JP2982502B2 - Expansion cylinder device for refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an expansion cylinder device for a refrigerator such as a reverse Stirling cycle refrigerator.

[0002]

2. Description of the Related Art A reverse Stirling cycle, for example, is known as a refrigeration cycle using a gas such as helium, hydrogen, or nitrogen which is hardly liquefied at a low temperature as a refrigerant gas. A refrigerator using this refrigeration cycle includes an expansion cylinder 1 and a compression cylinder 2 as shown in the schematic configuration example of FIG. 5, and these reciprocate within each other (expansion piston 3 and compression piston 4). )have. The cooling section 6 to which the cooled object 5 is attached is formed so as to hermetically seal the end face of the expansion cylinder 1. The expansion cylinder 1, the expansion piston 3 and the cooling unit 6 constitute an expansion cylinder device. The expansion cylinder 1 and the compression cylinder 2 are connected by a pipe 8, and refrigerant gas is stored in a regenerator 9 as a refrigerant gas passage built in the expansion piston 3.
And the expansion cylinder 1 via the communication passage 20 for the refrigerant gas
Space (hereinafter referred to as expansion space) 15 and compression cylinder 2
(Hereinafter referred to as a compression space) 16 are alternately transferred according to the process of a reverse Stirling cycle described later. In the pipe 8, the compressed refrigerant gas is radiated from its outer periphery or from a radiator provided in particular. Reference numeral 19 denotes a seal provided on the outer periphery of each piston in order to prevent refrigerant gas from leaking.

[0003] The reverse Stirling cycle basically consists of two isothermal strokes and two equal volume strokes as follows. In order to realize each of these strokes, the expansion piston 3 and the compression piston 4 are adjusted so as to move synchronously with a predetermined phase difference. (1) Isothermal compression stroke In the compression cylinder 1, the refrigerant gas in the compression space 16 is compressed. The heat generated by the compression is radiated to the outside from the pipe 8 to perform an isothermal process. (Expansion piston: center → top dead center, compression piston: bottom dead center → center) (2) Equivalent heat radiation process The regenerator in which the compressed refrigerant gas is already cooled in the previous cycle without changing its volume The heat is radiated to the expansion cylinder 9 and the temperature is lowered to be transferred to the expansion space 15 of the expansion cylinder 1. (Expansion piston: top dead center → center, compression piston: center → top dead center) (3) Isothermal expansion process The refrigerant gas in the expansion space 15 of the expansion cylinder 1 generates heat from the surroundings as the expansion piston 3 moves. Takes away and expands isothermally at low temperatures. (Expansion piston: center → bottom dead center, compression piston: top dead center → center) (4) Isothermal heat absorption process The refrigerant gas expanded at a low temperature passes through the regenerator 9 again without changing its volume. Is returned to the compression space 16. At this time, since the refrigerant gas absorbs heat from the regenerator 9,
The regenerator 9 is cooled, the temperature of the refrigerant gas rises, and one cycle ends. (Expansion piston: bottom dead center → center, compression piston: center → bottom dead center) The above is the outline of the basic reverse Stirling cycle. Cooled. That is, in this process, the low-temperature refrigerant gas is transferred to the expansion space 15 via the regenerator 9 and the end portion 1 of the expansion cylinder 1
A flows along the inner surface of A and absorbs heat from the cooled object 5 through the cooling section 6 and the end 1A to cool it. The state change of the refrigerant gas in the isothermal expansion process of (3) is actually slightly different from the above, and is a polytropic change which is intermediate between the isothermal change and the adiabatic change. Is further reduced from the equal volume heat radiation process of (2), but the cooling effect is smaller than that of the equal volume heat radiation process because there is almost no flow of the refrigerant gas.

In such a refrigerator, it is important to efficiently remove heat from the object 5 to be cooled and to reduce the time required to reduce the temperature to a predetermined cooling temperature as much as possible. An example of the prior art for this purpose is an expansion cylinder device having a configuration shown in FIG. In this expansion cylinder device, when the communication path 20 for the refrigerant gas provided at the top of the expansion piston 3 is opened obliquely in the immediate vicinity of the inner surface of the end 1A of the expansion cylinder 1, the refrigerant gas is discharged from the communication path 20 at a high speed. It focuses on the fact that a plurality of velocity components in the direction along the inner surface of the portion 1A and in the radial direction are given, that is, without providing a guide for the refrigerant gas with the velocity component in the direction along the inner surface of the end 1A of the expansion cylinder 1. Along the inner surface of the end 1A
And at the same time, the refrigerant gas vigorously collides with the inner surface of the end portion 1A with a velocity component in the radial direction to form a turbulent flow having a good heat transfer coefficient, thereby performing good cooling. Further, the reason why the refrigerant gas flows along the inner surface of the end portion 1A and absorbs heat from the cooled object through the cooling portion 6 and the end portion 1A is that the expansion piston moves up and down from the top dead center P1 while the refrigerant gas is transferred to the expansion cylinder. Focusing only on the movement during the movement to the vicinity of the center position P2 of the dead center, the end 1A of the expansion cylinder 1 is thickened from its end face to the vicinity of the center position P2 between the top and bottom dead centers of the expansion piston 3. By doing so, the thermal resistance is reduced without increasing the heat capacity more than necessary.

[0005]

Generally, the input of the refrigerator is a value obtained by multiplying the ratio of the difference between the high temperature and the low temperature of the refrigerant gas to the low temperature by the refrigerating output. The refrigeration output is the sum of the amount of refrigeration heat for cooling the object to be cooled and the amount of heat penetrating from, for example, the pipe wall of the expansion cylinder. Accordingly, in order to increase the refrigerating efficiency of the refrigerator, (1) the low-temperature side of the refrigerant gas is operated at the highest possible temperature while satisfying the required cooling temperature of the object to be cooled, and (2) the pipe wall of the expansion cylinder. It is necessary to reduce as much as possible the amount of heat penetrating from such as.

In the refrigerator using the above-mentioned expansion cylinder device, in order to increase the refrigeration efficiency of the refrigerator, the expansion cylinder end portion is thickened from its end surface to the vicinity of the center portion between the upper and lower dead centers of the expansion piston. By reducing the thermal resistance, the temperature difference between the object to be cooled and the refrigerant gas is reduced, and the low temperature side of the refrigerant gas is operated at a high temperature. There is a limit to the reduction of thermal resistance only by making the body thick (if the thick end is made extremely thick in order to reduce the thermal resistance, the heat capacity will increase and conversely the refrigeration efficiency will decrease). In addition, the communication path of the refrigerant gas at the top of the expansion piston is opened obliquely to improve the heat transfer coefficient between the refrigerant gas and the end of the expansion cylinder and the cooling unit, and similarly, the temperature difference between the cooled object and the refrigerant gas However, for example, the heat transfer area of the cooling unit is constant, and there is a limit in improving the heat transfer coefficient. Furthermore, since no measures have been taken against the amount of heat entering from the tube wall of the expansion cylinder except for increasing the thermal resistance by reducing the thickness of the tube wall, which is usually carried out, the amount of heat entering is frozen. There is a problem that the efficiency of the machine is reduced.

An object of the present invention is to solve the above-mentioned problems and to further increase the refrigeration efficiency of a refrigerator.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides an expansion cylinder in which an end surface is hermetically sealed by a cooling unit for cooling a cooled body to form an expansion space, and an expansion cylinder. Reciprocating in the expansion space facing the expansion space, and a regenerator as a refrigerant gas passage is provided therein, and an expansion piston that communicates with the expansion space. The expansion cylinder is made of a titanium alloy, and the cooling section is made of pure titanium. Alternatively, the end of the expansion cylinder on the cooling section side is formed to be thick. The thick end portion and the cooling portion are made of pure titanium, and the portion excluding the thick end portion and the cooling portion of the expansion cylinder is made of a titanium alloy. And a groove on the inner surface of the cooling unit,
For example, one or more grooves provided concentrically with respect to the central axis of the cooling unit, or one or more grooves provided radially with respect to the central axis of the cooling unit, or orthogonal to each other. Are provided with one or more grooves, respectively. Also, a groove on the inner surface of the thick end of the expansion cylinder, for example, one or more grooves provided parallel to the axis of the expansion cylinder, or one or more grooves provided parallel to the circumference of the inner surface. One or more grooves or grooves provided in a threaded manner with respect to the axis of the expansion cylinder are provided.

[0009]

In the expansion cylinder device for a refrigerator according to the present invention, since the expansion cylinder is made of a titanium alloy having a large thermal resistance, the amount of heat penetrating from the tube wall of the expansion cylinder can be reduced, and cooling can be performed. Since the portion is made of pure titanium having a small thermal resistance, the temperature difference between the object to be cooled and the refrigerant gas can be further reduced. In claim 2,
As the cooling cylinder side end of the expansion cylinder is formed thick,
The thermal resistance of the thick end is reduced, the temperature difference between the object to be cooled and the refrigerant gas is reduced, and operation can be performed with the low-temperature side of the refrigerant gas raised. According to a third aspect of the present invention, the cooling section side end of the expansion cylinder is formed to be thick, and the thick end and the cooling section are made of pure titanium having low thermal resistance. Since the part excluding the part and the cooling part is made of a titanium alloy having a large thermal resistance, the temperature between the object to be cooled and the refrigerant gas becomes smaller, and the amount of heat entering from the pipe wall of the expansion cylinder is reduced. Can be reduced. Claim 4
7 to 7 are grooves on the inner surface of the cooling unit, for example, one or more grooves provided concentrically with respect to the center axis of the cooling unit, or one or more grooves provided in the radial direction, or The heat transfer coefficient between the cooling part and the refrigerant gas is increased, and the temperature difference between the cooled object and the refrigerant gas is increased. Becomes smaller. Claims 8 to 11 are grooves on the inner surface of the thickened end of the expansion cylinder, for example one or more grooves provided parallel to the axis of the expansion cylinder, provided parallel to the circumference of this inner surface. Since one or more grooves or grooves formed in a screw shape with respect to the axis of the expansion cylinder are provided, the heat transfer coefficient between the thick end of the expansion cylinder and the refrigerant gas is reduced. The temperature difference between the object to be cooled and the refrigerant gas becomes smaller. These further increase the efficiency of the refrigerator.

[0010]

FIG. 1 is a sectional view showing a main part of a reference example of an expansion cylinder device of a refrigerator according to the present invention. The expansion cylinder device of the refrigerator shown in FIG. 1 is structurally similar to the conventional expansion cylinder device shown in FIG. 6, except that the expansion cylinder 1 is made of a titanium alloy. The thermal resistance of a titanium alloy is higher than the thermal resistance of stainless steel normally used for an expansion cylinder. For example, comparing stainless steel SUS304 with titanium alloy Ti-6A1-4V, 80-30
Calculated from the average thermal conductivity of 0K, Ti-6A1-4V
Has twice the thermal resistance of SUS304, and the amount of heat entering from the tube wall of the expansion cylinder 1 is reduced. FIG.
In FIG. 5, the end 1A of the expansion cylinder 1 on the side of the cooling section 6 is formed to be thick, but in the present invention, this end 1A is not formed to be thick, as shown in FIG. It is needless to say that the present invention is effective when applied to a normal expansion cylinder.

FIG. 2 shows an embodiment of the present invention, and FIG.
1 differs from FIG. 1 in that the entire expansion cylinder 1 is made of a titanium alloy, whereas FIG. 2 is a part made of a titanium alloy except for the thick end portion 1A of the expansion cylinder 1. The thick end portion 1A and the cooling portion 6 are made of pure titanium. Pure titanium has a thermal resistance of 1/8 at 80K, for example, compared to SUS304.
The temperature between the object to be cooled and the refrigerant gas decreases, and the operation can be performed with the low-temperature side of the refrigerant gas raised. Since the portion of the expansion cylinder 1 other than the thick end portion 1A is made of a titanium alloy, the amount of heat entering from the tube wall of the expansion cylinder 1 is reduced. In addition, as shown in FIG. 2, the cooling unit 6 and the end 1A of the expansion cylinder are manufactured integrally with pure titanium,
If the joined body 22 is joined to the portion 1B made of a titanium alloy excluding the thick end portion of the expansion cylinder 1 via the flange 21, the manufacture is easy.

FIG. 3 shows a different embodiment of the present invention.
Is provided with a groove 23 on the inner surface of the cooling section 6 in FIG.
The groove 23 increases the inner surface area of the cooling unit 6 and the groove 23 causes the refrigerant gas ejected at high speed from the communication passage 20 to be in a more turbulent state, so that the heat transfer coefficient between the cooling unit 6 and the refrigerant gas is increased. And the temperature difference between the object to be cooled and the refrigerant gas becomes smaller. This groove 23 is, for example, one or more grooves provided concentrically with respect to the central axis of the cooling unit 6 or one or more grooves provided radially with respect to the central axis of the cooling unit 6. Or one or more grooves provided so as to be orthogonal to each other, the manufacture is easy.

FIG. 4 shows yet another embodiment of the present invention.
FIG. 4 is a view in which a groove 24 is provided on the inner surface of the expansion cylinder end 1A of FIG. The groove 24 increases the inner surface area of the expansion cylinder end 1A, and the groove 24 causes the refrigerant gas ejected at a high speed from the communication passage 20 to be in a more turbulent state. Is increased, and the temperature difference between the object to be cooled and the refrigerant gas becomes smaller. The groove 24 is formed, for example, in the expansion cylinder 1
One or more grooves provided in parallel with the central axis of the cylinder, or one or more grooves provided in parallel with the circumference of the inner surface thereof, or a threaded shape with respect to the axis of the expansion cylinder 1 It is easy to manufacture if it is constituted by grooves or the like provided in the groove.

[0014]

According to the expansion cylinder device of the refrigerator of the present invention, the expansion cylinder is made of a titanium alloy having a large thermal resistance, and the cooling section is made of pure titanium having a small thermal resistance. The end portion is formed to be thick, and furthermore, the cooling portion and the thick end portion of the expansion cylinder are made of pure titanium, and the portion excluding the thick end portion and the cooling portion of the expansion cylinder is made of titanium. By forming a groove on the inner surface of the cooling part or the inner surface of the thick end of the expansion cylinder, the temperature difference between the object to be cooled and the refrigerant gas is reduced, and the expansion cylinder is made of an alloy. Since the amount of heat entering from the pipe wall is reduced, a refrigerator having extremely high refrigeration efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a reference example of an expansion cylinder device of a refrigerator according to the present invention.

FIG. 2 is a sectional view of a main part showing an embodiment of an expansion cylinder device of a refrigerator according to the present invention.

FIG. 3 is a sectional view of a main part showing still another embodiment of the expansion cylinder device of the refrigerator of the present invention.

FIG. 4 is a sectional view of a main part showing still another embodiment of the expansion cylinder device of the refrigerator according to the present invention.

FIG. 5 is a configuration diagram showing the principle of a reverse Stirling cycle refrigerator.

FIG. 6 is a perspective view showing an example of a conventional expansion cylinder device of a refrigerator including a partial cross section.

[Explanation of symbols]

 Reference Signs List 1 expansion cylinder 1A end of expansion cylinder 1B part excluding end 1A of expansion cylinder 1 3 expansion piston 6 cooling section 9 regenerator 15 expansion space 20 communication passage 23 groove 24 groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-110260 (JP, A) JP-A-5-313425 (JP, A) Japanese Utility Model Showa 62-102967 (JP, U) Japanese Utility Model Showa 58- 155570 (JP, U) Japanese Utility Model 4-132368 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) F25B 9/14 510 F25B 9/00

Claims (11)

(57) [Claims] An expansion cylinder whose end face is hermetically sealed by a cooling section for cooling an object to be cooled to form an expansion space, a reciprocating movement inside the expansion cylinder facing the expansion space, and a refrigerant. A regenerator as a gas passage is provided therein, and an expansion cylinder device for a refrigerator including an expansion piston communicating with the expansion space, wherein the expansion cylinder is made of a titanium alloy, and the cooling unit is made of pure titanium. An expansion cylinder device for a refrigerator. 2. The expansion cylinder device for a refrigerator according to claim 1, wherein an end portion of the expansion cylinder on the side of the cooling portion is formed to be thick. 3. An expansion cylinder whose end face is hermetically sealed by a cooling section for cooling a cooled body to form an expansion space, and an inside of the expansion cylinder reciprocatingly faces the expansion space and has a refrigerant. In an expansion cylinder device of a refrigerator, a regenerator as a gas passage is provided therein, and an expansion piston communicating with the expansion space. The expansion end of the refrigerator is characterized in that the thick end and the cooling part are made of pure titanium, and the part excluding the thick end and the cooling part of the expansion cylinder is made of a titanium alloy. Cylinder device. 4. The expansion cylinder device for a refrigerator according to claim 1, wherein a groove is provided on an inner surface of the cooling unit. 5. The expansion cylinder device for a refrigerator according to claim 4, wherein the groove on the inner surface of the cooling unit comprises one or more grooves provided concentrically with the center axis of the cooling unit. Characteristic expansion cylinder device for refrigerator. 6. The expansion cylinder device for a refrigerator according to claim 4, wherein the groove on the inner surface of the cooling unit comprises one or more grooves provided in a radial direction with respect to a center axis of the cooling unit. Characteristic expansion cylinder device for refrigerator. 7. The expansion cylinder device for a refrigerator according to claim 4, wherein the grooves on the inner surface of the cooling unit are each formed of one or more grooves provided to be orthogonal to each other. Expansion cylinder device for refrigerator. 8. The expansion cylinder device for a refrigerator according to claim 2, wherein a groove is provided on an inner surface of a thick end portion of the expansion cylinder. 9. The expansion cylinder device for a refrigerator according to claim 8, wherein the groove on the inner surface of the thick end of the expansion cylinder has one or more grooves provided parallel to the axis of the expansion cylinder. An expansion cylinder device for a refrigerator, comprising: 10. The expansion cylinder device for a refrigerator according to claim 8, wherein the groove on the inner surface of the thick end portion of the expansion cylinder is
An expansion cylinder device for a refrigerator, comprising one or more grooves provided in parallel on the circumference of the inner surface. 11. The expansion cylinder device for a refrigerator according to claim 8, wherein the groove on the inner surface of the thick end of the expansion cylinder is
An expansion cylinder device for a refrigerator, comprising a groove provided in a screw shape with respect to the axis of the expansion cylinder.