Semicircle concave backup ring

Abstract

To solve the problem that, when a backup ring with a square cross section is used in a sealing structure of a high-pressure hydrogen device, an O-ring pressed against the backup ring under pressure causes concentration of stress at four corners, thereby causing a crevice to lead to cracking, which results in a leak.SOLUTION: By making one of the top and bottom surfaces of a backup ring concave and semicircular, and making the surface face toward and cover an O-ring, stress is not concentrated, a crevice does not occur in the O-ring, and progression of cracking can be prevented, resulting in no leak.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a semicircular concave backup ring used in a sealing structure of high-pressure hydrogen equipment. [Background technology]

[0002] When rubber O-rings are used to seal high-pressure hydrogen, it has been known to use a plastic backup ring in combination to protect it from the effects of high pressure. Commercially available plastic backup rings have a square cross section. Summary of the Invention [Problem to be solved by the invention]

[0003] However, O-rings that continuously seal high-pressure hydrogen have been found to be damaged by the pressure, causing leaks. This suggests that backup rings, whether made of resin or rubber, do not fully prevent O-rings from being damaged by high pressure. Rubber backup rings with a square cross section can reduce the concentration of stress on the O-ring and extend the period until it is damaged to a certain extent, but this is not complete.

[0004] Destruction of O-rings due to high pressure specifically refers to cracks, which occur at points where stress is concentrated due to high pressure. Once a crack occurs in an O-ring, it leads to a leak. The concentration of stress on the O-ring is caused by the shape of the backup ring. The cross section of commercially available backup rings is square, and when an O-ring is pressed against this flat surface by pressure, it deforms from a round shape to a square. Stress concentrates at the four corners of the O-ring that are in contact with the backup ring, causing the cracks. In other words, if stress concentration at these four corners is prevented, the occurrence of cracks can be prevented and cracks will not occur. [Means for solving the problem]

[0005] As a method of preventing stress from concentrating on the four corners of an O-ring that has been pressurized and deformed into a square shape, the surface of the backup ring that comes into contact with the O-ring is made into a concave semicircular shape that covers the O-ring. The diameter of the semicircular shape is the width of the groove where the O-ring and backup ring are attached, and half of that is the radius of the semicircle. [Effects of the Invention]

[0006] No cracks occur in the O-ring due to stress concentration. [Brief explanation of the drawings]

[0007] [Figure 1] Semicircular concave backup ring of the present invention [Figure 2] An assembly diagram of the semicircular concave backup ring of the present invention [Figure 3] Sealing structure using the semicircular concave resin backup ring of this invention (when attached to the inner shaft and pressure is received on one side) [Figure 4] Sealing structure using the semicircular concave resin backup ring of this invention (when attached to the outer cylinder and pressure is received on one side) [Figure 5] Sealing structure using the semicircular concave resin backup ring of this invention (when attached to the inner shaft and pressure is applied on both sides) [Figure 6] Sealing structure using the semicircular concave resin backup ring of this invention (when attached to the outer cylinder and pressure is applied on both sides) [Figure 7] Sealing structure using the semicircular concave rubber backup ring of this invention (when attached to the inner shaft and pressure is received on one side) [Figure 8] Sealing structure using the semicircular concave rubber backup ring of this invention (when attached to the outer cylinder and pressure is received on one side) [Figure 9] Sealing structure using the semicircular concave rubber backup ring of this invention (when attached to the inner shaft and pressure is applied on both sides) [Figure 10] Sealing structure using the semicircular concave rubber backup ring of this invention (when attached to the outer cylinder and pressure is applied on both sides) [Figure 11] Test pressure vessels and test units [Figure 12] Appearance of O-ring after pressure cycle test (when semicircular concave resin backup ring is installed) [Figure 13] Appearance of O-ring after pressure cycle test (when a square cross-section resin backup ring is attached) [Figure 14] Behavior under high pressure hydrogen pressure (FEM analysis) (with semicircular concave resin backup ring) [Figure 15] Behavior under high-pressure hydrogen pressure (FEM analysis) (with a rectangular cross-section plastic backup ring) DETAILED DESCRIPTION OF THE INVENTION

[0008] The semicircular concave backup ring is designed as shown in Figure 1. The shape is shown as 1. The shape 101 is designed as a semicircular and concave shape. The dimensions of the semicircular concave backup ring are shown in the assembly diagram of Figure 2. The radius of the semicircle is half the groove width 102 of groove A. The inner diameter of the semicircular concave backup ring is the same as the groove diameter 103 of the inner shaft 3 to be installed. The outer diameter of the semicircular concave backup ring is the same as the groove diameter 104 of the outer cylinder 4. The height 105 of the semicircular concave backup ring can be designed according to the volume. It can be selected arbitrarily as long as the total volume of the O-ring and backup ring to be installed in groove A does not exceed the volume of groove A. The tolerances of each dimension can be set as needed.

[0009] Figures 3, 4, 5, and 6 show examples of using a resin semicircular concave backup ring. Resin semicircular concave backup ring 1 is used in combination with rubber O-ring 2. The semicircular concave backup ring is attached to the side opposite the side that receives pressure (pressure-receiving side) of the O-ring. The concave semicircular shape of semicircular concave backup ring 1 faces the O-ring side so that it covers the O-ring. Figures 3 and 4 show the case where pressure direction B is on one side, while Figures 5 and 6 show the case where pressure direction B is on both sides. Figures 3 and 5 show the case where the valve is installed on the inner shaft, and Figures 4 and 6 show the case where the valve is installed on the outer cylinder.

[0010] Figures 7, 8, 9, and 10 show examples of using a semicircular concave rubber backup ring. The semicircular concave rubber backup ring 1 is used in combination with a resin backup ring 5, which is attached next to the semicircular concave rubber backup ring 1. The concave semicircular shape of the semicircular concave backup ring 1 faces the O-ring so that it covers the O-ring. The surface of this resin backup ring 5 that comes into contact with the semicircular concave rubber backup ring is flat. Figures 7 and 8 show the case where the pressure direction B is on one side, while Figures 9 and 10 show the case where the pressure direction B is on both sides. Figures 7 and 9 show the case where the valve is attached to the inner shaft, and Figures 8 and 10 show the case where the valve is attached to the outer cylinder. A semicircular concave rubber backup ring can be used when durability is desired to be improved over that of a semicircular concave resin backup ring. [Example]

[0011] To compare the semicircular concave backup ring with the backup ring with a square cross section, a pressurization / depressurization cycle test using high-pressure hydrogen was conducted, and the jig shown in Figure 11 was fabricated and evaluated. Unit 51 fitted with an O-ring and backup ring was set in pressure vessel 50, and high-pressure hydrogen was applied from pressure vessel inlet 50a to 90 MPa in pressure direction B. Hydrogen passed through unit inlet 51a and unit flow channel groove 51b to reach groove 51c, and was designed so that if it leaked from groove 51c, hydrogen would leak from 50b and be detected. O-ring 2, backup ring 1 and backup ring 1a were fitted to groove 51c, and a structure was created in which O-ring 2 provided a seal. Backup ring 1 was made of resin and had a semicircular concave shape, and backup ring 1a was made of resin and had a square cross section. The pressure cycle conditions were 8 seconds per cycle, with the pressure increasing from 0 MPa to 90 MPa in 1 second, maintaining 90 MPa for 5 seconds, reducing the pressure to 0 MPa in 1 second, maintaining 0 MPa for 1 second, and then increasing the pressure again. This cycle was repeated 10,000 times. The sealing structure was designed as shown in Figure 5 (when attached to the inner cylinder and pressure is received on both sides), assuming that the pressure is reduced and the pressure is pulled in on the opposite side. After 10,000 cycles, the appearance of the O-ring and backup ring was observed. As a result, the appearance of the test O-ring fitted with the resin semicircular concave backup ring 1 was normal, as shown in Figure 12, and it passed 10,000 cycles. On the other hand, the appearance of the test O-ring fitted with the resin backup ring 1a with a square cross section was such that a crack had developed from the outer diameter to the inner diameter, as shown in Figure 13, and a leak occurred at 3,525 cycles. These results confirmed that making the backup ring semicircular concave protects the O-ring from the effects of high pressure and prevents cracks. [Example]

[0012] To compare the behavior of a semicircular concave resin backup ring and a square cross-section resin backup ring when pressurized to 90 MPa in pressure direction B, an analysis was conducted simulating high-pressure hydrogen. The analysis was performed using finite element analysis (FEM analysis). The analysis results for when a semicircular concave backup ring 1 was installed show no concentration of stress on the O-ring 2 at the contact surface, as shown in Figure 14. In contrast, the analysis results for when a backup ring 5 with a square cross section was installed show that stress is concentrated at the four corners of the O-ring 2, as shown in Figure 15. These results confirmed that the semicircular concave shape does not cause stress concentration in the O-ring. [Industrial Applicability]

[0013] It is expected to be used in the sealing structure of high-pressure hydrogen equipment. Examples include the hydrogen sealing structure of hydrogen compressors and hydrogen boosters installed in hydrogen filling facilities, hydrogen sealing structures of hydrogen dispensers, and hydrogen sealing structures of hydrogen tanks. It can also be used in hydrogen sealing structures for equipment installed in fuel cells or mobile vehicles powered by hydrogen. There is also the possibility of application to other products that are similar in use to sealing structures for high-pressure hydrogen. [Explanation of symbols]

[0014] 1 Semicircular concave backup ring 1a Cross-section square backup ring 2 rubber O-rings 3 Inner axis 4 outer cylinder 5 Cross-section square backup ring 50 Test pressure vessel 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 Semicircular concave 102 groove diameter 103 Inner shaft diameter and inner diameter of semicircular concave backup ring 104 Diameter of outer cylinder and outer diameter of semicircular concave backup ring A groove B Pressure direction

Claims

1. In a sealing structure for high-pressure fluid, a backup ring installed in the sealing structure has a semicircular shape with one of the upper and lower faces recessed, is positioned so as to cover a rubber O-ring that has the role of sealing the fluid, and protects the rubber O-ring from the effects of high pressure.

2. According to the first aspect of the present invention, the semicircular shape of the backup ring, one of the upper and lower surfaces of which is recessed, has a radius dimension that is half the width dimension of the groove in which it is mounted.

3. According to the first aspect of the present invention, the backup ring is made of a polymer material including resin and rubber.

4. According to claim 1, the backup ring is used together with a rubber O-ring that seals high-pressure hydrogen in a sealing structure configured in high-pressure hydrogen equipment.

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