JP4326353B2 - Ultra-low temperature refrigeration equipment - Google Patents

Description

  The present invention relates to an ultra-low temperature refrigeration apparatus, and more particularly to the configuration of the buffer tank.

  In general, in this type of ultra-low temperature refrigeration system that uses two or more types of refrigerants with different boiling points, the refrigerant with low boiling point components does not sufficiently condense at the start of operation of the apparatus, so the discharge pressure is low. It may rise and exceed the breakdown voltage of the device.

  For this reason, a separate buffer tank is provided, and this buffer tank and the refrigerant circuit are connected by a bypass pipe having a safety valve that operates when the pressure in the refrigerant circuit becomes higher than a predetermined pressure (for example, a design pressure resistance), By temporarily letting out the high-pressure refrigerant into the buffer tank, it is possible to operate with a lower discharge pressure.

Further, the refrigerant in the buffer tank is circulated by connecting the buffer tank and the suction side of the compressor with a return pipe (see, for example, Patent Document 1).
JP-A-6-159831

  However, in recent years, in order to increase the cooling capacity of the refrigeration apparatus, a low-boiling point refrigerant that maintains a gas phase state during operation and stoppage is often used, and thus a lack of capacity in the buffer tank becomes a problem. ing.

  In order to solve such a shortage of the capacity of the buffer tank, a buffer tank having a large volume may be used. However, it is difficult to secure a tank installation space simply by increasing the tank volume. In addition, since refrigerants with different boiling points have different specific gravities, there are refrigerant components that are difficult to circulate completely depending on the connection position of the return pipe. There is a risk that the cooling performance will be reduced due to fluctuations compared to the initial one.

  The present invention has been made in view of such points, and the object of the present invention is to improve the configuration of the ultra-low temperature refrigeration apparatus, thereby realizing an increase in the capacity of the buffer tank accompanying the lowering of the boiling point of the refrigerant. In addition, an object is to efficiently circulate the gas refrigerant in the buffer tank.

  In order to achieve the above object, the present invention provides a plurality of buffer tanks and connects the buffer tanks to each other by piping so that the gas refrigerant circulates smoothly in the tank, and the gas refrigerant stays in the tank. The gas refrigerant can be circulated efficiently.

That is, the invention of claim 1 is a compressor that compresses a mixed refrigerant obtained by mixing a plurality of types of refrigerants having different boiling points.
A condenser that cools and liquefies a high-boiling refrigerant among the mixed refrigerant discharged from the compressor;
A multi-stage gas-liquid separator that sequentially separates the mixed refrigerant liquefied by the condenser from a high boiling point refrigerant into a low boiling point refrigerant into a liquid refrigerant and a gas refrigerant;
A plurality of stages in which the primary-side gas refrigerant separated by the gas-liquid separators is cooled by heat exchange with the secondary-side liquid refrigerant separated and decompressed by the gas-liquid separators. A cascade heat exchanger,
A refrigerant circuit is connected to the cooler that evaporates the low-boiling point refrigerant that has flowed out from the cascade heat exchanger at the final stage of the plurality of stages and cools the cooling target to an ultra-low temperature level,
A plurality of buffer tanks for suppressing an abnormal increase in the discharge pressure of the compressor is connected to the refrigerant circuit ,
The plurality of buffer tanks comprises at least one first buffer tank and at least one second buffer tank,
The first and second buffer tanks are connected to each other by a communication circuit that circulates the gas refrigerant between the first and second buffer tanks,
The first buffer tank is connected to a refrigerant circuit on the discharge side of the compressor;
The communication circuit is connected to a refrigerant circuit on the suction side of the compressor on the way .

Therefore, according to the present invention, since a plurality of buffer tanks are connected to the refrigerant circuit, compared with a case where only one large-capacity tank is connected in order to solve the shortage of tank capacity, the inside of the factory or the like. It becomes easy to secure installation space. Further, since the tank capacity is increased by a plurality of buffer tanks, an abnormal increase in the discharge pressure of the compressor can be suppressed, which is advantageous for stable operation of the apparatus .

Further, since the first and second buffer tanks are connected to each other by the communication circuit, the refrigerant is circulated between the two tanks. As a result, it is possible to completely circulate refrigerant components having different specific gravities by suppressing the retention of gas refrigerant in the tank, and the component ratio of the mixed refrigerant in the device fluctuates compared to the beginning of the refrigerant charging, resulting in reduced cooling performance. Can be prevented.

Further, since the communication circuit is connected to the refrigerant circuit on the suction side of the compressor, the gas refrigerant flowing from the refrigerant circuit into the buffer tank and returning to the suction side of the compressor circulates smoothly in the tank. Thereby, the residence of the gas refrigerant in the tank can be more reliably suppressed .

As described above, according to the first aspect of the present invention, since the plurality of buffer tanks are connected to the refrigerant circuit, the discharge pressure of the compressor can be reduced by increasing the capacity of the buffer tank while securing the installation space. This is advantageous in suppressing abnormal rise and stable operation of the apparatus . Further, a plurality of buffer tanks comprising first and second buffer tank, which first and second buffer tank are connected to each other by a communicating circuit, halfway suction side of the refrigerant circuit of the compressor of the communication circuit Since the refrigerant that flows into the buffer tank from the refrigerant circuit and returns to the compressor suction side circulates smoothly in the tank, the retention of gas refrigerant in the tank can be more reliably suppressed. I can .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

< Reference form 1>
FIG. 1 shows an example of a layout of a vacuum film forming apparatus A according to a reference embodiment or an embodiment of the present invention, and 120 is a vacuum chamber in which a wafer (not shown) is formed while the inside is kept in a vacuum state. The vacuum chamber 120 has a loading / unloading port (not shown) that is opened and closed by an opening / closing door 123. A wafer to be deposited is loaded into the vacuum chamber 120 with the opening / closing door 123 open. Alternatively, the wafer after film formation is unloaded from the vacuum chamber 120. A vacuum pump 121 is connected to the vacuum chamber 120 via a communication passage 122, and a gate valve 124 is provided at a connection portion of the communication passage 122 with the vacuum chamber 120 to switch between the two to open or close. The vacuum chamber 120 is evacuated by the operation of the vacuum pump 121 with the open / close door 123 closed and the gate valve 124 opened.

The above vacuum deposition apparatus A and ultra-low temperature refrigeration system 10 is provided that constitutes a refrigeration system, the cryogenic coil (cooler) 52 which will be described later in this ultra-low temperature refrigeration system 10, in vacuum state of the vacuum pump 121 The gas and moisture to be cooled in the vacuum chamber 120 are directly cooled to an ultra-low temperature level, whereby the gas and the like are captured and the vacuum level in the vacuum chamber 120 is raised.

  On the other hand, FIG. 2 shows another example of the layout of the vacuum film-forming apparatus A. The cryocoil 52 of the refrigeration apparatus 10 is disposed not in the vacuum chamber 120 but in the middle of the communication path 122 and is formed by the vacuum pump 121. The vacuum level in the vacuum chamber 120 is increased by cooling and capturing the moisture in the communication path 122, that is, the moisture in the vacuum chamber 120 indirectly by the ultra-low temperature refrigeration apparatus 10 in a vacuum state. The other structure is the same as that of the vacuum film forming apparatus A shown in FIG.

  The ultra-low temperature refrigeration apparatus 10 generates refrigeration at an ultra-low temperature level of −100 ° C. or lower by using a non-azeotropic refrigerant mixture obtained by mixing five or six refrigerants having different boiling temperatures as refrigerants.

FIG. 3 shows the overall configuration of the ultra-low temperature refrigeration apparatus 10 according to Reference Embodiment 1 , wherein 1 is a closed cycle refrigerant circuit in which the mixed refrigerant is enclosed, and this refrigerant circuit 1 is a refrigerant pipe for various devices described below. Connected. Reference numeral 20 denotes a compressor that compresses a gas refrigerant. A pressure sensor 81 that detects a discharge pressure of the gas refrigerant is connected to a discharge portion of the compressor 20, and then a first oil separator 15 is connected. The first oil separator 15 separates the compressor lubricating oil mixed in the gas refrigerant discharged from the compressor 20 from the gas refrigerant, and the separated lubricating oil is supplied to the oil return pipe. 18 is returned to the suction side of the compressor 20. A water-cooled condenser 21 is connected to the refrigerant discharge portion of the first oil separator 15 to cool and condense the gas refrigerant discharged from the compressor 20 by heat exchange with the cooling water in the cooling water passage 11. The discharge side of the water-cooled condenser 21 is connected to the primary side of the auxiliary condenser 22 via a dryer 17 that removes moisture and contamination in the refrigerant. In the auxiliary condenser 22, the gas refrigerant from the water-cooled condenser 21 is supplied. It cools and condenses by exchanging heat with the low-temperature secondary reflux refrigerant sucked into the compressor 20. In this reference form , the water-cooled condenser 21 and the auxiliary condenser 22 constitute a condenser, and the condensers 21 and 22 condense and liquefy the gas refrigerant having the highest boiling temperature among the mixed refrigerants. It has become.

  A first gas-liquid separator 24 is connected to a primary-side discharge portion of the auxiliary capacitor 22, and the gas-liquid mixed refrigerant from the auxiliary capacitor 22 is converted into a liquid refrigerant and a gas by the first gas-liquid separator 24. Separated into refrigerant. The primary side of the cascade-type first heat exchanger 25 is provided in the gas refrigerant discharge portion of the first gas-liquid separator 24, and the same is provided in the liquid refrigerant discharge portion via the first capillary tube 26 as decompression means. The secondary side of the first heat exchanger 25 is connected to each other, and after the liquid refrigerant separated by the first gas-liquid separator 24 is decompressed by the first capillary tube 26, the secondary side of the first heat exchanger 25 is The gas refrigerant on the primary side is cooled by this evaporation, and the gas refrigerant having the second highest boiling point temperature in the mixed refrigerant is condensed and liquefied.

  Further, a second gas-liquid separator 30 is connected to the primary discharge section of the first heat exchanger 25, and the gas from the first heat exchanger 25 is connected to the second gas-liquid separator 30. The liquid mixed refrigerant is separated into a liquid refrigerant and a gas refrigerant. The gas refrigerant discharge part of the second gas-liquid separator 30 is the same as the primary side of the cascade-type second heat exchanger 31, and the liquid refrigerant discharge part is the same through a second capillary tube 32 as decompression means. The secondary side of the second heat exchanger 31 is connected to each other, and after the liquid refrigerant separated by the second gas-liquid separator 30 is decompressed by the second capillary tube 32, the secondary side of the second heat exchanger 31. The gas refrigerant on the primary side is cooled by this evaporation, and the gas refrigerant having the third highest boiling point temperature in the mixed refrigerant is condensed and liquefied.

  Further, in the same manner as in the connection structure, a third gas-liquid separator 36, a third heat exchanger 37, and a third capillary tube 38 are also provided at the primary discharge portion of the second heat exchanger 31. A fourth gas-liquid separator 42, a fourth heat exchanger 43, and a fourth capillary tube 44 are connected to the discharge section on the primary side in the third heat exchanger 37 (these connection structures are described above). Since it is the same as the connection structure of the first gas-liquid separator 24, the first heat exchanger 25, and the first capillary tube 26, detailed description thereof is omitted), and the liquid separated by the third gas-liquid separator 36 After the refrigerant is decompressed by the third capillary tube 38, the refrigerant is supplied to the secondary side of the third heat exchanger 37 and evaporated, and the gas refrigerant on the primary side is cooled by the evaporation. The fourth highest temperature gas refrigerant is condensed While being liquefied, the liquid refrigerant separated by the fourth gas-liquid separator 42 is decompressed by the fourth capillary tube 44 and then supplied to the secondary side of the fourth heat exchanger 43 to evaporate. The gas refrigerant on the side is cooled by heat exchange, and the gas refrigerant having the lowest boiling point temperature among the mixed refrigerants is condensed and liquefied.

  And the primary side of the subcooler (subcooler) 47 which consists of a heat exchanger is connected to the primary side discharge part in the said 4th heat exchanger 43, and the primary side discharge part of this subcooler 47 The refrigerant pipe connected to is branched into a main refrigerant pipe 2a and a sub refrigerant pipe 2b on the way.

  A fifth capillary tube 48 is connected in the middle of the auxiliary refrigerant pipe 2b. The downstream end of the sub refrigerant pipe 2b is connected to the secondary side of the same subcooler 47, and the secondary side of the subcooler 47 is connected to the secondary side of the fourth heat exchanger 43 via the refrigerant pipe. After the refrigerant discharged from the fourth heat exchanger 43 is connected to the primary side of the subcooler 47, a part of the refrigerant is decompressed by the fifth capillary tube 48 of the sub refrigerant pipe 2b, The liquid refrigerant is supplied to the secondary side of the subcooler 47 to evaporate, and the primary side gas refrigerant is cooled by the heat of evaporation.

  On the other hand, in the middle of the main refrigerant pipe 2a, a sixth capillary tube 53 and a cryocoil 52 are connected in series from the upstream side. The cryocoil 52 constitutes a main cooler, and cools water as a cooling target in the vacuum chamber 120 as shown in FIG. 1 or FIG. The downstream end of the main refrigerant pipe 2 a is connected to the refrigerant pipe between the secondary side of the fourth heat exchanger 43 and the secondary side of the subcooler 47, and from the primary side of the subcooler 47. The remaining portion of the discharged refrigerant is decompressed by the sixth capillary tube 53 of the main refrigerant pipe 2a, then supplied to the cryocoil 52 and evaporated, and the heat (evaporation target) in the vacuum chamber 120 is -100 ° C by the heat of evaporation. It cools to an ultra-low temperature level of the following temperature, traps its moisture and increases the vacuum level.

  In addition, the secondary side (and the cryocoil 52) of the supercooler 47, the fourth heat exchanger 43, the third heat exchanger 37, the second heat exchanger 31, the first heat exchanger 25, and the auxiliary condenser 22 are used. Are connected in series in the order of description by refrigerant piping, and the secondary side of the auxiliary capacitor 22 is connected to the suction side of the compressor 20, and the refrigerant gasified by evaporation in the mixed refrigerant is compressed into the compressor. 20 is inhaled.

  The cryocoil 52 is arranged in the vacuum chamber 120 so that the gas in the vacuum chamber 120 is directly cooled by the cryocoil 52. However, instead of the cryocoil 52, a brine cooler is provided, The brine cooler is connected to the heat absorption part located in the vacuum chamber 120 by a brine circuit, and in this brine cooler, the brine in the brine circuit is cooled to an ultra-low temperature level, and the same temperature level is applied to the heat absorption part in the vacuum chamber 120 by the brine. You may make it provide the cold of.

  The condensers 21 and 22, the heat exchangers 25, 31, 37, and 43 and the supercooler 47 may be any of a double tube structure, a plate structure, and a shell and tube structure. Further, instead of the capillary tubes 26, 32, 38, 44, other decompression means such as an expansion valve can be used.

Next, a description will be given of a circuit configuration of the bus Tsu fur tank. As shown in FIG. 3, 65 is a first buffer tank, 66 is a second buffer tank located below the first buffer tank 65, and these first and second buffer tanks 65, 66 are This is to suppress an abnormal increase in the discharge pressure of the compressor 20 by temporarily releasing a high-pressure gas refrigerant that is insufficiently condensed at the start of operation of the ultra-low temperature refrigeration apparatus 10.

  The first and second buffer tanks 65 and 66 are connected to each other by a communication circuit 68 for circulating a gas refrigerant between the tanks 65 and 66. The second buffer tank 66 and the refrigerant pipe between the gas refrigerant discharge part of the first gas-liquid separator 24 and the primary side of the first heat exchanger 25 are connected by a refrigerant inflow pipe 67. An electromagnetic on-off valve 82 that controls the inflow of the gas refrigerant into the first and second buffer tanks 65 and 66 is connected to the refrigerant inflow pipe 67. The refrigerant inflow pipe 67 is connected to a refrigerant return pipe 69 that returns the gas refrigerant in the first and second buffer tanks 65 and 66 to the refrigerant pipe on the suction side of the compressor 20.

  In addition, a fusible plug 80 is connected to the lower side of the first buffer tank 65. The fusible plug 80 melts itself by heat such as a fire to open the first buffer tank 65 and reduce the tank internal pressure.

  In FIG. 3, reference numeral 60 denotes a defrost circuit that supplies the high-temperature gas refrigerant (hot gas) discharged from the compressor 20 to the cryocoil 52 as it is, and is provided between the first oil separator 15 and the water-cooled condenser 21. The refrigerant pipe is connected to the refrigerant pipe between the sixth capillary tube 53 and the cryocoil 52. 61 is an electromagnetic on-off valve connected in the middle of the defrost circuit 60, 62 is an upstream side of the connection position with the downstream end of the defrost circuit 60 in the refrigerant pipe between the sixth capillary tube 53 and the cryocoil 52 (first 6 on the 6 capillary tube 53 side).

  A second oil separator 16 that separates compressor lubricating oil from gas refrigerant is disposed between the upstream end of the defrost circuit 60 and the electromagnetic on-off valve 61. The lubricating oil separated by the second oil separator 16 is returned to the suction side of the compressor 20 through the oil return pipe 18 in the same manner as the first oil separator 15.

  The vicinity of the electromagnetic on-off valve 61 of the defrost circuit 60, the vicinity of the electromagnetic on-off valve 62 between the sixth capillary tube 53 and the cryocoil 52, the outlet side of the cryocoil 52, and the secondary side of the fourth heat exchanger 43 The first to third manual on-off valves 71, 72, 73 are respectively disposed in the refrigerant pipes between the first and third manual open / close valves. These first to third manual on-off valves 71, 72, 73 are closed when the cryocoil 52 is replaced or maintained, so that the mixed refrigerant remaining in the piping does not leak to the outside. .

  Further, a refrigerant supply line 70 for supplying a mixed refrigerant into the refrigerant circuit 1 of the cryogenic refrigeration apparatus 10 is provided in the refrigerant pipe between the outlet side of the cryocoil 52 and the secondary side of the fourth heat exchanger 43. Is connected. The refrigerant supply pipe 70 also serves as a discharge pipe for discharging the mixed refrigerant from the refrigerant circuit 1. The refrigerant supply pipe 70 is provided with a supply opening / closing valve 75 that opens when the refrigerant is supplied or discharged.

Oite the configured reference embodiment as described above, when forming the wafer in a vacuum chamber 120 inside of the vacuum deposition apparatus A cryogenic refrigeration system 10 is operated, the vacuum chamber 120 inside (or communication passage 122 The gas inside) is cooled and trapped to an ultra-low temperature level of −100 ° C. or lower, and the vacuum chamber 120 is evacuated. That is, during operation of the cryogenic refrigeration apparatus 10, the defrost circuit 60 is closed by closing the electromagnetic on-off valve 61, and the main refrigerant pipe 2 a is opened by opening the electromagnetic on-off valve 62. As a result, the mixed refrigerant discharged from the compressor 20 is cooled by the water-cooled condenser 21 and then cooled by the secondary-side refrigerant returned to the compressor 20 by the auxiliary condenser 22, and the boiling point of the mixed refrigerant has the highest temperature. The gas refrigerant is condensed and liquefied. This refrigerant is separated into a gas refrigerant and a liquid refrigerant in the first gas-liquid separator 24, and the liquid refrigerant evaporates on the secondary side of the first heat exchanger 25 after being depressurized by the first capillary tube 26. The gas refrigerant from the first gas-liquid separator 24 is cooled by heat, and the gas refrigerant having the second highest boiling point temperature in the mixed refrigerant is condensed and liquefied. Thereafter, in the same manner, in the second to fourth heat exchangers 31, 37, 43, the gas refrigerant is condensed and liquefied in order from the highest boiling point temperature of the mixed refrigerant. The gas refrigerant having the lowest boiling point temperature is condensed and liquefied.

  The refrigerant discharged from the primary side of the fourth heat exchanger 43 is in a gas-liquid mixed state, and this gas-liquid mixed refrigerant passes through the primary side of the subcooler 47 and then passes through the main refrigerant pipe 2a and the sub refrigerant. It isolate | separates into the piping 2b. The refrigerant flowing into the sub refrigerant pipe 2b is decompressed by the fifth capillary tube 48 and then supplied to the secondary side of the subcooler 47 to evaporate. The evaporative heat causes supercooling from the fourth heat exchanger 43. The gas-liquid mixed refrigerant supplied to the primary side of the vessel 47 is further cooled.

  Further, the remaining refrigerant in the gas-liquid mixed state that flows into the main refrigerant pipe 2a after being discharged from the primary side of the subcooler 47 is decompressed by the sixth capillary tube 53, and after the decompression, it is evaporated by the cryocoil 52 to be evacuated. For example, chilling of −100 ° C. or lower is applied to the moisture in the chamber 120. The cold in the temperature of −100 ° C. or lower captures moisture in the vacuum chamber 120 and raises the vacuum level in the vacuum chamber 120.

  When the operation of the ultra-low temperature refrigeration apparatus 10 as described above is started, if the pressure sensor 81 detects that an abnormal increase in the discharge pressure of the compressor 20 has occurred due to insufficiently condensed gas refrigerant, the electromagnetic on-off valve 82 opens. Then, part of the gas refrigerant separated by the first gas-liquid separator 24 flows into the second buffer tank 66 through the refrigerant inflow pipe 67. Further, when the inflow amount of the gas refrigerant is large, it flows into the first buffer tank 65 through the communication circuit 68. When it is detected by the pressure sensor 81 that the abnormal increase in the discharge pressure has been resolved, the electromagnetic on-off valve 82 is closed, and passes through the refrigerant return pipe 69 from the first and second buffer tanks 65 and 66. Thus, the gas refrigerant is returned to the refrigerant pipe on the suction side of the compressor 20.

  On the other hand, during the defrost operation in which the wafer is not formed in the vacuum chamber 120 of the film forming apparatus A, the defrost circuit 60 is opened by opening the electromagnetic opening / closing valve 61 and the electromagnetic opening / closing valve 62 is closed. The refrigerant pipe 2a is closed, whereby the high-temperature gas refrigerant discharged from the compressor 20 is supplied to the cryocoil 52 through the defrost circuit 60, and capture of gas or the like in the cryocoil 52 is released.

  Next, when the inside of the vacuum chamber 120 is again evacuated after the defrost operation, the defrost circuit 60 is closed by closing the electromagnetic on-off valve 61 and the electromagnetic on-off valve 62 is opened in the same manner as described above. The main refrigerant pipe 2a is opened, and the low-boiling point refrigerant discharged from the primary side of the supercooler 47 evaporates in the cryocoil 52, thereby quickly cooling the inside of the vacuum chamber 120 from room temperature to an ultra-low temperature level.

  Therefore, since the first and second buffer tanks 65 and 66 are connected to the refrigerant circuit 1 as described above, compared with the case where only one large-capacity tank is connected in order to solve the shortage of the tank capacity. This makes it easier to secure the installation space for the tank.

  Furthermore, since the first and second buffer tanks 65 and 66 are connected to each other by the communication circuit 68, the gas refrigerant flows between the tanks 65 and 66, and the first and second buffer tanks 65 and 66 are inside. Thus, the refrigerant components having different specific gravity can be completely circulated, and the cooling performance can be prevented from being lowered due to the fluctuation of the component ratio of the mixed refrigerant in the refrigeration apparatus 10.

In addition, an electromagnetic on-off valve is connected to each of the refrigerant inflow pipe 67 and the refrigerant return pipe 69 to open and close the electromagnetic on-off valve in response to an abnormal increase in the discharge pressure of the compressor 20, and the first and second buffer tanks 65. , 66 or the amount of gas refrigerant returned from the first and second buffer tanks 65, 66 to the refrigerant circuit 1 may be controlled. The same applies to the following reference embodiments and embodiments.

In this reference embodiment, in the first to fourth heat exchangers 25, 31, 37, and 43, the refrigerant that flows toward the cryocoil 52 is returned to the primary side, and the refrigerant that recirculates from the cryocoil 52 to the compressor 20 is 2 Although it is configured to be introduced to the secondary side, conversely to this, the refrigerant that is directed to the cryocoil 52 may be introduced to the secondary side, and the refrigerant that is returned from the cryocoil 52 to the compressor 20 may be introduced to the primary side. Of course. Moreover, it is good also as a structure which combined these separately.

Further, in this preferred embodiment has been described a system for gas-liquid separation four steps, instead of this, it is possible even systems that perform gas-liquid separation three steps or less or five steps or more.

Moreover, although the water cooling system using the water cooling condenser 21 was shown in this reference form, it may replace with this and you may comprise in the system using an air cooling condenser.

<Implementation-shaped state>
Figure 4 is a refrigerant circuit cryogenic refrigeration system 10 according to the embodiment forms state of the present invention. The difference between the Reference Embodiment 1, since only the circuit configuration of the first and second buffer tanks 65 and 66, below, the same reference numerals denote the same parts as in Reference Embodiment 1, only the differences will be described ( Reference form 2 is the same).

  The first and second buffer tanks 65 and 66 are connected to each other by a communication circuit 68 for circulating the gas refrigerant between the tanks 65 and 66. The first buffer tank 65 and the refrigerant pipe between the gas refrigerant discharge part of the first gas-liquid separator 24 and the primary side of the first heat exchanger 25 are connected by a refrigerant inflow pipe 67. In the middle of the communication circuit 68, a refrigerant return pipe 69 for returning the gas refrigerant in the first and second buffer tanks 65, 66 to the refrigerant pipe on the suction side of the compressor 20 is connected. Further, the fusible plug 80 is connected to the first buffer tank 65.

  In the case of this embodiment, when the pressure sensor 81 detects that an abnormal increase in the discharge pressure of the compressor 20 has occurred due to insufficiently condensed gas refrigerant at the start of operation of the ultra-low temperature refrigeration apparatus 10, the electromagnetic on-off valve 82 is opened, and part of the gas refrigerant separated by the first gas-liquid separator 24 flows into the first buffer tank 65 through the refrigerant inflow pipe 67. A part of the gas refrigerant flows into the second buffer tank 66 through the communication circuit 68, and the rest passes through the refrigerant return pipe 69 and is returned to the refrigerant pipe on the suction side of the compressor 20. When the pressure sensor 81 detects that the abnormal increase in the discharge pressure has been resolved, the electromagnetic on-off valve 82 is closed and the gas refrigerant in the first and second buffer tanks 65 and 66 is returned to the refrigerant. The refrigerant is returned to the refrigerant pipe on the suction side of the compressor 20 through the pipe 69.

  In this way, since the middle of the communication circuit 68 is connected to the refrigerant circuit 1 on the suction side of the compressor 20, the gas that flows from the refrigerant circuit 1 into the first buffer tank 65 and returns to the suction side of the compressor 20. The refrigerant flows smoothly through the first and second buffer tanks 65 and 66. As a result, it is possible to completely circulate refrigerant components having different specific gravities by suppressing the stagnation of the gas refrigerant in the first and second buffer tanks 65 and 66, and the component ratio of the mixed refrigerant in the refrigeration apparatus 10. It is possible to prevent the cooling performance from being deteriorated due to fluctuations in the temperature.

In this embodiment, the positional relationship between the first and second buffer tanks 65 and 66 is the same as that in the first embodiment in which the second buffer tank 66 is disposed below the first buffer tank 65. It is not limited, For example, you may arrange | position by exchanging up and down, or may arrange | position and arrange in the horizontal direction. This also applies to the following reference embodiments .

< Reference form 2 >
FIG. 5 is a refrigerant circuit of the ultra-low temperature refrigeration apparatus 10 according to the second embodiment . The difference from the first embodiment or the embodiment is only the circuit configuration of the first and second buffer tanks 65 and 66.

  The first and second buffer tanks 65 and 66 are connected to each other by a communication circuit 68 for circulating the gas refrigerant between the tanks 65 and 66. The first buffer tank 65 and the refrigerant pipe between the gas refrigerant discharge part of the first gas-liquid separator 24 and the primary side of the first heat exchanger 25 are connected by a refrigerant inflow pipe 67. The second buffer tank 66 and the refrigerant pipe on the suction side of the compressor 20 are connected by a refrigerant return pipe 69. A fusible plug 80 is connected to the first buffer tank 65.

In the case of this reference form , when the pressure sensor 81 detects that an abnormal increase in the discharge pressure of the compressor 20 has occurred due to insufficiently condensed gas refrigerant at the start of operation of the ultra-low temperature refrigeration apparatus 10, the electromagnetic on-off valve 82 is opened, and part of the gas refrigerant separated by the first gas-liquid separator 24 flows into the first buffer tank 65 through the refrigerant inflow pipe 67. Then, the gas refrigerant flows into the second buffer tank 66 through the communication circuit 68 and returns to the refrigerant pipe on the suction side of the compressor 20 through the refrigerant return pipe 69. When the pressure sensor 81 detects that the abnormal increase in the discharge pressure has been resolved, the electromagnetic on-off valve 82 is closed and the gas refrigerant in the first and second buffer tanks 65 and 66 is returned to the refrigerant. The refrigerant is returned to the refrigerant pipe on the suction side of the compressor 20 through the pipe 69.

  As described above, the gas refrigerant flows into the first buffer tank 65 from the refrigerant inflow pipe 67, flows through the communication circuit 68 to the second buffer tank 66, and passes through the refrigerant return pipe 69 to compress the compressor 20. Therefore, the gas refrigerant flows smoothly between the tanks 65 and 66. As a result, it is possible to completely circulate refrigerant components having different specific gravities by suppressing the stagnation of the gas refrigerant in the first and second buffer tanks 65 and 66, and the component ratio of the mixed refrigerant in the refrigeration apparatus 10 can be reduced. Decrease in cooling performance due to fluctuations can be prevented.

  As described above, the present invention provides a plurality of buffer tanks for the ultra-low temperature refrigeration apparatus, and connects the tanks with a communication circuit to smoothly circulate the gas refrigerant in the tank, thereby allowing the gas refrigerant in the tank to be circulated. Is highly useful and has high industrial applicability because it is possible to suppress the stagnation of the refrigerant and to maintain a good component ratio of the refrigerant.

It is a schematic explanatory drawing of the vacuum film-forming apparatus which concerns on a reference form or embodiment of this invention. It is another schematic explanatory drawing of a vacuum film-forming apparatus. It is a refrigerant | coolant system | strain diagram which shows the whole structure of the ultra-low temperature freezing apparatus which concerns on the reference form 1. FIG. 4 is a view corresponding to FIG. 3 showing an embodiment of the present invention. Is a 3 corresponds diagram showing a reference embodiment 2.

10 Ultra-low temperature refrigeration equipment 20 Compressor 21 Water-cooled condenser (condenser)
22 Auxiliary condenser (condenser)
24 1st gas-liquid separator 25 1st heat exchanger 30 2nd gas-liquid separator 31 2nd heat exchanger 36 3rd gas-liquid separator 37 3rd heat exchanger 42 4th gas-liquid separator 43 4th heat Exchanger 52 Cryocoil (cooler)
65 First buffer tank 66 Second buffer tank 68 Communication circuit

Claims (1)

A compressor that compresses a mixed refrigerant in which a plurality of types of refrigerants having different boiling points are mixed;
A condenser that cools and liquefies a high-boiling refrigerant among the mixed refrigerant discharged from the compressor;
A multi-stage gas-liquid separator that sequentially separates the mixed refrigerant liquefied by the condenser from a high boiling point refrigerant into a low boiling point refrigerant into a liquid refrigerant and a gas refrigerant;
A plurality of stages in which the primary-side gas refrigerant separated by the gas-liquid separators is cooled by heat exchange with the secondary-side liquid refrigerant separated and decompressed by the gas-liquid separators. A cascade heat exchanger,
A refrigerant circuit is connected to the cooler that evaporates the low-boiling point refrigerant that has flowed out from the cascade heat exchanger at the final stage of the plurality of stages and cools the cooling target to an ultra-low temperature level,
A plurality of buffer tanks for suppressing an abnormal increase in the discharge pressure of the compressor is connected to the refrigerant circuit ,
The plurality of buffer tanks comprises at least one first buffer tank and at least one second buffer tank,
The first and second buffer tanks are connected to each other by a communication circuit that circulates the gas refrigerant between the first and second buffer tanks,
The first buffer tank is connected to a refrigerant circuit on the discharge side of the compressor;
The ultra-low temperature refrigeration apparatus, wherein the communication circuit is connected to a refrigerant circuit on the suction side of the compressor in the middle .

Images