Semicircular concave backup ring

Abstract

In the sealing structure of a high-pressure hydrogen device, when a backup ring with a square cross-section is used, the O-ring pressed against the backup ring under pressure will concentrate stress at the four corners, resulting in cracks and fissures. As a result, leakage occurs. 【Solution】By making one of the upper and lower surfaces of the backup ring semi-circular with a concave surface and covering the O-ring with that surface, the stress is not concentrated, no cracks occur in the O-ring, and the progression of cracks can be prevented. As a result, leakage does not occur.

Description

Technical Field

[0001] The present invention relates to a semi-circular concave backup ring used for the sealing structure of high-pressure hydrogen equipment.

Background Art

[0002] Conventionally, when using a rubber O-ring to seal high-pressure hydrogen, it is known to use a resin backup ring in combination for protection against the influence of high pressure. The cross-section of commercially available resin backup rings is square.

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, the O-ring that continuously seals high-pressure hydrogen has problems of being damaged by pressure and leaking. This suggests that regardless of whether the material of the backup ring is resin or rubber, it does not fully play a role in completely suppressing the destruction of the O-ring due to high pressure. For a rubber backup ring with a square cross-section, although it can suppress the stress concentration on the O-ring and extend the period to a certain extent before being destroyed, it is not perfect.

[0004] The destruction of the O-ring due to high pressure specifically refers to cracks. Cracks occur from the locations where stress is concentrated due to high pressure, and cracks occur. When cracks occur in the O-ring, leakage occurs. The stress concentration on the O-ring is caused by the shape of the backup ring. The cross-section of commercially available backup rings is square, and the O-ring pressed against its plane by pressure deforms from a round shape to a square shape. Stress is concentrated at the four corners of the O-ring in contact with the backup ring, and cracks occur. That is, if the stress concentration at these four corners is not generated, the occurrence of cracks can be prevented, and cracks will not occur.

Means for Solving the Problems

[0005] The present invention made to solve the above problems is a backup ring installed in a sealing structure for high-pressure fluid. The backup ring has a semi-circular shape with one of the upper and lower surfaces recessed, and is arranged to cover a rubber O-ring that serves to seal the fluid, protecting the rubber O-ring from the influence of high pressure. The semi-circular shape of the backup ring is characterized in that the radius dimension of the semi-circular shape is half of the groove width dimension to be mounted.

Advantages of the Invention

[0006] Cracks caused by stress concentration do not occur in the O-ring.

Brief Description of the Drawings

[0007]

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Mode for Carrying Out the Invention

[0008] The semi-circular concave backup ring is shown in the design in FIG. 1. The shape is shown in 1. The shape 101 is designed to be semi-circular and concave. Each dimension of the semi-circular concave backup ring is shown from the incorporation drawing in FIG. 2. The radius dimension of the semi-circle is set to be half of the groove width 102 of groove A. The inner diameter of the semi-circular concave backup ring is the same as the groove diameter 103 of the inner shaft 3 to be installed. The outer diameter of the semi-circular concave backup ring is the same as the groove diameter 104 of the outer cylinder 4. The height 105 of the semi-circular concave backup ring can be designed according to the volume. As long as the total volume of the O-ring and the backup ring installed in groove A does not exceed the volume of groove A, it can be arbitrarily selected. The tolerance of each dimension can be set as required.

[0009] Examples of the use of the resin semi-circular concave backup ring are shown in FIGS. 3, 4, 5, and 6. The resin semi-circular concave backup ring 1 is used in combination with the rubber O-ring 2. The semi-circular concave backup ring is installed on the side opposite to the side of the O-ring that receives pressure (pressure-receiving side). The concave semi-circular shape of the semi-circular concave backup ring 1 faces the O-ring side and covers the O-ring. FIGS. 3 and 4 show the case where the pressure direction B is on one side, and FIGS. 5 and 6 show the case where the pressure direction B is on both sides. FIGS. 3 and 5 show the case of installation on the inner shaft, and FIGS. 4 and 6 show the case of installation on the outer cylinder.

[0010] Examples of the use of a rubber semi-circular concave backup ring are shown in FIGS. 7, 8, 9, and 10. The rubber semi-circular concave backup ring 1 is used in combination with a resin backup ring 5, and the resin backup ring 5 is mounted next to the rubber semi-circular concave backup ring 1. The concave semi-circular shape of the semi-circular concave backup ring 1 faces the O-ring side so as to cover the O-ring. For this resin backup ring 5, the surface in contact with the rubber semi-circular concave backup ring is a flat surface. FIGS. 7 and 8 show the case where the pressure direction B is on one side, and FIGS. 9 and 10 show the case where the pressure direction B is on both sides. FIGS. 7 and 9 show the case of mounting on the inner shaft, and FIGS. 8 and 10 show the case of mounting on the outer cylinder. The rubber semi-circular concave backup ring can be used when it is desired to improve the durability compared to the resin semi-circular concave backup ring.

Example

[0011] In order to compare the semi-circular concave backup ring with the backup ring having a square cross-section, a high-pressure hydrogen pressure cycling test was carried out, and the jig shown in FIG. 11 was fabricated and evaluated. A unit 51 with an O-ring and a backup ring mounted on a pressure vessel 50 was set, and high-pressure hydrogen was pressurized from the pressure vessel inlet 50a at 90 MPa in the pressure direction B. Hydrogen passes through the unit inlet 51a and the unit flow path groove 51b and reaches the groove 51c. If leakage occurs in this groove 51c, hydrogen leaks from 50b and is designed to be detected. An O-ring 2, a backup ring 1, and a backup ring 1a are mounted in the groove 51c, and a structure is adopted in which the O-ring 2 seals. The backup ring 1 is a resin semi-circular concave shape, and the backup ring 1a is a resin square cross-section shape. The pressure cycle condition was set to 1 cycle in 8 seconds, with a pressure increase from 0 MPa to 90 MPa in 1 second, a holding of 90 MPa for 5 seconds, a pressure decrease to 0 MPa in 1 second, and a holding of 0 MPa for 1 second followed by a pressure increase again. This was repeated 10,000 cycles. Assuming that the sealing structure is drawn into the opposite side of the pressurization during decompression, FIG. 5 (the case of mounting on the inner cylinder and receiving pressure on both sides) was taken as an example. After 10,000 cycles, the appearances of the O-ring and the backup ring were observed. As a result, the appearance of the O-ring of the test body equipped with the resin semi-circular concave backup ring 1 was normal as shown in Fig. 12, and 10,000 cycles were cleared. On the other hand, the appearance of the O-ring of the test body equipped with the resin backup ring 1a with a square cross-section had cracks from the outer diameter to the inner diameter as shown in Fig. 13, and leakage occurred at 3,525 cycles. From this result, it was confirmed that by making the backup ring semi-circular concave, the O-ring can be protected from the influence of high pressure and the effect of preventing cracks can be achieved.

Example

[0012] Regarding the resin semi-circular concave backup ring and the resin backup ring with a square cross-section, in order to compare the behaviors when pressurized at 90 MPa in the pressure direction B, an analysis was carried out by simulating high-pressure hydrogen. The analysis was performed by finite element analysis (FEM analysis). The analysis result with the semi-circular concave backup ring 1 set shows that there is no stress concentration of the O-ring 2 on the grounding surface as shown in Fig. 14. On the contrary, the analysis result with the backup ring 5 with a square cross-section set shows that, as shown in Fig. 15, stress is concentrated at the four corners of the O-ring 2. From this result, it was confirmed that the semi-circular concave shape does not cause stress concentration on the O-ring.

Industrial Applicability

[0013] It is assumed to be used in the sealing structure of high-pressure hydrogen equipment. Examples include the hydrogen sealing structures of hydrogen compressors and hydrogen boosters installed in hydrogen filling facilities, the hydrogen sealing structure of hydrogen dispensers, and the hydrogen sealing structure of hydrogen tanks. Also included is the hydrogen sealing structure of equipment mounted on fuel cells or moving bodies powered by hydrogen. In addition, there is a possibility of application as long as it is similar to the sealing structure of high-pressure hydrogen.

Explanation of Reference Numerals

[0014] 1 Semi-circular concave backup ring 1a Backup ring with a square cross-section 2 Rubber O-ring 3 Inner shaft 4 Outer cylinder 5 Backup ring with a square cross-section 50 Pressure vessel for testing 50a High-pressure hydrogen inlet 50b High-pressure hydrogen outlet 51 Test unit 51a High-pressure hydrogen inlet 51b High-pressure hydrogen flow path 51c Groove 101 Semi-circular concave shape 102 Groove diameter 103 Diameter of the inner shaft and inner diameter of the semi-circular concave backup ring 104 Diameter of the outer cylinder and outer diameter of the semi-circular concave backup ring A Groove B Pressure direction

Claims

1. In a backup ring installed in a sealing structure for high-pressure fluid, the backup ring has a semi-circular shape with one of the upper and lower surfaces recessed, and is arranged to cover a rubber O-ring that serves to seal the fluid, and is adapted to protect the rubber O-ring from the influence of high pressure. The backup ring with the semi-circular shape is characterized in that the radius dimension of the semi-circular shape is half of the groove width dimension to be mounted.

2. The backup ring according to claim 1, characterized in that the backup ring is a polymer material containing resin and rubber.

3. The backup ring according to claim 1, characterized in that the backup ring is used together with a rubber O-ring that seals high-pressure hydrogen in a sealing structure constituted by high-pressure hydrogen equipment.

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