the annulus in a first direction and a control bead 34 projecting from the other side of the annulus in a second direction. A recess 36 extends between the support rims and below the bead. As seen in Fig. 2, the recess extends laterally by a distance of at least half of the width of the vertical projection of the bead, beyond the bead on each side of the bead. As such, it will be apparent that the beam section 31 may be stressed and deflected from its straight or rectilinear configuration as illustrated in Fig. 2 when the bolts (not shown) passing through openings 26 and securing the head H and block B of the engine are drawn together from the position as illustrated in Fig. 2 to those positions exemplified by Figs. 3-5, inclusive. Thus, as shown by Figs. 2-5 and by Fig. 6 which is a typical loading curve, the fire ring of the present invention resembles, in cross-section, an end supported single point loaded beam. The control bead 34 is the loading point and the bead height provides the deflection control for the beam, as may readily be seen in the transition from Fig. 2 to Fig. 3. The inside rim 32 and outside rim 32′ support the beam and the space between the feet 33, 33′, the coined section or recess 36, defines the length of the beam. When the compressive load caused by the torquing of the head and block via the bolts is applied, the bead 34 is pushed downwardly causing the beam section 31 to bend. This tends to rotate the inside corners 38, 38′ of the feet 33, 33′ outwardly or away from each other and to cause the top outermost corners of the fire ring to rotate relatively inwardly until they contact the head H, as illustrated in Fig. 3. During this portion of the loading, the beam section 31 bends and, as shown by section A-B of the curve (Fig. 6), the characteristics are elastic deformation at a relatively low load. As the head H is further drawn down towards block B, the forces on the fire ring act somewhat more complexly, and require much higher loading. Thus, as further compression occurs rotation of the support rims 32, 32′ for the beam, is reversed, i.e., the lower inside corners 38, 38′ of the feet are rotated inwardly toward each other (and the upper outer corners of the rims are rotated relatively outwardly) causing the beam section to be tensioned, particularly in its upper zone. The behavior in moving from the position of Fig. 3 to that of Fig. 4 is a combination of tension and bending and is illustrated in curve position B-C (Fig. 6), the characteristics of which are plastic deformation and high load. The load is significantly increased to the desired load ranges of typically used metals, such as stainless steel and low carbon steel, and is the portion of the curve in which effective sealing should take place. The stiffness of the curve can be adjusted in accordance with this invention by adjusting the length of the beam (i.e., the width of the recess) and the position of the bead along the length of the beam, as well as by adjusting the relative length of the bead versus the length of the recess (or beam). The C-D portion of the curve (Fig. 6) is one in which the head and block act in compression against the rims (as illustrated in Fig. 5), going beyond the relationship of Fig. 4 wherein the space between the head and block was substantially the same as the height of the support rims. In this portion of the curve, the slope of the curve becomes much steeper and stiffer because the rims are absorbing all of the added load. In this zone of the curve the fire ring resists excessive bolt load and thermal push. In deriving the curve A-D of Fig. 6, an annulus 30 of cold rolled steel was tested. Annulus 30, in a diametric transverse cross-section, was 3.81 mm (0.15 inch) wide and 1.5748 mm (0.062 inch) high. The recess width was 1.7018 mm (0.067 inch) with a recess depth of about 0.127 mm (0.005 inch) Each support rim was 0.9144 mm (0.036 inch) wide by 1.5748 mm (0.062 inch) high The bead was rectangular and the width was 0.762 mm (0.030 inch) by 0.0762 mm to 0.127 mm (0.003 to 0.005 inch) high. The bead was centered (in cross-sectional view) relative to the cross-sectional width of the annulus and projected upwardly therefrom. The inside diameter of the annulus was about 121.005 to 121.513 mm (4.764 to 4.784 inches). As pointed out, the curve A-D on Fig. 6 shows the behavior and loading capacity of a beam functioning embossed fire ring according to the present invention. It also shows a typical curve E schematically illustrating a load versus deflection curve encountered with a typical fire ring comprising an armor shrouding, a circular wire, and graphically illustrating the substantially improved characteristics of a beam functioning fire ring in accordance with the present invention. The dimensions of the fire ring of the present invention may vary, taking into consideration, however, that the ring must have a portion which functions as a beam, must have a projecting bead and a significantly wider recess, and that it must define a loading curve which progressively functions first under load as a beam, next elastically under a relatively low load, and thereafter in a plastic deformation mode under a higher load. Thus, the recess width in the annulus is at least twice the bead width and is preferably is at least three times the width of the bead. The bead height is no greater than the height of the recess and is preferably is no more than 60% of the height of the recess. The bead is spaced inwardly of the edge of the recess a distance at least equal to half the width of the bead. It will be apparent to those skilled in the art that modifictions may be made without departing from the spirit and scope of the present invention. Accordingly, the claims are intended to embrace all modifications within their scope.

Claims: A gasket assembly comprising an expansive main gasket body (12) having upper and lower main surfaces (14, 16) adapted to be disposed between the head (H) and block (B) of an internal combusion engine, and defining a plurality of openings, including at least one combustion opening (18), fluid openings (24) and bolt holes (26), and a fire ring (30) comprising an annulus positioned and disposed in each combustion opening (18), said fire ring (30) comprising, in radial cross-section, an annular beam (31), an annular bead (34) projecting from the beam in a first vertical direction and annular support feet (33, 33') projecting from the beam (31) in the opposite vertical direction and said feet (33, 33') defining an annular recess (36) therebetween, said bead (34) lying above said recess (36) and between said feet (33, 33'), said annular beam (31) having upper and lower parallel surfaces, said annular bead (34) projecting from one surface of the beam in the first vertical direction and said annular support feet (33, 33') projecting from the other surface of the beam (31), said annular recess being defined between said feet (33, 33') being rectangular in cross-section, characterized in that said bead (34) being offset radially from the vertical projection of the recess facing surface of each foot (33, 33') by a distance equal to at least one half of the radial width of said bead (34), and said bead height is no more than the height of the recess (36), said recess radial width is at least three times the width of the bead, said fire ring (30), in use, defining a loading curve which progressively first functions under load as a beam, next is elastically loaded under a relative low load, and thereafter is plastically deformed under a higher load. The gasket assembly in accordance with claim 1, and wherein the bead height of said fire ring (30) is no greater than 60 % of the height of the recess (36). The gasket assembly in accordance with claim 1, wherein said main gasket body (12) comprises a central core (20) and a pair of outer fiber-elastomer facings (22) providing said upper and lower main surfaces (14, 16). A method of sealing the cylinders of an internal combustion engine by a head gasket positioned between the head and block thereof, comprising the steps of providing a gasket assembly according to claim 1 between the head (H) and block (B), then loading the gasket body such that the fire ring is compressed between the head (H) and the block (B) to cause the fire ring (30) to function as a beam under said load further loading and compressing said fire ring so that it functions under load elastically, and finally loading and compressing said fire ring (30) so that it functions plastically under load.

Inventors: INCIONG, JOSEFINO T.
Applicants: FEL-PRO INCORPORATED
Application year: 1988
Main classification: F16J15
IPC codes: F16J15, F02F11