JPS59155588A - Pressure regulating device for compressor - Google Patents

Abstract

PURPOSE:To keep a delivery pressure in constant and reduce adverse effect on the life of the machine by a method wherein the upper and lower set values for the control of a choke valve and an air releasing valve are predetermined in accordance with the condition of installation and the set values are made correctable. CONSTITUTION:The compressor 1 is provided with a suction valve 4 at the suction side thereof and with the air releasing valve 5 at the delivery side thereo while the driving circuit of the suction valve 4 and the air releasing valve 5 is provided with a driver 10, a pressure regulator 8 and a setter 9 for setting the upper and lower values of the set values. These upper and lower limit values are determined previously in accordance with the condition of the installation while the set values are made correctable. According to this method, the upper and lower set values may be corrected in accordance with the flow amount upon that time, therefore, the delivery pressure may be controlled so as to be slightly higher when the flow amount is large while it may be controlled so as to be slightly lower when the flow amount is small. Accordingly, the delivery pressure may be maintained in constant and adverse effect on the life of the machine may be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pressure regulating device for a compressor, and particularly to a pressure regulating device suitable for determining a pressure setting value.

[Prior art]

Conventionally, in compressors that control the discharge pressure to a set value by opening and closing a throttle valve provided on the suction side and a blowoff valve provided on the discharge side, a compressor is provided to control the on/off of these valves. The upper and lower set values are determined in advance according to the conditions of the equipment, but the values are constant. Therefore, when the flow rate is high, the on operation time becomes longer,
Furthermore, once the switch is turned off, the pressure drops rapidly and the pressure does not rise easily even when the switch turns on. On the other hand, when the flow rate is low, the off-operation time is long, and once the on-operation is started, the pressure suddenly rises, and if the pressure exceeds the set value, the pressure will evaporate. In this way, if the ON or OFF operation time becomes extremely long or shortened, it becomes an obstacle to maintaining a constant discharge pressure, and it is not desirable from the viewpoint of the life of the machine. do not have.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a pressure regulating device that can maintain a constant discharge pressure and that does not affect the life of the machine.

[Summary of the invention]

The present invention is characterized by the opening and closing operation of the throttle valve provided on the suction side of the compressor and the blow-off valve provided on the discharge side.
In devices that control the discharge pressure to a set value, the upper and lower set values provided for on/off control of the valve are determined in advance according to the equipment conditions, and the set values can be corrected. be.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram of a screw compressor equipped with the pressure regulating device of the present invention. 1 is a screw compressor body, 2 is a check valve that prevents compressed air from flowing back into the compressor body 1, and 3 is a screw compressor body;
is the aftercooler. A suction valve 4 for opening and closing the suction port is provided on the suction side of the screw compressor. Further, on the discharge side of the screw compressor, there is provided an air discharge valve 5 that opens and closes an air outlet for discharging compressed air to the atmosphere. 6 is an electric motor that drives the compressor main body 1. 7 is a pressure detector that detects discharge pressure. Reference numeral 8 denotes a pressure regulating device having a function of opening and closing the suction valve 4 and the blowoff valve 5 based on the detection signal of this detector to control the discharge pressure to a set value. Reference numeral 9 denotes a setting device for setting an upper limit value and a lower limit value of the set value of the discharge pressure. 10
is a driver that opens and closes the suction valve 4 and the blowoff valve 5 in accordance with the output signal of the pressure regulator 8.

FIG. 2 is a time chart showing a basic pressure control method of an example of the pressure regulating device of the present invention.

The pressure control method of this pressure regulator 8 is an on-off control that opens and closes the valves 4 and 5 as shown in FIG. The on-action Lo is performed to close the air discharge valve 5 and the air discharge valve 5 is opened, and when the discharge pressure P reaches the lower limit value Pa of the set value, the off-action LF is performed to open the suction valve 4 and close the air discharge valve 5. It is something to do. By repeating this on-off operation according to changes in the discharge pressure P, the discharge pressure P is maintained between the upper limit value P1 and the lower limit value Pa of the set value. T.

indicates the on-operation time Lo, Tt indicates the off-operation time, and PA indicates the width of the set value.

The operation of an example of the pressure regulating device of the present invention will be explained in more detail using FIGS. 3 to 6.

FIG. 3 shows a method of correcting the upper limit value P6 of the set value in FIG. 2. As is clear from the figure, the upper limit value P3 is corrected to increase as the flow rate increases. As a result, when the flow rate is high, the discharge pressure is controlled to be a slightly high value. Therefore, the on-operation Lo time T1 does not take an unnecessarily long time, and even once the off-operation Ly occurs, the drop in the discharge pressure P is alleviated, so that the discharge pressure is maintained constant and the machine has a long service life. Also preferred. . -! In addition, the lower limit value is corrected so that it becomes smaller as the flow rate decreases. As a result, when the flow rate is low, the discharge pressure is controlled to a slightly low value. Therefore, the time Tt of the OFF operation Ly does not become unnecessarily long, and the increase in the discharge pressure is limited even after the ON operation is started, so the discharge pressure is maintained constant and is favorable for the life of the machine. .

FIG. 4 shows a method of correcting the lower limit value Pd of the installation value in FIG. 3. As is clear from the figure, the lower limit value Pd is corrected to become smaller as the flow rate decreases. This provides the effects described above.

FIG. 5 shows a method of correcting the upper limit value P3 and lower limit value PdO width Pm of the set values in FIG. As shown in the figure, as the flow rate increases, the width PA of the set value is decreased. As a result, when the flow rate is large, the discharge pressure is controlled to a slightly high value and maintained at a constant value. Further, as the flow rate decreases, the width Ph of the set value is increased.

This allows the discharge pressure to be controlled to a slightly lower value when the flow rate is low, which is favorable for the life of the machine.

In the above embodiments, a method of correcting the set value based on the flow rate has been described, but there are cases where it is difficult to detect the flow rate. In particular, as shown in FIG.
In the case of 7il-on/off control, the flow rate changes according to the opening/closing operation of the valves 4 and 5, so it is necessary to detect the flow rate over a certain period of time and find the average value, which is not easy. In this case, as shown in FIG. 2, it is better to use the on-operation time T, or the off-operation time Tt of the on-off control, which changes depending on the flow rate.

FIG. 6 is a diagram showing the relationship between the flow rate, the time T of the ON operation, and the time T of the OFF operation. Such a relationship can be determined quantitatively in advance once the equipment conditions are determined. Therefore, by measuring the ON operation time T1 or the OFF operation time Tt, the flow rate at that time can be determined. In this case, it is desirable to determine the flow rate from on/off operations within a certain period of time or a certain number of times.

In the above embodiments, the pressure regulating device 8 has a function of performing pressure control as shown in FIG. 2, and also stores relationships as shown in FIGS. 3 to 6 and processes them in accordance with the pressure control. , realized by electronic computers, etc.

〔Effect of the invention〕

According to the present invention, all of the upper and lower set values provided for on/off control of the discharge pressure can be corrected according to the flow rate at that time, so when the flow rate is high, the discharge pressure may be slightly higher. When the flow rate is low, the discharge pressure is controlled to be slightly lower. As a result, the operation of the on/off control is stabilized, so that the discharge pressure can be maintained constant and the adverse effect on the life of the machine can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a compressor equipped with an example of the pressure regulating device of the present invention, and FIGS. 2 to 6 are diagrams explaining the operation of the example of the pressure regulating device of the present invention. l...Compressor, 2...Check valve, 3...Aftercooler, 4...Suction valve, 5...Blowout valve, 6...Electric motor, 7...Pressure detector, 8...Pressure adjustment device, 9...
・Pressure setting device, IO\- Part 1 Fig.

Claims (1)

[Claims] 1. In a compressor in which the discharge pressure is controlled to a set value by opening and closing operations of a throttle valve provided on the suction side and a blowoff valve provided on the discharge side, the on/off control of the valve is 1. A pressure regulating device for a compressor, comprising pressure regulating means for predetermining upper and lower set values provided in a compressor according to equipment conditions, and for correcting the set values. 2. When the flow rate is high, the pressure adjustment means should be set to a high value.
2. The compressor pressure regulating device according to claim 1, wherein the set value is corrected to be lower when the flow rate is low. 3. The pressure adjusting means corrects the set value to be high when the ON operation of the on-off control is long, and to lower the set value when the OFF operation is long.
A pressure regulating device for a compressor as described in 2. 4. The pressure adjusting device for a compressor according to claim 1, wherein the pressure adjusting means is capable of correcting the width of the upper and lower set values.