High specific heat displacement piston and preparation method thereof and cold storage refrigerator

Abstract

The present invention discloses a high specific heat push piston and a preparation method thereof and a cold storage refrigerator, belonging to the technical field of low temperature refrigerators. The high specific heat push piston comprises a piston cylinder (121), the outer peripheral surface of the piston cylinder (121) is provided with a groove (123a), and the bottom of the recessed area formed by the groove (123a) is covered with a groove coating material layer (124) of a material different from that of the piston cylinder (121), and below the 50K temperature range, the volume specific heat of the material used in the groove coating material layer (124) is greater than the volume specific heat of the material used in the piston cylinder (121). The preparation method prepares the push piston by first covering the groove coating material layer (124), then covering the resin layer (122) and a corresponding turning process. The cold storage refrigerator comprises the above-mentioned push piston. The push piston of the present invention can increase the volume specific heat of the piston cylinder wall, enhance the heat exchange capacity for the leaked gas in the gap, and improve the performance of the refrigerator.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature refrigerators, and in particular to a high-specific-heat displacement piston capable of improving the heat exchange capacity of a refrigerator, a preparation method thereof, and a cold storage refrigerator. Background Art

[0002] Cold storage refrigerators include, for example, GM refrigerators and Stirling refrigerators. These refrigerators have a cylinder body and a push piston that reciprocates inside the cylinder body. During the design process, if the high-temperature airflow at the hot end of the piston does not pass through the cold storage material for heat exchange, and directly leaks from the gap between the piston and the cylinder to the low-temperature side, it will cause a loss of cooling capacity in the refrigerator. To avoid the above problems, spiral grooves or gas labyrinth seals are usually processed on the outer circumference of the piston. Specifically, if Figure 1 The spiral groove structure shown in Figure 1 The piston cylinder 121 shown in A is made of stainless steel to ensure that the shrinkage rate is consistent with the cylinder at low temperatures, and the outer peripheral surface of the piston cylinder 121 is covered with Figure 1 The resin layer 122 shown in B is made of a wear-resistant resin material, and the thickness of the resin layer 122 is generally not more than 0.5 mm. During the reciprocating movement of the piston, the piston can be prevented from scratching the inner wall of the cylinder. At the same time, a spiral groove is machined along the outer circumference of the resin layer 122, and the depth of the spiral groove is ensured to penetrate the resin layer 122. Further, when turning the spiral groove, part of the stainless steel base material on the outer circumference of the piston cylinder 121 is turned off, so that the stainless steel material of the piston cylinder 121 is exposed ( Figure 1 C). In this way, firstly, compared with the case where the gas flows parallel to the cylinder axis, the gas flow path of the gap leakage between the cylinder and the piston is increased, so that the leaked gas and the outer peripheral surface of the piston can exchange heat more fully; secondly, compared with the resin material, the volume specific heat and thermal conductivity of the stainless steel cylinder are greater. During the intake process, the temperature corresponding to the cylinder cooling the refrigerant gas and the temperature corresponding to the cylinder heating the refrigerant gas during the exhaust process, the difference between these two temperatures is relatively smaller, that is, within one cycle, the temperature change of the cylinder corresponding to the same position is smaller, which means that the heat exchange temperature difference is lower, the heat exchange efficiency is higher, and it is more conducive to improving the heat exchange of the leaked gas in the gap slit.

[0003] The following takes the secondary push piston 12 as an example to explain the push piston provided in the prior art in detail. For a two-stage refrigerator, the secondary push piston 12 is in a low temperature condition as a whole and cannot be sealed by a sealing ring. A spiral groove or labyrinth seal is usually used. Figure 1 Combined with Figure 7For explanation. The piston cylinder 121 is made of stainless steel to be consistent with the material of the cylinder 13, so as to ensure that the shrinkage rates of the two are the same at low temperatures. The outer peripheral surface of the piston cylinder 121 is covered with a resin layer 122 made of a wear-resistant resin material. The wear-resistant resin material is usually polytetrafluoroethylene, which has an extremely low friction coefficient and wear resistance. During the long-term movement of the piston, it can be ensured that the gap size between the outer periphery of the secondary push piston 12 and the inner periphery of the secondary cylinder 132 does not change significantly. In order to improve the performance of the refrigerator, on the basis of the above-mentioned technology, a spiral groove 123 is spirally turned along the outer peripheral surface of the secondary push piston 12 and along the axial extension direction of the secondary push piston 12. The depth of the spiral groove 123 must penetrate the thickness of the resin layer 122. Further, when turning the spiral groove 123, part of the stainless steel substrate on the outer peripheral surface of the main body of the piston cylinder 121 must be turned off to allow the wall to more effectively exchange heat with the gas. By the above method, the back of the spiral groove 123 on the outer peripheral surface of the secondary push piston 12 is covered with a resin layer 122, and the bottom is made of stainless steel. At this time, compared with the tiny slit between the secondary cylinder body 132 and the secondary push piston 12, the spiral groove 123 formed on the outer peripheral surface of the piston cylinder 121 has a lower flow resistance. In addition to the refrigerant gas flowing through the secondary cold storage material 12c, the part will flow in the spiral longer flow path forming the spiral groove 123, and exchange heat with the stainless steel material with a larger volume specific heat and heat transfer coefficient than the resin material, gradually reducing the incoming high-temperature airflow, preventing the high-temperature gas from directly entering the secondary expansion chamber 10, so this can suppress the decline in refrigeration capacity, thereby improving the refrigeration efficiency of the GM refrigerator. When it is above the 50K temperature range, the stainless steel material has a larger volume specific heat and can be made into a wire mesh for use as the primary cold storage material 11c. However, when the temperature drops below 50K, the volume specific heat of stainless steel decreases sharply, while the volume specific heat of the refrigerant helium gradually increases, reaching a peak near the 10K temperature range. Since the volume specific heat of stainless steel is small at low temperatures, the specific heat capacity per unit volume at the same height position on the cylinder wall is not enough to cool or heat the gas, which will increase the temperature difference at the same position on the cylinder wall within a cycle, that is, the heat exchange temperature difference increases, resulting in a decrease in heat exchange efficiency, and there may be insufficient heat exchange between the airflow from the gap between the cylinder and the piston and the wall of the piston cylinder 121. Therefore, in the lower temperature range, the piston cylinder 121 made of stainless steel is not conducive to the heat exchange of the gas in the gap slit. Summary of the invention

[0004] The purpose of the present invention is to provide a high specific heat displacement piston and a preparation method thereof and a cold storage refrigerator that can improve the heat exchange capacity of a refrigerator in order to solve the problems existing in the prior art.

[0005] The purpose of the present invention is to be solved by the following technical solutions:

[0006] A high specific heat push piston includes a piston cylinder, characterized in that: a groove is provided on the outer peripheral surface of the piston cylinder, and a groove covering material layer different from the material of the piston cylinder is covered at the bottom of the recessed area formed by the groove, and below the 50K temperature range, the volume specific heat of the material used in the groove covering material layer is greater than the volume specific heat of the material used in the piston cylinder.

[0007] The entire recessed area formed by the groove is covered with a groove covering material layer different from the material of the piston cylinder.

[0008] The thickness of the groove covering material layer is not less than 1 μm and not more than 1000 μm.

[0009] The thickness of the groove covering material layer is 200 μm to 700 μm.

[0010] The thickness of the groove covering material layer is 300 μm to 500 μm.

[0011] The piston cylinder is made of stainless steel.

[0012] The material used for the groove covering material layer is at least one of zinc, tin and bismuth, or one of the corresponding alloy materials of tin, zinc and bismuth.

[0013] The groove covering material layer is made of a magnetic material, and the volume specific heat of the magnetic material below the 50K temperature range is greater than the volume specific heat of the piston cylinder material.

[0014] The material used for the groove covering material layer is holmium copper.

[0015] The groove covering material layer covering 1 / 2 to 2 / 3 of the length of the groove on the piston cylinder is made of at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth; the groove covering material layer covering the remaining 1 / 3 to 1 / 2 of the length of the groove on the piston cylinder is made of holmium copper.

[0016] The outer circumferential surface of the piston cylinder is provided with grooves and spiral grooves or labyrinth grooves, and the length of the grooves accounts for 1 / 3 to 1 / 2 of the total length of the grooves and the spiral grooves or labyrinth grooves. At this time, the material used for the groove covering material layer covered by the groove is at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth.

[0017] The groove is a spiral or labyrinth-shaped groove formed on the outer peripheral surface of the piston cylinder.

[0018] The outer peripheral surface of the piston cylinder body opposite to the cylinder is covered with a resin layer made of wear-resistant resin material, and the thickness of the resin layer is controlled between 5μm and 500μm to prevent the corresponding cylinder inner wall from being scratched during the up and down movement of the push piston.

[0019] The resin layer is located on the ridges of the grooves on the piston cylinder.

[0020] A method for preparing a high specific heat push piston, characterized in that: the method for preparing the push piston is to prepare the outer surface of the push piston, and the steps of the preparation method are as follows:

[0021] a. Use stainless steel to make the piston cylinder, and turn spiral grooves or labyrinth grooves on the outer surface of the piston cylinder;

[0022] b. Cover the outer circumference of the piston cylinder with a material whose volume specific heat is greater than that of stainless steel below the 50K temperature range and fill the corresponding spiral grooves or labyrinth grooves to form a groove covering material layer;

[0023] c. The outer peripheral surface of the piston cylinder covered with the groove coating material layer is processed by a turning process until the stainless steel base material of the piston cylinder is exposed;

[0024] d. Spray or bond a wear-resistant resin material as a resin layer on the spiral groove or labyrinth groove area of ​​the entire piston cylinder;

[0025] e. Following the trajectory of the initial spiral groove or labyrinth groove, a new spiral or labyrinth groove is re-processed and the depth of the groove is ensured to penetrate the resin layer and reach the groove covering material layer, thus completing the outer surface preparation of the push piston.

[0026] The groove covering material layer in step b is made by electroplating, metal deposition or metal melting so that the corresponding material covers the outer peripheral surface of the piston cylinder and fills the corresponding spiral grooves or labyrinth grooves.

[0027] When the material used for the groove coating material layer in step b is selected from zinc, tin, bismuth or one of the corresponding alloy materials of tin, zinc and bismuth, then in step d, the wear-resistant resin material needs to be made into a resin layer in the shape of a pipe in advance, and then the entire resin layer is bonded to the outer circumferential surface of the piston cylinder processed in step c by low-temperature glue.

[0028] The material used for the groove coating material layer in step b is holmium copper, and in step d, the wear-resistant resin material is directly sprayed on the outer peripheral surface of the piston cylinder processed in step c through a spraying process to form a resin layer.

[0029] The depth of the groove in step e penetrates the resin layer and enables the entire recessed area formed by the groove to be covered with the groove covering material layer.

[0030] The depth of the groove in step e) penetrates the resin layer and allows the bottom of the recessed area formed by the groove to be covered with the groove covering material layer.

[0031] A cold storage refrigerator using the above-mentioned high specific heat push piston is characterized in that: the cold storage refrigerator includes the above-mentioned high specific heat push piston, and the high specific heat push piston is installed in the cylinder of the low-temperature refrigerator.

[0032] When the cold storage refrigerator adopts a single-stage cylinder, the high specific heat push piston is installed in the cylinder; when the cold storage refrigerator adopts a multi-stage cylinder, the high specific heat push piston is installed in the cylinder after the primary cylinder.

[0033] When the cold storage refrigerator is a single-stage refrigerator with a temperature of 20K to 30K, the material used for the covering material layer of the piston cylinder of the high specific heat push piston in the 1 / 3 to 1 / 2 length area close to the low temperature side is at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth.

[0034] When the cold storage refrigerator adopts a two-stage cylinder, the high specific heat push piston is a two-stage push piston installed in a two-stage cylinder body.

[0035] When the cold storage refrigerator is a two-stage refrigerator of 4.2K~10K, the material used for the groove covering layer covering 1 / 2~2 / 3 of the length of the groove on the piston cylinder of the secondary push piston is at least one of zinc, tin, and bismuth, or one of the alloy materials corresponding to tin, zinc, and bismuth respectively; the material used for the groove covering layer covering the remaining 1 / 3~1 / 2 of the length of the groove on the piston cylinder of the secondary push piston is holmium copper.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] The high specific heat push piston of the present invention selects a metal material with a large volume specific heat below the 50K temperature range as the covering material to prepare the groove coating material layer, which can improve the volume heat exchange capacity of the outer peripheral surface of the push piston, so that during the heat exchange with the airflow flowing in and out of the gap, its own temperature can remain stable, which can reduce the temperature difference between the gas flowing in and out, and ensure that when the gas leaked in the narrow gap between the cylinder and the push piston passes through the groove, the heat exchange between the airflow and the wall surface is more stable and reliable; that is, the wall volume specific heat of the piston cylinder is increased, the heat exchange capacity for the leaked gas in the gap is enhanced, and the performance of the refrigerator is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Attached Figure 1 is a flow chart of the preparation of a push piston in the prior art, wherein A is a schematic diagram of the structure of a piston cylinder, B is a schematic diagram of the structure of a resin layer covering the outer circumferential surface of the piston cylinder, and C is a schematic diagram of the structure of a push piston prepared in the prior art;

[0039] Attached Figure 2It is a schematic structural diagram of a push piston with a spiral groove of the present invention;

[0040] Attached Figure 3 The flowchart of the preparation of the high specific heat push piston of the present invention is shown in Figure 1, wherein A is a schematic diagram of the structure of a piston cylinder with spiral grooves or labyrinth grooves machined out, B is a schematic diagram of the structure of a piston cylinder covered with a groove coating material layer, C is a schematic diagram of the structure when the outer peripheral surface of the piston cylinder covered with the groove coating material layer is processed so that the piston cylinder is exposed to the position of the stainless steel substrate, D is a schematic diagram of the structure when a wear-resistant resin material is sprayed or bonded as a resin layer, and E is a schematic diagram of the structure of the high specific heat push piston prepared by the present invention;

[0041] Attached Figure 4 For attachment Figure 3 Schematic diagram of the combined structure of the AA section of the E part and the section of the secondary cylinder body;

[0042] Attached Figure 5 It is a schematic structural diagram of a high specific heat push piston with a labyrinth-shaped groove according to the present invention;

[0043] Attached Figure 6 A comparison diagram of the volume specific heat of the material used in the groove coating material layer of the present invention and the volume specific heat of the material used in the piston cylinder;

[0044] Attached Figure 7 The schematic diagram is a structural diagram of an embodiment of the present invention in which a high specific heat displacement piston is installed on a cold storage refrigerator.

[0045] Among them: 1-compressor; 2-hood assembly; 3-gas pipeline; 7-piston sealing ring; 8-heat chamber; 9-first-stage expansion chamber; 10-second-stage expansion chamber; 11-first-stage push piston; 11a-first-stage piston front hole; 11b-first-stage piston rear hole; 11c-first-stage cold storage material; 12-second-stage push piston; 12a-second-stage piston front hole; 12b-exhaust port; 12c-second-stage cold storage material; 13-cylinder; 131-first-stage cylinder body; 132-second-stage cylinder body; 13a-first-stage heat exchanger; 13b-second-stage heat exchanger; 121-piston cylinder body; 122-resin layer; 123-spiral groove; 123a-groove; 124-groove covering material layer; SUS304-stainless steel; Pb-lead; Zn-zinc; Sn-tin; Bi-bismuth; HoCu2-holmium copper. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0047] like Figure 2 , 4As shown in Figures 5 and 6, a high specific heat push piston includes a piston cylinder 121, and a resin layer 122 made of wear-resistant resin material is covered on the outer peripheral surface of the piston cylinder 121 opposite to the cylinder 13; a groove 123a is provided on the outer peripheral surface of the piston cylinder 121, and the groove 123a is a spiral or labyrinth-shaped groove formed on the outer peripheral surface of the piston cylinder 121, and the bottom of the recessed area formed by the groove 123a is covered with a groove-coating material layer 124 of a material different from that of the piston cylinder 121, and below the 50K temperature range, the volume specific heat of the material used in the groove-coating material layer 124 is greater than the volume specific heat of the material used in the piston cylinder 121. Another solution is: the entire recessed area formed by the groove 123a is covered with a groove-coating material layer 124 of a material different from that of the piston cylinder 121. The piston cylinder 121 is made of stainless steel, and the material used for the groove coating material layer 124 is at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth; or the material used for the groove coating material layer 124 is a magnetic material, and the volume specific heat of the magnetic material below the 50K temperature range is greater than the volume specific heat of the piston cylinder 121 material, and the material used for the groove coating material layer 124 is holmium copper. In addition, when the groove coating material layer 124 covering 1 / 2 to 2 / 3 of the length of the groove 123a on the piston cylinder 121 is at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth; the material used for the groove coating material layer 124 covering the remaining 1 / 3 to 1 / 2 of the length of the groove 123a on the piston cylinder 121 is holmium copper. Or when there are grooves 123a and spiral grooves or labyrinth grooves 123 on the outer circumferential surface of the piston cylinder 121, and the length of the groove 123a accounts for 1 / 3 to 1 / 2 of the total length of the groove 123a and the spiral grooves or labyrinth grooves 123, the material used for the groove covering material layer 124 covered by the groove 123a is at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth.

[0048] When the above-mentioned high specific heat push piston includes a primary push piston 11 and a secondary push piston 12 , the groove 123 a is located on the piston cylinder 121 of the secondary push piston 12 .

[0049] A cold storage refrigerator using the high specific heat push piston, the cold storage refrigerator includes the high specific heat push piston, and the high specific heat push piston is installed in the cylinder 13 of the low temperature refrigerator. When the cold storage refrigerator uses a single-stage cylinder 13, the high specific heat push piston is installed in the cylinder 13; and when the cold storage refrigerator is a single-stage refrigerator with a temperature of 20K to 30K, the material used for the covering material layer 122 of the piston cylinder 121 of the high specific heat push piston in the 1 / 3 to 1 / 2 length area close to the low temperature side is at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth. When the cold storage refrigerator uses a multi-stage cylinder 13, the high specific heat push piston is installed in the cylinder 13 after the primary cylinder 13; and when the cold storage refrigerator uses a two-stage cylinder 13, the high specific heat push piston is a secondary push piston 12 installed in the secondary cylinder 132. Further, when the cold storage refrigerator is a two-stage refrigerator of 4.2K to 10K, the groove coating material layer 124 covered by the groove 123a of 1 / 2 to 2 / 3 length on the piston cylinder 121 of the secondary push piston 12 is made of at least one of zinc, tin, and bismuth, or one of the alloy materials corresponding to tin, zinc, and bismuth; the groove coating material layer 124 covered by the groove 123a of the remaining 1 / 3 to 1 / 2 length on the piston cylinder 121 of the secondary push piston 12 is made of holmium copper. The cold storage refrigerator is any type of refrigerator with a reciprocating push piston, not limited to Gifford-McMahon refrigerator, Solvang refrigerator, pulse tube refrigerator, etc.

[0050] like Figure 7 As shown: the cold storage refrigeration machine comprises a compressor 1, a cover assembly 2, a gas pipeline 3, a cylinder 13, a primary push piston 11, and a secondary push piston 12. The compressor 1 inhales and compresses the refrigerant gas, and discharges it as high-pressure refrigerant gas. The gas pipeline 3 supplies the high-pressure refrigerant gas to the cover assembly 2. The cylinder 13 is a two-stage cylinder, the main body of which is made of 304 stainless steel, the primary cylinder 131 and the secondary cylinder 132 are coaxially arranged, and the inner diameter of the secondary cylinder 132 is smaller than the inner diameter of the primary cylinder 131; a primary heat exchanger 13a is welded on the end (cold end) of the primary cylinder 131 away from the cover assembly 2, and a secondary heat exchanger 13b is welded on the end (cold end) of the secondary cylinder 132 away from the cover assembly 2, and the above heat exchangers are all made of copper. The first-stage cylinder 131 is provided with a first-stage push piston 11, and the second-stage cylinder 132 is provided with a second-stage push piston 12. The first-stage push piston 11 and the second-stage push piston 12 are coaxially connected. Figure 7 The secondary push piston 12 moves in the cylinder 13 along the direction Z1 to Z2. Figure 7If the refrigerant moves in the middle and upper part (Z1 direction), the volume of the primary expansion chamber 9 and the secondary expansion chamber 10 increases; otherwise, the corresponding expansion volume decreases. Under the change of the expansion chamber volume, the incoming refrigerant gas passes through the primary piston front hole 11a to exchange heat with the primary cold storage material 11c inside the primary push piston 11, and then flows out from the primary piston rear hole 11b to the primary expansion chamber 9; a part of the gas expands in the primary expansion chamber 9, and the remaining gas flows into the secondary push piston 12 through the secondary piston front hole 12a, exchanges heat with the secondary cold storage material 12c inside the secondary push piston 12, and then flows out from the exhaust port 12b and enters the secondary expansion chamber 10. In the above process, the refrigerant gas transfers its own heat to the cold storage material, and the temperature changes from normal temperature to low temperature. Along the above gas flow direction, that is, the Z2 direction, the temperature of the cylinder 13, the primary push piston 11, and the secondary push piston 12 continuously decreases, forming a temperature gradient.

[0051] like Figure 7 As shown: the flow process of the refluxed gas is opposite to the above process. The refrigerant gas flows out from the secondary expansion chamber 10, exchanges heat with the secondary cold storage material 12c in the secondary push piston 12 through the exhaust port 12b, flows out from the front hole 12a of the secondary piston, mixes with the refrigerant gas in the primary expansion chamber 9, and then exchanges heat with the primary cold storage material 11c inside the primary push piston 11 through the rear hole 11b of the primary piston, and then enters the cover assembly 2 through the front hole 11a of the primary piston, and then flows to the low-pressure side of the compressor 1. In the above process, the refrigerant gas absorbs heat from the cold storage material and changes from low temperature to normal temperature.

[0052] By repeating the above actions, the primary cold storage material 11c, the secondary cold storage material 12c and the refrigerant gas are cooled. The low-temperature gas continuously expands and performs work in the primary expansion chamber 9 and the secondary expansion chamber 10, forming a cooling source. Through the heat transfer effect, the primary heat exchanger 13a and the secondary heat exchanger 13b are cooled.

[0053] According to different temperature zones, the secondary cold storage material 12c near the high temperature side generally uses lead, zinc, tin, and bismuth as heat exchange materials; near the low temperature side, magnetic cold storage material holmium copper is used. The selected material has a large volume specific heat in the corresponding temperature zone. During the intake and reflux process, at the same height position of the secondary push piston 12, the cold storage material can form a stable temperature. During the heat exchange with the gas, the temperature remains almost unchanged, only gradually decreasing along the axial direction. In this way, the cold storage material 12c inside the secondary push piston 12 forms a stable and continuous temperature gradient. During the intake process, the airflow is cooled step by step by the cold storage material and enters the expansion chamber for expansion refrigeration; during the reflux process, the gas is heated step by step by the cold storage material, and finally enters the low-pressure chamber of the compressor to complete a cycle.

[0054] For the primary push piston 11, the piston seal ring 7 is used to seal the gap between its outer peripheral surface and the inner wall of the primary cylinder body 131 of the cylinder 13. Since the piston seal ring 7 is installed on the room temperature side, that is, close to the cover assembly 2, the temperature is moderately at a higher temperature during operation, which can effectively prevent the refrigerant gas from entering the primary expansion chamber 9 through the gap between the outer surface of the primary push piston 11 and the inner wall of the primary cylinder body 131. The temperature of the primary heat exchanger 13a is roughly in the temperature range of 40K to 80K.

[0055] Taking the secondary push piston 12 as an example, in order to improve the heat exchange effect between the flowing gas in the spiral groove 123 and the secondary push piston 12, the preparation method of the high specific heat push piston provided by the present invention is further described in detail.

[0056] like Figure 3 As shown, first, the cylinder piston 121 is made of stainless steel, and an appropriate margin is left on the outer diameter for later use. At the same time, a spiral groove or a labyrinth groove 123 is turned on the outer circumference of the cylinder piston 121. The structure is as shown in FIG. Figure 3 As shown in A.

[0057] Secondly, by electroplating, metal deposition or metal melting, a material with a volume specific heat greater than that of stainless steel below the temperature range of 50K is coated along the outer circumference of the piston cylinder 121 and filled with the corresponding spiral grooves or labyrinth grooves 123 to form a groove coating material layer 124. The structure is as shown in FIG. Figure 3 As shown in B, Figure 3 The dotted shaded portion in B is the groove covering material layer 124. The groove covering material layer 124 may be made of a metal with a low melting point such as zinc, tin, bismuth, or a magnetic material such as holmium copper.

[0058] Next, the outer peripheral surface of the piston cylinder 121 covered with the groove coating material layer 124 is processed by turning until the piston cylinder 121 is exposed to the position of the stainless steel substrate, that is, the concave area of ​​the spiral groove or labyrinth groove 123 is covered with the groove coating material layer 124 ( Figure 3 The dotted shaded area in C), the back of the spiral groove or labyrinth groove 123 exposes the base stainless steel part ( Figure 3 (C) The piston cylinder 121 is cylindrical in shape as a whole.

[0059] Fourth, a wear-resistant resin material is sprayed or bonded on the piston cylinder 121 as the resin layer 122. Since zinc, tin, and bismuth are low-melting-point metals and cannot withstand the high temperature of several hundred degrees during the resin powder spraying process, the resin material can be made into a pipe-shaped resin layer 122 in advance, and the whole is bonded to the outer peripheral surface of the processed piston cylinder 121 by low-temperature glue (such as Figure 3 D) to achieve; the melting point of holmium copper is 915℃, which can be directly Figure 3 The piston cylinder 121 in C is sprayed, and a resin layer 122 made of wear-resistant resin material is formed on the outer peripheral surface of the piston cylinder 121.

[0060] Finally, along the original spiral groove or labyrinth groove 123 track, a new spiral groove 123a is re-processed, and it is ensured that the depth of the new spiral groove 123a can penetrate the resin material 122; further, the depth of the new spiral groove 123a is to turn away a portion of the groove covering material layer 124 covering the original spiral groove or labyrinth groove 123, and at least a portion of the groove covering material layer 124 is retained to cover the bottom of the concave area formed by the original spiral groove or labyrinth groove 123 ( Figure 3 E); further, a portion of the groove covering material layer 124 is retained to cover the surface of the recessed area formed by the original spiral groove or labyrinth groove 123 to form a groove 123a.

[0061] like Figure 2 As shown, the outer circumferential surface of the piston cylinder 121 is finally covered with a resin layer 122 made of a wear-resistant resin material, and at the same time, the recessed area formed by the groove 123a on the outer circumferential surface has a groove covering material layer 124 made of a covering material with a higher volume specific heat at least at the bottom; during the implementation process, the side wall of the groove 123a can be processed to also have the groove covering material layer 124.

[0062] In the embodiment of the present invention, the magnetic rare earth material HoCu2 or the noble metal indium can be used as the covering material. Figure 6 The structure of the labyrinth-shaped groove 123a is a labyrinth seal.

[0063] During the implementation, the thickness of the groove covering material layer 124 is selected to be between 1 μm and 1 mm according to the wall thickness of the cylinder 13. Figure 3 The wall thickness of the piston cylinder 121 corresponding to the concave part of the spiral groove 123 in A is equivalent. The thickness of the groove coating material layer 124 should not be too large, because too thick material is likely to increase axial heat leakage loss, and further, the thickness can be selected to be 200μm to 700μm, and more preferably, the thickness can be selected to be 300μm to 500μm.

[0064] It is further explained that in the implementation process of the present invention, lead (Pb) as a non-environmentally friendly material is not recommended as the covering material selected for the groove covering material layer 124 in the present invention.

[0065] Further explanation, for the two-stage refrigerator of 4.2K~10K. Figure 3The structure of B is prepared by the following measures: the covering material of the piston cylinder 121 in the area of ​​1 / 2 to 2 / 3 of the length from the high-temperature side is prepared with one of zinc, tin and bismuth to prepare the groove covering material layer 124; the covering material in the area of ​​1 / 3 to 1 / 2 of the length from the low-temperature side is prepared with holmium copper to prepare the groove covering material layer 124.

[0066] Further explanation, for a single-stage refrigerator with a temperature of 20K to 30K. Figure 3 The structure of B is prepared by the following measures: the covering material of the piston cylinder 121 in the 1 / 3 to 1 / 2 length area close to the low temperature side is prepared with one of zinc, tin and bismuth to prepare the groove coating material layer 124; the remaining length area of ​​the piston cylinder 121 close to the hot end has a higher temperature, and the volume specific heat of stainless steel is large, so the helium can be fully cooled or heated, and other materials do not need to be covered.

[0067] The high specific heat push piston of the present invention selects a metal material with a large volume specific heat below the 50K temperature zone as the covering material to prepare the groove coating material layer 124, which can improve the volume heat exchange capacity of the outer peripheral surface of the push piston, so that during the heat exchange with the airflow flowing in and out of the gap, its own temperature can remain stable, which can reduce the temperature difference between the incoming and outgoing gases, and ensure that when the gas leaked in the narrow gap between the cylinder and the push piston passes through the groove 123a, the heat exchange between the airflow and the wall surface is more stable and reliable; that is, the wall volume specific heat of the piston cylinder 121 is increased, the heat exchange capacity for the leaked gas in the gap is enhanced, and the performance of the refrigerator is improved.

[0068] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention; any technology not involved in the present invention can be realized by existing technologies.

Claims

1. A method for preparing a high specific heat displacement piston, characterized in that: A high specific heat displacement piston comprises a piston cylinder (121), wherein the outer peripheral surface of the piston cylinder (121) is provided with a groove (123a), and the entire recessed area formed by the groove (123a) is covered with a groove-coating material layer (124) of a material different from that of the piston cylinder (121); below a temperature range of 50K, the volume specific heat of the material used in the groove-coating material layer (124) is greater than the volume specific heat of the material used in the piston cylinder (121); the material used in the groove-coating material layer (124) is a magnetic material; and the groove (123a) on the piston cylinder (121) covers 1 / 2 to 2 / 3 of its length. The groove covering material layer (124) is made of at least one of zinc, tin and bismuth or one of the alloy materials corresponding to tin, zinc and bismuth; the groove covering material layer (124) covering the remaining 1 / 3 to 1 / 2 of the length of the groove (123a) on the piston cylinder (121) is made of holmium copper; the thickness of the groove covering material layer (124) is 300 μm to 500 μm; the outer peripheral surface of the piston cylinder (121) facing the cylinder (13) is covered with a resin layer (122) made of a wear-resistant resin material, and the thickness of the resin layer (122) is controlled to be between 5 μm and 500 μm; The preparation method of the push piston is to prepare the outer surface of the push piston, and the steps of the preparation method are as follows: a. The piston cylinder (121) is made of stainless steel, and a spiral groove or a labyrinth groove (123) is machined on the outer peripheral surface of the piston cylinder (121); b. Covering the outer circumferential surface of the piston cylinder (121) with a material having a volume specific heat greater than that of stainless steel in a temperature range below 50K and filling the corresponding spiral grooves or labyrinth grooves (123) to form a groove covering material layer (124); c. machining the outer peripheral surface of the piston cylinder (121) covered with the groove covering material layer (124) by a turning process until the piston cylinder (121) exposes the stainless steel base material; d. spraying or bonding a wear-resistant resin material as a resin layer (122) on the spiral groove or labyrinth groove (123) of the entire piston cylinder (121); e. Following the trajectory of the initial spiral groove or labyrinth groove (123), a new spiral or labyrinth groove (123a) is re-processed and the depth of the groove (123a) is ensured to be able to penetrate the resin layer (122) and reach the groove coating material layer (124), thereby completing the preparation of the outer surface of the push piston.

2. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The piston cylinder (121) is made of stainless steel.

3. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The piston cylinder (121) has a groove (123a) and a spiral groove or a labyrinth groove (123) on its outer circumferential surface, and the length of the groove (123a) accounts for 1 / 3 to 1 / 2 of the total length of the groove (123a) and the spiral groove or the labyrinth groove (123). In this case, the groove covering material layer (124) covered by the groove (123a) is made of at least one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth.

4. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The groove (123a) is a spiral or labyrinthine groove formed on the outer peripheral surface of the piston cylinder (121).

5. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The resin layer (122) is located on the ridge of the groove (123a) on the piston cylinder (121).

6. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The groove covering material layer (124) in step b is manufactured by using an electroplating process, a metal deposition process or a metal melting process so that the corresponding material covers the outer peripheral surface of the piston cylinder (121) and fills the corresponding spiral groove or labyrinth groove (123).

7. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: When the material used for the groove coating material layer (124) in step b is selected from one of zinc, tin, and bismuth, or one of the corresponding alloy materials of tin, zinc, and bismuth, then in step d, the wear-resistant resin material needs to be made into a resin layer (122) in the shape of a pipe in advance, and then the entire resin layer (122) is bonded to the outer peripheral surface of the piston cylinder (121) processed in step c by low-temperature glue.

8. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The material used for the groove coating material layer (124) in step b is holmium copper, and in step d, the wear-resistant resin material is directly sprayed on the outer peripheral surface of the piston cylinder (121) processed in step c by a spraying process to form a resin layer (122).

9. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The depth of the groove (123a) in step e penetrates the resin layer (122) and enables the entire recessed area formed by the groove (123a) to be covered with the groove covering material layer (124).

10. The method for preparing a high specific heat displacement piston according to claim 1, characterized in that: The depth of the groove (123a) in step e penetrates the resin layer (122) and enables the bottom of the recessed area formed by the groove (123a) to be covered with the groove covering material layer (124).

11. A cold storage refrigerator using a high specific heat push piston obtained by the method for preparing a high specific heat push piston according to any one of claims 1 to 10, characterized in that: The cold storage refrigerator comprises the above-mentioned high specific heat push piston, and the high specific heat push piston is installed in the cylinder of the cold storage refrigerator.

12. The cold storage refrigerator according to claim 11, characterized in that: When the cold storage refrigerator adopts a multi-stage cylinder, the high specific heat displacement piston is installed in the cylinder after the primary cylinder.

13. The cold storage refrigerator according to claim 11, characterized in that: When the cold storage refrigeration machine adopts a two-stage cylinder, the high specific heat displacement piston is a two-stage displacement piston (12) installed in a two-stage cylinder body (132).

14. The cold storage refrigerator according to claim 13, characterized in that: When the cold storage refrigerator is a two-stage refrigerator of 4.2K to 10K, the groove coating material layer (124) covering 1 / 2 to 2 / 3 of the length of the groove (123a) on the piston cylinder (121) of the secondary push piston (12) is made of at least one of zinc, tin, and bismuth, or one of the alloy materials corresponding to tin, zinc, and bismuth; and the groove coating material layer (124) covering the remaining 1 / 3 to 1 / 2 of the length of the groove (123a) on the piston cylinder (121) of the secondary push piston (12) is made of holmium copper.

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