JPH0742948B2 - Multi-stage oil-free compressor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage oil-free compressor equipped with an intake control valve.

[0002]

2. Description of the Related Art Conventionally, this is an example of a multi-stage type shown in FIG.
Two-stage oil-free screw compressors are known and
An intake control valve 3 is provided in a suction passage 2 of the stage compressor body 1, and an intermediate passage 5 between the first stage compressor body 1 and the second stage compressor body 4 is provided.
Further, an intercooler 6 and a drain separator 7 are provided, and a check valve 9 and an aftercooler 10 are provided in a discharge passage 8 of the second stage compressor body 7. Here, as will be described in detail later, the intake control valve 3 is provided together with a flow path (not shown), closes the suction flow path 2 of the first-stage compressor body 1, and reverse-checks with the second-stage compressor body 7. A no-load operation state in which the primary side portion 8a of the discharge flow path 8 with the valve 9 is in an atmosphere communication state, and a load operation state in which the suction flow path 2 is opened and the primary side portion 8a is in an atmosphere non-communication state. It is formed to be switchable to. This makes the first
The intake capacity of the stage compressor body 1 is adjusted.

Since the air compressed to about 2 kg / cm ² in the first compressor body 1 reaches a high temperature of about 180 ° C., an intermediate cooler 6 is provided in the intermediate flow path 5 and For example, in the case of the water cooling type, the compressed air is cooled to the cooling water inlet temperature plus about 15 ° C. At this time, condensed water (drain) is generated in the intercooler 6, and the condensed water is discharged to the second
If it is included in the intake air of the stage compressor body 7, the rotor and casing of the second stage compressor body 7 will be corroded. Therefore, a drain separator 7 is provided at the outlet of the intercooler 6 to separate condensed water from compressed air.

[0004]

In the above-mentioned conventional device,
Condensed water generated in the intercooler 6 is used as a drain separator 7
However, since the separation efficiency is not 100%, a small amount of condensed water is sucked into the second stage compressor body 7 together with the compressed air under the present circumstances. Second like this
There is no problem because a small amount of condensed water sucked into the main stage compressor body 7 is evaporated by the heat of compression during continuous operation. However, after a long time has passed after the compressor was stopped, the condensed water generated immediately before the stoppage, and the backflow from the aftercooler 10 through the check valve 9 during the no-load operation normally performed before the compressor is stopped. The condensed water, that is, the condensed water that has flowed backward for a short time until the check valve 9 is closed, or while the valve body is slightly hunting at the time of closing, particularly the second stage compressor body 7 Rust occurs on the. If this rust occurs, it will cause the performance of the second-stage compressor body 7 to deteriorate, and further cause the sticking phenomenon between the rotors.

In order to prevent the occurrence of this undesired phenomenon, there is a problem that before the compressor is stopped for a long time, a troublesome rust preventive measure such as enclosing dry nitrogen in the compressor body is required. . The present invention has been made to solve the above-mentioned conventional problems, and when the compressor is stopped, it can be operated easily and surely from the inside of the compressor body in a short time by simply performing a no-load operation. It is intended to provide a multi-stage oil-free compressor capable of eliminating condensed water.

[0006]

In order to solve the above-mentioned problems, the present invention provides a compressor body in which two or more stages are arranged in series,
The check valve provided in the discharge passage of the final stage compressor body and the suction passage of the first stage compressor body are closed, and the primary side of the discharge passage between the final stage compressor body and the check valve is closed. The intake air provided in the suction flow path is formed so as to be switchable to a no-load operation state in which a portion is in the atmosphere communication state and a load operation state in which the suction flow path is opened and the primary side portion is in the air non-communication state. A multi-stage oil-free compressor including a control valve and an intercooler in an intermediate flow path between the compressor bodies, wherein at least an intercooler between the first-stage compressor body and the first and second-stage compressor bodies The intermediate flow path portion between and, and a bypass flow path for communicating the space in the intake control valve for switching between the atmosphere communication state and the atmosphere non-communication state via an on-off valve, and the no load The above-mentioned on-off valve can be moved to the open state when shifting to the operating state. It was formed in.

[0007]

According to the above-mentioned invention, at the same time as the no-load operation performed before the compressor is stopped, at least a portion of the hot air discharged from the final stage compressor body is at least in the second stage compressor body. The drying operation leading to the suction side can be performed easily and surely.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a two-stage oil-free screw compressor according to the present invention, in which components substantially the same as those of the compressor shown in FIG. is there. In the compressor according to this embodiment, similarly to the above, the first-stage compressor body 1, the suction flow path 2, the intake control valve 3,
The second stage compressor body 4, an intermediate flow path 5, an intermediate cooler 6, a drain separator 7, a discharge flow path 8, a check valve 9, and an aftercooler 10 are provided. Here, the intake control valve 3 is a first partition on the side of the suction flow path 2 which is partitioned by the diaphragm 11.
The chamber 12 and the second chamber 13 on the side opposite to the suction flow path 2, and the third chamber 1 that is adjacent to the second chamber 13 via the partition wall 14 and is open to the atmosphere.
5, the partition wall 14 and the end portion of the valve rod 16 penetrating the partition wall 14a between the first chamber 12 and the suction flow path 2 on the suction flow path 2 side cooperate with the first valve seat 17 to suck the air. First to open and close the flow path 2
The valve body 18 connects the third chamber 15 to the discharge passage 8 at the end on the side of the third chamber 15, and more specifically to the primary side portion 8a of the discharge passage 8 which is the inlet side of the check valve 9. Second opening and closing of the opening 20 at one end of the discharge passage 19 in cooperation with the second valve seat 21
A valve body 22 is provided so as to be integrally operable with the valve rod 16.

A silencer 24 is provided in the atmosphere communicating portion 23 of the third chamber 15 and extends from the primary side portion 8a to the opening portion 2.
The noise generated when the compressed air is released to the outside of the machine via the third and third chambers 15 is suppressed. The valve rod 16 operates integrally with the diaphragm 11 in the axial direction via a sandwiching plate 25 that sandwiches the diaphragm 11, and the second chamber 1
A spring 26 fitted in 3 constantly biases the suction passage 2 side. Further, a three-way valve 28 having A, B, and C ports and a spherical valve body 27 inside, and D, on one side
A four-way solenoid valve 29 having an E port and F and G ports on the other side is provided. Of these, port A is filter 3
0 to the D port, the B port to the intermediate flow passage 5, and the C port to the suction flow passage 2 on the side opposite to the first stage compressor body 1 with respect to the first valve body 18 (hereinafter, this portion will be referred to as Suction channel 2 (X)
I said). The E port is the first valve body 1
8, the suction passage 2 on the side of the first-stage compressor body 1 (hereinafter,
This portion is referred to as the suction flow path 2 (Y)), the F port is in the second chamber 13, and the G port is in the first chamber 12 via the throttle valve 31.
Is in communication with.

Furthermore, the first-stage compressor body 1 and the intercooler 6 are connected from the atmosphere communicating portion 23 of the third chamber 15 via the solenoid valve 32.
There is provided a bypass flow passage 33 for the dry operation, which reaches a portion of the intermediate flow passage 5 between and. The solenoid valve 32 is controlled to open at the start and close at the end when shifting to the no-load operation described below by the operation of the operator. In addition, in FIGS. 1 and 2, the marks * indicate that they are continuous with each other.

Next, the operation of the compressor having the above structure will be described. FIG. 1 shows a load operating state of the compressor,
In the four-way solenoid valve 29, the D port and the G port are in communication with each other and the E port and the F port are in communication with each other, and the valve body 27 of the three-way valve 28 is caused by the pressure difference between the suction flow passage 2 (X) and the intermediate flow passage. The C port is closed. Then, the first of the intake control valve 3
The chamber 12 communicates with the intermediate flow path 5 through the G port and D port of the four-way solenoid valve 29, the filter 30, and the B port of the three-way valve 28, and is at a pressure higher than atmospheric pressure. On the other hand, the second chamber 13 of the intake control valve 3 communicates with the suction passage 2 through the F port and the E port of the four-way solenoid valve 29, and has the same atmospheric pressure. Therefore, the pressure in the first chamber 12 is
By overcoming the force of the second chamber 13 and the spring 26, the diaphragm 11, the valve rod 16, the first valve body 18, the second
The valve body 22 is pushed rightward in FIG. 1 to open the suction passage 2 and keep the opening 20 closed. As a result, the primary side portion 8a of the discharge channel 8 is kept in a state of not communicating with the atmosphere.
Further, during this load operation, the solenoid valve 32 is in a closed state.

The air sucked into the main body 1 of the first-stage compressor is compressed, heated, discharged into the intermediate flow path 5, cooled by the intermediate cooler 6, and the condensed water generated by this cooling is drained. After being separated and removed by the separator 7, it is sucked into the second stage compressor body 4. Further, the sucked air is compressed by the second stage compressor body 4, heated and discharged, passed through the check valve 9, cooled by the aftercooler 10, and then sent to the user side. Then, by the operator,
When an operation for shifting the compressor to a no-load operation state, for example, a push button switch operation is performed, the four-way solenoid valve 29 operates and the compressor enters the state shown in FIG.
Opens.

That is, in the four-way solenoid valve 29, the D port and the F port are in communication with each other, and the E port and the G port are in communication with each other.
The valve body 27 of the three-way valve 28 closes the b port on the side of the intermediate flow passage 5, while the spring 26 in the intake control valve 3 presses the first valve body 18 against the first valve seat 17 and the suction flow passage 2 Is closed, and when activated in this state, the pressure in the suction passage 2 (Y) and the intermediate passage 5 becomes lower than the atmospheric pressure. The suction passage 2 (Y) and the first chamber 12 and the suction passage 2 (X) and the second chamber 13 communicate with each other via the four-way solenoid valve 29, and the second chamber 13 has the same pressure. Pressure is atmospheric pressure,
The pressure in the chamber 12 becomes lower than the atmospheric pressure, and the pressure difference between the chamber 12 and the force of the spring 26 keeps the first valve body 18 in close contact with the first valve seat 17 and keeps the suction passage 2 closed. . In this case, it is necessary to keep the suction passage 2 (Y) completely in the vacuum state and continue the operation.
Since the discharge temperature is abnormally increased, which is not preferable, some air is sucked into the first-stage compressor body 1 through the suction hole 34 formed in the first valve body 18.

Then, in this no-load operation state in which the amount of intake air is only the air from the intake hole 34, the air is discharged from the second stage compressor body 4, and the discharge passage 19, the opening 20, and the third chamber 15 are discharged. A part of the heated compressed air discharged from the silencer 24 into the atmosphere via the air-conditioner is returned to the inlet side of the intercooler 6 through the bypass flow path 33 for a drying operation. In this case, the discharge pressure from the first stage compressor body 1 is a negative pressure of about -35 cmHg, and the discharge temperature of both the first and second stage compressor bodies 1 and 4 is 150 ° C.
It is about high temperature. When the air is in a positive pressure state, the condensation point of water vapor in the air is lowered and condensed water is easily generated. However, in the present invention, the discharge side of the first-stage compressor body 1 is in a negative pressure state or a positive pressure state. Even in a pressure state, the pressure level is lowered as much as possible and the temperature is set as high as possible to suppress the generation of condensed water and to evaporate the condensed water.

In the no-load operation and the dry operation, an electric circuit (not shown) is provided so that the compressor stops when one of the temperatures detected by the discharge temperature switches T1 and T2 rises to a set value. . Next, the pressure and temperature of each part when only the no-load operation is performed (the drying operation is not performed) (operation I), according to the present invention, that is, when the drying operation is also performed at the time of the no-load operation (operation II). The results of the comparison are as follows, and in the case of the present invention, the condensed water is in a state of being easily evaporated. Operation I Operation II Initial end PS2 (cmHG) -35 -15 -15 TS2 (° C) 30 30 70 TD1 (° C) 150 150 Upper limit TD2 (° C) 150 150 Upper limit

Here, PS2 is the suction pressure of the second-stage compressor body 4, TS2 is the suction temperature of the second-stage compressor body 4, and TD.
Reference numeral 1 indicates the discharge temperature of the first-stage compressor body 1, TD2 indicates the discharge temperature of the second-stage compressor body 1, and the upper limit value is 210 ° C. In the above embodiment, the compressor main body is arranged in two stages in series, but the present invention is not limited to this, and includes a compressor in which the compressor main body is arranged in three or more stages. The present invention is not limited to the screw compressor, and includes oil-free type compressors other than screw type compressors.

[0017]

As is apparent from the above description, according to the present invention, the compressor body arranged in series in two or more stages, the check valve provided in the discharge passage of the final stage compressor body, The suction passage of the main body of the first stage compressor is closed, and the primary side portion of the discharge passage between the main body of the final stage compressor and the check valve is in an atmosphere-free state, and the suction passage is Opened and formed so as to be switchable to a load operation state in which the primary side portion is in a state of not communicating with the atmosphere, an intake control valve provided in the suction flow passage, and an intercooler in an intermediate flow passage between the compressor bodies. In a multi-stage oil-free compressor provided, at least a portion of an intermediate flow path between the first-stage compressor body and an intermediate cooler between the first and second-stage compressor bodies, the atmosphere communication state, and the atmosphere. Communicates with the space inside the intake control valve, which is switched to the non-communication state, through an on-off valve. Provided with a bypass channel which, at the time of transition to the no-load operating state, are then transferable to form the on-off valve in the open state.

Therefore, the drying operation can be performed easily and surely before the compressor is stopped, and a part of the heated air discharged from the final stage compressor body is guided to the intermediate passage. Therefore, it is not necessary to operate for no load for a long time, and as a result, even if a long time has passed after the compressor was stopped, it is possible to prevent rust from occurring in the compressor body, especially in the second and subsequent stages. This has the effect of eliminating the need for cumbersome rust-proofing.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a load operating state of a two-stage oil-free screw compressor according to the present invention.

FIG. 2 is an overall configuration diagram showing a no-load operation state of a two-stage oil-free screw compressor according to the present invention.

FIG. 3 is an overall configuration diagram of a conventional two-stage oil-free screw compressor.

[Explanation of symbols]

 1 1st-stage compressor main body 2 Suction flow path 3 Intake control valve 4 2nd-stage compressor main body 5 Intermediate flow path 6 Intercooler 8 Discharge flow path 8a Primary part 9 Check valve 32 Solenoid valve 33 Bypass flow path

Claims (1)

[Claims] 1. A compressor body in which two or more stages are arranged in series,
The check valve provided in the discharge passage of the final stage compressor body and the suction passage of the first stage compressor body are closed, and the primary side of the discharge passage between the final stage compressor body and the check valve is closed. The intake air provided in the suction flow path is formed so as to be switchable to a no-load operation state in which a portion is in the atmosphere communication state and a load operation state in which the suction flow path is opened and the primary side portion is in the air non-communication state. A multi-stage oil-free compressor including a control valve and an intercooler in an intermediate flow path between the compressor bodies, wherein at least an intercooler between the first-stage compressor body and the first and second-stage compressor bodies The intermediate flow path portion between and, and a bypass flow path for communicating the space in the intake control valve for switching between the atmosphere communication state and the atmosphere non-communication state via an on-off valve, and the no load The above-mentioned on-off valve can be moved to the open state when shifting to the operating state. Multistage oil-free compressor, characterized in that formed on.