JP2019074181A - Air spring - Google Patents

Abstract

To provide an air spring capable of improving fire retardancy in a state of maintaining mechanical characteristics and physical characteristics of a cylindrical flexible member.SOLUTION: An air spring comprises an upper member 2, a lower member 3 arranged below the upper member 2, and a cylindrical flexible member 4 interposed between the upper member 2 and the lower member 3. The flexible member 4 comprises an outer layer 15, an inner layer 16, and an intermediate layer 17 interposed between the outer layer 15 and the inner layer 16. The outer layer 15 and the inner layer 16 are composed of a fire-retardant rubber composition. The intermediate layer is composed a reinforcement rubber layer where a reinforcement cord 18 is embedded in the fire-retardant rubber composition. An average thickness of a thickness Y of the inner layer 16 and a thickness X of the outer layer 15 are equal to or more than 1.1 times of a thickness Z of the intermediate layer 17.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a flame-retardant air spring suitably used for vehicles, in particular for railway vehicles.

  In recent years, in Europe, flameproof requirements have become strict in various fields, and EN45545-2 which is a new unified standard of Europe has come to be established also for railway vehicles. Since an air spring uses an organic material as a rubber-like elastic body, such as a cylindrical flexible member (diaphragm or the like), a stopper, etc., it is required to clear the above criteria for these members. With the above criteria, the amount of halogen-containing gas generated is also severely limited.

  In EN 45545-2, it is stipulated that the evaluation of the flame retardancy of the main rubber members used for rail vehicles is carried out by a heat generation test (hereinafter abbreviated as heat generation test) by the cone calorimeter method according to ISO 5660-1. It is required that the value of Maximum Average Rate of Heat Emission (hereinafter, MARHE) measured by this method is equal to or less than a predetermined value.

  Specifically, hazard levels (HL) 1 and 2 require MARHE values of 90 or less, and HL3 require MARHE values of 60 or less. The size of the test piece to be subjected to the heat generation test is 10 cm × 10 cm, and the thickness of the test piece is the same as the thickness of the diaphragm (however, the maximum thickness of the test piece is 25 mm or less).

  As a non-halogen flame retardant rubber which does not contain a halogen-based flame retardant, for example, as shown in Patent Document 1, a flame retardant rubber is disclosed in which magnesium hydroxide and red phosphorus are mixed with chloroprene rubber. Patent Document 2 discloses a flame retardant rubber composition containing a polyphosphate and aluminum hydroxide. As described above, as a non-halogen flame retardant rubber composition, one in which a phosphorus-based flame retardant and a metal hydroxide are combined and blended is known.

  By the way, since the upper end and the lower end are relatively displaced in the vertical and horizontal directions in use, a cylindrical flexible member such as a diaphragm constituting the air spring has good mechanical characteristics (modulus, tensile strength, etc.) Etc.) are required. Furthermore, it is also required to be excellent in physical properties such as weather resistance, heat resistance and aging resistance.

  In order to satisfy such requirements, a cylindrical flexible member generally has a reinforcing rubber layer in which a reinforcing cord is embedded as an intermediate layer, and a protective rubber layer (an outer layer and an inner layer) on the inside and the outside of the intermediate layer. The thing of the laminated structure in which is laminated is used. When making the cylindrical flexible member provided with the said laminated structure flame-retardant, it is possible to mix | blend a phosphorus-type flame retardant and a metal hydroxide in the rubber composition which comprises each layer.

JP, 2005-146256, A JP, 2010-047644, A

  However, the metal hydroxide used as a flame retardant is a powder, and when it is blended into the rubber composition, the flowability of the rubber composition is reduced. In particular, when a metal hydroxide is compounded into the rubber composition constituting the intermediate layer in which the reinforcing cords are embedded, the fluidity of the rubber composition is reduced, so that the unfilled portion between the reinforcing cords and the rubber composition There is a concern that the mechanical properties of the rubber may be reduced due to the remaining of the rubber and the adhesion between the reinforcing cord and the rubber composition. On the other hand, when the compounding amount of metal hydroxide is reduced, it is necessary to incorporate a large amount of a phosphorus-based flame retardant to exhibit flame retardancy, and also in this case, there is a concern that mechanical properties of the rubber may be deteriorated. .

  Moreover, when a flame retardant is not mix | blended with the rubber composition which comprises an intermediate | middle layer, it becomes necessary to maintain the flame retardance as the whole flexible member by raising the flame retardance of inner and outer layers, but it can be mixable. There is a limit to the amount of flame retardant. As a result, the flame retardance as the whole flexible member becomes a level close to HL specified in EN 45545-2 and may occur even when the heat generation test is performed a plurality of times.

  So, in this invention, it aims at providing the air spring which can improve a flame retardance, maintaining the mechanical characteristic and physical characteristic of a cylindrical flexible member.

  In order to solve the above problems, according to one aspect of the present invention, an upper member, a lower member disposed below the upper member, and a tubular member interposed between the upper member and the lower member An air spring comprising a flexible member, the flexible member comprising an outer layer and an inner layer, and an intermediate layer interposed between the outer layer and the inner layer, the outer layer and the inner layer being made of a flame retardant rubber The intermediate layer is composed of a reinforcing rubber layer in which a resin reinforcing cord is embedded in a non-combustible rubber composition, and the average thickness of the thickness of the inner layer and the thickness of the outer layer (hereinafter referred to It is characterized in that “the average thickness of the inner and outer layers” is 1.1 or more times the thickness of the intermediate layer.

  The flame retardancy in the present invention is evaluated by the MARHE value of the heat generation test defined in ISO 5660-1. In the present invention, the flame retardant rubber composition refers to one having a MARHE value satisfying a predetermined HL required by EN 45545-2 when a single rubber composed of the flame retardant rubber composition is subjected to the heat generation test. Say. As a result of conducting the above-mentioned heat generation test with various rubber compositions, the inventors obtained the knowledge that the MARHE value decreases as the thickness of the test piece of the heat generation test becomes larger, regardless of the rubber composition. The invention is completed.

  That is, in the present invention, as the rubber composition of the middle layer which greatly affects the mechanical properties, it is difficult to use a non-flame retardant rubber composition not containing a flame retardant as the rubber composition constituting the outer layer and the inner layer. A flame retardant rubber composition is used. Thereby, it becomes possible to suppress the fall of the mechanical characteristic as a cylindrical flexible member.

On the other hand, the rubber composition used in the intermediate layer is a non-flammable rubber composition. In the case of a general air spring, the thickness of the inner layer, the intermediate layer and the outer layer in the cylindrical flexible member is designed to be about the same thickness in each layer (in the case where the intermediate layer is two plies). In this case, the flame retardancy of the entire flexible member is reduced as compared to the case where the intermediate layer is provided with the flame retardancy. As a result, even if a large amount of a flame retardant is blended in the rubber composition constituting the inner and outer layers, the flame retardancy of the entire flexible member becomes a level close to the HL defined in EN 45545-2.

  Therefore, in the present invention, by increasing the average thickness of the inner and outer layers to 1.1 times or more the thickness of the intermediate layer, the MARHE value as the flexible member is lowered to stably clear the required HL. It becomes possible. Although the flexible member basically has a three-layer structure of an outer layer, an intermediate layer, and an inner layer, the present invention is not limited thereto, and rubber layers other than the three layers may be added to at least a part of the flexible member. Is also possible. In this case, the thickness of the flexible member may be adjusted depending on whether the rubber layer to be added is a flame retardant layer or a non-combustible layer.

  That is, the air spring comprises an upper member, a lower member disposed below the upper member, and a cylindrical flexible member interposed between the upper member and the lower member. The flexible member includes an outer layer and an inner layer, and an intermediate layer interposed between the outer layer and the inner layer, and the outer layer and the inner layer are a flame retardant layer formed of a flame retardant rubber composition, The intermediate layer is a non-combustible layer formed of a reinforced rubber layer having a reinforcing cord embedded in the non-flammable rubber composition, and the total thickness of the flame retardant layer is 2.2 of the thickness of the non-flammable layer. It may be doubled or more.

  The intermediate layer may have a single-layer structure in which the reinforcing rubber layer is a single layer, or may have a laminated structure in which a plurality of the reinforcing rubber layers are stacked. The flexible member may be formed such that the thickness of the middle portion is larger than the thickness of the lower and upper portions.

  According to the air spring according to one aspect of the present invention, in the flexible member, the noncombustible one is used as the rubber composition constituting the intermediate layer, and the flame retardant rubber as the rubber composition constituting the outer layer and the inner layer. Since the composition is used and the average thickness of the inner and outer layers of the flexible member is made 1.1 times or more of the thickness of the intermediate layer, the decrease in mechanical properties and physical properties of the flexible member is suppressed stably. It is possible to obtain an air spring capable of securing flame retardancy.

Longitudinal sectional view showing a first embodiment of an air spring according to the present invention A perspective view showing the flexible member of FIG. 1 Cross-sectional schematic view of the flexible member The cross-sectional schematic of the flexible member which shows 2nd Embodiment of this invention Graph showing relationship between thickness of flexible member and MARHE value in heat generation test

First Embodiment
Hereinafter, a first embodiment of the present invention will be described based on the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the air spring according to the present invention. 2 is a perspective view showing a flexible member used in the air spring of FIG. 1, and FIG. 3 is a schematic cross-sectional view of the flexible member.

  As shown in FIG. 1, the air spring 1 of the present embodiment is for a railway vehicle, and between the upper member 2, the lower member 3 disposed below the upper member 2, and the upper member 2 and the lower member 3. A cylindrical flexible member 4 such as a diaphragm or a bellows is provided. The upper member 2 is a member connecting the flexible member 4 and the vehicle body, and in the present embodiment, the upper surface plate is used, but not limited to this, for example, a part of the vehicle body is used as the upper member 2 May be The lower member 3 is a member for connecting the flexible member 4 and the bogie frame, and in the present embodiment, the elastic mechanism 7 generally referred to as a stopper is provided. However, the present invention is not limited thereto. It is good also as composition except.

  The lower member 3 includes an elastic mechanism 7, an annular belt-like lower surface plate 9 mounted from the upper outer periphery to the outer peripheral portion of the top plate 8 of the elastic mechanism 7, and a disk having a flange portion bolted to the top plate 8. And the upper member receiving portion 11 of

  The elastic mechanism 7 has a structure including a laminated rubber in which an annular elastic material layer 13 made of rubber and an annular hard plate 14 are alternately laminated between an annular top plate 8 and an annular bottom plate 12. . In the present embodiment, metal plates are used as the top plate 8, the bottom plate 12 and the hard plate 14. The elastic mechanism 7 may have a laminated rubber structure and have a function as a stopper, and may be a conical stopper or the like. Further, as described above, the lower member 3 may be configured without the elastic mechanism 7.

  At the upper end and the lower end of the flexible member 4, a thick bead portion in which a reinforcing rubber layer is wound around a bead core is formed. The upper end bead portion of the flexible member 4 is externally fitted to a disk-shaped bead receiving portion 2 a provided on the upper member 2. The lower end bead portion is externally fitted to a bead receiving portion 8 a provided on the top plate 8 of the elastic mechanism 7.

  As shown in FIG. 2, the flexible member 4 has a laminated structure including an outer layer 15 and an inner layer 16, and an intermediate layer 17 interposed between the outer layer 15 and the inner layer 16. The outer layer 15 and the inner layer 16 are composed of a flame retardant rubber composition, and the middle layer 17 is composed of a reinforced rubber layer 17 a in which a reinforcing cord 18 is embedded in a non-flame retardant rubber composition.

  Examples of the reinforcing cords include cords made of resin such as polyamide, polyester, rayon, polyvinyl alcohol and the like, but it is preferable to use cords made of polyamide in terms of strength. The reinforcing rubber layer may have a single-layer structure consisting of a single layer, but in terms of strength, it is preferable to have a laminated structure in which a plurality of layers are laminated. In particular, an even number of layers such as two layers is preferable in terms of balance of strength.

  As a rubber component of the rubber composition used for the air spring of the present invention, in addition to natural rubber, as synthetic rubber, diene rubber such as chloroprene rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber and the like And olefin rubbers such as ethylene-propylene-diene terpolymer and isobutylene-isoprene rubber, urethane rubbers, etc. These rubbers can be used alone or in combination of two or more. . In this embodiment, as the rubber component of the inner and outer layers, chloroprene excellent in physical properties such as weather resistance, heat resistance and aging resistance is used as a main component, and as the rubber component of the intermediate layer, mechanical characteristics are used. Natural rubber is used.

  In the present invention, it is desirable to use a non-halogen based flame retardant as the flame retardant. Examples of non-halogen flame retardants include metal hydroxides, metal oxides, phosphorouss, silicones, nitrogen compounds, organic metal compounds, etc. One may be used alone, or two or more may be used. It can also be used in combination. However, in order to maintain the mechanical properties and the physical properties of the flexible member 4 in a well-balanced manner, it is preferable to use a phosphorus-based flame retardant and a metal hydroxide in combination as appropriate.

  As phosphorus-based flame retardants, phosphates known to those skilled in the art can be used, and in particular, intomescent phosphates that form an intumescent (foam expansion layer) on the rubber surface during rubber combustion. Is preferred in that higher flame retardancy is obtained.

  As a metal hydroxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, calcium hydroxide etc. can be mentioned, These can be used individually by 1 type or in combination of 2 or more types. In particular, magnesium hydroxide and aluminum hydroxide are preferable in that higher flame retardancy can be obtained.

  The above-described flame retardant is compounded in the flame retardant rubber composition constituting the outer layer 15 and the inner layer 16, and the flame retardant is not compounded in the non-flame retardant rubber composition constituting the intermediate layer. The rubber composition used in the flexible member 4 includes, in addition to the above rubber component and flame retardant, sulfur, carbon black, a vulcanization accelerator, an antiaging agent, a vulcanization accelerator auxiliary, a vulcanization retarder, silica, Known compounding agents such as silane coupling agents, zinc oxide, stearic acid, plasticizers, softeners such as waxes and oils, processing aids and the like can be appropriately blended and used without impairing the effects of the present invention. .

  In the present embodiment, the intermediate layer 17 is configured of two plies of reinforcing rubber layers 17a and 17a. The average thickness (X + Y) / 2 of the inner and outer layers is at least 1.1 times the thickness Z of the intermediate layer. The thickness of each layer is different in rubber composition between the intermediate layer 17 and the inner and outer layers 15 and 16. Therefore, the cross section of the flexible member 4 is confirmed by optical analysis or surface analysis using X-ray or electron beam. be able to.

  FIG. 3 is a perspective view showing the shape of the flexible member before being incorporated into the air spring. As shown, the flexible member 4 is cylindrical and is formed so that the diameter of the middle portion 4b is larger than that of the upper portion 4a and the lower portion 4c. This middle portion 4b is an air spring incorporating the flexible member 4 When 1 is pressurized and put into use, it becomes a part exposed to the outside between the upper member 2 and the lower member 3.

  In FIG. 3, when the diameter of the upper end opening 4d of the flexible member 4 is d1, the diameter of the lower end opening 4e of the flexible member 4 is d2, and the diameter of the largest diameter portion 4f of the flexible member 4 is d3, the flexible member The upper portion 4a of the upper end opening 4d means an area from the end edge of the upper end opening 4d to the outer diameter of the flexible member being (d1 + d3) / 2, and the lower portion 4c of the flexible member is flexible from the end edge of the lower end opening 4e It means the region until the outer diameter of the member becomes (d2 + d3) / 2. And the middle part 4b of a flexible member means the field from the outer diameter of a flexible member to (d1 + d3) / 2 to (d2 + d3) / 2.

  The middle portion 4b of the flexible member 4 has a larger diameter than the upper portion 4a and the lower portion 4c when the flexible member is formed by vulcanization, so that the thickness tends to be thinner. As a result, the flame retardancy of the middle portion 4b May decrease. Therefore, in the unvulcanized rubber molded product before vulcanization molding of the flexible member 4, the thickness of the inner and outer layers of the portion constituting the intermediate portion 4b can be made thicker than the other portions after vulcanization. It is.

  In this case, the thickness of the flexible member may be increased in the entire area of the intermediate portion 4b, or the thickness of the flexible member may be increased in a band shape over the entire circumference of a part of the intermediate portion 4b. As a result, the thickness of the middle portion 4b of the flexible member after vulcanization can be made equal to or greater than the thicknesses of the upper portion 4a and the lower portion 4c, and the flame retardancy of the middle portion 4b of the flexible member 4 is excellent. Can be maintained.

Second Embodiment
The present embodiment is characterized in that a rubber layer is added to the middle portion 4b of the flexible member 4 to increase the thickness of the flexible member, and the other configuration is the same as that of the first embodiment.

  As shown in FIG. 4, in the present embodiment, the buffer rubber layer 19 is provided between the reinforcing rubber layer 17 a and the reinforcing rubber layer 17 a in the middle portion 4 b of the flexible member 4. That is, in the intermediate portion 4b, the thickness of the flexible member is reduced, so the cords 18 of the reinforcing cord layers 17a and 17a are close to each other. In such a situation, when an external force is applied to the air spring and the flexible member is displaced, the cords 18 and 18 may rub against each other, resulting in a possibility that the durability may be reduced.

  Therefore, by providing the buffer rubber layer 19 between the reinforcing rubber layer 17a and the reinforcing rubber layer 17a, contact between the cords 18 and 18 is prevented, and the durability of the flexible member 4 is maintained, and the flexible member It is possible to maintain good flame retardancy of the middle part 4b of

  When a nonflammable rubber composition is used as the buffer rubber layer 19, the buffer rubber layer 19 is the same nonflammable layer as the intermediate layer 17. Therefore, in this case, the total thickness of the outer layer 15 and the inner layer 16 which is the flame retardant layer is determined by adding the thickness of the buffer rubber layer 19 to the thickness of both layers of the reinforcing rubber layers 17a and 17a as the thickness of the flame retardant layer. However, it should be adjusted to be 2.2 times or more of the non-combustible layer.

  When a flame retardant rubber composition is used as the buffer rubber layer 19, the buffer rubber layer 19 is the same flame retardant layer as the outer layer 15 and the inner layer 16. Therefore, in this case, the total thickness of the outer layer 15, the inner layer 16 and the buffer rubber layer 19 which is the flame retardant layer is the thickness of the non-combustible layer where the thickness of the reinforcing rubber layers 17a and 17a is added It should be adjusted to be 2.2 times or more of the non-combustible layer. The buffer rubber layer 19 may be provided on the entire area of the middle portion 4 b or may be provided in a band shape over the entire circumference of a part of the middle portion 4 b.

  In this example, a flexible member was produced, and a heat generation test specified in EN 45545-2 was performed to evaluate flame resistance. The details will be described below.

[Production of flexible member]
First, as shown in Table 1, four rubber compositions were prepared (Compositions A to D). Three kinds of chloroprene rubber (CR), natural rubber (NR) and ethylene-propylene-diene terpolymer (EPDM) were used as rubber components of the rubber composition. HAF was used as carbon black. As a flame retardant, an intumescent phosphate and / or metal hydroxide was used. After blending each raw material in the amount shown in Table 1, the rubber composition was prepared by kneading with a Banbury mixer.

  Next, using the rubber compositions (composition A and composition B) prepared, as shown in Table 2, three types of flexible members having different thicknesses are produced (Sample 1, Sample 3 and Sample 4), The sample to be subjected to the heat generation test was cut into a size of 10 cm × 10 cm. The sample 1 and the sample 2 are samples of different thickness cut from the same flexible member.

  As a specific configuration of the flexible member, the composition A was used as a flame retardant rubber composition that constitutes the inner and outer layers, and the composition B was used as a non-flammable rubber composition that constitutes an intermediate layer. As a reinforcing cord, a polyamide cord having a diameter of 0.6 mm was used, and a rubber composition of composition B was topped to form a reinforcing rubber sheet, which was laminated in two plies to form an intermediate layer having a thickness of 1.8 mm. .

  The above-mentioned intermediate layer was laminated by being sandwiched between an inner layer and an outer layer of a predetermined thickness to form an unvulcanized rubber molded body, which was then set in a vulcanizing mold. Next, a rubber film called a bladder is disposed inside the unvulcanized rubber molded body, and the flexible member is heated by supplying steam to the bladder to heat and pressurize the unvulcanized rubber molded body. It was vulcanized and molded. The three types of flexible members obtained all met the mechanical properties and physical properties necessary for use in an air spring.

  In this example, a single-layer rubber sheet (samples 5 to 8) using a flame retardant rubber composition having a composition (composition C and composition D) different from the compositions A and B, in addition to the flexible member A single-layer rubber sheet (sample 9) using the flame retardant rubber composition of composition A was vulcanized and molded, cut to a size of 10 cm × 10 cm, and subjected to the heat generation test as in samples 1 to 4. .

[Fever test]
The heat generation test was implemented about nine types of samples (samples 1-9) shown in Table 2 according to ISO 5660-1. The heat generation rate was measured under the measurement conditions of a radiation amount of 25 kW / m ² every 20 seconds for the test time and for every 2 seconds of measurement interval to calculate MARHE. The results are shown in Table 2.

  In addition, the MARHE value is shown by the index display which sets the MARHE value of the sample 1 to 100 about the samples 1-4 and 9. FIG. The samples 5 to 6 are shown in the index display in which the MARHE value of the sample 5 is 100. The samples 7 to 8 are shown in the index display in which the MARHE value of the sample 7 is 100.

[Evaluation results]
FIG. 4 is a graph (black circle plot) showing the relationship between the thickness of samples 1 to 4 and the MARHE value. From this graph, it can be seen that the MARHE value is low, that is, the flame retardancy is high, in proportion to the thickness of the flexible member. This tendency was not only found in a specific rubber composition and structure, but a similar tendency was observed among samples 5 to 6 and samples 7 to 8 of monolayer structures having different rubber compositions. From this, it was confirmed that the flame retardancy increases as the thickness of the flexible member increases regardless of the rubber composition. The hazard levels (HL) of the samples 1 to 4 were the levels at which the samples 1 and 2 cleared the HL2, and the levels at which the samples 3 and 4 cleared the HL3.

  In the conventional air spring, the inner and outer layers of the flexible member are intended to protect the intermediate layer which is a reinforced rubber layer from the external environment, and there has been no idea of actively forming the intermediate layer thick. On the other hand, in the present invention, based on the findings of the above evaluation results, the flame retardant rubber composition is used only for the inner and outer layers of the flexible member, and the layer thickness is made thicker than the intermediate layer. It is possible to ensure the flame retardance while maintaining the performance of the mechanical properties and physical properties of the flexible member.

  In the ISO 5660-1 exotherm test, the test is performed at n = 3, and the average value of the MARHE values obtained in the three tests is adopted. From the result of measuring a plurality of samples of the same thickness cut from the same flexible member, it is known that the MARHE value varies within a range of about 10. On the other hand, according to the results of the graph of FIG. 4, the MARHE value decreases by 10 when the average thickness of the inner and outer layers is 2.0 mm when the thickness of the intermediate layer is 1.8 mm.

  That is, in a flexible member in which the thickness of the inner layer, the intermediate layer and the outer layer is the same, the composition for clearing the predetermined HL for the flame retardant rubber composition constituting the inner and outer layers is determined, and then the average thickness of the inner and outer layers is intermediate By forming the film at 1.1 times or more the layer, it is possible to reduce the MARHE value by about 10 as a whole in consideration of the variation in the MARHE value without changing the rubber composition.

  The MARHE value of sample 9 is noted in FIG. 4 (square plot). In sample 9, the MARHE value of a 5.2 mm thick rubber sheet composed of composition A is 60. Thereby, when all the rubber compositions which comprise a flexible member are used as a flame-retardant rubber composition (composition A), it is estimated that a MARHE value will be about 60. When the thickness of the intermediate layer is 1.8 mm using a non-combustible one as the rubber composition constituting the intermediate layer, the MARHE value is 60 if the thickness of the flexible member is 7.2 mm. Can. That is, the flame retardance level of the composition A can be maintained by setting the average thickness of the inner and outer layers 1.5 times that of the intermediate layer.

  When examining the sample 1 and the sample 2, both are cut out from the same flexible member. This flexible member was formed to have a thickness of 5.4 mm, and after being molded, it was incorporated into an air spring and actually used, and then the air spring was disassembled and the flexible member was taken out. The sample 1 was cut out from the lower part of the flexible member, and the sample 2 was cut out from the middle part of the flexible member. The thickness of the sample 1 is 5.4 mm, and the thickness of the sample 2 is 4.6 mm.

  The reason is that the pressure applied to the unvulcanized rubber molded body is increased at the intermediate portion by the bladder when the unvulcanized rubber molded body is vulcanized and formed, and as a result, the thickness of the intermediate portion is reduced. It was done. From this result, by thickening the thickness of the middle portion of the unvulcanized rubber molded body in advance, the thickness of the middle portion of the flexible member after vulcanization molding is equal to or greater than that of the upper and lower portions of the flexible member. The thickness can be maintained, and the flame resistance of the entire flexible member can be favorably maintained.

  The embodiment of the present invention has been described above, but the scope of the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention. For example, in the present embodiment, the thickness of the inner and outer layers may be different, and for example, the outer layer may be set thicker than the inner layer. Moreover, the air spring of the present invention is applicable not only to railway cars but also to vehicles such as trucks and buses.

  The constituent features disclosed in the present embodiment and the above modifications can be combined with each other, and by combining, new technical features can be formed.

REFERENCE SIGNS LIST 1 air spring 2 upper member 3 lower member 4 flexible member 7 elastic mechanism 8 top plate 9 lower plate 11 upper member receiving portion 12 bottom plate 13 elastic material layer 14 hard plate 15 outer layer 16 inner layer 17 intermediate layer 18 reinforcing cord

Claims (3)

An air spring comprising an upper member, a lower member disposed below the upper member, and a cylindrical flexible member interposed between the upper member and the lower member, the air spring comprising: The flexible member comprises an outer layer and an inner layer, and an intermediate layer interposed between the outer layer and the inner layer, wherein the outer layer and the inner layer are composed of a flame retardant rubber composition, and the intermediate layer is non-combustible Air comprising a reinforcing rubber layer in which a reinforcing cord is embedded in a rubber composition, and the average thickness of the thickness of the inner layer and the thickness of the outer layer is 1.1 times or more the thickness of the intermediate layer Spring. An air spring comprising an upper member, a lower member disposed below the upper member, and a cylindrical flexible member interposed between the upper member and the lower member, the air spring comprising: The flexible member comprises an outer layer and an inner layer, and an intermediate layer interposed between the outer layer and the inner layer, the outer layer and the inner layer being a flame retardant layer composed of a flame retardant rubber composition, the intermediate layer The layer is a non-combustible layer composed of a reinforced rubber layer having a reinforcing cord embedded in the non-flammable rubber composition, and the total thickness of the flame retardant layer is 2.2 times or more the thickness of the non-flammable layer An air spring characterized by being. The air spring according to claim 1 or 2, wherein the intermediate layer has a single-layer structure in which the reinforcing rubber layer is a single layer or a laminated structure in which a plurality of the reinforcing rubber layers are laminated.