Steel laminate gasket with seal protecting member

Abstract: A steel laminate gasket (A) of the invention is installed in an internal combustion engine having at least one fluid hole (Hw) therein. The gasket (A) includes a plurality of plates (A10, A11, A12) for constituting the steel laminate gasket having at least one hole corresponding to the fluid hole (Hw) of the engine, and a sealing device (A11a) to seal around the fluid hole of the engine. A supporting device (A11b) integrally formed on one of the plates is situated between a gasket edge portion (A11c) and a part of the sealing device (A11a) facing the gasket edge portion (A11c). Consequently, when the engine is operated, vibration of the gasket at the gasket edge portion is reduced.

Description: Background of the Invention and Related Art Statement The present invention relates to a steel laminate gasket with a seal protecting member near the outer periphery of the gasket. A gasket is installed between two engine parts to seal therebetween. In order to securely seal around a hole of the engine parts, the gasket is provided with sealing means around the hole, which provides high surface pressure when the gasket is tightened. When an engine is operated, the engine together with the gasket vibrates, wherein the vibration is especially severe at a periphery of the gasket. Especially, a cylinder head gasket receives a severe vibration at the periphery thereof. When the gasket vibrates, sealing pressure applied against the sealing means around the hole changes repeatedly. As a result, when the gasket is used for a long period of time, creep relaxation occurs at the sealing means. Also, when coatings are formed on the plates, the coatings may break or gradually flow outwardly by the vibration of the gasket. In Japanese Utility Model Applications No. 63-12261, No. 63-20827 and No. 63-53125, it was proposed that at least one protecting plate is formed at an edge portion of a gasket near a hole to be sealed, so that vibration of the gasket is reduced. In these inventions, vibration of the gasket is properly reduced, but it requires additional plates. EP-A-385 699 describes a metal laminate gasket having multiple concentric beads for sealing around holes, the gasket operates as intended, However, the gasket described is not adapted to deal with high vibration levels and consequent creep relaxation of the sealing beads. JP-A-2-67162 describes a gasket having a sealing bead around the entire gasket peripheral edge. However, it is not possible to exercise local, controlled pressure with respect to a fluid hole between the cylinder bore and the gasket. US-A-4 759 556 describes a gasket wherein bead portions remote from tightening bolt holes have a supporting bead which merges back into the main bead to equalise pressure. Accordingly, one object of the present invention is to provide a steel laminate gasket, in which sealing means around a hole is protected from vibration of the gasket. Another object of the invention is to provide a steel laminate gasket as stated above, wherein creep relaxation of the sealing means is substantially prevented. A further object of the invention is to provide a steel laminate gasket as stated above, wherein the flow of the seal coating formed on a gasket is substantially prevented. A still further object of the invention is to provide a steel laminate gasket as stated above, which can be easily and economically manufactured. Further objects and advantages of the invention will be apparent from the following description of the invention. Summary of the Invention In accordance with the present invention there is provided a steel laminate gasket for an internal combustion engine having a plurality of cylinder bores and at least one fluid hole therein, comprising, a plurality of plates for constituting the steel laminate gasket, each plate having first holes corresponding to the cylinder bores and at least one second hole corresponding to the fluid hole of the engine, said second hole being located between the first hole and a gasket edge portion and means for sealing around the fluid hole of the engine, said sealing means entirely surrounding the fluid hole, a supporting bead situated between the gasket edge portion and the sealing means facing the gasket edge portion, said supporting bead being integrally formed on one of the plates, said supporting bead operating as a bead which is effective for only partly supporting the sealing means and which extends only partly around the sealing means without extending around the entire edge of the gasket, said supporting bead being located separately and curving generally along the sealing means at a predetermined distance away from both the sealing means and the gasket edge portion so that when the gasket is tightened, the supporting bead receives a part of the tightening pressure applied to the sealing means and provides surface pressure higher than the surface pressure of the sealing means, the higher surface pressure being achieved by virtue of the supporting bead having a characteristic selected from at least one of: the supporting bead being higher than the sealing means; being formed on a plate which is thicker than the plate containing the sealing means; and, being formed on a plate which is harder than the plate containing the sealing means so as to protect the sealing means against creep relaxation. As a result, the vibration of the gasket at the gasket edge portion is partly supported by the supporting means to thereby protect the gasket. Consequently, creep relaxation of the sealing means is substantially prevented or reduced. Also, in case seal coatings are formed on outer surfaces or between the plates, the seal coatings on and around the sealing means do not flow outwardly. Leakage of fluid around the fluid hole is substantially prevented. The supporting means is a bead, which provides surface pressure higher than the surface pressure of the sealing means when the gasket is tightened. Also, the sealing means may be a bead integrally formed on one of the plates. Further, the bead for the supporting means is curved along the bead of the sealing means. The beads for the supporting means and the sealing means may be formed on the same plate or different plates. Brief Description of the Drawings Fig. 1 is a partial plan view of a first embodiment of a steel laminate gasket of the invention; Fig. 2A is an enlarged perspective section view taken along line 2-2 in Fig. 1; Fig. 2B is a perspective section view similar to Fig. 2A; Fig. 3 is an explanatory section view for showing a compressed condition of a gasket; and Fig. 4 is an enlarged perspective section view, similar to Fig. 2A, for showing a second embodiment of a steel laminate gasket of the invention. Detailed Description of Preferred Embodiments Referring to Figs. 1 and 2A, a first embodiment A of a steel laminate gasket of the present invention is shown. The gasket A is a cylinder head gasket and includes cylinder holes Hc, water holes Hw, oil holes Ho, bolt holes Hb and so on, as in the conventional gasket. In the gasket A, areas around the cylinder holes Hc are sealed by appropriate sealing means. However, since the sealing means for the cylinder holes Hc is not the subject matter of the present invention, the sealing means for the cylinder holes Hc is not explained. Any sealing means may be used for the cylinder holes Hc. Also, in the embodiments explained herein below, areas around the water holes Hw and oil holes Ho are sealed by beads. The beads are preferable, but it is possible to use any other sealing means around the water hole Hw and oil holes Ho. As shown in Fig. 2A, the gasket A comprises an upper plate A10, a middle plate A11 and a lower plate A12, which have the same configuration and extend over the entire area of the gasket A. The middle plate A11 is situated between the upper and lower plates A10, A12 and includes a bead A11a around the water hole Hw to seal therearound. The middle plate A11 further includes a bead A11b situated between the bead A11a and an edge A11c. The bead A11b curves generally along the bead A11a and is partly formed outside the bead A11a facing the edge A11c. The height of the bead A11b is higher than that of the bead A11a to provide surface pressure greater than that of the bead A11a when the gasket A is tightened. As clearly shown in Fig. 3, when the gasket A is situated between a cylinder head X and a cylinder block Y and is tightened, the beads A11a, A11b are compressed. The bead A11a seals around the water hole Hw, and the bead A11b partly supports the bead A11a. The bead A11b provides surface pressure P 1 higher than surface pressure P 2 of the bead A11a. As a result, a part of the bead A11a near the bead A11b or near the edge A11c is supported by the bead A11b. When the engine is actuated, the engine vibrates. Especially, the edge portions of a cylinder head gasket vibrate severely. As a result of the vibration, the sealing means near the edge portions of the cylinder head gasket is weakened. Further, since high temperature is applied to the cylinder head gasket, the cylinder head gasket is liable to be damaged. Especially, in case seal coatings are formed on or between the plates, the seal coatings on or around the sealing means may break or flow outwardly by the vibration and high temperature. In the present invention, the bead A11b is formed between the edge A11c and bead A11a, and supports a part of the tightening pressure applied to the bead A11a. Therefore, even if the gasket A is used for a long time, the bead A11a is not substantially damaged by the vibration of the engine. Namely, creep relaxation of the bead A11a is substantially prevented. Further, as shown in Fig. 2B, in case a seal coating A13 is formed on or around the bead A11a, the seal coating may not break or flow outside the bead A11a. Even if the seal coating flows from the bead A11a, the bead A11b prevents the flow of the seal coating beyond the same. Accordingly, sealing around the water hole Hw can be securely made. Fig. 4 shows a second embodiment B of a steel laminate gasket of the invention. The gasket B comprises an upper plate B10, a middle plate B11 with a bead B11a, and a lower plate B12, as in the gasket A. However, in the gasket B, the middle plate B11 does not have a bead between an edge B11c and the bead B11a. Instead, the plate B10 is provided with a bead B10a, which is located between the edge B11c and the bead B11a when the gasket B is assembled. The bead B10a partly curves along the bead B11a. The height of the bead B10a is higher than the height of the bead B11a, and the thickness of the plate B10 is thicker than the plate B11, so that when the gasket B is tightened, the bead B10a provides surface pressure higher than that of the bead B11a. Therefore, the bead B10a partly supports tightening pressure applied to the bead B11a to thereby protect the bead B11a. The hardness of the plate B10 may be greater than the plate B11. The gasket B operates as in the gasket A. In the present invention, the supporting means is situated near the sealing means at a predetermined distance away from the gasket edge portion. Therefore, when the engine is actuated, vibration of the gasket at the edge portion is significantly reduced. As a result, creep relaxation of the sealing means is substantially prevented. In case the seal coatings are formed on or between the plates, the seal coatings on or around the sealing means do not break or flow outwardly by the vibration of the gasket. Especially, the seal coatings do not flow beyond the supporting means. While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.

Claims: A steel laminate gasket (A;B) for an internal combustion engine having a plurality of cylinder bores (Hc) and at least one fluid hole (Hw) therein, comprising: a plurality of plates (A10,A11,A12;B10,B11,B12) for constituting the steel laminate gasket, each plate having first holes corresponding to the cylinder bores (Hc) and at least one second hole corresponding to the fluid hole (Hw) of the engine, said second hole being located between the first hole and a gasket edge portion (A11c; B11c), means (A11a;B11a) for sealing around the fluid hole of the engine, said sealing means entirely surrounding the fluid hole, and a supporting bead (A11b;B10a) situated between the gasket edge portion (A11c;B11c) and the sealing means facing the gasket edge portion, said supporting bead being integrally formed on one of the plates, said supporting bead (A11b; B10a) operating as a bead which is effective for only partly supporting the sealing means (A11a;B11a) and which extends only partly around the sealing means (A11a;B11a) without extending around the entire edge of the gasket, said supporting bead being located separately and curving generally along the sealing means at a predetermined distance away from both the sealing means and the gasket edge portion so that when the gasket is tightened, the supporting bead receives a part of the tightening pressure applied to the sealing means and provides surface pressure higher than the surface pressure of the sealing means, the higher surface pressure being achieved by virtue of the supporting bead having a characteristic selected from at least one of: the supporting bead being higher (A11b;B10a) than the sealing means; being formed on a plate (B10) which is thicker than the plate (B11) containing the sealing means; and, being formed on a plate (B10) which is harder than the plate (B11) containing the sealing means so as to protect the sealing means against creep relaxation. A steel laminate gasket according to claim 1, characterised in that said sealing means is a bead (A11a;B11a) integrally formed on one of the plates (A11;B11) for constituting the steel laminate gasket. A steel laminate gasket according to either claim 1 or claim 2, characterised in that said supporting bead (A11b) is formed on the same plate (A11) as the bead for sealing means (A11a). A steel laminate gasket according to claim 1, characterised by further comprising means (A13) for preventing fluid from flowing through the plates and formed between the plates, wherein said supporting bead (A11b), when said fluid flow preventing means (A13) formed between the plates flows toward the gasket edge portion, prevents the flow of the fluid flow preventing means (A13) from flowing beyond the supporting bead (A11b) to securely seal around the fluid hole.

Inventors: UDAGAWA TSUNEKAZU, UDAGAWA, TSUNEKAZU
Applicants: ISHIKAWA GASKET, ISHIKAWA GASKET CO. LTD.
Application year: 1991
Main classification: F16J15
IPC codes: C09K3, F16J15