WO2008082023A1

WO2008082023A1 - Gasket with inner plate having embossing

Info

Publication number: WO2008082023A1
Application number: PCT/KR2007/000100
Authority: WO
Inventors: Kyo-Nam Koo
Original assignee: Dongah Manufacturing Corp.
Priority date: 2006-12-28
Filing date: 2007-01-08
Publication date: 2008-07-10
Also published as: KR20080061457A; KR100845273B1

Abstract

A gasket with an inner plate having embossments is disclosed. The gasket of the present invention includes a pair of base plates (20a) and (20b), each of which has a base plate hole (21a), (21b) corresponding to a bore, a bead (22a), (22b) provided around the base plate hole, and a plurality of insert holes (23a), (23b). The gasket further includes an inner plate (10), which is provided between the base plates and has an inner plate hole (11) corresponding to the bore. The gasket is interposed between and coupled to junction surfaces of a cylinder head and a cylinder block by bolting to seal the junction surfaces. A plurality of embossments (12a), (12b), (12c) and (12d) is provided on the inner plate around the inner plate hole. The gasket having the above-mentioned construction compensates for a difference in dimensions of gaps between contact surfaces, thus enhancing the sealing ability thereof.

Description

[DESCRIPTION] IInvention Title] GASKET WITH INNER PLATE HAVING EMBOSSING

[Technical Field] The present invention relates, in general, to gaskets with inner plates having embossments and, more particularly, to a gasket which is used to form a seal between a cyl inder block and a cyl inder head of an internal combust ion engine to compensate for variation in gaps formed at the cylinder head due to bolt coupling, thus enhancing the sealing ability. [Background Art]

As well known to those skilled in the art, in devices, such as engines (internal combustion engines), hydraulic/pneumatic devices, etc., gaskets are interposed between junctions or contact surfaces between parts, through which fluid flows, to form a seal between the parts, thus preventing fluid leakage. In the case of a gasket for engines of vehicles, gaskets are provided between contact surfaces of a cylinder block and a cylinder head and between contact surfaces of the cylinder head and a cylinder head cover so as to serve as a sealing means, thus preventing high-pressure combustion gas from leaking from the combustion chamber of the engine. The combustion chamber in the engine forms a mechanical environment in which the pressure inside the cylinder varies according to a predetermined sequence during a four-stroke cycle, which includes an intake stroke, a compression stroke, an explosion stroke and an exhaust stroke. Particularly, in the explosion stroke, the pressure inside the cylinder is sufficient to exceed the coupling force of bolts for fastening the cylinder head and the cylinder block to each other. Thus, force pushing the cylinder head upwards (hereinafter, referred to simply as ' lift-up force' ) is generated, so that fine gaps are formed between the gasket and the cyl inder head or the cyl inder block. For example, in the compression-ignition engine, when lift-up force is applied to the cylinder head, it is lifted upwards from the upper surface of the cylinder blockby a distance ranging from 1OjMn(0.01mm) to 15μm(0.015mm). Thereby, variable gaps are formed between the cylinder head and the cylinder block. At this time, because the internal gas pressure is approximately 200 times atmospheric pressure, internal gas leaks through the gaps. Thus, the combustion efficiency of the engine is deteriorated. Such fine gaps are variably formed depending on the change in the load of the cylinder during the cycle. Therefore, in the engine, to maintain a satisfactory sealed state and to respond to fine gaps occurring in the explosion stroke, a gasket having superior elasticity and durability is required. In the case of gaskets for internal combustion engines according to conventional techniques, as shown in FIGS. 1 and 2, a gasket is interposed between a cylinder head and a cylinder block of an internal combustion engine and is brought into close contact with the lower surface of the cylinder head or a cylinder head cover using rivets. Furthermore, they are assembled together using locking bolts. The conventional gasket includes a metal plate Ia, Ib, which is made by laminating thin plates made of metal such that they can resist high temperatures and high pressures and have satisfactory elasticity and durability. Furthermore, the gasket has therein a bore 2a, 2b, corresponding to each cylinder of the combustion chamber of the engine, lubricant oil supply holes, cooling water supply holes, rivet insert holes and cylinder block assembly holes. FIG. 1 illustrates a conventional gasket having a folding type stopper structure 3. In this case, as shown in an enlarged view taken along the line A-A, a stopper 7, which is formed by folding the inner edge of a subsidiary plate 9 which is around the combustion chamber, is disposed inside and above a bead 5. FIG.2 illustrates a conventional gasket having a welding type stopper structure 4. As shown in an enlarged view taken along the line B-B, a ring-shaped stopper 8 is welded to the upper surface of the gasket inside a bead 6.

In the conventional gaskets having the above-mentioned constructions, the stopper 7, 8 primarily conducts a gas leakage prevention function, and the bead 5, 6 secondarily conducts a gas leakage prevention function using its elasticity. Here, the bead 5, 6 is provided around each hole, such as the bore 2a, 2b, each supply hole, each assembly hole, etc., and has a ring shape and an arc-shaped cross-section to provide elastic force. The bead elastically and si ight Iy moves upwards or downwards when gaps are formed between the cylinder block and the cylinder head by lift-up force, and vary depending on the lift-up force, thus maintaining the sealed state.

Furthermore, the stopper structure 4 supports the bead 5, 6 such that the bead 5, 6 is prevented from being compressed into a completely planar shape, as shown by the dotted line, thus serving to reduce internal stress applied to the junction edge of the bead. However, although the conventional gasket has the stopper structure, when the cylinder block and the cylinder head are coupled to each other using locking bolts after the gasket is interposed therebetween, the cylinder head is slightly bent by bolting force, so that gaps are formed around the bores. Particularly, the dimension of gaps formed adjacent to the bolts differs from the dimension of gaps around parts spaced apart from the bolts by relatively large distances, for example, around parts between bores (at positions at which the edges of the adjacent bores are adjacent to each other). As such, because the gaps between the contact surfaces are uneven, there are problems in that combustion gas may leak from portions between the bores, at which gaps between the contact surfaces are relatively large, or ingredients contained in gas are deposited at the portions, thus deteriorating the sealing ability of the gasket. [Disclosure] [Technical Problem] Accordingly, the present invent ion has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a gasket which is provided with an inner plate having embossments, which may have heights different from each other, so as to compensate for differences in dimensions of gaps in a cylinder head attributable to lift-up force, that is, differences in dimensions of gaps between contact surfaces, thus enhancing the sealing ability of the gasket. [Technical Solution]

In order to accomplish the above object, the present invention provides a gasket with an inner plate having embossments, including: a pair of base plates, each of which has a base plate hole corresponding to a bore, a bead provided around the base plate hole, and a plurality of insert holes; and the inner plate provided between the base plates and having an inner plate hole corresponding to the bore, the gasket being interposed between and coupled to junction surfaces of a cylinder head and a cylinder block by bolting to seal the junction surfaces, wherein the plurality of embossments is provided on the inner plate around the inner plate hole.

Preferably, each embossment may have a conical shape. In addition, each embossment may have a planar peak part to increase the area to which surface pressure is applied. Furthermore, the embossments may be provided around the inner plate hole in one or more rows to increase the area to which surface pressure is applied.

Particularly, in the present invention, of the embossments, embossments disposed adjacent to the bolt insert holes may be lower than remaining embossments. In detail, the embossments have heights such that, when the height of embossments disposed in a portion (X) between the bolt insert holes is denoted by Hl, the height of embossments disposed in a portion (Y) adjacent to the bolt insert holes is denoted by H2, and the height of embossments disposed in a portion (Z) between the bores is denoted by H3, the inequality H2 < Hl < H3 is satisfied. Meanwhile, a coating film may be applied to a valley portion defined in each of the embossments. [Advantageous Effects]

The present invention provides a gasket which is provided between a cylinder head and a cylinder block. In the gasket of the present invention, embossments, which may have heights different from each other, are formed on the inner plate of the gasket to compensate for the difference in dimensions of gaps between contact surfaces which is induced by a difference in the strain rate of a cylinder head when a lift-off phenomenon occurs, thus maintaining the compression displacement of beads, which conduct a sealing function, constant. Therefore, there are advantages in that the beads are prevented from cracking, and gas leakage is prevented. The technical spirit of the gasket with an inner plate having embossments according to the present invent ion has been described with reference only to an i 1 lustrat ive example, which is not intended to limit the present invention. Furthermore, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invent ion.

[Description of Drawings]

FIG. 1 is a plan view and a sectional view illustrating the construction of a conventional metal gasket for cylinder heads!

FIG.2 is a plan view and a sect ional view i 1 lustrating the construction of another conventional metal; and

FIG.3 is an exploded perspective view illustrating the construction of a gasket with an inner plate having embossments, according to the present invention!

FIGS.4 through 6 are perspective views showing several embodiments of the inner plate according to the embossment structure! FIG. 7 is a plan view showing the inner plate of FIG. 6;

FIG. 8 is a side sectional view showing the use of the gasket according to the present invention!

FIG.9 is a perspective view showing another embodiment of the inner plate according to the present invention! FIG. 10 is a plan view showing the inner plates of FIG.9 placed on a base plate;

FIG. 11 is a side sectional view of the inner plate of FIG. 9;

FIG. 12 is a perspective view showing the use of the present invention; and

FIG. 13 is a sectional view showing a coating film applied to the inner plate of

FIG. 9. [Best Mode] Hereinafter, a gasket with an inner plate having embossments according to the present invention will be described in detail with reference to the attached drawings.

FIG.3 is an exploded perspective view illustrating the construction of a gasket with an inner plate having embossments, according to the present invention. FIGS. 4 through 6 are perspective views showing several embodiments of the inner plate according to the embossment structure. FIG. 7 is a plan view showing the inner plate of FIG. 6. FIG. 8 is a side sectional view showing the use of the gasket according to the present invention. FIG.9 is a perspective view showing another embodiment of the inner plate according to the present invention. FIG. 10 is a plan view showing the inner plates of FIG.9 placed on a base plate. FIG. 11 is a side sectional view of the inner plate of FIG.9. FIG.12 is a perspective view showing the use of the present invention. FIG. 13 is a sectional view showing a coating film applied to the inner plate of FIG. 9. As shown in FIG.3, the gasket of the present invention, having a sealing function, is constructed such that the inner plate 10, which has inner plate holes 11 corresponding to respective bores, is interposed between upper and lower base plates 20a and 20b, which have thin plate shapes and respectively have base plate holes 21a and 21b corresponding to the bores. Furthermore, a bead 22, which has a ring shape and is convex upwards or downwards to provide elastic force, is integrally formed in each base plate at a position spaced apart from the inner edge of the corresponding base plate hole 21a, 21b by a predetermined distance. In detail, a first bead 22a, which is convex upwards, is formed in the upper base plate 20a, and a second bead 22b, which is convex downwards, is formed in the lower base plate 20b. As shown in FIG.8, the upper and lower base plates 20a and 20b are oriented such that concave surfaces of the first and second beads face each other on opposite sides of the inner plate 10. Thus, when the present invention is coupled between a cylinder head 31 and a cylinder block 30 by bolting (not shown) , the convex surfaces of the first and second beads respect ively contact the cyl inder head 31 and the cylinder block 30 to form a seal therebetween. Of course, the present invention is not limited to the structure of FIG. 3, in which the first bead 22a, which is convex upwards, is formed in the upper base plate 20a, and the second bead 22b, which is convex downwards, is formed in the lower base plate 20b. Alternatively, the present invention may be constructed such that a first bead, which is convex downwards, is formed in the upper base plate, and a second bead, which is convex upwards, is formed in the lower base plate, so that the first and second base plates are oriented such that the convex surfaces of the first and second beads face each other on opposite sides of the inner plate.

As shown in FIGS. 3 and 10, the inner plate 10 has a circular plate, which has a through hole in the central portion thereof. The circular plate has an integrated structure between bores. The inner plate hole 11, which is the through hole in the circular plate, communicates with the base plate holes 21a and 21b and the bore when the inner plate 10 are assembled with the base plates 20a and 20b.

As shown in FIG.3, preferably, the width a of the inner plate 10 is greater than the width b from the base plate hole 21 of the base plate 20 to the outer edge of the bead 22, but is less than the width c from the base plate hole 21 to the outermost edge of the base plate 20. As such, because the width a of the inner plate 10 is greater than the width b from the base plate hole 21 to the outer edge of the bead 22 but is less than the width c from the base plate hole 21 to the outermost edge of the base plate, the sum of the thicknesses of the base plates and the inner plate in the area surrounding the bore is greater than that in an area outside the bead, as shown in FIG.8. Thanks to this construction, when the cylinder head is coupled to the cylinder block by bolting, part of the cylinder head 31 is bent by a wedge effect, so that repulsive force is generated in a direction opposite the direction of explosion (the direction towards the cylinder head 31 from the bore) in the engine. As a result, lift-up force applied to the cylinder head 31 by explosions in the engine is restricted by the repulsive force. Particularly, a plurality of embossments 12a, 12b, 12c, 12d is provided on the inner plate around the inner plate hole 11 in the circumferential direction. As shown in FIG.3, the embossments 12a, 12b, 12c, 12d are disposed in the portion d surrounding the inner plate hole 11. Preferably, the embossments are formed such that, when the inner plate is assembled with the base plates, peak parts of the embossments 12a, 12b, 12c, 12d contact the surfaces of the base plates between the base plate holes 21 and the inner edges of the beads 22. In the present invention, when the gasket having the above-mentioned construction is interposed between and coupled to the cylinder head 31 and the cylinder block 30 by bolting, the elastic force of the embossments 12a, 12b, 12c, 12d prevents a gap from being formed by lift-up force around the bore of the cylinder head 31, which is slightly bent due to the bolt coupling, thus effectively maintaining the sealed state, and preventing the beads from being excessively compressed into a completely planar state. In the present invention, the embossing can be embodied in various structures. As a first embodiment of the embossment structure, the embossments may comprise conical embossments 12a, which are oriented such that peak parts thereof protrude in the same direction, as shown in FIG. 4. Furthermore, as a second embodiment of the embossment structure according to the structure, FIG.5 illustrates rectangular embossments 12b, which have planar peak parts which are oriented in the same direction. In detail, as shown in FIG.5, each embossment 12b is formed by protruding a part of the inner plate 10 in a hexahedral shape. In the same manner as the first embodiment, in the second embodiment of the present invention, the elastic force of the embossments prevents a gap from being formed by the lift-up force around the bore of the cylinder head 31, which is slightly bent due to the bolt coupling, thus effectively maintaining the sealed state, and preventing the beads from being exces 1sively compressed into a completely planar

I state. As well, the beads are prevented from being excessively compressed and becoming completely planarized. Particularly, because the peak part of each embossment 12b is planar, the contact area between the base plate and the embossments 12b is increased. Thus, the sealing ability can be increased. In addition, because the load applied per unit area can be dispersed, stress concentration is prevented. Thereby, vertical deformation of the cylinder head, which may be induced by stress concentration, is prevented. Here, an area of the planar surface of the peak part of each embossment 12b must be set in consideration of ease of the forming process and in consideration of the fact that the stress dispersing effect is increased as the area is increased. Meanwhi Ie, as a third embodiment according to the embossment structure, the present invention provides a structure such that embossments 12c are alternately oriented in upper and lower directions, as shown in FIG.6. In this case, as shown in FIG. 8, the embossments 12c can contact both the upper base plate 20a and the lower base plate 20b. As such, in the third embodiment, because the embossments 12c contact the opposite base plates, they can prevent a gap from being formed in the cylinder head 31 in opposite directions more effectively, compared to the first or second embodiments, in which the embossments 12a, 12b contact only one of the upper base plate 20a and the lower base plate 20b. In the case of the third embodiment, although each embossment 12c is illustrated as having a conical shape in FIG.6, each embossment 12c may have a shape such that a peak part thereof is planar, in the same manner as that of the second embodiment.

More preferably, in the first through third embodiments, as shown in FIG.7, the embossments 12, 12b, 12c are arranged in one or more rows to further increase the sealing effect of the gasket . In other words , one or more circumferential lines, along which the embossments 12a, 12b, 12c are arranged, are formed, thus further enhancing the sealing effect and the above-mentioned effects of preventing a gap from occurring at the cylinder head and of increasing the surface pressure area between the embossments and the base plates so as to disperse stress. Hereinafter, the operation and effect of the gasket having the inner plate according to the third embodiment will be explained with reference to FIG. 8. The gasket of the present invention has a laminated structure in which the lower base plate 20b, the inner plate 10 and the upper base plate 20a are sequentially laminated one on top of the other such that the peak part of the first bead 22a of the upper base plate 20a and the peak part of the second bead 22b of the lower base plate 20b respectively contact the cylinder head 31 and the cylinder block 30.

The gasket of the present invention having the above-mentioned structure is interposed at a predetermined position between the cylinder head 31 and the cylinder block 30, and is compressed therebetween by a fastening means, such as bolts, thus forming a seal between the cylinder head 31 and the cylinder block 30.

At this time, a change in the dimension of the gap between the cylinder head 31 and the cylinder block occurs due to the bolt coupling. Here, because gaps at portions spaced apart from the portions at which the bolts are tightened are wider than those near the boIt-tightened portions, portions between the bolt tightened portions and between the bores are cambered. Thereby, as shown in FIG. 12, the gap s between the contact surfaces becomes uneven in a shape like a wave. In the gasket of the present invention, the elasticity of the embossments 12a, 12b, 12c of the inner plate 10 compensate for this gap size difference between the bolt tightened portions and the other portions. In particular, in the second embodiment, because the peak part of each embossment 12b is planar, the surface pressure area D of the contact surface between the base plate and the embossments 12b is increased.

Meanwhile, FIGS. 9 through 11 illustrate a fourth embodiment according to the embossment structure of the present invent ion. The explanat ion of the components having the same structure and function as those of the first through third embodiments will be skipped. Furthermore, the same reference numerals will be used to designate the same components as those of the first through third embodiments.

The gasket according to the fourth embodiment of the present invention also includes embossments 12d, which are formed on the inner plate 10. Furthermore, each embossment may have a conical shape or a shape having a planar peak part, and the embossments may be alternately oriented in upper and lower directions. In an example, in FIGS.9 through 12, embossments having conical shapes, like the embossments of the first embodiment, are proposed as the fourth embodiment. The structure and function of the embossments 12dof the fourth embodiment is almost the same as those of the embodiments 12a, 12b and 12c of the first through third embodiments.

However, unlike the first through third embodiments, in the fourth embodiment, the embossments 12d are arranged around the inner plate hole 11 such that the embossments that are disposed adjacent to bolt insert holes 23a and 23b of the base plates are lower in height than the remaining embossments. In detail, as shown in FIGS.9 through 11, the embossments 12d have heights such that , when the height of embossments disposed in a port ion X between the bolt insert holes when the gasket is assembled to the base plates is denoted by Hl, the height of embossments disposed in a portion Y adjacent to the bolt insert holes is denoted by H2, and the height of embossments disposed in a portion Z between the bores is denoted by H3, the inequality H2 < Hl < H3 is satisfied. That is, the height H3 of the embossments disposed in the portion Z between the bores is highest . The height Hl of the embossments disposed in the portion X between the bolt insert holes is highest , next to the height H3. The height H2 of the embossments disposed in the portion Y adjacent to the bolt insert holes is lowest. The reason for this construction is that, when a lift-off phenomenon (in which the cylinder head is slightly lifted upwards) occurs while the engine is operated, the distance that the cylinder head is lifted upwards in the portion Z between the bores is highest, the distance that the cylinder head is lifted upwards in the portion X between the bolt insert holes is next highest , after that of the port ion Z, and the distance that the cylinder head is lifted upwards in the portion Y adjacent, to the bolt insert holes, is lowest because the greatest bolt tightening force is applied to the portion Y. In other words, to compensate for differences in the dimensions of gaps at the cylinder head 31, that is, differences in dimensions of gaps S between the contact surfaces, the fourth embodiment is constructed such that the embossments have different heights depending on the position thereof. Hereinafter, the operation and effect of the gasket having the inner plate according to the fourth embodiment will be explained with reference to FIG. 12. The gasket according to this embodiment also has a laminated structure in which the lower base plate 20b, the inner plate 10 and the upper base plate 20a are sequentially laminated one on top of the other such that the peak part of the first bead 22a of the upper base plate 20a and the peak part of the second bead 22b of the lower base plate 20b respectively contact the cylinder head 31 and the cylinder block 30.

The gasket of the present invention having the above-mentioned structure is interposed at a predetermined position between the cylinder head 31 and the cylinder block 30 and is compressed therebetween by a fastening means, such as bolts, thus forming a seal between the cylinder head 31 and the cylinder block 30.

While the engine is in operation, a change in the dimension of a gap between the cylinder head 31 and the cylinder block is induced by the lift-off phenomenon. Here, because a difference in gaps between the portion Z between the bores and the portion X between the bolt insert holes is induced, parts of the cylinder head are cambered. Thereby, as shown in FIG.12, the gap s between the contact surfaces becomes uneven in a shape like a wave. In the gasket of the present invention, the elasticity of the embossments 12d, which have different heights depending on the position thereof, compensate for this gap size difference around the bores. Meanwhile, as shown in FIG. 13, in the present invention, a coating film 13 may be applied to a valley portion defined in each embossment 12a, 12b, 12c, 12d. That is, after the embossments 12a, 12b, 12c, 12d are formed in the inner plate 10, the coating film 13, which is made of material such as rubber, is applied to the valley portion defined in each embossment 12a, 12b, 12c, 12d. The coating films 13 are realized by screen coating such that only required portions, that is, only the valley portions defined in the embossments 12a, 12b, 12c, 12d, are coated with the fi lms.

In detail, when the surface pressure between the gasket of the present invention and an object (cylinder head, cylinder block) is measured using a pressure sensing paper, in the case where no coating film is applied to the valley portions in the embossments, surface pressure is applied to ridge portions formed by the embossments but is not applied to the valley portions defined in the embossments. Therefore, the surface pressure becomes imbalanced. Such imbalance in the surface pressure deteriorates the effect of sealing contact surfaces between the gasket, the cylinder head 31 and the cylinder block 30. Therefore, preferably, the coat ing films 13 are applied to the valley portions defined in the embossments, so that surface pressure is applied to the valley portions of the embossments as well as to the ridge portions thereof, thus compensating for the surface pressure. Meanwhile, in FIG.13, although the case of the third embodiment has been explained as an example, the coating film 13 can also be used in the first, second and fourth embodiments, of course.

Claims

[CLAIMS]

[Claim 1]

A gasket with an inner plate having embossments, comprising: a pair of base plates (20a) and (20b), each of which has a base plate hole (21a), (21b) corresponding to a bore, a bead (22a), (22b) provided around the base plate hole, and a plurality of insert holes (23a), (23b); and the inner plate (10) provided between the base plates (20a) and (20b) and having an inner plate hole (11) corresponding to the bore, the gasket being interposed between and coupled to junction surfaces of a cylinder head (31) and a cylinder block (30) by bolting to seal the junction surfaces, wherein the plurality of embossments (12a), (12b), (12c) and(12d) is provided on the inner plate (10) around the inner plate hole (11).

[Claim 2]

The gasket with the inner plate having the embossments according to claim 1, wherein each of the plurality of embossments has a conical shape.

[Claim 3]

The gasket with the inner plate having the embossments according to claim 1, wherein each of the plurality of embossments has a planar peak part.

[Claim 4] The gasket with the inner plate having the embossments according to claim 1, wherein the embossments are provided around the inner plate hole in one or more rows.

[Claim 5]

The gasket with the inner plate having the embossments according to claim 1, wherein, of the embossments, embossments disposed adjacent to the bolt insert holes are lower than remaining embossments.

[Claim 6]

The gasket with the inner plate having the embossments according to claim 5, wherein the embossments have heights such that, when a height of embossments disposed in a portion (X) between the bolt insert holes is denoted by (Hl), a height of embossments disposed in a portion (Y) adjacent to the bolt insert holes is denoted by (H2), and a height of embossments disposed in a portion (Z) between the bores is denoted by (H3), an inequality H2 < Hl < H3 is satisfied. [Claim 7]

The gasket with the inner plate having the embossments according to any one of claims 1 through 6, wherein a coating fi Im is appl ied to a val ley portion defined in each of the embossments.