Integral free-piston stirling refrigerator device

Abstract

The present application discloses an integral free-piston Stirling refrigerator device, comprising a displacer structure, a power piston structure, and a vibration reduction assembly. The power piston structure comprises a power plate spring, a power bearing, and a power piston which are sequentially arranged in the axial direction, wherein the power plate spring is fixedly connected to the power bearing. The displacer structure comprises a first piston, a displacer plate spring, and a second piston which are sequentially arranged in the axial direction, wherein the displacer plate spring is connected to the first piston and the second piston by means of a first fastener, so that when the first piston and the second piston reciprocate under the action of an air pressure difference, the displacer plate spring radially supports the first piston and the second piston. In the device, a connecting rod mechanism in a conventional displacer structure is omitted, greatly reducing the motion damping of a displacer, and the hundred-watt cooling capacity is provided within a temperature interval of -196°C to -80°C.

Description

An integrated free piston Stirling refrigerator device Technical Field

[0001] The present application relates to the field of refrigeration and cryogenic technology, and in particular to an integral free-piston Stirling refrigerator device. Background Art

[0002] With the rapid development of molecular biology and life sciences, artificially created cryogenic environments are playing a vital role. Cryogenic storage technology has a wide range of applications in fields such as medicine and biology, including the preservation of blood and blood products, specialized pharmaceuticals, vaccines, human organs, and biological specimens. Generally speaking, the lower the temperature, the longer the sample's stable storage period. Different temperatures offer varying protective effects on biological specimens. -80°C is a common storage temperature for biological specimens. At this temperature, cellular DNA is relatively stable. Most biomacromolecules, such as RNA, proteins, and lipids, exhibit a certain degree of stability at -80°C, allowing biological specimens to be stored for several months. -196°C is the temperature of liquid nitrogen. At this temperature, physiological and biochemical activities within biological specimens essentially cease, allowing them to be preserved for decades. The establishment of cryogenic cold storage and freezers within the -196°C to -80°C temperature range requires appropriate refrigeration methods.

[0003] For temperatures between -196°C and -80°C, traditional single-stage vapor compression refrigeration often cannot reach this cryogenic temperature range and can only be achieved through relatively complex multi-stage cascade or mixed-refrigerant self-cascade refrigeration technology, resulting in a low refrigeration coefficient. Vapor compression refrigerators are not only bulky, complex, and inefficient in cryogenic temperatures, but the chlorofluorocarbon refrigerants they use also have a certain negative impact on ozone depletion and global warming. The Stirling refrigeration principle is based on the reverse Stirling cycle, utilizing the expansion of an alternating flow of compressible gas for refrigeration. Its theoretical efficiency is the Carnot efficiency. The refrigerant within the system is generally non-polluting inert helium, and there is no phase change during operation. The sealing method uses a gap seal. Stirling refrigerators have the advantages of low vibration, compact structure, small size, energy conservation and environmental protection, strong reliability, long service life, and a wide refrigeration temperature range.

[0004] Since the free-piston Stirling refrigerator was first proposed, the structural design of the displacer has been crucial to determining the cooling effect and overall structure. The existing displacer structure primarily consists of a thin rod connected to the power piston near the compression chamber. The rod passes through the power piston and the linear motor, and the end of the rod is connected to a displacer spring fixed within the back-pressure chamber, forming a free piston. The disadvantage of this piston-through-rod structure is that the power piston and displacer are prone to mutual motion interference, increasing the damping of the displacer and resulting in a decrease in cooling effect. It also increases the design difficulty of the power piston, resulting in low stability and difficult installation.

[0005] Therefore, the present application urgently needs to develop an integral free-piston Stirling refrigerator device, which eliminates the connecting rod mechanism in the conventional displacer structure, greatly reduces the damping of the displacer motion, and at the same time provides a cooling capacity of hundreds of watts in the temperature range of -196°C to -80°C, with the advantages of high cooling efficiency, environmental friendliness, long life and low vibration.

[0006] Summary of the Invention

[0007] The purpose of the present application is to provide an integral free-piston Stirling refrigerator device, which eliminates the connecting rod mechanism in the conventional displacer structure, greatly reduces the damping of the displacer movement, and at the same time provides a cooling capacity of hundreds of watts in the temperature range of -196°C to -80°C, with the advantages of high cooling efficiency, environmental friendliness, long life and low vibration.

[0008] A first aspect of the present application provides an integrated free-piston Stirling refrigerator device comprising:

[0009] It includes: a displacer structure and a power piston structure, wherein:

[0010] The power piston structure comprises a power leaf spring, a power bearing and a power piston arranged in sequence along the axial direction, wherein the power leaf spring is connected to the power bearing;

[0011] The displacer structure includes a first piston, a displacer plate spring, and a second piston sequentially arranged in the axial direction.

[0012] wherein the discharge plate spring is connected to the first piston and the second piston via a first fastener, such that when the first piston and the second piston reciprocate under the action of a gas pressure difference, the discharge plate spring radially supports the first piston and the second piston and provides axial stiffness to the first piston and the second piston;

[0013] During the refrigeration process, high-pressure gas flows back and forth in the expansion chamber of the second piston at one end away from the discharge plate spring and the compression chamber between the first piston and the power piston. The gas in the expansion chamber performs positive work on the discharger structure, thereby providing refrigeration.

[0014] In another preferred embodiment, the displacer structure and the power piston structure constitute the cylinder assembly and the piston assembly of the refrigerator device.

[0015] In another preferred example, the cylinder assembly includes a first cylinder, a second cylinder and a cylinder base, the cylinder base is located above the first cylinder, the upper end of the first cylinder is coaxially inserted into the cylinder base, and the lower end of the first cylinder is coaxially inserted into the second cylinder; the two ends of the discharge plate spring are fixedly connected to the first cylinder or the second cylinder, so as to realize the reciprocating motion of the first piston in the first cylinder, the reciprocating motion of the second piston in the second cylinder, and the sliding of the power piston in the first cylinder.

[0016] In another preferred example, the discharge plate spring is located between the first piston and the second piston.

[0017] In another preferred embodiment, the discharge leaf spring is composed of a double discharge leaf spring.

[0018] In another preferred example, the central axes of the first piston and the second piston are on the same straight line.

[0019] In another preferred embodiment, the central axes of the first piston and the second piston pass through the center point of the discharge leaf spring.

[0020] In another preferred example, the discharge plate spring is fixedly connected to the first piston and the second piston via a first fastener.

[0021] In another preferred example, the first piston, the second piston, and the discharge plate spring are coaxially installed.

[0022] In another preferred example, the first piston includes a cylindrical structure with a protruding bottom surface, the second piston includes a cylindrical structure with a protruding bottom surface, the first piston includes a first protruding bottom surface protruding toward the discharge plate spring, and the second piston includes a second protruding bottom surface protruding toward the discharge plate spring.

[0023] In another preferred example, the ejector structure further includes a first fastener, the first protruding bottom surface is provided with a first protruding portion, the second protruding bottom surface is provided with a second protruding portion, the first fastener passes through the ejection plate spring and is connected to the first protruding portion and the second protruding portion, thereby fixing the ejection plate spring to the first piston and the second piston.

[0024] In another preferred embodiment, the first protrusion is located at the center of the first protruding bottom surface, and the first protrusion is a cylindrical structure extending toward the discharge plate spring.

[0025] In another preferred embodiment, the second protrusion is located at the center of the second protrusion bottom surface, and the second protrusion is a cylindrical structure extending toward the discharge plate spring.

[0026] In another preferred embodiment, the first fastener is a stud.

[0027] In another preferred example, the first protrusion is a cylindrical structure with an internal thread, and the second protrusion is a cylindrical structure with an internal thread. The internal thread cooperates with the external thread of the stud to complete the connection. Preferably, an appropriate amount of thread glue is applied when the first protrusion and the second protrusion are threadedly connected to the stud.

[0028] In another preferred example, when the discharge leaf spring is connected to the first protrusion and the second protrusion by the first fastener, the end face of the first protrusion is in contact with one surface of the discharge leaf spring, and the end face of the second protrusion is in contact with the other surface of the discharge leaf spring.

[0029] In another preferred example, the maximum axial distance between the first protruding bottom surface of the first piston and the discharge plate spring should be greater than the maximum amplitude of the discharger structure, and the maximum axial distance between the second protruding bottom surface of the second piston and the discharge plate spring should also be greater than the maximum amplitude of the discharger structure.

[0030] In another preferred example, the ejector structure further includes a first cylinder and a second cylinder, and both ends of the ejector plate spring are fixedly connected to the first cylinder or the second cylinder, thereby realizing reciprocating motion of the first piston in the first cylinder and reciprocating motion of the second piston in the second cylinder.

[0031] In another preferred embodiment, the ends of both ends of the discharge leaf spring away from the center are fixedly connected to the end surface of the first cylinder through a second fastener.

[0032] In another preferred embodiment, the second fastener is a hexagon socket screw.

[0033] In another preferred example, the second cylinder includes a connecting section and a accommodating section. The connecting section is located outside the first cylinder in the radial direction of the cylinder, and a gap between the connecting section and the first cylinder is sealed.

[0034] In another preferred example, the first cylinder and the second cylinder are gap-sealed by a cylinder seal.

[0035] In another preferred embodiment, the interface between the connecting section of the second cylinder and the first cylinder is coated with glue, thereby fixing the second cylinder and the first cylinder.

[0036] In another preferred example, the first cylinder is inserted into the connecting section of the second cylinder.

[0037] In another preferred embodiment, a plurality of grooves are provided on the inner wall of the accommodating section to reduce the amount of air cross-talk between the compression chamber and the expansion chamber through the gap, which has a positive effect on the sealing effect.

[0038] In another preferred embodiment, the positional relationship between the first piston, the second piston and the discharge plate spring must satisfy the following formula:

[0039] Wherein, m1 is the mass of the first piston, m2 is the mass of the second piston, L1 is the axial distance between the center point of the first piston and the center point of the discharge leaf spring along the axial direction of the first piston, L2 is the axial distance between the center point of the second piston and the center point of the discharge leaf spring along the axial direction of the second piston, g is the acceleration due to gravity, k is the radial stiffness of the discharge leaf spring, and δ is the air gap height between the outer wall surface of the first piston and the inner wall surface of the first cylinder.

[0040] In another preferred embodiment, the power piston is designed as a hollow structure, and the power piston includes a power piston housing and a power piston end cover.

[0041] The first piston is designed as a hollow structure, comprising a first piston outer shell and a first piston top cover, the first piston outer shell and the first piston top cover being sealed by a first piston seal, and the first piston outer shell is a cylindrical structure with a convex bottom surface;

[0042] The second piston is designed as a hollow structure. The second piston includes a second piston outer shell and a second piston top cover. The second piston outer shell and the second piston top cover are fixedly connected and sealed by threads. The second piston outer shell is a cylindrical structure with a protruding bottom surface.

[0043] In another preferred example, the first piston outer shell and the first piston top cover are fixed by a first piston fastener.

[0044] In another preferred embodiment, the first piston outer shell is a cylindrical structure with a bottom surface.

[0045] In another preferred example, the second piston outer shell is a cylindrical structure with a bottom surface.

[0046] In another preferred example, the first piston outer shell and the second piston outer shell are close to the discharge leaf spring and are arranged opposite to each other.

[0047] In another preferred embodiment, the first piston is made of aluminum alloy, and the second piston is made of engineering plastic.

[0048] In another preferred embodiment, the outer surface of the first piston is sprayed with a wear-resistant lubricating coating, preferably, sprayed with a Teflon coating.

[0049] In another preferred embodiment, the first cylinder is made of aluminum alloy, and the second piston is made of engineering plastic.

[0050] In another preferred embodiment, the inner cylinder wall surface of the first cylinder is polished and hard-oxidized.

[0051] In another preferred example, the device also includes a vibration damping assembly, which is located above the displacer structure and the power piston structure. The vibration damping assembly includes a power vibration damping mechanism and a damping vibration damping mechanism. The power vibration damping mechanism is used to eliminate the vibration of the refrigerator's fundamental frequency, and the damping vibration damping mechanism is used to weaken high-frequency vibrations. The damping vibration damping mechanism is located above the power vibration damping mechanism.

[0052] In another preferred embodiment, the power vibration damping mechanism includes multiple groups of power vibration damping leaf springs, counterweights, and large power vibration damping screws, and the power vibration damping leaf springs and the counterweights are fixed together by the large power vibration damping screws;

[0053] The damping vibration reduction mechanism includes a damping filler, a damping disc, a gasket, a damping vibration reduction plate spring, and a large damping vibration reduction screw arranged in sequence along the axial direction. The damping vibration reduction plate spring, the gasket, and the damping disc are connected and fixed by the large damping vibration reduction screw.

[0054] In another preferred example, the device also includes a shell assembly and a cold finger assembly arranged at the lower end of the shell assembly; the vibration damping assembly, the ejector structure and the power piston structure are arranged in the shell assembly and the cold finger assembly, and the cold finger assembly includes a cold finger base, a hot end heat dissipation copper ring, a heat regenerator shell, a cold end heat dissipation copper ring, and a cold finger end cover that are coaxially connected in sequence; and a hot end heat dissipation filler, a heat regenerator, a cold end heat dissipation filler, a hot end limit steel ring, a heat regenerator limit ring, and a cold end limit steel ring that are arranged in sequence along the axial direction.

[0055] In another preferred embodiment, the hot end heat dissipation filler, the regenerator, and the cold end heat dissipation filler are arranged between the second cylinder and the hot end heat dissipation copper ring, the regenerator shell, and the cold end heat dissipation copper ring;

[0056] The hot end limiting steel ring, the regenerator limiting ring, and the cold end limiting steel ring are used to fix the hot end heat dissipation filler, the regenerator, and the cold end heat dissipation filler respectively.

[0057] In another preferred embodiment, a linear motor assembly is further included. The linear motor assembly is located above the cylinder base, and the linear motor assembly includes an outer magnetic yoke, a permanent magnet mover, an inner magnetic yoke, and a coil.

[0058] In another preferred example, the permanent magnet mover includes a permanent magnet, a permanent magnet lower support ring, a permanent magnet upper support ring, and a transmission connecting plate.

[0059] In another preferred example, an outer yoke upper support ring is provided at the upper end of the outer yoke, and an outer yoke lower support ring is provided at the lower end. The outer yoke upper support ring, the outer yoke, and the outer yoke lower support ring are axially stacked and fixed on the cold finger base.

[0060] In another preferred example, the permanent magnet mover is fixed to the power bearing by a tightening nut, the power leaf spring is arranged on the support ring on the outer magnetic yoke, and the power leaf spring and the support ring on the outer magnetic yoke are fastened together by a third screw, and the inner magnetic yoke is fixed on the cylinder base.

[0061] In another preferred example, the housing assembly includes an annular housing and a housing end cover, the lower end surface of the annular housing is fixedly connected to the cold finger base, and the upper end surface of the annular housing is fixedly connected to the housing end cover.

[0062] In another preferred example, the housing assembly further includes a wiring terminal and an air-filled copper tube, wherein the wiring terminal is used to connect the lead of the coil, the wiring terminal is arranged on one side of the annular housing, and the air-filled copper tube is arranged on the other side of the annular housing.

[0063] A second aspect of the present application provides an integrated free-piston Stirling refrigerator device, comprising a vibration reduction assembly, wherein the vibration reduction assembly is located above the displacer structure and the power piston structure, the vibration reduction assembly comprising a power vibration reduction mechanism and a damping vibration reduction mechanism, the power vibration reduction mechanism being used to eliminate vibrations at the fundamental frequency of the refrigerator, and the damping vibration reduction mechanism being used to reduce high-frequency vibrations; the damping vibration reduction mechanism being located above the power vibration reduction mechanism;

[0064] The power vibration reduction mechanism includes multiple groups of power vibration reduction leaf springs, counterweight blocks, and large power vibration reduction screws, and the power vibration reduction leaf springs and counterweight blocks are fixed together by the large power vibration reduction screws;

[0065] The damping vibration reduction mechanism includes a damping filler, a damping disc, a gasket, a damping vibration reduction plate spring, and a large damping vibration reduction screw arranged in sequence along the axial direction. The damping vibration reduction plate spring, the gasket, and the damping disc are connected and fixed by the large damping vibration reduction screw.

[0066] In another preferred embodiment, the device further comprises a displacer structure and a power piston structure, wherein the power piston structure comprises a power leaf spring, a power bearing and a power piston sequentially arranged in the axial direction, wherein the power leaf spring is connected to the power bearing;

[0067] The displacer structure includes a first piston, a displacer plate spring, and a second piston sequentially arranged in the axial direction.

[0068] wherein the discharge plate spring is connected to the first piston and the second piston via a first fastener, such that when the first piston and the second piston reciprocate under the action of a gas pressure difference, the discharge plate spring radially supports the first piston and the second piston and provides axial stiffness to the first piston and the second piston;

[0069] During the refrigeration process, high-pressure gas flows back and forth in the expansion chamber of the second piston at one end away from the discharge plate spring and the compression chamber of the first piston at one end away from the discharge plate spring. The gas in the expansion chamber does positive work on the discharger structure, thereby providing refrigeration.

[0070] In another preferred example, it also includes a shell assembly and a cold finger assembly arranged at the lower end of the shell assembly; the vibration damping assembly, the ejector structure and the power piston structure are arranged in the shell assembly and the cold finger assembly, and the cold finger assembly includes a cold finger base, a hot end heat dissipation copper ring, a heat regenerator shell, a cold end heat dissipation copper ring, and a cold finger end cover that are coaxially connected in sequence; as well as a hot end heat dissipation filler, a heat regenerator, a cold end heat dissipation filler, a hot end limit steel ring, a heat regenerator limit ring, and a cold end limit steel ring that are arranged in sequence along the axial direction.

[0071] In another preferred embodiment, a linear motor assembly is further included. The linear motor assembly is located above the cylinder base, and the linear motor assembly includes an outer magnetic yoke, a permanent magnet mover, an inner magnetic yoke, and a coil.

[0072] In another preferred example, the housing assembly includes an annular housing and a housing end cover, the lower end surface of the annular housing is fixedly connected to the cold finger base, and the upper end surface of the annular housing is fixedly connected to the housing end cover.

[0073] In another preferred embodiment, the first piston includes a cylindrical structure with a protruding bottom surface, and the second piston includes a cylindrical structure with a protruding bottom surface. The first piston includes a first protruding bottom surface that protrudes toward the discharge plate spring, and the second piston includes a second protruding bottom surface that protrudes toward the discharge plate spring. In another preferred embodiment, the ejector structure further includes a first fastener, wherein the first protruding bottom surface is provided with a first protrusion, and the second protruding bottom surface is provided with a second protrusion. The first fastener passes through the discharge plate spring and connects with the first and second protrusions, thereby fixedly connecting the discharge plate spring to the first and second pistons.

[0074] In another preferred example, the ejector structure further includes a first cylinder and a second cylinder, and both ends of the ejector plate spring are fixedly connected to the first cylinder or the second cylinder, thereby realizing reciprocating motion of the first piston in the first cylinder and reciprocating motion of the second piston in the second cylinder.

[0075] In another preferred embodiment, the power piston is designed as a hollow structure, and the power piston includes a power piston housing and a power piston end cover.

[0076] The first piston is designed as a hollow structure, comprising a first piston outer shell and a first piston top cover, the first piston outer shell and the first piston top cover being sealed by a first piston seal, and the first piston outer shell is a cylindrical structure with a convex bottom surface;

[0077] The second piston is designed as a hollow structure. The second piston includes a second piston outer shell and a second piston top cover. The second piston outer shell and the second piston top cover are fixedly connected and sealed by threads. The second piston outer shell is a cylindrical structure with a protruding bottom surface.

[0078] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features described in detail below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be listed here one by one. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. It should be understood that the drawings described below are merely some implementation examples of the present invention, and those skilled in the art can also derive other implementation examples based on these drawings without inventive effort.

[0080] FIG1 is a schematic diagram of an integrated free-piston Stirling refrigerator device according to an embodiment of the present application;

[0081] FIG2 is a schematic diagram of the structure of an ejector of a free piston Stirling refrigerator according to an embodiment of the present application;

[0082] FIG3 is a schematic cross-sectional view of the displacer structure of a free piston Stirling refrigerator device according to an embodiment of the present application;

[0083] FIG4 is a schematic structural diagram of a discharge plate spring of an ejector structure according to an embodiment of the present application;

[0084] FIG5 is a schematic structural diagram of a vibration reduction assembly according to an embodiment of the present application.

[0085] In the accompanying drawings, the reference numerals are as follows: 1-first piston; 10-first protruding bottom surface; 101-first protruding portion; 11-first piston outer housing; 12-first piston top cover; 13-first piston seal; 14-first piston fastener; 2-second piston; 20-second protruding bottom surface; 201-second protruding portion; 21-second piston outer housing; 22-second piston top cover; 3-discharge leaf spring; 31-first fastener; 32-second fastener; 40-cylinder base; 41-first cylinder; 42-second cylinder; 43-cylinder seal; 421-connecting section; 422-accommodating section; 4221-groove; 51-power leaf spring; 52-power bearing; 53-power piston housing; 54-power piston end cover; 55-fastening piece; 61-Power vibration damping plate spring; 62-Counterweight; 63-Power vibration damping large screw; 64-First welding ring; 65-First screw; 71-Damping filler; 72-Damping disc; 73-Gasket; 74-Damping vibration damping plate spring; 75-Damping vibration damping large screw; 76-Second welding ring; 77-Second screw; 81-Cold finger base; 82-Hot end heat dissipation copper ring; 83-Regenerator shell; 84-Cold end heat dissipation copper ring; 85-Cold finger end cover; 86-Hot end heat dissipation filler; 87-Regenerator; 88-Cold end heat dissipation filler; 89-Hot end limit steel ring; 810-Regenerator limit ring; 811-Cold end limit steel ring; 91-Outer magnetic yoke; 911-Outer magnetic yoke upper support ring; 912-Outer magnetic yoke lower support ring; 92-Inner magnetic yoke; 93-Coil; 94- Permanent magnet; 95-permanent magnet lower support ring; 96-permanent magnet upper support ring; 97-transmission connecting plate; 98-fastening nut; 99-third screw; 1001-annular housing; 1002-housing end cover; 1003-connecting terminal; 1004-inflatable copper tube; L1-axial distance between the center point of the first piston and the center point of the discharge plate spring along the axial direction of the first piston; L2-axial distance between the center point of the second piston and the center point of the discharge plate spring along the axial direction of the second piston; δ-air gap height between the outer wall surface of the first piston and the inner wall surface of the first cylinder. DETAILED DESCRIPTION

[0086] Through extensive and in-depth research, the inventors have developed for the first time an integral free-piston Stirling refrigerator device. By setting a dynamic vibration reduction mechanism and a damping vibration reduction mechanism, the vibration reduction component of the present application can not only eliminate the vibration of the refrigerator's fundamental frequency, but also weaken high-frequency vibrations, thereby enhancing the stability of the refrigerator device; at the same time, the device is provided with a unique ejector structure, which abandons the slender connecting rod structure of the ejector plate spring known in the prior art, eliminates the direct interference and wear between the ejector and other components of the refrigerator, greatly reduces friction damping, and takes into account the characteristics of air tightness, low axial heat conduction and low mass, thereby achieving a better cooling effect.

[0087] As used herein, "ejector" and "ejector structure" are used interchangeably.

[0088] As used herein, "housing," "casing," and "housing body" are used interchangeably.

[0089] As used herein, “axial distance” refers to a distance along the axial direction of the first piston or the second piston.

[0090] As used herein, "hot end piston," "hot end discharge piston," and "first piston" refer to the same component;

[0091] As used herein, "cold end piston," "cold end discharge piston," and "second piston" refer to the same component;

[0092] As used herein, "first cylinder" and "hot end cylinder" refer to the same component;

[0093] As used herein, "second cylinder" and "cold-end cylinder" refer to the same component;

[0094] It should be noted that in this patent application, relational terms such as first and second, etc., are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. Without further limitation, an element specified by the phrase "comprising a" does not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element. In this patent application, reference to performing an action in accordance with an element means performing the action in accordance with at least that element, including two situations: performing the action in accordance with that element alone, and performing the action in accordance with that element and other elements. Expressions such as "plurality," "multiple times," and "many" include "two," "twice," "two kinds," and "more than two," "more than two times," and "more than two kinds."

[0095] In the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0096] Main advantages of the present invention

[0097] (a) The refrigerator device of the present application is provided with a dynamic vibration reduction mechanism and a damping vibration reduction mechanism so that the vibration reduction assembly of the present application can not only eliminate the vibration of the refrigerator's fundamental frequency, but also reduce high-frequency vibration;

[0098] (b) The combination of the dynamic vibration reduction mechanism and the damping vibration reduction mechanism of the refrigerator device of the present application improves the vibration reduction effect of the refrigerator and enhances the stability of the refrigerator device, and is suitable for working environments with high vibration requirements;

[0099] (c) The ejector structure of the present application eliminates the slender connecting rod structure of the ejector plate spring known in the prior art. By removing redundant parts other than the cylinder that can directly wear against the ejector, the friction damping of the ejector structure is greatly reduced during movement.

[0100] (d) The displacer structure of the present application eliminates direct interference and wear between the displacer piston and other components of the refrigerator, thereby improving the refrigeration efficiency and stability of the refrigerator;

[0101] (e) The ejector structure of the present application solves the problem of excessive distance between the ejector leaf spring and the ejector piston in the prior art by arranging the ejector leaf spring between the first piston and the second piston. This makes the coaxiality of the entire ejector easy to control, reduces the difficulty of installation, and improves stability.

[0102] (f) The ejector structure of the present application is smaller in size, which reduces the weight of the refrigerator and reduces the difficulty of installation.

[0103] In the following description, many technical details are provided to help readers better understand this application. However, those skilled in the art will understand that even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can be implemented.

[0104] The displacer is a key component of a free-piston Stirling refrigerator, regulating the phase of the working fluid flow within the refrigerator. A Stirling refrigerator consists of alternating oscillations between the compression piston and the displacer. High-pressure gas (helium) flows back and forth between the compression chamber, the hot-end radiator, the regenerator, the cold-end heat exchanger, and the expansion chamber. During a single refrigerator cycle, the gas in the expansion chamber performs positive work on the displacer, generating cooling capacity in the expansion chamber. Simultaneously, the displacer transfers the work done by the gas in the expansion chamber to the compression chamber, recovering acoustic work and improving the refrigerator's efficiency.

[0105] A free-piston Stirling refrigerator is a pneumatic refrigerator, meaning the movement of the displacer is driven by the pressure difference between the compression and expansion chambers, without any additional force driving its motion or phasing the internal gases. In a free-piston Stirling refrigerator, the displacer is directly connected to the displacer spring and is independent of the compression system, effectively acting as a "free" piston. The mass of the displacer, the stiffness of the displacer spring, and the damping during the displacer's motion play a key role in its phasing function.

[0106] The present application provides an ejector structure for a free-piston Stirling refrigerator. The structure adopts a dual-cylinder-dual ejector, which can reduce the damping of the ejector movement process, reduce the axial heat conduction from the hot end through the cylinder and the ejector to the cold end (for example, the second piston is made of engineering plastic with a low thermal conductivity coefficient), reduce the cross-flow between the compression chamber and the expansion chamber through the ejector, ensure the stable operation of the ejector, reduce the difficulty of installation, and improve the stability and cooling efficiency of the refrigerator.

[0107] Integral free piston Stirling refrigerator device

[0108] Referring to Figure 1, the refrigerator device of the present application includes a housing assembly, a cold finger assembly arranged at the lower end of the housing assembly, a power piston structure, a displacer structure, a vibration damping assembly, and a linear motor assembly arranged in sequence axially. The vibration damping assembly, the displacer structure, and the power piston structure are arranged within the housing assembly and the cold finger assembly. The piston assembly (first piston, second piston, and power piston) included in the refrigerator device of the present application slides within the cylinder assembly (first cylinder, second cylinder), and the piston assembly and the cylinder assembly together constitute the displacer structure and power piston structure of the refrigerator device described in the present application.

[0109] Vibration damping components

[0110] Referring to Figure 5, the vibration reduction assembly is located above the displacer structure and the power piston structure. The vibration reduction assembly includes a power vibration reduction mechanism and a damping vibration reduction mechanism. The power vibration reduction mechanism is used to eliminate the vibration of the fundamental frequency of the refrigerator, and the damping vibration reduction mechanism is used to weaken the high-frequency vibration; the damping vibration reduction mechanism is located above the power vibration reduction mechanism.

[0111] The power vibration reduction mechanism includes multiple groups of power vibration reduction plate springs 61, counterweights 62, and large power vibration reduction screws 63, which fix the power vibration reduction plate springs 61 and the counterweights 62 together through the large power vibration reduction screws 63; the damping vibration reduction mechanism includes a damping filler 71, a damping disc 72, a gasket 73, a damping vibration reduction plate spring 74, and a large damping vibration reduction screw 75 arranged in sequence along the axial direction, and the damping vibration reduction plate spring 74, the gasket 73, and the damping disc 72 are connected and fixed through the large damping vibration reduction screws 75.

[0112] The vibration reduction assembly is composed of a power vibration reduction mechanism and a damping vibration reduction mechanism. The power vibration reduction mechanism is used to eliminate the vibration of the refrigerator's fundamental frequency, and the damping vibration reduction mechanism is used to reduce the refrigerator's high-frequency vibration. It has a simple structure, low installation difficulty, and greatly reduces the vibration of the refrigerator. It can be used to work in environments with high vibration requirements.

[0113] Other components

[0114] The cold finger assembly includes a cold finger base 81, a hot end heat dissipation copper ring 82, a heat regenerator shell 83, a cold end heat dissipation copper ring 84, and a cold finger end cover 85, which are coaxially connected in sequence; and a hot end heat dissipation filler 86, a heat regenerator 87, a cold end heat dissipation filler 88, and a hot end limit steel ring 89, a heat regenerator limit ring 810, and a cold end limit steel ring 811, which are arranged in sequence along the axial direction.

[0115] The linear motor assembly is located above the cylinder base 40 , and includes an outer magnetic yoke 91 , a permanent magnet mover, an inner magnetic yoke 92 , and a coil 93 .

[0116] The housing assembly includes an annular housing 1001 and a housing end cover 1002 . The lower end surface of the annular housing 1001 is fixedly connected to the cold finger base 81 , and the upper end surface of the annular housing 1001 is fixedly connected to the housing end cover 1002 .

[0117] Discharger structure

[0118] 2 , the displacer structure includes a double cylinder (a first cylinder 41 and a second cylinder 42 ), a double piston displacer (a first piston 1 and a second piston 2 ), and a displacer plate spring 3 ; the displacer plate spring 3 is disposed between the first piston 1 and the second piston 2 ;

[0119] The first piston 1 and the second piston 2 are connected and fixed to the first piston 1, the second piston 2 and the discharge plate spring 3 by a first fastener 31, so that when the first piston 1 and the second piston 2 reciprocate under the action of the gas pressure difference, the discharge plate spring 3 radially supports the first piston 1 and the second piston 2 and provides axial stiffness for the first piston 1 and the second piston 2. During the refrigeration process, the high-pressure gas flows back and forth in the expansion chamber of the second piston 2 away from the discharge plate spring 3 and the compression chamber between the first piston 1 and the power piston. The gas in the expansion chamber performs positive work on the discharger structure, thereby providing refrigeration.

[0120] In one embodiment, the first fastener 31 is a stud of appropriate size. In one embodiment, the discharge leaf spring 3 comprises a double discharge leaf spring. In one embodiment, the central axes of the first piston 1 and the second piston 2 are collinear. In one embodiment, the central axes of the first piston 1 and the second piston 2 pass through the center point of the discharge leaf spring. In one embodiment, the discharge leaf spring 3 is fixedly connected to the first piston 1 and the second piston 2 via the first fastener 31. In one embodiment, the first piston 1, the second piston 2, and the discharge leaf spring 3 are coaxially mounted.

[0121] Discharge leaf spring

[0122] 3 and 4 , FIG. 3 shows a schematic cross-sectional view of the ejector structure of a free piston Stirling refrigerator; FIG. 4 shows a schematic structural view of the ejector plate spring of the ejector structure;

[0123] Both ends of the discharge leaf spring 3 are fixedly connected to the first cylinder 41 or the second cylinder 42 , thereby enabling the first piston 1 to reciprocate in the first cylinder 41 and the second piston 2 to reciprocate in the second cylinder 42 .

[0124] In one embodiment, the ends of the discharge leaf spring 9 (the ends away from the center of the discharge leaf spring) are connected and secured to the end surface of the first cylinder 41 (the end facing the second cylinder 42) via second fasteners 32. In one embodiment, the second fasteners 32 are second hexagon socket head cap screws. In one embodiment, the edges (ends) of the discharge leaf spring 3 away from the center are connected to the first cylinder 41 via screws.

[0125] First cylinder and second cylinder

[0126] 2 to 4 , the ejector structure of the present application adopts a double-cylinder structure, which includes a first cylinder 41 and a second cylinder 42 . The first piston 1 reciprocates in the first cylinder 41 , and the second piston 2 reciprocates in the second cylinder 42 .

[0127] The second cylinder 42 includes a connecting section 421 and a accommodating section 422. In the radial direction of the cylinder, the connecting section 421 is located on the outside of the first cylinder 41. In other words, the first cylinder 41 is inserted into the connecting section 421 of the second cylinder 42, wherein the gap between the connecting section 421 and the first cylinder 41 is sealed.

[0128] In one embodiment, a plurality of grooves 4221 are provided on the inner wall of the accommodating section 422 to reduce the amount of cross-flow between the compression chamber and the expansion chamber through the gap, which has a positive effect on the sealing effect.

[0129] In one embodiment, the first cylinder 41 and the second cylinder 42 are gap-sealed by a cylinder seal 43. In one embodiment, the first cylinder 41 and the second cylinder 42 are gap-sealed by an O-ring and the interface between them is secured with glue. In one embodiment, the interface between the connecting section 421 of the second cylinder 42 and the first cylinder 41 is coated with glue to secure the second cylinder 42 to the first cylinder 41.

[0130] For the first cylinder, the power piston (not shown) and the first piston reciprocate and vibrate inside the cylinder, playing the role of gas sealing. The air gap between the first cylinder and the first piston (hot end ejector piston) is very small to ensure good airtightness.

[0131] The first piston and the second piston

[0132] Referring to Figures 2 to 4, the first piston 1 includes a cylindrical structure with a protruding bottom surface, and the second piston 2 includes a cylindrical structure with a protruding bottom surface. The first piston 1 includes a first protruding bottom surface 10 protruding toward the discharge leaf spring 3, and the second piston 2 includes a second protruding bottom surface 20 protruding toward the discharge leaf spring 3. The first protruding bottom surface 10 and / or the second protruding bottom surface 20 are arranged to avoid the end or edge of the discharge leaf spring 3, away from the center, from colliding with the first piston 1 and / or the second piston 2 during the movement of the piston.

[0133] In one embodiment, the ejector structure further includes a first fastener 31. The first protruding bottom surface 10 is provided with a first protrusion 101, and the second protruding bottom surface 20 is provided with a second protrusion 201. The first fastener 31 passes through the ejector leaf spring 3 and connects with the first protrusion 101 and the second protrusion 201, thereby securing the ejector leaf spring 3 to the first and second pistons 1 and 2. In one embodiment, the first protrusion 101 is located at the center of the first protruding bottom surface 10 and is a cylindrical structure extending toward the ejector leaf spring 3. In one embodiment, the second protrusion 201 is located at the center of the second protruding bottom surface 20 and is a cylindrical structure extending toward the ejector leaf spring 3. In one embodiment, the first fastener 31 is a stud.

[0134] In one embodiment, the first protrusion 101 is a cylindrical structure with an internal thread, and the second protrusion 201 is a cylindrical structure with an internal thread. The internal thread cooperates with the external thread of the stud to complete the connection. Preferably, an appropriate amount of thread glue is applied when the first protrusion 101 and the second protrusion 201 are threadedly connected to the stud.

[0135] In one embodiment, when the discharge leaf spring 3 is connected to the first protrusion 101 and the second protrusion 201 by the first fastener 31, the end surface of the first protrusion 101 is in contact with one surface of the discharge leaf spring 3, and the end surface of the second protrusion 201 is in contact with the other surface of the discharge leaf spring.

[0136] In one embodiment, the axial distance between the first protruding bottom surface 10 of the first piston 1 and the discharge plate spring 3 should be greater than the maximum amplitude of the discharger structure, and the axial distance between the second protruding bottom surface 20 of the second piston 2 and the discharge plate spring 3 should also be greater than the maximum amplitude of the discharger structure.

[0137] To achieve good airtightness, the first piston 1 should maintain a small gap with the first cylinder 3. However, under the action of gravity, the first piston may deviate from the center position and even contact the wall of the cylinder. To prevent the ejector from contacting the wall and causing a significant increase in friction, it is assumed that the axial distance between the geometric center of the first piston and the center of the ejector leaf spring (or the axial distance between the center point of the first piston and the center point of the ejector leaf spring along the axial direction of the first piston) L1, the axial distance between the center point of the second piston (the second piston outer shell 21 and the second piston top cover 22) and the center of the ejector leaf spring along the axial direction of the second piston L2, the weight of the first piston 1 m1, the weight of the second piston 2 m2, the radial stiffness of the ejector leaf spring 3, and the air gap δ between the first piston and the cylinder should maintain a certain relationship.

[0138] The positional relationship among the first piston 1, the second piston 2 and the discharge plate spring 3 can satisfy the following formula:

[0139] Where m1 is the mass of the hot-end discharge piston, m2 is the mass of the cold-end discharge piston, L1 is the axial distance between the center of the hot-end discharge piston and the center of the discharge leaf spring, L2 is the axial distance between the center of the cold-end discharge piston and the center of the discharge leaf spring, g is the acceleration due to gravity, k is the radial stiffness of the discharge leaf spring 9, and δ is the air gap height between the hot-end discharge piston wall and the hot-end cylinder inner wall. See Figure 3, where L1, L2, and δ are schematically illustrated.

[0140] (a) First piston

[0141] To reduce the mass of the displacer and make it lighter, the first piston 1 adopts a hollow structure. The first piston 1 includes a first piston outer shell 11 and a first piston top cover 12. The first piston outer shell 11 and the first piston top cover 12 are sealed by a first piston seal 13. The first piston outer shell 11 and the first piston top cover 12 are connected and fixed by a first piston fastener 14. In one embodiment, the first piston seal 13 is an O-ring. In another embodiment, the first piston fastener 14 is a hexagon socket head cap screw. Preferably, the first piston outer shell 11 is a cylindrical structure with a bottom surface.

[0142] In one embodiment, the first piston housing 11, the first piston top cover 12, the O-ring and several screws constitute the first piston assembly. The first piston housing 11 and the first piston top cover 12 are sealed by the O-ring to prevent the loss of compression work caused by the gas in the compression chamber entering and exiting the first piston assembly. The first piston housing 11 and the first piston top cover 12 are fastened by eight screws.

[0143] To prevent direct collision between the first piston and the deformed discharge leaf spring during movement, the first piston housing has a certain slope on the side near the cold end (second piston) or the discharge leaf spring 3. The magnitude of the slope is determined by the maximum amplitude of the discharger assembly. In other words, the first piston housing includes a first protruding bottom surface 10 facing the discharge leaf spring 3, thereby creating a slope on the bottom surface of the first piston housing. The maximum axial distance between the first protruding bottom surface 10 of the first piston 1 and the discharge leaf spring 3 should be greater than the maximum amplitude of the discharger structure. At the same time, the first piston housing (hot end piston housing) of the discharger has a cylindrical protrusion (first protrusion 101) on the side near the expansion chamber (or near the discharge leaf spring). The center of the protrusion is internally threaded to facilitate connection with the discharge leaf spring 3 and the second piston 2.

[0144] (b) Second piston

[0145] To reduce the mass of the displacer and make it lighter, the second piston 2 adopts a hollow structure. Preferably, to reduce internal empty volume and control mass, the second piston is filled with a rollable lightweight material. The second piston 2 comprises a second piston outer shell 21 and a second piston top cover 22, which are fixedly connected and sealed via internal and external threads. Preferably, the first piston outer shell 11 and the second piston outer shell 21 are arranged opposite each other near the displacer leaf spring 3. Preferably, the second piston outer shell is a cylindrical structure with a bottom surface.

[0146] Similarly, to prevent the second piston from colliding with the discharge leaf spring during movement, the second piston outer shell has a certain slope on the side close to the discharge leaf spring. The size of the slope is determined by the maximum amplitude of the discharger assembly. In other words, the second piston outer shell includes a second protruding bottom surface 20 facing the discharge leaf spring 3, thereby making the bottom surface of the second piston shell have a slope, and the maximum axial distance between the second protruding bottom surface 20 of the second piston 2 and the discharge leaf spring 3 should be greater than the maximum amplitude of the discharger structure. The second piston outer shell has a boss (second protrusion 201) close to the discharge leaf spring, and the center of the boss has an internal threaded hole of a certain depth.

[0147] In one embodiment, a stud passes through the internal threads of the protrusion (first protrusion 101) or the boss (second protrusion 201) of the first and second piston outer shells, and connects the discharge leaf spring to the first and second piston outer shells and fixes them with glue applied on the surface of the screw.

[0148] Power piston structure

[0149] The power piston structure includes a power leaf spring 51, a power bearing 52 and a power piston arranged in sequence along the axial direction. The power piston is placed in the first cylinder 41 and slides back and forth. The power piston is designed as a hollow structure. The power piston includes a power piston housing 53 and a power piston end cover 54. The power piston is arranged opposite to the first piston 1. During the refrigeration process, the gas compression chamber is between the power piston and the first piston 1.

[0150] The power leaf spring 51 is fixedly connected to the power bearing 52 , and the power bearing 52 is fastened to the permanent magnet mover of the linear motor assembly to form a whole.

[0151] Materials of each component

[0152] The existing displacer structure consists of a single piston, which runs through the compression chamber at the hot end and the expansion chamber at the cold end. Displacer structures are generally made of aluminum alloy, stainless steel, or polymer (engineering plastic). Metal displacer structures have low thermal deformation, high strength, high machining accuracy, and high thermal conductivity. The gap between the cylinder and the displacer can be designed to be very small, resulting in good airtightness, low shuttle loss, and low pumping loss. However, the disadvantage is that the axial heat conduction from the compression chamber to the expansion chamber is large, and the mass of the displacer is also large. Polymer materials generally have low strength, low machining accuracy, large thermal deformation, and low thermal conductivity. Their advantages are low axial heat conduction from the compression chamber to the expansion chamber through the displacer body and low mass. Their disadvantage is that a certain gap must be maintained between the displacer and the cylinder to prevent direct friction between the displacer and the cylinder due to temperature changes, resulting in a significant increase in the displacer's damping.

[0153] The various problems caused by the use of a single material for the displacer structure (as mentioned above) are solved by minimizing the axial heat conduction loss as much as possible while ensuring the airtightness between the compression chamber and the expansion chamber (reducing shuttle loss and pumping loss) to improve the efficient cooling effect of the refrigerator.

[0154] Therefore, in order to reduce the transfer of heat from the hot end to the cold end of the refrigerator through the cylinder, and at the same time to maintain a small gap between the piston and the cylinder, in the technical solution of the present application, the cylinder structure and the ejector structure are both made of a mixture of two materials, wherein the first cylinder is made of metal material, such as aluminum alloy, stainless steel, titanium alloy, etc., and the second cylinder is made of a high molecular polymer (engineering plastic) with low thermal conductivity and high strength, and the first cylinder and the second cylinder are connected by an O-ring and glue is used to bond the two.

[0155] Preferably, the first piston 1 is made of aluminum alloy with high strength and low density, and the hot end discharge piston surface is evenly sprayed with a wear-resistant and lubricating coating such as Teflon. The second piston 2 is made of engineering plastic with low thermal conductivity, low temperature resistance, and low thermal expansion coefficient.

[0156] Preferably, the first cylinder 41 is made of an aluminum alloy material with high thermal conductivity and high strength, wherein the inner cylinder wall surface of the first cylinder 41 is polished and hard-oxidized.

[0157] The second cylinder 42 is made of engineering plastics with low thermal conductivity, high strength and low thermal expansion coefficient. The inner wall surface of the accommodating section 422 of the second cylinder 42 adopts a sealing structure with multiple grooves 4221.

[0158] In order to make the purpose, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that these are only some examples that the present invention may take, but are not intended to limit the scope of the present invention.

[0159] Example

[0160] Integral free piston Stirling refrigerator device

[0161] 1 , this embodiment provides an integrated free-piston Stirling refrigerator device, which is composed of a cold finger assembly, a linear motor assembly, a cylinder assembly, a piston assembly, a housing assembly, and a vibration damping assembly.

[0162] The piston assembly consists of a power piston structure and a discharge piston structure (described in detail below). The discharge piston structure consists of a first piston 1 (hot-end discharge piston) and a second piston 2 (cold-end discharge piston). The hot-end discharge piston consists of a hot-end discharge piston housing (first piston outer housing 11) and a hot-end discharge piston end cap (first piston top cap 12), while the cold-end discharge piston (second piston 2) consists of a cold-end discharge piston housing (second piston outer housing 21) and a cold-end discharge piston end cap (second piston top cap 22). Both the hot and cold-end discharge pistons are designed as hollow structures with cylindrical protrusions at their ends. The cylindrical protrusions are internally threaded and secured to the two sides of the discharge leaf spring 3 via studs (first fasteners 31). The cold-end discharge piston is made of a lightweight engineering plastic with low thermal conductivity and low thermal expansion coefficient; the hot-end discharge piston is made of a lightweight aluminum alloy with high strength and hardness, and its surface is evenly sprayed with a Teflon coating. The hot-end discharge piston slides back and forth in the first cylinder 41 (hot-end cylinder), and the cold-end discharge piston slides back and forth in the second cylinder 42 (cold-end cylinder). The power piston structure consists of a power leaf spring 51, a power bearing 52, and a power piston. The power piston is designed as a hollow structure, and the power piston consists of a power piston housing 53 and a power piston end cover 54. The power bearing 52 and the power piston are both made of a lightweight, high-strength aluminum alloy material. The power piston and the power bearing 52 are fastened together by screws, and the power piston is placed in the hot-end cylinder 41 and slides back and forth.

[0163] The vibration reduction assembly consists of a dynamic vibration reduction mechanism and a damping vibration reduction mechanism. The dynamic vibration reduction mechanism is used to eliminate vibrations at the refrigerator's fundamental frequency, while the damping vibration reduction mechanism is used to reduce high-frequency vibrations. The dynamic vibration reduction mechanism consists of a dynamic vibration reduction plate spring 61, a counterweight 62, and a large dynamic vibration reduction screw 63. The counterweight 62 has an internally threaded through-hole drilled in its center, and the large dynamic vibration reduction screw 63 secures the counterweight 62 and several dynamic vibration reduction plate springs 61 together. A first weld ring 64 is welded to the inside of the housing. This first weld ring 64 has several through-holes drilled into it. The outer ring of the dynamic vibration reduction plate spring 61 also has several through-holes drilled into it. The dynamic vibration reduction plate spring 61 is mounted to the first weld ring 64 using a first screw 65 and nut. The damping vibration reduction mechanism, axially from top to bottom, includes a damping filler 71, a damping disc 72, a washer 73, a damping vibration reduction plate spring 74, and a large damping vibration reduction screw 75. A second weld ring 76 is welded to the inside of the housing. Damping filler 71 is composed of axially stacked copper wire mesh and is bonded to housing end cap 1002 using thermally conductive silicone. A threaded hole is drilled in the center of damping disc 72. Large damping screw 75 secures damping plate spring 74, backing ring 73, and damping disc 72. Second screw 77 and nut secure damping plate spring 74 to second welding ring 76.

[0164] The cold finger assembly consists of a cold finger end cap 85, a cold end heat sink copper ring 84, a regenerator housing 83, a hot end heat sink copper ring 82, a cold finger base 81, a cold end heat sink filler 88, a regenerator 87, a hot end heat sink filler 86, a cold end limit steel ring 811, a regenerator limit ring 810, and a hot end limit steel ring 89. The cold finger end cap 85, cold end heat sink copper ring 84, regenerator housing 83, hot end heat sink copper ring 82, and cold finger base 81 are coaxially mounted and welded together using vacuum brazing, with coaxiality controlled within 0.005 mm. The hot-end heat dissipation filler 86 and the cold-end heat dissipation filler 88 adopt a folded copper sheet structure and are pressed into the corresponding positions on the inner side of the cold finger by a hydraulic press; the regenerator 87 adopts a wound polymer film or stainless steel wire mesh filler; the cold-end limiting steel ring 811, the regenerator limiting ring 810, and the hot-end limiting steel ring 810 are pressed into the corresponding positions in sequence to fix the cold-end and hot-end heat dissipation fillers 88, 86 and the regenerator 87.

[0165] The cylinder assembly consists of a first cylinder 41 (hot-end cylinder), a second cylinder 42 (cold-end cylinder), and a cylinder base 40. The hot-end cylinder 41 is constructed of an aluminum alloy with good thermal conductivity, while the cold-end cylinder 42 is constructed of lightweight engineering plastic with low thermal conductivity and low thermal expansion coefficient. The hot-end cylinder 41 and the cold-end cylinder 42 are coaxially assembled and secured using adhesive. The inner surface of the cylinder base 40 is machined with several annular grooves. The hot-end cylinder 41 is coaxially inserted into the cylinder base and sealed to the cylinder base 40 via an O-ring. Several through-holes are drilled in the bottom surface of the cylinder base 40, and several screw holes are machined in the upper end surface of the hot-end cylinder 11. Screws secure the cylinder base 40 to the hot-end cylinder 11. The cylinder base 40 is securely connected to the cold finger base 81 via screws. A slot is opened in the center of the hot end cylinder 41 to allow the compression chamber to form a passage with the expansion chamber through the hot end heat dissipation filler 86, the regenerator 87, and the cold end heat dissipation filler 88.

[0166] The linear motor assembly includes an outer yoke 91, a permanent magnet mover, an inner yoke 92, and a coil 93. The permanent magnet mover consists of a permanent magnet 94, a lower permanent magnet support ring 95, an upper permanent magnet support ring 96, and a transmission connecting plate 97. The outer yoke 91, the outer yoke upper support ring 911, and the outer yoke lower support ring 912 are axially stacked and fixed to the cold finger base 81 via stud nuts. The stud nuts fasten the annular permanent magnet 94, the lower permanent magnet support ring 95, the upper permanent magnet support ring 96, and the transmission connecting plate 97 into a single unit, and magnetize the entire radial ring. The permanent magnet mover is fastened to the power bearing 52 via a fastening nut 98 to form a single unit. The power leaf spring 51 is placed on the outer yoke upper support ring 911 and fastened via a third screw 99. The power leaf spring 51 has a circular hole at its center, and the tail end of the power bearing 52 has several internal threads. The end of the power bearing 52 passes through the circular hole, so that the bottom surface of the power leaf spring 51 aligns with the upper end of the fastening nut 98. The center of the power leaf spring 51 and the power bearing 52 are fastened together using the fastening plate 55 and screws. The coil 93 is evenly and tightly wound around the hollow portion of the inner magnetic yoke 92, forming a single unit. The inner magnetic yoke 92 has an axial through-hole structure and is fixed to the cylinder base 40 using stud nuts. The center position deviation of the permanent magnet 94, outer magnetic yoke 91, and inner magnetic yoke 92 is controlled within 0.1mm.

[0167] The housing assembly includes an annular housing 1001, a housing end cap 1002, a terminal block 1003, and a gas-filled copper tube 1004. One side of the annular housing 1001 is welded to the cold finger base 81 using argon arc welding, and the other side is welded to the housing end cap 1002 using argon arc welding. A through hole is machined into the side of the housing 1001, and the terminal block 1003 is welded to the housing 1001 using energy storage welding, and the two leads of the coil 93 are connected to the inside of the refrigerator terminal block 1003. There is a circular hole on the other side of the housing 1001, and the gas-filled copper tube 1004 is welded to the housing 1001 using brazing. It is worth mentioning that all parts need to be dried in a drying oven at high temperature for a certain period of time before installation.

[0168] Discharger structure

[0169] This embodiment also provides an ejector structure for a free-piston Stirling refrigerator device, which adopts a dual-cylinder-dual-piston structure, as shown in Figures 2 to 4. The device includes: a first piston 1, a second piston 2, a discharge plate spring 3, a first cylinder 41, and a second cylinder 42.

[0170] The first piston 1, the second piston 2, and the discharge leaf spring 3 are arranged along the axial direction, with the discharge leaf spring 3 disposed between the first piston 1 and the second piston 2. The discharge leaf spring 3 is connected to the first piston 1 and the second piston 2 via a first fastener 31, so that when the first piston 1 and the second piston 2 reciprocate under the action of the gas pressure difference, the discharge leaf spring 3 radially supports the first piston 1 and the second piston 2 and provides axial stiffness for the first piston 1 and the second piston 2.

[0171] Specifically, referring to Figure 3 , the first piston 1 includes a first piston outer housing 11 and a first piston top cover 12. The first piston outer housing 11 and the first piston top cover 12 are sealed by a first O-ring (an example of the first piston seal 13) and secured together by a first hexagon socket screw (an example of the first piston fastener 14). The first piston outer housing 11 is a cylindrical structure with a protruding bottom surface. The first piston 1 includes a first protruding bottom surface 10 that protrudes toward the discharge leaf spring 3. The first protruding bottom surface 10 is provided with a cylindrical protrusion 101 (i.e., a first protrusion 101) facing the discharge leaf spring 3. The center of the protruding cylinder is internally threaded.

[0172] The second piston 2 includes a second piston outer shell 21 and a second piston top cover 22, which are fixedly connected and sealed by internal and external threads. The second piston outer shell 21 is a cylindrical structure with a protruding bottom surface. The second piston outer shell 21 includes a second protruding bottom surface 20 that protrudes toward the discharge leaf spring 3. The second protruding bottom surface 20 is provided with a boss (i.e., a second protrusion 201) facing the discharge leaf spring 3. The center of the boss has an internal threaded hole of a certain depth. This allows the first piston 1, the second piston 2, and the discharge leaf spring 3 to be connected and fixed by a stud 31 of a suitable size. The stud 31 passes through the protrusion (first protrusion 101) of the first protruding bottom surface, the discharge leaf spring 3, and the boss 201 (i.e., second protrusion 201) of the second protruding bottom surface 20. The installation coaxiality of the first piston 1, the second piston 2, and the discharge leaf spring 3 is controlled within 0.005mm.

[0173] The discharge leaf spring 3 is connected and fixed to the upper end surface of the first cylinder 41 by a second hexagon socket screw (ie, an example of the second fastener 32 ), and the coaxiality of the discharge leaf spring 3 and the first cylinder 41 is controlled within 0.005 mm.

[0174] The first cylinder 41 and the second cylinder 42 are sealed by a second O-ring (ie, an example of a cylinder seal 43) and the interface between the two is glued and fixed. The installation coaxiality of the first cylinder 41 and the second cylinder 42 is controlled within 0.005 mm.

[0175] In this embodiment, the first piston 1 is made of a high-strength, low-density aluminum alloy, and the hot-end discharge piston surface is uniformly sprayed with a wear-resistant, lubricating coating such as Teflon. The second piston 2 is constructed of an engineering plastic with low thermal conductivity, low-temperature resistance, and a low thermal expansion coefficient. The first cylinder 1 is constructed of a high-strength, high-thermal-conductivity aluminum alloy. The inner cylinder wall of the hot-end cylinder is polished and hard-anodized. The second cylinder 2 is constructed of an engineering plastic with low thermal conductivity, high strength, and a low thermal expansion coefficient, and the inner cylinder wall utilizes a multi-groove sealing structure.

[0176] Displacer structure installation steps:

[0177] (1) Place an O-ring of appropriate size on the boss of the first piston top cover, and fix the first piston top cover to the first piston outer shell with 8 screws.

[0178] (2) Fill the second piston outer shell with lightweight material evenly, and then fix the second piston top cover to the second piston thread.

[0179] (3) Insert a stud of appropriate size and length through the circular hole in the center of the discharge plate spring 3, and connect the first piston and the second piston through threads. The raised end surface of the second piston outer shell (i.e., the end surface of the first protrusion 101 of the first protruding bottom surface 10) and the raised end surface of the first piston outer shell (i.e., the end surface of the second protrusion 201 of the first protruding bottom surface 10) are flush with the two surfaces of the discharge plate spring, and an appropriate amount of thread glue is applied during the threaded connection. It should be noted that during the installation process, the coaxiality of the discharge plate spring, the first piston (the first piston outer shell 11 and the first piston top cover 12) and the second piston (the second piston outer shell 21 and the second piston top cover 22) should be maintained, and the coaxiality needs to be maintained within 0.005mm.

[0180] (4) The discharge leaf spring is coaxially mounted on the end face of the first cylinder using eight screws. The coaxiality is required to be within 0.005 mm.

[0181] (5) Finally, the first cylinder 41 and the second cylinder 42 are sealed by an O-ring and a proper amount of anaerobic glue is filled in the gap between the two to ensure the fixation of the two. The coaxiality should be controlled within 0.005 mm during the installation process.

[0182] It is worth mentioning that all parts need to be dried in a drying oven at high temperature for a certain period of time before installation.

[0183] The applicant would like to emphasize that the displacer structure of this embodiment abandons the practice of using a displacer base placed inside the compression chamber and a displacer plate spring provided inside the displacer, and removes unnecessary parts other than the cylinder that can directly wear against the displacer, thereby greatly reducing the damping while ensuring excellent air tightness between the displacer and the cylinder (small shuttle loss and pump air loss), without increasing the empty volume of the compression chamber or the expansion chamber, small axial heat conduction of the displacer, and no impact on the maximum power of the refrigerator, simplifying the structure of the refrigerator and reducing the installation difficulty while ensuring the safe and reliable operation of the refrigerator.

[0184] The specification of this application records a large number of technical features, which are distributed in various technical solutions. If all possible combinations of technical features of this application (i.e., technical solutions) are to be listed, the specification will be too lengthy. In order to avoid this problem, the various technical features disclosed in the above-mentioned invention content of this application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions are all deemed to have been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that play the same role. Technically, only one of them can be used, and it is impossible to use them at the same time. Feature E can be technically combined with feature C. Then, the solution of A+B+C+D should not be considered as having been recorded because it is technically infeasible, while the solution of A+B+C+E should be considered as having been recorded.

[0185] All documents mentioned in this application are considered to be included in their entirety in the disclosure of this application so that they can be used as a basis for modification when necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art may make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. An integral free piston Stirling refrigerator device, characterized in that: include: The ejector structure and the power piston structure, wherein: The power piston structure comprises a power leaf spring (51), a power bearing (52) and a power piston which are sequentially arranged in the axial direction, wherein the power leaf spring (51) is connected to the power bearing (52); The displacer structure comprises a first piston (1), a displacer plate spring (3), and a second piston (2) which are sequentially arranged in the axial direction. The discharge plate spring (3) is connected to the first piston (1) and the second piston (2) through a first fastener (31), so that when the first piston (1) and the second piston (2) reciprocate under the action of a gas pressure difference, the discharge plate spring (3) radially supports the first piston (1) and the second piston (2) and provides axial rigidity for the first piston (1) and the second piston (2); During the refrigeration process, high-pressure gas flows back and forth in the expansion chamber of the second piston (2) at one end away from the discharge plate spring (3) and the compression chamber between the first piston (1) and the power piston. The gas in the expansion chamber performs positive work on the discharger structure, thereby providing refrigeration.

2. The refrigerator device according to claim 1, characterized in that: The device also includes a vibration reduction assembly, which is located above the ejector structure and the power piston structure. The vibration reduction assembly includes a power vibration reduction mechanism and a damping vibration reduction mechanism. The power vibration reduction mechanism is used to eliminate the vibration of the fundamental frequency of the refrigerator, and the damping vibration reduction mechanism is used to weaken high-frequency vibration; the damping vibration reduction mechanism is located above the power vibration reduction mechanism.

3. The refrigerator device according to claim 2, characterized in that: The power vibration reduction mechanism comprises a plurality of groups of power vibration reduction leaf springs (61), a counterweight block (62), and a large power vibration reduction screw (63), and the power vibration reduction leaf springs (61) and the counterweight block (62) are fixed together by the large power vibration reduction screw (63); The damping vibration reduction mechanism comprises a damping filler (71), a damping disk (72), a gasket (73), a damping vibration reduction plate spring (74), and a large damping vibration reduction screw (75) which are sequentially arranged in the axial direction, and the damping vibration reduction plate spring (74), the gasket (73), and the damping disk (72) are connected and fixed by the large damping vibration reduction screw (75).

4. The refrigerator device according to claim 3, characterized in that: The first piston (1) comprises a cylindrical structure with a protruding bottom surface, the second piston (2) comprises a cylindrical structure with a protruding bottom surface, the first piston (1) comprises a first protruding bottom surface (10) protruding toward the discharge plate spring (3), and the second piston (2) comprises a second protruding bottom surface (20) protruding toward the discharge plate spring (3).

5. The refrigerator device according to claim 4, characterized in that: The ejector structure further comprises a first fastener (31), the first protruding bottom surface (10) is provided with a first protruding portion (101), the second protruding bottom surface (20) is provided with a second protruding portion (201), the first fastener (31) passes through the ejector leaf spring (3) and is connected to the first protruding portion (101) and the second protruding portion (201), so that the ejector leaf spring (3) is fixedly connected to the first piston (1) and the second piston (2).

6. The refrigerator device according to claim 5, characterized in that: The ejector structure further comprises a first cylinder (41) and a second cylinder (42), and both ends of the ejector plate spring (3) are fixedly connected to the first cylinder (41) or the second cylinder (42), so that the first piston (1) can reciprocate in the first cylinder (41) and the second piston (2) can reciprocate in the second cylinder (42).

7. The refrigerator device according to claim 6, characterized in that: The power piston is designed as a hollow structure, and comprises a power piston housing (53) and a power piston end cover (54). The first piston (1) is designed as a hollow structure, comprising a first piston outer shell (11) and a first piston top cover (12), the first piston outer shell (11) and the first piston top cover (12) being sealed by a first piston seal (13), and the first piston outer shell (11) being a cylindrical structure with a protruding bottom surface; The second piston (2) is designed as a hollow structure. The second piston (2) comprises a second piston outer shell (21) and a second piston top cover (22). The second piston outer shell (21) and the second piston top cover (22) are fixedly connected and sealed by threads. The second piston outer shell (21) is a cylindrical structure with a protruding bottom surface.

8. The refrigerator device according to claim 7, characterized in that: The device further comprises a shell component and a cold finger component arranged at the lower end of the shell component; the vibration reduction component, the ejector structure and the power piston structure are arranged in the shell component and the cold finger component; the cold finger component comprises a cold finger base (81), a hot end heat dissipation copper ring (82), a heat regenerator shell (83), a cold end heat dissipation copper ring (84) and a cold finger end cover (85) which are coaxially connected in sequence; and a hot end heat dissipation filler (86), a heat regenerator (87), a cold end heat dissipation filler (88) which are arranged in sequence in the axial direction, a hot end limit steel ring (89), a heat regenerator limit ring (810) and a cold end limit steel ring (811) which are arranged in sequence in the axial direction.

9. The refrigerator device according to claim 8, characterized in that: It also includes a linear motor assembly, which is located above the cylinder base (40) and includes an outer magnetic yoke (91), a permanent magnet mover, an inner magnetic yoke (92), and a coil (93).

10. The refrigerator device according to claim 9, characterized in that The housing assembly comprises an annular housing (1001) and a housing end cover (1002); the lower end surface of the annular housing (1001) is fixedly connected to the cold finger base (81); and the upper end surface of the annular housing (1001) is fixedly connected to the housing end cover (1002).

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