Booster pump and low-temperature fluid supply system

Abstract

The present invention comprises a cylinder (52) that has a compression chamber, a piston (53) that is movably supported by the cylinder and compresses a low-temperature fluid in the compression chamber, piston rings (71) that are provided to an outer peripheral portion of the piston, and a wear ring (72) that is provided at the outer peripheral portion of the piston on the low-pressure side of the piston rings, wherein the wear ring has communication portions (82) that communicate between a high-pressure-side region and a low-pressure-side region.

Description

Boost pump and cryogenic fluid supply system

[0001] The present disclosure relates to a boost pump and a cryogenic fluid supply system.

[0002] As a system for achieving carbon neutrality, it is considered to apply hydrogen gas as fuel. Hydrogen is stored in a tank in the state of liquid hydrogen, the liquid hydrogen stored in the tank is vaporized into hydrogen gas, and the hydrogen gas is supplied to, for example, a fuel cell or a hydrogen engine. The hydrogen supply system includes a boost pump for boosting the pressure of liquid hydrogen. The boost pump has a cylinder having a compression chamber and a piston for compressing the cryogenic fluid in the compression chamber, and the piston is movably supported by a cylinder block. A piston ring is mounted on the outer peripheral portion of the piston to prevent leakage of the high-pressure cryogenic fluid from the compression chamber. As such a piston ring, for example, there is one described in Patent Document 1 below.

[0003] Japanese Patent Application Laid-Open No. 2019-120403

[0004] The piston is not only equipped with a piston ring on its outer peripheral portion but also a wear ring. The piston ring prevents leakage of the compressed cryogenic fluid. The wear ring functions as a bearing for supporting the piston with respect to the cylinder. Since the piston reciprocates inside the cylinder, the piston ring wears due to long-term use, and wear powder is generated. The wear powder of the piston ring flows to the low-pressure side inside the cylinder and accumulates on the wear ring. At this time, when the wear powder enters the sliding portion between the wear ring and the cylinder, there is a problem that it promotes the wear of the wear ring when the piston moves and reduces the life of the wear ring.

[0005] The present disclosure solves the above-described problems, and an object thereof is to provide a boost pump and a cryogenic fluid supply system that suppress wear of the wear ring and achieve a long life.

[0006] A booster pump according to the present disclosure for achieving the above objectives comprises a cylinder having a compression chamber, a piston movably supported in the cylinder for compressing a low-temperature fluid in the compression chamber, a piston ring provided on the outer circumference of the piston, and a wear ring provided on the outer circumference of the piston on a lower-pressure side than the piston ring, wherein the wear ring has a communication portion that connects a high-pressure side region and a low-pressure side region.

[0007] Furthermore, the cryogenic fluid supply system of this disclosure comprises a compressor that compresses the cryogenic fluid using the booster pump, an evaporator that vaporizes the cryogenic fluid compressed by the compressor, and a dispenser that supplies the gas vaporized by the evaporator.

[0008] The booster pump and cryogenic fluid supply system of this disclosure can suppress wear on the wear ring and extend its lifespan.

[0009] Figure 1 is a schematic diagram showing the overall configuration of the hydrogen supply system of this embodiment. Figure 2 is a longitudinal cross-sectional view showing the compressor of this embodiment. Figure 3 is a cross-sectional view showing the piston and cylinder. Figure 4 is a perspective view showing the wear ring. Figure 5 is a plan view showing the wear ring. Figure 6 is a side view showing the wear ring. Figure 7 is a cross-sectional view showing the wear ring mounted on the piston. Figure 8 is a perspective view showing a first modified example of the wear ring. Figure 9 is a perspective view showing a second modified example of the wear ring. Figure 10 is a perspective view showing a third modified example of the wear ring. Figure 11 is a cross-sectional view showing a third modified example of the wear ring.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0011] [Embodiment] <Hydrogen Supply System> Figure 1 is a schematic diagram showing the overall configuration of the hydrogen supply system of this embodiment.

[0012] As shown in Figure 1, the hydrogen supply system (low-temperature fluid supply system) 10 supplies (replenishes) liquid hydrogen stored in the liquefied hydrogen storage tank 11 as hydrogen gas at a predetermined pressure to the power source of the vehicle 12. Here, the power source is, for example, a fuel cell or a hydrogen engine, and is mounted on the vehicle 12. The hydrogen supply system 10 is, for example, a so-called hydrogen station that supplies (replenishes) hydrogen gas, which is the fuel, to the power source of the vehicle 12. However, the hydrogen supply system 10 is not limited to supplying hydrogen gas to the power source of the vehicle 12, but also includes supplying hydrogen gas to the tank of a trailer for transporting hydrogen. Furthermore, the hydrogen supply system 10 operates similarly when supplying compressed low-temperature fluids (for example, liquid hydrogen, liquid nitrogen, liquid oxygen, liquefied carbon dioxide, liquefied natural gas, liquefied propane gas, etc.) rather than just hydrogen.

[0013] The hydrogen supply system 10 includes a compressor 21, an evaporator 22, and a dispenser 23. The compressor 21 compresses liquid hydrogen (low-temperature fluid) supplied from the liquefied hydrogen storage tank 11 to a predetermined high pressure (high-pressure state). The evaporator 22 generates hydrogen gas by vaporizing the high-pressure liquid hydrogen compressed by the compressor 21. The dispenser 23 fills the power source of the vehicle 12 with the hydrogen gas generated by the evaporator 22.

[0014] The compression device 21 compresses the liquid hydrogen stored in the liquefied hydrogen storage tank 11 to a predetermined high pressure, but the configuration is not limited to this.

[0015] The compression device 21 comprises a drive unit 31 and a booster pump 32. The drive unit 31, although not shown, comprises a drive motor and a drive mechanism. The drive motor is an electric motor that can be driven by power supplied from an external source. The rotational speed of the drive motor is controlled by an inverter (not shown). The drive mechanism has a crank mechanism and converts the rotational power of the drive motor into linear reciprocating power. The drive motor transmits the rotational power to the drive mechanism, and the drive mechanism transmits the linear reciprocating power to the booster pump 32. The booster pump 32 is operated by the drive unit 31 and compresses liquid hydrogen. The drive unit 31 may have a reduction gear between the drive motor and the drive mechanism.

[0016] <Compression device> Figure 2 is a longitudinal cross-sectional view showing the compression device of this embodiment.

[0017] As shown in Figure 2, the compression device 21 has a drive unit 31 and a booster pump 32, and the drive unit 31 has a drive motor 33 and a drive mechanism 34. The compression device 21 (boostering pump 32) is a device for increasing the pressure of liquid hydrogen, which is an extremely cold liquid, to high pressure (about 90 MPa).

[0018] <Drive Unit> The drive mechanism 34 includes an eccentric shaft 41, a rotating body 42, a link 43, a pivot shaft 44, a crosshead 45, and a housing 46.

[0019] The eccentric shaft portion 41 is cylindrical in shape and arranged along the horizontal direction. The eccentric shaft portion 41 is rotatably supported about an axis O1 along the horizontal direction. The tip of the output shaft 33a of the drive motor 33 is connected to the eccentric shaft portion 41. When the drive motor 33 is driven, the output shaft 33a rotates, and the rotational power of the output shaft 33a is transmitted to the eccentric shaft portion 41, causing the eccentric shaft portion 41 to rotate.

[0020] The rotating body 42 is disc-shaped, positioned outside the eccentric shaft portion 41, and rotatable integrally with the eccentric shaft portion 41. The rotating body 42 has a center along the axis O2, and the center of the rotating body 42 (axis O2) and the center of the eccentric shaft portion 41 (axis O1) are offset radially. That is, the center of the eccentric shaft portion 41 (axis O1) is located eccentrically with respect to the center of the rotating body 42 (axis O2). When the eccentric shaft portion 41 rotates, the rotating body 42 oscillates around the axis O1.

[0021] The link section 43 constitutes a crank mechanism and converts rotational power into linear reciprocating power, which is then transmitted to the booster pump 32. The link section 43 has an upper annular section 43a, a connecting section 43b, and a lower annular section 43c. The upper annular section 43a is ring-shaped. The upper annular section 43a is positioned on the outside of the rotating body 42 via a bearing section (not shown) and is rotatable relative to the rotating body 42. The lower annular section 43c is ring-shaped. The connecting section 43b is positioned between the upper annular section 43a and the lower annular section 43c and integrally connects the upper annular section 43a and the lower annular section 43c.

[0022] When the eccentric shaft portion 41 rotates and the rotating body 42 oscillates around the axis O1, the link portion 43 is activated. Specifically, the upper annular portion 43a of the link portion 43 oscillates around the axis O1 due to the rotation of the rotating body 42, and the oscillating power of the upper annular portion 43a is transmitted to the lower annular portion 43c via the connecting portion 43b, causing the lower annular portion 43c to reciprocate linearly in the vertical direction while rotating around an axis O3 parallel to the axes O1 and O2.

[0023] The upper end of the oscillating shaft portion 44 is connected to the lower end of the lower annular portion 43c of the link portion 43. The lower end of the oscillating shaft portion 44 is connected to the upper end of the piston 53 of the booster pump 32, which will be described later. The oscillating shaft portion 44 is pivotable between the lower annular portion 43c and the piston 53, around an oscillating axis that is horizontal to the lower annular portion 43c and the piston 53.

[0024] The crosshead 45 has a bottomed cylindrical shape that covers the lower annular portion 43c from the outside. The housing 46 is positioned on the outer circumference of the crosshead 45. The housing 46 is supported by a frame (not shown), and the crosshead 45 is supported so as to be movable along the vertical direction relative to the housing 46. The lower annular portion 43c of the link portion 43 is rotatably supported by the crosshead 45. When the eccentric shaft portion 41 and the rotating body 42 rotate and the link portion 43 reciprocates along the vertical direction, the lower annular portion 43c and the crosshead 45 reciprocate along the vertical direction relative to the housing 46.

[0025] <Booster Pump> As shown in Figure 2, the booster pump 32 comprises a casing 51, a cylinder 52, a piston 53, and a discharge pipe 54.

[0026] <Casing> The casing 51 is a pressure vessel for storing liquid hydrogen and is also an insulated vacuum vessel. The support plate 61 is arranged horizontally and installed on a frame (not shown). The support plate 61 has a through hole 61a located on the axis O4 along the vertical direction. The casing 51 has a casing body 51a, an intermediate flange portion 51b, a support cylinder portion 51c, and an upper flange portion 51d. The casing body 51a is an insulated structure with a bottomed cylindrical shape, and an internal liquid storage chamber 62 is formed therein. The intermediate flange portion 51b is disc-shaped, and a circular hole is formed at its center. The intermediate flange portion 51b is integrally fastened to the upper end of the casing body 51a. The intermediate flange portion 51b has a support cylinder portion 51c, which has a smaller diameter than the casing body 51a, integrally provided at its upper part. The support cylinder portion 51c has an upper flange portion 51d, which is larger in diameter than the support cylinder portion 51c, integrally provided at its upper end, and a circular hole is formed in the center of the upper flange portion 51d. The casing 51 is fastened with bolts so that the upper flange portion 51d is in close contact with the lower surface of the support plate 61. In other words, the upper end of the casing 51 is suspended and supported by the support plate 61.

[0027] The casing 51 has a supply pipe 63 and a gas discharge pipe 64 connected to the side of the casing body 51a. The supply pipe 63 is a pipe for supplying liquid hydrogen from an external source to the liquid storage chamber 62 of the casing 51. The supply pipe 63 is located near the bottom of the casing 51. The gas discharge pipe 64 is a pipe for discharging the vaporized components (hydrogen gas) in the liquid storage chamber 62 to the outside. The gas discharge pipe 64 is located above and spaced apart from the supply pipe 63. The liquid storage chamber 62 stores liquid hydrogen, and the liquid level of the liquid hydrogen is adjusted to be below the level of the gas discharge pipe 64.

[0028] <Cylinder> The cylinder 52 is a container for compressing liquid hydrogen. The cylinder 52 has a cylinder body 52a and a flange portion 52b. The cylinder body 52a has a bottomed cylindrical shape, and a compression chamber 65 is provided on the lower side inside. The cylinder body 52a has a flange portion 52b which is larger in diameter than the cylinder body 52a integrally provided at the upper end, and the flange portion 52b has an opening in the center. The cylinder 52 is fitted into the through hole 61a of the support plate 61 by the flange portion 52b and is placed on the upper surface of the upper flange portion 51d of the casing 51. That is, the upper end of the cylinder 52 is suspended and supported by the support plate 61. In addition, a sealing member (not shown) is provided between the flange portion 52b of the cylinder 52 and the upper flange portion 51d of the casing 51.

[0029] A suction valve 66 is provided at the bottom of the cylinder 52. The suction valve 66 is for introducing liquid hydrogen from the liquid storage chamber 62 into the compression chamber 65. In other words, the suction valve 66 is a check valve and opens when the pressure in the compression chamber 65 is lower than the pressure in the liquid storage chamber 62, allowing liquid hydrogen from the liquid storage chamber 62 to be introduced into the compression chamber 65. On the other hand, it closes when the pressure in the compression chamber 65 is higher than the pressure in the liquid storage chamber 62, preventing liquid hydrogen from the compression chamber 65 from flowing back into the liquid storage chamber 62. In Figure 2, the suction valve 66 is shown exposed outside the cylinder 52, but Figure 2 is a schematic diagram, and in reality, the suction valve 66 is provided inside the cylinder 52.

[0030] A discharge valve 67 is provided on the lower side of cylinder 52. The discharge valve 67 is for discharging (releasing) the high-pressure liquid water compressed in the compression chamber 65 to the outside. In other words, the discharge valve 67 is a check valve and opens when the pressure in the compression chamber 65 becomes higher than the pressure on the discharge side, discharging the high-pressure liquid hydrogen from the compression chamber 65 to the outside. On the other hand, it closes when the pressure in the compression chamber 65 becomes lower than the pressure on the discharge side, preventing the high-pressure liquid hydrogen from the discharge side from flowing back into the compression chamber 65. In Figure 2, the discharge valve 67 is shown exposed to the outside of cylinder 52, but Figure 2 is a schematic diagram, and in reality, the discharge valve 67 is provided inside cylinder 52.

[0031] <Piston> The piston 53 has an elongated cylindrical shape and is positioned along an axis O4 that runs vertically. The outer diameter of the piston 53 is constant throughout the entire direction of the axis O4. The upper end of the piston 53 is connected to the drive unit 31, and the lower part is positioned inside the cylinder 52. The piston 53 is provided with a piston ring 71 and wear rings 72 and 73 at its lower end. The piston ring 71 and wear rings 72 and 73 will be described later.

[0032] The cylinder 52 has a piston 53 positioned inside, which demarcates a compression chamber 65 at its lower end. The piston 53 reciprocates within the cylinder 52 along the direction of the axis O4 by the drive unit 31. When the piston 53 moves upward within the cylinder 52, the volume of the compression chamber 65 expands, the pressure decreases, and liquid hydrogen is drawn in. When the piston 53 moves downward within the cylinder 52, the volume of the compression chamber 65 contracts, the pressure increases, and the liquid hydrogen is compressed. The cylinder 52 is provided with a sealing member on the inner circumferential surface of the opening of the flange portion 52b to seal the gap between it and the outer circumferential surface of the piston 53.

[0033] <Discharge Piping> The discharge piping 54 is a pipe for discharging the high-pressure liquid hydrogen compressed in the compression chamber 35 to the outside. The discharge piping 54 is located inside the casing 51, adjacent to the cylinder 52. The discharge piping 54 is arranged vertically, its lower end is connected to the lower part of the cylinder 52, and it communicates with the compression chamber 65 via the discharge valve 67. The upper end of the discharge piping 54 extends to the outside, passing through the top of the casing 51, and is supported by the top of the casing 51.

[0034] <Operation of the Compressor> As shown in Figure 2, when the drive motor 33 is driven, the eccentric shaft portion 41 rotates and the rotating body 42 oscillates. Then, the link portion 43 operates, converting the rotational power into linear reciprocating power, which is transmitted to the booster pump 32 via the oscillating shaft portion 44. When the booster pump 32 operates, first, in the suction process in which the piston 53 rises, liquid hydrogen in the casing 51 is drawn into the compression chamber 65. Next, in the compression process in which the piston 53 descends, the liquid hydrogen in the compression chamber 65 is compressed, and high-pressure liquid hydrogen is discharged into the discharge pipe 54.

[0035] <Piston Rings and Wear Rings> Figure 3 is a cross-sectional view of the piston and cylinder.

[0036] As shown in Figure 3, the cylinder 52 has a fitting hole 70 formed inside. The piston 53 is supported in the fitting hole 70 of the cylinder 52 so as to be movable in the axial direction. The piston 53 and the fitting hole 70 have a circular cross-sectional shape centered on the axis O4. The outer diameter of the piston 53 is slightly smaller than the inner diameter of the fitting hole 70. The piston 53 is provided with a piston ring 71 and wear rings 72 and 73. Multiple piston rings 71 (three in this embodiment) are mounted on the outer circumference of the piston 53 at intervals in the direction of the axis O4. However, the number of piston rings 71 is not limited. The piston rings 71 are mounted in an annular groove formed on the outer circumference of the piston 53. The piston rings 71 have an annular shape centered on the axis O4 and are made of a resin material (for example, PTFE material mainly composed of polytetrafluoroethylene, or PAN-based carbon fiber). The piston ring 71 can maintain liquid-tightness and airtightness with respect to the inner circumferential surface of the fitting hole 70 of the cylinder 52.

[0037] Wear rings 72 and 73 are provided above and below the piston rings 71 in the direction of the axis O4. That is, wear ring 72 is provided above the piston rings 71 in the direction of the axis O4 with a gap between them, and wear ring 73 is provided below the piston rings 71 in the direction of the axis O4 with a gap between them. However, wear ring 73 is not an essential component. Also, multiple wear rings 72 and 73 may be provided. Wear rings 72 and 73 are fitted into annular grooves formed on the outer circumference of the piston 53. Wear rings 72 and 73 are annular in shape with the axis O4 as the center and are made of a resin material (for example, PTFE material mainly composed of polytetrafluoroethylene, or PAN-based carbon fiber). In this case, wear rings 72 and 73 are harder than piston rings 71. Wear rings 72 and 73 support the piston 53 in the fitting hole 70 of the cylinder 52.

[0038] The piston ring 71 and wear rings 72 and 73 mounted on the piston 53 divide the piston 53 into a high-pressure side region 201 and a low-pressure side region 202. Here, the high-pressure side region 201 is the region below the wear ring 72 in the direction of axis O4, that is, the region on the compression chamber 65 side, and the low-pressure side region 202 is the region above the wear ring 72 in the direction of axis O4, that is, the region on the opposite side from the compression chamber 65.

[0039] In the cylinder 52, the compression chamber 65 is partitioned by the placement of the piston 53 in the fitting hole 70. The compression chamber 65 is equipped with an intake valve 66 and a discharge valve 67. When the piston 53 rises, the volume of the compression chamber 65 increases, the intake valve 66 opens, and liquid hydrogen is drawn into the compression chamber 56. On the other hand, when the piston 53 descends, the volume of the compression chamber 65 decreases, the liquid hydrogen in the compression chamber 65 is compressed, and when a predetermined pressure is reached, the discharge valve 67 opens, and the high-pressure liquid hydrogen is discharged to the outside.

[0040] <Wearing> Figure 4 is a perspective view showing the wearing, Figure 5 is a plan view showing the wearing, and Figure 6 is a side view showing the wearing.

[0041] The wear ring 72 will now be described in detail. As shown in Figure 4, the wear ring 72 is provided above the multiple piston rings 71 in the direction of the axis O4. As shown in Figures 4 to 6, the wear ring 72 has a C-shaped ring form in plan view. The wear ring 72 has a rectangular cross-sectional shape, but is not limited to a rectangular cross-sectional shape; it may be partially curved or have other shapes. The wear ring 72 has one end 72a in the circumferential direction and the other end 72b in the circumferential direction. The one end 72a and the other end 72b of the wear ring 72 face each other. The wear ring 72 is provided with a joint portion 81 for assembly into the piston 53 (see Figure 3). In low temperature conditions, the joint portion 81 is formed due to the difference in the coefficient of linear expansion between the wear ring 72 and the piston rings 71.

[0042] The wearing ring 72 is provided with a communication part 82. The communication part 82 communicates the high-pressure side region 201 and the low-pressure side region 202 (both are shown in FIG. 3) inside the cylinder 52. The communication part 82 has a first communication part 83 and a second communication part 84. The first communication part 83 is the joint part 81. The second communication part 84 is a communication groove. There is one first communication part 83 (joint part 81), and a plurality of second communication parts (communication grooves) 84 are provided. However, the number of the second communication parts (communication grooves) 84 is not limited, and it may be one or more, and the number may be singular or plural. Also, the second communication part 84 may be provided only at a position radially opposed to the joint part 81 (a position shifted by 180 degrees in the circumferential direction).

[0043] A plurality of communication parts 82 (the first communication part 83 and the second communication part 84) are provided at intervals (preferably, equal intervals) in the circumferential direction of the wearing ring 72. The communication groove as the second communication part 84 is a recess provided on the outer peripheral surface 85 of the wearing ring 72. The communication parts 82 (the first communication part 83 and the second communication part 84) are inclined in the circumferential direction with respect to the axial direction of the wearing ring 72. That is, the first communication part 83 is the joint part 81, and one end part 72a and the other end part 72b are inclined. The second communication part 84 is a communication groove and is inclined in the circumferential direction with respect to the axial direction of the wearing ring 72. The inclination angle is preferably greater than 0 degrees and not more than 45 degrees with respect to the axial direction of the wearing ring 72.

[0044] Note that the communication groove as the second communication part 84 has a constant width and depth in the longitudinal direction, but it may be gradually enlarged toward the high-pressure side. Also, the communication groove as the second communication part 84 has a linear shape, but it may have a bent shape or a curved shape.

[0045] FIG. 7 is a cross-sectional view showing a wearing ring attached to a piston.

[0046] As shown in Fig. 7, annular groove portions 53a and 53b are provided on the outer peripheral portion of the piston 53. The piston ring 71 is disposed in the groove portion 53a of the piston 53. The wear ring 72 is disposed in the groove portion 53b of the piston 53. The wear ring 72 is disposed on the low-pressure side region 101 side with respect to the piston ring 71, that is, on the side opposite to the high-pressure side region 201 where the compression chamber 56 is located. The piston ring 71 and the wear ring 72 attached to the piston 53 contact the inner peripheral surface of the fitting hole 70 of the cylinder 52 by their own elastic forces with their outer peripheral surfaces 74 and 85.

[0047] When the piston 53 rises, the volume of the compression chamber 65 (high-pressure side region 201) increases, and liquid hydrogen is sucked into the compression chamber 56. Then, when the piston 53 descends, the volume of the compression chamber 65 (high-pressure side region 201) decreases, and the liquid hydrogen in the compression chamber 65 is compressed and discharged to the outside. When the piston 53 moves axially with respect to the cylinder 52, the piston ring 71 and the wear ring 72 attached to the piston 53 slide with their outer peripheral surfaces 74 and 85 with respect to the inner peripheral surface of the fitting hole 70 of the cylinder 52.

[0048] At this time, the piston ring 71 generates wear powder by sliding its outer peripheral surface 74 on the inner peripheral surface of the fitting hole 70 of the cylinder 52. When the wear powder generated by the wear of the piston ring 71 and the pressure in the compression chamber 65 (high-pressure side region 201) increase as the piston 53 descends, the wear powder may flow to the wear ring 72 side together with the fluid (hydrogen) and accumulate on the wear ring 72.

[0049] However, the wear ring 72 is provided with a plurality of communication portions 82 (first communication portion 83, second communication portion 84). Therefore, the wear powder flowing from the piston ring 71 to the wear ring 72 side flows through the communication portion 82 to the low-pressure side region 202 from the wear ring 72. Then, the accumulation of wear powder on the wear ring 72 is suppressed.

[0050] <Modification Example of Wear Ring> Fig. 8 is a perspective view showing a first modification example of the wear ring.

[0051] As shown in Figure 8, the wear ring 72A has a C-shaped ring form in plan view. The wear ring 72A has one end 72a in the circumferential direction and the other end 72b in the circumferential direction. The wear ring 72 has one end 72a and the other end 72b facing each other. When the wear ring 72A is mounted on the piston 53 (see Figure 3), a gap is created between the one end 72a and the other end 72b, forming a joint portion 91.

[0052] The wear ring 72A is provided with a communication portion 92. The communication portion 92 connects the high-pressure side region 201 and the low-pressure side region 202 (see Figure 3) inside the cylinder 52. The communication portion 92 has a first communication portion 93 and a second communication portion 94. The first communication portion 93 is a joint portion 91. The second communication portion 94 is a communication groove. There is one first communication portion 93 (joint portion 91), and there are multiple second communication portions (communication grooves) 94. However, the number of second communication portions (communication grooves) 94 is not limited.

[0053] Multiple connecting portions 92 (first connecting portion 93, second connecting portion 94) are provided at intervals (preferably evenly spaced) in the circumferential direction of the wear ring 72A. The connecting groove, which serves as the second connecting portion 94, is a recess provided on the outer circumferential surface 85 of the wear ring 72A. The connecting portions 92 (first connecting portion 93, second connecting portion 94) are parallel to the axial direction of the wear ring 72A. That is, the first connecting portion 93 is a joint portion 91, with one end 72a and the other end 72b aligned in the axial direction. The second connecting portion 94 is a connecting groove, which is aligned in the axial direction of the wear ring 72A.

[0054] Figure 9 is a perspective view showing a second modified example of the wearing.

[0055] As shown in Figure 9, the wear ring 72B is provided with a communication portion 102. The communication portion 102 connects the high-pressure side region 201 and the low-pressure side region 202 (both shown in Figure 3) inside the cylinder 52. The communication portion 102 has a first communication portion 93 and a second communication portion 84. The first communication portion 93 is a joint portion 91. The second communication portion 84 is a communication groove. There is one first communication portion 93 (joint portion 91) and multiple second communication portions (communication grooves) 84 are provided.

[0056] Multiple connecting portions 102 (first connecting portion 93, second connecting portion 84) are provided at intervals (preferably evenly spaced) in the circumferential direction of the wear ring 72B. The first connecting portion 93 is a joint portion 91, with one end 72a and the other end 72b aligned in the axial direction. The second connecting portion 84 is a connecting groove, which is inclined in the circumferential direction with respect to the axial direction of the wear ring 72.

[0057] Figure 10 is a perspective view showing a third modified example of Wearing, and Figure 11 is a cross-sectional view showing a third modified example of Wearing.

[0058] As shown in Figures 10 and 11, the wear ring 72C is provided with a communication portion 112. The communication portion 112 connects the high-pressure side region 201 and the low-pressure side region 202 (see Figure 3) inside the cylinder 52. The communication portion 102 has a first communication portion 83 and a second communication portion 114. The first communication portion 83 is a joint portion 81. The second communication portion 114 is a communication groove. Multiple communication portions 112 (first communication portion 83, second communication portion 114) are provided at intervals in the circumferential direction of the wear ring 72C. The communication groove as the second communication portion 114 is a recess provided on the inner circumferential surface 86, the upper end surface 87, and the lower end surface 88 of the wear ring 72C. Specifically, the second communication section 114 has a first communication groove 112a, a second communication groove 112b, and a third communication groove 112c. The first communication groove 112a is formed on the upper end surface 87 of the wear ring 72C, the second communication groove 112b is formed on the inner circumferential surface 867 of the wear ring 72C, and the third communication groove 112c is formed on the lower end surface 88 of the wear ring 72C. The first communication groove 112a communicates with the second communication groove 112b, and the second communication groove 112b communicates with the third communication groove 112c. The second communication groove 112b in the communication section 112 may be inclined in the circumferential direction with respect to the axial direction of the wear ring 72, or it may be parallel to the axial direction.

[0059] As shown in Figure 11, the piston ring 71 is positioned in the groove 53a of the piston 53. The wear ring 72C is positioned in the groove 53b of the piston 53. When the piston 53 moves axially relative to the cylinder 52, the outer circumferential surfaces 74 and 85 of the piston ring 71 and wear ring 72C mounted on the piston 53 slide against the inner circumferential surface of the fitting hole 70 of the cylinder 52. At this time, wear particles are generated as the outer circumferential surface 74 of the piston ring 71 slides against the inner circumferential surface of the fitting hole 70 of the cylinder 52. When the piston 53 descends and the pressure in the compression chamber 65 (high-pressure side region 201) rises, the wear particles generated by the wear of the piston ring 71 may flow to the wear ring 72C side along with the fluid (hydrogen) and accumulate on the wear ring 72. However, the wear ring 72C is provided with a plurality of communication parts 112 (first communication part 83, second communication part 114). Therefore, wear particles that flow from the piston ring 71 to the wear ring 72C side flow through the communication section 82 to the low-pressure region 202 below the wear ring 72. In other words, in the second communication section 114, wear particles flow through the third communication groove 112c, the second communication groove 112b, and the first communication groove 112a to the low-pressure region 202. As a result, the accumulation of wear particles on the wear ring 72 is suppressed.

[0060] [Effects of this embodiment] The boost pump according to the first embodiment comprises a cylinder 52 having a compression chamber 65, a piston 53 movably supported by the cylinder 52 and compressing liquid hydrogen (low-temperature fluid) in the compression chamber 65, a piston ring 71 provided on the outer circumference of the piston 53, and wear rings 72, 72A, 72B, 72C provided on the outer circumference of the piston 53 on the lower pressure side than the piston ring 71, wherein the wear rings 72, 72A, 72B, 72C have communication portions 82, 92, 102, 112 that connect the high-pressure side region 201 and the low-pressure side region 202.

[0061] According to the first embodiment of the booster pump, when the piston 53 moves inside the cylinder 52, wear particles are generated as the outer surface 74 of the piston ring 71 slides against the inner surface of the cylinder 52. These wear particles flow together with the fluid (hydrogen) towards the wear rings 72, 72A, 72B, and 72C, and are discharged to the low-pressure region 202 through the communication sections 82, 92, 102, and 112. As a result, the accumulation of wear particles on the wear rings 72, 72A, 72B, and 72C is suppressed, and the lifespan of the wear rings 72, 72A, 72B, and 72C can be extended.

[0062] The boost pump according to the second embodiment is the boost pump according to the first embodiment, further comprising multiple connecting sections 82, 92, 102, and 112 spaced apart in the circumferential direction of the wear rings 72, 72A, 72B, and 72C. This allows the generated wear particles to be smoothly discharged from the connecting sections 82, 92, 102, and 112 to the low-pressure side region 202.

[0063] The third embodiment of the boost pump is a boost pump according to the first or second embodiment, further comprising: a wear ring having joint portions 81, 91 at positions where their circumferential ends face each other; and a communication portion 82, 92, 102, 112 having a first communication portion 83, 93 provided on the joint portions 81, 91 and a second communication portion 84, 94, 114 provided at positions other than the joint portions 81, 91. As a result, by providing not only the first communication portion 83, 93 provided on the joint portions 81, 91 but also the second communication portion 84, 94, 114 at positions other than the joint portions 81, 91, the generated wear particles can be smoothly discharged from the communication portion 82, 92, 102, 112 to the low-pressure side region 202.

[0064] The fourth embodiment of the boost pump is a boost pump according to any one of the first to third embodiments, and further, the communication portions 82 and 102 are inclined circumferentially with respect to the axial direction of the wear rings 72 and 72B. As a result, when the piston 53 moves inside the cylinder 52, axial stress acts on the wear rings 72, 72B and 72C as they slide against the inner circumferential surface of the cylinder 52, but the inclination of the communication portions 82 and 102 reduces the stress concentration acting on the communication portions 82 and 102.

[0065] The boost pump according to the fifth embodiment is a boost pump according to any one of the first to third embodiments, and furthermore, the connecting portions 92 and 102 are parallel to the axial direction of the wear ring 72A. This makes it easier to process the connecting portions 92 and 102, thereby simplifying the structure and reducing processing costs.

[0066] The boost pump according to the sixth embodiment is a boost pump according to the third embodiment, wherein the first communication portion 93 is parallel to the axial direction of the wear ring 72B, and the second communication portion 84 is inclined circumferentially with respect to the axial direction of the wear ring 72B. This makes it easier to process the first communication portion 93, simplifies the structure and reduces processing costs, and reduces stress concentration acting on the second communication portion 84.

[0067] The seventh embodiment of the boost pump is a boost pump according to any one of the first to sixth embodiments, further comprising: a piston 53 having an annular groove 53b on its outer circumference; wear rings 72, 72A, and 72B arranged in the groove 53b; and communication grooves 82, 92, and 102 on the outer surface 58. This facilitates the machining of the communication parts 82, 92, and 102, thereby simplifying the structure and reducing machining costs.

[0068] The eighth embodiment of the boost pump is a boost pump according to any one of the first to fifth embodiments, further comprising: a piston 53 having an annular groove 53b on its outer circumference; a wear ring 72C positioned in the groove 53b, with communication grooves as communication portions 112 provided on its inner circumferential surface 86, upper end surface 87, and lower end surface 88. This allows the outer circumferential surface of the wear ring 72C to slide appropriately against the inner circumferential surface of the cylinder 52, thereby properly supporting the piston 53.

[0069] The hydrogen supply system (low-temperature fluid supply system) according to the ninth embodiment comprises a compressor 21 that compresses liquid hydrogen (low-temperature fluid) using a booster pump 32 according to any one of the first to sixth embodiments, an evaporator 22 that vaporizes the liquid hydrogen compressed by the compressor 21, and a dispenser 23 that supplies the hydrogen gas vaporized by the evaporator 22. As a result, the accumulation of wear particles on the wear rings 72, 72A, 72B, and 72C is suppressed by the booster pump 32, and the lifespan of the wear rings 72, 72A, 72B, and 72C can be extended.

[0070] 10 Hydrogen supply system (low-temperature fluid supply system) 11 Liquefied hydrogen storage tank 12 Vehicle 21 Compressor 22 Evaporator 23 Dispenser 31 Drive unit 32 Booster pump 33 Drive motor 34 Drive mechanism 41 Eccentric shaft 42 Rotating body 43 Link section 44 Oscillating shaft 45 Crosshead 46 Housing 51 Casing 52 Cylinder 53 Piston 54 Discharge piping 61 Support plate 62 Liquid storage chamber 63 Supply pipe 64 Gas discharge pipe 65 Compression chamber 66 Intake valve 67 Discharge valve 70 Fitting hole 71 Piston ring 72, 72A, 72B, 72C Wear ring 73 Wear ring 81, 91 Joint section 82, 92, 102, 112 Connecting section 83, 93 First connecting section 84, 94, 114 Second connecting section 85 Outer surface 86 Inner surface 87 Upper end surface 88 Lower end surface 201 High pressure side region 202 Low pressure side region

Claims

1. A booster pump comprising: a cylinder having a compression chamber; a piston movably supported by the cylinder and compressing a low-temperature fluid in the compression chamber; a piston ring provided on the outer circumference of the piston; and a wear ring provided on the outer circumference of the piston on the lower-pressure side than the piston ring, wherein the wear ring has a communication portion that connects a high-pressure side region and a low-pressure side region.

2. The boost pump according to claim 1, wherein a plurality of the communicating portions are provided at intervals in the circumferential direction of the wear ring.

3. The wear ring has a joint portion at a position where its circumferential ends face each other, and the communication portion has a first communication portion provided at the joint portion and a second communication portion provided at a position other than the joint portion, the boost pump according to claim 2.

4. The boost pump according to claim 1, wherein the communication portion is inclined circumferentially with respect to the axial direction of the wear ring.

5. The boost pump according to claim 1, wherein the communication portion is parallel to the axial direction of the wear ring.

6. The boost pump according to claim 3, wherein the first communication portion is parallel to the axial direction of the wear ring, and the second communication portion is inclined circumferentially with respect to the axial direction of the wear ring.

7. The boost pump according to claim 1, wherein the piston has an annular groove on its outer circumference, and the wear ring is positioned in the groove and has a communication groove as the communication portion on its outer circumference.

8. The boost pump according to claim 1, wherein the piston has an annular groove on its outer circumference, the wear ring is positioned in the groove, and a communication groove serving as the communication portion is provided on its inner circumferential surface, upper end surface, and plate end surface.

9. A cryogenic fluid supply system comprising: a compression device for compressing a cryogenic fluid using a booster pump as described in claim 1; an evaporation device for vaporizing the cryogenic fluid compressed by the compression device; and a dispenser for supplying the gas vaporized by the evaporation device.

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