Reciprocating pump

Abstract

To provide a reciprocating pump having a piston ring exhibiting higher sealing performance.SOLUTION: The reciprocating pump includes: a pump main body having a piston that compresses a liquid and a cylinder that covers the piston from the outside; a drive unit for reciprocating the piston in a reciprocating direction; and a piston ring provided in a gap between the piston and the cylinder. An annular groove is formed on an outer peripheral surface of the piston. A space inside the cylinder is partitioned by the piston ring into a high-pressure region through which the compressed liquid flows and a low-pressure region in which an internal pressure is lower than that in the high-pressure region. The piston ring has a high-pressure-side ring disposed on a high-pressure-region side in the annular groove and a low-pressure-side ring provided on a low-pressure-region side in the annular groove with respect to the high-pressure-side ring. A cutout surface that retreats toward the high-pressure-region side is formed at an end edge on an outer peripheral side of a surface facing the low-pressure-region side in the low-pressure-side ring.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a reciprocating pump.

Background Art

[0002] A reciprocating pump has been used as a device for compressing liquid hydrogen. This type of pump is capable of boosting the pressure of liquid hydrogen up to about 90 Mpa, for example. Specifically, the reciprocating pump mainly includes a piston that reciprocates in the axial direction and a cylinder that covers the piston from the outside. As the piston reciprocates in the cylinder, the liquid hydrogen is sequentially compressed and taken out to the outside. The piston is driven by a drive unit.

[0003] An annular groove extending in the circumferential direction is formed on the outer peripheral surface of the piston, and a piston ring is inserted into the annular groove. The piston ring is composed of a high-pressure side ring and a low-pressure side ring, for example, as described in Patent Document 1 below. In either ring, the surface facing the reciprocating direction is generally flat.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, when the end face of the low-pressure side ring is flat, the edge on the outer peripheral side of the low-pressure side ring may be deformed so as to be pushed into the inside of the gap (that is, the low-pressure region side) by the pressure on the high-pressure region side (about 90 MPa, for example). Then, the contact area between the outer peripheral surface of the low-pressure side ring and the inner peripheral surface of the cylinder decreases by the amount of the deformation. As a result, there are problems such as a decrease in sealing performance and uneven wear on the outer peripheral surface of the ring.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a reciprocating pump having a piston ring that exhibits higher sealing performance.

Means for Solving the Problems

[0007] In order to solve the above problems, a reciprocating pump according to the present disclosure includes a pump body having a piston that compresses a liquid and a cylinder that covers the piston from the outside, a drive unit that reciprocates the piston in a reciprocating direction with respect to the cylinder, and a piston ring provided in a gap between the piston and the cylinder. An annular groove that is recessed toward the inner peripheral side and extends in the circumferential direction of the outer peripheral surface is formed on the outer peripheral surface of the piston. The space inside the cylinder is partitioned by the piston ring into a high-pressure region through which the compressed liquid flows and a low-pressure region having a lower internal pressure than the high-pressure region. The piston ring has a high-pressure side ring disposed on the high-pressure region side in the annular groove and a low-pressure side ring provided on the low-pressure region side in the annular groove with respect to the high-pressure side ring. A notch surface that retreats toward the high-pressure region side is formed at an outer peripheral side edge of a surface of the low-pressure side ring facing the low-pressure region side.

Effects of the Invention

[0008] According to the present disclosure, it is possible to provide a reciprocating pump having a piston ring that exhibits higher sealing performance.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0010] <First Embodiment> Hereinafter, a reciprocating pump 100 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 5.

[0011] (Configuration of Reciprocating Pump 100) The reciprocating pump 100 is a device for boosting a cryogenic liquid such as liquid hydrogen to a high pressure (about 90 MPa). As shown in FIG. 1, the reciprocating pump 100 includes a piston 1, a cylinder 2, a drive unit 3, a casing 4, a check valve 5, a discharge pipe 6, and a discharge valve 7. The piston 1 and the cylinder 2 constitute a pump body 9.

[0012] (Configuration of Piston 1) The piston 1 has a columnar piston body 10 extending in the vertical direction and centered on the axis O, a wear ring 11 attached to the piston body 10, and a piston ring 12. The dimension of the piston body 10 in the radial direction is constant throughout the direction of the axis O. The wear ring 11 is provided at the tip of the piston body 10. The wear ring 11 has an annular shape centered on the axis O and is formed of a resin material.

[0013] One wear ring 11 is provided at the lower end of the piston body 10, and another wear ring 11 is provided at a distance from the wear ring 11 in the direction of the axis O. A plurality (six as an example) of piston rings 12 arranged at intervals in the direction of the axis O are provided between these pair of wear rings 11. The wear ring 11 is provided to guide the piston body 10 along the inner peripheral surface of the cylinder 2 described later. On the other hand, the piston ring 12 is provided to maintain liquid tightness and air tightness with the inner peripheral surface of the cylinder 2. The configuration of the piston ring 12 will be described later.

[0014] (Configuration of the cylinder 2) The cylinder 2 has a bottomed cylindrical shape that covers the piston 1 from the outer peripheral side. The piston 1 is inserted into the cylinder 2 through the upper opening h of the cylinder 2. The space below the tip of the piston 1 inside the cylinder 2 is a compression chamber 21. A check valve 5 for guiding liquid hydrogen to the compression chamber 21 is provided at the bottom of the cylinder 2. This check valve 5 is capable of allowing liquid hydrogen to flow in only in the direction from the outside of the cylinder 2 into the compression chamber 21. In other words, even if the pressure in the compression chamber 21 increases, the liquid hydrogen does not flow out of the cylinder 2 through the check valve 5.

[0015] On the side surface of the cylinder 2, a discharge pipe 6 is connected to the portion facing the above-mentioned compression chamber 21. The discharge pipe 6 is provided for taking out the liquid hydrogen compressed in the compression chamber 21 to the outside of the cylinder 2. A discharge valve 7 is provided on this discharge pipe 6. The discharge valve 7 is configured to allow the liquid hydrogen to flow only in the direction from the compression chamber 21 to the outside when the pressure in the compression chamber 21 reaches a predetermined value or more.

[0016] (Configuration of the drive unit 3) The above-mentioned piston 1 reciprocates in the direction of the axis O by being given a driving force by the drive unit 3 within the cylinder 2. The drive unit 3 reciprocates the piston 1 within the cylinder 2 by means of an electric motor (not shown) and a link mechanism.

[0017] (Configuration of the casing 4) The casing 4 is a container that covers the above-mentioned cylinder 2 from the outside. The casing 4 has a bottomed cylindrical casing body 41, a supply pipe 42, and a gas discharge pipe 43. The supply pipe 42 is a pipe for guiding liquid hydrogen from an external supply source into the casing body 41 (liquid storage chamber 44). The supply pipe 42 is provided near the bottom surface of the casing body 41. The gas discharge pipe 43 is provided for discharging the components (gas components) vaporized in the liquid storage chamber 44 to the outside. The gas discharge pipe 43 is provided at a position spaced above the supply pipe 42. Also, the liquid level of the liquid hydrogen in the liquid storage chamber 44 is adjusted to be located below this gas discharge pipe 43. Incidentally, the above-mentioned discharge pipe 6 extends to the outside of this casing 4.

[0018] (Configuration of the piston ring 12) Next, with reference to FIGS. 2 to 5, the configuration of the piston ring 12 will be described in detail. The piston ring 12 divides the space within the cylinder 2 into a high-pressure region V1 and a low-pressure region V2 that are continuous in the direction of the axis O. The high-pressure region V1 is the region on the compression chamber 21 side within the cylinder 2, and the low-pressure region V2 is the region located opposite to the compression chamber 21 with the piston ring 12 interposed therebetween. In the following description, the high-pressure region V1 side may be simply referred to as the "high-pressure side", and the low-pressure region V2 side may be simply referred to as the "low-pressure side".

[0019] As shown in Fig. 2, the piston ring 12 is accommodated in an annular groove 30 formed on the outer peripheral surface of the piston body 10. The annular groove 30 extends in the circumferential direction centered on the axis O and is a groove having a rectangular cross-section that is recessed on the inner peripheral side. The annular groove 30 is formed by a bottom wall surface 31, a low-pressure side wall surface 32, and a high-pressure side wall surface 33. The bottom wall surface 31 is a surface facing the outer peripheral side and has a cylindrical surface shape centered on the axis O. The low-pressure side wall surface 32 has an annular shape that expands from the edge on the low-pressure side (that is, the upper side) of the bottom wall surface 31 toward the outer peripheral side. In a cross-sectional view including the axis O, the low-pressure side wall surface 32 extends in the radial direction. The high-pressure side wall surface 33 has an annular shape that expands from the edge on the high-pressure side (that is, the lower side) of the bottom wall surface 31 toward the outer peripheral side. In a cross-sectional view including the axis O, the high-pressure side wall surface 33 extends in the radial direction.

[0020] The piston ring 12 includes a high-pressure side ring 50, a low-pressure side ring 60, a backup ring 70, and a spring member 80. The high-pressure side ring 50 is disposed on the high-pressure side in the annular groove 30, that is, below in the vertical direction. The low-pressure side ring 60 is disposed on the low-pressure side in the annular groove 30, that is, above the high-pressure side ring 50. The high-pressure side ring 50 and the low-pressure side ring 60 are in contact with each other in the direction of the axis O.

[0021] Here, as shown in Fig. 3, the low-pressure side ring 60 has an annular shape centered on the axis O. Further, an opening called a joint P is formed in a part of the circumferential direction of the low-pressure side ring 60. This joint P is provided to deform the low-pressure side ring 60 so as to expand and fit it into the annular groove 30 of the piston body 10 from the outer peripheral side. The high-pressure side ring 50 also has an annular shape in which a joint P similar to that of the low-pressure side ring 60 is formed. On the other hand, as shown in Fig. 4, the joint P of the high-pressure side ring 50 and the joint P of the low-pressure side ring 60 are at positions 180° different in the circumferential direction. That is, if the joints P overlap each other, leakage of liquid will occur through the joints P. In order to prevent leakage, the phases of the joints P are different from each other as described above.

[0022] As shown in FIG. 2, the high-pressure side ring 50 has a first outer peripheral surface 51, a first contact surface 52, a first inner peripheral surface 53, and a first bottom surface 54. The first outer peripheral surface 51 is a surface facing the outer peripheral side and has a cylindrical surface shape centered on the circumferential direction of the axis O. The first outer peripheral surface 51 slides in the direction of the axis O as the piston 1 reciprocates while being in surface contact with the inner peripheral surface of the cylinder 2. The first contact surface 52 is a surface facing the low-pressure side (i.e., the upper side) and has an annular shape centered on the axis O. The first contact surface 52 extends in the radial direction with respect to the axis O in a cross-sectional view including the axis O. The first contact surface 52 is in surface contact with the low-pressure side ring 60. The first inner peripheral surface 53 is a surface facing the inner peripheral side and has a cylindrical surface shape centered on the circumferential direction of the axis O. The first bottom surface 54 is a surface facing the high-pressure side and faces the high-pressure side wall surface 33 of the annular groove 30.

[0023] The low-pressure side ring 60 has a second outer peripheral surface 61, a second contact surface 62, a second inner peripheral surface 63, a second bottom surface 64, and a notch surface 65. The second outer peripheral surface 61 is a surface facing the outer peripheral side and has a cylindrical surface shape centered on the circumferential direction of the axis O. The second outer peripheral surface 61 slides in the direction of the axis O as the piston 1 reciprocates while being in surface contact with the inner peripheral surface of the cylinder 2. The second contact surface 62 is a surface facing the low-pressure side (i.e., the upper side) and has an annular shape centered on the axis O. The second contact surface 62 extends in the radial direction with respect to the axis O in a cross-sectional view including the axis O. The second contact surface 62 is in surface contact with the low-pressure side wall surface 32 of the annular groove 30. The second inner peripheral surface 63 is a surface facing the inner peripheral side and has a cylindrical surface shape centered on the circumferential direction of the axis O. The second bottom surface 64 is a surface facing the high-pressure side and is in surface contact with the first contact surface 52 of the high-pressure side ring 50.

[0024] The notch surface 65 extends between the second abutment surface 62 and the second outer peripheral surface 61. The notch surface 65 recedes toward the high-pressure side in a cross-sectional view including the axis O. More specifically, the notch surface 65 extends from the low-pressure side toward the high-pressure side as it goes from the inner peripheral side to the outer peripheral side. In the present embodiment, the angle formed by the notch surface 65 with respect to the axis O is constant throughout the entire radial direction. Also, as shown in FIG. 5, when the dimension of the gap in the radial direction between the outer peripheral surface of the piston body 10 and the inner peripheral surface of the cylinder 2 is G, the dimension A in the radial direction of the notch surface 65 is set to satisfy G≦A≦2G. That is, the inner peripheral side edge of the notch surface 65 is at the same radial position as the outer peripheral side edge of the low-pressure side wall surface 32 of the annular groove 30, or is located radially inside the outer peripheral side edge. More desirably, G≦A≦1.8G. Most desirably, G≦A≦1.5G. Also, in the present embodiment, the dimension of the low-pressure side ring 60 in the direction of the axis O is equivalent to the dimension of the high-pressure side ring 50 in the direction of the axis O. Here, the “same” or “equivalent” mentioned herein refers to substantial identity, and a slight error is allowed.

[0025] As a material for constituting the high-pressure side ring 50 and the low-pressure side ring 60, a resin material is preferably used. Specifically, at least one selected from the group including PTFE (polytetrafluoroethylene), PI (polyimide), PAI (polyamideimide), PPA (polyphthalamide), PPS (polyphenylene sulfide), PSU (polysulfone), and PES (polyethersulfone) is preferably used as the main component. Since these resin materials are relatively soft, it is possible to realize seizure during sliding with the cylinder 2 and to ensure flame retardancy when the liquid is a combustible substance.

[0026] As shown in FIG. 2, the backup ring 70 is provided on the inner peripheral side of the above-described high-pressure side ring 50 and low-pressure side ring 60. The backup ring 70 has an annular shape centered on the axis O. The dimension of the backup ring 70 in the direction of the axis O is equivalent to the sum of the dimensions of the high-pressure side ring 50 and the low-pressure side ring 60 in the direction of the axis O. The backup ring 70 is urged from the inner peripheral side by a spring member 80. The spring member 80 is an annular elastic body that urges the backup ring 70 to expand its diameter toward the outer peripheral side. By being pressed from the inner peripheral side by these backup ring 70 and spring member 80, the high-pressure side ring 50 and the low-pressure side ring 60 are configured to always be in sliding contact with the inner peripheral surface of the cylinder 2. For this reason, a certain space is formed between the inner peripheral surface of the backup ring 70 and the bottom wall surface 31 of the annular groove 30.

[0027] (Function and Effect) When operating the above-described reciprocating pump 100, first, with liquid hydrogen supplied into the cylinder 2 by the supply pipe 42, the piston 1 is reciprocated in the cylinder 2 by the drive unit 3. As a result, the liquid hydrogen in the cylinder 2 is sequentially compressed to a high-pressure state. The high-pressure liquid hydrogen is taken out to the outside through the discharge pipe 6.

[0028] Here, different from the above-described configuration, when the notch surface 65 is not formed and the end surface of the low-pressure side ring 160 is flat, the edge on the outer peripheral side of the low-pressure side ring 160 may be deformed so as to be pushed into the inside of the gap (that is, toward the low-pressure region V2 side) by the pressure on the high-pressure region V1 side (for example, about 90 MPa). (Refer to the reference example shown in FIG. 11). Then, due to the amount of such deformation, the contact area between the outer peripheral surface of the low-pressure side ring 160 and the inner peripheral surface of the cylinder 2 decreases. As a result, there are problems that the sealing performance of the low-pressure side ring 160 deteriorates and uneven wear occurs on the outer peripheral surface of the low-pressure side ring 160. In order to solve this problem, each of the above-described configurations is adopted in the present embodiment.

[0029] According to the above configuration, the notch surface 65 is pre-formed in the outer peripheral region that is easily deformed by pressure. Thus, even when a high pressure is applied to the outer peripheral edge, the deformation toward the low-pressure region V2 side can be allowed to a certain extent due to the notched portion. Therefore, the possibility that a part of the low-pressure side ring 60 is pushed into the gap between the piston 1 and the cylinder 2 can be reduced. As a result, a decrease in the contact area between the low-pressure side ring 60 and the cylinder 2 is avoided. Also, the detachment of the deformed part can be avoided. Therefore, a decrease in seal performance is avoided, and the reciprocating pump 100 can be stably operated over a long period of time. The notch surface 65 extends from the low-pressure region V2 side toward the high-pressure region V1 side as it goes from the inner peripheral side toward the outer peripheral side.

[0030] According to the above configuration, the notch surface 65 extends from the low-pressure side toward the high-pressure side as it goes from the inner peripheral side toward the outer peripheral side. Thereby, the notch surface 65 can be formed only by chamfering, so that the ease of processing can be realized. Therefore, the costs required for maintenance and manufacture of the reciprocating pump 100 can be reduced.

[0031] According to the above configuration, the dimension of the notch surface 65 in the radial direction is within a range that is equal to or greater than the dimension of the gap between the piston 1 and the cylinder 2 in the radial direction and is equal to or less than twice the dimension of the gap in the radial direction. Thereby, with a margin, the deformation of the low-pressure side ring 60 and the resulting decrease in seal performance can be avoided. Therefore, it becomes possible to continue operating the reciprocating pump 100 stably over an even longer period of time.

[0032] The first embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure.

[0033] <Second Embodiment> Next, a second embodiment of the present disclosure will be described with reference to FIG. 6. For components having the same configuration as those in the first embodiment described above, the same reference numerals are assigned and detailed descriptions thereof are omitted.

[0034] As shown in FIG. 6, in this embodiment, the cross-sectional shape of the low-pressure side ring 60 is different from that in the first embodiment. Specifically, in addition to the second outer peripheral surface 61, the second contact surface 62, the second inner peripheral surface 63, the second bottom surface 64, and the notch surface 65 described above, the low-pressure side ring 60 further has a second notch surface 66.

[0035] The second notch surface 66 is provided between the second bottom surface 64 and the second outer peripheral surface 61. The second notch surface 66 recedes toward the low-pressure side. More specifically, in a cross-sectional view including the axis O, the second notch surface 66 extends from the high-pressure side toward the low-pressure side as it goes from the inner peripheral side to the outer peripheral side. The angle formed by the second notch surface 66 with respect to the axis O is constant throughout the entire radial direction. Also, it is desirable that the dimension of the second notch surface 66 in the radial direction be set within the same numerical range as the dimension of the notch surface 65 in the radial direction described in the first embodiment.

[0036] (Function and Effect) According to the above configuration, in addition to the notch surface 65 formed on the surface facing the low-pressure region V2 side, the second notch surface 66 is also formed on the surface facing the low-pressure region V2 side. As a result, in addition to being able to avoid a decrease in sealing performance caused by a part of the ring being pushed into the gap between the piston 1 and the cylinder 2, it becomes unnecessary to define the assembling direction of the low-pressure side ring 60 during the assembling operation. Therefore, it becomes possible to improve the efficiency and speed of the assembling operation. Also, it becomes possible to reduce the possibility of malfunction of the final product due to assembling errors.

[0037] The second embodiment of the present disclosure has been described above. It should be noted that various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure.

[0038] <Third Embodiment> Next, a third embodiment of the present disclosure will be described with reference to FIG. 7. Note that the same components as those in the above embodiments are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0039] In this embodiment, the shapes of the high-pressure side ring 50 and the low-pressure side ring 60 (that is, the configurations of the surfaces of these rings) are the same as those in the first embodiment described above. On the other hand, the dimensions of the high-pressure side ring 50 and the low-pressure side ring 60 in the axial direction of the axis O are different from those in the first embodiment. Specifically, when the dimension of the high-pressure side ring 50 in the axial direction of the axis O is X and the dimension of the low-pressure side ring 60 in the axial direction of the axis O is Y, X ≥ 1.5Y is satisfied. More preferably, X ≥ 1.7Y. Most preferably, X ≥ 2.0Y.

[0040] (Function and effect) Here, openings (joints P) for fitting these members to the piston 1 are formed in a part of the circumferential direction of the high-pressure side ring 50 and the low-pressure side ring 60. In general, the joint P of the high-pressure side ring 50 and the joint P of the low-pressure side ring 60 are assembled so that their positions in the circumferential direction are different by 180°. By the way, wear may occur in the low-pressure side ring 60 toward the radially inner side due to long-term operation. Then, the joint P of the low-pressure side ring 60 is deformed so as to spread to both sides in the circumferential direction. As a result, a part of the high-pressure side ring 50 is deformed so as to bulge toward the low-pressure region V2 side through the joint P, and finally, the high-pressure side ring 50 may be damaged. However, according to the above configuration, since the dimension of the high-pressure side ring 50 in the reciprocating direction is set larger than that of the low-pressure side ring 60, the rigidity of the high-pressure side ring 50 is improved. Thereby, it is possible to make it difficult to cause the deformation at the joint P as described above. Therefore, deterioration and deformation of the piston ring 12 due to long-term operation are suppressed, and it becomes possible to continuously operate the reciprocating pump 100 stably for a longer period.

[0041] <Other embodiments> The above has described each embodiment of the present disclosure. Note that various changes and modifications can be made to the above-described respective configurations without departing from the gist of the present disclosure.

[0042] <First Modification Example> As a first modification example of the low-pressure side ring 60, it is also possible to adopt the configuration shown in FIG. 8. In the example of this figure, the cutout surface 65 has a convex curved surface shape that protrudes toward the low-pressure side. The cutout surface 65 may be arc-shaped or a curved surface with a gradually changing curvature. Further, this modification example can be applied in combination to any of the first to third embodiments described above.

[0043] According to the above configuration, since the cutout surface 65 has a convex curved surface shape that protrudes toward the low-pressure region V2 side, stress concentration at the cutout surface 65 can be avoided. On the contrary, when corners are formed at the outer peripheral side or the inner peripheral side edge of the cutout surface 65, stress concentration may occur at the corners, and there is also a possibility of defects such as cracks. However, according to the above configuration, since such corners are not formed, the possibility of stress concentration can be significantly reduced. As a result, the reciprocating pump 100 can be continuously operated stably for a longer period.

[0044] <Second Modification Example> As a second modification example of the low-pressure side ring 60, it is also possible to adopt the configuration shown in FIG. 9. In the example of this figure, the cutout surface 65 has a concave curved surface shape that is recessed toward the high-pressure side. The cutout surface 65 may be arc-shaped or a curved surface with a gradually changing curvature. Further, this modification example can be applied in combination to any of the first to third embodiments described above.

[0045] According to the above configuration, since the notch surface 65 is in the shape of a concave curved surface that is concave toward the high-pressure region V1 side, stress concentration on the notch surface 65 can be avoided. On the contrary, if a corner is formed at the outer peripheral side or the inner peripheral side edge of the notch surface 65, stress concentration may occur at the corner, and defects such as cracks may occur. However, according to the above configuration, since such a corner is not formed, the possibility of stress concentration can be significantly reduced. As a result, the reciprocating pump 100 can be continuously operated stably for a longer period.

[0046] <Third Modified Example> As a third modified example of the low-pressure side ring 60, it is also possible to adopt the configuration shown in FIG. 10. In the example of this figure, the notch surface 65 has a first surface 67 and a second surface 68. The first surface 67 faces the outer peripheral side. The second surface 68 extends from the high-pressure side edge of the first surface 67 toward the outer peripheral side. As an example, the first surface 67 and the second surface 68 are perpendicular to each other in a cross-sectional view including the axis O. Note that this modified example can be applied in combination to any of the above-described first to third embodiments.

[0047] According to the above configuration, since the notch surface 65 has the first surface 67 and the second surface 68, it has a rectangular cross-sectional shape. Thereby, the visibility of the notch surface 65 itself is improved. That is, it becomes possible to easily visually recognize on which surface the notch surface 65 is formed. Therefore, the efficiency and speed of the assembly work can be realized. Also, the possibility of malfunction of the final product due to assembly errors can be reduced.

[0048] <Other Modified Examples> Furthermore, in each of the above embodiments, an example in which the reciprocating pump 100 is used to compress liquid hydrogen has been described. However, the reciprocating pump 100 can also be suitably used for compressing cryogenic liquefied gases such as liquefied carbon dioxide, liquefied natural gas, and liquefied petroleum gas.

[0049] <Supplementary Note> The reciprocating pump 100 described in each embodiment is understood as follows, for example.

[0050] (1) The reciprocating pump 100 according to the first aspect includes a pump body 9 having a piston 1 that compresses a liquid and a cylinder 2 that covers the piston 1 from the outside, a drive unit 3 that reciprocates the piston 1 in the reciprocating direction with respect to the cylinder 2, and a piston ring 12 provided in a gap between the piston 1 and the cylinder 2. An annular groove 30 that is recessed toward the inner peripheral side and extends in the circumferential direction of the outer peripheral surface is formed on the outer peripheral surface of the piston 1. The space in the cylinder 2 is partitioned by the piston ring 12 into a high-pressure region V1 through which the compressed liquid flows and a low-pressure region V2 having a lower internal pressure than the high-pressure region V1. The piston ring 12 has a high-pressure side ring 50 disposed on the high-pressure region V1 side in the annular groove 30 and a low-pressure side ring 60 provided on the low-pressure region V2 side in the annular groove 30 with respect to the high-pressure side ring 50. A notch surface 65 that retreats toward the high-pressure region V1 side is formed at the outer peripheral side edge of the surface of the low-pressure side ring 60 facing the low-pressure region V2 side.

[0051] According to the above configuration, the notch surface 65 is pre-formed in the outer peripheral side region that is easily deformed by pressure. Thereby, even when a high pressure is applied to the outer peripheral side edge, the deformation toward the low-pressure region V2 side can be allowed to a certain extent by the amount that is cut out. Therefore, the possibility that a part of the low-pressure side ring 60 is pushed into the gap between the piston 1 and the cylinder 2 can be reduced.

[0052] (2) The reciprocating pump 100 according to the second aspect is the reciprocating pump 100 of (1), and the notch surface 65 extends from the low-pressure region V2 side toward the high-pressure region V1 side from the inner peripheral side toward the outer peripheral side.

[0053] According to the above configuration, the notch surface 65 is formed in advance in the outer peripheral region that is easily deformed by pressure. Thereby, even when a high pressure is applied to the edge of the outer peripheral side, the deformation toward the low-pressure region V2 side can be allowed to a certain extent by the amount that is cut out. Therefore, the possibility that a part of the low-pressure side ring 60 is pushed into the gap between the piston 1 and the cylinder 2 can be reduced.

[0054] (3) The reciprocating pump 100 according to the third aspect is the reciprocating pump 100 of (1), and the notch surface 65 has a convex curved surface shape that protrudes toward the low-pressure region V2 side.

[0055] According to the above configuration, since the notch surface 65 has a convex curved surface shape that protrudes toward the low-pressure region V2 side, stress concentration on the notch surface 65 can be avoided.

[0056] (4) The reciprocating pump 100 according to the fourth aspect is the reciprocating pump 100 of (1), and the notch surface 65 has a concave curved surface shape that is concave toward the high-pressure region V1 side.

[0057] According to the above configuration, since the notch surface 65 has a concave curved surface shape that is concave toward the high-pressure region V1 side, stress concentration on the notch surface 65 can be avoided.

[0058] (5) The reciprocating pump 100 according to the fifth aspect is the reciprocating pump 100 of (1), and the notch surface 65 has a first surface 67 facing the outer peripheral side and a second surface 68 that extends outward from the edge of the first surface 67 on the high-pressure region V1 side.

[0059] According to the above configuration, since the notch surface 65 has the first surface 67 and the second surface 68, it has a rectangular cross-sectional shape. Thereby, the visibility of the notch surface 65 itself is improved. Therefore, the efficiency and speed of the assembly work can be realized.

[0060] (6) The reciprocating pump 100 according to the sixth aspect is the reciprocating pump 100 according to any one of the aspects (1) to (5), and the dimension of the cutout surface 65 in the radial direction is set within a range that is equal to or greater than the dimension of the gap in the radial direction and equal to or less than twice the dimension of the gap in the radial direction.

[0061] According to the above configuration, it is possible to avoid the deformation of the low-pressure side ring 60 with a margin and the resulting deterioration of the sealing performance.

[0062] (7) The reciprocating pump 100 according to the seventh aspect is the reciprocating pump 100 according to any one of the aspects (1) to (6), and the dimension of the high-pressure side ring 50 in the reciprocating direction is set to be 1.5 times or more the dimension of the low-pressure side ring 60 in the reciprocating direction.

[0063] According to the above configuration, since the dimension of the high-pressure side ring 50 in the reciprocating direction is set to be larger than that of the low-pressure side ring 60, the rigidity is improved. As a result, it is possible to make it difficult for deformation to occur at the joint P.

[0064] (8) The reciprocating pump 100 according to the eighth aspect is the reciprocating pump 100 according to any one of the aspects (1) to (7), and a second cutout surface 66 that retreats toward the low-pressure region V2 side is formed at the outer peripheral edge of the surface of the low-pressure side ring 60 facing the high-pressure region V1 side.

[0065] According to the above configuration, in addition to the cutout surface 65 formed on the surface facing the low-pressure region V2 side, the second cutout surface 66 is also formed on the surface facing the low-pressure region V2 side. As a result, in addition to being able to avoid deterioration of the sealing performance, it is no longer necessary to define the assembly direction of the low-pressure side ring 60 during the assembly work.

Explanation of Reference Numerals

[0066] 1... Piston 2... Cylinder 3... Driving part 4... Casing 5... Check valve 6... Discharge pipe 7... Discharge valve 9... Pump body 10... Piston body 11... Wear ring 12... Piston ring 21... Compression chamber 30... Annular groove 31... Bottom wall surface 32... Low-pressure side wall surface 33... High-pressure side wall surface 41... Casing body 42... Supply pipe 43... Gas discharge pipe 44... Liquid storage chamber 50... High-pressure side ring 51... First outer peripheral surface 52... First contact surface 53... First inner peripheral surface 54... First bottom surface 60... Low-pressure side ring 61... Second outer peripheral surface 62... Second contact surface 63... Second inner peripheral surface 64... Second bottom surface 65... Notch surface 66... Second notch surface 67... First surface 68... Second surface 70... Backup ring 80... Spring member 100... Reciprocating pump h... Opening O... Axis P... Joint V1... High-pressure region V2... Low-pressure region

Claims

1. A pump body having a piston for compressing a liquid and a cylinder covering the piston from the outside, a drive unit for reciprocating the piston in a reciprocating direction with respect to the cylinder, a piston ring provided in a gap between the piston and the cylinder, comprising: An annular groove that is recessed toward the inner peripheral side and extends over the circumferential direction of the outer peripheral surface is formed on the outer peripheral surface of the piston. The space inside the cylinder is partitioned by the piston ring into a high-pressure region through which the compressed liquid flows and a low-pressure region having a lower internal pressure than the high-pressure region. The piston ring a high-pressure side ring disposed on the high-pressure region side in the annular groove, and a low-pressure side ring provided on the low-pressure region side in the annular groove with respect to the high-pressure side ring. having A reciprocating pump in which a notch surface that retreats toward the high-pressure region side is formed at the outer peripheral side edge of the surface of the low-pressure side ring facing the low-pressure region side.

2. The reciprocating pump according to claim 1, wherein the notch surface extends from the low-pressure region side toward the high-pressure region side as it goes from the inner peripheral side to the outer peripheral side.

3. The reciprocating pump according to claim 1, wherein the notch surface has a convex curved surface shape that is convex toward the low-pressure region side.

4. The reciprocating pump according to claim 1, wherein the notch surface has a concave curved surface shape that is concave toward the high-pressure region side.

5. The reciprocating pump according to claim 1, wherein the notch surface has a first surface facing the outer peripheral side and a second surface that extends from the edge of the first surface on the high-pressure region side toward the outer peripheral side.

6. The reciprocating pump according to any one of claims 1 to 5, wherein the dimension of the notch surface in the radial direction is set within a range that is equal to or greater than the dimension of the gap in the radial direction and equal to or less than twice the dimension of the gap in the radial direction.

7. The reciprocating pump according to any one of claims 1 to 5, wherein the dimension of the high-pressure side ring in the reciprocating direction is set to be 1.5 times or more the dimension of the low-pressure side ring in the reciprocating direction.

8. The reciprocating pump according to any one of claims 1 to 5, wherein a second notch surface that retreats toward the low-pressure region side is formed at the outer peripheral side edge of the surface of the low-pressure side ring facing the high-pressure region side.

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