JPH04203382A - Oil cooled type screw compressor - Google Patents

Abstract

PURPOSE:To reduce a high frequency noise and vibration of a rotor by a method wherein a discharged oil recovering pipe for a bearing at a discharging side is separated at a female rotor and a male rotor, a solenoid valve and an orifice for metering an amount of recovered oil are arranged in parallel at the recovery pipe at the female rotor side and they are connected to a suction port. CONSTITUTION:Discharged oil at a female rotor passes through a recovery pipe 16 under a differential pressure between an inside part of a D cover 12 and an inside part of a suction port 17 and the discharged oil is recovered into the suction port 17. A solenoid valve 14 and an orifice 15 for adjusting an amount of recovered oil are arranged in parallel to the recovering pipe 16. Under a full load operation, the solenoid valve 14 is opened and the discharged oil at the female rotor is recovered from both the solenoid valve 14 and the orifice 15. Under an unloading operation, the solenoid valve 14 is closed in response to an electrical signal of a pressure switch 27. Due to this fact, the discharged oil at the female rotor is recovered into a suction port 17 only through the orifice 15 and thus an amount of recovered oil can be adjusted to be low in its volume.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vibration reduction device for a female rotor of an oil-cooled screw compressor or a screw refrigerator that includes a male rotor and a female rotor.

[Conventional technology]

A conventional device will be explained with reference to FIGS. 4 and 5.

As shown in FIG. 4, a male rotor 1 and a female rotor 2 mesh with each other with appropriate backlash and are housed in a casing 3 and a D casing 4. Fitted into the casing 3 are bearings 5.6 that support the radial loads on the suction sides of the male rotor 1 and female rotor 2, respectively. Also, fitted into the D casing 4 are bearings 7 and 9 that support the radial load on the discharge side of the male rotor 1 and the female rotor 2, and bearings 8 and 10 that support the thrust load. A mechanical seal 14 is attached to the casing 3 for shaft sealing on the suction side of the male rotor 1. Oil is supplied to the meshing surfaces of the male rotor 1 and the female rotor 2 for lubrication, sealing, and cooling, and to the bearings for lubrication.

The male rotor 1 is rotationally driven via the V-pulley 15, and the female rotor 2 is driven by the male rotor 1.

The intake air is drawn into the intake port 13 through the unloader valve 16, compressed between the rotors, and then discharged from the discharge boat 26 provided in the casing 3. The discharged high-pressure air and oil are separated in oil by an oil separator 18, pass through a pressure regulating valve 19 and a check valve 20, are cooled by two aftercoolers, are discharged, and are used as consumed air.

The oil separated by the oil separator 18 is transferred to the oil cooler 2.
The compressor is cooled at step 4, passes through an oil filter 25, and is supplied with oil to the rotor's meshing portion and each bearing due to the differential pressure between the oil separator 18 and the compressor body. The bearings on the discharge side are supplied with oil through the oil supply hole 17 provided in the D casing 4.
10 is refueled.

After the oil that has passed through the bearing is drained into the D cover 11, it is collected into the suction port 13 through the first recovery pipe 12 within the difference between the inside of the D cover 11 and the suction port 13.

As the amount of consumed air decreases, the pressure within the oil separator 18 increases. The pressure switch 22 detects the discharge pressure when the amount of consumed air becomes about half of the amount of air discharged from the compressor, and the electric signal from this pressure switch 22 closes the unloader valve 16 to cut off the intake air. The air discharge solenoid valve 23 is opened to release the compressed air in the oil separator 18 to the atmosphere to reduce the load on the compressor and perform an unload operation.

During unload operation, the suction pressure becomes negative pressure, and the discharge pressure differs from the pressure cuff kgf/cJ-g during full load operation.
It is maintained at a low pressure of about 2 kgt/aiT-g.

FIG. 5 shows a sectional view perpendicular to the axis of the male rotor 1 and the female rotor 2 in a state where their tooth surfaces are in mesh with each other. Male rotor 1 in the diagram
The female rotor 2 rotates in the direction shown by the arrow, and the female rotor 2 is driven by contacting the advancing surface of the tooth surface of the male rotor 1 and rotates in the direction shown by the arrow.

[Problem to be solved by the invention]

The above conventional technology has the following problems. In Fig. 5, the rotational torque acting on the female rotor 2 is the gas torque determined by the discharge pressure and the suction pressure (as shown by the solid line in the figure, the acting direction is opposite to the rotational direction of the female rotor 2, A plow is placed on the side that presses the male rotor 2 against the forward movement surface of the male rotor 1.
), and torque due to the inertia of the female rotor 2 that is generated when rotation is transmitted to the female rotor 2 on the driven side, and torque that is generated due to advancement and delay in the rotation direction due to uneven rotation of the female rotor 2, and gas torque. There is a torque (collectively referred to as inertial torque) caused by the fluctuation. This inertial torque acts in the same direction as the rotational direction of the female rotor 2, as shown by the broken line in the figure, and moves the female rotor 2 toward the forward movement surface of the male rotor 1. It pulls away from the surface and acts on the backward movement side. Both the gas torque and the inertia torque change depending on the rotation angle of the female rotor. During operation, if the gas torque is always larger than the inertial torque, the female rotor 2 will always be in contact with the forward surface side of the male rotor 1, and an ideal rotational transmission will be performed.On the other hand, if the gas torque is smaller than the inertial torque, The female rotor 2 comes into contact with the reversing surface on the opposite side to the driving surface.

During unloading, the gas torque decreases because the discharge pressure is as low as about 2 kgf/aJ-g, and depending on the rotation angle of the female rotor 2, the gas torque becomes larger or smaller than the inertial torque. Furthermore, during unloading, the discharge pressure decreases, so the amount of oil supplied to the bearings 8 to 10 on the discharge side, which flows due to the differential pressure between the oil separator 18 and the compressor body, decreases. Therefore, the dynamic friction torque (which acts in the same direction as the gas torque and cancels out the inertial torque) due to stirring of the oil within the bearing is reduced. Therefore, during unloading, the female rotor 2 does not always come into contact with the forward moving surface of the male rotor 1, but alternately contacts the forward moving surface and the backward moving surface of the male rotor 1 during one rotation.

Because so-called tooth surface separation imaging is more likely to occur, harsh high-frequency noise and excessive vibrations are generated due to the teeth of the rotors hitting each other. Furthermore, since the rotor surface is abnormally worn due to tooth striking, the performance of the compressor is significantly reduced due to air leakage from this worn portion.

An object of the present invention is to eliminate tooth flank separation of the female rotor 2.

[Means to solve the problem]

Separate the recovery piping for the discharge side bearing waste oil between the female rotor side and the female rotor side, and connect a solenoid valve and an orifice to throttle the amount of recovered oil in parallel to the recovery piping on the female rotor side for suction. Connect to port. The recovery piping on the male rotor side is connected to the suction port through a separate piping from that on the female rotor side.

6. When unloading, the solenoid valve is closed by the electric signal from the pressure switch, and opened when the load is full. As a result, when the female rotor is fully loaded, the drained oil passes through both the solenoid valve and the orifice and is collected into the suction bow 1~, but when unloaded, it is collected only from the orifice, reducing the amount of oil collected. This allows oil to accumulate inside the bearing.

[Effect]

By tightening and reducing the amount of oil collected in the discharge side bearing of the female rotor during unloading, it is possible to make the bearing section full of oil. In this state, the dynamic frictional resistance caused by the stirring of oil by the bearing is far greater than in the full load state. This dynamic frictional resistance relieves the inertia torque of the female rotor, which acts in the opposite direction to the rotational direction of the female rotor (in the opposite direction to the inertia torque acting on the female rotor during unloading), and the gas torque is larger than the inertia torque. can be maintained.

This makes it difficult for the female rotor to separate from the forward movement surface of the male rotor, and it is possible to eliminate tooth flank separation of the rotor.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. In FIG. 1, a pair of male rotor 1 and female rotor 2 are housed in a casing 3 and a D casing 4, meshing with each other with a certain backlash. Bearings 5 and 6 are fitted into the casing 3 to support the radial loads on the suction sides of the male rotor 1 and female rotor 2, respectively. Furthermore, bearings 7 and 9 that support the radial load on the discharge side of the male rotor 1 and female rotor 2, and bearings 8 and 10 that support the thrust load are fitted into the D casing 4. A mechanical seal 19 is attached to the casing 3 to seal the shaft of the male rotor 1 on the suction side. Oil is supplied to the meshing surfaces of the male rotor 1 and the female rotor 2 for lubrication, sealing, and cooling, and to the bearings for lubrication. The male rotor 1 is rotationally driven through a V-pulley 20, and the female rotor 2 is driven by the male rotor 1.

The intake air is drawn into the intake port 17 through the unloader valve 21, compressed between the rotors, and then discharged from the discharge port 18 provided in the casing 3. After oil is separated from the discharged high-pressure air and oil by an oil separator 23, the air passes through a pressure regulating valve 24 and a check valve 25, is cooled by an aftercooler 26, and is discharged to be used as consumed air. The oil separated by the oil separator 23 is cooled by the oil cooler 29, passes through the oil filter 30,
The meshing portion of the rotor and each bearing are supplied with oil by the differential pressure between the oil separator 23 and the compressor body. Oil is supplied to the bearings on the discharge side through oil supply holes 22 provided in the D casing 4 to each of the bearings 7 to 10.

The oil that has passed through the bearing is drained into the D cover 11 on the male rotor side and into the D cover 12 on the female rotor side. The drained oil on the male rotor side is recovered into the suction boat 17 through the recovery plumber 3 due to the differential pressure between the inside of the D cover 11 and the inside of the suction port 17. - On the female rotor side, drain oil from D cover 1.
2 and the suction boat 17, the recovery plumber 6
The oil is collected into the suction boat 17 through the pipe, and the plumber 6 is equipped with a solenoid valve 14 and an orifice 15 in parallel to limit the amount of oil collected. During full load operation, this solenoid valve 14 is opened, and the drain oil on the female rotor side is drained through the solenoid valve 14.
and orifice 15.

When the amount of air consumption decreases, the pressure within the oil separator 23 increases. The pressure switch 27 detects the discharge pressure when the amount of air consumed becomes approximately half of the amount of air discharged from the compressor,
In response to the electric signal from the pressure switch 27, the unloader valve 21 is opened to cut off the intake air, and the discharge solenoid valve 28 is opened to release the compressed air in the oil separator 23 to the atmosphere, thereby reducing the load on the compressor. Reduce the load and perform unloading operation. During this unloading operation, the suction pressure becomes negative pressure, and the discharge pressure becomes pressure cuff kgf/a#- at full load.
The pressure is maintained at a low level of approximately 2 kgf/a#-g.

During unloading operation, the above-mentioned solenoid valve 4 is closed by an electric signal from the pressure switch 27. Therefore, during unloading, the drained oil on the female rotor side is collected only from the -10- orifice 15 and into the suction port 17.
The amount of recovered oil can be reduced.

FIG. 2 shows a longitudinal sectional view of the bearing portion on the discharge side of the female rotor 2 in order to explain the vertical mounting positions of the solenoid valve 14 and the orifice 15. Holes for oil recovery are provided at the top and bottom of the D cover 12, an orifice 15 is provided at the top, and a solenoid valve 14 is provided at the bottom. During unloading, the solenoid valve 14 is closed and oil is collected only from the orifice 15.
The bearings 9 and 10 of the female rotor 2 can be filled with oil. This makes it possible to increase dynamic frictional resistance due to stirring of oil in the bearing.

FIG. 3 shows a cross-sectional view in a direction perpendicular to the axis of the male rotor 1 and the female rotor 2 in a state where they are in mesh with each other.

The arrow in the figure indicates the direction of torque acting on the female rotor 2 during the unloading operation. The solid line with the arrow indicates the gas torque exerted by air pressure, and the dashed line indicates the inertial torque (1
1110 - shows the sum of the inertia torque generated when the rotation is transmitted to the rotor 2 by the male rotor 1 and the torque generated due to the advance and lag in the rotational direction due to uneven rotation of the male rotor 2. - The dashed line indicates the bearing of the female rotor 2. 9 and 10 are shown. During operation, the gas torque and the dynamic friction of the bearing (1-lux) act in the direction of pressing the female rotor 2 against the forward-moving surface, which is the drive-side tooth surface of the male rotor 1, and the inertial torque pushes the female rotor 2 away from the forward-moving surface of the male rotor 1. Acts in the direction of pulling it apart.

〔Effect of the invention〕

According to the present invention, the dynamic friction torque generated in the bearing of the female rotor during unloading increases. Since this torque acts in the direction of pressing the female rotor against the forward movement surface of the male rotor, the phenomenon in which the female rotor separates from the forward movement surface and the tooth surface is less likely to occur. Therefore, it is possible to reduce the harsh high-frequency noise caused by the rattling of the tooth surfaces of the rotors and the vibration of the rotor.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a screw compressor and an air and oil piping system diagram showing one embodiment of the present invention. Figure 2 is a longitudinal sectional view of the discharge side bearing of the female rotor in Figure 1, and Figure 3 is a
Figure 1 is a cross-sectional view taken in a direction perpendicular to the axis of the male and female rotors in a meshed state, Figure 4 is a diagram of the air and oil piping system of a conventional screw compressor, and Figure 5 is , is a sectional view taken in the direction of the force perpendicular to the axis of the male rotor 1 and the female rotor 2 in the meshed state of FIG. 4. 1... Male rotor, 2... Female rotor, 3... Casing, 4... D casing, 5, 6, 7, 8, 9.1
0...bearing, 11.12...D cover, 13.16...
・Recovery piping, 14... Solenoid valve, 15... Orifice, 17... Suction port, 18... Discharge port, 19...
・Mechanical seal, 20...Pulley, 21...Unloader valve, 22...Oil filler port, 23...Oil separator, 24...Pressure regulating valve, 25...Check valve, 26...
Aftercooler, 27...Pressure switch, 28...
Air release valve, 29 ・Oi base lV

Claims (1)

[Claims] 1. In a screw compressor main body formed by a pair of male and female rotors that mesh with each other, in order to reduce tooth surface separation vibration of the female rotor that occurs during unloading,
An oil-cooled screw compressor, characterized in that an electromagnetic valve is provided in an oil recovery pipe that supplies oil to a discharge side bearing of the female rotor, so as to have a function of reducing the amount of recovered oil during unloading.