Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Reexamination Certificate
2000-09-20
2002-05-21
Capossela, Ronald (Department: 3744)
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
C060S520000
Reexamination Certificate
active
06389819
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Patent Application No. 11(1999)-265702 filed on Sep. 20, 1999, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to a refrigerator. More particularly, the present invention pertains to a pulse tube refrigerator having improved cooling efficiency or cooling power.
BACKGROUND OF THE INVENTION
Recent research and development of a pulse tube refrigerator has led to the development of a supercooling refrigerator. The pulse tube refrigerator provides cooling by using adiabatic expansion of an operating gas in a pulse tube refrigerator.
Various types of pulse tube refrigerators are disclosed in publications concerning cooling technology (e.g., ISTEC Journal, Vol.9, No.3 “Pulse Tube Cryocooler”).
One traditional type of pulse tube refrigerator is shown in FIG.
7
. As shown in
FIG. 7
, this pulse tube refrigerator
81
includes a compressor
82
, a cooling device
83
, a regenerator
84
, a cold head
85
, a pulse tube
86
, a radiator
87
, an orifice
88
, and a buffer tank
89
, which are connected in series. A cooling part
90
is accommodated in a vacuum vessel
81
a and consists of the cooling device
83
, the regenerator
84
, the cold head
85
, the pulse tube
86
and the radiator
87
.
The compressor
82
includes a compression cylinder
91
and a compression piston
92
that is positioned in the compression cylinder
91
for reciprocating movement. A compression chamber
93
is defined between a front surface of the compression piston
92
and the cooling device
83
. The compressor
82
moves by applying a driving force generated by a driving unit such as a motor (not shown in
FIG. 7
) so that the compression piston
92
reciprocates in the compression cylinder
91
. An operating gas in the pulse tube refrigerator
81
is thus compressed and expanded alternately.
Heat generated in the pulse tube refrigerator
81
is conducted to the cooling device
83
and the radiator
87
, and is heat exchanged therein. The heat exchanged by the cooling device
83
is discharged to a coolant flowing in a first cooling path
94
. The heat exchanged by the radiator
87
is discharged to a coolant flowing in a second cooling path
95
.
Regenerative material
96
is located in the regenerator
84
for effecting heat exchange of the operating gas. A plurality of layered mesh screens made of stainless steel or phosphor bronze may be used as the regenerative material
96
. When the operating gas flows from the hot end of the regenerator
84
which is connected with the cooling device
83
to the cold end of the regenerator
84
which is connected to the cold head
85
, the operating gas is cooled by discharging heat to the regenerative material
95
. When the operating gas flows from the cold end of the regenerator
84
to the hot end of the regenerator
84
, the operating gas is heated by absorbing heat from the regenerative material
96
.
The cold head
85
is connected to the cold end of the regenerator
84
. A cooling object attaches with the cold head
85
and the object is cooled.
The pulse tube
86
is connected to the cold head
85
. The pulse tube
85
is a hollow cylindrical tube and is generally made of stainless steel.
The radiator
87
is connected to the buffer tank
89
via the orifice
88
. The buffer tank
89
and the orifice
88
are used as a phase shifter, which adjusts the amount of phase difference between a pressure oscillation and a displacement of the operating gas.
The operation of the pulse tube refrigerator is described below. As the compressor
82
is driven, the compression piston
92
reciprocates in the compression cylinder
93
. When the compression piston
92
moves forward, the operating gas in the compression chamber
93
and the cooling part
90
connected to the compression chamber
93
is compressed and moves from the compression chamber
93
to the cooling part
90
. When the compression piston
92
moves rearward, the operating gas in the compression chamber
93
and the cooling part
90
expands and the operating gas in the cooling part
90
moves from the cooling part
90
to the compression chamber
93
.
By repeating the reciprocating movement of the compression piston
92
in the compression cylinder
91
, the pressure in the pulse tube
86
alternately oscillates from high pressure to low pressure and the operation gas moves reciprocally in the pulse tube
86
. Then, an amount of the phase difference between the pressure oscillation and displacement of the operating gas in the pulse tube
86
is adjusted by the buffer tank
89
and the orifice
88
. Therefore, the operating gas in the pulse tube
83
moves to the hot end side of the pulse tube
86
and is adiabatically compressed at the hot end. After that, it moves to the cold end side of the pulse tube
86
and is adiabatically expanded at the cold end. The heat generated by the substantially adiabatic compression at the hot end of the pulse tube
86
is conducted to the radiator
87
and is heat exchanged. The cold generated by the substantially adiabatic expansion at the cold end of the pulse tube
86
is conducted to the cold head
85
. By repeating the operation described above, cold is generated at the cold head
85
.
The traditional type of pulse tube refrigerator described above is inferior to a Stirling type refrigerator with respect to its cooling power. The Stirling type refrigerator has an expansion piston and the expansion work of the operation gas in the Stirling type refrigerator can be used to move the expansion piston. On the contrary, the traditional pulse tube refrigerator does not utilize the expansion piston. Therefore, the expansion work of the operating gas in the pulse tube refrigerator is changed to heat and the heat is discharged to the atmosphere by the radiator. Because the expansion work of the operating gas in the pulse tube refrigerator cannot be used as the work that contributes to generating the cold, the cooling power of the pulse tube refrigerator is inferior to the cooling power of the Stirling type refrigerator.
A need thus exists for a pulse tube refrigerator having improved cooling power.
SUMMARY OF THE INVENTION
One aspect of the present invention involves a pulse tube refrigerator that includes a series of cooling parts having one end side and an opposite end side, and a pressure oscillation source. Each cooling part is comprised of at least a regenerator, a cold head, and a pulse tube which are connected in series. The pressure oscillation source is connected to one of the cooling parts disposed at one end side of the series.
The expansion work generated in one cooling part can be used as compression work of the other cooling part that is connected to the one cooling part. The compression work of the other cooling part contributes to generate cold. Therefore, the expansion work of the operating gas in one cooling part can be used efficiently for cold generation in the other cooling part, and an improvement of the cooling power can be achieved.
The cooling parts include a first cooling part and a second cooling part. The first cooling part is defined by at least a first regenerator, a first cold head, and a first pulse tube. The first regenerator possesses a hot end and a cold end, and the hot end of the first regenerator is connected to the pressure oscillation source. The first cold head is connected to the cold end of the first regenerator. The first pulse tube has a hot end and a cold end, and the cold end of the first pulse tube is connected to the first cold head. The second cooling part includes at least a second regenerator, a second cold head, and a second pulse tube. The second regenerator has a hot end and a cold end, and the hot end of the second regenerator is connected to the first pulse tube. The second cold head is connected with the cold end of the second regenerator. The second pulse tube has a hot end and a cold end, and the cold end of the second pulse tube is conne
Inoue Tatsuo
Kawano Shin
Nogawa Masafumi
Zhu Shaowei
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Capossela Ronald
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