JPH05215423A - Stirling freezer - Google Patents

Abstract

PURPOSE:To obtain a longlife Stirling freezer in which the number of suspension springs used can be reduced and suspension springs whose spring is thin and whose spring constant is little can be employed. CONSTITUTION:In a Stirling freezer, at least one of a first suspension spring 9 and a second suspension spring 4 is provided with gas springs 16 and 17 forming a resonance system together with the suspension springs 9 and 4. Alternatively, the same effect can be obtained by replacing the gas springs with coil springs 18 and 19 which are provided in the same manner as above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Stirling refrigerator, which is preferably used for cooling an infrared element or liquefying air.

[0002]

2. Description of the Related Art FIG. 3 shows, for example, the document "Progress of a small Stirling cycle cooler for space flight" (Development).
of a small Stirling cycle cooler for spacefligh
t applications) (Author: ST Werrett, GD.
Peskett, G.M. Davey, T. W. Bradshaw and J.
Delderfield, Journal name: Adv. In Cryo-genic Eng.
Vol. 31 pp. (791-799, 1986) is a sectional side view showing a schematic configuration of a conventional Stirling refrigerator. In the figure, 1 is a compressor cylinder, and a compressor piston 2 reciprocates inside the compressor cylinder 1. Reference numeral 3 is a compressor case to which the compressor cylinder 1 is fixed. Reference numerals 4a and 4b denote second suspension springs that support the compressor piston 2 such that the compressor piston 2 can reciprocate without coming into contact with the compressor cylinder 1. Reference numeral 5a is a yoke fixed to the compressor case 3, 5b is a permanent magnet closely attached to the yoke 5a, 5c is a coil fixed to the compressor piston 2, and the yoke 5a, the permanent magnet 5b, and the coil 5c are the compressor piston 2 A linear motor 5 that reciprocates is configured.
The compressor C is composed of these 1 to 5.

Reference numeral 6 is a cold finger which is an expander, 7 is a displacer provided inside the cold finger 6 so as to be swingable in the axial direction, and 8 is the cold finger 6.
It is a cold finger case in which is fixed. Reference numerals 9a and 9b denote first suspension springs that support the displacer 7 so that the displacer 7 can reciprocate without coming into contact with the cold finger 6. Reference numeral 10a is a yoke fixed to the cold finger case 8, 10b is a permanent magnet closely attached to the yoke 10a, 10c is a coil fixed to the displacer 7, and the yoke 10a, the permanent magnet 10b, and the coil 10c reciprocate in the displacer 7. The linear motor 10 is constructed. The operating surface 7a on the left side of the displacer 7 in the drawing forms a boundary with the expansion space 11, and this expansion space 11
Is a first compression space 12 between the working surface 7b on the right side of the displacer 7 and the cold finger case 8, and a second compression space 13 between the working surface 2a on the left side of the drawing of the compressor piston 2 and the compressor case 3. A working space is constituted by a heat storage device 14 provided in the displacer 7, a communication passage 15 formed of a connecting pipe that communicates the first compression space 12 and the second compression space 13, a space inside the communication passage 15, and the like.

FIG. 4 is a diagram schematically showing the shapes of the first and second suspension springs 9a, 9b, 4a, 4b shown in the above-mentioned document, for example. 24 is the compressor piston 2
Or a central hole connected to the displacer 7,
Reference numeral 25 is a fixed end fixed to the compressor case 3 or the cold finger case 8, and 26 is a compressor piston 2
Alternatively, it is a beam that supports the displacer 7,
Is a slit.

Next, the operation of the conventional Stirling refrigerator constructed as above will be described. When an alternating current equal to the resonance frequency of the system is passed through the coil 5c, a Lorentz force periodic in the axial direction acts on the coil 5c due to the interaction between this alternating current and the magnetic field generated by the annular permanent magnet 5b. As a result, the system composed of the compressor piston 2 and the second suspension springs 4a and 4b is brought into resonance, and the compressor piston 2 vibrates in the axial direction. The vibration of the compressor piston 2 causes a periodic pressure change in the working gas enclosed in the working space composed of the expansion space 11, the first compression space 12, the second compression space 13, the communication passage 15, and the heat accumulator 14. .. This pressure fluctuation causes the displacer 7 to generate a periodic alternating vibration force in the axial direction.

In this way, the displacer 7 including the heat accumulator 14 reciprocates axially in the cold finger 6 at the same frequency as the compressor piston 2 but at different phases. A linear motor 10 including a yoke 10a, a permanent magnet 10b and a coil 10c controls the movement of the displacer 7 so that the displacer 7 moves with respect to the compressor piston 2 with a predetermined appropriate stroke and phase difference. When the compressor piston 2 and the displacer 7 move while maintaining an appropriate phase difference, the working gas enclosed in the working space constitutes a thermodynamic cycle known as the "reverse Stirling cycle", and mainly the expansion space 11 Generate cold heat. Regarding the principle of such "reverse Stirling cycle" and its cold heat generation,
For example, the document "Cryocoolers" (Author:
G. Walker, Magazine Names: Plenum Press, New York,
Pp. 177-123, 1983).

The principle will be briefly described below. Second compression space 1 compressed by compressor piston 2
The working gas in 3 has its compression heat cooled while flowing through the communication passage 15, and flows into the first compression space 12 and the heat storage unit 14. The working gas enters the expansion space 11 after being pre-cooled by the cold heat stored in the heat storage unit 14 before the half cycle. And
When most of the working gas enters the expansion space 11, expansion starts and cold heat is generated in the expansion space 11. Working gas is
Next, in the reverse order, the cold heat is discharged to the heat storage unit 14 and returns through the flow path to enter the second working space 13. Then, when most of the working gas returns to the second working space 13, the compression starts again, and the process proceeds to the next cycle. Through the above process, the "reverse Stirling cycle" is completed and cold heat is generated.

[0008]

Since the conventional Stirling refrigerator is constructed as described above, the second suspension spring 4 constituting the resonance system of the compressor piston 2 is formed.
It is necessary that a and 4b support the compressor piston 2 so as not to contact the compressor cylinder 1 and have a predetermined spring constant for the axial movement of the compressor piston 2. The spring constant of the suspension spring is proportional to the cube of the spring thickness, and the generated stress is proportional to the square of the thickness. Usually, if the thickness is set so that the generated stress is equal to or less than the allowable stress value of the spring material, the spring constant becomes very small, so that a very large number of suspension springs are required. If the thickness of the springs is increased and the spring constant per one is increased in order to reduce the number of springs, the stress generated in the springs increases, which causes a problem that the life of the springs is shortened.

The present invention has been made in order to solve the above-mentioned problems of the prior art. It is possible to reduce the number of suspension springs to be used and use a suspension spring having a thin spring and a small spring constant. The purpose is to obtain a Stirling refrigerator with a long life.

[0010]

A Stirling refrigerator according to the present invention comprises at least one of a first suspension spring and a second suspension spring a gas spring which cooperates with the suspension spring to form a resonance system. It is configured as follows.

In a Stirling refrigerator according to another invention of the present invention, at least one of the first suspension spring and the second suspension spring is provided with a coil spring that cooperates with the suspension spring to form a resonance system. It is composed.

[0012]

The gas spring of the present invention operates by forming a resonance system with the displacer or the compressor piston, thereby eliminating the need to increase the axial spring constant of the first or second suspension spring, and thus the suspension spring. The thickness of the suspension spring can be reduced, and the stress generated in the suspension spring can be reduced.

[0013]

【Example】

Example 1. FIG. 1 is a sectional view showing a Stirling refrigerator according to an embodiment of the present invention. In the figure, 16 is a gas spring provided on the compressor C side.
Is a compressor gas spring piston 16a, a compressor gas spring cylinder 16b, and a compressor gas spring chamber 16c composed of the compressor gas spring piston 16a and the compressor gas spring cylinder 16b. It is configured. Reference numeral 17 denotes a gas spring provided on the side of the displacer 7, which includes a displacer gas spring piston 17a, a displacer gas spring cylinder 17b, a displacer gas spring piston 17a and a displacer gas spring cylinder 17b which are connected to and interlock with the displacer 7. It is composed of a spring chamber 17c and the like. The suspension spring 4 is thinner than the conventional one and has a small spring constant.
The other reference numerals are the same as those in the above-mentioned conventional device, and thus the description thereof is omitted.

The operation of this embodiment will be described below.
The spring constant Kcg obtained in the compressor gas spring chamber 16c, which is composed of the compressor gas spring piston 16a and the compressor gas spring cylinder 16b, is assumed to be the adiabatic change of the ideal gas. It is expressed by the following equation.

Kcg = Pog · k · Acg / Vog Acg: Compressor gas spring piston cross-sectional area Pog: Compressor gas spring chamber average gas pressure Vog: Compressor gas spring chamber average volume k: Specific heat ratio (= Cp / Cv) Cp: Constant pressure specific heat Cv: Constant volume specific heat

The compressor piston 2 is operated by forming a resonance system with a spring having a predetermined spring constant Kc at the operating frequency of the Stirling refrigerator. When, for example, the compressor gas spring chamber average volume Vog is adjusted so that the compressor gas spring constant Kcg becomes equal to a predetermined spring constant Kc, the compressor piston 2 forms a resonance system at the operating frequency of the Stirling refrigerator,
It is operated by vibrating efficiently. Similarly, a displacer gas spring chamber 17c composed of a displacer gas spring piston 17a and a displacer gas spring cylinder 17b.
The spring constant Kdg obtained by the equation (3) is expressed by the following equation with respect to a slight change of the displacer, assuming an adiabatic change of the ideal gas.

Kdg = Pod · k · Adg / Vod Adg: Displacer gas spring piston cross-sectional area Pod: Displacer gas spring chamber average gas pressure Vod: Displacer gas spring chamber average volume

The displacer 7 is operated by forming a resonance system with a spring having a predetermined spring constant Kd at the operating frequency of the Stirling refrigerator. Displacer gas spring constant K
If, for example, the displacer gas spring chamber average volume Vod is adjusted so that dg becomes equal to a predetermined spring constant Kd, the displacer 7 constitutes a resonance system at the operating frequency of the Stirling refrigerator and is efficiently vibrated and operated. .. The Stirling refrigerator of the above-mentioned embodiment is operated as described above and generates cold heat in the expansion space 11 according to the same principle as the conventional one.

In the above embodiment, the displacer and the compressor piston are operated by forming a resonance system with the displacer gas spring and the compressor piston gas spring, respectively. Therefore, since it is not necessary to increase the axial spring constant of the suspension spring, it is possible to reduce the thickness of the suspension spring, so that the stress generated in the suspension spring can be reduced and the life of the suspension spring can be extended. Therefore, it is possible to obtain the effect that the Stirling refrigerator also has a long life.

Example 2. FIG. 2 is a sectional view showing a Stirling refrigerator according to another embodiment of the present invention.
In the figure, 18 is a coil spring provided between the displacer 7 and the cold finger case 8, and this coil spring 18 constitutes a resonance system with the displacer 7. A coil spring 19 is interposed between the compressor piston 1 and the compressor case 3, and the coil spring 19 constitutes a resonance system with the compressor piston 1.

In the Stirling refrigerator of this embodiment, the gas springs 16 and 17 in the first embodiment are replaced by coil springs 18,
In this embodiment, the same effect as in the first embodiment can be obtained.

Although the gas spring or the coil spring is provided in both the compressor C and the displacer 7 in the first and second embodiments, the present invention is not limited to this, and either the compressor or the displacer 7 is provided. Even if a gas spring or a coil spring is provided, a considerable effect can be expected. A gas spring may be provided on one of the compressor and the displacer, and a coil spring may be provided on the other. The shapes and structures of the gas spring and the coil spring shown in the above embodiment are not limited to those in the embodiment. Further, it goes without saying that the displacer 7, cold finger 6, linear motors 5, 10 and the like are not limited to those of the embodiment.

[0023]

As described above, the Stirling refrigerator according to the present invention has at least one of the first suspension spring and the second suspension spring a gas spring that cooperates with the suspension spring to form a resonance system. With this configuration, the number of suspension springs to be used can be reduced, suspension springs having a small spring thickness and a small spring constant can be used, and a Stirling refrigerator having a long life can be obtained.

In a Stirling refrigerator according to another aspect of the present invention, at least one of the first suspension spring and the second suspension spring is provided with a coil spring that cooperates with the suspension spring to form a resonance system. With this configuration, a suspension spring having a thin spring and a small spring constant can be used as in the case of the above invention, and a Stirling refrigerator having a long life can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a Stirling refrigerator according to an embodiment of the present invention.

FIG. 2 is a sectional side view showing a Stirling refrigerator according to another embodiment of the present invention.

FIG. 3 is a cross-sectional side view showing a conventional Stirling refrigerator.

FIG. 4 is a plan view showing an example of a suspension spring.

[Explanation of symbols]

 C compressor 1 compressor cylinder 2 compressor piston 4 second suspension spring 6 cold finger (expander) 7 displacer 9 first suspension spring 11 expansion space 12 first compression space 13 second compression space 15 communication passage 16 gas Spring 17 Gas spring 18 Coil spring 19 Coil spring

[Procedure amendment]

[Submission date] April 28, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art FIG. 3 shows, for example, the document "Development of a Small Stirling Cooler for Space" (Development of a small Stirr).
ling cycle cooler for spaceflight applications)
(Author: ST Werrett, GD Peskett, GD Da
vey, T.S. W. Bradshaw and J. Delderfield, Journal name: Adv. In Cryo-genic Eng. Vol. 31 pp. 7
91-799, 1986) is a sectional side view showing a schematic configuration of a conventional Stirling refrigerator. In the figure, 1 is a compressor cylinder, and a compressor piston 2 reciprocates inside the compressor cylinder 1. Reference numeral 3 is a compressor case to which the compressor cylinder 1 is fixed. Four
Reference numerals a and 4b are second suspension springs that support the compressor piston 2 so that the compressor piston 2 can reciprocate without coming into contact with the compressor cylinder 1. 5a is a yoke fixed to the compressor case 3, 5b is a permanent magnet closely attached to the yoke 5a, 5c
Is a coil fixed to the compressor piston 2, and the yoke 5a, the permanent magnet 5b, and the coil 5c constitute a linear motor 5 that reciprocates the compressor piston 2. The compressor C is composed of these 1 to 5.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

Kcg = Pog · k · Acg ² / Vog Acg: Compressor gas spring piston cross-sectional area Pog: Compressor gas spring chamber average gas pressure Vog: Compressor gas spring chamber average volume k: Specific heat ratio (= Cp / Cv ) Cp: Specific pressure specific heat Cv: Constant volume specific heat

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Kdg = Pod · k · Adg ² / Vod Adg: Displacer gas spring piston cross-sectional area Pod: Displacer gas spring chamber average gas pressure Vod: Displacer gas spring chamber average volume

Claims (2)

[Claims] 1. An expander, a displacer disposed inside the expander, one end of which is in contact with the expansion space and the other end of which is in contact with the first compression space, and which holds the displacer axially movably. No. 1 suspension spring, a compressor having a cylinder and a piston and having a second compression space for compressing the working gas, a second suspension spring holding at least one of the cylinder and the piston so as to be movable in the axial direction, A communication passage that connects the compression space and the second compression space, and a gas spring that is provided opposite to at least one of the first suspension spring and the second suspension spring and cooperates with the suspension spring to form a resonance system are provided. A Stirling refrigerator that is characterized. 2. An expander, a displacer disposed inside the expander, one end of which is in contact with the expansion space and the other end of which is in contact with the first compression space, the first displacer holding the displacer axially movably. No. 1 suspension spring, a compressor having a cylinder and a piston and having a second compression space for compressing the working gas, a second suspension spring holding at least one of the cylinder and the piston so as to be movable in the axial direction, A communication passage that connects the compression space and the second compression space, and a coil spring that is provided in opposition to at least one of the first suspension spring and the second suspension spring and cooperates with the suspension spring to form a resonance system. A Stirling refrigerator that is characterized.