JPS61236968A - piston - 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 Application of the Invention] The present invention relates to pistons, particularly to pistons used in reciprocating expanders of cryogenic refrigeration equipment.

[Background of the invention]

A piston in a reciprocating expander of a cryogenic refrigeration system is made of a highly insulating plastic material in order to reduce the amount of heat entering the cylinder chamber.

(For example, medium boiler, Claude cycle @ compact refrigerator 1
, Cryogenic Engineering Association Refrigeration Subcommittee Seminar Materials, September 12, 1980, Ya Matsubara, "Refrigerating Systems of Cryoelectronics", Cryogenic Engineering, Vol. 159].

(1980) However, pistons made of highly insulating plastic materials such as phenolic resin and nylon.

Due to temperature changes, dimensional changes and bending occur more than 10 times as much as pistons made of metal materials such as stainless steel. In order to continue smooth operation even if the piston is deformed as shown in 2, the gap between the piston and cylinder must be increased in advance to account for the amount of piston deformation 1
However, there was a problem of increased cooling loss. On the other hand, in order to prevent cooling loss, it is necessary to reduce the deformation of the piston during operation, but this requires complicated methods such as annealing at high temperatures and adding heat cycle tests between room temperature and low temperature. The problem was that it required extensive processing.

[Purpose of the invention]

The purpose of the present invention is to create a piston that can suppress deformation due to changes in temperature and humidity without performing complicated treatments such as annealing treatment. It is about providing.

[Summary of the invention]

The present invention is characterized in that after a laminated material made by laminating a highly insulating plastic material and thread cloth is processed into the shape of a piston, a film of the plastic material is formed on the processed surface, and annealing is performed. This is an attempt to suppress the deformation of the piston due to changes in temperature and humidity without performing complicated treatments.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 1 to 4.

Therefore, the piston 20 reciprocates inside the cylinder o in synchronization with the exhaust of a working gas, for example, helium gas. The high-pressure helium gas supplied from the gas port 12 expands in the cylinder interior 12 to generate cold air, and is then discharged from the gas outlet 3. here,
In order to prevent cold air from escaping toward the high temperature side of the cylinder (outer chamber), it is necessary not only to provide a seal ring (5) but also to make the space between the cylinder O and the piston 20 as small as possible. is necessary.

In FIGS. 2 and 3 (A-human sectional view in FIG. 2).

In this case, 21 pieces of plastic material, such as phenolic resin, and 22 pieces of P cloth are stacked alternately in concentric circles mt
The M-layer material 23 is first machined in this case to ensure the required piston accuracy.

Due to this machining, the dimensions of the piston change, with the base fabric 22 exposed on the machined surface. In this case, since the laminated material 23 itself has no directionality and bends less, the piston also bends less. Therefore, in order to suppress the dimensional change of the piston, the machined surface is coated with, for example, phenol resin varnish to a thickness of 5 to 30 μm, as shown in FIG.

Thereafter, by drying at a temperature of 80 to 100° C. for about 1 hour, a hard coating 24 with low hygroscopicity is formed on the machined surface.

As shown in Fig. 2, the moisture absorption rate is as high as 1% in the C-machined product, whereas as shown in Fig. 4, the coating 24
The moisture absorption rate is 0.1% or less, and as a result, the change in the five dimensions is small.

In this example, the piston is formed from a laminated material with no directionality, and a coating is formed on the machined surface, so complex treatments such as annealing for deformation of the piston due to changes in temperature and humidity are performed. It can be suppressed without rubbing.

Note that the shape of the laminated material may be rod-like or hollow-tubular. Alternatively, a hollow tubular laminated material may be used for the body portion of the piston, and a flat laminated material may be used for the end plate portion of the piston, and the coating may be formed after the two are tied together with screws. If the thickness of the 1ξ coating becomes uneven or too thick, the surface of the coating may be machined to correct it.

〔Effect of the invention〕

As described above, the present invention has the effect of suppressing deformation of the piston due to changes in temperature and humidity without performing complicated treatments such as annealing treatment.

[Brief explanation of drawings]

Fig. 2 is a longitudinal sectional view of a cylinder portion of a reciprocating expander showing an embodiment of a piston according to the present invention;
FIG. 4 is a cross-sectional view showing the machining process of the piston shown in FIG. 1. 20... Piston, 23... Laminated material, 24... (lIIl!

Claims (1)

[Claims] 1. A piston characterized in that a laminated material made by laminating a highly insulating plastic material and thread cloth is processed into the shape of a piston, and then a film of plastic material is formed on the processed surface.