JP7090017B2 - gasket - Google Patents

Description

The present invention relates to a sealing technique, particularly to a gasket structure.

Gaskets are used to seal between stationary members. In particular, in facilities such as chemical factories, power plants, steelworks, internal combustion engines such as automobiles, and their exhaust pipe systems, fluids such as water, oil, steam, and gas are in a high temperature and high pressure state, so gaskets should withstand them. The situation is harsh. As the material of the gasket used for sealing in this harsh situation, mica having excellent heat resistance is adopted (see, for example, Patent Document 1 and Patent Document 2).

Mica is roughly divided into soft mica (phlogopite, KMg ₃ (AlSi ₃ ) O ₁₀ (OH) ₂ ) and hard mica (muscovite, KAl ₂ (AlSi ₃ ) O ₁₀ (OH) ₂ ). Soft mica has excellent heat resistance and sealing properties, and hard mica has excellent electrical insulation. Therefore, in many cases, soft mica is used for the gasket (see, for example, Patent Document 1). Gaskets made from soft mica are generally spiral. In a spiral gasket, a sealing material (filler) such as soft mica is formed in a sheet shape together with a binder (acrylic or silicone adhesive), and this sheet is wound in a spiral shape to form multiple layers in the radial direction. It refers to a product molded in an annular shape (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 02-195077 International Publication No. 2016/125486

Pipes included in the exhaust system of an internal combustion engine, such as the exhaust pipe of an automobile, generally receive high heat from the exhaust gas, and continue to receive vibration and shock from the engine and the like. Therefore, the flange used for the connection portion of these pipes tends to have an increase in strain due to heat, vibration, impact, etc. over time, such as surface opening. The gasket is required to have restoration performance that follows the distortion of the connection portion. That is, it is necessary that the gasket is deformed according to the thermal strain of the connecting portion and the like to maintain its own sealing property. However, although soft mica has high sealing properties, it has relatively low stability. As a result, when the strain is excessive, it is difficult to maintain a sufficiently high sealing property with a conventional gasket using soft mica.

An object of the present invention is to solve the above-mentioned problems, and in particular, by combining high sealing property and high resilience, sufficient sealing property is provided regardless of distortion of the connection portion due to heat, vibration, and impact. The purpose is to provide a gasket that can be maintained high.

The gasket in one aspect of the invention has a spirally wound sealing material. This sealing material includes soft mica layers and hard mica layers alternately laminated in the radial direction.

The sealing material may have a metal foil at least on the inner peripheral portion. The sealing material may contain a soft mica layer on the innermost side in the radial direction. The sealing material may include a base layer in which soft mica is laminated on the front surface and hard mica is laminated on the back surface. This base layer may be formed into an annular shape by being wound in a spiral shape and then pressed in the axial direction.

In the above-mentioned gasket according to the present invention, soft mica having high sealing property and hard mica having high resilience are alternately layered. Due to this structure, this gasket has both high sealing performance and high resilience. As a result, the gasket can maintain a sufficiently high sealing property regardless of the increase in distortion of the connection portion due to heat, vibration, and impact over time.

(A) is a schematic diagram of an exhaust pipe of an automobile. (B) is a cross-sectional view of a flange connection portion included in the exhaust pipe. (A) is a plan view of the gasket according to the embodiment of the present invention, (b) is a front view, and (c) is a cross-sectional view taken along the straight line cc shown by (a). (A) is a perspective view showing a state in which a band-shaped sealing material is wound in a spiral shape. (B) is a developed view of an example of this sealing material, and (c) is a developed view of another example. (A) is an enlarged cross-sectional view of the vicinity of the gasket 25 shown in FIG. 1 (b) before the occurrence of thermal strain. (B) is an enlarged cross-sectional view of this vicinity after the occurrence of thermal strain. (A) is a schematic diagram of an apparatus for measuring the sealing property and the restorability of a gasket. In (b), the apparatus of (a) is used for each of the gasket I in which the sealing material contains only the soft mica layer, the gasket II containing only the hard mica layer, and the gasket 25 including the laminated structure of the soft mica and the hard mica. It is a table which shows the value of the leakage amount and the restoration amount obtained by the measurement used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Usage of gasket]
FIG. 1A is a schematic diagram of an exhaust pipe of an automobile. The engine 11 of the automobile 10 mixes gasoline with air and burns it, and converts the pressure of the air-fuel mixture that expands at that time into mechanical power. The air-fuel mixture 13 after combustion is discharged from the engine 11 to the outside air through the exhaust pipe 12. The exhaust pipe 12 generally includes a plurality of joints including a connection portion with the engine 11. Flange connections are typically used for these fittings.

FIG. 1B is a cross-sectional view of a flange connection portion included in the exhaust pipe 12. The "flange connection portion" refers to the following pipe connection structure. At the openings of the pipes 21 and 22 to be connected, "flange" (an annular member having an inner diameter equal to the opening of the pipe and an outer diameter larger than the pipe) 23 and 24 called "flange" are coaxially provided. There is. A state in which a gasket 25 is sandwiched between the flange 23 of one pipe 21 (hereinafter referred to as "first flange") and the flange 24 of the other pipe 22 (hereinafter referred to as "second flange"). It is fastened by a bolt 26 and a nut 27. The gasket 25 is formed by molding a sealing material in an annular shape, and is embedded in an annular groove carved on the surface of the first flange 23. As the sealing material, a substance having a high sealing ability, that is, a sealing property for the fluid passing through the pipes 21 and 22, is selected. Since the high-temperature (about 800 degrees Celsius) gas 13 immediately after combustion flows through the exhaust pipe 12 of the automobile 10, particularly the connection portion with the engine 11, a sealing material having high heat resistance is required for the gasket 25.

[Gasket structure]
FIG. 2A is a plan view of the gasket 25 according to the embodiment of the present invention, FIG. 2B is a front view, and FIG. 2C is a cross-sectional view taken along the straight line cc shown in FIG. be. The gasket 25 has a thin annular shape. The sealing material contains soft mica (phlogopite, KMg ₃ (AlSi ₃ ) O ₁₀ (OH) ₂ ) and hard mica (muscovite, KAl ₂ (AlSi ₃ ) O ₁₀ (OH) ₂ ). In particular, as shown in FIG. 2 (c), they form independent layers 31 and 32, respectively. The soft mica layer 31 and the hard mica layer 32 are alternately arranged in the radial direction of the gasket 25 (horizontal direction in FIG. 2C). The mica layers 31 and 32 are bonded by a binder such as a silicone resin adhesive (not shown). Further, on the inner peripheral side of the gasket 25, a metal foil 33 is inserted between the mica layers 31 and 32. The metal foil 33 is, for example, a stainless steel foil, which serves to reinforce the laminated structure of mica and maintain the annular shape of the entire gasket 25.

[Manufacturing method of gasket]
FIG. 3A is a perspective view showing a state in which the band-shaped sealing material is spirally wound. The gasket 25 belongs to the spiral shape and is manufactured by using the band-shaped sealing material 30, for example, as follows. The sealing material 30 includes, for example, a base layer in which soft mica paper 31 and hard mica paper 32 are bonded to each other one by one. "Mica paper" refers to paper made by crushing mica raw ore. The soft mica paper 31 and the hard mica paper 32 have the same thickness. The band of the sealing material 30 is spirally wound, for example, in three layers with the soft mica layer 31 inside, fitted into an annular mold, and then pressed in the axial direction (press molding). ). As a result, the entire sealing material 30 is solidified into an annular shape, and inside, the soft mica layer 31 and the hard mica layer 32 have a zigzag shape in the axial direction of the gasket 25 (vertical direction in FIG. 2C). It bends. Due to this bending, the mica layers 31 and 32 are firmly bonded to each other, and the entire sealing material 30 retains the desired annular shape.

FIG. 3B is a developed view of an example of the sealing material 30, and FIG. 3C is a developed view of another example. The zigzag shape of the soft mica layer 31 and the hard mica layer 32 is formed by the mica layers 31 and 32 following the bending of the metal foil 33 during press molding. As shown in FIG. 3B, the metal foil 33 overlaps the soft mica paper 31 at the end portion of the band-shaped sealing material 30 located inside when wound in a spiral shape. .. When the sealing material 30 is spirally wound in this state, the hard mica paper 32 overlaps the metal foil 33. In this way, the metal leaf 33 is sandwiched between the soft mica paper 31 and the hard mica paper 32. In addition, as shown in FIG. 3C, the metal foil 33 may be sandwiched between mica papers over the entire length of the sealing material 30. The mass ratio of the metal foil 33 to the mica layers 31 and 32 is limited so that the presence of the metal foil 33 does not impair the sealing property and the restorability of the gasket 25. For example, when the metal foil 33 is a stainless steel foil, the total mass of the soft mica paper 31 and the hard mica paper 32 is limited to three times or more the mass of the metal foil 33. Therefore, the metal leaf 33 contained over the entire length as shown in FIG. 3 (c) is in the axial direction (vertical direction in the figure) than the metal leaf 33 contained only in the end portion as shown in FIG. 3 (b). ) Is narrow.

[Necessity of stability]
FIG. 4A is an enlarged cross-sectional view of the vicinity of the gasket 25 shown in FIG. 1B before the occurrence of thermal strain. While the temperature of the exhaust pipe 12 is sufficiently low, the fastening pressure between the bolt 26 and the nut 27 causes the two flanges 23 and 24 to come into close contact with each other without a gap, and the gasket 25 is pushed into the groove of the first flange 23. Has been done. As a result, the sealing property between the gasket 25 and the second flange 24 is sufficiently high.

FIG. 4B is an enlarged cross-sectional view of the vicinity of the gasket 25 shown in FIG. 1B after the occurrence of thermal strain. While a high-temperature gas is flowing through the exhaust pipe 11 with the operation of the engine 11, the heat released by the gas causes thermal expansion in the pipes 21 and 22. When the inflow of gas into the exhaust pipe 12 is stopped by stopping the engine 11, the pipes 21 and 22 contract with cooling. Thermal strain generally occurs in the pipes 21 and 22 due to the repetition of this thermal expansion and contraction due to cooling. If the vibrations generated by the engine 11 or the vibrations received from the outside while the automobile 10 is running, or the deformation of the pipes 21 and 22 due to the impact is excessive, the flanges 23 and 24 are spaced apart from each other and the gap 40 is formed. Occurs (opening of the surface). If the contact pressure between the gasket 25 and the second flange 24 drops excessively with the appearance of the gap 40, the sealing property against gas is impaired. For the purpose of preventing this, the gasket 25 has high resilience. Stability refers to the ability to return to the original shape as the external pressure decreases from the state of being deformed by receiving external pressure. When the flanges 23 and 24 are in contact with each other without a gap as shown in FIG. 4A, the gasket 25 is contracted in the axial direction of the gasket 25 due to the pressure from the second flange 24. Even if a surface opening as shown in FIG. 4B occurs between the flanges 23 and 24 due to distortion of the pipes 21 and 22 due to heat, vibration, and impact, the resilience of the gasket 25 should be sufficiently high. For example, the gasket 25 expands in the axial direction in response to a decrease in pressure from the second flange 24, protrudes from the groove of the first flange 23, and maintains the contact pressure with the second flange 24 at a sufficiently high level. In this way, the sealing property between the gasket 25 and the second flange 24 is maintained sufficiently high regardless of the surface opening between the flanges 23 and 24.

[Both sealing and stability]
As shown in FIG. 2 (c), the gasket 25 includes a hard mica layer 32 in addition to the soft mica layer 31. Due to this two-layer structure, the gasket 25 exhibits sufficiently high resilience in addition to high sealing property, as described below.

FIG. 5A is a vertical cross-sectional view of an apparatus for measuring the sealing property and the restorability of the gasket. The device includes a pressurizing table 50, flange connections 51 and 52, a gasket 53, and a sealing frame 54. The pressurizing table 50 is formed by supporting two flat steel plates 501 and 502 horizontally with an interval in the vertical direction. This interval is variable, and the amount of change can be measured by two dial gauges 503. The flange connecting portions 51 and 52 are sandwiched between two steel plates 501 and 502 of the pressurizing table 50. The lower flange 51 is provided with a flow path 511 that penetrates from the side surface to the upper surface. This flow path 511 is connected to the compressor through a flow meter (for example, a mass flow meter). Compressed air is sent from this compressor through the flow meter and the flow path 511 into the gap between the flange connecting portions 51 and 52. The gasket 53 is sandwiched between the flange connecting portions 51 and 52 and embedded in an annular groove carved on the upper surface of the lower flange 51. Since the upper surface of the gasket 53 is designed to be higher than the upper surface of the lower flange 51, the upper flange 52 contacts only the upper surface of the gasket 53 and is separated from the upper surface of the lower flange 51. The sealing frame 54 is an annular member and surrounds the gaps between the flange connecting portions 51 and 52. An O-ring (not shown) is sandwiched between the sealing frame 54 and the flange connecting portions 51 and 52 to prevent compressed air from leaking from the gap between the flange connecting portions 51 and 52. The sealing frame 54 is provided with one radial through hole (not shown). The compressed air leaking from the gap between the flange connecting portions 51 and 52 is designed to escape to the outside air only through this through hole.

The sealing property is measured by the following procedure. The flange connecting portions 51 and 52 are fastened with a constant pressure by a clamp (not shown). Compressed air is sent from the compressor to the gap between the flange connecting portions 51 and 52 through the flow path 511 of the lower flange 51, and a constant pressure is applied to the gap for a certain period of time. If compressed air leaks from the gap through the gasket 53 during this period, the flow rate (leakage amount) is measured by a flow meter.

The stability measurement is performed by the following procedure. First, by pressurizing the two steel plates 501 and 502 of the pressurizing table 50 with a press machine, a constant pressure in the axial direction is applied to the flange connecting portions 51 and 52 for a certain period of time. As a result, the gasket 53 is compressed in the axial direction. After that, when the pressure is released, the gasket 53 expands, and the steel plate 501 on the upper side of the pressurizing table 50 is lifted accordingly. This amount of increase, that is, the amount of restoration of the gasket 53 is measured using the dial gauge 503.

FIG. 5B shows FIG. 5 for each of the gasket I in which the sealing material contains only the soft mica layer, the gasket II containing only the hard mica layer, and the gasket 25 including the laminated structure of the soft mica and the hard mica. It is a table which shows the value of the leakage amount and the restoration amount obtained by the measurement using the apparatus of (a). Five types of samples were produced for each of the gaskets I, II and 25, and the leakage amount and the restoration amount were measured for each sample. Gasket I had an average leakage amount of less than 10 cc / min between samples, but an average restoration amount of less than 0.1 mm. The average value of leakage between the samples of Gasket II reached about 200 cc / min, which was more than 10 times that of Gasket I. This means that Gasket II has a lower sealing property than Gasket I. However, on the other hand, the average value of the amount of restoration between the samples of Gasket II reached about 0.14 mm, which was about twice that of Gasket I. This means that Gasket II has higher resilience than Gasket I. That is, although hard mica is inferior in sealing property to soft mica, it is excellent in resilience. In the gasket 25 according to the embodiment of the present invention, the average value of the leakage amount between the samples was about 40 cc / min, and the average value of the restored amount was about 0.14 mm. That is, although the sealing property of the gasket 25 is not as high as that of the gasket I, the gasket 25 is sufficiently higher than the gasket II and has the same high resilience as the gasket II. This indicates that the two-layer structure of soft mica and hard mica has not only the high sealing property of soft mica but also the high resilience of hard mica.

[Advantages of Embodiment]
The gasket 25 according to the above embodiment of the present invention contains both soft mica having high sealing property and hard mica having high resilience, and in particular, each of them alternately forms layers 31 and 32. Due to this two-layer structure, the gasket 25 has high resilience in addition to high sealing performance. As a result, even if a surface opening occurs between the flanges 23 and 24 due to deformation of the pipes 21 and 22 due to heat, vibration, and impact, the gasket 25 expands accordingly to the second flange. The contact pressure with 24 can be maintained, and the sealing property can be sufficiently maintained.

[Modification example]
(1) The band-shaped sealing material 30 shown in FIG. 3A is made by laminating soft mica paper 31 and hard mica paper 32 one by one. The sealing material according to the embodiment of the present invention is not limited to this structure, but has a structure in which a soft mica layer and a hard mica layer are independently contained, and the advantages, sealing properties and restorability of each are sufficiently high. Anything is fine. For example, instead of alternately arranging the soft mica layer and the hard mica layer one layer at a time in the radial direction of the gasket 25, for example, for every three layers of one layer, two layers of the soft mica layer are stacked. The ratio of the number of layers between the layers and the hard mica layer may be set to other than 1: 1. In addition, the thickness of mica paper may be different between soft mica and hard mica.

(2) The sealing material 30 shown in FIGS. 3 (b) and 3 (c) includes a metal foil 33 as a reinforcing material. In addition, the metal leaf 33 may be omitted if sufficient strength and shape accuracy can be maintained with mica paper alone.

25 Gasket 30 Sealing material 31 Soft mica layer 32 Hard mica layer 33 Metal leaf

Claims (3)

A gasket with a spirally wound sealing material.
The sealing material is
Includes soft mica layers and hard mica layers stacked alternately in the radial direction,
The soft mica layer is located on the innermost side in the radial direction of the sealing material.
A gasket characterized by that . The gasket according to claim 1, wherein the sealing material has at least a metal foil on the inner peripheral portion. The sealing material is
Includes a base layer with soft mica laminated on the front surface and hard mica laminated on the back surface.
The gasket according to claim 1 or 2 , wherein the base layer is formed into an annular shape by being wound in a spiral shape and then pressed in an axial direction.

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