Screw Compressor

Abstract

To provide a liquid supply type screw compressor capable of saving energy by reducing the shaft power required for stirring liquid.SOLUTION: A liquid supply type screw compressor has: a male rotor side bore 22A in which a teeth part 13A of a male rotor 11A is housed; a female rotor side bore 22B in which a teeth part 13B of a female rotor 11B is housed; a low pressure side cusp 23 and a high pressure side cusp 24 that are boundaries between a wall surface of the male rotor side bore 22A and a wall surface of the female rotor side bore 22B; and a pocket 29 that is located adjacent to the low pressure side cusp 23 in the rotor axial direction and is formed to be depressed outward in the rotor radial direction from the wall surface of the male rotor side bore 22A and the wall surface of the female rotor side bore 22B. The pocket 29 is formed of inclined surfaces 30A, 30B. The inclined surface 30A extends from the wall surface of the male rotor side bore 22A beyond a virtual plane C1 including the low pressure side cusp 23 and the high pressure side cusp 24.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid feed screw compressor that compresses gas while supplying liquid to a working chamber. [Background technology]

[0002] A liquid-fed screw compressor compresses a gas (e.g., air) while supplying a liquid (e.g., oil) to the working chamber. The purpose of supplying the liquid is to cool the gas during the compression process, seal gaps in the working chamber, and lubricate the rotor.

[0003] A liquid feed screw compressor includes, for example, a male rotor and a female rotor that rotate while meshing with each other, a male rotor side bore that houses the teeth of the male rotor, a female rotor side bore that houses the teeth of the female rotor, a low-pressure side cusp and a high-pressure side cusp that are the boundary between the wall surface of the male rotor side bore and the wall surface of the female rotor side bore, a male rotor side working chamber that is formed in the tooth grooves of the male rotor and compresses gas, and a female rotor side working chamber that is formed in the tooth grooves of the female rotor and compresses gas.

[0004] The male rotor working chamber and the female rotor working chamber move from one side to the other in the rotor axial direction as the male rotor and the female rotor rotate, changing their volumes. This allows the compressor to sequentially perform an intake stroke in which gas is drawn in through the intake passage, a compression stroke in which the gas is compressed, and a discharge stroke in which the compressed gas is discharged through the discharge passage.

[0005] In the above-described liquid feed screw compressor, a blow-out flow occurs from the high-pressure working chamber to the low-pressure working chamber through the meshing portion between the male rotor and the female rotor (in other words, the gap between the male rotor and the female rotor). Depending on the compressor structure, the liquid contained in the compressed gas may turn into a high-temperature mist and blow out into the suction passage.

[0006] Therefore, the liquid-feed screw compressor of Patent Document 1 has ribs arranged in the suction passage and pockets formed by the ribs. The pockets are located adjacent to the low-pressure cusps in the rotor axial direction and are recessed radially outward from the wall surfaces of the male rotor bore and the female rotor bore. The ribs and pockets prevent liquid contained in the compressed gas from spraying into the suction passage. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-174830 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the prior art has room for improvement as follows.

[0009] The rib in Patent Document 1 has a structure that is line-symmetrical about a first imaginary plane that includes the low-pressure side cusp and the high-pressure side cusp. Therefore, the pocket in Patent Document 1 is formed of a first inclined surface that extends from the wall surface of the male rotor-side bore so as not to exceed the first imaginary plane and is inclined so that the greater the distance from the wall surface of the male rotor-side bore, the greater the distance from the wall surface of the male rotor-side bore becomes, and a second inclined surface that extends from the wall surface of the female rotor-side bore so as not to exceed the first imaginary plane and is inclined so that the greater the distance from the wall surface of the female rotor-side bore, the greater the distance from the second imaginary plane becomes.

[0010] The liquid ejected from the male rotor side working chamber and the female rotor side working chamber passes through the pocket and flows back into the male rotor side working chamber and the female rotor side working chamber. According to the structure of the pocket described above, the distribution ratio of the liquid flowing from the pocket into the male rotor side working chamber is approximately the same as the distribution ratio of the liquid flowing from the pocket into the female rotor side working chamber.

[0011] However, since the male rotor generally has a larger outer diameter than the female rotor, it rotates at a higher speed than the female rotor. As a result, the liquid that flows into the male rotor working chamber is agitated at a higher speed than the liquid that flows into the female rotor working chamber. Therefore, if the distribution ratio of the liquid flowing from the pocket into the female rotor working chamber is increased and the distribution ratio of the liquid flowing from the pocket into the male rotor working chamber is decreased, the shaft power required to agitate the liquid can be reduced, thereby saving energy.

[0012] The present invention has been made in view of the above circumstances, and one of its objects is to reduce the shaft power required for agitating a liquid to thereby save energy. [Means for solving the problem]

[0013] The present invention includes a plurality of means for solving the above-mentioned problems, and one example thereof is a liquid feed screw compressor having a male rotor and a female rotor which rotate while meshing with each other, a male rotor side bore for accommodating the teeth of the male rotor, a female rotor side bore for accommodating the teeth of the female rotor, a low-pressure side cusp and a high-pressure side cusp which are boundary lines between a wall surface of the male rotor side bore and a wall surface of the female rotor side bore, a male rotor side working chamber formed in a tooth groove of the male rotor for compressing a gas, a female rotor side working chamber formed in a tooth groove of the female rotor for compressing a gas, and a liquid feed nozzle which supplies a liquid to the male rotor side working chamber and the female rotor side working chamber, and further includes a pocket formed so as to be recessed radially outward from the wall surface of the male rotor side bore and the wall surface of the female rotor side bore, the pocket being formed by a first inclined surface that extends from the wall surface of the male rotor side bore so as to exceed a first imaginary plane including the low-pressure side cusp and the high-pressure side cusp, and is inclined so as to become increasingly separated from a second imaginary plane including the axial center of the male rotor and the axial center of the female rotor as the pocket becomes greater away from the wall surface of the male rotor side bore, and a second inclined surface that extends from the wall surface of the female rotor side bore so as not to exceed the first imaginary plane, and is inclined so as to become increasingly separated from the second imaginary plane as the pocket becomes greater away from the wall surface of the female rotor side bore. The bottom of the pocket, which is the boundary between the first inclined surface and the second inclined surface, is not located on the first imaginary plane, but is located closer to the axial center of the female rotor than the first imaginary plane. . [Effects of the Invention]

[0014] According to the present invention, the shaft power required for agitating the liquid can be reduced, thereby achieving energy savings.

[0015] Problems, configurations, and effects other than those described above will become clear from the following description. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram illustrating a configuration of a liquid feed screw compressor according to a first embodiment of the present invention. [Figure 2]1 is an axial cross-sectional view showing the structure of a compressor main body according to a first embodiment of the present invention. [Figure 3] 1 is an axial cross-sectional view showing the structure of a compressor main body according to a first embodiment of the present invention. [Figure 4] 1 is a radial cross-sectional view showing the structure of a compressor body according to a first embodiment of the present invention. [Figure 5] FIG. 5 is an axial cross-sectional view showing the structure of a compressor main body according to a second embodiment of the present invention. [Figure 6] FIG. 5 is a radial cross-sectional view showing the structure of a compressor body according to a second embodiment of the present invention. [Figure 7] FIG. 10 is an axial cross-sectional view showing the structure of a compressor body according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A first embodiment of the present invention will be described with reference to Figs. 1 to 4. Fig. 1 is a schematic diagram showing the configuration of a liquid feed screw compressor in this embodiment. Figs. 2 and 3 are axial cross-sectional views showing the structure of a compressor main body in this embodiment. Fig. 4 is a radial cross-sectional view showing the structure of a compressor main body in this embodiment. Note that Fig. 2 corresponds to the cross-sectional view taken along section II-II in Fig. 4, and Fig. 3 corresponds to the cross-sectional view taken along section III-III in Fig. 4. Fig. 4 corresponds to the cross-sectional view taken along section IV-IV in Fig. 2 or Fig. 3.

[0018] The screw compressor of this embodiment includes a motor 1, a compressor body 2 driven by the motor 1 and compressing a gas (e.g., air), a gas-liquid separator 3 that separates the compressed gas discharged from the compressor body 2 from the liquid (e.g., oil) contained therein, and a liquid pipe 4 that supplies the liquid separated by the gas-liquid separator 3 to the working chamber of the compressor body 2. The liquid pipe 4 is provided with a cooler 5 that cools the liquid, a filter 6 that removes impurities from the liquid, and the like.

[0019] The compressor body 2 includes a male rotor 11A, a female rotor 11B, and a casing 12 that houses the male rotor 11A and the female rotor 11B.

[0020] The male rotor 11A has a toothed portion 13A having a plurality of spirally extending teeth (four in this embodiment), an intake-side shaft 14 connected to one axial side (left side in Fig. 2) of the toothed portion 13A, and a discharge-side shaft 15 connected to the other axial side (right side in Fig. 2) of the toothed portion 13A. The intake-side shaft 14 of the male rotor 11A is rotatably supported by an intake-side bearing 16, and the discharge-side shaft 15 of the male rotor 11A is rotatably supported by an exhaust-side bearing 17.

[0021] Similarly, the female rotor 11B has a toothed portion 13B having a plurality of (six in this embodiment) spirally extending teeth, a suction-side shaft portion (not shown) connected to one axial side of the toothed portion 13B, and a discharge-side shaft portion (not shown) connected to the other axial side of the toothed portion 13B. The suction-side shaft portion of the female rotor 11B is rotatably supported by a suction-side bearing (not shown), and the discharge-side shaft portion of the female rotor 11B is rotatably supported by a discharge-side bearing (not shown).

[0022] The suction side shaft 14 of the male rotor 11A passes through the casing 12 and is connected to the rotating shaft of the motor 1. When the motor 1 is driven, the male rotor 11A rotates, and the teeth 13A of the male rotor 11A mesh with the teeth 13B of the female rotor 11B, causing the female rotor 11B to also rotate.

[0023] The casing 12 is composed of a main casing 18, an intake side casing 19 connected to one axial side of the main casing 18 (left side in Figure 2), and a discharge side casing 20 connected to the other axial side of the main casing 18 (right side in Figure 2).

[0024] The main casing 18 has a male rotor bore 22A that accommodates the teeth 13A of the male rotor 11A and forms a male rotor working chamber 21A in the tooth spaces, and a female rotor bore 22B that accommodates the teeth 13B of the female rotor 11B and forms a female rotor working chamber 21B in the tooth spaces. The bores 22A and 22B partially overlap each other, and have a low-pressure side cusp 23 and a high-pressure side cusp 24 as the boundary between their wall surfaces.

[0025] The male rotor side working chamber 21A and the female rotor side working chamber 21B move from one side to the other in the rotor axial direction as the male rotor 11A and the female rotor 11B rotate, changing their volumes. This allows for an intake stroke in which gas is drawn in through the intake passage 25, a compression stroke in which the gas is compressed, and a discharge stroke in which the compressed gas is discharged through the discharge passage 26 to be carried out in sequence. Note that the intake passage 25 in this embodiment is arranged so as to overlap with the tooth portions 13A of the male rotor 11A and the tooth portions 13B of the female rotor 11B when viewed from the rotor radial direction, and extends in the rotor radial direction.

[0026] The main casing 18 has a liquid supply nozzle 27 that supplies liquid to the male rotor side working chamber 21A and the female rotor side working chamber 21B. The purpose of supplying liquid is to cool the gas during the compression stroke, seal gaps in the working chambers, and lubricate the rotors.

[0027] In the compressor body 2 described above, a blow-out flow is generated from the high-pressure working chamber toward the low-pressure working chamber through the meshing portion between the male rotor 11A and the female rotor 11B (in other words, the gap between the male rotor 11A and the female rotor 11B). Depending on the structure of the compressor body 2, there is a possibility that the liquid contained in the compressed gas will turn into high-temperature mist and blow out into the intake passage 25.

[0028] Therefore, the compressor body 2 of this embodiment has ribs 28 disposed in the intake passage 25 and extending in the rotor axial direction, and pockets 29 formed by the ribs 28 (in other words, formed so as not to directly communicate with the intake passage 25). The pockets 29 are located adjacent to the low-pressure-side cusp 23 in the rotor axial direction and are recessed radially outward (upper side in FIG. 4 ) from the wall surfaces of the male rotor-side bore 22A and the female rotor-side bore 22B. The pockets 29 are formed so as to be larger than the width H1 of the meshing portion between the male rotor 11A and the female rotor 11B (more specifically, the distance between the position where the tooth tips of the male rotor 11A pass and the position where the tooth tips of the female rotor 11B pass on a line perpendicular to the axial center O1 of the male rotor 11A and the axial center O2 of the female rotor 11B) and smaller than the width H2 between the axial center O1 of the male rotor 11A and the axial center O2 of the female rotor 11B. The ribs 28 and the pockets 29 prevent the liquid contained in the compressed gas from spraying out into the intake passage 25 .

[0029] The most significant feature of this embodiment is that the rib 28 is not symmetrical about an imaginary plane C1 that includes the low-pressure side cusp 23 and the high-pressure side cusp 24. The pocket 29 is formed by inclined surfaces 30A and 30B of the rib 28. The inclined surface 30A of the rib 28 extends beyond the wall surface of the male rotor-side bore 22A and exceeds the imaginary plane C1. The greater the distance from the wall surface of the male rotor-side bore 22A, the greater the inclination becomes relative to an imaginary plane C2 that includes the axial center O1 of the male rotor 11A and the axial center O2 of the female rotor 11B. The inclined surface 30B of the rib 28 extends from the wall surface of the female rotor-side bore 22B without exceeding the imaginary plane C2. The greater the distance from the wall surface of the female rotor-side bore 22B, the greater the inclination becomes relative to the imaginary plane C2. Therefore, the boundary between the inclined surface 30A and the inclined surface 30B of the rib 28 (in other words, the bottom of the pocket 29) is located closer to the axial center O2 of the female rotor 11B than the imaginary plane C1.

[0030] The above-described structure of the pocket 29 provides the following advantages. Most of the lubricating oil ejected from the male rotor-side working chamber 21A and the female rotor-side working chamber 21B and flowing into the pocket 29 collides with the inclined surface 30A or 30B of the rib 28 due to inertial force, moves along the inclined surface 30A or 30B, and collects near the boundary between the inclined surface 30A and the inclined surface 30B. Subsequently, most of the lubricating oil collected near the boundary between the inclined surface 30A and the inclined surface 30B of the rib 28 flows into the female rotor-side working chamber 21B due to its own weight. Therefore, the distribution ratio of the liquid flowing from the pocket 29 into the female rotor-side working chamber 21B can be increased, and the distribution ratio of the liquid flowing from the pocket 29 into the male rotor-side working chamber 21A can be decreased. Here, the liquid flowing into the male rotor-side working chamber 21A is agitated at a higher speed than the liquid flowing into the female rotor-side working chamber 21B. Therefore, the shaft power required for agitating the liquid can be reduced, thereby achieving energy savings.

[0031] A second embodiment of the present invention will be described with reference to Figs. 5 and 6. Fig. 5 is an axial cross-sectional view showing the structure of a compressor body in this embodiment. Fig. 6 is a radial cross-sectional view showing the structure of a compressor body in this embodiment. Note that Fig. 5 corresponds to the cross-sectional view taken along section VV in Fig. 6, and Fig. 6 corresponds to the cross-sectional view taken along section VI-VI in Fig. 5. Note that in this embodiment, parts equivalent to those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0032] Intake passage 25A of this embodiment extends in the rotor radial direction and is arranged so as not to overlap with tooth portion 13A of male rotor 11A and tooth portion 13B of female rotor 11B when viewed in the rotor radial direction. Pocket 29A of this embodiment is different from pocket 29 of the first embodiment in that it is formed so as to directly communicate with intake passage 25A.

[0033] Like the pocket 29 of the first embodiment, the pocket 29A of this embodiment is positioned adjacent to the low-pressure side cusp 23 in the rotor axial direction, and is formed so as to be recessed radially outward (upper side in FIG. 6) from the wall surfaces of the male rotor-side bore 22A and the female rotor-side bore 22B. The pocket 29A is also formed so as to be larger than the width H1 of the meshing portion between the male rotor 11A and the female rotor 11B, and smaller than the width H2 between the axial center O1 of the male rotor 11A and the axial center O2 of the female rotor 11B.

[0034] In this embodiment, the pocket 29A is formed by inclined surfaces 30A and 30B. The inclined surface 30A extends beyond the wall surface of the male rotor bore 22A so as to exceed the imaginary plane C1, and the greater the distance from the wall surface of the male rotor bore 22A, the greater the inclination relative to the imaginary plane C2. The inclined surface 30B extends from the wall surface of the female rotor bore 22B so as not to exceed the imaginary plane C2, and the greater the distance from the wall surface of the female rotor bore 22B, the greater the inclination relative to the imaginary plane C2. Therefore, the boundary between the inclined surfaces 30A and 30B (in other words, the bottom of the pocket 29A) is located closer to the axial center O2 of the female rotor 11B than the imaginary plane C1.

[0035] In this embodiment configured as above, similarly to the first embodiment, the shaft power required for stirring the liquid can be reduced, thereby achieving energy savings.

[0036] In the second embodiment, the pocket 29A is formed to directly communicate with the intake passage 25A (i.e., the male rotor side working chamber 21A and the female rotor side working chamber 21B take in gas via the intake passage 25A and the pocket 29A), but this is not limiting. For example, as in the modified example shown in Fig. 7, the pocket 29A may be formed so as not to directly communicate with the intake passage 25A by a partition wall 31 extending in the rotor radial direction. This may prevent liquid contained in the compressed gas from spraying into the intake passage 25A.

[0037] Although not specifically described in the first and second embodiments, the inclined surface 30A may be formed of at least one flat surface, at least one curved surface, or a combination thereof. The inclined surface 30B may be formed of at least one flat surface, at least one curved surface, or a combination thereof. [Explanation of symbols]

[0038] 11A...male rotor, 11B...female rotor, 13A, 13B...teeth, 21A...male rotor side working chamber, 21B...female rotor side working chamber, 22A...male rotor side bore, 22B...female rotor side bore, 23...low pressure side cusp, 24...high pressure side cusp, 25, 25A...suction passage, 27...liquid supply nozzle, 29, 29A...pocket, 30A, 30B...inclined surface

Claims

1. a male rotor and a female rotor that rotate while meshing with each other; a male rotor bore for accommodating the teeth of the male rotor; a female rotor bore for accommodating the teeth of the female rotor; a low-pressure side cusp and a high-pressure side cusp that are boundary lines between a wall surface of the male rotor side bore and a wall surface of the female rotor side bore; a male rotor side working chamber formed in a tooth groove of the male rotor and compressing a gas; a female rotor side working chamber formed in a tooth groove of the female rotor and compressing a gas; a liquid supply nozzle for supplying liquid to the male rotor side working chamber and the female rotor side working chamber, a pocket positioned adjacent to the low-pressure side cusp in the rotor axial direction and recessed radially outward from the wall surfaces of the male rotor bore and the female rotor bore, The pocket is a first inclined surface that extends from a wall surface of the male rotor side bore beyond a first imaginary plane that includes the low-pressure side cusp and the high-pressure side cusp, and that is inclined so that the greater the distance from the wall surface of the male rotor side bore, the greater the distance from a second imaginary plane that includes the axial center of the male rotor and the axial center of the female rotor; a second inclined surface extending from a wall surface of the female rotor side bore so as not to exceed the first imaginary plane, and inclined so as to deviate more from the second imaginary plane as the wall surface of the female rotor side bore becomes larger, a bottom of the pocket, which is a boundary between the first inclined surface and the second inclined surface, is not positioned on the first imaginary plane but is positioned closer to the axial center of the female rotor than the first imaginary plane.

2. 2. The liquid feed screw compressor according to claim 1, a pocket formed so as to be larger than the width of the meshing portion between the male rotor and the female rotor and smaller than the width between the axial centers of the male rotor and the female rotor;

3. 2. The liquid feed screw compressor according to claim 1, the pockets are arranged so as to overlap with the teeth of the male rotor and the teeth of the female rotor when viewed from the rotor radial direction, and are formed so as not to directly communicate with suction flow paths communicating with the male rotor side working chamber and the female rotor side working chamber.

4. In the liquid-feed screw compressor according to claim 1, a casing that houses the male rotor and the female rotor, 10. An oil-lubricated screw compressor, wherein the casing is configured so that the male rotor side working chamber and the female rotor side working chamber take in gas from the rotor axial direction.

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