JPH0634216A - Expansion cylinder device of refrigerator - Google Patents

Abstract

PURPOSE:To improve a refrigerating efficiency by reducing the quantity of heat penetrating from the tube wall of an expansion cylinder and by lessening a temperature difference between a body to be cooled and a refrigerant gas, in an expansion cylinder device of a refrigerator. CONSTITUTION:An expansion cylinder 1 is constructed of a titanium alloy having a large thermal resistance. Besides, the end part 1A on the cooling part 6 side of the expansion cylinder 1 is so shaped as to have a large thickness. Moreover, the cooling part 6 is constructed of pure titanium of which the thermal resistance is small.

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 is known, for example, as a refrigeration cycle in which a gas such as helium, hydrogen, or nitrogen that is difficult to liquefy at low temperature is used as a refrigerant gas. A refrigerator utilizing this refrigeration cycle is provided with an expansion cylinder 1 and a compression cylinder 2 as shown in the schematic configuration example of FIG. 5, and these pistons (expansion piston 3 and compression piston 4 reciprocate inside). )have. The cooling unit 6 to which the cooled body 5 is attached is formed so as to hermetically seal the end surface of the expansion cylinder 1. The expansion cylinder device, 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 the refrigerant gas is 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
And the space 16 (hereinafter referred to as a compression space) are alternately transferred in accordance with the process of the reverse Stirling cycle described later. The heat of the compressed refrigerant gas is radiated from the outer periphery of the pipe 8 or a radiator provided in particular. Reference numeral 19 is a seal provided on the outer circumference of each piston in order to prevent refrigerant gas from leaking.

The reverse Stirling cycle basically consists of two isothermal steps and two isovolume steps as described below. In order to realize each of these strokes, the expansion piston 3 and the compression piston 4 are adjusted so as to synchronously move with a predetermined phase difference. (1) Isothermal compression process 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 and becomes an isothermal process. (Expansion piston: central part → top dead center, compression piston: bottom dead center → center part) (2) Equal volume heat dissipation process Regenerator in which compressed refrigerant gas is already cooled in the previous cycle without changing volume The heat is radiated to 9 and the temperature becomes low, and the temperature is 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 stroke The refrigerant gas in the expansion space 15 of the expansion cylinder 1 generates heat from the surroundings as the expansion piston 3 moves. It robs and expands isothermally at low temperature. (Expansion piston: central part → bottom dead center, compression piston: top dead center → center part) (4) Endothermic endothermic process Refrigerant gas expanded at a low temperature passes through the regenerator 9 again without changing its volume, and then the compression cylinder 2 Is returned to the compressed space 16. At this time, the refrigerant gas absorbs heat from the regenerator 9,
The regenerator 9 is cooled, the temperature of the refrigerant gas rises, and one cycle is completed. (Expansion piston: bottom dead center → center, compression piston: center → bottom dead center) The above is the outline of the basic reverse Stirling cycle.
The cooled object 5 is cooled mainly in the equal volume heat dissipation step (2). That is, in this process, the refrigerant gas having a low temperature through the regenerator 9 is transferred to the expansion space 15,
It flows along the inner surface of the end portion 1A of the expansion cylinder 1 and absorbs heat from the cooled object 5 through the cooling part 6 and the end portion 1A to cool it. In addition, the state change of the refrigerant gas in the isothermal expansion process of (3) actually becomes a polytropic change that is intermediate between the isothermal change and the adiabatic change, which is slightly different from the above. Is lower than that in the isochoric heat dissipation step, but the cooling effect is smaller than that in the isochoric heat dissipation step because there is almost no refrigerant gas flow.

In such a refrigerator, the object to be cooled 5
Efficiently removes heat and lowers the temperature to the specified cooling temperature.
It is important to shorten the time required for lowering as much as possible. this
As an example of the prior art for
There is a device. In this expansion cylinder device, the expansion piston
3 The refrigerant gas communication passage 20 provided at the top of the expansion cylinder
When opening diagonally in the immediate vicinity of the inner surface of the end portion 1A of 1,
The refrigerant gas ejected from the communication passage 20 at high speed is
Given multiple velocity components in the direction along the plane and in the radial direction,
It is focused on that the expansion cylinder 1
The refrigerant gas is guided by the velocity component in the direction along the inner surface of the end 1A.
The cooling part 6 along the inner surface of the end 1A without providing
Circulates up to, and at the same time the refrigerant gas with a radial velocity component
The inner surface of the end portion 1A is vigorously collided to cause a disturbance with a good heat transfer coefficient.
To ensure good cooling.
It was done. In addition, the refrigerant gas flows along the inner surface of the end 1A.
From the object to be cooled through the flow cooling unit 6 and the end 1A.
It absorbs heat while the refrigerant gas is transferred to the expansion cylinder.
That is, the expansion piston is at the top dead center P₁From the top and bottom dead center
Part position P₂Focus on only while moving to the neighborhood
The end portion 1A of the expansion cylinder 1 from the end face
Central position P between top and bottom dead centers of ton 3 ₂Thick wall up to the vicinity
To increase the heat capacity more than necessary
It is designed to reduce heat resistance.

[0005]

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

In the refrigerator using the above-mentioned expansion cylinder device, in order to enhance the refrigerating efficiency of the refrigerator, the end of the expansion cylinder is thick-walled from its end face to the vicinity of the central position between the upper and lower dead centers of the expansion piston. By reducing the heat resistance, the temperature difference between the cooled object and the refrigerant gas is reduced, and the low temperature side temperature of the refrigerant gas is operated at a high temperature. There is a limit to the reduction of thermal resistance just by making it fleshy (if the thick end is made extremely thick to reduce the thermal resistance, the heat capacity increases and conversely the refrigeration efficiency decreases). In addition, the communication passage 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 portion, and similarly, the temperature difference between the cooled object and the refrigerant gas is increased. Although the heat transfer area of the cooling unit is constant, there is a limit to the improvement of the heat transfer coefficient. Furthermore, with respect to the amount of heat entering from the pipe wall of the expansion cylinder, no measures have been taken other than increasing the thermal resistance by reducing the thickness of the pipe wall that is usually performed, so the amount of entering heat 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 further improve the refrigerating efficiency of the refrigerator.

[0008]

In order to achieve the above-mentioned object, the present invention relates to an expansion cylinder whose end surface is hermetically sealed by a cooling part for cooling an object to be cooled to form an expansion space, and this expansion cylinder. In the expansion cylinder device of a refrigerator provided with a regenerator that reciprocates the inside of the expansion surface facing the expansion space, and a regenerator as a passage of a refrigerant gas is provided therein, and an expansion piston communicating with the expansion space. The expansion cylinder is made of titanium alloy. Further, this expansion cylinder has a thickened end portion on the cooling section side. Furthermore, these cooling parts are made of pure titanium.
Alternatively, in the expansion cylinder, an end portion on the cooling portion side is formed thick, and the thick end portion and the cooling portion are made of pure titanium, and a portion excluding the thick end portion of the expansion cylinder is Use a titanium alloy. And a groove on the inner surface of the cooling part, for example one or more grooves concentrically provided with respect to the central axis of the cooling part, or one or more grooves provided radially with respect to the central axis of the cooling part. Grooves, or one or more grooves each provided orthogonal to each other are provided. Also, a groove is formed on the inner surface of the thick-walled end of the expansion cylinder, for example, one or more grooves provided parallel to the axis of the expansion cylinder, or 1 provided on the circumference of the inner surface in parallel. There may be one or more grooves, or a groove threaded on the shaft of the expansion cylinder.

[0009]

In the expansion cylinder device for a refrigerator of the present invention as defined in claim 1 or 2, since the expansion cylinder is made of a titanium alloy having a high thermal resistance, the amount of heat penetrating from the wall of the expansion cylinder can be reduced. Further, in claim 2, since the end of the expansion cylinder on the cooling portion side is formed thick, the thermal resistance of the thick end is reduced, and the temperature difference between the cooled object and the refrigerant gas is reduced. Can be reduced, and the temperature on the low temperature side of the refrigerant gas can be increased to operate. In claim 3,
Since the cooling part in claim 1 or 2 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 made smaller. According to a fourth aspect of the present invention, the end portion of the expansion cylinder on the cooling portion side is formed thick, and the thick end portion and the cooling portion are made of pure titanium having a small thermal resistance. Since the parts excluding the parts are made of a titanium alloy having a high thermal resistance, the temperature between the object to be cooled and the refrigerant gas becomes smaller and the amount of heat entering from the wall of the expansion cylinder can be reduced. According to claims 5 to 8, grooves are formed on the inner surface of the cooling section, for example, one or more grooves provided concentrically with respect to the central axis of the cooling section, or one or more grooves provided in the radial direction. ,
Alternatively, one or more grooves provided so as to be orthogonal to each other are provided, and the heat transfer coefficient between the cooling part and the refrigerant gas is increased, so that the cooling target and the refrigerant gas are cooled. The temperature difference becomes smaller. Claims 9 to 12 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 this expansion cylinder,
Since one or more grooves provided in parallel on the circumference of the inner surface or grooves provided in a screw shape with respect to the axis of the expansion cylinder are provided, the thick-walled end portion of the expansion cylinder is provided. The heat transfer coefficient between the refrigerant gas and the refrigerant gas increases, and the temperature difference between the cooled object and the refrigerant gas decreases. These enhance the efficiency of the refrigerator.

[0010]

1 is a cross-sectional view of a main part showing an embodiment of an expansion cylinder device for a refrigerator according to the present invention. The expansion cylinder device of the refrigerator of the present invention 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 titanium alloy is higher than that of stainless steel which is usually used for expansion cylinders. For example, stainless steel SUS
Comparing 304 and titanium alloy Ti-6A1-4V, the average thermal conductivity of 80 to 300K is converted to Ti-6.
The thermal resistance of A1-4V is twice that of SUS304, and the amount of heat penetrating from the tube wall of the expansion cylinder 1 is reduced. In addition, in FIG. 1, the end portion 1A of the expansion cylinder 1 on the side of the cooling portion 6 is formed thick, but the present invention is the same as in FIG. 5 where the end portion 1A is not formed thick. Of course, it is effective when applied to a normal expansion cylinder as shown.

FIG. 2 shows a different embodiment of the present invention.
1 differs from FIG. 1 in that the entire expansion cylinder 1 is made of titanium alloy in FIG. 1, whereas the part of the expansion cylinder 1 excluding the thick-walled end 1A is made of titanium alloy. The thick-walled end portion 1A of the expansion cylinder and the cooling portion 6 are made of pure titanium. Pure titanium is SUS3
Compared with 04, for example, the thermal resistance at 80K is 1/8, and the temperature between the cooled object and the refrigerant gas becomes smaller,
It is possible to operate by increasing the low temperature side temperature of the refrigerant gas. And
Since the portion of the expansion cylinder 1 excluding the thick-walled 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.
The end portion 1A of the expansion cylinder and the end portion 1A of the expansion cylinder are integrally made of pure titanium, and the combined body 22 is joined to the portion 1B made of titanium alloy excluding the thick end portion of the expansion cylinder 1 via the flange 21. Then it is easy to manufacture.

FIG. 3 shows a further different embodiment of the invention,
In FIG. 3, a groove 23 is provided on the inner surface of the cooling unit 6 of FIG. This groove 23 increases the inner surface area of the cooling unit 6,
In addition, the groove 23 causes the refrigerant gas ejected from the communication passage 20 at a high speed 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 refrigerant gas between the cooled object and the refrigerant gas is increased. The temperature difference becomes smaller. The groove 23 is, for example, one or more grooves concentrically provided with respect to the central axis of the cooling unit 6, or one or more grooves radially provided 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, it is easy to manufacture. It is needless to say that the groove 23 has the same effect when applied to the embodiment shown in FIG.

FIG. 4 shows a further different embodiment of the invention,
FIG. 4 shows a groove 24 formed 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 makes the refrigerant gas ejected from the communication passage 20 at a high speed into a more turbulent state. The heat transfer coefficient is increased, and the temperature difference between the cooled object and the refrigerant gas becomes smaller. This groove 24 is, for example, the expansion cylinder 1
One or more grooves provided parallel to the central axis of, or one or more grooves provided parallel to the circumference of this inner surface, or threaded with respect to the axis of this expansion cylinder 1. It is easy to manufacture if it is configured with a groove provided on the. It is needless to say that the groove 24 has the same effect when applied to the embodiment shown in FIG.

[0014]

In 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 end of the expansion cylinder on the cooling portion side is formed thick. Part is made of pure titanium with low thermal resistance. Furthermore, the cooling part and the thick end of this expansion cylinder are made of pure titanium, and the part excluding the thick end of the expansion cylinder is made of titanium alloy. Further, by providing a groove on the inner surface of the cooling section or the inner surface of the thick end of the expansion cylinder, the temperature difference between the cooled object and the refrigerant gas is reduced, and the tube wall of the expansion cylinder is formed. Since the amount of heat penetrating from is reduced, a refrigerator with extremely high refrigeration efficiency can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of an expansion cylinder device for a refrigerator according to the present invention.

FIG. 2 is a sectional view of an essential part showing a different embodiment of the expansion cylinder device of the refrigerator of the present invention.

FIG. 3 is a sectional view of an essential part showing a further different embodiment of the expansion cylinder device of the refrigerator of the present invention.

FIG. 4 is a sectional view of an essential part showing a further different embodiment of the expansion cylinder device for a refrigerator of the present invention.

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

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

[Explanation of symbols]

 1 Expansion Cylinder 1A End of Expansion Cylinder 1B Except End 1A of Expansion Cylinder 3 Expansion Piston 6 Cooling Section 9 Regenerator 15 Expansion Space 20 Communication Passage 23 Groove 24 Groove

Claims (12)

[Claims] 1. An expansion cylinder whose end surface is hermetically sealed by a cooling part for cooling an object to be cooled to form an expansion space; and an inside of this expansion cylinder which reciprocates so as to face the expansion space, and a refrigerant. In an expansion cylinder device of a refrigerator having a regenerator as a gas passage provided therein and an expansion piston communicating with the expansion space, the expansion cylinder is made of a titanium alloy. Expansion cylinder device. 2. The expansion cylinder device for a refrigerator according to claim 1, wherein an end of the expansion cylinder on the cooling portion side is formed thick. 3. The expansion cylinder device for a refrigerator according to claim 1 or 2, wherein the cooling portion is made of pure titanium. 4. An expansion cylinder whose end face is hermetically sealed by a cooling part for cooling an object to be cooled to form an expansion space, and the inside of this expansion cylinder reciprocates to face the expansion space, and a refrigerant. In an expansion cylinder device of a refrigerator having a regenerator as a gas passage provided therein and an expansion piston communicating with the expansion space, the expansion cylinder has a thick end portion on the cooling unit side. An expansion cylinder device for a refrigerator, wherein the thick-walled end portion and the cooling portion are made of pure titanium, and a portion excluding the thick-walled end portion of the expansion cylinder is made of titanium alloy. 5. An expansion cylinder device for a refrigerator according to any one of claims 1 to 3 or 4, wherein a groove is provided on an inner surface of the cooling part. 6. The expansion cylinder device for a refrigerating machine according to claim 5, wherein the groove on the inner surface of the cooling portion comprises one or more grooves concentrically provided with respect to the central axis of the cooling portion. An expansion cylinder device for a refrigerator. 7. The expansion cylinder device for a refrigerating machine according to claim 5, wherein the groove on the inner surface of the cooling portion comprises one or more grooves provided in the radial direction with respect to the central axis of the cooling portion. An expansion cylinder device for a refrigerator. 8. The expansion cylinder device for a refrigerating machine according to claim 5, wherein the grooves on the inner surface of the cooling portion are each formed of one or more grooves provided so as to be orthogonal to each other. Expansion cylinder device for refrigerator. 9. An expansion cylinder device for a refrigerator according to claim 2, 3 or 4, wherein a groove is provided on an inner surface of a thick end of the expansion cylinder. 10. The expansion cylinder device for a refrigerator according to claim 9, wherein the groove on the inner surface of the thick-walled end portion of the expansion cylinder comprises:
An expansion cylinder device for a refrigerator, comprising one or more grooves provided in parallel to the axis of the expansion cylinder. 11. The expansion cylinder device for a refrigerator according to claim 9, wherein the groove on the inner surface of the thick-walled end portion of the expansion cylinder comprises:
An expansion cylinder device for a refrigerator, comprising one or more grooves provided in parallel on the circumference of the inner surface. 12. The expansion cylinder device for a refrigerator according to claim 9, 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.