JPH03217763A - Cryogenic refrigerator - Google Patents

Abstract

PURPOSE:To hold a pressure difference between the high pressures side and the low pressure side of a compressor constant by regulating the opening of a motor-driven expansion valve provided in a bypass tube for maintaining the pressure difference constant by returning fluid from the high pressure side to the low pressure side of the compressor by a controller which is operated by detecting pressures of discharge and suction tubes of the compressor. CONSTITUTION:A motor-driven expansion valve 19 provided in a bypass tube 18 connected to a high pressure tube 7 between an oil separator 3 and an adsorber 4 and a low pressure tube 9 on the inlet side of an accumulator 6 is controlled in its opening by a controller 23 which calculates the difference of the pressures detected by a first pressure sensor 21 mounted in the tube 7 on the outlet side of a compressor 1 and detected by a second pressure sensor 22 provided in the tube 9, and a pressure difference between the fluid sucked to the compressor 1 and the discharged fluid is held constant. The valve 19 rapidly sets the pressure difference between the tubes 7 and 9 connected to the compressor 1 to zero by fully opening the valve when the compressor 1 is stopped. Further, the valve 19 can be optimally regulated at the pressure difference between the discharge side and the suction side of the compressor 1 under the control of the valve opening by the pressures detected by the sensors 21, 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field This invention relates to a cryogenic refrigeration system that maintains a constant pressure difference between a high pressure side and a low pressure side of a compressor.

(Example) Conventional technology A conventional cryogenic refrigeration system is, for example,
The structure is as shown in the publication. here,
A conventional example will be explained with reference to this publication. In Figure 4,
50.51 is a compressor and pressure regulating valve; 52. 53 is an automatic valve linked to the power supply of the compressor 50, 54 is a high-pressure device consisting of a filter, 55 is a cryogenic expander, and 56 and 57 are a return path and a gas holder.

In the cryogenic refrigeration system with this structure, fluid compressed by the compressor 50, for example, helium gas, is transferred to the return path 5 through the pressure regulating valve 51.
6 to adjust the pressure of the fluid supplied to the cryogenic expander 55, and then pass through the automatic valve 52, high-pressure equipment 54, and automatic valve 53 to generate cold air in the cryogenic expander 55, and when stopped, the automatic valve 52 , 53 are closed to confine the fluid within the high-pressure device 54 in a high-pressure state within this high-pressure device.

(C) Problems to be Solved by the Invention However, since the pressure regulating valve 51 operates based on the pressure difference between the high pressure and the low pressure at the front and rear, the actual pressure between the suction side and the discharge side of the compressor 50 may vary. The compressor 5o did not operate according to the actual operating pressure, and there was a period when the refrigerating capacity became unstable.

This invention solves the above-mentioned problem, and aims to provide a cryogenic refrigeration system that can maintain a constant pressure difference between the high pressure side and the low pressure side of the compressor.

[2] Means for Solving the Problems This invention connects a compressor, a main heat exchanger, an oil separator, an adsorber, and a cryogenic expander with piping, and connects the suction side of the compressor and the outlet side of the oil separator. In a cryogenic refrigeration system in which a bypass pipe is provided between the bypass pipe and the bypass pipe, an electric expansion valve is provided in the bypass pipe, and a control device for controlling the opening degree of the electric expansion valve is connected to the discharge pipe and the suction pipe of the compressor. It is composed of a sensor that detects the pressure of the sensor, and a controller that calculates the output from this sensor.

(E) Function This invention is configured as described above, so that the opening degree of the electric expansion valve is controlled by a signal from a control device that calculates the output from a sensor that detects the pressure between the discharge pipe and suction pipe of the compressor. The pressure difference between the high pressure and the low pressure of the compressor is maintained constant to enable optimum operation.

(f) Examples The present invention will be explained below based on the examples shown in FIGS. 1 and 2.

1 is a compressor that compresses fluid such as helium gas, 2 is a main heat exchanger, 3 is an oil separator, 4 is an adsorber, 5 is a cryogenic expander, and 6 is an accumulator. Compressor 1
A high pressure pipe 7 is connected between the and the cryogenic expander 5 via an oil separator 3 and an adsorber 4. An intake valve 8 is provided in the high pressure pipe 7 on the inlet side of the cryogenic expander 5. A low pressure pipe 9 is connected between the cryogenic expander 5 and the compressor 1 via an accumulator 6. An exhaust valve 10 is installed in the low pressure pipe 9 on the outlet side of the cryogenic expander 5.
is provided. The compressor 1 is comprised of a closed container 11 in which oil is stored at the bottom, and a compression element (not shown) housed within this container. Reference numeral 12 denotes an oil supply pipe for supplying the oil in the closed container 11 into the compression element, and this oil supply pipe is provided with an oil cooler 13 for cooling the oil. Reference numeral 14 denotes an auxiliary heat exchanger, and this auxiliary heat exchanger discharges the fluid compressed by the compression element outside the closed container 1 to cool it, and then introduces it into the closed container 1 again. 15 is an oil return pipe, and this oil return pipe is connected between the oil separator 3 and the outlet side of the accumulator 6. Reference numerals 16 and 17 are capillary tubes for reducing pressure provided in the oil supply pipe 12 and the oil return pipe 15, respectively.

A bypass pipe 18 is connected to the high pressure pipe 7 between the oil separator 3 and the adsorber 4 and the low pressure pipe 9 on the inlet side of the accumulator 6, and this bypass pipe is provided with an electric expansion valve 19. Reference numeral 20 denotes a control device that controls the opening degree of the electric expansion valve 19, and this control device includes a first pressure sensor 2 attached to the high pressure pipe 7 between the compressor and the main heat exchanger 2.
1, a second pressure sensor 22 attached to the low pressure pipe 9 between the exhaust valve 10 and the accumulator 6, and a mount roller 23 that calculates the outputs from the first and second pressure sensors 21 and 22. There is.

In the cryogenic refrigeration system configured as described above, the fluid compressed by the compressor 1 is cooled by the auxiliary heat exchanger 14, and then flows into the closed container 11 again, and is transferred from the high pressure pipe 7 to the main heat exchanger. 2. The fluid cooled by this main heat exchanger is separated from most of the oil contained therein by an oil separator 3. When the fluid flowing out from the oil separator passes through the adsorber 4, oil particles that cannot be separated by the oil separator 3 are adsorbed by the adsorber 4, so that the oil is sufficiently removed. When the intake valve 8' is open, the fluid leaving the adsorber 3 enters the cryogenic expander 5 and expands to generate cold. Furthermore, when the exhaust valve 10 is opened, the cold fluid exchanges heat within the cryogenic expander 5 and returns to the compressor 1 via the accumulator 6 after becoming approximately equal to the outside air temperature. There is. The intake valve 8 and the exhaust valve 10 are alternately opened and closed to allow fluid to flow into the cryogenic expander 5 from the high pressure pipe 7 side and flow out to the low pressure pipe 9 side.

The oil stored at the bottom of the closed container 11 flows out through an oil supply pipe 12, is cooled by an oil cooler 13, is depressurized by a decompression capillary tube 16, and is returned to the outlet side of the accumulator 6 to become a fluid. I try to mix it up. Further, the oil separated by the oil separator 3 is depressurized from the oil return pipe 15 by a depressurizing cabillary tube 17 and returned to the outlet side of the accumulator 6 to be mixed with the fluid. The temperature of the oil returned to the compressor 1 is suppressed from increasing due to compression of the fluid supplied from the accumulator 6 to the compressor.

An electric expansion valve 19 installed in a bypass pipe 18 connected to a high-pressure pipe 7 between the oil separator 3 and the adsorber 4 and a low-pressure pipe 9 on the inlet side of the accumulator 6 is connected to the high-pressure pipe 7 on the outlet side of the compressor 1. The controller 23 calculates the difference between the pressures detected by the first pressure sensor 21 attached to the pipe 7 and the second pressure sensor 22 attached to the low pressure pipe 9 and controls the valve opening. This makes it possible to maintain a constant pressure difference between the fluid injected and the fluid discharged. In addition, the electric expansion valve 19 can quickly reduce the pressure difference between the high pressure pipe 7 and the low pressure pipe 9 connected to the compressor 1 to zero by fully opening the valve when the compressor 1 is stopped. We are making it possible to do so.

Additionally, the electric expansion valve 19 has first and second pressure sensors 21,
By controlling the valve opening degree with the pressure detected at 22,
There is no need to consider the pressure loss of the fluid reaching the bypass pipe 18, and the pressure difference between the discharge side and the suction side of the compressor 1 can be adjusted optimally.

This invention detects the pressure on the suction side and the pressure on the discharge side of the compressor 1 using first and second pressure sensors 21 and 22 to control the valve opening degree of the electric expansion valve 19 provided in the bypass pipe 18. This makes it possible to keep the pressure difference between the high and low pressures of the fluid compressed by the compressor 1 constant.

In the above explanation, the pressure sensors 21 and 22 were attached to the high pressure pipe 7 and the low pressure pipe 9, respectively, but as shown in FIG. Needless to say, the same effect can be obtained even if the differential pressure sensor 24 is provided in between.

(G) Effects of the Invention As described above, according to the present invention, an electric expansion valve is installed in a bypass pipe to return fluid from the high pressure side to the low pressure side of the compressor to keep the pressure difference between the high pressure side and the low pressure side constant. Since the opening degree of the compressor is adjusted by a control device that detects the pressure between the discharge pipe and suction pipe of the compressor and operates the compressor, the pressure can be adjusted without having to consider the pressure loss of the fluid. This allows the pressure difference between the high pressure side and low pressure side of the machine to be constant. Moreover,
In this invention, since the pressure setting of the control device can be changed arbitrarily, the setting can be changed during operation.

[Brief explanation of drawings]

Fig. 1 is a cooling circuit diagram of a cryogenic refrigerator showing one embodiment of the present invention, Fig. 2 is a main part cooling circuit diagram showing a compressor pressure control device, and Fig. 3 is a similar diagram of another embodiment. FIG. 4 is a cooling circuit diagram of a conventional example. 1... Compressor, 2... Main heat exchanger, 3... Oil separator, 4... Adsorber, 7...
- High pressure pipe, 9... Low pressure pipe, 18... Bypass pipe, 19... Electric expansion valve, 20... Control device,
21... First pressure sensor, 22... Second pressure sensor, 23... Controller, 24... Differential pressure sensor.

Claims (1)

[Claims] 1. A cryogenic refrigeration system in which a compressor, a main heat exchanger, an oil separator, an adsorber, and a cryogenic expander are connected via piping, and a bypass pipe is provided between the suction side of the compressor and the outlet side of the oil separator. In the apparatus, the bypass pipe is provided with an electric expansion valve, and a control device that controls the opening degree of the electric expansion valve is connected to a sensor that detects the pressure between the discharge pipe and the suction pipe of the compressor, and this sensor. A cryogenic refrigeration device characterized by comprising a controller that calculates an output from the cryogenic refrigeration device.