JPH0332747Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to the structure of an exhaust pipe connection in an automobile engine, etc., and in particular to an exhaust pipe in which a gasket is sandwiched between flanges provided on each member constituting the exhaust system. Related to pipe connection structure.

(Prior Art) In general, an engine exhaust system includes an exhaust manifold whose one end is branched into multiple parts and connected to the engine, a catalytic converter that removes harmful components from exhaust gas, and a muffler that reduces exhaust noise. It has a configuration in which connecting pipes, etc. that connect these components are connected in a line, and the flanges provided at the ends of these components are joined by tightening members such as bolts, but they are not connected to each other. A gasket made of asbestos, copper, or the like is interposed between the flanges to prevent leakage of exhaust gas from the connecting portion.

By the way, in such a connection structure of an exhaust system, there may be a case where the amount of tightening of the flanges is insufficient and the surface pressure between the flanges and the gasket interposed therebetween is insufficient. In contrast, for example, according to Japanese Utility Model Application Publication No. 54-107725, when a gasket is interposed between opposing flanges, there is a gap between the tip of a pipe integral with one flange and the other flange. A structure is shown in which a gap is created corresponding to the tightening allowance of the gasket. According to this structure, when the flange is tightened until the gap disappears, the gasket is tightened by a predetermined amount, and the gasket and The required surface pressure will always be obtained between both flanges.

However, in such an exhaust system connection structure, in addition to the problem of insufficient tightening amount as described above, there are the following problems. That is, when high-temperature exhaust gas passes through the exhaust system during engine operation, the gasket is exposed to high temperatures and gradually deteriorates over the course of operating time, thereby reducing the surface pressure between the gasket and the flange. Furthermore, the flange that clamps the gasket is also thermally deformed due to the high heat of the exhaust gas, resulting in a partial reduction in the surface pressure between the flange and the gasket, and the creation of a gap.

Furthermore, because the flange cannot be made large due to space limitations, it may not be possible to ensure a sufficient contact area between the flange and the gasket, that is, a sufficient sealing area. One possible way to deal with this is to increase the area of contact between the flanges and gaskets by providing concave and convex portions corresponding to the flanges and gaskets, but in that case, the thicknesses of the gaskets and flanges will not be uniform, and When exposed to the heat of exhaust gas, the amount of thermal expansion becomes uneven in each part, causing unnatural thermal deformation, which may partially reduce the surface pressure between the flange and gasket, or cause gaps to increase. It happens. In addition, regarding this type of problem, the applicant has filed an earlier application (U.S. Pat.
No. 54044) (Utility Model Publication No. 45464) proposed a gasket structure that was improved from a different perspective than the present case.

(Purpose of the invention) The present invention deals with the above-mentioned problems in the structure of the connection part of the exhaust system. By improving the structure of the gasket, a sufficient sealing area can be secured between the gasket and the flange, and
To provide an exhaust pipe connection structure that does not cause the surface pressure between the flange and the gasket to decrease or become uneven even if the gasket deteriorates or the flange is thermally deformed due to the heat of exhaust gas. The purpose is to realize this and thereby reliably prevent leakage of exhaust gas from the connection.

(Structure of the invention) In order to achieve the above object, the present invention is characterized by the following structure.

That is, in an exhaust pipe connection structure in which a gasket is interposed between mutually opposing flanges provided at the ends of each member constituting the exhaust system of an engine, at least one of the flanges has a contact surface with the gasket. A ring-shaped concave portion is provided, and a ring-shaped convex portion that fits into the concave portion is provided on the surface of the gasket that faces the flange, and the gasket is formed of a thermally expandable material, and at least the convex portion of the gasket The end face where the part is provided, the inner circumferential surface, and the outer circumferential surface are covered with a thin metal plate. Here, the above-mentioned thermally expandable material is a material such as intalum mat, which is a mixture of a thermally expandable substance such as vermiculite and ceramic fibers, and a board made of a thermally expandable material with a constant density is It has a characteristic that when heated while both surfaces are pressed by other members, it always has a substantially constant expansion force regardless of its thickness.

According to the above configuration, the recess of the flange and the protrusion of the gasket are fitted into each other and face each other, so that the sealing area at the connection portion is increased. In addition, the thermally expandable substance contained in the thermally expandable material such as the interram mat used in the gasket has the property that its volume increases as the temperature rises, so the flange will expand due to the heat of the exhaust gas. Even if the gasket is unnaturally thermally deformed, the gasket will not follow this thermal expansion and create a gap between the flange and the gasket.In particular, the gasket will not expand due to the expansion of the convex part of the gasket fitted into the concave part of the flange. The fit between the concave portion and the convex portion is maintained tightly, and by using a thermally expandable material having a uniform density, the surface pressure on the contact surface between the gasket and the flange becomes substantially uniform over the entire surface thereof. In addition, since at least the end face, inner and outer circumferential surfaces of the gasket where the convex portion is provided are covered with a thin metal plate, the shape of the convex portion of the thermally expandable material is maintained, and the thermal expansion material is The material is protected from the intrusion of particulates in exhaust gas from the inside, water from the outside, etc., and changes in its properties are prevented.

(Effect of the invention) As described above, according to the invention, when each member constituting the exhaust system of an engine is connected with a gasket interposed between the flanges provided at the ends thereof, the above-mentioned flanges and The surface that comes into contact with the gasket,
In other words, the area of the sealing surface is increased, and even if the flange is thermally deformed due to the heat of the exhaust gas, no gap will be formed on the contact surface, and the contact pressure on the contact surface is spread over the entire surface. It becomes almost uniform. As a result, the sealing performance at the connection parts of each component of the engine exhaust system is significantly improved, and
The sealing performance is maintained for a long period of time, and leakage of exhaust gas from the connection is reliably prevented.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In general, an engine exhaust system includes an exhaust manifold with one end branched into multiple parts and connected to the cylinder head of the engine, a catalytic converter that removes harmful components from exhaust gas, and a muffler that reduces exhaust noise. However, these members are connected in a line either directly or via a connecting exhaust pipe, but
In this embodiment, as shown in FIG. 1, an upstream pipe section 2a of a catalytic converter 2 is connected to a collecting part 1 of an exhaust manifold, and a silencer connection pipe is connected to a downstream pipe section 2b of the catalytic converter 2. It has a configuration in which an exhaust pipe 3 is connected. The connecting portions of the exhaust system components 1, 2, and 3 are arranged so that the flanges 4, 5, 6, and 7 provided at the ends of these members face each other, and there is a gap between the opposing flanges 4, 5. Gaskets 8 and 8 are interposed between 6 and 7, respectively, and these are fastened using bolts 9 and nuts 10.

Next, the structure of the connecting portion will be explained with reference to FIGS. 2 to 4. Note that the following description refers to the downstream pipe portion 2b of the catalytic converter 2 and the upstream end portion 3a of the connecting exhaust pipe 3.
Although the connection section with this will be explained, the other connection sections have the same structure.

First, the gasket 8 is provided with a large-diameter exhaust flow hole 8a in the center, which communicates the insides of the pipe portions 2b and 3a located on the downstream side, respectively, and the gasket 8 and Two bolt insertion holes 8 are provided in the flanges 6 and 7 on both sides.
b, 8b, 6a, 6a, 7a, 7a are provided,
The bolts 9, 9 are inserted into each of these holes.

Therefore, the downstream end surface 6b of the flange 6 of the upstream tube portion 2b and the flange 7 of the downstream tube portion 3a
These pipe portions 2 are connected to the upstream end surface 7b in
Ring-shaped recesses 6c and 7 surround b and 3a.
In addition, ring-shaped protrusions 8e and 8f are formed on the upper and downstream surfaces 8c and 8d of the gasket 8, respectively, in correspondence with these, and the gasket 8 is sandwiched between the flanges 6 and 8. When the gasket 7 is tightened, the convex portions 8e, 8f of the gasket 8 and the concave portions 6c, 7c of the flanges 6, 7 fit into each other.

On the other hand, the gasket 8 is mainly composed of an interram mat 11 which is a thermally expandable material. Here, this interlaminar mat 11 is a mixture of a thermally expandable material such as vermiculite and ceramic fibers, and has the property of increasing its volume when heated, and especially as shown in FIG. If the density is constant, when both surfaces are heated while being pressed by other members, the expansion force against the pressing members on both sides is always approximately constant regardless of the thickness of the plate.

Incidentally, since the interram mat 11 easily collapses, in order to maintain its shape, in this embodiment, both surfaces of the interram mat 11 are covered with metal thin plates 12 and 13.
covered with. Of these, the first thin metal plate 12 covers the upstream end face 8cc of the gasket 8 and the periphery of the bolt insertion holes 8b, and the second thin metal plate 13 covers the downstream end face 8d of the gasket 8 and the surrounding area of the bolt insertion holes 8b. It covers the inner and outer peripheral surfaces.

According to the above configuration, when the gasket 8 is interposed between the flanges 6 and 7 facing each other and both the flanges 6 and 7 are tightened using the bolts 9 and 9 and the nuts 10 and 10, both surfaces 8c of the gasket 8 ,8
The convex portions 8e and 8f provided at
c and 7c, respectively, and each of these surfaces 8
c, 6b and 8d, 7b will be in contact with each other.
Therefore, the contact area is increased compared to when these surfaces are flat, and the sealing performance of the joint by the flanges 6 and 7 is accordingly improved.

On the other hand, when high-temperature exhaust gas discharged from the combustion chamber passes through the exhaust system during engine operation, the heat of this exhaust gas causes the flanges 6 and 7 to
and gasket 8 become hot, especially the flange 6,
7 is provided with recesses 6c and 7c, so it is unnaturally thermally deformed. However, since the interram mat 11 constituting the gasket 8 thermally expands following the thermal deformation of the flanges 6 and 7, the end surfaces 6b and 7 of the flanges 6 and 7
b and both surfaces 8c and 8d of the gasket 8 are kept in close contact with each other without creating a gap. In that case, if the density of the interram mat 11 is constant, the expansion force on the flanges 6 and 7 will always be approximately constant despite the presence of unevenness, so that the gasket 8 and the flanges 6 and 7 on both sides The contact pressure on the contact surfaces becomes approximately uniform over the entire surface. This significantly improves the sealing performance of the joint between the flanges 6 and 7, and reliably prevents leakage of exhaust gas from the joint.

Here, since the first and second thin metal plates 12 and 13 are provided around the interram mat 11, the shapes of the protrusions 8e and 8f are maintained, and the second thin metal plate 13 is connected to the gasket 8. Since the outer peripheral surface of the interram mat 11 is also covered, the interram mat 11 is protected from the intrusion of fine particles in the exhaust gas from the inside and the intrusion of water from the outside, and its characteristics are maintained. Furthermore, since these plates 12 and 13 are thin plates, they do not hinder the thermal expansion of the interram mat 11.

In the above embodiment, the convex portions 8e and 8f are provided on both end surfaces 8c and 8d of the gasket 8, respectively, and both surfaces are covered with the thin metal plates 12 and 13, but the following configuration may also be used. .

In other words, as shown in FIG.
A concave portion 6c' is provided only on the end surface 6b' of the gasket 8', and a convex portion 8e' is also formed on one surface 8c' of the gasket 8' to correspond to the concave portion 6c', and the shape of the convex portion 8e' is A thin metal plate 12' may be provided only on the surface 8c' so as to hold it, and as shown in FIG. may be provided closer to the inner periphery, and with this structure, the sealing area between the flanges 6', 7'' and the gaskets 8', 8'' increases, and the thermal deformation of the flanges increases the sealing area. Also, uniform surface pressure can be obtained.

[Brief explanation of the drawing]

Figures 1 to 4 show the first embodiment of the present invention, where Figure 1 is an external view of the main parts of the exhaust system, Figure 2 is a sectional view of the connection in the exhaust system, and Figure 3 is the connection. FIG. 4 is a partially enlarged view of FIG. 2, and FIGS. FIG. 7 is a graph showing the characteristics of the interlaminar mat. 6, 6', 7, 7', 7''...flange, 6c,
6c', 7c, 7c''...Concave portion, 8, 8', 8''...Gasket, 8e, 8e', 8f, 8f''...Protrusion, 1
1...Thermal expansion material (interam mat), 12,1
2', 13...Thin metal plate.

Claims (1)

[Scope of utility model registration request] An exhaust pipe connection structure in which a gasket is sandwiched between opposing flanges, wherein a ring-shaped recess is provided on the surface of at least one of the flanges that faces the gasket, and the gasket faces the flange. The surface is provided with a ring-shaped protrusion that fits into the recess, and the gasket is made of a thermally expandable material made of a mixture of a thermally expandable substance and ceramic fibers, and at least the An exhaust pipe connection structure characterized in that an end surface provided with a convex portion, an inner circumferential surface, and an outer circumferential surface are covered with a thin metal plate.