Pulse tube refrigerator

Abstract

To improve cooling efficiency of a pulse tube refrigerator, it is found that creating two conditions in the refrigerator, particularly in a regenerator is effective. In a first condition, working fluid in the regenerator should be compressed or expanded without having any displacement thereof, while it should be displaced without compression or expansion in a second condition. In order to realize this idea, a fluid displacement control valve assembly including two relief valves is disposed between a pulse tube and a buffer tank. Each of the relief valves is a normally closed one-way valve, and the valves open in opposite directions to one another when a pressure difference between the pulse tube and the buffer tank reaches a predetermined value, thus allowing the working fluid to be displaced after its compression from the pulse tube to the buffer tank and after its expansion from the buffer tank to the pulse tube. Further, an electro-magnetic valve is installed in parallel with a set of the regenerator and the pulse tube. The electro-magnetic valve is controlled so that it opens or closes in an alternate timing with the fluid displacement control valve assembly, thus making it possible to pressurize the working fluid from both ends of the set of the regenerator and the pulse tube and to bring a cool end portion which cools off an article to be cooled to a neighborhood of a nodal point of a standing wave generated by a compressor.