CN116772445B - Ejector structure for free piston Stirling refrigerator - Google Patents

Abstract

The application discloses an ejector structure for a free piston Stirling refrigerator, which comprises: the first piston, the leaf spring and the second piston that the axial set gradually, leaf spring one side and first piston are connected, the opposite side and the second piston of leaf spring are connected to make when first piston and second piston reciprocating motion under the atmospheric pressure difference effect, leaf spring radial stay first piston and second piston and provide axial rigidity for first piston and second piston, in the refrigeration process, high-pressure gas reciprocating flow in the expansion chamber of the one end of keeping away from the leaf spring of second piston and the compression chamber of the one end of keeping away from the leaf spring of first piston, the gas in the expansion chamber is positive work to the ejector structure, thereby provide refrigeration. The structure eliminates a connecting rod mechanism in the conventional ejector structure, greatly reduces the motion damping of the ejector and has high stability.

Description

Ejector structure for free piston Stirling refrigerator

Technical Field

The application relates to the technical field of refrigeration and low temperature, in particular to an ejector structure for a free piston Stirling refrigerator.

Background

The Stirling refrigeration principle is based on reverse Stirling cycle, the compressible gas with alternating flow is utilized for expansion refrigeration, the theoretical efficiency is Carnot efficiency, working medium in the system is pollution-free inert gas helium, no phase change is caused in the operation process, a sealing mode adopts gap sealing, the refrigerating machine can flexibly adjust the refrigeration temperature and the refrigeration capacity by changing the stroke and the frequency of a driving piston, and the device has the advantages of low vibration, compact structure, small volume, energy conservation, environmental protection, strong reliability, long service life, wen Ouan refrigeration and the like.

In stirling refrigerators, there are two piston-structured components, a power piston and an ejector piston, respectively. Wherein the ejector piston extends through the cold and hot ends. The power piston has a certain phase difference with the ejector piston, and the phase of the ejector piston generally leads the power piston. The phase difference between the power piston and the ejector piston has a great influence on the refrigeration efficiency; the prior Stirling refrigerator has more phase difference between a power piston and an ejector piston by a mechanical structure or independently controlling two parts, the ejector of the later developed free piston Stirling refrigerator is not independently controlled or connected with the power piston by a mechanical structure, but is independently fixed on a plate spring, two ends of the ejector are respectively a compression cavity and an expansion cavity, a certain phase difference exists between pressure waves of the expansion cavity and the compression cavity due to the existence of low-porosity structures such as a radiator, a regenerator and the like between the compression cavity and the expansion cavity in a gas channel, the ejector receives gas force under the action of gas pressure difference from two sides of the compression cavity and the expansion cavity, periodic reciprocating motion process can be generated by the ejector under the action of self inertia force, spring force of the plate spring, damping force in the motion process and the action of the gas force, and forms a certain phase difference with the power piston.

Since the proposed free piston stirling cooler, the structural design of the ejector has been a key to determine the cooling effect and overall structure. The prior art ejector structure mainly comprises an ejector, a compression chamber and a thin rod, wherein the thin rod penetrates through a power piston, the thin rod penetrates through the power piston and the linear motor, and the tail end of the thin rod is fixedly connected with the plate spring fixed in the back pressure cavity to form a free piston. The piston rod penetrating structure has the defects that mutual motion interference is easy to generate between the power piston and the ejector, the damping of the ejector is increased, the refrigeration effect is reduced, the design difficulty of the power piston is increased, the stability is low, and the installation difficulty is high.

Accordingly, there is a great need in the present application to develop an ejector structure for a free piston stirling refrigerator that eliminates the linkage mechanism in the conventional ejector structure, greatly reduces the ejector motion damping, and has high stability.

Disclosure of Invention

The application aims to provide an ejector structure for a free piston Stirling refrigerator, which eliminates a connecting rod mechanism in a conventional ejector structure, greatly reduces piston motion damping and has high stability.

The present application provides an ejector structure for a free piston Stirling refrigerator, comprising:

a first piston, a plate spring and a second piston which are axially and sequentially arranged,

the leaf spring is connected with the first piston and the second piston through a first fastener, so that when the first piston and the second piston reciprocate under the action of air pressure difference, the leaf spring radially supports the first piston and the second piston and provides axial rigidity for the first piston and the second piston;

in the refrigerating process, high-pressure gas flows back and forth in an expansion cavity at one end of the second piston far away from the plate spring and a compression cavity at one end of the first piston far away from the plate spring, and the gas in the expansion cavity performs positive work on the ejector structure, so that refrigeration is provided.

In another preferred embodiment, the leaf spring is located between the first and second pistons.

In another preferred embodiment, the leaf springs are double leaf springs.

In another preferred embodiment, the central axes of the first piston and the second piston are on the same straight line.

In another preferred embodiment, the central axes of the first piston and the second piston pass through the center point circle center of the plate spring.

In another preferred embodiment, the leaf spring is fixedly connected to the first piston and the second piston by a first fastener.

In another preferred embodiment, the first piston, the second piston, and the leaf spring are coaxially mounted.

In another preferred embodiment, the first piston comprises a cylindrical structure with a convex bottom surface, the second piston comprises a cylindrical structure with a convex bottom surface, the first piston comprises a first convex bottom surface protruding towards the leaf spring, and the second piston comprises a second convex bottom surface protruding towards the leaf spring.

In another preferred embodiment, the ejector structure further includes a first fastener, the first convex bottom surface is provided with a first protrusion, the second convex bottom surface is provided with a second protrusion, and the first fastener passes through the leaf spring and is connected with the first protrusion and the second protrusion, thereby fixedly connecting the leaf spring with the first piston and the second piston.

In another preferred embodiment, the first protruding portion is located at the center of the first protruding bottom surface, and the first protruding portion is a cylindrical structure extending toward the leaf spring.

In another preferred embodiment, the second protruding portion is located at the center of the second protruding bottom surface, and the second protruding portion is a cylindrical structure extending toward the leaf spring.

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

In another preferred embodiment, the first protruding portion is a cylindrical structure with internal threads inside, the second protruding portion is a cylindrical structure with internal threads inside, the internal threads are matched with the external threads of the stud to complete connection, and preferably, a proper amount of thread compound is coated when the first protruding portion and the second protruding portion are in threaded connection with the stud.

In another preferred embodiment, when the connection of the leaf spring with the first protrusion and the second protrusion by the first fastener is completed, the end face of the first protrusion is fitted with one surface of the leaf spring, and the end face of the second protrusion is fitted with the other surface of the leaf spring.

In another preferred embodiment, the maximum axial distance of the first convex bottom surface of the first piston from the leaf spring should be greater than the maximum amplitude of the ejector structure, and the maximum axial distance of the second convex bottom surface of the second piston from the leaf spring should also be greater than the maximum amplitude of the ejector structure.

In another preferred embodiment, the device further comprises a first cylinder and a second cylinder, wherein two ends of the plate spring are fixedly connected with the first cylinder or the second cylinder, so that the first piston reciprocates in the first cylinder, and the second piston reciprocates in the second cylinder.

In another preferred embodiment, the ends of the leaf spring at the positions far away from the center are fixedly connected with the end face of the first cylinder through second fasteners.

In another preferred embodiment, the second fastener is a socket head cap screw.

In another preferred embodiment, the second cylinder comprises a connecting section and a receiving section, the connecting section being located outside the first cylinder in the radial direction of the cylinder, the connecting section being gap-sealed with the first cylinder.

In another preferred embodiment, the first cylinder and the second cylinder are gap sealed by a cylinder seal.

In another preferred embodiment, an interface between the connection section of the second cylinder and the first cylinder is coated with adhesive, thereby fixing the second cylinder and the first cylinder.

In a further preferred embodiment, the first cylinder is inserted into the connecting section of the second cylinder.

In another preferred embodiment, the first cylinder has an inner diameter identical to an inner diameter of the receiving section of the second cylinder, and the second cylinder includes a connecting section having an inner diameter greater than the inner diameter of the receiving section of the second cylinder.

In another preferred embodiment, a plurality of grooves are formed in the inner wall of the accommodating section, so that the air leakage amount between the compression cavity and the expansion cavity passing through gaps is reduced, and the sealing effect is positively achieved.

In another preferred embodiment, the positional relationship of the first piston, the second piston and the leaf spring is required to satisfy the following formula:

wherein m1 is the mass of the first piston, m2 is the mass of the second piston, L1 is the axial distance between the first piston center point and the plate spring center point along the axial direction of the first piston, L2 is the axial distance between the second piston center point and the plate spring center point along the axial direction of the second piston, g is the gravitational acceleration, k is the radial stiffness of the plate spring, and delta is the air gap height between the first piston outer wall surface and the first cylinder inner wall surface.

In another preferred embodiment, the first piston is a hollow structure, the first piston includes a first piston outer housing and a first piston cap, the first piston outer housing and the first piston cap are sealed by a first piston seal.

In another preferred embodiment, the first piston outer housing and the first piston cap are secured by a first piston fastener.

In another preferred embodiment, the first piston outer housing has a cylindrical structure with a bottom surface.

In another preferred embodiment, the second piston outer housing has a cylindrical structure with a bottom surface.

In another preferred embodiment, the second piston comprises a second piston outer housing and a second piston top cover, which are fixedly connected and sealed by threads.

In another preferred embodiment, the first piston outer housing and the second piston outer housing are disposed adjacent to and opposite the leaf spring.

In another preferred embodiment, the first piston is made of an aluminum alloy material and the second piston is made of an engineering plastic.

In another preferred embodiment, the outer surface of the first piston is sprayed with a wear resistant lubricating coating, preferably a teflon coating.

In another preferred embodiment, the first cylinder is made of an aluminum alloy material and the second piston is made of an engineering plastic.

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

The application also provides a free piston Stirling refrigerator comprising the ejector structure.

It is understood that within the scope of the present application, the above-described technical features of the present application and technical features specifically described below (e.g., in the examples) may be combined with each other to constitute new or preferred technical solutions. And are limited to a space, and are not described in detail herein.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is to be understood that the drawings described below are merely examples of embodiments of the present application and that other embodiments may be made by those skilled in the art without inventive effort.

FIG. 1 is a schematic diagram of an ejector configuration of a free piston Stirling refrigerator according to an embodiment of the application;

FIG. 2 is a schematic cross-sectional view of the ejector structure of a free piston Stirling refrigerator according to an embodiment of the application;

FIG. 3 is a schematic structural view of a leaf spring of the ejector structure according to an embodiment of the present application;

fig. 4 is a schematic view of the structure of a second cylinder (in which a second piston is disposed) according to an embodiment of the present application.

In the drawings, the marks are as follows:

1-first piston

10-first convex bottom surface

101-first projection

11-first piston outer housing

12-first piston top cover

13-first piston seal

14-first piston fastener

2-second piston

20-second convex bottom surface

201-second protrusion

21-second piston outer housing

22-second piston top cap

3-leaf spring

31-first fastener

32-second fastener

4-first cylinder

5-second cylinder

51-connecting segment

52-receiving section

522-groove

6-cylinder seal

L1-axial distance of the first piston center point from the leaf spring center point in the axial direction of the first piston

L2-axial distance of the second piston center point from the leaf spring center point in the axial direction of the second piston

Delta-height of air gap between outer wall surface of first piston and inner wall surface of first cylinder

Detailed Description

Through extensive and intensive research, the inventor firstly develops a discharger structure for a free piston Stirling refrigerator, the structure abandons a plate spring slender connecting rod structure known in the prior art, and through arranging a double-cylinder, double-piston and plate spring matching structure, the heat leakage loss of a hot end of the discharger to a cold end is reduced, the direct interference and abrasion of the discharger and other parts of the refrigerator are eliminated, the friction damping is greatly reduced, and the characteristics of air tightness, low axial heat conduction and low quality are simultaneously considered, so that the refrigerating effect is better. The plate spring is arranged between the double pistons, so that the distance between the plate spring and the center of the ejector is greatly reduced, the ejector moves more stably, and the long service life of the refrigerator is ensured.

Terminology

As used herein, "ejector" and "ejector structure" are used interchangeably.

As used herein, "housing," "housing," and "outer housing" are used interchangeably.

As used herein, "axial distance" refers to a distance in the axial direction of the first piston or the second piston.

As used herein, "warm end piston", "warm end drain piston" and "first piston" refer to the same component;

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

as used herein, "first cylinder" and "hot end cylinder" refer to the same component;

as used herein, "second cylinder" and "cold end cylinder" refer to the same component;

it should be noted that in the present patent application, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. In the present patent application, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, and two cases are included: the act is performed solely on the basis of the element and is performed on the basis of the element and other elements. Multiple, etc. expressions include 2, 2 times, 2, and 2 or more, 2 or more times, 2 or more.

In the present application, all directional indications (such as up, down, left, right, front, rear, etc.) are merely used to explain the relative positional relationship, movement conditions, etc. between the components under a certain specific posture (as shown in the drawings), and if the specific posture is changed, the directional indication is changed accordingly.

The main advantages of the application

(a) The ejector structure of the application eliminates the long and thin connecting rod structure of the leaf spring known in the prior art, and greatly reduces friction damping in the moving process by removing redundant parts except the air cylinder which can be directly worn with the ejector;

(b) The ejector structure eliminates direct interference and abrasion between the ejector piston and other parts of the refrigerator, and improves the refrigeration efficiency and stability of the refrigerator;

(c) According to the ejector structure, the plate spring is arranged between the first piston and the second piston, so that the problem that the distance between the plate spring and the ejection piston is overlarge in the prior art is solved, the coaxiality of the whole ejector is easy to control, the installation difficulty is reduced, and the stability is high;

(d) The ejector structure of the application has smaller volume, reduces the weight of the refrigerator and reduces the installation difficulty.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be understood by those skilled in the art that the claimed application may be practiced without these specific details and with various changes and modifications from the embodiments that follow.

The ejector is an important structure of the free piston Stirling refrigerator, and plays a role in regulating the flow of working medium in the refrigerator. The stirling cooler is a process of alternately oscillating a compression piston and an ejector, with high pressure gas (helium) flowing back and forth between a compression chamber, a hot side heat sink, a regenerator, a cold side heat exchanger, and an expansion chamber. In one cycle of the operation of the refrigerator, the gas in the expansion cavity performs positive work on the ejector and generates refrigerating capacity in the expansion cavity, and meanwhile, the ejector transmits the work performed by the gas in the expansion cavity to the compression cavity, so that the effect of recovering sound work is achieved, and the refrigerating efficiency of the refrigerator is improved.

The free piston stirling cooler is a pneumatic cooler in that the displacement of the ejector in the cooler is caused by the pressure differential between the compression and expansion chambers and no additional force is applied to drive its movement and phase modulation of the internal gas. For free piston Stirling refrigerators, the ejector is directly connected to the leaf spring and is independent of the compression system, i.e. a "free" piston. The mass of the ejector, the rate of the leaf spring and the amount of damping during movement of the ejector play a key role in the phasing function of the ejector.

The application provides an ejector structure for a free piston Stirling refrigerator, which adopts a double-cylinder-double-ejector, can reduce damping in the movement process of the ejector, reduces axial heat conduction from a hot end to a cold end through a cylinder and the ejector (for example, a second piston is made of engineering plastic materials and has small heat conductivity coefficient), reduces air leakage of a compression cavity and an expansion cavity through the ejector, ensures stable operation of the ejector, reduces installation difficulty, and improves the stability and refrigeration efficiency of the refrigerator.

Ejector structure for free piston Stirling refrigerator

Referring to fig. 1, the ejector structure includes a double cylinder (first cylinder 4, second cylinder 5), a double piston ejector (first piston 1 and second piston 2), a leaf spring 3; the plate spring 3 is arranged between the first piston 1 and the second piston 2;

the first piston 1 and the second piston 2 are fixedly connected with the first piston 1, the second piston 2 and the plate spring 3 through the first fastening piece 31, so that when the first piston 1 and the second piston 2 reciprocate under the action of air pressure difference, the 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 refrigeration, high-pressure air flows reciprocally in an expansion cavity of one end, far from the plate spring 3, of the second piston 2 and a compression cavity of one end, far from the plate spring 3, of the first piston 1, and air in the expansion cavity flows reciprocally in an expansion cavity of one end, far from the plate spring 3, of the second piston 2 and a compression cavity of one end, far from the plate spring 3, of the first piston 1, and the air in the expansion cavity applies positive work on the ejector structure, thereby providing refrigeration. Doing positive work, thereby providing refrigeration.

In one embodiment, the first fastener 31 is a suitably sized stud. In one embodiment, the leaf springs 3 are double leaf springs. In an embodiment, the central axes of the first piston 1 and the second piston 2 are collinear. In an embodiment, the central axes of the first piston 1 and the second piston 2 pass through the center point circle center of the leaf spring. In one embodiment, the leaf spring 3 is fixedly connected to the first piston 1 and the second piston 2 by a first fastener 31. In one embodiment, the first piston 1, the second piston 2 and the leaf spring 3 are coaxially mounted.

Leaf spring

Referring to fig. 2 and 3, fig. 2 shows a schematic cross-sectional view of the ejector structure of a free piston stirling cooler; fig. 3 shows a schematic structural view of a leaf spring of an ejector structure according to an embodiment of the present application;

the two ends of the plate spring 3 are fixedly connected with the first cylinder 4 or the second cylinder 5, so that the first piston 1 reciprocates in the first cylinder 4, and the second piston 2 reciprocates in the second cylinder 5.

In one embodiment, both ends of the plate spring 3 (ends away from the center of the plate spring) are connected and fixed to the end face of the first cylinder 4 (end face toward the second cylinder 5) by the second fastener 32. In one embodiment, the second fastener 32 is a second socket head cap screw. In one embodiment, the edge (end) of the leaf spring 3 remote from the center is connected to the first cylinder 4 by a screw.

First and second cylinders

Referring to fig. 1 to 4, the ejector structure of the present application takes the form of a double cylinder comprising a first cylinder 4 and a second cylinder 5, a first piston 1 reciprocating within the first cylinder 4 and a second piston 2 reciprocating within the second cylinder 5;

the second cylinder 5 comprises a connecting section 51 and a receiving section 52 (see fig. 4, which shows a schematic view of the second cylinder 5 for a clearer illustration), said connecting section 51 being located outside the first cylinder 4 in the radial direction of the cylinder, so to speak, the first cylinder 4 being inserted into the connecting section 51 of said second cylinder 5, wherein the connecting section 51 is gap-sealed with said first cylinder 4.

In one embodiment, a plurality of grooves 522 are formed on the inner wall of the accommodating section 52 to reduce the amount of air that can get through between the compression chamber and the expansion chamber, which has a positive effect on the sealing effect.

In one embodiment, the first cylinder 4 and the second cylinder 5 are gap sealed by a cylinder seal 6. In one embodiment, the first cylinder 4 and the second cylinder 5 are in clearance seal by an O-shaped sealing ring and are glued and fixed on the interface of the two. In an embodiment, the interface of the connecting section 51 of the second cylinder 5 with the first cylinder 4 is coated with glue, thereby fixing said second cylinder 5 and said first cylinder 4.

For the first cylinder, the power piston (not shown) and the first piston vibrate reciprocally in the cylinder, so as to play a role of gas seal, and an air gap between the first cylinder and the first piston (hot end discharger piston) is small so as to ensure better air tightness.

First and second pistons

Referring to fig. 1-3, the first piston 1 comprises a cylindrical structure with a convex bottom surface, the second piston 2 comprises a cylindrical structure with a convex bottom surface, the first piston 1 comprises a first convex bottom surface 10 protruding towards the plate spring 3, the second piston 2 comprises a second convex bottom surface 20 protruding towards the plate spring 3, wherein the first convex bottom surface 10 and/or the second convex bottom surface 20 are arranged to avoid collision with the first piston 1 and/or the second piston 2 at the end or edge of the plate spring 3, away from the centre, during movement of the piston.

In an embodiment, the ejector structure further includes a first fastening member 31, the first projecting bottom surface 10 is provided with a first projecting portion 101, the second projecting bottom surface 20 is provided with a second projecting portion 201, and the first fastening member 31 passes through the leaf spring 3 and is connected with the first projecting portion 101 and the second projecting portion 201, thereby fixedly connecting the leaf spring 3 with the first piston 1 and the second piston 2. In one embodiment, the first protrusion 101 is located at the center of the first protrusion bottom surface 10, and the first protrusion 101 has a cylindrical structure extending toward the leaf spring 3. In one embodiment, the second protrusion 201 is located at the center of the second protrusion bottom 20, and the second protrusion 201 has a cylindrical structure extending toward the leaf spring 3. In one embodiment, the first fastener 31 is a stud.

In an embodiment, the first protruding portion 101 is a cylindrical structure with internal threads inside, the second protruding portion 201 is a cylindrical structure with internal threads inside, and the internal threads are matched with the external threads of the stud to complete connection, and preferably, a proper amount of thread compound is coated when the first protruding portion 101 and the second protruding portion 201 are in threaded connection with the stud.

In an embodiment, when the connection of the leaf spring 3 with the first projection 101 and the second projection 201 by the first fastener 31 is completed, the end face of the first projection 101 is fitted with one surface of the leaf spring 3, and the end face of the second projection 201 is fitted with the other surface of the leaf spring.

In an embodiment, the axial distance of the first convex bottom surface 10 of the first piston 1 from the leaf spring 3 should be larger than the maximum amplitude of the ejector structure, and the axial distance of the second convex bottom surface 20 of the second piston 2 from the leaf spring 3 should also be larger than the maximum amplitude of the ejector structure.

For better tightness, the first piston 1 should keep a small gap with the first cylinder 4, but the first piston may deviate from the center position under the action of gravity and even contact the wall surface of the cylinder. In order to prevent the ejector from contacting the wall surface to cause a large increase in friction, it is assumed that the geometric center of the first piston is at a center axial distance L1 from the center of the flat spring (or the axial distance of the first piston center point in the axial direction of the first piston from the center point of the flat spring), the second piston (the second piston outer case 21 and the second piston top cover 22) is at a center axial distance L2 from the center point of the second piston in the axial direction of the second piston from the center axial distance L2 of the flat spring, the weight m1 of the first piston 1, the weight m2 of the second piston 2, the radial stiffness of the flat spring 3, the air gap between the first piston and the cylinder The relationship should be maintained in a certain way,

the positional relationship of the first piston 1, the second piston 2, and the leaf spring 3 may satisfy the following formula:

wherein 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 position of the hot end discharge piston center and the center of the plate spring, L2 is the axial distance between the position of the cold end discharge piston center and the center of the plate spring, g is the gravitational acceleration, k is the radial stiffness of the plate spring 3, and delta is the air gap height between the hot end discharge piston wall surface and the hot end cylinder inner wall surface. See fig. 2, wherein L1, L2, δ are schematically shown.

(a) First piston

In order to reduce the quality of the ejector, the first piston 1 is of a hollow structure, the first piston 1 comprises 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 sealing piece 13, and the first piston outer shell 11 and the first piston top cover 12 are fixedly connected by a first piston fastening piece 14. In one embodiment, the first piston seal 13 is an O-ring seal. In one embodiment, the first piston fastener 14 is a socket head cap screw. Preferably, the first piston outer housing 11 is a cylindrical structure with a bottom surface.

In an embodiment, the first piston outer housing 11, the first piston top cover 12, the O-ring and the plurality of screws form a first piston assembly, the first piston outer housing 11 and the first piston top cover 12 are sealed by the O-ring to prevent loss of compression work caused by gas in the compression chamber entering and exiting the interior of the first piston assembly, and the first piston outer housing 11 and the first piston top cover 12 are fastened by eight screws.

In order to avoid direct collision of the first piston with the deformed leaf spring during movement, the side of the first piston housing near the cold end (second piston) or near the leaf spring 3 has a slope, the magnitude of which is determined by the maximum amplitude of the ejector assembly. In other words, the first piston housing comprises a first convex bottom surface 10 facing the leaf spring 3, whereby the bottom surface of the first piston housing is sloped, and the first convex bottom surface 10 of the first piston 1 should be at a maximum axial distance from the leaf spring 3 that is greater than the maximum amplitude of the ejector structure; meanwhile, the first piston housing (hot end piston housing) of the ejector has a cylindrical boss (first protrusion 101) at a side close to the expansion chamber (or close to the plate spring), and the center of the boss is formed with an internal thread to facilitate connection with the plate spring 3 and the second piston 2.

(b) Second piston

In order to reduce the ejector mass, which is lighter, the second piston 2 is of hollow construction, preferably filled internally with a spoolable lightweight material in order to reduce the hollow volume and control the mass inside. The second piston 2 comprises a second piston outer shell 21 and a second piston top cover 22, and the second piston outer shell 21 and the second piston top cover 22 are fixedly connected and sealed through internal and external threads. Preferably, the first and second piston outer housings 11, 21 are oppositely arranged close to the leaf springs 3. Preferably, the second piston outer housing has a cylindrical structure with a bottom surface.

Likewise, in order to avoid that the second piston collides with the leaf spring during movement, the second piston housing has a slope on the side close to the leaf spring, the magnitude of which slope is determined in dependence on the maximum amplitude of the ejector assembly, i.e. the second piston housing comprises a second convex bottom surface 20 facing the leaf spring 3, whereby the bottom surface of the second piston housing is sloped, and the maximum axial distance of the second convex bottom surface 20 of the second piston 2 from the leaf spring 3 should be larger than the maximum amplitude of the ejector structure. The second piston outer housing back plate spring has a boss (second projection 201) with an internally threaded hole of depth in the center of the boss.

In one embodiment, a stud extends through the internal threads of the boss (first protrusion 101) or boss (second protrusion 201) of the first and second piston housings, and connects the leaf spring to the first and second piston housings and fixes the leaf spring to the surface of the screw by applying glue.

Materials of each component

The ejector structure in the prior art consists of a single piston, the ejector penetrates through a compression cavity at the hot end and an expansion cavity at the cold end, the ejector structure generally selects aluminum alloy, stainless steel or high-molecular polymer (engineering plastic), and the ejector structure made of metal materials has the advantages of small thermal deformation, high strength, high processing precision and higher heat conductivity coefficient. The clearance between the air cylinder and the ejector can be designed to be small, the air tightness is good, and the shuttle loss and the pumping loss are small; however, the disadvantage is that the axial heat transfer from the compression chamber to the expansion chamber is greater and the mass of the ejector is also greater. For the high polymer material, the strength is generally lower, the processing precision is low, the thermal deformation amount is larger, and the heat conductivity coefficient is small; the device has the advantages that the axial heat conduction from the compression cavity to the expansion cavity through the ejector body is smaller, and the weight is lighter; the disadvantage is that a certain gap is kept between the ejector and the cylinder to prevent direct friction between the ejector and the cylinder due to temperature change, resulting in a great increase in the damping of the ejector.

The ejector structure adopts various problems (as described above) brought by single materials, and reduces axial heat conduction loss as far as possible while guaranteeing the air tightness (reducing shuttle loss and pumping loss) between the compression cavity and the expansion cavity so as to improve the high-efficiency refrigeration effect of the refrigerator.

Therefore, in order to reduce the heat transfer of the refrigerator from the hot end to the cold end through the cylinder, and simultaneously in order to maintain a small gap between the piston and the cylinder, in the technical scheme of the application, the cylinder structure and the ejector structure are both made of two materials in a mixed mode, wherein the first cylinder is made of metal materials such as aluminum alloy, stainless steel, titanium alloy and the like, the second cylinder is made of high-molecular polymers (engineering plastics) with low heat conductivity coefficient and high strength, and the first cylinder and the second cylinder are connected through an O-shaped sealing ring and are adhered by glue.

Preferably, the first piston 1 is made of an aluminum alloy material with higher strength and lower density, and the surface of the hot end discharge piston is uniformly sprayed with a Teflon and other wear-resistant lubricating coating. The second piston 2 is made of engineering plastics with small heat conductivity, low temperature resistance and low thermal expansion coefficient.

Preferably, the first cylinder 4 is made of an aluminum alloy material with high heat conductivity and high strength, wherein the inner cylinder wall surface of the first cylinder 4 is polished and oxidized hard.

The second cylinder 5 is made of engineering plastics with small heat conductivity coefficient, high strength and low thermal expansion coefficient, and the inner wall surface of the accommodating section 52 of the second cylinder 5 is of a sealing structure with a plurality of grooves 522.

Free piston Stirling refrigerator device

A refrigerator comprising the above ejector structure.

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. It should be understood that these are merely examples of what the reader may take and are not intended to limit the scope of the invention.

Examples

The present embodiment provides an ejector structure for a free piston stirling refrigerator employing a double cylinder-double piston structure as shown in fig. 1-4, the apparatus comprising: a first piston 1, a second piston 2, a leaf spring 3, a first cylinder 4, and a second cylinder 5.

Wherein the first piston 1, the second piston 2, the leaf spring 3 are arranged in the axial direction, the leaf spring 3 being arranged between the first piston 1 and the second piston 2. The plate spring 3 is connected with the first piston 1 and the second piston 2 through the first fastening member 31, so that the plate spring 3 radially supports the first piston 1 and the second piston 2 and provides axial rigidity to the first piston 1 and the second piston 2 when the first piston 1 and the second piston 2 reciprocate under the action of the air pressure difference;

Specifically, referring to fig. 2, the first piston 1 includes a first piston outer case 11 and a first piston top cover 12, the first piston outer case 11 and the first piston top cover 12 being sealed by a first O-ring seal (i.e., one example of a first piston seal 13) and fixed by a first socket head cap screw (i.e., one example of a first piston fastener 14). The first piston outer shell 11 is of a cylindrical structure with a convex bottom surface, the first piston 1 comprises a first convex bottom surface 10 protruding towards the plate spring 3, the first convex bottom surface 10 is provided with a cylindrical protrusion 101 (namely, a first convex part 101) facing the plate spring 3, and the center of the cylindrical protrusion is provided with an internal thread;

the second piston 2 comprises a second piston outer housing 21 and a second piston top cover 22, and the second piston outer housing 21 and the second piston top cover 22 are fixedly connected and sealed through internal and external threads. The second piston outer case 21 is a cylindrical structure with a protruding bottom surface, the second piston outer case 21 includes a second protruding bottom surface 20 protruding toward the plate spring 3, the second protruding bottom surface 20 is provided with a boss (i.e., a second protruding portion 201) facing the plate spring 3, and the center of the boss has an internal threaded hole with a certain depth, so that the first piston 1, the second piston 2 and the plate spring 3 are fixed by a stud of a proper size, and the stud passes through the protrusion (first protruding portion 101) of the first protruding bottom surface, the plate spring 3, and the boss 201 (i.e., the second protruding portion 201) of the second protruding bottom surface 20. Wherein, the mounting coaxiality of the first piston 1, the second piston 2 and the plate spring 3 is controlled within 0.005 mm.

The plate spring 3 is fixedly connected with the upper end face of the first cylinder 4 through a second socket head cap screw (namely one example of a second fastener 32), and the coaxiality of the plate spring 3 and the first cylinder 4 is controlled within 0.005 mm.

The first cylinder 4 and the second cylinder 5 are gap-sealed by a second O-ring seal (i.e. one example of a cylinder seal 6) and are glued and fixed on the interface of the two. Wherein, the installation coaxiality of the first cylinder 4 and the second cylinder 5 is controlled within 0.005 mm.

In this embodiment, the first piston 1 is made of an aluminum alloy material with higher strength and lower density, and the surface of the hot end discharge piston is uniformly sprayed with a wear-resistant lubricating coating such as teflon. The second piston 2 is made of engineering plastics with small heat conductivity, low temperature resistance and low thermal expansion coefficient. The first cylinder 4 is made of an aluminum alloy material with high heat conductivity and high strength, wherein the inner cylinder wall surface of the hot-end cylinder is polished and oxidized hard. The second cylinder 5 is made of engineering plastics with small heat conductivity, high strength and low thermal expansion coefficient, and the inner wall surface of the cylinder is of a multi-groove sealing structure.

The installation step comprises the following steps:

(1) The O-shaped ring with proper size is sleeved at the boss of the first piston top cover, and the first piston top cover is connected and fixed with the first piston shell body through 8 screws.

(2) And uniformly filling the light material on the second piston outer shell, and then fixing the second piston top cover and the second piston through threads.

(3) A stud with proper size and length is penetrated into a round hole in the center of the plate spring 3, the first piston assembly is connected with the second piston through threads, the convex end surface of the second piston outer shell (namely, the end surface of the first convex bottom surface 10 of the first convex portion 101) and the convex end surface of the first piston outer shell (namely, the end surface of the second convex bottom surface 10 of the second convex portion 201) are flush and attached to two surfaces of the plate spring, and proper amount of thread glue is coated during threaded connection. It should be noted that the coaxiality of the leaf spring, the first piston assembly (the first piston outer housing 11 and the first piston top cover 12) and the second piston assembly (the second piston outer housing 21 and the second piston top cover 22) should be maintained during the installation, and the coaxiality should be maintained within 0.005mm.

(4) The leaf spring is coaxially mounted on the end face of the first cylinder by eight screws, and the coaxiality is required to be within 0.005mm.

(5) Finally, the first cylinder 4 and the second cylinder 5 are sealed through an O-shaped sealing ring, and proper anaerobic adhesive is filled in a gap between the first cylinder 4 and the second cylinder to ensure the fixation of the first cylinder and the second cylinder, and the coaxiality in the installation process is controlled to be 0.005mm.

It is worth mentioning that all parts need to be dried in a drying oven for a certain time before being installed.

The applicant wants to emphasize that the ejector structure of the present embodiment eliminates the use of the ejector base placed inside the compression chamber and the plate spring disposed inside the ejector, and eliminates redundant parts that can be directly worn away from the ejector except the cylinder, thereby greatly reducing damping, ensuring excellent air tightness (small shuttle loss and pumping loss) between the ejector and the cylinder, not increasing the empty volume of the compression chamber or the expansion chamber, small axial heat conduction of the ejector, not affecting the maximum power of the refrigerator, simplifying the structure of the refrigerator, and ensuring safe and reliable operation of the refrigerator with small installation difficulty.

The numerous technical features described in the description of the present application are distributed among the various technical solutions, which can make the description too lengthy if all possible combinations of technical features of the present application (i.e., technical solutions) are to be listed. In order to avoid this problem, the technical features disclosed in the above summary of the application, the technical features disclosed in the following embodiments and examples, and the technical features disclosed in the drawings may be freely combined with each other to constitute various new technical solutions (these technical solutions are regarded as already described in the present specification) unless such a combination of technical features is technically impossible. For example, in one example, feature a+b+c is disclosed, in another example, feature a+b+d+e is disclosed, and features C and D are equivalent technical means that perform the same function, technically only by alternative use, and may not be adopted simultaneously, feature E may be technically combined with feature C, and then the solution of a+b+c+d should not be considered as already described because of technical impossibility, and the solution of a+b+c+e should be considered as already described.

All references mentioned in this disclosure are to be considered as being included in the disclosure of the application in its entirety so that modifications may be made as necessary. Further, it is understood that various changes or modifications of the present application may be made by those skilled in the art after reading the above disclosure, and such equivalents are intended to fall within the scope of the application as claimed.

Claims (10)

1. An ejector structure for a free piston stirling cooler comprising:

a first piston (1), a leaf spring (3) and a second piston (2) which are arranged in sequence in the axial direction,

the leaf spring (3) is connected with the first piston (1) and the second piston (2) through a first fastener (31), so that the leaf 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) when the first piston (1) and the second piston (2) reciprocate under the action of air pressure difference;

during refrigeration, high-pressure gas flows back and forth in an expansion cavity at one end of the second piston (2) far away from the plate spring (3) and a compression cavity at one end of the first piston (1) far away from the plate spring (3), and the gas in the expansion cavity performs positive work on the ejector structure, so that refrigeration is provided;

The first piston (1) comprises a cylindrical structure with a convex bottom surface, the second piston (2) comprises a cylindrical structure with a convex bottom surface, the first piston (1) comprises a first convex bottom surface (10) protruding towards the leaf spring (3), and the second piston (2) comprises a second convex bottom surface (20) protruding towards the leaf spring (3);

the ejector structure further comprises a first fastener (31), wherein the first protruding bottom surface (10) is provided with a first protruding part (101), the second protruding bottom surface (20) is provided with a second protruding part (201), and the first fastener (31) penetrates through the plate spring (3) and is connected with the first protruding part (101) and the second protruding part (201), so that the plate spring (3) is fixedly connected with the first piston (1) and the second piston (2);

the positional relationship among the first piston (1), the second piston (2) and the plate spring (3) needs to satisfy the following formula:wherein m1 is the mass of the first piston, m2 is the mass of the second piston, L1 is the axial distance between the first piston center point and the plate spring center point along the axial direction of the first piston, L2 is the axial distance between the second piston center point and the plate spring center point along the axial direction of the second piston, g is the gravitational acceleration, k is the radial stiffness of the plate spring, and delta is the outer wall surface of the first piston and the first piston The height of the air gap between the inner wall surfaces of the air cylinder.

2. The ejector structure of claim 1, wherein the first fastener (31) is a stud, the first projection (101) is a cylindrical structure with internal threads inside, and the second projection (201) is a cylindrical structure with internal threads inside, the internal threads mating with external threads of the stud to complete the connection.

3. The ejector structure of claim 1, wherein an end face of the first projection engages one surface of the leaf spring and an end face of the second projection engages the other surface of the leaf spring upon completion of the connection of the leaf spring to the first projection and the second projection by the first fastener.

4. The ejector structure according to claim 1, characterized in that the maximum axial distance of the first convex bottom surface (10) of the first piston (1) from the leaf spring (3) should be larger than the maximum amplitude of the ejector structure, and the maximum axial distance of the second convex bottom surface (20) of the second piston (2) from the leaf spring (3) should be larger than the maximum amplitude of the ejector structure.

5. The ejector structure of claim 1, wherein the first piston, the second piston, and the leaf spring are coaxially mounted.

6. The ejector structure according to claim 1, further comprising a first cylinder (4) and a second cylinder (5), wherein both ends of the plate spring (3) are fixedly connected to the first cylinder (4) or the second cylinder (5), thereby realizing a reciprocating motion of the first piston (1) in the first cylinder (4) and a reciprocating motion of the second piston (2) in the second cylinder (5).

7. The ejector structure according to claim 6, characterized in that the second cylinder (5) comprises a connecting section (51) and a receiving section (52), the connecting section (51) being located outside the first cylinder (4) in the radial direction of the cylinder, the connecting section (51) being gap-sealed with the first cylinder (4).

8. The ejector structure according to claim 1, characterized in that the first piston (1) is a hollow structure, the first piston (1) comprising a first piston outer housing (11) and a first piston cap (12), the first piston outer housing (11) and the first piston cap (12) being sealed by a first piston seal (13).

9. The ejector structure according to claim 8, characterized in that the second piston (2) is a hollow structure, the second piston (2) comprising a second piston outer housing (21) and a second piston top cap (22), the second piston outer housing (21) and the second piston top cap (22) being fixedly connected and sealed by threads.

10. A stirling cooler for a free piston comprising an ejector structure according to any one of claims 1 to 9.