1. Field of the Invention
The present invention relates to a cryogenic refrigerator including a refrigerant tube comprising two tubes that are arranged on a cooling stage substantially parallel to each other and are in communication with each other through a gas passage formed in the cooling stage. More particularly, the present invention relates to a cryogenic refrigerator suitable for a regenerative type cryogenic refrigerator such as a GM (Gifford-McMahon) type and a pulse tube type, which can effectively reduce vibration of a cooling stage due to oscillating gas pressure and can reduce the size of the cryogenic refrigerator.
2. Description of the Related Art
As a small-sized cryogenic refrigerator applied to a medical MRI diagnostic machine, a cryopump, and the like, a GM cryogenic refrigerator shown in
The GM cryogenic refrigerator 100 shown in
On the other hand, the pulse tube refrigerator 120 shown in
However, the GM cryogenic refrigerator 100 and the pulse tube cryogenic refrigerator 120 that are conventionally known has a problem that pressure oscillation of the gas in the refrigerant tube 110, 130 causes elastic extension and contraction of the refrigerant tube 110, 130, which causes the cooling stage 102, 122 to vibrate. In addition, according to the pulse tube cryogenic refrigerator 120, vibration can be reduced as a whole because it includes no portion mechanically driven, such as the displacer 112 in the GM cryogenic refrigerator 100. However, the pulse tube cryogenic refrigerator 120 is not much different from the GM cryogenic refrigerator 100 in terms of the aforementioned vibration of the cooling stage caused by elastic extension and contraction of the refrigerant tube.
As a solution of the above problem, Publication of Japanese Patent No. 2995144 (Patent Document 2) has proposed a refrigerator including two displacers that are driven in phase or in reversed phase so as to reduce vibration.
This conventionally known refrigerator has a certain effect on reduction of vibration by inertial force because vibration reduction is achieved by forming the cylinder, a connecting member of a cooling portion, and a supporting member to have polygonal shapes so as to increase the mechanical strength. However, there is a limit to reduction of vibration caused by elastic extension and contraction of the refrigerant tube in this refrigerator.
The present invention was made in order to solve the above problems. It is an object of the present invention to provide a cryogenic refrigerator that can effectively reduce vibration of a cooling stage caused by oscillating gas pressure and can reduce its size.
According to the present invention, in a cryogenic refrigerator having a refrigerant tube comprising two tubes that are arranged on a cooling stage substantially parallel to each other and are in communication with each other through a gas passage formed in the cooling stage, a plurality of such refrigerant tubes are provided, and oscillating gas pressures in those refrigerant tubes have phase differences, thereby canceling the vibration of the cooling stage. Thus, the aforementioned problems can be solved.
The tubes of the plurality of respective refrigerant tubes may be arranged at substantially constant intervals along a circumferential direction of the cooling stage in such a manner that the two tubes of each refrigerant tube are located at the farthest positions from each other.
Alternatively, the tubes of the plurality of respective refrigerant tubes may be arranged at substantially constant intervals along the circumferential direction of the cooling stage in such a manner that the two tubes of each refrigerant tube are located at the closest positions to each other.
In a case where N refrigerant tubes are provided and N is an integer larger than one, the phase difference may be set to 360/N degrees.
The two tubes may comprise a regenerator and a pulse tube or may comprise a regenerator and a cylinder accommodating a displacer therein.
Moreover, according to the present invention, in a cryogenic refrigerator having refrigerant tubes each comprising a single cylinder arranged on a cooling stage, N refrigerant tubes are arranged along a circumferential direction of the cooling stage at substantially constant intervals, where N is an integer larger than one, and oscillating gas pressures in the N refrigerant tubes have phase differences of 360/N degrees, thereby solving the aforementioned problems.
According to the cryogenic refrigerator, vibration of the cooling stage caused by the oscillating gas pressure can be effectively reduced and the size reduction can be achieved.
The above and other novel features and advantages of the present invention are described in or will become apparent from the following detailed description of preferred embodiments.
The preferred embodiments will be described with reference to the drawings, wherein like elements have been denoted throughout the figures with like reference numerals, and wherein:
Preferred embodiments of the present invention will be described in detail, with reference to the accompanying drawings.
As shown in the perspective view of
As shown in cross sectional views of
The second refrigerant tube 18 has the same structure as the first refrigerant tube 16. The second refrigerant tube 18 includes a second pulse tube 18A and a second regenerator 18B that are substantially cylindrical and are arranged on the cooling stage 14 to be in substantially parallel to each other. High-temperature ends of the second pulse tube 18A and the second regenerator 18B are secured to the high-temperature end block 12, while low-temperature ends thereof are secured to the cooling stage 14. In addition, the low-temperature ends of the second pulse tube 18A and the second regenerator 18B are in communication with each other through a gas passage 18C formed in the cooling stage 14.
The above four tubes, i.e., the first pulse tube 16A and the first regenerator 16B of the first refrigerant tube 16 and the second pulse tube 18A and the second regenerator 18B of the second refrigerant tube 18 are arranged along the circumferential direction of the cooling stage 14 at substantially constant intervals in such a manner that the first pulse tube 16A and the first regenerator 16B are located at the farthest positions from each other (the same is true for the second pulse tube 18A and the second regenerator 18B). The gas passage 16C of the first refrigerant tube 16 crosses with the gas passage 18C of the second refrigerant tube 18 at two-level crossing around the center of the cooling stage 14.
Next, effects of the cryogenic refrigerator 10 will be described with reference to
As shown in
On the other hand, as shown in
As described above, in the cooling stage 14 of the cryogenic refrigerator 10, the displacement caused by extension and contraction of the first refrigerant tube 16 and that caused by extension and contraction of the second refrigerant tube 18 occur, respectively.
However, the cryogenic refrigerator 10 is arranged in such a manner that the oscillating gas pressure P1 in the first refrigerant tube 16 and the oscillating gas pressure P2 in the second refrigerant tube 18 have a phase difference of 180 degrees therebetween, as shown in
According to the cryogenic refrigerator 10 of this embodiment of the present invention, a plurality of refrigerant tubes are provided in such a manner that oscillating gas pressures therein have phase differences. Thus, the vibration of the cooling stage 14 can be canceled out, resulting in effective reduction of the vibration and the size reduction.
In addition, four tubes, i.e., the first pulse tube 16A and the first regenerator 16B of the first refrigerant tube 16 and the second pulse tube 18A and the second regenerator 18B of the second refrigerator 18 are arranged at substantially constant intervals along the circumferential direction of the cooling stage 14 in such a manner that the first pulse tube 16A and the first regenerator 16B are located at the farthest positions from each other (the same is true for the second pulse tube 18A and the second regenerator 18B). Therefore, the effect of reducing the vibration can be further enhanced.
The degree of the effect of reducing the vibration is varied depending on material for the cooling stage 14, the size thereof, or the like. However, experiments by the inventor of the present application shows, even allowing the cooling stage 14 to be formed of elastic material, the vibration can be reduced to a tenth to a hundredth of the conventional vibration while the size is kept within a practical range.
The size and the structure of the cryogenic refrigerator of the present invention is not limited to those of the cryogenic refrigerator 10 in the above embodiment. The cryogenic refrigerator of the present invention can have various structure, as long as it includes a plurality of refrigerant tubes which have oscillating gas pressures with phases differences therebetween in such a manner that those phase differences act to cancel the vibration of the cooling stage.
Therefore, as shown in
Moreover, the cryogenic refrigerator of the present invention may include three or more refrigerant tubes. For example, as shown in
In the above embodiments, each of the first and second refrigerant tubes 16 and 18 is formed by the pulse tube and the regenerator. However, the present invention is not limited thereto. Each refrigerant tube may be formed by the regenerator and a cylinder accommodating the displacer therein, for example.
Moreover, the present invention can be applied to a cryogenic refrigerator including a cylinder (refrigerant tube) 36 in which a displacer 34 incorporating a regenerator 32 therein is arranged to reciprocate within the cylinder 36. In this case, the same effects as those mentioned above can be achieved by providing N cylinders 36 along the circumferential direction of a cooling stage 38 substantially constant intervals and giving oscillating gas pressures in those N cylinders 36 phase differences of 360/N degrees, where N is an integer larger than one. It should be noted that the present invention can also be applied to a multistage cryogenic refrigerator including two or more stages of regenerators.
The disclosure of Japanese Patent Application No. 2003-165908 filed on Jun. 11, 2003 including specification, drawings, and claims is incorporated herein by reference in its entirety.
Although only a limited number of the embodiments of the present invention have been described, it should be understood that the present invention is not limited thereto, and various modifications and variations can be made without departing from the spirit and scope of the invention defined in the accompanying claims.
Number | Date | Country | Kind |
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2003-165908 | Jun 2003 | JP | national |
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6694730 | O'Baid et al. | Feb 2004 | B2 |
Number | Date | Country |
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56-66657 | Jun 1981 | JP |
06-034213 | Feb 1994 | JP |
06-159835 | Jun 1994 | JP |
2002-106993 | Apr 2002 | JP |
2003-148826 | May 2003 | JP |
Number | Date | Country | |
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20050028534 A1 | Feb 2005 | US |