Diaphragm for air spring, and air spring

Abstract

To provide a diaphragm for an air spring capable of supplying air to a diaphragm even when a bead part is sealed between a lower member and an upper member, and an air spring.SOLUTION: A diaphragm 3 comprises a pair of annular bead parts 31, 32. The bead part 31 includes a bead inner surface 31a facing axially inward, and a ventilation passage forming part 80 is provided on the bead inner surface 31a. The air passage forming part 80 is configured to form an air passage that connects an area Ai radially inward of the bead inner surface 31a to an area Ao radially outward, between the bead inner surface 31a and an imaginary plane VP that is in contact with the bead inner surface 31a so as to be perpendicular to an axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a diaphragm used in an air spring and an air spring including the diaphragm. [Background technology]

[0002] Conventionally, air springs are installed in railway vehicles, automobiles, various industrial machines, and the like. Air springs generally have a structure in which a cylindrical diaphragm is interposed between a lower member and an upper member. The diaphragm has a pair of annular bead portions, one of which is attached to the lower member and the other to the upper member. This ensures the airtightness of the diaphragm, and its internal space acts as an air chamber, providing elasticity. Such air spring structures are described, for example, in Patent Documents 1 and 2.

[0003] The installation process for air springs involves first installing the air spring on the object to be installed, such as a railway vehicle (installation process), and then supplying air to the diaphragm (air supply process). During the installation process, the air spring is in a deflated state (punctured state), so the upper member, which has been lowered by the weight of the object to be installed, comes into contact with the lower member (see Figure 4). Meanwhile, during the air supply process, the diaphragm expands as air is filled in, putting the air spring in an inflated state, so the upper member, which has been raised by the action of internal pressure, moves away from the lower member (see Figure 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-13426 [Patent Document 2] Japanese Patent Application Publication No. 2019-108919 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors' investigation into the installation of air springs revealed that the bead portion of the diaphragm can cause problems when transitioning from a deflated state to an inflated state. More specifically, they discovered that if the bead portion becomes misaligned due to slight dimensional variations in the diaphragm, the bead portion will seal the gap between the lower and upper members that are close to each other in the deflated state (see Figure 5), preventing the supply of air to the diaphragm.

[0006] It is believed that this phenomenon of a misaligned bead portion sealing the gap between the lower and upper members is not limited to air spring installation work. Although the probability of this occurring is not high, it could also occur, for example, during maintenance work, when air is released from an inflated air spring to temporarily deflate it, and then air is supplied to return it to the inflated state.

[0007] The present disclosure has been made in consideration of the above-described circumstances, and its purpose is to provide a diaphragm for an air spring and an air spring that can supply air to the diaphragm even when a bead portion seals between a lower member and an upper member. [Means for solving the problem]

[0008] The diaphragm for an air spring of the present disclosure comprises a pair of bead portions forming an annular shape, at least one of the pair of bead portions including a bead inner surface facing axially inward, and an air passage forming portion is provided on the bead inner surface, and the air passage forming portion is configured to form an air passage that leads from a region radially inward of the bead inner surface to a region radially outward of the bead inner surface, between the bead inner surface and an imaginary plane that is in contact with the bead inner surface perpendicular to the axial direction.

[0009] The air spring of the present disclosure is configured by interposing the above-described air spring diaphragm between a lower member and an upper member. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a longitudinal cross-sectional view showing an air spring according to an embodiment of the present disclosure; [Figure 2] Vertical cross section of an air spring diaphragm [Figure 3] A plan view showing the lower plate and the inner surface of the bead [Figure 4] A longitudinal cross-sectional view showing the air spring in a deflated state during the installation process. [Figure 5] A longitudinal cross-sectional view showing the air spring in a deflated state during the installation process. [Figure 6] A side view showing a groove as an air passage forming portion. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present disclosure will be described with reference to the drawings.

[0012] FIG. 1 is a longitudinal cross-sectional view of an air spring according to this embodiment, showing half of the air spring cut along a central axis P (the same applies to FIGS. 4 and 5). As shown in FIG. 1, air spring 10 has a structure in which an air spring diaphragm 3 (hereinafter simply referred to as "diaphragm 3") is interposed between a lower member 1 and an upper member 2. Lower member 1 is disposed below upper member 2. Diaphragm 3 has a pair of annular bead portions 31 and 32. Bead portion 31 is attached to lower member 1, and bead portion 32 is attached to upper member 2, thereby ensuring the airtightness of diaphragm 3.

[0013] In this embodiment, an example is shown in which the air spring 10 is an air spring for a railway vehicle that is installed in a railway vehicle. The lower member 1 is connected to the top surface of a bogie 91, which is the attachment counterpart on the suspension side. The upper member 2 is connected to the bottom surface of a carbody 92, which is the attachment counterpart on the suspended side. The bogie 91 and the carbody 92 are shown in a simplified manner. An upper panel 6, which will be described later, is formed by a member separate from the bottom surface of the carbody 92, but may be formed by a part of the bottom surface of the carbody 92. It should be noted that the air spring of the present disclosure is not limited to air springs for railway vehicles, and may also be air springs used in automobiles, various industrial machines, etc.

[0014] Fig. 2 is a longitudinal cross-sectional view of the diaphragm 3. The diaphragm 3 is an annular membrane having a bead portion 31, a bead portion 32, and a main body portion 33 therebetween, and is formed into a cylindrical shape as a whole. The diaphragm 3 is formed from an elastic material such as rubber, and is flexible. Fig. 2 shows the cross-sectional shape of the diaphragm 3 in a state where it is assembled into the air spring 10, but the cross-sectional shape of the diaphragm 3 before it is assembled into the air spring 10 may be different.

[0015] Here, the axial direction is the direction along the central axis P, and corresponds to the height direction of the air spring 10 (the up-down direction in Figs. 1 and 2). The side closer to the internal space of the diaphragm 3 is the axially inner side, and the opposite side is the axially outer side. Therefore, the axially inner side of the bead portion 31 and the lower member 1 is the upper side, and the axially inner side of the bead portion 32 and the upper member 2 is the lower side. The radial direction is the direction perpendicular to the central axis P, and corresponds to the left-right direction in Figs. 1 and 2. The side closer to the central axis P is the radially inner side, and the side away from the central axis P is the radially outer side. The circumferential direction is the direction around the central axis P.

[0016] 2, the bead portion 31 includes a bead inner surface 31a facing inward in the axial direction, a bead bottom surface 31b facing inward in the radial direction, and a bead outer surface 31c facing outward in the axial direction. The bead inner surface 31a extends radially outward from the axially inner end of the bead bottom surface 31b, and the bead outer surface 31c extends radially outward from the axially outer end of the bead bottom surface 31b. In the diaphragm 3 assembled into the air spring 10, the bead inner surface 31a faces the internal space of the diaphragm 3, while the bead bottom surface 31b and the bead outer surface 31c are in close contact with (the bead seat portion 41 of) the lower member 1 (see FIG. 1).

[0017] A ring-shaped bead core 34 extending in the circumferential direction is embedded in each of the pair of bead portions 31, 32. The bead core 34 is formed, for example, from a bundle of bead wires and has a generally rectangular cross section. A reinforcing layer 35 is embedded in the diaphragm 3, and the reinforcing layer 35 is folded back in the bead portions 31, 32 so as to sandwich the bead core 34. In this embodiment, the reinforcing layer 35 is formed by laminating multiple plies (specifically, two plies) each made of reinforcing cords arranged in a predetermined direction and coated with rubber. Organic fibers such as nylon are preferably used for the reinforcing cords.

[0018] In this embodiment, the pair of bead portions 31, 32 have different inner diameters. The inner diameter of the bead portion 31 is smaller than the inner diameter of the bead portion 32, and the bead inner surface 31a of the bead portion 31, which has the relatively smaller inner diameter, faces the lower surface of the upper plate 6, which will be described later. In this embodiment, a so-called Mann-type diaphragm 3 is used, but this is not limited to this. Therefore, for example, the inner diameter of the bead portion 31 may be substantially the same as the inner diameter of the bead portion 32, or the inner diameter of the bead portion 31 may be larger than the inner diameter of the bead portion 32.

[0019] As shown in Figure 1, the lower member 1 has a lower surface plate 4 formed in a disk shape, with a bead portion 31 attached to its outer periphery. The lower member 1 is provided with a bead seat portion 41 to which the bead portion 31 is attached in a self-sealing manner. The internal pressure of the diaphragm 3 presses the bead portion 31 downward, causing it to come into close contact with the bead seat portion 41, thereby sealing the gap between the diaphragm 3 and the lower member 1.

[0020] The bead seat portion 41 has a tapered surface 41t that tapers axially inward. The bead bottom surface 31b of the bead portion 31 abuts against the tapered surface 41t from the radially outer side. With this configuration, even if the inner diameter of the bead portion 31 expands due to aging or other reasons, the bead portion 31 is pressed downward by the action of internal pressure and comes into close contact with the bead seat portion 41, ensuring a proper fitting pressure and maintaining a sealed state.

[0021] An elastic mechanism 5 that functions as a stopper is disposed below the lower plate 4. The elastic mechanism 5 includes a top plate 51, a bottom plate 52, and a laminated rubber body 53 sandwiched between them. The laminated rubber body 53 has a structure in which rubber as an elastic body and steel plates as rigid bodies are alternately laminated, and is formed into a cylindrical shape as a whole. In this embodiment, the rubber and steel plates are formed into ring-shaped plates parallel to the radial direction, but this is not limiting. For example, a conical stopper structure in which the rubber and steel plates are formed into a tapered cylindrical shape that tapers toward the upper side may be used. The elastic mechanism 5 may also be omitted.

[0022] The lower plate 4 is formed with a larger diameter than the top plate 51 and is configured so as to be able to fit over the top plate 51. The lower plate 4 is provided with through holes 42 for attaching fasteners 45 that fasten the lower plate 4 to the top plate 51. The through holes 42 are formed at multiple locations (six locations in this embodiment) in the circumferential direction as shown in FIG. 3. The heads of the fasteners 45 are housed in the through holes 42 so as not to protrude above the upper surface of the lower plate 4. The fasteners 45 and fasteners 63, which will be described later, are, for example, bolts.

[0023] A sliding sheet 43 is attached to the upper surface of the lower plate 4. The sliding sheet 43 is made of a material with excellent sliding properties, such as a fluororesin (e.g., PTFE). The upper surface of the sliding sheet 43 is located higher than the upper surface of the lower plate 4. Therefore, if the air spring 10 becomes deflated due to a puncture or the like during use, the upper member 2, which has descended together with the car body 92, comes into contact with the lower member 1 via the sliding sheet 43 and is supported by the elastic mechanism 5. The sliding sheet 43 reduces frictional resistance when the lower member 1 and the upper member 2 slide against each other while traveling in this state.

[0024] The sliding sheet 43 is disposed at a position that avoids the through holes 42. Furthermore, a void 44 where no sliding sheet 43 is attached is formed at at least one location in the circumferential direction. The void 44 opens to the center and outer periphery of the lower panel 4 in a plan view as shown in FIG. 3. In the example of FIG. 3(A), a sliding sheet 43 that is rectangular in plan view is disposed in each space between adjacent through holes 42 in the circumferential direction. The shape of the sliding sheet 43 is not particularly limited, and for example, a sliding sheet 43 that is arc-shaped in plan view as shown in FIG. 3(B) may be used. In FIG. 3(A), voids 44 are formed in six locations, and in FIG. 3(B), voids 44 are formed in three locations.

[0025] 1, the upper member 2 includes a disk-shaped upper surface plate 6 and a ring-shaped bead retainer 7 attached to the underside of the outer periphery of the upper surface plate 6 via a fastener 63, with the bead portion 32 mounted between them. The upper member 2 is provided with a bead seat portion 61 to which the bead portion 32 is fastened. The bead portion 32 is pressed upward by the fastening action of the fastener 63, and is brought into close contact with the bead seat portion 61, thereby sealing the gap between the diaphragm 3 and the upper member 2.

[0026] A cylindrical boss 21 is fitted into the through hole in the center of the upper plate 6. The boss 21 is connected to a compressor (not shown) and functions as an air inlet for supplying air to the diaphragm 3. The upper plate 6 is formed with a larger diameter than the lower plate 4. The lower surface of the upper plate 6, which faces the upper surface of the lower plate 4, is formed with a sliding plate 62. Therefore, in the deflated state, the lower member 1 and the upper member 2 abut via the sliding sheet 43 and the sliding plate 62 (see FIG. 4). The sliding plate 62 is made of a material with excellent sliding properties, such as stainless steel, and absorbs horizontal displacement with little resistance in a deflated state caused by a puncture or other condition during use. The upper plate 6 is not limited to a structure in which the sliding plate 62 is disposed on its underside.

[0027] The installation work of air spring 10 includes an installation process in which air spring 10 is installed on a railway vehicle as an installation object, and an air supply process in which air is supplied to diaphragm 3 after the installation process. In the installation process, air has not yet been charged into diaphragm 3, and air spring 10 is in a deflated state as shown in Figure 4, so that upper member 2 abuts against lower member 1. In the air supply process, air flowing in from boss portion 21 is sent to diaphragm 3 through cavity 44. When diaphragm 3 expands due to the charging of air, air spring 10 enters an inflated state, and the internal pressure causes upper member 2 to rise and separate from lower member 1 as shown in Figure 1.

[0028] 5, when the air supply process is performed, the bead inner surface 31a, which is arranged axially inward (upper) than the upper surface of the lower plate 4, may come into contact with the lower surface of the upper plate 6, causing the bead portion 31 to seal between the lower member 1 and the upper member 2, which may prevent the supply of air to the diaphragm 3 (although the upper member 2 is spaced apart from the lower member 1 in FIG. 5, it is possible that the upper member 2 may come into contact with the lower member 1). Therefore, in this embodiment, the configuration described below is adopted so that air can be supplied to the diaphragm 3 even when the bead portion 31 seals between the lower member 1 and the upper member 2 in this way.

[0029] The diaphragm 3 has a pair of annular bead portions 31, 32, of which the bead portion 31 includes a bead inner surface 31a facing inward (upward) in the axial direction. As shown in FIGS. 2 and 3, an air passage forming portion 80 is provided on the bead inner surface 31a. The air passage forming portion 80 is configured to form an air passage between the bead inner surface 31a and an imaginary plane VP that is in contact with the bead inner surface 31a perpendicular to the axial direction and the bead inner surface 31a, from an area Ai radially inward of the bead inner surface 31a to an area Ao radially outward of the bead inner surface 31a. The imaginary plane VP is a plane that represents a mating member (i.e., the lower surface of the top plate 6) that can come into contact with the bead inner surface 31a in a deflated state.

[0030] According to this configuration, when the bead portion 31 seals the gap between the lower member 1 and the upper member 2 as shown in Figure 5, an air passage is formed between the bead inner surface 31a and the lower surface of the upper plate 6. This air passage connects the radially inner region Ai to the radially outer region Ao, and therefore functions as a flow path for sending air that has flowed between the lower member 1 and the upper member 2 (mainly through the gap 44) into the inside of the diaphragm 3. Therefore, air can be supplied to the diaphragm 3 even when the bead portion 31 seals the gap between the lower member 1 and the upper member 2.

[0031] In this embodiment, a case has been described in which the bead portion 31 seals between the lower member 1 and the upper member 2 during the installation work of the air spring 10. However, the phenomenon in which a misaligned bead portion 31 seals between the lower member 1 and the upper member 2 is not limited to the installation work of the air spring 10. Although the probability of this occurring is not high, for example, during maintenance work, the above phenomenon may occur when air is released from an inflated air spring 10 to temporarily set it in a deflated state, and then air is supplied to set it in an inflated state again, and in that case too, the diaphragm 3 provides a similar effect.

[0032] As described above, the air passage forming portion 80 forms an air passage that allows air to pass between the bead inner surface 31a and the lower surface of the upper plate 6 (more specifically, movement from the radially inner region Ai to the radially outer region Ao) when the bead inner surface 31a abuts against the lower surface of the upper plate 6 in a deflated state. While it is possible to provide an air passage forming portion in the mating member that may abut against the bead inner surface 31a (i.e., the upper plate 6), in this embodiment, no air passage forming portion is provided in the upper plate 6 from the viewpoint of preventing damage to the sliding sheet 43 when the sliding sheet 43 is displaced horizontally in a deflated state and preventing an increase in processing costs. However, the present invention is not limited to this, and an air passage forming portion may also be provided on the lower surface of the upper plate 6 in addition to the bead inner surface 31a.

[0033] In this embodiment, the air passage forming portion 80 is formed by a groove 81 recessed axially outward. The groove 81 is provided in at least one location in the circumferential direction, but by providing the groove 81 in multiple locations in the circumferential direction (two locations in this embodiment) as shown in FIG. 3, air can be efficiently supplied to the diaphragm 3. The groove 81 extends parallel to the radial direction, but is not limited to this as long as it forms an air passage that connects the region Ai radially inward of the bead inner surface 31a to the region Ao radially outward. The groove 81 is provided, for example, by providing a groove-forming protrusion on the vulcanization molding die for the diaphragm 3, or by groove processing the diaphragm 3 after vulcanization molding.

[0034] FIG. 6 is a side view of the groove 81 as viewed in the radial direction, corresponding to the view of the arrow X in FIG. 2. In this embodiment, a rectangular groove 81 is formed as shown in FIG. 6(A). The groove 81 has a width W81 (maximum width) and a depth D81 (maximum depth), and these dimensions are not particularly limited. However, from the viewpoint of ensuring a cross-sectional area of ​​the groove so that air can be supplied efficiently, the width W81 is preferably 1 mm or more. Furthermore, from the viewpoint of preventing the groove 81 from collapsing in the deflated state as shown in FIG. 5, the width W81 is preferably 5 mm or less.

[0035] From the viewpoint of preventing the grooves 81 from collapsing in a deflated state as shown in Fig. 5, the depth D81 is preferably 3 mm or more. Furthermore, the depth D81 is desirably large enough so that the bottom of the grooves 81 does not reach embedded objects such as the reinforcing layer 35 (see Fig. 2). One example is a groove 81 having a width W81 of 5 mm and a depth D81 of 3 mm. In this embodiment, the width W81 and the depth D81 are each constant along the extension direction of the grooves 81, but at least one of them may be varied along the extension direction of the grooves 81.

[0036] The groove shape is not particularly limited, and various shapes such as those shown in Figures 6(B) to 6(G) can be used. In the examples of Figures 6(A) to 6(F), the width W81 is larger than the depth D81. This groove shape is convenient for making the width W81 appropriately large to ensure the groove cross-sectional area while keeping the depth D81 appropriately small to avoid exposure of the reinforcing layer 35. In the example of Figure 6(G), the depth D81 is larger than the width W81. This groove shape is convenient for preventing the groove 81 from collapsing in the deflated state shown in Figure 5. The depth D81 and the width W81 may be the same size.

[0037] The air passage forming portion 80 is not limited to the groove 81 as long as it can form an air passage as described above, and may be formed, for example, by a protrusion that protrudes inward in the axial direction. The protrusion may be a linear protrusion extending along the radial direction or a point-like protrusion arranged at intervals in the circumferential direction. However, when the air spring 10 is in a deflated state due to a puncture or the like during use and the lower member 1 and the upper member 2 slide against each other, such a protrusion may interfere and affect the sliding. Therefore, it is preferable that the air passage forming portion 80 be formed by a groove as in this embodiment.

[0038] As described above, the air spring 10 is provided with the bead seat portion 41 to which the bead portion 31 including the bead inner surface 31a is attached by a self-sealing method, and the tapered surface 41t is formed on the bead seat portion 41. With this configuration, even slight dimensional variations, such as when the inner diameter of the bead portion 31 is relatively small or the outer diameter of the bead seat portion 41 is relatively large, can easily cause the bead portion 31 to shift axially inward, which can cause the deflated state shown in Fig. 5. Therefore, the structure in which the air passage forming portion 80 is provided on the bead inner surface 31a as in this embodiment is particularly useful.

[0039] In this embodiment, an example has been shown in which the bead portion 31, including the bead inner surface 31a on which the air passage forming portion 80 is provided, is attached by a self-sealing method, but this is not limiting and a structure in which it is attached by a fastening method may also be used. This is because even in the fastening method, if the fastening becomes slightly loose and the bead portion becomes misaligned, the gap between the lower member 1 and the upper member 2 may be sealed by the bead portion and enter a deflated state.

[0040] In this embodiment, an example is shown in which the bead portion 31, which has the relatively smaller inner diameter of the pair of bead portions 31, 32, is provided with the air passage forming portion 80, but this is not limited to this. For example, if the bead portion 31 has the same diameter as the bead portion 32, a deflated state in which the space between the lower member 1 and the upper member 2 is sealed by the bead portions may be created when one of the misaligned bead portions abuts against the other bead portion. Therefore, an air passage forming portion may be provided on the bead inner surface 31a of the bead portion 31 facing the bead portion 32 and / or on the bead inner surface of the bead portion 32 facing the bead portion 31.

[0041] It will be understood by those skilled in the art that the above-described embodiments are examples of the following aspects.

[0042] [1] The air spring diaphragm of the present disclosure includes a pair of annular bead portions. At least one of the pair of bead portions includes a bead inner surface facing axially inward. The bead inner surface is provided with an air passage forming portion, and the air passage forming portion is configured to form an air passage that connects a region radially inward of the bead inner surface to a region radially outward of the bead inner surface between the bead inner surface and an imaginary plane that is tangent to the bead inner surface and perpendicular to the axial direction. With this configuration, air can be supplied to the diaphragm even if the bead portions seal between a lower member and an upper member during installation of the air spring.

[0043] [2] In the diaphragm for an air spring according to the above item [1], the air passage forming portion may be formed by a groove recessed outward in the axial direction.

[0044] [3] In the diaphragm for an air spring according to the above item [2], the width of the groove may be 1 mm or more.

[0045] [4] In the air spring diaphragm of the above [2] or [3], the depth of the groove may be 3 mm or more.

[0046] [5] In the air spring diaphragm of any one of [1] to [4] above, the pair of bead portions may have different inner diameters, and the air passage forming portion may be provided in the bead portion of the pair of bead portions having the relatively smaller inner diameter.

[0047] [6] The air spring of the present disclosure is configured by interposing the air spring diaphragm according to any one of [1] to [5] above between a lower member and an upper member. With this configuration, air can be supplied to the diaphragm even if the bead portion seals the gap between the lower member and the upper member during installation of the air spring.

[0048] [7] In the air spring of the above [6], a bead seat portion may be provided to which the bead portion including the bead inner surface is attached by a self-sealing method.

[0049] [8] In the air spring of the above [7], the bead seat portion may be formed with a tapered surface that tapers axially inward.

[0050] Although the embodiments of the air spring diaphragm and air spring according to the present disclosure have been described with reference to the drawings, the specific configurations should not be considered to be limited to these embodiments. The scope of the present invention is indicated not only by the description of the above-described embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0051] The air spring diaphragm and air spring according to the present disclosure are not limited to the above-described embodiments, and are not limited to the above-described effects. The air spring diaphragm and air spring according to the present disclosure can be improved or modified in various ways without departing from the spirit thereof. Furthermore, the configurations employed in the above-described embodiments can be combined in any desired manner. [Explanation of symbols]

[0052] 1 lower member, 2 upper member, 3 air spring diaphragm, 4 lower surface plate, 6 upper surface plate, 31 bead portion, 31a bead inner surface, 32 bead portion, 41 bead seat portion, 41t tapered surface, 80 air passage forming portion, 81 groove

Claims

1. A pair of annular bead portions is provided, At least one of the pair of bead portions includes a bead inner surface facing inward in the axial direction, an air passage forming portion is provided on the inner surface of the bead, The air spring diaphragm is configured so that the air passage forming portion forms an air passage between the bead inner surface and an imaginary plane that is in contact with the bead inner surface perpendicular to the axial direction and the bead inner surface, the air passage leading from a region radially inward of the bead inner surface to a region radially outward of the bead inner surface.

2. 2. The diaphragm for an air spring according to claim 1, wherein the air passage forming portion is formed by a groove recessed axially outward.

3. 3. The diaphragm for an air spring according to claim 2, wherein the width of the groove is 1 mm or more.

4. 3. The diaphragm for an air spring according to claim 2, wherein the depth of said groove is 3 mm or more.

5. The pair of bead portions have different inner diameters, 2. The diaphragm for an air spring according to claim 1, wherein the air passage forming portion is provided in the bead portion having the relatively smaller inner diameter of the pair of bead portions.

6. An air spring comprising a diaphragm for an air spring according to any one of claims 1 to 5 interposed between a lower member and an upper member.

7. 7. The air spring according to claim 6, wherein the bead portion including the bead inner surface is provided with a bead seat portion to which the bead portion is attached by a self-sealing method.

8. 8. The air spring according to claim 7, wherein the bead seat portion is formed with a tapered surface that tapers axially inward.

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