Metallic gasket

Abstract: A metallic gasket (1) according to the present invention includes two base plates (10-1)(10-2) made of an elastic material. One base plate (10-1)is provided with an array of beads (4) in association with an odd-numbered combustion chamber bore (3), only one end segments of which are provided with stoppers (11), while the other base plate (10-2) is provided with an array of beads (4) in association with an even-numbered combustion chamber bore (3), only one end segments of which are provided with stoppers (11).The base plates (10-1)(10-2) are then antisymmetrically laminated together.

Description: The present invention relates to a metallic gasket designed to be interposed between the joining surfaces of a cylinder head and a cylinder block which form part of an internal combustion engine, thereby preventing leakages of combustion gas, cooling water, lubricating oil, etc. Between the joining surfaces of a cylinder block and a cylinder head forming part of an internal combustion engion, there is interposed a gasket to impart a sealing function thereto. Of particular importance is a seal to be provided around a combustion chamber. A failure in providing sufficient sealing to the combustion chamber would cause a leakage of the combustion gas from within, resulting in a pressure drop. According to one approach for solving this problem, an array of beads are located concentrically with a combustion chamber bore formed in an elastic base plate of a metallic gasket. As the metallic gasket is clamped in place by means of bolts, the beads produce repulsive force, which is in turn used to provide a sealing function to the peripheral edge of the combustion chamber. In order to prevent the breaking-down of the beads by fatigue in this case, for instance, stoppers are located on flat segments of the metallic gasket between the combustion chamber bore and the beads, thereby limiting the amplitude of the beads. In recent years, however, higher-performance and weight-saving engines of smaller size and larger displacement have been in great demand, resulting in a drop of their rigidity. Beads themselves, on the other hand, are more likely to break down by fatigue, since their inter-bolt amplitude of vibration cannot be limited without recourse to stoppers. This problem may possibly be solved by measuring gaps occurring at the time when a metallic gasket is mounted and clamped in place and providing stoppers of a size corresponding to such gaps. Figure 11 is a schematic view, partly cut-away and sectioned, of one typical example of conventional metallic gaskets. Referring to Fig. 11, reference numerals 10-1 and 10-2 stand for base plates made of an elastic material and 12 an auxiliary plate. The base plates with the auxiliary plate located between them are provided with angular or arched beads 4-1 and 4-2 in the same direction. The auxiliary plate 12 is provided with a stopper 11 at its one end in association with a combustion chamber bore to limit the amplitude of the beads by vibration. According to the above arrangement, it would be required to increase the bores of cylinders for the purpose of obtaining a further increase in displacement. However, if the bores of cylinders are increased in a given space, then it is required to arrange them more closely, resulting in a reduction of the inter-cylinder spaces; where arched beads are used, it is impossible to obtain stopper locations of sufficient width. In this case, it may be envisaged to reduce the width of the arched beads, but some limitation is placed upon the bead width. For instance, when the stopper is 1.5 mm or below in width, a pressure produced by bolting is received at an area so narrow that a very high pressure is applied to the stopper. In addition to such a high pressure produced by bolting, the amplitude of vibration by the operation of an engine is applied to the stopper in the form of waves. Consequently, the sealing surface for the engine deforms, making sealing gradually incomplete. The same problem occurs with the metallic gasket of EP-A-0 330 126, which discloses the features of the preamble of claim 1. The present invention seeks to provide a metallic gasket which is applicable to a closely cylindered engine and solves the above mentioned problem. Figure 1 is a schematic view of one embodiment of the metallic gasket according to this invention, Fig. 1(a) being a sectional view taken along the line A-A' in Figure 2 to be referred to just below, Fig. 1(b) a sectional view taken along the line B-B' and Fig.1(c) a sectional view taken along the line C-C', Figure 2 is a schematic plan view, partly cut-away, of that metallic gasket, Figure 3 provides an illustration of how the metallic gasket operates, Figure 4 is a view illustrating pressures acting on parts of the metallic gasket, when it is built in an engine and bolted in place, Figure 5 is a view illustrating pressures acting on parts of the metallic gasket during thermal deformation, when an engine with the metallic gasket built in it is in operation, Figure 11 is a view illustrative of a conventional metallic gasket. The present invention will now be explained more specifically but not exclusively with reference to the accompanying drawings. Fig. 1 is a sectional view illustrative of one embodiment of the metallic gasket according to this invention, and Fig. 2 is a schematic plan view, partly cutaway, of the metallic gasket wherein the sections along the lines A-A', B-B' and C-C' are shown in Figs. 1(a), 1(b) and 1(c), respectively. Referring first to the general plan arrangement shown in Fig. 2, a metallic gasket body, shown at 1 , includes a base plate 10 made of an elastic material. The plate 10 has openings 3 located in association with combustion chamber bores, each of which is provided at its outer edge with a concentric array of beads 4. Reference numeral 5 is a bolt hole through which a bolt or screw is inserted to fix the metallic gasket in place when it is built in an engine, 6 a hole through which cooling water circulates, and 7 an oil hole. Elements forming the metallic gasket are made integral by fixing means 2. It is noted that reference numeral 11 stands for a position at which a stopper is to be located. Referring then to Fig. 1, there is a sectional view of the metallic gasket. In Fig. 1, the same parts as in Fig. 2 are indicated by the same reference numerals. As illustrated in Fig. 1(a), the gasket body includes two base plates 10-1 and 10-2 formed of an elastic material, which are laminated together. The first base plate 10-1 is provided with a stepped bead 16-1. A stopper 11-1 is located at only an opening located corresponding to any one of odd-numbered cylinders #1, #3, ···. The stopper may be formed of any known material and fixed in place by any known means such as thermal spraying. Referring to the geometry of the stepped bead, the length l₁ of one flat upper segment, on which the stopper 11-1 is to be located, preferably accounts for 30 % to 40 % inclusive of the full length l between the adjacent bores. It is then required that l₁ > l₂ wherein l₂ is the length of another flat upper segment on which no stopper is to be located. The second base plate 10-2, on the other hand, is located below, or laminated on the lower side of, the first base plate 10-1 and, contrary to the first base plate 1, is provided with an outward stopper 11-2 for only an opening located corresponding to any one of even-numbered cylinders #2, #4, ···. The second base plate 10-2 is otherwise similar to the first base plate 10-1. In other words, the first base plate 10-1 is provided with the stopper only for the cylinder #1 but is not for the cylinder #2, while the second base plate 10-2 is provided with the stopper only for the cylinder #2. However, if the two base plates remain laminated together, then the stopper 11-1 for the cylinder #1 and the stopper 11-2 for the cylinder #2 would act synergistically to produce an effect similar to that achieved with a stopper located between both the cylinders. As understood from the foregoing, the two base plates 10-1 and 10-2 each including an array of stepped beads are antisymmetrically located between the adjacent cylinders. Consequently, when the two base plates are in a laminated state, the stepped beads engage each other through bends 17-1 and 17-2 on the middle portions of their associated slopes. In other words, the bend 17-1 of the bead of the first base plate engages centrally the slope (or incline) of the second base plate 10-2, while the bend 17-2 of the bead of the second base plate engages centrally the slope (or incline) of the first base plate 10-1. Accordingly, when the metallic gasket is clamped in place, a deformation stress taking place at the bends adds to the spring stress of the stepped beads, resulting in a further increase in the spring constant. This in turn makes it possible to apply a pressure higher than a combined spring stress of the first and second base plates. To put it another way, the pressure increase is obtained by a two-stage spring action. In an arrangement located between bolts as shown in Fig. 1(b), the length W₁ of the slope of each stepped bead is made shorter than W₂ in an arrangement located at a bolt position as shown in Fig. 1(c), thereby increasing the spring constant. This is because at a location between the bolted positions (B-B') the gasket is clamped in place with a less clamping force. In order to make up for such a less clamping force, W₁ should be made shorter so as to increase the spring constant. At the bolted position (C-C'), on the other hand, the gasket is clamped in place with a clamping force so large that the spring constant can remain reduced. In the arrangement shown in Figure 1(b) or 1(c), the bend of each bead of one base plate engages centrally the slope of each bead of the associated base plate, as in the arrangement shown Figure 1(c). Figure 3 is a sectional view taken along the line D-D' of Fig. 2, providing an illustration of how the metallic gasket operates. In other words, Figure 3 is a view illustrating an arrangement between the cylinders #2 and #3 as counted from the left. Thus, the stopper 11-1 provided on the first base plate 10-1 is located on its right-handed flat segment (in association with the cylinder #3), while the stopper 11-2 provided on the second base plate 10-2 is located on the its left-handed flat segment (in association with the cylinder #2). As the metallic gasket is clamped in place by means of clamping bolts (not shown), it first engages the engine at the bends 18-1 and 18-2 of the first and second base plates 10-1 and 10-2 and the right- and left-handed portions of the stoppers 11-1 and 11-2, respectively. Then, the slopes 19-1 and 19-2 of the first and second base plates 10-1 and 10-2 come into simultaneous contact with the bends 10-2 and 17-1 of the second and first base plates 10-2 and 10-1, respectively. As the clamping force is further increased in this state, the stoppers 11-1 and 11-2 located at the ends of the first and second base plates close to the combustion chamber come into flat contact with the engine. As a result, only slight gaps are left at the ends 20-1 and 20-2 of the stoppers 11-1 and 11-2 located halfway between the associated cylinders. Thus, the resulting spring stress is the sum of the initial spring constant attained by the stepped beads and the spring constant obtained incidental to the engagement of the slopes with the bends in the course of deformation. In other words, more increased pressures are applied across the bends 18-1 and 17-2 and the bends 18-2 and 17-1. At the ends 20-1 and 20-2 in particular, an additional stress attained by the engagement of the slopes with the bends 17-1 and 17-2 adds to the initial single spring stress of the stepped beads, resulting in a further increase in the pressure applied to the metallic gasket. Figure 4 shows pressures applied to parts of the metallic gasket at the time of assembly, with the magnitude of pressures as ordinate. In connection with Fig. 4, it is noted that combustion chamber bores are positioned on both sides of the illustrated arrangement, with the outermost ends of the stoppers receiving increased pressures Figure 5 illustrates pressures applied to parts of the metallic gasket at the time of thermal deformation, showing that pressures applied to the outermost ends of the stoppers increase symmetrically. While the foregoing embodiment has been described with reference to using only two base plates, it should be understood that the present invention is not limited thereto. For instance, an auxiliary plate may be sandwiched between two main base plates. The above embodiments have been described while making no particular reference to what forms the stoppers. It should be understood, however, that they may be formed by the thermal spraying or plating of metals, made of flat metal materials or molded of metal materials. According to the present invention as detailed above, an array of beads are provided on each of two base plates which are antisymmetrically laminated together. One base plate is provided with an array of beads in association with an odd-numbered combustion chamber bore and the other base plate is provided with an array of beads in association with an even-numbered combustion chamber bore, while stoppers are located on the outside of the laminate. Thus, it is possible to provide a metallic gasket of a simplified structure, which can successfully be used with engines, whether of small size or of high performance.

Claims: A metallic gasket for a multi-cylindered internal combustion engine, said gasket including a base plate which is made of an elastic metal plate and provided with an array of stepped beads at its peripheral edge located in sealing association with a combustion chamber bore for sealing of the combustion chamber; characterised in that said base plate is divided into two parts, each of which is provided with an array of stepped beads, first stoppers are located on flat segments of a first array of stepped beads on the first base plate part, said flat segments of said first array being positioned in association with an odd-numbered cylinder, while second stoppers are located on flat segments of a second array of stepped beads on the second base plate part, said flat segments of said second array being positioned in association with an even-numbered cylinder, and said first and second base plate parts are antisymmetrically laminated together with said first and second stoppers facing outwards. A metallic gasket as claimed in Claim 1, wherein when said base plate parts are antisymmetrically laminated together, the bends of the respective stepped beads engage the centers of slopes of the associated beads. A metallic gasket as claimed in Claim 1 or 2, wherein the length l₁ of said flat segments to be provided with said stoppers accounts for 30 % to 40 % inclusive of the full length l between the adjacent combustion chamber bores. A metallic gasket as claimed in Claim 3, wherein l₁ > l₂ wherein l₁ is the length of the flat segments on which said stoppers are located and l₂ is the length of flat segments on which no stoppers are located.

Inventors: UETA IKKOH C O NIHON METAL GAS, UETA KOSAKU C O NIHON METAL GA, UETA, IKKOH, C/O NIHON METAL GASKET CO. LTD., UETA, KOSAKU, C/O NIHON METAL GASKET CO. LTD.
Applicants: NIHON METAL GASKET, NIHON METAL GASKET CO. LTD
Application year: 1990
Main classification: F16J15
IPC codes: F02F11, F16J15