Cryogenic refrigerator

Patent metadata

Field	Value
Publication number	US-9829218-B2
Application number	US-201615221726-A
Country	US
Kind code	B2
Filing date	Jul 28, 2016
Priority date	Sep 28, 2011
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A cryogenic refrigerator includes a cylinder, a displacer configured to be moved back and forth in the cylinder by a drive unit, an inlet valve configured to be opened in supplying a refrigerant gas into the cylinder, an exhaust valve configured to be opened in exhausting the refrigerant gas from the cylinder, and an expansion space formed in the cylinder and configured to generate a cooling by expanding the refrigerant gas caused by back and forth movement of the displacer. A moving speed of the displacer in the vicinity of a bottom dead center is set to be faster than the moving speed of the displacer in the vicinity of a top dead center.

First claim

What is claimed is:

1. A Gifford-McMahon refrigerator comprising:
a compressor having an inlet and an outlet;
a cylinder;
a displacer provided in the cylinder, the displacer defining a room temperature chamber between a top wall of the cylinder and a top surface of the displacer and an expansion space between a bottom wall of the cylinder and a bottom surface of the displacer, wherein the expansion space is surrounded by a cooling stage and is configured to generate a cooling by expanding a refrigerant gas caused by back and forth movement of the displacer;
a drive unit configured to move the displacer back and forth in the cylinder;
an inlet valve provided in a first flow passage connecting the outlet of the compressor with the room temperature chamber and configured to be opened in supplying the refrigerant gas to the room temperature chamber; and
an exhaust valve provided in a second flow passage connecting the inlet of the compressor with the room temperature chamber and configured to be opened in returning the refrigerant gas from the room temperature chamber to the compressor,
wherein the drive unit includes
a drive chamber to allow a driver gas for driving the displacer,
a high-pressure valve provided in a supply pipe connecting the outlet of the compressor with the drive chamber and configured to supply the driver gas to the drive chamber by being opened, and
a low-pressure valve provided in a return pipe connecting the inlet of the compressor with the drive chamber and configured to return the driver gas from the drive chamber to the compressor, and
wherein a first period of time when the low-pressure valve is opened is set longer than a second period of time when the high-pressure valve is opened.

2. The Gifford-McMahon refrigerator as claimed in claim 1 , wherein the low-pressure valve is opened after the inlet valve is opened and is closed after the inlet valve is closed.

3. The Gifford-McMahon refrigerator as claimed in claim 2 , wherein the exhaust valve is opened after the inlet valve is closed, and the low-pressure valve is closed before the exhaust valve is closed.

4. The Gifford-McMahon refrigerator as claimed in claim 1 , wherein the high-pressure valve is opened after the exhaust valve is opened, and is closed after the exhaust valve is closed.

5. The Gifford-McMahon refrigerator as claimed in claim 4 , wherein the inlet valve is opened after the exhaust valve is closed, and the high-pressure valve is closed before the inlet valve is closed.

6. The Gifford-McMahon refrigerator as claimed in claim 1 , further comprising:
a drive piston integrally formed with the displacer at a high-temperature end of the displacer, the drive chamber being formed between a high-temperature end of the cylinder and the drive piston; and
a sealing member provided between the high-temperature end of the cylinder and the drive piston, the sealing member forming the drive chamber and hermetically separating the drive chamber from the room temperature chamber.

7. The Gifford-McMahon refrigerator as claimed in claim 1 , wherein a flow passage resistance is provided between the high-pressure valve and the drive chamber.

8. A method of operating a Gifford-McMahon refrigerator, the Gifford-McMahon refrigerator including:
a compressor having an inlet and an outlet;
a cylinder;
a displacer provided in the cylinder, the displacer defining a room temperature chamber between a top wall of the cylinder and a top surface of the displacer and an expansion space between a bottom wall of the cylinder and a bottom surface of the displacer, wherein the expansion space is surrounded by a cooling stage and is configured to generate a cooling by expanding a refrigerant gas caused by back and forth movement of the displacer;
a drive unit configured to move the displacer back and forth in the cylinder;
an inlet valve provided in a first flow passage connecting the outlet of the compressor with the room temperature chamber and configured to be opened in supplying the refrigerant gas to the room temperature chamber; and
an exhaust valve provided in a second flow passage connecting the inlet of the compressor with the room temperature chamber and configured to be opened in returning the refrigerant gas from the room temperature chamber to the compressor,
wherein the drive unit includes
a drive chamber to allow a driver gas for driving the displacer,
a high-pressure valve provided in a supply pipe connecting the outlet of the compressor with the drive chamber and configured to supply the driver gas to the drive chamber by being opened, and
a low-pressure valve provided in a return pipe connecting the inlet of the compressor with the drive chamber and configured to return the driver gas from the drive chamber to the compressor, the method comprising steps of:
opening the high-pressure valve while closing the low-pressure valve for a first period of time to move the displacer down by setting a first pressure in the room temperature chamber lower than a second pressure in the drive chamber; and
opening the low-pressure valve while closing the high-pressure valve for a second period of time that is longer than the first period of time to move the displacer up by setting the first pressure in the room temperature chamber higher than the second pressure in the drive chamber.

9. The method as claimed in claim 8 , further comprising step of:
opening the inlet valve; and
closing the opened inlet valve,
wherein the step of opening the low-pressure valve while closing the high-pressure valve starts after the step of opening the inlet valve and finishes after the step of closing the opened inlet valve.

10. The method as claimed in claim 9 , further comprising a step of:
opening the exhaust valve; and
closing the opened exhaust valve,
wherein the step of opening the exhaust valve is performed after finishing the step of closing the opened inlet valve, and the step of closing the opened exhaust valve finishes after finishing the step of opening the low-pressure valve while closing the high-pressure valve.

11. The method as claimed in claim 8 , wherein the step of opening the high-pressure valve while closing the low-pressure valve starts between the steps of opening the exhaust valve and closing the opened exhaust valve, and finishes before finishing the step of closing the opened exhaust valve.

12. The method as claimed in claim 11 , wherein the step of opening the inlet valve is performed after finishing the step of closing the opened exhaust valve, and the step of opening the high-pressure valve while closing the low-pressure valve starts before the step of opening the inlet valve.

Assignees

• Sumitomo Heavy Industries

Inventors

• Xu Mingyao

Classifications

• F25B2309/1406

  Pulse-tube cycles with pulse tube in co-axial or concentric geometrical arrangements · CPC title

• F25B9/14 Primary

  characterised by the cycle used, e.g. Stirling cycle · CPC title

• F25B31/00

  Compressor arrangements · CPC title