JP2005207637A - Extremely low temperature refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extremely low temperature refrigerating device with a defrost circuit, preventing the supply of lubricating oil to a cooler by reliably removing the lubricating oil without impairing the cooling efficiency thereof. <P>SOLUTION: In the extremely low temperature refrigerating device, a first oil separator 15 is connected to a discharge portion of a compressor 20 and the first oil separator 15 is connected to an inlet side of a cryo-coil 52 via the defrost circuit 60. To the defrost circuit 60, a second oil separator 16 is connected for separating from gas refrigerant the lubricating oil which is not completely removed by the first oil separator 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultra-low temperature refrigeration apparatus for generating an ultra-low temperature level of cold, and more particularly to a countermeasure for suppressing the solidification of compressor lubricating oil by the defrost circuit.

  Conventionally, for example, as disclosed in Patent Document 1, a mixed refrigerant composed of several kinds of refrigerants having different boiling point temperatures is sequentially condensed from a refrigerant having a high boiling point temperature to a refrigerant having a low boiling point temperature. A so-called mixed refrigerant type ultra-low temperature refrigeration apparatus is known in which a refrigerant having an evaporating temperature is finally evaporated to obtain a desired ultra-low temperature. This type of ultra-low temperature refrigeration apparatus is installed, for example, in a vacuum chamber of a vacuum film forming apparatus used for manufacturing a wafer or the like, and is used to capture a gas in the vacuum chamber and raise a vacuum level.

  In such an ultra-low temperature refrigeration apparatus, the mixed refrigerant flows through a refrigerant circuit including a compressor, a condenser, a multi-stage gas-liquid separator and a cascade heat exchanger, and a cooler (evaporator). It has become. And after condensing mainly high boiling point refrigerant in the condenser, it is separated into liquid refrigerant and gas refrigerant in the first stage gas-liquid separator, and on the primary side of the first stage cascade heat exchanger, The gas refrigerant and the liquid refrigerant decompressed after being separated are heat-exchanged and cooled. In the second and subsequent cascade heat exchangers, heat exchange is performed in the same manner, and the liquid refrigerant flowing out from the primary side of the final stage cascade heat exchanger is decompressed to evaporate the low boiling point refrigerant in the cooler. In this way, a very low temperature level of cold is supplied. Further, the refrigerant cooled by this cooler is returned to the secondary side of the final stage cascade heat exchanger and returned to the compressor while passing through the secondary side of the cascade heat exchanger of each stage. Yes.

In the ultra-low temperature refrigeration apparatus, since lubricating oil is mixed in the mixed refrigerant in order to prevent seizure of the sliding contact portion or the like in the compressor, there is no oil between the discharge side of the compressor and the condenser. A separator is provided, and the oil is removed from the mixed refrigerant by the oil separator. As a result, the lubricating oil is supplied to the cooler and solidifies, thereby preventing the cooling efficiency from being lowered.
Japanese Patent Laid-Open No. 2-67855

  By the way, in the vacuum film forming apparatus, the cooling target gas is captured by the cooler. Therefore, when the film formation is not performed, the normal operation of the refrigeration apparatus is stopped and the gas capturing by the cooler is released. There is a need to. Therefore, with respect to the ultra-low temperature refrigeration system, the discharge side of the compressor and the cooler are connected by a defrost circuit, and the cooler is defrosted by supplying the discharge gas of the compressor to the cooler. . However, in that case, if there is lubricating oil that could not be removed by the oil separator at the start of the defrost operation, it will be distributed to the cooler that is still at an ultra-low temperature level through the defrost circuit. This causes a problem that the lubricating oil is solidified.

  Therefore, in order to solve this problem, it is conceivable to arrange a plurality of oil separators in series between the discharge side of the compressor and the condenser. However, in this method, the pressure due to the resistance of the mixed refrigerant flow is considered. Loss occurs, and another problem that cooling efficiency is reduced arises.

  The present invention has been made in view of such points, and the object of the present invention is to improve the cooling efficiency of the ultra-low temperature refrigeration apparatus provided with the defrost circuit as described above by improving the circuit configuration. The purpose is to reliably remove the lubricating oil without damaging it so that the lubricating oil is not supplied to the cooler.

  In the present invention, the oil separator used at the time of defrosting is not provided between the discharge side of the compressor and the condenser but in the defrost circuit to remove the lubricating oil from the mixed refrigerant flowing into the defrost circuit. I tried to do it.

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 point refrigerant among the mixed refrigerant discharged from the compressor;
A first oil separator that removes mixed lubricating oil from the mixed refrigerant that reaches the condenser from the discharge side of 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 each gas-liquid separator is cooled by heat exchange with the secondary-side liquid refrigerant separated and decompressed by each gas-liquid separator. A cascade heat exchanger,
A cooler that evaporates the low-boiling-point refrigerant that has flowed out of the cascade heat exchanger at the final stage of the plurality of stages and depressurized to cool the object to be cooled to an ultra-low temperature level;
A defrost circuit for supplying the mixed refrigerant discharged from the compressor to the cooler at the time of defrosting the cooler;
The defrost circuit is provided with a second oil separator for removing lubricating oil from the mixed refrigerant.

  Therefore, according to the present invention, since the second oil separator for removing the lubricating oil from the mixed refrigerant is disposed in the defrost circuit, the lubricating oil in the mixed refrigerant is transferred from the defrost circuit to the cooler at the time of defrosting. It is possible to suppress the supply and solidification in the cooler.

  Further, an increase in pressure loss as in the case where a plurality of oil separators are arranged in series between the discharge side of the compressor and the condenser can be suppressed. Thereby, the effect which suppresses the above cooling efficiency fall is acquired, circulating a mixed refrigerant | coolant favorably.

  Furthermore, by disposing the second oil separator in the defrost circuit, it is possible to share parts with the refrigeration apparatus not provided with the defrost circuit, which is advantageous in reducing the equipment cost. Also, maintenance work such as replacement can be easily performed.

The invention of claim 2 is the ultra-low temperature refrigeration apparatus according to claim 1,
The defrost circuit has an open / close valve that opens at the time of defrost.
The second oil separator is disposed between the upstream end of the defrost circuit and the on-off valve.

  Therefore, according to the present invention, the second oil separator is disposed between the upstream end of the defrost circuit and the on-off valve. Therefore, by closing the on-off valve, the suction side of the compressor It is possible to suppress the pressure difference between the former and the second oil separator from being higher than the latter. That is, the second oil separator and the compressor are connected to return the separated lubricating oil to the compressor suction side, and between the compressor suction side and the second oil separator. If the pressure difference in the former is higher than that in the latter, the lubricating oil may flow backward from the compressor toward the second oil separator, but it is arranged downstream of the second oil separator. If the open / close valve is closed, the occurrence of the pressure difference as described above can be suppressed to prevent the backflow of the lubricating oil, and the lubricating oil can be smoothly recirculated.

The invention of claim 3 is the ultra-low temperature refrigeration apparatus according to claim 1 or 2,
The second oil separator is arranged at a position where the distance to the upstream end of the defrost circuit is shorter than the distance to the downstream end of the defrost circuit.

  Therefore, according to the present invention, the second oil separator is disposed at a position where the distance to the upstream end of the defrost circuit is shorter than the distance to the downstream end of the defrost circuit. Thus, the lubricating oil having a low viscosity can be separated, and the lubricating oil can be removed more reliably.

  As described above, according to the first aspect of the present invention, since the oil separator that removes the lubricating oil from the mixed refrigerant is disposed in the defrost circuit of the cryogenic refrigeration apparatus, the lubrication in the mixed refrigerant at the time of defrosting is performed. Pressure loss as when oil is supplied from the defrost circuit to the cooler and solidifies in the cooler, and multiple oil separators are arranged in series between the compressor and the condenser Therefore, it is possible to improve the cooling efficiency while ensuring good circulation of the mixed refrigerant.

  According to the second aspect of the present invention, the oil separator is disposed between the upstream end of the defrost circuit and the on-off valve, so that the on-off valve is closed between the suction side of the compressor and the oil separator. In the former, it is possible to suppress the occurrence of a pressure difference higher than that of the latter, and it is possible to prevent the lubricating oil from flowing backward from the suction side of the compressor toward the oil separator. Smooth reflux can be achieved.

  According to the invention of claim 3, by arranging the oil separator on the upstream side of the defrost circuit, it is possible to recover the lubricating oil having a high temperature and low viscosity, and more reliably removing the lubricating oil. It can be performed.

  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.

  FIG. 1 shows an example of a layout of a vacuum film-forming apparatus A according to an embodiment of the present invention. Reference numeral 120 denotes a vacuum chamber in which a wafer (not shown) is formed while the inside is kept in a vacuum state. A loading / unloading port (not shown) that is opened and closed by an opening / closing door 123 is opened at 120, and a wafer to be deposited is loaded into the vacuum chamber 120 or deposited while the opening / closing door 123 is opened. The subsequent wafer 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 vacuum film forming apparatus A is provided with an ultra-low temperature refrigeration apparatus 10 constituting the refrigeration system of the present invention, and a vacuum coil 121 of the vacuum pump 121 is evacuated by a cryocoil (cooler) 52 described later of the ultra-low temperature refrigeration apparatus 10. In this state, by directly cooling the gas (air or gas) and moisture to be cooled in the vacuum chamber 120 to the ultra-low temperature level, the gas is captured and the vacuum level in the vacuum chamber 120 is raised. Yes.

  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 gas and moisture in the communication path 122 by the ultra-low temperature refrigeration apparatus 10 in an evacuated state, that is, indirectly in the vacuum chamber 120. I have to. 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. Reference numeral 1 denotes a closed cycle refrigerant circuit in which the mixed refrigerant is enclosed. The refrigerant circuit 1 is formed by connecting various devices described below through refrigerant piping. A compressor 20 compresses the gas refrigerant, and a first oil separator 15 is connected to a discharge portion of the compressor 20. 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 embodiment, the water-cooled condenser 21 and the auxiliary condenser 22 constitute a condenser, and both the condensers 21 and 22 condense and liquefy the gas refrigerant having the highest boiling point 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 a gas (air or gas) or moisture 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, and then supplied to the cryocoil 52 to evaporate. The evaporation heat causes gas and moisture (cooling target) in the vacuum chamber 120 to be − The vacuum level is increased by cooling to an ultra-low temperature level of 100 ° C. or lower and capturing the gas and moisture.

  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, the circuit configuration of the defrost circuit, which is a feature of the present invention, will be described. As shown in FIG. 3, the defrost circuit 60 is for supplying the high-temperature gas refrigerant (hot gas) discharged from the compressor 20 to the cryocoil 52 as it is, and the first oil separator 15 and the water cooling A refrigerant pipe between the capacitors 21 and a refrigerant pipe between the sixth capillary tube 53 and the cryocoil 52 are connected. 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).

  Between the upstream end of the defrost circuit 60 and the electromagnetic on-off valve 61, a second oil separator 16 for separating the compressor lubricating oil from the gas refrigerant is disposed. 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. Here, the second oil separator 16 is connected to the upstream end of the defrost circuit 60 so as to separate the lubricating oil having a high temperature and a low viscosity so that the lubricating oil can be removed more reliably. It is disposed at a position where the distance is shorter than the distance to the downstream end of the defrost circuit 60 (the upper half of the defrost circuit 60).

  When the vacuum chamber 120 of the vacuum film forming apparatus A shown in FIG. 1 is in a vacuum state to perform film formation on a wafer, the defrost circuit 60 is closed by opening the electromagnetic opening / closing valve 61 and the electromagnetic opening / closing valve 62 is opened. By opening the main refrigerant pipe 2a, the cryocoil 52 evaporates the low boiling point refrigerant and cools and captures the gas and moisture in the vacuum chamber 120, while opening the open / close door 123 and forming the wafer in the vacuum chamber 120. At the time of defrosting in a state where no film is formed, the defrost circuit 60 is opened by opening the electromagnetic on-off valve 61 and the main refrigerant pipe 2 a is closed by closing the electromagnetic on-off valve 62, so that the high temperature discharged from the compressor 20 The gas refrigerant (hot gas) is supplied to the cryocoil 52 through the defrost circuit 60 as it is, and the trapping of gas or the like in the cryocoil 52 is returned. It is way.

  Reference numeral 65 denotes a buffer tank for preventing an abnormal increase in the discharge pressure of the compressor 20 due to insufficiently condensed gas refrigerant at the start of operation of the cryogenic refrigeration apparatus 10. 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.

  In the embodiment configured as described above, when a wafer is formed in the vacuum chamber 120 of the vacuum film forming apparatus A, the ultra-low temperature refrigeration apparatus 10 is operated and the inside of the vacuum chamber 120 (or the communication path 122). The gas is cooled to an ultralow temperature level of −100 ° C. or lower and captured, 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 gas or moisture in the chamber 120. The chilling at a temperature of −100 ° C. or lower traps gas and moisture in the vacuum chamber 120 and raises the vacuum level in the vacuum chamber 120.

  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.

  At that time, since the second oil separator 16 for removing the lubricating oil from the mixed refrigerant is disposed in the defrost circuit 60, the lubricating oil in the mixed refrigerant discharged from the compressor 20 at the time of defrosting is supplied to the defrost circuit 60. Even if it cannot be completely removed by the first oil separator 15, it can be further removed by the second oil separator 16, and the supply of lubricating oil from the defrost circuit 60 to the cryocoil 52 is suppressed. Can do. Thereby, it is possible to prevent the lubricating oil from being cooled and solidified in the cryocoil 52 that is still at the ultra-low temperature level at the start of the defrost operation, and to ensure good circulation of the mixed refrigerant. As a result, the evacuation time in the vacuum chamber 120 and the film formation process time can be shortened and the efficiency can be improved.

  Further, the second oil separator 16 is disposed at a position where the distance to the upstream end of the defrost circuit 60 is shorter than the distance to the downstream end of the defrost circuit 60, so that the temperature is high and the viscosity is high. This is advantageous in separating the lubricating oil in a low state, and the lubricating oil can be more reliably removed.

  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.

  By closing the electromagnetic on-off valve 61, the lubricating oil separated by the second oil separator 16 is collected on the suction side of the compressor 20. Here, since the second oil separator 16 is disposed between the upstream end of the defrost circuit 60 and the electromagnetic opening / closing valve 61, the suction side of the compressor 20 and the second oil separator 16 are arranged. In the former, it is possible to suppress the occurrence of a higher pressure difference than the latter. As a result, it is possible to prevent the lubricating oil from flowing backward from the suction side of the compressor 20 toward the second oil separator 16 and to smoothly recirculate the lubricating oil to the compressor 20.

  In the present embodiment, in the first to fourth heat exchangers 25, 31, 37, and 43, the refrigerant that goes to the cryocoil 52 is returned to the primary side, and the refrigerant that recirculates from the cryocoil 52 to the compressor 20 is the secondary. In contrast to this, the refrigerant flowing toward the cryocoil 52 may be introduced to the secondary side, and the refrigerant returning 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.

  Moreover, although the system which performs gas-liquid separation 4 steps | paragraphs was shown in this embodiment, it replaces with this and this invention is applicable also to the system which performs gas-liquid separation 3 steps | paragraphs or 5 steps or more.

  In the present embodiment, the water cooling system using the water cooling condenser 21 is shown. However, instead of this, a system using an air cooling condenser may be used.

  As described above, the present invention can suppress that the lubricating oil in the mixed refrigerant is supplied to the cooler from the defrost circuit and solidified in the cooler at the time of defrosting for the ultra-low temperature refrigeration apparatus provided with the defrost circuit, Furthermore, since it is possible to suppress an increase in pressure loss due to the resistance of the mixed refrigerant flow, it is possible to obtain a highly practical effect that it is possible to improve the cooling efficiency while ensuring good circulation of the mixed refrigerant. It is extremely useful and has high industrial applicability.

It is a schematic explanatory drawing of the vacuum film-forming apparatus which concerns on embodiment of this invention. It is another schematic explanatory drawing of a vacuum film-forming apparatus. It is a refrigerant | coolant system diagram which shows the whole structure of the ultra-low-temperature freezing apparatus which concerns on embodiment of this invention.

Explanation of symbols

10 Ultra-low temperature refrigeration equipment 15 First oil separator 16 Second oil separator 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)
60 Defrost circuit

Claims (3)

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 point refrigerant among the mixed refrigerant discharged from the compressor;
A first oil separator that removes mixed lubricating oil from the mixed refrigerant that reaches the condenser from the discharge side of 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 each gas-liquid separator is cooled by heat exchange with the secondary-side liquid refrigerant separated and decompressed by each gas-liquid separator. A cascade heat exchanger,
A cooler that evaporates the low-boiling-point refrigerant that has flowed out of the cascade heat exchanger at the final stage of the plurality of stages and depressurized to cool the object to be cooled to an ultra-low temperature level;
A defrost circuit for supplying the mixed refrigerant discharged from the compressor to the cooler at the time of defrosting the cooler;
An ultra-low temperature refrigeration apparatus, wherein a second oil separator for removing lubricating oil from the mixed refrigerant is disposed in the defrost circuit. In the ultra-low temperature refrigeration apparatus according to claim 1,
The defrost circuit has an open / close valve that opens at the time of defrost.
The ultra-low temperature refrigeration apparatus, wherein the second oil separator is disposed between an upstream end of the defrost circuit and the on-off valve. In the ultra-low temperature refrigeration apparatus according to claim 1 or 2,
The ultra-low temperature refrigeration apparatus, wherein the second oil separator is disposed at a position where the distance to the upstream end of the defrost circuit is shorter than the distance to the downstream end of the defrost circuit.

Images