Oil-cooled screw compressor

Abstract

To provide an oil-cooled screw compressor which can efficiently and stably collect a lubricant, and can suppress the stagnation of an excess lubricant.SOLUTION: An oil-cooled screw compressor comprises a compressor main body 1 having a pair of screw rotors 11, and a gear chamber 24 for accommodating a power transmission gear 21 for transmitting rotation to the pair of screw rotors 11 therein, and having an oil discharge port 24a of a lubricant at a bottom face. The oil discharge port 24a communicates with an oil flow-in port 12af which opens at a casing 12 so as to be located between suction-side end faces 11ab, 11bb of the pair of screw rotors 11, and a suction-side inner wall face 12ae opposing the suction-side end faces 11ab, 11bb. The casing 12 has a declining inclination part 12ah declining toward a bottom part 12ag of the casing 12 which opposes one lower end of one of the pair of screw rotors 11, and the oil flow-in port 12af is arranged in a position higher than the bottom part 12ag of the casing 12 at the inclination part 12ah.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an oil-cooled screw compressor.

Background Art

[0002] In an oil-cooled gas compressor that transmits the rotation of a drive motor to a compressor main body via a power transmission gear, efficiently recovering the lubricating oil supplied to the power transmission gear leads to reducing the power loss caused by the lubricating oil being agitated by the power transmission gear, and thus is essential for improving efficiency.

[0003] For example, in the oil-cooled screw compressor of Patent Document 1, communication ports are provided not only at the lower part but also at the upper part of the partition wall that separates the suction passage (suction chamber) and the gear chamber, and the lubricating oil in mist form by each gear of the speed increasing device is mixed with the suction air and made to flow into the suction passage, suppressing excessive retention of the lubricating oil in the gear chamber and reducing the power loss associated with the agitation of the lubricating oil of the speed increasing gear.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, as a structure for effectively recovering the lubricating oil, unlike the oil-cooled screw compressor of Patent Document 1, a communication passage that connects the lower part of the suction passage and the gear chamber is provided without providing a communication port at the upper part of the partition wall, and the differential pressure between the suction pressure of the suction passage and the pressure inside the gear chamber is utilized to cause the lubricating oil accumulated in the lower part of the gear chamber to flow into the suction passage through the communication passage.

[0006] However, in this structure, if the communication passage is not filled with lubricating oil, no pressure difference will be generated between the suction passage and the gear chamber. Therefore, when the communication passage is not filled with lubricating oil, the lubricating oil cannot be efficiently recovered, and there is a risk that surplus lubricating oil will stagnate in the gear chamber.

[0007] As another structure, there is one in which the opening of the communication passage is provided on the side wall of the bore chamber in which a pair of screw rotors are accommodated. In this case, since the centrifugal force of the screw rotor acts in the direction opposite to the inflow direction of the lubricating oil, it is difficult to smoothly flow the lubricating oil into the bore chamber.

[0008] Of course, if the force for sucking the lubricating oil is greater than the centrifugal force of the screw rotor, the lubricating oil can be easily flowed into the bore chamber. However, the suction pressure at the opening of the communication passage in the bore chamber differs between the tooth portions and groove portions of the rotating screw rotor, and greatly fluctuates when the tooth portions and groove portions pass through the opening. Therefore, it is difficult to stably recover the lubricating oil.

[0009] Furthermore, as a modification of the above other structure, there is one in which the opening of the communication passage is provided below the lower end of either one of the pair of screw rotors. However, in this case, surplus lubricating oil is likely to stagnate between either one of the pair of screw rotors and the opening, and there is a risk that efficient recovery of the lubricating oil will be hindered.

[0010] An object of the present invention is to provide an oil-cooled screw compressor that can efficiently and stably recover lubricating oil and suppress the stagnation of surplus lubricating oil.

Means for Solving the Problems

[0011] To achieve the above object, the present invention provides a compressor main body including a pair of screw rotors and a casing having a bore chamber that rotatably accommodates the pair of screw rotors in a meshed state, and a power transmission gear that accommodates inside the rotation of a drive motor transmitted to the pair of screw rotors via a rotor shaft, and a gear chamber having an oil discharge port for discharging lubricating oil at the bottom surface. The oil discharge port communicates with an oil inlet that opens in the casing so as to be located between the suction side end surface of the pair of screw rotors and the suction side inner wall surface facing the suction side end surface of the pair of screw rotors. The casing has an inclined portion with a downward gradient that descends toward the bottom of the casing facing the lower end of either one of the pair of screw rotors, and the oil inlet is provided at a position higher than the bottom of the casing in the inclined portion.

Effect of the Invention

[0012] According to the present invention, it is possible to suppress the stagnation of surplus lubricating oil in the gear chamber and suppress the influence of centrifugal force accompanying the rotation of the pair of screw rotors on the inflow of lubricating oil, so that the lubricating oil can be efficiently and stably recovered, and the power loss caused by the lubricating oil being agitated by the power transmission gear can be reduced. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] Hereinafter, with reference to the drawings, the configuration and operation of the oil-cooled screw compressor according to the first to third embodiments of the present invention will be described. In each figure, the same reference numerals denote the same parts.

[0015] (First Embodiment) FIG. 1 is a schematic view of a horizontal cross-section of the oil-cooled screw compressor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1. FIG. 3 is a cross-sectional view taken along the line III-III of FIGS. 1 and 2.

[0016] The oil-cooled screw compressor of the present embodiment is a compressor having a compressor main body 1 and a power transmission device 2, and the rotational speed of a drive motor (not shown) can be increased, for example, by the power transmission device 2 and transmitted to the compressor main body 1.

[0017] The compressor main body 1 is a device for compressing gas, and includes a pair of screw rotors 11 and a casing 12 having a bore chamber 12c that rotatably houses the pair of screw rotors 11 in a meshed state.

[0018] The pair of screw rotors 11 includes a drive-side screw rotor 11a and a driven-side screw rotor 11b. In the present embodiment, the drive-side screw rotor 11a is a male-type screw rotor (male rotor 11a), the driven-side screw rotor 11b is a female-type screw rotor (female rotor 11b), and the male rotor 11a and the female rotor 11b mesh with each other and rotate.

[0019] The male rotor 11a has a male rotor tooth portion 11aa, a suction-side rotor shaft 11ac that protrudes from the suction-side end face 11ab of the male rotor tooth portion 11aa, and a discharge-side rotor shaft 11ae that protrudes from the discharge-side end face 11ad of the male rotor tooth portion 11aa.

[0020] On the male rotor tooth portion 11aa, a plurality of spiral male teeth (lobes) are formed, and tooth grooves are formed between the plurality of male teeth. The suction side rotor shaft 11ac is rotatably supported by the suction side bearing 13a, and extends into the power transmission device 2, for example, from a through hole 12aaa provided in the suction side side wall 12aa on the power transmission device 2 side of the casing 12. A driven gear 21b is fixed to the suction side rotor shaft 11ac extending into the power transmission device 2. Further, the discharge side rotor shaft 11ae is rotatably supported by a plurality (three in this embodiment) of discharge side bearings 13b.

[0021] The female rotor 11b has a female rotor tooth portion 11ba, a suction side rotor shaft 11bc protruding from the suction side end face 11bb of the female rotor tooth portion 11ba, and a discharge side rotor shaft 11be protruding from the discharge side end face 11bd of the female rotor tooth portion 11ba.

[0022] On the female rotor tooth portion 11ba, a plurality of spiral female teeth are formed, and tooth grooves are formed between the plurality of female teeth. The suction side rotor shaft 11bc is rotatably supported by the suction side bearing 13c. The discharge side rotor shaft 11be is rotatably supported by a plurality (three in this embodiment) of discharge side bearings 13d.

[0023] The casing 12 is a housing that covers the pair of screw rotors 11, and includes a main casing 12a and a discharge side casing 12b. In the casing 12, a bore chamber 12c is formed to accommodate the male rotor tooth portion 11aa of the male rotor 11a and the female rotor tooth portion 11ba of the female rotor 11b in a meshed state with each other.

[0024] The bore chamber 12c is formed by two axially overlapping cylindrical spaces, and is formed by closing an opening on one axial side (the left side of the main casing 12a in FIGS. 1 and 2) formed in the main casing 12a with the discharge side casing 12b.

[0025] The bore chamber 12c has the following three inner walls. The male-side inner peripheral wall 12ca, which is the first inner wall, is an inner wall that covers the outer side in the radial direction of the male rotor tooth portion 11aa and is formed as a curved surface. The female-side inner peripheral wall 12cb, which is the second inner wall, is an inner wall that covers the outer side in the radial direction of the female rotor tooth portion 11ba and is formed as a curved surface. The discharge-side inner wall 12cc, which is the third inner wall, is an inner wall that faces the discharge-side end surface 11ad of the male rotor tooth portion 11aa and the discharge-side end surface 11bd of the female rotor tooth portion 11ba and is formed as a plane. Note that on the suction side (the right side in FIGS. 1 and 2) of the male rotor tooth portion 11aa and the female rotor tooth portion 11ba, a suction-side inner wall 12cd (see FIGS. 1 and 3) that is in close contact with a part of the suction-side end surface 11ab of the male rotor tooth portion 11aa and a part of the suction-side end surface 11bb of the female rotor tooth portion 11ba is formed so as to cover the meshing portion of the male rotor tooth portion 11aa and the female rotor tooth portion 11ba from below.

[0026] A plurality of male-side working chambers with the suction side (the right side in FIGS. 1 and 2) open are formed by the male rotor tooth portion 11aa, the male-side inner peripheral wall 12ca, and the discharge-side inner wall 12cc. Also, a plurality of female-side working chambers with the suction side (the right side in FIGS. 1 and 2) open are formed by the female rotor tooth portion 11ba, the female-side inner peripheral wall 12cb, and the discharge-side inner wall 12cc. The plurality of male-side working chambers and the plurality of female-side working chambers are such that the male rotor 11a and the female rotor 11b mesh with each other and rotate, and when they reach a position in close contact with the suction-side inner wall 12cd, the suction side (the right side in FIGS. 1 and 2) is closed by the suction-side inner wall 12cd.

[0027] Suction-side bearing chambers 12ab and 12ac for housing the suction-side bearings 13a and 13c are provided in the suction-side side wall 12aa of the main casing 12a. Discharge-side bearing chambers 12bb and 12bc for housing the discharge-side bearings 13b and 13d are provided in the discharge-side casing 12b. Also, a discharge-side cover 12d for fixing the discharge-side bearing 13b and closing the discharge-side bearing chamber 12bb, and a discharge-side cover 12e for fixing the discharge-side bearing 13d and closing the discharge-side bearing chamber 12bc are attached to the discharge-side casing 12b.

[0028] As shown in FIG. 2, a suction passage 12ad is provided upstream of the bore chamber 12c in the main casing 12a. The suction passage 12ad is a passage that communicates the outside of the main casing 12a with the suction-side opening of the bore chamber 12c.

[0029] An oil inlet 12af that opens into the main casing 12a is provided in the suction passage 12ad so as to be located between the suction-side end faces 11ab and 11bb of the pair of screw rotors 11 and the suction-side inner wall surface 12ae of the main casing 12a facing the suction-side end faces 11ab and 11bb.

[0030] Further, as shown in FIG. 3, the main casing 12a has an inclined portion 12ah with a downward slope that descends toward the bottom 12ag of the main casing 12a facing the lower end of one of the pair of screw rotors 11 (male rotor 11a in this embodiment). And the oil inlet 12af is provided at a position higher than the bottom 12ag of the main casing 12a in the inclined portion 12ah.

[0031] Also, the oil inlet 12af is preferably located at a position on the inner peripheral surface 12ai of the main casing 12a that rises in the rotational direction (rotational direction 11af in this embodiment) of one of the pair of screw rotors (male rotor 11a in this embodiment) from the bottom 12ag of the main casing 12a.

[0032] As shown in FIG. 2, a first oil supply passage 12aj for supplying lubricating oil into the bore chamber 12c is provided in the main casing 12a. Also, a discharge passage 12bf for discharging a mixture of compressed gas and lubricating oil from the bore chamber 12c to the outside of the casing 12 is provided in the discharge-side casing 12b. The discharge passage 12bf communicates the discharge-side opening of the bore chamber 12c with the outside of the casing 12.

[0033] Also, a second oil supply passage 12ba for supplying lubricating oil into the discharge-side bearing chambers 12bb and 12bc and a first communication passage 12bd that communicates the discharge-side bearing chambers 12bb and 12bc with the bore chamber 12c are provided in the discharge-side casing 12b.

[0034] The power transmission device 2 is a device that increases the rotational speed of a drive motor (not shown), for example, and transmits it to the compressor main body 1, and includes a pair of power transmission gears 21 and a gear case 22.

[0035] The pair of power transmission gears 21 includes a drive gear 21a fixed to a drive shaft 23 (see FIG. 1) coupled to the output shaft of a drive motor (not shown), and a driven gear 21b fixed to the suction side rotor shaft 11ac of the male rotor 11a. The drive gear 21a and the driven gear 21b mesh with each other, and the rotation of the drive motor is transmitted to the pair of screw rotors 11 via the suction side rotor shaft 11ac.

[0036] Depending on the gear ratio between the drive gear 21a and the driven gear 21b, the rotational speed of the suction side rotor shaft 11ac can be increased or decreased with respect to the rotational speed of the drive motor. Thereby, the oil-cooled screw compressor of the present embodiment can set the pair of screw rotors 11 to a predetermined rotational speed without changing the drive motor.

[0037] The gear case 22 is attached to the end face 12ak of the suction side wall 12aa of the main casing 12a, and is a housing that forms a gear chamber 24 for housing the power transmission gear 21 therein between the inner peripheral surface of the gear case 22 and the end face 12ak.

[0038] A third oil supply passage 22a (see FIG. 2) is provided in the gear case 22 above the pair of power transmission gears 21. Lubricating oil is supplied from the third oil supply passage 22a to the pair of power transmission gears 21. Further, an oil discharge port 24a for discharging the lubricating oil is provided on the bottom surface of the gear chamber 24. The oil discharge port 24a communicates with an oil inlet 12af via a second communication passage 12al provided in the main casing 12a.

[0039] Note that the oil discharge port 24a of the present embodiment is preferably provided only at the bottom of the gear chamber 24. As a result, the lubricating oil accumulated on the bottom surface of the gear chamber 24 flows into and fills the second communication passage 12al from the oil discharge port 24a, eliminating the gas flow between the suction passage 12ad and the gear chamber 24 and forming a pressure difference between the suction passage 12ad and the gear chamber 24.

[0040] Figure 4 is an oil supply system diagram of the oil-cooled screw compressor according to the first embodiment of the present invention. The oil-cooled screw compressor according to the present embodiment supplies lubricating oil to the bore chamber 12c, the discharge-side bearing chambers 12bb, 12bc, and the gear chamber 24. The lubricating oil is used for lubricating the male and female rotors 11a, 11b and the discharge-side bearings 13b, 13d, cooling the compressed gas in the bore chamber 12c, and sealing the gaps between the male and female rotors 11a, 11b and the wall surfaces of the bore chamber 12c (the male-side inner peripheral wall 12ca and the female-side inner peripheral wall 12cb), and the gaps at the meshing portions of the male rotor 11a and the female rotor 11b.

[0041] As shown in Figure 4, the oil-cooled screw compressor of the present embodiment is provided with an external liquid supply system 3 for supplying lubricating oil. The external liquid supply system 3 includes a gas-liquid separator 31, a lubricating oil cooler 32, an oil filter 33, and a pipeline 34 connecting them.

[0042] The gas-liquid separator 31 is a device that separates the lubricating oil contained in the compressed gas from the compressed gas discharged from the discharge passage 12bf. The compressed gas from which the lubricating oil has been removed is supplied to external equipment (not shown). On the other hand, the separated lubricating oil is stored in the lower part.

[0043] The lubricating oil stored in the lower part of the gas-liquid separator 31 is cooled by the lubricating oil cooler 32 and then filtered for foreign substances by the oil filter 33. The lubricating oil filtered by the oil filter 33 flows into the first pipeline 34a, the second pipeline 34b, and the third pipeline 34c that branch from the pipeline 34 connected to the oil filter 33. The lubricating oil flowing into the first pipeline 34a is supplied to the first oil supply passage 12aj, the lubricating oil flowing into the second pipeline 34b is supplied to the second oil supply passage 12ba, and the lubricating oil flowing into the third pipeline 34c is supplied to the third oil supply passage 22a.

[0044] Note that the lubricating oil is preferably circulated through the external liquid supply system 3 by using the pressure of the compressed gas flowing into the gas-liquid separator 31 without using a power source such as a pump.

[0045] The first oil supply passage 12aj is an oil supply passage provided in the main casing 12a to supply lubricating oil to the pair of screw rotors 11 in the bore chamber 12c. The lubricating oil supplied into the bore chamber 12c from the first oil supply passage 12aj is discharged into the gas-liquid separator 31 together with the compressed gas from the discharge flow passage 12bf and recovered by the gas-liquid separator 31.

[0046] The second oil supply passage 12ba is an oil supply passage provided in the discharge-side casing 12b to supply lubricating oil to the discharge-side bearing chambers 12bb and 12bc. The lubricating oil supplied to the discharge-side bearing chambers 12bb and 12bc by the second oil supply passage 12ba lubricates the discharge-side bearings 13b and 13d.

[0047] The lubricating oil that has lubricated the discharge-side bearings 13b and 13d is discharged into the bore chamber 12c from the first communication passage 12bd that communicates the discharge-side bearing chamber 12bb provided in the discharge-side casing 12b with the bore chamber 12c. The lubricating oil discharged into the bore chamber 12c is discharged into the gas-liquid separator 31 together with the compressed gas from the discharge flow passage 12bf and recovered by the gas-liquid separator 31.

[0048] The third oil supply passage 22a is an oil supply passage provided in the gear case 22 to supply lubricating oil into the gear chamber 24. The lubricating oil supplied into the gear chamber 24 from the third oil supply passage 22a lubricates a pair of power transmission gears 21. The lubricating oil that has lubricated the pair of power transmission gears 21 accumulates on the bottom surface of the gear chamber 24. As described above, an oil discharge port 24a is provided on the bottom surface of the gear chamber 24. The oil discharge port 24a communicates with the oil inlet 12af through the second communication passage 12al. Therefore, the lubricating oil that has accumulated on the bottom surface of the gear chamber 24 is discharged from the oil discharge port 24a into the second communication passage 12al, and the lubricating oil that has passed through the second communication passage 12al flows into the suction passage 12ad from the oil inlet 12af. The lubricating oil that has flowed into the suction passage 12ad flows into the bore chamber 12c and is discharged together with the gas compressed from the discharge passage 12bf into the gas-liquid separator 31, where it is recovered.

[0049] As described above, the second communication passage 12al is a passage that communicates the oil discharge port 24a and the oil inlet 12af, and is provided on the suction-side wall 12aa of the main casing 12a. The second communication passage 12al is connected in series to the third oil supply passage 22a via the gear chamber 24. Therefore, all the lubricating oil supplied from the third oil supply passage 22a flows into the suction passage 12ad through the second communication passage 12al.

[0050] Next, the operation of the screw compressor according to the first embodiment will be described with reference to FIGS. 1 to 4.

[0051] By rotating a drive motor connected to the drive-side shaft 23, the drive gear 21a of the power transmission device 2 is rotated. When the drive gear 21a rotates, the driven gear 21b that meshes with the drive gear 21a rotates. When the driven gear 21b rotates, the suction-side rotor shaft 11ac rotates, and the male rotor 11a rotates. When the male rotor 11a rotates, the male rotor tooth portion 11aa and the female rotor tooth portion 11ba that meshes with it rotate.

[0052] When the male rotor tooth part 11aa and the female rotor tooth part 11ba rotate, the working chambers on both the male and female sides formed by the male and female rotor tooth parts 11aa, 11ba and the bore chamber 12c suck in gas axially from the suction side to the discharge side, and then compress the gas sucked in axially from the suction side to the discharge side. As a result, the gas is sucked into the bore chamber 12c from the suction flow path 12ad shown in FIG. 2, compressed, discharged from the discharge flow path 12bf to the gas-liquid separator 31, separated from the lubricating oil in the gas-liquid separator 31, and supplied to each device.

[0053] The lubricating oil separated by the gas-liquid separator 31 and stored in the lower part of the gas-liquid separator 31 is cooled by the lubricating oil cooler 32, filtered for foreign matters by the oil filter 33, and flows into the first pipeline 34a, the second pipeline 34b, and the third pipeline 34c.

[0054] The lubricating oil flowing into the first pipeline 34a is supplied to the first oil supply path 12aj, lubricates the male rotor 11a and the female rotor 11b, and cools the compressed gas in the bore chamber 12c. In addition, the lubricating oil supplied to the first oil supply path 12aj seals the gaps between the male and female rotors 11a, 11b and the wall surfaces of the bore chamber 12c (the male-side inner peripheral wall 12ca and the female-side inner peripheral wall 12cb), and the gaps at the meshing parts of the male rotor 11a and the female rotor 11b. The lubricating oil that has lubricated the male rotor 11a and the female rotor 11b is discharged from the discharge flow path 12bf to the gas-liquid separator 31 together with the compressed gas and recovered by the gas-liquid separator 31.

[0055] The lubricating oil flowing into the second pipeline 34b is supplied to the second oil supply path 12ba, flows into the discharge-side bearing chamber 12bc, and lubricates the discharge-side bearings 13b, 13d. The lubricating oil that has lubricated the discharge-side bearings 13b, 13d is discharged into the bore chamber 12c through the first communication path 12bd, discharged from the discharge flow path 12bf to the gas-liquid separator 31 together with the compressed gas, and recovered by the gas-liquid separator 31.

[0056] The lubricating oil flowing into the third pipeline 34c is supplied to the third oil supply passage 22a and flows into the gear chamber 24 to lubricate the pair of power transmission gears 21. The lubricating oil that has lubricated the pair of power transmission gears 21 accumulates on the bottom surface of the gear chamber 24 and flows into the oil discharge port 24a. The lubricating oil flowing into the oil discharge port 24a accumulates in the second communication passage 12al, and eventually the gas cannot flow through the second communication passage 12al.

[0057] Here, it is preferable that the gear chamber 24 is provided with an oil discharge port 24a for discharging lubricating oil only at the bottom of the gear chamber 24. Thereby, the gear chamber 24 and the suction passage 12ad that communicate with each other lose the gas flow between the suction passage 12ad and the gear chamber 24 due to the second communication passage 12al being filled with lubricating oil, and a pressure difference is formed between the suction passage 12ad and the gear chamber 24. Since the internal pressure of the suction passage 12ad becomes negative compared to the gear chamber 24 because the pair of screw rotors 11 suck gas, the lubricating oil accumulated in the second communication passage 12al is sucked into the suction passage 12ad from the oil inlet 12af.

[0058] The lubricating oil sucked into the suction passage 12ad from the oil inlet 12af flows downward toward the bottom 12ag along the inclined portion 12ah shown in FIG. 3 and flows into the bore chamber 12c. The lubricating oil flowing into the bore chamber 12c is discharged from the discharge passage 12bf to the gas-liquid separator 31 together with the compressed gas and is recovered by the gas-liquid separator 31.

[0059] [Effect] In the oil-cooled screw compressor according to the comparative example in which the oil inlet is provided on the side wall of the bore chamber 12c, since the centrifugal force of the pair of screw rotors 11 acts in the direction opposite to the inflow direction of the lubricating oil, it is difficult to smoothly flow the lubricating oil into the bore chamber 12c. If the force for sucking the lubricating oil is greater than the centrifugal force of the pair of screw rotors 11, the lubricating oil can easily flow into the bore chamber. However, the suction pressure at the oil inlet 12af provided on the side wall of the bore chamber 12c varies depending on the tooth portions and groove portions of the pair of rotating screw rotors 11, and it greatly fluctuates when the tooth portions and groove portions pass through the oil inlet 12af, so it is difficult to stably recover the lubricating oil.

[0060] On the one hand, in this embodiment, the oil inlet 12af is located between the suction side end faces 11ab and 11bb of the pair of screw rotors 11 and the suction side inner wall surface 12ae facing the suction side end faces 11ab and 11bb. Thereby, it becomes difficult to be affected by the centrifugal force of the pair of screw rotors 11 and the fluctuation of the suction pressure on the outer periphery of the pair of screw rotors 11, so that the lubricating oil can be recovered smoothly and stably.

[0061] Furthermore, the casing 12 has an inclined portion 12ah with a downward slope that descends toward the bottom portion 12ag (see FIG. 3) of the casing 12 facing the lower end of one of the pair of screw rotors 11 (the male rotor 11a in this embodiment). The oil inlet 12af is provided at a position higher than the bottom portion 12ag of the casing 12 in the inclined portion 12ah. Therefore, the lubricating oil flowing in from the oil inlet 12af flows along the inclined portion 12ah to the lower end of one of the pair of screw rotors 11 (the male rotor 11a in this embodiment) and flows into the bore chamber 12c. Therefore, no surplus lubricating oil stagnates between one of the pair of screw rotors 11 and the oil inlet 12af, and the lubricating oil can be recovered effectively.

[0062] Also, in this embodiment, an oil discharge port 24a for discharging lubricating oil is provided on the bottom surface of the gear chamber 24. Therefore, it is possible to prevent surplus lubricating oil from stagnating in the gear chamber 24. Further, the lubricating oil accumulated on the bottom surface of the gear chamber 24 is discharged from the oil discharge port 24a to the second communication passage 12al. When the lubricating oil discharged into the second communication passage 12al fills the second communication passage 12al, the air pressure in the suction passage 12ad becomes lower than the air pressure in the gear chamber 24 due to the suction pressure of the pair of screw rotors 11. Thereby, the lubricating oil accumulated on the bottom surface of the gear chamber 24 can be efficiently flowed into the suction passage 12ad by the differential pressure.

[0063] From these, the oil-cooled screw compressor of this embodiment can efficiently and stably recover the lubricating oil, can prevent surplus lubricating oil from stagnating in the gear chamber 24, and can reduce the power loss caused by the lubricating oil being agitated by the power transmission gear 21.

[0064] Further, the oil inlet 12af is located at a position on the inner peripheral surface 12ai of the casing 12 that rises in the rotational direction 11af of either one of the pair of screw rotors 11 (the male rotor 11a in this embodiment) from the bottom 12ag of the casing 12. Thereby, the lubricating oil that overflows from the oil inlet 12af flows in a direction opposite to the rotational direction 11af of either one of the pair of screw rotors 11 (the male rotor 11a in this embodiment). Therefore, it is possible to prevent the lubricating oil flowing in from the oil inlet from being dragged by the rotation of either one of the pair of screw rotors 11 (the male rotor 11a in this embodiment) and stagnating on the rotation direction side, as in the case where the oil inlet is provided at the bottom 12ag of the casing 12.

[0065] (Second Embodiment) The configuration of the oil-cooled screw compressor according to the second embodiment will be exemplified and described with reference to FIGS. 5 and 6. FIG. 5 is a horizontal cross-sectional view of the oil-cooled screw compressor according to this embodiment. FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5. In FIGS. 5 and 6, those having the same reference numerals as those shown in FIGS. 1 to 4 are the same parts, and thus the detailed description thereof is omitted.

[0066] The difference between the oil-cooled screw compressor according to this embodiment and the oil-cooled screw compressor according to the first embodiment is the position of the oil inlet 212af. That is, the oil inlet 212af of the oil-cooled screw compressor according to this embodiment is located at a position that rises in a direction opposite to the rotational direction (the rotational direction 211af in this embodiment) of either one of the pair of screw rotors 11 (the female rotor 11b in this embodiment) from the bottom 212ag of the casing 12.

[0067] Further, as shown in FIG. 6, the second communication passage 212al extends downward from the oil inlet 212af and then extends to the bottom surface side of the gear chamber 24. And an oil discharge port (not shown) provided on the bottom surface of the gear chamber 24 is formed at the tip of the second communication passage 212al.

[0068] Further, it is preferable that the inclined portion 212ah inclines toward the bottom portion 212ag of the casing 12 facing the lower end of the screw rotor 11 with the smaller outer diameter among the pair of screw rotors 11 (female rotor 11b in this embodiment). The oil inlet 212af is preferably provided at a position higher than the bottom portion 212ag of the casing 12 of the inclined portion 212ah.

[0069] [Effect] In this embodiment, the oil inlet 212af is located at a position on the inner peripheral surface 212ai of the casing 12 where it rises in a direction opposite to the rotation direction 211af of either one of the pair of screw rotors 11 from the bottom portion 212ag of the casing 12. As a result, the lubricating oil overflowing from the oil inlet 212af not only flows along the inclined portion 212ah with a downward gradient in the same direction as the rotation direction 211af of either one of the pair of screw rotors 11 (female rotor 11b in this embodiment), but is also dragged by the end face of the female rotor 11b and flows to the lower end of the female rotor 11b, so that the oil can be recovered more effectively.

[0070] In addition, since the lubricating oil is recovered while further suppressing the influence of the centrifugal force caused by the rotation of the pair of screw rotors 11, the lubricating oil can be recovered more efficiently and stably, further suppressing the stagnation of surplus lubricating oil in the gear chamber, and further reducing the power loss caused by the lubricating oil being agitated by the power transmission gear.

[0071] Further, it is preferable that the inclined portion 212ah slopes toward the bottom portion 212ag of the casing 12 facing the lower end of the screw rotor 11 with the smaller outer diameter among the pair of screw rotors 11 (female rotor 11b in this embodiment). The centrifugal force caused by the rotation of the pair of screw rotors 11 is smaller for the screw rotor 11 with the smaller outer diameter (female rotor 11b in this embodiment) than for the screw rotor 11 with the larger outer diameter (male rotor 11a in this embodiment).

[0072] In this embodiment, the inclined portion 212ah slopes toward the bottom 212ag of the casing 12 facing the lower end of the screw rotor (female rotor 11b) with the smaller outer diameter among the pair of screw rotors 11, and the oil inlet 212af is provided at a position higher than the bottom 212ag of the casing 12 in the inclined portion 212ah. Thereby, the influence of the centrifugal force due to the rotation of one of the pair of screw rotors 11 on the lubricating oil overflowing from the oil inlet 212af can be suppressed. For example, the stirring power of the lubricating oil by one of the pair of screw rotors 11 can be reduced. As a result, the lubricating oil can be efficiently and stably recovered, the stagnation of excess lubricating oil in the gear chamber 24 can be suppressed, and the power loss caused by the lubricating oil being stirred by the power transmission gear 21 can be reduced.

[0073] (Third Embodiment) The configuration of the oil-cooled screw compressor according to the third embodiment will be illustrated and described with reference to FIG. 7. FIG. 7 is a cross-sectional view of the II-II cross section shown in FIG. 1 in the oil-cooled screw compressor according to the third embodiment. In FIG. 7, the components denoted by the same reference numerals as those shown in FIGS. 1 to 4 are the same parts, and thus their detailed description will be omitted.

[0074] The difference between the oil-cooled screw compressor according to the present embodiment and the oil-cooled screw compressors according to the first and second embodiments lies in the extending direction of the inclined portion. That is, the oil inlets 12af and 212af according to the first and second embodiments are located at positions rising in either the rotation direction of one of the pair of screw rotors 11 or the opposite direction. Therefore, the inclined portions 12ah and 212ah of the oil-cooled screw compressors according to the first and second embodiments extend along either the rotation direction of one of the pair of screw rotors 11 or the opposite direction. On the other hand, the inclined portion 312ah of the oil-cooled screw compressor according to the present embodiment extends along the axial direction of the pair of screw rotors 11.

[0075] [Effect] The lubricating oil that has overflowed from the oil inlet 12af of the oil-cooled screw compressor according to the present embodiment flows down along the inclined portion 312ah extending in the axial direction of the pair of screw rotors 11 and flows into the bore chamber 12c. Therefore, since the lubricating oil flows down in the direction in which the pair of screw rotors 11 suck in gas, the influence of the centrifugal force of the pair of screw rotors 11 and the fluctuation of the suction pressure on the outer periphery of the pair of screw rotors 11 can be suppressed. Therefore, the lubricating oil can be recovered smoothly and stably, the stagnation of surplus lubricating oil in the gear chamber 24 can be further suppressed, and the power loss caused by the lubricating oil being agitated by the power transmission gear 21 can be further reduced.

[0076] Note that the present invention is not limited to the above-described embodiments, and various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Also, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

[0077] Note that the embodiments of the present invention may also be as follows. For example, the lubricating oil may be circulated through the external liquid supply system 3 using a power source such as a pump. Also, in the first embodiment, the oil inlet 12af is located at a position that rises in the rotation direction 11af of the male rotor 11a. However, it is not limited to this, and the oil inlet 12af may be located at a position that rises in the direction opposite to the rotation direction 11af. Also, in the second embodiment, the oil inlet 212af is located at a position that rises in the direction opposite to the rotation direction 211af of the female rotor 11b. However, it is not limited to this, and the oil inlet 212af may be located at a position that rises in the rotation direction 211af. Also, the first communication passage may be provided inside the pair of screw rotors 11, and the oil inlet of the first communication passage may be located between the suction side end faces 11ab, 11bb of the pair of screw rotors 11 and the suction side inner wall surface 12ae facing the suction side end faces 11ab, 11bb.

Description of Reference Numerals

[0078] 1…Compressor body, 2…Power transmission device, 3…External liquid supply system, 11…Pair of screw rotors, 11a…Male rotor (driving side screw rotor), 11aa…Male rotor tooth part, 11ab…Suction side end face, 11ac…Suction side rotor shaft, 11ad…Discharge side end face, 11ae…Discharge side rotor shaft, 11af…Rotation direction, 11b…Female rotor (driven side screw rotor), 11ba…Female rotor tooth part, 11bb…Suction side end face, 11bc…Suction side rotor shaft, 11bd…Discharge side end face, 11be…Discharge side rotor shaft, 12…Casing, 12a…Main casing, 12aa…Suction side side wall, 12ad…Suction flow path, 12ae…Suction side inner wall surface, 12af…Oil inlet, 12ag…Bottom, 12ah…Inclined part, 12ai…Inner peripheral surface, 12ak…End face, 12al…Second communication path, 12b…Discharge side casing, 12bf…Discharge flow path, 12c…Bore chamber, 21…Power transmission gear, 22…Gear case, 22a…Third oil supply path, 23…Driving side shaft, 24…Gear chamber, 24a…Oil discharge port, 31…Gas-liquid separator, 32…Lubricating oil cooler, 33…Oil filter, 34…Pipeline, 211af…Rotation direction, 212af…Oil inlet, 212ag…Bottom, 212ah…Inclined part, 212al…Second communication path, 312ae…Oil inlet, 312ah…Inclined part

Claims

1. A compressor body comprising: a pair of screw rotors; and a casing having a bore chamber that rotatably accommodates the pair of screw rotors in a meshed state. A gear chamber that houses a power transmission gear inside for transmitting the rotation of a drive motor to the pair of screw rotors via a rotor shaft, and has an oil discharge port at the bottom surface for discharging lubricating oil. The oil discharge port communicates with an oil inlet that opens in the casing so as to be positioned between the suction side end surface of the pair of screw rotors and the suction side inner wall surface facing the suction side end surface of the pair of screw rotors. The casing has an inclined portion with a downward slope that descends toward the bottom of the casing facing the lower end of either one of the pair of screw rotors. The oil inlet is provided at a position higher than the bottom of the casing in the inclined portion. An oil-cooled screw compressor characterized by this.

2. In the oil-cooled screw compressor according to Claim 1, The oil inlet is located at a position on the inner peripheral surface of the casing that rises in the rotational direction of either one of the pair of screw rotors from the bottom of the casing. An oil-cooled screw compressor characterized by this.

3. In the oil-cooled screw compressor according to Claim 1, The oil inlet is located at a position on the inner peripheral surface of the casing that rises in the direction opposite to the rotational direction of either one of the pair of screw rotors from the bottom of the casing. An oil-cooled screw compressor characterized by this.

4. In the oil-cooled screw compressor according to Claim 1, The inclined portion is inclined toward the bottom of the casing facing the lower end of the screw rotor with the smaller outer diameter among the pair of screw rotors. An oil-cooled screw compressor characterized by this.

5. In the oil-cooled screw compressor according to Claim 1, The inclined portion extends along the axial direction of the pair of screw rotors. An oil-cooled screw compressor characterized by this.

Images