Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Patent
1993-07-14
1994-11-08
Capossela, Ronald C.
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
60520, F25B 900
Patent
active
053615883
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a cryogenic refrigerator using a Gifford MacMahon (GM) cycle or the like, and more particularly to a cryogenic refrigerator having the function of raising the temperature of a cooling portion in a cryogenic condition to the normal temperature.
For example, in a cryopump using a cryogenic refrigerator utilizing a Gifford MacMahon cycle, for raising the temperature of a cooling portion to the normal temperature, there have heretofore been used a method of introducing dry nitrogen gas into a vacuum vessel and a method of flowing electric current through a heater, provided at the cooling portion, to produce Joule heat by which the temperature is raised; however, either of these methods requires some special equipment, and besides has a problem that a panel temperature does not rise quickly.
Therefore, there has been proposed in U.S. Pat. No. 4,520,630, a method in which a drive motor for a refrigerator is reversely rotated to operate a refrigeration cycle reversely, thereby raising the temperature. This method has a problem that during a temperature-raising mode operation, the phase of a displacer becomes inconsistent with a valve opening-closing timing, so that a sufficient temperature-raising effect can not be obtained.
DISCLOSURE OF THE INVENTION
It is an object of this invention to provide a cryogenic refrigerator using a Gifford MacMahon (GM) cycle, in which the time required for raising the temperature of a cooling portion to the normal temperature can be shortened using a method of reversely operating a refrigeration cycle, without the use of any special equipment for raising the temperature of the cooling portion.
In order to achieve the above object, according to the present invention, there is provided a cryogenic refrigerator of the Gifford MacMahon cycle-type comprising at least one cylinder; at least one displacer which has a regenerator therein and is reciprocally movable within the cylinder; upper and lower empty chambers provided within the cylinder and disposed exteriorly of opposite ends of the displacer, the both empty chambers being communicated with each other via the regenerator within the displacer; a rotary valve device for controlling the flow of refrigerant gas under high pressure into the empty chambers and for controlling the flow of the refrigerant gas under low pressure from the empty chambers; and a reversible motor for rotating the rotary valve device in normal and reverse directions and for controlling the reciprocal movement of the displacer, wherein when the rotary valve device is rotated in the normal direction, the refrigerant gas in the lower empty chamber is subjected to an adiabatic expansion to produce cold, and when the rotary valve device is rotated in the reverse direction, the refrigerant gas in the lower empty chamber is subjected to an adiabatic compression to produce heat; the cryogenic refrigerator being characterized by the provision of means by which the timing of opening and closing of the rotary valve device with respect to the reciprocal movement of the displacer during the rotation in the normal direction is made different from the timing during the rotation in the reverse direction.
In a preferred embodiment of the present invention, the rotary valve device comprises a fixed valve body, and a valve plate rotatably supported in face-to-face contact with the valve body, and the means by which the timing of opening and closing of the rotary valve device with respect to the reciprocal movement of the displacer during the rotation in the normal direction is made different from the timing during the rotation in the reverse direction comprises an engagement groove formed in a rear surface of the valve plate and extending circumferentially over a predetermined angle, and a pin portion provided on a crank driven by the reversible motor and engaged in the engagement groove in the valve plate. Therefore, there is provided a feature that during the rotation of the crank in a normal or a reverse direction, the valve plate
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patent: 4520630 (1985-06-01), Sarcia
patent: 4622823 (1986-11-01), Ishizawa et al.
Asami Hiroshi
Suzuki Mitsuru
Capossela Ronald C.
Sumitomo Heavy Industrie's, Ltd.
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