Patent Application
20070157632
1. Field of the Invention
The present invention generally relates to pulse tube cryogenic coolers. More particularly, the present invention relates to a pulse tube cryogenic cooler wherein a heat exchanger is provided at an end part of a pulse tube.
2. Description of the Related Art
Generally, a pulse tube cryogenic cooler consisted of a pressure vibration generating device, a regenerator, a pulse tube, a phase control mechanism, and others. Such a pulse tube cryogenic cooler is quieter than a Gifford McMahon (GM) cryogenic cooler or a Stirling type cryogenic cooler. Therefore, application of the pulse tube cryogenic cooler as a cooling device of various test or analyzing devices such as an electron microscope or a Nuclear Magnetic Resonance (NMR) apparatus has been expected.
Referring to
The high pressure valve 3a and the low pressure valve 3b are switched at a designated cycle. Therefore, helium gas having a high pressure and generated by the helium compressor 1 is supplied to the regenerator 2 at the designated cycle.
Upper ends of the regenerator 2 and the pulse tube 6 are supported by a housing 12. The housing 12 is made of stainless steel.
In addition, lower ends of the regenerator 2 and the pulse tube 6 are connected to each other by a connection path 4. More specifically, a heat exchanger 5b is provided at the lower end of the pulse tube 6. This heat exchanger 5b and a low temperature part 2b of the regenerator 2 are connected by the connection path 4.
Furthermore, a buffer tank 8 is connected to a high temperature end, namely an upper end, of the pulse tube 6 via a heat exchanger 5a and an orifice 7a.
In addition, a bypass path 9 is provided between a pipe connecting the pressure vibration generating device and the regenerator 2 and a pipe connecting the pulse tube 6 and the buffer tank 8. An orifice 7b is provided in this bypass path 9.
The regenerator 2 is filled with a cold storage material such as wire gauze made of copper or stainless. A punching plate made of aluminum or the like or a copper mesh 10 is stacked inside the heat exchangers 5a and 5b as a heat exchanging member. A numerical reference 11 denotes a rectifier.
In the above-discussed pulse tube cryogenic cooler, when the high pressure valve 3a is opened and the low pressure valve 3b is closed so that an operation mode is started, helium gas compressed by the compressor 1 and having high pressure flows into the regenerator 2.
The helium gas flowing into the regenerator 2 is cooled by the cold storage material provided in the regenerator 2 so that the temperature of the helium gas is decreased. The helium gas flows from the low temperature part 2b of the regenerator 2 to the heat exchanger 5b via the connection path 4 so as to be further cooled and flows into the low temperature side of the pulse tube 6.
Gas having low pressure and already existing in the pulse tube 6 is compressed by the operation gas newly flowing in. Therefore, pressure in the pulse tube 6 becomes higher than pressure in the buffer tank 8. Because of this, the operation gas in the pulse tube 6 flows into the buffer tank 8 via the orifice 7a.
When the high pressure valve 3a is closed and the low pressure valve 3b is opened, the operation gas in the pulse tube 6 flows into the low temperature part 2b of the regenerator 2. The operation gas passes an inside of the regenerator 2 and flows from the high temperature part 2a to the compressor 1 via the low pressure valve 3b.
As discussed above, the high temperature end of the pulse tube 5a and the high temperature part 2a of the regenerator 2 are connected by the bypass path 9 having the orifice 7b. Because of this, the phase of pressure change and the phase of volume change of the operation gas occur with a constant phase difference.
Due to the phase difference, a cold state is generated as the operation gas is expanded at the low temperature end of the pulse tube 6. By repeating the above-discussed steps, the pulse tube cryogenic cooler works as a cryogenic cooler. In the above-discussed double inlet type pulse tube cryogenic cooler, the phase difference can be adjusted by adjusting the orifice 7b provided in the bypass path 9.
In addition, the heat exchanger 5a is provided at the upper end of the pulse tube 6 and the heat exchanger 5b is provided at the lower end of the pulse tube 6 in order to improve cooling efficiency and increase the heat transfer property.
More specifically, as shown in
On the other hand, a structure shown in
A heat exchanging main part 13 is provided in the heat exchanger 5c. The heat exchanging main part 13 has vertical slits 14 and a circular-shaped slit 15. A large number of the vertical slits 14 are formed in upper and lower directions in
The circular-shaped slit 15 is connected to lower end parts of the vertical slits 14 and extends in a horizontal direction in
In the heat exchanger 5c having the above-discussed structure, heat is transferred between helium gas and the heat exchanging main part 13 in a step during which helium gas passes the vertical slits 14 formed in the heat exchanging main part 13.
In the meantime, in order to improve cooling in the pulse tube cryogenic cooler, it is crucial to efficiently take out the cold state generated by adiabatic expansion of the operation gas in the pulse tube 6. Because of this, it is crucial to increase the heat exchanging property in the heat exchanger 5b provided at the low temperature side of the pulse tube 6.
However, in the related art heat exchanger 5b shown in
In addition, in the case of the heat exchanging by using the mesh 10 made of aluminum or copper, the ratio of the heat exchanging area to a dead volume is low and therefore the dead volume is large. Because of this, the heat exchanging property of the heat exchanger 5b is degraded.
On the other hand, in the related art heat exchanger 5c shown in
However, in the heat exchanger 5c shown in
Therefore, a structure of the heat exchanging main part 13 is complicated. Hence, a manufacturing efficiency of the heat exchanging main part 13 is low so that the manufacturing cost is increased.
In addition, a part where cold state is obtained, namely a position thermally connecting to a cooling subject is limited to the lower end of the pulse tube 6. Therefore, there is a limitation to cooling the cooling subject.
Accordingly, embodiments of the present invention may provide a novel and useful pulse tube cryogenic cooler, in which one or more of the problems described above are eliminated.
More specifically, the embodiments of the present invention may provide a pulse tube cryogenic cooler having a heat exchanger whereby high heat exchanger effectiveness can be achieved and cost can be saved.
The embodiments of the present invention may also provide a pulse tube cryogenic cooler, including:
a pressure vibration generating device configured to generate pressure vibration in operation gas;
a regenerator connected to the pressure vibration generating device;
a pulse tube connected to the regenerator; and
a phase control mechanism connected to the pulse tube;
wherein a heat exchanger is provided at a part where the regenerator and the pulse tube are connected.
According to the above-mentioned pulse tube cryogenic cooler of the embodiments of the present invention, it is possible to improve heat exchanger effectiveness of the heat exchanger and make a cooling process area wide. Accordingly, it is possible to improve usability of the pulse tube cryogenic cooler.
Other objects, features, and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
A description will now be given, with reference to
First, the two-stage double inlet type pulse tube cryogenic cooler 20A of the embodiment of the present invention is discussed with reference to
The pulse tube cryogenic cooler 20A is a two-stage type and therefore has a first stage regenerator 22A and a second stage regenerator 22B as regenerators. In addition, the pulse tube cryogenic cooler 20A has a first stage pulse tube 26A and a second stage pulse tube 26B as pulse tubes.
A high temperature part 30a of the first stage regenerator 22A, an upper end of the first stage pulse tube 26A, and an upper end of the second stage pulse tube 26B are supported by a flange 32.
The first stage regenerator 22A and the second stage regenerator 22B are directly connected to each other. In other words, a low temperature part 30b of the first stage regenerator 22A is connected to a high temperature part 31a of the second stage regenerator 22B.
In addition, the low temperature part 30b of the first stage regenerator 22A and the lower end of the first stage pulse tube 26A are connected by a connection path 24A. Furthermore, a low temperature part 31b of the second stage regenerator 22B and the lower end of the second stage pulse tube 26B are connected by a second connection path 24B.
Furthermore, a helium compressor 21, a high pressure valve 23a and a low pressure valve 23b form a pressure vibration generating device. The high pressure valve 23a is provided at an output side of high pressure gas of the helium compressor 21. The low pressure valve 23b is provided at a gas receiving side of the helium compressor 21.
This pressure vibration generating device is connected to the high temperature part 30a of the first stage regenerator 22A. The high pressure valve 23a and the low pressure valve 23b are switched at a designated cycle.
Therefore, operation gas, helium gas in this embodiment, having a high pressure and generated by the helium compressor 21 is supplied to the first stage regenerator 22A at the designated cycle.
A high temperature end (upper end) of the first stage pulse tube 26A and a first stage buffer tank 28A are connected by a pipe 35b. An orifice 27a is provided at the pipe 35b.
In addition, a first bypass path 29A is provided between a pipe 35a and the high temperature end of the first pulse tube 26A. The pipe 35a connects the pressure vibration generating device and the first stage regenerator 22A. An orifice 27b is provided at the first bypass path 29A.
On the other hand, a high temperature end (upper end) of the second stage pulse tube 26B and a second stage buffer tank 28B are connected by a pipe 35c. An orifice 27c is provided at the pipe 35c.
In addition, a second bypass path 29B is provided between the pipe 35a and the high temperature end of the second pulse tube 26B. An orifice 27d is provided at the second bypass path 29B.
In the above-discussed pulse tube cryogenic cooler 20A, when the high pressure valve 23a is opened and the low pressure valve 23b is closed so that an operation mode is started, helium gas compressed by the compressor 21 and having high pressure flows into the first stage regenerator 22A via the pipe 35a.
The helium gas flowing into the first stage regenerator 22A is cooled by the cold storage material provided in the first stage regenerator 22A so that the temperature of the helium gas is decreased. A part of the helium gas flows from the low temperature part 30b of the first stage regenerator 22A to the lower temperature end (lower end) of the first stage pulse tube 26A via the connection path 24A.
Helium gas having a low pressure and already existing in the first stage pulse tube 26A is compressed by the operation gas newly flowing in. Therefore, the pressure in the first stage pulse tube 26A becomes higher than the pressure in the first stage buffer tank 28A.
Because of this, the helium gas in the first stage pulse tube 26A flows into the first stage buffer tank 28A via the orifice 27a.
When the high pressure valve 23a is closed and the low pressure valve 23b is opened, the helium gas in the first stage pulse tube 26A flows in the low temperature part of the first stage regenerator 22A. The helium gas passes inside of the first stage regenerator 22A and flows from the high temperature part 30a to the compressor 21 via the low pressure valve 23b.
As discussed above, the high temperature end of the first stage pulse tube 26A and the pipe 35a are connected by the first bypass path 29A having the orifice 27b.
Because of this, the phase of pressure change and the phase of volume change of the operation gas occur with a constant phase difference. Due to the phase difference, a cold state is generated as the helium gas is expanded at the low temperature end (lower end) of the first stage pulse tube 26A.
In the operation mode started by opening the high pressure valve 23a and closing the low pressure valve 23b, helium gas not flowing into the first stage pulse tube 26A in the helium gas flowing from the helium compressor 21 to the first stage regenerator 22A via the pipe 35a flows from the first stage regenerator 22A to the second stage regenerator 22B.
At this time, as discussed above, the helium gas cooled by the first stage pulse tube 26A flows back into the low temperature part 30b of the first stage regenerator 22A. Therefore, the low temperature part 30b is cooled.
Accordingly, the helium gas flowing from the first stage regenerator 22A to the second stage regenerator 22B is cooled by the first stage pulse tube 26A and then flows to the high temperature part 31a of the second stage regenerator 22B.
The helium gas flowing into the second stage regenerator 22B is cooled by the cold storage material provided in the second stage regenerator 22B so that temperature of the helium gas is further decreased and the helium gas arrives at the low temperature part 31b. Then, the helium gas passes the cooling stage member 50 and flows into the lower temperature end (lower end) of the second stage pulse tube 26B.
Helium gas having a low pressure and already existing in the second stage pulse tube 26B is compressed by the helium gas newly flowing in. Therefore, the pressure in the second stage pulse tube 26B becomes higher than the pressure in the second stage buffer tank 28B.
Because of this, the helium gas in the second stage pulse tube 26B flows into the second stage buffer tank 28B via the orifice 27c.
When the high pressure valve 23a is closed and the low pressure valve 23b is opened, the helium gas in the second stage pulse tube 26B flows back into the low temperature part 31b of the second stage regenerator 22B. The helium gas flowing into the low temperature part 30b of the second stage regenerator 22B further passes inside of the first stage regenerator 22A and flows from the high temperature part 30a to the compressor 21 via the low pressure valve 23b.
In addition, as discussed above, the high temperature end of the second stage pulse tube 26B and the pipe 35a are connected by the second bypass path 29B having the orifice 27d.
Because of this, even in the second stage pulse tube 26B, the phase of pressure change and the phase of volume change of the helium gas (the operation gas) occur with a constant phase difference. Due to the phase difference, a cold state as the helium gas is expanded at the low temperature end (lower end) of the second stage pulse tube 26B is generated.
In the above-discussed two-stage double inlet type pulse tube cryogenic cooler 20A shown in
In addition, the helium gas cooled by the first stage regenerator 22A and the first stage pulse tube 26A is further cooled by the second regenerator 22B and the second stage pulse tube 26B. Therefore, the temperature at the cooling side of the second stage pulse tube 26B can be a cryogenic temperature, for example at 4 K (Kelvin).
Next, a two-stage four-valve type pulse tube cryogenic cooler 20B is discussed with reference to
Referring to
The pipe 35d connected to the first stage pulse tube 26A is connected to a supplying side (a high pressure side) of a helium compressor 21 via an orifice 27e and a high pressure valve 33a. In addition, the pipe 35g connected to the second stage pulse tube 26B is connected to the supplying side (the high pressure side) of the helium compressor 21 via an orifice 27f and a high pressure valve 34a.
Furthermore, the pipe 35e connected to the high temperature end of the first stage pulse tube 26A is connected to the gas receiving side (the low pressure side) of the helium compressor 21 via the orifice 27b and the low pressure valve 33b. In addition, the pipe 35f connected to the high temperature end of the second stage pulse tube 26B is connected to a gas receiving side (the low pressure side) of the helium compressor 21 via the orifice 27d and the low pressure valve 34b.
Thus, in the two-stage four-valve type pulse tube cryogenic cooler 20B, the pipes 35d and 35g connected to the high pressure side of the helium compressor 21 and the pipes 35e and 35f connected to the low pressure side of the helium compressor 21 are connected to the high temperature ends of the pulse tubes 26A and 26B, respectively.
In addition, the orifices 27b, 27d, 27e, and 27f, the high pressure valves 33a and 34a, and the low pressure valves 33b and 34b are provided at the pipes 35d through 35g. Therefore, flow of the helium gas in the pipes 35d through 35g can be controlled.
In the two-stage four-valve type pulse tube cryogenic cooler 20B shown in
By adjusting the orifices 27b, 27d, 27e, and 27f and the valves 33a, 33b, 34a, and 34b, it is possible to adjust the phase of pressure change and the phase of volume change of the helium gas (the operation gas) between the first stage regenerator 22A and the first stage pulse tube 26A, and the phase of pressure change and the phase of volume change of the helium gas between the second stage regenerator 22B and the second stage pulse tube 26B, with a constant phase difference. As a result of this, it is possible to perform highly efficient cooling by the pulse tubes 26A and 26B.
Next, the cooling stage member 50 of the embodiment of the present invention is discussed.
As discussed above, the cooling stage member 50 connects the low temperature part 31b of the second stage regenerator 22B and the lower end of the second stage pulse tube 26B.
The cooling stage main body 51 and the lid 52 are made of materials having high coefficients of thermal conductivity such as copper. The cooling stage main body 51 is a disk-shaped member. The lid 52 is provided so as to cover the cooling stage main body 51.
Plural slits 53 are formed in the cooling stage main body 51. In this example, the slits 53 are formed as linear grooves.
On the other hand, a cooling tube connection hole 54 and a pulse tube connection hole 55 are formed in the lid 52. The second stage regenerator 22B is connected into the cooling tube connection hole 54. The low temperature end of the second stage pulse tube 26B is connected to the pulse tube connection hole 55.
Where the lid 52 is attached to the cooling stage main body 51, the cooling tube connection hole 54 and the pulse tube connection hole 55 face the slits 53.
Accordingly, as seen in plan view in
In addition, a part of the top surface of the cooling stage main body 51 where the slits 53 are not formed comes in contact with an inside surface of the lid 52 when the lid 52 is attached to and seals the cooling stage main body 51
As long as the cooling stage main body 51 and the lid 52 come in contact with each other so as to be sealed, there is no limitation in a way of connection between the cooling stage main body 51 and the lid 52.
As discussed above, in the operation mode, helium gas flows in both directions between the second stage regenerator 22B and the second stage pulse tube 26B. In this example, the helium gas passes through the slits 53 formed in the cooling stage main body 51 so as to flows between the second stage regenerator 22B and the second stage pulse tube 26B.
In other words, the slits 53 work as flow paths where helium gas flows between the second stage regenerator 22B and the second stage pulse tube 26B.
Referring to
In addition, from the points of view of process-ability and heat exchangeability (discussed below) of the slit 53, it is preferable that the width W of the slit 53 be equal to or greater than approximately 0.15 mm and equal to or less than approximately 0.50 mm and height H of the slit 53 be equal to approximately 4.5 mm.
As a method for processing this slit 53, an etching method or the like may be applied. However, it is preferable to apply a wire cutting method. In a case where the wire cutting method is applied as the method for processing this slit 53, it is possible to form the slits (grooves) 53 easily and at low cost.
The cooling stage 50 having the structure discussed above, as shown in
Accordingly, the low temperature part 31b of the second stage regenerator 22B and the low temperature end of the second stage pulse tube 26B are connected by the cooling stage member 50. More specifically, helium gas passes through the slits 53 formed in the cooling stage member 50 and flows between the second stage regenerator 22B and the second stage pulse tube 26b.
As shown in
Because of this, heat exchange effectiveness between the operation gas and the stage member can be improved so that the stage member can be cooled efficiently.
Thus, in this example unlike the related art shown in
Because of this, it is possible to heighten freedom of design of the cooling stage member 50, make a space where heat exchanging is increased, and improve cooling efficiency.
In addition, as compared with a structure of the related art where the subject of cooling is cooled at the lower end of the pulse tube 6, cooling process can be implemented in a relatively wide area. Therefore, it is possible to improve usability of the pulse tube cryogenic coolers 20A and 20B.
Furthermore, in this example, the cooling stage member 50 is formed by two members, namely the cooling stage main body 51 and the lid 52. The connection holes 54 and 55 are formed in the lid 52 and the slits 53 are formed in the cooling stage main body 51.
Because of this, as compared to a structure where the slits 53 and the connection holes 54 and 55 are formed in the same member, it is possible to form the slits 53 and the connection holes 54 and 55 easily and at low cost.
In addition, in this example, the slits 53 are formed in the cooling stage main body 51 in a body by using the wire cutting method.
Because of this, as compared to the structure of the related art where the plate member is connected to the stage member by brazing or the like and the slits are formed, it is possible to make heat resistance of the slit 53 low and improve heat exchange effectiveness of the cooling stage member 50 even if the slits 53 are formed.
Meanwhile
In the above-discussed example, linear slits 53 are used as a flow path whereby helium gas flows between the second stage regenerator 22B and the second stage pulse tube 26B. On the other hand, in an example shown in
Thus, slits connecting the second stage regenerator 22B and the second stage pulse tube 26B are not limited to linear slits but may have a curved shape shown in
In addition, in an example shown in
In this structure, the area where the helium gas contacts the piercing member 57 can be made wider so that the heat exchange effectiveness between the helium gas and the piercing member 57 can be further improved.
Thus, according to the above-discussed embodiment of the present invention, it is possible to provide a pulse tube cryogenic cooler, including a pressure vibration generating device configured to generate pressure vibration in operation gas; a regenerator connected to the pressure vibration generating device; a pulse tube connected to the regenerator; and a phase control mechanism connected to the pulse tube; wherein a heat exchanger is provided at a part where the regenerator and the pulse tube are connected.
In the above-mentioned pulse tube cryogenic cooler, the heat exchanger is provided not inside the pulse tube but at the part where the regenerator and the pulse tube are connected. Because of this, it is possible to make a space where heat exchanging takes place wide so that cooling efficiency can be improved.
In addition, it is possible to perform a cooling process in a range relatively wider than the low end part of the pulse tube. Hence, it is possible to improve usability.
In the above mentioned pulse tube cryogenic cooler, the heat exchanger may include a regenerator connection part where the regenerator is connected; a pulse tube connection part where the pulse tube is connected; and a stage member where a plurality of flow paths are formed so as to connect the regenerator connection part and the pulse tube connection part and thereby the operation gas flows between the regenerator connection part and the pulse tube connection part.
In the above-mentioned pulse tube cryogenic cooler, the regenerator connection part and the pulse tube connection part are connected by plural flow paths formed in the stage member
Because of this, when the operation gas flows between the regenerator connection part and the pulse tube connection part, a contact area where the operation gas contacts the stage member can be made wider than that in a case of a single flow path.
Accordingly, it is possible to improve heat exchange effectiveness between the operation gas and the stage member so that the stage member can be cooled efficiently.
In the above-mentioned pulse tube cryogenic cooler, the flow paths may be slits.
Since the slit can be easily formed, it is possible to form the flow path easily and at low cost.
In the above-mentioned pulse tube cryogenic cooler, a lid part configured to cover and seal the stage member may be provided; and the regenerator connection part and the pulse tube connection part may bee provided at the lid part so as to face the slits.
In the above-mentioned pulse tube cryogenic cooler, the regenerator connection part and the pulse tube connection part are provided in the lid part and the slits are formed in the stage member. Because of this, it is possible to separately form the regenerator connection part, the pulse tube connection part, and the slits at the lid part and the stage member which are independent respectively.
Accordingly, as compared to a structure where the regenerator connection part, the pulse tube connection part, and the slits are formed in the same member, it is possible to form the regenerator connection part, the pulse tube connection part, and the slits easily and at low cost.
In the above-mentioned pulse tube cryogenic cooler, the slits may be formed in a body with the stage member.
In the above-mentioned pulse tube cryogenic cooler, as compared to a structure where the plate member is connected to the stage member by brazing or the like and the slits are formed, it is possible to make heat resistance of the slits low.
Therefore, even if the slits are formed, it is possible to improve the heat exchange effectiveness of the heat exchanger.
According to the above-discussed embodiment of the present invention, it is possible to provide a superconducting apparatus including the pulse tube cryogenic cooler discussed above, a cryopump including the pulse tube cryogenic cooler discussed above, a cryogenic measuring and analyzing apparatus including the pulse tube cryogenic cooler discussed above, and a nuclear magnetic resonance apparatus including the pulse tube cryogenic cooler discussed above.
The present invention is not limited to these embodiments, but variations and modifications may be made without departing from the scope of the present invention.
For example, helium gas is used as the operation gas in the above-discussed examples. However, the present invention is not limited to this. For example, nitrogen, hydrogen, or the like may be used as the operation gas.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2005-102743 | Mar 2005 | JP | national |
