JPS6162760A - Piston for cold accumulation type expansion machine and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a regenerator expander used in a helium refrigerator of a nuclear magnetic 11113 device, and particularly relates to a regenerator that is suitable for preventing magnetic field disturbance; .

[Conventional technology]

In recent years, demand for cryogenic products has increased, and nuclear magnetic resonance apparatuses using liquid helium are being actively developed. As shown in Figures 8 to 10, the expander of the small helium refrigerator intended for the equipment in this building has a bottomed seven-cylinder cylinder 6 whose upper open end is sealed with a piston flange 3, and the inside of this cylinder. A piston 5 filled with a cold storage material 7 is fitted into the piston 5.

In accordance with the operation of the piston, high-pressure helium gas is introduced into the piston, compressed, and then expanded to cool the cold storage material 7. A projecting wall having a diameter smaller than the inner diameter of the cylinder is provided on the piston flange 3 to project inward of the cylinder, and a piston pressure chamber 9 is formed between the outer surface of the projecting wall 8 and the inner surface of the cylinder 6. Inside the cylinder, the upper part of the piston is slidably fitted into a piston pressure chamber 9 via a shield ring 4. The cylinder flange 3 is provided with three first flow passages that communicate with the piston pressure chamber 9 and a second flow passage 3B that communicates with the inside of the piston 5, and the rotary pulp 2 is in sliding contact with the upper surface thereof. It is located. This rotary pulp 2 is driven by a motor 11, and first and second flow passages 3 are formed in the piston 7 flange 3.
It has a structure in which first and second intake holes 2A and 2B, which are bored at positions corresponding to holes A and 3B, are sequentially communicated with each other. In addition, the one-rotation pulp 2 is provided with an exhaust # (not shown) that simultaneously communicates with the first and second communication passages 3A and 3B in order to exhaust the piston pressure chamber 9 and the high-pressure gas inside the piston at once. . 12 is a motor and a cover for pumping the rotating pulp.

Next, the operation of the above expander will be explained.

The high-pressure helium gas supplied into the cover 12 is supplied to the piston pressure chamber 9 through two intake holes of the rotary pulp 2 driven by the motor 11 and the first communication passage 3A of the piston flange 3. Here, the high pressure helium gas is
As shown in FIG. 9, press the end of the piston to push the piston 5 down. Next, the rotary pulp 2 is rotated to align the two second intake holes with the second communication hole 3B of the piston 7 flange, and the high-pressure helium gas in the cover is introduced into the piston 5. As shown in FIG. 12, the high-pressure helium gas that has entered the piston is sent out between the cylinder 5 and the piston from the holes 13.14 at the bottom of the piston through the filled regenerator 7, pushing up the piston 5 and filling the piston pressure chamber. 9. Compress the high pressure helium gas. When the piston 5 is pushed up to the top, the exhaust groove of the rotary pulp communicates with the first and second communication passages 3A and 3B of the piston 7 flange, and the high pressure gas in the piston pressure chamber 9 and the piston 5 is exhausted all at once, causing expansion. The cold storage material is cooled by the low-temperature gas.

[Problem that the invention seeks to solve]

In the conventional device described above, austenitic stainless steel is used for the piston and cylinder in order to prevent magnetic field disturbance. However, metal has a problem of poor durability.

In addition, the cold storage material is filled with lead or copper balls with a diameter of 0.2 to 1.0 m, and while the piston is driving, it flows out from the piston hole to the inner surface of the cylinder together with high pressure gas, and the piston This affects the movement of the cold storage material and causes the cold storage material to oscillate, resulting in a decrease in performance.

Recently, piston 5. The use of ceramics has been considered to improve the durability of the cylinder 6.

However, no effective solution has been found to deal with the shaking and outflow of the cold storage material.

An object of the present invention is to provide a ceramic piston that does not cause magnetic field disturbance or outflow of regenerator material due to piston operation.

[Means for Solving the Problems and Their Effects] The piston of the regenerator expander of the present invention has a piston outer shell made of a dense ceramic body, and the inside thereof is filled with a porous ceramic body.

According to the above configuration, even if the regenerative expander is used in a magnetic field, the piston, which is the operating part, is made of non-magnetic material, so the magnetic field will not be disturbed and its influence on magnetic application equipment will be minimized. It can be eliminated. In addition, since the cold storage material is filled as an integrated body, there is no relative movement between it and the outer shell of the piston during the reciprocating motion of the piston, and there is no possibility that it will flow out to the outside. It also disappears.

Next, in the method for manufacturing a piston according to the second invention, ceramic particles coated with ceramic powder having a melting point lower than that of the particle material are filled inside a ceramic cylinder, and then sintered to bond the ceramic particles to each other. At the same time, it is characterized in that it is fixed to the ceramic cylindrical body.

According to the above configuration, at the same time as sintering and forming the cold storage material,
Since the cold storage material and the ceramic cylindrical body are fixed and integrated, the number of manufacturing steps is reduced.

Further, the method for manufacturing a piston according to the third invention includes preforming a cylindrical porous ceramic body, immersing the porous ceramic body in a ceramic slurry, and forming an outer ceramic layer on the surface of the porous body. It is characterized by being sintered after drying.

According to the above structure, a ceramic layer is formed on the surface of the porous body by capillarity of the porous ceramic body, and alumina is well penetrated into the porous body, thereby reducing the occurrence of cracks during sintering.

Furthermore, the method for manufacturing a piston according to the fourth invention involves impregnating the interior of a cylindrical three-dimensional network resin with ceramic powder, forming a ceramic powder layer on the outer periphery, and then sintering it by heating and raising the temperature. In addition, the three-dimensional network resin is burned out to form a dense ceramic material on the outer periphery and a porous ceramic material inside.

According to the above configuration, the piston can be manufactured with a minimum number of steps, and by changing the shape of the three-dimensional network resin and the size of the mesh, a desired piston can be easily manufactured.

〔Example〕

The present invention will be explained in detail below.

(Embodiment of the first invention) The ceramic particles 9 are made of alumina powder with a diameter of 0.2 to 0.5
It is made by granulating fl into fl and firing at about 1650°C.

When the ceramic particles 1 are filled into a ceramic cylinder and fired, each particle has at least one contact surface or contact point with an adjacent particle, as shown in FIG. 1(a). In this state, when the temperature is raised to the firing temperature of ceramics, the particles are sintered at the contact point or surface of the particles and are bonded to each other as shown in Figure 1(b), forming a network of porous ceramic particles. A quality structure is created.

In addition, when using large ceramic particles, it is necessary to increase the contact area by applying an auxiliary agent or high pressure to strengthen the bond between the particles.

On the other hand, the cylindrical body 5 forming the outer shell of the piston shown in FIG. A piston 10 is configured. The ceramic porous structure 7 allows high-pressure helium gas to pass therethrough and also acts as a cold storage material.

According to this embodiment, the cylindrical body 5 forming the outer shell of the piston and the porous body 7 serving as the cool storage material can be manufactured separately, so that it is easy to obtain one that meets the usage conditions.

(Embodiment of the second invention) After coating the surface of ceramic particles with talc 2 dissolved in water, which has a melting point lower than that of the particle material, the ceramic particles have a diameter of 0.
Classify into 2 to 0.7 m. As shown in Figure 2(a), K
The ceramic particles 1 coated with Merck are filled in a ceramic cylinder 19 and sintered at 1400° C., which is higher than the sintering temperature of talc. As a result, the Merck on the surface of the ceramic particles melts, and the particles are firmly bonded to each other, forming a network-like porous body, as shown in FIG. 2(b).

(Embodiment of the third invention) An auxiliary agent is added to alumina particles granulated to a diameter of 0.2 to 1.0, and the mixture is placed in a mold and pressure-molded. This molded body is 1200
After temporary sintering at .degree. C., the porous cylindrical body 20 is manufactured by machining. This porous cylindrical body 20 is made of alumina slurry IJ-21 (100 parts of powder with an average particle size of 2 microns) as shown in FIG.
The porous material is immersed in 15 parts of water, and alumina Ni22 is formed on the surface of the porous material due to capillary action. After drying this porous cylindrical body 20, it is sintered at 350°C.

The ceramic porous cylindrical body obtained in the above step is machined into a piston of a regenerator expander.

(Embodiment of the fourth invention) As the three-dimensional network resin, foamed urethane 3 shown in FIG.
This foamed urethane is made into a cylinder using 0 and placed in the plaster cast hood 31. Alumina slurry (average particle size of alumina 2.4 microns, 100 parts alumina, 15 parts water) is poured into the plaster mold, and the moisture in the alumina is absorbed into the plaster mold 31, forming alumina 7t133 on the outer periphery. 1) Alumina 2) is impregnated into the inside of the urethane foam 30 and solidified. After sufficiently drying, the sintering temperature (1
650℃) to burn out the foamed ureon and sinter it, creating a continuous three-dimensional mesh space 33 inside.
A ceramic porous body 34 having the following is produced. If the outer shape of the ceramic porous body shown in Fig. 7 is machined,
You will get a piston.

[Effects of the Invention] As described above, according to the present invention, since the piston containing the cold storage material is made of a non-magnetic material, the magnetic field is not disturbed by the operation of the piston, and the bonding of the ceramic particles that are the cold storage material is prevented. Since the force is strong, it is possible to prevent the regenerator material from swinging during piston operation and from flowing out due to the high pressure gas flowing through the regenerator material, thereby improving performance and durability.

In addition, ceramic pistons can be manufactured with fewer steps and with a higher yield.

[Brief explanation of drawings]

Figure 1 shows a ceramic cylinder filled with ceramic grains; Figure 1 (al is a diagram showing the state before sintering;
Figure 1 (b) shows the state after sintering, Figure 2 shows the ceramic cylinder filled with ceramic grains coated with Merck, and Figure 2 (a) shows the state before sintering. Figure 2(b) is a diagram showing the state of sintering, Figure 3 is a diagram showing the method of manufacturing a piston using a preformed porous ceramic body, and Figure 4 is a diagram showing the state of sintering. Partially enlarged views of the porous body, and FIGS. 5 to 7 show examples of the third invention. FIG. 5 is a diagram showing a three-dimensional network resin, and FIG. 6 is a three-dimensional network formed by a plaster mold. Figure 7 shows the formation of alumina on shaped resin, and Figure 7 shows the ceramic after sintering.
;;rr Figure 8 (a), (b), and (C) are explanatory diagrams of the operation of a regenerator type tensioner using a ceramic piston.

Claims (7)

[Claims] (1) A piston for a regenerator expander, characterized in that the outer shell of the piston is made of a dense ceramic body, and the inside thereof is filled with a regenerator material made of a porous ceramic body. (2) The regenerator expander according to claim 1, wherein the ceramic porous body is formed by adhering ceramic particles filled in a ceramic cylinder to the cylinder and the particles to each other. piston. (3) A piston for a regenerative expander according to claim 1, characterized in that a preformed ceramic porous body is fixed inside a ceramic cylindrical body. (4) After filling the inside of the ceramic cylinder with ceramic particles coated with ceramic powder having a lower melting point than the particle material, sintering the ceramic particles to bond them to each other and at the same time fixing them to the ceramic cylinder. A method for manufacturing a piston for a regenerator expander characterized by: (5) A cylindrical porous ceramic body is preformed, the porous ceramic body is immersed in a ceramic slurry, a ceramic layer is formed on the surface of the porous body, and after drying, sintering is performed to form a ceramic porous body. A method for manufacturing a piston for a regenerator expander, characterized in that a ceramic skin is formed on the surface of a porous body. (6) While impregnating the inside of the cylindrical three-dimensional network resin, a ceramic layer is formed on the outer periphery, and after drying, the three-dimensional network resin is heated and sintered. A method for manufacturing a regenerator expansion piston characterized by burning out the material to form a dense ceramic material on the outer periphery and forming a porous material on the inside. (7) A piston control method for a regenerative expander according to claim 6, wherein the three-dimensional network resin is foamed urethane.