Anti-electromagnetic interference G-M refrigerator

Abstract

The anti-electromagnetic interference G-M refrigerating machine comprises a cover body, a refrigerating machine air cylinder and a rotating motor, the rotating motor is arranged in a motor housing, the motor housing is fixed to the side face of the cover body, the cover body is fixed to an air cylinder flange through a screw, an insulation spacer is arranged between the screw and the cover body, and the cover body is made of hard anodic aluminum oxide. By changing the electrical insulation performance of the cover body, the problems that the electrical insulation performance of the G-M refrigerator is poor in the use process of a low-temperature system, and particularly electromagnetic signals generated in the operation process of a motor interfere with measurement of weak signals in a tested sample are solved.

Description

Technical Field

[0001] The invention relates to a GM refrigerator, in particular to an electromagnetic interference resistant GM refrigerator. Background Art

[0002] Cryogenic technology is widely used in cutting-edge science and technology, especially in the field of precision signal measurement, such as the properties of two-dimensional quantum materials, quantum computing, etc. In the process of measuring samples, the circuit environment of the test sample needs to be insulated from the external mains to avoid external interference during the measurement process and avoid measurement errors.

[0003] Small cryogenic refrigerators, including Gifford-McMahon refrigerators and pulse-tube refrigerators, developed rapidly in the early part of this century and have gradually replaced traditional liquid helium to become the mainstream means of providing low-temperature experimental environments. Because pulse tube refrigerators have no moving parts that need to be driven inside, they only rely on gas columns to connect the cold and hot ends. They can form stable electrical insulation properties through external pressure drivers and are widely used in various high-end scientific instruments and equipment. The GM refrigerator has a piston installed inside the cylinder. The piston is driven to reciprocate by a rotating motor installed on the top of the refrigerator, driving the internal refrigerant gas to complete the cooling.

[0004] Considering the overall sealing, mechanical stability, and material cost-effectiveness of small cryogenic refrigerators, all GM refrigerators on the market at this stage use aluminum alloy as the cover, and the rotating motor and the refrigerator cylinder are directly installed and fixed through the cover. Since the cylinder is usually directly connected to the object to be measured by solid-solid connection, the electromagnetic signal generated by the rotation of the motor usually brings unnecessary signal interference to small signal measurement, especially temperature measurement, when electrical insulation between the object to be measured and the motor cannot be achieved. Therefore, it is very important to achieve electrical insulation between the rotating motor and the cylinder flange of the GM refrigerator.

[0005] The existing cryogenic system using GM refrigerator as the main cooling source generally achieves electrical insulation by adding insulating materials at the hot end, especially when the cylinder flange is fixedly connected to the room temperature flange of the cryogenic system, and at the cold end, using the insulating properties of the refrigerant gas helium. For example, the vibration-damping heat exchange cavity disclosed in CN114739031B achieves electrical insulation between the GM refrigerator and the dilution refrigerator by this principle. The premise for achieving this electrical insulation method is that the connection between the GM refrigerator and the cryogenic system needs to be adjusted by structure to ensure that the two are completely physically isolated. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a GM refrigerator that can achieve electrical insulation between the refrigerator cylinder and the rotating motor without changing the existing GM refrigerator structure, thereby achieving the purpose of electrical insulation between the experimental device and the refrigerator.

[0007] Technical solution: The electromagnetic interference-resistant GM refrigerator described in the present invention includes a cover body, a refrigerator cylinder and a rotating motor. The rotating motor is arranged in a motor cover, and the motor cover is fixed to the side of the cover body. The cover body is fixed to the cylinder flange by screws. An insulating gasket is arranged between the screws and the cover body. The cover body is made of hard anodized aluminum.

[0008] Furthermore, the cover body made of hard anodized aluminum material is processed by a hard anodizing process on the cover body made of aluminum alloy material, and a dense oxide layer is formed on the surface.

[0009] Furthermore, the thickness of the oxide layer is 5 to 500 μm.

[0010] Furthermore, the material of the cover body is replaced by polyetheretherketone or polyvinyl chloride instead of hard anodized aluminum.

[0011] Furthermore, the insulating gasket has a "convex" structure in cross section, with a through hole in the center for the screw to pass through, the small diameter portion of the insulating gasket is embedded in the mounting hole of the cover body, and the large diameter portion is against the top surface of the cover body.

[0012] Furthermore, the insulating gasket is made of any one of alumina ceramics, G10, and bakelite.

[0013] Furthermore, there are four screws, which are distributed at four corners on the cover.

[0014] Furthermore, the rotating motor is connected to 220V AC power via a motor interface on the motor housing.

[0015] Furthermore, a low-pressure pipeline interface and a high-pressure pipeline interface are provided on the motor housing, serving as an inlet and an outlet for supplying the gaseous working medium required for the operation of the GM refrigerator.

[0016] Furthermore, the refrigerator cylinder is a two-stage cylinder structure and is equipped with a two-stage cold end heat exchanger.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0018] The present invention changes the electrical insulation performance of the cover material and eliminates the damage to the anodized surface caused by the screws through insulating gaskets to prevent unnecessary electrical contact. Without changing the structure of the existing GM refrigerator, the present invention can achieve electrical insulation between the rotating motor and the cylinder and prevent the electrical signal (fixed frequency or variable frequency signal) driving the rotating motor from interfering with the temperature, electrical or magnetic measurement signals.

[0019] The present invention is applicable to all GM refrigerators on the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of an electromagnetic interference resistant GM refrigerator provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Attached Figure 1 The reference numerals in the figures are as follows:

[0023] 1. Cover; 2. Low-pressure pipeline interface; 3. High-pressure pipeline interface; 4. Motor interface; 5. Cylinder flange; 6. First-stage cylinder; 7. First-stage cold-end heat exchanger; 8. Second-stage cylinder; 9. Second-stage cold-end heat exchanger; 10. Screws; 11. Insulating gasket; 12. Motor cover; 13. Rotating motor.

[0024] like Figure 1 As shown, an embodiment of the present invention provides an electromagnetic interference resistant GM refrigerator, including a housing 1, a refrigerator cylinder and a rotary motor 13. The refrigerator cylinder includes a primary cylinder 6 and a secondary cylinder 8. A primary cold end heat exchanger 7 is welded and fixed to the primary cylinder 6, and a secondary cold end heat exchanger 9 is welded and fixed to the secondary cylinder 8. A primary piston is arranged inside the primary cylinder 6, and a secondary piston is arranged inside the secondary cylinder 8. The primary and secondary pistons are fixedly connected by a guide rod and can reciprocate up and down in the cylinder. The piston is filled with cold storage material.

[0025] The rotating motor 13 is arranged in the motor housing 12, and the motor housing 12 is fixed to the side of the housing 1. The rotating motor 13 is connected to the 220V mains through the motor interface 4 on the motor housing 12, and rotates at a fixed frequency after being connected to the power supply. The rotating motor 13 is a main body that needs to be electrically insulated. The motor housing 12 is also provided with a low-pressure pipeline interface 2 and a high-pressure pipeline interface 3, which serve as the inlet and outlet of the gas working medium required for the operation of the GM refrigerator.

[0026] The cover 1 is fixed to the cylinder flange 5 by screws 10. There are four screws 10, which are distributed at four corners on the cover 1. An insulating gasket 11 is arranged between the screws 10 and the cover 1. The insulating gasket 11 has a "convex" structure in cross section, and has a through hole in the center for the screw 10 to pass through. The small diameter part of the insulating gasket 11 is embedded in the mounting hole of the cover 1, and the large diameter part is against the top surface of the cover 1.

[0027] The housing 1 is provided with crank connecting rod, crank cam, plane rotary valve and other components, wherein the crank cam drives the crank connecting rod to reciprocate up and down under the drive of the rotary motor 13, and then drives the primary and secondary pistons to reciprocate up and down. The plane rotary valve is a key component for connecting high and low pressure pipelines. By switching the plane rotary valve, the high and low pressure inside the GM refrigerator are switched in a certain sequence, so that the high-pressure refrigerant gas expands in the expansion chamber of the GM refrigerator to generate cold, and then is transferred to the object to be cooled through the primary and secondary cold end heat exchangers.

[0028] The material of the cover body 1 is a material with excellent electrical insulation performance and strong hardness, such as hard anodized aluminum, to achieve the electrical insulation function between the rotating motor 13, the cover body 1 and the refrigerator cylinder. After the cover body 1 is machined from the commonly used aluminum alloy material, it is hard anodized to form a dense oxide layer on the surface of the aluminum alloy with a thickness of 5 to 500 μm. Table 1 shows some electrical insulation performance test results. After that, the motor housing 12 and the rotating motor 13 are installed in the side opening of the cover body 1, and the bottom opening is installed on the cylinder flange 5 using screws 10 to block the electrical path between the screws 10 and the refrigerator cylinder.

[0029] Table 1

[0030] Anodized layer thickness / micrometer Electrical insulation performance (megohm) 50 20 100 50 150 200

[0031] The insulating gasket 11 is made of insulating material, such as hard materials such as alumina ceramics, G10, bakelite, etc. The function of the insulating gasket 11 is to prevent the cover body 1 from contacting with the screw 10 by friction and the like and prevent the cover body 1 from being electrically connected.

[0032] In some embodiments, the cover body 1 may also be made of engineering plastic materials such as polyetheretherketone (PEEK) and polyvinyl chloride (PVC).

[0033] In some embodiments, the refrigerator cylinder may also be a single-stage cylinder structure.

[0034] Based on the electrical insulation method of the present invention, on the one hand, it is possible to easily achieve excellent insulation performance between the motor and the cylinder without changing the existing GM refrigerator structure, with extremely low processing costs, and solve the poor electrical insulation performance of the GM refrigerator during use in the low-temperature system, especially the electromagnetic signal generated during the operation of the motor interferes with the measurement of weak signals in the sample being tested; on the other hand, it can greatly simplify the electrical insulation transformation during the integration of the low-temperature system and reduce the system manufacturing cost. The GM refrigerator structure described in the embodiment of the present invention is a prior art, so its structure is not described in detail. The improvement of the present invention over the prior art is that the electrical insulation performance of the cover is improved for the purpose of electrical insulation and an insulating gasket is provided to eliminate unnecessary electrical contact caused by damage to the anodized layer when the screws are fixed.

Claims

1. A GM refrigerator with electromagnetic interference resistance, comprising a housing (1), a refrigerator cylinder and a rotary motor (13), wherein the rotary motor (13) is arranged in a motor housing (12), and the motor housing (12) is fixed to a side of the housing (1), characterized in that: The cover body (1) is fixed to the cylinder flange (5) by means of screws (10); an insulating gasket (11) is arranged between the screws (10) and the cover body (1); and the cover body (1) is made of hard anodized aluminum.

2. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The hard anodized aluminum cover (1) is made of an aluminum alloy and is processed by a hard anodizing process, so that a dense oxide layer is formed on the surface.

3. The electromagnetic interference resistant GM refrigerator according to claim 2, characterized in that: The thickness of the oxide layer is 5 to 500 μm.

4. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The material of the cover body (1) is replaced by polyetheretherketone or polyvinyl chloride instead of hard anodized aluminum.

5. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The insulating gasket (11) has a convex cross-section and has a through hole in the center for the screw (10) to pass through. The small diameter portion of the insulating gasket (11) is embedded in the mounting hole of the cover body (1), and the large diameter portion abuts against the top surface of the cover body (1).

6. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The material of the insulating gasket (11) is any one of alumina ceramics, G10 and bakelite.

7. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The number of the screws (10) is four, and they are distributed at four corners on the cover body (1).

8. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The rotating motor (13) is connected to a 220V mains electricity via a motor interface (4) on the motor housing (12).

9. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The motor housing (12) is provided with a low-pressure pipeline interface (2) and a high-pressure pipeline interface (3) serving as an inlet and an outlet for supplying gaseous working fluid required for the operation of the GM refrigerator.

10. The electromagnetic interference resistant GM refrigerator according to claim 1, characterized in that: The refrigerator cylinder is a two-stage cylinder structure and is equipped with a two-stage cold end heat exchanger.

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