Screw compressors and gas compression equipment

Abstract

To provide a screw compressor and gas compression equipment that facilitate uniform lubrication and cooling of radial plain bearings. [Solution] The screw compressor comprises a screw rotor, a radial sliding bearing including a sleeve having a bearing surface on its inner circumference and rotatably supporting the screw rotor, an oil supply passage formed in the sleeve for supplying oil to the bearing surface, and a recess provided so as to be recessed from the bearing surface and through which the oil supply passage opens, wherein the recess has a first end and a second end which are both ends in the axial direction, the first end being the upstream end of the two ends in the axial direction from the suction port to the discharge port of the screw compressor, and the axial distance between the opening of the oil supply passage opening into the recess and the first end is shorter than the axial distance between the opening and the second end.

Description

[Technical Field]

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

[0002] Plain bearings are used as radial bearings in rotating machinery.

[0003] Patent Document 1 describes a journal bearing (radial sliding bearing) equipped with a bearing metal (bearing sleeve) through which a rotating shaft is inserted. The bearing surface, which is the inner circumferential surface of the bearing metal, is provided with lubrication grooves, and lubricating oil is supplied to the bearing surface through these grooves. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-159411 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, in radial sliding bearings installed in screw compressors, there is a pressure difference between both ends of the bearing sleeve (or both ends of the bearing surface) in the axial direction during the operation of the screw compressor. Oil supplied to the recesses (lubrication grooves) provided on the bearing surface of the bearing sleeve flows from the recesses towards each end of the bearing sleeve. If this flow rate difference is large, the bearing sleeve cannot be lubricated and cooled evenly, making it difficult for the bearing temperature to become uniform.

[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 facilitate uniform lubrication and cooling of radial sliding bearings. [Means for solving the problem]

[0007] A screw compressor according to at least one embodiment of the present invention is Screw rotor and, A radial sliding bearing that includes a sleeve having a bearing surface on its inner circumference and rotatably supports the screw rotor, The sleeve has an oil supply passage formed therein for supplying oil to the bearing surface, A recess is provided so as to be recessed from the bearing surface, and the oil supply passage opens into a recess, A screw compressor equipped with, The recess has a first end and a second end, which are both ends in the axial direction, and the first end is located on the upstream side of the two ends in the axial direction toward the discharge port of the screw compressor in the first direction. The axial distance between the opening of the oil supply passage that opens into the recess and the first end is shorter than the axial distance between the opening and the second end.

[0008] Furthermore, a gas compression system according to at least one embodiment of the present invention is The screw compressor described above, configured to compress gas, An oil separator for separating the oil from the mixture of compressed gas and oil discharged from the screw compressor, Equipped with, The oil from the oil separator is supplied to the recess. [Effects of the Invention]

[0009] According to at least one embodiment of the present invention, a screw compressor and gas compression equipment are provided that facilitate uniform lubrication and cooling of radial sliding bearings. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a gas compression system including a screw compressor according to one embodiment. [Figure 2] This is a schematic cross-sectional view in plan view of a screw compressor according to one embodiment. [Figure 3]It is a schematic diagram showing a cross-section perpendicular to the axial direction of the rotor shaft and radial plain bearing of a screw compressor according to an embodiment. [Figure 4] It is a diagram showing the B-B cross-section of the radial plain bearing shown in FIG. 3. [Figure 5] It is a diagram showing the B-B cross-section of the radial plain bearing shown in FIG. 3. [Figure 6] It is an enlarged partial diagram showing the B-B cross-section of a radial plain bearing according to an embodiment. [Figure 7] It is an enlarged partial diagram showing the B-B cross-section of a radial plain bearing according to an embodiment. [Figure 8] It is a schematic diagram showing a cross-section perpendicular to the axial direction of a radial plain bearing according to an embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0011] Several embodiments of the present invention will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements and the like of components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, and are merely illustrative examples.

[0012] (Configuration of Gas Compression Equipment) FIG. 1 is a schematic diagram of a gas compression facility including a screw compressor according to some embodiments. As shown in the drawing, 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 sucked gas and discharge the compressed gas. In the drawing, reference symbol Ps indicates the suction pressure of the screw compressor 2, and reference 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 and other purposes. The oil supplied to the screw compressor 2 is discharged together with the compressed gas.

[0014] The configuration of the screw compressor 2 will be described later, but in general terms, the screw compressor 2 comprises a pair of screw rotors (male rotor 15 and female rotor 17) each containing rotor shafts 14 and 16, and radial sliding bearings 18 for rotatably supporting the rotor shafts 14 and 16, respectively. The radial sliding bearings 18 include a radial sliding bearing 18A located axially on the intake port 52 side (see Figure 2), which will be described later, and a radial sliding bearing 18B located axially on the discharge port 54 side (see Figure 2), which will be described later. Oil is supplied to the radial sliding bearings 18 via an oil supply line 10 for lubrication and cooling.

[0015] 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 back to the screw compressor 2 (radial sliding bearing 18, etc.) via the oil supply line 10. Typically, the oil separated in the oil separator 4 is pressurized by the pump 8 before being supplied to the screw compressor 2 via the oil supply line 10. In this case, the pressure of the oil supplied to the screw compressor 2, Poil, is higher than the discharge pressure Pd (Poil = Pd + α). Alternatively, the oil separated in the oil separator 4 may be cooled by the cooler 6 before being pressurized by the pump 8.

[0016] (Screw compressor configuration) Figure 2 is a schematic cross-sectional view in plan view of a screw compressor according to one embodiment. As shown in Figure 2, the screw compressor 2 comprises a pair of screw rotors (male rotor 15 and female rotor 17) including a pair of rotor shafts 14, 16, and a casing 12 that houses the pair of screw rotors.

[0017] A pair of rotor shafts 14 and 16 are rotatably supported by radial sliding bearings 18A and 18B and a thrust bearing 20, respectively. Each bearing is supplied with pressure oil from a pressure pot via an oil supply line 10.

[0018] 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, along with the casing 12, forms multiple tooth groove spaces (chambers) along the axial direction of the rotor shafts 14 and 16.

[0019] 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 rotationally driven by the motor. The female rotor 17, which meshes with the male rotor 15, is rotationally 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 while meshed, the tooth groove space moves axially from the suction side to the discharge side.

[0020] The oil supplied to the bearing is discharged from the casing 12 and returned to the relatively low-pressure space (a space with a pressure slightly higher than the discharge pressure Ps, Ps+β (see Figure 1)) of the screw rotor housing in the casing 12 via the return line 28 (see Figures 1 and 2). Although Figure 2 shows the oil supply lines to each bearing section branching off from the oil supply line 10 and the return lines 28 from each section as external lines, they may also be lines provided inside the casing.

[0021] Gas is drawn into the aforementioned tooth groove space from the intake space 50 formed within the casing 12 via the intake port 52. As the male rotor 15 and female rotor 17 rotate, the tooth groove space moves axially from the end of the screw rotor on the intake port 52 side toward the end on the discharge port 54 side. In this process, the volume of the tooth groove space decreases after the intake port 52 is closed, so 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. The discharge port 54 is formed by an opening provided at the discharge end of the casing 12.

[0022] Herein, in this specification, the direction from the suction port 52 to the discharge port 54 in the axial direction is defined as the first direction.

[0023] Figure 3 is a schematic diagram showing a cross-section perpendicular to the axial direction of the rotor shaft 14 and radial sliding bearings 18 (18A, 18B) of a screw compressor 2 according to one embodiment. Figures 4 and 5 show cross-sections of the radial sliding bearings shown in Figure 3, respectively. Figure 4 shows a cross-section of the radial sliding bearing 18A on the intake port 52 side, and Figure 5 shows a cross-section of the radial sliding bearing 18B on the discharge port 54 side. Figures 6 and 7 are enlarged views showing a part of the cross-section of the radial sliding bearings according to one embodiment, respectively. Figure 6 is an enlarged view of the cross-section of the radial sliding bearing shown in Figure 3, and Figure 7 is an enlarged view of the cross-section of the radial sliding bearing according to another embodiment.

[0024] In the following explanation, the radial sliding bearings 18(18A, 18B) supporting the rotor shaft 14 that constitutes the male rotor 15 will be described with reference to the diagram, but the same explanation can be applied to the radial sliding bearings 18(18A, 18B) supporting the rotor shaft 16 that constitutes the female rotor 17.

[0025] As shown in Figures 3 to 5, the radial sliding 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 upstream end face 60a and a downstream end face 60b in the first direction. The bearing surface 62 also has a first upstream end 62a and a second downstream end 62b in the first direction.

[0026] As shown in Figures 4 and 5, the first end 62a and the second end 62b of the bearing surface 62 do not necessarily coincide with the upstream end face 60a and the downstream end face 60b of the sleeve 60. That is, as shown in Figures 4 and 5, the bearing surface 62 may be formed only in a portion of the axial extension range of the sleeve 60. Alternatively, the first end 62a and the second end 62b of the bearing surface 62 may coincide with the upstream end face 60a and the downstream end face 60b of the sleeve 60.

[0027] The sleeve 60 may include a flange 61 for axial positioning of the sleeve 60. As shown in the figure, the flange 61 of the radial sliding bearing 18A provided on the intake port 52 side in the axial direction may be provided at the upstream end of the radial sliding bearing 18A in the first direction. The flange 61 of the radial sliding bearing 18B provided on the discharge port 54 side in the axial direction may be provided at the downstream end of the radial sliding bearing 18A in the first direction.

[0028] As shown in Figure 3, the bearing surface 62 of the sleeve 60 may have a perfectly circular contour centered on the central axis O in a cross-section perpendicular to the axial direction of the rotor shaft 14. Alternatively, the bearing surface 62 of the sleeve 60 may have a non-circular contour such as a substantially elliptical shape.

[0029] A bearing gap 64 is formed between the bearing surface 62 and the outer circumferential surface 19 of the rotor shaft 14.

[0030] The screw compressor 2 is equipped with an oil supply passage 66 that communicates with the bearing gap 64. In the embodiment shown in Figure 3, the oil supply passage 66 includes an oil supply hole 68 provided in the sleeve 60. The oil supply passage 66 may also include a passage 56 (see Figure 2) provided in the casing 12. Alternatively, the oil supply passage 66 may include a groove 70 (see Figures 4 and 5) provided circumferentially on the outer surface of the sleeve 60. Oil from the oil separator 4 (see Figure 1) is supplied to the bearing gap 64 via the oil supply line 10 (see Figure 1) and the oil supply passage 66 (passage 56, groove 70, and oil supply hole 68).

[0031] As shown in Figures 3 to 7, in some embodiments, the bearing surface 62 of the sleeve 60 is provided with a recess 72 through which an oil supply passage 66 opens. The recess 72 is provided so as to be recessed from the bearing surface 62. The recess 72 may include a bottom surface 74 through which the oil supply passage 66 opens, and a pair of side wall surfaces 76 (see Figures 4 and 5) provided at the axial end of the recess 72. The bottom surface 74 may have a curved surface that curves along the circumferential direction, as shown in Figures 3 to 6, or it may have a flat surface.

[0032] In the exemplary embodiments shown in Figures 3 to 6, the recess 72 includes a bottom surface 74 and a pair of side wall surfaces 76, as well as a pair of side wall surfaces 75 (see Figures 3 and 6) provided at the circumferential end of the recess 72. When the recess 72 is viewed radially, the bottom surface 74 is surrounded by the pair of side wall surfaces 76 and the pair of side wall surfaces 75.

[0033] In the exemplary embodiment shown in Figure 7, the recess 72 includes a bottom surface 74 that curves along an arc with a greater curvature than the bearing surface 62 when viewed from the axial direction, and a pair of side wall surfaces 76 (see Figures 4 and 5) provided at the axial end of the recess 72. When viewed from the axial direction, the intersection 74a of the arc containing the bottom surface 74 and the bearing surface 62 forms the circumferential end of the recess 72.

[0034] As shown in Figures 3 to 7, 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 side wall surfaces 76 located at both ends of the recess 72 (see Figures 3 to 7), and by side wall surfaces 75 (see Figure 6) or circumferential ends (see Figure 7) located at both ends in the circumferential direction of the recess 72.

[0035] The recess 72 has two ends in the axial direction, a first end 72a and a second end 72b. The first end 72a is the upstream end in the first direction described above, and the second end 72b is the downstream end in the first direction described above. In the exemplary embodiments shown in Figures 3 to 7, a pair of side wall surfaces 76 provided at the axial ends of the recess 72 include the first end 72a and the second end 72b of the recess 72.

[0036] In some embodiments, as shown in Figure 3, for example, a pair of recesses are provided on both sides of the central axis O of the radial sliding bearing 18 when viewed from the axial direction.

[0037] In some embodiments, the axial distance L1 between the opening 69 of the oil supply passage 66 opening into the recess 72 and the first end 72a of the recess 72 is shorter than the axial distance L2 between the opening 69 and the second end 72b of the recess 72.

[0038] In the screw compressor 2, of the two ends of the bearing surface 62 of the sleeve 60 of the radial sliding bearing 18, the pressure at the first end 62a, which is located upstream in the first direction, is higher than that at the second end 62b, which is located downstream. This is because, in the case of the radial sliding bearing 18A on the intake port 52 side, the pressure at the first end 62a of the bearing surface 62 is Ps + β (pressure in the return line 28), and the pressure at the second end 62b of the bearing surface 62 is the intake pressure Ps (<(Ps + β)). Also, in the case of the radial sliding bearing 18B on the discharge port 54 side, the pressure at the first end 62a of the bearing surface 62 is the discharge pressure Pd, and the pressure at the second end 62b of the bearing surface 62 is Ps + β (pressure in the return line 28; Pd > (Ps + β)).

[0039] Therefore, of the two ends of the recess 72 provided on the bearing surface 62 of the sleeve 60, the first end 72a, which is located upstream in the first direction, will have a higher pressure than the second end 72b, which is located downstream.

[0040] According to the above embodiment, the opening 69 of the oil supply passage 66 for supplying oil to the recess 72 provided in the bearing surface 62 of the sleeve 60 is located relatively upstream in the first axial direction (closer to the first end 72a of the recess 72). That is, of the first end 72a and the second end 72b of the recess 72, the distance (L2) to the second end 72b is relatively long, as the pressure is lower and the pressure difference with the pressure at the opening 69 of the oil supply passage 66 (high pressure equal to or greater than the discharge pressure (Pd+α)) is large. Therefore, the amount of oil flowing from the opening 69 to the second end 72b of the recess 72 in the axial direction can be increased compared to the amount of oil flowing from the opening 69 to the first end 72a of the recess 72 in the axial direction. As a result, it becomes easier to supply oil uniformly in the axial direction to the bearing gap 64 in the region between the first end 72a and the second end 72b of the recess 72 in the axial direction. Thus, it becomes easier to uniformly lubricate and cool the radial sliding bearing 18.

[0041] In some embodiments, the ratio S / A of the area of ​​the recess 72 (see Figures 6 and 7) and the area of ​​the bearing gap 64 (see Figures 6 and 7) included in the angular range θ (see Figures 6 and 7) where the recess 72 exists around the central axis O of the radial sliding bearing 18 is 30 or more and 60 or less within a cross section perpendicular to the axial direction is 30 or more.

[0042] The area S of the recess 72 described above is the area enclosed by the recess 72 and the circle containing the bearing surface 62 in a cross section perpendicular to the axial direction. Furthermore, the area A of the bearing gap 64 described above is the area of ​​the portion of the bearing gap 64 included in the angular range θ described above in a cross section perpendicular to the axial direction when the central axis of the rotor shaft 14 coincides with the central axis O of the radial sliding bearing 18 (i.e., when the width of the bearing gap 64 is constant around the entire circumference).

[0043] In the above configuration, the ratio S / A is 30 or more, and the area S of the recess 72 is relatively large, so an appropriate amount of oil can be supplied to the bearing surface 62. Also, in the above configuration, the ratio S / A is 60 or less, and the area S of the recess 72 is relatively small, so a pressure gradient can be formed inside the recess 72 in the axial direction according to the length of the flow path (the length between the opening 69 of the oil supply passage 66 and the first end 72a and second end 72b of the recess 72). Therefore, as already mentioned, the pressure gradient between the opening 69 and the first end 72a of the recess 72 and the pressure gradient between the opening 69 and the second end 72b of the recess 72 can be made to be about the same, making it easier to supply oil uniformly to the bearing gap 64 in the axial direction. Thus, according to the above embodiment, it becomes easier to lubricate and cool the radial sliding bearing 18 uniformly while supplying an appropriate amount of oil.

[0044] Incidentally, when gas is dissolved in oil, the viscosity of the oil decreases. In a sliding bearing, if the viscosity of the oil decreases, the bearing oil film may not be formed sufficiently, which may cause problems such as wear and vibration. In this regard, the recess 72 provided on the bearing surface 62 degasssed gas dissolved in the oil and also prevents the degassed air bubbles from flowing out into the bearing gap 64, thereby maintaining the viscosity of the oil supplied to the bearing gap 64 and suppressing a decrease in the load capacity of the radial sliding bearing 18.

[0045] Here, the oil supplied to the recess 72 is depressurized at the opening 69 of the oil supply passage 66. On the other hand, the pressure (Ps+β and Ps, or Pd and Ps+β) at both ends of the bearing surface 62 (first end 62a and second end 62b) is constant. Also, since the recess 72 has a certain cross-sectional area S, the axial pressure gradient is relatively gentle, while the area outside the recess 72 (the area between the first end 72a / second end 72b of the recess 72 and the first end 62a / second end 62b of the bearing surface 62) is a bearing gap 64 with a small cross-sectional area A, resulting in a relatively steep axial pressure gradient. These pressure gradients, and the degree of depressurization at the opening 69 of the oil supply passage 66 in the recess 72, change according to the degree of restriction (S / A) by the bearing gap 64.

[0046] In the above-described embodiment, since the ratio S / A is 30 or more, the degree of restriction by the bearing gap 64 is not too small, so the degree of pressure reduction at the opening 69 of the oil supply passage 66 in the recess 72 does not become too large, and the amount of gas removed from the oil does not become too large. Therefore, it is possible to suppress the outflow of the removed gas into the bearing gap 64, the resulting decrease in the viscosity of the oil in the bearing gap 64, and the occurrence of a cavitation region in the bearing gap 64. Also, in the above-described embodiment, since the ratio S / A is 60 or less, the degree of restriction by the bearing gap 64 is not too large, so the degree of pressure reduction at the opening 69 of the oil supply passage 66 in the recess 72 does not become too small, and the gas in the oil is appropriately removed. Therefore, it is possible to suppress the decrease in the viscosity of the oil supplied to the bearing gap 64. Thus, according to the above-described embodiment, it is possible to maintain the viscosity of the oil in the bearing gap 64 within an appropriate range, suppress the decrease in the load capacity of the radial sliding bearing 18, and to make it easier to uniformly lubricate and cool the radial sliding bearing 18 as described above.

[0047] In some embodiments, when L0 is the distance between the first end 62a and the second end 62b of the bearing surface 62 in the axial direction, b1 is the distance between the first end 72a of the recess 72 and the first end 62a of the bearing surface 62 in the axial direction, and b2 is the distance between the second end 72b of the recess 72 and the second end 62b of the bearing surface 62 in the axial direction, the ratio b1 / L0 of distance b1 to distance L0, and the ratio b2 / L0 of distance b2 to distance L0 are 0.1 or more and 0.2 or less (see Figures 4 and 5).

[0048] In the above-described embodiment, the ratios b1 / L0 and b2 / L0 are 0.1 or greater, and the distances b1 and b2 between the ends of the recess 72 (first end 72a and second end 72b) and the ends of the bearing surface 62 (first end 62a and second end 62b) are sufficiently large relative to the length L0 of the bearing surface 62 in the axial direction, so that the degree of constriction by the bearing gap 64 is not too small. As a result, the degree of pressure reduction at the opening 69 of the oil supply passage 66 in the recess 72 does not become too large, and the amount of degassing from the oil does not become too large. As a result, it is possible to suppress the outflow of degassed gas into the bearing gap 64, the resulting decrease in the viscosity of the oil in the bearing gap 64, and the generation of cavitation regions in the bearing gap 64. Furthermore, in the above-described embodiment, the ratios b1 / L0 and b2 / L0 are 0.2 or less, and the length of the recess 72 in the axial direction (L0-(b1+b2)=L1+L2) is somewhat long compared to the distances b1 and b2 between the end of the recess 72 and the end of the bearing surface 62, so the degree of constriction by the bearing gap 64 is not too great. As a result, the degree of pressure reduction at the opening 69 of the oil supply passage 66 in the recess 72 is not too small, and gas in the oil is properly degassed. As a result, a decrease in the viscosity of the oil supplied to the bearing gap 64 can be suppressed. Therefore, according to the above embodiment, it becomes easier to uniformly lubricate and cool the radial sliding bearing 18 while appropriately supplying oil to it, while suppressing a decrease in the load capacity of the radial sliding bearing 18.

[0049] In some embodiments, the ratio a / D of the circumferential length a (see Figures 4 to 7) of the bearing surface 62 included in the angular range θ where the recess 72 exists around the central axis O of the radial sliding bearing 18, to the diameter D (see Figure 3) of the bearing surface 62, is 0.3 or more and 0.4 or less.

[0050] In the above-described embodiment, the ratio a / D is 0.3 or more, the circumferential length a of the recess 72 relative to the diameter D of the bearing surface 62 is relatively long, and the area occupied by the recess 72 in the circumferential direction is relatively wide, so the flow velocity of the oil in the recess 72 can be suppressed, thereby ensuring the residence time of the oil in the recess 72. Therefore, the oil can be properly degassed in the recess 72. Also, in the above-described embodiment, the ratio a / D is 0.4 or less, the circumferential length a of the recess 72 relative to the diameter D of the bearing surface 62 is relatively short, and the area occupied by the recess 72 in the circumferential direction is relatively narrow, so a wide range of loads can be appropriately borne. Therefore, according to the above embodiment, it becomes easier to lubricate and cool uniformly while suppressing a decrease in load capacity and enabling the bearing of a wide range of loads.

[0051] Figure 8 is a schematic diagram showing cross-sections perpendicular to the axial direction of the rotor shafts 14 and 16 and the radial sliding bearings 18 that support the rotor shafts 14 and 16, respectively, of a screw compressor 2 according to one embodiment. In Figure 8, reference numerals 15a and 17a indicate the tooth tip raceways (outermost positions) of the male rotor 15 and female rotor 17, respectively.

[0052] As shown in Figure 8, when viewed from the axial direction, the discharge port 54 of the screw compressor 2 is located horizontally between the central axis O1 of the rotor shaft 14 and the central axis O2 of the rotor shaft 16, and vertically offset from the central axis O1 of the rotor shaft 14 and the central axis O2 of the rotor shaft 16. Also, when viewed from the axial direction, the discharge port 54 is formed in the region including the intersection point P0 of the tooth tip raceway 15a of the male rotor 15 and the tooth tip raceway 17a of the female rotor 17.

[0053] Radial load F generated on radial sliding bearing 18 A ,F B The magnitude and direction of the radial load F generated on the radial sliding bearing 18 are determined by the pressure distribution around the rotor shafts 14 and 16. Around the rotor shafts 14 and 16, the pressure is highest at the discharge port 54 side and lowest at the opposite side (the suction side). This pressure difference generates the radial load F on the radial sliding bearing 18. A,F B As shown in Figure 8, it points diagonally upwards.

[0054] Therefore, in some embodiments, the radial sliding bearing 18 is configured to appropriately withstand the aforementioned diagonally upward radial load, such that when viewed from the axial direction, a straight line A2 perpendicular to a straight line A1 connecting a pair of recesses 72, which are provided on either side of the central axis O(O1,O2) of the radial sliding bearing 18, is such that the radial load F A F B They are provided so as to be aligned in the direction of the radial sliding bearing 18. That is, in some embodiments, when viewed from the axial direction, the straight line A1 connecting the pair of recesses 72 provided on either side of the central axis O(O1,O2) of the radial sliding bearing 18 is provided so as to be aligned in a direction perpendicular to the straight line A2 in the direction connecting the discharge port 54 and the central axis O(O1,O2) of the radial sliding bearing 18.

[0055] For example, the radial sliding bearing 18 may be provided such that, when viewed from the axial direction, the straight line A2 connecting the discharge port 54 and the central axis O(O1,O2) of the radial sliding bearing 18 aligns with the direction of the straight lines Lc and Ld passing through the intersection point P0 of the tooth tip raceway 15a of the male rotor 15 and the tooth tip raceway 17a of the female rotor 17, and the central axis O1 of the rotor shaft 14 or the central axis O2 of the rotor shaft 16.

[0056] In one embodiment, a radial sliding bearing 18 may be provided such that, when viewed from the axial direction, the angle θ1 or θ2 (see Figure 6) between the straight line Lc or Ld passing through the intersection P0 and the central axis O1 or O2 of the rotor shaft 14 or 16 and the straight line La or Lb extending in the direction of the straight line A2 is 30 degrees or less.

[0057] Alternatively, in one embodiment, the radial plain bearing 18 may be provided such that, when viewed from the axial direction, the aforementioned straight line A2 is located within the region Z1 or Z2 between the aforementioned straight line Lc or Ld and the straight line Le or Lf. Here, the straight lines Le and Lf are straight lines respectively passing through the point farthest from the straight line Lx in the circumferential direction in the opening area of the discharge port 54 and the central axes O1, O2 of the rotor shafts 14, 16 (see FIG. 8).

[0058] Further, for example, the radial plain bearing 18 may be provided such that, when viewed from the axial direction, an angle B2 (see FIG. 8) between a straight line Lx passing through the central axis O1 or O2 of the pair of rotor shafts 14 or 16 and a straight line La or Lb in the direction of the aforementioned straight line A2 satisfies the following formula (a). B2=(B1+B3) / 2 …(a) Here, B1 in the above formula (a) represents an angle between the aforementioned straight line Lx and the aforementioned straight line Le or Lf, and B3 in the above formula (a) represents an angle between the aforementioned straight line Lx and the aforementioned straight line Lc or Ld (see FIG. 8). The aforementioned angle B1 is determined by the designed volume ratio of the screw compressor 2.

[0059] As described above, in the screw compressor 2, the radial load F generated in the radial plain bearing 18 A ,F B the magnitude and direction of are determined by the pressure distribution around the rotor shafts 14, 16, and the radial load F generated in the radial plain bearing 18 A ,F B is directed obliquely upward as shown in FIG. 8. In this regard, according to the above embodiment, the radial plain bearing 18 is provided such that the straight line A1 connecting the pair of recesses 72 to each other extends along a direction orthogonal to the direction connecting the discharge port 54 and the central axis O of the radial plain bearing 18. Therefore, the load of the rotor shafts 14, 16 can be appropriately borne by the radial plain bearing 18, and as already described, the radial plain bearing 18 can be easily uniformly lubricated and cooled.

[0060] The content described in each of the above embodiments can be understood, for example, as follows.

[0061] [1] A screw compressor (2) according to at least one embodiment of the present invention is Screw rotor (15,17) and A radial sliding bearing (18) that rotatably supports the screw rotor, including a sleeve (60) having a bearing surface (62) on its inner circumference, The sleeve is formed with an oil supply passage (66) for supplying oil to the bearing surface, A recess (72) is provided so as to be recessed from the bearing surface, and the oil supply passage opens into it, A screw compressor equipped with, The recess has a first end (72a) and a second end (72b) which are both ends in the axial direction, and the first end is located on the upstream side of the two ends in the axial direction toward the first direction toward the discharge port (54) of the screw compressor. The axial distance (L1) between the opening (69) of the oil supply passage that opens into the recess and the first end is shorter than the axial distance (L2) between the opening and the second end.

[0062] In a screw compressor, of the two ends of the bearing surface of the sleeve of a radial plain bearing in the axial direction, the first end, located upstream in the first direction, is under higher pressure than the second end, located downstream. According to the configuration described in [1] above, the opening of the oil supply passage for supplying oil to the recess provided on the bearing surface of the sleeve is located relatively upstream in the first direction in the axial direction (closer to the first end 72a of the recess). That is, of the first and second ends of the recess, the distance to the second end, which is under lower pressure and has a larger pressure difference with the pressure at the opening of the oil supply passage (high pressure equal to or greater than the discharge pressure (Pd+α)), is relatively long. For this reason, the amount of oil flowing from the opening to the second end of the recess in the axial direction can be increased compared to the amount of oil flowing from the opening to the first end of the recess in the axial direction. As a result, it becomes easier to supply oil uniformly in the axial direction to the bearing gap in the region between the first and second ends of the recess in the axial direction. Thus, it becomes easier to lubricate and cool the radial plain bearing uniformly.

[0063] [2] In some embodiments, in the configuration of [1] above, Within the cross-section perpendicular to the axial direction, the ratio S / A of the area S of the recess to the area A of the bearing clearance (64) included in the angular range (θ) where the recess exists around the central axis (O) of the radial sliding bearing is 30 or more and 60 or less.

[0064] In the configuration described in [2] above, the ratio S / A is 30 or more, and the area S of the recess is relatively large, so an appropriate amount of oil can be supplied to the bearing surface. Also, in the configuration described in [2] above, the ratio S / A is 60 or less, and the area S of the recess is relatively small, so a pressure gradient can be formed inside the recess in the axial direction according to the length of the flow path (the length between the oil supply port and the first and second ends of the recess). Therefore, as described in [1] above, the pressure gradient between the opening of the oil supply passage and the first end of the recess can be made to be about the same as the pressure gradient between the opening of the oil supply passage and the second end of the recess, making it easier to supply oil uniformly to the bearing gap in the axial direction. Thus, according to the configuration described in [2] above, it is easier to lubricate and cool the radial sliding bearing uniformly while supplying an appropriate amount of oil.

[0065] Incidentally, when gas is dissolved in oil, the viscosity of the oil decreases. In sliding bearings, if the viscosity of the oil decreases, the bearing oil film may not form sufficiently, which may lead to problems such as wear and vibration. In this regard, the recess provided on the bearing surface plays a role in maintaining the viscosity of the oil supplied to the bearing gap by degassing the gas dissolved in the oil and preventing the degassed air bubbles from flowing out into the bearing gap, thereby suppressing a decrease in the load capacity of the radial sliding bearing.

[0066] In the configuration described in [2] above, since the ratio S / A is 30 or more, the degree of restriction due to the bearing gap is not too small, so the degree of pressure reduction at the opening of the oil supply passage in the recess does not become too large, and the amount of gas removed from the oil does not become too large. Therefore, it is possible to suppress the outflow of the removed gas into the bearing gap, the resulting decrease in the viscosity of the oil in the bearing gap, and the occurrence of cavitation regions in the bearing gap. Also, in the configuration described in [2] above, since the ratio S / A is 60 or less, the degree of restriction due to the bearing gap is not too large, so the degree of pressure reduction at the opening of the oil supply passage in the recess does not become too small, and the gas in the oil is properly removed. Therefore, it is possible to suppress the decrease in the viscosity of the oil supplied to the bearing gap. Thus, according to the configuration described in [2] above, it is possible to maintain the viscosity of the oil in the bearing gap within an appropriate range, suppress the decrease in the load capacity of the radial plain bearing, and to lubricate and cool the radial plain bearing uniformly as described above.

[0067] [3] In some embodiments, in the configuration of [1] or [2] above, The bearing surface (62) of the sleeve has a first end (62a) and a second end (62b) which are both ends in the axial direction, and the first end of the bearing surface is the one located on the upstream side in the first direction of the two ends of the bearing surface. When L0 is the distance between the first end of the bearing surface and the second end of the bearing surface in the axial direction, b1 is the distance between the first end of the recess and the first end of the bearing surface in the axial direction, and b2 is the distance between the second end of the recess and the second end of the bearing surface in the axial direction, the ratio b1 / L0 of distance b1 to distance L0 and the ratio b2 / L0 of distance b2 to distance L0 are 0.1 or more and 0.2 or less.

[0068] In the configuration described in [3] above, the ratios b1 / L0 and b2 / L0 are 0.1 or greater, and the distances b1 and b2 between the end of the recess and the end of the bearing surface are relatively large relative to the length L of the bearing surface in the axial direction, so the degree of restriction by the bearing gap 64 is not too small. As a result, the degree of pressure reduction at the opening 69 of the oil supply passage 66 in the recess 72 does not become too large, and the amount of degassing from the oil does not become too large. As a result, the outflow of degassed gas into the bearing gap 64, the resulting decrease in the viscosity of the oil in the bearing gap 64, and the generation of a cavitation region in the bearing gap 64 can be suppressed. Furthermore, in the configuration described in [3] above, the ratios b1 / L0 and b2 / L0 are 0.2 or less, and the length of the recess in the axial direction (L0-(b1+b2)) is relatively long relative to the distances b1 and b2 between the end of the recess and the end of the bearing surface, so the degree of restriction by the bearing gap 64 is not too large. Therefore, the degree of pressure reduction at the opening 69 of the oil supply passage 66 in the recess 72 does not become too small, and gas in the oil is properly degassed. As a result, a decrease in the viscosity of the oil supplied to the bearing gap 64 can be suppressed. Therefore, the configuration described in [3] above makes it easier to uniformly lubricate and cool the radial sliding bearing while appropriately supplying oil to it, while suppressing a decrease in load capacity.

[0069] [4] In some embodiments, in any of the configurations described in [1] to [3] above, The ratio a / D of the length a of the bearing surface in the circumferential direction to the diameter D of the bearing surface, which is included in the angular range (θ) where the recess exists around the central axis of the radial sliding bearing, is 0.3 or more and 0.4 or less.

[0070] In the configuration described in [4] above, the ratio a / D is 0.3 or greater, the circumferential length a of the recess relative to the diameter D of the bearing surface is relatively long, and the area occupied by the recess in the circumferential direction is relatively wide, so the flow velocity of the oil in the recess can be suppressed, thereby ensuring the residence time of the oil in the recess. Therefore, proper degassing of the oil can be performed in the recess. Also, in the configuration described in [4] above, the ratio a / D is 0.4 or less, the circumferential length a of the recess relative to the diameter D of the bearing surface is relatively short, and the area occupied by the recess in the circumferential direction is relatively narrow, so a wide range of loads can be appropriately borne. Therefore, the configuration described in [4] above makes it possible to uniformly lubricate and cool the system while suppressing a decrease in load capacity and enabling it to handle a wide range of loads.

[0071] [5] In some embodiments, in any of the configurations described in [1] to [4] above, The recess is surrounded by a dam (including, for example, side wall surfaces 75 and / or 76).

[0072] According to the configuration described in [5] above, a recess surrounded by a dam is provided on the bearing surface, so as described in [1] above, it is possible to suppress the expansion of the difference in oil flow rate from the recess toward both ends of the bearing surface of the sleeve in the axial direction, making it easier to uniformly lubricate and cool the radial sliding bearing.

[0073] [6] In some embodiments, in any of the configurations described in [1] to [5] above, The screw compressor is, A pair of recesses are provided on both sides of the central axis of the radial sliding bearing when viewed from the axial direction, The system includes the discharge port for discharging the fluid compressed by the screw rotor, The radial sliding bearing is provided such that, when viewed from the axial direction, the straight line (A1) connecting the pair of recesses is aligned in a direction perpendicular to the direction connecting the discharge port and the central axis of the radial sliding bearing.

[0074] In a screw compressor, the magnitude and direction of the radial load generated on the radial sliding bearing are determined by the pressure distribution around the rotor shaft, and the radial load generated on the radial sliding bearing is obliquely upward when viewed from the axial direction. In this respect, according to the configuration of [6] above, when viewed from the axial direction, the radial sliding bearing is provided such that the straight line connecting the pair of recesses is aligned in a direction perpendicular to the direction connecting the discharge port and the central axis of the radial sliding bearing. This allows the radial bearing to appropriately bear the load of the rotor shaft, and as described in [1] above, it becomes easier to uniformly lubricate and cool the radial sliding bearing.

[0075] [7] A gas compression apparatus (1) according to at least one embodiment of the present invention is A screw compressor (2) as described in any one of the above [1] to [6], configured to compress gas, An oil separator (4) for separating the oil from the mixture of compressed gas and oil discharged from the screw compressor, Equipped with, The oil from the oil separator is supplied to the recess.

[0076] In a screw compressor, of the two ends of the bearing surface of the sleeve of a radial plain bearing, the first end, located upstream in the first direction, is under higher pressure than the second end, located downstream. According to the configuration described in [7] above, the opening of the oil supply passage for supplying oil to the recess provided on the bearing surface of the sleeve is located relatively upstream in the first direction in the axial direction (closer to the first end of the recess), so that the pressure gradient between the first end of the recess and the first end of the bearing surface can be made to be approximately the same as the pressure gradient between the second end of the recess and the second end surface of the bearing surface. Therefore, the expansion of the difference in oil flow rate from the recess to both ends of the bearing surface of the sleeve in the axial direction can be suppressed. Thus, the radial plain bearing can be lubricated and cooled more uniformly.

[0077] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0078] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. Furthermore, in this specification, expressions describing shapes such as quadrilaterals and cylindrical shapes shall not only represent geometrically precise quadrilaterals and cylindrical shapes, but also shapes that include uneven surfaces, chamfered surfaces, etc., to the extent that the same effect can be achieved. Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components. [Explanation of Symbols]

[0079] 1. Gas compression equipment 2 Screw compressor 4 Oil separator 6 Cooler 8 pumps 10 Oil supply line 12 Casing 14 Rotor shaft 15 Male rotor 15a orbit 16 rotor shaft 17 Female rotor 17a orbit 18 Radial plain bearings 18A Radial Plain Bearing 18B Radial Plain Bearing 19 Outer surface 20 Thrust bearings 24 Axle seal section 28 Return Line 30 Balance Pistons 42 Balance piston chamber 45 Containment space 50 Suction space 52 Inhalation Ports 54 Discharge Ports 56 aisle 60 sleeves 60a End face 60b end face 61 Guard section 62 Bearing surface 62a 1st end 62b 2nd end 64 Bearing clearance 66 Refueling Route 68 Fuel filler port 69 Aperture 70 groove 72 recesses 72a 1st end 72b 2nd end 74 Bottom 74a Circumferential end 75 Side wall 76 Side wall A area O center axis O1 center axis O2 center axis P0 intersection Pd discharge pressure Poil pressure Ps Inhalation pressure S area θ Angle range

Claims

1. Screw rotor and, A radial sliding bearing that includes a sleeve having a bearing surface on its inner circumference and rotatably supports the screw rotor, The sleeve has an oil supply passage formed therein for supplying oil to the bearing surface, A recess is provided so as to be recessed from the bearing surface, and the oil supply passage opens into a recess, A screw compressor equipped with, The recess has a first end and a second end, which are both ends in the axial direction, and the first end is located on the upstream side of the two ends in the axial direction, in the first direction from the suction port to the discharge port of the screw compressor. The axial distance between the opening of the oil supply passage that opens into the recess and the first end is shorter than the axial distance between the opening and the second end. Screw compressor.

2. Within the cross-section perpendicular to the axial direction, the ratio S / A of the area S of the recess to the area A of the bearing clearance included in the angular range where the recess exists around the central axis of the radial sliding bearing is 30 or more and 60 or less. The screw compressor according to claim 1.

3. The bearing surface of the sleeve has a first end and a second end, which are both ends in the axial direction, and the first end is the one of the two ends of the bearing surface that is located on the upstream side in the first direction. When L0 is the distance between the first end of the bearing surface and the second end of the bearing surface in the axial direction, b1 is the distance between the first end of the recess and the first end of the bearing surface in the axial direction, and b2 is the distance between the second end of the recess and the second end of the bearing surface in the axial direction, the ratio b1 / L0 of distance b1 to distance L0 and the ratio b2 / L0 of distance b2 to distance L0 are 0.1 or more and 0.2 or less. The screw compressor according to claim 1 or 2.

4. The ratio a / D of the length a in the circumferential direction of the bearing surface, which is included in the angular range where the recess exists around the central axis of the radial sliding bearing, to the diameter D of the bearing surface, is 0.3 or more and 0.4 or less. The screw compressor according to claim 1 or 2.

5. The aforementioned recess is surrounded by a dam. The screw compressor according to claim 1 or 2.

6. A pair of recesses are provided on both sides of the central axis of the radial sliding bearing when viewed from the axial direction, The system includes the discharge port for discharging the fluid compressed by the screw rotor, The radial sliding bearing is provided such that, when viewed from the axial direction, the straight line connecting the pair of recesses is aligned in a direction perpendicular to the direction connecting the discharge port and the central axis of the radial sliding bearing. The screw compressor according to claim 1 or 2.

7. A screw compressor according to claim 1 or 2, configured to compress gas, An oil separator for separating the oil from the 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 recess. Gas compression equipment.

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