Specification
SPECIFICATION
Metal Gasket
Technical Field [0001]
The present invention relates to a metal gasket for sealing the joint surface between two structures when connecting the structures, specifically, to a metal gasket for sealing the joint surface between the cylinder head and cylinder block of an internal combustion engine. [0002]
Metal gaskets have been used in various technical fields. One example of those is a metal gasket for a cylinder head, which seals the joint surface between the cylinder head and cylinder block of an internal combustion engine. Such metal gaskets for a cylinder head include one configured to have a grommet part which has a folded over shape of a metal plate and surrounds a combustion chamber hole.
In recent years, the combustion gas pressure in the combustion chamber hole to be sealed tends to be raised in order to increase the output power and the efficiency of internal combustion engines. To secure the sealing, therefore, it is necessary to raise the tightening contact pressure of the joint surface between the cylinder head and the cylinder block. In this case, however, an excessive tightening contact pressure is likely to be applied locally, which may deform the cylinder head and the cylinder block, or damage the metal gasket. Therefore, it becomes more important to adjust the tightening contact pressure distribution at the joint surface between the cylinder head and the cylinder block in order to provide the tightening contact pressure which exert sufficient gas seal performance and avoid local application of an excessive tightening contact pressure. [0003]
To cope with the above, e.g., to cope with a case where a predetermined .tightening contact pressure distribution changes finely, there has been a proposal of a coated layer with an adequate thickness to the metallic thin plate portion adjoining to the grommet part thereby setting the difference in tightening contact pressure between the grommet part and the adjoining part so as to match with the contact pressure difference in the required tightening contact pressure distribution (refer to, for example, Patent document 1). Patent Document 1: Japanese Patent Application Laid-Open No. HI 1-315931
[0004]
While the gasket described in the Patent Document 1 can adjust the tightening contact pressure distribution in the radial direction of the combustion chamber hole to be sealed, it cannot adjust the distribution in the circumferential direction of the combustion chamber hole. In consideration of the case where the metal gasket is actually inserted between the cylinder head and the cylinder block to tighten them, however, the tightening contact pressure to be applied to the grommet part and a region adjoining thereto has different distributions depending on the circumferential positions of the combustion chamber hole due to the position of the fastening bolt, the stiffness of the cylinder head and the cylinder block, or the like. Therefore, the gasket described in the Patent Document 1 cannot provide an adequate tightening contact pressure distribution over the entire perimeter of the combustion chamber hole, therefore, it is difficult to realize a suitable seal. [0005]
To cope with that, it is possible to consider changing the thickness of the grommet part in the circumferential direction to obtain a predetermined tightening contact pressure distribution.
However, since a change in thickness is very fine, extremely elaborate thickness adjustment is required at the initial stage of thickness adjustment, and it is likely to - cause a change in tightening contact pressure distribution and a variation of products performance due to an environmental change, a delicate deformation, or the like. It is therefore inevitable to make designs inferior in flexibility and robustness. [0006]
In a case where the fastening bolt is fastened to locally tighten the cylinder head in the process of assembling the cylinder head, it is difficult to maintain the parallelism of the joint surface between the cylinder head and the cylinder block, therefore it is very difficult to obtain an adequate tightening contact pressure distribution at the initial stage of assembly. Even if an adequate tightening contact pressure distribution is obtained at the initial stage, it is difficult to hold the optimal tightening contact pressure distribution due to a time-dependent in the dimension (thicknesswise dimension) change of the load applying direction, which is caused by the creep property of the gasket. Therefore, it is difficult to obtain the optimal tightening contact pressure distribution at the initial stage of assembly, and to stably maintain the optimal tightening contact pressure distribution for a long period of time.
Disclosure of the Invention
[0007]
Accordingly, it is an object of the present invention to provide a metal gasket which can easily obtain an optimal tightening contact pressure distribution at the initial stage of assembly and can stably maintain the optimal tightening contact pressure distribution even for a long time of usage. [0008]
One aspect of a metal gasket according to the invention is a metal gasket comprising a body with approximately flat plate shape in which an opening is provided, and a grommet part having a folded over portion formed by folding back a thin plate, said f folded over portion surrounding the opening, wherein a flange portion is formed at the grommet part, said flange portion is a portion where the thin plate extended from the folded over portion overlaps the body, and a width of the flange portion is not uniform in the same grommet part. Brief Description of the Drawings [0009]
Fig. 1 is a drawing showing one embodiment of a metal gasket according to the invention, specifically showing a plan view in Fig. 1 (a), showing partial cross-sectional views thereof in Fig. 1 (b) and (c), and showing a partial cross-sectional view when the body is a three-layer structure in Fig. 1 (d).
Fig. 2 is a drawing showing another embodiment of the metal gasket according to the invention, specifically showing a plan view in Fig.2 (a), showing partial cross-sectional views thereof in Fig. 2 (b) to (d) ,and showing a partial cross-sectional view when the body is a three-layer structure in Fig.2 (e).
Fig. 3 is a drawing showing a further embodiment of the metal gasket according to the invention, specifically showing a plan view in Fig.3 (a), showing partial cross-sectional views thereof in Fig. 3 (b) to (c) ,and showing a partial cross-sectional view when the body is a three-layer structure in Fig 3 (d)
Fig. 4 is a drawing showing a further embodiment of the metal gasket according to the invention, specifically showing a plan view in Fig.4 (a), showing partial cross-sectional views thereof in Fig. 4 (b) to (c) ,and showing a partial cross-sectional view when the body is a three-layer structure in Fig.4 (d)
Fig. 5 is a cross-sectional view showing a further embodiment of a grommet part according to the invention.
Fig. 6 is a cross-sectional view showing a further embodiment of the metal gasket according to the invention
Detailed Description of the Invention
[0010]
General Description
One embodiment of a metal gasket according to the present invention is a metal gasket comprising a body with approximately flat plate shape in which an opening is provided, and a grommet part having a folded over portion formed by folding back a thin plate, said f folded over portion surrounding the opening, wherein a flange portion -is formed at the grommet part, said flange portion is a portion where the thin plate extended from the folded over portion overlaps the body, and a width of the flange portion is not uniform in the same grommet part. [0011]
Although the metal gasket according to the invention is applicable to sealing of the joint surface of any structure, it is particularly suitable for sealing of the joint surface of a cylinder head and a cylinder block of an internal combustion engine which are exposed to a high temperature and high pressure in case of fastening the cylinder head and the cylinder block. It is more effective to use the metal gasket according to the invention in a diesel engine with a high pressure ratio among internal combustion engines because the combustion gas pressure in the diesel engine becomes higher. [0012]
There can be a case where a body with approximately flat plate shape has a
concavo-convex portion or a bent portion, and a case where it comprises one member or
a plurality of members. In a case where the body comprises a plurality of members,
there may, for example, be a laminated structure which comprises different materials, or
a structure having a coating layer provided outside a core member. ~
As the material for the body excluding the coating layer, all metallic materials including stainless steel, carbon steel, aluminum, copper, and a heat-resistant alloy can be used, and an optimal material can be used according to the working pressure and operating temperature.
As the coating layer, an arbitrary organic material including rubber or fluorocarbon resin, or an inorganic material can also be coated, and metal powders of molybdenum dioxide, aluminum, stainless steel or the like can also be coated. The coating layer may be coated directly on the metal of the core member, or can also be coated an outer thin plate arranged outside the core member. In case of providing the coating layer, its elasticity can allow the sealing performance to be maintained even if slight deformation occurs. An opening provided in the body can have an arbitrary sectional shape including a circular shape or a rectangular shape.
[0013]
The grommet part can be formed integral with the body, or can be formed by members) different from the body as will be described later. In the case where the grommet part is formed integral with the body, for example, the grommet part can be formed by forming a folded over portion using the outer thin plate arranged outside the core member. The interior of this folded over portion can be hollow, or can have a core member as will be described later. The flange portion of the grommet part can be provided on both sides of the body, or can be provided only on one side thereof.
As the material for the grommet part, it is possible to use all metallic materials including stainless steel, carbon steel, aluminum, copper, and a heat-resistant alloy, and an optimal material can be used according to the working pressure and operating temperature as well as the in case of the body. A coating layer using an arbitrary material can be provided as well as in the case of the body. [0014]
The width of the flange portion which overlaps the body shows the "overlap width" at which the thin plate extended from the folded over portion of the grommet part overlaps the body. When the tightening load is applied to the gasket, it is thought that the load is mainly received at a part of the folded over portion and the flange portion of the grommet part. Therefore, in the case that the same tightening contact pressure is received, when the width of the flange portion is wide, i.e., the overlap width is large, the tightening contact pressure in this region becomes smaller, whereas when the width of the flange portion is narrow, i.e., the overlap width is small, the tightening contact pressure in the region becomes larger.
The width of the flange portion can be changed locally, or can be changed continuously. When the flange portion is provided on both sides of the body, the widthwise dimension of the flange portion can be changed in the same mode on both sides, or the widthwise dimension of the flange portion can be changed in different modes on the respect sides. In this case, a mode in which the widthwise dimension of the flange portion on one side is changed while the widthwise dimension of the flange portion on the other side is not changed is also included. [0015]
In the embodiment, even in a case where an excessive tightening load or a tightening load which is too low to keep the sealing performance is applied to the peripheral region of one opening depending on the position, an adequate tightening contact pressure in the peripheral region of the opening can be obtained by adjusting the width of the flange portion of the grommet part.
Since there are few time-dependent changes in tightening contact pressure distribution which are caused by the creep property or the like, the gasket can be used stably for a long period of time. Further, the flange portion of the grommet part can provide a surface-contact seal, so that the effective seal area can be increased, thus making it possible to obtain a gasket structure which suites various seal conditions. For example, even if the joint surfaces of structures to be connected are not in parallel, it is easier to form an effective sealing surface widely. [0016]
Further, another embodiment of the metal gasket according to the invention is a metal gasket wherein in a case of inserting the metal gasket between two structures, and connecting the two structures by a fastening member to seal a joint surface of the two structures, the width of the flange portion is determined so as to form a predetermined tightening contact pressure distribution in a peripheral region of the opening, based on a position of the fastening member and stiffness of the structures. [0017]
In the case of inserting the metal gasket between two structures, and connecting the two structures by a fastening member to seal the joint surface, the tightening load in the peripheral region of the opening takes different values depending on the positions according to the position of the fastening member or the influence of the stiffness of the structures. For example, such influence can be analyzed according to the structural mechanics and the width of the flange portion can be determined so as to obtain the optimal tightening contact pressure distribution in the peripheral region of the opening In this case, computer analysis using the finite element method or the like is also effective means. [0018]
Furthermore, a further embodiment of the metal gasket according to the invention is a metal gasket, wherein a core member is provided inside the folded over portion of the grommet part. [0019]
Here, as the core member, a core member which has a circular sectional shape, for example, can be used, a core member which has a rectangular sectional shape can also be used, and a core member which has any other arbitrary sectional shape can be used as well. As the material for the core member, all metallic materials including stainless steel, carbon steel, aluminum, copper, and a heat-resistant alloy, can be used. [0020]
In the embodiment, since the core member is provided inside the folded over
portion, the tightening load can be received at folded over portion of the grommet more surely. When the core member has a large elasticity, sealing performance can be maintained even if relatively large deformation occurs. [0021]
Furthermore, a further embodiment of the metal gasket according to the invention is a metal gasket, wherein the grommet part is formed by a member different from the body. [0022]
In the embodiment, since the grommet part is formed by a member different from the body, flexibility of the material and the shape can be increased, and the combination of the grommet part and the body can provide the optimal tightening contact pressure distribution under broad conditions. In the case that the grommet part is formed by a member different from the body, since the flange portion can be provided on both sides of the body in principle, a greater variety of fine adjustments of the tightening contact pressure can be realized by adjusting the width of the flange portion. [0023]
Moreover, a further embodiment of the metal gasket according to the invention is a metal gasket, wherein a thickness of the grommet part is not uniform in the same grommet part, and a predetermined tightening contact pressure distribution in a peripheral region of the opening is formed by a combination of a widthwise dimension of the flange portion, and a thicknesswise dimension of the grommet part. [0024]
According to the embodiment, the combination of the widthwise dimension of the flange portion and the thicknesswise dimension of the grommet part, i.e., the tightening contact pressure at the folded over portion of the grommet part and the tightening contact pressure at the flange portion can be adjusted finely by changing not only the widthwise dimension of the flange portion but also the thicknesswise dimension of the grommet part, so that the optimal tightening contact pressure .distribution in the peripheral region of the opening can be obtained more effectively. [0025]
Furthermore, a further embodiment of the metal gasket according to the invention is a metal gasket, wherein in case of sealing a joint surface between a cylinder head and cylinder block of an internal combustion engine having a plurality of cylinders, a shape of the flange portion of the metal gasket to be mounted differs cylinder by cylinder.
[0026]
According to the embodiment, in case of using the metal gasket to seal the joint surface between the cylinder head and cylinder block, there may be a case where the tightening load and the tightening contact pressure differ cylinder by cylinder, so that the use of metal gaskets whose grommet parts have flange portions with different shapes for the individual cylinders can provide the optimal tightening pressure power distribution in the whole cylinder head and cylinder block. [0027] Effect of the Invention
As described above, with the gasket according to the invention, the adequate tightening contact pressure in the peripheral region of the opening can be easily obtained at the initial stage of assembly by adjusting the width of the flange portion of the grommet part, and there are few time-dependent changes in tightening contact pressure distribution which are caused by the creep property or the like, thus making it possible to stably use the gasket for a long period of time.
Further, the flange portion of the grommet part can provide a surface-contact seal, so that the effective seal area can be increased, thus making it possible to obtain a gasket structure which suites various seal conditions. [0028] Description of the Illustrated Embodiment
The embodiment of the metal gasket according to the invention is described below in detail using the drawings. Here, (a) of each of Figs. 1 to 4 shows a plan view showing a part.of a metal gasket 2 provided with a plurality of openings 6, and (b) and (c) show the partial cross-sectional views as seen from the direction of the arrow shown in (a). Figs. 1 and 2 show the shape of a grommet 8 which is attached to the opening 6 arranged at an end among the plurality of openings 6 provided at the metal gasket 2, and Figs. 3 and 4 show the shape of the grommet 8 which is attached to the opening 6 arranged at a mid-position (position which is not an end) among the plurality of openings 6 provided at the metal gasket 2. The following describes the top side of the sheet as the top side, the bottom side of the sheet as the bottom side, the right-hand side of the sheet as the right-hand side, and the left-hand side of the sheet as the left.
The metal gasket 2 according to the invention can be used to seal the joint surface of every structure, and.can exert high seal performance in sealing particularly under the environment where it is exposed to a high temperature and high pressure. For example, the gasket is applicable to the sealing of the joint surface between the cylinder head and cylinder blocks of an internal combustion engine, and is exposed to a
higher pressure especially in a case of a diesel engine with a high compression ratio, so
that it is especially effective to use the metal gasket according to the invention.
[0029]
(Description of Embodiment Shown in Fig. 1)
To begin with, one embodiment of the metal gasket according to the invention is described using Fig. 1.
First, the general structure of the metal gasket 2 having a plurality of openings 6 provided therein is described using Fig. 1(a). The metal gasket 2 has a body 4 with approximately flat plate shape and a grommet part 8. The body 4 has a plurality of openings 6, and the grommet part 8 is attached to each opening 6. This structure is the same in embodiments shown in Figs. 1 to 4 Though the shape of the grommet part 8, especially the shape of the flange portion 8b of the grommet part 8 differs in the individual drawings, the other shapes are the same in principle. The sectional shape of the opening 6 provided in the body 4 can have an arbitrary shape including^ circular shape or a rectangular shape. [0030]
According to the embodiment, the body 4 and the grommet part 8 are formed by
different members, and the grommet part 8 is inserted into the body 4 in the opening 6,
thus forming a single metal gasket 2. However, such construction is not restrictive,
and the body 4 and the grommet part 8 can be formed integrally as in the embodiment
shown in Fig. 6, as will be described later.
[0031]
The body 4 with approximately flat plate shape need not have a completely flat plate-like shape, and includes one with some concavo-convex portions or bent portions. For example, a spring-like sealing mechanism can be formed by providing concavo-convex portions in such a way as to surround the opening 6.
The body 4 may be formed by one member, or may be formed by a plurality of members. In a case where the body 4 is formed by a plurality of members, there may be a laminated structure which comprises different materials, for example, or a structure having a coating layer provided outside a core member.
As the material for the body 4 excluding the coating layer, all metallic materials including stainless steel, carbon steel, aluminum, copper, and a heat-resistant alloy can be used, and an optimal material can be used according to the working pressure and operating temperature.
[0032]
As the coating layer, an arbitrary organic material including rubber or fluorocarbon resin, or an inorganic material can also be coated, and metal powders of molybdenum dioxide, aluminum, stainless steel or the like can also be coated. The coating layer may be coated directly on the metal of the core member, or can also be coated an outer thin plate arranged outside the core member. In case of providing the coating layer, its elasticity can allow the sealing performance to be maintained even if slight deformation occurs. [0033]
The dimensions of the body 4 can take arbitrary values according to the use; in case of usage in sealing the joint surface between the cylinder head and cylinder block, for example, the planar dimensions are determined according to the dimensions of the cylinder head and cylinder block, and the dimension of the opening 6 is determined according to the dimension of the combustion chamber hole of the internal combustion engine. As the thicknesswise dimension of the body 4, 0.3 mm to 1.5 mm can be illustrated, however which is not restrictive. [0034]
Bolt holes 10 are formed at four locations around each opening 6. This metal gasket 2 is inserted between structures (not shown) to be joined, and fastening bolts (not shown) are inserted into the bolt holes of the structures and the bolt holes 10 of the metal gasket 2 to fasten the two structures. Therefore, the tightening force of the fastening bolts causes the metal gasket 2 to receive a tightening load. [0035]
Next, the structure of the grommet part 8 to be attached to the opening 6 of the body 4 is described in detail using the partial cross-sectional views shown in Fig. 1(b) and Fig. 1(c). Fig. 1(b) is the partial cross-sectional view as seen from the arrow A in Fig. 1(a), and Fig. 1(c) is the partial cross-sectional view as seen from the arrow B in Fig 1(a).
Both of the cross-sectional views show similar basic structures, and the grommet part 8 has a folded over portion 8a formed by folding a thin plate back, and a flange portion 8b at which the thin plate extended from the folded over portion 8a overlaps the body 4. In Fig. 1(b) and Fig. 1(c), a region where the thin plate extended from the folded over portion 8a overlaps the surface of the body 4 is shown as the flange portion 8b, and a region on the left-hand side thereof is shown as the folded over portion 8a.
The manner in which the grommet part 8 is attached to the body 4 will be described such that; as the body 4 with approximately flat plate shape is inserted into the internal space of the folded over portion 8a which is produced by folding back the thin plate, thus making both members fixed. The opening 6 is surrounded by the folded over portion 8a of the grommet part 8.
Although the widthwise dimension of the flange portion 8b differs in Fig. 1(b) and Fig 1(c), the basic structure is the same. The difference in the widthwise dimension of the flange portion 8b will be described later. [0036]
As the material for the grommet part 8, it is possible to use all metallic materials including stainless steel, carbon steel, aluminum, copper, and a heat-resistant alloy, and an optimal material can be used according to the working pressure and operating temperature as well as in the case of the body 4. A coating layer using an arbitrary material can be provided as well as in the case of the body.
As the thicknesswise dimension of the thin plate forming the grommet part, 0.1 mm to 0.4 mm can be illustrated, however which is not restrictive. [0037]
As shown in Fig. 1(a), according to the embodiment, the width of the flange portion 8b of the grommet part 8 has a narrow region as shown by the arrow A, and a large region as shown by the arrow B. The width of the flange portion 8b shows the "overlap width" at which the thin plate extended from the folded over portion 8a of the grommet part 8 overlaps the body 4. As shown in Fig. 1(b) and Fig. 1(c), the grommet part 8 protrudes from the surface of the body 4 by the thickness of the thin piaffe forming the grommet part 8, so that when the tightening load is applied to the metal gasket 2 by using the fastening bolts, the load is mainly received by the grommet part 8, more specifically, by a part of the folded over portion 8a and the flange portion 8b.
Therefore, in case that the same tightening contact pressure is received,- when the width of the flange portion 8b is wide, i.e., the overlap width is large, the tightening contact pressure in this region becomes smaller, whereas when the width of the flange portion 8b is narrow, i.e., the overlap width is small, the tightening contact pressure in the region becomes larger. [0038]
As shown in Fig. 1(a), in the embodiment, the shape of the grommet part 8 which is attached to the opening 6 at an end among a plurality of openings 6 provided in
the body 4 is shown. In this case, the fastening bolts (only the bolt holes 10 are shown in Fig. 1(a)) arranged at the right and left of the opening 6 shown in the center in Fig. 1(a) are described. As for the upper and lower fastening bolts on the left-hand side of the opening 6, the opening 6 exists only on one side, whereas, as for the upper and lower fastening bolts on the right-hand side of the opening 6, the openings 6 exist on both sides. That is, the fastening bolts arranged on the left-hand side will apply a load to one opening 6, while the fastening bolts arranged on the right-hand side will apply a load to two openings 6. Therefore,.the tightening load applied by the fastening bolts arranged on the left-hand side become twice the load applied by the fastening bolts arranged on the right-hand side in principle.
If the entire widthwise dimension of the flange portion 8b of one grommet part 8 is made uniform, the tightening contact pressure which is received by the region on the left-hand side of the grommet part 8 (the flange portion 8b and a part of the folded over portion 8a) becomes a very large value as compared with the tightening contact pressure which is received by the region on the right-hand side of the grommet part 8 (the flange portion 8b and a part of the folded over portion 8a). The tightening contact pressure applied to each position of the grommet part 8 is influenced not only by the position of the fastening bolt but also by the shape and stiffness of the structure. When a comparatively large tightening load is applied as a whole to exert sufficient sealing performance, especially, an excessive tightening load is likely to be applied particularly in a region near the fastening bolt. [0039]
To cope with that, in the embodiment, a region of the flange portion 8b of the grommet part 8 which has a large width is provided at a region close to the geometrical locations of the left fastening bolts. This prevents an excessive tightening contact pressure from occurring, thus making it possible to form the optimal tightening contact pressure distribution in the peripheral region of the opening 6. In this case, for example, the profile of the flange portion 8b which can form the optimal tightening contact pressure distribution can be defined by the computer structure analysis using the finite element method or the like.
As shown in Fig. 1(c) which is the partial cross-sectional view as seen from the arrow B in Fig. 1(a), in the embodiment, the flange portion 8b of the grommet 8 is formed on both sides of the body 4, and the flange portion 8b has the same widthwise dimension on both sides of the body 4. That is, the width of the flange portion 8b is widened in the same manner. However, such is not restrictive, and, as shown in Fig. 2(c), the widthwise dimensions of the flange portion 8b may be made different on the
upper and lower sides of the body 4, or, as shown in Fig 6, the flange portion 8b can be provided only on one side of the body 4.
The sectional shape of the region where the width of the flange portion 8b of the grommet part 8 is not made large is shown in Fig. 1(b) which is the partial cross-sectional view as seen from the arrow A in Fig. 1(a). [0040]
As described above, Fig. 1 shows one embodiment of the grommet part 8 attached to the opening 6 arranged at an end among a plurality of openings 6 provided in the metal gasket 2, and even if a large tightening load is applied by the fastening bolts arranged at the end portion of the metal gasket 2, the adequate tightening contact pressure in the peripheral region of the opening 6 can be obtained by making the width of the flange portion 8b of the grommet part 8 larger according to the load.
Since there are few time-dependent changes in tightening contact pressure distribution which are caused by the creep property or the like, the metal gasket can be used stably for a long period of time. Further, the flange portion 8b of the grommet part 8 can provide a surface-contact seal, so that the effective seal area can be increased, thus making it possible to obtain a gasket structure which suites various seal conditions. For example, even if the joint surfaces of structures to be fastened are not in parallel, it is easier to form a wide effective sealing surface. [0041]
As described above, by adjusting the thickness of the grommet part 8 in addition to adjusting the widthwise dimension of the flange portion 8b of the grommet part 8, the combination of both can adjust the tightening contact pressure distribution more effectively. In this case, it is comparatively easy to change the thicknesswise dimension of the grommet part 8 which is formed by folding back the thin plate, thereby allowing the tightening contact pressure to be adjusted effectively.
While the inside of the folded over portion 8a is hollow in the embodiment as shown in Figs 1(b) and 1(c), a core member 12 can be provided inside the folded over portion 8a as shown in Fig. 5(a) and Fig. 5(b). In this case, the thicknesswise dimension of the grommet part 8 can be changed by modifying the core member 12. [0042]
Although the body 4 is formed by one member in Figs. 1(b) and 1(c), which is not restrictive, the body 4 structured to have a lamination of a plurality of members can be used as well as shown in Fig. 1(d). Like Fig. 1(c), Fig. 4(d) is a cross-sectional view as seen from the arrow B in Fig. 1(a), and shows an outer layer member 4b and an outer layer member 4c laminated on both sides of a core member 4a. However, the
body 4 is not limited to a three-layer structure, but can comprise an arbitrary number of
layers.
[0043]
Further, in case of using the metal gasket to seal the joint surface between the cylinder head and cylinder block, there may be a case where the tightening load and the tightening contact pressure differ cylinder by cylinder, so that the metal gaskets 2 whose grommet parts 8 have flange portions 8 b with different shapes for the individual cylinders can be used. In case of a.4-cylinder internal combustion engine, for example, there may be a case where the shapes of the flange portions 8b of the grommet parts 8 of the metal gasket 4 to be attached to cylinders #1 to #4 differ from one another. [0044] (Description of Grommet Part 8 and Other Embodiments)
Next, other embodiments of the grommet part 8 of the metal gasket 2 according to the invention are described using Figs. 2 to 4.
First, another embodiment of the grommet part 8 attached to the opening 6 arranged at an end among a plurality of openings 6 provided in the metal gasket 2 is described using Fig. 2. Although the embodiment and the embodiment shown in Fig. 1 differ in the shape of the flange portion 8b of the grommet part 8, other points are identical. Therefore, the different points are focused in the following description [0045]
As shown in Fig. 2(a), the width of the flange portion 8b in the region on the left-hand side of the grommet 6 becomes larger in the embodiment as well as the embodiment shown in Fig 1, but the width of the flange portion 8b in the entire left-hand region is large in the embodiment, whereas the width is partly large in Fig. 1. As shown in Fig. 2(c) which is the partial cross-sectional view as seen from the arrow B in Fig. 2(a), on the other hand, the flange portion 8b on the top side is wide, whereas a . flange portion 8b' on the bottom side is not wide.
In the case of joining the cylinder head and cylinder block of an internal combustion engine, for example, the structure of the embodiment can secure sealing performance by lowering the tightening contact pressure of the cylinder head side (above) which has a comparatively low strength and increasing the tightening contact pressure of the cylinder block (below) which has a comparatively high strength. [0046]
Although the width of the flange portion 8b on the right-hand side in the drawing is not large in the embodiment shown in Fig. 1, there is a region where the
width of the flange portion 8b is large at positions near the positions where the fastening bolts are arranged as shown in Fig. 2(a) in the embodiment. As shown in Fig. 2(d) which is the partial cross-sectional view as seen from the arrow C in Fig. 2(a), the width is made larger on the top side as well as the bottom side in this region. Fig 2(b) is the partial cross-sectional view as seen from the arrow A in Fig. 2(a), and shows the sectional shape of the region where the width of the flange portion 8b is not large.
As described above, the embodiment can provide the optimal tightening contact pressure in the peripheral region of the opening 6 as well as the above-described embodiment. [0047]
Although the body 4 is formed by one member in Figs. 2(b) to 2(d), which is not restrictive, the body 4 structured to have a lamination of a plurality of members can also be used as shown in Fig. 2(e). Like Fig. 2(d), Fig. 2(e) is a cross-sectional view as seen from the arrow C in Fig. 2(a), and shows the outer layer member 4b and the outer layer member 4c laminated on both sides of the core member 4a. However, the body 4 is not limited to a three-layer structure, but can comprise an arbitrary number of layers. [0048]
Next, one embodiment of the grommet part 8 attached to the opening 6 arranged at a mid-position (position which is not an end) among a plurality of openings 6 provided in the metal gasket 2 is described using Fig. 3. Although the embodiment and the embodiment shown in Fig 1 differ in the shape of the flange portion 8b of the grommet part 8, other points are identical. Therefore, the different points are focused in the following description. [0049]
According to the embodiment, the wide-width region of the flange portion 8b of the grommet part 8 is provided locally at four locations near the locations of the fastening bolts. This prevents an excessive tightening contact pressure from being produced in the region which is strongly influenced by the tightening force of the fastening bolts, thereby making it possible to acquire an adequate tightening pressure distribution.
Here, Fig. 3(b) which is a partial cross-sectional view as seen from the arrow A in Fig. 3(a) shows the sectional shape of the region where the widthwise dimension of the flange portion 8b of the grommet part 8 is not made large. Fig. 3(c) which is a partial cross-sectional view as seen from the arrow B in Fig 3(a) shows the sectional shape of the region where the widthwise dimension of the flange portion 8b of the
grommet part 8 is made large. [0050]
Although the body 4 is formed by one member in Figs. 3(b) and 3(c), which is not restrictive, the body 4 structured to have a lamination of a plurality of members can also be used as shown in Fig. 3(d). Like Fig. 3(c), Fig. 3(d) is a cross-sectional view as seen from the arrow B in Fig. 3(a), and shows the outer layer member 4b and the outer layer member 4c laminated on both sides of the core member 4a. However, the body 4 is not limited to a three-layer structure, but can comprise an arbitrary number of layers. [0051]
Next, another embodiment of the grommet part 8 attached to the opening 6 arranged at a mid-position (position which is not an end) among a plurality of openings 6 provided in the metal gasket 2 is described using Fig. 4. Although the embodiment and the embodiment shown in Fig. 3 differ in the shape of the flange portion 8b of the grommet part 8, other points are identical. Therefore, the different points are focused in the following description. [0052]
According to the embodiment shown in Fig 3, the region where the width of the flange portion 8b of the grommet part 8 is large is provided locally. That is, the widthwise dimension of the flange portion 8b of the grommet part 8 changes discontinuously. However, in the embodiment, as shown in Fig.4(a), the widthwise dimension of the flange portion 8b of the grommet part 8 changes continuously and the flange portion 8b of the grommet part 8 has a continuous smooth outer shape. \ Such a continuous change in the widthwise dimension of the flange portion 8b of the grommet part 8 can allow an adequate tightening pressure distribution to be formed more finely. In this case, for example, the profile of the flange portion 8b which can form the optimal tightening contact pressure distribution can also be defined by the computer structure analysis using the finite element method or the like.
Here, Fig. 4(b) which is a partial cross-sectional view as seen from the arrow A in Fig. 4(a) shows the sectional shape at the point where the widthwise dimension of the flange portion 8b of the grommet part 8 is made narrowest. Fig. 4(c) which is a partial cross-sectional view as seen from the arrow B in Fig. 4(a) shows the sectional shape at the point where the widthwise dimension of the flange portion 8b of the grommet part 8 is made widest [0053]
Although the body 4 is formed by one member in Figs 4(b) and 4(c), which is not restrictive, the body 4 structured to have a lamination of a plurality of members can also be used as shown in Fig. 4(d). Like Fig. 4(c), Fig. 4(d) is a cross-sectional view as seen from the arrow B in Fig. 4(a), and shows the outer layer member 4b and the outer layer member 4c laminated on both sides of the core member 4a. However, the body 4 is not limited to a three-layer structure, but can comprise an arbitrary number of layers. [0054]
(Description of Other Embodiments of Metal Gasket According to the Invention)
Fig. 5 is a partial cross-sectional view showing a surrounding structure of the grommet part 8, and shows the embodiment in which the core member 12 is provided inside the folded over portion 8a of the grommet part 8. Fig 5(a) shows the grommet part 8 provided with the core member 12 which has a circular sectional shape, and Fig. 5(b) shows the grommet part 8 provided with the core member 12 which has a rectangular sectional shape. Accordingly, the core member 12 with the optimal sectional shape can be selected according to the use or the operating conditions. In the grommet part 8 of the embodiment, the strength of the core member 12 can allow a greater load to be received.
As described above, the thickness of the grommet 8 can be changed by changing the core member 12, and the optimal tightening contact pressure distribution can be formed by combining a change in the widthwise dimension of the flange portion 8b of the grommet part 8, and a change in the thicknesswise dimension of the grommet part 8. [0055]
Fig. 6 is a cross-sectional view showing the structure of the metal gasket 2 including the body 4 and the grommet part 8; the grommet part 8 is formed integral with the body 4 in the embodiment.
To begin with, the embodiment shown in Fig. 6(a) is described. The body 4- has a three-layer structure which has the outer layer member 4b and the outer layer member 4c laminated on both sides of the core member 4a. Further, the lower outer layer member 4b extends beyond the core member 4a, and is folded over (folded back) to form the folded over portion 8a, and the outer layer member 4b overlaps the outer layer member 4c of the body 4 to form the flange portion 8b. While the embodiment has the flange portion 8b on the top side as in the foregoing embodiments, it does not have the flange portion 8b on the bottom side. It is to be noted however that the
widthwise dimension of the upper flange portion 8b can be changed in arbitrary modes
as well as the embodiments shown in Figs. 1 to 4.
[0057]
The embodiments of the metal gasket according to the invention are not limited to the foregoing embodiments, and other various embodiments are included in the invention. [0056]
[Description of Reference Numerals] 2 Metal gasket 4 Body
4a Core member 4b Outer layer member 4c Outer layer member 6 Opening 8 Grommet part 8a Folded over portion 8b, and 8b' flange portion 10 Bolt hole 12 Core ember
CLAIMS
1. A metal gasket comprising:
a body with approximately flat plate shape in which an opening is provided; and a grommet part having a folded over portion formed by folding back a thin plate, said folded over portion surrounding the opening,
wherein a flange portion is formed at the grommet part, said flange portion is a portion where the thin plate extended from the folded over portion overlaps the body, and a width of the flange portion is not uniform in the same grommet part.
2. The metal gasket according to claim 1, wherein in a case of inserting the
metal gasket between two structures, and connecting the two structures by a fastening
member to seal a joint surface of the two structures, .
the width of the flange portion is determined so as to form a predetermined tightening contact pressure distribution in a peripheral region of the opening, based on a position of the fastening member and stiffness of the structures.
3. The metal gasket according to claim 1 or 2, wherein a core member is
provided inside the folded over portion of the grommet part.
4. The metal gasket according to any one of claims 1 to 3, wherein the
grommet part is formed by a member different from the body. —
5. The metal gasket according to any one of claims 1 to 4, wherein a thickness
of the grommet part is not uniform in the same grommet part, and
a predetermined tightening contact pressure distribution in a peripheral region of the opening is formed by a combination of a widthwise dimension of the flange portion, and a thicknesswise dimension of the grommet part.
6. The metal gasket according to any one of claims 1 to 5, wherein in case of
sealing a joint surface between a cylinder head and cylinder block of an internal
combustion engine having a plurality of cylinders, a shape of the flange portion of the
metal gasket to be mounted differs cylinder by cylinder.
