JP2020091010A - gasket - Google Patents

Abstract

To effectively prevent the leakage of an exhaust gas to the outside.SOLUTION: In a gasket 40 interposed between an external peripheral face 13A and a seal face F22A in a pipe joint part 20 having a flange part F2 having a seal face F22A for connecting a first pipe-shaped body 13 and a second pipe-shaped body 14, and facing either of the first and second pipe-shaped bodies 13, 14 while separating from the outside of a radial direction toward the external peripheral face 13A of the other of the pipe-shaped bodies 13, 14, the gasket comprises: a core member 45 which is formed of a shape memory alloy, and formed into a disc circular shape, and whose inside diameter is formed into a large diameter larger than an outside diameter of the external peripheral face 13A, and whose outside diameter is formed into a small diameter smaller than an inside diameter of the seal face F22A; and a seal member 46 for covering a surface which faces at least the seal face F22A out of the surface of the core member 45. When the core member 45 is heated to a prescribed temperature or higher, the core member makes the seal member 46 pressure-contact with the seal face F22A by being expanded to the outside of the radial direction by a shape memory effect.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a gasket, and particularly to a gasket provided in an exhaust system of an engine.

Generally, a pipe joint portion is provided in an exhaust system of an engine, and a gasket for sealingly joining the exhaust pipes is provided between the flange surfaces of the exhaust pipes arranged to face each other in the pipe joint portion. It is provided. Such a gasket includes a core material such as stainless steel and an expanded graphite sheet wound around the core material, and presses the expanded graphite sheet against the flange surface to seal the gap (for example, Patent Document 1). ~3).

JP, 2012-36916, A JP, 2007-182948, A JP 04-145189A

By the way, in the seal structure in which the expanded graphite sheet of the gasket is pressed against the flange surface, when the expanded graphite sheet is worn or worn, surface pressure cannot be secured on the pressure contact surface between the flange of the exhaust pipe and the expanded graphite sheet, and exhaust gas is generated. It may leak out.

The technique of the present disclosure aims to effectively prevent leakage of exhaust gas to the outside.

The technique of the present disclosure connects the first tubular body and the second tubular body, and separates one of the first and second tubular bodies from the outer side in the radial direction on the outer peripheral surface of the other tubular body. In a pipe joint portion including a flange portion having a sealing surface facing the sealing surface, a gasket interposed between the outer peripheral surface and the sealing surface, which is formed in a ring shape with a shape memory alloy and has an inner diameter A core member having a diameter larger than the outer diameter of the outer peripheral surface and a diameter smaller than the inner diameter of the sealing surface, and at least a surface of the core member facing the sealing surface is covered. A sealing member is provided, and the core member expands radially outward by a shape memory effect when heated at a predetermined temperature or higher, so that the sealing member is brought into pressure contact with the sealing surface.

Further, it is preferable that the seal member is made of expanded graphite.

Further, it is preferable that the core member is formed so that both ends of the shape-memory alloy wire material are overlapped with each other so as to have an annular shape as a whole.

According to the technique of the present disclosure, leakage of exhaust gas to the outside can be effectively prevented.

1 is a schematic overall configuration diagram showing an exhaust system of an engine according to the present embodiment. It is a typical sectional view showing a pipe joint part concerning this embodiment. (A) is a typical sectional view showing an important section of a pipe joint part before assembly concerning this embodiment. (B) is a schematic front view showing the gasket according to the present embodiment. It is a typical sectional view showing the pipe fitting part after the assembly concerning this embodiment. FIG. 3 is a schematic cross-sectional view showing a state of the gasket according to the present embodiment when the engine is stopped (at low temperature). FIG. 3 is a schematic cross-sectional view showing a state of the gasket according to the present embodiment when the engine is driven (at high temperature). It is a typical sectional view showing a pipe joint part concerning other embodiments.

Hereinafter, the gasket according to the present embodiment will be described with reference to the accompanying drawings. The same parts are designated by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

FIG. 1 is a schematic overall configuration diagram showing an exhaust system of an engine according to the present embodiment.

The engine 10 is provided with an exhaust manifold 11 that collects exhaust gas derived from each cylinder. An exhaust passage 12 is connected to the exhaust manifold 11 to guide exhaust gas to the atmosphere via an exhaust purification device (not shown). The exhaust passage 12 is provided with a first exhaust pipe 13 (an example of a first tubular body), a pipe joint portion 20, a second exhaust pipe 14 (an example of a second tubular body), and the like in order from the exhaust upstream side. There is. The first exhaust pipe 13 and the second exhaust pipe 14 are coaxially connected to each other via the pipe joint portion 20. The first exhaust pipe 13 and the second exhaust pipe 14 are formed of, for example, tubular steel pipes.

FIG. 2 is a schematic cross-sectional view showing the pipe joint portion 20 according to this embodiment.

The pipe joint portion 20 connects the downstream end portion 16 of the first exhaust pipe 13 and the upstream end portion 17 of the second exhaust pipe 14 that is arranged to face the downstream end portion 16 of the first exhaust pipe 13 with a predetermined gap. . The downstream end 16 of the first exhaust pipe 13 and the upstream end 17 of the second exhaust pipe 14 are preferably formed to have the same diameter. Specifically, the pipe joint portion 20 includes a first flange F1, a second flange F2, and a gasket 40.

The first flange F1 includes a cylindrical portion F11 and an annular portion F13. The inner diameter of the cylindrical portion F11 is formed to be substantially the same as the outer diameter of the downstream end portion 16 of the first exhaust pipe 13, and the cylindrical portion F11 is upstream from the downstream end of the first exhaust pipe 13 by a predetermined amount L. It is closely fixed by welding or the like to the outer periphery of the downstream end 16 offset to the side. The annular portion F13 extends radially outward from the downstream end of the cylindrical portion F11. A plurality of insertion holes 1A into which the bolts 31 are inserted are formed at a predetermined pitch in the circumferential direction at the radial center of the annular portion F13.

The second flange F2 (an example of a flange portion) includes a cylindrical portion F21, a diameter-enlarged portion F22, and an annular portion F23. The inner diameter of the cylindrical portion F21 is formed to be substantially the same as the outer diameter of the upstream end portion 17 of the second exhaust pipe 14, and the cylindrical portion F21 is closely fixed to the outer circumference of the upstream end portion 17 by welding or the like. ing. The enlarged diameter portion F22 extends obliquely from the upstream end of the cylindrical portion F21. Specifically, the expanded diameter portion F22 has an inner peripheral surface F22A (an example of a sealing surface) that is inclined with respect to the axial direction. The inner peripheral surface F22A is formed so as to face the outer peripheral surface 13A (an example of the outer peripheral surface) of the first exhaust pipe 13 while being separated from the radially outer side. The enlarged diameter portion F22 is formed so that the inner peripheral surface F22A can come into pressure contact with a part of the gasket 40 (an inclined surface 47 described later). The annular portion F23 extends radially outward from the upstream end of the expanded diameter portion F22. A plurality of insertion holes 2A, into which the bolts 31 are inserted, are formed at a predetermined pitch in the circumferential direction in the radial center of the annular portion F23.

The first flange F1 and the second flange F2 are configured such that the flange surfaces facing each other are pressed against each other by fastening the bolts 31 and the nuts 32 inserted into the insertion holes 1A and 2A. A gasket 40 that seals the gap is provided in the facing space between the first flange F1 and the enlarged diameter portion F22 of the second flange F2.

The gasket 40 is formed in an annular shape, and in order to seal the gap between the first exhaust pipe 13 and the second exhaust pipe 14, the gasket 40 is provided on the outer peripheral surface 13A on the downstream side of the first flange F1 of the first exhaust pipe 13. In the externally fitted state, it is interposed between the first flange F1 and the second flange F2 facing each other. The gasket 40 includes an annular core member 45 and an annular seal member 46 that covers the outer periphery of the core member 45.

FIG. 3A is a schematic cross-sectional view showing a main part of the pipe joint section 20 before assembly according to the present embodiment. FIG. 3B is a schematic front view showing the gasket 40 according to the present embodiment. FIG. 4 is a schematic cross-sectional view showing the pipe joint section 20 after assembly according to the present embodiment.

The core member 45 is preferably formed by winding a shape-memory alloy wire into a substantially spiral shape or a spiral shape by rolling the shape of the shape-memory alloy wire into an annular shape so that both ends 45H and 45T in the circumferential direction overlap each other, as shown in FIG. It is formed into a shape. More specifically, the core member 45 has an inner diameter larger than the outer diameter of the outer peripheral surface 13A of the first exhaust pipe 13 and a smaller outer diameter than the inner diameter of the inner peripheral surface F22A of the expanded diameter portion F22. Has been formed. Further, the core member 45 has a shape memory effect in the radial direction of the seal portion when heat of a predetermined temperature or higher (for example, 100° C.) is applied in a high temperature atmosphere such as when the high temperature exhaust gas flows through the exhaust passage 12 at high exhaust temperature. It is formed so as to spread to the outside. Examples of shape memory alloys include titanium-nickel alloys, iron-manganese-silicon alloys, and the like.

The seal member 46 is made of expanded graphite and covers the entire surface of the core member 45. Here, the expanded graphite is one in which a chemical substance is inserted between layers of flaky graphite, and examples of the inserted chemical substance include nitric acid, potassium permanganate, sulfuric acid and the like. The seal member 46 is formed, for example, by winding an expanded graphite sheet around the core member 45. A radial cross section of the gasket 40 including the core member 45 and the seal member 46 is substantially rectangular.

Specifically, the seal member 46 that forms the outer periphery of the gasket 40 includes an upstream end surface 41 that is in pressure contact with the first flange F1, an inner peripheral surface 42 that is in pressure contact with the outer peripheral surface 13A of the downstream end portion 16, and a second flange. It has a downstream end face 43 facing F2, an outer peripheral face 44, and an inclined face 47 formed by obliquely cutting the corners of the downstream end face 43 and the outer peripheral face 44. As shown in FIG. 4, in a state where the first flange F1 and the second flange F2 are fastened by the bolts 31 and the nuts 32, the upstream end surface 41 is the annular portion F13 of the first flange F1 and the inclined surface 47 is the first. The gap between the first exhaust pipe 13 and the second exhaust pipe 14 is sealed by being pressed against the expanded diameter portion F22 of the two flanges F2.

Next, the function and effect of the gasket 40 according to this embodiment will be described.

FIG. 5 is a schematic cross-sectional view showing a state of the gasket 40 according to the present embodiment when the engine is stopped (at low temperature). FIG. 6 is a schematic cross-sectional view showing a state of the gasket 40 according to the present embodiment when the engine is driven (at high temperature).

As shown in FIG. 5, when the seal member 46 of the gasket 40 is worn or the first flange F1 and the second flange F2 that are in pressure contact with the seal member 46 have dimensional defects, the engine is stopped (at low temperature) or the like. In a low temperature atmosphere, a gap may occur between the inclined surface 47 and the enlarged diameter portion F22 of the second flange F2.

In the present embodiment, as shown in FIG. 6, even when the seal member 46 of the gasket 40 is worn or the first flange F1 and the second flange F2 have dimensional defects, the core member 45 is When heated above a predetermined temperature, it expands radially outward of the seal portion. When the core member 45 expands to the outside in the radial direction, the seal member 46 on the outer peripheral side also expands to follow the outside in the radial direction, and the inclined surface 47 comes into pressure contact with the expanded diameter portion F22. Thereby, even if the seal member 46 is worn or the first flange F1 and the second flange F2 have dimensional defects, it is possible to effectively prevent the exhaust gas from leaking to the outside.

Further, the core member 45 of the gasket 40 is formed into a circular ring shape so that both ends 45H and 45T overlap each other (see FIG. 3B). That is, even in a state where the core member 45 expands outward in the radial direction under a high temperature atmosphere, the overlapping of the both end portions 45H and 45T is maintained, and the surface pressure and the sealing property are effective over the entire circumference in the circumferential direction. Can be secured.

[Other]
It should be noted that the present disclosure is not limited to the above-described embodiment, and may be appropriately modified and implemented without departing from the spirit of the present disclosure.

For example, as shown in FIG. 7, the inner peripheral surface F22A of the expanded diameter portion F22 of the second flange F2 is curved in a concave shape, and the inclined surface 47 of the gasket 40 is formed in a convex shape corresponding to the concave shape of the inner peripheral surface F22A. Alternatively, the inner peripheral surface F22A and the inclined surface 47 may be slidably pressed against each other. In addition, the bolt 35, the nut 36, and the coil spring 37 that is externally fitted to the bolt 35 are assembled, and the first flange F1 and the second flange F2 are pressed and urged toward each other. And the second exhaust pipe 14 may be configured to be capable of relative angular displacement. Even in such a configuration, the gasket 40 can exert the same operational effect as that of the above-described embodiment.

Further, the application of the present disclosure is not limited to the exhaust system of the engine, but can be widely applied to a pipe joint portion of a tubular body that allows a fluid other than exhaust to flow, such as an intake system.

10 engine 11 exhaust manifold 12 exhaust passage 13 first exhaust pipe (first tubular body)
13A Outer peripheral surface 14 Second exhaust pipe (second tubular body)
20 Pipe joint part F1 1st flange F2 2nd flange (flange part)
F22 Expanded portion F22A Inner peripheral surface (sealing surface)
40 gasket 45 core member 46 seal member 47 inclined surface

Claims (3)

The first tubular body and the second tubular body are connected to each other, and one of the first tubular body and the second tubular body has a sealing surface facing the outer peripheral surface of the other tubular body away from the radially outer side. In a pipe joint portion including a flange portion, a gasket interposed between the outer peripheral surface and the sealing surface,
A core member formed of a shape memory alloy in an annular shape, the inner diameter of which is larger than the outer diameter of the outer peripheral surface, and the outer diameter of which is smaller than the inner diameter of the sealing surface,
A seal member that covers at least the surface of the core member that faces the seal surface,
When the core member is heated at a predetermined temperature or higher, the core member expands radially outward due to a shape memory effect to bring the seal member into pressure contact with the seal surface. The gasket according to claim 1, wherein the seal member is made of expanded graphite. The gasket according to claim 1 or 2, wherein the core member is formed so that both ends of a shape-memory alloy wire are overlapped with each other to form an annular shape.

Images