JPH0749029Y2 - Oil-free screw compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an oil-free screw compressor that does not inject oil into a rotor chamber.

(Prior Art) Conventionally, an oil-free type screw compressor shown in FIG. 3 is known.

This screw compressor goes through ports a and b of intake control valve 1, then screw compressor main body 2, primary cooler 3, check valve in order.
The first and the fourth coolers 5 and the drain separating / discharging means 6 reach the receiver tank 7 and extend from there to the location where the compressed gas is used.
It branches from the passage 8 and the portion between the primary cooler 3 and the check valve 4 of the first passage 8 to the c and d ports of the intake control valve 1 which do not communicate with the a and b ports. The pressure switch 10 is provided between the check valve 4 and the secondary cooler 5 so as to detect the pressure of this portion, and the pressure switch 10 controls the pressure of this portion. If it is less than the set value, open ports a and b, and close ports c and d.If it exceeds the set value, close or throttle ports a and b and open ports c and d. It is formed on.

When the amount of compressed gas used is large and the pressure detected by the pressure switch 10 reaches the lower limit set value, for example, 6 kg / cm ² G, the signals from the pressure switch 10 open ports a and b,
With the c and d ports closed, all the discharge gas from the screw compressor body 2 is sent to the receiver tank 7 for full load operation. On the other hand, when the amount of compressed gas used decreases and the pressure detected by the pressure switch 10 reaches the upper limit set value, for example, 7 kg / cm ² G, the pressure switch 10
The a and b ports are closed or throttled by the signal from the same time, and at the same time, the c and d ports are opened and the discharge gas from the screw compressor main body 2 is discharged to the outside of the machine through the c and d ports by the second flow passage 9. The unloading operation for releasing the gas is performed, and the check valve 4 prevents the gas in the receiver tank 7 from flowing into the second flow passage 9.

In actual operation, the full load operation and the unload operation are alternately repeated, and FIG. 4 shows an example of the relationship between time and pressure during this operation. During operation, b indicates unloading operation, the solid line indicates the pressure P1 detected by the pressure switch 10, and the chain line indicates the pressure P2 at the portion between the check valve 4 and the screw compressor body 2.
Is shown.

(Problems to be Solved by the Invention) In the above-mentioned conventional device, when the full load operation is switched to the unload operation, the gas on the downstream side of the check valve 4 remains until the check valve 4 is completely closed. A backflow that returns to the upstream side of the check valve 4 occurs, and at this time, the corrosive dust in the first flow path 8 also accompanies the backflow gas, and thus a clearance that causes a backflow is formed in the seat surface of the check valve 4. Furthermore, during full load operation, the water in the gas is condensed in the pipe forming the flow path in the secondary cooler 5 and is deposited as drain, and this drain flows to the upstream side of the check valve 4 together with the backflow gas during the above switching. Backflow. When the check valve 4 is not working properly, it flows back to the primary cooler 3 and further to the screw compressor body 2, and this drain causes the check valve 4 or the pipe between the primary cooler 3 and the secondary cooler 5,
There are problems such as corrosion of the screw rotor and casing in the screw compressor body 2.

The present invention has been made in view of the above conventional problems,
An oil-free screw compressor that can prevent corrosive debris in the check valve and prevent corrosion of the check valve, upstream piping of the secondary cooler, screw rotor in the screw compressor body, casing, etc. It is the one we are trying to provide.

(Means for Solving the Problems) In order to solve the above problems, according to the present invention, after passing through the a and b ports communicating with each other of the intake air control valve, the screw compressor using the screw rotor is installed in order from the screw compressor body. The first and second flow paths passing through the secondary cooler, the check valve, the secondary cooler, and the drain separating and discharging means, and the portion between the primary cooler and the check valve of this flow path are branched to form the a and b ports. And a second flow path reaching the c and d ports of the intake control valve that do not communicate with each other, and a pressure switch is provided on the downstream side of the check valve so as to detect the pressure of the downstream side portion. The signals from this pressure switch open ports a and b when the pressure in this part is below the set value, and close ports c and d, while when the pressure exceeds this value, a and b A screw compressor formed so that the b port is closed or throttled and the c and d ports are opened. In the above, an on-off valve is provided in a branch flow path branched from a portion between the check valve and the secondary cooler of the first flow path, and when the pressure exceeds the set value, a predetermined time Only, a controller for opening the on-off valve is provided.

(Operation) With the above configuration, when switching from full load operation to unload operation, the drain in the secondary cooler flows back toward the check valve together with gas and corrosive dust, but from the branch flow path. Drain and corrosive waste will be discharged.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a screw compressor according to the present invention, which is substantially the same as the screw compressor shown in FIG. 3 except for a drain processing section and a pressure detecting section described below, and parts corresponding to each other. Are denoted by the same reference numerals and description thereof will be omitted.

As shown in the figure, in this screw compressor, the pressure switch 11 is attached to the receiver tank 7 so that the internal pressure can be detected, while the branch flow that branches from the first flow path 8 between the check valve 4 and the secondary cooler 5. Along with the passage 12, this branch passage 12
An on-off valve 13 is provided in the valve, and the on-off valve 13 is operated via a controller 14 based on a signal from the pressure switch 11.

When the pressure P detected by the pressure switch 11 is equal to or lower than the predetermined upper limit set pressure P _S , that is, when P ≦ P _S , the on-off valve 13 is closed via the controller 14 while P
In the case of> P _S, the on-off valve 13 is opened via the controller 14 for a predetermined set time T _S , and drainage and corrosive dust flowing back from the branch flow path before reaching the check valve 4. It is designed to be discharged.

Next, based on FIG.
The control will be described more specifically.

First, the device is switched on and the control starts, and in the first step (# 1), the set pressure P _S (for example, 7 k
Scan g / cm ² G).

In the second step (# 2), the pressure P detected by the pressure switch 11 is compared with the set pressure P _{S. If} P> P _S , the process proceeds to the third step (# 3), and if P ≦ P _S , the Proceed to 6 steps (# 6).

In the third step, the set time T _S (for example, 5 seconds) is read.

In the fourth step (# 4), the drive unit of the on-off valve 13, for example, the solenoid V _SOL is turned on to open the on-off valve 13, and at the same time,
Activate the built-in timer.

In the fifth step (# 5), the elapsed time T in the timer is compared with the set time T _S. If T> T _S , proceed to the sixth step. If T ≦ T _S , return to the fourth step. .

In the 6th step, turn off the solenoid V _SOL and open / close the valve.
Close 13 and go back to step 1. After that, the same process as above is repeated.

In the above embodiment, the pressure switch 11 is attached to the receiver tank 7, but the present invention is not limited to this, and if the pressure switch 11 is provided on the downstream side of the check valve 4. Good.

In addition, as shown by the alternate long and short dash line in FIG. 1, the screw compressor main body 2 is branched between the primary cooler 3 and the check valve 4.
The flow passage 15 reaching the rotor chamber may be provided, and by doing so, the gas cooled by the primary cooler 3 is sent to the rotor chamber, and the temperature of the gas discharged from the screw compressor body 2 is lowered. be able to.

(Effects of the Invention) As is apparent from the above description, according to the present invention, after passing through the a and b ports of the intake air control valve that communicate with each other, the screw compressor using the screw rotor is primary in order. The first flow path passing through the cooler, the check valve, the secondary cooler, and the drain separating and discharging means, and the portion between the primary cooler and the check valve of this flow path are branched to form the a and b ports. Has a second flow path reaching the c and d ports of the intake control valve that are not in communication with each other, and a pressure switch is provided on the downstream side of the check valve so as to detect the pressure of the downstream side portion. , When the pressure in this part is less than the set value, the ports a and b are opened, and the ports c and d are closed according to the signal from this pressure switch. In a screw compressor that is formed so that the port is closed or throttled and the c and d ports are opened. In addition, an on-off valve is provided in a branch flow path branched from a portion between the check valve and the secondary cooler of the first flow path, and when the pressure exceeds the set value, a certain time is required. Only, a controller for opening the on-off valve is provided.

Therefore, when switching from full-load operation to unload operation, the drain in the secondary cooler flows back toward the check valve along with the gas and corrosive dust, but the drain and corrosive dust are discharged from the branch flow path. Prevents clogging of corrosive dust inside the check valve, as well as piping upstream of the secondary cooler, check valve,
This has the effect of preventing corrosion of the screw rotor and casing inside the screw compressor body.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a screw compressor according to the present invention, FIG. 2 is a diagram showing a control flow in a controller in FIG. 1, FIG. 3 is an overall configuration diagram of a conventional screw compressor, and FIG. FIG. 4 is a diagram showing an example of pressure change in the apparatus shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Intake control valve, 2 ... Screw compressor main body, 3 ... Primary cooler, 4 ... Check valve, 5 ... Secondary cooler, 6 ... Drain separation discharge means, 8 ... First flow path, 9 ... Second flow Line, 11 ... Pressure switch, 12 ... Branch flow passage, 13 ... Open / close valve, 14 ... Controller.

Claims (1)

[Scope of utility model registration request] 1. A primary cooler, a non-return valve, a secondary cooler, and a drain separating and discharging means in order from a screw compressor main body using a screw rotor after passing through a and b ports communicating with each other of an intake control valve. C, d ports of the intake control valve that branch from the first flow path that passes through and the portion between the primary cooler and the check valve of this flow path and that do not communicate with the a and b ports And a second flow path to the check valve, and a pressure switch is provided on the downstream side of the check valve so as to detect the pressure of the downstream side portion, and the pressure of this portion is set by a signal from the pressure switch. When the value is less than the value, ports a and b are opened and ports c and d are closed.On the other hand, when it exceeds the set value, ports a and b are closed or throttled and ports c and d are opened. In the screw compressor formed as described above, a portion between the check valve and the secondary cooler in the first flow path. An oil-free type that is provided with an on-off valve in the branch flow path branched from and a controller that opens the on-off valve for a certain period of time when the pressure exceeds the set value. Screw compressor.