Piston and reciprocating compressors

Abstract

To extend a life of a piston ring by keeping a state that difference of differential pressure between piston rings is eased even if time has passed, in a piston equipped with the plurality of piston rings.SOLUTION: A piston 20 is equipped with a piston body 22 formed with a plurality of ring grooves 24, and a plurality of piston rings 30 disposed in the respective ring grooves 24. In the piston 20, a leaking groove 40 is formed on a low-pressure side surface 28 of the ring groove 24. While the piston ring 30 abuts on a cylinder 10 and abuts on the low-pressure side surface 28, the leaking groove 40 ensures the communication between a high-pressure side space 52 and a low-pressure side space 54 with respect to the piston ring 30.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a piston and a reciprocating compressor. [Background technology]

[0002] Patent Document 1 discloses a piston ring including a seal ring with a gap and a backup ring that is disposed in contact with the inner circumference of the seal ring and transmits gas pressure evenly to the seal ring. In the piston ring of Patent Document 1, the backup ring is engaged with a protrusion of the seal ring to prevent the gaps from overlapping and the rings from sticking to each other, thereby improving the sealing performance of the piston ring. However, in this configuration, because the piston ring has high sealing performance, when used in a high-pressure compressor, a large differential pressure is applied to some piston rings, which may shorten the life of the piston ring.

[0003] In response to this, Patent Document 2 discloses a reciprocating compressor equipped with piston rings configured to leak gas from their gaps. In Patent Document 2, the size of the gap between the gaps of each piston ring is adjusted to become smaller from the high pressure side to the low pressure side. That is, in this reciprocating compressor, the differential pressure loaded on each piston ring is made more uniform, thereby suppressing the progression of localized piston ring wear, thereby attempting to extend the life of the piston ring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-32935 A [Patent Document 2] JP 2008-157076 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the reciprocating compressor of Patent Document 2, the size of the gap between the piston rings is adjusted to equalize the pressure difference. However, in this reciprocating compressor, the piston rings wear over time due to the reciprocating motion of the pistons, and the size of each gap may change to a size different from the set size. For this reason, it becomes difficult to maintain the state in which the pressure difference between the piston rings is adjusted over time, and a large pressure difference may be applied to some piston rings, which may shorten the life of the piston rings.

[0006] Therefore, an object of the present invention is to extend the life of a piston ring in a piston having a plurality of piston rings by maintaining a state in which the difference in differential pressure between the plurality of piston rings is reduced even over time. [Means for solving the problem]

[0007] In order to achieve the above object, a piston according to the present invention is a piston used in a reciprocating compressor having a cylinder, and includes a piston body in which a plurality of ring grooves are formed, and a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body. At least two of the plurality of ring grooves have at least one leakage groove formed on a low pressure side surface, and the leakage groove is configured to ensure communication between a space on the high pressure side relative to the piston ring corresponding to the leakage groove and a space on the low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, and the number of the leakage grooves is adjusted between the at least two ring grooves in which the leakage grooves are formed. The at least two ring grooves include a first ring groove and a second ring groove which is a different ring groove on a side to which a smaller pressure difference than that of the first ring groove is applied, and the number of leakage grooves provided in the first ring groove is greater than the number of leakage grooves provided in the second ring groove. .

[0008] In the piston configured in this manner, gas leaks from the high-pressure space to the low-pressure space through the leakage groove, so that the differential pressure applied to the piston rings can be reduced. Therefore, in a plurality of piston rings to which different differential pressures are applied, the difference in differential pressure between the piston rings is alleviated, so that it is possible to prevent a large differential pressure from being applied to some of the piston rings. In addition, since the leakage groove is disposed in a ring groove that is less susceptible to the sliding of the piston, it is possible to prevent the leakage groove from wearing over time. Therefore, in a piston having multiple piston rings, the difference in differential pressure between the multiple piston rings can be maintained in a state where it is alleviated even over time, so that the life of the piston rings can be extended. Moreover, since the number of leakage grooves is adjusted between at least two ring grooves, the flow rate of gas leaking from the high pressure side space to the low pressure side space can be adjusted between the multiple ring grooves.

[0009] The piston body may include a piston shaft, a first piston member fitted onto the piston shaft, and a second piston member that may be configured separately from the first piston member and fitted onto the piston shaft. The first piston member may have the low pressure side surface on which the leakage groove is formed, the second piston member may have a high pressure side surface disposed opposite to the low pressure side surface, and the ring groove may be formed between the first piston member and the second piston member.

[0010] In this embodiment, since the first piston member and the second piston member are configured as separate bodies, it is possible to more easily process the leakage groove on the low pressure side surface before assembling the piston body.

[0011] A piston according to the present invention is a piston used in a reciprocating compressor having a cylinder, comprising: a piston body in which a plurality of ring grooves are formed; and a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body, at least two of the plurality of ring grooves have at least one leakage groove formed on a low pressure side surface, and the leakage groove is configured to ensure communication between a space on a high pressure side relative to the piston ring corresponding to the leakage groove and a space on a low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, The number of leakage grooves formed in the ring groove on the side to which a larger pressure difference is applied among the at least two ring grooves is greater than the number of leakage grooves formed in the other ring groove on the side to which a smaller pressure difference is applied, The leakage groove is formed The number of the leakage grooves is adjusted between the at least two ring grooves. R .

[0012] In this embodiment, since the number of leakage grooves is adjusted between at least two ring grooves, the flow rate of gas leaking from the high pressure side space to the low pressure side space can be adjusted between multiple ring grooves. The number of leakage grooves can be increased for a piston ring with a large differential pressure, and decreased for a piston ring with a small differential pressure. This makes it possible to more effectively reduce the difference in differential pressure between multiple piston rings.

[0013] The piston according to the present invention is used in a reciprocating compressor having a cylinder, and includes a piston body having a plurality of ring grooves formed therein, and a plurality of piston rings disposed in the plurality of ring grooves of the piston body, respectively. At least two of the plurality of ring grooves each have a leakage groove formed on a low pressure side surface, and The leakage groove is configured to ensure communication between a space on the high pressure side relative to the piston ring corresponding to the leakage groove and a space on the low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, and the flow path area of ​​the leakage groove is adjusted between the at least two ring grooves in which the leakage groove is formed. The at least two ring grooves include a first ring groove and a second ring groove which is a ring groove on a side to which a smaller pressure difference than that of the first ring groove is applied, and a flow area of ​​a leakage groove provided in the first ring groove is larger than a flow area of ​​a leakage groove provided in the second ring groove. .

[0014] In the piston configured in this manner, gas leaks from the high-pressure space to the low-pressure space through the leakage groove, so that the differential pressure applied to the piston rings can be reduced. Therefore, in a plurality of piston rings to which different differential pressures are applied, the difference in differential pressure between the piston rings is alleviated, so that it is possible to prevent a large differential pressure from being applied to some of the piston rings. In addition, since the leakage groove is disposed in a ring groove that is less susceptible to the sliding of the piston, it is possible to prevent the leakage groove from wearing over time. Therefore, in a piston having multiple piston rings, the difference in differential pressure between the multiple piston rings can be maintained in a state where it is alleviated even over time, so that the life of the piston rings can be extended. Furthermore, since the flow passage area of ​​the leakage groove is adjusted between at least two ring grooves, the flow rate of gas flowing from the high pressure side space to the low pressure side space can be adjusted between a plurality of ring grooves. A piston according to the present invention is a piston used in a reciprocating compressor having a cylinder, comprising: a piston body in which a plurality of ring grooves are formed; and a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body, at least two of the plurality of ring grooves have at least one leakage groove formed on a low pressure side surface, and the leakage groove is configured to ensure communication between a space on a high pressure side relative to the piston ring corresponding to the leakage groove and a space on a low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, A flow path area of ​​a leakage groove formed in a ring groove on a side to which a larger differential pressure is applied, among the at least two ring grooves, is made larger than a flow path area of ​​a leakage groove formed in another ring groove on a side to which a smaller differential pressure is applied, The leakage groove is formed The flow area of ​​the leakage groove is adjusted between the at least two ring grooves. R . In this embodiment, the flow passage area can be made larger for the piston ring with a larger differential pressure and the flow passage area can be made smaller for the piston ring with a smaller differential pressure, thereby more effectively reducing the difference in differential pressure between the multiple piston rings.

[0015] The piston may be provided in a reciprocating compressor including a cylinder that slidably houses the piston, and a crank mechanism. Effect of the Invention

[0016] According to the present invention, in a piston having a plurality of piston rings, the difference in differential pressure between the plurality of piston rings can be maintained in a reduced state even over time, thereby extending the life of the piston rings. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view illustrating a schematic view of a part of a reciprocating compressor according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic view of a part of the piston according to the first embodiment. [Diagram 3] FIG. 2 is a schematic diagram illustrating a portion of a piston according to the first embodiment. [Figure 4] FIG. 3 is an enlarged view illustrating a ring groove of the piston body according to the first embodiment. [Diagram 5] 3(a) to 3(c) are schematic diagrams illustrating a ring groove according to the first embodiment. [Figure 6] 6(a) to 6(c) are cross-sectional views illustrating a leakage groove according to a second embodiment. [Figure 7] FIG. 11 is a schematic diagram showing a part of a piston body according to a third embodiment. [Figure 8] FIG. 11 is a schematic diagram showing a part of a piston body according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (First embodiment) 1 is a schematic cross-sectional view showing a configuration of a part of a reciprocating compressor according to a first embodiment (hereinafter referred to as "compressor 100"). In the following description, directional indicators such as "upper" and "lower" are used. These directional indicators are intended only for the purpose of clarifying the description and should not be interpreted in a limiting manner.

[0019] 1, the compressor 100 includes a cylinder 10, a piston 20 disposed within the cylinder 10, an inlet valve 12 and a discharge valve 14 disposed on the side surfaces of the cylinder 10, and a cylinder head 16 disposed on an upper surface 10A of the cylinder 10. The compressor 100 further includes a crank mechanism (not shown) that is disposed below the cylinder 10 and causes the piston 20 to reciprocate up and down within the cylinder 10.

[0020] The cylinder 10 is formed with a cylindrical internal space 10B that extends in one direction and opens to a top surface 10A of the cylinder 10, and the opening of the top surface 10A is closed by a cylinder head 16. The cylinder 10 is formed with a suction passage 10E that extends laterally from the internal space 10B and opens to a side surface of the cylinder 10, and a discharge passage 10F that extends from the internal space 10B to the side opposite to the aforementioned side and opens to a side surface of the cylinder 10 opposite to the suction passage 10E.

[0021] The suction passage 10E is provided with a suction valve 12 coupled to the side surface of the cylinder 10. The suction valve 12 is a check valve that allows gas to flow from the outside into the internal space 10B, and is connected to a pipe (not shown) for supplying gas from the outside to the internal space 10B.

[0022] The discharge flow path 10F is provided with a discharge valve 14 coupled to the side surface of the cylinder 10. The discharge valve 14 is a check valve that allows gas to flow from the internal space 10B to the outside, and is connected to a pipe (not shown) for flowing the gas discharged from the internal space 10B.

[0023] The piston 20 is disposed coaxially with the cylinder 10 in the internal space 10B, and has an axial length shorter than that of the cylinder 10. In the internal space 10B of the cylinder 10, a portion between the piston 20 and the cylinder head 16 functions as a compression chamber 10C. The suction passage 10E and the discharge passage 10F each communicate with the compression chamber 10C.

[0024] As shown in Figures 2 and 3, the piston 20 includes a cylindrical piston body 22 and a plurality of piston rings 30 arranged on the outer circumferential surface of the piston body 22. The outer diameter of the piston body 22 is slightly smaller than the diameter of the inner circumferential surface of the cylinder 10. Therefore, an annular piston gap 50 is formed between the outer circumferential surface of the piston body 22 and the inner circumferential surface of the cylinder 10. Note that the piston gap 50 is exaggerated in Figures 1 and 3 compared to the actual size.

[0025] A plurality of ring grooves 24 extending in the circumferential direction and spaced apart from one another are formed on the outer circumferential surface of the piston body 22. A piston ring 30 is disposed in each ring groove 24. The plurality of piston rings 30 are sealing members provided to prevent gas from the compression chamber 10C from leaking through the piston gap 50 to the crank mechanism side. Each piston ring 30 is annular and has a joint as if the ring was cut.

[0026] The multiple ring grooves 24 include ring grooves 24A, 24B, 24C... 24X, 24Y, and 24Z arranged in that order from the compression chamber 10C side. That is, the ring groove 24A is the ring groove arranged at a position closest to the compression chamber 10C, and the ring groove 24Z is the ring groove arranged at a position closest to the crank mechanism side.

[0027] 4, each ring groove 24 includes an inner bottom surface 26, a high pressure side 27, and a low pressure side 28. The ring groove 24 defines a space with a rectangular cross section for disposing a piston ring 30 therein.

[0028] The inner bottom surface 26 is formed in a cylindrical shape of the piston body 22 and faces the inner peripheral surface of the piston ring 30. The diameter of the annular inner bottom surface 26 is smaller than the outer diameter of the piston body 22 and smaller than the inner diameter of the piston ring 30. Therefore, a bottom side gap 33 is formed between the inner bottom surface 26 and the piston ring 30. The length of the inner bottom surface 26 in the axial direction of the piston 20 is slightly larger than the width of the piston ring 30 (the axial length of the piston 20). Therefore, a side side gap 34 communicating with the bottom side gap 33 is formed between the high pressure side surface 27 or the low pressure side surface 28 and the piston ring 30.

[0029] The high-pressure side surface 27 is an annular side surface that defines the end face of the ring groove 24 on the compression chamber 10C side, connects the edge of the inner bottom surface 26 closer to the compression chamber 10C to the outer circumferential surface of the piston body 22, and faces downward (toward the crank mechanism). The high-pressure side surface 27 faces the high-pressure side surface of the piston ring 30.

[0030] The low-pressure side surface 28 is an annular side surface that defines the end surface of the ring groove 24 on the crank mechanism side, and connects an edge of the inner bottom surface 26 closer to the crank mechanism to the outer circumferential surface of the piston body 22, and faces upward (toward the compression chamber 10C). The low-pressure side surface 28 faces the low-pressure side surface of the piston ring 30.

[0031] When the piston ring 30 is in contact with the inner circumferential surface of the cylinder 10 and the low-pressure side surface 28 of the ring groove 24, the piston gap 50 between the cylinder 10 and the piston 20 is divided by the piston ring 30 into a high-pressure side space 52 and a low-pressure side space 54. The high-pressure side space 52 is a space closer to the compression chamber 10C than the piston ring 30. The low-pressure side space 54 is a space closer to the crank mechanism than the piston ring 30.

[0032] A leakage groove 40 is formed in the low-pressure side surface 28 of the ring groove 24, extending from the inner bottom surface 26 to the outer circumferential surface of the piston body 22. The leakage groove 40 has an inner end that opens to communicate with a bottom side gap 33 in the ring groove 24, and an outer end that opens to the outer circumferential surface of the piston body 22. Therefore, when the piston ring 30 is in contact with the low-pressure side surface 28, a flow passage that communicates between the high-pressure side space 52 and the low-pressure side space 54 is formed by the leakage groove 40, the bottom side gap 33, and the side side gap 34.

[0033] The leakage grooves 40 may be provided in each ring groove 24, or may be provided in some of the ring grooves 24. The same number of leakage grooves 40 may be provided in each ring groove 24, or different numbers of leakage grooves 40 may be provided. For example, Figs. 5(a) to (c) show examples in which eight, four, and two leakage grooves 40 are formed on the low-pressure side surface 28 of the ring groove 24. That is, the number of leakage grooves 40 is adjusted between the multiple ring grooves 24. As a result, the flow rate of gas flowing from the high-pressure side space 52 to the low-pressure side space 54 is adjusted between the multiple ring grooves 24.

[0034] The number of leakage grooves 40 provided on the low pressure side surface 28 of the ring groove 24 is not limited to eight, four, or two. For example, six, three, one, or any other number of leakage grooves 40 may be provided on the low pressure side surface 28. Furthermore, when multiple leakage grooves 40 are provided on the low pressure side surface 28, the multiple leakage grooves 40 may be disposed at equal intervals from each other, or may be disposed at unequal intervals from each other.

[0035] In each ring groove 24, the number of leakage grooves 40 is adjusted according to the magnitude of the pressure difference applied to the piston ring 30 arranged in the ring groove 24. For example, the ring groove 24A of the piston ring 30 arranged at the position closest to the compression chamber 10C and prone to a large pressure difference is provided with the largest number of leakage grooves 40 (e.g., eight). Since the pressure difference of the piston ring 30 in the ring groove 24B adjacent to the low pressure side of the ring groove 24A is smaller than the pressure difference of the piston ring 30 in the ring groove 24A, the ring groove 24B is provided with the same number of leakage grooves 40 as the ring groove 24A or fewer (e.g., four). Furthermore, since the pressure difference of the piston ring 30 in the ring groove 24C adjacent to the low pressure side of the ring groove 24B is smaller than the pressure difference of the piston ring 30 in the ring groove 24B, the ring groove 24C is provided with the same number of leakage grooves 40 as the ring groove 24B or fewer (e.g., two). Alternatively, the leakage groove 40 may not be provided in the ring groove 24C.

[0036] Similarly, for example, the ring groove 24Z of the piston ring 30, which is disposed at the position closest to the crank mechanism and is likely to have a large pressure difference, is provided with the largest number of leakage grooves 40 (e.g., eight). Since the pressure difference of the piston ring 30 of the ring groove 24Y adjacent to the high pressure side of the ring groove 24Z is smaller than the pressure difference of the piston ring 30 of the ring groove 24Z, the ring groove 24Y is provided with the same number of leakage grooves 40 as the ring groove 24Z or fewer (e.g., four). Furthermore, since the pressure difference of the piston ring 30 of the ring groove 24X adjacent to the high pressure side of the ring groove 24Y is smaller than the pressure difference of the piston ring 30 of the ring groove 24Y, the ring groove 24X is provided with the same number of leakage grooves 40 as the ring groove 24Y or fewer (e.g., two). Alternatively, the ring groove 24X may not be provided with any leakage grooves 40.

[0037] (Driving operation and effects) During operation of the compressor 100, the piston 20 slides within the cylinder 10 in accordance with the reciprocating motion of the crank mechanism, and the compression chamber 10C repeatedly undergoes compression and expansion. As the compression chamber 10C undergoes compression and expansion, gas is sucked into the compression chamber 10C from the outside via the suction valve 12, and pressurized gas is discharged from the compression chamber 10C to the outside via the discharge valve 14.

[0038] A part of the gas pressurized in the compression chamber 10C flows into the piston gap 50 between the cylinder 10 and the piston 20. This gas passes through the ring groove 24 and leaks to the crank mechanism side. At this time, a pressure difference is applied to each piston ring 30. This pressure difference is caused by the difference in pressure between the high-pressure side space 52 and the low-pressure side space 54 of each piston ring 30. Due to this pressure difference, each piston ring 30 comes into contact with the low-pressure side surface 28 of the ring groove 24 while contacting the inner peripheral surface of the cylinder 10.

[0039] The compressor 100 is configured such that the pressure of the gas leaking from the compression chamber 10C to the crank mechanism side is distributed to the multiple piston rings 30 so that a large differential pressure is not applied to each piston ring 30. This distributed differential pressure is not uniform among the piston rings 30, and differences occur between the piston rings 30. In other words, a relatively large differential pressure may be applied to some piston rings 30, and in such a case, wear of the piston rings 30 to which the relatively large differential pressure is applied may progress easily.

[0040] However, in this embodiment, the ring groove 24 is provided with the leakage groove 40, and gas leaks from the high pressure side space 52 to the low pressure side space 54 through the leakage groove 40, so that the differential pressure applied to each piston ring 30 is reduced. Therefore, even if a difference in differential pressure occurs between each piston ring 30, the difference in differential pressure between each piston ring 30 can be alleviated by reducing the differential pressure of the piston ring 30 by the leakage groove 40 for the ring groove 24 of the piston ring 30 with a large differential pressure. Therefore, it is possible to suppress a large differential pressure from being applied to some piston rings 30.

[0041] Furthermore, since the leakage groove 40 is formed on the low-pressure side surface 28 of the ring groove 24, wear and deformation due to sliding of the piston 20 are unlikely to occur. Therefore, in the compressor 100, the pressure difference between the piston rings 30 can be kept reduced even over time, so that the lifespan of the multiple piston rings 30 can be extended.

[0042] Furthermore, since the number of leakage grooves 40 is adjusted among the multiple ring grooves 24, the pressure difference applied to each piston ring 30 can be reduced according to the number of leakage grooves 40. That is, by increasing the number of leakage grooves 40 for piston rings 30 that are subjected to a large pressure difference and decreasing the number of leakage grooves 40 for piston rings 30 that are subjected to a small pressure difference, the difference in pressure difference between piston rings 30 can be more effectively alleviated.

[0043] Second embodiment As shown in FIGS. 6(a) to 6(c), the compressor 100 of the second embodiment differs from the compressor 100 of the first embodiment in that the flow passage area of ​​the leakage groove 40 is adjusted.

[0044] For example, Figures 6(a) to 6(c) show examples of leakage grooves 40 in which the flow area is changed by changing the groove depth or groove width. The groove depth of leakage groove 40B in Figure 6(b) is a groove depth 2D larger than the groove depth 1D of leakage groove 40A in Figure 6(a), and the flow area of ​​leakage groove 40B is larger than the flow area of ​​leakage groove 40A. The groove width of leakage groove 40C in Figure 6(c) is a groove width 2W larger than the groove width 1W of leakage groove 40A in Figure 6(a), and the flow area of ​​leakage groove 40C is larger than the flow area of ​​leakage groove 40A.

[0045] In the compressor 100 configured in this manner, the flow path area of ​​the leakage groove 40 is adjusted between the multiple ring grooves 24, so that the pressure difference applied to each piston ring 30 can be reduced according to the flow path area. That is, by making the flow path area of ​​the leakage groove 40 larger for the piston ring 30 to which a large pressure difference is applied and making the flow path area of ​​the leakage groove 40 smaller for the piston ring 30 to which a small pressure difference is applied, the difference in pressure difference between the piston rings 30 can be more effectively alleviated.

[0046] Third embodiment The compressor 100 of the third embodiment differs from the compressor 100 of the first embodiment in that the piston body 22 is configured to be disassembled.

[0047] As shown in Fig. 7, the piston body 22 includes a cylindrical piston shaft 67 extending in one direction, and a plurality of piston members 60 fitted onto the piston shaft 67. As shown in Fig. 7, the plurality of piston members 60 include a first piston member 61, a second piston member 62, and an intermediate piston member 63 that are configured separately from each other.

[0048] The first piston member 61, the second piston member 62 and the intermediate piston member 63 are components that form one ring groove 24. The piston body 22 has a large number of first piston members 61, second piston members 62 and intermediate piston members 63.

[0049] The intermediate piston member 63 is disposed between the first piston member 61 and the second piston member 62. The outer diameter of the first piston member 61 is equal to the outer diameter of the second piston member 62. The outer diameter of the intermediate piston member 63 is smaller than the outer diameter of the first piston member 61 and smaller than the inner diameter of the piston ring 30.

[0050] The first piston member 61, the second piston member 62, and the intermediate piston member 63 are fitted onto the piston shaft 67 to form the ring groove 24. That is, the ring groove 24 is formed between the first piston member 61 and the second piston member 62. At this time, the upper surface of the first piston member 61 functions as the low-pressure side surface 28 of the ring groove 24, the lower surface of the second piston member 62 functions as the high-pressure side surface 27 of the ring groove 24, and the outer circumferential surface of the intermediate piston member 63 functions as the inner bottom surface 26 of the ring groove 24. A leakage groove 40 is formed in the upper surface of the first piston member 61 that functions as the low-pressure side surface 28.

[0051] In the compressor 100 configured in this manner, the leakage groove 40 can be machined in the first piston member 61, which has a surface that functions as the low-pressure side surface 28, when the piston body 22 is disassembled into the first piston member 61, the second piston member 62, and the intermediate piston member 63, making it easier to machine the leakage groove 40.

[0052] In the third embodiment, the piston body 22 corresponding to each ring groove 24 can be disassembled into three piston members 61 to 63, but this is not limited thereto. For example, as shown in Fig. 8, a portion of the piston body 22 corresponding to one ring groove 24 may be configured to be disassembled into a first piston member 61 and a second piston member 62 whose outer circumferential surface is formed in a stepped shape.

[0053] In this case, the second piston member 62 includes a cylindrical first portion 62a having an outer diameter smaller than the outer diameter of the first piston member 61 and smaller than the inner diameter of the piston ring 30, and a cylindrical second portion 62b adjacent to the first portion 62a in the axial direction of the piston 20 and having an outer diameter the same as that of the first piston member 61.

[0054] The cylindrical outer peripheral surface of the first portion 62a functions as the inner bottom surface 26 of the ring groove 24. The second portion 62b has a downward surface that connects the upper edge of the first portion 62a and the lower edge of the second portion 62b and functions as the high pressure side surface 27 of the ring groove 24.

[0055] The second piston member 62 is fitted onto the piston shaft 67 with the lower surface of the first portion 62a in contact with the upper surface of the first piston member 61. As a result, a ring groove 24 is formed between the first piston member 61 and the second piston member 62.

[0056] It should be noted that the explanation of the other configurations, operations and effects will be omitted, but the explanations of the first and second embodiments can be applied to the third embodiment.

[0057] The embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Industrial Applicability]

[0058] The technology described in relation to the above-mentioned embodiments can be suitably applied to various technical fields where gas compression is required. [Explanation of symbols]

[0059] 100 Compressor 10. Cylinder 20. Piston 22 Piston body 24 Ring groove 27 High pressure side 28 Low pressure side 30 Piston ring 40 Leakage groove 52 High pressure space 54 Low pressure space 61... First piston member 62... Second piston member 67 Piston shaft

Claims

1. A piston for use in a reciprocating compressor having a cylinder, A piston body having a plurality of ring grooves formed therein; a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body, At least two of the plurality of ring grooves have at least one leakage groove formed on a low pressure side surface, the leakage groove is configured to ensure communication between a space on a high pressure side relative to the piston ring corresponding to the leakage groove and a space on a low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, The number of the leakage grooves is adjusted between the at least two ring grooves in which the leakage grooves are formed, the at least two ring grooves include a first ring groove and a second ring groove which is another ring groove on a side to which a smaller differential pressure than the first ring groove is applied, and the number of the leakage grooves provided in the first ring groove is greater than the number of the leakage grooves provided in the second ring groove. piston.

2. The piston body is A piston shaft, a first piston member fitted onto the piston shaft; a second piston member configured separately from the first piston member and fitted onto the piston shaft, the first piston member has the low pressure side surface on which the leakage groove is formed, the second piston member has a high pressure side disposed opposite the low pressure side, The piston of claim 1 , wherein the ring groove is formed between the first piston member and the second piston member.

3. A piston for use in a reciprocating compressor having a cylinder, A piston body having a plurality of ring grooves formed therein; a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body, At least two of the plurality of ring grooves have at least one leakage groove formed on a low pressure side surface, the leakage groove is configured to ensure communication between a space on a high pressure side relative to the piston ring corresponding to the leakage groove and a space on a low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, the number of leakage grooves formed in the ring groove on a side to which a larger pressure difference is applied is greater than the number of leakage grooves formed in the other ring groove on a side to which a smaller pressure difference is applied, between the at least two ring grooves in which the leakage grooves are formed. piston.

4. A piston for use in a reciprocating compressor having a cylinder, A piston body having a plurality of ring grooves formed therein; a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body, At least two of the plurality of ring grooves each have a leakage groove formed on a low pressure side surface, the leakage groove is configured to ensure communication between a space on a high pressure side relative to the piston ring corresponding to the leakage groove and a space on a low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, Between the at least two ring grooves in which the leakage groove is formed, a flow area of ​​the leakage groove is adjusted, the at least two ring grooves include a first ring groove and a second ring groove which is another ring groove on a side to which a smaller differential pressure than the first ring groove is applied, and the flow area of ​​the leakage groove provided in the first ring groove is larger than the flow area of ​​the leakage groove provided in the second ring groove. piston.

5. A piston for use in a reciprocating compressor having a cylinder, A piston body having a plurality of ring grooves formed therein; a plurality of piston rings respectively disposed in the plurality of ring grooves of the piston body, At least two of the plurality of ring grooves each have a leakage groove formed on a low pressure side surface, the leakage groove is configured to ensure communication between a space on a high pressure side relative to the piston ring corresponding to the leakage groove and a space on a low pressure side relative to the piston ring corresponding to the leakage groove when the piston ring corresponding to the leakage groove is in contact with the cylinder and the low pressure side surface, A piston, wherein the flow area of ​​the leakage groove formed in the ring groove on the side to which a larger pressure difference is applied, among the at least two ring grooves, is adjusted so that the flow area of ​​the leakage groove formed in the ring groove on the side to which a smaller pressure difference is applied is larger than the flow area of ​​the leakage groove formed in the other ring groove on the side to which a smaller pressure difference is applied.

6. A reciprocating compressor comprising: the piston according to any one of claims 1 to 5; and a cylinder into which the piston is inserted.

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