JP6664843B2 - GM refrigerator - Google Patents

Description

  The present invention relates to a GM (Gifford-McMahon) refrigerator.

  A GM refrigerator, which is a typical example of a cryogenic refrigerator, generates a cryogenic temperature using a GM cycle. For this purpose, the GM refrigerator properly adjusts the periodic pressure fluctuation in the expansion space including the intake of the working gas into the expansion space, the adiabatic expansion and the exhaust, and the periodic volume change of the expansion space due to the reciprocating motion of the displacer. It is configured to synchronize.

JP-A-5-313426

  A general basic configuration of a GM refrigerator has one compressor and one expander (that is, a combination of one displacer and its driving unit). As one configuration example derived therefrom, a refrigerator having two displacers arranged in parallel with one displacer drive unit and alternately performing an intake operation to an expansion space corresponding to each displacer has been proposed. Alternate intake operation of the two expanders can result in reduced pressure fluctuations in the compressor and thereby improved compressor efficiency. This can contribute to improving the efficiency of the refrigerator.

  However, driving two displacers with one drive requires a relatively large drive that generates a corresponding drive torque. In addition, the parallel arrangement of two expanders tends to increase the floor area of the refrigerator.

  The present invention has been made in view of such a situation, and one of exemplary objects of an embodiment of the present invention relates to a GM refrigerator having a plurality of displacers, and reduces the driving torque of the displacers while reducing the compressor torque. The goal is to improve efficiency.

  According to one aspect of the present invention, a GM refrigerator includes a first cold head including a first displacer that can reciprocate in an axial direction, and a first cylinder that forms a first gas chamber between the first displacer and the first displacer. A second displacer disposed coaxially with the first displacer and capable of axially reciprocating integrally with the first displacer; and a second cylinder forming a second gas chamber between the second displacer and the second displacer. A second cold head disposed opposite to the first cold head, and a common cold head coupled to the first displacer and the second displacer to drive axial reciprocation of the first displacer and the second displacer. A drive mechanism, and the first gas chamber generating a pressure difference between the first gas chamber and the second gas chamber to assist the common drive mechanism. Rudoheddo and and a working gas circuit connected to the second cold head.

  According to one aspect of the present invention, a GM refrigerator includes a first cold head including a first displacer that can reciprocate in an axial direction, and a first cylinder that forms a first gas chamber between the first displacer and the first displacer. A second displacer disposed coaxially with the first displacer and capable of axially reciprocating integrally with the first displacer; and a second cylinder forming a second gas chamber between the second displacer and the second displacer. And a second cold head disposed opposite to the first cold head.

  It should be noted that any combination of the above-described components, and any replacement of the components and expressions of the present invention between methods, apparatuses, systems, and the like are also effective as embodiments of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, regarding the GM refrigerator which has a some displacer, the efficiency of a compressor can be improved, reducing the drive torque of those displacers.

1 is a cross-sectional view schematically illustrating a GM refrigerator according to an embodiment of the present invention. FIG. 2 is an external view schematically showing the GM refrigerator shown in FIG. 1. It is a figure which shows an example of operation | movement of the GM refrigerator shown in FIG. 1 is a cross-sectional view schematically illustrating a GM refrigerator according to an embodiment of the present invention. 1 is a cross-sectional view schematically illustrating a GM refrigerator according to an embodiment of the present invention. FIG. 6A shows the upward movement assisting force acting on the scotch yoke when the displacer coupling shown in FIG. 5 moves upward, and FIG. 6B shows the upward movement assisting force acting on the scotch yoke when the displacer coupling moves downward. This indicates the downward movement assist force. 1 is a cross-sectional view schematically illustrating a GM refrigerator according to an embodiment of the present invention.

  Hereinafter, embodiments for implementing the present invention will be described in detail with reference to the drawings. In the description, the same elements will be denoted by the same reference symbols, without redundant description. The configuration described below is an exemplification, and does not limit the scope of the present invention in any way.

  FIG. 1 is a sectional view schematically showing a GM refrigerator 10 according to an embodiment of the present invention. FIG. 2 is an external view schematically showing the GM refrigerator 10 shown in FIG. FIG. 3 is a diagram showing an example of the operation of the GM refrigerator 10 shown in FIG.

  The GM refrigerator 10 includes a compressor 12 for compressing a working gas (for example, helium gas), and a plurality of cold heads for cooling the working gas by adiabatic expansion. Cold heads are also called expanders. As described later in detail, the compressor 12 supplies a high-pressure working gas to the cold head. The cold head is provided with a regenerator for pre-cooling the working gas. The pre-cooled working gas is further cooled by expansion in the cold head. The working gas is recovered by the compressor 12 through the regenerator. The working gas cools the regenerator as it passes through the regenerator. The compressor 12 compresses the recovered working gas and supplies it to the expander again.

  The GM refrigerator 10 includes a first cold head 14a and a second cold head 14b that are arranged to face each other. Further, the GM refrigerator 10 includes a common drive mechanism 40 for the first cold head 14a and the second cold head 14b. The first cold head 14a is arranged on one side with respect to the common drive mechanism 40, and the second cold head 14b is arranged on the other side with respect to the common drive mechanism 40. Further, the GM refrigerator 10 includes a working gas circuit 70 that connects the compressor 12 to the first cold head 14a and the second cold head 14b.

  The first cold head 14a is a single-stage type. The first cold head 14a includes a first displacer 16a that can reciprocate in the axial direction, and a first cylinder 18a that houses the first displacer 16a. The axial reciprocation of the first displacer 16a is guided by the first cylinder 18a. Usually, the first displacer 16a and the first cylinder 18a are cylindrical members extending in the axial direction, respectively, and the inner diameter of the first cylinder 18a is slightly larger than the outer diameter of the first displacer 16a. Here, the axial direction is the vertical direction in FIG. 1 (arrow C).

  The first displacer 16a forms a first expansion chamber 20a at one axial end with the first cylinder 18a, and forms a first room temperature chamber 22a with the first cylinder 18a at the other axial end. . The first room temperature chamber 22a is located near the common drive mechanism 40, and the first expansion chamber 20a is located far from the common drive mechanism 40. In that sense, the first room temperature chamber 22a is formed at the proximal end of the first cold head 14a, and the first expansion chamber 20a is formed at the distal end of the first cold head 14a. At the distal end of the first cold head 14a, a first cooling stage 24a fixed to the first cylinder 18a so as to enclose the first expansion chamber 20a is provided.

  When the first displacer 16a moves in the axial direction, the first expansion chamber 20a and the first room temperature chamber 22a complementarily increase or decrease in volume. That is, when the first displacer 16a moves upward, the first expansion chamber 20a expands and the first room temperature chamber 22a narrows. The reverse is also true.

  The first displacer 16a includes a built-in first regenerator 26a. The first displacer 16a has a first inlet channel 28a in its upper lid portion, which connects the first regenerator 26a to the first room temperature chamber 22a. In addition, the first displacer 16a has a first outlet flow path 30a that connects the first regenerator 26a to the first expansion chamber 20a in its cylindrical portion. Alternatively, the first outlet channel 30a may be provided on the lower lid of the first displacer 16a. In addition, the first displacer 16a includes a first inlet rectifier 32a inscribed in the upper lid, and a first outlet rectifier 34a inscribed in the lower lid. The first regenerator 26a is sandwiched between such a pair of rectifiers.

  The first cold head 14a includes a first seal portion 36a that closes a clearance formed between the first cylinder 18a and the first displacer 16a. The first seal portion 36a is, for example, a slipper seal, and is attached to a cylindrical portion or an upper lid portion of the first displacer 16a.

  Thus, the first seal portion 36a is located near the common drive mechanism 40, and the first outlet channel 30a is located away from the common drive mechanism 40 and near the first cooling stage 24a. In other words, the first seal portion 36a is attached to the proximal portion of the first displacer 16a, and the above-described first outlet channel 30a is formed at the distal portion of the first displacer 16a.

  The working gas flows into the first regenerator 26a from the first room temperature chamber 22a through the first inlet channel 28a. More precisely, the working gas flows from the first inlet passage 28a through the first inlet rectifier 32a into the first regenerator 26a. The working gas flows from the first regenerator 26a into the first expansion chamber 20a via the first outlet rectifier 34a and the first outlet passage 30a. When the working gas returns from the first expansion chamber 20a to the first room temperature chamber 22a, it passes through the reverse route. That is, the working gas returns from the first expansion chamber 20a to the first room temperature chamber 22a through the first outlet channel 30a, the first regenerator 26a, and the first inlet channel 28a. The working gas that bypasses the first regenerator 26a and flows through the clearance is blocked by the first seal portion 36a.

  The second cold head 14b is disposed on the side opposite to the first cold head 14a with respect to the common drive mechanism 40 as described above, but has the same configuration as the first cold head 14a except for that point. Therefore, the second cold head 14b is a single-stage type similarly to the first cold head 14a, and has the same shape and dimensions as the first cold head 14a.

  The second cold head 14b includes a second displacer 16b disposed coaxially with the first displacer 16a and capable of reciprocating in the axial direction integrally with the first displacer 16a, and a second cylinder 18b for housing the second displacer 16b. . The axial reciprocation of the second displacer 16b is guided by the second cylinder 18b. Usually, the second displacer 16b and the second cylinder 18b are cylindrical members extending in the axial direction, respectively, and the inner diameter of the second cylinder 18b is slightly larger than the outer diameter of the second displacer 16b.

  The second displacer 16b forms a second expansion chamber 20b at one axial end with the second cylinder 18b, and forms a second room temperature chamber 22b with the second cylinder 18b at the other axial end. . The second room temperature chamber 22b is located near the common drive mechanism 40, and the second expansion chamber 20b is located far from the common drive mechanism 40. In that sense, the second room 22b is formed at the proximal end of the second cold head 14b, and the second expansion chamber 20b is formed at the distal end of the second cold head 14b. At the distal end of the second cold head 14b, a second cooling stage 24b fixed to the second cylinder 18b so as to enclose the second expansion chamber 20b is provided.

  When the second displacer 16b moves in the axial direction, the second expansion chamber 20b and the second room temperature chamber 22b increase or decrease the volume complementarily. That is, when the second displacer 16b moves down, the second expansion chamber 20b expands and the second room temperature chamber 22b narrows. The reverse is also true.

  The second displacer 16b includes a built-in second regenerator 26b. The second displacer 16b has a second inlet flow passage 28b in its upper lid portion, which connects the second regenerator 26b to the second room temperature chamber 22b. In addition, the second displacer 16b has a second outlet passage 30b in its cylindrical portion, which connects the second regenerator 26b to the second expansion chamber 20b. Alternatively, the second outlet channel 30b may be provided in the lower lid of the second displacer 16b. In addition, the second displacer 16b includes a second inlet rectifier 32b inscribed in the upper lid and a second outlet rectifier 34b inscribed in the lower lid. The second regenerator 26b is sandwiched between such a pair of rectifiers.

  The second cold head 14b includes a second seal portion 36b that closes a clearance formed between the second cylinder 18b and the second displacer 16b. The second seal portion 36b is, for example, a slipper seal, and is attached to a cylindrical portion or an upper lid portion of the second displacer 16b.

  Thus, the second seal portion 36b is located near the common drive mechanism 40, and the second outlet passage 30b is located away from the common drive mechanism 40 and near the second cooling stage 24b. In other words, the second seal portion 36b is attached to the proximal portion of the second displacer 16b, and the above-described second outlet channel 30b is formed at the distal portion of the second displacer 16b.

  The working gas flows into the second regenerator 26b from the second room temperature chamber 22b through the second inlet channel 28b. More precisely, the working gas flows from the second inlet passage 28b through the second inlet rectifier 32b into the second regenerator 26b. The working gas flows into the second expansion chamber 20b from the second regenerator 26b via the second outlet rectifier 34b and the second outlet passage 30b. When the working gas returns from the second expansion chamber 20b to the second room temperature chamber 22b, it passes through the reverse route. That is, the working gas returns from the second expansion chamber 20b to the second room temperature chamber 22b through the second outlet channel 30b, the second regenerator 26b, and the second inlet channel 28b. The working gas that bypasses the second regenerator 26b and flows through the clearance is blocked by the second seal portion 36b.

  The GM refrigerator 10 is installed at the site where the GM refrigerator 10 is used in the illustrated direction. That is, the GM refrigerator 10 is installed vertically so that the first cold head 14a is arranged vertically downward and the second cold head 14b is arranged vertically upward. The second cold head 14b is set upside down with the first cold head 14a. The first cold head 14a directs the first expansion chamber 20a vertically downward, while the second cold head 14b directs the second expansion chamber 20b vertically upward. Alternatively, the GM refrigerator 10 may be installed in a horizontal or other orientation.

  The common drive mechanism 40 includes a reciprocating drive source 42 for driving the first displacer 16a and the second displacer 16b to reciprocate in the axial direction. The reciprocating drive source 42 includes a rotary drive source 44 (for example, a motor) having a rotary output shaft 46, a scotch yoke 48 connected to the rotary output shaft 46 so as to convert the rotation of the rotary output shaft 46 into an axial reciprocation, Is provided.

  The common drive mechanism 40 includes a first connecting rod 50a and a second connecting rod 50b. The first connecting rod 50a extends in the axial direction from the reciprocating drive source 42 and connects the reciprocating drive source 42 to the first displacer 16a. The second connecting rod 50b extends in the axial direction from the reciprocating drive source 42 on the side opposite to the first connecting rod 50a, and connects the reciprocating drive source 42 to the second displacer 16b. The first displacer 16a, the first connecting rod 50a, the second connecting rod 50b, and the second displacer 16b are disposed coaxially.

  More specifically, the first connecting rod 50a extends axially from the scotch yoke 48 to the first displacer 16a to connect the scotch yoke 48 to the first displacer 16a. The first connecting rod 50a rigidly connects the proximal portion of the first displacer 16a to the scotch yoke 48. The first connecting rod 50a is supported by the first bearing portion 38a so as to be movable in the axial direction. The first bearing 38a is provided between the scotch yoke 48 and the first displacer 16a.

  The second connecting rod 50b extends axially from the scotch yoke 48 to the second displacer 16b and connects the scotch yoke 48 to the second displacer 16b. The second connecting rod 50b rigidly connects the proximal portion of the second displacer 16b to the scotch yoke 48. The second connecting rod 50b is supported by the second bearing 38b so as to be movable in the axial direction. The second bearing 38b is disposed between the scotch yoke 48 and the second displacer 16b.

  As shown in FIG. 2, the common drive mechanism 40 includes a drive mechanism housing 52. The first cylinder 18a is fixed to one side of the drive mechanism housing 52, and the second cylinder 18b is fixed to the other side of the drive mechanism housing 52. The second cylinder 18b is arranged coaxially with the first cylinder 18a. 2, the compressor 12 is not shown for simplicity.

  The drive mechanism housing 52 houses the reciprocating drive source 42 and the scotch yoke 48 shown in FIG. The first connecting rod 50a and the second connecting rod 50b have their proximal ends housed in the drive mechanism housing 52 similarly to the scotch yoke 48. The distal ends of the first connecting rod 50a and the second connecting rod 50b are housed in the first cylinder 18a and the second cylinder 18b, respectively, like the first displacer 16a and the second displacer 16b. The first bearing portion 38a is provided at or near the boundary between the first cylinder 18a and the drive mechanism housing 52. The second bearing portion 38b is provided at or near the boundary between the second cylinder 18b and the drive mechanism housing 52. The first bearing portion 38a and the second bearing portion 38b are configured as seal portions for maintaining the airtightness of the first cylinder 18a and the second cylinder 18b with respect to the drive mechanism housing 52, respectively.

  Thus, the common drive mechanism 40 is connected to the first displacer 16a and the second displacer 16b so as to drive the axial reciprocation of the first displacer 16a and the second displacer 16b. The first displacer 16a and the second displacer 16b constitute a single displacer connector 16 fixedly connected to each other. The relative position of the second displacer 16b with respect to the first displacer 16a does not change during the axial reciprocation of the first displacer 16a and the second displacer 16b.

  Therefore, the axial reciprocating motions of the first displacer 16a and the second displacer 16b are in opposite phases. When the first displacer 16a is located at its top dead center (i.e., the proximal end dead center), the second displacer 16b is located at its bottom dead center (i.e., the distal end dead center). When the first displacer 16a moves from top dead center to bottom dead center (ie, when the first displacer 16a moves from the proximal end to the distal end of the first cold head 14a to narrow the first expansion chamber 20a). The second displacer 16b moves from bottom dead center to top dead center (ie, moves from the distal end to the proximal end of the second cold head 14b such that the second displacer 16b widens the second expansion chamber 20b).

  As shown in FIG. 2, the GM refrigerator 10 is provided with a refrigerant circulation circuit 54. The GM refrigerator 10 cools the refrigerant (for example, liquid nitrogen) flowing in the refrigerant circuit 54. The refrigerant cooled by the GM refrigerator 10 is supplied to the object to be cooled (not shown) through the refrigerant circuit 54. The refrigerant used for cooling the object to be cooled is recovered through the refrigerant circuit 54 and is re-cooled by the GM refrigerator 10.

  The refrigerant circulation circuit 54 includes a first refrigerant cooling unit 54a thermally coupled to the first cold head 14a, a second refrigerant cooling unit 54b thermally coupled to the second cold head 14b, and a first refrigerant cooling unit. A connecting refrigerant pipe 54c that connects the 54a to the second refrigerant cooling unit 54b is provided. The refrigerant circuit 54 includes a supply pipe 54d and a recovery pipe 54e. The first refrigerant cooling unit 54a and the second refrigerant cooling unit 54b are spiral refrigerant pipes surrounding the first cooling stage 24a and the second cooling stage 24b, respectively. The first refrigerant cooling unit 54a is cooled by the first cooling stage 24a, and the second refrigerant cooling unit 54b is cooled by the second cooling stage 24b. The connection refrigerant pipe 54c is connected to one end of the first refrigerant cooling unit 54a, and the supply pipe 54d is connected to the other end. The connection refrigerant pipe 54c is connected to one end of the second refrigerant cooling unit 54b, and the recovery pipe 54e is connected to the other end.

  The connection refrigerant pipe 54c is provided with a detachable connection mechanism 54f. Therefore, when the connecting mechanism 54f is removed, the connecting refrigerant pipe 54c is separated into a part on the first refrigerant cooling part 54a side and a part on the second refrigerant cooling part 54b side. The connection mechanism 54f facilitates disassembly of the refrigerant circuit 54. This helps to improve the efficiency of the maintenance work of the GM refrigerator 10.

  The flow direction of the refrigerant in the refrigerant circuit 54 is shown by arrows. The refrigerant flows from the recovery pipe 54e to the supply pipe 54d through the second refrigerant cooling section 54b, the connecting refrigerant pipe 54c, and the first refrigerant cooling section 54a. As described above, the refrigerant is first cooled in the second refrigerant cooling unit 54b, and then cooled in the first refrigerant cooling unit 54a.

  The cold head has the highest refrigeration capacity when it is installed with its expansion chamber oriented vertically downward. As described above, the first cold head 14a has the first expansion chamber 20a vertically downward, but the second cold head 14b does not. Therefore, the temperature of the second cooling stage 24b is higher than that of the first cooling stage 24a. According to the refrigerant circuit configuration described above, the collected relatively high-temperature refrigerant is first cooled by the high-temperature second cold head 14b, and then cooled by the low-temperature first cold head 14a. Therefore, the heat exchange efficiency between the refrigerant and the GM refrigerator 10 can be improved.

  The GM refrigerator 10 also includes a sub-vacuum container 56 for accommodating the second cold head 14b and the second refrigerant cooling unit 54b, and a first vacuum head 14a for attaching the sub-vacuum container 56 to another main vacuum container 58. A flange portion 60. The first cold head 14a and the first refrigerant cooling unit 54a are housed in a main vacuum vessel 58.

  The auxiliary vacuum container 56 is attached to the proximal end of the second cylinder 18b, and the flange portion 60 is attached to the proximal end of the first cylinder 18a. The sub-vacuum vessel 56 is connected to the flange portion 60 by a connection pipe 62 that connects the sub-vacuum vessel 56 to the main vacuum vessel 58 in an airtight manner. The connection pipe 62 provides a passage for guiding the supply pipe 54d and the connection refrigerant pipe 54c from the main vacuum vessel 58 to the sub vacuum vessel 56. The connection pipe 62 has a bellows part in the middle.

  The second cold head 14b and the second refrigerant cooling unit 54b are covered and hidden by the sub-vacuum vessel 56, and only the first cold head 14a and the first refrigerant cooling unit 54a are exposed. Therefore, in the operation of attaching the GM refrigerator 10 to the main vacuum vessel 58, the operator can handle the GM refrigerator 10 in the same manner as a general GM refrigerator having a single cold head.

  The working gas circuit 70 shown in FIG. 1 includes a first gas chamber (ie, a first expansion chamber 20a and / or a first room temperature chamber 22a) and a second gas chamber (ie, a second expansion chamber 20b and / or a second room temperature chamber 22b). ). This pressure differential acts on the displacer linkage 16 to assist the common drive mechanism 40. In FIG. 1, when the displacer connecting body 16 moves downward (that is, when the first (second) displacer 16 a (16 b) moves from the upper (lower) dead center to the lower (upper) dead center, the working gas circuit 70 Increases the pressure of the second gas chamber with respect to the first gas chamber. By doing so, the downward movement of the displacer connector 16 can be assisted by the pressure difference between the first gas chamber and the second gas chamber. The reverse is also true.

  The working gas circuit 70 includes a valve section 72. The valve section 72 includes a first intake valve V1, a first exhaust valve V2, a second intake valve V3, and a second exhaust valve V4. The valve section 72 is housed in the drive mechanism housing 52 shown in FIG. The valve section 72 may take the form of a rotary valve. In that case, the valve section 72 may be connected to the rotation output shaft 46 so as to be driven to rotate by the rotation of the rotation drive source 44. Alternatively, the valve unit 72 may include a plurality of individually controllable control valves and a control unit that controls the control valves.

  The first intake valve V1 is configured to determine a first intake period A1 of the first cold head 14a. The first intake valve V1 is provided in a first intake passage 74a that connects the discharge port of the compressor 12 to the first room temperature chamber 22a of the first cold head 14a. In the first intake period A1 (that is, when the first intake valve V1 is open), the working gas flows from the discharge port of the compressor 12 to the first room temperature chamber 22a. Conversely, when the first intake valve V1 is closed, the supply of the working gas from the compressor 12 to the first room temperature chamber 22a is stopped.

  The first exhaust valve V2 is configured to determine a first exhaust period A2 of the first cold head 14a. The first exhaust valve V2 is disposed in a first exhaust passage 76a that connects the suction port of the compressor 12 to the first room temperature chamber 22a of the first cold head 14a. In the first exhaust period A2 (that is, when the first exhaust valve V2 is open), the working gas flows from the first room temperature chamber 22a to the suction port of the compressor 12. When the first exhaust valve V2 is closed, the collection of the working gas from the first room temperature chamber 22a to the compressor 12 is stopped. As illustrated, a part of the first exhaust passage 76a may be common to the first intake passage 74a on the first room temperature room 22a side.

  Similarly, the second intake valve V3 is configured to determine a second intake period A3 of the second cold head 14b. The second intake valve V3 is provided in a second intake passage 74b that connects the discharge port of the compressor 12 to the second room temperature chamber 22b of the second cold head 14b. In the second intake period A3 (that is, when the second intake valve V3 is open), the working gas flows from the discharge port of the compressor 12 to the second room temperature room 22b. When the second intake valve V3 is closed, the supply of the working gas from the compressor 12 to the second room temperature chamber 22b is stopped. As illustrated, a part of the second intake passage 74b may be common to the first intake passage 74a on the compressor 12 side.

  The second exhaust valve V4 is configured to determine a second exhaust period A4 of the second cold head 14b. The second exhaust valve V4 is provided in a second exhaust passage 76b that connects the suction port of the compressor 12 to the second room temperature chamber 22b of the second cold head 14b. In the second exhaust period A4 (that is, when the second exhaust valve V4 is open), the working gas flows from the second room temperature chamber 22b to the suction port of the compressor 12. When the second exhaust valve V4 is closed, the collection of the working gas from the second room temperature chamber 22b to the compressor 12 is stopped. As illustrated, a part of the second exhaust passage 76b may be common to the second intake passage 74b on the second room temperature room 22b side. Further, a part of the second exhaust passage 76b may be common to the first exhaust passage 76a on the compressor 12 side.

  FIG. 3 illustrates a first intake period A1, a first exhaust period A2, a second intake period A3, and a second exhaust period A4. In FIG. 3, one cycle of the axial reciprocation of the displacer coupling body 16 is represented in association with 360 degrees, so that 0 degree corresponds to the start point of the cycle and 360 degrees corresponds to the end point of the cycle. 90 degrees, 180 degrees, and 270 degrees correspond to a 1/4 cycle, a half cycle, and a 3/4 cycle, respectively.

  The first intake period A1 and the second exhaust period A4 are in the range of 0 to 135 degrees, and the first exhaust period A2 and the second intake period A3 are in the range of 180 degrees to 315 degrees. The first intake period A1 alternates with the first exhaust period A2, and the second intake period A3 alternates with the second exhaust period A4. At 0 degrees, the first (second) displacer 16a (16b) is located at or near the lower (upper) dead center, and at 180 degrees, the first (second) displacer 16a (16b) is at the upper (lower) dead center or It is located in the vicinity.

  The operation of the GM refrigerator 10 having the above configuration will be described. When the first displacer 16a is located at or near the bottom dead center of the first cylinder 18a, the first intake period A1 is started (0 degrees in FIG. 3). The first intake valve V1 is opened, and high-pressure gas is supplied from the discharge port of the compressor 12 to the first room temperature chamber 22a of the first cold head 14a. The gas is cooled while passing through the first regenerator 26a and enters the first expansion chamber 20a. While gas flows into the first cold head 14a, the first displacer 16a moves from bottom dead center to top dead center. The first intake valve V1 closes, and the first intake period A1 ends (135 degrees in FIG. 3). The first displacer 16a continues to move toward the top dead center. Thus, the volume of the first expansion chamber 20a is increased and the first expansion chamber 20a is filled with the high-pressure gas.

  When the first displacer 16a is at or near the top dead center, the first exhaust period A2 is started (180 degrees in FIG. 3). The first exhaust valve V2 is opened, and the first cold head 14a is connected to the suction port of the compressor 12. The high-pressure gas is expanded and cooled in the first expansion chamber 20a. The expanded gas is recovered by the compressor 12 through the first room temperature chamber 22a while cooling the first regenerator 26a. While gas flows out of the first cold head 14a, the first displacer 16a moves from top dead center to bottom dead center. The first exhaust valve V2 closes, and the first exhaust period A2 ends (315 degrees in FIG. 3). The first displacer 16a continues to move toward the bottom dead center. Thus, the volume of the first expansion chamber 20a is reduced and the low-pressure gas is discharged.

  The first cold head 14a cools the first cooling stage 24a by repeating such a cooling cycle (that is, a GM cycle). Therefore, the refrigerant is cooled in the first refrigerant cooling unit 54a.

  The second cold head 14b operates simultaneously with the above-described operation of the first cold head 14a. When the second displacer 16b is at or near the top dead center, the second exhaust period A4 starts (0 degrees in FIG. 3). The second exhaust valve V4 is opened, and the second cold head 14b is connected to the suction port of the compressor 12. The high-pressure gas is expanded and cooled in the second expansion chamber 20b. The expanded gas is recovered by the compressor 12 through the second room temperature chamber 22b while cooling the second regenerator 26b. While gas flows out of the second cold head 14b, the second displacer 16b moves from top dead center to bottom dead center (upward in FIG. 1). The second exhaust valve V4 is closed, and the second exhaust period A4 ends (135 degrees in FIG. 3). The second displacer 16b continues to move toward the bottom dead center. Thus, the volume of the second expansion chamber 20b is reduced, and the low-pressure gas is discharged.

  When the second displacer 16b is located at or near the bottom dead center of the second cylinder 18b, the second intake period A3 is started (180 degrees in FIG. 3). The second intake valve V3 opens, and high-pressure gas is supplied from the discharge port of the compressor 12 to the second room temperature chamber 22b of the second cold head 14b. The gas is cooled while passing through the second regenerator 26b, and enters the second expansion chamber 20b. While gas flows into the second cold head 14b, the second displacer 16b moves from bottom dead center to top dead center (downward in FIG. 1). The second intake valve V3 closes, and the second intake period A3 ends (135 degrees in FIG. 3). The second displacer 16b continues to move toward the top dead center. Thus, the volume of the second expansion chamber 20b is increased and the second expansion chamber 20b is filled with the high-pressure gas.

  As described above, the second cold head 14b repeats the same cooling cycle (that is, the GM cycle) in a phase opposite to that of the first cold head 14a. Thereby, the second cooling stage 24b is cooled, and the refrigerant is cooled in the second refrigerant cooling unit 54b.

  There is a so-called “gas assist” technology that uses gas pressure to reduce the driving torque in an expander of a GM refrigerator. Typical gas assist is realized by distributing a part of the supplied working gas to a gas assist chamber in an expander isolated from an expansion space. The working gas supplied to the gas assist chamber cannot contribute to the PV work in the expansion space. Therefore, the gas assist has a disadvantage that the PV work, that is, the refrigeration capacity may be reduced.

  However, in the above-described embodiment, the first intake period A1 overlaps the second exhaust period A4. Therefore, when gas is supplied from the compressor 12 to the first cold head 14a, gas is recovered from the second cold head 14b to the compressor 12. At this time, the first expansion chamber 20a has a higher pressure than the second expansion chamber 20b, and this pressure difference urges the displacer connecting body 16 upward in FIG. Since the direction of the urging force coincides with the moving direction of the displacer connector 16, the common drive mechanism 40 can be assisted by the pressure difference.

  Further, since the first exhaust period A2 overlaps the second intake period A3, when the gas is recovered from the first cold head 14a, the gas is supplied to the second cold head 14b, and the first expansion chamber 20a becomes the second expansion chamber. The pressure becomes lower than 20b. This pressure differential urges the displacer linkage 16 downward in FIG. Therefore, also in the first exhaust period A2, the common driving mechanism 40 can be assisted by the pressure difference, as in the first intake period A1.

  Thus, the operation of each of the first cold head 14a and the second cold head 14b itself provides gas assist to the displacer linkage 16. The working gas is not consumed in a dedicated gas assist chamber as in the typical gas assist configuration described above, and therefore no loss of PV work occurs. Further, since the driving torque generated by the common driving mechanism 40 for driving the displacer coupling body 16 can be reduced, the driving mechanism can be downsized.

  To obtain such an advantage, the first intake period A1 does not need to exactly match the second exhaust period A4. The second exhaust period A4 may be at least partially overlapped with the first intake period A1. Similarly, the first exhaust period A2 may not exactly match the second intake period A3. The second intake period A3 may be at least partially overlapped with the first exhaust period A2.

  In the above-described embodiment, the second intake period A3 does not overlap with the first intake period A1. Further, the second exhaust period A4 does not overlap with the first exhaust period A2. As described above, the timing of intake and exhaust from the compressor 12 to the first cold head 14a is completely different from the timing of intake and exhaust from the compressor 12 to the second cold head 14b. By doing so, the fluctuation between the high and low pressures of the compressor 12 can be suppressed, and the efficiency of the compressor 12 can be improved.

  To obtain such an advantage, it is not necessary that the intake and exhaust timings of the two cold heads are completely shifted. The second intake period A3 is preferably delayed by at least 150 degrees from the first intake period A1. In addition, or instead, the second evacuation period A4 may be delayed from the first evacuation period A2 by preferably 150 degrees or more.

  Note that the first intake period A1 and the second exhaust period A4 may have different lengths. Similarly, the first exhaust period A2 and the second intake period A3 may have different lengths. The difference between the intake period and the exhaust period may be, for example, within 20 degrees or within 5 degrees. In this manner, the difference in refrigeration capacity between the first cold head 14a and the second cold head 14b may be adjusted.

  Further, the first intake period A1 and the first exhaust period A2 may have different lengths. Similarly, the second intake period A3 and the second exhaust period A4 may have different lengths. Also in this case, the difference between the intake period and the exhaust period may be, for example, within 20 degrees or within 5 degrees.

  Furthermore, in the above-described embodiment, since the GM refrigerator 10 is installed such that the two cold heads facing each other are vertically oriented, the installation floor area can be reduced.

  In the GM refrigerator 10 described with reference to FIGS. 1 to 3, the common drive mechanism 40 is assisted by the working gas circuit 70. However, it is also possible to drive the displacer connection 16 only by the pressure difference between the two cold heads. That is, as illustrated in FIG. 4, the GM refrigerator 10 does not need to include the common drive mechanism 40.

  FIG. 4 is a cross-sectional view schematically illustrating the GM refrigerator 10 according to an embodiment of the present invention. The GM refrigerator 10 includes a first connecting rod 50a and a second connecting rod 50b, which are mutually connected in the axial direction. The first displacer 16a is connected to the second displacer 16b via the first connecting rod 50a and the second connecting rod 50b such that the axial reciprocating motion of the first displacer 16a has an opposite phase to the axial reciprocating motion of the second displacer 16b. Are linked. The relative position of the second displacer 16b with respect to the first displacer 16a does not change during the axial reciprocation of the first displacer 16a and the second displacer 16b. The first displacer 16a, the first connecting rod 50a, the second connecting rod 50b, and the second displacer 16b are disposed coaxially.

  The first connecting rod 50a and the second connecting rod 50b constitute a single connecting rod 50 fixedly connected to each other. Alternatively, the first connecting rod 50a and the second connecting rod 50b may be fixedly connected to each other via an intermediate member.

  The first connecting rod 50a has a first sectional area S1 in a plane perpendicular to the axial direction, and the second connecting rod 50b has a second sectional area S2 in a plane perpendicular to the axial direction. The first cross-sectional area S1 is equal to the second cross-sectional area S2. For example, the first connecting rod 50a may have a circular cross section having a first diameter, and the second connecting rod 50b may have a circular cross section having a second diameter equal to the first diameter. The first connecting rod 50a and the second connecting rod 50b typically have the same cross-sectional shape, but they may have different cross-sectional shapes.

  The working gas circuit 70 is configured to drive the first displacer 16a and the second displacer 16b to reciprocate in the axial direction. The working gas circuit 70 is connected to the first cold head 14a and the second cold head 14b so as to generate a pressure difference between the first gas chamber and the second gas chamber.

  In the GM refrigerator 10 shown in FIG. 4, the valve timing shown in FIG. 3 can be adopted similarly to the GM refrigerator 10 shown in FIG.

  The first intake period A1 overlaps the second exhaust period A4. Therefore, when gas is supplied from the compressor 12 to the first cold head 14a, gas is recovered from the second cold head 14b to the compressor 12. At this time, the first expansion chamber 20a has a higher pressure than the second expansion chamber 20b. Thus, the displacer connection 16 can move upward due to the pressure difference.

  Further, the first exhaust period A2 overlaps with the second intake period A3. When the gas is recovered from the first cold head 14a, the gas is supplied to the second cold head 14b, and the pressure of the first expansion chamber 20a becomes lower than that of the second expansion chamber 20b. Due to the pressure difference, the displacer connection 16 can move downward.

  Thus, the GM refrigerator 10 having no common drive mechanism 40 can be provided. The GM refrigerator 10 is configured as a gas differential pressure drive type. When the valve unit 72 is configured as a rotary valve, as described above, the GM refrigerator 10 rotates the rotary drive source (for example, the rotary drive source 44) connected to the rotary valve so as to rotate the rotary valve. May be provided.

  In the GM refrigerator 10 shown in FIG. 1 as well, the first connecting rod 50a has a first cross-sectional area in a plane perpendicular to the axial direction, and the second connecting rod 50b has a first sectional area in a plane perpendicular to the axial direction. It has two cross-sectional areas. The first cross-sectional area S1 is equal to the second cross-sectional area S2. For example, the first connecting rod 50a may have a circular cross section having a first diameter, and the second connecting rod 50b may have a circular cross section having a second diameter equal to the first diameter.

  FIG. 5 is a sectional view schematically showing a GM refrigerator 10 according to an embodiment of the present invention. In the GM refrigerator 10 described with reference to FIGS. 1 to 4, the first connecting rod 50a and the second connecting rod 50b have the same sectional area. However, as shown in FIG. 5, the first connecting rod 50a and the second connecting rod 50b may have different cross-sectional areas.

  The first connecting rod 50a has a first sectional area S1 in a plane perpendicular to the axial direction, and the second connecting rod 50b has a second sectional area S2 in a plane perpendicular to the axial direction. The first cross-sectional area S1 is different from the second cross-sectional area S2. For example, the first cross-sectional area S1 is larger than the second cross-sectional area S2. For example, the first connecting rod 50a has a circular cross section having a first diameter, and the second connecting rod 50b has a circular cross section having a second diameter. The second diameter is smaller than the first diameter.

  Even in this manner, the working gas circuit 70 can generate a pressure difference that assists the common drive mechanism 40. The operation of each of the first cold head 14a and the second cold head 14b itself provides gas assist to the displacer linkage 16.

  In addition, the GM refrigerator 10 shown in FIG. 5 has an asymmetric gas assist configuration in which the first cross-sectional area S1 is different from the second cross-sectional area S2. Different assisting forces are applied to the displacer connector 16 according to the direction of movement of the displacer connector 16.

  FIG. 6A shows an upward movement assisting force Fup acting on the scotch yoke 48 when the displacer coupling 16 shown in FIG. 5 moves upward, and FIG. 6B shows a case where the displacer coupling 16 moves downward. The downward movement assist force Fdown acting on the scotch yoke 48 is shown.

  The scotch yoke 48 is housed in an internal space 53 of the drive mechanism housing 52. As described above, the first bearing portion 38a and the second bearing portion 38b seal the first room temperature chamber 22a and the second room temperature chamber 22b from the internal space 53, respectively. The internal space 53 is communicated with the discharge port of the compressor 12 shown in FIG. 1, and is therefore constantly maintained at a low pressure PL.

  When the displacer coupling body 16 moves upward, the first room temperature chamber 22a is at a high pressure PH and the second room temperature chamber 22b is at a low pressure PL. Therefore, the upward movement assisting force Fup is expressed as Fup = (PH-PL) S1. . On the other hand, when the displacer coupling body 16 moves upward, the first room temperature chamber 22a is at a low pressure PL and the second room temperature chamber 22b is at a high pressure PH. Is done. Therefore, when the first cross-sectional area S1 is larger than the second cross-sectional area S2, the upward movement assist force Fup is larger than the downward movement assist force Fdown.

  The GM refrigerator 10 can be installed in the orientation shown in the field where it is used. That is, the GM refrigerator 10 can be installed vertically so that the first cold head 14a is arranged vertically downward and the second cold head 14b is arranged vertically upward. In this case, the load of the driving source (for example, the rotary driving source 44) may be different depending on the moving direction of the displacer connecting body 16. For example, due to the weight of the displacer connector 16, the load on the drive source (for example, the rotary drive source 44) can be greater when the displacer connector 16 moves up than when the displacer connector 16 moves down.

  The GM refrigerator 10 shown in FIG. 5 can make the driving load uniform by employing an asymmetric gas assist configuration. For example, when the first cross-sectional area S1 is larger than the second cross-sectional area S2, the upward movement assist force Fup becomes larger than the downward movement assist force Fdown. Thereby, the influence of the weight of the displacer connector 16 can be at least partially canceled. This helps to equalize the refrigerating performance of the first cold head 14a and the second cold head 14b. Further, since the peak value of the driving load can be reduced by equalizing the driving load, the asymmetric gas assist configuration is also useful for downsizing the driving source.

  In some embodiments, the internal space 53 of the drive mechanism housing 52 may be maintained at a predetermined pressure different from the low pressure PL. Similarly, different assisting forces can be applied to the displacer connector 16 according to the moving direction of the displacer connector 16.

  In one embodiment, the first cross-sectional area S1 of the first connecting rod 50a may be smaller than the second cross-sectional area S2 of the second connecting rod 50b. For example, the first connecting rod 50a has a circular cross section having a first diameter, the second connecting rod 50b has a circular cross section having a second diameter, and the first diameter may be smaller than the second diameter. . By doing so, the upward movement assist force Fup can be made smaller than the downward movement assist force Fdown.

  FIG. 7 is a cross-sectional view schematically illustrating a GM refrigerator 10 according to an embodiment of the present invention. The GM refrigerator 10 shown in FIG. 7 does not have the common drive mechanism 40 like the GM refrigerator 10 shown in FIG.

  The GM refrigerator 10 includes a first connecting rod 50a and a second connecting rod 50b, which are mutually connected in the axial direction. The first displacer 16a is connected to the second displacer 16b via the first connection rod 50a and the second connection rod 50b such that the axial reciprocation of the first displacer 16a has an opposite phase to the axial reciprocation of the second displacer 16b. Are linked. The relative position of the second displacer 16b with respect to the first displacer 16a does not change during the axial reciprocation of the first displacer 16a and the second displacer 16b.

  The first connecting rod 50a and the second connecting rod 50b constitute a single connecting rod 50 fixedly connected to each other. Alternatively, the first connecting rod 50a and the second connecting rod 50b may be fixedly connected to each other via an intermediate member.

  The first connecting rod 50a has a first sectional area S1 in a plane perpendicular to the axial direction, and the second connecting rod 50b has a second sectional area S2 in a plane perpendicular to the axial direction. The first cross-sectional area S1 is different from the second cross-sectional area S2. For example, the first cross-sectional area S1 is larger than the second cross-sectional area S2. For example, the first connecting rod 50a has a circular cross section having a first diameter, and the second connecting rod 50b has a circular cross section having a second diameter. The second diameter is smaller than the first diameter.

  In the GM refrigerator 10 shown in FIG. 7, similarly to the GM refrigerator 10 shown in FIG. 1, the valve timing shown in FIG. 3 can be adopted.

  Also in this case, the GM refrigerator 10 can be configured as a gas differential pressure drive type. Also, different driving forces can be applied to the displacer connector 16 according to the moving direction of the displacer connector 16. Thereby, the upward movement and the downward movement of the displacer connector 16 can be made symmetrical. The refrigeration performance of the first cold head 14a and the second cold head 14b can be made uniform.

  The present invention has been described based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above embodiment, and that various design changes are possible, various modifications are possible, and such modifications are also within the scope of the present invention. By the way.

  For example, the two cold heads may have different configurations. The first cold head 14a may have a different size than the second cold head 14b, thereby having a different refrigerating capacity than the second cold head 14b. Alternatively, one or both cold heads may be multi-stage (for example, two-stage).

  The reciprocating drive source 42 may include a linear motor that drives the first displacer 16a and the second displacer 16b to reciprocate in the axial direction.

  10 GM refrigerator, 14a first cold head, 14b second cold head, 16a first displacer, 16b second displacer, 18a first cylinder, 18b second cylinder, 40 common drive mechanism, 42 reciprocal drive source, 44 rotary drive Source, 46 rotation output shaft, 48 scotch yoke, 50a first connecting rod, 50b second connecting rod, 54a first refrigerant cooling unit, 54b second refrigerant cooling unit, 54c connecting refrigerant pipe, 54f connecting mechanism, 56 sub vacuum vessel , 58 main vacuum vessel, 60 flange part, 70 working gas circuit, V1 first intake valve, A1 first intake period, V2 first exhaust valve, A2 first exhaust period, V3 second intake valve, A3 second intake period V4 2nd exhaust valve, A4 2nd exhaust period.

Claims (14)

A first cold head including: a first displacer that can reciprocate in the axial direction; and a first cylinder that forms a first gas chamber between the first displacer and the first displacer.
A second displacer arranged coaxially with the first displacer and reciprocally movable in the axial direction integrally with the first displacer; and a second cylinder forming a second gas chamber between the second displacer and the second displacer. A second cold head facing the first cold head,
A common drive mechanism coupled to the first displacer and the second displacer to drive the first displacer and the second displacer to reciprocate in the axial direction;
A working gas circuit connected to the first cold head and the second cold head to generate a pressure difference between the first gas chamber and the second gas chamber to assist the common drive mechanism. ,
The first cold head includes a first cooling stage at an end remote from the second cold head, and the second cold head includes a second cooling stage at an end remote from the first cold head. GM refrigerator according to claim Rukoto equipped. The common drive mechanism,
A reciprocating drive source,
A first connecting rod extending in the axial direction from the reciprocating drive source and connecting the reciprocating drive source to the first displacer;
A second connecting rod extending in the axial direction from the reciprocating drive source on a side opposite to the first connecting rod and connecting the reciprocating drive source to the second displacer.
The GM refrigerator according to claim 1, wherein the axial reciprocation of the first displacer has an opposite phase to the axial reciprocation of the second displacer. The reciprocating drive source includes a rotary drive source having a rotary output shaft, and a scotch yoke coupled to the rotary output shaft so as to convert rotation of the rotary output shaft into axial reciprocation,
The first connecting rod extends axially from the scotch yoke to the first displacer to connect the scotch yoke to the first displacer;
The GM refrigerator according to claim 2, wherein the second connecting rod extends in an axial direction from the scotch yoke to the second displacer and connects the scotch yoke to the second displacer.   The first connecting rod has a first sectional area in a plane perpendicular to the axial direction, the second connecting rod has a second sectional area in a plane perpendicular to the axial direction, and the first sectional area is The GM refrigerator according to claim 2, wherein the GM refrigerator has the same sectional area as the second sectional area.   The first connecting rod has a first sectional area in a plane perpendicular to the axial direction, the second connecting rod has a second sectional area in a plane perpendicular to the axial direction, and the first sectional area is The GM refrigerator according to claim 2, wherein the GM refrigerator is different from the second cross-sectional area. The working gas circuit includes:
A first intake valve for defining a first intake period of the first cold head;
A second intake valve for defining a second intake period of the second cold head;
A first exhaust valve that determines a first exhaust period of the first cold head to at least partially overlap the second intake period;
The GM refrigeration according to any one of claims 1 to 5, further comprising: a second exhaust valve that determines a second exhaust period of the second cold head so as to at least partially overlap the first intake period. Machine. The second inspiration period is delayed from the first inspiration period, and / or
The GM refrigerator according to claim 6, wherein the second exhaust period is delayed from the first exhaust period. A first refrigerant cooling unit thermally coupled to the first cold head;
A second refrigerant cooling unit thermally coupled to the second cold head;
A connection refrigerant pipe connecting the first refrigerant cooling unit to the second refrigerant cooling unit, further comprising:
The GM refrigerator according to any one of claims 1 to 7, wherein the connection refrigerant pipe is provided with a detachable connection mechanism. A sub-vacuum container containing the second cold head and the second refrigerant cooling unit;
The GM refrigerator according to claim 8, further comprising: a flange portion for attaching the first cold head to the sub vacuum container and another main vacuum container. The first cold head is a first single-stage cold head;
The GM refrigerator according to claim 8 or 9, wherein the second cold head is a second single-stage cold head. A first cold head comprising: a first displacer that can reciprocate in the axial direction; and a first cylinder that forms a first gas chamber between the first displacer and the first displacer.
A second displacer arranged coaxially with the first displacer and reciprocally movable in the axial direction integrally with the first displacer; and a second cylinder forming a second gas chamber between the second displacer and the second displacer. A second cold head disposed opposite to the first cold head ,
The first cold head includes a first cooling stage at an end remote from the second cold head, and the second cold head includes a second cooling stage at an end remote from the first cold head. GM refrigerator according to claim Rukoto equipped. 12. The apparatus of claim 11 , further comprising a working gas circuit connected to the first cold head and the second cold head to generate a pressure difference between the first gas chamber and the second gas chamber. 2. The GM refrigerator according to item 1. A first connecting rod and a second connecting rod connected to each other in the axial direction, wherein the first displacer has a phase opposite to that of the second displacer in axial reciprocation of the first displacer. Connected to the second displacer via the first connecting rod and the second connecting rod to have
The first connecting rod has a first sectional area in a plane perpendicular to the axial direction, the second connecting rod has a second sectional area in a plane perpendicular to the axial direction, and the first sectional area is GM refrigerator according to claim 11 or 12, characterized in that equal to the second cross-sectional area. A first connecting rod and a second connecting rod connected to each other in the axial direction, wherein the first displacer has a phase opposite to that of the second displacer in axial reciprocation of the first displacer. Connected to the second displacer via the first connecting rod and the second connecting rod to have
The first connecting rod has a first sectional area in a plane perpendicular to the axial direction, the second connecting rod has a second sectional area in a plane perpendicular to the axial direction, and the first sectional area is GM refrigerator according to claim 11 or 12, characterized in that different from the second cross-sectional area.

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