JP2941109B2 - Pulse tube refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse tube refrigerator which uses a pulse tube and does not require an expansion piston reciprocating at a low temperature.

[0002]

2. Description of the Related Art A Stirling cycle consisting of two isothermal processes and an equal volume process includes a working fluid (helium, argon,
This is a closed cycle device using hydrogen or the like, and has been developed as an external combustion engine or a refrigerator. In a refrigerator using this Stirling cycle, mechanical vibrations generated by reciprocating motion of a long expansion piston having a low temperature are transmitted to a cold head to generate noise in a sensor or the like.
Also, the contact between the outer peripheral surface of the long expansion piston and the inner peripheral surface of the cylinder generates wear powder and contaminates the working fluid and the regenerator. This causes deterioration of the performance of the refrigerator and failure.

In order to solve the above-mentioned disadvantages of the refrigerator using the Stirling cycle, a pulse tube refrigerator (Tatsuo Inoue, Low Temperature Engineering Vol. 26 No.
2 (1991)). In this method, a radiator, a regenerator (cold storage), a cold head, and a pulse tube orifice are connected in series between a compression space and a buffer tank, and a low temperature is generated using a working gas such as helium as a medium. I have.

A characteristic feature of the pulse tube refrigerator is that a cylindrical pulse tube made of metal, ceramic, or a composite material thereof is used. This pulse tube maintains a considerably large temperature gradient during the operation of the refrigerator, and has a heat insulating effect. However, as is known, refrigerators using pulse tubes are not always efficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a means using a combination of a pulse tube and a normal temperature expansion piston in place of the conventionally used pulse tube, orifice and buffer tank. Basically used.

According to the present invention, specifically, a compressed space,
In a pulse tube refrigerator in which a plurality of radiators, regenerators, a cold head, a pulse tube, and a low-temperature generation system having an expansion space are connected in a heat exchange relationship, four pairs are formed by a pair of compression pistons arranged in a horizontally opposed manner. A compression space is formed, and an expansion piston is connected with a phase angle to a crankshaft for operating both compression pistons, and a pair of expansion spaces is formed by the expansion pistons. Provided is a pulse tube refrigerator to be communicated with.

[0008]

[Function] Since two sets of the four compression spaces are connected to each other, a large compression space can be secured, and the volume of the expansion space can be easily set to 6.6 to 30% of the volume of the compression space. Can be.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. The pulse tube refrigerator 1 has a compression space 6 defined in a cylinder 5 by a compression piston 4 reciprocating by a rod 3 connected to a crankshaft 2. Another rod 7 connected to the crankshaft 2 reciprocates the expansion piston 9 in the cylinder 8 to make the volume of the expansion space 10 variable.

The expansion space 10 is kept at a normal temperature, and the crank angle of the rods 3 and 7 is set such that the expansion space 10
Is selected so as to advance with a certain phase difference in the range of 10 to 45 degrees. Preferably, the phase difference is 20-30.
Degree.

The compression space 6 includes a radiator 11, a regenerator 12,
It communicates with the expansion space 10 via the cold head 13 and the pulse tube 14. The regenerator 10 is filled with a regenerator material such as a mesh of stainless steel or bronze, a group of lead of small balls, and rare earths. The portion configured in this manner is referred to as a first heat system.

A second heat system is provided in parallel with the first heat system. In the second heat system, the same components as those in the first heat system are indicated by dashes, and the description thereof is omitted. As is clear from FIG. 1, the regenerator of the second heat system differs from the first heat system in that it has two parts, 12'-1 and 12'-2.

The first heat system and the second heat system include a cold head 13 of the first heat system and both regenerators 12 'of the second heat system.
-1 and 12'-2 are connected in a heat exchange 15 relationship. Such coupling allows the low temperature of the cold head 13 of the first thermal system to be transmitted to the working fluid of the second thermal system, so that a cryogenic temperature can be generated in the second thermal system.

An example of FIG. 2 will be described. The same parts as those in the example shown in FIG. In comparison with FIG. 2 and FIG. 1, in the example of FIG.
In addition to the juxtaposition of 4 'and the juxtaposition of both expansion pistons 9, 9', the pulse tubes 14, 14 'of both heat systems are arranged concentrically, so that the example of FIG. This is different from the example of FIG. However, the basic operation is the same between FIG. 1 and FIG.

FIG. 3 shows an arrangement example of each element in the example of FIG. The regenerator 12 'is centered on the pulse tube 14' of the second heat system.
-1, 12'-2, the regenerator 12 and the pulse tube 14 are grouped into a cylindrical shape in a substantially concentric relationship. As a result, both heat systems can be made compact.

FIG. 4 shows an arrangement example of each element in the example of FIG. Also in this example, the regenerators 12'-1, 12'-2, the pulse tube 14, and the regenerator 12 are arranged in a cylindrical shape concentrically around the pulse tube 14 '. The cold head 13 of the first heat system exchanges heat between the regenerators 12'-1 and 12'-2 of the second heat system. This configuration is effective for compacting both heat systems.

FIGS. 3 and 4 show preferred specific examples of the arrangement of the regenerator and the pulse tube. FIGS. 5 and 6 show specific structures around the crankshaft 2. The two double-acting pistons 4, 4 'are arranged horizontally opposed to each other, and four sets of compression spaces 6,
6, 6 'and 6', one of the compression spaces 6, 6 operating in the same phase is made conductive and the other compression space 6 ', 6' is made conductive.

The expansion piston 9 is the same as the crankcase 1.
6 to form two expansion spaces 10, 10 '. The crank angle of both rods 3, 3 ', 6 is in the range of 10 to 45 degrees. As is clear from FIGS. 5 and 6, the pistons 6, 6 ', 9, 9' and the rods 3, 3 ', 7 can be accommodated in the crankcase 16, and are connected to the compression space and the expansion space. By connecting the tubes to the regenerators and pulse tubes of FIGS. 3 and 4, a compact refrigerator can be constructed.

The phase angles of the compression pistons 4, 4 'and the expansion pistons 9, 9' are set to the same or different angle combinations,
The volume of each compression space and each expansion space may be made variable so as to obtain the expected low temperature in the cold head. This can be changed by selecting the angle of the crank section with respect to the crankshaft.

The examples shown in FIGS. 7 and 8 reciprocate both pistons 4 and 9 using linear motors 17 and 18 instead of the crankshaft 2. Expansion piston 9
Controls the energization of the two linear motors 17 and 18 so as to advance at a phase angle of 10 to 45 degrees with respect to the compression piston 4. A buffer tank 19 is provided at a portion opposite to the compression space 6 via the compression piston 4. Compression space 16
The communication between the control valve 20 and the buffer tank 19 is made by a flexible pipe having a control valve 20 and a filter 21. The control valve 20 and the filter 21 serve to increase the purity of the working fluid by removing impurities in the working fluid and to control the pressure of the working fluid.

In the example shown in FIG. 8, a second buffer tank 22 is constructed by using a convex piston 9a as an expansion piston. The movement of both pistons 4, 9, 9a can be regulated by a position sensor. The examples shown in FIG. 7 or FIG. 8 are juxtaposed, but the cold heads 13 are made common (for example, several cold heads 13 are arranged in a concentric cylindrical shape), so that one large cold head has the same cold and hot temperatures. May be generated. Further, as shown in FIGS. 1 and 2, the cold head 13 may be used as pre-cooling for another low-temperature generation system, and heat exchange may be performed at this portion with another low-temperature generation system.

In each case, the volume of the expansion space is preferably in the range of 6.6-30% of the volume of the compression space.
The required volume of the compression space may be ensured by several compression pistons.

The example shown in FIGS. 7 and 8 is a linear motor 1
The two pistons 4, 9 are operated by using the crankshaft 2 and the electric motor M instead of the linear motors 17, 18, as shown in FIG. May be reciprocated.

In the example shown in FIG. 10, when the expansion work in the expansion space 10 becomes large, the temperature of the expansion space becomes lower than normal temperature (for example, when the freezing temperature is 80K and the expansion work is 50).
If it exceeds W, the temperature of the expansion space drops to about 250K if the heat radiation effect is not sufficient.) It is effective to prevent this. The heat from the compression space 6 is transmitted to the working fluid in the expansion space 10 using the radiator 23 to prevent the temperature of the expansion space 10 from decreasing. The reference numerals shown in FIG. 10 indicate the same parts as those used in other examples.

In order to supply a high-purity working fluid to the compression space 6, a filter 21 may be disposed between the pressurizing valve 24 and the pressure reducing valve 25. As a result, the working fluid from the crankcase is supplied to the compression space 6 as high-purity working fluid via the filter 21 and the pressure control valve 20.

Referring to FIG. In the example shown in FIG. 1, when the refrigerating temperature TE is kept constant at 80 K and the crank angle is increased from 0 ° to 30 °, the coefficient of performance (ratio of refrigerating output to power consumption) becomes 0.01 from 0.01. It rises to .027. At 40K, the maximum coefficient of performance is when the crank angle is 22 degrees. As is clear from FIG. 11, there is an optimum crank angle corresponding to the freezing temperature, but the value is in the range of 20 to 30 degrees.

[0027]

According to the present invention, since the low-temperature movable part is not required, that is, since the expansion piston can be kept at room temperature, manufacture and maintenance become easy, and a plurality of cycles can be performed. The refrigeration output can be adjusted. Practical refrigeration capacity is improved compared with the conventional case.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of the present invention.

FIG. 2 is an explanatory diagram of another example of the present invention.

FIG. 3 is a cross-sectional view showing a specific configuration of an example of the present invention.

FIG. 4 is a cross-sectional view showing a specific configuration of another example of the present invention.

FIG. 5 is a longitudinal sectional view of a crankshaft portion.

FIG. 6 is a cross-sectional view of a crankshaft portion.

FIG. 7 is a sectional view of an example using a linear motor.

FIG. 8 is a cross-sectional view of another example using a linear motor.

FIG. 9 is a plan view of an example in which a crankshaft is applied to the example of FIG.

FIG. 10 is an explanatory diagram showing another example of the present invention.

FIG. 11 is a graph showing a relationship between a crank angle and a coefficient of performance.

[Explanation of symbols]

 2 Crankshaft 3, 3 ', 7, 7' Rod 4, 4 'Compression piston 6, 6' Compression space 9, 9 'Expansion piston 10, 10' Expansion space 12, 12 'Regenerator 13, 13' Cold head 14 , 14 'Pulse tube 17,18 Linear motor 19,20 Puffer tank

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F25B 9/00 311

Claims (2)

(57) [Claims] 1. A pulse tube refrigerator in which a plurality of low-temperature generating systems having a compression space, a radiator, a regenerator, a cold head, a pulse tube, and an expansion space are connected in a heat exchange relationship. Four pairs of compression spaces are created by the pair of compression pistons, and expansion pistons are connected at a phase angle to a crankshaft for operating both compression pistons, and a pair of expansion spaces are formed by the expansion pistons. A pulse tube refrigerator that connects the compression spaces that operate in phase. 2. The pulse tube refrigerator according to claim 1, wherein the crank angle of the expansion piston is advanced by 90 degrees from the compression piston.