JP3549145B2 - Internal pressure regulator of screw compressor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internal pressure adjusting device for a screw compressor.
[0002]
[Prior art]
In recent years, screw compressors have been widely used in various fields. As an example of such a screw compressor, an oil supply type screw compressor that supplies oil for cooling, internal lubrication, and sealing will be described with reference to FIG. The oil-filled screw compressor includes a compressor body 1 that sucks and compresses air, an air filter 2 that purifies the sucked air, a motor (not shown) serving as a drive source of the compressor body 1, and stores oil. Oil tank 3, oil separator 4 for removing oil from compressed air, aftercooler 5 for cooling compressed air, dryer 6 for removing moisture and oil from compressed air cooled by aftercooler 5, cooling oil And an exhaust cleaner 8 for removing oil from compressed air released into the atmosphere during no-load operation.
[0003]
In the compressor main body 1, a pair of screw rotors 10 are housed in a stator 9, and the screw rotors 10 are rotatably held by bearings 11 and mesh with each other. The stator 9 has a suction port 12 through which air is sucked into the stator 9 and a discharge port 13 through which compressed air compressed by rotation of the screw rotor 10 is discharged. A suction pipe 14 is connected between the suction port 12 and the air filter 2, and a suction valve 15 for intermittently sucking air from the suction port 12 into the stator 9 is provided in the suction pipe 14. I have.
[0004]
A first discharge pipe 16 is connected between the discharge port 13 and the oil tank 3, and a second discharge pipe 17 is connected between the oil tank 3 and the oil separator 4. A third discharge pipe 18 is connected between the aftercooler 5 and a fourth discharge pipe 19 between the aftercooler 5 and the dryer 6. A compressed air supply pipe 20 is connected between the dryer 6 and a working device (not shown) that receives a supply of compressed air. A fifth discharge pipe 21 is connected between the oil separator 4 and the exhaust cleaner 8.
[0005]
An oil supply pipe 22 for supplying oil to the compressor body 1 is connected between the oil tank 3 and the compressor body 1. The oil supply pipe 22 has a structure in which a supply flow path is switched by a temperature control valve 23. One supply flow path is a flow path for directly supplying to the compressor body 1 when the temperature of the oil is lower than the set temperature, and the other supply flow path is cooled by the oil cooler 7 when the temperature of the oil is higher than the set temperature. This is a flow path for supplying.
[0006]
At the time of load operation, the suction valve 15 is opened, air in the atmosphere passes through the air filter 2 and is sucked into the stator 9 from the suction port 12, and the sucked air is compressed by the rotation of the screw rotor 10. Compressed air is generated. The compressed air reaches the dryer 6 via the first, second, third, and fourth discharge pipes 16, 17, 18, and 19, and the compressed air is supplied to the work implement via the supply pipe 20.
[0007]
On the other hand, during the no-load operation, the suction valve 15 is closed, and no air is sucked into the stator 9 from the atmosphere. When the screw rotor 10 is rotationally driven in such a state, the air remaining in the stator 9 is compressed and discharged from the discharge port 13. The compressed air discharged from the discharge port 13 during the no-load operation reaches the exhaust cleaner 8 via the first, second, and fifth discharge pipes 16, 17, and 21, and is discharged from the exhaust cleaner 8 into the atmosphere.
[0008]
[Problems to be solved by the invention]
When the refueling screw compressor is operated under no load, the inside of the stator 9 gradually approaches a vacuum state. When the pressure difference in the stator 9 between the load operation and the no-load operation increases, the pressure difference causes the bearing 11 that supports the screw rotor 10 to move between the sliding parts, and the bearing 11 reduces internal wear. This shortens the service life.
[0009]
In view of the above, the present invention provides a method for applying a constant residual pressure to a stator during a no-load operation of a screw compressor, and the sliding between bearings in a bearing for supporting a screw rotor, which is generated when the inside of the stator is vacuumed. It is an object of the present invention to provide an internal pressure adjusting device for a screw compressor, which prevents movement of a screw and prevents internal wear of a bearing.
[0010]
[Means for Solving the Problems]
The internal pressure adjusting device for a screw compressor according to claim 1, wherein a pair of screw rotors rotatably held in a stator via bearings are driven to rotate, and the stator is rotated through a suction port formed in the stator. In a screw compressor for sucking air into the inside and compressing the same, and discharging compressed air from a discharge port formed in the stator, a suction valve for intermittently sucking air from the suction port into the stator is provided. A non-load operation discharge path for guiding compressed air discharged from the discharge port during a no-load operation in which the suction valve is closed and the screw rotor is rotationally driven is provided, and a discharge path is provided along the flow direction of the air sucked from the suction port. In addition, a return passage communicating with the downstream side of the suction valve and a relief passage communicating with the atmosphere are formed at the distal end of the discharge path during the no-load operation.
[0011]
Therefore, when the compressed air that has compressed the residual air in the stator is discharged from the discharge port during the no-load operation, the compressed air is guided in the discharge path during the no-load operation, and a part of the compressed air passes through the return passage. It is returned into the stator and the remaining part is released to the atmosphere through a relief passage. When the pressure in the stator becomes equal to or less than the set value, air in the atmosphere flows into the stator through the escape passage and the return passage.
For this reason, since a fixed residual pressure always acts in the stator during the no-load operation, the movement between the sliding parts of the bearing that supports the screw rotor, which occurs when the inside of the stator becomes vacuum, is prevented. Thus, internal wear of the bearing is prevented.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. Note that the same portions as those described in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. The basic structure of the refueling screw compressor of the present embodiment is the same as that of the refueling screw compressor shown in FIG. 3, and a pair of screw rotors 10 are rotatably inserted into stator 9 via bearings 11. It has a held compressor body 1, an air filter 2, an oil tank 3, an oil separator 4, an after cooler 5, an oil cooler 7, a dryer 6, and the like.
[0013]
The stator 9 has a suction port 12 through which air is sucked into the stator 9 and a discharge port 13 through which compressed air compressed by rotation of the screw rotor 10 is discharged. A suction pipe 14 is connected between the suction port 12 and the air filter 2, and a suction valve 15 for intermittently sucking air from the suction port 12 into the stator 9 is provided in the suction pipe 14. I have.
[0014]
A first discharge pipe 16 is connected between the discharge port 13 and the oil tank 3, and a second discharge pipe 17 is connected between the oil tank 3 and the oil separator 4. A third discharge pipe 18 is connected between the aftercooler 5 and a fourth discharge pipe 19 between the aftercooler 5 and the dryer 6. A compressed air supply pipe 20 is connected between the dryer 6 and a working device (not shown) that receives a supply of compressed air.
[0015]
A sixth discharge pipe 24 is connected to the oil separator 4 in addition to the third discharge pipe 18. And. The first and second discharge pipes 16 and 17 and the sixth discharge pipe 24 form a no-load operation discharge path 25 for guiding compressed air discharged from the discharge port 13 during no-load operation. A return passage 26 and a relief passage 27 are formed at the leading end of the discharge passage 25 during the no-load operation. The return passage 26 communicates with the downstream side of the suction valve 15 along the flow direction of the air flowing through the suction pipe 14. The relief passage 27 communicates with the upstream side of the suction valve 15 along the flow direction of the air flowing through the suction pipe 14.
[0016]
In the middle of the return passage 26, a throttle portion 28 for restricting the flow of air and a check valve 29 for preventing backflow of air from inside the stator 9 are provided.
[0017]
In such a configuration, at the time of load operation, the suction valve 15 is opened, air in the atmosphere passes through the air filter 2 and is sucked into the stator 9 from the suction port 12, and the sucked air is rotated by the rotation of the screw rotor 10. It is compressed to produce compressed air. The compressed air reaches the dryer 6 via the first, second, third, and fourth discharge pipes 16, 17, 18, and 19, and the compressed air is supplied to the work implement via the supply pipe 20.
[0018]
Next, the suction valve 15 is closed during the no-load operation. When the screw rotor 10 is driven to rotate in this state, the air remaining in the stator 9 is compressed and discharged from the discharge port 13. The compressed air discharged from the discharge port 13 during the no-load operation is guided through the discharge path 25 during the no-load operation including the first, second, and sixth discharge pipes 16, 17, and 24, and a part thereof is returned to the return passage. It is returned into the stator 9 through 26, and the remaining part is discharged to the atmosphere through a relief passage 27. When such a no-load operation is continued for a certain period of time and the pressure in the stator 9 becomes equal to or lower than the set value, air in the atmosphere flows in from the tip of the release passage 27 and flows into the stator 9 through the return passage 26. .
[0019]
Therefore, even during the no-load operation, the inside of the stator 9 does not become a vacuum state, and a constant residual pressure acts in the stator 9, and the residual pressure in the stator 9 reverses the direction in which compressed air is sent to the screw rotor 10. The force in the direction (direction of arrow A) always acts. Therefore, during the load operation and during the no-load operation, the force acting on the screw rotor 10 in the direction of arrow A does not occur or disappear, and the screw is repeatedly generated and disappears. The rotor 10 is prevented from moving in the axial direction or the direction perpendicular to the axial direction. The movement between the sliding portions of the bearing 11 (between the ring member 11a and the roller member 11b) accompanying the movement of the screw rotor 10 is prevented, and accordingly, the internal wear of the bearing 11 is prevented. Longer lifespan.
[0020]
Further, since a constant residual pressure acts in the stator 9 during the no-load operation, a constant residual pressure also acts in the oil tank 3 communicated with the stator 9. Therefore, it is possible to prevent the oil tank 3 from being in a vacuum state and generating oil smoke, so that the remaining amount of oil in the oil tank 3 can always be checked satisfactorily.
[0021]
In the present embodiment, the description has been given by taking as an example a lubricating screw compressor employing a lubricating lubrication system, but the present invention is also applicable to a screw compressor employing a lubricating lubrication system. Can be.
[0022]
【The invention's effect】
According to the internal pressure adjusting device for a screw compressor according to the first aspect of the present invention, a constant residual pressure can always be applied to the inside of the stator even during the no-load operation. It is possible to prevent the movement between the sliding parts of the bearing that supports the screw rotor, which is caused by the state, to prevent the internal wear of the bearing, and to prolong the life of the bearing.
[Brief description of the drawings]
FIG.
It is a circuit diagram showing the structure of the oil supply type screw compressor showing one embodiment of the present invention.
FIG. 2
It is a longitudinal front view which expands and shows the structure of a compression main body.
FIG. 3
It is a circuit diagram showing the structure of the oil supply type screw compressor of the conventional example.
[Explanation of symbols]
9 Stator 10 Screw rotor 11 Bearing 12 Suction port 13 Discharge port 15 Suction valve 25 No-load operation discharge path 26 Return path 27 Escape path

Claims (1)

A pair of screw rotors rotatably held in the stator via bearings are driven to rotate, and air is sucked into the stator from an inlet formed in the stator and compressed, forming compressed air in the stator. In the screw compressor which discharges from the discharged discharge port,
A suction valve for intermittently sucking air from the suction port into the stator; and closing the suction valve to rotate the screw rotor, thereby guiding compressed air discharged from the discharge port during a no-load operation. A discharge path at the time of load operation is provided, and a return path communicating with the downstream side of the suction valve along a flow direction of the air sucked from the suction port and a release path communicating with the atmosphere are provided at the discharge path at the time of no load operation. An internal pressure adjusting device for a screw compressor, wherein the internal pressure adjusting device is formed at a tip end of a screw compressor.

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