Screw compressor

Abstract

To provide a screw compressor capable of securing a liquid recovery amount from a bearing chamber to an operation chamber without increasing pressure of the bearing chamber.SOLUTION: A screw compressor includes a liquid recovering mechanism 70 for recovering liquid for lubrication supplied to a bearing 7 from a bearing chamber 52 to a storage chamber 45. The liquid recovering mechanism 70 includes a liquid supply groove 72 that is opened on an inner peripheral surface 47 of the storage chamber 45 at a position of a joining surface 41a of a casing 4, and extends in a circumferential direction of the inner peripheral surface 47, an introduction passage 73 formed at the position of the joining surface 41a and connected to one side end part on a rear side in a rotation direction of a screw rotor 3 of the liquid supply groove 72, and a recovery passage 71 for connecting the bearing chamber 52 and the introduction passage 73. In a connection part 74 of the liquid supply groove 72 and the introduction passage 73, a surface including a tangent line L1 of one side end part 72aP on a bottom face 72a of the liquid supply groove 72 is a boundary surface for the introduction passage 73. The connection part 74 is configured so that an opening area S1 of an opening 74a opened on the inner peripheral surface 47 is smaller than a boundary surface area S2.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a screw compressor, and more particularly to a screw compressor in which lubricating liquid supplied to a bearing supporting a screw rotor is recovered into a casing. [Background technology]

[0002] A screw compressor includes a screw rotor, a bearing that rotatably supports the screw rotor, and a casing that houses the screw rotor and the bearing. The screw compressor draws in and compresses gas by increasing and decreasing the volume of a working chamber formed by the tooth grooves of the screw rotor and the inner wall surface of the casing as the screw rotor rotates. The bearing is lubricated by a liquid (e.g., lubricating oil) supplied from outside the compressor.

[0003] In many screw compressors, a structure is adopted in which the liquid that lubricates the bearings is collected in a suction space formed upstream of the working chamber in the casing. In this structure, the liquid collected in the suction space is heated by the lubrication of the bearings and is in a relatively high temperature state. Therefore, when the low-temperature suction gas that flows into the suction space is heated by the high-temperature liquid collected in the suction space, suction loss occurs. Therefore, by collecting the liquid in the bearing chamber in the working chamber instead of in the suction space in the casing, suction loss can be suppressed and energy saving can be improved.

[0004] As a measure to address this problem, for example, there is a technology described in Patent Document 1. The oil-cooled screw compressor described in Patent Document 1 is equipped with an oil recovery passage formed in a discharge casing and a recessed portion provided in an open end face of the oil recovery passage and configured to be long in the circumferential direction of the screw rotor in order to recover the oil that has lubricated the discharge-side bearing from a bearing chamber that houses the discharge-side bearing to the screw rotor side. This recessed portion is formed at a position communicating with the working space of the screw rotor, where the pressure is lower than that of the bearing chamber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2012-36879 Summary of the Invention [Problem to be solved by the invention]

[0006] The oil-cooled screw compressor described in Patent Document 1 uses the pressure difference between the bearing chamber and the working chamber as a driving force for recovering oil from the bearing chamber to the working space (working chamber) of the screw rotor. In order to recover the oil in the bearing chamber to the working chamber, a driving force is required that resists the flow resistance of the recovery path through which the oil flows and exceeds the centrifugal force generated by the rotation of the screw rotor. However, when the driving force for recovering the oil is to be obtained by the pressure difference between the bearing chamber and the working chamber as in the technology described in Patent Document 1, it is considered that a sealing mechanism is required to prevent oil leakage into a low-pressure space adjacent to the bearing chamber (for example, the suction space for the suction-side bearing chamber). If such a sealing mechanism is newly provided, new problems such as the occurrence of sliding loss, the risk of reduced reliability, and increased manufacturing costs will occur. Therefore, a force other than the pressure difference between the bearing chamber and the working chamber is required as a driving force for recovering oil from the bearing chamber to the working chamber.

[0007] The inventors of the present application have discovered a means of utilizing the shear force generated in the liquid by contact with the rotating screw rotor as the driving force for recovering the liquid from the bearing chamber to the working chamber. The liquid is accelerated in the direction of movement of the screw rotor by being dragged by the shear force generated in the liquid by contact with the screw rotor. This makes it possible to draw the liquid in the bearing chamber into the working chamber.

[0008] In the technology described in Patent Document 1, it seems possible to use the shear force generated in the liquid by contact with the rotating screw rotor as the driving force for liquid recovery from the bearing chamber to the working chamber. Since a shear force is generated in the oil present in the recess in the tangential direction of the rotation direction of the screw rotor, the effect of drawing the oil in the recess into the working chamber is obtained. However, the inventors of the present application found that when the shear force of the liquid is used as the driving force for liquid recovery from the bearing chamber to the working chamber, there are structural conditions to ensure a sufficient amount of liquid recovery. In the case of the connection structure between the recess and the oil recovery passage described in Patent Document 1 (see FIG. 6), even if the effect of drawing the oil in the recess into the working chamber is obtained, there is a risk that a backflow vortex will be generated when the liquid flows from the oil recovery passage into the recess, which will significantly reduce the amount of oil recovered from the bearing chamber to the working chamber.

[0009] The present invention has been made to solve the above problems, and an object of the present invention is to provide a screw compressor that can ensure the recovery of the amount of liquid from the bearing chamber to the working chamber without increasing the pressure in the bearing chamber. [Means for solving the problem]

[0010] The present application employs the configuration described in the claims as a means for solving the above problems. One example of a screw compressor includes at least one screw rotor, a bearing for rotatably supporting the screw rotor, a housing chamber for rotatably housing the screw rotor and a bearing chamber in which the bearing is disposed, a casing forming a working chamber together with the screw rotor, and a liquid recovery mechanism for recovering lubricating liquid supplied to the bearing from the bearing chamber into the housing chamber, the casing including a first casing segment and a second casing segment joined to each other, the liquid recovery mechanism forming the housing chamber at the position of the joint surface of the casing. the screw rotor has a bearing chamber and a fluid supply groove that opens onto an inner circumferential surface, which is a part of the wall surface formed by the fluid supply groove, and extends circumferentially around the inner circumferential surface; an inlet passage that is formed at the position of the joint surface and is connected to one end of the fluid supply groove that is located on the rear side in the rotational direction of the screw rotor; and a recovery passage that connects the bearing chamber and the inlet passage, the fluid supply groove and the inlet passage being connected via a connection part, and the connection part is configured so that a surface including a tangent to the one end on a bottom surface of the fluid supply groove forms a boundary surface with respect to the inlet passage, and the connection part is configured so that the opening area of ​​an opening that opens onto the inner circumferential surface is smaller than the area of ​​the boundary surface. Effect of the Invention

[0011] According to one embodiment of the present invention, by making the opening area on the inner circumferential surface of the connection between the liquid supply groove and the introduction passage smaller than the area of ​​the boundary surface with the introduction passage, the acceleration of the liquid in the connection portion due to the rotating screw rotor is suppressed, and therefore it is possible to suppress the backflow vortex that occurs when liquid is introduced from the introduction passage into the liquid supply groove via the connection portion. Therefore, when the shear force generated in the liquid due to contact with the screw rotor is used as the driving force for flowing the liquid in the liquid supply groove into the accommodation chamber (working chamber), it is possible to ensure the necessary flow rate flowing from the introduction passage into the liquid supply groove. In other words, it is possible to ensure the recovery amount of liquid from the bearing chamber to the working chamber without increasing the pressure in the bearing chamber. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0012] [Figure 1] 1 is a vertical sectional view showing a screw compressor according to a first embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of the screw compressor according to the first embodiment shown in FIG. 1, taken along the line II-II of the arrows. [Diagram 3] 3 is a cross-sectional view of the screw compressor according to the first embodiment shown in FIG. 1, taken along the line III-III of the arrows. [Figure 4] 4 is a diagram showing a structure of a liquid recovery mechanism on a joint surface of a casing (main casing) when the screw compressor according to the first embodiment shown in FIG. 1 is viewed from the direction of arrows IV-IV. FIG. [Diagram 5] 5 is a schematic diagram showing, in an enlarged state, a liquid recovery mechanism of the screw compressor according to the first embodiment shown in an area indicated by the symbol F in FIG. 4. [Figure 6] 3 is a schematic diagram showing the structure of a liquid recovery mechanism of a screw compressor according to a comparative example to the liquid recovery mechanism of the screw compressor according to the first embodiment. FIG. [Figure 7] 6 is an explanatory diagram showing the operation of the liquid recovery mechanism of the screw compressor according to the first embodiment shown in FIG. 5. [Figure 8] 6 is a schematic diagram showing the structure of an introduction passage and a liquid supply groove of a liquid recovery mechanism in a screw compressor according to a modified example of the first embodiment, in an enlarged state similar to that in FIG. 5. [Figure 9] 4 (arrows IV-IV in FIG. 1). FIG. 5 is a view showing a screw compressor according to a second embodiment of the present invention, as viewed in the same direction as FIG. [Figure 10] 4 (arrows IV-IV in FIG. 1). FIG. 5 is a view showing a screw compressor according to a third embodiment of the present invention, as viewed in the same direction as FIG. [Figure 11] 2 (arrows II-II in FIG. 1). FIG. 3 is a longitudinal sectional view of a screw compressor according to a fourth embodiment of the present invention, as viewed in the same direction as FIG. [Figure 12] 13 is a schematic diagram showing the structure of a connection between an inlet passage and a liquid supply groove of a liquid recovery mechanism in a screw compressor according to another embodiment of the present invention, as viewed from inside the accommodation chamber of the casing. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a screw compressor according to the present invention will be described with reference to the drawings. In this description, a twin-rotor screw compressor will be described as an example.

[0014] [First embodiment] The configuration of a screw compressor according to a first embodiment of the present invention will be described with reference to Figs. 1 and 2. Fig. 1 is a longitudinal sectional view showing the screw compressor according to the first embodiment. Fig. 2 is a sectional view of the screw compressor according to the first embodiment shown in Fig. 1, seen from the direction of arrows II-II. In Fig. 1, the left side is the suction side of the screw compressor, and the right side is the discharge side. Here, the "suction side" refers to the side in the axial direction of the screw compressor that sucks in gas, and the "discharge side" refers to the side in the axial direction of the screw compressor that discharges gas.

[0015] In FIG. 1, the screw compressor 1 is a liquid-feed type in which a liquid (e.g., oil or water) is supplied from the outside to the inside of the compressor. The screw compressor 1 includes a male rotor 2 and a female rotor 3 as a pair of screw rotors that rotate while meshing with each other, and a casing 4 that rotatably houses the male rotor 2 and the female rotor 3 in an intermeshed state. The male rotor 2 and the female rotor 3 are rotatable around an axis A1 and an axis A2, respectively, and the male rotor 2 and the female rotor 3 are arranged so that the axes A1 and A2 are parallel to each other. The male rotor 2 is rotatably supported on both sides in the axial direction (left-right direction in FIG. 1) by a suction side bearing 5 and a discharge side bearing 6 (composed of two bearings in FIG. 1). The female rotor 3 is rotatably supported on both sides in the axial direction by a suction side bearing 7 and a discharge side bearing 8 (composed of two bearings in FIG. 1).

[0016] The male rotor 2 is composed of a rotor tooth portion 21 having a plurality of helical male teeth (lobes) 21a, and a suction side shaft portion 22 and a discharge side shaft portion 23 provided on both axial ends of the rotor tooth portion 21. The rotor tooth portion 21 has a suction side end face 21b and a discharge side end face 21c perpendicular to the axial direction (axis A1) at one axial end (left end in FIG. 1) and the other axial end (right end in FIG. 1), respectively. Tooth grooves are formed between the male teeth 21a of the rotor tooth portion 21. The suction side shaft portion 22 is configured to extend, for example, outside the casing 4, and is connected to a rotation drive source such as an electric motor (not shown). A shaft seal member 9 is arranged between the suction side shaft portion 22 of the male rotor 2 and the casing 4 to seal the gap therebetween. The shaft seal member 9 is, for example, an oil seal or a mechanical seal.

[0017] The female rotor 3 is composed of a rotor tooth portion 31 having a plurality of spiral female teeth (lobes) 31a, and a suction side shaft portion 32 and a discharge side shaft portion 33 provided on both axial end portions of the rotor tooth portion 31. The rotor tooth portion 31 has a suction side end face 31b and a discharge side end face 31c perpendicular to the axial direction (axis A2) at one axial end (left end in FIG. 1) and the other axial end (right end in FIG. 1), respectively. Tooth grooves are formed between the female teeth 31a of the rotor tooth portion 31.

[0018] The casing 4 includes a main casing 41 and a discharge side casing 42 as a first casing segment and a second casing segment that are joined to each other along a dividing plane perpendicular to the axes A1, A2 of the male and female rotors 2, 3. The main casing 41 is configured so that the discharge side casing 42 is joined to its discharge side (right side in FIG. 1), and has a discharge side joint surface 41a perpendicular to the axes A1, A2 of the male and female rotors 2, 3.

[0019] The casing 4 has an accommodation chamber 45 therein that accommodates the rotor teeth 21 of the male rotor 2 and the rotor teeth 31 of the female rotor 3 in a mutually meshed state. The accommodation chamber 45 is formed by closing the opening on one axial side (the right side in Figs. 1 and 2) of two partially overlapping cylindrical spaces (bores) formed in the main casing 41 with the discharge side casing 42, and has a male side bore 45a that accommodates most of the rotor teeth 21 of the male rotor 2 and a female side bore 45b that accommodates most of the rotor teeth 31 of the female rotor 3. The wall surfaces forming the accommodation chamber 45 are composed of a substantially cylindrical first inner circumferential surface 46 located radially outward of the rotor tooth portion 21 of the male rotor 2, a substantially cylindrical second inner circumferential surface 47 located radially outward of the rotor tooth portion 31 of the female rotor 3, a suction side inner wall surface 48 on one axial side (left side in FIG. 1) facing the suction side end faces 21b, 31b of the rotor tooth portions 21, 31 of both the male and female rotors 2, 3, and a discharge side inner wall surface 49 on the other axial side (right side in FIG. 1) facing the discharge side end faces 21c, 31c of the rotor tooth portions 21, 31 of both the male and female rotors 2, 3. That is, the suction side end of the accommodation chamber 45 in the axial direction is the suction side inner wall surface 48, and the discharge side end in the axial direction is the discharge side inner wall surface 49. The casing 4 is configured such that a main casing 41 and a discharge side casing 42, which are separated at the position of a discharge side inner wall surface 49 of the accommodation chamber 45, are joined to each other.

[0020] A plurality of working chambers C are formed by the rotor teeth 21, 31 of the male and female rotors 2, 3 and the inner wall surface of the casing 4 (the first inner circumferential surface 46, the second inner circumferential surface 47, the suction side inner wall surface 48, and the discharge side inner wall surface 49 of the accommodation chamber 45) that surrounds them. Each working chamber C increases in volume with the rotation of the screw rotor to draw in gas from the outside of the casing 4 (suction stroke), and compresses the gas by decreasing in volume with the rotation of the screw rotor (compression stroke). The screw compressor 1 is configured so that a liquid such as oil or water is supplied to the working chamber C during the suction stroke or compression stroke. The purpose of supplying the liquid to the working chamber C is to cool the compressed gas in the working chamber C, lubricate the male rotor 2 and the female rotor 3, and seal gaps between the male and female rotors 2, 3 and the wall surface of the accommodation chamber 45 (the inner wall surface of the casing 4) and gaps in the meshing portion between the male rotor 2 and the female rotor 3.

[0021] The suction side bearing 5 on the male rotor 2 side and the suction side bearing 7 on the female rotor 3 side are disposed at the suction side end (the axial end opposite to the opening) of the main casing 41. The suction side casing 43 is attached to the suction side end of the main casing 41, and the main casing 41 and the suction side casing 43 form a suction side bearing chamber 51 in which the suction side bearing 5 on the male rotor 2 side is disposed and a suction side bearing chamber 52 in which the suction side bearing 7 on the female rotor 3 side is disposed. The suction side bearing chamber 51 and the suction side bearing chamber 52 are mutually communicated by an internal space formed in the suction side casing 43. The suction side bearing chambers 51 and 52 are at approximately atmospheric pressure. The screw compressor 1 is configured such that a lubricating liquid such as oil or water is supplied from the outside to the suction side bearing 5 on the male rotor 2 side and the suction side bearing 7 on the female rotor 3 side.

[0022] The discharge side casing 42 is provided with a discharge side bearing chamber 54 in which the discharge side bearing 6 on the male rotor 2 side is disposed, and a discharge side bearing chamber 55 in which the discharge side bearing 8 on the female rotor 3 side is disposed. The discharge side bearing chambers 54, 55 are at approximately atmospheric pressure. The screw compressor 1 is configured so that a lubricating liquid such as oil or water is supplied from the outside to the discharge side bearing 6 on the male rotor 2 side and the discharge side bearing 8 on the female rotor 3 side.

[0023] As shown in Figs. 1 and 2, the casing 4 is provided with an intake passage 61 and an intake space 62 for sucking external gas into the working chamber C. The intake passage 61 is, for example, a passage having one side open to the outer wall surface of the main casing 41 and the other side (downstream side) connected to the intake space 62. The intake space 62 is formed in a position facing the intake side end faces 21b, 31b of the rotor teeth portions 21, 31 of the male and female rotors 2, 3 in the main casing 41. The casing 4 is provided with a discharge passage 64 for discharging compressed gas from the working chamber C to the outside of the casing 4. The discharge passage 64 connects the accommodation chamber 45 (working chamber C) to the outside of the casing 4, and is formed, for example, across both the main casing 41 and the discharge side casing 42. The suction flow passage 61 and the discharge flow passage 64 are formed on opposite sides of a reference line L (see FIG. 4) that passes through the axis A1 of the male rotor 2 and the axis A2 of the female rotor 3. That is, with respect to the reference line L (see FIG. 4), in FIG. 2, the suction flow passage 61 is located on the upper side, while the discharge flow passage 64 is located on the lower side.

[0024] 2, the casing 4 has a liquid recovery mechanism 70 that recovers the lubricating liquid (e.g., lubricating oil) supplied to the suction side bearings 5, 7 into the working chamber C during the suction stroke or into the working chamber C at the start of the compression stroke when the suction stroke has been changed to the compression stroke. The screw compressor 1 according to this embodiment is characterized by the liquid recovery mechanism 70. The liquid recovery mechanism 70 does not recover the liquid into the working chamber C using the pressure difference between the working chamber C and the suction side bearing chambers 51, 52 in which the suction side bearings 5, 7 are arranged as a driving force, but has a structure that draws the liquid to be recovered into the working chamber C using the shear force generated by contact with the rotating screw rotor as a driving force.

[0025] In the screw compressor 1 configured as described above, the male rotor 2 shown in FIG. 1 is driven by a rotary drive source (not shown), and the female rotor 3 is also rotated. As a result, the working chamber C moves in the axial direction with the rotation of both the male and female rotors 2 and 3. The working chamber C gradually increases in volume from zero, and enters a suction stroke in which gas is sucked in from the suction passage 61 of the casing 4 shown in FIG. 2 through the suction space 62. Thereafter, when the volume of the working chamber C approaches its maximum value, communication with the suction space 62 is blocked, and the volume gradually decreases with the rotation of both the male and female rotors 2 and 3, entering a compression stroke in which air is compressed. When the working chamber C communicates with the discharge passage 64, the compressed gas in the working chamber C is discharged through the discharge passage 64 to an external liquid supply system (not shown).

[0026] The external liquid supply system is composed of, for example, a gas-liquid separator, a liquid cooler, and a pipe line (both not shown) connecting them. The liquid mixed in the compressed gas discharged from the screw compressor 1 is separated by the gas-liquid separator. The compressed gas from which the liquid has been removed by the gas-liquid separator is supplied to an external device as necessary, while the liquid separated from the compressed gas by the gas-liquid separator is cooled by a liquid cooler. The liquid cooled by the liquid cooler is again supplied to the working chamber C, the suction side bearings 5, 7, and the discharge side bearings 6, 8 of the screw compressor 1 shown in FIG. 1. The liquid supplied to the suction side bearings 5, 7 (suction side bearing chambers 51, 52) lubricates the suction side bearings 5, 7, and then is recovered (supplied) into the accommodation chamber 45 via a liquid recovery mechanism 70 connected to the suction side bearing chambers 51, 52.

[0027] Next, the configuration of the liquid recovery mechanism of the screw compressor according to the first embodiment will be described with reference to Fig. 2 to Fig. 4. Fig. 3 is a cross-sectional view of the screw compressor according to the first embodiment shown in Fig. 1, seen from the direction of arrows III-III. Fig. 4 is a diagram showing the structure of the liquid recovery mechanism on the joint surface of the casing (main casing) when the screw compressor according to the first embodiment shown in Fig. 1 is seen from the direction of arrows IV-IV. In Fig. 4, the thick arrow indicates the rotation direction of the screw rotor.

[0028] 2 to 4, the liquid recovery mechanism 70 according to this embodiment is a path that extends from the suction side bearing chambers 51, 52 of the casing 4 to the joint surface 41a of the main casing 41 with the discharge side casing 42, and extends to an opening on the second inner circumferential surface 47 that is a part of the wall surface of the accommodation chamber 45 of the casing 4. Specifically, the liquid recovery mechanism 70 is composed of, for example, a recovery path 71 (see FIGS. 2 and 3) that extends from the suction side bearing chambers 51, 52 of the casing 4 to the joint surface 41a of the main casing 41, a liquid supply groove 72 (see FIG. 4) that opens onto the second inner circumferential surface 47 of the casing 4 at the position of the joint surface 41a of the main casing 41, and an introduction path 73 (see FIG. 4) for guiding the liquid in the recovery path 71 to the liquid supply groove 72.

[0029] The recovery path 71 of the liquid recovery mechanism 70 connects an introduction path 73 located on the joint surface 41a of the main casing 41 to the suction side bearing chambers 51, 52 of the casing 4. As shown in Figures 2 and 3, for example, the recovery path 71 is made up of a first recovery path section 711, a second recovery path section 712, a third recovery path section 713, and a fourth recovery path section 714, in that order from the upstream side.

[0030] 3, the first recovery path section 711 is connected to the lower part of the suction side bearing chamber 51 on the male rotor 2 side, and is also connected to the lower part of the suction side bearing chamber 52 on the female rotor 3 side. The first recovery path section 711 is configured as a hole section formed in the suction side end section of the main casing 41, and extends in the arrangement direction of the male and female rotors 2, 3. The hole section as the first recovery path section 711 opens on the outer wall surface of the main casing 41 in the arrangement direction of the male and female rotors 2, 3, and the opening is closed by a first plug 81.

[0031] 2 and 3, one side of the second recovery path portion 712 is connected to the first recovery path portion 711, and the other side is connected to the third recovery path portion 713. The second recovery path portion 712 is configured as a hole portion formed in a position between the suction side bearing 5 (suction side bearing chamber 51) and the suction side bearing 7 (suction side bearing chamber 52) in the main casing 41, and extends in a direction perpendicular to a plane including the axis A1 of the male rotor 2 and the axis A2 of the female rotor 3. The other side of the second recovery path portion 712 opens onto an outer wall surface on the opening side of the suction side flow passage 61 in the main casing 41.

[0032] 2, the third recovery path part 713 is a pipe attached to the main casing 41. One side of the third recovery path part 713 is connected to the opening of the second recovery path part 712 of the main casing 41, and the other side is connected to the opening of the fourth recovery path part 714 on the outer wall surface of the main casing 41.

[0033] The third recovery path portion 713 can also be configured as a hole formed in the main casing 41, rather than as a pipe. In this configuration, it is formed at a position that avoids the suction passage 61 formed in the main casing 41. This configuration does not require piping, which has the advantage of reducing the number of parts and saving space for arranging the piping.

[0034] As shown in Figs. 2 and 4, the fourth recovery passage 714 has one side connected to the third recovery passage 713 (piping) and the other side connected to the introduction passage 73. The fourth recovery passage 714 is configured as a hole formed in the main casing 41. One side of the fourth recovery passage 714 opens onto the outer wall surface of the opening side of the suction side flow passage 61 in the main casing 41, and the other side opens onto the joint surface 41a of the discharge side of the main casing 41. That is, the other side end (the downstream end of the recovery passage 71) connected to the introduction passage 73 of the fourth recovery passage 714 is configured as a hole 41h provided so as to open on the joint surface 41a of the main casing 41 at a position away from the wall surfaces 46 and 47 of the storage chamber 45 of the casing 4, as shown in Fig. 4.

[0035] 4, the fluid supply groove 72 is a groove that opens onto the second inner circumferential surface 47 of the casing 4 at the position of the joint surface 41a on the discharge side of the main casing 41, extends along the circumferential direction of the second inner circumferential surface 47, and has a depth direction toward the radially outer side of the female rotor 3. The fluid supply groove 72 is disposed (opens) at a circumferential position on the second inner circumferential surface 47 that corresponds to the region where the working chamber C is in the suction stroke at the position of the discharge side end face 31c of the female rotor 3, or the region where the compression stroke begins immediately after the suction stroke has transitioned to the compression stroke. The circumferential position of the second inner peripheral surface 47 corresponding to the region where the working chamber C is in the suction stroke or the region where the compression stroke starts at the position of the discharge side end face 31c of the female rotor 3 is, as shown in Fig. 4, above the reference line L (the side where the suction passage 61 is formed) and in the vicinity thereof (a predetermined range along the rotation direction of the female rotor 3 from the connection line) to the first inner peripheral surface 46 of the casing 4. The liquid supply groove 72 is configured so that the liquid flows in the same direction as the rotation direction of the female rotor 3. That is, the liquid supply groove 72 is configured so that the liquid in the introduction passage 73 is introduced to one end located on the rear side in the rotation direction of the female rotor 3, and the other end located on the front side in the rotation direction of the female rotor 3 is the downstream end.

[0036] The liquid supply groove 72 is formed by forming a first groove 41g1 on the joint surface 41a of the main casing 41 by machining or the like, extending along the second inner surface 47 so as to open onto the second inner surface 47 of the casing 4, and joining the discharge side casing 42 to the joint surface 41a of the main casing 41 so as to close the opening of the first groove 41g1 on the joint surface 41a.

[0037] The introduction passage 73 is formed at the position of the joint surface 41a of the main casing 41, and introduces the liquid in the fourth recovery passage portion 714 of the recovery passage 71 to one end of the liquid supply groove 72. One side of the introduction passage 73 is connected to an opening on the joint surface 41a of the main casing 41 at the fourth recovery passage portion 714, and the other side is connected to one end of the liquid supply groove 72 located on the rear side in the rotation direction of the female rotor 3 (the left end of the liquid supply groove 72 in FIG. 4). The introduction passage 73 is provided so that the second groove 41g2 dug in the axial direction on the joint surface 41a of the main casing 41 is connected to the first groove 41g1 by machining or the like and is connected to the opening of the hole portion 41h, and is configured by joining the discharge side casing 42 to the joint surface 41a of the main casing 41 to close the opening of the second groove 41g2 on the joint surface 41a.

[0038] In the liquid recovery mechanism 70 of this embodiment, the liquid supply groove 72 and the introduction passage 73 are configured to utilize the shear force generated in the liquid by contact with the rotating female rotor 3 as the driving force for recovering liquid from the suction side bearing chambers 51, 52 to the working chamber C, and the connection structure between the liquid supply groove 72 and the introduction passage 73 (see Figure 5 described below) is characterized.

[0039] Next, the details of the structure of the liquid supply groove and the introduction passage in the liquid recovery mechanism of the screw compressor according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a schematic diagram showing an enlarged state of the liquid recovery mechanism of the screw compressor according to the first embodiment shown in the region indicated by the symbol F in Fig. 4.

[0040] 5, as described above, the liquid supply groove 72 is a groove dug from the second inner circumferential surface 47 of the casing 4 to the radially outer side of the female rotor 3 at the position of the joint surface 41a on the discharge side of the main casing 41, and has a bottom surface 72a at a position radially outer of the female rotor 3 than the second inner circumferential surface 47 of the casing 4. It is desirable to set the depth of the liquid supply groove 72 (the radial position of the bottom surface 72a relative to the second inner circumferential surface 47) relatively shallow, and is set, for example, within a range that is affected by the shear force (viscous force) generated in the liquid by contact with the tips of the female teeth 31a of the rotating female rotor 3.

[0041] As described above, the liquid supply groove 72 is a groove extending along the circumferential direction of the second inner peripheral surface 47. The liquid supply groove 72 is configured such that one end (the left end of the liquid supply groove 72 in FIG. 5) located on the rear side in the rotation direction of the female rotor 3 is connected to the introduction passage 73, and the other end 72b (the right end of the liquid supply groove 72 in FIG. 5) located on the front side in the rotation direction of the female rotor 3 is the downstream end of the liquid recovery mechanism 70. The liquid supply groove 72 is configured, for example, such that the length in the extension direction is greater than the thickness of the tooth tip of the female rotor 3. The liquid supply groove 72 is configured, for example, such that the groove width (the amount of digging from the joint surface 41a of the main casing 41 to the axial direction of the female rotor 3) is approximately constant in the extension direction.

[0042] In detail, the liquid supply groove 72 and the introduction path 73 are defined as follows. In FIG. 5, a straight line L1 is a tangent to a connection position 72aP on the bottom surface 72a of the liquid supply groove 72 with the introduction path 73. A straight line L2 is a straight line passing through the connection position 72aP on the bottom surface 72a of the liquid supply groove 72 and the axis A2 of the female rotor 3. In this case, the portion located downstream of the straight line L2 is defined as the liquid supply groove 72, and the portion located upstream of the straight line L1 is specified as the introduction path 73. Furthermore, the portion located between the straight lines L1 and L2 is specified as a connection portion 74 that connects the liquid supply groove 72 and the introduction path 73. In other words, the liquid supply groove 72 and the introduction path 73 are connected via the connection portion 74.

[0043] The liquid supply groove 72 defined as described above has an opening 72d that opens onto the second inner circumferential surface 47 of the casing 4 at a position downstream of the straight line L2. Moreover, the connection portion 74 has an opening 74a that opens onto the second inner circumferential surface 47 of the casing 4 at a position upstream of the straight line L2. The opening 74a of the connection portion 74 and the opening 72d of the liquid supply groove 72 are continuous on the second inner circumferential surface 47, and the opening 74a of the connection portion 74 is located rearward (cusp side) of the opening 72d of the liquid supply groove 72 in the rotational direction of the female rotor 3.

[0044] The connecting portion 74 has a boundary surface with respect to the introduction passage 73 that is a surface including a straight line L1 which is a tangent line to the connection position 72aP on the bottom surface 72a of the liquid supply groove 72, and a boundary surface with respect to the liquid supply groove 72 that is a surface including a straight line L2 passing through the connection position 72aP on the bottom surface 72a of the liquid supply groove 72 and the axis A2 of the female rotor 3. The connecting portion 74 is a characteristic part of the liquid recovery mechanism 70 according to the present embodiment. Specifically, for the connecting portion 74, when the opening area of the opening 74a on the second inner peripheral surface 47 (the product of the circumferential length of the second inner peripheral surface 47 and the axial recess amount from the joint surface 41a of the main casing 41) is S1, and the area on the boundary surface with respect to the introduction passage 73 (the upstream flow path cross-sectional area) is S2, the opening area S1 of the opening 74a is configured to be smaller than the upstream flow path cross-sectional area S2 (S1 < S2). That is, the liquid supply groove 72 and the introduction passage 73 are connected such that the opening area S1 of the connecting portion 74 is smaller than the area S2.

[0045] The connecting portion 74 having the above-described structure can be configured, for example, by connecting the introduction passage 73 to the liquid supply groove 72 with an obtuse inclination without connecting it at a right angle to the extending direction of the liquid supply groove 72. Specifically, the introduction passage 73 is formed, for example, to bend from the fourth part 714 of the recovery passage 71 toward the liquid supply groove 72, and is composed of an upstream first introduction part 731 and a downstream second introduction part 732. The first introduction part 731 extends from the opening on the joint surface 41a of the main casing 41 in the fourth part 714 of the recovery passage 71 toward the second inner peripheral surface 47 side in a direction substantially orthogonal to the second inner peripheral surface 47. The second introduction part 732 extends from the downstream end of the first introduction part 731 toward the second inner peripheral surface 47 side so as to be inclined in the rotation direction of the female rotor 3 with respect to the direction orthogonal to the second inner peripheral surface 47. It is desirable that the introduction passage 73 has a relatively wide flow path cross-sectional area in order to minimize the flow resistance. For example, the width of the second groove 41g2 formed on the joint surface 41a of the main casing 41 is set to be larger than the depth of the liquid supply groove 72 (the distance from the second inner peripheral surface 47 to the bottom surface 72a). Note that the introduction passage 73 can also be set to have a relatively large depth (axial recess amount) from the joint surface 41a of the main casing 41 of the second groove 41g2 in order to make the flow path cross-sectional area relatively large.

[0046] Next, the action and effect of the liquid recovery mechanism of the screw compressor according to the first embodiment will be explained in comparison with a liquid recovery mechanism of a screw compressor of a comparative example. First, the configuration and structure of the liquid recovery mechanism of the screw compressor of the comparative example will be explained with reference to Fig. 6. Fig. 6 is a schematic diagram showing the structure of a liquid recovery mechanism of a screw compressor according to a comparative example to the liquid recovery mechanism of the screw compressor of the first embodiment. In Fig. 6, the dashed arrows indicate the flow of liquid. In Fig. 6, the same reference numerals as those in Figs. 1 to 5 denote similar parts, and detailed explanations thereof will be omitted.

[0047] In the liquid recovery mechanism 170 of the comparative screw compressor shown in FIG. 6, it is possible to define the liquid supply groove 72, the introduction passage 173, and the connection portion 174 therebetween, as in the first embodiment. Specifically, the liquid supply groove 72 of the liquid recovery mechanism 170 of the comparative example is defined as a portion located downstream of the straight line L2, and has a structure similar to that of the first embodiment. The introduction passage 173 of the liquid recovery mechanism 170 of the comparative example is defined as a portion located upstream of the straight line L1, and the connection portion 174 connecting the liquid supply groove 72 and the introduction passage 173 is specified as a portion located between the straight lines L1 and L2. The introduction passage 173 and the connection portion 174 have a structure different from that of the introduction passage 73 and the connection portion 74 of the first embodiment.

[0048] Inlet passage 173 of the comparative example is connected to liquid supply groove 72 so as to be approximately perpendicular to the extending direction of liquid supply groove 72. Therefore, connection portion 174 is configured so that opening area S1 of opening 74a on second inner circumferential surface 47 is the same as area S2 (upstream flow path cross-sectional area) on the boundary surface (surface including straight line L1) with respect to inlet passage 173 (S1=S2). In other words, liquid supply groove 72 and inlet passage 173 of the comparative example are connected so that opening area S1 of connection portion 174 is the same as area S2 of the boundary surface.

[0049] In the comparative liquid recovery mechanism 170 configured in this manner, of the liquid filling the liquid supply groove 72 and the connection portion 174, the portions in the areas of the opening 74a of the connection portion 174 and the opening 72d of the liquid supply groove 72 adhere to the teeth of the rotating female rotor 3. As a result, the liquid in the areas of the openings 74a, 72d is dragged by the moving teeth, generating a shear force in the liquid present in the liquid supply groove 72 and the connection portion 174. As a result, the liquid in the connection portion 174 and the liquid supply groove 72 is accelerated in the same direction as the tangential direction to the rotation direction of the female rotor 3.

[0050] At this time, if the liquid in connection part 174 of liquid recovery mechanism 170 of the comparative example can flow into liquid supply groove 72 and flow toward the other end 72b of liquid supply groove 72, it will eventually flow out into the working chamber C, making it possible to recover the liquid in suction side bearing chambers 51, 52 into the working chamber C without utilizing the pressure difference between suction side bearing chambers 51, 52 and the working chamber C in the suction stroke or the working chamber C at the start of the compression stroke. This is because the flow of liquid in connection part 174 and liquid supply groove 72 must satisfy the continuity equation, so that the liquid in introduction path 173 and further in recovery path 71 upstream thereof will flow toward the liquid supply groove 72 side by the amount of the liquid that flowed out from opening 72d of liquid supply groove 72 to the working chamber C.

[0051] However, the inventors of the present application found that in the case of the structure of inlet passage 173 and connecting portion 174 of liquid recovery mechanism 170 of the comparative example, the liquid in connecting portion 174 does not easily flow into liquid supply groove 72. The flow path cross-sectional area of ​​inlet passage 173 is set large in consideration of flow resistance, while the depth of liquid supply groove 72 (the distance from second inner circumferential surface 47 of casing 4 to bottom surface 72a of liquid supply groove 72) needs to be set shallow within the range of the influence of shear force of the liquid. Here, liquid supply groove 72 and inlet passage 173 of liquid recovery mechanism 170 of the comparative example are connected so that the opening area S1 of opening 174a of connecting portion 174 and the area S2 of the boundary surface with inlet passage 173 are the same. In the case of such a connection structure, it has been found that the opening area S1 on the second inner circumferential surface 47 of the connection part 174 is relatively too large, and as indicated by the dashed arrow, a vortex flow (reverse flow vortex) V is generated in the connection part 174, in which part of the liquid in the connection part 174 accelerated by the female rotor 3 does not flow into the liquid supply groove 72 but flows back toward the introduction passage 173. In other words, if the opening area S1 of the connection part 174 is too large, the acceleration generated in the liquid in the connection part 174 becomes large, and it becomes difficult for the liquid to pass through the narrow inlet of the liquid supply groove 72 (the boundary surface including the straight line L2).

[0052] As a result, in liquid recovery mechanism 170 of the comparative example, the amount of liquid recovered from suction side bearing chambers 51, 52 to working chamber C is significantly reduced. To recover liquid from suction side bearing chambers 51, 52, a configuration is generally adopted in which the pressure difference with respect to suction side bearing chambers 51, 52 is used as a driving force. For this reason, it is not anticipated that the shear force of the liquid generated by contact with the rotating screw rotor will be used as a driving force for recovering the liquid, and sufficient consideration has not been given to a suitable structure that utilizes this shear force.

[0053] Next, the operation and effect of the liquid recovery mechanism of the screw compressor according to the first embodiment will be described with reference to Fig. 5 and Fig. 7. Fig. 7 is an explanatory diagram showing the operation and effect of the liquid recovery mechanism of the screw compressor according to the first embodiment shown in Fig. 5. In Fig. 7, the dashed arrows indicate the flow of liquid. 5, in the liquid recovery mechanism 70 of the screw compressor 1 according to this embodiment, the liquid supply groove 72 and the introduction passage 73 are connected so that the opening area S1 of the opening 74a of the connection part 74 is smaller than the area S2 of the boundary surface (the surface including the straight line L1) with respect to the introduction passage 73. That is, the flow path cross-sectional area S2 of the introduction passage 73 is secured to be relatively large, while the opening area S1 on the second inner circumferential surface 47 of the connection part 74 is made relatively small.

[0054] As a result, the acceleration of the liquid in the connection portion 74 located on the upstream side of the liquid supply groove 72 by the female rotor 3 is suppressed more than in the case of the structure of the connection portion 174 of the liquid recovery mechanism 170 of the comparative example. Therefore, the backflow vortex V (see FIG. 6) near the boundary surface (plane including the straight line L2) of the liquid supply groove 72, which was generated in the liquid recovery mechanism 170 of the comparative example, is suppressed, so that the liquid in the connection portion 74 easily flows into the liquid supply groove 72 as shown in FIG. 7, and the flow rate of the liquid flowing from the connection portion 74 toward the other end portion 72b of the liquid supply groove 72 and flowing out to the working chamber C is sufficiently secured (see the dashed arrow in FIG. 7). As a result, the liquid in the introduction passage 73 and the recovery passage 71 on the upstream side thereof flows continuously toward the liquid supply groove 72 side by the flow rate of the liquid flowing out from the liquid supply groove 72 to the working chamber C, so that the liquid in the suction side bearing chambers 51, 52 can be recovered to the working chamber C without increasing the pressure in the suction side bearing chambers 51, 52. Therefore, a simpler structure can be adopted than in the case of a configuration in which the pressure in the suction side bearing chambers 51, 52 is increased and used as the driving force for liquid recovery, and it is possible to avoid the recovery of liquid into the suction space 62, which would result in large suction losses, thereby contributing to improving the energy efficiency of the compressor.

[0055] As described above, the screw compressor 1 according to the first embodiment includes a pair of screw rotors, the male rotor 2 and the female rotor 3, the suction side bearings 5, 7 and the discharge side bearings 6, 8 (bearings) that rotatably support the male rotor 2 and the female rotor 3 (screw rotors), the casing 4 that has an accommodation chamber 45 that rotatably accommodates the male rotor 2 and the female rotor 3 (screw rotors), and suction side bearing chambers 51, 52 and discharge side bearing chambers 54, 55 (bearing chambers) in which the suction side bearings 5, 7 and the discharge side bearings 6, 8 (bearings) are arranged and forms a working chamber C together with the male rotor 2 and the female rotor 3 (screw rotors), and a liquid recovery mechanism 70 that recovers the lubricating liquid supplied to the suction side bearings 5, 7 and the discharge side bearings 6, 8 (bearings) from the suction side bearing chambers 51, 52 (bearing chambers) into the accommodation chamber 45. The casing 4 includes a main casing 41 and a discharge side casing 42 as a first casing segment and a second casing segment that are joined to each other. The liquid recovery mechanism 70 has a liquid supply groove 72 that opens on the second inner circumferential surface 47 (inner circumferential surface) that is a part of the wall surface forming the storage chamber 45 at the position of the joint surface 41a of the casing 4 and extends in the circumferential direction of the second inner circumferential surface 47 (inner circumferential surface), an introduction passage 73 that is formed at the position of the joint surface 41a and is connected to one end of the liquid supply groove 72 that is located on the rear side in the rotation direction of the female rotor 3 (screw rotor), and a recovery passage 71 that connects the suction side bearing chambers 51, 52 (bearing chambers) and the introduction passage 73. The liquid supply groove 72 and the introduction passage 73 are connected via a connection part 74. The connection part 74 has a surface including a tangent L1 of one end 72aP on the bottom surface 72a of the liquid supply groove 72 as a boundary surface with the introduction passage 73. The connection part 74 is configured so that the opening area S1 of the opening 74a that opens on the second inner circumferential surface 47 (inner circumferential surface) is smaller than the area S2 of the boundary surface.

[0056] According to this configuration, the opening area S1 on the second inner circumferential surface 47 (inner circumferential surface) at the connection portion 74 between the liquid supply groove 72 and the introduction passage 73 is made smaller than the area S2 of the boundary surface with the introduction passage 73, so that the acceleration of the liquid in the connection portion 74 by the rotating female rotor 3 (screw rotor) is suppressed, and the backflow vortex V generated when the liquid is introduced from the introduction passage 73 to the liquid supply groove 72 through the connection portion 74 can be suppressed. Therefore, when the shear force generated in the liquid by contact with the female rotor 3 (screw rotor) is used as the driving force for flowing the liquid in the liquid supply groove 72 into the accommodation chamber 45 (operation chamber C), the necessary flow rate from the introduction passage 73 to the liquid supply groove 72 can be secured. In other words, the amount of liquid recovered from the suction side bearing chambers 51, 52 (bearing chambers) to the operation chamber C can be secured without increasing the pressure in the suction side bearing chambers 51, 52 (bearing chambers).

[0057] Furthermore, in the liquid recovery mechanism 70 of the screw compressor 1 of this embodiment, the liquid supply groove 72 is arranged at a circumferential position on the second inner surface 47 (inner surface) corresponding to the area where the working chamber C is in the suction stroke at the position of the joint surface 41a.

[0058] According to this configuration, the liquid in the suction side bearing chambers 51, 52 (bearing chambers) can be recovered in the working chamber C during the suction stroke, avoiding the suction space 62 where large suction losses are expected, thereby contributing to improving the energy efficiency of the compressor 1.

[0059] In the liquid recovery mechanism 70 of the screw compressor 1 according to this embodiment, the liquid supply groove 72 is configured so that its length in the extending direction is greater than the thickness of the tooth tip of the female rotor 3 (screw rotor).

[0060] According to this configuration, regardless of the rotation angle of the female rotor 3 (screw rotor), the opening 72d of the liquid supply groove 72 is not completely blocked by the teeth of the female rotor 3 (screw rotor), and therefore the liquid is not prevented from flowing out from the opening 72d of the liquid supply groove 72 to the working chamber C. Therefore, a sufficient flow rate of liquid can be ensured to flow out from the opening 72d of the liquid supply groove 72 to the working chamber C.

[0061] In the liquid recovery mechanism 70 of the screw compressor 1 according to the present embodiment, the introduction passage 73 is connected to the liquid supply groove 72 at an obtuse angle relative to the extension direction of the liquid supply groove 72 .

[0062] With this configuration, it is possible to realize a connection portion 74 with a simple shape, in which the opening area S1 of the opening 74a opening onto the second inner surface 47 (inner surface) is smaller than the area S2 of the boundary surface with the introduction passage 73.

[0063] In the liquid recovery mechanism 70 of the screw compressor 1 according to the present embodiment, a first groove 41g1 is provided on the joint surface 41a of the casing 4 so as to open to the second inner circumferential surface 47 (inner circumferential surface), a hole portion 41h is provided so as to open at a position away from the wall surfaces 46, 47 of the storage chamber 45, and a second groove 41g2 is formed so as to be connected to the first groove 41g1 and to the opening of the hole portion 41h. The liquid supply groove 72 is configured by blocking the opening of the first groove 41g1 on the joint surface 41a by the joint between the main casing 41 and the discharge side casing 42 (the first casing segment and the second casing segment). The introduction passage 73 is configured by blocking the opening of the second groove 41g2 on the joint surface 41a by the joint between the main casing 41 and the discharge side casing 42 (the first casing segment and the second casing segment). A fourth recovery path portion 714 (downstream end portion) of the recovery path 71 is formed by a hole portion 41h.

[0064] According to this configuration, the liquid supply groove 72 and the introduction passage 73 as structural parts that utilize the shear force generated in the liquid by contact with the rotating female rotor 3 (screw rotor) as a driving force for recovering the liquid from the suction side bearing chambers 51, 52 (bearing chambers) to the working chamber C can be formed simply by providing the first groove 41g1 and the second groove 41g2 by machining or the like on the joint surface 41a of the casing 4. Therefore, the structural part that utilizes the shear force generated in the liquid is easy to manufacture.

[0065] Furthermore, the liquid recovery mechanism 70 of the screw compressor 1 according to this embodiment recovers liquid in the suction side bearing chambers 51, 52 in which the suction side bearings 5, 7 supporting the axial suction sides of the male rotor 2 and female rotor 3 (screw rotors) are disposed. With this configuration, liquid is recovered from the suction side bearing chambers 51, 52 (bearing chambers) to the working chamber C without increasing the pressure in the suction side bearing chambers 51, 52 (bearing chambers), making it unnecessary to provide a separate sealing mechanism for preventing leakage of liquid from the suction side bearing chambers 51, 52 (bearing chambers) to the adjacent suction space.

[0066] Furthermore, in the screw compressor 1 according to this embodiment, the casing 4 is configured to be divided at the position of the axial discharge side end in the accommodation chamber 45, and the first casing segment is the main casing 41 in which the space of the accommodation chamber 45 is formed and which is open on the axial discharge side, and the second casing segment is the discharge side casing 42 which is joined to the main casing 41 and closes the opening of the main casing 41.

[0067] According to this configuration, the liquid supply groove 72 and introduction path 73 of the liquid recovery mechanism 70 are formed at the joint surface 41a of the main casing 41, which is located at the axial discharge side end of the storage chamber 45, which is the position farthest from the suction space 62 adjacent to the axial suction side end of the storage chamber 45 of the casing 4, so that the effect of the liquid recovered from the liquid supply groove 72 to the working chamber C on the suction space 62 can be extremely reduced.

[0068] [Modification of the first embodiment] Next, a screw compressor according to a modified example of the first embodiment will be described with reference to Fig. 8. Fig. 8 is a schematic diagram showing the structure of the introduction passage and liquid supply groove of the liquid recovery mechanism in the screw compressor according to a modified example of the first embodiment in an enlarged state similar to Fig. 5. In Fig. 8, the same reference numerals as those in Figs. 1 to 7 denote similar parts, and therefore detailed description thereof will be omitted.

[0069] A liquid recovery mechanism 70A of a screw compressor according to a modification of the first embodiment shown in Figure 8 differs from liquid recovery mechanism 70 of the first embodiment (see Figure 5) in that the structure of connecting portion 74A interposed between introduction path 73 and liquid supply groove 72 is different. Other than that, the structure of liquid recovery mechanism 70A according to this modification is similar to the structure of liquid recovery mechanism 70 according to the first embodiment.

[0070] Specifically, connecting portion 74A does not have an opening 74a that opens onto the second inner circumferential surface 47 of casing 4 at a position upstream of straight line L2. That is, connecting portion 74 is connected to liquid supply groove 72 without opening onto the second inner circumferential surface 47 of casing 4. That is, connecting portion 74A is configured such that the opening area S1 of opening 74a on the second inner circumferential surface 47 is 0 (S2>S1=0). Therefore, in liquid recovery mechanism 70A, only opening 72d of liquid supply groove 72 opens onto the second inner circumferential surface 47.

[0071] According to the above-mentioned modification of the first embodiment, as in the first embodiment, the opening area S1 on the second inner circumferential surface 47 (inner circumferential surface) at the connection portion 74A between the liquid supply groove 72 and the introduction passage 73 is made smaller than the area S2 of the boundary surface with the introduction passage 73, so that the acceleration of the liquid in the connection portion 74A by the rotating female rotor 3 (screw rotor) is suppressed, and the backflow vortex V generated when the liquid is introduced from the introduction passage 73 to the liquid supply groove 72 through the connection portion 74A can be suppressed. Therefore, when the shear force generated in the liquid by contact with the female rotor 3 (screw rotor) is used as the driving force for flowing the liquid in the liquid supply groove 72 into the accommodation chamber 45 (operation chamber C), the necessary flow rate from the introduction passage 73 to the liquid supply groove 72 can be secured. That is, the amount of liquid recovered from the suction side bearing chambers 51, 52 (bearing chambers) to the operation chamber C can be secured without increasing the pressure of the suction side bearing chambers 51, 52 (bearing chambers).

[0072] Furthermore, in liquid recovery mechanism 70A according to this modified example, connection portion 74A is configured so that opening area S1 of opening 74a on second inner circumferential surface 47 is zero.

[0073] According to this configuration, since the connection part 74A does not open on the second inner peripheral surface 47 (inner peripheral surface), the liquid in the connection part 74A is not accelerated due to contact with the rotating female rotor 3 (screw rotor). Therefore, the backflow vortex V generated when the liquid is introduced from the introduction passage 73 to the liquid supply groove 72 via the connection part 74A is further suppressed, so that the flow rate of the liquid flowing from the introduction passage 73 to the liquid supply groove 72 can be further increased. In other words, the amount of liquid recovered from the suction side bearing chambers 51, 52 (bearing chambers) to the working chamber C can be increased without increasing the pressure in the suction side bearing chambers 51, 52 (bearing chambers).

[0074] [Second embodiment] Next, a screw compressor according to a second embodiment of the present invention will be described with reference to Fig. 9. Fig. 9 is a view of the screw compressor according to the second embodiment as seen from the same arrow direction as Fig. 4 (arrow IV-IV in Fig. 1). In Fig. 9, the thick arrow indicates the rotation direction of the screw rotor. In Fig. 9, the same reference numerals as those in Figs. 1 to 8 denote similar parts, and therefore detailed description thereof will be omitted.

[0075] A liquid recovery mechanism 70B of a screw compressor 1 according to the second embodiment shown in Figure 9 differs from the liquid recovery mechanism 70 according to the first embodiment (see Figure 4) in that the liquid recovery mechanism 70B has not one recovery path from the suction side bearing chambers 51, 52 to the working chamber C on the female rotor 3 side, but branches into two on the joint surface 41a of the casing 4. Other than that, the structure of the liquid recovery mechanism 70B according to the present embodiment is similar to the structure of the liquid recovery mechanism 70 according to the first embodiment.

[0076] Specifically, liquid recovery mechanism 70B includes, in addition to one path of first liquid supply groove 72 and first introduction path 73 similar to those in the first embodiment, another path of second liquid supply groove 75 and second introduction path 76 at the position of joint surface 41a on the discharge side of main casing 41. Since first liquid supply groove 72 and first introduction path 73 are similar to those in the first embodiment, a description thereof will be omitted.

[0077] The second liquid supply groove 75 has a structure similar to that of the first liquid supply groove 72. That is, the second liquid supply groove 75 is a groove that opens on the second inner peripheral surface 47 of the casing 4 at the position of the joint surface 41a on the discharge side of the main casing 41, extends along the circumferential direction of the second inner peripheral surface 47, and has a depth direction toward the radially outer side of the female rotor 3. The second liquid supply groove 75 is located forward of the first liquid supply groove 72 in the rotation direction of the female rotor 3, but is arranged (opens) at a circumferential position corresponding to the region where the working chamber C is in the suction stroke or the region where the compression stroke starts at the position of the discharge side end surface 31c of the female rotor 3. The second liquid supply groove 75 is configured so that the liquid flows in the same direction as the rotation direction of the female rotor 3, and is configured so that the liquid in the introduction passage 73 is introduced to one end located on the rear side in the rotation direction of the female rotor 3, and the other end located on the front side in the rotation direction of the female rotor 3 is the downstream end. The second liquid supply groove 75 is formed by providing a third groove 41g3 on the joint surface 41a of the main casing 41 by machining or the like, extending along the second inner surface 47 so as to open onto the second inner surface 47 of the casing 4, and by joining the discharge side casing 42 to the joint surface 41a of the main casing 41 so as to close the opening of the third groove 41g3 on the joint surface 41a.

[0078] The second introduction passage 76, like the first introduction passage 73, is formed at the position of the joint surface 41a of the main casing 41, and introduces the liquid in the fourth recovery passage part 714 of the recovery passage 71 to one end of the second liquid supply groove 75. One side of the second introduction passage 76 is connected to an opening on the joint surface 41a of the main casing 41 in the fourth recovery passage part 714, and the other side is connected to one end of the second liquid supply groove 75 located on the rear side in the rotation direction of the female rotor 3 (the left end of the second liquid supply groove 75 in FIG. 9). The second introduction passage 76 is configured such that a fourth groove 41g4 dug in the axial direction on the joint surface 41a of the main casing 41 is connected to the third groove 41g3 by machining or the like, and the discharge side casing 42 is joined to the joint surface 41a of the main casing 41 to close the opening of the fourth groove 41g4 on the joint surface 41a.

[0079] The connection portion between the second liquid supply groove 75 and the second introduction path 76 has a structure similar to that of the connection portion 74 between the first liquid supply groove 72 and the first introduction path 73 (see FIG. 5).

[0080] According to the second embodiment described above, as in the first embodiment, the acceleration of the liquid in the connection between the liquid supply grooves 72, 75 and the introduction passages 73, 76 due to the rotating female rotor 3 (screw rotor) is suppressed, so that it is possible to suppress the backflow vortex V that occurs when the liquid is introduced from the introduction passages 73, 76 to the liquid supply grooves 72, 75 through the connection portion. Therefore, when the shear force generated in the liquid due to contact with the female rotor 3 (screw rotor) is used as the driving force for moving the liquid in the liquid supply grooves 72, 75 into the accommodation chamber 45 (working chamber C), it is possible to ensure the necessary flow rate from the introduction passages 73, 76 to the liquid supply grooves 72, 75. In other words, it is possible to ensure the recovery amount of the liquid from the suction side bearing chambers 51, 52 (bearing chambers) to the working chamber C without increasing the pressure in the suction side bearing chambers 51, 52 (bearing chambers).

[0081] Furthermore, liquid recovery mechanism 70B according to the present embodiment has a plurality of liquid supply grooves 72, 75 and introduction paths 73, 76. Liquid supply grooves 72, 75 are arranged at intervals in the circumferential direction of second inner circumferential surface 47 (inner circumferential surface).

[0082] According to this configuration, the shear force generated in the liquid by contact with the female rotor 3 (screw rotor) for the multiple liquid supply grooves 72, 75 can be used as a driving force, thereby efficiently recovering liquid from the suction side bearing chambers 51, 52 (bearing chambers) to the accommodating chamber 45 (working chamber C).

[0083] [Third embodiment] Next, a screw compressor according to a third embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 is a view of the screw compressor according to the third embodiment as seen from the same arrow direction as Fig. 4 (arrow IV-IV in Fig. 1). In Fig. 10, the thick arrow indicates the rotation direction of the screw rotor. In Fig. 10, the same reference numerals as those in Figs. 1 to 9 denote similar parts, and therefore detailed description thereof will be omitted.

[0084] A liquid recovery mechanism 70C of a screw compressor 1 of the third embodiment shown in Figure 10 differs from the liquid recovery mechanism 70 of the first embodiment (see Figure 4) in that, in addition to a path for recovering liquid from the suction side bearing chambers 51, 52 to the working chamber C on the female rotor 3 side, the liquid recovery mechanism 70C of the present embodiment is provided with a path for recovering liquid from the suction side bearing chambers 51, 52 to the working chamber C on the male rotor 2 side. Other structures of the liquid recovery mechanism 70C of the present embodiment are similar to the structures of the liquid recovery mechanism 70 of the first embodiment.

[0085] Specifically, the liquid recovery mechanism 70C includes a first liquid supply groove 72 and a first introduction passage 73 which are paths for recovering liquid to the working chamber C on the female rotor 3 side and which are similar to those in the first embodiment, as well as a second liquid supply groove 75C and a second introduction passage 76C which are paths for recovering liquid to the working chamber C on the male rotor 2 side, located at the position of the joint surface 41a on the discharge side of the main casing 41. The first liquid supply groove 72 and the first introduction passage 73 are similar to those in the first embodiment, and therefore a description thereof will be omitted.

[0086] The second liquid supply groove 75C is a groove that opens on the first inner circumferential surface 46 that constitutes a part of the wall surface of the housing chamber 45 of the casing 4 at the position of the joint surface 41a on the discharge side of the main casing 41, extends along the circumferential direction of the first inner circumferential surface 46, and has a depth direction toward the radially outer side of the male rotor 2. The second liquid supply groove 75C is disposed (opens) at a circumferential position corresponding to the region where the working chamber C is in the suction stroke or the region where the compression stroke starts at the position of the discharge side end surface 21c of the male rotor 2. The second liquid supply groove 75C is configured so that the liquid flows in the same direction as the rotation direction of the male rotor 2, and is configured so that the liquid in the second introduction passage 76C is introduced to one end (the right end in FIG. 10) located on the rear side of the rotation direction of the male rotor 2, and the other end (the left end in FIG. 10) located on the front side of the rotation direction of the male rotor 2 is the downstream end. The second liquid supply groove 75C is formed by providing a third groove 41g3C on the joint surface 41a of the main casing 41 by machining or the like, extending along the first inner surface 46 so as to open onto the first inner surface 46 of the casing 4, and by joining the discharge side casing 42 to the joint surface 41a of the main casing 41 so as to close the opening of the third groove 41g3C on the joint surface 41a.

[0087] The second introduction passage 76C is formed at the position of the joint surface 41a of the main casing 41, and introduces the liquid in the fourth recovery passage part 714 of the recovery passage 71 to one end of the second liquid supply groove 75C. One side of the second introduction passage 76C is connected to an opening on the joint surface 41a of the main casing 41 in the fourth recovery passage part 714, and the other side is connected to one end of the second liquid supply groove 75C located on the rear side in the rotation direction of the female rotor 3 (the left end of the second liquid supply groove 75C in FIG. 9). The second introduction passage 76C is provided so that a fourth groove 41g4C dug in the axial direction on the joint surface 41a of the main casing 41 is connected to the third groove 41g3C by machining or the like, and is configured by joining the discharge side casing 42 to the joint surface 41a of the main casing 41 to close the opening on the joint surface 41a of the fourth groove 41g4C.

[0088] The connection portion between the second liquid supply groove 75C and the second introduction path 76C has a structure similar to that of the connection portion 74 between the first liquid supply groove 72 and the first introduction path 73 (see FIG. 5).

[0089] According to the above-mentioned third embodiment, as in the first embodiment, the acceleration of the liquid in the connection part between the first liquid supply groove 72 and the introduction passage 73 due to the rotating female rotor 3 (screw rotor) is suppressed, so that it is possible to suppress the backflow vortex V that occurs when the liquid is introduced from the first introduction passage 73 to the first liquid supply groove 72 through the connection part. Similarly, the acceleration of the liquid in the connection part between the second liquid supply groove 75C and the introduction passage 76C due to the rotating male rotor 2 (screw rotor) is suppressed, so that it is possible to suppress the backflow vortex V that occurs when the liquid is introduced from the second introduction passage 76C to the second liquid supply groove 75C through the connection part. Therefore, when the shear force generated in the liquid due to contact with the female rotor 3 and the male rotor 2 (screw rotor) is used as the driving force for flowing the liquid in the liquid supply grooves 72 and 75C into the accommodation chamber 45 (operation chamber C), it is possible to ensure the necessary flow rate from the introduction passages 73 and 76C to the liquid supply grooves 72 and 75C. That is, the amount of liquid recovered from the suction side bearing chambers 51, 52 (bearing chambers) to the working chamber C can be ensured without increasing the pressure in the suction side bearing chambers 51, 52 (bearing chambers).

[0090] The screw compressor 1 according to the present embodiment includes a pair of screw rotors, a male rotor 2 and a female rotor 3, and an accommodation chamber 45 of the casing 4 has a first inner circumferential surface 46 located radially outward of the male rotor 2 (one of the pair of screw rotors) and a second inner circumferential surface 47 located radially outward of the female rotor 3 (the other of the pair of screw rotors). The liquid recovery mechanism 70C has a plurality of liquid supply grooves 72, 75C and introduction paths 73, 76C. The liquid supply groove 75C (one of the liquid supply grooves) is configured to open onto the first inner circumferential surface 46 at the position of the joint surface 41a of the casing 4 and extend in the circumferential direction of the first inner circumferential surface 46. The liquid supply groove 72 (another of the liquid supply grooves) is configured to open onto the second inner circumferential surface 47 at the position of the joint surface 41a of the casing 4 and extend in the circumferential direction of the second inner circumferential surface 47.

[0091] According to this configuration, the shear force generated in the liquid by contact with the male rotor 2 (screw rotor) for the liquid supply groove 75C (one of the liquid supply grooves) can be used as a driving force, and the shear force generated in the liquid by contact with the female rotor 3 (screw rotor) for the liquid supply groove 72 (another of the liquid supply grooves) can be used as a driving force, so that liquid can be efficiently recovered from the suction side bearing chambers 51, 52 (bearing chambers) to the accommodating chamber 45 (working chamber C).

[0092] [Fourth embodiment] Next, a screw compressor according to a fourth embodiment of the present invention will be described with reference to Fig. 11. Fig. 11 is a vertical sectional view of the screw compressor according to the fourth embodiment, taken from the same arrow direction as Fig. 2 (arrow II-II in Fig. 1). In Fig. 11, the same reference numerals as those in Figs. 1 to 10 denote similar parts, and therefore detailed description thereof will be omitted.

[0093] A liquid recovery mechanism 70D of a screw compressor 1 according to the fourth embodiment shown in Figure 11 differs from liquid recovery mechanism 70 according to the first embodiment (see Figure 2) in that the liquid recovery mechanism 70D does not recover liquid supplied to the suction side bearings 5, 7, but is configured to recover liquid supplied to the discharge side bearings 6, 8. Other than that, the structure of liquid recovery mechanism 70D according to the present embodiment is similar to the structure of liquid recovery mechanism 70 according to the first embodiment.

[0094] Specifically, the liquid recovery mechanism 70D is a path that extends from the discharge side bearing chambers 54, 55 (see FIG. 1) of the casing 4 to the position of the joint surface 41a of the main casing 41 and to an opening on the second inner circumferential surface 47 of the casing 4. Specifically, the liquid recovery mechanism 70D is composed of, for example, a recovery path 71D that extends from the discharge side bearing chambers 54, 55 of the casing 4 to the joint surface 42a of the discharge side casing 42 with the main casing 41, a liquid supply groove (not shown in FIG. 11) that opens onto the second inner circumferential surface 47 of the casing 4 at the position of the joint surface 41a of the main casing 41, and an introduction path 73D for guiding the liquid in the recovery path 71D to the liquid supply groove. The liquid supply groove of this embodiment has a structure similar to that of the liquid supply groove 72 of the first embodiment, and therefore a description thereof will be omitted.

[0095] The recovery passage 71D of the liquid recovery mechanism 70D connects the introduction passage 73 located on the joint surface 41a of the main casing 41 with the discharge side bearing chambers 54 and 55 of the casing 4. The recovery passage 71D is composed of a recovery passage first section 711D, a recovery passage second section 712D, and a recovery passage fourth section 714D, in that order from the upstream side. The recovery passage first section 711 is connected to the discharge side bearing chambers 54 and 55. The recovery passage first section 711 is configured as a hole section formed in the discharge side casing 42. The recovery passage second section 712D is connected on one side to the recovery passage first section 711D and on the other side to the recovery passage fourth section 714D. The recovery passage second section 712D is configured as a hole section formed in the discharge side casing 42, and extends in a direction perpendicular to a plane including the axis A1 of the male rotor 2 and the axis A2 of the female rotor 3. The other side of the second recovery path portion 712D opens onto the outer wall surface of the discharge side casing 42 on the opposite side to the discharge side flow path 64, and this opening is closed by the second plug .

[0096] One side of the fourth recovery path portion 714D is connected to the second recovery path portion 712D, and the other side is connected to the introduction path 73D. The fourth recovery path portion 714D is configured as a hole portion formed in the discharge side casing 42. One side of the fourth recovery path portion 714D opens onto the end face of the discharge side casing 42 opposite to the joint surface 42a, and the other side opens onto the joint surface 42a of the discharge side casing 42. One opening of the hole portion constituting the fourth recovery path portion 714D is blocked by a third plug 83.

[0097] The introduction path 73D is formed at the position of the joint surface 41a of the main casing 41, and is configured to overlap a part of an opening of the recovery path fourth part 714D of the recovery path 71D on the joint surface 42a of the discharge side casing 42. As a result, the introduction path 73D is connected to the downstream end of the recovery path fourth part 714D of the recovery path 71D. The connection structure (connection part) between the introduction path 73D and the liquid supply groove is similar to the connection structure (connection part 74) between the introduction path 73 and the liquid supply groove 72 in the first embodiment, and therefore a description thereof will be omitted.

[0098] According to the above-described fourth embodiment, as in the first embodiment, the amount of liquid recovered from the discharge side bearing chambers 54, 55 (bearing chambers) to the working chamber C can be ensured without increasing the pressure in the discharge side bearing chambers 54, 55 (bearing chambers).

[0099] Moreover, the liquid recovery mechanism 70D of the screw compressor 1 according to this embodiment recovers liquid from the discharge side bearing chambers 54, 55 in which the discharge side bearings 6, 8 supporting the axial discharge sides of the male rotor 2 and the female rotor 3 (screw rotors) are disposed. With this configuration, liquid is recovered from the discharge side bearing chambers 54, 55 to the working chamber C without increasing the pressure in the discharge side bearing chambers 54, 55, so there is no need to provide a separate seal mechanism for preventing leakage of liquid from the discharge side bearing chambers 54, 55 to the adjacent low pressure space. Also, the recovery passage 71 connecting the discharge side bearing chambers 54, 55 and the introduction passage 73D can be formed only by a hole formed in the casing 4 (discharge side casing 42) without using piping, which allows the configuration of the liquid recovery mechanism 70D to be simplified.

[0100] [Other embodiments] The present invention is not limited to the above-described embodiment, but includes various modified examples. The above-described embodiment has been described in detail to easily explain the present invention, and is not necessarily limited to those having all of the configurations described. That is, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0101] For example, in the above-mentioned first to fourth embodiments, a twin-rotor screw compressor including a pair of screw rotors 2, 3 and a casing 4 rotatably housing both screw rotors 2, 3 has a liquid recovery mechanism 70, 70A, 70B, 70C, 70D that recovers liquid from the suction bearing chamber 51, 52 or the discharge-side bearing chamber 54, 55 to the working chamber C. However, the configuration and structure of the liquid recovery mechanism 70, 70A, 70B, 70D other than that of the above-mentioned third embodiment can be applied to a single-rotor screw compressor having only one screw rotor. That is, even in a single-rotor screw compressor, a structure similar to the liquid supply groove 72 and the introduction path 73, 73D of the above-mentioned liquid recovery mechanism 70, 70A, 70B, 70D can be obtained by providing a liquid supply groove that opens to the inner circumferential surface of the housing chamber at the position of the joint surface of the casing and an introduction path that is connected to one side of the liquid supply groove at the position of the joint surface of the casing.

[0102] It is also possible to combine the liquid recovery mechanism 70 of the first embodiment and the liquid recovery mechanism 70D of the fourth embodiment. That is, the liquid recovery mechanism can simultaneously recover the liquid in the suction bearing chambers 51, 52 and the discharge side bearing chambers 54, 55 into the accommodation chamber 45 (working chamber C) of the casing. In this case, it is possible to recover the liquid from the suction bearing chambers 51, 52 and the discharge side bearing chambers 54, 55 into the working chamber C via one liquid supply groove 72. It is also possible to recover the liquid from the suction bearing chambers 51, 52 into the working chamber C via one liquid supply groove 72, and recover the liquid from the discharge side bearing chambers 54, 55 into the working chamber C via another liquid supply groove.

[0103] In the above-described embodiment, an example of a structure in which the casing 4 is divided into the main casing 41 and the discharge-side casing 42 so as to be joined at the position of the discharge-side inner wall surface 49, which is the axial discharge-side end of the storage chamber 45, has been shown. However, the casing may also be configured to join a first casing segment and a second casing segment that are divided at a dividing surface (see, for example, the two-dot chain line S shown in FIG. 1) perpendicular to the axes A1 and A2 within a predetermined axial range from the axial discharge-side end (the position of the discharge-side inner wall surface 49) of the storage chamber 45. Even in the case of this configuration, it is possible to form the liquid supply groove and the introduction path of the liquid recovery mechanism at the position of the joining surface of the first casing segment and the second casing segment.

[0104] In the above-described embodiment, an example has been shown in which the length of the liquid supply groove 72 in the extension direction is set to be greater than the thickness of the tooth tips of the female rotor 3. However, the liquid supply groove can also be configured so that its length in the extension direction is smaller than the thickness of the tooth tips of the female rotor 3. Even in this case, the effect of impeding the outflow of liquid from the liquid supply groove to the working chamber is not significant.

[0105] Further, in the above-described embodiment, the connection portion 74 between the liquid supply groove 72 and the introduction passage 73 in the liquid recovery mechanism 70 is configured such that the opening area S1 of the opening portion 74a is smaller than the area S2 (flow path cross-sectional area) of the boundary surface with respect to the introduction passage 73 (S1 < S2). At this time, as shown in FIG. 5, the connection portion 74 is configured such that the opening area S1 is smaller than the area S2 due to the difference between the width on the joint surface 41a in the opening portion 74a and the width on the joint surface 41a in the boundary surface (the surface including the straight line L1).

[0106] However, as shown in FIG. 12, the connection portion 74F of the liquid recovery mechanism 70F can also be configured such that the opening area S1 is smaller than the area S2 due to the difference between the depth D1 (axial distance) from the joint surface 41a of the main casing 41 in the opening portion 74a and the depth D2 from the joint surface 41a of the main casing 41 in the boundary surface (the surface including the straight line L1). That is, the connection portion 74F is configured such that the depth D1 of the opening portion 74a is smaller than the depth D2 of the boundary surface. Also with this configuration, since the opening area S1 on the second inner peripheral surface 47 in the connection portion 74F is smaller than the area S2 of the boundary surface with the introduction passage 73, the acceleration of the liquid in the connection portion 74F by the rotating female rotor 3 (screw rotor) is suppressed, and the reverse flow vortex V generated when the liquid is introduced from the introduction passage through the connection portion 74F into the liquid supply groove 72 can be suppressed.

[0107] Also, in the above-described embodiment, an example of the configuration in which the introduction passage 73 of the liquid recovery mechanism 70 is bent and connected to the liquid supply groove 72 is shown. However, the introduction passage can also be configured to extend linearly and be connected to the liquid supply groove 72.

Explanation of Reference Numerals

[0108] REFERENCE SIGNS LIST 1...screw compressor, 2...male rotor (screw rotor), 3...female rotor (screw rotor), 4...casing, 5, 7...suction side bearing (bearing), 6, 8...discharge side bearing (bearing), 41...main casing (first casing segment), 41a...joint surface, 42...discharge side casing (second casing segment), 45...accommodating chamber, 46...first inner circumferential surface (inner circumferential surface), 47...second inner circumferential surface (inner circumferential surface), 51, 52...suction side bearing chamber (bearing chamber), 54, 55...discharge side bearing chamber (bearing chamber), 70, 70A, 70B, 70C, 70D, 70F...liquid recovery mechanism, 71, 71D...recovery passage, 72...liquid supply groove, 72a...bottom surface, 73, 73D...introduction passage, 74, 74A, 74F...connection portion; 74a...opening portion; 75, 75C...second liquid supply groove; 76, 76C...second introduction passage; L1...tangent line; S1...opening area; S2...area; C...operating chamber

Claims

1. At least one screw rotor; a bearing that rotatably supports the screw rotor; a casing including a housing chamber for rotatably housing the screw rotor and a bearing chamber in which the bearing is disposed, the casing forming an operating chamber together with the screw rotor; a liquid recovery mechanism that recovers the lubricating liquid supplied to the bearing from the bearing chamber into the accommodation chamber, the casing includes a first casing segment and a second casing segment joined together; The liquid recovery mechanism includes: a liquid supply groove that opens onto an inner circumferential surface that is a part of a wall surface that forms the storage chamber at a position of a joint surface of the casing and extends in a circumferential direction of the inner circumferential surface; an introduction passage formed at the joint surface and connected to one end of the liquid supply groove located on the rear side in the rotation direction of the screw rotor; a recovery passage connecting the bearing chamber and the introduction passage, the liquid supply groove and the introduction path are connected via a connection part; the connection portion has a surface including a tangent to the one end portion on a bottom surface of the liquid supply groove as a boundary surface with respect to the introduction path, The connecting portion is configured so that an opening area of ​​the opening that opens onto the inner circumferential surface is smaller than an area of ​​the boundary surface. Screw compressor.

2. 2. The screw compressor according to claim 1, The fluid supply groove is disposed at a circumferential position on the inner peripheral surface corresponding to a region where the working chamber is in a suction stroke at the position of the joint surface. Screw compressor.

3. 2. The screw compressor according to claim 1, The length of the liquid supply groove in the extending direction is greater than the thickness of the tooth tip of the screw rotor. Screw compressor.

4. 2. The screw compressor according to claim 1, The introduction passage is connected to the liquid supply groove at an obtuse angle with respect to the extending direction of the liquid supply groove. Screw compressor.

5. 2. The screw compressor according to claim 1, The connection portion is configured so that the opening area of ​​the opening is zero. Screw compressor.

6. 2. The screw compressor according to claim 1, the liquid recovery mechanism includes a plurality of the liquid supply grooves and the introduction paths; The liquid supply grooves are arranged at intervals in the circumferential direction of the inner circumferential surface. Screw compressor.

7. 2. The screw compressor according to claim 1, The at least one screw rotor is composed of a pair of screw rotors, The housing chamber of the casing has a first inner circumferential surface located radially outward of one of the pair of screw rotors and a second inner circumferential surface located radially outward of the other of the pair of screw rotors, the liquid recovery mechanism includes a plurality of the liquid supply grooves and the introduction paths; one of the liquid supply grooves is configured to open onto the first inner circumferential surface at the position of the joint surface of the casing and to extend in a circumferential direction of the first inner circumferential surface; Another one of the liquid supply grooves is configured to open onto the second inner circumferential surface at the position of the joint surface of the casing and to extend in a circumferential direction of the second inner circumferential surface. Screw compressor.

8. 2. The screw compressor according to claim 1, a first groove is provided on the joint surface of the casing so as to open into the inner circumferential surface; a hole portion is provided on the joint surface of the casing so as to open at a position away from a wall surface of the storage chamber; a second groove is provided on the joint surface of the casing so as to be connected to the first groove and to an opening of the hole portion; the liquid supply groove is configured such that an opening of the first groove on the joining surface is closed by joining the first casing segment and the second casing segment, the introduction passage is configured such that an opening of the second groove on the joining surface is closed by joining the first casing segment and the second casing segment, The downstream end of the recovery path is constituted by the hole. Screw compressor.

9. 9. The screw compressor according to claim 8, The connection portion is configured such that a depth of the opening from the joining surface of the casing is smaller than a depth of the boundary surface from the joining surface of the casing. Screw compressor.

10. 2. The screw compressor according to claim 1, the bearing is a suction side bearing that supports an axial suction side of the screw rotor, The bearing chamber is a suction side bearing chamber in which the suction side bearing is disposed. Screw compressor.

11. 2. The screw compressor according to claim 1, the bearing is a discharge side bearing that supports an axial discharge side of the screw rotor, The bearing chamber is a discharge-side bearing chamber in which the discharge-side bearing is disposed. Screw compressor.

12. 2. The screw compressor according to claim 1, The casing is configured to be divided at a position of a discharge side end of the accommodation chamber in an axial direction, the first casing segment is a main casing in which the space of the accommodation chamber is formed and which is open on an axial discharge side, The second casing segment is a discharge-side casing that is joined to the main casing and closes an opening of the main casing. Screw compressor.

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