Screw compressor and gas compression facility

Abstract

To provide a screw compressor and gas compression facility capable of achieving both of effective suppression of oil leakage on a balance piston, and prevention of damage by contact of members to each other or proper assemblability of the screw compressor.SOLUTION: A screw compressor includes: a pair of rotor shafts; a balance piston disposed on at least one of the rotor shafts; a balance piston chamber positioned at a suction side in an axial direction with respect to the balance piston; and a stationary member having an inner peripheral surface opposed to an outer peripheral surface of the balance piston. The balance piston has a balance piston chamber, and a communication passage communicated to an oil reservoir between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary member inside, and the communication passage includes a radial flow passage extending along a radial direction in the balance piston.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to screw compressors and gas compression equipment. [Background technology]

[0002] In order to reduce the load on the thrust bearing in a screw compressor, a balance piston is sometimes provided on the rotor shaft of the screw compressor. Oil having a pressure equal to or greater than the discharge pressure of the screw compressor is introduced into the balance piston chamber that faces the end face of the balance piston, and a force in the opposite direction to the thrust gas load acting on the rotor shaft (thrust load acting on the rotor shaft due to the difference between the suction pressure and discharge pressure of the screw compressor) is applied to 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 in which a balance piston is provided on a rotor shaft. In this screw compressor, a labyrinth (unevenness) is provided on the outer peripheral surface of the balance piston, and this labyrinth seal is designed to suppress 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 casing facing the outer peripheral surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 62-19658 Summary of the Invention [Problem to be solved by the invention]

[0005] 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 member (such as a casing or a sleeve) facing the outer circumferential surface, it is conceivable to narrow the gap as much as possible. However, narrowing the gap may cause problems such as damage due to contact between the balance piston and the stationary member, or reduced ease of assembly of the screw compressor.

[0006] In view of the above circumstances, at least one embodiment of the present invention aims to provide a screw compressor and gas compression equipment that can effectively suppress oil leakage from the balance piston while preventing damage due to contact between components or achieving good assembly of the screw compressor. [Means for solving the problem]

[0007] At least one embodiment of the screw compressor according to the present invention comprises: A pair of rotor shafts; a balance piston provided on at least one of the rotor shafts; a balance piston chamber located on the suction side of the balance piston in the axial direction; a stationary member having an inner circumferential surface facing an outer circumferential surface of the balance piston; Equipped with the balance piston has therein a communication passage that communicates with the balance piston chamber and an oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary member, The communication passage includes a radial passage extending radially within the balance piston.

[0008] In addition, the gas compression equipment according to at least one embodiment of the present invention includes: a screw compressor as described above configured to compress a gas; an oil separator for separating the oil from a mixture of compressed gas and oil discharged from the screw compressor; Equipped with. Effect of the Invention

[0009] According to at least one embodiment of the present invention, there is provided a screw compressor and gas compression equipment that can effectively suppress oil leakage from the balance piston while preventing damage due to contact between components or achieving good assembly ease of the screw compressor. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a gas compression facility according to one embodiment. [Diagram 2] FIG. 1 is a schematic cross-sectional view of a screw compressor according to one embodiment in a plan view. [Diagram 3] FIG. 1 is a schematic cross-sectional view of a screw compressor according to one embodiment in a plan view. [Figure 4] FIG. 3 is an enlarged view showing a part of the schematic diagram of the screw compressor 2 shown in FIG. [Diagram 5] FIG. 5 is a view of the balance piston shown in FIG. 4 as seen from the radial outside. [Figure 6] 5 is a view showing a cross section AA of the balance piston shown in FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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 components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0012] (Gas Compression Equipment Configuration) 1 is a schematic diagram of a gas compression facility including a screw compressor according to some embodiments. As shown in the figure, the gas compression facility 1 includes a screw compressor 2, an oil separator 4, a cooler 6, and a pump 8.

[0013] The screw compressor 2 is configured to compress and discharge the sucked gas. In the drawing, the symbol Ps indicates the suction pressure of the screw compressor 2, and the symbol Pd indicates the discharge pressure of the screw compressor 2. Oil is supplied to the screw compressor 2 via an oil supply line 10 for cooling, lubrication, etc. The oil supplied to the screw compressor 2 is discharged together with the compressed gas.

[0014] The oil separator 4 is configured to separate oil from a mixture of compressed gas and oil discharged from the screw compressor 2. The oil separated in the oil separator 4 is supplied again to the screw compressor 2 via the oil supply line 10. Typically, the oil separated in the oil separator 4 is pressurized by the pump 8 and then supplied to the screw compressor 2 via the oil supply line 10. In this case, the pressure Poil of the oil supplied to the screw compressor 2 is higher than the discharge pressure Pd (Poil=Pd+α). The oil separated in the oil separator 4 may be cooled in the cooler 6 and then pressurized by the pump 8. The oil separated in the oil separator 4 may also be cooled in the cooler 6 and then differentially supplied to the screw compressor via the oil supply line 10' without passing through the pump 8.

[0015] (Screw Compressor Configuration) 2 and 3 are schematic cross-sectional views in plan view of a screw compressor according to one embodiment. As shown in Fig. 2 and Fig. 3, the screw compressor 2 includes a pair of screw rotors (a male rotor 15 and a female rotor 17) including a pair of rotor shafts 14, 16, and a casing 12 that houses the pair of screw rotors.

[0016] The pair of rotor shafts 14, 16 are rotatably supported by radial bearings 18, 19, 20, 21 and thrust bearings 22, 23. Oil under pressure Poil is supplied to each bearing via an oil supply line 10.

[0017] The male rotor 15 and the female rotor 17 have helical teeth that mesh with each other. A plurality of tooth gap spaces (chambers) are formed along the axial direction of the rotor shafts 14, 16 by the meshing of the teeth of the male rotor 15 and the female rotor 17 and the casing 12.

[0018] The rotor shaft 14 that constitutes the male rotor 15 is connected to the output shaft of a motor (not shown) and is configured to be rotated and driven by the motor. The female rotor 17 that meshes with the male rotor 15 is rotated and driven 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. When the male rotor 15 and the female rotor 17 rotate in the meshed state, the cutting edge groove space moves in the axial direction from the suction side to the discharge side.

[0019] In the exemplary embodiment shown in Fig. 2, the rotor shaft 14 is configured such that the connection portion 11 located at the suction side end of both ends of the rotor shaft 14 is connected to the output shaft of the motor. That is, the screw compressor 2 shown in Fig. 2 is a suction side driven screw compressor 2.

[0020] In the exemplary embodiment shown in Fig. 3, the rotor shaft 14 is configured such that the connection portion 11 located at the discharge side end of both ends of the rotor shaft 14 is connected to the output shaft of the motor. That is, the screw compressor 2 shown in Fig. 3 is a discharge side driven screw compressor 2.

[0021] A shaft seal portion 24 for suppressing leakage of gas through the penetration portion of the casing 12 by the rotor shaft 14 is provided. The shaft seal portion 24 may be configured to receive oil under pressure through the oil supply line 10.

[0022] The oil supplied to the bearings and shaft seal portion 24 is discharged from the casing 12 and returned via a return line 28 to a relatively low-pressure space in the screw rotor accommodating portion of the casing 12.

[0023] Gas is drawn into the tooth groove space from the suction space 50 formed in the casing 12 via the suction port 52. When the male rotor 15 and the female rotor 17 rotate, the tooth groove space moves axially from the suction side to the discharge side in accordance with the rotation of these screw rotors. During this process, the volume of the tooth groove space decreases after the suction port 52 is closed, and the gas in the tooth groove space is compressed. When the tooth groove space reaches the discharge port 54 and communicates with the discharge space (not shown) formed in the casing 12, the compressed gas in the tooth groove space is discharged into the discharge space.

[0024] In some embodiments, the screw compressor 2 includes a disk-shaped balance piston 30 provided on at least one of the pair of rotor shafts 14, 16. In an exemplary embodiment shown in FIG. 2, the balance piston 30 is provided on the discharge side end of the rotor shaft 14 that constitutes the male rotor 15. In an exemplary embodiment shown in FIG. 3, the balance piston 30 is provided on the suction side end of the rotor shaft 14 that constitutes the male rotor 15. As shown in FIGS. 2 and 3, the balance piston 30 is accommodated in an accommodation space 45 formed inside the casing 12. The balance piston 30 is fixed to the rotor shaft 14 and rotates together with the rotor shaft 14.

[0025] Fig. 4 is an enlarged view showing a part of the schematic diagram of the screw compressor 2 shown in Fig. 2. The balance piston 30 shown in Fig. 3 basically has the same configuration as the balance piston 30 shown in Fig. 2 (Fig. 4). Fig. 5 is a view of the balance piston 30 shown in Fig. 4 as seen from the radial outside. Fig. 6 is a view showing the AA cross section of the balance piston 30 shown in Fig. 4.

[0026] 4, the balance piston 30 has an outer circumferential surface 31, and also has two axial end faces, that is, a first end face 32 and a second end face 34. The first end face 32 is located on the axial intake side, and the second end face 34 is located on the axial discharge side.

[0027] An outer peripheral surface 31 of the balance piston 30 faces an inner peripheral surface 13 of a stationary member (the casing 12 in this embodiment), 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 casing 12 (stationary member). Note that in some embodiments, a sleeve (stationary member) fixed to the casing 12 may be provided on the outer periphery of the balance piston 30, so that the outer peripheral surface 31 of the balance piston 30 faces the inner peripheral surface of the sleeve (stationary member).

[0028] The accommodation space 45 in which the balance piston 30 is accommodated has a first chamber (balance piston chamber) 42 facing the first end face 32 of the balance piston 30, and a second chamber (low pressure chamber) 44 facing the second end face 34 of the balance piston 30. The first chamber (balance piston chamber) 42 is located on the suction side in the axial direction with respect to the balance piston 30. The second chamber (low pressure chamber) 44 is located on the discharge side in the axial direction with respect to the balance piston 30.

[0029] The first chamber (balance piston chamber) 42 is supplied with oil (relatively high-pressure oil discharged from the screw compressor 2) separated in the oil separator 4 (see FIG. 1). The first chamber 42 may be supplied with oil (Poil=Pd+α) pressurized by the pump 8 via the oil supply line 10, or the oil (Poil=Pd) separated in the oil separator 4 may be supplied as is (without being pressurized by the pump) via the oil supply line 10' (see FIG. 1). The oil from the oil supply line 10 (or 10') is supplied to the first chamber 42 via an oil supply passage 46 provided in the casing 12.

[0030] A part of the oil supplied to the first chamber 42 leaks into the second chamber 44 through a gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the casing 12. As shown in Figures 2 and 3, the oil in the second chamber 44 is collected in the return line 28 through an oil drain passage 48 provided in the casing 12, and is returned to the relatively low-pressure space of the screw rotor housing portion of the casing 12.

[0031] A seal portion 26 for preventing oil from leaking from the first chamber 42 through the gap between the casing 12 and the rotor shaft 14 may be provided.

[0032] When 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 on the suction side of the balance piston 30, a force (a force in the axial direction from the suction side to the discharge side) in the opposite direction to the thrust gas load acting on the rotor shaft 14 (a 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.

[0033] 2 to 5, in some embodiments, the balance piston 30 has a communication passage 36 formed inside the balance piston 30. The communication passage 36 communicates with a first chamber (balance piston chamber) 42, and also communicates with an oil reservoir 40 formed between an outer circumferential surface 31 of the balance piston 30 and an inner circumferential surface 13 of the casing 12 (stationary member). As shown in FIG. 4, the communication passage 36 includes a radial flow passage 38 extending radially inside the balance piston 30.

[0034] The oil reservoir 40 is a space formed between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the casing 12 (stationary member), and has a radial size larger than the gap G. As shown in Figs. 4 to 6, the oil reservoir 40 may include a groove 41 provided on the outer peripheral surface 31 of the balance piston 30. A plurality of grooves 41 (a plurality of oil reservoirs 40) positioned apart in the circumferential direction may be formed between the balance piston 30 and the casing 12. Note that Figs. 2 and 3 show two oil reservoirs 40 provided at positions 180 degrees apart in the circumferential direction. Alternatively, although not particularly shown, the oil reservoir 40 may include a circumferential groove continuing in the circumferential direction.

[0035] The balance piston 30 may be provided with a plurality of communication passages 36, each having a radial flow passage 38. In the embodiment shown in Figures 2 and 3, two communication passages 36 corresponding to the two oil reservoirs 40, respectively, are provided.

[0036] The communication passage 36 includes a first open end 36a that opens to the first end face 32 of the balance piston 30, and a second open end 36b that opens to a portion of the outer circumferential surface 31 of the balance piston 30 that forms the oil reservoir 40. In the embodiment shown in FIG. 4, the second open end 36b is one end of a radial flow passage 38. As shown in FIG. 4, the communication passage 36 may include an axial flow passage 37 that is connected to the radial flow passage 38 and extends along the axial direction. In the exemplary embodiment shown in FIG. 4, the first open end 36a is one end of the axial flow passage 37.

[0037] In the configuration according to the embodiment described above, oil from the first chamber (balance piston chamber) 42 is introduced into the communication passage 36 formed inside the balance piston 30, pressurized by centrifugal force due to the rotation of the rotor shaft 14 in the radial flow passage 38, and supplied to the oil reservoir 40 between the outer circumferential surface 31 of the balance piston 30 and the inner circumferential surface 13 of the casing 12 (stationary member). That is, oil with a pressure slightly higher than that of the first chamber (balance piston chamber) 42 is supplied to the oil reservoir 40, so that 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 circumferential surface 31 of the balance piston 30 and the inner circumferential surface 13 of the casing 12 (stationary member) can be effectively suppressed. Therefore, even if the gap G between the outer circumferential surface 31 of the balance piston 30 and the inner circumferential surface 13 of the casing 12 (stationary member) is made wider to some extent, oil leakage through the gap G can be appropriately suppressed. Therefore, according to the above-described embodiment, it is possible to prevent damage caused by contact between the balance piston 30 and the casing 12 (stationary member), or to effectively suppress oil leakage from the balance piston 30 while achieving good assembly ease of the screw compressor 2.

[0038] In some embodiments, the width W2 of the oil reservoir 40 in the axial direction (see FIG. 5) may be ¼ or more and ½ or less of the width W1 of the balance piston 30 in the axial direction (see FIG. 5). If the width W2 of the oil reservoir 40 is ¼ or more of the width W1 of the balance piston 30, Since the oil pressurized by the radial flow passage 38 is supplied to a relatively wide area of ​​the outer circumferential surface 31 of the balance piston 30, it is easy to suppress oil leakage from the first chamber (balance piston chamber) 42 through the gap G. In addition, if the width W2 of the oil reservoir 40 is 1 / 2 or less of the width W1 of the balance piston 30, the distance L2 (see FIG. 5) in the axial direction between the oil reservoir 40 and the second end face 34 is not too short, so that a certain degree of pressure loss between the oil reservoir 40 and the second end face 34 is secured, and it is easy to suppress the movement of oil from the oil reservoir toward the second chamber (low pressure chamber) 44 side (the second end face 34 side). This makes it possible to more effectively suppress oil leakage through the gap G between the outer circumferential surface 31 of the balance piston 30 and the inner circumferential surface 13 of the casing 12 (stationary member).

[0039] In some embodiments, the distance L1 (see FIG. 5) between the oil reservoir 40 and the first end face 32 in the axial direction is shorter than the distance L2 (see FIG. 5) between the oil reservoir 40 and the second end face 34 in the axial direction. For example, the distance L1 between the oil reservoir 40 and the first end face 32 in the axial direction may be equal to or less than ½ of the distance L2 between the oil reservoir 40 and the second end face 34 in the axial direction.

[0040] In the above-described embodiment, the distance L2 in the axial direction between the oil reservoir 40 and the second end face 34 (the end face on the second chamber (low pressure chamber) 44 side) of the balance piston 30 is relatively long, so that a certain degree of pressure loss between the oil reservoir 40 and the second end face 34 can be secured, making it easier to suppress the movement of oil from the oil reservoir 40 toward the second chamber (low pressure chamber) 44 side (the second end face 34 side). This makes it possible to more effectively suppress oil leakage through the gap G between the outer circumferential surface 31 of the balance piston 30 and the inner circumferential surface 13 of the casing 12 (stationary member).

[0041] In some embodiments, the radial length L3 (see FIG. 4) of the radial flow passage 38 is ⅓ or more of the difference L4 (=r1−r2) (see FIG. 4) between the outer radius r1 and the inner radius r2 of the first end face 32. Alternatively, the radial length L3 of the radial flow passage 38 may be ½ or more or ⅔ or more of the difference L4 (=r1−r2) between the outer radius r1 and the inner radius r2 of the first end face 32.

[0042] According to the above-described embodiment, since the radial length L3 of the radial flow passage 38 is relatively long, the oil guided from the first chamber (balance piston chamber) 42 to the radial flow passage 38 is easily pressurized by the centrifugal force caused by the rotation of the rotor shaft 14. Therefore, relatively high-pressure oil is easily supplied to the oil reservoir 40, so that the leakage of oil through the gap G between the outer circumferential surface 31 of the balance piston 30 and the inner circumferential surface 13 of the casing 12 (stationary member) can be more effectively suppressed.

[0043] In some embodiments, the outer peripheral surface 31 of the balance piston 30 is formed as a smooth surface. That is, in some embodiments, the outer peripheral surface 31 of the balance piston 30 does not have any irregularities that would form a labyrinth seal.

[0044] In the above embodiment, since the outer peripheral surface 31 of the balance piston 30 is a smooth surface, a boundary layer is formed on the surface of the outer peripheral surface 31 due to the rotation of the rotor shaft 14 (i.e., due to the rotation of the balance piston 30). This boundary layer inhibits the movement of oil in the axial direction in the gap G between the outer peripheral surface 31 of the balance piston 30 and the inner peripheral surface 13 of the casing 12 (stationary member). Therefore, the leakage of oil through the gap G can be more effectively suppressed.

[0045] In the above description, as the screw compressor according to some embodiments, an oil-injected screw compressor including an oil separator and in which oil from the oil separator is supplied to the screw rotor, etc., has been described, but the above-mentioned balance piston can also be applied to an oil-free screw compressor that does not include an oil separator. That is, the screw compressor according to some embodiments may be an oil-free screw compressor. In the case of an oil-free screw compressor, oil from an oil reservoir such as an oil tank may be pressurized by a pump and supplied to the balance piston.

[0046] The contents described in each of the above embodiments can be understood, for example, as follows.

[0047] [1] At least one embodiment of the screw compressor (2) of the present invention comprises: A pair of rotor shafts (14, 16); a balance piston (30) provided on at least one of the rotor shafts (14); A balance piston chamber (e.g., a first chamber 42) located on the suction side of the balance piston in the axial direction; a stationary member (e.g., a casing 12) having an inner peripheral surface (13) facing an outer peripheral surface (31) of the balance piston; Equipped with the balance piston has therein a communication passage (36) that communicates with the balance piston chamber and an oil reservoir (40) between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary member, The communication passage includes a radial flow passage (38) extending radially within the balance piston.

[0048] In the above-mentioned configuration [1], oil from the balance piston chamber is introduced into a communication passage formed inside the balance piston, pressurized by centrifugal force due to the rotation of the rotor shaft in the radial flow passage, and supplied to an oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary member. That is, oil with a pressure slightly higher than that of the balance piston chamber is supplied to the oil reservoir, so that 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 member 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 member is made wider to some extent, oil leakage through the gap can be appropriately suppressed. Therefore, according to the above-mentioned configuration [1], it is possible to prevent damage due to contact between the balance piston and the stationary member, or to effectively suppress oil leakage from the balance piston while realizing good assembly of the screw compressor.

[0049] [2] In some embodiments, in the configuration of [1] above, The balance piston has a first end surface (32) facing the balance piston chamber and a second end surface (34) opposite to the first end surface in the axial direction, A distance (L1) between the oil reservoir and the first end face in the axial direction is shorter than a distance (L2) between the oil reservoir and the second end face in the axial direction.

[0050] According to the configuration [2] above, the distance in the axial direction between the oil reservoir and the first end face of the balance piston (the end face on the balance piston chamber side) is shorter than the distance in the axial direction between the oil reservoir and the second end face of the balance piston (the end face on the low pressure chamber side). Therefore, it is possible to secure a certain degree of pressure loss between the oil reservoir and the second end face, and to suppress the movement of oil from the oil reservoir toward the low pressure chamber side (the second end face side). This makes it possible to more effectively suppress oil leakage through the gap between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary member.

[0051] [3] In some embodiments, in the configuration of [1] or [2] above, The balance piston has a first end surface (32) facing the balance piston chamber, The length (L3) of the radial flow passage in the radial direction is equal to or greater than 1 / 3 of the difference (L4) between the outer radius and the inner radius of the first end face.

[0052] According to the configuration [3] above, the radial length of the radial flow passage is 1 / 3 of the difference between the outer radius and the inner radius of the first end face, which is relatively long, so that the oil guided to the radial flow passage is easily pressurized by the centrifugal force caused by the rotation of the rotor shaft. Therefore, relatively high-pressure oil is easily supplied to the oil reservoir, so that oil leakage through the gap between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary member can be more effectively suppressed.

[0053] [4] In some embodiments, in any one of the configurations [1] to [3] above, The oil reservoir includes a groove (41) formed in the outer circumferential surface of the balance piston.

[0054] According to the above configuration [4], the oil reservoir includes a groove formed in the outer peripheral surface of the balance piston, so that the oil reservoir can be formed relatively easily by machining the balance piston.

[0055] [5] In some embodiments, in any one of the configurations [1] to [4] above, The outer circumferential surface of the balance piston is a smooth surface.

[0056] According to the configuration of [5] above, since the outer peripheral surface of the balance piston is a smooth surface, 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). This boundary layer inhibits the movement of oil in the axial direction in the gap between the outer peripheral surface of the balance piston and the inner peripheral surface of the stationary member. Therefore, it is possible to more effectively suppress the leakage of oil through the gap.

[0057] [6] At least one embodiment of the gas compression equipment (1) of the present invention comprises: A screw compressor (2) according to any one of claims [1] to [5] configured to compress a gas; an oil separator (4) for separating the oil from a mixture of compressed gas and oil discharged from the screw compressor; Equipped with.

[0058] In the above-mentioned configuration [6], oil from the balance piston chamber is introduced into a communication passage formed inside the balance piston, pressurized by centrifugal force in the radial flow passage, and supplied to an oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary member. That is, oil with a pressure slightly higher than that of the balance piston chamber is supplied to the oil reservoir, so that 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 member 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 member is made wider to some extent, oil leakage through the gap can be appropriately suppressed. Therefore, according to the above-mentioned configuration [6], it is possible to prevent damage due to contact between the balance piston and the stationary member, or to effectively suppress oil leakage from the balance piston while realizing good assembly of the screw compressor.

[0059] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0060] In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," do not only strictly represent such a configuration, but also represent a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect is obtained. In addition, in this specification, the expressions "comprise," "include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements. [Explanation of symbols]

[0061] 1 Gas compression equipment 2 Screw compressor 4 Oil separator 6 Cooler 8. Pump 10 Oil supply line 10' Oil Supply Line 11 Connection 12 Casing 13 Inner surface 14 Rotor shaft 15 Male Rotor 16 Rotor shaft 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 Seal part 28 Return Line 30 Balance piston 31 Outer surface 32 First end surface 34 Second end face 36 Communication path 36a 1st open end 36b 2nd open end 37 Axial flow passage 38 Radial flow passage 40 Oil Puddle 41 Groove 42 1st chamber (balance piston chamber) 44 Chamber 2 (Low Pressure Chamber) 45 Containment Space 46 Fuel Line 48 Oil drain path 50 Suction space 52 Intake port 54 Discharge port G Gap L1 distance L2 distance Pd Discharge pressure Ps Intake pressure r1 outer radius r2 inner radius

Claims

1. A pair of rotor shafts; a balance piston provided on at least one of the rotor shafts; a balance piston chamber located on the suction side of the balance piston in the axial direction; a stationary member having an inner circumferential surface facing an outer circumferential surface of the balance piston; A screw compressor comprising: the balance piston has therein a communication passage that communicates with the balance piston chamber and an oil reservoir between the outer circumferential surface of the balance piston and the inner circumferential surface of the stationary member, The communication passage includes a radial flow passage extending radially within the balance piston. Screw compressor.

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

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

4. The oil reservoir includes a groove formed on the outer circumferential surface of the balance piston. The screw compressor according to claim 1 or 2.

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

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

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