Non-contact packed piston for ultralow-temperature refrigerator

Abstract

The invention discloses a non-contact packed piston for an ultralow-temperature refrigerator. The non-contact packed piston is located in a cylinder, adopts a cylindrical structure, and comprises a cylindrical piston base body and a wear-resistant coating coating the outer surface of the piston base body, wherein the wear-resistant coating is cylindrical and has a certain thickness; a plurality of grooves are formed in the outer circular surface of the wear-resistant coating; and the inner circular surface of the wear-resistant coating takes the shape of a smooth cylinder matched with the outline of the piston base body. According to the non-contact packed piston, processing of the piston base body is avoided, stress changes in the cooling process are reduced, and the cylindricity of the piston base body in a low-temperature state is guaranteed to ensure the overall sealing performance.

Description

Technical field [0001] The invention relates to the technical field of piston sealing devices, in particular to a non-contact sealing piston for ultra-low temperature refrigerators. Background technique [0002] In recent years, with the rapid development of large cryogenic vacuum pumps, high and low temperature superconducting devices, nuclear magnetic resonance imaging (MRI), infrared detectors, and low temperature optoelectronic devices, the industrial demand for ultra-low temperature refrigerators is also increasing. The development of ultra-low temperature refrigerators It has become an important research direction in the field of cryogenic technology. The traditional sealing structure is to add a piston seal ring outside the piston, and the seal ring is in close contact with the inner wall of the cylinder to achieve its sealing purpose. This piston seal ring type sealing structure has many disadvantages as follows: First, the wear between the piston seal ring and the cylin...

AI Technical Summary

Problems solved by technology

There are many following disadvantages in the sealing structure of this piston seal ring type: firstly, the wear between the piston seal ring and the cylinder causes its short life, and as the working time goes on, the wear and tear of the seal ring will increase. The gas leakage of the refrigerator increases the cold loss of the refrigerator, so the piston seal ring needs to be replaced frequently, and the replacement of the piston ring will affect the stability of the refrigeration performance of the refrigerator; in addition, because the piston seal ring is Working at low temperature, the incomplete sealing caused by the cold shrinkage of the piston ring is unavoidable, which will inevitably lead to a decrease in the cooling capacity of the piston refrigerator and fluctuations in the cooling temperature

like figure 1 As shown, the problem existing in the structure: the surface of the piston base 1 is directly machined with a groove 2, which causes the strength of the groove to be weaker than that of other parts of the piston base 1. Due to the existence of stress, the radial direction of the piston base 1 at low temperature The stress will remain in the groove 2, causing the deformation of the groove 2, and then the coaxiality of the piston base 1 will decrease, and the piston will scratch the cylinder.

This kind of sealing structure is relatively complicated, which makes the processing and assembly of the piston more difficult.

In addition, the materials of the piston jacket and the piston lining are different. Pistons made of different materials have gaps due to different shrinkage rates. At low temperatures, especially at ultra-low temperatures in the liquid helium temperature zone, the gap between the labyrinth seals increases continuously as the temperature decreases. Large, which affects the overall sealing performance of the labyrinth piston at low temperatures

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