JP2025038543A - Screw compressors and gas compression equipment - Google Patents

Abstract

To provide a screw compressor and a gas compression facility that can support a rotor shaft appropriately while reducing an oil supply amount to a bearing or allowing for downsizing of a bearing.SOLUTION: A screw compressor comprises a rotor shaft, and a radial slide bearing including a sleeve having a bearing surface on an inner periphery and rotatably supporting the rotor shaft. The bearing surface of the sleeve has a non-circular contour defined by a major axis and a minor axis in a cross section perpendicular to an axial direction of the rotor shaft, and comprises an oil supply path communicating with an oil reservoir part formed between a portion of the bearing surface including the end part of the major axis and an outer peripheral surface of the rotor shaft.SELECTED DRAWING: Figure 3

Description

This disclosure relates to screw compressors and gas compression equipment.

Plain bearings are used as radial bearings in rotating machinery.

Patent document 1 discloses a radial sliding bearing in which the bearing surface has a contour that is perfectly circular in a cross section perpendicular to the axial direction of the rotating shaft.

Japanese Patent Application Publication No. 7-332364

Meanwhile, screw compressors, which are subject to heavy loads, use rotor shafts with large diameters. When the rotor shaft diameter is large, the circumferential speed of the rotor shaft increases, which increases friction loss between the rotor shaft and the radial bearings, and also requires the supply of a large amount of oil to remove the heat generated by friction. Also, in screw compressors, some of the oil supplied to the bearings enters the compression section and is pressurized together with the gas, so as mentioned above, a large amount of oil supply increases the mixing loss in the compression section.

In view of the above, at least one embodiment of the present invention aims to provide a screw compressor and gas compression equipment that can properly support the rotor shaft while reducing the amount of oil supplied to the bearings or enabling the bearings to be made smaller.

At least one embodiment of the screw compressor according to the present invention comprises:
A rotor shaft;
a radial plain bearing including a sleeve having a bearing surface on an inner circumference thereof and rotatably supporting the rotor shaft;
the bearing surface of the sleeve has a non-circular contour defined by a major axis and a minor axis in a cross section perpendicular to an axial direction of the rotor shaft,
An oil supply passage is provided which communicates with an oil reservoir formed between a portion of the bearing surface including the end of the long shaft and the outer circumferential surface of the rotor shaft.

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
The oil from the oil separator is configured to be supplied to the oil sump.

At least one embodiment of the present invention provides a screw compressor and gas compression equipment that can properly support the rotor shaft while reducing the amount of oil supplied to the bearings or allowing the bearings to be made smaller.

FIG. 1 is a schematic diagram of a gas compression facility according to one embodiment. FIG. 1 is a schematic cross-sectional view of a screw compressor according to one embodiment of the present invention, as viewed from above. 1 is a schematic diagram showing a cross section perpendicular to the axial direction of a rotor shaft and a radial plain bearing of a screw compressor according to one embodiment. FIG. FIG. 4 is a view showing a cross section taken along the line BB of the radial sliding bearing shown in FIG. FIG. 4 is a view showing a cross section taken along the line BB of the radial sliding bearing shown in FIG. 1 is a schematic diagram showing a cross section perpendicular to the axial direction of a rotor shaft and a radial plain bearing of a screw compressor according to one embodiment. FIG.

Below, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention and are merely illustrative examples.

(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.

The screw compressor 2 is configured to compress and discharge the sucked gas. In the figure, 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.

The configuration of the screw compressor 2 will be described later, but in outline, the screw compressor 2 comprises a pair of screw rotors (male rotor 15 and female rotor 17) each including rotor shafts 14, 16, and radial plain bearings 18 for rotatably supporting the rotor shafts 14, 16. The radial plain bearings 18 include a radial plain bearing 18A located on the suction side in the axial direction, and a radial plain bearing 18B located on the discharge side in the axial direction. Oil is supplied to the radial plain bearings 18 via an oil supply line 10 for lubrication and cooling.

The oil separator 4 is configured to separate oil from the 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 (radial plain bearing 18, etc.) 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.

(Configuration of the screw compressor)
Fig. 2 is a schematic cross-sectional view in a plan view of a screw compressor according to one embodiment. As shown in Fig. 2, 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.

The pair of rotor shafts 14, 16 are rotatably supported by radial plain bearings 18A, 18B and thrust bearings 20, respectively. Oil at pressure Poil is supplied to each bearing via an oil supply line 10.

The male rotor 15 and the female rotor 17 have helical teeth that mesh with each other. The meshing of the teeth of the male rotor 15 and the female rotor 17 and the casing 12 form multiple tooth groove spaces (chambers) along the axial direction of the rotor shafts 14, 16.

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 a meshed state, the tooth groove space moves in the axial direction from the suction side to the discharge side.

A shaft seal 24 is provided at the penetration of the casing 12 by the rotor shaft 14 to prevent gas leakage through the penetration. Oil at pressure Poil may be supplied to the shaft seal 24 via the oil supply line 10.

Oil supplied to the bearings and shaft seals 24 is discharged from the casing 12 and returned to the relatively low-pressure space of the screw rotor housing of the casing 12 via a return line 28 (see Figures 1 and 2). Note that the oil supply lines branching off from the oil supply line 10 to the bearings and shaft seals, and the return lines 28 from each part are shown as external lines in Figure 2, but may also be lines provided inside the casing.

Gas is drawn into the tooth groove space from the suction space 50 formed in the casing 12 through 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 the tooth groove space 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. The discharge port 54 is formed by an opening provided on the end face of the casing 12.

The screw compressor 2 may be provided with a balance piston 30 provided on at least one of the pair of rotor shafts 14, 16. The balance piston 30 is accommodated in an accommodation space 45 formed inside the casing 12. In the exemplary embodiment shown in FIG. 2, the balance piston 30 is provided at the end of the discharge side of the rotor shaft 14 constituting the male rotor 15. Relatively high-pressure oil is supplied from the oil supply line 10 to the balance piston chamber 42 facing the end face of the suction side of the balance piston 30. As a result, 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 end face of the balance piston 30. This reduces the load on the thrust bearing 20.

Figure 3 is a schematic diagram showing a cross section perpendicular to the axial direction of the rotor shaft 14 and radial plain bearings 18 (18A, 18B) of a screw compressor 2 according to one embodiment. Figures 4 and 5 are diagrams showing the B-B cross sections of the radial plain bearings shown in Figure 3. Figure 4 shows a cross section of the radial plain bearing 18A on the suction side, and Figure 5 shows a cross section of the radial plain bearing 18B on the discharge side.

In the following, the radial plain bearings 18 (18A, 18B) that support the rotor shaft 14 that constitutes the male rotor 15 will be explained with reference to the figures, but the same explanation can also be applied to the radial plain bearings 18 (18A, 18B) that support the rotor shaft 16 that constitutes the female rotor 17.

As shown in Figures 3 to 5, the radial plain bearing 18 includes a sleeve 60 having a bearing surface 62 on its inner circumference. As shown in Figures 4 and 5, the sleeve 60 has an axial end face 60a on the suction side and an axial end face 60b on the discharge side.

As shown in Figures 4 and 5, the suction end 62a and discharge end 62b of the bearing surface 62 in the axial direction do not have to coincide with the suction end face 60a and discharge end face 60b of the sleeve 60. In other words, as shown in Figures 4 and 5, the bearing surface 62 may be formed only in a partial area of the extension range of the sleeve 60 in the axial direction.

The sleeve 60 may include a flange 61 for positioning the sleeve 60 in the axial direction. As shown in the figure, the flange 61 of the radial plain bearing 18A provided on the suction side in the axial direction may be provided at the end of the suction side of the radial plain bearing 18A. The flange 61 of the radial plain bearing 18B provided on the discharge side in the axial direction may be provided at the end of the discharge side of the radial plain bearing 18A.

As shown in FIG. 3, the bearing surface 62 of the sleeve 60 has a non-circular contour defined by a major axis AL and a minor axis AS in a cross section perpendicular to the axial direction of the rotor shaft 14. In the exemplary embodiment shown in FIG. 3, the contour of the bearing surface 62 in a cross section perpendicular to the axial direction has a generally elliptical shape having a major axis AL and a minor axis AS.

An oil reservoir 64 is formed between the portion of the bearing surface 62 including the ends EL1, EL2 of the long axis AL and the outer peripheral surface 19 of the rotor shaft 14. The oil reservoir 64 is a portion where the distance between the bearing surface 62 and the outer peripheral surface 19 of the rotor shaft 14 is relatively wide. The distance between the portion of the bearing surface 62 including the ends ES1, ES2 of the short axis AS and the outer peripheral surface 19 of the rotor shaft 14 is relatively narrow.

The screw compressor 2 is provided with an oil supply passage 66 that communicates with the oil reservoir 64. In the embodiment shown in FIG. 3, the oil supply passage 66 includes an oil supply hole 68 provided in the sleeve 60. The oil supply passage 66 may include a passage 56 (see FIG. 2) provided in the casing 12. The oil supply passage 66 may also include a groove 70 (see FIGS. 4 and 5) provided circumferentially on the outer circumferential surface of the sleeve 60. Oil from the oil separator 4 (see FIG. 1) is supplied to the oil reservoir 64 via the oil supply line 10 (see FIG. 1) and the oil supply passage 66 (passage 56, groove 70, and oil supply hole 68).

In the above embodiment, since the bearing surface 62 of the sleeve 60 has a non-circular contour defined by the long axis AL and the short axis AS in a cross section perpendicular to the axial direction, a relatively large oil reservoir 64 is formed between the portion of the bearing surface 62 including the ends EL1 and EL2 of the long axis AL and the outer circumferential surface 19 of the rotor shaft 14. Therefore, the fresh oil (relatively cold oil) supplied to the relatively large oil reservoir 64 through the oil supply passage 66 is easily drawn into the sliding surface as the rotor shaft 14 rotates, improving the cooling efficiency. In addition, since the bearing surface 62 of the sleeve 60 has the above-mentioned non-circular contour, the circumferential range R1 in which the gap between the bearing surface 62 and the outer circumferential surface 19 of the rotor shaft 14 is narrow (i.e., the range in which the gap between the portion including the ends ES1 and ES2 of the short axis AS and the outer circumferential surface 19 of the rotor shaft 14 is narrow; see FIG. 3) is relatively small. Therefore, the friction loss between the rotor shaft and the sleeve can be reduced. Therefore, according to the above embodiment, the rotor shaft 14 can be properly supported while reducing the amount of oil supplied to the radial plain bearing 18 or while enabling the radial plain bearing 18 to be made smaller.

As shown in Figures 3 to 5, in some embodiments, the bearing surface 62 of the sleeve 60 is provided with a recess 72 into which the oil supply passage 66 opens. The recess 72 may include a bottom surface 74 into which the oil supply passage 66 opens, and a side wall surface 76 that is provided to surround the bottom surface 74.

In the above embodiment, the bearing surface 62 of the sleeve 60 is provided with a recess 72 into which the oil supply passage 66 opens, so that the oil supplied from the oil supply passage 66 can be retained in the recess 72. As a result, oil can be smoothly supplied to the space between the bearing surface 62 and the outer peripheral surface 19 of the rotor shaft 14 via the recess 72.

As shown in Figures 3 to 5, the recess 72 provided in the bearing surface 62 may be surrounded by a dam. That is, when viewed from the radial direction, the recess 72 may be closed by a side wall surface 76 that surrounds the recess 72.

In conventional screw compressors with a relatively large rotor shaft diameter, in order to supply a large amount of oil to the bearing, it was necessary to provide an oil escape groove (a groove provided on the bearing surface that communicates with the recess) to drain the oil from the recess in the bearing surface where the oil may accumulate. In this regard, as already mentioned, in the above embodiment, since only a small amount of oil needs to be supplied to the bearing, it is possible to realize a configuration in which the recess 72 is surrounded by a dam and there is no oil escape groove, thereby reducing the amount of oil supplied to the bearing.

In some embodiments, the axial distance L1 (see Figures 4 and 5) between the axial suction end 72a of the recess 72 and the opening 69 of the oil supply passage 66 on the bearing surface 62 is shorter than the axial distance L2 (see Figures 4 and 5) between the axial discharge end 72b of the recess 72 and the opening 69 of the oil supply passage 66 on the bearing surface 62.

According to the above-described embodiment, the opening 69 of the oil supply passage 66 is located axially closer to the suction end 72a than to the discharge end 72b of the recess 72. In other words, the opening 69 of the oil supply passage 66 is provided at a relatively high-pressure side position in the recess 72, so that the oil supplied from the oil supply passage 66 to the recess 72 flows in a balanced manner toward the relatively high-pressure suction end 72a and the relatively low-pressure discharge end 72b, making it easier to properly lubricate and cool the radial plain bearing 18.

Figure 6 is a schematic diagram showing a cross section perpendicular to the axial direction of the rotor shafts 14 and 16 of a screw compressor 2 according to one embodiment, and the radial plain bearings 18 that support the rotor shafts 14 and 16, respectively. In Figure 6, reference numerals 15a and 17a indicate the orbits (positions of the outermost circumference) of the tooth tips of the male rotor 15 and the female rotor 17, respectively.

As shown in FIG. 6, when viewed from the axial direction, the discharge port 54 of the screw compressor 2 is located between the axial center O1 of the rotor shaft 14 and the axial center O2 of the rotor shaft 16 in the horizontal direction, and is positioned offset from the axial center O1 of the rotor shaft 14 and the axial center O2 of the rotor shaft 16 in the vertical direction. Also, when viewed from the axial direction, the discharge port 54 is formed in an area including the intersection P0 of the orbit 15a of the tooth tips of the male rotor 15 and the orbit 17a of the tooth tips of the female rotor 17.

The magnitude and direction of the radial loads FA, FB generated in the radial plain bearing 18 are determined by the pressure distribution around the rotor shafts 14, 16. Around the rotor shafts 14, 15, the pressure is highest at the position on the discharge port 54 side, and lowest at the opposite position (the position on the suction side). Due to this pressure difference, the radial loads FA, FB generated in the radial plain bearing 18 are directed diagonally upward as shown in Figure 6.

Therefore, in some embodiments, the radial plain bearing 18 is provided so that the minor axis AS of the profile of the bearing surface 62 is aligned along the direction of the radial loads FA and FB described above so that the radial plain bearing 18 can appropriately receive the above-mentioned radial load in the diagonally upward direction. That is, in some embodiments, the radial plain bearing 18 supporting the rotor shaft 14 constituting the male rotor 15 is provided so that the minor axis AS of the profile of the bearing surface 62 is aligned along the direction connecting the discharge port 54 and the axial center O1 of the rotor shaft 14 when viewed from the axial direction. Also, the radial plain bearing 18 supporting the rotor shaft 16 constituting the female rotor 17 is provided so that the minor axis AS of the profile of the bearing surface 62 is aligned along the direction connecting the discharge port 54 and the axial center O2 of the rotor shaft 16 when viewed from the axial direction.

For example, the radial plain bearing 18 may be arranged such that, when viewed from the axial direction, the minor axis AS of the contour of the bearing surface 62 of the radial plain bearing 18 is aligned along the intersection P0 of the orbit 15a of the tooth tips of the male rotor 15 and the orbit 17a of the tooth tips of the female rotor 17, and along the straight line L3, L4 passing through the axial center O1 of the rotor shaft 14 or the axial center O2 of the rotor shaft 16.

In one embodiment, the radial plain bearing 18 may be provided so that, when viewed from the axial direction, the angle θ1 or θ2 (see FIG. 6) between the straight line L3 or L4 passing through the intersection point P0 and the axial center O1 or O2 of the rotor shaft 14 or 16 and the straight line L1 or L2 extending in the direction of the minor axis AS of the contour of the bearing surface 62 is 30 degrees or less.

Alternatively, in one embodiment, the radial plain bearing 18 may be provided so that, when viewed from the axial direction, the minor axis AS of the profile of the bearing surface 62 is located within the region Z1 or Z2 between the above-mentioned straight line L3 or L4 and the straight line L5 or L6. Here, the straight lines L5 and L6 are straight lines passing through the point in the opening region of the discharge port 54 that is the furthest from the straight line L0 in the circumferential direction, and the axial centers O1 and O2 of the rotor shafts 14 and 16, respectively (see FIG. 6).

Furthermore, for example, the radial plain bearing 18 may be provided so that, when viewed from the axial direction, the angle B (see Figure 6) between a straight line L0 passing through the axial center O1 or O2 of a pair of rotor shafts 14 or 16 and a straight line L1 or L2 in the direction of the minor axis AS satisfies the following formula (a).
B=(A+C)/2...(a)
Here, A in the above formula (a) represents the angle between the above-mentioned straight line L0 and the above-mentioned straight line L5 or L6, and C in the above formula (a) represents the angle between the above-mentioned straight line L0 and the above-mentioned straight line L3 or L4 (see FIG. 6). Note that the above-mentioned angle A is determined by the design volume ratio of the screw compressor 2.

As described above, in the screw compressor 2, the magnitude and direction of the radial loads FA, FB generated on the radial plain bearing 18 are determined by the pressure distribution around the rotor shafts 14, 16, and the radial loads FA, FB generated on the radial plain bearing 18 are obliquely upward as shown in FIG. 6. In this regard, according to the above-mentioned embodiment, the radial plain bearing 18 is provided so that the minor axis AS of the profile of the bearing surface 62 is aligned along the direction connecting the discharge port 54 and the axial centers O1, O2 of the rotor shafts 14, 16. Therefore, the radial plain bearing 18 can appropriately bear the load of the rotor shafts 14, 16, and, as already described, the amount of oil supplied to the radial plain bearing 18 can be reduced or the radial plain bearing 18 can be made smaller.

The contents described in each of the above embodiments can be understood, for example, as follows:

[1] At least one embodiment of the screw compressor (2) of the present invention comprises:
A rotor shaft (14, 16);
a radial plain bearing (18) including a sleeve (60) having a bearing surface (62) on an inner periphery thereof, the radial plain bearing (18) rotatably supporting the rotor shaft,
The bearing surface of the sleeve has a non-circular profile defined by a major axis (AL) and a minor axis (AS) in a cross section perpendicular to the axial direction of the rotor shaft,
The bearing surface includes an oil supply passage (66) that communicates with an oil reservoir (64) that is formed between a portion of the bearing surface that includes the ends (EL1, EL2) of the long shaft and the outer circumferential surface (19) of the rotor shaft.

In the above configuration [1], the bearing surface of the sleeve has a non-circular contour defined by the major axis and the minor axis in a cross section perpendicular to the axial direction, so that a relatively large oil reservoir is formed between the portion of the bearing surface including the end of the major axis and the outer circumferential surface of the rotor shaft. Therefore, the fresh oil (relatively cold oil) supplied to the relatively large oil reservoir through the oil supply passage is easily drawn into the sliding surface as the rotor shaft rotates, improving the cooling efficiency. In addition, since the bearing surface of the sleeve has the above-mentioned non-circular contour, the circumferential range in which the gap between the bearing surface and the outer circumferential surface of the rotor shaft is narrow is relatively small. Therefore, the friction loss between the rotor shaft and the sleeve can be reduced. Therefore, according to the above configuration [1], the rotor shaft can be properly supported while reducing the amount of oil supplied to the bearing or while enabling the bearing to be made smaller.

[2] In some embodiments, in the configuration of [1] above,
The screw compressor comprises:
A discharge port (54) is provided for discharging a fluid compressed by a screw rotor (e.g., a male rotor 15 and a female rotor 17) including the rotor shaft,
The radial plain bearing is disposed such that, when viewed from the axial direction, the minor axis of the contour of the bearing surface extends along a direction connecting the discharge port and an axial center (O1, O2) of the rotor shaft.

In a screw compressor, the magnitude and direction of the radial load generated in the radial plain bearing is determined by the pressure distribution around the rotor shaft, and the radial load generated in the radial plain bearing is diagonally upward when viewed from the axial direction. In this regard, according to the configuration of [2] above, the radial plain bearing is provided so that the minor axis of the outline of the bearing surface is aligned with the direction connecting the discharge port and the axial center of the rotor shaft, so that the radial bearing can appropriately bear the load of the rotor shaft, and as described in [1] above, the amount of oil supplied to the bearing can be reduced or the bearing can be made smaller.

[3] In some embodiments, in the configuration of [1] or [2] above,
The screw compressor comprises:
The bearing surface has a recess (72) into which the oil supply passage opens.

According to the configuration of [3] above, a recess into which the oil supply passage opens is provided on the bearing surface of the sleeve, so that the oil supplied from the oil supply passage can be retained in the recess. This allows oil to be smoothly supplied to the space between the bearing surface and the outer peripheral surface of the rotor shaft via the recess.

[4] In some embodiments, in the configuration of [3] above,
The recess is surrounded by a dam (eg, including a sidewall surface 76).

In conventional screw compressors with a relatively large rotor shaft diameter, in order to supply a large amount of oil to the bearings, it was necessary to provide an oil escape groove to drain the oil from the recesses where the oil could accumulate. In this regard, in the configuration of [4] above, as described in [1] above, the amount of oil supplied to the bearings is small, so by using a configuration in which the recesses are surrounded by a dam and there is no oil escape groove, the amount of oil supplied to the bearings can be reduced.

[5] In some embodiments, in the configuration of [3] or [4] above,
The recess has a suction side end (72a) and a discharge side end (72b) which are both ends in the axial direction,
A distance (L1) in the axial direction between an opening (69) of the oil supply passage that opens into the recess and the suction side end is shorter than a distance (L2) in the axial direction between the opening and the discharge side end.

According to the configuration of [5] above, the opening of the oil supply passage is located axially closer to the suction end of the recess than to the discharge end. In other words, the opening of the oil supply passage is located at a relatively high-pressure side of the recess, so that the oil supplied from the oil supply passage to the recess flows in a balanced manner toward the relatively high-pressure suction end and the relatively low-pressure discharge end, making it easier to properly lubricate and cool the bearing.

[6] At least one embodiment of the gas compression equipment of the present invention comprises:
A screw compressor (2) according to any one of the above [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
The oil from the oil separator is configured to be supplied to the oil sump.

In the configuration of [6] above, the bearing surface of the sleeve has a non-circular contour defined by the major axis and the minor axis in a cross section perpendicular to the axial direction, so that a relatively large oil supply passage is formed between the portion of the bearing surface including the end of the major axis and the outer circumferential surface of the rotor shaft. Therefore, the fresh oil (relatively cold oil) supplied to the relatively large oil reservoir through the oil supply passage is easily drawn into the sliding surface as the rotor shaft rotates, improving the cooling efficiency. In addition, since the bearing surface of the sleeve has the non-circular contour described above, the circumferential range in which the gap between the bearing surface and the outer circumferential surface of the rotor shaft is narrow is relatively small. Therefore, the friction loss between the rotor shaft and the sleeve can be reduced. Therefore, according to the configuration of [6] above, the rotor shaft can be properly supported while reducing the amount of oil supplied to the bearing or while enabling the bearing to be made smaller.

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 variations on the above-described embodiments and appropriate combinations of these embodiments.

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.

1 Gas compression equipment 2 Screw compressor 4 Oil separator 6 Cooler 8 Pump 10 Oil supply line 12 Casing 14 Rotor shaft 15 Male rotor 15a Raceway 16 Rotor shaft 17 Female rotor 17a Raceway 18 Radial plain bearing 18A Radial plain bearing 18B Radial plain bearing 19 Outer circumferential surface 20 Thrust bearing 24 Shaft seal portion 28 Return line 30 Balance piston 42 Balance piston chamber 45 Storage space 50 Suction space 52 Suction port 54 Discharge port 56 Passage 60 Sleeve 60a End surface 60b End surface 61 Flange portion 62 Bearing surface 62a Suction side end 62b Discharge side end 64 Oil reservoir portion 66 Oil supply passage 68 Oil supply hole 69 Opening 70 Groove 72 Recess 72a Suction side end 72b Discharge side end 74 Bottom surface 76 Side wall surface AL Long axis AS Short axis EL1 End EL2 End ES1 End ES2 End O1 Shaft center O2 Shaft center P0 Intersection Pd Discharge pressure Poil Pressure Ps Suction pressure R1 Circumferential range

Claims (6)

A rotor shaft;
a radial plain bearing including a sleeve having a bearing surface on an inner circumference thereof and rotatably supporting the rotor shaft;
the bearing surface of the sleeve has a non-circular contour defined by a major axis and a minor axis in a cross section perpendicular to an axial direction of the rotor shaft,
a screw compressor including an oil supply passage communicating with an oil reservoir formed between a portion of the bearing surface including an end of the long shaft and an outer peripheral surface of the rotor shaft; a discharge port for discharging a fluid compressed by the screw rotor including the rotor shaft;
2. The screw compressor according to claim 1, wherein the radial plain bearing is arranged such that, when viewed from the axial direction, the minor axis of the contour of the bearing surface is aligned along a direction connecting the discharge port and an axial center of the rotor shaft. The screw compressor according to claim 1 or 2, further comprising a recess provided in the bearing surface, the recess having an opening into the oil supply passage. The screw compressor according to claim 3 , wherein the recess is surrounded by a dam. The recess has a suction end and a discharge end which are opposite ends in the axial direction,
The screw compressor according to claim 3 , wherein a distance in the axial direction between an opening of the oil supply passage that opens into the recess and the suction side end is shorter than a distance in the axial direction between the opening and the discharge side end. 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;
Equipped with
A gas compression plant configured such that the oil from the oil separator is supplied to the oil sump.

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