Cryogenic refrigerator with electric insulation function

Abstract

The cryogenic refrigerator with the electric insulation function comprises an air cylinder, a cover body and an electric insulation part, the cover body is assembled on the top of the air cylinder, the electric insulation part is arranged between the cover body and the air cylinder, and the electric insulation part is used for blocking an electric circuit between the cover body and the air cylinder. According to the utility model, the electrical insulation function of the G-M refrigerator can be realized, and the interference of the application of the frequency conversion technology on temperature and other measuring components is prevented.

Description

Technical Field

[0001] The utility model relates to an ultra-low temperature refrigerator, in particular to an ultra-low temperature refrigerator with an electrical insulation function. Background Art

[0002] GM (Gifford-McMahon) refrigerator is one of the two most widely used regenerative cryogenic refrigerators. Its first-stage cooling temperature can reach below 40K, and its second-stage cooling temperature can reach below 3K.

[0003] Figure 1 The figure shows the structure of an existing GM refrigerator, which uses helium as the refrigerant. Considering factors such as strength, thermal conductivity, and helium isolation capacity, the cylinder 30 is made of stainless steel. A primary displacer 40 and a secondary displacer 50 are provided in the cylinder 30 (the end with a higher temperature of the displacer is called the high-temperature end, and the end with a lower temperature is called the low-temperature end). A seal is provided on the outer circumference of the primary displacer 40, and a spiral groove structure is used throughout the length of the secondary displacer 50 to achieve low-temperature sealing. The displacer is filled with cold storage material, which accumulates cold during the cold blowing period of the GM refrigerator and exchanges heat with the refrigerant during the hot blowing period to cool the refrigerant.

[0004] The crank connecting rod 22 and the plane rotary valve 23 are accommodated inside the housing 21, and the crank connecting rod 22 reciprocates up and down inside the housing 21. The housing 21 has a high-pressure air inlet and a low-pressure air return port, which are respectively connected to the high-pressure pipeline 11 and the low-pressure pipeline 12. The helium compressor 10 inhales the low-pressure refrigerant gas discharged from the GM refrigerator from the low-pressure pipeline 12, and compresses it through the internal vortex pressure pack. The generated high-pressure refrigerant gas is supplied to the GM refrigerator through the high-pressure pipeline 11. Through the switching of the plane rotary valve 23, the switching of high and low pressure inside the GM refrigerator is realized according to a certain sequence, so that the high-pressure refrigerant gas expands in the expansion chamber of the GM refrigerator to generate cold, which is transferred to the object to be cooled through the primary cold end heat exchanger 31 and the secondary cold end heat exchanger 32.

[0005] The rotary motor 20 is used as the driving source (usually an electromagnetic motor) of the plane rotary valve 23 and the displacer in the GM refrigerator, and drives the plane rotary valve 23 and the displacer to move simultaneously through the crank cam 24. The cover 21 is generally made of aluminum, and the crank connecting rod 22 is generally made of stainless steel. Considering factors such as weight, thermal conductivity, and hardness, the cylinder material of the first-stage displacer 40 is bakelite, and the second-stage displacer 50 is generally made of metal materials such as stainless steel, but bakelite can also be used.

[0006] GM refrigerators are usually used as equipment to provide low-temperature cooling sources and are widely used in fields such as cryogenic pumps. The components that are in direct contact with the object to be cooled are the cylinder 30, the primary cold end heat exchanger 31 and the secondary cold end heat exchanger 32. Usually, the primary cold end heat exchanger 31 and the secondary cold end heat exchanger 32 are made of copper and welded on the cylinder 30. They are components that directly export cold energy and are also components that are in direct contact with measuring devices. The operation of various functions of the cryogenic pump is achieved by arranging temperature sensors at the primary cold end and the secondary cold end of the GM refrigerator.

[0007] At present, commercial intelligent cryopumps mostly use variable frequency GM refrigerator cold head and variable frequency compressor technology to achieve the rapid cooling and regeneration function of the cryopump. Therefore, the application of the inverter will cause great interference to various test components including temperature testing, resulting in measurement errors. Since the GM refrigerator has a reciprocating piston, a rotating motor is generally required to drive the piston movement. Therefore, it can only be used as an integral type. The rotating motor is connected to the component directly installed with the measuring element, and electrical insulation cannot be achieved. Utility Model Content

[0008] Purpose of the utility model: The purpose of the utility model is to provide an ultra-low temperature refrigerator with electrical insulation function to prevent the application of frequency conversion technology from interfering with temperature and other measuring components.

[0009] Technical solution: The ultra-low temperature refrigerator with electrical insulation function described in the utility model includes a cylinder and a cover body assembled on the top of the cylinder, and also includes an electrical insulating member arranged between the cover body and the cylinder, and the electrical insulating member is used to block the electrical path between the cover body and the cylinder.

[0010] Furthermore, the cover body is connected to the cylinder by a fastening screw, and the electrical insulating part includes an insulating gasket and an insulating bushing. The insulating gasket is arranged between the nut end of the fastening screw and the cover body, and the aperture of the fastening screw mounting hole on the cover body is larger than the outer diameter of the screw rod of the fastening screw; the insulating bushing is arranged between the cover body and the cylinder.

[0011] Furthermore, the insulating gasket has a first upper ring portion, a first lower ring portion and a first middle opening portion, the outer diameter of the first upper ring portion is larger than the outer diameter of the first lower ring portion; the first lower ring portion is embedded in the mounting hole of the cover body fastening screw, and the lower end surface of the first upper ring portion is in contact with the upper end surface of the cover body; the diameter of the first middle opening portion is larger than the outer diameter of the screw portion of the fastening screw.

[0012] Furthermore, a spring washer is arranged between the nut end of the fastening screw and the insulating washer, and the upper end surface of the first upper ring portion is fitted with the lower end surface of the spring washer; the outer diameter of the first upper ring portion is larger than the outer diameter of the spring washer.

[0013] Furthermore, the thickness of the first upper ring portion is 5 to 10 mm.

[0014] Furthermore, the insulating liner ring has a second upper ring portion, a second lower ring portion, a second middle opening portion, an external sealing groove and an internal sealing groove. The diameter of the second middle opening portion is slightly larger than the outer diameter of the lower end portion of the cover body, the outer diameter of the second lower ring portion is slightly smaller than the inner diameter of the cylinder, an external seal is installed in the external sealing groove, and an internal seal is installed in the internal sealing groove; the upper end face of the second upper ring portion is in contact with the cover body, and the lower end face of the second upper ring portion is in contact with the cylinder.

[0015] Furthermore, the thickness of the second upper ring portion is 10 to 15 mm.

[0016] Furthermore, the electrical insulating member is an electrical insulating member made of polyetheretherketone.

[0017] Beneficial effects: Compared with the prior art, the utility model has the following advantages: the utility model can realize the electrical insulation function of the GM refrigerator and prevent the application of frequency conversion technology from interfering with temperature and other measuring components. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the existing GM refrigerator;

[0019] Figure 2 It is a structural schematic diagram of an ultra-low temperature refrigerator with electrical insulation function provided by an embodiment of the utility model;

[0020] Figure 3 It is a structural schematic diagram of an insulating gasket in an embodiment of the utility model;

[0021] Figure 4 It is a structural schematic diagram of the insulating liner ring in the embodiment of the utility model;

[0022] Figure 5 It is a detailed installation diagram of the insulating gasket and the insulating liner ring in the embodiment of the utility model. DETAILED DESCRIPTION

[0023] The utility model is further described below in conjunction with the accompanying drawings.

[0024] Attached Figures 1 to 5 The reference numerals in the figures are as follows:

[0025] 10. Helium compressor; 11. High-pressure pipeline; 12. Low-pressure pipeline; 20. Rotating motor; 21. Cover; 22. Crank connecting rod; 23. Planar rotary valve; 24. Crank cam; 25. Fastening screw; 26. Spring washer; 30. Cylinder; 31. Primary cold-end heat exchanger; 32. Secondary cold-end heat exchanger; 40. Primary displacer; 50. Secondary displacer; 60. Insulating gasket; 601. First upper ring portion; 602. First lower ring portion; 603. First middle opening portion; 70. Insulating lining ring; 701. Second upper ring portion; 702. Second lower ring portion; 703. Second middle opening portion; 704. External sealing groove; 705. Internal sealing groove; 80. Internal sealing member; 81. External sealing member.

[0026] like Figures 2 to 5 As shown, an embodiment of the utility model provides an ultra-low temperature refrigerator with electrical insulation function, including a cover body 21, a cylinder 30 and an electrical insulation member, wherein the cover body 21 is assembled on the top of the cylinder 30 by fastening screws 25, and the electrical insulation member is arranged between the cover body 21 and the cylinder 30 to block the electrical path between the cover body 21 and the cylinder 30.

[0027] Specifically, the electrical insulating member is divided into an insulating gasket 60 and an insulating bushing 70 according to different installation locations. The electrical insulating member needs to have good electrical insulation performance. At the same time, in the GM refrigerator, the electrical insulating member also needs to withstand a certain pressure. For example, the tightening torque of the fastening screw 25 generally reaches 15 to 25 N·m, and it also needs to be easy to process and shape. In this embodiment, the material of the electrical insulating member is polyetheretherketone (PEEK), but it is not limited to this material, and other materials with excellent electrical insulation performance and strong hardness can also be used.

[0028] The insulating gasket 60 is arranged between the nut end of the fastening screw 25 and the cover 21. The cover 21 has a fastening screw installation hole, and the hole diameter of the fastening screw installation hole is larger than the outer diameter of the screw shaft of the fastening screw 25. In other words, after the fastening screw 25 is installed, its screw shaft does not contact the inner wall surface of the fastening screw installation hole of the cover 21. The number of fastening screws 25 is four (i.e., 25a to 25d in the figure), so the insulating gasket 60 is also configured as four pieces (i.e., 60a to 60d in the figure).

[0029] The insulating gasket 60 has a first upper ring portion 601, a first lower ring portion 602 and a first middle opening portion 603. The outer diameter of the first upper ring portion 601 is larger than the outer diameter of the first lower ring portion 602. After installation, the first lower ring portion 602 is inserted into the mounting hole of the fastening screw of the cover body 21, and the lower end surface of the first upper ring portion 601 is in contact with the upper end surface of the cover body 21; the diameter of the first middle opening portion 603 is larger than the outer diameter of the screw portion of the fastening screw 25. In addition, a spring washer 26 is provided between the nut end of the fastening screw 25 and the insulating gasket 60, and the upper end surface of the first upper ring portion 601 is in contact with the lower end surface of the spring washer 26; the outer diameter of the first upper ring portion 601 is larger than the outer diameter of the spring washer 26.

[0030] In order to ensure the insulating gasket 60's ability to withstand the torque of the fastening screw 25 and facilitate installation, in this embodiment, the thickness of the first upper ring portion 601 is 5 to 10 mm.

[0031] The insulating bushing 70 is arranged between the cover body 21 and the cylinder 30, and has a second upper ring portion 701, a second lower ring portion 702, a second middle opening portion 703, an outer sealing groove 704 and an inner sealing groove 705. The diameter of the second middle opening portion 703 is slightly larger than the outer diameter of the lower end of the cover body 21, the outer diameter of the second lower ring portion 702 is slightly smaller than the inner diameter of the cylinder 30, an outer sealing member 81 is installed in the outer sealing groove 704, and an inner sealing member 80 is installed in the inner sealing groove 705. After installation, the upper end surface of the second upper ring portion 701 is in contact with the cover body 21, and the lower end surface of the second upper ring portion 701 is in contact with the cylinder 30.

[0032] The inside of the cylinder 30 is under high pressure (generally 15 bar to 17 bar) and the outside is under ambient pressure. The function of the internal seal 80 and the external seal 81 is to prevent the high-pressure refrigerant gas in the cylinder 30 from leaking through the gap between the insulating liner ring 70 and the cylinder 30 and the cover body 21, resulting in the problem that the GM refrigerator cannot work normally due to too low pressure.

[0033] The insulating collar 70 needs to bear the weight of the entire motor 20, the cover 21 and other parts as well as the tightening torque of the tightening screws 25. In this embodiment, the thickness of the second upper ring portion 701 is 10-15 mm.

[0034] The utility model is based on the following GM refrigeration mechanical and electrical circuit technical analysis and design:

[0035] First, the components of the GM refrigerator that use frequency conversion technology include the helium compressor 10 and the rotary motor 20. The high-pressure pipeline 11 and the low-pressure pipeline 12 connecting the helium compressor 10 and the cover 21 are generally metal braided hoses, and the metal material covered on the surface is stainless steel. The helium compressor 10 has a relatively complex structure and many internal electronic control systems, including circuits for controlling the movement of the pressure bag and circuits for supplying the cold head. Therefore, the helium compressor 10 and the cover 21 are connected through high and low pressure pipelines to form an electrical path. The rotary motor 20 and the cover 21 are in direct contact, and an electrical path is directly formed. In addition, since the primary displacer is made of bakelite, which has electrical insulation properties, the GM refrigerator is electrically insulated. The nut end of the fastening screw 25 acts on the cover 21, and the threaded end acts on the flange side of the cylinder 30, fixing the cover 21 and the cylinder 30 as one, thereby also forming an electrical path between the cover 21 and the cylinder 30 through the connection of the fastening screw 25.

[0036] Through the above technical analysis, it can be known that by blocking the electrical path between the GM refrigerator cover 21 and the cylinder 30, a GM refrigerator with electrical insulation function can be realized.

[0037] The utility model blocks the electrical path between the cover 21 and the cylinder 30 through the electrical insulating member, which can achieve a better insulation effect, so that the GM refrigerator can be used in more occasions and prevent the application of frequency conversion technology from interfering with temperature and other measuring components.

Claims

1. A cryogenic refrigerator with electrical insulation function, comprising a cylinder (30) and a cover (21) mounted on the top of the cylinder (30), characterized in that: It also includes an electrical insulating member arranged between the cover body (21) and the cylinder (30), and the electrical insulating member is used to block the electrical path between the cover body (21) and the cylinder (30).

2. The ultra-low temperature refrigerator according to claim 1, characterized in that: The cover body (21) and the cylinder (30) are connected via a fastening screw (25); the electrical insulating member comprises an insulating gasket (60) and an insulating bushing (70); the insulating gasket (60) is arranged between the nut end of the fastening screw (25) and the cover body (21); the diameter of the fastening screw installation hole on the cover body (21) is larger than the outer diameter of the screw rod of the fastening screw (25); and the insulating bushing (70) is arranged between the cover body (21) and the cylinder (30).

3. The ultra-low temperature refrigerator according to claim 2, characterized in that: The insulating gasket (60) comprises a first upper ring portion (601), a first lower ring portion (602) and a first middle opening portion (603); the outer diameter of the first upper ring portion (601) is greater than the outer diameter of the first lower ring portion (602); the first lower ring portion (602) is embedded in the mounting hole of the fastening screw of the cover body (21), and the lower end surface of the first upper ring portion (601) is in contact with the upper end surface of the cover body (21); the diameter of the first middle opening portion (603) is greater than the outer diameter of the screw portion of the fastening screw (25).

4. The ultra-low temperature refrigerator according to claim 3, characterized in that: A spring washer (26) is also provided between the nut end of the fastening screw (25) and the insulating washer (60), and the upper end surface of the first upper ring portion (601) is in contact with the lower end surface of the spring washer (26); the outer diameter of the first upper ring portion (601) is greater than the outer diameter of the spring washer (26).

5. The ultra-low temperature refrigerator according to claim 3, characterized in that: The thickness of the first upper ring portion (601) is 5 to 10 mm.

6. The ultra-low temperature refrigerator according to claim 2, characterized in that: The insulating liner ring (70) comprises a second upper ring portion (701), a second lower ring portion (702), a second middle opening portion (703), an external sealing groove (704) and an internal sealing groove (705); the diameter of the second middle opening portion (703) is slightly larger than the outer diameter of the lower end portion of the cover body (21); the outer diameter of the second lower ring portion (702) is slightly smaller than the inner diameter of the cylinder (30); an external sealing component (81) is installed in the external sealing groove (704); and an internal sealing component (80) is installed in the internal sealing groove (705); the upper end surface of the second upper ring portion (701) is in contact with the cover body (21); and the lower end surface of the second upper ring portion (701) is in contact with the cylinder (30).

7. The ultra-low temperature refrigerator according to claim 6, characterized in that: The thickness of the second upper ring portion (701) is 10 to 15 mm.

8. The ultra-low temperature refrigerator according to claim 1, characterized in that: The electrical insulating member is an electrical insulating member made of polyetheretherketone.

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