JPS5823518B2 - Oil-cooled screw compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil-cooled screw compressor that can arbitrarily adjust the thrust force generated from the discharge side to the suction side by driving a rotor.

As is well known, a screw compressor rotates a pair of male and female rotors in mesh to compress a gas body and increase the pressure to a predetermined pressure. A thrust force is generated in the direction, and if left as it is, it will not only cause problems in the meshing of the rotors and reduce compression efficiency, but also cause the end surface of the rotor to come into contact with the suction side wall of the rotor chamber, causing the compressor to malfunction. It also causes a state where it does not work.

For this reason, a thrust bearing is usually provided to support the thrust force, but simply providing a thrust bearing has the problem that the thrust force is large and the life of the bearing is short.

A method devised to deal with this problem is a system in which a balance piston is provided, which will be explained based on FIG. A balance piston 6 is attached to the rotor 5, and a hydraulic pump 7 applies hydraulic pressure to the balance piston 6 to generate an anti-thrust force F2, thereby canceling out the thrust force F generated by meshing rotation of the rotor 4. is being done.

By the way, in an oil-cooled screw compressor, the oil injected into the balance piston 6 is the same as the oil injected into the bearing 1°2. This is done by a hydraulic pump 7.

Furthermore, the used oil after being injected into the bearing section is delivered to the low pressure section of the compressor (the suction port 12, the low pressure side of the rotor chamber, etc.),
The oil enters the rotor chamber and is discharged from the outlet 8 together with the oil injected into the rotor 4, and is circulated through the oil separator 9, oil cooler 10, and oil pump 7.

However, in such a balance piston system, as shown in Fig. 2, pressure oil is injected from the oil supply hole 13 and the anti-thrust force F2 is generated by the oil pressure, but this anti-thrust force F2 is Once the diameter of the balance piston 6 is determined, it is uniquely determined.

That is, if the discharge pressure from the oil pump 7 is now P2 and the pressure on the suction side of the compressor is Pl, the cylinder chamber 14 on the bearing side is connected to the suction side as described above, so the pressure is P.
1, and the pressure in the cylinder chamber 15 is P2.

Also, assuming that the diameter of the large diameter portion of the balance piston 6 is 0 and the diameter of the small diameter portion is D2, the anti-thrust force F2 is determined by only the differential pressure (P2 Pt) between both ends of the balance piston 6 as shown in the equation below. I end up.

F2= -(D,"-D2') (P2-P, )4 Therefore, even if the operating conditions change and the thrust force F changes, the anti-thrust force F2 will not change, so an inappropriate anti-thrust force will occur. It will work.

As a conventional technique to avoid this, for example,
It is disclosed in Japanese Patent No. 70911.

This is to control the oil pressure P2 injected into the balance piston 6 according to operating conditions, and a control valve or automatic valve is provided in the oil supply piping system, and the valve is operated by inputting the inlet pressure and outlet pressure of the compressor. It is necessary to control the injection hydraulic pressure P2 itself by controlling it, and the control technology is not just adding a control valve or an automatic valve, but also requires a control device to control the valve, so the equipment panel and its operation are difficult to control. This becomes complicated and expensive.

The present invention has been made in view of the above-mentioned state of the prior art, with the object of providing an oil-cooled screw compressor that has a simple configuration and can arbitrarily adjust the anti-thrust force F2 at low cost. Regulation.

The basic technical idea is to control the differential pressure (P2P1) at both ends of the balance piston 6 instead of controlling the piston. A cylinder chamber is provided adjacent to the suction side of the rotor chamber, a bearing is installed in at least one of the protruding rotor shaft ends in the cylinder chamber, and a hydraulic piston is pressed by a spring so as to be in constant contact with the bearing. In the oil-cooled screw compressor, the hydraulic piston is provided with a bypass passage that communicates the rotor chamber side and the opposite rotor chamber side of the cylinder chamber via a valve resiliently supported by a spring.

The present invention will be described below in detail based on the drawings. FIG. 3 is a cross-sectional front view showing one embodiment. In the figure, 20 is a rotor rotatably supported by bearings 21, 22, 23; is a cylinder chamber provided adjacent to the suction side of the rotor chamber 25.

Inside the cylinder chamber 24, a hydraulic piston 26 is slidably placed in contact with the wall surface 27 of the cylinder chamber 24 via an O-ring 2B.

A thrust bearing 29 is fixed to the end of the rotor shaft 30 with a bolt 31 and a washer 32, and the hydraulic piston 26 is constantly in contact with the end face of the bearing 29 by a spring 33, thereby preventing the outer ring of the bearing 29 from rotating. ing.

The other end of the spring 33 is supported by a presser cover 34.

Reference numeral 35 denotes an oil filling hole for pressing the hydraulic piston 26.

Reference numeral 36 denotes a relief valve, which is always elastically supported by a spring 43. When a hydraulic pressure greater than the spring force of this spring 43 is applied, the valve 36 moves to the left in the figure, and a hole 37. 38, spring chamber 39, rotor chamber 25 via hole 40
The structure is such that oil flows into the side cylinder chamber 24 to release excess hydraulic pressure.

Next, the thrust bearing mechanism of the compressor having the above configuration will be explained. As the compressor is driven, the rotation of the rotor 20 generates a thrust force F3 from the discharge port 42 side to the suction port 41 side. When oil is filled from the oil filler port 35 and hydraulic pressure is applied, the hydraulic piston 26 is pressed and an anti-thrust force F4 is generated, which reduces the thrust force F3.

At this time, if the hydraulic piston 26 is not provided with a bypass path, once the diameter of the hydraulic piston 26 is determined, the anti-thrust force F4 will be uniquely determined only by the pressure difference between both ends of the hydraulic piston 26, and during normal operation Even if the anti-thrust force is appropriate, if the operating conditions change, the anti-thrust force may become excessive and cause problems.

Therefore, when the pressure difference exceeds a certain value, the relief valve 36 releases the oil to the opposite side of the piston 26.
Holes 37 and 38, a spring chamber 39, and a hole 40) are formed, and the pressure difference is controlled to below a certain value by the spring force F of the spring 43.

That is, as shown in FIG. 4, at the position of the relief valve 36, if the diameter of the valve seat is d, the following equation holds true.

−d2P −−d P +F 4 ,', F=−d2(P2−PI) Therefore, if the spring 43 is selected so that the spring force of the spring 43 is F, the differential pressure of (P2−P,) can be set arbitrarily. can be adjusted to

As detailed above, according to the present invention, there is no need to change the oil pressure injected into the hydraulic screw, so there is no need for any extra hydraulic operation, and therefore no complicated control elements are required.
This has the effect that the configuration is extremely simple and inexpensive.

Note that the present invention is not limited to a one-stage compressor, but a two-stage compressor.
It goes without saying that it can be applied to a stage compressor, and also shows remarkable effects in a two-stage compressor.

In other words, a normal 2-stage system with an unload valve only on the first stage side
In a stepped compressor, the operating conditions are such that the intermediate pressure becomes equal to the suction pressure during unloading, but at this time, the anti-thrust force by the hydraulic piston may become too large than the thrust force, but it is necessary to By providing this, this problem can be solved.

For example, suction pressure 1 ata, intermediate pressure 4 ata, discharge pressure 14
In ATA's two-stage compressor, there is a hydraulic pressure on the second stage side2)
When installing a pressure difference △P, △P=14-4=10a
ta, and the appropriate hydraulic piston diameter is determined,
When the first stage side is unloaded, the intermediate pressure becomes equal to the suction pressure, so the pressure difference △P becomes 13 ata (△P = 14-), and the anti-thrust force by the hydraulic piston becomes larger than the thrust force, causing the rotor end face on the discharge side to comes into contact with the casing.

However, if a bypass path is provided, this phenomenon of excessive anti-thrust force can be avoided and normal compression work can be performed.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram explaining the principle of a conventional balance piston system, Fig. 2 is a partially enlarged view of the same figure, Fig. 3 is a cross-sectional front view of an oil-fed screw compressor according to the present invention, and Fig. 4 is an explanatory diagram of the operation of the relief valve. 1. 2, 3... Bearing, 4... Rotor, 5... Loaf shaft, 6... Balance piston, 7... Pump, 8 ...Discharge port, 9...Oil separator, 10...Cooler, 12...Suction port, 20...Rotor,
21゜22, 23...Bearing, 24...
・Cylinder chamber, 25... Rotor chamber, 26...
...Hydraulic piston, 28...0 ring, 33
... Spring, 34 ... Lid, 35 ...
...Oil filler port, 36...Relief valve, 39...
・Spring chamber, 41...Suction port, 42...
Discharge port, 43... Spring.

Claims (1)

[Claims] 1. A cylinder chamber is provided adjacent to the suction side of a rotor chamber that rotatably supports a pair of male and female rotors, a bearing is installed in at least one of the protruding rotor shaft ends in the cylinder chamber, and the bearing A hydraulic piston is provided that is biased by a spring so as to be in constant contact with the hydraulic piston, and a bypass passage is provided to the hydraulic piston that communicates a rotor chamber side of the cylinder chamber with a side opposite to the rotor chamber via a valve that is resiliently supported by a spring. Oil-cooled screw compressor.