Screw-type fluid machine

Abstract

To suppress a gas leakage via a shaft hole part in a screw-type fluid machine.SOLUTION: A screw-type compressor 1 includes a casing 2. The casing 2 includes: an air inlet 11; an outlet 22; a rotor storing part 14; bearing storing parts 21f, 21m which store bearings 40f, 40m for axially supporting shaft parts 31f, 31m on the other end side of a screw rotor 30; and shaft hole parts 25f, 25m which are arranged between the rotor storing part 14 and the bearing storing parts 21f, 21m, in which the shaft parts 31f, 31m are inserted, and which communicate with supply paths 26f, 26m, and are configured to suppress a gas leakage from the rotor storing part 14 to the bearing storing parts 21f, 21m by liquid supplied from the supply paths 26f, 26m. In an axial direction of the screw rotor 30, center lines Cf2, Cm2 of the shaft hole parts 25f, 25m are positioned at a distance from the outlet 22 with respect to center lines Cf1, Cm1 of the bearing storing parts 21f, 21m.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] A screw compressor, which is one type of screw-type fluid machine, compresses gas by rotating and meshing a pair of male and female screw rotors inside a casing. The casing has an intake port at one end and a discharge port at the other end. The screw compressor draws gas in through the intake port, compresses the gas inside the casing, and discharges the compressed gas from the discharge port. Therefore, the pressure of the gas inside the casing gradually increases from one end to the other end.

[0003] The high-pressure side (other end) of the casing is provided with not only a discharge port but also a shaft hole for inserting the shaft of the screw rotor. Therefore, there is a risk of high-pressure gas leaking through the shaft hole, and it is necessary to suppress gas leakage through the shaft hole.

[0004] For example, Patent Document 1 discloses a screw compressor in which a seal member is attached to the axial hole portion to suppress gas leakage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-69186 Summary of the Invention [Problem to be solved by the invention]

[0006] Since the screw rotor compresses gas by rotational meshing, a pressure distribution exists in the circumferential direction, i.e., there are high-pressure tooth groove portions and low-pressure tooth groove portions. As mentioned above, there is a risk of gas leaking from the high-pressure tooth groove portions in particular through the axial hole, and it is therefore necessary to suppress gas leakage. However, the screw compressor of Patent Document 1 does not have a structure that corresponds to such a circumferential pressure distribution, and therefore there is room for improvement.

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

[0008] The present invention provides A screw type fluid machine comprising a casing that rotatably houses a screw rotor having a main body and shaft portions provided on one end side and the other end side of the main body, The casing comprises: a first port at one end of the main body through which a relatively low-pressure gas passes; a second port at the other end of the main body through which a relatively high-pressure gas passes; a rotor accommodating portion that communicates with the first port and the second port and accommodates the main body portion; a bearing accommodating 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 accommodating portion and the bearing accommodating portion, through which the shaft portion is inserted, that communicates with a supply passage, and that is configured to suppress leakage of the gas from the rotor accommodating portion to the bearing accommodating portion by liquid supplied from the supply passage; Equipped with The present invention provides a screw type fluid machine, wherein, as viewed in the axial direction of the screw rotor, the center line of the axial hole portion is positioned farther from the second port than the center line of the bearing accommodating portion.

[0009] According to this configuration, the center line of the axial hole portion is located farther from the second port than the center line of the bearing accommodation portion. This allows the axial hole portion to be spaced away from the high-pressure tooth groove portion (near the second port) of the screw rotor, thereby suppressing gas leakage through the axial hole portion. While a typical screw-type fluid machine employs a concentric structure in which the center line of the axial hole portion and the center line of the bearing accommodation portion coincide, the above configuration employs an eccentric structure in which the center line of the axial hole portion is farther from the second port than in a concentric structure. In an eccentric structure, the gap between the axial hole portion and the shaft portion at the high-pressure tooth groove portion is narrower than in a concentric structure, making it easier to seal the gap with liquid. Therefore, gas leakage from the high-pressure tooth groove portion through the axial hole portion can be effectively suppressed. Here, screw-type fluid machines include screw-type compressors and screw-type expanders. When the screw-type fluid machine is a screw-type compressor, the first port constitutes an intake port, and the second port constitutes a discharge port. When the screw type fluid machine is a screw type expander, the first port constitutes an exhaust port, and the second port constitutes an intake port.

[0010] When viewed in the axial direction of the screw rotor, the center line of the axial hole portion may be located farther from the second port than the center of the rotation axis of the screw rotor.

[0011] With this configuration, the axial hole can be positioned away from the high-pressure tooth groove of the screw rotor based on the center line of the bearing accommodating portion as well as the rotational axis of the screw rotor. Also, gas leakage during operation can be reliably suppressed through the axial hole.

[0012] The bearing may be a rolling bearing, The center line of the bearing may coincide with the center of the rotation axis of the screw rotor.

[0013] With this configuration, self-excited vibration of the screw rotor, which often becomes a problem with bearings other than rolling bearings when the center line of the bearing and the center of the rotor's rotational axis do not coincide, is suppressed, and the screw-type fluid machine can be driven stably. Specifically, by adopting rolling bearings and ensuring that the center line of the bearing and the center of the rotor's rotational axis coincide, it is possible to suppress wobble of the screw rotor's rotational axis even when a bearing is used.

[0014] The shaft hole may have a circular shape in a cross section perpendicular to the center line of the shaft hole.

[0015] According to this configuration, the structure of the shaft hole portion can be simplified.

[0016] The axial hole portion may be provided so that the entire area of the axial hole portion is located inside the root circle of the main body portion when viewed in the axial direction of the screw rotor. Also, in a cross section perpendicular to the center line of the axial hole portion, the root circle of the main body portion may be larger than the diameter of the axial hole portion.

[0017] According to this configuration, the axial hole can be arranged so that it is closed by the tooth bottom of the main body of the screw rotor, and gas leakage through the axial hole can be more effectively suppressed. [Effects of the Invention]

[0018] According to the present invention, leakage of gas through the axial hole portion can be suppressed in a screw fluid machine. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a top perspective view of a screw fluid machine according to an embodiment of the present invention; [Figure 2] FIG. 2 is a bottom perspective view of the screw fluid machine of FIG. 1. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 2 is a longitudinal cross-sectional view of the screw fluid machine of FIG. 1 taken along line VI-VI. [Figure 7] Enlarged view of part VII in Figure 6. [Figure 8] FIG. 2 is a schematic cross-sectional view of a screw rotor and a rotor accommodating portion. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0021] 1 and 2, a screw type fluid machine 1 according to an embodiment of the present invention is, for example, a screw type compressor. Therefore, hereinafter, the screw type fluid machine 1 will also be referred to as a screw type compressor 1. For the sake of explanation, in each drawing, the X direction is the left-right direction, the Y direction is the front-rear direction, and the Z direction is the up-down direction. However, these directions do not limit the arrangement direction of the screw type compressor 1, but are set for the convenience of explanation.

[0022] The screw compressor 1 takes in external air, compresses it internally, and discharges it, but may compress any gas other than air.

[0023] The screw compressor 1 has a casing 2 that serves as an exterior. The casing 2 rotatably houses a screw rotor 30 (see FIG. 6) described below.

[0024] In this embodiment, the casing 2 has a rotor casing 10 having a rotor accommodating portion 14 that accommodates a screw rotor 30 (described later), and a bearing casing 20 that is disposed on the front side of the rotor casing 10 .

[0025] 3, the rotor casing 10 has an intake port (first port) 11 through which air at a relatively low pressure (atmospheric pressure in this embodiment) passes. In this embodiment, the intake port 11 is provided in the upper part of the rotor casing 10. In addition, an annular flange portion 13 that forms a joint surface with the bearing casing 20 is provided at the front end of the rotor casing 10.

[0026] The rotor casing 10 has a rotor accommodating section 14 that accommodates main body sections 32f, 32m (see FIG. 6) of the screw rotor 30 (described later). The rotor accommodating section 14 is a double-tube shape with parallel center lines Cf1, Cm1 extending in the front-rear direction. The rotor accommodating section 14 communicates with the intake port 11.

[0027] 4 to 6, the bearing casing 20 has a discharge port (second port) 22 through which air at a relatively high pressure (higher than atmospheric pressure in this embodiment) passes. In this embodiment, the discharge port 22 is provided so as to open at the rear and bottom of the bearing casing 20, and communicates with the rotor accommodating section 14. In addition, an annular flange portion 23 is provided at the rear of the bearing casing 20, which forms the joint surface with the rotor casing 10. The flange portion 23 forms the periphery of a flat end wall 24 provided at the rear of the bearing casing 20. The end wall 24 has the discharge port 22 provided as a through-hole.

[0028] The bearing casing 20 has cylindrical bearing accommodating portions 21f, 21m as holes having center lines Cf1, Cm1, respectively. In this embodiment, the bearing accommodating portions 21f, 21m are cylindrical. The bearing accommodating portions 21f, 21m accommodate bearings 40f, 40m that support shaft portions 31f, 31m on the other end side (front side) of the screw rotor 30, which will be described later. Note that in this embodiment, the center lines of the bearing accommodating portions 21f, 21m, the bearings 40f, 40m, and the rotor accommodating portion 14 coincide with each other. Therefore, the same reference symbols Cf1, Cm1 are used for the center lines. Such duplicate reference symbols will be treated in the same manner hereinafter.

[0029] The bearing casing 20 has shaft holes 25f, 25m disposed between the rotor housing 14 and the bearing housings 21f, 21m. In this embodiment, the shaft holes 25f, 25m are cylindrical and have parallel center lines Cf2, Cm2 extending in the front-rear direction, respectively, and are configured as through-holes in the end wall 24. Shafts 31f, 31m are inserted into the shaft holes 25f, 25m, respectively.

[0030] In this embodiment, the cross-sectional shape of the shaft holes 25f, 25m perpendicular to the center lines Cf2, Cm2 is circular. That is, the shaft holes 25f, 25m are cylindrical. However, the cross-sectional shape of the shaft holes 25f, 25m is not limited to circular, and may be other shapes such as a rounded rectangle or an ellipse. For example, if the cross-sectional shape of the shaft holes 25f, 25m is a rounded rectangle formed by two parallel lines of equal length and two semicircles, the center of the cross-section of the shaft holes 25f, 25m is the intersection of the major axis and a line connecting the midpoints of the parallel lines. For example, if the cross-sectional shape of the shaft holes 25f, 25m is elliptical, the center of the cross-section of the shaft holes 25f, 25m is the intersection of the major axis and the minor axis. Furthermore, the shaft holes 25f, 25m do not have to be formed directly in the bearing casing 20 but may be formed indirectly via a separate member such as a washer or sleeve.

[0031] In this embodiment, a liquid is used to lubricate the bearings 40f, 40m and to prevent air leakage from the rotor housing 14 to the bearing housings 21f, 21m. The liquid may be, for example, oil or water. The bearing casing 20 is formed with supply passages 26f, 26m through which the liquid flows. The supply passages 26f, 26m are fluidly connected to a liquid supply source provided outside the casing 2, allowing the liquid to flow from the supply source to the axial holes 25f, 25m. Therefore, the axial holes 25f, 25m are connected to the liquid supply passages 26f, 26m, and are configured to prevent air leakage from the rotor housing 14 to the bearing housings 21f, 21m by the liquid supplied from the supply passages 26f, 26m. The liquid that seals the axial holes 25f, 25m in this manner also serves to lubricate the bearings 40f, 40m.

[0032] 6 to 8, the screw rotor 30 has a female rotor 30f and a male rotor 30m that mesh with each other. In Figures 6 and 7, only the male rotor 30m is shown, and the female rotor 30f is located behind the male rotor 30m (behind the plane of the paper in Figures 6 and 7). The configuration of the female rotor 30f is generally the same as the configuration of the male rotor 30m, so in Figures 6 and 7, the configuration of the female rotor 30f is also indicated by reference characters in parentheses.

[0033] The female rotor 30f and the male rotor 30m each have a shaft portion 33f, 33m at one end (rear side), a central body portion 32f, 32m, and a shaft portion 31f, 31m at the other end (front side). The shaft portions 33f, 33m at one end are positioned near the intake port 11, and the shaft portions 31f, 31m at the other end are positioned near the discharge port 22. The body portions 32f, 32m each have complementary male and female teeth that mesh with each other.

[0034] The shaft portions 33f and 33m on one end side are journaled by bearings 41f and 41m, respectively, within the rotor casing 10. The shaft portions 31f and 31m on the other end side are journaled by bearings 40f and 40m, respectively, within the bearing casing 20.

[0035] In this embodiment, bearings 40f, 40m and bearings 41f, 41m are rolling bearings having center lines Cf1, Cm1. Specifically, bearings 40f, 40m and bearings 41f, 41m may be angular contact ball bearings, ball bearings, or cylindrical roller bearings. However, the types of bearings 40f, 40m and bearings 41f, 41m are not particularly limited. Furthermore, bearings 41f, 41m are housed in rotor casing 10, and bearings 40f, 40m are housed in bearing housing portions 21f, 21m of bearing casing 20, respectively.

[0036] In this embodiment, a shaft portion 33m on one end of the male rotor 30m is mechanically connected to a motor 50. The male rotor 30m is rotated by the motor 50, and the female rotor 30f is rotated in conjunction with the rotation of the male rotor 30m.

[0037] The positional relationship among the female rotor 30f, the male rotor 30m, the shaft hole portions 25f and 25m, and the bearing housing portions 21f and 21m will be described.

[0038] Referring to FIGS. 6 and 7, the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located 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 line of the shaft hole portion and the center line of the bearing housing portion coincide is adopted. However, in the configuration of the present embodiment, an eccentric structure in which the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m are separated 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 upward by a value dz in the vertical direction from the center lines Cf1 and Cm1 of the bearing housing portions 21f and 21m. As a result, the gaps between the shaft portions 31f and 31m and the shaft hole portions 25f and 25m are narrower at the lower part than at the upper part (FIG. 7: D1 < D2). In the present embodiment, liquid supply passages 26f and 26m communicate with the side portions of the shaft hole portions 25f and 25m, and liquid is supplied so as to seal the gaps 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 gap between the shaft hole portions 25f and 25m and the shaft portions 31f and 31m in the vicinity of the discharge port 22 becomes narrower, and it becomes easier to seal the gap with liquid. Note that although the gap is large at the upper part of the shaft hole portions 25f and 25m, this portion is far from the discharge port 22 and is a low-pressure tooth groove portion where low-pressure air exists, so even a small amount of lubricating sealing liquid hardly causes air leakage through the gap.

[0039] Referring to FIG. 8, the center lines Cf2 and Cm2 of the shaft hole portions 25f and 25m are located farther from the discharge port 22 than the center lines Cf1 and Cm1 of the bearing housing portions 21f and 21m. Note that FIG. 8 is a schematic cross-sectional view of the screw rotor 30 and the rotor housing portion 14, and the hatching indicating that it is a cross section is omitted for clarity of illustration. In FIG. 8, the hatched portion Hp indicates the high-pressure tooth groove portion.

[0040] The center lines Cf2, Cm2 of the shaft holes 25f, 25m are located farther from the discharge port 22 and the high-pressure tooth groove portion (see the hatched area Hp) than the center lines Cf1, Cm1 of the bearing accommodating portions 21f, 21m. Specifically, the discharge port 22 and the high-pressure tooth groove portion (see the hatched area Hp) are located below, and the center lines Cf2, Cm2 of the shaft holes 25f, 25m are located above the center lines Cf1, Cm1 of the bearing accommodating portions 21f, 21m by a value dz in the vertical direction and outward by a value dx in the horizontal direction. Preferably, the value dz is a positive number, and the center lines Cf2, Cm2 of the shaft holes 25f, 25m are located above the center lines Cf1, Cm1 of the bearing accommodating portions 21f, 21m. Furthermore, if the value dz is sufficiently large, the value dx may be a negative number. In other words, as long as the center lines Cf2, Cm2 of the shaft hole portions 25f, 25m are positioned sufficiently above the center lines Cf1, Cm1 of the bearing accommodating portions 21f, 21m, the center lines Cf2, Cm2 of the shaft hole portions 25f, 25m may be positioned more inward in the left-right direction than the center lines Cf1, Cm1 of the bearing accommodating portions 21f, 21m.

[0041] In this embodiment, the bearings 40f, 40m and the bearing accommodating portions 21f, 21m have common center lines Cf1, Cm1, respectively. That is, the bearings 40f, 40m are arranged in the bearing accommodating portions 21f, 21m so that the center lines of the bearings 40f, 40m and the bearing accommodating portions 21f, 21m coincide (Cf1, Cm1).

[0042] In this embodiment, the center lines of the bearing accommodating portions 21f, 21m and the rotational axis center of the screw rotor also coincide (Cf1, Cm1). Therefore, the center lines Cf2, Cm2 of the shaft holes 25f, 25m are located farther from the discharge port 22 and the high-pressure tooth groove portion (see the shaded area Hp) than the rotational axis centers Cf1, Cm1 of the screw rotor 30. The rotational axis center of the screw rotor 30 here refers to the rotational axis center of the screw rotor 30 during operation. At least during operation, the center lines of the bearing accommodating portions 21f, 21m coincide with the rotational axis center of the screw rotor 30 (Cf1, Cm1). Because there is play in the bearings when the screw rotor 30 is stopped, the screw rotor 30 may be positioned lower than when it is operating due to its own weight. That is, when stopped, the rotational axis center of the screw rotor 30 may be positioned lower than the center line of the bearings. On the other hand, during operation, the difference in thermal expansion between the inner and outer rings of the bearing reduces the play of the bearing, and the center of the rotation axis of the screw rotor 30 substantially coincides with the center line of the bearing.

[0043] In this embodiment, in a cross section perpendicular to the center lines Cf2, Cm2 of the axial holes 25f, 25m (see FIG. 8), the diameters of the root circles 34f, 34m inscribed in the tooth roots of the main body portions 32f, 32m of the screw rotor 30 are larger than the diameters Rf2, Rm2 of the axial holes 25f, 25m. For example, the shape of the root circles 34f, 34m inscribed in the tooth roots of the main body portions 32f, 32m of the screw rotor 30 is a circle having diameters Rf1, Rm1 larger than the diameters Rf2, Rm2 of the axial holes 25f, 25m. In the cross section shown in the figure, the axial holes 25f, 25m completely overlap the root circles 34f, 34m. That is, when viewed in the axial direction of the screw rotor 30, the axial holes 25f, 25m are provided so that the entire areas of the axial holes 25f, 25m are positioned inside the root circles 34f, 34m of the main bodies 32f, 32m.

[0044] The screw compressor 1 of this embodiment provides the following advantages.

[0045] Because the center lines Cf2, Cm2 of the axial holes 25f, 25m are located farther from the discharge port 22 than the center lines Cf1, Cm1 of the bearing accommodation portions 21f, 21m, the axial holes 25f, 25m can be located away from the high-pressure tooth groove portion Hp of the screw rotor 30, thereby suppressing air leakage through the axial holes 25f, 25m. Specifically, because the eccentric structure described above is employed in this embodiment, the gap D1 between the axial holes 25f, 25m and the shaft portions 31f, 31m in the high-pressure tooth groove portion Hp is narrower than in a concentric structure, making it easier to seal the gap with liquid. Therefore, air leakage from the high-pressure tooth groove portion Hp through the axial holes 25f, 25m can be effectively suppressed.

[0046] Furthermore, the axis of rotation of the screw rotor 30 can be taken into consideration as well as the center line of the bearing accommodating portions 21f, 21m as a criterion for moving the axial holes 25f, 25m away from the high-pressure tooth groove portion Hp of the screw rotor 30. Therefore, gas leakage through the axial holes 25f, 25m can be more effectively suppressed. In this embodiment, the center line of the bearing accommodating portions 21f, 21m and the axis of rotation of the screw rotor 30 coincide (Cf1, Cm1).

[0047] Furthermore, self-excited vibration of the screw rotor 30, which often becomes a problem with bearings other than rolling bearings when the center line of the bearing and the center of the rotor's rotation axis do not coincide, is suppressed, enabling stable operation of the screw compressor 1. Specifically, by having the center line of the bearings 40f, 40m coincide with the center line of the bearing accommodating portions 21f, 21m (Cf1, Cm1), wobble of the rotation axis of the screw rotor 30 can be suppressed even when rolling bearings (for example, angular contact ball or cylindrical roller bearings) 40f, 40m are used.

[0048] Furthermore, since the shaft holes 25f and 25m are cylindrical, the structure of the shaft holes 25f and 25m can be simplified.

[0049] Furthermore, the tooth bottoms of the main bodies 32f, 32m of the screw rotor 30 can be arranged to close the axial holes 25f, 25m, which can more effectively prevent air from leaking through the axial holes 25f, 25m.

[0050] Although specific embodiments of the present invention and their modifications have been described above, the present invention is not limited to the above-described embodiments and can be implemented with various modifications within the scope of the present invention.

[0051] For example, in the above embodiment, the screw type fluid machine 1 is a compressor, but the screw type fluid machine 1 may be a screw type expander. In this case, the second port 22 serves as an air inlet, the first port 21 serves as an exhaust port, the screw rotor 30 rotates in the opposite direction, and the motor 50 functions as a generator. [Explanation of symbols]

[0052] 1. Screw-type fluid machinery (screw compressors, screw expanders) 2 Casing 10 rotor casing 11 Intake port (first port) 13 Flange 14 rotor housing 20 Bearing casing 21f, 21m bearing housing 22 Outlet (second port) 23 Flange 24 End Wall 25f,25m shaft hole 26f,26m supply route 30 screw rotor 30f female rotor 30m male rotor 31f, 31m shaft section 32f,32m Main body 33f, 33m shaft section 34f, 34m Root circle 40f, 40m bearings 41f, 41m bearings 50 motor

Claims

1. A screw-type fluid machine comprising a casing that rotatably houses a screw rotor having a main body and shaft portions provided at one end and the other end of the main body, The aforementioned casing is One end of the main body has a first port through which a relatively low-pressure gas passes, At the other end of the main body, there is a second port through which a relatively high-pressure gas passes, A rotor housing that communicates with the first port and the second port and houses the main body, A bearing housing portion that accommodates a bearing that supports the shaft portion on the other end, A shaft hole is positioned between the rotor housing and the bearing housing, through which the shaft is inserted, communicating with a supply passage, and configured to suppress the leakage of the gas from the rotor housing to the bearing housing by the liquid supplied from the supply passage. Equipped with, A screw-type fluid machine in which, when viewed in the axial direction of the screw rotor, the center line of the shaft hole is located further from the second port than the center line of the bearing housing.

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

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

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

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

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

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