JPH0643645Y2 - Cryogenic refrigerator - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial field of application The present invention is used in a cryopump, a helium liquefaction device, etc., and connects a compressor and an expander in an annular pipe, and the working gas compressed by the compressor is used. The present invention relates to a cryogenic refrigerating apparatus that obtains cryogenic cold by performing adiabatic expansion with an expander.

(B) Conventional technology This type of cryogenic refrigeration system is described in, for example, “Vacuum Technology Manual”
It is used in cryopumps as disclosed in (0). In such a cryogenic refrigeration system, when the expander side is at a high temperature immediately after the start of operation, the specific volume of the working gas in the expander is large and the flow resistance becomes large, so the discharge side pressure of the compressor rises. Therefore, the discharge side pipe of the compressor and the suction side pipe are connected by a bypass pipe having a pressure control valve, and the working gas on the discharge side of the compressor is released to the suction side, so that the discharge side pressure rises abnormally in the initial stage of operation. Was prevented.

(C) Problems to be solved by the device However, in the above-mentioned cryogenic refrigeration system, since the pressure control valve whose valve opening changes depending on the differential pressure between the primary side pressure and the secondary side pressure is used There was a problem that the amount of bypass in the initial stage was so large that the refrigerating capacity of the device was reduced. Further, if the secondary side pressure is raised and the operation is continued due to some abnormality, the primary side pressure (discharge side pressure) cannot be prevented from abnormally increasing.

It is an object of the present invention to solve the above-mentioned problems of the prior art, to improve the refrigerating capacity in the initial operation of the device, and to improve the reliability.

(D) Means for Solving the Problems In the present invention, a compressor, a cooler, an adsorber, an expander, a check valve having a forward direction from the expander to the compressor, and a buffer tank are annularly piped. In the connected cryogenic refrigeration system, the piping from the compressor outlet to the adsorber and the piping from the check valve to the buffer tank are connected by a bypass piping equipped with an atmospheric pressure differential pressure control valve. is there.

(E) Operation With this configuration, the bypass amount of the bypass pipe is determined by the pressure difference between the discharge side pressure of the compressor and the atmospheric pressure, so that the discharge side pressure is always kept almost constant and the refrigeration capacity of the initial operation is reduced. Less decrease. Further, since the primary pressure of the pressure control valve is adjusted independently of the secondary pressure, the primary pressure (discharge pressure) becomes abnormally high even if the secondary pressure (suction pressure) is abnormal. Don't worry. Further, when the working gas flows to the suction side of the compressor through the bypass pipe, the sudden increase in the suction side pressure is absorbed by the buffer tank, and a large increase in the pressure sucked into the compressor is avoided. Further, since the check valve prevents the working gas flowing through the bypass pipe from flowing to the expander, it is possible to prevent impurities from flowing into the expander together with the working gas.

(F) Embodiments Hereinafter, embodiments of the present invention shown in the drawings will be described in detail.

In FIG. 1, the second discharge port 2 of the compressor 1, the first cooler 3,
The adsorber 4, the expander 5, the check valve 6 having the direction from the expander 5 to the compressor 1 as the forward direction, the buffer tank 7, and the first suction port 8 of the compressor 1 are sequentially connected in an annular pipe. . Further, a second cooler 11 is connected between the first discharge port 9 and the second suction port 10 of the compressor 1 by piping. Further, the discharge side pipe 12 of the compressor 1 and the suction side pipe 13 between the check valve 6 and the buffer tank 7 are connected by a bypass pipe 15 having a pressure adjusting valve 14.

The pressure regulating valve 14 is of the atmospheric pressure difference type as shown in FIG. The pressure adjusting valve 14 has a coil spring 17 housed in a diaphragm chamber 16 open to the atmosphere, and a differential pressure between the sum of the spring pressure of the coil spring 17 and the atmospheric pressure and the pressure of the working gas flowing in through the primary side port 18. The diaphragm 19 is deformed according to, and the flow rate of the working gas flowing out to the secondary side port 21 is adjusted by the valve body 20 connected to the diaphragm 19, and the primary side port 18 is connected to the discharge side pipe 12. The secondary port 21 is connected to the suction pipe 13.

When the compressor 1 starts operating, the working gas (helium gas) is compressed into high temperature and high pressure. The high-temperature and high-pressure working gas is discharged from the first discharge port 9 together with the oil, and the second cooler 11
Sent to. And after being cooled here, the second inlet
Returning from 10 to the compressor 1, the oil is separated. The working gas from which the oil has been separated is discharged from the second discharge port 2,
When sequentially flowing through the cooler 3 and the adsorber 4, it is cooled to room temperature and impurities contained in the working gas are removed. After that, the working gas is supplied to the expander 5, where adiabatic expansion is performed and cold is generated. Then, the working gas exhausted from the expander 5 sequentially passes through the check valve 6 and the buffer tank 7 and is sucked into the compressor 1 from the first suction port 8. By repeating the above operation, cold is accumulated in the expander 5, and extremely low temperature cold is obtained.

At the beginning of operation of the compressor 1, the temperature on the expander 5 side is high, and the specific volume and flow resistance of the working gas in the expander 5 are large. Therefore, the discharge side pressure of the compressor 1 becomes high.
At this time, the valve body 20 of the pressure regulating valve 14 moves in the direction of the arrow to increase the valve opening degree, thereby increasing the bypass amount of the working gas. At this time, the compressor 1 using the bypassed working gas
The sudden increase of the secondary side pressure is absorbed by the buffer tank. Further, the check valve 6 prevents the working gas bypassed without passing through the adsorber 4 from flowing into the expander 5, and the impurities in the working gas do not flow into the expander 5. After that, when the discharge side pressure becomes lower as the temperature on the expander 5 side decreases, the valve body 20 of the pressure regulating valve 14 moves in the direction opposite to the arrow shown in the drawing to reduce the valve opening degree, and the working gas bypass amount. To reduce.

According to the present embodiment, since the atmospheric pressure differential type pressure adjusting valve 14 is provided in the bypass pipe 15 that connects the discharge side pipe 12 and the suction side pipe 13 of the compressor 1, the discharge side pressure of the compressor 1 and the large The bypass amount of the bypass pipe 15 is determined by the pressure difference between the atmospheric pressure (in this embodiment, the sum of the atmospheric pressure and the spring pressure), and the discharge side pressure can always be kept substantially constant. Therefore, it is possible to prevent the deterioration of the refrigerating capacity in the initial operation of the device as much as possible,
It is possible to shorten the cooldown time from the start of operation until the steady temperature is obtained on the expander 5 side. Further, since the primary side pressure of the pressure adjusting valve 14 is adjusted independently of the secondary side pressure, even if the secondary side pressure (suction side pressure) is operated with an increase due to some abnormality, the primary side pressure (discharge side pressure pressure)
It is possible to prevent an abnormal rise in temperature. Furthermore, the compressed working gas is supplied to the external cooler 11, cooled here, and then returned to the compressor 1 to be discharged again. Therefore, even when the secondary side pressure is low, the discharge gas temperature is You can prevent it from getting hot.

Further, the pressure adjusting valve 14 is opened and the working gas is bypassed.
When flowing through 15, the buffer tank 7
It is avoided that the secondary side pressure of the compressor 1 rises significantly and is absorbed by the bypass pipe 15 because the working gas from the compressor 1 does not flow through the adsorber 4 when the pressure regulating valve 14 is opened. As a result, the impurities are not adsorbed on the adsorber 14, and the adsorber 14 can be used for a longer time. Further, the check valve 6 prevents the working gas bypassed without passing through the adsorber 4 from flowing into the expander 5, and prevents the impurities in the working gas from flowing into the expander 5. It is possible to prevent the malfunction of No. 5 and stabilize the operation.

(G) Effect of the device Since the device of the present invention is configured as described above, it is possible to shorten the cool down time by minimizing the decrease in the refrigerating capacity in the initial operation of the device, and to reduce the pressure on the discharge side of the compressor. Not only can it stabilize regardless of the suction side pressure and prevent an abnormal rise in the discharge side pressure, but it is also possible to avoid a significant rise in the suction side pressure of the compressor by the buffer tank when the pressure control valve opens. Furthermore, impurities are not adsorbed on the adsorber, the adsorber can be used for a longer period of time, and management such as replacement of the adsorber can be simplified. Further, the check valve 6 prevents the working gas bypassed without passing through the adsorber from flowing into the expander, and the impurities in the working gas are prevented from flowing into the expander, so that the expander malfunctions due to the impurities. Can be prevented and the operation can be stabilized, and the refrigerating capacity and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a piping system diagram of a cryogenic refrigeration system showing an embodiment of the present invention, and FIG. 2 is a schematic sectional view showing an example of an atmospheric pressure difference type pressure regulating valve used in the present invention. 1 ... Compressor, 2 ... Cooler, 4 ... Adsorber, 5 ... Expander, 6 ... Check valve, 7 ... Buffer tank, 12 ...
Discharge side piping, 13 …… Suction side piping, 14 …… Pressure adjusting valve, 15
...... Bypass piping.

Claims (1)

[Scope of utility model registration request] 1. A cryogenic refrigeration system in which a compressor, a cooler, an adsorber, an expander, a check valve having a forward direction from the expander to the compressor, and a buffer tank are connected in an annular pipe. A cryogenic refrigeration system characterized in that the pipe from the discharge port of the compressor to the adsorber and the pipe from the check valve to the buffer tank are connected by a bypass pipe equipped with an atmospheric pressure difference type pressure control valve. .