Screw type fluid machine

Abstract

A screw compressor (1) is provided with a housing (2). The housing (2) is provided with an intake port (11), a discharge port (22), a rotor housing section (14), bearing housing sections (21f, 21m) for housing bearings (40f, 40m) for axially supporting shaft sections (31f, 31m) on the other end side of the screw rotor (30), and shaft hole sections (25f, 25m) which are disposed between the rotor housing section (14) and the bearing housing sections (21f, 21m) and through which the shaft sections (31f, 31m) are inserted. The rotor housing section (14) is configured so as to communicate with the supply paths (26f, 26m) and so as to suppress leakage of gas from the rotor housing section (14) to the bearing housing sections (21f, 21m) by means of the liquid supplied from the supply paths (26f, 26m). When viewed in the axial direction of the screw rotor (30), the center lines (Cf2, Cm2) of the shaft hole sections (25f, 25m) are located farther from the discharge port (22) than the center lines (Cf1, Cm1) of the bearing housing sections (21f, 21m).

Description

Technical Field

[0001] The present invention relates to a screw-type fluid machine. Background Art

[0002] A screw compressor, which is one of screw-type fluid machines, compresses gas by the rotational meshing of a pair of male and female screw rotors inside a housing. The housing is provided with a suction port on one end side and a discharge port on the other end side. The screw compressor sucks gas from the suction port, compresses the gas inside the housing, and discharges the compressed gas from the discharge port. Therefore, the pressure of the gas inside the housing gradually increases from one end side toward the other end side.

[0003] On the high-pressure side (the other end side) of the housing, not only is a discharge port provided, but also a shaft hole portion for inserting the shaft portion of the screw rotor is provided. Therefore, there is a possibility that high-pressure gas leaks through the shaft hole portion, and it is necessary to suppress the leakage of gas through the shaft hole portion.

[0004] For example, Patent Document 1 discloses a screw compressor in which a sealing member is installed in the above-mentioned shaft hole portion to suppress gas leakage.

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-69186.

[0006] However, since the screw rotor compresses gas by rotational meshing, there is a pressure distribution in the circumferential direction, that is, there are high-pressure tooth groove portions and low-pressure tooth groove portions. In particular, there is a possibility that gas leaks through the shaft hole portion from the high-pressure tooth groove portion as described above, and it is necessary to suppress the leakage of gas. However, the screw compressor of Patent Document 1 does not have a structure corresponding to such a circumferential pressure distribution, so there is room for improvement. Summary of the Invention

[0007] An object of the present invention is to suppress the leakage of gas through a shaft hole portion in a screw-type fluid machine.

[0008] The present invention provides a screw-type fluid machine including a housing rotatably accommodating a screw rotor, the screw rotor having a main body portion and shaft portions provided at one end side and the other end side of the main body portion, respectively. In the screw-type fluid machine,

[0009] the housing includes:

[0010] a first port through which relatively low-pressure gas passes on one end side of the main body portion;

[0011] a second port through which relatively high-pressure gas passes on the other end side of the main body portion;

[0012] a rotor accommodating portion communicating with the first port and the second port and accommodating the main body portion;

[0013] A bearing housing that houses a bearing for axially supporting the shaft portion on the other end side;

[0014] A shaft hole portion is disposed between the rotor housing portion and the bearing housing portion, through which the shaft portion is inserted, and is configured to communicate with a supply path so as to suppress leakage of the gas from the rotor housing portion to the bearing housing portion by means of the liquid supplied from the supply path;

[0015] When viewed in the axial direction of the screw rotor, the center line of the shaft hole portion is located farther from the second port than the center line of the bearing housing portion.

[0016] According to this structure, since the center line of the shaft hole portion is located farther from the second port than the center line of the bearing housing portion, the shaft hole portion can be separated from the high-pressure tooth groove portion (near the second port) of the screw rotor, and gas leakage through the shaft hole portion can be suppressed. In a general screw-type fluid machine, a concentric structure in which the center line of the shaft hole portion and the center line of the bearing housing portion are aligned is adopted, but in the above structure, an eccentric structure in which the center line of the shaft hole portion is deviated from the second port compared with the concentric structure is adopted. In the eccentric structure, compared with the concentric structure, the clearance between the shaft hole portion of the high-pressure tooth groove portion and the shaft portion becomes narrower, and it is easy to seal this clearance with liquid. Thus, gas leakage from the high-pressure tooth groove portion through the shaft hole portion can be effectively suppressed. Here, the screw-type fluid machine includes a screw compressor and a screw expander. When the screw-type fluid machine is a screw compressor, the first port constitutes a suction port, and the second port constitutes a discharge port. When the screw-type fluid machine is a screw expander, the first port constitutes an exhaust port, and the second port constitutes a gas supply port.

[0017] Alternatively, when viewed in the axial direction of the screw rotor, the center line of the shaft hole portion is located farther from the second port than the center of the rotation axis of the screw rotor.

[0018] According to this structure, as a reference for separating the shaft hole portion from the high-pressure tooth groove portion of the screw rotor, not only the center line of the bearing housing portion but also the center of the rotation axis of the screw rotor is considered. In addition, leakage of gas generated during operation can be effectively suppressed through the shaft hole portion.

[0019] Alternatively, the bearing is a rolling bearing, and the center line of the bearing coincides with the center of the rotation axis of the screw rotor.

[0020] According to this structure, when the center line of the bearing and the center of the rotation axis of the rotor do not coincide, self-excited vibration of the screw rotor, which often becomes a problem when using a bearing other than a rolling bearing, is suppressed, and the screw-type fluid machine can be stably driven. Specifically, on the basis of using a rolling bearing, the center line of the bearing and the center of the rotation axis of the rotor coincide, so that the wobbling of the rotation axis of the screw rotor can be suppressed even when using a bearing.

[0021] Alternatively, in a cross-section perpendicular to the center line of the aforementioned shaft hole portion, the shape of the aforementioned shaft hole portion is circular.

[0022] According to this structure, the structure of the shaft hole portion can be simplified.

[0023] Alternatively, when viewed in the axial direction of the aforementioned screw rotor, the shaft hole portion is arranged such that the entire area of the shaft hole portion is located inside the root circle of the teeth of the aforementioned main body portion. Further, in a cross-section perpendicular to the center line of the shaft hole portion, the root circle of the teeth of the main body portion may be larger than the diameter of the shaft hole portion.

[0024] According to this structure, it can be configured to seal the shaft hole portion by means of the bottom portion of the teeth of the main body portion of the screw rotor, and the leakage of gas through the shaft hole portion can be more effectively suppressed.

[0025] Advantages of the Invention

[0026] According to the present invention, leakage of gas through the shaft hole portion can be suppressed in a screw-type fluid machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a perspective view from above of a screw-type fluid machine according to an embodiment of the present invention.

[0028] Figure 2 is Figure 1 a perspective view from below of the screw-type fluid machine.

[0029] Figure 3 is a perspective view of the rotor housing.

[0030] Figure 4 is a perspective view from the front of the bearing housing.

[0031] Figure 5 is a perspective view from the rear of the bearing housing.

[0032] Figure 6 is Figure 1 a longitudinal sectional view of the screw-type fluid machine taken along line VI-VI.

[0033] Figure 7 is Figure 6 an enlarged view of part VII.

[0034] Figure 8 is a schematic cross-sectional view of the screw rotor and the rotor receiving portion. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0036] Refer to Figure 1 and2 , a screw-type fluid machine 1 according to an embodiment of the present invention is, for example, a screw compressor. Therefore, the screw-type fluid machine 1 will also be referred to as a screw compressor 1 hereinafter. For the sake of explanation, in each figure, the X direction is set as the left-right direction, the Y direction is set as the front-back direction, and the Z direction is set as the up-down direction. However, this does not limit the arrangement direction of the screw compressor 1, and it is a setting for the convenience of explanation.

[0037] The screw compressor 1 sucks in external air, compresses it inside, and discharges it. However, any gas other than air can also be used as the compression target.

[0038] The screw compressor 1 has a housing 2 as a casing. The housing 2 rotatably accommodates a screw rotor 30 (refer to Figure 6 ) described later.

[0039] In the present embodiment, the housing 2 has a rotor housing 10 and a bearing housing 20 disposed on the front side of the rotor housing 10. The rotor housing 10 has a rotor accommodating portion 14 for accommodating a screw rotor 30 described later.

[0040] Also refer to Figure 3 , the rotor housing 10 has an air inlet (first port) 11 through which air at a relatively low pressure (atmospheric pressure in the present embodiment) passes. In the present embodiment, the air inlet 11 is provided at the upper part of the rotor housing 10. In addition, a ring-shaped flange portion 13 constituting a joint surface for joining with the bearing housing 20 is provided at the front end of the rotor housing 10.

[0041] The rotor housing 10 has a rotor accommodating portion 14 for accommodating main body portions 32f, 32m (refer to Figure 6 ) of a screw rotor 30 described later. The rotor accommodating portion 14 is a double-cylindrical shape having parallel center lines Cf1, Cm1 extending in the front-back direction. The rotor accommodating portion 14 communicates with the air inlet 11.

[0042] Also refer to Figures 4 to 6 , the bearing housing 20 has an air outlet (second port) 22 through which air at a relatively high pressure (higher than atmospheric pressure in the present embodiment) passes. In the present embodiment, the air outlet 22 is provided to open at the rear and lower parts of the bearing housing 20 and communicates with the rotor accommodating portion 14. In addition, a ring-shaped flange portion 23 constituting a joint surface for joining with the rotor housing 10 is provided at the rear of the bearing housing 20. The flange portion 23 constitutes a peripheral portion around a flat end wall 24 provided at the rear of the bearing housing 20. The air outlet 22 is provided as a through hole in the end wall 24.

[0043] The bearing housing 20 has cylindrical bearing receiving portions 21f and 21m as holes respectively having center lines Cf1 and Cm1. In the present embodiment, the bearing receiving portions 21f and 21m are cylindrical. The bearing receiving portions 21f and 21m house bearings 40f and 40m that axially support shaft portions 31f and 31m on the other end side (front side) of a screw rotor 30 to be described later. In addition, in the present embodiment, the center lines of the bearing receiving portions 21f and 21m, the bearings 40f and 40m, and the rotor receiving portion 14 coincide. Therefore, the same reference numerals Cf1 and Cm1 are given to this center line. Such repeated reference numerals are treated in the same way later.

[0044] The bearing housing 20 has shaft hole portions 25f and 25m disposed between the rotor receiving portion 14 and the bearing receiving portions 21f and 21m. In the present embodiment, the shaft hole portions 25f and 25m are cylindrical shapes respectively having parallel center lines Cf2 and Cm2 extending in the front - rear direction, and are configured as through - holes of an end wall 24. The shaft portions 31f and 31m are respectively inserted through the shaft hole portions 25f and 25m.

[0045] In the present embodiment, the cross - sectional shape of the shaft hole portions 25f and 25m perpendicular to the center lines Cf2 and Cm2 is circular. That is, the shaft hole portions 25f and 25m are cylindrical. However, the cross - sectional shape of the shaft hole portions 25f and 25m is not limited to circular, and may be other shapes such as a rounded rectangle or an ellipse. In addition, for example, when the cross - sectional shape of the shaft hole portions 25f and 25m is a rounded rectangle formed by two parallel lines of equal length and two semi - circles, the center of the cross - section of the shaft hole portions 25f and 25m is the intersection of the line connecting the mid - points of the parallel lines and the major axis. Further, for example, when the cross - sectional shape of the shaft hole portions 25f and 25m is an ellipse, the center of the cross - section of the shaft hole portions 25f and 25m is the intersection of the major axis and the minor axis. In addition, the shaft hole portions 25f and 25m may be formed directly with respect to the bearing housing 20, or may be formed indirectly via another component such as a gasket or a sleeve.

[0046] In the present embodiment, a liquid is used for lubricating the bearings 40f and 40m and suppressing the leakage of air from the rotor receiving portion 14 to the bearing receiving portions 21f and 21m. The liquid is, for example, oil, water, etc. Supply paths 26f and 26m through which the liquid flows are formed in the bearing housing 20. The supply paths 26f and 26m are fluid - connected to a supply source of the liquid provided outside the housing 2, and can cause the liquid to flow from the supply source to the shaft hole portions 25f and 25m. Therefore, the shaft hole portions 25f and 25m are configured to communicate with the supply paths 26f and 26m of the liquid, and suppress the leakage of air from the rotor receiving portion 14 to the bearing receiving portions 21f and 21m by means of the liquid supplied from the supply paths 26f and 26m. In addition, the liquid that closes the shaft hole portions 25f and 25m in this way is used for lubricating the bearings 40f and 40m.

[0047] Reference Figures 6 to 8 As shown in Figures 6 to 8 , the screw rotor 30 has a female rotor 30f and a male rotor 30m that mesh with each other. Figure 6 、 7 Only the male rotor 30m is shown in 7 , and the female rotor 30f is located behind the male rotor 30m ( Figure 6 、 7 behind the plane of the paper in Figure 6 ). Since the structure of the female rotor 30f is substantially the same as that of the male rotor 30m, Figure 6 、 7 the structure of the female rotor 30f in 7 is also indicated by reference numerals in parentheses.

[0048] The female rotor 30f and the male rotor 30m each have shaft portions 33f, 33m on one end side (rear side), body portions 32f, 32m in the center, and shaft portions 31f, 31m on the other end side (front side). The shaft portions 33f, 33m on one end side are arranged near the suction port 11, and the shaft portions 31f, 31m on the other end side are arranged near the discharge port 22. The body portions 32f, 32m each have male and female complementary teeth that mesh with each other.

[0049] The shaft portions 33f, 33m on one end side are respectively supported by bearings 41f, 41m in the rotor housing 10. The shaft portions 31f, 31m on the other end side are respectively supported by bearings 40f, 40m in the bearing housing 20.

[0050] In the present embodiment, the bearings 40f, 40m and the bearings 41f, 41m are rolling bearings having center lines Cf1, Cm1. Specifically, the bearings 40f, 40m and the bearings 41f, 41m may be angular contact ball bearings, ball bearings, or cylindrical roller bearings. However, the types of the bearings 40f, 40m and the bearings 41f, 41m are not particularly limited. In addition, the bearings 41f, 41m are accommodated in the rotor housing 10, and the bearings 40f, 40m are respectively accommodated in the bearing accommodation portions 21f, 21m of the bearing housing 20.

[0051] In the present embodiment, the shaft portion 33m on one end side of the male rotor 30m is mechanically connected to the motor 50. The male rotor 30m rotates by means of the motor 50, and the female rotor 30f rotates as the male rotor 30m rotates.

[0052] The positional relationship among the female rotor 30f, the male rotor 30m, the shaft hole portions 25f, 25m, and the bearing accommodation portions 21f, 21m will be described.

[0053] Reference Figure 6 、 7, the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located at positions farther from the discharge port 22 than the center lines Cf1 and Cm1 of the bearing housing portions 21f and 21m. In a general screw compressor, a concentric structure in which the center lines of the shaft hole portion and the bearing housing portion coincide is adopted, but in the structure of the present embodiment, an eccentric structure in which the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m deviate from the discharge port 22 compared to the concentric structure is adopted. In the illustrated example, the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located above the center lines Cf1 and Cm1 of the bearing housing portions 21f and 21m by a value dz in the vertical direction. Accordingly, the clearances between the shaft portions 31f and 31m and the shaft hole portions 25f and 25m become narrower in the lower part than in the upper part ( Figure 7 : D1 < D2). In the present embodiment, liquid supply paths 26f and 26m are connected to the side portions of the shaft hole portions 25f and 25m, and liquid is supplied to seal the clearances between the shaft hole portions 25f and 25m and the shaft portions 31f and 31m. Thus, in the eccentric structure, compared to the concentric structure, the clearances between the shaft hole portions 25f and 25m and the shaft portions 31f and 31m near the discharge port 22 become narrower, and it is easy to seal the clearances with liquid. Further, in the upper portions of the shaft hole portions 25f and 25m, the clearances become larger, but this portion is far from the discharge port 22 and is a low-pressure tooth groove portion where low-pressure air is present, so even if a small amount of lubricating sealing liquid is used, air leakage through the clearances is less likely to occur.

[0054] Refer to Figure 8 , the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located at positions farther from the discharge port 22 than the center lines Cf1 and Cm1 of the bearing housing portions 21f and 21m. Further, Figure 8 is a schematic cross-sectional view of the screw rotor 30 and the rotor housing portion 14, but the hatching indicating the cross-section is omitted for clarity of illustration. Figure 8 In, the hatched portion Hp indicates the high-pressure tooth groove portion.

[0055] The centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located at positions farther from the discharge port 22 and the high-pressure tooth groove portion (refer to the hatched portion Hp) than the centerlines Cf1 and Cm1 of the bearing housing portions 21f and 21m, respectively. Specifically, the discharge port 22 and the high-pressure tooth groove portion (refer to the hatched portion Hp) are located below, and the centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located above the centerlines Cf1 and Cm1 of the bearing housing portions 21f and 21m in the vertical direction by a value dz and are located outside in the left-right direction by a value dx. Preferably, the value dz is a positive number, and the centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located above the centerlines Cf1 and Cm1 of the bearing housing portions 21f and 21m. Further, if the value dz is large enough, the value dx can also be a negative number. In other words, if the centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located sufficiently above the centerlines Cf1 and Cm1 of the bearing housing portions 21f and 21m, the centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m can also be located inside in the left-right direction compared to the centerlines Cf1 and Cm1 of the bearing housing portions 21f and 21m.

[0056] In the present embodiment, the bearings 40f and 40m and the bearing housing portions 21f and 21m respectively have a common centerline Cf1 and Cm1. That is, the bearings 40f and 40m are arranged in the bearing housing portions 21f and 21m such that the centerlines of the bearings 40f and 40m and the centerlines of the bearing housing portions 21f and 21m coincide (Cf1, Cm1).

[0057] In the present embodiment, the centerlines of the bearing housing portions 21f and 21m and the rotation axis center of the screw rotor also coincide (Cf1, Cm1). Therefore, the centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located at positions farther from the discharge port 22 and the high-pressure tooth groove portion (refer to the hatched portion Hp) than the rotation axis center Cf1 and Cm1 of the screw rotor 30. The rotation axis center of the screw rotor 30 mentioned here refers to the rotation axis center of the screw rotor 30 during operation, and at least during operation, the centerlines of the bearing housing portions 21f and 21m coincide with the rotation axis center of the screw rotor 30 (Cf1, Cm1). When stopped, due to the clearance of the bearing, there is a case where the screw rotor 30 is located below compared to when it is operating due to the self-weight of the screw rotor 30. That is, when stopped, there is a case where the rotation axis center of the screw rotor 30 is located below the centerline of the bearing. On the other hand, during operation, due to the thermal expansion difference between the inner ring and the outer ring of the bearing, the clearance of the bearing becomes smaller, and the rotation axis center of the screw rotor 30 substantially coincides with the centerline of the bearing.

[0058] In the present embodiment, in a cross-section perpendicular to the centerlines Cf2 and Cm2 of the shaft hole portions 25f and 25m (refer to Figure 8) In [description], the diameters of the bottom circles 34f and 34m inscribed in the bottom parts of the teeth of the main body parts 32f and 32m of the screw rotor 30 are larger than the diameters Rf2 and Rm2 of the shaft hole parts 25f and 25m. For example, the shapes of the bottom circles 34f and 34m inscribed in the bottom parts of the teeth of the main body parts 32f and 32m of the screw rotor 30 are circles having diameters Rf1 and Rm1 larger than the diameters Rf2 and Rm2 of the shaft hole parts 25f and 25m. In the illustrated cross-section, the shaft hole parts 25f and 25m completely overlap the bottom circles 34f and 34m. That is, when viewed along the axial direction of the screw rotor 30, the shaft hole parts 25f and 25m are arranged such that all regions of the shaft hole parts 25f and 25m are located inside the bottom circles 34f and 34m of the main body parts 32f and 32m.

[0059] The screw compressor 1 according to the present embodiment has the following effects.

[0060] Since the center lines Cf2 and Cm2 of the shaft hole parts 25f and 25m are located farther from the discharge port 22 than the center lines Cf1 and Cm1 of the bearing housing parts 21f and 21m, the shaft hole parts 25f and 25m can be separated from the high-pressure tooth groove part Hp of the screw rotor 30, and leakage of air through the shaft hole parts 25f and 25m can be suppressed. Specifically, in the present embodiment, the aforementioned eccentric structure is adopted, so that the gap D1 between the shaft hole parts 25f and 25m and the shaft parts 31f and 31m at the high-pressure tooth groove part Hp becomes narrower compared with the concentric structure, and it is easy to seal the gap with liquid. Thus, leakage of air from the high-pressure tooth groove part Hp through the shaft hole parts 25f and 25m can be effectively suppressed.

[0061] In addition, as a reference for separating the shaft hole parts 25f and 25m from the high-pressure tooth groove part Hp of the screw rotor 30, not only the center lines of the bearing housing parts 21f and 21m can be considered but also the rotation axis of the screw rotor 30 can be considered. Thus, leakage of gas through the shaft hole parts 25f and 25m can be more effectively suppressed. Further, in the present embodiment, the center lines of the bearing housing parts 21f and 21m and the rotation axis of the screw rotor 30 coincide (Cf1, Cm1).

[0062] In addition, self-excited vibration of the screw rotor 30, which often becomes a problem when using bearings other than rolling bearings when the center lines of the bearings and the center of the rotation axis of the rotor do not coincide, is suppressed, and the screw compressor 1 can be stably driven. Specifically, the center lines of the bearings 40f and 40m and the center lines of the bearing housing parts 21f and 21m coincide (Cf1, Cm1), so that wobbling of the rotation axis of the screw rotor 30 can be suppressed even when using rolling bearings (for example, angular contact ball type or cylindrical roller type bearings) 40f and 40m.

[0063] In addition, since the shaft hole portions 25f and 25m are cylindrical, the structure of the shaft hole portions 25f and 25m can be simplified.

[0064] In addition, it can be arranged such that the tooth bottom portions of the main body portions 32f and 32m of the screw rotor 30 close the shaft hole portions 25f and 25m, and air leakage through the shaft hole portions 25f and 25m can be more effectively suppressed.

[0065] As described above, the specific embodiments of the present invention and their modified examples have been described, but the present invention is not limited to the above-described manner, and various changes can be made within the scope of the invention for implementation.

[0066] For example, in the above-described embodiment, the case where the screw-type fluid machine 1 is a compressor has been described as an example, but the screw-type fluid machine 1 may also be a screw expander. In this case, the second port 22 constitutes a gas supply port, the first port 21 constitutes an exhaust port, the rotation direction of the screw rotor 30 is opposite, and the motor 50 functions as a generator.

[0067] Explanation of Reference Numerals

[0068] 1 Screw-type fluid machine (screw compressor, screw expander)

[0069] 2 Housing

[0070] 10 Rotor housing

[0071] 11 Suction port (first port)

[0072] 13 Flange portion

[0073] 14 Rotor accommodation portion

[0074] 20 Bearing housing

[0075] 21f, 21m Bearing accommodation portion

[0076] 22 Discharge port (second port)

[0077] 23 Flange portion

[0078] 24 End wall

[0079] 25f, 25m Shaft hole portion

[0080] 26f, 26m Supply path

[0081] 30 Screw rotor

[0082] 30f Female rotor

[0083] 30m Male rotor

[0084] 31f, 31m Shaft portion

[0085] 32f and 32m main bodies

[0086] 33f and 33m shafts

[0087] 34f and 34m root circles

[0088] 40f and 40m bearings

[0089] 41f and 41m bearings

[0090] 50 motor

Claims

1. A screw-type fluid machine includes a housing that rotatably accommodates a screw rotor. The screw rotor has a main body portion and shaft portions provided at one end side and the other end side of the main body portion, respectively. In the screw-type fluid machine, the housing includes: a first port through which a relatively low-pressure gas passes on one end side of the main body portion; a second port through which a relatively high-pressure gas passes on the other end side of the main body portion; a rotor accommodation portion that communicates with the first port and the second port and accommodates the main body portion; a bearing accommodation portion that accommodates a bearing that axially supports the shaft portion on the other end side; a shaft hole portion that is disposed between the rotor accommodation portion and the bearing accommodation portion, through which the shaft portion is inserted, and is configured to communicate with a supply path and suppress leakage of the gas from the rotor accommodation portion to the bearing accommodation portion by means of a liquid supplied from the supply path; When viewed in the axial direction of the screw rotor, the center line of the shaft hole portion is located at a position farther from the second port than the center line of the bearing accommodation portion.

2. The screw-type fluid machine according to claim 1, wherein when viewed in the axial direction of the screw rotor, the center line of the shaft hole portion is located at a position farther from the second port than the center of rotation axis of the screw rotor.

3. The screw-type fluid machine according to claim 2, wherein the bearing is a rolling bearing, and the center line of the bearing coincides with the center of rotation axis of the screw rotor.

4. The screw-type fluid machine according to claim 2 or 3, wherein in a cross-section perpendicular to the center line of the shaft hole portion, the shape of the shaft hole portion is circular.

5. The screw-type fluid machine according to claim 4, wherein when viewed in the axial direction of the screw rotor, the shaft hole portion is provided such that the entire region of the shaft hole portion is located inside the root circle of the main body portion.

6. The screw-type fluid machine according to claim 5, wherein in a cross-section perpendicular to the center line of the shaft hole portion, the root circle of the main body portion is larger than the diameter of the shaft hole portion.

Images