JPS62177363A - Gasket for exhaust manifold - Google Patents

Abstract

PURPOSE:To obtain sufficient effective clamping force even with a reduced clamping force of a clamping bolt a cylinder head by making into contact with the flange part of an exhaust manifold in a linear contact manner. CONSTITUTION:A gasket body 31 is formed by laminating plural metal plates 32, 33, 34. A gas passage hole 35 is provided on the gasket body 31, and beads 37-40 are projected outwardly on the metal plates 32, 33, surrounding the periphery of the gas passage hole 35, respectively. Also, a metal grommet 43 is installed on the peripheral edge of the gas passage hole 35. The thickness t1 of the part where the grommet 43 is installed is smaller than the thickness t2 between the top parts of the bead part 37-40. By this structure, sufficient effective clamping force can be obtained with small clamping force.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gasket for an exhaust manifold that is installed at a joint between a cylinder head and an exhaust manifold of an internal combustion engine.

Problems to be Solved by the Prior Art and the Invention FIG. 1 shows an example of how an exhaust manifold gasket is installed. An exhaust manifold gasket 5 is interposed at the joint with the section 4 to prevent leakage of high temperature exhaust gas.

Incidentally, in recent years, engines have tended to have higher horsepower and higher rotation speeds, and this trend has led to an increase in combustion pressure and an increase in heat load. At the same time, in recent years, there has been a trend toward lighter engines, and this trend has led to a decrease in the rigidity of the cylinder head 1.

Furthermore, thermal deformation of the exhaust manifold 3 is also extremely large due to the following reasons (a) to (C).

(a) As the thermal load applied to the cylinder head 1 is increasing as described above, the exhaust manifold 3 joined to the cylinder head 1 is also simultaneously subjected to a large thermal load.

(b) The number of manifold tightening bolts 6 that connect the exhaust manifold 3 to the cylinder head 1 is generally two to three, which is relatively small.

(C) As the weight of the engine is reduced, the rigidity of the exhaust manifold 3 is also reduced.

Moreover, the thermal deformation of the exhaust manifold 3 described above includes not only static components but also many dynamic components that make cyclic movements (the broken line 3' in FIG. 1 indicates the exhaust manifold 3). thermal deformation, h indicates the amount of deformation).

For this reason, in recent years, the joint between the cylinder head 1 and the exhaust manifold 3 has become an environment where gas leaks are very likely to occur.

Moreover, if the tightening load of the tightening bolts 6 is made too large, it will limit the thermal expansion of the exhaust manifold 3, which will cause cracks to occur in the exhaust manifold 3, which has low rigidity, and cause further gas leakage. There is even a risk of it developing into a leak.

Under such harsh environments, exhaust manifold gaskets are required to have the following physical properties.

(a) Even if the bolt tightening force is reduced, sufficient effective tightening pressure can be obtained to maintain a gas seal.

(b) It has a large ability to absorb thermal deformation and structural deformation (deformation other than thermal deformation) of the flange portion of the exhaust manifold.

(c) It also has a large ability to absorb cyclic movements due to thermal deformation and structural deformation of the flange portion of the exhaust manifold.

(d) There is little property deterioration such as fatigue (plastic deformation).

However, as will be explained next, conventional general gaskets for exhaust manifolds cannot satisfy the above-mentioned required physical properties, and it has become difficult to maintain a good gas seal.

FIGS. 2 and 3 show a gasket for an exhaust manifold of a type that has been used in large quantities in the past. A sheet-like compressible fiber material 9 is coated on both sides of a steel plate 8 with claws 7 raised on both sides. The main body 10 is constructed by shaping the crimped material into the shape of the flange part of the exhaust manifold,
Further, a metal grommet 12 is attached to the main body 10 around the gas passage hole 11.

This gasket receives compressive stress at the metal grommet 12 and uses the compressive elasticity of the main body 10 to perform gas sealing, but the contact between the grommet 12 and the flange of the cylinder head and exhaust manifold is surface. Since the contact area becomes large, it is difficult to obtain sufficient effective tightening pressure unless the tightening force of the bolt is increased.

Also, the temperature of the exhaust manifold joint is 600 to 700.
'C, but since the compressible fiber material 9 was generally composed of a mixture of asbestos and rubber, the thermal properties deteriorated significantly, and the main body 10 exhibited a sagging phenomenon.
The bolt torque decreased, which often resulted in gas leakage (curve A in FIG. 12 shows the relationship between the tightening time of the gasket and the amount of sagging).

Further, curve A in FIG. 11 shows the compressive stress-strain curve of this gasket. As is clear from curve A, this gasket compressed relatively little when subjected to compressive stress and had poor ability to absorb thermal and structural deformations of the exhaust manifold.

In Fig. 11, the solid line section shows the compression curve (i.e., the relationship between compressive stress and compressibility ratio when increasing the compressive stress), and the broken line section shows the restoring curve (i.e., when the compression stress is decreased). The relationship between compressive stress and compressibility of
It is expressed in compressive load per cm.

FIG. 4 shows another example of a conventional exhaust manifold gasket, in which the main body 13 is made of a plurality of laminated steel plates, a wire ring 16 is arranged in the gas passage hole 14, and the wire ring 16 and the main body 13 are connected to each other. Metal grommets 1 to 15 are attached to the grommets 1 to 15.

In this gasket, due to the presence of the wiring 16,
Since the grommet 15 can be in line contact with the cylinder head and the flange portion of the exhaust manifold, sufficient effective tightening pressure can be obtained even if the bolt tightening force is small.

In addition, since the main body 13 has a metal plate laminate structure with excellent heat resistance, the main body 13 does not exhibit a sticky phenomenon due to deterioration of thermal characteristics as in the case of the conventional gasket shown in FIG. Curve B in Figure 12 shows the relationship between the tightening time and the amount of sagging of this gasket.)
.

However, the stress-strain curve of this gasket is 11th
The disadvantage is that the amount of compression is small when subjected to compressive stress, as shown by curve B in the figure, and it is impossible to absorb thermal and structural deformation of the exhaust manifold.

FIG. 5 shows still another example of a conventional gasket, in which metal plates 19.20 are laminated on both sides of a metal plate 17.18, and metal plates 19.20 are laminated on both sides of a metal plate 17.18.
0 are provided with bead portions 22 and 23, respectively, and a metal grommet 24 is attached to each of the bead portions 22 and 23.

In this gasket, due to the presence of the bead portions 22 and 23, the contact between the grommet 24 and the flange portion of the cylinder head and exhaust manifold can be made into a line contact, so even if the bolt tightening force is small, it is still sufficient. Effective tightening pressure can be obtained.

In addition, due to the presence of the bead portions 22 and 23, the amount of compression when compressive stress is applied is large (the compressive stress-strain curve of this gasket is as shown in curve C in Fig. 11), and the exhaust manifold undergoes large thermal deformation. and an initial ability to absorb structural deformations.

However, as seen in the restoring curve part (broken line part) of curve C, the rebound resilience is weak, so it lacks the ability to absorb the cyclic movement of the thermal deformation and structural deformation of the flange part of the exhaust manifold. , and bead part 2
Since there is a space 25.26 between 2.23 and the metal plate 18, as the operation progresses, the bead portion 22.23 becomes more prone to sagging, resulting in gas leakage (as shown in Fig. 12). Curve C shows the relationship between the tightening time of this gasket and the amount of settling).

OBJECTS OF THE INVENTION The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional art, and can fully satisfy all of the required physical properties (a) to (d) above, and can extremely easily perform gas
An object of the present invention is to provide a gasket for an exhaust manifold that can obtain an optimal sealing surface pressure and can also prevent gas leakage between laminated metal plates constituting a gasket body.

Means for Solving the Problems The exhaust manifold gasket according to the present invention is an exhaust manifold gasket interposed at the joint between the cylinder head and the exhaust manifold of an internal combustion engine, and is made by laminating a plurality of metal plates. A gasket body, a gas passage hole provided in the gasket body, and a first metal plate and a second metal plate disposed on the outermost side of the back of the plurality of metal plates, respectively, around the gas passage hole. and a metal grommet attached to the peripheral edge of the gas passage hole in the main body, and the thickness tl of the grommet attachment part is , the thickness is smaller than the thickness t2 of the apex portion of the bead portion.

Function In the present invention, since the bead is provided, the contact between the cylinder head and the flange of the exhaust manifold is a line contact, so even if the tightening force of the tightening bolt is reduced, sufficient Effective tightening force can be obtained.

Further, since the bead is provided, the amount of compression when compressive stress is applied is large, and the ability to absorb thermal deformation and structural deformation of the flange portion of the exhaust manifold is large.

In addition, since beads are provided on both the first metal plate and the second metal plate, the amount of compression is large and the rebound resilience is also large, so thermal deformation of the flange of the exhaust manifold and The ability to absorb cyclic movements of deformation is also great, and seal gaps are much less likely to occur.

In addition, a space is created inside the door, but since the grommet is attached to the gasket body, the amount of bead settling is limited, so as the bead becomes more severe as the operation progresses, the gas There is no possibility of leakage. Therefore, a gas seal can be stably maintained for a long period of time.

In addition, when the tightening bolt is tightened until the flange of the cylinder head and exhaust manifold contacts the grommet, the amount of deformation of the bead becomes equivalent to (12-11>), and the amount of deformation of the bead becomes equal to The above deformation is limited, and the compressive stress at this time is also (
t2-11). therefore,(
By appropriately setting the size of t2-tl), the optimum gas seal surface pressure can be obtained very easily.

Furthermore, the gas sealing performance can be further improved because a seal can be further maintained at the grommet portion and a secondary seal can be maintained at the rough bead portion.

EXAMPLES Hereinafter, the present invention will be roughly described in detail based on examples shown in the drawings.

6 to 8 show an embodiment of the present invention, in which the gasket body 31 includes a first metal plate 32, a second metal plate 33, and a third metal plate 34, each made of an aluminized steel plate. This gasket body 31 is provided with gas passage holes 35 and bolt holes 36.

The upper first metal plate 32 of the three metal plates constituting the gasket body 31 has two annular bead portions 37.3 each surrounding the gas passage hole 35.
8 are provided, and both of these beads 37, 38 are convex toward the outside. Similarly, two beads 39 and 40 are respectively provided on the lower second metal plate 33 of the three metal plates constituting the gasket body 31 so as to surround the gas passage hole 35. has been
These beads 39 and 40 are also convex toward the outside.

Furthermore, beads 41.42 are discontinuously provided on the outer peripheries of the first metal plate 32 and the second metal plate 33, respectively, and these beads 41.42 also protrude outward. has been done.

A metal grommet 43 made of stainless steel or the like is provided around the bolt hole 36 in the gasket body 31.
is attached, and this grommet 43 holds the main body 31 from both upper and lower sides.

Here, the thickness tl of the grommet 43 mounting portion is the thickness t2 of the apex portions of the beads 37, 38, 39, and 40.
It is more compact.

In this gasket, due to the presence of beads 37 to 40,
Since the contact between the cylinder head and the flange portion (not shown) of the exhaust manifold is a line contact, sufficient effective tightening force can be obtained even if the tightening force of the tightening bolt is small.

In addition, since the beads 37 to 40 are provided on the first metal plate 32 and the second metal plate 33, the amount of compression when subjected to compressive stress is large (the curve in Fig. 11 indicates that this gasket compressive stress-strain curve), has a large ability to absorb thermal deformation and structural deformation of the exhaust manifold flange.

In addition, the surface pressure of the gas seal part is 8-OKl/cm
In this gasket, the amount of compression of the repeats 37 to 40 is limited by the grommet 43, as will be explained in detail later. Therefore, in the curve shown in FIG. The increase in load is stopped when it reaches /cm.

In addition, since the beads 37 to 40 are provided on both the first metal plate 32 and the second metal plate 33, the amount of compression is large and the rebound resilience is also large, so the flange part of the exhaust manifold is heated. The ability to absorb cyclic movements of deformation and structural deformation is also greater and seal gaps are much less likely to occur.

Further, in this gasket, spaces are created inside the beads 37 to 40, but the grommet 43 is located inside the gasket body 31.
Since the amount of settling of the beads 37 to 40 is limited by being attached to the
There is no chance that the 40 will become too stiff and cause a gas leak. Therefore, a gas seal can be stably maintained for a long period of time (the curved line in FIG. 12 shows the relationship between the tightening time of the gasket and the amount of settling).

Furthermore, when the tightening bolt is tightened until the flange of the cylinder head and exhaust manifold contacts the grommet 43, the amount of deformation of the beads 37 to 40 is (1
2-11>, and the bead 3
Further variations between 7 and 40 parts are restricted. The compressive stress at this time also has a magnitude corresponding to (12-11>. Therefore, by appropriately setting the magnitude of (12-11>), it is extremely easy to obtain the optimum surface pressure for the gas seal. be able to.

In addition, with this gasket, the gas sealing performance can be further improved because a seal can be further maintained at the grommet 43 and a secondary seal can be maintained at roughly the beads 37 to 40.

Further, by attaching the grommet 35 to the gasket body 31, gas leakage between the metal plates 32 and 33 can be prevented.

Figures 9 and 10 show other embodiments of the invention. In this embodiment, the gasket body 31 is formed by laminating only two metal plates, a first metal plate 32 and a second metal plate 33. The other structure is the same as that of the previous embodiment. In this embodiment, parts corresponding to those in the previous embodiment are designated by the same reference numerals.

This example also has the same effect as the above example.
be qed.

Effects of the Invention As described above, the exhaust manifold gasket according to the present invention has the following features: (a) Even if the bolt tightening force is reduced, sufficient effective tightening pressure can be obtained.

(b) The amount of compression when subjected to compressive stress is large, and the ability to absorb thermal deformation and structural deformation of the flange portion of the exhaust manifold is large.

(c) It has high rebound resilience and has a high ability to absorb cyclic movements due to thermal deformation and structural deformation of the flange portion of the exhaust manifold.

(d) There is little characteristic deterioration such as sagging, and gas sealing can be maintained stably for a long period of time.

(E) By appropriately setting the size difference of (12-11), the optimum gas seal surface pressure can be obtained very easily.

(f) Gas sealing performance can be further improved because a seal can be maintained further at the grommet section and a secondary seal can be maintained at the rough bead section.

(G) It is also possible to prevent gas leakage between the laminated metal plates that make up the gasket body.

It is possible to obtain excellent effects such as

[Brief explanation of drawings]

Figure 1 is a sectional view showing a general example of how an exhaust manifold gasket is installed, Figure 2 is a plan view showing an example of a conventional exhaust manifold gasket, and Figure 3 is the line ■-■ in Figure 2. Fig. 4 is a cross-sectional view showing another conventional exhaust manifold gasket (the cross-sectional position corresponds to the line ■-■ in Fig. 2), and Fig. 5 is a cross-sectional view showing another conventional exhaust manifold gasket. 6 is a plan view showing an embodiment of the gasket for exhaust manifold according to the present invention, and FIG. 8 is a sectional view taken along the line ■--■ in FIG. 6, and FIG. 9 is a sectional view taken along the line ■--■ in FIG. 10 is a sectional view corresponding to FIG. 8 of the same embodiment, FIG. 11 is a compressive stress-strain diagram of the conventional gasket and the embodiment, and FIG. 12 is a diagram of the conventional gasket. It is a characteristic diagram showing the relationship between the tightening time and the amount of settling in the gasket and the example. 31... Gasket body, 32... First metal plate,
33... Second metal plate, 35... Gas passage hole, 37
~40...Bead portion, 43...Metal grommet. Patent applicant Neesan Gasket Co., Ltd. Agent
Patent Attorney Oshiki Izumi No. 1 N □°n Figure 2 Figure 3 Figure 4 Figure 16 Figure 5 To Figure 6 I C Figure 11 Compression ratio (%) Figure 12

Claims (1)

[Scope of Claim] A gasket for an exhaust manifold that is installed at a joint between a cylinder head and an exhaust manifold of an internal combustion engine, comprising: a gasket body formed by laminating a plurality of metal plates; and a gasket provided on the gasket body. A gas passage hole, and a first metal plate and a second metal plate disposed on the outermost side of the plurality of metal plates, each protruding outward so as to surround the gas passage hole. and a metal grommet attached to the peripheral edge of the gas passage hole of the main body, and the grommet attachment portion has a thickness t_
1 is a gasket for an exhaust manifold, characterized in that the thickness is smaller than the thickness t_2 of the apex portion of the bead portion.