Sealing device

Abstract

A sealing device (1) is for sealing an annular gap. The sealing device (1) is provided with one seal ring (2). The one seal ring (2) exhibits desired sealing performance with respect to a fluid even in a low-temperature environment.

Description

sealing device

[0001] The present invention relates to a sealing device, and more particularly to a sealing device that can be suitably used even with low viscosity fluids.

[0002] A sealing device having a seal ring has been used to seal a gap between a reciprocating member and a cylindrical hole into which the member is inserted. The seal ring is attached to, for example, a piston of a pump, and allows the piston to pump the fluid while preventing or suppressing fluid leakage (see, for example, Patent Document 1).

[0003] JP 2016-014481 A

[0004] Conventionally, sealing devices have been required to have a structure that can seal fluid pumped by a pump without leaking, even in low-temperature environments. For example, sealing devices that have a multi-stage closure structure formed by arranging multiple seal rings in series to seal the fluid in low-temperature environments are known. However, a simpler structure is required for such sealing devices.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a sealing device that can obtain desired sealing performance against fluids with a simple structure even in a low-temperature environment.

[0006] In order to achieve the above object, the sealing device according to the present invention is a sealing device for sealing an annular gap, and is provided with one seal ring, and the one seal ring exhibits desired sealing performance against fluids even in a low-temperature environment.

[0007] In the sealing device according to one aspect of the present invention, the fluid is a low viscosity fluid.

[0008] In a sealing device according to one aspect of the present invention, the seal ring is a seal ring for sealing an annular gap, is arc-shaped around an axis, and has a pair of circumferential ends, the pair of ends being configured to form a gap, and the radial width at the pair of ends is smaller than the radial width at the central portion between the pair of ends.

[0009] In a sealing device according to one aspect of the present invention, the seal ring has an inner peripheral surface facing the inner peripheral side and an outer peripheral surface facing the outer peripheral side, the width is the width between the inner peripheral surface and the outer peripheral surface, the inner peripheral surface has no radial steps, and the outer peripheral surface has no radial steps.

[0010] In the sealing device according to one aspect of the present invention, the ratio of the radial width at the pair of end portions to the radial width at the central portion is a value between 0.2 and 0.6.

[0011] In a sealing device according to one aspect of the present invention, the value of the radial width is continuous around the axis.

[0012] In a sealing device according to one aspect of the present invention, the radial width increases from one of the pair of ends toward the central portion, and the radial width increases from the other of the pair of ends toward the central portion.

[0013] In a sealing device according to one aspect of the present invention, the outer peripheral surface is along a cylindrical surface having the axis as its central axis, and the inner peripheral surface is along a cylindrical surface having a central axis that is radially shifted from the axis.

[0014] A sealing device according to one aspect of the present invention is intended to seal a fluid having a viscosity lower than that of water.

[0015] A sealing device according to one aspect of the present invention is used to seal a gap between a reciprocating member and a cylindrical hole into which the member is inserted.

[0016] According to the sealing device of the present invention, it is possible to obtain the desired sealing performance against fluids with a simple structure even in a low temperature environment.

[0017] Fig. 1 is a front view of a sealing device according to an embodiment of the present invention. Fig. 2 is a perspective view of the sealing device. Fig. 3 is a cross-sectional view showing the sealing device in an in-use state where it is attached between a piston and a cylinder of a pump that pumps a liquid. Fig. 4 is a cross-sectional view showing the sealing device in an in-use state where it is attached between a piston and a cylinder of a pump that pumps a liquid. Fig. 5 is a diagram showing a schematic configuration of a sealing performance testing device for carrying out a sealing performance test of the sealing device. Fig. 6 is a diagram showing the results of the sealing performance test.

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] The sealing device 1 according to the embodiment of the present invention is a sealing device for sealing an annular gap and is used in a pump that pumps liquid. The pump in which the sealing device 1 is used is, for example, a pump that pumps cryogenic liquid fuel for general industrial use. For example, the cryogenic liquid fuel may be liquid hydrogen fuel. Specifically, the sealing device 1 is used to seal an annular gap between a piston, which is a reciprocating member, and a cylinder having a cylindrical hole into which the piston is inserted. Note that application of the sealing device according to the present invention is not limited to pumps that pump liquid. The sealing device according to the present invention can be used in other pumps, other devices, mechanisms, structures, etc.

[0020] Fig. 1 is a front view of a sealing device 1 according to an embodiment of the present invention, and Fig. 2 is a perspective view of the sealing device 1. The sealing device 1 includes one seal ring 2. The one seal ring 2 exhibits desired sealing performance against fluids even in a low-temperature environment. The configuration of the sealing device 1 will be specifically described below.

[0021] The seal ring 2 is arc-shaped around the axis x1 and has a pair of end portions 10, 20 in the circumferential direction. The pair of end portions 10, 20 form a gap 2a. The radial widths t1, t2 of the seal ring 2 at the pair of end portions 10, 20 are smaller than the radial width t3 at a central portion 3 between the pair of end portions 10, 20 (hereinafter also referred to as the "central portion"). The configuration of the seal ring 2 will be described in detail below. Note that Figures 1 and 2 show the seal ring 2 in a free state where no external force is applied. The radial direction is a direction perpendicular to the axis x1.

[0022] As shown in Figures 1 and 2, the seal ring 2 is a generally arc-shaped member with ends, and is shaped to be housed in an annular groove. The cross-sectional shape of the seal ring 2 taken along a plane including the axis x1 is, for example, rectangular or generally rectangular. As shown in Figures 1 and 2, the seal ring 2 is not annular in its free state, and a gap 30 extending in the circumferential direction is formed between the end 10 and the end 20. As will be described later, in its used state, the seal ring 2 elastically deforms upon contact with the inner circumferential surface of the cylinder, and the end 10, 20 overlap in the direction of the axis x1, forming a gap 2a.

[0023] The seal ring 2 has an inner circumferential surface 4 that faces the inner circumferential side (inward in the radial direction) and an outer circumferential surface 5 that faces the outer circumferential side (outward in the radial direction). The inner circumferential surface 4 is a smooth surface without any radial steps, and is, for example, a cylindrical surface along a cylindrical surface extending along the axis x2. Similarly, the outer circumferential surface 5 is a smooth surface without any radial steps, and is, for example, a cylindrical surface along a cylindrical surface extending along the axis x1. The seal ring 2 also has side surfaces 6 and 7 that are arcuately extending surfaces facing the axis x. The side surfaces 6 and 7 are back-to-back with each other in the axis x direction and extend between the inner circumferential surface 4 and the outer circumferential surface 5.

[0024] The radial width (width t) of the seal ring 2 is continuous around the axis x1. The width t of the seal ring 2 is the distance between the inner peripheral surface 4 and the outer peripheral surface 5 in the radial direction. The width t of the seal ring 2 increases from the end portion 10 toward the central portion 3. As described above, the central portion 3 is the central portion of the seal ring 2 between the end portion 10 and the end portion 20, i.e., the central portion between the end portion 10 and the end portion 20 in the circumferential direction of the seal ring 2. The width t of the seal ring 2 also increases from the end portion 20 toward the central portion 3. The width t of the seal ring 2 between the end portion 10 and the central portion 3 and the width t of the seal ring 2 between the end portion 20 and the central portion 3 increase, for example, in the same or approximately the same manner.

[0025] Specifically, for example, as shown in FIG. 1 , the width t of the seal ring 2 gradually increases from the end portion 10 toward the central portion 3. Similarly, specifically, for example, as shown in FIG. 1 , the width t of the seal ring 2 gradually increases from the end portion 20 toward the central portion 3. Furthermore, the width t of the seal ring 2 between the end portion 10 and the central portion 3 and the width t of the seal ring 2 between the end portion 20 and the central portion 3 gradually increase in the same or approximately the same manner. Note that the width t of the seal ring 2 does not have to gradually increase from the end portion 10 toward the central portion 3. For example, the width t of the seal ring 2 may have a certain range between the end portion 10 and the central portion 3. Similarly, the width t of the seal ring 2 does not have to gradually increase from the end portion 20 toward the central portion 3. For example, the width t of the seal ring 2 may have a certain range between the end portion 20 and the central portion 3.

[0026] The outer peripheral surface 5 of the seal ring 2 is, for example, a cylindrical surface or a substantially cylindrical surface with the axis x1 as its central axis or approximately central axis. The diameter r1 of the outer peripheral surface 5 is, for example, larger than the diameter of the inner peripheral surface of a cylinder of a pump to which the seal ring 2 is applied, which will be described later. The inner peripheral surface 4 of the seal ring 2 is, for example, a cylindrical surface or a substantially cylindrical surface with the axis x2 as its central axis or approximately central axis. The diameter r2 of the inner peripheral surface 4 is larger than the diameter of the bottom surface of a groove formed in a piston of a pump to which the seal ring 2 is applied, which will be described later. The axis x2 is radially offset from the axis x1 toward the gap 30. Furthermore, the axis x2 is, for example, parallel or approximately parallel to the axis x1. Specifically, for example, as shown in FIG. 1 , the axis x2 is radially offset from the axis x1 by a predetermined distance (distance d) toward the center 31 of the gap 30. As shown in FIG. 1 , the center 31 of the gap 30 is located at the middle of the gap 30 in the circumferential direction.

[0027] As described above, the widths t1 and t2 of the seal ring 2 at the end portions 10 and 20 are smaller than the width t3 at the center portion 3 of the seal ring 2. The width t1 of the seal ring 2 at the end portion 10 is, for example, the width t at the end (end 4a) of the inner circumferential surface 4 (see FIGS. 1 and 2). Similarly, the width t2 of the seal ring 2 at the end portion 20 is, for example, the width t at the end (end 4b) of the inner circumferential surface 4 (see FIGS. 1 and 2). For example, the thickness ratio R1 (t1 / t3), which is the ratio of the width t1 at the end portion 10 to the width t3 at the center portion 3, is between 0.2 and 0.6. In other words, the thickness ratio R1 (t1 / t3) is between 0.2 and 0.6. Furthermore, the thickness ratio R2 (t2 / t3), which is the ratio of the width t2 at the end portion 20 to the width t3 at the center portion 3, is, for example, between 0.2 and 0.6. That is, the thickness ratio R2 (t2 / t3) is a value between 0.2 and 0.6. The thickness ratio R1 (t1 / t3) and the thickness ratio R2 (t2 / t3) are the same or substantially the same value, and hereinafter both thickness ratios are collectively referred to as the thickness ratio R.

[0028] As described above, the width t of the seal ring 2 increases from the ends 10, 20 toward the central portion 3, and the thickness ratio around the circumferential direction of the seal ring 2 increases from the ends 10, 20 toward the central portion 3, becoming 1 at the central portion 3.

[0029] The seal ring 2 is configured to form a gap 2a having, for example, a known special step-cut shape. As shown in FIG. 1 , the ends 10 and 20 are respectively formed with stepped portions 11 and 21 that form the special step-cut shape. The stepped portion 11 is formed on the outer periphery side of the inner periphery surface 4 and extends circumferentially on both sides of the end 4a at the end 10 of the inner periphery surface 4. Similarly, the stepped portion 12 is formed on the outer periphery side of the inner periphery surface 4 and extends circumferentially on both sides of the end 4b at the end 20 of the inner periphery surface 4. The stepped portion 11 is provided, for example, on the side surface 6 side to form a step in the side surface 6, and the stepped portion 21 is provided, for example, on the side surface 7 side to form a step in the side surface 7. When the seal ring 2 is in use, the seal ring 2 elastically deforms, and the step portions 11 and 12 overlap in the direction of the axis x1. In other words, the step portions 11 and 12 overlap each other within a predetermined range in the circumferential direction, forming a joint 2a with a special step-cut shape. Note that the joint 2a formed in the seal ring 2 when in use is not limited to the special step-cut shape and may be, for example, a step-cut shape, a straight-cut shape, or a bias-cut shape. In other words, the shape for forming the joint 2a of the end portions 10, 20 is not limited to the special step-cut shape and may be, for example, a step-cut shape, a straight-cut shape, or a bias-cut shape.

[0030] The seal ring 2 is made of resin. Examples of resin materials that form the seal ring 2 include polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyimide (PI), and polyamide-imide (PAI). The resin material of the seal ring 2 may contain, for example, a filler for improving sliding characteristics and strength. As described above, the seal ring 2 is used in a pump that pumps liquid. The pumped liquid to be sealed is, for example, a low-viscosity liquid. When the sealing device 1 is used in a low-temperature environment, a material with a small linear expansion coefficient is preferred for the material of the seal ring 2. For example, the material of the seal ring 2 may have a linear expansion coefficient of 15×10 －５ / °C. When the sealing device 1 is used in a low-temperature environment, PEEK, which has a small linear expansion coefficient, is preferred as the resin material for the seal ring 2. A low-temperature environment is, for example, an environment where the ambient temperature is lower than the atmospheric temperature. Specifically, for example, a low-temperature environment is an environment where the ambient temperature is −253°C or an environment where the ambient temperature is lower than −253°C.

[0031] The operation of the sealing device 1 having the above-described configuration will be described below. Figures 3 and 4 are cross-sectional views showing the sealing device 1 in use, attached between the piston 101 and cylinder 110 of a pump 100 that pumps liquid. Figure 3 shows a cross section taken along a plane including the axis x of the cylinder 110, and Figure 4 shows a cross section perpendicular to the axis x. Note that the seal ring 2 is not shown in cross section in Figure 4.

[0032] 3 and 4, an annular groove 103 is formed in the outer peripheral surface 102 of the piston 101. The groove 103 accommodates only one seal ring 2, with the inner peripheral surface 4 of the seal ring 2 facing a bottom surface 103a of the groove 103. In the pump 100, the piston 101 with the seal ring 2 attached to the groove 103 is inserted into a hole 112 of a cylinder 110. In the pump 100, as the piston 101 reciprocates within the hole 112 of the cylinder 110, the liquid is pushed by the piston 101 and is pumped in the direction of arrow a.

[0033] As described above, the diameter of the outer peripheral surface 5 of the seal ring 2 is larger than the diameter of the inner peripheral surface 111 that defines the bore 112 of the cylinder 110. Therefore, in the pump 100, the seal ring 2 contacts the inner peripheral surface 111 of the cylinder 110 and elastically deforms, bending inward to form a gap 2a. That is, the outer peripheral surface 5 of the seal ring 2 is pressed inward by the inner peripheral surface 111 of the cylinder 110, causing the seal ring 2 to elastically deform, and the step portion 11 at the end 10 and the step portion 12 at the end 20 of the seal ring 2 overlap in the direction of the axis x1 within a predetermined range in the circumferential direction, forming a gap 2a with a special step-cut shape. As a result, the diameter of the outer peripheral surface 5 of the seal ring 2 is reduced, and the outer peripheral surface 5 of the seal ring 2 faces the inner peripheral surface 111 of the cylinder 110 over the entire circumference around the axis x.

[0034] The width t of the seal ring 2 decreases, i.e., becomes thinner, from the central portion 3 toward the end portions 10, 20. Therefore, when the seal ring 2 is fitted into the hole 112 of the cylinder 110, both sides of the seal ring 2 elastically deform so as to bend toward the axis x, centered around the central portion 3. The portions of the seal ring 2 with smaller width t are pressed more against the inner circumferential surface 111 and elastically deform so as to bend more. The end portions 10, 20 of the seal ring 2 and their vicinity are smaller in width, i.e., thinner, and more easily elastically deformed so as to bend toward the inner circumferential surface 111. Therefore, the seal ring 2 deforms when fitted into the hole 111 of the cylinder 110, forming a gap 2a, and the outer circumferential surface 5 faces the inner circumferential surface 111 of the cylinder 110 over the entire circumference around the axis x.

[0035] In order for the outer peripheral surface 5 of the seal ring 2 at and near the ends 10, 20 thereof to contact the inner peripheral surface 111 of the cylinder 110 in the pump 100, the ends 10, 20 thereof and their vicinity must elastically deform so as to bend inward along the inner peripheral surface 111 of the cylinder 110. The width t of the seal ring 2 at and near the ends 10, 20 thereof becomes smaller toward the ends 10, 20, making the ends 10, 20 thereof and their vicinity more likely to deform along the inner peripheral surface 111 of the cylinder 110. Therefore, in the pump 100, even at and near the ends 10, 20 of the seal ring 2, where a gap is likely to form between the outer peripheral surface 5 and the inner peripheral surface 111 of the cylinder 110, the outer peripheral surface 5 of the seal ring 2 deforms to fit along the inner peripheral surface 111 of the cylinder 110, thereby preventing a gap from being formed between the outer peripheral surface 5 and the inner peripheral surface 111 of the cylinder 110. Therefore, at the ends 10, 20 of the seal ring 2 and their vicinity, a radial gap formed between the outer peripheral surface 5 and the inner peripheral surface 111 of the cylinder 110 is small, and the circumferential range of this gap is also small. Thus, in the pump 100, the outer peripheral surface 5 of the seal ring 2 is in contact with the inner peripheral surface 111 of the cylinder 110 over almost the entire circumference around the axis x, and the resulting gap is small. Alternatively, at the ends 10, 20 of the seal ring 2 and their vicinity, there is no radial gap formed between the outer peripheral surface 5 and the inner peripheral surface 111 of the cylinder 110, and in the pump 100, the outer peripheral surface 5 of the seal ring 2 is in contact with the inner peripheral surface 111 of the cylinder 110 over the entire circumference around the axis x, and no gap is formed.

[0036] The deviation (distance d) of the axis x2 of the inner surface 4 of the seal ring 2 from the axis x1 of the outer surface 5 is set, for example, as described above, so that the seal ring 2 elastically deforms along the inner surface 111 of the cylinder 110.

[0037] In this way, in the pump 100, the seal ring 2 can bring the outer peripheral surface 5 of the seal ring 2 into contact with the inner peripheral surface 111 of the cylinder 110 over approximately the entire circumference or the entire circumference around the axis x. Furthermore, a radial gap formed between the outer peripheral surface 5 of the seal ring 2 and the inner peripheral surface 111 of the cylinder 110 is small or absent, and the circumferential range of this gap is small. Therefore, even if the liquid pumped by the piston 101 in the cylinder 110 is a low-viscosity liquid, the sealing device 1 prevents the pumped liquid from leaking from the outer peripheral surface 5 of the seal ring 2 and the inner peripheral surface 111 of the cylinder 110 by using one seal ring 2. As a result, the sealing device 1 can improve the pumping efficiency of the pump 100 by using one seal ring 2. In this way, the sealing device 1 does not achieve sealing by arranging multiple seal rings in series and providing multiple stages of blocking structures as in the past, but can maintain sealing performance or suppress deterioration of sealing performance with a simple structure of a single seal ring 2, even when the fluid being pumped becomes a low-viscosity liquid. Therefore, the sealing device 1 can achieve the desired sealing performance for low-viscosity fluids with a single seal ring 2. Note that low viscosity means a viscosity lower than that of water, for example.

[0038] Furthermore, because the seal ring 2 is elastically deformable so as to bend more easily from the central portion 3 toward the ends 10, 20, even when the seal ring 2 shrinks in a low-temperature environment, the outer peripheral surface 5 of the seal ring 2 can be kept in contact with the inner peripheral surface 111 of the cylinder 110 over approximately the entire circumference or the entire circumference around the axis x. In other words, in a low-temperature environment, the seal ring 2 shrinks so that a gap is created between the outer peripheral surface 5 of the seal ring 2 and the inner peripheral surface 111 of the cylinder 110, but as this shrinkage occurs, the elastically deformed seal ring 2 deforms toward its natural state, so the outer peripheral surface 5 of the seal ring 2 maintains contact with the inner peripheral surface 111 of the cylinder 110 over approximately the entire circumference or the entire circumference around the axis x.

[0039] In order to maintain contact between the outer peripheral surface 5 of the seal ring 2 and the inner peripheral surface 111 of the cylinder 110 over approximately the entire circumference or the entire circumference around the axis x even when the seal ring 2 shrinks in a low-temperature environment, for example, the diameter r1 of the outer peripheral surface 5 is adjusted. Specifically, the diameter r1 of the outer peripheral surface 5 is adjusted so that, in a state in which the seal ring 2 is elastically deformed, the outer peripheral surface 5 of the seal ring 2 and the inner peripheral surface 111 of the cylinder 110 maintain contact over approximately the entire circumference or the entire circumference around the axis x even when the seal ring 2 shrinks in a low-temperature environment. The diameter r1 of the outer peripheral surface 5 is adjusted in accordance with, for example, the diameter of the inner peripheral surface 111 of the cylinder 110. In this case, when not thermally shrunk, the seal ring 2 elastically deforms due to the strong restraining force from the cylinder 110, but the ends 10, 20 of the seal ring 2 and their vicinity are easily deformed along the inner surface 111 of the cylinder 110, thereby preventing a gap from forming between the outer surface 5 and the inner surface 111 of the cylinder 110.

[0040] As described above, the sealing device 1 according to the present embodiment can maintain sealing performance against fluids or suppress deterioration of sealing performance even in a low-temperature environment with a single seal ring 2. Therefore, the sealing device 1 according to the present embodiment can exhibit desired sealing performance with a single seal ring 2 even in a low-temperature environment. This desired sealing performance is sealing performance that is arbitrarily set by a user or the like depending on, for example, the application target and application situation of the sealing device 1. Specifically, for example, the desired sealing performance is set by setting the amount of leakage from the sealed target for a predetermined usage time under predetermined usage conditions such as a predetermined temperature and atmospheric pressure.

[0041] Furthermore, since the material of the seal ring 2 has a lower linear expansion coefficient, the shrinkage of the seal ring 2 in a low-temperature environment can be suppressed more effectively. Therefore, using a material with a low linear expansion coefficient for the seal ring 2 is effective in maintaining sealing performance against fluids or suppressing deterioration of sealing performance in a low-temperature environment. Furthermore, as described above, the sealing device 1 according to this embodiment can maintain sealing performance against low-viscosity fluids or suppress deterioration of sealing performance with a single seal ring 2. Therefore, the sealing device 1 according to this embodiment can exhibit desired sealing performance against low-viscosity fluids with a single seal ring 2.

[0042] 3, when the piston 101 moves in the direction of arrow a, the side surface 7 of the seal ring 2 comes into contact with the side surface 103b of the groove 103 in the piston 101, thereby sealing the annular gap between the piston 101 and the inner circumferential surface 111 of the cylinder 110. On the other hand, when the piston 101 moves in the direction of arrow b, the side surface 6 of the seal ring 2 comes into contact with the side surface 103c of the groove 103 in the piston 101, thereby sealing the annular gap between the piston 101 and the inner circumferential surface 111 of the cylinder 110. Furthermore, when the piston 101 is in use, the axis x of the cylinder 110 and the axis x1 of the outer circumferential surface 5 of the seal ring 2 coincide or approximately coincide.

[0043] Next, a sealing performance test for evaluating the sealing performance of the sealing device 1 will be described. FIG. 5 is a diagram showing a schematic configuration of a sealing performance test apparatus 200 for conducting a sealing performance test of the sealing device 1. As shown in FIG. 5, the sealing performance test apparatus 200 has a pseudo piston 201 and a pseudo cylinder 210 that respectively simulate the piston 101 and the cylinder 110 of the pump 100 described above. The pseudo piston 201 has an outer circumferential surface 202 similar to the outer circumferential surface 102 of the piston 101, and a groove 203 similar to the groove 103 of the piston 101 is formed in the outer circumferential surface 202. The pseudo cylinder 210 also has an inner circumferential surface 211 similar to the inner circumferential surface 111 of the cylinder 110, and a hole 212 is formed in the inner circumferential surface 211. The pseudo piston 201, with the seal ring 2 of the sealing device 1 accommodated in the groove 203, is inserted into the hole 212 of the pseudo cylinder 210, and the seal ring 2 is in a usage state similar to a usage state attached to the pump 100. 5, the pseudo-cylinder body 210 is cylindrical and has open ends, which are closed by lids 213 and 214. Tube members 215 and 216 are attached to the lids 213 and 214, respectively, and pass through the lids 213 and 214 to communicate with the hole 212. The pseudo-piston body 201 is supported immovably by the lids 213 and 214.

[0044] In the sealing performance test, the sealing performance test device 200 is placed in a container 220 containing a cooling medium L, as shown in FIG. 5, and is submerged in the cooling medium L. However, the tips of the pipe members 215 and 216 protrude from the surface of the cooling medium L. The cooling medium L is, for example, liquid nitrogen (LN ２ ). In this state, when the seal ring 2 in the seal performance testing device 200 reached a predetermined test temperature, a test fluid pressurized to a predetermined test pressure P was introduced from the pipe member 215 into the hole 212, and this state was maintained, and the leakage amount of the test fluid that leaked over a predetermined time period was measured. The leakage amount of the test fluid was measured by recovering the test fluid leaking from the seal ring 2 from the pipe member 216 and measuring it. Nitrogen gas was used as the test fluid. The test conditions were a test temperature of approximately -190°C and a test pressure P of 0.5 MPa to 8 MPa.

[0045] Furthermore, two seal rings 2 were prepared: a seal ring 2 (Test Example 1) having a thickness ratio R of 0.3, and a seal ring 2 (Test Example 2) having a thickness ratio R of 0.55. A sealing performance test was conducted on Test Examples 1 and 2. A sealing performance test was also conducted on a conventional seal ring (Comparative Example 1) in which the width t of the seal ring was uniform over the entire circumferential direction, using the above-described sealing performance test device 200. Fig. 6 is a diagram showing the results of the sealing performance test on the seal ring 2 (Test Examples 1 and 2) and the conventional seal ring (Comparative Example 1).

[0046] As shown in Figure 6, the leakage amount in Test Example 1 (thickness ratio P 0.3) was 95% less than that in Comparative Example 1. Furthermore, the leakage amount in Test Example 2 (thickness ratio P 0.55) was 70% less than that in Comparative Example 1. Thus, it can be seen that the seal ring 2 of the sealing device 1 can significantly improve the sealing performance for low-viscosity fluids compared to conventional seal rings. Furthermore, the relationship between the thickness ratio R and the leakage amount is expected to be as shown by the dotted line in Figure 6.

[0047] As described above, according to the sealing device 1 of the embodiment of the present invention, the single seal ring 2 can maintain the sealing performance for the fluid even in a low-temperature environment, or can suppress the deterioration of the sealing performance for the fluid even in a low-temperature environment. In this way, according to the sealing device 1 of the embodiment of the present invention, the desired sealing performance for the fluid can be obtained with a simple structure, even in a low-temperature environment. Furthermore, according to the sealing device 1 of the embodiment of the present invention, the single seal ring 2 can maintain the sealing performance or suppress the deterioration of the sealing performance even when the object to be sealed has a low viscosity. In this way, according to the sealing device 1 of the embodiment of the present invention, the simple structure can obtain the desired sealing performance for the low-viscosity fluid.

[0048] Although the present invention has been described above through the above embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0049] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. Furthermore, the above-described embodiments do not limit the scope of the present invention, and the present invention may include any and all applications. The components of the above-described embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those illustrated and may be modified as appropriate. For example, the present invention includes differences that arise during implementation due to manufacturing tolerances, etc. Furthermore, components illustrated in different embodiments may be partially substituted or combined within the scope of technical inconsistency. Furthermore, the various configurations may be selectively combined as appropriate to achieve at least some of the above-described problems and effects.

[0050] For example, the cross-sectional shape of the seal ring 2 is not limited to a rectangular or approximately rectangular shape. For example, the inner peripheral surface 5 of the seal ring 2 may have a protrusion that protrudes inward, and the cross-sectional shape of the seal ring 2 may be T-shaped. Furthermore, a plurality of seal rings 2 may be arranged side by side for use. For example, a plurality of grooves 103 may be formed in the piston 101 at intervals in the direction of the axis x, and a seal ring 2 may be attached to each of these grooves 103. Furthermore, the application of the seal ring 2 is not limited to the above-described pumps that are subjected to static pressure, but may also be one that is subjected to dynamic pressure. For example, the seal ring 2 may be used to seal between a shaft that rotates around its axis and a through-hole through which the shaft passes, or may be provided between an outer member and an inner member that rotate relative to each other.

[0051] 1 Sealing device, 2 Seal ring, 2a Gap, 3 Center, 4 Inner peripheral surface, 5 Outer peripheral surface, 6, 7 Side, 10, 20 End, 11, 21 Step portion, 30 Gap, 31 Center, 100 Pump, 101 Piston, 102 Outer peripheral surface, 103 Groove, 103a Bottom surface, 103b, 103c Side, 110 Cylinder, 111 Inner peripheral surface, 112 Hole, 200 Seal performance test device, 201 Piston dummy body, 202 Outer peripheral surface, 203 Groove, 210 Cylinder dummy body, 211 Inner peripheral surface, 212 Hole, 213, 214 Lid, 215, 216 Pipe member, 220 Container, d Distance, R, R1, R2 Wall thickness ratio, r1, r2 Diameter, t, t1, t2, t3 Width (radial width), x, x1, x2 Axis

Claims

1. A sealing device for sealing an annular gap, comprising one seal ring, the one seal ring exhibiting desired sealing performance against fluids even in a low-temperature environment.

2. The sealing device according to claim 1, wherein the fluid is a low viscosity fluid.

3. The sealing device according to claim 1 or 2, wherein the seal ring is a seal ring for sealing an annular gap, is arc-shaped about an axis, and has a pair of circumferential ends, the pair of ends being configured to form a joint, and the radial width at the pair of ends is smaller than the radial width at a central portion between the pair of ends.

4. The sealing device according to claim 3, wherein the seal ring has an inner peripheral surface facing the inner peripheral side and an outer peripheral surface facing the outer peripheral side, the width is the width between the inner peripheral surface and the outer peripheral surface, the inner peripheral surface has no radial steps, and the outer peripheral surface has no radial steps.

5. The sealing device according to claim 4, wherein the ratio of the radial width at the pair of ends to the radial width at the central portion is between 0.2 and 0.

6.

6. The sealing device according to claim 3, wherein the radial width value is continuous around the axis.

7. The sealing device according to claim 6, wherein the radial width increases from one of the pair of ends toward the central portion, and the radial width increases from the other of the pair of ends toward the central portion.

8. A sealing device as claimed in claim 4, wherein the outer peripheral surface is along a cylindrical surface having the axis as a central axis, and the inner peripheral surface is along a cylindrical surface having a central axis radially offset from the axis.

9. The sealing device according to claim 1, which is intended to seal a fluid having a lower viscosity than water.

10. The sealing device according to claim 1, used to seal a gap between a reciprocating member and a cylindrical hole into which said member is inserted.

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