JP2019174061A - Cryogenic refrigerator - Google Patents

Abstract

To improve the temperature increase efficiency of reverse temperature increase in a cryogenic refrigerator.SOLUTION: A cryogenic refrigerator 10 comprises: a reversible motor 40; a displacer 24 reciprocating in the axial direction; a cylinder 28 defining an expansion space 34 between the cylinder and the displacer 24, the expansion space having a maximum volume at a displacer top dead center; a refrigerator stage 32 thermally coupled to the expansion space 34; and a rotary valve 58 for switching between air intake and exhaust of the expansion space 34 in synchronization with the axial direction reciprocation of the displacer 24 such that the refrigerator stage 32 is cooled during forward rotation of the reversible motor 40 and the refrigerator stage 32 is heated during reverse rotation of the reversible motor 40. When a single cycle of the axial direction reciprocation of the displacer 24 is set to be 360 degrees, the phase of air intake start timing for the expansion space 34 during reverse rotation of the reversible motor 40 advances in the range of 0 degree to 10 degrees relative to the displacer top dead center.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cryogenic refrigerator.

  A cryogenic refrigerator represented by a Gifford-McMahon (GM) refrigerator typically includes a displacer that reciprocates in an axial direction and a motor that drives the displacer. The displacer is mechanically connected to the motor, and the displacer is reciprocated in the axial direction by the motor. In such a motor-driven GM refrigerator, a so-called reverse temperature raising technique is conventionally known. Using the reverse temperature increase, the temperature of the cooled GM refrigerator can be increased, for example, to room temperature.

JP-A-7-35070

  One of the exemplary purposes of an aspect of the present invention is to improve the temperature raising efficiency of the reverse temperature rise in the cryogenic refrigerator.

  According to an aspect of the present invention, a cryogenic refrigerator includes a reversible motor, a displacer that reciprocates in the axial direction by forward rotation and reverse rotation of the reversible motor, and a cylinder that houses the displacer. A cylinder defining an expansion space with the displacer having a maximum volume at a top dead center and a minimum volume at a displacer bottom dead center; a refrigerator stage thermally coupled to the expansion space; Intake of the expansion space in synchronism with the axial reciprocation of the displacer so that the refrigerator stage is cooled when the reversible motor rotates forward and the refrigerator stage is heated when the reverse motor rotates backward And a rotary valve for switching between exhaust and exhaust. When the period of the axial reciprocation of the displacer is 360 °, the phase of the intake start timing of the expansion space when the reversible motor is reverse is greater than 0 ° with respect to the displacer top dead center. It is progressing within the following range.

  In addition, what replaced the component and expression of this invention between methods, apparatuses, systems, etc. is also effective as an aspect of this invention.

  ADVANTAGE OF THE INVENTION According to this invention, the temperature increase efficiency of reverse temperature increase in a cryogenic refrigerator can be improved.

1 schematically shows the overall configuration of a cryogenic refrigerator according to an embodiment. It is a disassembled perspective view which shows schematically the drive mechanism of the expander of the cryogenic refrigerator which concerns on a certain embodiment. It is a disassembled perspective view which shows roughly the rotary valve mechanism of the cryogenic refrigerator which concerns on a certain embodiment. It is a figure which illustrates the timing chart of the cooling operation of the cryogenic refrigerator which concerns on a certain embodiment. It is a figure which illustrates the timing chart of the reverse temperature rising operation of the cryogenic refrigerator which concerns on a certain embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. The scales and shapes of the respective parts shown in the drawings are set for convenience in order to facilitate explanation, and are not limitedly interpreted unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a diagram schematically illustrating a cryogenic refrigerator according to an embodiment. FIG. 2 is an exploded perspective view schematically showing a drive mechanism of an expander of a cryogenic refrigerator according to an embodiment. FIG. 3 is an exploded perspective view schematically showing a rotary valve mechanism of a cryogenic refrigerator according to an embodiment.

  The cryogenic refrigerator 10 includes a compressor 12 that compresses working gas (also referred to as refrigerant gas) and an expander 14 that cools the working gas by adiabatic expansion. The working gas is, for example, helium gas. The expander 14 is also called a cold head. The expander 14 is provided with a regenerator 16 for precooling the working gas. The cryogenic refrigerator 10 includes a gas pipe 18 including a first pipe 18a and a second pipe 18b that connect the compressor 12 and the expander 14, respectively. The illustrated cryogenic refrigerator 10 is a single-stage GM refrigerator.

  As is known, a working gas having a first high pressure is supplied to the expander 14 from the discharge port 12a of the compressor 12 through the first pipe 18a. Due to the adiabatic expansion in the expander 14, the working gas is depressurized from the first high pressure to a lower second high pressure. The working gas having the second high pressure is recovered from the expander 14 to the suction port 12b of the compressor 12 through the second pipe 18b. The compressor 12 compresses the recovered working gas having the second high pressure. Thus, the working gas is again boosted to the first high pressure. In general, both the first high pressure and the second high pressure are considerably higher than the atmospheric pressure. For convenience of explanation, the first high pressure and the second high pressure are also simply referred to as high pressure and low pressure, respectively. Typically, the high pressure is, for example, 2-3 MPa, and the low pressure is, for example, 0.5-1.5 MPa. The differential pressure between the high pressure and the low pressure is, for example, about 1.2 to 2 MPa.

  The expander 14 includes an expander movable part 20 and an expander stationary part 22. The expander movable portion 20 is configured to be capable of reciprocating in the axial direction (vertical direction in FIG. 1) with respect to the expander stationary portion 22. The moving direction of the expander movable portion 20 is indicated by an arrow A in FIG. The expander stationary part 22 is configured to support the expander movable part 20 so as to be capable of reciprocating in the axial direction. The expander stationary part 22 is configured as an airtight container that houses the expander movable part 20 together with high-pressure gas (including the first high-pressure gas and the second high-pressure gas).

  The expander movable part 20 includes a displacer 24 and a displacer drive shaft 26 that drives the reciprocation thereof. The displacer 24 incorporates a regenerator 16. A cool storage material is filled in the internal space of the displacer 24, whereby the cool storage 16 is formed in the displacer 24. The displacer 24 has, for example, a substantially cylindrical shape extending in the axial direction, and has an outer diameter and an inner diameter that are substantially uniform in the axial direction. Therefore, the regenerator 16 also has a substantially cylindrical shape extending in the axial direction.

  The expander stationary portion 22 roughly has a two-part configuration including a cylinder 28 and a drive mechanism housing 30. The axially upper part of the expander stationary part 22 is a drive mechanism housing 30, and the axially lower part of the expander stationary part 22 is a cylinder 28, which are firmly connected to each other. The cylinder 28 is configured to guide the reciprocating movement of the displacer 24. The cylinder 28 extends from the drive mechanism housing 30 in the axial direction. The cylinder 28 has a substantially uniform inner diameter in the axial direction, and thus the cylinder 28 has a substantially cylindrical inner surface extending in the axial direction. This inner diameter is slightly larger than the outer diameter of the displacer 24.

  The expander stationary part 22 includes a refrigerator stage 32. The refrigerator stage 32 is fixed to the end of the cylinder 28 on the side opposite to the drive mechanism housing 30 in the axial direction. The refrigerator stage 32 is provided to conduct the cold generated by the expander 14 to other objects. The object is attached to the refrigerator stage 32 and is cooled by the refrigerator stage 32 during operation of the cryogenic refrigerator 10. The refrigerator stage 32 may be called a cooling stage or a heat load stage.

  The cylinder 28 is divided into an expansion space 34 and an upper space 36 by the displacer 24. The displacer 24 defines an expansion space 34 with the cylinder 28 at one axial end and an upper space 36 with the cylinder 28 at the other axial end. The expansion space 34 has a maximum volume at the top dead center of the displacer 24 and a minimum volume at the bottom dead center of the displacer 24. The upper space 36 has a minimum volume at the top dead center of the displacer 24 and a maximum volume at the bottom dead center of the displacer 24. The refrigerator stage 32 is fixed to the cylinder 28 so as to enclose the expansion space 34. The refrigerator stage 32 is thermally coupled to the expansion space 34.

  During the operation of the cryogenic refrigerator 10, the regenerator 16 has a regenerator high-temperature part 16a on one side (upper side in the figure) in the axial direction and a regenerator low-temperature part 16b on the opposite side (lower side in the figure). . Thus, the regenerator 16 has a temperature distribution in the axial direction. The other components of the expander 14 (eg, the displacer 24 and the cylinder 28) surrounding the regenerator 16 have an axial temperature distribution as well, so that the expander 14 has a high temperature section on one axial side during its operation. A low temperature part is provided on the other side in the axial direction. The high temperature part has a temperature of about room temperature, for example. The low temperature part varies depending on the use of the cryogenic refrigerator 10, but is cooled to a certain temperature included in a range of about 100 K to about 10 K, for example.

  In this document, the terms axial direction, radial direction, and circumferential direction are used for convenience of explanation. The axial direction represents the moving direction of the expander movable part 20 relative to the expander stationary part 22 as illustrated by the arrow A. The radial direction represents a direction perpendicular to the axial direction (lateral direction in the figure), and the circumferential direction represents a direction surrounding the axial direction. When an element of the expander 14 is relatively close to the refrigerator stage 32 with respect to the axial direction, it may be called “lower”, and when it is relatively far away, it may be called “upper”. Therefore, the high temperature part and the low temperature part of the expander 14 are located in the upper part and the lower part in the axial direction, respectively. These expressions are only used to help understand the relative positional relationship between the elements of the expander 14 and are not related to the placement of the expander 14 when installed in the field. For example, the expander 14 may be installed with the refrigerator stage 32 facing upward and the drive mechanism housing 30 facing downward. Or the expander 14 may be installed so that an axial direction may correspond to a horizontal direction.

  The terms “axial direction”, “radial direction”, and “circumferential direction” are also used for the rotary valve mechanism. In this case, the axial direction represents the direction of the rotary shaft of the rotary valve mechanism. The axial direction of the rotary valve mechanism is perpendicular to the axial direction of the cryogenic refrigerator 10, that is, the moving direction of the expander movable part 20.

  The expander 14 is supported by the expander stationary portion 22 and includes a drive mechanism 38 that drives the displacer 24. The drive mechanism 38 includes a reversible motor 40 and a Scotch yoke mechanism 42. The displacer drive shaft 26 forms a part of the scotch yoke mechanism 42. The displacer drive shaft 26 is connected to the scotch yoke mechanism 42 so as to be driven in the axial direction by the scotch yoke mechanism 42. Accordingly, the reciprocating movement of the displacer 24 in the axial direction is driven by the forward rotation and the reverse rotation of the motor 40 that can rotate in reverse.

  The drive mechanism 38 is accommodated in a low-pressure gas chamber 37 defined inside the drive mechanism housing 30. The second pipe 18b is connected to the drive mechanism housing 30, whereby the low-pressure gas chamber 37 communicates with the suction port 12b of the compressor 12 through the second pipe 18b. Therefore, the low pressure gas chamber 37 is always maintained at a low pressure.

  The cryogenic refrigerator 10 is configured to perform a cooling operation when the reversible motor 40 rotates in a predetermined direction and to perform a temperature rising operation when the reversible motor 40 rotates in the opposite direction. The rotation direction in which the cryogenic refrigerator 10 is cooled is referred to as “forward rotation”, and the rotation direction in which the cryogenic refrigerator 10 is heated is referred to as “reverse rotation”. FIG. 2 shows a rotating shaft 40a of the reversible motor 40. Here, the clockwise rotation of the rotation shaft 40a of the reversible motor 40 is forward rotation (arrow B direction), and the counterclockwise rotation of the rotation shaft 40a of the reversible motor 40 is reverse rotation (arrow C direction).

  As shown in FIG. 2, the scotch yoke mechanism 42 includes a crank 44 and a scotch yoke 46. The crank 44 is fixed to the rotation shaft 40 a of the reversible motor 40. The crank 44 has a crank pin 44a at a position eccentric from the position where the rotation shaft 40a is fixed. Therefore, when the crank 44 is fixed to the rotating shaft 40a, the crank pin 44a extends in parallel with the rotating shaft 40a of the reversible motor 40 and is eccentric from the rotating shaft 40a.

  The scotch yoke 46 includes a yoke plate 48 and a roller bearing 50. The yoke plate 48 is a plate-like member. An upper shaft 52 is connected to the upper center of the scotch yoke 46 so as to extend upward, and a displacer drive shaft 26 is connected to the lower center of the scotch yoke 46 so as to extend downward. As shown in FIG. 1, the upper shaft 52 is supported by a first sliding bearing 54 so as to be movable in the axial direction, and the displacer drive shaft 26 is supported by a second sliding bearing 56 so as to be movable in the axial direction. The Therefore, the upper shaft 52 and the displacer drive shaft 26, and thus the yoke plate 48, and thus the scotch yoke 46 are configured to be movable in the axial direction.

  A laterally long window 48 a is formed at the center of the yoke plate 48. The horizontally elongated window 48a extends in a direction intersecting, for example, a direction orthogonal to the direction in which the upper shaft 52 and the displacer drive shaft 26 extend (that is, the axial direction). The roller bearing 50 is disposed in the horizontally elongated window 48a so as to be able to roll. An engagement hole 50a that engages with the crank pin 44a is formed at the center of the roller bearing 50, and the crank pin 44a passes through the engagement hole 50a.

  The first sliding bearing 54 and the second sliding bearing 56 are provided in the drive mechanism housing 30 of the expander stationary portion 22. A seal portion such as a slipper seal or a clearance seal is provided at the lower end portion of the second sliding bearing 56 or the drive mechanism housing 30, for example, so that the low pressure gas chamber 37 is isolated from the upper space 36. Yes. There is no direct gas flow between the low pressure gas chamber 37 and the upper space 36.

  When the reversible motor 40 is driven and the rotary shaft 40a rotates, the roller bearing 50 engaged with the crank pin 44a rotates so as to draw a circle. As the roller bearing 50 rotates to draw a circle, the scotch yoke 46 reciprocates in the axial direction. At this time, the roller bearing 50 reciprocates in the lateral window 48a in a direction intersecting the axial direction.

  As shown in FIG. 1, the displacer 24 is connected to a displacer drive shaft 26. The displacer drive shaft 26 extends from the low pressure gas chamber 37 through the upper space 36 to the displacer 24. For this reason, when the scotch yoke 46 moves in the axial direction, the displacer 24 reciprocates in the cylinder 28 in the axial direction.

  The expander 14 is synchronized with the axial reciprocation of the displacer 24 so that the refrigerator stage 32 is cooled when the reversible motor 40 is rotated forward and the refrigerator stage 32 is heated when the reverse motor 40 is rotated reversely. And a rotary valve 58 for switching between intake and exhaust of the expansion space 34. The rotary valve 58 functions as a part of a supply path for supplying high-pressure gas to the expansion space 34 and functions as a part of a discharge path for discharging low-pressure gas from the expansion space 34. The rotary valve 58 is configured to switch the working gas supply function and the discharge function in synchronization with the reciprocating movement of the displacer 24, thereby controlling the pressure in the expansion space 34. The rotary valve 58 is connected to the drive mechanism 38 and is accommodated in the drive mechanism housing 30.

  Further, the expander 14 includes a housing gas flow path 64, a displacer upper lid gas flow path 66, and a displacer lower lid gas flow path 68. The high-pressure gas flows into the expansion space 34 from the first pipe 18a through the rotary valve 58, the housing gas flow path 64, the upper space 36, the displacer upper lid gas flow path 66, the regenerator 16, and the displacer lower lid gas flow path 68. The return gas from the expansion space 34 is received by the low pressure gas chamber 37 via the displacer lower cover gas flow path 68, the regenerator 16, the displacer upper cover gas flow path 66, the upper space 36, the housing gas flow path 64, and the rotary valve 58. .

  The housing gas flow path 64 is formed through the drive mechanism housing 30 for gas flow between the expander stationary part 22 and the upper space 36.

  The upper space 36 is formed between the expander stationary part 22 and the displacer 24 on the regenerator high temperature part 16a side. More specifically, the upper space 36 is sandwiched between the drive mechanism housing 30 and the displacer 24 in the axial direction, and is surrounded by the cylinder 28 in the circumferential direction. The upper space 36 is adjacent to the low pressure gas chamber 37. The upper space 36 is also called a room temperature room. The upper space 36 is a variable volume formed between the expander movable part 20 and the expander stationary part 22.

  The displacer top gas channel 66 is at least one opening of the displacer 24 formed so as to communicate the regenerator high temperature portion 16a with the upper space 36. The displacer lower lid gas flow path 68 is at least one opening of the displacer 24 formed so as to communicate the regenerator low-temperature part 16 b with the expansion space 34. A seal portion 70 that seals the clearance between the displacer 24 and the cylinder 28 is provided on the side surface of the displacer 24. The seal portion 70 may be attached to the displacer 24 so as to surround the displacer upper lid gas flow channel 66 in the circumferential direction.

  The expansion space 34 is formed between the cylinder 28 and the displacer 24 on the regenerator low temperature portion 16b side. The expansion space 34 is a variable volume formed between the expander movable part 20 and the expander stationary part 22 in the same manner as the upper space 36, and the volume of the expansion space 34 is increased by the relative movement of the displacer 24 with respect to the cylinder 28. It varies in a complementary manner to the volume of 36. Since the seal portion 70 is provided, there is no direct gas flow between the upper space 36 and the expansion space 34 (that is, a gas flow that bypasses the regenerator 16).

  The rotary valve 58 includes a rotor valve member 60 and a stator valve member 62. The rotor valve member 60 is connected to the output shaft of the reversible motor 40 so as to rotate by the rotation of the reversible motor 40. The rotor valve member 60 is in surface contact with the stator valve member 62 so as to rotate and slide with respect to the stator valve member 62. The stator valve member 62 is fixed to the drive mechanism housing 30. The stator valve member 62 is configured to receive high-pressure gas entering the drive mechanism housing 30 from the first pipe 18a.

  An alternate long and short dash line Y shown in FIG. 3 represents the rotation axis of the rotary valve 58. The stator valve member 62 has a flat stator side rotational sliding surface 71, and the rotor valve member 60 has a flat rotor side rotational sliding surface 72. The stator side rotational sliding surface 71 and the rotor side rotational sliding surface 72 are both perpendicular to the rotational axis Y. The stator-side rotational sliding surface 71 and the rotor-side rotational sliding surface 72 are in surface contact with each other, thereby preventing refrigerant gas from leaking.

  The stator valve member 62 is fixed in the drive mechanism housing 30 with a stator valve fixing pin 73. The stator valve fixing pin 73 engages with the stator valve end surface 74 located on the opposite side of the rotation axis direction of the stator side rotation sliding surface 71 of the stator valve member 62 to restrict the rotation of the stator valve member 62.

  The rotor valve member 60 is rotatably supported by a rotor valve bearing 75 shown in FIG. An arcuate engagement groove 77 is formed on the rotor valve end surface 76 of the rotor valve member 60 on the scotch yoke mechanism 42 side, as shown in FIG. The rotor valve end surface 76 is located on the opposite side to the rotor-side rotational sliding surface 72 of the rotor valve member 60 in the rotational axis direction. The rotor valve member 60 includes a rotor valve outer peripheral surface 78 that connects the rotor side rotational sliding surface 72 to the rotor valve end surface 76. The rotor valve outer peripheral surface 78 is supported by the rotor valve bearing 75 and faces the low pressure gas chamber 37.

  As shown in FIG. 2, the tip of the crank pin 44 a of the scotch yoke mechanism 42 enters the engagement groove 77. As the rotary shaft 40 a of the reversible motor 40 rotates, the crank pin 44 a rotates forward or reverse, and the crank pin 44 a engages with the end portion 77 a on the circumferential direction one side or the end portion 77 b on the other circumferential side of the engagement groove 77. In this case, the movement of the crank 44, that is, the rotation of the rotating shaft 40 a of the reversible motor 40 is transmitted to the rotor valve member 60, and the rotor valve member 60 rotates forward or backward with respect to the stator valve member 62. When the reversible motor 40 rotates the crank pin 44 a, the rotor valve member 60 rotates in synchronization with the scotch yoke mechanism 42.

  The engagement groove 77 and the crank pin 44a have a predetermined angle (for example, not less than 200 ° and less than 360 °) between the forward rotation and the reverse rotation of the rotor valve member 60 and the rotation shaft 40a of the reversible motor 40. 280 °). Therefore, the intake / exhaust timing of the rotary valve 58 with respect to the reciprocating movement of the displacer 24 is determined when the rotary shaft 40a and the rotor valve member 60 are rotated forward (that is, when the cryogenic refrigerator 10 is cooled), and It differs depending on when 60 reverses (that is, when the cryogenic refrigerator 10 is heated).

  As shown in FIG. 3, the stator valve member 62 has a high-pressure gas inlet 79 and a gas inlet 80. The high-pressure gas inlet 79 is opened at the center of the stator-side rotational sliding surface 71 and is formed so as to penetrate the center of the stator valve member 62 in the direction of the rotation axis Y. The high-pressure gas inlet 79 communicates with the discharge port 12a of the compressor 12 through the first pipe 18a (see FIG. 1). The gas circulation port 80 is opened radially outward with respect to the high-pressure gas inflow port 79 in the stator side rotational sliding surface 71. The gas circulation port 80 is formed in an arcuate groove centered on the high-pressure gas inlet 79.

  The stator valve member 62 has a communication passage 81 formed through the stator valve member 62 so as to connect the gas flow port 80 to the housing gas flow path 64. Therefore, the gas circulation port 80 is finally communicated with the expansion space 34 via the communication path 81 and the housing gas flow path 64. The communication passage 81 has one end opened to the gas flow port 80 and the other end opened to the side surface of the stator valve member 62. A portion of the communication passage 81 on the gas flow port 80 side extends in the direction of the rotation axis Y, and a portion of the communication passage 81 on the housing gas flow path 64 side extends in the radial direction so as to be orthogonal thereto. In the intake stroke of the cryogenic refrigerator 10, high-pressure gas flows through the gas circulation port 80 and the communication passage 81, while low-pressure return gas from the expansion space 34 flows through the gas circulation port 80 and the communication passage 81 in the exhaust process.

  The rotor valve member 60 has a rotor valve high-pressure recess 82 and a rotor valve opening 83. The rotor-side rotational sliding surface 72 is in surface contact with the stator-side rotational sliding surface 71 around the rotor valve high-pressure recess 82. Similarly, the rotor-side rotational sliding surface 72 is in surface contact with the stator-side rotational sliding surface 71 around the rotor valve opening 83.

  The rotor valve high-pressure recess 82 is opened in the rotor-side rotational sliding surface 72 and is formed in an oval groove. The rotor valve high-pressure recess 82 extends radially outward from the center of the rotor-side rotational sliding surface 72. The depth of the rotor valve high-pressure recess 82 is shorter than the length of the rotor valve member 60 in the rotation axis direction, and the rotor valve high-pressure recess 82 does not penetrate the rotor valve member 60. One end of the rotor valve high-pressure recess 82 in the radial direction is located on the rotor-side rotary sliding surface 72 at a location corresponding to the high-pressure gas inlet 79. Therefore, the rotor valve high-pressure recess 82 is always connected to the high-pressure gas inlet 79. The other end in the radial direction of the rotor valve high-pressure recess 82 is formed so as to be positioned substantially on the same circumference as the gas flow port 80 of the stator valve member 62.

  Thus, the rotary valve 58 is configured as an intake valve. The rotor valve high-pressure recess 82 communicates the high-pressure gas inlet 79 with the gas circulation port 80 in a part of one period of rotation of the rotor valve member 60 (for example, the intake process), and in the remaining part of the one period (for example, the exhaust process). The high-pressure gas inlet 79 is formed so as not to communicate with the gas circulation port 80. Two sections consisting of the rotor valve high-pressure recess 82 and the high-pressure gas inlet 79, or three sections consisting of the rotor valve high-pressure recess 82, the high-pressure gas inlet 79, and the gas flow port 80 communicate with each other in the rotary valve 58. A high pressure region (or high pressure flow path) is formed. The rotor valve member 60 is disposed adjacent to the stator valve member 62 so as to seal the high pressure region and isolate it from the low pressure ambient environment (ie, the low pressure gas chamber 37). The rotor valve high-pressure recess 82 is provided as a flow direction changing portion or a channel turn-back portion in the high-pressure channel of the rotary valve 58.

  On the other hand, the rotor valve opening 83 is an arc-shaped hole that penetrates from the rotor-side rotational sliding surface 72 of the rotor valve member 60 to the rotor valve end surface 76, and forms a low-pressure channel that communicates with the low-pressure gas chamber 37. As an example, the rotor valve opening 83 penetrates the rotor valve member 60 into the engagement groove 77. The rotor valve opening 83 is located substantially on the opposite side in the radial direction from the outer end of the rotor valve high-pressure recess 82 with respect to the central portion of the rotor-side rotational sliding surface 72. The rotor valve opening 83 is formed so as to be positioned substantially on the same circumference as the gas flow port 80 of the stator valve member 62. In this way, the rotary valve 58 is configured as an exhaust valve. The rotor valve member 60 is formed so that the gas circulation port 80 communicates with the low-pressure gas chamber 37 in at least a part of the period during which the high-pressure gas inlet 79 is disconnected from the gas circulation port 80 (for example, an exhaust process).

  FIG. 4 is a diagram illustrating a timing chart of the cooling operation of the cryogenic refrigerator 10 according to an embodiment. In FIG. 4, the valve timing of the rotary valve 58 (shown by a solid line) and the axial position of the displacer 24 (shown by a one-dot chain line) are shown in time series over one cycle of the axial reciprocation of the displacer 24. Yes. One period of the axial reciprocation of the displacer 24 is associated with 360 °. In other words, the horizontal axis in FIG. 4 represents the rotation angle of the reversible motor 40 and the phase of the rotary valve 58. At 0 ° (360 °), the displacer 24 is located at the top dead center, and the volume of the expansion space 34 is maximized. At 180 °, the displacer 24 is located at the bottom dead center, and the volume of the expansion space 34 is minimized. At 90 ° and 270 °, the displacer 24 is located at the midpoint between the top dead center and the bottom dead center. The cooling operation of the cryogenic refrigerator 10 will be described with reference to FIGS.

  First, the case where the cryogenic refrigerator 10 is cooled will be described. In the cooling operation, the reversible motor 40 is rotated forward to engage the crank pin 44a with the end 77a of the engagement groove 77 of the rotor valve member 60, and the rotor valve member 60 is rotated forward.

  Prior to the displacer 24 reaching top dead center, the rotary valve 58 is switched to connect the suction port 12 b of the compressor 12 to the expansion space 34. Thus, the exhaust process of the cooling operation is started. For example, the rotary valve 58 as an exhaust valve is opened between 300 ° and 360 ° (−60 ° and 0 °). In the illustrated example, the exhaust start timing in the cooling operation is set to a phase of about 310 °, for example.

  At this time, the high-pressure gas in the expansion space 34 is expanded and cooled. The expanded gas enters the regenerator 16 from the expansion space 34 through the displacer lower lid gas flow path 68. The gas is cooled while passing through the regenerator 16. The gas returns from the regenerator 16 to the compressor 12 through the housing gas flow path 64, the rotary valve 58, and the low pressure gas chamber 37. While the gas flows out of the expansion space 34, the displacer 24 moves downward in the axial direction in the cylinder 28 from the top dead center to the bottom dead center. Thereby, the volume of the expansion space 34 is reduced, and the low pressure gas is discharged from the expansion space 34. Prior to the displacer 24 reaching bottom dead center, for example, between 120 ° and 180 °, or between 120 ° and 150 °, the rotary valve 58 as the exhaust valve is closed, and the exhaust process is performed. finish. In the illustrated example, the exhaust end timing in the cooling operation is set to a phase of about 130 ° to 135 °, for example.

  Prior to the displacer 24 reaching the bottom dead center, the rotary valve 58 is switched to connect the discharge port 12a of the compressor 12 to the expansion space 34. Thus, the intake step of the cooling operation is started. Between the end of the exhaust process and the arrival at the bottom dead center of the displacer 24, the rotary valve 58 as an intake valve is opened. In the illustrated example, the intake start timing in the cooling operation is set to a phase of about 145 °, for example.

  The high-pressure gas enters the regenerator high temperature section 16 a from the rotary valve 58 through the housing gas flow path 64, the upper space 36, and the displacer upper lid gas flow path 66. The gas is cooled while passing through the regenerator 16, and enters the expansion space 34 from the regenerator low temperature portion 16 b through the displacer lower lid gas flow path 68. While the gas flows into the expansion space 34, the displacer 24 moves axially upward in the cylinder 28 from the bottom dead center to the top dead center. Thereby, the volume of the expansion space 34 is increased. Thus, the expansion space 34 is filled with high-pressure gas. Prior to the displacer 24 reaching top dead center, for example, between 270 ° and 360 °, or between 270 ° and 300 °, the rotary valve 58 as the intake valve is closed, and the intake process is performed. finish. When the intake process ends, the exhaust process starts again. In the illustrated example, the intake end timing in the cooling operation is set to a phase of about 285 °, for example.

  The above is one refrigeration cycle in the cryogenic refrigerator 10. The cryogenic refrigerator 10 cools the refrigerator stage 32 to a desired temperature by repeating the refrigeration cycle. Therefore, the cryogenic refrigerator 10 can cool the object thermally coupled to the refrigerator stage 32 to a cryogenic temperature.

  FIG. 5 is a diagram illustrating a timing chart of the reverse temperature raising operation of the cryogenic refrigerator 10 according to an embodiment. In FIG. 5, as in FIG. 4, the valve timing of the rotary valve 58 (indicated by a solid line) and the axial position of the displacer 24 (indicated by a one-dot chain line) are measured over one cycle of the axial reciprocation of the displacer 24. Shown in series. The reverse temperature raising operation of the cryogenic refrigerator 10 will be described with reference to FIGS. 1 to 3 and 5.

  In the reverse temperature raising operation, the reverse rotation of the reversible motor 40 causes the crank pin 44 a to idle along the engagement groove 77 of the rotor valve member 60 and engage with the end 77 b of the engagement groove 77. Thereby, the rotor valve member 60 rotates in the reverse direction. Therefore, as described above, the intake / exhaust timing of the rotary valve 58 in the reverse temperature rising operation is different from the intake / exhaust timing of the rotary valve 58 in the cooling operation with respect to the reciprocating motion of the displacer 24.

  Prior to the displacer 24 reaching top dead center, the rotary valve 58 is switched to connect the discharge port 12 a of the compressor 12 to the expansion space 34. Thus, the intake process of the reverse temperature raising operation is started. For example, the rotary valve 58 as the intake valve is opened between 330 ° and 360 °, more specifically, between 350 ° and 360 °, for example. As described above, the phase of the intake start timing of the expansion space 34 during the reverse rotation of the reversible motor 40 advances in the range of greater than 0 ° and less than or equal to 10 ° with respect to the top dead center of the displacer 24.

  In the illustrated example, the intake start timing in the reverse temperature rising operation is set to a phase of, for example, about 355 ° to 360 °. In this way, the phase of the intake start timing of the expansion space 34 when the reverse-rotatable motor 40 is reverse may advance in the range of more than 0 ° and 5 ° or less with respect to the top dead center of the displacer 24.

  In the intake process, high-pressure gas flows into the expansion space 34 from the rotary valve 58 through the regenerator 16. While the gas flows into the expansion space 34, the displacer 24 moves axially downward in the cylinder 28 from the top dead center to the bottom dead center. The refrigerant gas in the expansion space 34 is further compressed to a higher pressure, and the temperature rises. Prior to the displacer 24 reaching the bottom dead center, for example, between 120 ° and 180 °, or between 120 ° and 150 °, the rotary valve 58 as the intake valve is closed, and the intake process is performed. finish. In the example shown in the drawing, the intake end timing in the reverse temperature rising operation is set to a phase of, for example, about 130 ° to 135 °.

  Prior to the displacer 24 reaching the bottom dead center, the rotary valve 58 is switched to connect the suction port 12b of the compressor 12 to the expansion space 34. Thus, the exhaust process of the reverse temperature raising operation is started. Between the end of the intake process and the arrival at the bottom dead center of the displacer 24, for example, between 135 ° and 180 °, the rotary valve 58 as the exhaust valve is opened, and the exhaust process is started. As described above, the phase of the exhaust start timing of the expansion space 34 during the reverse rotation of the reversible motor 40 advances in the range from 0 ° to 45 ° with respect to the bottom dead center of the displacer 24. In the illustrated example, the exhaust start timing in the reverse temperature raising operation is set to a phase of, for example, about 145 °.

  In the exhaust process, the working gas is recovered from the expansion space 34 to the compressor 12 via the regenerator 16 and the rotary valve 58. While the gas flows out of the expansion space 34, the displacer 24 moves axially upward in the cylinder 28 from the bottom dead center to the top dead center. The volume of the expansion space 34 is increased and filled with low pressure gas. Prior to the displacer 24 reaching the top dead center, for example, between 300 ° and 360 °, the rotary valve 58 as an exhaust valve is closed, and the exhaust process ends. When the exhaust process ends, the intake process starts again. In the example shown in the figure, the exhaust end timing in the reverse temperature raising operation is set to a phase of about 330 °, for example.

  The above is one heating cycle in the cryogenic refrigerator 10. The cryogenic refrigerator 10 can heat the refrigerator stage 32 to a desired temperature by the compression heat of the working gas by repeating the heating cycle.

  According to the present embodiment, the phase of the intake start timing of the expansion space 34 during the reverse rotation of the reversible motor 40 advances in the range of greater than 0 ° and less than or equal to 10 ° with respect to the top dead center of the displacer 24. Thereby, the temperature increase efficiency of the reverse temperature increase in the cryogenic refrigerator 10 can be improved. The refrigerator stage 32 can be heated from extremely low temperature to room temperature in a shorter time.

  Here, as a first comparative example, the phase of the intake start timing of the expansion space 34 during the reverse rotation of the reversible motor 40 coincides with the top dead center of the displacer 24 or is somewhat delayed from the top dead center of the displacer 24. Think if you are.

  According to the experiment result by the present inventor, in the example in which the phase of the intake start timing is advanced by about 5 ° with respect to the top dead center of the displacer 24, the temperature increase from 100K to 300K of the refrigerator stage 32 is about 42 minutes. Completed with. On the other hand, in the first comparative example in which the phase of the intake start timing is delayed by about 5 ° with respect to the top dead center of the displacer 24, other conditions are the same as those in the example, and from 100K of the refrigerator stage 32. It took about 50 minutes to raise the temperature to 300K. In the first comparative example, the temperature raising time is about 20% longer than that of the example.

  According to the inventor's consideration, the temperature increase efficiency of the example is higher than that of the first comparative example mainly for the following two reasons.

  First, due to the pressure loss experienced when the working gas flows into the expansion space 34, the temperature increase efficiency is inferior in the first comparative example compared to the example. The main cause of pressure loss is due to the working gas flowing through the regenerator 16. It takes some time for the working gas to flow from the upper space 36 through the regenerator 16 to the expansion space 34. Therefore, the timing at which the working gas actually flows into the expansion space 34 is slightly delayed from the intake start timing at which the rotary valve 58 as the intake valve opens. Also during this delay, the displacer 24 moves down and the expansion space 34 becomes narrower. As the expansion space 34 becomes narrower, the generated heat of compression becomes smaller and the temperature raising efficiency also decreases.

  On the other hand, according to the embodiment, the intake start timing precedes the top dead center of the displacer 24 in the range of 0 ° to 10 °. While the displacer 24 is moving upward toward the top dead center, the intake process is started, and the pressurization of the expansion space 34 can be completed when the displacer 24 is located at or near the top dead center. Therefore, in the embodiment, the expansion space 34 is wider than in the first comparative example. Therefore, the generated heat of compression is increased and the temperature raising efficiency is improved.

  Second, due to the relative speed of the working gas and the displacer 24, the temperature increase efficiency is inferior in the first comparative example as compared to the example. In the intake process, the working gas flows downward from the upper space 36 to the expansion space 34. In the first comparative example, since the displacer 24 has already moved down at the intake start timing, the relative speed between the working gas and the displacer 24 becomes relatively small. Therefore, the time for the working gas and the regenerator 16 to contact with each other becomes longer, and the heat exchange between the working gas and the regenerator 16 is promoted. The working gas is cooled by the regenerator 16, and as a result, the temperature of the working gas flowing into the expansion space 34 is lowered. This is also a factor for delaying the temperature rise of the refrigerator stage 32.

  In contrast, according to the embodiment, as described above, the intake start timing precedes the top dead center of the displacer 24 in the range of 0 ° to 10 ° and the displacer 24 is directed toward the top dead center. The intake process is started during the upward movement. Therefore, the direction of the working gas flow and the moving direction of the displacer 24 are opposite to each other at the intake start timing, and the relative speed between the working gas and the displacer 24 is significantly larger than that in the first comparative example. Therefore, in the embodiment, compared with the first comparative example, heat exchange between the working gas and the regenerator 16 is suppressed, the temperature of the working gas flowing into the expansion space 34 is increased, and the temperature rise of the refrigerator stage 32 is promoted. The

  As another advantage, according to this embodiment, the load of the reversible motor 40 caused by the working gas flowing through the displacer 24 can be reduced. As described above, the phase of the intake start timing of the expansion space 34 during the reverse rotation of the reversible motor 40 advances in the range of greater than 0 ° and less than or equal to 10 ° with respect to the top dead center of the displacer 24.

  The pressure change in the cylinder 28 is greatest immediately after the intake start timing. The axial reaction force acting on the displacer 24 due to this pressure change also becomes maximum immediately after the intake start timing. When the displacer 24 is positioned near top dead center, the crank pin 44a passes through the approximately 12 o'clock position in counterclockwise rotation. At this time, the moving direction of the crank pin 44 a is substantially orthogonal to the axial direction of the displacer 24. The axial reaction force acting on the displacer 24 has little or no negligible component in the moving direction of the crank pin 44a. Therefore, the load on the reversible motor 40 is significantly reduced and is advantageous.

  On the other hand, for example, consider a case where the intake start timing precedes the top dead center of the displacer 24 by 70 ° or more. In this case, the intake start timing may coincide with the timing at which the crank pin 44a passes through the approximately 3 o'clock position in the counterclockwise rotation. At this time, the moving direction of the crank pin 44a is upward in the axial direction. A downward force in the axial direction acts on the displacer 24 due to a change in gas pressure at the start of intake. Almost all of this force becomes a component opposite to the direction of movement of the crank pin 44a, so that the motor load is significantly increased and a large motor capable of generating a large driving torque may be required.

  Further, according to the present embodiment, the phase of the exhaust start timing of the expansion space 34 during the reverse rotation of the reversible motor 40 advances in the range of 0 ° to 45 ° with respect to the bottom dead center of the displacer 24. . If it does in this way, it will become easy to design the rotary valve 58 so that the refrigerating performance of the cryogenic refrigerator 10 and the temperature increase efficiency of reverse temperature increase may be compatible.

  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 the above, the embodiment has been described with reference to a single-stage GM refrigerator. The present invention is not limited to this, and the working gas flow path configuration according to the embodiment is applied to a two-stage or multi-stage GM refrigerator or other cryogenic refrigerator that drives a reciprocating motion of a displacer by a motor. Is possible.

  10 cryogenic refrigerator, 24 displacer, 28 cylinder, 32 refrigerator stage, 34 expansion space, 40 reversible motor, 58 rotary valve.

Claims (2)

Reversible motor,
A displacer that reciprocates in the axial direction by forward rotation and reverse rotation of the reversible motor;
A cylinder for housing the displacer, the cylinder defining an expansion space between the displacer and having a maximum volume at a displacer top dead center and a minimum volume at a displacer bottom dead center;
A refrigerator stage thermally coupled to the expansion space;
The expansion space is synchronized with the axial reciprocation of the displacer so that the refrigerator stage is cooled when the reversible motor rotates forward and the refrigerator stage is heated when the reverse motor rotates backward. A rotary valve that switches between intake and exhaust,
When one cycle of the reciprocating motion of the displacer in the axial direction is 360 °, the phase of the intake start timing of the expansion space when the reversible motor is reversely rotated is greater than 0 ° and 10 ° with respect to the top dead center of the displacer. Cryogenic refrigerator characterized by advancing in the range below °.   2. The phase of exhaust start timing of the expansion space during reverse rotation of the reversible motor is advanced in a range from 0 ° to 45 ° with respect to the displacer bottom dead center. The cryogenic refrigerator described.

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