Pushing piston and low-temperature refrigerator
By using polyethers, fluoroplastics, polyimides and other materials to make the piston shell, the problem of high water absorption rate of bakelite is solved, and the performance stability and production efficiency of the refrigerator are improved.
Patent Information
- Application Number
- CN202422513217.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-08-05
- Estimated Expiration
- 2034-10-17
AI Technical Summary
The existing piston material has high water absorption rate, resulting in dimensional changes, affecting the performance stability and production efficiency of the refrigerator.
Use polyethers, fluoroplastics, polyimides, polysulfides, and polyamide materials to make the piston shell, or combine it with bakery materials to reduce water absorption and improve tribological properties.
Significantly reduces the water absorption deformation of the piston cylinder and improves the performance stability and production efficiency of the refrigerator.
Smart Images
Figure CN223190581U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a refrigerator, in particular to a push piston and a low-temperature refrigerator. Background Art
[0002] Cold storage refrigerators, such as GM refrigerators and Stirling refrigerators, have a cylinder body and a reciprocating push piston. The push piston is typically made of a cylindrical piston shell that encloses a cold storage material. The cylindrical piston shell is typically made of inexpensive Bakelite. Bakelite (also known as bakelite) is made from a cotton or glass cloth base, impregnated with phenolic resin or epoxy resin, and then hot-pressed through a mold to form a rod with a prototype cross-section. It has high mechanical strength and is suitable for piston construction. However, this material has a high water absorption rate, generally exceeding 1.7%, and its dimensions change significantly after absorbing water. Because the push piston has a small clearance in the cylinder, even the slightest dimensional deformation can cause performance degradation or mechanical failure. Therefore, pistons made of Bakelite often undergo a tedious baking process to remove water, resulting in low mass production efficiency.
[0003] Furthermore, because the high-pressure airflow from the compressor always contains trace amounts of water vapor, it is absorbed by the piston as it passes through it. Over time, the Bakelite outer shell of the cylinder will begin to deform. Because the gap between the piston and cylinder is very small, sufficient deformation can cause direct contact between the cylinder and piston, increasing piston wear. The resulting dust will contaminate the refrigerator's performance and even cause excessive friction, leading to piston-cylinder seizures and mechanical failure. Utility Model Content
[0004] Purpose of the utility model: The utility model provides a push piston and a low-temperature refrigerator, which can reduce the water absorption of the push piston and improve production efficiency.
[0005] Technical solution: The present invention provides a push piston, which is installed in a cylinder and includes a primary push piston and a secondary push piston which are coaxially connected and move synchronously in the cylinder;
[0006] The first-stage push piston is installed in the first-stage cylinder body of the cylinder, and the second-stage push piston is installed in the second-stage cylinder body of the cylinder; wherein the first-stage cylinder body and the second-stage cylinder body are coaxially connected;
[0007] The first-stage push piston includes a first cylindrical piston shell, and the second-stage push piston includes a second cylindrical piston shell. The first cylindrical piston shell and the second cylindrical piston shell are a single-layer structure as a whole, and a shell made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide is selected, or the first cylindrical piston shell and the second cylindrical piston shell are both a composite structure of more than two layers, one of which is a bakelite material shell, and the remaining layers are shells made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide.
[0008] Furthermore, the first-stage push piston also includes a first cold storage material filled inside the first cylindrical piston shell, a first air flow channel arranged on the high-temperature side of the first-stage push piston and connected to the first cold storage material, and a second air flow channel arranged on the low-temperature side of the first-stage push piston and connected to the first cold storage material; the bottom surface of the first-stage push piston and the bottom of the first-stage cylinder body are enclosed to form a first-stage expansion chamber.
[0009] Furthermore, the secondary push piston also includes a third air flow channel arranged on the top of the second cylindrical piston shell, which is filled with the second cold storage material inside the second cylindrical piston shell; wherein, the third air flow channel is used to connect the second cold storage material and the first-stage expansion chamber.
[0010] Furthermore, a second-stage heat exchanger is provided at one end of the second-stage cylinder away from the first-stage cylinder, and the second-stage heat exchanger and the bottom surface of the secondary push piston are enclosed to form a second-stage expansion chamber.
[0011] Furthermore, an exhaust port is arranged on the bottom side of the second cylindrical piston shell, and the exhaust port is used to connect the second cold storage material and the second-stage expansion chamber.
[0012] Furthermore, a sealing ring is provided on the outer peripheral surface of the top of the first-stage push piston, and the gap between the outer peripheral surface of the first-stage push piston and the first-stage cylinder body is sealed by the sealing ring.
[0013] Based on the same inventive concept, the present invention provides a low-temperature refrigerator, comprising a compressor, a cover assembly, a gas pipeline, a cylinder and the push piston;
[0014] The output end of the compressor is connected to the cover assembly through a gas pipeline. The cylinder is installed on the cover assembly, and a push piston is arranged inside the cylinder to use the push piston to exchange heat with the refrigerant gas entering the cover assembly.
[0015] Furthermore, a first-stage heat exchanger is fixedly provided on one end of the first-stage cylinder body of the cylinder away from the cover assembly.
[0016] Furthermore, the low-temperature refrigerator is a pulse tube refrigerator.
[0017] Beneficial effect: Compared with the existing technology, the significant technical effect of the utility model is: by adding a cylindrical piston shell, the shell is made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide, which can greatly reduce the deformation of the piston cylinder due to water absorption and improve the performance stability of the refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 This is a schematic structural diagram of a low-temperature refrigerator of the present utility model;
[0019] Figure 2 for Figure 1 Positional relationship diagram of the first cylindrical piston housing and the first stage cylinder body;
[0020] Figure 3 Schematic diagram of the structure of the first cylindrical piston housing in Example 2;
[0021] Figure 4 This is a schematic structural diagram of the first cylindrical piston housing in Example 3. DETAILED DESCRIPTION
[0022] The technical solution of the present invention is described in detail below in conjunction with specific implementation methods and the accompanying drawings.
[0023] Example 1
[0024] like Figure 1 As shown, the push piston of the present invention is installed in a cylinder 13 and includes a coaxially connected primary push piston 11 and a secondary push piston 12. The primary push piston 11 and the secondary push piston 12 move synchronously in the cylinder 13. The primary push piston 11 is installed in a first-stage cylinder body 131 of the cylinder 13, and the secondary push piston 12 is installed in a second-stage cylinder body 132 of the cylinder 13; the first-stage cylinder body 131 and the second-stage cylinder body 132 are coaxially connected.
[0025] The primary push piston 11 comprises a first cylindrical piston housing 114, a first cold storage material 113 filled within the first cylindrical piston housing 114, a first airflow channel 111 located on the high-temperature side of the first push piston 11 and connected to the first cold storage material 113, and a second airflow channel 112 located on the low-temperature side of the first push piston 11 and connected to the first cold storage material 113. The bottom surface of the first push piston 11 and the bottom of the first-stage cylinder 131 together form the first-stage expansion chamber 9. A top cover 115 is located on the top of the first cylindrical piston housing 114, while a bottom cover 116 is located on the bottom. The cylindrical cavity formed by the first cylindrical piston housing 114, the top cover 115, and the bottom cover 116 is used to hold the first cold storage material 113. The first airflow channel 111 is typically located on the top cover 115, while the second airflow channel 112 is typically located on the bottom cover 116. The second airflow channels 112 are evenly distributed along the circumference of the bottom cover 116, though this is not shown in the structural diagram but does not affect the implementation of this solution. The first air flow channel 111 , the first cold storage material 113 , and the second air flow channel 112 are connected, and the air flow can flow back and forth.
[0026] like Figure 1 and Figure 2 As shown, a sealing ring 7 is provided on the outer circumference of the top of the first-stage push piston 11, and the sealing ring 7 seals the gap d between the outer circumference of the first-stage push piston 11 and the first-stage cylinder 131. The first-stage push piston 11 reciprocates up and down along Z1-Z2 in the first-stage cylinder. A small gap d exists between the outer circumference of the first cylindrical piston housing 114 and the inner circumference of the first-stage cylinder 131 to prevent wear of the first-stage cylinder 131 and the first-stage push piston 11. This dimension is generally designed based on thermal calculations, and changes in this dimension will cause changes in the performance of the refrigerator. Therefore, during the refrigerator manufacturing process, the inner diameter of the first-stage cylinder 131 and the outer circumference of the first cylindrical piston housing 114 of the first-stage push piston 11 are strictly controlled.
[0027] The secondary push piston 12 includes a second cylindrical piston housing 124, a third air flow channel 121 arranged at the top of the second cylindrical piston housing 124, and a second cold storage material 123 filled in the second cylindrical piston housing 124. The third air flow channel 121 is used to connect the second cold storage material 123 and the first-stage expansion chamber 9. A second-stage heat exchanger 134 is provided at one end of the second-stage cylinder 132 away from the first-stage cylinder 131. The second-stage heat exchanger 134 and the bottom surface of the secondary push piston 12 are enclosed to form a second-stage expansion chamber 10. An exhaust port 122 is arranged on the bottom side of the second cylindrical piston housing 124. The exhaust port 122 is used to connect the second cold storage material 123 and the second-stage expansion chamber 10.
[0028] In this embodiment, the first cylindrical piston shell 114 and the second cylindrical piston shell 124 are made of a material different from bakelite to form a cylindrical body. Generally, they can be made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide.
[0029] Polyimide materials can be used preferentially. Table 1 shows the weight gain changes of bakelite and polymer resin materials represented by polyimide after absorbing water in humid air.
[0030] Table 1:
[0031] Weight gain changes 24 hours 48 hours 72 hours 96 hours 120 hours 144 hours bakelite 10g 21g 32g 42g 52g 65g polyimide 0.5g 1.1g 1.8g 2.5g 3.4g 4.7g
[0032] Since bakelite is made of cotton cloth or glass cloth as the base material, which is impregnated with phenolic resin or epoxy resin respectively and hot-pressed into a rod with a prototype cross-section through a molding mold, it can be seen from Table 1 that after the cotton cloth layer absorbs too much water, the thickness size between layers will change, thereby causing the outer diameter of the first-stage push piston 11 to change, generally showing a non-uniform change characteristic, that is, the outer diameter becomes elliptical.
[0033] The first cylindrical piston housing 114 made of polyimide, which is generally a thermoplastic material, not only has low water absorption, but also has good tribological properties, which is conducive to the long-term stable operation of the first-stage push piston 11 in the first-stage cylinder 131.
[0034] During implementation, the top cover 115 and bottom cover 116 of the primary push piston 11 can continue to be made of bakelite. Due to the constraints imposed by the first cylindrical piston housing 114, their radial dimensions will not change significantly. Alternatively, one of the top cover 115 or bottom cover 116 can be integrally formed with the first cylindrical piston housing 114. For example, the aforementioned materials can be integrally machined into a single piece, and then the remaining component can be assembled.
[0035] In this embodiment, the material selected is a non-metallic material with a thermal conductivity lower than that of stainless steel. Preferably, a material with a thermal conductivity close to that of bakelite is selected for implementation to avoid heat leakage in the axial direction of the primary push piston 11.
[0036] The working process of the push piston introduced in this scheme is as follows:
[0037] like Figure 1 As shown, the primary push piston 11 and the secondary push piston 12 are coaxially connected and, driven by a drive mechanism (not shown), move together within the cylinder 13 along the Z1-Z2 direction. When the primary and secondary push pistons 11, 12 move upward (Z1 direction) in the figure, the volumes of the first-stage expansion chamber 9 and the second-stage expansion chamber 10 increase. Conversely, the corresponding expansion volumes decrease.
[0038] Under the above-mentioned change in expansion volume, the incoming refrigerant gas passes through the first airflow channel 111 and exchanges heat with the first cold storage material 113 inside the first-stage push piston 11. It then flows out through the second airflow channel 112. A portion of the gas expands within the first-stage expansion chamber 9, and the remaining gas flows into the second-stage push piston 12 through the third airflow channel 121, exchanging heat with the second cold storage material 123 inside. It then flows out through the exhaust port 122 and enters the second-stage expansion chamber 10. During this process, the refrigerant gas transfers its own heat to the cold storage material, causing its temperature to drop from room temperature to a low temperature.
[0039] Along the above-mentioned gas flow direction, that is, the Z2 direction, the temperatures of the cylinder 13 and the first-stage push piston 11 and the second-stage push piston 12 are continuously reduced, forming a temperature gradient.
[0040] The return gas flows in the opposite direction to the above process. The refrigerant gas flows out of the second-stage expansion chamber 10, exchanges heat with the second cold storage material 123 in the second-stage push piston 12 through the exhaust port 122, flows out of the third air flow channel 121, and mixes with the refrigerant gas in the first-stage expansion chamber 9. Then, it passes through the second air flow channel 112 and exchanges heat with the first cold storage material 113 in the first-stage push piston 11. Then, it passes through the first air flow channel 111, enters the cover assembly 2, and then flows to the low-pressure side of the compressor 1. In this process, the refrigerant gas absorbs heat from the cold storage material, and the temperature changes from low temperature to room temperature.
[0041] By repeating the above steps, the first and second regenerator materials 113, 123, and the refrigerant gas are cooled. The low-temperature gas continuously expands and generates work within the first and second expansion chambers 9, 10, forming a cooling source. This heat transfer cools the first and second heat exchangers 133, 134. The temperature of the first heat exchanger 133 is approximately between 40 and 80 Kelvin.
[0042] A sealing ring 7 is used to seal the gap between the outer circumference of the first-stage push piston 11 and the cylinder 13. Since the sealing ring 7 is installed on the room temperature side, that is, close to the cover assembly 2, during operation, the temperature is moderately high, which effectively prevents refrigerant gas from entering the first-stage expansion chamber 9 through the gap between the first-stage push piston 11 and the first-stage cylinder.
[0043] In addition, in this embodiment, the description is given for a two-stage refrigerator, but the invention is not limited thereto and is also applicable to a push piston of a single-stage refrigerator.
[0044] In addition, in this embodiment, the refrigerator is any type of refrigerator having a reciprocating push piston, for example, a Stirling refrigerator, a Solvang refrigerator, etc.
[0045] In this embodiment, the refrigerator is a pulse tube refrigerator that is also applicable to a case where the piston does not move.
[0046] Example 2
[0047] This embodiment differs from Example 1 in that both first cylindrical piston housing 114 and second cylindrical piston housing 124 are composite structures of two or more layers, one of which is made of bakelite, and the remaining layers are made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide. In other words, first cylindrical piston housing 114 and second cylindrical piston housing 124 radially comprise at least one cylindrical layer made of a material other than bakelite, have a lower water absorption rate than bakelite, and a lower thermal conductivity than stainless steel.
[0048] like Figure 3 As shown, in this embodiment, the first cylindrical piston shell 114 and the second cylindrical piston shell 124 are both designed as a two-layer composite structure, including an inner cylinder and an outer cylinder, the inner cylinder is a bakelite material shell 112, and the outer cylinder adopts a shell 110 made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide.
[0049] Compared with Example 1, this embodiment can further reduce costs. At the same time, by controlling the amount of bakelite used, the total amount of water vapor absorbed by the piston 11 can be controlled.
[0050] During production, the outer cylinder is arranged radially outside the inner cylinder, and the inner cylinder is pressed into the outer cylinder by using a bakelite cylinder. Other methods are also possible.
[0051] The thickness of the outer cylinder can be compared with the thickness of the inner cylinder and selected to be between 0.3 and 3 times the thickness of the inner cylinder.
[0052] Example 3
[0053] like Figure 4 As shown, in this embodiment, the first cylindrical piston shell 114 and the second cylindrical piston shell 124 are also designed as a two-layer composite structure, and both include an inner cylinder and an outer cylinder. The difference from Example 1 is that the outer cylinder adopts a shell 110 made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide, and the outer cylinder is a bakelite material shell 112.
[0054] Example 4
[0055] like Figure 1As shown, this embodiment relates to a low-temperature refrigerator, which is any type of refrigerator with a reciprocating push piston, and is not limited to a Stirling refrigerator, a Gifford-McMahon refrigerator, etc. The low-temperature refrigerator includes a compressor 1, a cover assembly 2, a gas pipeline 3, a cylinder 13, and a push piston as described in Example 1. The output end of the compressor 1 is connected to the cover assembly 2 through the gas pipeline 3. The compressor 1 sucks in and compresses the refrigerant gas, and discharges it as high-pressure refrigerant gas. The gas pipeline 3 supplies the high-pressure refrigerant gas to the cover assembly 2. The cylinder 13 is mounted on the cover assembly 2, and a push piston is provided inside the cylinder 13, which is used to exchange heat with the refrigerant gas entering the cover assembly 2.
[0056] The cylinder 13 is a two-stage cylinder. The main body is made of 304 stainless steel. It is generally made by precision processing of 304 stainless steel, and the size can be guaranteed. The first-stage cylinder body 131 and the second-stage cylinder body 132 are coaxially arranged. The inner diameter of the second-stage cylinder body is smaller than the inner diameter of the first-stage cylinder body 131. A first-stage heat exchanger 133 is fixedly provided on the end of the first-stage cylinder body 131 of the cylinder 13 away from the cover assembly 2. In this embodiment, the first-stage heat exchanger 133 is welded to the end of the first-stage cylinder body 131 away from the cover assembly 2; and the second-stage heat exchanger 134 is welded to the end of the second-stage cylinder body 132 away from the cover assembly 2. The above-mentioned heat exchangers are all made of copper.
[0057] The cylindrical piston housing that pushes the piston includes at least one radially extending layer of a cylindrical shell made of a material different from bakelite, with a water absorption rate lower than bakelite and a thermal conductivity lower than stainless steel. The cylindrical shell is made of one or more of polyether, fluoroplastic, polyimide, polysulfide, and polyamide. The cryogenic refrigerator is a pulse tube refrigerator.
Claims
1. A push piston, characterized in that: The push piston is installed in the cylinder (13), and comprises a primary push piston (11) and a secondary push piston (12) which are coaxially connected and move synchronously in the cylinder (13); The first-stage push piston (11) is installed in a first-stage cylinder body (131) of the cylinder (13), and the second-stage push piston (12) is installed in a second-stage cylinder body (132) of the cylinder (13); wherein the first-stage cylinder body (131) and the second-stage cylinder body (132) are coaxially connected; The first-stage push piston (11) includes a first cylindrical piston shell (114), and the second-stage push piston (12) includes a second cylindrical piston shell (124). The first cylindrical piston shell (114) and the second cylindrical piston shell (124) are overall single-layer structures, and the shell is made of one of polyether, fluoroplastic, polyimide, polysulfide, and polyamide. Alternatively, the first cylindrical piston shell (114) and the second cylindrical piston shell (124) are both composite structures of two or more layers, one of which is a bakelite shell, and the remaining layers are shells made of one of polyether, fluoroplastic, polyimide, polysulfide, and polyamide.
2. The push piston according to claim 1, characterized in that: The first-stage push piston (11) further includes a first cold storage material (113) filled in the interior of the first cylindrical piston housing (114), a first air flow channel (111) arranged on the high-temperature side of the first-stage push piston (11) and in communication with the first cold storage material (113), and a second air flow channel (112) arranged on the low-temperature side of the first-stage push piston (11) and in communication with the first cold storage material (113); the bottom surface of the first-stage push piston (11) and the bottom of the first-stage cylinder (131) enclose a first-stage expansion chamber (9).
3. The push piston according to claim 2, characterized in that: The secondary push piston (12) further includes a third air flow channel (121) arranged at the top of the second cylindrical piston housing (124), which is filled with a second cold storage material (123) inside the second cylindrical piston housing (124); wherein the third air flow channel (121) is used to connect the second cold storage material (123) and the first-stage expansion chamber (9).
4. The push piston according to claim 1, characterized in that: A second-stage heat exchanger (134) is provided at one end of the second-stage cylinder (132) away from the first-stage cylinder (131), and the second-stage heat exchanger (134) and the bottom surface of the secondary push piston (12) are enclosed to form a second-stage expansion chamber (10).
5. The push piston according to claim 3, characterized in that: An exhaust port (122) is arranged on the bottom side of the second cylindrical piston housing (124).
6. The push piston according to claim 1, characterized in that: A sealing ring (7) is provided on the outer peripheral surface of the top of the first-stage pushing piston (11), and the gap between the outer peripheral surface of the first-stage pushing piston (11) and the first-stage cylinder body (131) is sealed by the sealing ring (7).
7. A low-temperature refrigerator, characterized in that: It comprises a compressor (1), a cover assembly (2), a gas pipeline (3), a cylinder (13), and a push piston according to any one of claims 1 to 6; The output end of the compressor (1) is connected to the cover assembly (2) via a gas pipeline (3); the cylinder (13) is mounted on the cover assembly (2) and a push piston is provided inside the cylinder to perform heat exchange on the refrigerant gas entering the cover assembly (2).
8. The cryogenic refrigerator according to claim 7, wherein: A first-stage heat exchanger (133) is fixedly provided on an end of the first-stage cylinder body (131) of the cylinder (13) away from the cover assembly (2).
9. The cryogenic refrigerator according to claim 7, wherein: The low-temperature refrigerator is a pulse tube refrigerator.