JP4185598B2 - Oil-cooled screw compressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oil-cooled screw compressor that uses oil for cooling a working gas, and more particularly to an oil-cooled screw compressor configured in two stages.
[0002]
[Prior art]
In the oil-cooled screw compressor, during the load operation, the female rotor becomes a load with respect to the rotation of the male rotor, and a load torque acts. The torque absorbed by the female rotor is as small as about 5% of the torque applied to the male rotor. On the other hand, during the unloading operation, a negative torque is generated that tries to advance the female rotor in the rotational direction. Therefore, a tooth surface separation phenomenon occurs in which the female rotor is separated from the original driven tooth surface. Once this tooth surface separation phenomenon occurs, it tends to occur repeatedly with the gap in the rotational direction of the rotor as the limit. In this case, the rotational speed varies periodically, and annoying noise is generated. In the worst case, the tooth surface of the rotor is damaged.
[0003]
There are two methods for unloading the compressor: a method of closing the suction throttle valve and a method of reducing the discharge pressure simultaneously with closing the suction throttle valve. Whichever method is used, the load torque acting on the female rotor during the unload operation is greatly reduced. Therefore, it becomes difficult to keep the load torque positive at all the rotation angles of the rotor, and the tooth surface separation phenomenon is likely to occur.
[0004]
Therefore, the screw compressor that less likely the tooth surfaces separated by changing the teeth of Russia over data is considered. Japanese Patent Laid-Open No. 2-252991 discloses that the torque acting on the female rotor in the screw vacuum pump is always negative, thereby reducing the vibration and noise of the pump. Further, JP-A-55-57688 and JP-A-55-96391 disclose that a dynamic damper or a damping mechanism is attached to the shaft end of the female rotor of the screw compressor to prevent occurrence of tooth surface separation. ing.
[0005]
[Problems to be solved by the invention]
Since a large oil-cooled screw compressor consumes a large amount of power, a two-stage compressor capable of obtaining high efficiency is used. In this two-stage oil-cooled screw compressor, when the valve on the suction side is closed for unloading operation, the suction pressure in the low-pressure stage decreases to a vacuum pressure of 0.01 MPa or less in absolute pressure (hereinafter referred to as the present specification). (All pressures are expressed in absolute pressure.) At the same time, the discharge pressure of the low-pressure stage is about 0.03 MPa, which is a pressure lower than the atmospheric pressure. On the other hand, in the high pressure stage, the suction pressure is about 0.03 MPa, and when the suction throttle method is used, the discharge pressure is about 8 MPa. Therefore, the high-pressure stage side is similar to the unloading operation conditions of a single stage machine. In this case, when negative torque is generated and the suction pressure is extremely close to the vacuum pressure, vibration and noise are likely to occur due to tooth surface separation. On the other hand, on the low pressure stage side, the pressure on the suction side and the discharge side of the compressor is lower than the atmospheric pressure, and torque for pressing the female rotor against the driven tooth surface is less likely to be generated on the discharge side. Therefore, the female rotor tends to be further away from the driven tooth surface than the high pressure stage, and noise and vibration are likely to occur due to the tooth surface separation phenomenon.
[0006]
Among the various methods proposed to suppress the tooth surface separation phenomenon, in the method of correcting the tooth profile of the rotor, a negative torque is not necessarily applied to the female rotor depending on the pressure conditions on the suction side and the discharge side. Cannot be suppressed, and there is a problem that the operating conditions are limited. Further, the method described in Japanese Patent Laid-Open No. 2-252991 is effective only in a vacuum pump in which only a state corresponding to the unload operation of the compressor is executed, and a screw in which the load operation and the unload operation are repeated. Not suitable for compressors.
[0007]
Further, in the method described in Japanese Patent Laid-Open Nos. 55-57688 and 55-96391 in which a dynamic damper or a damping mechanism is attached to the end of the female rotor shaft of the compressor to prevent tooth surface separation, There are problems such as difficulty in tuning and strength evaluation and difficulty in obtaining desired damping force and durability.
[0008]
The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to suppress generation of tooth surface separation vibration of a low-pressure female rotor in an oil-cooled screw compressor. Another object of the present invention is to provide a highly reliable oil-cooled two-stage screw compressor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the first feature of the present invention is that it has a male rotor and a female rotor, compresses the working gas, a bearing of the drive shaft, a drive gear attached to the drive shaft, and the male A gear case that houses a driven gear attached to the rotor, and an oil pump that is disposed in the female rotor and sucks oil stored in the gear case . Preferably, the compressor body has a low pressure stage and a high pressure stage, and an oil pump is provided in the low pressure stage.
[0010]
In order to achieve the above object, the second feature of the present invention includes: a low-pressure stage male rotor and a female rotor; a high-pressure stage male rotor and a female rotor; a drive shaft bearing; a drive gear attached to the drive shaft; The low-pressure stage male rotor and the driven gear attached to the high-pressure stage male rotor, the bearing, the drive gear and the gear case in which the driven gear is housed, and the drive shaft extending outside the gear case. A shaft sealing mechanism provided in the existing portion, and an oil pump for sucking oil accumulated between the shaft sealing mechanism and each of the rotors, and the oil pump is arranged at the shaft end of the female rotor of the low-pressure stage. It is set. Preferably, the outlet of the oil pump is connected to any one of the suction side of the low pressure stage, the suction side of the high pressure stage, or the discharge side of the high pressure stage. The above in any of the features, mounting the drive shaft overhang on the male rotor, it is desirable to dispose a bearing for supporting one of this only the side drive shaft of the drive shaft.
[0011]
Since the power for driving the oil pump always acts as a load for the female rotor in the low pressure stage, the load torque is increased and the generation of negative torque can be suppressed. Also the magnitude of the load caused by the oil pump, can be changed by the Turkish changing the position connecting the outlet of the oil pump.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an embodiment of an oil-cooled screw compressor according to the present invention, and is a diagram showing the flow of working gas and lubricating oil, and FIG. 2 is a diagram of an oil-cooled screw compressor according to the present invention. FIG. 3 is a cross-sectional view of the oil-cooled screw compressor shown in FIG. 2.
[0013]
The two-stage oil-cooled screw compressor includes a low pressure stage 45 and a high pressure stage 50. The low-pressure stage male rotor 2 and the low-pressure stage female rotor 3 constituting the low-pressure stage 45 are supported by cylindrical roller bearings 15 and 16 so that the suction-side shaft part can rotate, and angular ball bearings 13 and 14 rotate the discharge-side shaft part. Supported as possible. The cylindrical roller bearings 15 and 16 and the angular ball bearings 13 and 14 are held in the casing 1.
[0014]
The working gas is sucked into the low pressure stage male rotor 2 and the low pressure stage female rotor 3 from the suction filter 6 via the suction throttle valve 7. Oil is injected into the sucked gas in the compression process of the low pressure stage 45. The working gas discharged from the low pressure stage 45 flows into the intermediate stage passage 32 which is a space sandwiched between the low pressure stage and the high pressure stage of the casing. Oil is also injected into the intermediate stage passage 32 to cool the compressed gas. The cooled compressed gas is sucked into a space formed by the high-pressure stage male rotor 4 and the high-pressure stage female rotor 5. The high-pressure stage male rotor 4 and the high-pressure stage female rotor 5 are supported by cylindrical roller bearings 19 and 20 so that the suction side shaft portion is rotatable, and angular ball bearings 17 and 18 are rotatably supported by the discharge side shaft portion. Like the low-pressure stage bearings, these bearings are held in the casing 1. The working gas that has been further pressurized to a predetermined pressure by the high-pressure stage male rotor 4 and the high-pressure stage female rotor 5 is discharged from the high-pressure stage discharge port 31.
[0015]
A low pressure stage driven gear 10 and a high pressure stage driven gear 11 are attached to the low pressure stage male rotor 2 and the high pressure stage male rotor 4, respectively. Further, a drive gear 12 is attached to the drive shaft 37, and the tapered roller bearing 22 is rotatably supported on one side and the cylindrical roller bearing 21 is rotatably supported on the other side across the drive gear. The portion the drive shaft 37 extends outside the Giyake scan 24 and a shaft seal mechanism 23 is provided, the oil in the gear case 24 is prevented from flowing out. The low-pressure stage and high-pressure stage suction-side bearings 15, 16, 19, and 20, the drive shaft bearings 22 and 21, and the gears 10, 11, and 12 are forcibly lubricated with lubricating oil. Then, the oil after lubricating the bearings and the gears falls to the lower part of the gear case 24 .
[0016]
An oil pump 8 is connected to the shaft end of the female rotor 3 of the low pressure stage 45. The oil pump 8 is rotationally driven by the female rotor 3. Inlet 25 of the lower and the oil pump 8 of Giyake scan 24 is connected by a pipe 27, the lubricating oil accumulated in the lower portion of the gear case 24 oil pump 8 sucks. A pipe 28 is connected to the discharge port 26 of the oil pump 8, and the lubricating oil sucked from the lower part of the gear case is collected on the suction side of the low pressure stage 45.
[0017]
The oil pump 8 prevents the gear case 24 from being filled with oil. At the same time, the inside of the gear case 24 is maintained at substantially the atmospheric pressure or lower pressure by the suction action of the oil pump 8. Thereby, the pressure which acts on the shaft seal device 23 can be suppressed low.
[0018]
The oil-cooled two-stage screw compressor is generally a large machine of 150 kW or more, and the drive shaft 37 is also enlarged. In particular, as shown in FIG. 3, when the motor rotor 35 is connected to the drive shaft 37 in an overhang shape, the drive shaft 37 must be thickened to ensure strength. As a result, the peripheral speed of the shaft seal portion of the shaft seal device 23 is increased. Therefore, in order to ensure the reliability of the shaft seal portion, it is necessary to keep the pressure inside the gear case 24 as low as possible.
[0019]
Hereinafter, a case of a general air compressor will be described as an example. The discharge pressure of this general air compressor is 0.8 Mpa. When the compressor enters the unload operation state, the suction throttle valve 7 is closed. At this time, the suction side of the low-pressure stage rotors 2 and 3 is reduced to a vacuum pressure of about 0.01 MPa. At the same time, the discharge pressure in the low-pressure stage also becomes a vacuum pressure of about 0.03 MPa. As described above, the torque absorbed by the female rotor even in the full load state is about 5% of the input torque of the male rotor. Therefore, in the unload operation state in which the pressure level is lowered, the low pressure stage female rotor hardly generates torque to be pressed against the driven tooth surface. As a result, depending on the rotational position of the rotor, a negative torque is generated, and the female rotor is liable to cause tooth surface separation vibration, which causes a large increase in noise of the compressor. The same phenomenon is likely to occur on the high-pressure stage 50 side, but since the discharge pressure of the high-pressure stage during unloading operation is always higher than the discharge pressure of the low-pressure stage, noise during unloading in the case of a two-stage compressor The source is mainly the female rotor 3 in the low pressure stage. Therefore, in the present invention, the oil pump 8 is attached to the rotating shaft of the low-pressure stage female rotor 3, and the oil pump 8 is driven by the torque transmitted to the low-pressure stage female rotor 3.
[0020]
By attaching the oil pump 8 to the rotating shaft of the low-pressure stage female rotor 3, a constant torque is consumed in the low-pressure stage female rotor 3 part during both the load operation and the unload operation. The oil pump 8 has a large-sized compressor, particularly the large-diameter drive shaft shown in FIGS. 2 and 3, and improves the reliability of the shaft seal portion of the compressor in which the motor is mounted in an overhang shape. It is essential. Therefore, only by changing the arrangement of these indispensable components, no extra power is required, and noise generation can be reduced while saving energy.
[0021]
Although the torque transmitted to the female rotor during the load operation is as small as about 5%, it is known that tooth surface separation can be prevented with this small torque. On the other hand, the negative torque generated in the female rotor during the unloading operation is not so great if the rotor tooth profile is appropriately selected. Therefore, it is sufficiently possible to cover the negative torque during the unload operation and to compensate the amount corresponding to the torque transmitted to the female rotor during the load operation with the absorption torque of the oil pump. Thereby, the tooth surface separation vibration and noise increase of the female rotor can be prevented.
[0022]
In FIG. 1, the outlet 26 of the oil pump 8 is connected to the compressor suction side by a pipe 28, connected to the low pressure stage discharge side by a pipe 29, or connected to the high pressure stage discharge side by using a pipe 30. To do. Thereby, the absorption torque of the oil pump 8 can be adjusted. That is, since the pressure of the outlet 26 of the oil pump 8 changes depending on the position where the oil recovered from the bottom of the gear case 24 is returned, the absorbed torque can be adjusted. As another method of adjusting the absorption torque of the oil pump 8, there is a method of adding a flow resistance to the oil pump outlet 26 side within a range where the suction capability of the oil pump 8 is not reduced.
[0023]
As described above, according to this embodiment, even if the suction pressure of the compressor changes, if the pipe connection is made according to the change of the suction pressure, the tooth surface separation vibration due to the negative torque generation of the low-pressure stage female rotor. Can be prevented, and an increase in noise of the compressor can be prevented.
[0024]
【The invention's effect】
According to the present invention, in a two-stage oil-cooled screw compressor, it is possible to suppress tooth surface separation vibration and associated noise generated in a low-pressure stage female rotor during unloading. Moreover, the reliability of a shaft seal part can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of an embodiment of an oil-cooled screw compressor according to the present invention.
FIG. 2 is a longitudinal sectional view of an embodiment of the oil-cooled compressor according to the present invention, and a top view thereof.
FIG. 3 is a longitudinal sectional view of the embodiment shown in FIG. 2 and a front view thereof.
[Explanation of symbols]
1; casing, 2; low-pressure stage male rotor,
3; low-pressure stage female rotor, 4; high-pressure stage male rotor,
5; high-pressure stage female rotor, 6; suction filter,
7: Suction throttle valve, 8: Oil pump,
10; low-pressure stage driven gear,
11: high-pressure stage driven gear, 12: driving gear,
13-22; bearing, 23; shaft seal,
24; gear case, 25; oil pump inlet,
26; oil pump outlet, 27; oil suction pipe,
28 to 30; oil outlet pipe, 31; high-pressure stage discharge,
32; low-pressure stage discharge; 35; motor rotor;
36; motor stator, 37; drive shaft,
45; low pressure stage, 50; high pressure stage.

Claims (5)

A compressor body having a male rotor and a female rotor and compressing the working gas;
A gear case that houses a bearing of the drive shaft, a drive gear attached to the drive shaft, and a driven gear attached to the male rotor;
An oil pump that is disposed in the female rotor and sucks oil stored in the gear case;
Oil-cooled screw compressor equipped with   The oil-cooled screw compressor according to claim 1, wherein the compressor body has a low-pressure stage and a high-pressure stage, and the oil pump is provided in the low-pressure stage. A low-pressure stage male and female rotor;
A high-pressure stage male and female rotor;
A bearing of the drive shaft, a drive gear attached to the drive shaft, and a driven gear attached to the low-pressure stage male rotor and the high-pressure stage male rotor;
A gear case in which the bearing, the driving gear, and the driven gear are stored;
A shaft sealing mechanism provided on a portion of the drive shaft that extends outside the gear case;
An oil pump for sucking oil accumulated between the shaft seal mechanism and each of the rotors;
An oil-cooled screw compressor in which the oil pump is disposed at a shaft end of the female rotor of the low-pressure stage.   The oil-cooled screw compressor according to claim 3, wherein an outlet of the oil pump is connected to any one of a suction side of the low-pressure stage, a suction side of the high-pressure stage, or a discharge side of the high-pressure stage. .   The drive shaft is attached to the male rotor in an overhang shape, and a bearing for supporting the drive shaft is disposed only on one side of the drive shaft. Oil-cooled screw compressor.

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