JP2022133726A - screw compressor - Google Patents

Abstract

To provide a screw compressor in which an appropriate amount of gas and oil according to a change in the size of a working space is released from the working space, thereby suppressing abnormal high pressure especially at beginning of closing of the working space.SOLUTION: A screw compressor includes a male rotor 10, a female rotor 20, which mesh with each other, and a casing 30 that houses the male rotor 10 and the female rotor 20 and is provided with a suction port 31 and a discharge port 32. There are formed inside the casing 30, a suction space S1 communicating with the suction port 31, a discharge space S2 communicating with the discharge port 32, and a working space S3 located between the male rotor 10 and the female rotor 20. The casing 30 is provided with a recess 33 that provides communication between the discharge space S2 and the working space S3 so as to open in a discharge side wall surface 30a facing discharge side end surfaces 12a and 22a. The recess 33 has a plurally-stepped shape in which an opening edge 33b of an opening portion 33a is continuous with the opening edge 32a of the discharge port 32, and the depth becomes shallower toward the tip 33c of the opening portion 33a.SELECTED DRAWING: Figure 4

Description

The present invention relates to screw compressors.

A screw compressor compresses gas by meshing a male rotor and a female rotor in a casing. In particular, in an oil-fed screw compressor, the male rotor and female rotor are cooled, sealed, lubricated, and the like by supplying oil into the casing.

When the male rotor and the female rotor are meshed with each other and the teeth of the male rotor fit into the tooth spaces of the female rotor, a closed working space is formed between the tip of the male rotor and the tooth spaces of the female rotor. The working space, with trapped gas and oil, shrinks with the rotation of the male and female rotors and eventually disappears. As a result, the gas and oil in the working space are compressed to a significantly high pressure, possibly generating an abnormally high pressure.

When the abnormally high pressure is generated, the male rotor and the female rotor may vibrate and be damaged. To avoid this, it is therefore necessary to reduce the pressure in the working space to a suitable pressure. For example, Patent Document 1 discloses a screw compressor that allows gas and oil to escape from the working space to the discharge port through the recessed portion by providing a recessed portion in the wall surface facing the rotor discharge side end face of the casing. machine is disclosed. This prevents gas and oil from being trapped in the working space, thereby reducing the pressure in the working space.

JP 2008-82273 A

In the configuration of the screw compressor of Patent Literature 1, it is necessary to make the recesses sufficiently large in order to allow sufficient amounts of gas and oil to escape from the working space. However, there are cases in which structures such as bearings and oil supply passages are arranged in the wall surface portion of the casing that forms the recess, and it may not be possible to form the recess large.

Also, as described above, the working space becomes smaller as the male and female rotors rotate, so the amount of gas and oil required to escape from the working space decreases as the working space shrinks. However, Patent Literature 1 does not consider changes over time in the amount of gas and oil to be released from the working space, and there is room for improvement. In particular, if a sufficient amount of gas and oil cannot escape when the working space begins to be closed, abnormally high pressure may occur.

An object of the present invention is to release an appropriate amount of gas and oil from the working space in accordance with changes in the size of the working space in a screw compressor, and to suppress abnormally high pressure especially at the beginning of closing of the working space.

The present invention includes a male rotor and a female rotor that mesh with each other, and a casing that houses the male rotor and the female rotor and is provided with a suction port and a discharge port, and the casing communicates with the suction port. A suction space, a discharge space communicating with the discharge port, and a working space located between the male rotor and the female rotor are formed, and face the discharge side end surfaces of the male rotor and the female rotor. A recess that communicates with the discharge space and the working space is provided so as to open on the discharge side wall surface of the casing, and the opening edge of the opening of the recess is continuous with the opening edge of the discharge port. Provided is a screw compressor having a plurality of stages whose depth is shallower toward the tip of the opening.

According to this configuration, gas and oil can be released to the discharge space, and abnormally high pressure in the working space can be suppressed. Especially when the working space at the beginning of confinement is large, a large amount of gas and oil can escape to the discharge space by utilizing the deep portion of the recess. Then, when the working space is small, the shallow portion of the recess can be utilized to allow a small amount of gas and oil to escape to the discharge space. Therefore, an appropriate amount of gas and oil can be released from the working space in accordance with changes in the size of the working space, and in particular, abnormally high pressure at the beginning of closing of the working space can be suppressed. In addition, since the plurality of stepped recesses are formed in accordance with changes in the size of the working space, it is not necessary to form the recesses deeper than necessary. Therefore, it is effective in terms of design without interfering with the arrangement of other components such as bearings and oil supply passages.

The casing has a tongue-shaped portion that partially closes the working space and partially partitions the discharge space and the working space, and has a tongue-shaped portion extending in a direction in which the rotation axis of the female rotor extends. The discharge space may extend on the opposite side of the tongue from the female rotor.

According to this configuration, the operating space can be partially blocked by the tongue-like portion, so that the sealing efficiency in the casing can be improved and the compression efficiency can be improved. In addition, since the discharge space is widened on the back side of the tongue-shaped portion (on the opposite side of the tongue-shaped portion to the female rotor in the direction in which the rotational axis of the female rotor extends), the working space is released to the discharge space through the recess. The amount of gas and oil can be increased.

The tip of the opening of the recess may extend to an imaginary line connecting respective center points of the male rotor and the female rotor, or may extend across the imaginary line.

According to this configuration, gas and oil can escape from the working space until just before the working space becomes smaller and disappears. More specifically, since the working space is located near the virtual line just before the working space becomes smaller and disappears, the tip of the recess extends to that position, so that the working space that has become smaller just before it disappears is filled with gas. and oil can escape.

The stepped shape of the recess may be at least partially chamfered.

With this configuration, gas and oil can flow smoothly from the working space to the discharge space via the recess.

ADVANTAGE OF THE INVENTION According to this invention, it is a screw compressor.

Sectional drawing in the suction side end part of the compression part of the screw compressor which concerns on 1st Embodiment of this invention. FIG. 2 is a cross-sectional view of the discharge-side end portion of the screw compressor according to the first embodiment of the present invention, with the male rotor and the female rotor removed from the compression section; FIG. 3 is a cross-sectional view of a portion of the discharge side wall of the casing taken along line III-III of FIG. 2; 4 is a perspective view of the discharge sidewall of the casing; FIG. 1 is a first cross-sectional view showing rotating male and female rotors; FIG. FIG. 2 is a second cross-sectional view showing the rotating male rotor and female rotor; FIG. 3 is a third cross-sectional view showing the rotating male rotor and female rotor; FIG. 4 is a fourth cross-sectional view showing the rotating male rotor and female rotor; FIG. 5 is a fifth cross-sectional view showing the rotating male rotor and female rotor; 6 is a sixth sectional view showing the rotating male rotor and female rotor; FIG. FIG. 6 is a cross-sectional view showing the working space in FIG. 5; FIG. 7 is a cross-sectional view showing the working space in FIG. 6; FIG. 8 is a sectional view showing the working space in FIG. 7; FIG. 9 is a sectional view showing the working space in FIG. 8; FIG. 10 is a cross-sectional view showing the working space in FIG. 9; FIG. 11 is a sectional view showing the working space in FIG. 10; The perspective view of the discharge side wall of the casing of the screw compressor which concerns on 2nd Embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
A configuration of a compression section 1 of a screw compressor according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. In the drawing, X indicates the rotation axis direction of a male rotor 10 and a female rotor 20, which will be described later. Also, in a cross section perpendicular to the rotation axis direction (X direction), it is a direction (Y direction) parallel to a straight line passing through the rotation axis of the male rotor 10 and the rotation axis of the female rotor 20, and is the horizontal direction in FIG. is labeled Y. In addition, in a cross section perpendicular to the X direction, the direction is perpendicular to the Y direction, and the vertical direction is indicated by symbol Z in FIG. The upper side in the Z direction may be simply referred to as the upper side, and the lower side in the Z direction may simply be referred to as the lower side. However, this arrangement is shown as an example, and does not limit the arrangement direction of the screw compressor.

1 and 2, compression section 1 includes male rotor 10 and female rotor 20 that mesh with each other, and casing 30 that accommodates male rotor 10 and female rotor 20 .

The casing 30 is provided with an intake port 31 (schematically shown in FIG. 1) for sucking air and a discharge port 32 (shown by hatching in FIG. 2) for discharging air. In this embodiment, the suction port 31 is provided in the upper portion of the casing 30 and the discharge port 32 is provided in the lower portion of the casing 30 . Accordingly, in the compression unit 1, gas is taken in from above through the inlet 31, compressed inside, and discharged downward through the outlet 32. As shown in FIG. In the present embodiment, air is taken as an example of the gas to be compressed.

A suction space S<b>1 communicating with the suction port 31 and a discharge space S<b>2 communicating with the discharge port 32 are defined in the casing 30 . The suction space S<b>1 and the discharge space S<b>2 are separated by the male rotor 10 and the female rotor 20 . Although the entire casing 30 is made of casting, only the inner surface of the casing 30 is shown here for clarity of illustration.

The male rotor 10 has a rotating shaft member 11 and a body portion 12 fixed around the rotating shaft member 11 . Similarly, the female rotor 20 has a rotary shaft member 21 and a body portion 22 fixed around the rotary shaft member 21 . The male rotor 10 and the female rotor 20 are rotationally driven by a motor (not shown) within the casing 30 and mesh with each other to compress air. In this embodiment, the male rotor 10 has four teeth and the female rotor 20 has six teeth. When the male rotor 10 and the female rotor 20 are meshed with each other and the teeth of the male rotor 10 fit into the tooth spaces of the female rotor 20, working spaces S3 are formed between the tooth tips of the male rotor 10 and the tooth spaces of the female rotor 20. be done. Details of the working space S3 will be described later.

3 and 4, the casing 30 has a discharge space S2 so as to open to a discharge side wall surface 30a facing the discharge side end surfaces 12a, 22a of the main body portions 12, 22 of the male rotor 10 and the female rotor 20, respectively. and the working space S3. The recess 33 is recessed in the X direction. The recessed portion 33 is provided so as to communicate with an operating space S3 formed between the tooth tip of the male rotor 10 and the tooth groove of the female rotor 20 at the discharge side end portion of the compression portion 1 . That is, the working space S3 communicates with the ejection space S2 through the recess 33. As shown in FIG. It should be noted that the recess 33 of this embodiment is obtained by machining the cast casing 30 . Determination of whether or not there is a recess can be made by measuring the surface roughness. Moreover, it is also possible to judge from the difference in properties between the casting surface and the machined surface by visual confirmation.

The recess 33 has an opening 33a, and an opening edge 33b of the opening 33a is continuous with an opening edge 32a of the discharge port 32. As shown in FIG. Therefore, the opening 33a of the recess 33 has one end that is continuous with the discharge port 32 and the other end that is a dead end. That is, the opening 33 a of the recess 33 is continuous with the ejection port 32 . More specifically, the opening 33 a of the recess 33 has one end continuous with the ejection port 32 and the other end not continuous with the ejection port 32 . The opening 33a has a shape that allows air and oil to escape from the working space S3 to the discharge space S2 through the recess 33 from immediately after the working space S3 is closed until the capacity of the working space S3 becomes substantially zero. If so, it is not particularly limited. For example, the shape of the opening 33a is an elongated shape extending in one direction from one end to the other end.

The concave portion 33 has a multi-stage shape with a shallower depth toward the tip 33c of the opening 33a. That is, in this embodiment, the depth of the concave portion 33 is shallower from one end to the other end. The tip 33c of the opening 33a of the recess 33 means an end that is not continuous with the ejection port 32. As shown in FIG. The shallower depth toward the tip 33c of the opening 33a of the recess 33 means that the depth is not continuous with the discharge port 32 than the depth to the bottom of the recess 33 facing the opening edge 32a that is continuous with the discharge port 32. It is intended that the depth to the bottom of the recess 33 facing the opening edge 33b is shallower. As shown in FIG. 3, in this embodiment, the recess 33 has a two-step shape. The recess 33 has a first stepped portion 34 and a second stepped portion 35 , and the first stepped portion 34 is formed above the second stepped portion 35 (on the tip 33 c side). An opening 33 a of the recess 33 facing the first step 34 forms a tip 33 c of the opening 33 a of the recess 33 . The first stepped portion 34 has a depth of d1, and the second stepped portion 35 has a depth of d2. In the present embodiment, the depth d1 is smaller than the depth d2 (d1<d2) when the depth is shallower toward the tip of the opening 33a. The depth d1 is intended to be the distance between the end surface of the first stepped portion 34 parallel to the ejection side wall surface 30a and the ejection side wall surface 30a. The depth d2 is intended to be the distance between the end face of the second stepped portion 35 parallel to the ejection side wall surface 30a and the ejection side wall surface 30a. If the end face of the first stepped portion 34 or the end face of the second stepped portion 35 is not parallel to the discharge side wall face 30a, the end face of the first stepped portion 34 or the end face of the second stepped portion 35 is pulled from the discharge side wall face 30a. d1 or d2 is the shortest distance among the perpendiculars. Depth d1 is smaller than depth d2, and the specific depth is not limited as long as first stepped portion 34 does not reach oil supply passage 36, which will be described later. The specific height in the Z direction of the second stepped portion 35 is not limited as long as the second stepped portion 35 does not reach the oil supply passage 36 . The first stepped portion 34 has a chamfered portion 34a in which a right-angled corner portion is chamfered. The second stepped portion 35 has an obtuse-angled corner portion 35a that is not chamfered. An oil supply passage 36 for supplying oil to a bearing (not shown) is provided inside the casing 30 near the first stepped portion 34 .

Referring particularly to FIG. 2, the recess 33 extends up to an imaginary line L connecting the center point Pm of the male rotor 10 and the center point Pf of the female rotor 20 in the vertical direction (Z direction). The tip of the concave portion 33 reaches an imaginary line L connecting the center point Pm of the male rotor 10 and the center point Pf of the female rotor 20 in the vertical direction (Z direction). Alternatively, the recess 33 may extend across the imaginary line L. In this embodiment, the recess 33 is formed so that the depth of the recess 33 becomes shallower as it approaches the imaginary line L on the ejection side wall surface 30a.

5 to 10 and 11 to 16, the working space S3 whose size changes as the male rotor 10 and the female rotor 20 rotate, and the positional relationship between the working space S3 and the recess 33 will be described. do. 5 to 10 are cross-sectional views of the discharge side end of the compression section of the screw compressor according to the first embodiment of the present invention.

5 to 10 sequentially show how the male rotor 10 and the female rotor 20 rotate in the direction of arrow A. FIG. 11 to 16 show the working space S3 in FIGS. 5 to 10, respectively.

As the male rotor 10 and female rotor 20 rotate, a working space S3 is formed in which air and oil are trapped. The working space S3 is the largest in the state of FIG. 5 (FIG. 11) immediately after closing, and becomes smaller in the subsequent states of FIGS. 6 to 10 (FIGS. 12 to 16).

11 to 16 show enlarged views in which the operating space S3 and the vicinity of the recess 33 are enlarged (see the two-dot chain line circle). In the enlarged view, the overlap region R between the working space S3 and the recess 33 is hatched. The overlap region R indicates a flow path for releasing air and oil in the working space S3 to the discharge space S2. The larger the overlap region R, the more air and oil can escape from the working space S3 to the discharge space S2. Also, the greater the depth (in the X direction) of the overlap region R, the more air and oil can escape from the working space S3 to the discharge space S2.

11 to 13 at the beginning of confinement, the recess 33 has a relatively large area corresponding to the second stepped portion 35 to the chamfered portion 34a (see FIGS. 3 and 4) where the depth of the recessed portion 33 is deeper than the first stepped portion 34. overlap region R is formed. After that, in FIGS. 14 to 16, the working space S3 gradually becomes smaller, and the depth of the concave portion 33 reaches the chamfered portion 34a to the first stepped portion 34 (see FIGS. 3 and 4), which is shallower than the second stepped portion 35. Together, a relatively small overlapping region R is formed. Accordingly, the size of the flow path (the groove defined by the recess 33) for releasing air and oil also changes in accordance with the changing size of the working space S3.

According to this embodiment, air and oil can be released from the working space S3 to the discharge space S2 via the recess 33, and an abnormally high pressure in the working space S3 can be suppressed. In particular, when the working space S3 at the start of confinement is large, a large amount of air and oil can escape to the discharge space S2 by utilizing the deep portion (second stepped portion 35) of the recess 33. When the working space S3 is small, a shallow portion (first stepped portion 34) of the recess 33 can be utilized to allow a small amount of air and oil to escape to the discharge space S2. Therefore, an appropriate amount of air and oil can be released to the discharge space S2 in accordance with the size of the working space S3, and an abnormally high pressure can be effectively suppressed particularly when the working space S3 begins to be closed. In addition, since it is not necessary to form the concave portion 33 deeper than necessary, the arrangement of other components such as the bearing (not shown) and the oil supply passage 36 is not hindered, which is effective in terms of design.

2 and 16, since the recessed portion 33 extends up to the imaginary line L, air and oil can escape until just before the working space S3 becomes smaller and disappears. More specifically, since the working space S3 is positioned near the virtual line L just before the working space S3 becomes smaller and disappears, the tip 33c of the recess 33 extends to that position, so that the working space S3 becomes smaller just before it disappears. Air and oil can also escape from space S3.

Further, since the first stepped portion 34 is provided with the chamfered portion 34a, air and oil can smoothly flow from the working space S3 to the discharge space S2 via the recessed portion 33. As shown in FIG.

(Second embodiment)
The screw compressor of the second embodiment shown in FIG. 17 differs from that of the first embodiment in the configuration of the discharge side wall surface 30a. The configuration other than this is substantially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

FIG. 17 of this embodiment corresponds to FIG. 4 of the first embodiment. In this embodiment, the casing 30 has a tongue-like portion 37 that partially closes the working space S3 and partially partitions the discharge space S2 and the working space S3.

The tongue-shaped portion 37 is a thin plate, and is formed by cutting the casing 30 so as to be connected to the recess 33 inside the discharge side wall 30a in which the discharge port 32 is formed. As a result, in the direction (X direction) in which the rotational axis of the female rotor 20 extends, the casing 30 extends along the imaginary line L direction (Y direction) on the rear side of the tongue-shaped portion 37 (opposite side to the female rotor 20). A notched space 38 is formed. The cutout space 38 is formed so as to connect with the recess 33 , and the ejection space S<b>2 is enlarged by the cutout space 38 .

According to this embodiment, since the working space S3 can be partially blocked by the tongue-like portion 37, the sealing efficiency in the casing 30 can be improved, and the compression efficiency can be improved. In addition, since the discharge space S2 is widened on the back side of the tongue-shaped portion 37 (on the opposite side of the tongue-shaped portion 37 to the female rotor 20 in the direction in which the rotation axis of the female rotor 20 extends), the operation is more efficient than in the first embodiment. The amount of air and oil released from the space S3 to the discharge space S2 via the recess 33 can be increased.

As described above, specific embodiments and modifications thereof of the present invention have been described, but the present invention is not limited to the above embodiments, and various changes can be made within the scope of the present invention. For example, the recess 33 may have three or more stages. Further, in the multi-stepped shape of the concave portion 33, all the steps may be chamfered, or a part of the steps may be chamfered. Alternatively, the cutout space 38 may be formed by casting.

Reference Signs List 1 compression part 10 male rotor 11 rotary shaft member 12 main body 12a discharge side end surface 20 female rotor 21 rotary shaft member 22 main body 22a discharge side end surface 30 casing 30a wall surface (discharge side wall surface)
31 Suction port 32 Discharge port 32a Opening edge 33 Recess 33a Opening 33b Opening edge 33c Tip 34 First stepped portion 34a Chamfered portion 35 Second stepped portion 35a Corner 36 Oil supply channel 37 Tongue 38 Notched space S1 Suction space S2 ejection space S3 working space R overlapping region

Claims (4)

a male rotor and a female rotor meshing with each other;
a casing containing the male rotor and the female rotor and provided with a suction port and a discharge port, wherein the casing includes a suction space communicating with the suction port, a discharge space communicating with the discharge port, A working space is formed between the male rotor and the female rotor,
a concave portion communicating between the discharge space and the working space is provided so as to open in a discharge side wall surface of the casing facing the discharge side end surfaces of the male rotor and the female rotor,
The screw compressor, wherein the recess has a plurality of steps, the opening edge of which is continuous with the opening edge of the discharge port, and the depth of which decreases toward the tip of the opening. The casing has a tongue-shaped portion that partially closes the working space and extends to partially partition the discharge space and the working space,
2. The screw compressor according to claim 1, wherein said discharge space is widened on a side of said tongue-like portion opposite to said female rotor in the direction in which said female rotor's rotating shaft extends. 3. According to claim 1, wherein the tip of the opening of the recess extends to a virtual line connecting the respective center points of the male rotor and the female rotor, or straddles the virtual line. The described screw compressor. 4. A screw compressor according to any one of claims 1 to 3, wherein the multi-stage shape of the recess is at least partially chamfered.

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