JP2019190678A - Active buffer pulse tube refrigerator - Google Patents

Abstract

To suppress an increase in size of an active buffer pulse tube refrigerator comprising a plurality of cold heads.SOLUTION: A pulse tube refrigerator 10 comprises a plurality of cold heads 14. Each of the cold heads 14 comprises a pulse tube 16, a regenerator 18, a main pressure switching valve 24a for alternately connecting a compressor discharge port 12a and a compressor suction port 12b to a high-temperature end of the regenerator 18, and an auxiliary pressure switching valve 24b connected to a high-temperature end of the pulse tube 16. The pulse tube refrigerator 10 comprises a first buffer volume B1 connected to the high-temperature end of the pulse tube 16 of each of the cold heads 14 via the auxiliary pressure switching valve 24b and shared as a first pressure source by the plurality of cold heads 14, and a second buffer volume B2 connected to the high-temperature end of the pulse tube 16 of each of the cold heads 14 via the auxiliary pressure switching valve 24b and shared as a second pressure source by the plurality of cold heads 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an active buffer type pulse tube refrigerator (hereinafter also referred to as an active buffer pulse tube refrigerator).

  The pulse tube refrigerator includes a vibration flow source, a regenerator, a pulse tube, and a phase control mechanism as main components. There are several ways to generate an oscillating flow. For example, a so-called GM (Gifford-McMahon) system using a combination of a compressor and a periodic flow path switching valve and a Stirling system that generates a vibration flow by a harmonically oscillating piston are known. Further, GM pulse tube refrigerators are classified into several types such as a double inlet type, an active buffer type, and a four-valve type depending on the configuration of the phase control mechanism.

JP-A-11-94382

  When the object to be cooled is large, a single pulse tube refrigerator is equipped with multiple cold heads, and these are operated in parallel to provide a pulse tube refrigerator design that provides the refrigerating capacity required for the object. May be adopted.

  In general, an active buffer pulse tube refrigerator includes a buffer tank provided independently of a compressor and connected to a high temperature end of the pulse tube. Gas inflow and outflow from the buffer tank to the pulse tube are used for phase control. . Since there is no need to distribute the gas flow rate that the compressor can provide to phase control, the advantage of the active buffer pulse tube refrigerator is that it is easier to increase the efficiency of the refrigerator than other systems such as the double inlet type and the 4-valve type. There is.

  On the other hand, active buffer pulse tube refrigerators can typically require a fairly large buffer tank to achieve the desired phase control. When the active buffer pulse tube refrigerator has a plurality of cold heads, a buffer tank is provided for each cold head. Typically, each cold head is equipped with a plurality of buffer tanks, and each is used as a different pressure source (for example, three buffer tanks for each cold head are a high pressure source and an intermediate pressure source). , And as a low pressure source). The volume of individual buffer tanks can often be at least several times the volume of the pulse tube or regenerator.

  Therefore, a considerably large space is required to install an active buffer pulse tube refrigerator provided with a plurality of cold heads. Therefore, although the active buffer pulse tube refrigerator has an advantage that high efficiency is easily realized, the applicable applications can be restricted.

  One exemplary object of an aspect of the present invention is to provide a technique for suppressing an increase in size of an active buffer pulse tube refrigerator having a plurality of cold heads.

  According to an aspect of the present invention, the active buffer pulse tube refrigerator is a plurality of cold heads, each cold head having a pulse tube hot end and a pulse tube cold end, a regenerator hot end, A regenerator having a regenerator low-temperature end communicating with the pulse tube low-temperature end, a main pressure switching valve for alternately connecting a compressor discharge port and a compressor suction port to the regenerator high-temperature end, and the pulse A plurality of cold heads connected to the high temperature end of the pipe, and a first pressure having a first pressure connected to the high temperature end of the pulse pipe of each cold head via the sub pressure switching valve of the cold head. A first buffer volume shared by the plurality of cold heads as a pressure source, and a pulse tube high temperature end of each cold head are connected to each cold head via a sub pressure switching valve of the cold head. It is, and a second buffer volume is shared by the plurality of the cold head as a second pressure source having a second pressure different from the first pressure.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, an increase in size of an active buffer pulse tube refrigerator having a plurality of cold heads is suppressed.

It is a figure showing roughly the whole composition of the active buffer pulse tube refrigerator concerning a certain embodiment. It is the schematic which shows the working gas circuit structure of the active buffer pulse tube refrigerator which concerns on a certain embodiment. It is the schematic which shows the example valve timing applicable to the active buffer pulse tube refrigerator which concerns on an embodiment. It is the schematic which shows the example valve timing applicable to the active buffer pulse tube refrigerator which concerns on an embodiment. It is the schematic which shows the example valve timing applicable to the active buffer pulse tube refrigerator which concerns on an embodiment. It is a figure which shows schematically the active buffer pulse tube refrigerator which concerns on other embodiment. It is a figure which shows schematically the active buffer pulse tube refrigerator which concerns on other embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. Moreover, the structure described below is an illustration and does not limit the scope of the present invention at all. In the drawings referred to in the following description, the size and thickness of each constituent member are for convenience of description, and do not necessarily indicate actual dimensions and ratios.

  FIG. 1 is a diagram schematically showing an overall configuration of an active buffer pulse tube refrigerator (hereinafter also simply referred to as a pulse tube refrigerator) according to an embodiment. FIG. 2 is a schematic diagram showing a working gas circuit configuration of the active buffer pulse tube refrigerator shown in FIG.

  The pulse tube refrigerator 10 includes a plurality of compressors 12 and a plurality of cold heads 14. Each of the plurality of cold heads 14 includes a pulse tube 16, a regenerator 18, a cooling stage 20 that cools an object to be cooled 19, a flange portion 22, and a valve portion 24. The valve unit 24 includes a main pressure switching valve 24a and a sub pressure switching valve 24b.

  As will be described in detail later, the pulse tube refrigerator 10 is configured as a so-called three-buffer type active buffer pulse tube refrigerator, and includes a first buffer volume B1, a second buffer volume B2, and a third buffer volume B3. . The first buffer volume B1 is shared by the plurality of cold heads 14 as a first pressure source having a first pressure. The second buffer volume B2 is shared by the plurality of cold heads 14 as a second pressure source having a second pressure different from the first pressure. The third buffer volume B3 is shared by the plurality of cold heads 14 as a third pressure source having a third pressure different from the first pressure and the second pressure.

  The pulse tube refrigerator 10 has the same number of compressors 12 and cold heads 14, and a compressor 12 is provided for each cold head 14. For simplicity of explanation, FIG. 1 shows a case where the pulse tube refrigerator 10 has two compressors 12 and two cold heads 14. In the following, for the sake of convenience of explanation, when the two compressors 12 are distinguished from each other, they are referred to as a first compressor and a second compressor, and when the two cold heads 14 are distinguished from each other, the first cold head and the second compressor 12 are referred to. This is called a cold head.

  However, the number of compressors 12 may be different from the number of cold heads 14. For example, the number of compressors 12 may be less than the number of cold heads 14. At least one compressor 12 may be shared by two or more cold heads 14. Further, the number of compressors 12 and cold heads 14 is not limited to two, and may be any number. The pulse tube refrigerator 10 may include three or more compressors 12 and three or more cold heads 14.

  The pulse tube refrigerator 10 is a single-stage pulse tube refrigerator. However, the pulse tube refrigerator 10 may be a multistage (for example, two-stage) pulse tube refrigerator.

  The compressor 12 and the main pressure switching valve 24a constitute a vibration flow generation source of the pulse tube refrigerator 10. The oscillating flow source is configured to generate pressure oscillation of the working gas in the pulse tube 16 through the regenerator 18 by the switching operation of the main pressure switching valve 24a from the steady flow of the working gas generated by the compressor 12. . The phase control mechanism of the pulse tube refrigerator 10 is configured by the first buffer volume B1, the second buffer volume B2, the third buffer volume B3, and the auxiliary pressure switching valve 24b. The phase control mechanism is configured to delay the phase of the displacement vibration of the gas element (also referred to as a gas piston) in the pulse tube 16 with respect to the pressure vibration of the working gas by the opening / closing operation of the sub pressure switching valve 24b. Appropriate phase lag can cause PV work at the cold end of the pulse tube 16 to cool the working gas. The cooling stage 20 is cooled by heat exchange with the cooled working gas.

  The compressor 12 includes a compressor discharge port 12a and a compressor suction port 12b, and is configured to compress the recovered low-pressure PL working gas to generate a high-pressure PH working gas. The working gas is supplied from the compressor discharge port 12a to the pulse tube 16 through the regenerator 18, and the working gas is recovered from the pulse tube 16 to the compressor suction port 12b through the regenerator 18. The compressor discharge port 12a and the compressor suction port 12b function as a high pressure source and a low pressure source of the pulse tube refrigerator 10, respectively. The working gas is also called a refrigerant gas, for example, helium gas.

  The pulse tube refrigerator 10 is provided with a high pressure line 13 a and a low pressure line 13 b for each set of the compressor 12 and the cold head 14. The high-pressure line 13 a connects the compressor discharge port 12 a to the valve unit 24 of the cold head 14. The working gas of high pressure PH is supplied from the compressor 12 to the cold head 14 through the high pressure line 13a. The low pressure line 13 b connects the compressor suction port 12 b to the valve unit 24 of the cold head 14. The working gas of low pressure PL is recovered from the cold head 14 to the compressor 12 through the low pressure line 13b. The high-pressure line 13a and the low-pressure line 13b may be rigid or flexible pipes that connect the compressor 12 and the cold head 14, respectively.

  The pulse tube 16 has a pulse tube hot end 16a and a pulse tube cold end 16b, and extends from the pulse tube hot end 16a to the pulse tube cold end 16b. The pulse tube hot end 16a and the pulse tube cold end 16b may also be referred to as a first end and a second end of the pulse tube 16, respectively. Similarly, the regenerator 18 has a regenerator high-temperature end 18a and a regenerator low-temperature end 18b, and extends from the regenerator high-temperature end 18a to the regenerator low-temperature end 18b. The regenerator high temperature end 18a and the regenerator low temperature end 18b may also be referred to as a first end and a second end of the regenerator 18, respectively.

  The pulse tube cold end 16b and the regenerator cold end 18b are structurally connected and thermally coupled by the cooling stage 20. A cooling stage communication path 26 is formed in the cooling stage 20. Through the cooling stage communication path 26, the pulse tube cold end 16b is in fluid communication with the regenerator cold end 18b. Therefore, the working gas supplied from the compressor 12 can flow from the regenerator cold end 18b to the pulse tube cold end 16b through the cooling stage communication path 26. The return gas from the pulse tube 16 can flow from the pulse tube low temperature end 16 b to the regenerator low temperature end 18 b through the cooling stage communication path 26.

  In the exemplary configuration, the pulse tube 16 is a cylindrical tube having a hollow inside, and the regenerator 18 is a cylindrical tube filled with a regenerator material, both of which are adjacent to each other in the center of each. The axes are arranged parallel. The pulse tube 16 and the regenerator 18 extend in the same direction from the cooling stage 20, and the pulse tube high temperature end 16 a and the regenerator high temperature end 18 a are arranged on the same side with respect to the cooling stage 20. In this way, the pulse tube 16, the regenerator 18, and the cooling stage 20 are arranged in a U shape.

  The object to be cooled 19 is directly installed on the cooling stage 20 or is thermally coupled to the cooling stage 20 via a rigid or flexible heat transfer member. The pulse tube refrigerator 10 can cool the object 19 by conduction cooling from the cooling stage 20. In the illustrated example, a cooling stage 20 is provided for each cold head 14, and the pulse tube refrigerator 10 has a plurality of cooling stages 20. In an embodiment, the plurality of cooling stages 20 may be configured as one cooling stage connected to each other. In the illustrated example, the cooling stage 20 of each of the plurality of cold heads 14 is thermally coupled to one common object 19 to be cooled, but is not limited thereto. A plurality of cooling stages 20 may be thermally coupled to a plurality of objects to be cooled.

  As an example, the object 19 to be cooled by the pulse tube refrigerator 10 is a solid material such as a superconducting electromagnet or other superconducting device, or an infrared imaging device or other sensor, but is not limited thereto. Needless to say, the pulse tube refrigerator 10 can also cool the gas or liquid that contacts the cooling stage 20.

  On the other hand, the pulse tube high temperature end 16 a and the regenerator high temperature end 18 a are connected by a flange portion 22. The flange portion 22 is attached to a support portion 28 such as a support base or a support wall on which the pulse tube refrigerator 10 is installed. The support portion 28 may be a wall material of the heat insulating container or the vacuum container or the other part that houses the cooling stage 20 and the object 19 to be cooled (along with the regenerator 18 and the pulse tube 16). In the illustrated example, a flange portion 22 is provided for each cold head 14, and the pulse tube refrigerator 10 has a plurality of flange portions 22. In an embodiment, the plurality of flange portions 22 may be configured as one flange portion connected to each other.

  The regenerator 18 and the pulse tube 16 extend from one main surface of the flange portion 22 to the cooling stage 20, and a valve portion 24 is provided on the other main surface of the flange portion 22. Therefore, when the support part 28 comprises a part of a heat insulation container or a vacuum vessel, when the flange part 22 is attached to the support part 28, the regenerator 18, the pulse tube 16, and the cooling stage 20 are in the said container. The valve portion 24 is disposed outside the container.

  Thus, the compressor 12 and the valve part 24 are arrange | positioned at ambient environment (for example, room temperature atmospheric pressure environment). The first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 are also arranged in the surrounding environment. The regenerator 18, the pulse tube 16, and the cooling stage 20 are disposed in an environment (for example, a cryogenic vacuum environment) isolated from the surrounding environment.

  The valve portion 24 does not need to be directly attached to the flange portion 22. The valve unit 24 may be arranged separately from the cold head 14 of the pulse tube refrigerator 10 and may be connected to the cold head 14 by a rigid or flexible pipe. Thus, the vibration flow generation source and the phase control mechanism of the pulse tube refrigerator 10 may be arranged separately from the cold head 14.

  Further, the pulse tube refrigerator 10 has a pulse tube communication path 30, a regenerator communication path 32, a first buffer line 34, a second buffer line 36, and a third buffer line 38. The pulse tube communication path 30 extends from the high temperature end 16a of the pulse tube and branches to a first buffer line 34, a second buffer line 36, and a third buffer line 38 via a sub pressure switching valve 24b. The regenerator communication passage 32 extends from the regenerator high temperature end 18a and branches into a high pressure line 13a and a low pressure line 13b via a main pressure switching valve 24a.

  The first buffer line 34 merges from the sub pressure switching valve 24b of each of the plurality of cold heads 14 to the first buffer volume B1. The second buffer line 36 merges from the sub pressure switching valve 24b of each of the plurality of cold heads 14 to the second buffer volume B2. The third buffer line 38 merges from the sub pressure switching valve 24b of each of the plurality of cold heads 14 to the third buffer volume B3. The first buffer line 34, the second buffer line 36, and the third buffer line 38 are respectively rigid to connect the first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 with the plurality of cold heads 14. Flexible piping may be used.

  In this way, the first buffer volume B1 is connected to the pulse tube high temperature end 16a of each cold head 14 via the auxiliary pressure switching valve 24b of the cold head 14. The first buffer volume B1 is shared by the plurality of cold heads 14 as a high pressure source having a high pressure PH.

  Similarly, the second buffer volume B2 is connected to the pulse tube high temperature end 16a of each cold head 14 via the sub pressure switching valve 24b of the cold head 14. The second buffer volume B2 is shared by the plurality of cold heads 14 as a low pressure source having a low pressure PL.

  Further, the third buffer volume B3 is connected to the pulse tube high temperature end 16a of each cold head 14 via the auxiliary pressure switching valve 24b of the cold head 14. The third buffer volume B3 is shared by the plurality of cold heads 14 as an intermediate pressure source having an intermediate pressure PM. The intermediate pressure may be an average pressure of high pressure and low pressure (that is, PM = (PH−PL) / 2).

  The first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 are each configured as a separate buffer tank.

  Since the pulse tube refrigerator 10 is an active buffer type, no bypass path is provided for fluidly communicating the pulse tube high temperature end 16a and the regenerator high temperature end 18a. Therefore, the working gas cannot flow directly between the pulse tube high temperature end 16a and the regenerator high temperature end 18a. As described above, all the working gas flowing between the pulse tube 16 and the regenerator 18 passes through the cooling stage communication path 26. However, if required, the pulse tube refrigerator 10 may include a bypass passage that fluidly connects the pulse tube high temperature end 16a and the regenerator high temperature end 18a.

  An exemplary configuration of the valve unit 24 will be described. The main pressure switching valve 24a is configured to alternately connect the regenerator high temperature end 18a to the compressor discharge port 12a and the compressor suction port 12b. The main pressure switching valve 24a includes a main intake opening / closing valve V1 that connects the compressor discharge port 12a to the regenerator high temperature end 18a, and a main exhaust opening / closing valve V2 that connects the compressor intake port 12b to the regenerator high temperature end 18a. .

  The main pressure switching valve 24a is configured such that the main intake opening / closing valve V1 and the main exhaust opening / closing valve V2 are exclusively opened. That is, it is prohibited to open the main intake opening / closing valve V1 and the main exhaust opening / closing valve V2 simultaneously. When the main intake opening / closing valve V1 is opened, the main exhaust opening / closing valve V2 is closed, and when the main exhaust opening / closing valve V2 is opened, the main intake opening / closing valve V1 is closed. The main intake opening / closing valve V1 and the main exhaust opening / closing valve V2 may be temporarily closed together.

  When the main intake opening / closing valve V1 is open, the working gas is supplied from the compressor discharge port 12a to the regenerator 18 through the high pressure line 13a, the main intake opening / closing valve V1, the regenerator communication passage 32, and the regenerator high temperature end 18a. . On the other hand, when the main exhaust opening / closing valve V2 is open, the working gas is collected from the regenerator 18 to the compressor inlet 12b through the regenerator high temperature end 18a, the regenerator communication path 32, the main exhaust opening / closing valve V2, and the low pressure line 13b. Is done.

  The sub pressure switching valve 24b connects the first buffer volume B1 to the pulse tube high temperature end 16a when the main pressure switching valve 24a connects the regenerator high temperature end 18a to the compressor outlet 12a, and the main pressure switching valve 24a stores the cold. The second buffer volume B2 is connected to the pulse tube high temperature end 16a when the compressor high temperature end 18a is connected to the compressor suction port 12b. Further, the auxiliary pressure switching valve 24b is used when the main pressure switching valve 24a does not connect the regenerator high temperature end 18a to either the compressor discharge port 12a or the compressor suction port 12b (that is, to the compressor discharge port 12a). And the connection to the compressor inlet 12b), the third buffer volume B3 is configured to connect to the pulse tube hot end 16a.

  The auxiliary pressure switching valve 24b includes a first buffer opening / closing valve V3 that connects the first buffer volume B1 to the pulse tube high temperature end 16a, and a second buffer opening / closing valve V4 that connects the second buffer volume B2 to the pulse tube high temperature end 16a. And a third buffer opening / closing valve V5 for connecting the third buffer volume B3 to the high-temperature end 16a of the pulse tube. The remaining two of the first buffer opening / closing valve V3, the second buffer opening / closing valve V4, and the third buffer opening / closing valve V5 are closed when one of them is opened. These three buffer open / close valves may be temporarily closed together.

  When the first buffer opening / closing valve V3 is open, the working gas flows from the first buffer volume B1 to the pulse tube 16 through the first buffer line 34, the first buffer opening / closing valve V3, the pulse tube communication path 30, and the pulse tube high temperature end 16a. Supplied. When the second buffer opening / closing valve V4 is open, the working gas flows from the pulse tube 16 to the second buffer volume B2 through the pulse tube high temperature end 16a, the pulse tube communication passage 30, the second buffer opening / closing valve V4, and the second buffer line 36. Collected.

  If the pressure in the third buffer volume B3 is higher than the pressure in the pulse tube 16 when the third buffer opening / closing valve V5 is open, the third buffer line 38, the third buffer opening / closing valve V5, and the pulse from the third buffer volume B3. The working gas is supplied to the pulse tube 16 through the tube communication path 30 and the pulse tube high temperature end 16a. On the other hand, if the pressure in the third buffer volume B3 is lower than the pressure in the pulse tube 16, the pulse tube 16 passes through the pulse tube high temperature end 16a, the pulse tube communication path 30, the third buffer opening / closing valve V5, and the third buffer line 38. The working gas is recovered in the three buffer volume B3.

  There can be various specific configurations of the valve unit 24. The group of valves (V1 to V5) may be configured to operate at mechanically determined valve timing. For example, the valve unit 24 may take the form of a rotary valve. In this case, a group of valves (V1 to V5) are incorporated in the valve unit 24 and are driven in synchronization. The valve portion 24 is configured such that the valves (V1 to V5) are appropriately switched by rotational sliding of the valve disk (or valve rotor) with respect to the valve main body (or valve stator). A group of valves (V1 to V5) are switched in the same cycle during operation of the pulse tube refrigerator 10, whereby the five open / close valves (V1 to V5) periodically change the open / close state. The five open / close valves (V1 to V5) are opened / closed at different phases.

  In some embodiments, the group of valves (V1-V5) may take the form of a plurality of individually controllable valves. Each valve (V1 to V5) may be an electromagnetic on-off valve. The group of valves (V1 to V5) may be configured to automatically open and close at a predetermined valve timing. Alternatively, in one embodiment, the group of valves (V1 to V5) may be a combination of a rotary valve and a valve that can be individually controlled.

  In general, one cycle of the refrigeration cycle of the pulse tube refrigerator 10 is divided into an intake process and an exhaust process. The intake process and the exhaust process are repeated alternately.

  In the intake process, intake (main intake) from the compressor 12 to the pulse tube 16 through the regenerator 18 is performed. A preliminary intake from the third buffer volume B3 to the pulse tube 16 is performed prior to the main intake, and simultaneously with the main intake (or some time before the main intake), the first buffer volume B1 to the pulse tube 16 are supplied. Inhalation to is also performed. At the end of the main intake, the first buffer volume B1 is connected to the compressor discharge port 12a through the regenerator 18 and the pulse tube 16, so that the pressure of the first buffer volume B1 is recovered to the high pressure PH by the compressor 12.

  In the exhaust process, exhaust (main exhaust) from the pulse tube 16 to the compressor 12 through the regenerator 18 is performed. Prior to the main exhaust, preliminary exhaust from the pulse tube 16 to the third buffer volume B3 is performed, and simultaneously with the main exhaust (or some time before the main exhaust), the pulse tube 16 and the second buffer volume B2 The exhaust to is also performed. At the end of the main exhaust, the second buffer volume B2 is connected to the compressor inlet 12b through the regenerator 18 and the pulse tube 16, so that the pressure of the second buffer volume B2 is recovered to the low pressure PL by the compressor 12.

  In theory, in order to improve the performance of the pulse tube refrigerator 10, it is theoretically preferable that the intake air from the first buffer volume B1 to the pulse tube 16 is started somewhat before the main intake air. In this case, the first buffer opening / closing valve V3 is opened earlier than the main intake opening / closing valve V1. Similarly, the exhaust from the pulse tube 16 to the second buffer volume B2 preferably starts somewhat before the main exhaust. In this case, the second buffer opening / closing valve V4 is opened earlier than the main exhaust opening / closing valve V2.

  However, for the large-sized pulse tube refrigerator 10 having a large refrigeration capacity, in order to secure the flow rate of the working gas flowing through the main pressure switching valve 24a, the intake air from the first buffer volume B1 to the pulse tube 16 as described above. Is preferably started simultaneously with the main inspiration. Similarly, the exhaust from the pulse tube 16 to the second buffer volume B2 is preferably started simultaneously with the main exhaust. If it does in this way, the fall of the gas flow rate of the main pressure switching valve 24a by opening a buffer opening-and-closing valve (V3, V4) in advance will be controlled, and the performance of pulse tube refrigerator 10 can be improved.

  With such a configuration, the pulse tube refrigerator 10 generates high-pressure PH and low-pressure PL working gas pressure oscillations in the pulse tube 16. Displacement vibration of the working gas, that is, reciprocation of the gas piston occurs in the pulse tube 16 with an appropriate phase delay in synchronization with the pressure vibration. The movement of the working gas that periodically reciprocates up and down in the pulse tube 16 while maintaining a certain pressure is often referred to as a “gas piston” and is often used to describe the operation of the pulse tube refrigerator 10. When the gas piston is at or near the pulse tube high temperature end 16a, the working gas expands at the pulse tube low temperature end 16b to generate cold. By repeating such a refrigeration cycle, the pulse tube refrigerator 10 can cool the cooling stage 20. Therefore, the pulse tube refrigerator 10 can cool the object 19 to be cooled.

  3-5 are schematic diagrams illustrating exemplary valve timings applicable to the active buffer pulse tube refrigerator shown in FIGS. 1 and 2, respectively. The upper part of each figure shows valve timings of the valves (V11 to V51) of the first cold head over one cycle (360 °) of the refrigeration cycle of the pulse tube refrigerator 10. Similarly, in the lower part of each figure, the valve timing of each valve (V12 to V52) of the second cold head is shown over one cycle of the refrigeration cycle of the pulse tube refrigerator 10. Thus, in the following, for convenience of explanation, the subscript “1” is attached to the valves (V11 to V51) of the first cold head, and the subscript “2” is attached to the valves (V12 to V52) of the second cold head. To distinguish. In the figure, a solid line indicates a period during which the valve is open, and a broken line indicates a period during which the valve is closed.

  As shown in FIGS. 3 to 5, the main pressure switching valve 24a of the first cold head operates so that the main intake opening / closing valve V11 and the main exhaust opening / closing valve V21 open alternately. The auxiliary pressure switching valve 24b of the first cold head operates to open in order of the first buffer opening / closing valve V31, the third buffer opening / closing valve V51, the second buffer opening / closing valve V41, and the third buffer opening / closing valve V51. The main intake opening / closing valve V11 is opened simultaneously with the first buffer opening / closing valve V31, and the main exhaust opening / closing valve V21 is opened simultaneously with the second buffer opening / closing valve V41.

  Similarly, the main pressure switching valve 24a of the second cold head operates so that the main intake opening / closing valve V12 and the main exhaust opening / closing valve V22 open alternately. The auxiliary pressure switching valve 24b of the first cold head operates to open in order of the first buffer opening / closing valve V32, the third buffer opening / closing valve V52, the second buffer opening / closing valve V42, and the third buffer opening / closing valve V52. The main intake opening / closing valve V12 is opened simultaneously with the first buffer opening / closing valve V32, and the main exhaust opening / closing valve V22 is opened simultaneously with the second buffer opening / closing valve V42.

  Thus, the valve timing of the main pressure switching valve 24a of each cold head 14 is determined so that the compressor discharge port 12a and the compressor suction port 12b are alternately connected to the regenerator high temperature end 18a. The valve timing of the sub pressure switching valve 24b of each cold head 14 is determined so as to connect different buffer volumes (B1 to B3) to the pulse tube high temperature end 16a of the cold head 14 in order.

  In the first example of the valve timing shown in FIG. 3, a plurality of cold heads 14 are operated in the same phase. That is, the first cold head and the second cold head have no phase difference in valve timing.

  Therefore, the first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 are used by the plurality of cold heads 14 at the same timing. Specifically, the first buffer opening / closing valve V31 of the first cold head and the first buffer opening / closing valve V32 of the second cold head are simultaneously opened, and the high pressure PH is supplied from the first buffer volume B1 to the plurality of cold heads 14 at the same timing. The working gas is supplied. The second buffer opening / closing valve V41 of the first cold head and the second buffer opening / closing valve V42 of the second cold head are opened simultaneously, and the working gas of low pressure PL is recovered from the plurality of cold heads 14 to the second buffer volume B2 at the same timing. Is done. The third buffer opening / closing valve V51 of the first cold head and the third buffer opening / closing valve V52 of the second cold head are opened simultaneously, and the working gas is supplied and discharged between the plurality of cold heads 14 and the third buffer volume B3. .

  In the second example of the valve timing shown in FIG. 4, the plurality of cold heads 14 are operated in opposite phases. The first and second cold heads have a half cycle (180 °) phase difference in valve timing. During the intake process (exhaust process) of the first cold head, the exhaust process (intake process) of the second cold head is performed.

  Therefore, the first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 are used by the plurality of cold heads 14 at completely different timings. For example, when the first buffer opening / closing valve V31 of the first cold head is opened and the first cold head communicates with the first buffer volume B1, the first buffer opening / closing valve V32 of the second cold head is closed and the second cold opening / closing valve V31 is closed. The head is separated from the first buffer volume B1. The same applies to the second buffer volume B2 and the third buffer volume B3.

  In the third example of the valve timing shown in FIG. 5, the plurality of cold heads 14 are operated out of phase with each other. The valve timings of the main pressure switching valves 24a of the plurality of cold heads 14 have a phase difference ΔT, and similarly, the valve timings of the sub pressure switching valves 24b also have a phase difference ΔT.

  As shown in FIG. 5, the valve timing of the second cold head is delayed by a phase difference ΔT from the valve timing of the first cold head. The opening timing of the first buffer opening / closing valve V32 of the second cold head is delayed by a phase difference ΔT from the opening timing of the first buffer opening / closing valve V31 of the first cold head. The same applies to the other valves (V1, V2, V4, V5). The phase difference ΔT may be smaller than 180 °, for example. In this case, the intake process and the exhaust process of the second cold head are started in the middle of the intake process and the exhaust process of the first cold head, respectively.

  The phase difference ΔT may be an arbitrary magnitude, and may be within 90 °, for example. Alternatively, the phase difference ΔT may be 180 ° or more. The second example shown in FIG. 4 corresponds to the case where the phase difference ΔT is 180 °.

  By the way, in the conventional typical three-buffer type active buffer pulse tube refrigerator, three buffer tanks are individually installed for each of the plurality of cold heads. Two cold heads require a total of 6 buffer tanks.

  According to the pulse tube refrigerator 10 according to the embodiment, the first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 shared by the plurality of cold heads 14 are provided. Compared to the existing active buffer pulse tube refrigerator, it is only necessary to have a smaller number of buffer tanks, so that the space required for installing the pulse tube refrigerator 10 can be reduced. The increase in size of the active buffer pulse tube refrigerator is suppressed, the installation of the refrigerator is facilitated, and the active buffer pulse tube refrigerator can be used in more application fields.

  Further, according to the inventor's study, even when the total volume of these three buffer volumes (B1 to B3) is smaller than the total buffer volume in the conventional type having six buffer tanks, the same refrigeration capacity is obtained. It is possible to provide. As an example, assuming that the volume of one buffer tank is 10 liters, the volume of six buffer tanks in the conventional type is 60 liters. For example, in the first example of the valve timing shown in FIG. 3, even if the total volume of the three buffer volumes (B1 to B3) is less than 60 liters, the same refrigeration capacity can be provided.

  In the second example of valve timing shown in FIG. 4, the first cold head and the second cold head are operated in opposite phases, and these two cold heads 14 simultaneously use one buffer volume (B1 to B3). There is nothing to do. The individual buffer volumes (B1 to B3) need only have the capacity required for the operation of one cold head 14. Therefore, the total volume of the three buffer volumes (B1 to B3) is significantly reduced as compared with the first example. In the above example, in contrast to the conventional 60 liters, in the embodiment, about 30 liters is required, which is about half. The increase in size of the active buffer pulse tube refrigerator is suppressed.

  In the second example, the other cold head 14 is separated from the buffer volume at the timing when one cold head 14 uses the buffer volume. It can be regarded as a tube refrigerator 10. It is expected that there will be little or no adverse performance impacts such as reduced refrigeration capacity due to buffer volume sharing.

  In the third example of the valve timing shown in FIG. 5, the valve timing of the sub pressure switching valve 24 b of each cold head 14 is set such that different buffer volumes (B 1 to B 3) are sequentially directed to the pulse tube high temperature end 16 a of the cold head 14. It is prescribed to connect to. The valve timings of the sub pressure switching valves 24b of the plurality of cold heads 14 have a phase difference ΔT.

  Also in the third example, the total volume of the three buffer volumes (B1 to B3) is not as large as the second example, but is considerably reduced compared to the first example. The increase in size of the active buffer pulse tube refrigerator is suppressed. Further, the influence on the refrigerating capacity due to the sharing of the buffer volume is also reduced as compared with the first example.

  In addition, since the phase difference ΔT can be set to an arbitrary value in the third example, there is an advantage that it can be easily expanded to the pulse tube refrigerator 10 having three or more cold heads 14. For example, when there are N cold heads (N is an integer of 2 or more), the valve timing of the cold head 14 can be evenly shifted by 360 ° / N. However, it is possible to operate even if it is unevenly shifted.

  FIG. 6 is a diagram schematically showing an active buffer pulse tube refrigerator according to another embodiment. The embodiment shown in FIG. 6 is common to the above-described embodiment except for the phase control mechanism of the pulse tube refrigerator 10. Below, it demonstrates centering around a different structure of both, and demonstrates a common structure easily or abbreviate | omits description.

  As shown in FIG. 6, the third buffer volume B <b> 3 may be provided for each cold head 14. The first buffer volume B1 and the second buffer volume B2 are shared by the plurality of cold heads 14.

  Thus, it is not necessary for all the buffer volumes installed in the pulse tube refrigerator 10 to be shared by the plurality of cold heads 14. Only one or two of the first buffer volume B1, the second buffer volume B2, and the third buffer volume B3 may be shared by the plurality of cold heads 14. In this case as well, the advantage of suppressing the increase in size of the active buffer pulse tube refrigerator can be obtained as in the above-described embodiment.

  FIG. 7 is a diagram schematically showing an active buffer pulse tube refrigerator according to another embodiment. The embodiment shown in FIG. 7 is common to the above-described embodiment except for the phase control mechanism of the pulse tube refrigerator 10. Below, it demonstrates centering around a different structure of both, and demonstrates a common structure easily or abbreviate | omits description.

  The pulse tube refrigerator 10 is configured as a so-called two-buffer type active buffer pulse tube refrigerator. Therefore, the pulse tube refrigerator 10 has the first buffer volume B1 and the second buffer volume B2, but does not have the third buffer volume B3. In this case as well, the advantage of suppressing the increase in size of the active buffer pulse tube refrigerator can be obtained as in the above-described embodiment.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way.

  In an embodiment, the pulse tube refrigerator 10 may be configured as a so-called four-buffer type active buffer pulse tube refrigerator. The pulse tube refrigerator 10 may further include a fourth buffer volume shared by the plurality of cold heads 14 as a fourth pressure source having a fourth pressure. The fourth buffer volume may be connected to the pulse tube high temperature end 16 a of each cold head 14 via the auxiliary pressure switching valve 24 b of the cold head 14. The fourth pressure of the fourth buffer volume may be a pressure different from the pressures of the first buffer volume B1, the second buffer volume B2, and the third buffer volume B3.

  10 pulse tube refrigerator, 12 compressor, 12a compressor discharge port, 12b compressor suction port, 14 cold head, 16 pulse tube, 16a pulse tube high temperature end, 16b pulse tube low temperature end, 18 regenerator, 18a regenerator high temperature End, 18b Cold storage low temperature end, 24a Main pressure switching valve, 24b Sub pressure switching valve, B1 first buffer volume, B2 second buffer volume, B3 third buffer volume.

Claims (3)

Multiple cold heads, each cold head
A pulse tube having a pulse tube hot end and a pulse tube cold end;
A regenerator having a regenerator high temperature end and a regenerator low temperature end communicating with the pulse tube low temperature end;
A main pressure switching valve for alternately connecting a compressor discharge port and a compressor suction port to the regenerator high temperature end;
A plurality of cold heads including a sub-pressure switching valve connected to the high-temperature end of the pulse tube;
A first buffer volume that is connected to the high temperature end of each cold head pulse tube via a secondary pressure switching valve of the cold head and is shared by the plurality of cold heads as a first pressure source having a first pressure;
A second pressure source connected to the high temperature end of each cold head through a secondary pressure switching valve of the cold head and shared by the plurality of cold heads as a second pressure source having a second pressure different from the first pressure. And an active buffer pulse tube refrigerator.   Connected to the high temperature end of the pulse tube of each cold head via a sub pressure switching valve of the cold head, and to the plurality of cold heads as a third pressure source having a third pressure different from the first pressure and the second pressure. The active buffer pulse tube refrigerator according to claim 1, further comprising a shared third buffer volume.   The valve timings of the sub pressure switching valves of each cold head are determined so that different buffer volumes are connected in order to the high-temperature end of the pulse tube of the cold head, and the valve timings of the sub pressure switching valves of the plurality of cold heads are determined. The active buffer pulse tube refrigerator according to claim 1 or 2, wherein the active buffer pulse tube refrigerator has a phase difference from each other.

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