Screw compressor and gas compression equipment

Abstract

A screw compressor is provided with: a pair of rotor shafts; the balance piston is arranged on at least one rotor shaft; a balance piston chamber located on the suction side in the axial direction with respect to the balance piston; and a stationary member having an inner peripheral surface facing an outer peripheral surface of the balance piston, the balance piston having a communication passage inside, the communication passage communicating with the balance piston chamber and an oil reservoir between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary member. The communication path includes a radial flow path extending in a radial direction within the balancing piston.

Description

Technical Field

[0001] This disclosure relates to screw compressors and gas compression equipment. Background Technology

[0002] To reduce the load on the thrust bearing in a screw compressor, a balance piston is sometimes installed on the rotor shaft. Oil with a pressure equal to or higher than the discharge pressure of the screw compressor is introduced into the balance piston chamber, which is faced by the end face of the balance piston. This causes a force acting in the opposite direction to the gas thrust load acting on the rotor shaft (the thrust load acting on the rotor shaft due to the difference between the screw compressor's intake and discharge pressures) to act on the rotor shaft via the end face of the balance piston, thereby reducing the load on the thrust bearing.

[0003] Patent Document 1 describes a screw compressor with a balance piston mounted on the rotor shaft. In this screw compressor, a labyrinth (undulation) is provided on the outer peripheral surface of the balance piston. This labyrinth seal prevents oil leakage from the balance piston chamber through the gap between the outer peripheral surface of the balance piston and the inner peripheral surface of the housing opposite to the outer peripheral surface.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 62-19658 Summary of the Invention

[0005] (a) Technical problems to be solved However, in order to reduce oil leakage through the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component (housing, sleeve, etc.) opposite to the outer circumferential surface, it is considered to minimize this gap. On the other hand, narrowing the gap may cause damage due to contact between the balance piston and the stationary component, or reduce the assemblability of the screw compressor.

[0006] In view of the above, the object of at least one embodiment of the present invention is to provide a screw compressor and a gas compression device that can effectively suppress oil leakage of the balance piston, prevent damage caused by contact between components, and ensure good assemblability of the screw compressor.

[0007] (II) Technical Solution The screw compressor of at least one embodiment of the present invention comprises: A pair of rotor shafts; A balance piston, which is disposed on at least one of the rotor shafts; A balance piston chamber, which is located on the axial suction side relative to the balance piston; and A stationary component having an inner circumferential surface facing the outer circumferential surface of the balance piston. The balance piston has an internal communication passage that connects to the balance piston chamber and to the oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component. The connecting path includes a radial flow path extending radially within the balancing piston.

[0008] Furthermore, the gas compression apparatus of at least one embodiment of the present invention includes: The aforementioned screw compressor is configured to compress gas; and An oil separator is used to separate the oil from the mixture of compressed gas and oil discharged from the screw compressor.

[0009] (III) Beneficial Effects According to at least one embodiment of the present invention, a screw compressor and a gas compression device are provided, which can effectively suppress oil leakage of the balance piston, prevent damage caused by contact between components, and ensure good assemblability of the screw compressor. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a gas compression device according to one embodiment.

[0011] Figure 2 This is a schematic cross-sectional view of a screw compressor according to one embodiment, viewed from above.

[0012] Figure 3 This is a schematic cross-sectional view of a screw compressor according to one embodiment, viewed from above.

[0013] Figure 4 It means Figure 2 An enlarged view of a portion of the schematic diagram of the screw compressor 2 shown.

[0014] Figure 5 Viewed from the radial outer side Figure 4 The diagram shows the balance piston.

[0015] Figure 6 It means Figure 4 The diagram shows the AA section of the balance piston. Detailed Implementation

[0016] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the constituent components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0017] (Structure of gas compression equipment) Figure 1This is a schematic diagram of a gas compression device including a screw compressor with some embodiments. As shown in the figure, the gas compression device 1 includes a screw compressor 2, an oil separator 4, a cooler 6, and a pump 8.

[0018] The screw compressor 2 is configured to compress and discharge the intake gas. The symbol Ps in the figure represents the intake pressure of the screw compressor 2, and the symbol Pd represents the discharge pressure of the screw compressor 2. Oil is supplied to the screw compressor 2 via the oil supply line 10 for cooling, lubrication, etc. The oil supplied to the screw compressor 2 is discharged together with the compressed gas.

[0019] Oil separator 4 is configured to separate oil from the mixture of compressed gas and oil discharged from screw compressor 2. The oil separated by oil separator 4 is then supplied back to screw compressor 2 via oil supply line 10. Typically, the oil separated by oil separator 4 is pressurized by pump 8 and supplied to screw compressor 2 via oil supply line 10. In this case, the pressure Poil of the oil supplied to screw compressor 2 is higher than the discharge pressure Pd (Poil = Pd + α). Alternatively, the oil separated by oil separator 4 can be cooled by cooler 6 and then pressurized by pump 8. Furthermore, the oil separated by oil separator 4 can also be cooled by cooler 6 and supplied to screw compressor via oil supply line 10' under differential pressure without pump 8.

[0020] (Structure of a screw compressor) Figure 2 and Figure 3 These are schematic cross-sectional views of a screw compressor according to one embodiment, viewed from above. Figure 2 and Figure 3 As shown, the screw compressor 2 includes: a pair of screw rotors (male rotor 15 and female rotor 17) including a pair of rotor shafts 14 and 16, and a housing 12 for housing the pair of screw rotors.

[0021] A pair of rotor shafts 14 and 16 are supported for rotation by radial bearings 18, 19, 20, 21 and thrust bearings 22, 23, respectively. Pressurized oil is supplied to each bearing via oil supply line 10.

[0022] The male rotor 15 and the female rotor 17 have helical teeth that mesh with each other. Through the meshing of the teeth of the male rotor 15 and the female rotor 17 and the housing 12, multiple tooth groove spaces (cavities) are formed along the axial direction of the rotor shafts 14 and 16.

[0023] The rotor shaft 14 constituting the male rotor 15 is connected to the output shaft of a motor (not shown) and is configured to be driven by the motor's rotation. The female rotor 17, which meshes with the male rotor 15, is driven to rotate by the rotation of the male rotor 15. The female rotor 17 rotates in the opposite direction to the rotation of the male rotor 15. If the male rotor 15 and the female rotor 17 rotate in a meshing state, the tooth space moves axially from the suction side to the discharge side.

[0024] exist Figure 2 In the exemplary embodiment shown, the rotor shaft 14 is configured such that the connecting portion 11 at the suction side of both ends of the rotor shaft 14 is connected to the output shaft of the motor. That is, Figure 2 The screw compressor 2 shown is an intake-side driven screw compressor 2.

[0025] exist Figure 3 In the exemplary embodiment shown, the rotor shaft 14 is configured such that the connecting portion 11 at the discharge side end of the rotor shaft 14 is connected to the output shaft of the motor. That is, Figure 3 The screw compressor 2 shown is a discharge-side driven screw compressor 2.

[0026] A shaft seal 24 is provided in the through portion of the rotor shaft 14 of the housing 12 to prevent gas leakage through the through portion. Pressurized oil can also be supplied to the shaft seal 24 via the oil supply line 10.

[0027] The oil supplied to the bearing and shaft seal 24 is discharged from the housing 12 and returned to the relatively low-pressure space of the screw rotor housing 12 via the return pipe 28.

[0028] Gas is drawn into the toothed space through the intake space 50 formed within the housing 12 via the intake port 52. As the male rotor 15 and female rotor 17 rotate, the toothed space moves axially from the intake side towards the discharge side. During this process, the volume of the toothed space decreases after the intake port 52 is closed, thus compressing the gas within the toothed space. If the toothed space reaches the discharge port 54, it communicates with the discharge space (not shown) formed within the housing 12, and the compressed gas within the toothed space is discharged into the discharge space.

[0029] In some embodiments, the screw compressor 2 includes a disc-shaped balance piston 30 disposed on at least one of a pair of rotor shafts 14, 16. Figure 2 In the exemplary embodiment shown, a balance piston 30 is provided at the discharge side end of the rotor shaft 14 constituting the male rotor 15. Figure 3 In the exemplary embodiment shown, a balance piston 30 is provided at the end of the rotor shaft 14 constituting the male rotor 15 on the suction side. For example... Figure 2 and Figure 3 As shown, the balance piston 30 is housed in a storage space 45 formed inside the housing 12. The balance piston 30 is fixed to the rotor shaft 14 and rotates together with the rotor shaft 14.

[0030] Figure 4 It means Figure 2 An enlarged view of a portion of the schematic diagram of the screw compressor 2 shown. Furthermore, Figure 3 The balance piston 30 shown basically has the same characteristics as Figure 2 ( Figure 4 It has the same structure as the balance piston 30 shown in the figure. Figure 5 Viewed from the radial outer side Figure 4 The diagram shows the balance piston 30. Figure 6 It means Figure 4 The diagram shows the AA section of the balance piston 30.

[0031] like Figure 4 As shown, the balance piston 30 has an outer peripheral surface 31, and a first end face 32 and a second end face 34 as two axial end faces. The first end face 32 is located on the axial suction side, and the second end face 34 is located on the axial discharge side.

[0032] The outer peripheral surface 31 of the balance piston 30 faces the inner peripheral surface 13 of the stationary component (in this embodiment, the housing 12), and a gap G is formed between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component). Furthermore, in some embodiments, a sleeve (stationary component) fixed to the housing 12 may be provided on the outer peripheral side of the balance piston 30, with the outer peripheral surface 31 of the balance piston 30 facing the inner peripheral surface of the sleeve (stationary component).

[0033] The receiving space 45 for accommodating the balance piston 30 has: a first chamber (balance piston chamber) 42 facing a first end face 32 of the balance piston 30, and a second chamber (low-pressure chamber) 44 facing a second end face 34 of the balance piston 30. The first chamber (balance piston chamber) 42 is located on the axial suction side relative to the balance piston 30. The second chamber (low-pressure chamber) 44 is located on the axial discharge side relative to the balance piston 30.

[0034] The first chamber (balance piston chamber) 42 is supplied with oil from the oil separator 4 (see reference). Figure 1 The separated oil (relatively high-pressure oil discharged from screw compressor 2) can also be supplied to the first chamber 42 via oil supply line 10, pressurized by pump 8 (Poil = Pd + α), or it can be supplied directly (without pump pressurization) via oil supply line 10' (see reference). Figure 1Oil (Poil = Pd) separated by oil separator 4 is supplied to first chamber 42. Oil from oil supply line 10 (or 10') is supplied to first chamber 42 via oil supply line 46 provided in housing 12.

[0035] A portion of the oil supplied to the first chamber 42 leaks into the second chamber 44 through the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12. For example... Figure 2 and Figure 3 As shown, the oil in the second chamber 44 is recovered to the return pipe 28 via the oil drain passage 48 provided in the housing 12, and returned to the relatively low-pressure space of the screw rotor housing in the housing 12.

[0036] Alternatively, a sealing part 26 may be provided to prevent oil leakage from the first chamber 42 through the gap between the housing 12 and the rotor shaft 14.

[0037] If relatively high-pressure oil is introduced from the oil supply line 10 (or 10') into the first chamber (balance piston chamber) 42 facing the first end face 32 of the balance piston 30 on the suction side, a force (a force in the axial direction from the suction side to the discharge side) acting in the opposite direction to the gas thrust load acting on the rotor shaft 14 (the thrust load acting on the rotor shaft 14 in the axial direction from the discharge side to the suction side due to the difference between the suction pressure Ps and the discharge pressure Pd of the screw compressor 2) acts on the rotor shaft 14 via the first end face 32 of the balance piston 30. This reduces the load on the thrust bearing 22.

[0038] like Figures 2-5 As shown, in some embodiments, the balance piston 30 has a communication passage 36 formed inside the balance piston 30. The communication passage 36 communicates with the first chamber (balance piston chamber) 42 and with the oil reservoir 40 formed between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary member). Figure 4 As shown, the connecting path 36 includes a radial flow path 38 extending radially inside the balance piston 30.

[0039] The oil reservoir 40 is formed between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component), and is a space whose radial dimension is larger than the clearance G. Figures 4-6 As shown, the oil reservoir 40 may include a groove 41 disposed on the outer peripheral surface 31 of the balance piston 30. Alternatively, multiple grooves 41 (multiple oil reservoirs 40) separated in the circumferential direction may be formed between the balance piston 30 and the housing 12. Furthermore, in Figure 2 and Figure 3 The diagram shows two oil reservoirs 40 positioned 180 degrees apart in the circumferential direction. Alternatively, although not specifically shown, the oil reservoirs 40 may also comprise circumferentially continuous grooves.

[0040] Alternatively, the balance piston 30 may be provided with multiple connecting passages 36, each having a radial flow path 38. Figure 2 and Figure 3 In the embodiment shown, two connecting paths 36 are provided, each corresponding to one of the two oil storage sections 40.

[0041] The connecting passage 36 includes a first open end 36a opening on the first end face 32 of the balance piston 30 and a second open end 36b forming a partial opening in the outer peripheral surface 31 of the balance piston 30 to form an oil reservoir 40. Figure 4 In the embodiment shown, the second opening end 36b is one end of the radial flow path 38. For example... Figure 4 As shown, the connecting path 36 may also include an axial flow path 37 that is connected to the radial flow path 38 and extends axially. Figure 4 In the exemplary embodiment shown, the first opening end 36a is one end of the axial flow path 37.

[0042] In the structure of the above embodiment, oil from the first chamber (balance piston chamber) 42 is introduced into the connecting passage 36 formed inside the balance piston 30. In the radial flow path 38, it is pressurized by the centrifugal force generated by the rotation of the rotor shaft 14 and supplied to the oil reservoir 40 between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component). That is, since oil with a pressure slightly higher than that of the first chamber (balance piston chamber) 42 is supplied to this oil reservoir 40, the movement of oil from the first chamber (balance piston chamber) 42 to the opposite second chamber (low-pressure chamber) 44 through the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component) can be effectively suppressed. Therefore, even if the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component) is increased to a certain extent, oil leakage through this gap G can be appropriately suppressed. Therefore, according to the above embodiments, damage caused by contact between the balance piston 30 and the housing 12 (stationary part) can be prevented, or good assemblability of the screw compressor 2 can be achieved, and oil leakage of the balance piston 30 can be effectively suppressed.

[0043] In some embodiments, the width W2 of the axially extending oil reservoir 40 (refer to...) Figure 5 It can also be the width W1 of the axially oriented balance piston 30 (refer to...). Figure 5The width W2 of the oil reservoir 40 is more than 1 / 4 and less than 1 / 2 of the width W1 of the balance piston 30. If the width W2 of the oil reservoir 40 is more than 1 / 4 of the width W1 of the balance piston 30, oil pressurized by the radial flow path 38 is supplied to a relatively wide area of ​​the outer peripheral surface 31 of the balance piston 30, thus easily suppressing oil leakage from the first chamber (balance piston chamber) 42 through the gap G. Furthermore, if the width W2 of the oil reservoir 40 is less than 1 / 2 of the width W1 of the balance piston 30, the axial distance L2 between the oil reservoir 40 and the second end face 34 (refer to...) Figure 5 The gap between the oil reservoir 40 and the second end face 34 is not too short, thus ensuring that the pressure loss between the oil reservoir 40 and the second end face 34 is minimized, and the movement of oil from the oil reservoir towards the second chamber (low-pressure chamber) 44 (second end face 34 side) can be suppressed more effectively. As a result, oil leakage through the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary part) can be suppressed more effectively.

[0044] In some embodiments, the distance L1 between the axially oriented oil reservoir 40 and the first end face 32 (refer to...) Figure 5 The distance L2 between the axial oil reservoir 40 and the second end face 34 (refer to) Figure 5 (Short). For example, the distance L1 between the axial oil reservoir 40 and the first end face 32 can also be less than 1 / 2 of the distance L2 between the axial oil reservoir 40 and the second end face 34.

[0045] In the above embodiment, the distance L2 between the axial oil reservoir 40 and the second end face 34 (the end face on the side of the second chamber (low-pressure chamber) 44) of the balance piston 30 is relatively long. Therefore, the pressure loss between the oil reservoir 40 and the second end face 34 is ensured to a certain extent, and the movement of oil from the oil reservoir 40 toward the side of the second chamber (low-pressure chamber) 44 (the side of the second end face 34) is easily suppressed. As a result, oil leakage through the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component) can be more effectively suppressed.

[0046] In some embodiments, the radial length L3 of the radial flow path 38 (refer to...) Figure 4 L4 is the difference between the outer radius r1 and the inner radius r2 of the first end face 32 (= r1-r2) (refer to...) Figure 4 The radial length L3 of the radial flow path 38 can be more than 1 / 3 of the difference between the outer radius r1 and the inner radius r2 of the first end face 32, or more than 2 / 3 of the difference L4 (=r1-r2).

[0047] According to the above embodiment, the radial length L3 of the radial flow path 38 is relatively long, so the oil guided from the first chamber (balance piston chamber) 42 to the radial flow path 38 is easily pressurized by the centrifugal force generated by the rotation of the rotor shaft 14. Therefore, the relatively high-pressure oil is easily supplied to the oil reservoir 40, thus more effectively suppressing oil leakage through the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary part).

[0048] In some embodiments, the outer peripheral surface 31 of the balance piston 30 is formed by a smooth surface. That is, in some embodiments, the outer peripheral surface 31 of the balance piston 30 does not have the following irregularities that form a labyrinth seal.

[0049] In the above embodiment, the outer peripheral surface 31 of the balance piston 30 is a smooth surface, so a boundary layer is formed on the surface of the outer peripheral surface 31 by the rotation of the rotor shaft 14 (i.e., by the rotation of the balance piston 30). This boundary layer hinders the axial movement of oil in the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the housing 12 (stationary component). Therefore, oil leakage through this gap G can be more effectively suppressed.

[0050] Furthermore, in the above description, the screw compressor described as one of some embodiments is an oil-supply type screw compressor that includes an oil separator and supplies oil from the oil separator to the screw rotor, etc. However, the aforementioned balance piston can also be applied to an oil-free screw compressor that does not include an oil separator. That is, the screw compressor in some embodiments can also be an oil-free screw compressor. In the case of an oil-free screw compressor, oil from an oil storage section such as an oil tank can be pressurized by a pump and supplied to the balance piston.

[0051] The contents described in the above embodiments are as follows.

[0052] [1] The screw compressor 2 of at least one embodiment of the present invention comprises: A pair of rotor shafts, 14 and 16; A balance piston 30 is disposed on at least one of the rotor shafts 14; The balance piston chamber (e.g., first chamber 42) is located on the axial suction side relative to the balance piston; and A stationary component (e.g., housing 12) has an inner peripheral surface 13 facing the outer peripheral surface 31 of the balance piston. The balance piston has an internal communication passage 36 that communicates with the balance piston chamber and the oil reservoir 40 between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary component. The connecting path includes a radial flow path 38 extending radially within the balance piston.

[0053] In the structure described above [1], oil from the balance piston chamber is introduced into a connecting passage formed inside the balance piston. In the radial flow path, it is pressurized by the centrifugal force generated by the rotation of the rotor shaft and supplied to the oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component. That is, since oil with a pressure slightly higher than that of the balance piston chamber is supplied to this oil reservoir, the movement of oil from the balance piston chamber to the low-pressure chamber on the opposite side via the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component can be effectively suppressed. Therefore, even if the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component is widened to a certain extent, oil leakage via this gap can be appropriately suppressed. Therefore, according to the structure described above [1], damage caused by contact between the balance piston and the stationary component can be prevented, or good assemblability of the screw compressor can be achieved, and oil leakage from the balance piston can be effectively suppressed.

[0054] [2] In some embodiments, in the structure described in [1] above, The balancing piston has a first end face 32 facing the balancing piston chamber and a second end face 34 on the opposite side of the first end face in the axial direction. The distance L1 between the oil storage section and the first end face in the axial direction is shorter than the distance L2 between the oil storage section and the second end face in the axial direction.

[0055] According to the structure described above [2], the distance between the axial oil reservoir and the first end face (the end face on the chamber side of the balance piston) of the balance piston is shorter than the distance between the axial oil reservoir and the second end face (the end face on the low-pressure chamber side) of the balance piston. Therefore, the pressure loss between the oil reservoir and the second end face can be ensured to a certain extent, and the movement of oil from the oil reservoir towards the low-pressure chamber side (the second end face side) can be suppressed. As a result, oil leakage through the gap between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary component can be suppressed more effectively.

[0056] [3] In some embodiments, in the structure described in [1] or [2] above, The balancing piston has a first end face 32 facing the balancing piston chamber. The length L3 of the radial flow path in the radial direction is more than 1 / 3 of the difference L4 between the outer radius and the inner radius of the first end face.

[0057] According to the structure described above [3], the radial length of the radial flow path is 1 / 3 of the difference between the outer radius and the inner radius of the first end face, which is relatively long. Therefore, the oil guiding the radial flow path is easily pressurized by the centrifugal force generated by the rotation of the rotor shaft. Therefore, it is easy to supply relatively high pressure oil to the oil reservoir, thus more effectively suppressing oil leakage through the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component.

[0058] [4] In some embodiments, in any of the structures described in [1] to [3] above, The oil reservoir includes a groove 41 formed on the outer peripheral surface of the balance piston.

[0059] According to the structure described above [4], the oil reservoir includes a groove formed on the outer peripheral surface of the balance piston. Therefore, by machining the balance piston, the oil reservoir can be formed relatively easily.

[0060] [5] In some embodiments, in any of the structures described in [1] to [4] above, The outer peripheral surface of the balance piston is a smooth surface.

[0061] According to the structure described above [5], the outer peripheral surface of the balance piston is a smooth surface, so a boundary layer is formed on the surface of the outer peripheral surface by the rotation of the rotor shaft (i.e., by the rotation of the balance piston). Through this boundary layer, the axial movement of oil in the gap between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary component is hindered. Therefore, oil leakage through this gap can be suppressed more effectively.

[0062] [6] The gas compression apparatus 1 according to at least one embodiment of the present invention includes: The screw compressor 2 according to any one of claims [1] to [5] is configured to compress a gas; and Oil separator 4, which is used to separate the oil from the mixture of compressed gas and oil discharged by the screw compressor.

[0063] In the structure described above [6], oil from the balance piston chamber is introduced into a connecting passage formed inside the balance piston, pressurized by centrifugal force in a radial flow path, and supplied to the oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component. That is, since oil with a pressure slightly higher than that of the balance piston chamber is supplied to this oil reservoir, the movement of oil from the balance piston chamber to the low-pressure chamber on the opposite side through the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component can be effectively suppressed. Therefore, even if the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary component is widened to a certain extent, oil leakage through this gap can be appropriately suppressed. Therefore, according to the structure described above [6], damage caused by contact between the balance piston and the stationary component can be prevented, or good assemblability of the screw compressor can be achieved, and oil leakage from the balance piston can be effectively suppressed.

[0064] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and also includes modifications to the above embodiments and appropriate combinations of these embodiments.

[0065] In this specification, expressions such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," which indicate relative or absolute configuration, do not only refer to configuration in a strict sense, but also to a state of relative displacement of angle or distance with tolerance or to the extent that the same function can be obtained.

[0066] For example, expressions such as "same," "equal," and "homogeneous" that indicate that things are in an equal state do not only mean that they are strictly equal, but also that there is a difference in degree or that they can achieve the same function.

[0067] Furthermore, in this specification, the terms "quadrilateral shape," "cylindrical shape," etc., which refer to shapes, not only refer to shapes in a strictly geometric sense, but also to shapes that include concave and convex parts, chamfered parts, etc., within the range that can achieve the same effect.

[0068] Furthermore, in this specification, the expressions "have," "possess," "comprise," "include," or "have" one of the constituent elements are not exclusive expressions that exclude the existence of other constituent elements.

[0069] Explanation of reference numerals in the attached figures 1. Gas compression equipment 2 Screw compressor 4. Oil separator 6. Cooler 8 pumps 10. Oil supply lines 10' oil supply line 11 Connecting parts 12. Shell 13 Inner circumferential surface 14 Rotor shaft 15 Male Rotor 16 Rotor shafts 17. Female rotor 18 Radial bearings 19 Radial bearings 20 Radial bearing 21 Radial bearing 22 Thrust bearing 23 Thrust bearing 24 Shaft seal 26 Sealing section 28 Return Pipeline 30 Balanced Piston 31 Outer Peripheral Surface 32 First end face 34 Second end face 36 Connecting Paths 36a First Opening End 36b Second Opening End 37 Axial Flow Path 38 Radial Flow Path 40 Oil Storage Department 41 slots 42 First Chamber (Balance Piston Chamber) 44 Second Chamber (Low-Pressure Chamber) 45 Storage space 46. ​​Fuel supply line 48 Oil drain line 50 Inhalation space 52 Inhalation Port 54 Discharge Port G gap L1 distance L2 distance Pd discharge pressure Ps Inhalation pressure r1 outer radius r2 inner radius

Claims

1. A screw compressor comprising: a pair of rotor shafts; a balance piston provided to at least one of the rotor shafts; a balance piston chamber located on an axial suction side with respect to the balance piston; and a stationary member having an inner peripheral surface facing an outer peripheral surface of the balance piston, the balance piston having a communication passage inside thereof, the communication passage communicating with the balance piston chamber and an oil reservoir portion between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary member, the communication passage including a radial flow path extending in a radial direction within the balance piston.

2. The screw compressor according to claim 1, wherein the balance piston has a first end surface facing the balance piston chamber and a second end surface on a side opposite to the first end surface in the axial direction, and a distance between the oil reservoir portion and the first end surface in the axial direction is shorter than a distance between the oil reservoir portion and the second end surface in the axial direction.

3. The screw compressor according to claim 1 or 2, wherein the balance piston has a first end surface facing the balance piston chamber, and a length of the radial flow path in the radial direction is 1 / 3 or more of a difference between an outer radius and an inner radius of the first end surface.

4. The screw compressor according to claim 1 or 2, wherein the oil reservoir portion includes a groove formed in the outer peripheral surface of the balance piston.

5. The screw compressor according to claim 1 or 2, wherein the outer peripheral surface of the balance piston is a smooth surface.

6. A gas compression apparatus comprising: the screw compressor according to claim 1 or 2 configured to compress a gas; and an oil separator for separating oil from a mixture of compressed gas and oil discharged from the screw compressor. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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