JP4088396B2 - Screw compressor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screw compressor, and more particularly to an oil recovery device from a shaft seal device.
[0002]
[Prior art]
A pair of male and female screw rotors that are axially parallel to each other and have opposite torsional directions, and a bore that accommodates these screw rotors through a minute gap, and an intake port on one end surface of the bore and an other end surface In an oil supply type screw compressor having a casing with a discharge port formed therein and provided with a suction throttle valve for restricting the intake amount, the intake side shaft end of the Osloter is extended to the outside of the casing for driving, and the pulley Or a coupling is installed. Inside the casing, there is a bearing for supporting the rotor, which is supplied with oil for lubrication. A seal device is used to seal the lubricating oil on the shaft on the intake side of the thruster.
[0003]
Here, there is a slight leakage of the lubricating oil from the shaft seal device, and this is caused by the air passing through the suction throttle valve using a pipe that connects the recovery of the lubricating oil to the primary side of the suction throttle valve. It was recovered using the differential pressure between the negative pressure and the atmospheric pressure outside the shaft seal device.
[0004]
Further, due to the mechanism of the screw compressor, when the capacity adjustment is started and the intake air is limited, the fluid to be compressed becomes insufficient and the negative pressure on the suction side of the compression chamber increases. In this state, the tooth surface of the meslotter that is originally contacted between the male and meslotter and is driven by the oslotter is separated and rotation is unstable. As a result, abnormal vibration and noise that do not occur during normal operation occur. As a countermeasure, a system is adopted in which a small amount of intake air is supplied to the compression chamber even in a low load region to relieve negative pressure and prevent tooth surface separation.
[0005]
[Problems to be solved by the invention]
The following are the problems of the prior art.
[0006]
The oil leaked from the shaft seal device is collected in the groove outside the shaft seal, and is then sucked up by the negative pressure of the suction throttle valve and collected again into the compressor body. The pressure becomes lower as the load is lower when the capacity is adjusted with the full load state at the maximum. Therefore, depending on the layout of the shaft seal device and the suction throttle valve, the recovery becomes insufficient due to a decrease in the intake air amount. In particular, when the intake air amount is zero, there is a possibility that sufficient recovery capability cannot be exhibited. Lubricating oil that could not be recovered may scatter to the outside, adhere to the driving belt, and cause slippage.
[0007]
An object of the present invention is to provide a low-cost and stable recovery capability for lubricating oil by sharing a negative pressure relief piping and a recovery piping for lubricating oil leaking from the shaft seal device.
[0008]
[Means for Solving the Problems]
A pipe is provided from directly below the groove portion outside the shaft seal device, and this pipe is branched and connected to two places on the primary side and the secondary side of the suction throttle valve. A throttle mechanism is provided in order to adjust the check mechanism and the recovery capability in the middle of the pipe connected to the secondary side of the suction throttle valve after branching according to circumstances.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a piping connection system diagram of the first embodiment of the present invention. FIG. 2 is a partial cross-sectional view when a mechanical seal is used for the shaft seal device. The screw compressor of the present invention is provided with a compressor body 1 and a suction throttle valve 2, and the compressor body temporarily stores lubricating oil leaked outside from a shaft seal device 3 such as a mechanical seal. A groove 11 is provided. The recovery pipe 4 connected from the lower part of the groove is branched into two directions, one side being connected to the suction throttle valve primary side port 21 and the other side being connected to the secondary side port 22. A check valve 5 is connected in the middle of the piping to the suction throttle valve secondary side.
[0010]
The suction throttle valve is for restricting the amount of intake air of the screw compressor corresponding to the amount of use by the user. There is a valve 24 that is movable by a spring 23 and air pressure inside, and the intake air amount is controlled by opening and closing this valve. To do. The primary side of the suction throttle valve refers to the upstream side from the internal movable valve, and the secondary side refers to the downstream side of the movable valve to the compression chamber inlet.
[0011]
The operation will be described below for each operation pattern of the screw compressor.
[0012]
1) In the case of a compressor having an activation method in which the suction throttle valve is once closed in order to reduce the power at the time of startup, the intake air amount is zero, so no negative pressure is generated on the primary side of the suction throttle valve. However, leaking lubricating oil from the mechanical seal portion is recovered by the negative pressure generated on the secondary side, and the negative pressure is reduced.
[0013]
2) Since a negative pressure is generated on both the primary and secondary sides of the suction throttle valve during full load operation, the lubricating oil can be recovered.
[0014]
3) When adjusting the capacity, the opening of the movable valve in the suction throttle valve is adjusted according to the decrease in the amount of user use, and the amount of intake air is limited. This control reduces the amount of air passing through the suction throttle valve. Accordingly, the negative pressure on the primary side also decreases, but a stable negative pressure is generated on the secondary side, and the lubricating oil is recovered by the negative pressure on the secondary side. Further, air is supplied into the compression chamber by a pipe connected from the primary side to the secondary side, and the negative pressure is relaxed to suppress an increase in vibration and noise due to tooth surface separation of the rotor.
[0015]
4) During stoppage operation, the compressor body has a pressure gradient from almost atmospheric pressure on the suction side to high pressure on the discharge side and pressure gradient. If stopped in this state, compressed air and lubricating oil on the discharge side will move to the suction side. Backflow. Normally, control is performed so that the movable valve in the suction throttle valve is completely closed earlier than the reverse flow speed so that air and lubricating oil do not leak out of the compressor body. The mechanical seal oil recovery pipe connected to the secondary side of the suction throttle valve where high-pressure compressed air / lubricating oil flows back in this way has a check valve, but there is a slight amount of leakage due to the delay in closing the check valve. . This leakage becomes pressure pulsation and starts to flow back to the mechanical seal, but is dispersed at the point where it joins the piping to the suction throttle primary side and does not reach the external groove of the mechanical seal. Therefore, the lubricating oil does not jump out from the external groove, and the periphery of the external groove is kept clean.
[0016]
A second embodiment of the present invention will be described with reference to FIG. In this embodiment, description of items common to the first embodiment is omitted. FIG. 3 is a piping connection system diagram of the second embodiment. A throttle mechanism 6 having a passage narrower than the inner diameter of the pipe is provided between the check throttle mechanism provided on the recovery pipe to the suction throttle valve secondary side and the suction throttle valve. Depending on the layout of the compressor, if the lubricating oil that has leaked can be recovered sufficiently even if the differential pressure with the external groove on the mechanical seal is small, the recovery capacity is adjusted with a throttle. The operation of this embodiment is the same as that of the first embodiment, and the lubricating oil leaked from the shaft seal mechanism is recovered. This embodiment has the following effects. First, since the amount of intake air for reducing negative pressure can be adjusted, an increase in power consumption at low loads can be minimized. Further, at the time of stoppage, leakage from the secondary side of the suction throttle valve due to the delay in closing the check mechanism can be reduced.
[0017]
A third embodiment of the present invention will be described with reference to FIG. In this embodiment, the description of items common to the above-described embodiment is omitted. FIG. 4 is a piping connection system diagram of the third embodiment. The solenoid valve 51 is used for the check mechanism provided on the recovery pipe to the suction throttle valve secondary side. This embodiment operates as follows. The solenoid valve is opened during operation, and the solenoid valve is closed as soon as a stop command is received. When stopped, compressed air and lubricating oil on the discharge side flow back to the suction side in the compressor body, but the solenoid valve closes faster than this reverse flow speed, so leakage from the suction throttle valve secondary side due to the closing delay Can be eliminated.
[0018]
【The invention's effect】
As described above, according to the present invention, oil can be recovered over the entire intake air amount, and negative pressure can be relaxed in a low load region at the same time. Further, by installing a throttle for adjusting the flow rate between the check valve and the suction throttle valve, it is possible to reduce the amount of leakage to the mechanical seal side due to the delay in closing the check valve at the time of stoppage.
[Brief description of the drawings]
FIG. 1 is a piping connection system diagram of a first embodiment of the present invention.
FIG. 2 is a partial cross-sectional view using a mechanical seal as a shaft seal mechanism.
FIG. 3 is a piping connection system diagram of a second embodiment of the present invention.
FIG. 4 is a piping connection system diagram of a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Screw compressor main body, 2 ... Suction throttle valve, 3 ... Mechanical seal, 4 ... Recovery piping, 5 ... Non-return mechanism, 6 ... Throttle, 11 ... Mechanical seal external groove, 21 ... Suction throttle valve primary side port, 22 ... Suction throttle valve secondary side port, 23 ... Spring, 24 ... Movable valve, 51 ... Solenoid valve.

Claims (1)

In a lubricated screw compressor, a pipe is provided to collect the lubricating oil that leaks from the shaft seal device of the Osloter. A screw compressor characterized in that a check mechanism is provided on a recovery pipe to the secondary side.

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