Displacement compressor

Abstract

Provided is a displacement compressor (100) that supplies a liquid into a compression chamber (6) and compresses a gas, the displacement compressor (100) comprising: a cylindrical swirl chamber (7c); a liquid introduction path (71b) that is connected to the swirl chamber (7c) such that the center axis of the liquid introduction path (71b) is offset with respect to the center axis of the swirl chamber (7c), and that generates a swirl flow in the swirl chamber (7c) by supplying the liquid to the swirl chamber (7c); a shaft-like member (7d) provided in the swirl chamber (7c) and extending in the axial direction of the swirl chamber (7c); and an injection hole (7e) which is provided in an end portion of the swirl chamber (7c) on the compression chamber (6) side in the axial direction, and through which the liquid that has become a swirl flow around the shaft-like member (7d) is injected into the compression chamber (6). The outermost diameter of the shaft-like member (7d) is smaller than the minimum diameter of the injection hole (7e).

Description

Positive displacement compressor

[0001] The present invention relates to a positive displacement compressor.

[0002] Some positive displacement compressors are of the liquid supply type, in which liquid is supplied into the compression chamber for sealing internal gaps within the compressor, cooling the working gas during the compression stroke, and lubricating sliding parts.

[0003] Some liquid-feed type positive displacement compressors include a liquid feed mechanism that includes a swirl nozzle that atomizes the liquid supplied into the compression chamber by causing a swirling motion. The swirl nozzle introduces liquid into, for example, a cylindrical port through an inlet having a central axis eccentric to the central axis of the port, generating a swirling flow of the liquid within the port, thereby injecting the atomized liquid into the compression chamber. For example, Figures 12 and 13 of Patent Document 1 disclose a compressor that includes a substantially cylindrical lubricant port, an offset inlet for lubricant extending along an axis offset from the central axis of the lubricant port and connected to a side of the lubricant port, and a discharge orifice that discharges the lubricant introduced into the lubricant port through the inlet and given a swirling motion into the compression chamber.

[0004] US Patent Application Publication No. 2019 / 0093659

[0005] The purpose of atomizing the liquid supplied to the compression chamber is to seal a wider range of internal gaps, to promote the cooling effect of the working gas by increasing the surface area of ​​the liquid, and to prevent oil film breakdown in sliding parts by spreading the lubricant (liquid) over a wider area.

[0006] In the swirl nozzle of Patent Document 1, centrifugal force acting on the swirling liquid in the lubricant port lowers the liquid level at the center of the swirling motion, causing the working gas downstream of the discharge orifice to flow toward the center of the lubricant port, creating a generally conical space. This space becomes a volume (dead volume) that does not contribute to compression in a positive displacement compressor, and the generally conical working gas generated at the center of the swirling liquid in the lubricant port repeatedly expands and compresses as the compressor operates, increasing shaft power and potentially reducing compressor efficiency.

[0007] 3-8 of Patent Document 1 discloses a liquid supply mechanism in which a nozzle insert having a blade and a support for holding the blade is inserted into a lubricant port, but the central axis of the lubricant passage, which is the lubricant inlet in this liquid supply mechanism, is not offset from the central axis of the lubricant port, and therefore does not qualify as a swirl nozzle. Furthermore, although the blade of the nozzle insert imparts a swirling motion to the lubricant, inserting the blade into a flow path for a highly viscous liquid such as a lubricant increases the pressure loss of the liquid, raising concerns that the amount of liquid supplied to the compression chamber may be reduced.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a positive displacement compressor that supplies liquid into a compression chamber by swirling, and that can reduce the dead volume of the compression chamber.

[0009] In order to achieve the above object, the positive displacement compressor of the present invention is a positive displacement compressor that supplies liquid into a compression chamber and compresses gas, and includes: a cylindrical swirl chamber; a liquid inlet passage that is connected to the swirl chamber so that its central axis is offset from the central axis of the swirl chamber, and that generates a swirling flow in the swirl chamber by supplying liquid to the swirl chamber; a shaft-shaped member that is provided in the swirl chamber and extends in the axial direction of the swirl chamber; and an injection hole that is provided at the end of the swirl chamber on the compression chamber side in the axial direction, and that injects the liquid that has become a swirling flow around the shaft-shaped member into the compression chamber, and the outermost diameter of the shaft-shaped member is smaller than the minimum diameter of the injection hole.

[0010] According to the present invention, in a positive displacement compressor that supplies liquid into a compression chamber by swirling it, the dead volume of the compression chamber can be reduced, thereby suppressing a decrease in compression efficiency.

[0011] FIG. 1 is a longitudinal cross-sectional view of a displacement type compressor according to a first embodiment of the present invention (a cross-sectional view taken along the XY plane along the rotation axis of the male rotor). FIG. 2 is a schematic cross-sectional view taken along II-II in FIG. 1. FIG. 3 is a schematic cross-sectional view taken along III-III in FIG. 1. FIG. 4 is an enlarged schematic view of region IV in FIG. 2. FIG. 5 is a schematic perspective view showing the shape of liquid injected into a compression chamber from a liquid supply mechanism according to a comparative example. FIG. 6 is a schematic cross-sectional view taken along VI-VI in FIG. 5. FIG. 7 is a longitudinal cross-sectional view of a displacement type compressor according to a second embodiment of the present invention (a cross-sectional view taken along the XY plane along the rotation axis of the male rotor). FIG. 8 is a schematic cross-sectional view taken along VIII-VIII in FIG. 7. FIG. 9 is a schematic longitudinal cross-sectional view of a male side swirl chamber according to a third embodiment of the present invention (a cross-sectional view taken along the YZ plane along the central axis of the male side swirl chamber). FIG. 11 is another example of an enlarged schematic view of region IV in FIG. 2.

[0012] The configuration and operation of displacement compressors according to first to third embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals in each drawing indicate the same parts. The directions of the plan views and cross-sectional views are specified by mutually orthogonal X, Y, and Z axes, with +X being "right," -X being "left," +Y being "up," -Y being "down," +Z being "front," and -Z being "rear."

[0013] In addition, the terms "axial direction," "circumferential direction," and "radial direction" used in this paper are defined as follows: "axial direction" refers to the direction along the rotational axis of the male and female rotors. "circumferential direction" refers to the direction along the rotational direction (or the opposite rotational direction) of the male and female rotors, i.e., the circumferential direction centered on the rotational axis. "radial direction" refers to the direction perpendicular to the rotational axis of the male and female rotors, i.e., the radial direction of a circle centered on the rotational axis of each of the male and female rotors. Furthermore, "inner peripheral side" refers to the inside in the radial direction (inner diameter side), and "outer peripheral side" refers to the opposite direction, i.e., the outside in the radial direction (outer diameter side).

[0014] (First embodiment) Fig. 1 is a longitudinal cross-sectional view (a cross-sectional view taken along the XY plane along the rotation axis of the male rotor) of a displacement compressor according to a first embodiment. Fig. 2 is a schematic cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a schematic cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is an enlarged schematic view of region IV in Fig. 2.

[0015] The positive displacement compressor 100 according to this embodiment is a liquid feed screw compressor. As shown in Fig. 1, the positive displacement compressor 100 includes a screw rotor 1, a casing 2 that houses the screw rotor 1, a motor 3 that drives the screw rotor 1, an intake passage 4 that is a passage for sucking in gas, and a discharge passage 5 that is a passage for discharging compressed gas.

[0016] The screw rotor 1 is a component for compressing gas, and includes a male rotor 11 and a female rotor 12 (see FIG. 2) that meshes with the male rotor 11.

[0017] The male rotor 11 has a male rotor tooth portion 11b with a plurality of twisted male teeth (lobes) 11a (four in this embodiment as shown in Figure 2). A suction-side shaft portion 11c protrudes along the rotation axis AX1 of the male rotor 11 from the male rotor tooth portion 11b on the suction flow path 4 side (-X side in Figure 1), and a discharge-side shaft portion 11d protrudes along the rotation axis AX1 from the male rotor tooth portion 11b on the discharge flow path 5 side (+X side in Figure 1).

[0018] The female rotor 12 has a female rotor tooth portion 12b having a plurality of twisted female teeth (lobes) 12a (six in this embodiment as shown in FIG. 2) that mesh with a plurality of male teeth (lobes) 11a. In addition, a suction-side shaft portion 12c (not shown) protrudes along the rotation axis AX2 of the female rotor 12 from the female rotor tooth portion 12b on the suction flow path 4 side (the -X side in FIG. 1) of the female rotor tooth portion 12b, and a discharge-side shaft portion 12d (not shown) protrudes along the rotation axis AX2 (not shown) from the female rotor tooth portion 12b on the discharge flow path 5 side (the +X side in FIG. 1) of the female rotor tooth portion 12b.

[0019] The casing 2 comprises a main casing 21 that houses the screw rotor 1, a suction side casing 22 that covers the side surface 21a of the main casing 21 on the suction flow path 4 side, a discharge side casing 23 that covers the side surface 21b of the main casing 21 on the discharge flow path 5 side, and a cover 24 that covers the bearing hole 23a provided in the discharge side casing 23.

[0020] The main casing 21 includes an intake passage 4, a discharge port 21h that discharges compressed gas into the discharge passage 5, a compression chamber 6 that accommodates the male rotor tooth portion 11b and the female rotor tooth portion 12b of the screw rotor 1 and compresses the gas, and a fluid supply mechanism 7 for supplying a fluid (lubricating oil) to the compression chamber 6 (in this embodiment, a male side fluid supply mechanism 71 that supplies a fluid into the compression chamber 6 on the male rotor tooth portion 11b side).

[0021] The main casing 21 also has two bearing holes 21c (only one of which is shown in Figure 1) that accommodate bearings 8 (e.g., radial roller bearings 8a) that support each of the suction side shaft portions 11c and 12c, and two through holes 21e that penetrate the bottom surfaces 21d of the two bearing holes 21c to allow each of the suction side shaft portions 11c and 12c to protrude toward the motor 3.

[0022] The suction side casing 22 is provided with a shaft seal hole 22a that accommodates a shaft seal device (e.g., a mechanical seal) 9 that seals the suction side shaft portion 11c, and a through hole 22c that penetrates the bottom surface 22b of the shaft seal hole 22a to allow the suction side shaft portion 11c to protrude toward the motor 3.

[0023] The discharge side casing 23 is provided with a discharge flow path 5, two bearing holes 23a (only one of which is shown in Figure 1) that accommodate bearings 8 (e.g., a radial roller bearing 8a and a radial ball bearing 8b) that support each of the discharge side shaft portions 11d, 12d, and two through holes 23c that penetrate the bottom surfaces 23b of the two bearing holes 23a to allow each of the discharge side shaft portions 11d, 12d to protrude toward the cover 24.

[0024] The motor 3 includes a rotor 31 that is connected to the suction side shaft portion 11c and rotates the male rotor 11, a stator 32 that covers the rotor 31 via an air gap and generates magnetism that rotates the rotor 31, and a motor casing 33 that houses the stator 32.

[0025] When the rotor 31 of the motor 3 rotates, the male rotor teeth portion 11b rotates counterclockwise, as shown by the arrow in Figure 2, because the male teeth 11a and female teeth 12a are meshed, the female rotor teeth portion 12b rotates clockwise. Here, the gap between the tips of the multiple male teeth 11a and the male side cylindrical surface 21f that faces the tips of the multiple male teeth 11a in the main casing 21 is several μm to several mm. Similarly, the gap between the tips of the multiple female teeth 12a and the female side cylindrical surface 21g that faces the tips of the multiple male teeth 11a in the main casing 21 is several μm to several mm.

[0026] Since fluid (lubricating oil) is supplied to compression chamber 6 from fluid supply mechanism 7 (at least one of male side fluid supply mechanism 71 and female side fluid supply mechanism 72), these gaps are sealed with the lubricating oil. Therefore, gas flows from suction flow path 4 into male side space 6a, which is sandwiched between two circumferentially adjacent male teeth 11a of the multiple male teeth 11a and male side cylindrical surface 21f, and female side space 6b, which is sandwiched between two circumferentially adjacent female teeth 12a of the multiple female teeth 12a and female side cylindrical surface 21g. The gas that has flowed into male side space 6a and female side space 6b is compressed by the meshing of male teeth 11a and female teeth 12a, and is discharged from discharge flow path 5 via discharge port 21h.

[0027] Fluid supply mechanism 7 (male side fluid supply mechanism 71) comprises fluid supply passage 7a (male side fluid supply passage 71a) to which liquid lubricating oil is supplied from an external oil supply system (not shown), a cylindrical swirl chamber 7c (male side swirl chamber 71c) that swirls the flow of liquid introduced from fluid supply passage 7a via inlet passage 7b (male side inlet passage 71b) to generate a swirling flow, a shaft-shaped member 7d (male side shaft-shaped member 71d) provided within swirl chamber 7c and extending along axis AX2 of swirl chamber 7c, and an injection hole 7e (male side injection hole 71e) provided at the end of swirl chamber 7c facing compression chamber 6 in the direction of axis AX2 and that injects the liquid that has become a swirling flow around shaft-shaped member 7d into swirl chamber 7c. Inlet passage 7b, swirl chamber 7c, shaft-shaped member 7d, and injection hole 7e form a fluid supply nozzle (swirl nozzle) that discharges liquid (lubricating oil) into compression chamber 6.

[0028] The displacement compressor 100 of this embodiment includes one male-side fluid supply mechanism 71 that supplies lubricating oil to the male rotor tooth portion 11b, but is not limited to this. For example, it may include a plurality of male-side fluid supply mechanisms 71, or it may include one or more female-side fluid supply mechanisms 72 (not shown) that supply lubricating oil into the compression chambers 6 on the female rotor tooth portion 12b side, or it may include one or more male-side fluid supply mechanisms 71 and one or more female-side fluid supply mechanisms 72. The displacement compressor 100 may also include one driving screw rotor (the male rotor 11 in this embodiment) and at least one driven screw rotor (the female rotor 12 in this embodiment), in which case the injection holes 7e may be configured to inject liquid toward either the driving screw rotor 11 or the driven screw rotor 12.

[0029] 1, male side fluid supply passage 71a is, for example, a cylindrical space extending from the outer peripheral surface of main casing 21 that covers male rotor tooth portion 11b toward the end of male side inlet passage 71b on the suction flow passage 4 side (the -X side in FIG. 1). Male side fluid supply passage 71a is connected to piping of an external oil supply system (not shown).

[0030] Male inlet passage (71b) is a cylindrical cavity that connects male liquid supply passage (71a) and male swirl chamber (71c) and is provided inside main casing (21). As shown in Figure 1, male inlet passage (71b) preferably extends along axis AX1. Furthermore, the central axis of male inlet passage (71b) does not intersect with central axis AX2 of male swirl chamber (71c), which is a cylindrical cavity, but is eccentric with respect to central axis AX2, as shown in Figure 4. In other words, male side swirl chamber (71c) and male side inlet passage (71b) that supplies liquid to male side swirl chamber (71c) are connected so that the central axis of male side inlet passage (71b) is offset from central axis AX2 of male side swirl chamber (71c), and when liquid is supplied to male side swirl chamber (71c) via male side inlet passage (71b), the liquid swirls along the cylindrical inner circumferential surface of male side swirl chamber (71c), thereby generating a swirl (swirling flow) of the liquid around male side axial member (71d) within male side swirl chamber (71c). Furthermore, male side inlet passage (71b) and male side swirl chamber (71c) are preferably connected by a surface that extends in the direction of the liquid flow, so that the flow of liquid flows smoothly without turbulence at the boundary between male side inlet passage (71b) and male side swirl chamber (71c).

[0031] Male side swirl chamber 71c is a cylindrical cavity provided inside main casing 21. Male side swirl chamber 71c is arranged so that central axis AX2 of male side swirl chamber 71c faces male rotor tooth portion 11b, and it is preferable that central axis AX2 is perpendicular to male side cylindrical surface 21f.

[0032] Male side injection hole (71e) is a through hole that connects male side swirl chamber (71c) with compression chamber 6, and is preferably a circular hole. Male side swirl chamber (71c) preferably has an opposing surface (71f) that faces male side injection hole (71e) within male side swirl chamber (71c).

[0033] Male side shaft member 71d is disposed within male side swirling chamber 71c and extends in the direction of axis AX2 of male side swirling chamber 71c. Male side shaft member 71d has an outermost diameter Φ1 smaller than the minimum diameter Φ2 of male side injection hole 71e. When male side injection hole 71e is viewed from the compression chamber 6 side, male side shaft member 71d is positioned so that the entire male side shaft member 71d is contained within male side injection hole 71e. It is preferable that the central axis AX2 of male side shaft member 71d coincide with the central axis of male side injection hole 71e. It is preferable that the end of male side shaft member 71d facing male side injection hole 71e be positioned within male side injection hole 71e. It is preferable that male side shaft member 71d be cylindrical. Furthermore, it is preferable that male side shaft member 71d extend from opposing surface 71f, as shown in FIG. 4 . Furthermore, male side axial member (71d) may be formed integrally with opposing surface (71f) of male side swirling chamber (71c), or may be formed separately from opposing surface (71f) of male side swirling chamber (71c) and fixed to opposing surface (71f).

[0034] Furthermore, it is preferable that distance D between the end of male side axial member (71d) on the male side injection hole (71e) side and open end (71g) of male side injection hole (71e) on the compression chamber 6 side be 0 to 1 mm.

[0035] [Effects] Here, a liquid supply mechanism in which male side axial member 71d is removed from male side liquid supply mechanism 71 of the present embodiment (liquid supply mechanism 107 in FIG. 5) will be referred to as a comparative example, and the problems associated with this comparative example will be first described, followed by an explanation of the effects of the present embodiment.

[0036] Fig. 5 is a schematic perspective view showing the shape of the liquid 10 injected into the compression chamber 6 from the liquid supply mechanism 107 according to the comparative example. Fig. 6 is a schematic cross-sectional view taken along line VI-VI in Fig. 5 .

[0037] In the comparative example, liquid 10 supplied to a liquid supply passage (not shown) flows into swirl chamber 107c via inlet passage 107b. The central axis of inlet passage 107b, like the central axis of male inlet passage 71b in the first embodiment, does not intersect with central axis AX2 of swirl chamber 107c, which is a cylindrical gap, but is eccentric with respect to central axis AX2. Inlet passage 107b and swirl chamber 107c are connected by a surface extending in the direction of liquid flow so that the liquid flows smoothly without turbulence at the boundary between inlet passage 107b and swirl chamber 107c. As a result, liquid flowing from inlet passage 107b into swirl chamber 107c swirls within swirl chamber 107c and is released from injection hole 107e into compression chamber 6, forming a radial liquid film, as shown in FIG. 5 .

[0038] At this time, centrifugal force acts on the liquid 10 released into the compression chamber 6, causing the liquid level at the center of the swirling motion (i.e., the central axis AX) to drop, forming an inverted cone-shaped void 10a in the male side swirling chamber 71c. The compressed gas in the compression chamber 6 compressed by the screw rotor 1 can flow into void 10a. In other words, this void 10a becomes a volume (dead volume) that does not contribute to compression in the compressor, and the compressed air that has flowed into void 10a repeatedly expands and compresses as the compressor operates, increasing the shaft power and potentially reducing the efficiency of the compressor.

[0039] In contrast, male side fluid supply mechanism 71 of this embodiment has a swirl nozzle in which male side swirl chamber 71c and male side inlet passage 71b are connected so that their central axes are offset, and the outermost diameter of male side shaft member 71d provided within male side swirl chamber 71c is smaller than the minimum diameter of male side injection hole 71e provided at the compressor-side end of male side swirl chamber 71c in the axial direction. By configuring the swirl nozzle in this manner, the presence of male side shaft member 71d, whose outermost diameter is smaller than the minimum diameter of male side injection hole 71e, suppresses the generation of gap 10a, thereby reducing the volume (dead volume) of gap 10a and thereby suppressing a decrease in compression efficiency. This suppresses an increase in shaft power due to repeated expansion and compression of compressed air within gap 10a during compressor operation, thereby suppressing a decrease in compressor efficiency.

[0040] Furthermore, male side fluid supply mechanism 71 of this embodiment includes male side shaft member 71d that is provided within male side swirl chamber 71c and extends in the direction of axis AX2 of male side swirl chamber 71c, with the end of male side shaft member 71d on the male side injection hole 71e side being located within male side injection hole 71e. By locating male side shaft member 71d within male side injection hole 71e in this manner, the dead volume associated with the generation of swirling flow can be further reduced, thereby further suppressing a decrease in compressor efficiency.

[0041] Male side shaft member (71d) is preferably cylindrical, which makes it possible to easily impart a swirling component to the velocity of liquid (10) within male side swirling chamber (71c), thereby suppressing the occurrence of pressure loss within male side swirling chamber (71c).

[0042] It is preferable that male side swirl chamber (71c) has an opposing surface that faces male side injection hole (71e) within male side swirl chamber (71c), and male side shaft member (71d) extends from the opposing surface, thereby making it possible to easily release liquid (10) within male side swirl chamber (71c) into compression chamber 6.

[0043] It is preferable that distance D between the end of male axial member (71d) on the injection hole (male injection hole (71e) side) and opening end (71g) of male injection hole (71e) on the compression chamber 6 side be 0 to 1 mm. This makes it possible to reduce the volume (dead volume) of gap (10a) while taking into account processing errors.

[0044] Height H1 of male side shaft-shaped member (71d) in the Y-axis direction may be lower than height H2 of male side swirl chamber (71c) in the Y-axis direction as shown in Figure 10. In this case, the number of processing steps required to form male side shaft-shaped member (71d) can be reduced, and the contact area between the swirling oil film and the shaft-shaped member wall surface can be reduced, thereby reducing flow resistance.

[0045] Second Embodiment Fig. 7 is a longitudinal sectional view (a sectional view taken along the XY plane along the rotation axis of the male rotor) of a displacement compressor 200 according to a second embodiment of the present invention. Fig. 8 is a schematic sectional view taken along line VIII-VIII in Fig. 7.

[0046] The displacement type compressor 200 according to this embodiment differs from the displacement type compressor 100 according to the first embodiment in that the fluid supply mechanism 27 includes a casing plate 27i and a shaft-shaped part 27j.

[0047] The casing plate 27i is a plate attached to the outer peripheral surface of the main casing 221. The shaft-shaped part 27j is a male screw fixed to a shaft-shaped part fixing portion 27h (threaded hole) provided on the casing plate 27i.

[0048] The liquid supply path 27a, the introduction path 27b, the swirl chamber 27c, and the shaft-shaped member 27d that constitute the liquid supply mechanism 27 have the following features.

[0049] That is, the liquid supply passage 27a is a flow path formed by a hole penetrating the casing plate 27i. The inlet passage 27b is a flow path in which a groove provided on the outer peripheral surface of the main casing 221 is covered by the casing plate 27i, and one end (the end on the suction passage 4 side in this embodiment) is provided so as to communicate with the liquid supply passage 27a. In addition, the inlet passage 27b preferably extends along the axis AX1.

[0050] The swirl chamber 27c is a space formed by covering a cylindrical recess provided on the outer peripheral surface of the main casing 221 with a casing plate 27i. The end of the introduction passage 27b on the discharge flow passage 5 side (the +X side in FIG. 7) is connected to the swirl chamber 27c, and an injection hole 7e is provided on the compression chamber 6 side.

[0051] The shaft-shaped member 27d is a male threaded portion of a shaft-shaped part 27j, which is a male screw. The male threaded portion is fastened to a female threaded portion provided in a shaft-shaped part fixing part 27h, which is a through hole provided in a surface of a casing plate 27i covering the swirl chamber 27c that faces the injection hole 7e within the swirl chamber 27c.

[0052] Specifically, a shaft-shaped part fixing portion 27h, which is a screw hole, is provided on the surface of a casing plate 27i covering the swirl chamber 27c that faces the injection hole 7e within the swirl chamber 27c.

[0053] A shaft-shaped part 27j, which is a male screw, is fastened to the shaft-shaped part fixing part 27h from the outside toward the inside of the casing 220. A shaft-shaped member 27d, which is the male screw portion of the shaft-shaped part 27j, is provided in the swirl chamber 7c and extends in the direction of the axis AX2 of the swirl chamber 7c, and an end of the shaft-shaped member 27d is disposed in the injection hole 7e.

[0054] [Effect] The liquid supply mechanism 7 of the first embodiment is provided inside the side wall that covers the screw rotor 1 of the main casing 21. On the other hand, the liquid supply mechanism 27 of this embodiment is formed by grooves and recesses provided on the outer peripheral surface of the main casing 221, a casing plate 27i that covers them, through holes and screw holes provided in the casing plate 27i, and male screws fastened to the screw holes in the casing plate 27i. Therefore, the liquid supply mechanism 27 of this embodiment enables a significant reduction in the number of steps compared to the liquid supply mechanism 7 of the first embodiment.

[0055] 9 is a schematic vertical cross-sectional view of swirl chamber 37c according to a third embodiment of the present invention (a schematic cross-sectional view taken along the YZ plane along central axis AX2 of male side swirl chamber 371). The positive displacement compressor according to this embodiment differs from positive displacement compressor 200 according to the second embodiment in shaft-shaped component fixing portion 37h and shaft-shaped component 37j.

[0056] That is, the casing plate 37i according to this embodiment is provided with a shaft-shaped component fixing portion 37h, which is a recess having a female thread portion 37k, on the surface of the casing plate 37i facing the injection hole 7e. The shaft-shaped component 37j is provided with a male thread portion 37l that fastens to the female thread portion 37k of the shaft-shaped component fixing portion 37h, and a shaft-shaped member 37d having an inverted truncated cone shape whose diameter increases toward the injection hole 7e.

[0057] [Effects] In this embodiment, the shaft-shaped member 37d has an inverted truncated cone shape whose diameter expands toward the injection hole 7e. In other words, in this embodiment, the shape of the shaft-shaped member 37d is made similar to the outer shape of the liquid (lubricating oil) that swirls within the swirl chamber 37c and is discharged from the injection hole 7e into the compression chamber 6 in an inverted cone shape. By approximating the shapes of the two elements in this manner, the flow resistance of the shaft-shaped member 37d to the swirling motion of the liquid within the swirl chamber 37c can be reduced, thereby reducing the pressure loss of the liquid when it is discharged into the compression chamber 6. This increases the flow rate of the liquid passing through the injection hole 7e, thereby increasing the flow velocity of the liquid and increasing the relative velocity difference between the compressed air and the liquid. This promotes the breakup of the liquid injected from the injection hole 7e into the compression chamber 6 by the compressed air, resulting in atomization of the liquid over a shorter distance. In other words, this embodiment is expected to have the effect of further reducing the diameter of droplets within the compression chamber 6.

[0058] The swirl chamber 37c is provided with a facing surface of a casing plate 37i that faces the injection hole 7e within the swirl chamber 37c, and the shaft-shaped member 37d is attached by fastening a male threaded portion 37l of the shaft-shaped member 37j to a female threaded portion 37k of a shaft-shaped member fixing portion 37h, which is a recessed portion provided on the facing surface. Therefore, the shaft-shaped member 37d of this embodiment can reduce the number of manufacturing steps compared to the shaft-shaped member 7d of the first embodiment.

[0059] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0060] The present invention may be embodied in the following manner. In the above description, the positive displacement compressor is a liquid feed screw compressor. However, the present invention is not limited to this. The positive displacement compressor may be a liquid feed reciprocating compressor, a liquid feed rotary compressor, or a liquid feed scroll compressor.

[0061] DESCRIPTION OF SYMBOLS 1...Screw rotor, 2,220...Casing, 3...Motor, 4...Suction passage, 5...Discharge passage, 6...Compression chamber, 7,27,271...Liquid supply mechanism, 7e...Injection hole, 10...Liquid, 10a...Gap, 11...Male rotor, 11a...Male teeth (lobe), 11b...Male rotor teeth portion, 12...Female rotor, 12a...Female teeth (lobe), 12b...Female rotor teeth portion, 21,221...Main casing, 71...Male side liquid supply mechanism, 71a... Male side fluid supply passage, 71b...male side introduction passage, 71c, 271c, 371c...male side swirl chamber, 71d, 271d, 371d...male side shaft-shaped member, 71e...male side injection hole, 100, 200...positive displacement compressor, 271a...oil supply hole, 271b...introduction passage, ...swirl chamber, 271h, 371h...shaft-shaped part fixing portion, 271i, 371i...casing plate, 271j, 371j...shaft-shaped part, 371k...female thread portion, 371l...male thread portion

Claims

1. A positive displacement compressor which supplies liquid into a compression chamber and compresses a gas, comprising: a cylindrical swirl chamber; a liquid inlet passage connected to the swirl chamber so that its central axis is offset from the central axis of the swirl chamber, and which generates a swirling flow in the swirl chamber by supplying liquid to the swirl chamber; a shaft-shaped member provided in the swirl chamber and extending in the axial direction of the swirl chamber; and an injection hole provided at the end of the swirl chamber on the compression chamber side in the axial direction, and which injects the liquid that has become a swirling flow around the shaft-shaped member into the compression chamber, wherein the outermost diameter of the shaft-shaped member is smaller than the minimum diameter of the injection hole.

2. A positive displacement compressor according to claim 1, characterized in that the end of said shaft member on the injection hole side is disposed within said injection hole.

3. A positive displacement compressor according to claim 1, characterized in that the shaft member is cylindrical in shape.

4. A volumetric compressor as claimed in claim 1, characterized in that the shaft-shaped member is a male threaded portion of a male screw, the swirl chamber is provided with an opposing surface that faces the injection hole within the swirl chamber, and the male threaded portion is fastened to a female threaded portion provided on the opposing surface.

5. A positive displacement compressor according to claim 1, characterized in that the shaft member has an inverted truncated cone shape whose diameter expands toward the injection hole.

6. A positive displacement compressor as claimed in claim 1, characterized in that the swirl chamber is provided with an opposing surface that faces the injection hole within the swirl chamber, and the shaft-shaped member extends from the opposing surface.

7. A positive displacement compressor as claimed in claim 1, characterized in that the swirl chamber is provided with an opposing surface which faces the injection hole within the swirl chamber, and the shaft-shaped member is attached to a through hole or recess provided in the opposing surface.

8. A displacement type compressor as claimed in claim 1, characterized in that the distance between the end of the shaft member on the injection hole side and the opening end of the injection hole on the compression chamber side is 0 to 1 mm.

9. A positive displacement compressor as claimed in claim 1, characterized in that one driving screw rotor and at least one driven screw rotor are provided within the compression chamber, and liquid is injected from the injection hole toward either the driving screw rotor or the driven screw rotor.