JP2002168187A - Oil-cooled two-stage screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an abnormal rise of an intermediate stage pressure in an oil-cooled two-stage screw compressor. SOLUTION: The oil-cooled two-stage screw compressor for compressing a suction air with the rotation of a pair of male and female screw rotors meshing each other comprises a space 26 formed on the lower side of a high pressure stage suction port 14 in communication with an intermediate stage flow path ranging from a lower pressure stage discharge port 11 to the high pressure stage suction port 14, a partition wall 27 provided between the space 26 and a discharge path 18 for the high pressure stage compressor 6, a bypass opening 28 provided in the partition wall for allowing communication between the space 26 and the discharge path 18, and a relief valve 29 provided in the bypass opening 28 for opening the bypass opening 28 in response to a pressure in the space 26 (11, 12, 13).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil-cooled screw two-stage compressor having a built-in relief valve for preventing an abnormal increase in pressure in an intermediate stage passage in a screw two-stage compressor.

[0002]

2. Description of the Related Art As a conventional oil-cooled screw two-stage compressor, Japanese Patent Application Laid-Open No. 9-53583 is known. In this compressor, as shown in FIG. 7, a gear case 102 containing a drive gear 101 is connected to a drive motor (not shown), and a low-pressure stage compressor body 103 and a high-pressure stage compressor body 1 are provided on one side surface thereof.
04 are connected in the up-down direction and the compressors 103, 103
104 is configured to be driven.

An air intake port 106 is provided above the cylinder 105 of the low-pressure stage compressor body 103, and a compressed air discharge port 107 is provided below the cylinder 105, and an intermediate stage passage 113 ( 7), the suction port 1 of the high-pressure stage compressor main body 104 communicating with the internal space 109 formed in the gear case 102 and opening below the internal space.
08. The high-pressure stage compressor body 10
A high pressure discharge port 110 is provided at one lower side of 4, and the discharge port is connected to a receiver tank (not shown) by a discharge pipe 111.

Further, a relief valve 112 (FIG. 8) is fixed in the vicinity of the center of the gear case 102, and a discharge port of the relief valve is provided at a discharge port of the low-pressure stage compressor when the pressure in the internal space 109 exceeds a predetermined pressure. A pipe (not shown) for connecting the compressed air discharged from 103 to the receiver tank is connected.

[0005] The relief valve 112 is provided for the purpose of operating in the event that any abnormality occurs in the high-pressure stage compressor main body 104. When the suction is stopped or the compression operation is no longer performed, the compression operation is performed only by the low-pressure stage compressor main body 103, so that the low-pressure stage compressor main body 1 is placed in the internal space 109 of the gear case 102.
When the compressed air discharged from the compressor 03 accumulates and the compression action is continued in this state, the pressure in the low-pressure stage compressor main body 103 and the internal space 109 rises beyond the design pressure, and the low-pressure stage compressor main body 103 and the gear case 102 The relief valve 112 may supply compressed air discharged from the low-pressure stage compressor main body 103 directly into the receiver tank when the high-pressure stage compressor main body 104 has an abnormality. Prevent various serious accidents to be triggered.

[0006]

The relief valve of the conventional oil-cooled screw two-stage compressor is mounted on a gear case which is a part of the compressor body, and its discharge port is connected to a receiver tank by piping. I have.

However, the compressor main body has a built-in rotating body such as a driving gear and a screw rotor, whereas the receiver tank has no vibrating body, but is accompanied by the pulsation of the compressed air fed from the compressor main body. The two naturally have different vibration systems, such as slight vibration.

[0008] For this reason, if the pipes are firmly connected with steel pipes or the like, the pipe connection between the compressor main body and the receiver tank may be damaged by fatigue due to stress concentration due to vibration.

As a countermeasure, a flexible pipe (rubber hose, flexible metal pipe, or the like) that can absorb vibration from both vibrators is usually used instead of the steel pipe. However, there is a problem that not only a large number of parts are required as a whole, such as a large number of connection joints for connecting the flexible pipe, but also the entire apparatus is complicated by piping.

In addition, the above-mentioned flexible pipe and its joint for connection are more expensive than steel pipes and also require a large number of assembling steps for piping, so that the entire apparatus is expensive.

Further, the fixed portion between the relief valve and the compressor main body and the connection portion between the pipes are gradually loosened in the course of long-term use, causing problems such as leakage of compressed air and oil.

Further, when the compressor body is stopped, the lubricating oil circulating in the compressor flows down and stays near the suction port of the lowermost high-pressure compressor body. A so-called oil lock phenomenon occurs in which the oil flowing down from the suction port of the high-pressure stage compressor is sucked and compressed.

[0013] This phenomenon is intended to compress incompressible oil, and large power is required.
This not only causes start-up congestion of the driving motor, but also causes damage or destruction of each part of the compressor.

Accordingly, the present invention is to simplify the above-described relief valve and its piping system to reduce the number of assembling steps.
In addition, the pipe connection is removed to prevent leakage, and various problems such as the start-up traffic jam caused by the oil lock phenomenon are eliminated.
It is an object to provide a stage compressor.

[0015]

In order to achieve the above object, in an oil-cooled screw two-stage compressor according to the present invention, an oil-cooled screw which compresses intake air by meshing rotation of a pair of male and female screw rotors. In the two-stage screw type compressor, a space is formed below the high-pressure stage suction port and communicates with the intermediate stage flow path from the low-pressure stage discharge port to the high-pressure stage suction port. A bypass opening is provided in the partition so as to allow communication between the space and the discharge passage, and a relief valve for opening the bypass opening in accordance with the pressure in the space is provided in the bypass opening. It is characterized by the following (claim 1).

Further, the relief valve may be configured to open the bypass opening when a pressure in a space communicating with the intermediate stage flow path exceeds a predetermined pressure (claim 2). This makes it possible to suppress an abnormal increase in the pressure in the intermediate stage flow passage and the space even if the compression action is stopped due to an abnormality in the high-pressure compressor, and to simplify the piping around the compressor to reduce the cost. Can be configured.

The relief valve may be configured to open the bypass opening when a pressure in a space communicating with the intermediate stage flow passage exceeds a pressure in a discharge passage of a high pressure stage compressor. (Claim 3).

With this configuration, the oil remaining at the bottom of the gear case at the time of starting the compressor is discharged from the bypass opening to the discharge passage, so that the oil is not sucked from the high pressure stage suction port of the high pressure stage compressor.

Further, the relief valve may have a piston slidable by the bias of a spring, and the bypass opening may be opened and closed by sliding of the piston. The relief valve may include an open / close valve that is rotatable by the bias of a spring, and may open and close the bypass opening by turning the open / close valve.

In this way, during normal operation of the compressor body, the bypass opening is closed, and if the pressure in the intermediate stage flow path and the space rises abnormally due to abnormality of the high-pressure compressor, the bypass opening is closed. It can be quickly opened to prevent the abnormal rise.

In a two-stage oil-cooled screw compressor which compresses intake air by meshing rotation of a pair of male and female screw rotors, a pair of female and female members of the high-pressure stage compressor are located below the high-pressure stage suction port. A space is formed below the high-pressure stage cylinder that houses the screw rotor, and communicates with the intermediate-stage flow path from the low-pressure stage discharge port to the high-pressure stage intake port through a communication passage in the gear case that houses and arranges the drive gear, The bottom in the gear case communicates with a space communicating with the high-pressure stage suction port and the intermediate-stage flow path, and the space and the discharge passage of the high-pressure stage compressor are adjacent to each other via a partition, and the partition has a bypass. An opening may be provided, and a relief valve may be provided to open the bypass opening when the pressure in the space exceeds the pressure in the discharge passage of the high-pressure compressor (claim 6).

With this configuration, the oil remaining at the gear case bottom at the start of the compressor is discharged to the discharge passage, so that a large amount of oil does not flow into the high-pressure stage suction port of the high-pressure stage compressor.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of an oil-cooled screw two-stage compressor body (hereinafter referred to as a compressor body) of the present invention, and FIG. 2 is a side view of the compressor body viewed from the left in FIG.

A gear case 2 is disposed on one side of the compressor body 1, and the gear case contains a speed-increasing gear device 3 which is transmitted by a driving motor (not shown).
On the other hand, a low-pressure stage cylinder 5 of the low-pressure stage compressor 4 is mounted above the left side surface of the gear case 2, and a high-pressure stage cylinder 7 of the high-pressure stage compressor 6 is mounted below the lower side. Are installed side by side.

In each of the compressor stages, a pair of male and female low-pressure screw rotors 8 (hereinafter referred to as low-pressure rotors) and a high-pressure screw rotor 16 (hereinafter referred to as high-pressure rotors) are stored. The compression action is performed by driving the device 3.

A low-pressure stage suction port 9 is provided above the low-pressure stage compressor 4, and air in the atmosphere flows in from the low-pressure stage suction port 9 and the low-pressure stage rotor 8 rotates to rotate the low-pressure stage rotor 8. After being compressed to a predetermined pressure in the space 10, the gear case 2 passes through a low-pressure-stage discharge passage 12 that is formed as an internal passage below the low-pressure-stage cylinder from a low-pressure-stage discharge port 11 that opens to one side of the low-pressure stage cylinder 5. The inner communication passage 13 is circulated.

The communication passage 13 is such that the entire space formed in the gear case 2 serves as a flow passage for the compressed air discharged from the low-pressure compressor 4. 2 flows into the high-pressure stage working space 15 from the high-pressure stage suction port 14 of the high-pressure stage compressor communicating with the lower part, and is compressed to the rated pressure by the rotation of the high-pressure stage rotor 16.

The high-pressure stage suction port 14 is in contact with most of the suction-side end face (right side in the figure) of the high-pressure stage cylinder 7 with the communication passage 13 so that the compressed air is supplied to the high-pressure stage rotor shaft 24.
Is sucked from above and below a suction-side end face formed across the.

The compressed air is supplied to the high pressure stage discharge port 17.
From the discharge tank 18 through a discharge passage 18 and a discharge pipe 19 to a receiver tank (not shown) arranged separately.

On the other hand, the outer peripheral portion of the main shaft 20 on the drive motor side (right side in the figure) of the speed increasing gear device 3 built in the gear case 2 is:
A shaft sealing device 21 fitted to the gear case 2 seals the inside and the outside of the gear case. Further, a shaft seal 23 is similarly fitted to the low-pressure stage rotor shaft 22 of the low-pressure stage compressor 4 to seal the inside of the gear case 2 and the space between the low-pressure action spaces 10. Thus, the operating gear case 2 of the compressor body 1
The inside is at the same pressure as the pressure of the compressed air discharged from the low-pressure stage compressor 4.

The bottom 25 of the gear case 2 communicates with a space 26 formed below the high-pressure cylinder 7 of the high-pressure compressor 6 as shown in FIG. This space 26 is adjacent to a space communicating with the discharge passage 18 with a partition wall 27 of the high-pressure stage cylinder 7 interposed therebetween, and a bypass opening 28 is formed in the partition wall to allow a piston 30 of a relief valve 29 to be described later. It can be opened and closed by sliding. In addition, this space 26
An intermediate stage flow path from the low pressure stage discharge port 11 to the high pressure stage suction port 14 through the low pressure stage discharge passage 12 formed by an internal passage below the low pressure stage cylinder and the communication passage 13 in the gear case 2. Communicating.

The high pressure stage cylinder 7
Piston 30 slidable along hole 31 drilled below
, A spring 32 for urging the piston in a direction to seat it in the bypass opening 28, and a cover 33 for seating and supporting one of the springs. The cover 33 is bolted to a flange 34 formed below the high-pressure cylinder 7 so that the piston 3
0 and the cover 33 and the gap 37 and the discharge passage 18
Are communicated through an escape passage 36 so that the gap 37 and the discharge passage 18 have the same pressure. The spring 32 is set to a tension enough to keep the bypass opening 28 closed at normal times. When the pressure in the space 26 exceeds the pressure in the discharge passage 18, the piston 30 slides downward in the figure. When the pressure in the space 26 falls below the pressure in the discharge passage 18, the bias of the spring 32 causes the piston 30 to slide upward in the drawing to close the bypass opening 28. It has become.

Therefore, when the bypass opening 28 communicates with the valve opening of the piston 30, the compressed air compressed by the low-pressure stage compressor 4 is fed from the space 26 to the adjacent discharge passage 18 via the bypass opening 28.

The relief valve 29 acts when, for example, some abnormality occurs in the high-pressure compressor 6 and causes fatal damage such as damage to the high-pressure rotor 16 or damage to the drive unit in the high-pressure compressor. When the compression operation is no longer performed, the compression operation is performed only by the low-pressure stage compressor 4 to the final discharge pressure (rated pressure).

On the other hand, the low-pressure stage compressor 4 is designed so as to compress the sucked air at a predetermined low-pressure pressure, which is the first stage. If the compression to the final discharge pressure is continued, there is a risk that each part (bearing, gear case, etc.) of the compressor may be destroyed, and there is a danger that a further serious accident may be caused.
Therefore, it is provided to prevent such an accident.

Next, the operation of the present embodiment will be described.
First, when a driving motor (not shown) starts and the low-pressure stage rotor 8 of the low-pressure stage compressor 4 rotates by power transmission from the speed-increasing gear unit 3, air in the atmosphere is sucked in from the low-pressure stage suction port 9 and the low-pressure stage working space. After being compressed to a first predetermined pressure in 10, it is discharged from a low pressure stage discharge port 11.

The discharged compressed air is supplied to the low-pressure stage discharge passage 1
2, the high-pressure compressor 6 through the communication passage 13 of the gear case 2
After being sucked through the high pressure stage suction port 14 and sucked from the suction port, the pressure is increased to the rated pressure by the rotation of the high pressure stage rotor 16 forming the high pressure stage working space 15, and the high pressure stage discharge port 17
Is discharged from. Thereafter, the pressure is fed to the discharge passage 18 and supplied to the consumer side from a receiver tank (not shown) via the discharge pipe 19.

At this time, the space 26 adjacent to the high pressure compressor 6 with the partition wall 27 interposed therebetween and the discharge passage 1 on the high pressure pressure side
The bypass opening 28 between 8 is closed by the piston 30 of the relief valve 29.

When the operation of the high-pressure stage compressor 6 is stopped for some reason during the operation of the compressor body 1, the high-pressure stage compressor 6 stops the suction of the compressed air in the communication passage 13 and the space 26. Since the low-pressure stage compressor 4 continues the compression operation as it is, the pressure in the low-pressure stage discharge passage 12 and the communication passage 13 and the space 26 in the gear case 2 gradually rises above a predetermined pressure (hereinafter referred to as an intermediate pressure).

Then, the inside of the discharge passage 18 is
The pressure drops because there is no discharge of compressed air. When the pressure in the space 26 exceeds the pressure in the discharge passage 18, the piston 30 slides downward in FIG.
8, the compressed air in the space 26 is bypassed and circulates in the discharge passage 18, and then is pressure-fed from the discharge pipe 19 into the receiver tank.

In this way, even if the high-pressure compressor does not perform the compression action, a serious accident can be avoided by the action of the relief valve.

When the compressor body 1 is stopped in this state, the piston 30 of the relief valve closes the bypass opening 28 by the urging of the spring 32, and the backflow air from the receiver tank is released by the low pressure stage compressor body 4. To prevent inflow.

In this case, the bypass opening is not opened until the pressure in the receiver tank reaches a predetermined pressure. The opening time of the bypass opening is determined by various circumstances such as the temperature and the state of accumulation of oil. .

For example, even during normal operation, immediately after the start of the compressor body 1, the space 26
When the pressure on both sides exceeds a certain pressure difference determined by the tension of the spring 32 or the like, the piston 30 opens the bypass opening 28 and lubricating oil accumulated under the gear case is discharged to the discharge passage 18. Since it is discharged, it does not flow into the working space 15 on the suction side of the high-pressure compressor 6.

When the compressor body 1 is started, the pressure in the space 26 is higher until the pressure in the receiver tank reaches a predetermined pressure.
By opening the valve and temporarily opening the bypass opening 28, the lubricating oil remaining in the space 26 is discharged from the bypass passage to the discharge passage, so that the oil lock phenomenon at the start of the compressor can also be prevented.

The relief valve 29 according to the present embodiment comprises the piston 30 and the cover 3 as shown in FIG.
Instead of eliminating the escape passage 36 that connects the gap 37 formed between the three and the discharge passage 18, an atmosphere opening hole 39 that communicates the gap 37 of the piston 30 with the atmosphere is formed substantially in the center of the cover 33. O 3 for sealing is provided around the outer periphery of the piston 30.
-The ring 38 may be attached.

The spring 32 constructed as described above
When the pressure between the low-pressure stage discharge passage 12 and the space 26 exceeds a predetermined pressure, the tension of the spring 3
The tension is set such that the piston 30 is slid downwardly in the figure against the bias of 2 to open the bypass opening 28.

When the operation of the high-pressure stage compressor 6 stops for some reason during the operation of the compressor body 1, the pressure between the low-pressure stage discharge passage 12 and the space 26 gradually increases, and the spring 32 When the pressure reaches the pressure against the urging, the piston 30 slides downward in the drawing to open the bypass opening 28. Then, the compressed air in the space 26 bypasses and flows into the discharge passage 18 to avoid damage to the gear case 2 and other devices including the low-pressure stage compressor 4.

FIG. 5 is a longitudinal sectional view of the second embodiment of the present invention in which the high-pressure compressor 6 is cut at right angles to the axis of the high-pressure rotor 16. It is arranged substantially perpendicular to the axis of the rotor 16 and substantially horizontally.

Hereinafter, the same members as those described in the first embodiment will be described using the same reference numerals. Below the high-pressure compressor 6, a space 26a communicating with the communication passage 13 (FIG. 1) is formed on the left side of the drawing with the partition wall 27a interposed therebetween, and a discharge passage 18a is formed on the right side thereof.

A relief valve 29 is disposed below the high-pressure cylinder 7a on the discharge passage 18a side. One side of a piston 30 abuts a bypass opening 28a formed in a partition wall 27a. Is closed. On the other hand, the other side of the piston 30 is isolated from the outside by the cover 33.

The second embodiment is configured as described above. In the event that the high-pressure compressor 6 does not function due to any abnormality and the pressure in the space 26a rises abnormally, the spring 32 is biased. In contrast, the piston 30 is slid to the right in the drawing to open the bypass opening 28a.

As a result, the compressed air on the side of the intermediate stage flow path is discharged from the discharge passage 18a and the discharge pipe 1 through the bypass opening 28a.
9 (FIG. 1), so that damage to the gear case 2 and other devices, including the low-pressure stage compressor 4, is avoided.

FIG. 6 shows a third embodiment of the present invention, in which the structure of the relief valve is a swing type valve. Hereinafter, only portions different from the second embodiment will be described.

The discharge passage 18b below the high-pressure cylinder 7a
A swing-type relief valve 40 is disposed on the side, and a seat portion 43 of a swing valve 42 abuts against a valve seat 41 of a bypass opening 28b formed in the partition wall 27b,
The space between the space 26b communicating with the intermediate passage and the discharge passage 18b is shielded.

The swing valve 42 is rotatable in a counterclockwise direction (A direction) in the figure by a pivot pin 44. During normal operation, the torsion coil spring 45 biases the valve seat on the bypass opening side. 41 and the seat part 4 on the swing valve side
3 are in contact with each other and hold the shield between the space 26b and the discharge passage 18b.

If the pressure in the space 26b rises abnormally due to the abnormality of the high-pressure compressor 6, the torsion coil spring 45 is used when the pressure exceeds a predetermined intermediate stage pressure as described in the first embodiment. By rotating the swing valve 42 against the urging force, the bypass opening 28b is opened and the compressed air is pressure-fed to the discharge passage 18a and the discharge pipe 19 (FIG. 1).

Accordingly, damage to the gear case 2 and other devices including the low-pressure stage compressor 4 can be avoided.

[0059]

As described above, the present invention relates to an oil-cooled screw two-stage compressor for compressing intake air by meshing rotation of a pair of male and female screw rotors. A space communicating with the intermediate stage flow passage from the discharge port to the high-pressure stage suction port is formed, and a partition is provided between the space and the discharge passage of the high-pressure stage compressor. A bypass opening is provided to allow communication, and a relief valve is provided in the bypass opening to open the bypass opening in accordance with the pressure in the space. However, it is possible to suppress an abnormal increase in the intermediate stage pressure, prevent start-up congestion at the time of restarting the compressor body, and simplify the piping around the compressor to make it inexpensive.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an oil-cooled screw two-stage compressor main body of the present invention.

FIG. 2 is a side view of the compressor body of the first embodiment as viewed from the left.

FIG. 3 is a mounting cross-sectional view of a relief valve according to the first embodiment.

FIG. 4 is another example of the relief valve in the first embodiment.

FIG. 5 is a sectional view of a relief valve according to a second embodiment;

FIG. 6 is a sectional view of a relief valve according to a third embodiment;

FIG. 7 is a longitudinal sectional view of a conventional oil-cooled screw two-stage compressor main body.

FIG. 8 is a side view of a conventional compressor main body viewed from the left.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor main body 2 Gear case 3 Speed-up gear device 4 Low-pressure stage compressor 6 High-pressure stage compressor 8 Low-pressure stage rotor 9 Low-pressure stage suction port 11 Low-pressure stage discharge port 12 Low-pressure stage discharge passage 13 Communication passage 16 High-pressure stage rotor 18 Discharge passage 26 space 27 partition wall 28 bypass opening 29 relief valve

Claims (6)

[Claims] 1. An oil-cooled screw two-stage compressor for compressing intake air by meshing rotation of a pair of male and female screw rotors, wherein a portion from a low-pressure stage discharge port to a high-pressure stage suction port is provided below a high-pressure stage suction port. Forming a space communicating with the intermediate stage flow path, providing a partition between the space and the discharge passage of the high-pressure compressor, providing a bypass opening in the partition so as to allow communication between the space and the discharge passage, An oil-cooled screw two-stage compressor, wherein a relief valve that opens the bypass opening in accordance with the pressure in the space is provided in the bypass opening. 2. The relief valve according to claim 1, wherein the relief valve is configured to open the bypass opening when a pressure in a space communicating with the intermediate stage flow path exceeds a predetermined pressure. Oil-cooled screw two-stage compressor. 3. The relief valve according to claim 1, wherein the relief valve is configured to open the bypass opening when a pressure in a space communicating with the intermediate stage flow passage exceeds a pressure in a discharge passage of the high pressure stage compressor. The oil-cooled screw two-stage compressor according to claim 1, wherein: 4. The relief valve according to claim 1, wherein said relief valve has a piston which is slidable by biasing of a spring, and wherein said piston is slid to open and close said bypass opening. The two-stage oil-cooled screw compressor according to any one of the preceding claims. 5. The relief valve according to claim 1, wherein said relief valve has an open / close valve which is rotatable by the bias of a spring, and wherein said bypass opening is opened and closed by rotation of said open / close valve. The oil-cooled screw two-stage compressor according to any one of claims 1 to 3. 6. An oil-cooled screw two-stage compressor for compressing intake air by meshing rotation of a pair of male and female screw rotors, wherein the pair of female and female members of the high-pressure compressor is located below the high-pressure stage suction port. A space is formed below the high-pressure stage cylinder that houses the screw rotor, and communicates with the intermediate-stage flow path from the low-pressure stage discharge port to the high-pressure stage intake port through a communication passage in the gear case that houses and arranges the drive gear, The bottom in the gear case communicates with a space communicating with the high-pressure stage suction port and the intermediate-stage flow path, and the space and the discharge passage of the high-pressure stage compressor are adjacent to each other via a partition, and the partition has a bypass. An oil-cooled screw two-stage compressor, comprising an opening and a relief valve for opening a bypass opening when the pressure in the space exceeds the pressure in the discharge passage of the high-pressure stage compressor.