Composite seal material

Abstract

This composite seal material (1) comprises: a first seal member (10) disposed in an annular shape around a central axis (a1); and a second seal member (20) that is disposed in an annular shape so as to circumscribe the first seal member (10) and that is located on the outer side of the first seal member (10). The second seal member (20) includes, on the radially outer surface thereof, an 11th annular protrusion section (211) and a 12th annular protrusion section (212) that protrude radially outward. A surface between the 11th annular protrusion section (211) and the 12th annular protrusion section (212) includes a recess section (213) that is recessed radially inward. This composite seal material (1) makes it possible to maintain sealing properties between the first seal member (10) and the second seal member (20) even after heat cycling.

Description

Composite sealing material

[0001] The present invention relates to a structure of a composite sealing material.

[0002] For example, as a conventional composite sealing material, one disclosed in Japanese Unexamined Patent Application Publication No. 2024-139045 (Patent Document 1) can be mentioned. This composite sealing material employs a composite structure of resin and rubber aiming at low gas permeability. The second sealing member (made of synthetic resin) positioned outside the composite sealing member includes a first arm portion and a second arm portion provided so as to sandwich the outside of the first sealing member (made of rubber) positioned on the inner side in the axial direction of a shaft. When the angle at which the inner side of the first arm intersects the inner side of the second arm is α1 degrees, and the angle at which the outer side of the first arm intersects the outer side of the second arm is α2 degrees, a configuration that satisfies α1 > α2 is employed.

[0003] Japanese Unexamined Patent Application Publication No. 2024-139045

[0004] In the composite sealing material with the above structure, although the amount of gas leakage is small at normal temperature, there is concern that sealing performance may decrease after heat cycles are applied. When the composite sealing material after heat cycles is checked, the composite sealing material undergoes torsional deformation, and there have been cases where sufficient sealing performance is not obtained between the first sealing member (made of rubber) and the second sealing member (made of synthetic resin).

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a composite sealing material having a configuration capable of maintaining sealing performance between the first sealing member and the second sealing member even after a heat cycle.

[0006] [1]: A composite sealing material according to one aspect of the present disclosure includes: a first sealing member annularly arranged around a central axis; and a second sealing member annularly arranged so as to circumscribe the first sealing member and positioned outside the first sealing member, wherein the second sealing member includes an 11th annular convex portion and a 12th annular convex portion protruding in an outer diameter direction on a surface in the outer diameter direction, and the outer surface between the 11th annular convex portion and the 12th annular convex portion includes a concave portion recessed toward an inner diameter side.

[0007] [2] The composite sealing material according to [1], wherein the first sealing member and the second sealing member have shapes that are symmetrical in the direction of the central axis with respect to a virtual plane perpendicular to the central axis, and the 11th annular projection and the 12th annular projection are provided at positions that are symmetrical with respect to the virtual plane.

[0008] [3]: The composite sealing material according to [1] or [2], wherein the second sealing member includes a 21st annular projection and a 22nd annular projection projecting in the direction in which the central axis extends on the surface in which the central axis extends, the 11th annular projection and the 21st annular projection are located on one side in the direction in which the central axis extends, the surface of the 11th annular projection and the surface of the 21st annular projection are connected so as to be recessed inward, the 12th annular projection and the 22nd annular projection are located on the other side in the direction in which the central axis extends, and the surface of the 12th annular projection and the surface of the 22nd annular projection are connected so as to be recessed inward.

[0009] [4] The composite sealing material according to [3], wherein the first sealing member and the second sealing member have shapes that are symmetrical in the direction of the central axis with respect to a virtual plane perpendicular to the central axis, and the 21st annular projection and the 22nd annular projection are provided at positions that are symmetrical with respect to the virtual plane.

[0010] [5] The composite sealing material according to [4], wherein the radial thickness of the second sealing member on the virtual plane is the thinnest compared to the radial thickness between the 21st annular protrusion and the 22nd annular protrusion.

[0011] [6]: The composite seal material according to any one of [1] to [5], wherein the first seal member includes a joint extending toward the second seal member, the surface of which has a first flat portion provided on one side in the direction in which the central axis extends and a second flat portion provided on the other side in the direction in which the central axis extends, a first inclined portion that gradually moves away from the center as it extends inward from the first flat portion, and a second inclined portion that gradually moves away from the center as it extends inward from the second flat portion, and the second seal member includes a receiving recess that receives the joint in accordance with the outer shape of the joint of the first seal member.

[0012] [7] The composite sealing material according to [6], wherein the first sealing member and the second sealing member have shapes that are symmetrical in the direction of the central axis with respect to a virtual plane perpendicular to the central axis, the first flat portion and the second flat portion are provided in positions that are symmetrical with respect to the virtual plane, the first inclined portion is provided so as it moves inward from the first flat portion, it gradually moves away from the virtual plane, and the second inclined portion is provided so as it moves inward from the second flat portion, it gradually moves away from the virtual plane.

[0013] [8]: The composite sealing material according to any one of [1] to [7], wherein the first sealing member is made of rubber, and the second sealing member is made of a synthetic resin that is harder than the first sealing member.

[0014] [9]: A composite sealing material in another aspect of the Disclosure comprising: a first sealing member arranged annularly around a central axis; and a second sealing member arranged annularly inscribed within the first sealing member and located inside the first sealing member, wherein the second sealing member includes an eleventh annular projection and a twelfth annular projection projecting in the inward direction on its inward diameter surface, and the surface between the eleventh annular projection and the twelfth annular projection includes a recess recessed toward the outward diameter.

[0015] This composite sealing material makes it possible to provide a composite sealing material that has a configuration that can maintain sealing performance between the first sealing member and the second sealing member even after a heat cycle.

[0016] This is a perspective view of the composite seal material of Embodiment 1. This is a plan view of the composite seal material of Embodiment 1. This is a cross-sectional view taken along the line III-III in Figure 2. This is an enlarged cross-sectional view of the composite seal material of Embodiment 1. This is a cross-sectional view showing the composite seal material of Embodiment 1 in use (no load). This is a cross-sectional view showing the composite seal material of Embodiment 1 in use (compressed). This is a cross-sectional view showing the composite seal material of Embodiment 1 in use (heated). This is a cross-sectional view of the composite seal material of Embodiment 2 corresponding to the view taken along the line III-III in Figure 2. This is a plan view of the composite seal material of Embodiment 3.

[0017] The composite sealing material in this embodiment will be described below with reference to the figures. In each embodiment described below, when the number, quantity, etc. are mentioned, the scope of the present invention is not necessarily limited to the number, quantity, etc., unless otherwise specified. Also, the same reference numeral will be used for the same part or equivalent part, and redundant explanations will not be repeated. The cross-sectional views shown in Figures 3 to 9 are cross-sections viewed along a virtual plane containing the central axis a1. In the figures, the direction in which the central axis a1 extends means the upward and downward directions.

[0018] (Embodiment 1: Composite sealing material 1) The composite sealing material 1 of this embodiment will be described with reference to Figures 1 to 3.

[0019] The composite seal material 1 has an annular shape overall. The composite seal material 1 comprises a first seal member 10 arranged annularly around a central axis a1, and a second seal member 20 arranged annularly so as to be circumstantial to the first seal member 10 and located outside the first seal member 10. In this embodiment, the first seal member 10 is made of rubber, and the second seal member 20 is made of a synthetic resin that is harder than the first seal member 10. The combination of materials used for the first seal member 10 and the second seal member 20 can be selected as appropriate and is not limited to the combination in this embodiment.

[0020] The rubber used in the first sealing member 10 can be either natural rubber or synthetic rubber.

[0021] A synthetic resin that is harder than the first sealing member 10 and used in the second sealing member 20 is preferably a fluoroelastomer + resin (an engineering plastic mainly composed of PPS (polyphenylene sulfide resin)). For example, examples of fluororesins include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluoroethylene propene copolymer), ETFE (ethylene tetrafluoroethylene copolymer), PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), and PMP (polymethylpentene).

[0022] Examples of resin materials include PPS (polyphenylene sulfide), PI (polyimide), PAI (polyamide-imide), PEI (polyetherimide), PAI (polyamide-imide), PBI (polybenzimidazole), PEK (polyether ketone), PEEK (polyether ether ketone), UHPE (ultra-high molecular weight polyethylene), LCP (liquid crystal polymer), and PGA (polyglycolic acid).

[0023] (Specific Shape of the Second Seal Member 20) Referring to Figure 3, the specific shape of the second seal member 20 will be described using its cross-sectional shape. The second seal member 20 includes an 11th annular projection 211 and a 12th annular projection 212 projecting in the outer diameter direction on its outer diameter surface. The outer surface between the 11th annular projection 211 and the 12th annular projection 212 includes a recess 213 that is recessed in the inner diameter direction.

[0024] Furthermore, the second sealing member 20 preferably includes a 21st annular projection 221 and a 22nd annular projection 222 projecting in the direction in which the central axis a1 extends, on the surface facing the direction in which the central axis a1 extends. The 11th annular projection 211 and the 21st annular projection 221 are located on one side (upper side in Figure 3) in the direction in which the central axis a1 extends, and the surfaces of the 11th annular projection 211 and the 21st annular projection 221 are connected so as to be recessed inward (region RU). The 12th annular projection 212 and the 22nd annular projection 222 are located on the other side (lower side in Figure 3) in the direction in which the central axis a1 extends, and the surfaces of the 12th annular projection 212 and the 22nd annular projection 222 are connected so as to be recessed inward (region RD).

[0025] The second sealing member 20 includes a receiving recess 230 that receives the connecting portion 11 of the first sealing member 10 in accordance with its external shape. The surface shape of the receiving recess 230 is molded to conform to the external shape of the connecting portion 11 of the first sealing member 10.

[0026] (Specific shape of the first sealing member 10) The first sealing member 10 includes a connecting portion 11 that extends toward the second sealing member 20. The surface of the connecting portion 11 has a first flat portion 111 provided on one side (upper side in Figure 3) in the direction in which the central axis a1 extends, a second flat portion 112 provided on the other side (lower side in Figure 3) in the direction in which the central axis a1 extends, a first inclined portion 113 that gradually moves away from the center as it extends inward from the first flat portion 111, and a second inclined portion 114 that gradually moves away from the center as it extends inward from the second flat portion 112.

[0027] A curved surface 115 that protrudes toward the inner diameter is provided on the surface of the first sealing member 10 on the side of the central axis a1.

[0028] In the above-described embodiment of the second sealing member 20, the second sealing member 20 preferably has a shape that is symmetrical in the direction of the central axis a1 with respect to a virtual plane VP that is perpendicular to the central axis a1. The 11th annular projection 211 and the 12th annular projection 212 are preferably provided at positions that are symmetrical with respect to the virtual plane VP. The 21st annular projection 221 and the 22nd annular projection 222 are preferably provided at positions that are symmetrical with respect to the virtual plane VP.

[0029] In the above-described embodiment of the first sealing member 10, the first sealing member 10 preferably has a shape that is symmetrical in the direction of the central axis a1 with respect to a virtual plane VP that is perpendicular to the central axis a1. The first flat portion 111 and the second flat portion 112 preferably are provided in positions that are symmetrical with respect to the virtual plane VP. The first inclined portion 113 preferably is provided so that it gradually moves away from the virtual plane VP as it moves inward from the first flat portion 111. The second inclined portion 114 preferably is provided so that it gradually moves away from the virtual plane VP as it moves inward from the second flat portion 112.

[0030] Referring to Figure 4, the radial thickness W2 of the second sealing member 20 on the virtual plane VP is preferably set to be the thinnest compared to the radial thickness W3 between the 21st annular protrusion 221 and the 22nd annular protrusion 222.

[0031] In the second sealing member 20, the width W1 of the 21st annular projection 221 is preferably 0.1 mm or more. The first inclination angle α1 is preferably about 0° to 30°. The same applies to the 22nd annular projection 222. The recess amount d1 of the recess 213 (recess amount from the 11th annular projection 211 / 12th annular projection 212) is preferably a value greater than 0 mm. The angle α2 between the first inclined portion 113 and the second inclined portion 114 is preferably 0° to 120°.

[0032] (Installation on the device 100) Next, referring to Figures 5 to 7, the state in which the composite sealing material 1 is installed in the groove 110 provided on the side of the device 100 (when unloaded), the state when the composite sealing material 1 is compressed by the device 100, and the state when heated will be described.

[0033] As shown in Figure 5, in the unloaded state with the composite sealing material 1 installed in the groove 110 provided on the side of the device 100, the flange 200 first contacts the 21st annular projection 221 of the second sealing member 20. Note that the shape of the groove 110 is not limited to the ordinary square groove shown in the figure, and known grooves such as dovetail grooves, single dovetail grooves, and L-shaped grooves can be used.

[0034] As shown in Figure 6, when the flange 200 is in contact with the device 100, the first sealing member 10 and the second sealing member 20 of the composite sealing material 1 are compressed inside the groove 110. In this state, the composite sealing material 1 is greatly compressed in the vertical direction and expands in the horizontal direction inside the groove 110, as shown in the figure.

[0035] The 11th annular projection 211 and the 12th annular projection 212 of the second sealing member 20 come into contact with the outer surface 110a of the groove 110 and undergo compression deformation. Furthermore, the recess 213 located between the 11th annular projection 211 and the 12th annular projection 212 also bulges out toward the outer surface 110a and comes into contact with it, undergoing compression deformation.

[0036] The 21st annular projection 221 and the 22nd annular projection 222 are compressed and deformed by the flange 200 and the bottom surface 110b of the groove 110, and also compress the joint portion 11 of the first sealing member 10. As a result, the joint portion 11 pushes the first sealing member 10 toward the inner side surface 110c of the groove 110 along the first inclined portion 113 and the second inclined portion 114, causing the curved surface 115 to be pressed against the inner side surface 110c.

[0037] As shown in Figure 7, even when the first sealing member 10 is heated while it remains in the compressed state shown in Figure 6, the first sealing member 10 and the second sealing member 20 are pressed against the inner wall surface of the groove 110.

[0038] In particular, as described above, the 11th annular projection 211 and the 12th annular projection 212 of the second sealing member 20 abut against the outer surface 110a of the groove 110 and undergo compression deformation. Furthermore, the recess 213 located between the 11th annular projection 211 and the 12th annular projection 212 also bulges out and abuts against the outer surface 110a, undergoing compression deformation. This makes it possible to prevent the composite sealing material 1 from rotating (twisting) in the direction of arrow R in Figure 7.

[0039] Furthermore, as shown in Figure 4, by configuring the second sealing member 20 so that its radial thickness W2 on the virtual plane VP is the thinnest compared to the radial thickness W3 between the 21st annular protrusion 221 and the 22nd annular protrusion 222, it is possible to facilitate bulging toward the outer surface 110a of the recess 213 and prevent rotation (twisting) of the composite sealing material 1 in the direction of arrow R in Figure 7.

[0040] Furthermore, the 21st annular projection 221 and the 22nd annular projection 222 are also compressed and deformed by the flange 200 and the bottom surface 110b of the groove 110, which also prevents the composite seal material 1 from rotating (twisting) in the direction of arrow R in Figure 7.

[0041] Furthermore, the coupling portion 11 pushes the first seal member 10 toward the inner side surface 110c of the groove 110 along the first inclined portion 113 and the second inclined portion 114, and the curved surface 115 is pressed against the inner side surface 110c. This also makes it possible to prevent rotation (twisting) of the composite sealing material 1 in the direction of arrow R in FIG. 7.

[0042] As described above, according to the composite sealing material 1 of the present embodiment, the sealing mechanism adopting a double structure of the first seal member 10 made of rubber and the second seal member 20 made of synthetic resin can achieve higher sealing performance than that of each single material.

[0043] Furthermore, by configuring the first seal member 10 to include the coupling portion 11 extending to be inserted into the second seal member 20, high restoring performance can be obtained. Specifically, when the composite sealing material 1 is heated and cooled, the second seal member 20 made of synthetic resin may undergo torsional deformation during the thermal expansion and contraction process. By adopting the shape of the present disclosure described above, the composite sealing material conforms better to the inner wall surface of the groove during compression, thereby enabling suppression of torsional deformation.

[0044] Furthermore, by providing the 21st annular protrusion 221 and the 22nd annular protrusion 222 on the second seal member 20 made of synthetic resin, even when the composite sealing material 1 undergoes large thermal expansion due to heating, adjustment is performed to prevent the contact width between the flange 200 and the composite sealing material 1 and between the composite sealing material 1 and the bottom surface 110b of the groove 110 from becoming excessively large (by generating the gap S (see FIG. 7)), thereby making it easy to maintain the sealing performance of the composite sealing material 1 after cooling. This is because if the contact area is excessively large, the contact area will similarly remain large even when the temperature returns to normal temperature, resulting in a decrease in surface pressure, and this configuration avoids a decrease in sealing performance.

[0045] In the composite sealing material 1 according to the first embodiment described above, as the most preferable embodiment, in addition to the configuration in which (i) the second seal member 20 is provided with an eleventh annular convex portion 211, a twelfth annular convex portion 212, and a concave portion 213, the following configurations are further included: (ii) a configuration in which the radial thickness W2 of the second seal member 20 on the virtual plane VP is set to be the smallest when compared with the radial thickness W3 between a twenty-first annular convex portion 221 and a twenty-second annular convex portion 222; (iii) a configuration in which the second seal member 20 is provided with the twenty-first annular convex portion 221 and the twenty-second annular convex portion 222; and (iv) a configuration in which the first seal member 10 is provided with a first inclined portion 113 and a second inclined portion 114. However, it is also possible to appropriately select the configurations from (ii) to (iv) and adopt a configuration that combines them with (i).

[0046] Further, among the configurations disclosed in (i) to (iv), only any one configuration may be employed, or a configuration in which any configurations are appropriately selected and arbitrarily combined may be employed.

[0047] (Embodiment 2: Composite sealing material 1A) A composite sealing material 1A according to Embodiment 2 will be described with reference to Fig. 8. The composite sealing material 1 according to Embodiment 1 includes a first seal member 10 annularly arranged around a central axis a1, and a second seal member 20 annularly arranged so as to circumscribe the first seal member 10 and located outside the first seal member 10. On the other hand, the composite sealing material 1A of the present embodiment has the second seal member 20A annularly arranged so as to inscribe the first seal member 10A and located inside the first seal member 10A. That is, the first seal member 10A has a form in which the inner diameter side and the outer diameter side are inverted compared with the form of the composite sealing material 1 according to Embodiment 1.

[0048] (Specific shape of second seal member 20A) A specific shape of the second seal member 20A will be described using a cross-sectional shape with reference to Fig. 8. The second seal member 20A includes, on an inner diameter-direction surface, an eleventh annular convex portion 211A and a twelfth annular convex portion 212A that protrude in the inner diameter direction. A surface between the eleventh annular convex portion 211A and the twelfth annular convex portion 212A includes a concave portion 213A recessed toward the outer diameter side.

[0049] Furthermore, the second sealing member 20A preferably includes a 21st annular projection 221A and a 22nd annular projection 222A projecting in the direction in which the central axis a1 extends, on the surface facing the direction in which the central axis a1 extends. The 11th annular projection 211A and the 21st annular projection 221A are located on one side (upper side in Figure 3) in the direction in which the central axis a1 extends, and the surfaces of the 11th annular projection 211A and the 21st annular projection 221A are connected so as to be recessed inward (region RU). The 12th annular projection 212A and the 22nd annular projection 222A are located on the other side (lower side in Figure 3) in the direction in which the central axis a1 extends, and the surfaces of the 12th annular projection 212A and the 22nd annular projection 222A are connected so as to be recessed inward (region RD).

[0050] The second sealing member 20A includes a receiving recess 230A that receives the connecting portion 11A of the first sealing member 10A in accordance with its external shape. The surface shape of the receiving recess 230A is molded to conform to the external shape of the connecting portion 11A of the first sealing member 10A.

[0051] (Specific shape of the first sealing member 10A) The first sealing member 10A includes a connecting portion 11A that extends toward the second sealing member 20A. The surface of the connecting portion 11A has a first flat portion 111A provided on one side (upper side in Figure 3) in the direction in which the central axis a1 extends, a second flat portion 112A provided on the other side (lower side in Figure 3) in the direction in which the central axis a1 extends, a first inclined portion 113A that gradually moves away from the center as it extends outward from the first flat portion 111A, and a second inclined portion 114A that gradually moves away from the center as it extends outward from the second flat portion 112A.

[0052] The outer surface of the first sealing member 10 is provided with a curved surface 115A that protrudes toward the outer diameter.

[0053] In the above-described form of the second sealing member 20A, it is preferable that the second sealing member 20A has a shape that is symmetrical in the direction of the central axis a1 with respect to a virtual plane VP that is perpendicular to the central axis a1. It is preferable that the 11th annular projection 211A and the 12th annular projection 212A are provided at positions that are symmetrical with respect to the virtual plane VP. It is preferable that the 21st annular projection 221A and the 22nd annular projection 222A are provided at positions that are symmetrical with respect to the virtual plane VP.

[0054] In the above-described form of the first sealing member 10A, the first sealing member 10A preferably has a shape that is symmetrical in the direction of the central axis a1 with respect to a virtual plane VP that is perpendicular to the central axis a1. The first flat portion 111A and the second flat portion 112A are preferably provided in positions that are symmetrical with respect to the virtual plane VP. The first inclined portion 113A is preferably provided so that it gradually moves away from the virtual plane VP as it moves inward from the first flat portion 111A. The second inclined portion 114A is preferably provided so that it gradually moves away from the virtual plane VP as it moves inward from the second flat portion 112A.

[0055] For other components, it is preferable to adopt the same specifications as the composite sealing material 1 in Embodiment 1.

[0056] As described above, the composite sealing material 1A in this embodiment can also be used to obtain the same effects and advantages as those explained using Figures 5 to 7.

[0057] (Embodiment 3: Composite sealant 1B) The composite sealant 1 and composite sealant 1A in Embodiments 1 and 2 above are assumed to have an annular shape as a whole when viewed from above. However, the composite sealant of this disclosure is not limited to an annular shape. For example, the composite sealant 1B shown in Figure 9 has a rectangular annular shape as a whole. Even with this shape of composite sealant 1B, the same effects and advantages as the composite sealant described above can be obtained.

[0058] In the embodiments described above, the composite sealing material is shown in a form that is symmetrical with respect to the virtual plane VP. However, it is not necessarily limited to a form that is symmetrical with respect to the virtual plane VP. It is also possible to adopt an asymmetrical composite sealing material form to match the shape of the groove used (such as a regular groove (square groove), dovetail groove, single dovetail groove, L-shaped groove, etc.).

[0059] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of equivalents of the claims are intended.

[0060] 1, 1A, 1B Composite sealing material, 10, 10A First sealing member, 11, 11A Joint, 20, 20A Second sealing member, 100 Device, 110 Groove, 110a Outer side surface, 110b Bottom surface, 110c Inner side surface, 111, 111A First flat section, 112, 112A Second flat section, 113, 113A First inclined section, 114, 114A Second inclined section, 115, 115A Curved surface, 200 Flange, 211, 211A Eleventh annular protrusion, 212, 212A Twelfth annular protrusion, 213, 213A Recess, 221, 221A Twenty-first annular protrusion, 222, 222A Twenty-second annular protrusion, 230, 230A Receiving recess.

Claims

1. A composite sealing material comprising: a first sealing member arranged in an annular manner around a central axis; and a second sealing member arranged in an annular manner so as to be circumstantial to the first sealing member and located outside the first sealing member, wherein the second sealing member includes an eleventh annular projection and a twelfth annular projection projecting in the outer diameter direction on its outer diameter surface, and the surface between the eleventh annular projection and the twelfth annular projection includes a recess that is recessed toward the inner diameter side.

2. The composite sealing material according to claim 1, wherein the first sealing member and the second sealing member have shapes that are symmetrical in the direction of the central axis with respect to a virtual plane perpendicular to the central axis, and the 11th annular projection and the 12th annular projection are provided at positions that are symmetrical with respect to the virtual plane.

3. The composite sealing material according to claim 1, wherein the second sealing member includes a 21st annular projection and a 22nd annular projection projecting in the direction in which the central axis extends on the surface facing the direction in which the central axis extends, the 11th annular projection and the 21st annular projection are located on one side facing the direction in which the central axis extends, the surface of the 11th annular projection and the surface of the 21st annular projection are connected so as to be recessed inward, and the 12th annular projection and the 22nd annular projection are located on the other side facing the direction in which the central axis extends, the surface of the 12th annular projection and the surface of the 22nd annular projection are connected so as to be recessed inward.

4. The composite sealing material according to claim 3, wherein the first sealing member and the second sealing member have shapes that are symmetrical in the direction of the central axis with respect to a virtual plane perpendicular to the central axis, and the 21st annular projection and the 22nd annular projection are provided at positions that are symmetrical with respect to the virtual plane.

5. The composite sealing material according to claim 4, wherein the radial thickness of the second sealing member on the virtual plane is the thinnest compared to the radial thickness between the 21st annular protrusion and the 22nd annular protrusion.

6. The composite seal material according to claim 1, wherein the first seal member includes a connecting portion extending toward the second seal member, the surface of the connecting portion having a first flat portion provided on one side in the direction in which the central axis extends and a second flat portion provided on the other side in the direction in which the central axis extends, a first inclined portion that gradually moves away from the center as it extends inward from the first flat portion, and a second inclined portion that gradually moves away from the center as it extends inward from the second flat portion, and the second seal member includes a receiving recess that receives the connecting portion in accordance with the outer shape of the connecting portion of the first seal member.

7. The composite sealing material according to claim 6, wherein the first sealing member and the second sealing member have shapes that are symmetrical in the direction of the central axis with respect to a virtual plane perpendicular to the central axis, the first flat portion and the second flat portion are provided at positions that are symmetrical with respect to the virtual plane, the first inclined portion is provided so as it extends inward from the first flat portion, it gradually moves away from the virtual plane, and the second inclined portion is provided so as it extends inward from the second flat portion, it gradually moves away from the virtual plane.

8. The composite sealing material according to claim 1, wherein the first sealing member is made of rubber, and the second sealing member is made of a synthetic resin that is harder than the first sealing member.

9. A composite sealing material comprising: a first sealing member arranged in an annular manner around a central axis; and a second sealing member arranged in an annular manner so as to be inscribed within the first sealing member and located inside the first sealing member, wherein the second sealing member includes an eleventh annular projection and a twelfth annular projection projecting in the inward direction on its inner diameter surface, and the surface between the eleventh annular projection and the twelfth annular projection includes a recess that is recessed toward the outer diameter side.

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