A built-in air-extraction cryogenic vacuum pump

Abstract

The application discloses a built-in gas extraction low-temperature vacuum pump, which prolongs a heat transfer path of a refrigerator by designing a heat transfer mechanism on a first-stage cold head and a second-stage cold head of the refrigerator, and installs a cold screen and an adsorption array at the end of the heat transfer mechanism to form an insertion cylinder which can be inserted into the inside of a vacuum cavity to be extracted, and the insertion cylinder is sealed by a sealing flange to form a built-in gas extraction structure to directly extract gas molecules in the vacuum cavity to be extracted, compared with a traditional low-temperature vacuum pump, the built-in gas extraction low-temperature vacuum pump reduces the setting of a vacuum shell, effectively solves the problem that a pumping speed of the low-temperature vacuum pump is limited by a pump port area, expands the gas inlet area of the low-temperature vacuum pump from the pump port to the internal space of the whole vacuum cavity to be extracted, and significantly improves the pumping speed and the gas extraction capacity of the low-temperature vacuum pump, and meanwhile, the insertion cylinder can be deeply inserted into the vacuum cavity to be extracted to synchronously extract gas molecules at a deep position in the vacuum cavity to be extracted, thereby significantly reducing a pressure gradient in the vacuum cavity to be extracted and improving the overall gas extraction uniformity.

Description

Technical Field

[0001] This invention belongs to the field of vacuum equipment technology and relates to a cryogenic vacuum pump, specifically a cryogenic vacuum pump with built-in pumping mechanism. Background Technology

[0002] Cryogenic vacuum pumps achieve high vacuum by trapping gas molecules through cryogenic condensation and adsorption. For example... Figure 1 As shown, the cryogenic vacuum pump mainly consists of a vacuum housing, a refrigerator, a cold shield, a baffle, and an adsorption array. Gas molecules enter the adsorption array inside the cryogenic vacuum pump from the pump port and are condensed and adsorbed at low temperature, achieving an oil-free and clean pumping process.

[0003] Traditional cryogenic vacuum pumps are typically installed on the outside of the cavity to be evacuated. The pump inlet flange is connected to the flange of the cavity, and a vacuum is achieved by trapping gas. Since the cross-sectional area of ​​the pump inlet is fixed, the number of gas molecules that can be pumped into the vacuum chamber to contact the cold shield and adsorption array per unit time is also fixed, thus limiting the pumping speed and pumping capacity. Furthermore, the pumping speed of gas molecules within the cavity exhibits a spatial decreasing relationship: gas molecules near the pump inlet experience the highest pumping speed and vacuum level, while those further away from the inlet experience the lowest pumping speed and worst vacuum level. This makes it difficult to achieve uniform and effective evacuation of the entire cavity. Summary of the Invention

[0004] To address the technical problems existing in the background art, this invention proposes a cryogenic vacuum pump with built-in pumping, which changes the existing pump inlet structure to a built-in pumping structure that extends deep into the vacuum chamber to be pumped, significantly improving the pumping speed and pumping capacity of the cryogenic vacuum pump, reducing the pressure gradient in the vacuum chamber to be pumped, and improving the overall pumping uniformity.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A cryogenic vacuum pump with built-in air extraction includes: a sealing flange, a cold shield, an adsorption array, and a refrigerator. The cold shield is located on one side of the sealing flange, and the refrigerator is located on the other side of the sealing flange. The adsorption array is located inside the cold shield. The cold shield is connected to the first stage of the refrigerator, and the adsorption array is connected to the second stage of the refrigerator, forming a tube with a temperature that decreases progressively from the outside to the inside. This tube is inserted into the cavity to be evacuated through the air extraction port, and the air extraction port is sealed by the sealing flange. The cold shield has an air inlet channel to form a built-in air extraction structure at the end away from the refrigerator. A baffle is installed in the air inlet channel to shield the adsorption array from direct thermal radiation by gas molecules outside the air inlet channel.

[0007] Furthermore, the cold screen is connected to the first stage of the refrigerator through a first heat transfer mechanism to maintain the surface temperature of the cold screen at a low temperature of 70K-80K, and the adsorption array is connected to the second stage of the refrigerator through a second heat transfer mechanism to maintain the surface temperature of the adsorption array at an ultra-low temperature of 10K-20K.

[0008] Furthermore, both the first heat transfer mechanism and the second heat transfer mechanism adopt a heat pipe structure filled with a gas with a high thermal conductivity, so as to effectively transfer the cooling capacity of the refrigerator to the cold screen at the end of the first heat transfer mechanism and the adsorption array at the end of the second heat transfer mechanism, respectively.

[0009] Furthermore, the heat pipe structure of the first heat transfer mechanism is a sealed container filled with nitrogen / neon / hydrogen as the heat transfer medium, and the heat pipe structure of the second heat transfer mechanism is a sealed container filled with hydrogen / helium as the heat transfer medium.

[0010] Furthermore, the air intake channel is configured as an axially oriented slot on the side of the cold screen inserted into the vacuum chamber, and the other side of the cold screen opposite the axially oriented slot is connected to the first heat transfer mechanism.

[0011] Furthermore, the baffle is arranged along the long strip groove and connected to the side wall of the cold screen. The baffle has multiple sets of blades arranged in a louvered or herringbone pattern, and a tortuous channel for gas molecules to pass through is formed between any two adjacent sets of blades.

[0012] Furthermore, multiple sets of blades employ rotatable airflow regulating vanes to adjust the intake area of ​​the intake channel.

[0013] Furthermore, the adsorption array includes: a central support member and multiple layers of condensing plates. The central support member is arranged perpendicular to the elongated through groove. The end of the central support member away from the elongated through groove is connected to the second heat transfer mechanism. The multiple layers of condensing plates are spaced apart along the axial direction of the central support member.

[0014] Furthermore, a layer of activated carbon is evenly distributed on the surface of the condenser plate.

[0015] The beneficial effects of this invention are as follows: The built-in low-temperature vacuum pump provided in this application extends the heat transfer path of the refrigerator by designing a heat transfer mechanism on each of the primary and secondary cold heads. The cold screen and adsorption array are respectively installed at the end of the heat transfer mechanism to form a plug that can be inserted into the vacuum chamber to be evacuated. The plug is sealed by a sealing flange to form a built-in pumping structure, which directly extracts gas molecules from the vacuum chamber to be evacuated. Compared with traditional low-temperature vacuum pumps, the vacuum shell is reduced, which effectively solves the problem that the pumping speed of the low-temperature vacuum pump is limited by the pump inlet area. The inlet area of ​​the low-temperature vacuum pump is expanded from the pump inlet to the entire internal space of the vacuum chamber to be evacuated, thereby significantly improving the pumping speed and pumping capacity of the low-temperature vacuum pump. At the same time, by inserting the plug into the vacuum chamber to be evacuated, gas molecules in the depth of the vacuum chamber to be evacuated can be extracted simultaneously, which significantly reduces the pressure gradient in the vacuum chamber to be evacuated and improves the overall pumping uniformity. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a cryogenic vacuum pump in the prior art.

[0017] Figure 2 This is a three-dimensional schematic diagram of the cryogenic vacuum pump of the present invention.

[0018] Figure 3 This is a cross-sectional schematic diagram of the cryogenic vacuum pump of the present invention.

[0019] Figure 4 This is a three-dimensional schematic diagram of the cold screen of the present invention.

[0020] Figure 5 This is a three-dimensional schematic diagram of the adsorption array of the present invention.

[0021] Figure 6 This is a schematic diagram of the staged collection process using a cryogenic vacuum tube pump. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figures 2-5As shown, this invention provides a built-in cryogenic vacuum pump, comprising: a sealing flange 1, a cold shield 2, an adsorption array 3, and a refrigerator 4. The cold shield 2 is first-stage connected to the refrigerator 4 to maintain its surface temperature at a low temperature. The adsorption array 3 is second-stage connected to the refrigerator 4 to maintain its surface temperature at an ultra-low temperature. When gas molecules collide sequentially with the surfaces of the cold shield 2 and the adsorption array 3, because the surface temperatures of the cold shield 2 and the adsorption array 3 are far below the temperature corresponding to the saturated vapor pressure of the gas, the gas molecules lose kinetic energy and directly change from a gaseous phase to a solid phase (sublimation), condensing into a layer of frost. This reduces the gas molecule density, achieving and maintaining a high vacuum or even an ultra-high vacuum.

[0024] A cold shield 2 is positioned on one side of the sealing flange 1, a refrigerator 4 is positioned on the other side of the sealing flange 1, and an adsorption array 3 is positioned inside the cold shield 2. This forms a tube with a gradually decreasing temperature from the outside to the inside at the end furthest from the refrigerator 4. In use, the tube is inserted into the vacuum chamber through the extraction port, and the extraction port is sealed by the sealing flange 1. The cold shield 2 has an inlet channel, forming a built-in extraction structure to extract gas molecules from the vacuum chamber. Compared to traditional cryogenic vacuum pumps, this design reduces the need for a vacuum housing, effectively solving the problem of the pumping speed being limited by the pump port area. It expands the inlet area of ​​the cryogenic vacuum pump from the pump port to the entire internal space of the vacuum chamber, significantly improving the pumping speed and pumping capacity. Simultaneously, the tube, located directly inside the vacuum chamber, can simultaneously extract gas molecules from the depths of the chamber, significantly reducing the pumping speed gradient and improving overall pumping uniformity.

[0025] Specifically, the refrigerator 4 employs a two-stage Gifford-McMahon GM refrigerator or a pulse tube refrigerator. The cold shield 2 is connected to the first stage of the refrigerator 4 via a first heat transfer mechanism 6, maintaining the surface temperature of the cold shield 2 at a low temperature of 70K-80K, forming a low-temperature thermal shield that blocks heat radiation from the vacuum chamber at a room temperature of 300K, ensuring the ultra-low temperature operating environment of the innermost adsorption array 3 and significantly reducing the heat load on the refrigerator 4. Simultaneously, the low temperature of 70K-80K on the surface of the cold shield 2 is sufficient to condense and capture major gaseous components such as water vapor (H2O) and carbon dioxide (CO2), which have higher saturated vapor pressures. Therefore, the cold shield 2 itself is also an important condensation surface.

[0026] The air inlet channel is configured as an elongated slot 21 axially formed on the side of the cold screen 2, inserted into the vacuum chamber to be evacuated. This increases the air inlet area and longitudinally expands the evacuation coverage, improving the overall vacuum uniformity of the vacuum chamber. The other side of the cold screen 2 opposite to the elongated slot 21 is connected to the first heat transfer mechanism 6. A baffle 5 is installed inside the air inlet channel, positioned along the elongated slot 21 and connected to the side wall of the cold screen 2. Through the heat conduction of the cold screen 2, the baffle 5 maintains a low temperature synchronized with the cold screen 2, thus shielding the adsorption array 3 from direct thermal radiation from external gas molecules.

[0027] Specifically, the baffle 5 has multiple sets of blades 51 arranged in a louvered or herringbone pattern. Between any two adjacent sets of blades 51, a tortuous channel is formed for gas molecules to pass through, preventing gas molecules from directly radiating the coldest adsorption array 3 surface along a straight path. Instead, gas molecules can only enter through multiple reflections. With each reflection, the gas molecules transfer some heat to the baffle structure 5, thus greatly reducing the direct impact of high-temperature gas molecules and thermal radiation on the cryogenic adsorption array 3. Each set of blades 51 employs a rotatable airflow regulating vane, allowing adjustment of the air intake area of ​​the intake channel by rotating one or more sets of airflow regulating vanes to meet different pumping speed requirements.

[0028] The adsorption array 3 is connected to the second stage of the refrigerator 4 via a second heat transfer mechanism 7 to maintain the surface temperature of the adsorption array 3 at an ultra-low temperature of 10K-20K. The adsorption array 3 includes a central support 31 and multiple layers of condensing plates 32. The central support 31 is perpendicular to the elongated slot 21, and one end of the central support 31 away from the elongated slot 21 is connected to the second heat transfer mechanism 7. The multiple layers of condensing plates 32 are spaced apart along the axial direction of the central support 31. The ultra-low temperature of 10K-20K on the surface of the condensing plates 32 allows for the condensation and capture of gases such as nitrogen (N2), oxygen (O2), and argon (Ar), which have relatively low saturated vapor pressures. However, for gases that still have high saturated vapor pressure at extremely low temperatures, condensation alone cannot effectively capture them. Therefore, a layer of activated carbon with a huge specific surface area is uniformly arranged on the surface of the condenser plate 32. At extremely low temperatures of 10K-20K, gas molecules are firmly bound to the surface of the activated carbon micropores through physical adsorption, thereby capturing difficult-to-condense gas molecules such as hydrogen (H2), helium (He), and neon (Ne) through low-temperature adsorption.

[0029] Specifically, both the first heat transfer mechanism 6 and the second heat transfer mechanism 7 adopt heat pipe structures filled with high thermal conductivity gas. Due to the extremely low heat transfer temperature difference of the heat pipe structure, it supports long-distance transfer of cold energy, thereby breaking through the temperature gradient limitation of traditional solid heat conduction and realizing long-distance and efficient transfer of cold energy. The cooling capacity of the refrigerator 4 is effectively transferred to the cold screen 2 at the end of the first heat transfer mechanism 6 and the adsorption array 3 at the end of the second heat transfer mechanism 7, respectively. While ensuring that the cold screen 2 and the adsorption array 3 work stably within the target temperature range, the heat transfer path of the heat pipe structure is extended, further increasing the gas inlet area of ​​the low-temperature vacuum pump. In actual use, it can be designed according to the reserved space in the vacuum chamber to be evacuated, making the design of the vacuum chamber to be evacuated and the vacuum performance guarantee more flexible. The first heat transfer mechanism 6 has a heat pipe structure that is a sealed container filled with nitrogen / neon / hydrogen as the heat transfer medium, while the second heat transfer mechanism 7 has a heat pipe structure that is filled with hydrogen / helium as the heat transfer medium. This achieves precise temperature matching, with different heat transfer media adapting to different temperature zones, improving heat transfer efficiency, significantly enhancing cold energy transfer capacity, reducing cold energy loss, and ensuring efficient maintenance of the 70K–80K and 10K–20K temperature ranges. Since the heat transfer medium inside the heat pipe structure is a gas at room temperature, it will be cooled or liquefied at low temperatures during cold energy transfer. After cooling or liquefaction, the gas pressure decreases, leading to a reduction in heat transfer efficiency. To ensure the heat pipe effect, a gas replenishment and pressurization mechanism is connected to the outside of the first heat transfer mechanism 6 and the second heat transfer mechanism 7, respectively. The internal pressure values ​​of the heat pipe structures of the first and second heat transfer mechanisms 6 and 7 are used as criteria to automatically replenish gas and increase pressure.

[0030] In summary, during the operation of this application, the insert consisting of the cold shield 2 and the adsorption array 3 is inserted into the interior of the vacuum chamber through the evacuation port, and the evacuation port is sealed by the sealing flange 1. Figure 6 As shown, gas molecules at room temperature (300K) in the vacuum chamber can directly enter the cold screen 2 through the inlet channel. They first encounter the baffle 5, and the gas molecules collide multiple times between the baffles 5. If they are water vapor or carbon dioxide, they will be condensed and captured on the surface of the baffle 5 or cold screen 2 at a low temperature of 80K. The remaining gas molecules continue to penetrate into the interior of the cold screen 2. When the remaining gas molecules reach the surface of the adsorption array 3 at an ultra-low temperature of 10K, gas molecules such as nitrogen, oxygen, and argon are condensed and captured by the condenser plate 32, while gas molecules such as hydrogen, helium, and neon are adsorbed and captured by the activated carbon on the surface of the condenser plate 32. This forms a stable temperature gradient of 300K (vacuum chamber) → 80K (cold screen / baffle) → 10K (adsorption array), realizing the efficient and low-energy operation of the cryogenic vacuum pump.

[0031] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A cryogenic vacuum pump with built-in air extraction, characterized in that, include: The components are a sealing flange (1), a cold screen (2), an adsorption array (3), and a refrigerator (4). The cold screen (2) is located on one side of the sealing flange (1), and the refrigerator (4) is located on the other side of the sealing flange (1). The adsorption array (3) is located inside the cold screen (2). The cold screen (2) is connected to the first stage of the refrigerator (4), and the adsorption array (3) is connected to the second stage of the refrigerator (4). The components form a tube with a temperature that gradually decreases from the outside to the inside, which is inserted into the cavity to be evacuated from the air extraction port and the air extraction port is sealed by the sealing flange (1). The cold screen (2) is provided with an air inlet channel to form a built-in air extraction structure at the end away from the refrigerator (4). A baffle (5) is provided in the air inlet channel to shield the direct thermal radiation of gas molecules outside the air inlet channel to the adsorption array (3).

2. The cryogenic vacuum pump according to claim 1, characterized in that, The cold screen (2) is connected to the first stage of the refrigerator (4) through the first heat transfer mechanism (6) to maintain the surface temperature of the cold screen (2) at a low temperature of 70K-80K. The adsorption array (3) is connected to the second stage of the refrigerator (4) through the second heat transfer mechanism (7) to maintain the surface temperature of the adsorption array (3) at an ultra-low temperature of 10K-20K.

3. The cryogenic vacuum pump according to claim 2, characterized in that, Both the first heat transfer mechanism (6) and the second heat transfer mechanism (7) adopt heat pipe structures filled with gas with high thermal conductivity, so as to effectively transfer the cooling capacity of the refrigerator (4) to the cold screen (2) at the end of the first heat transfer mechanism (6) and the adsorption array (3) at the end of the second heat transfer mechanism (7).

4. The cryogenic vacuum pump according to claim 3, characterized in that, The heat pipe structure of the first heat transfer mechanism (6) is a sealed container filled with nitrogen / neon / hydrogen as the heat transfer medium, and the heat pipe structure of the second heat transfer mechanism (7) is a sealed container filled with hydrogen / helium as the heat transfer medium.

5. The cryogenic vacuum pump according to claim 2, characterized in that, The air intake channel is configured as an axially oriented long strip groove (21) that is inserted into the vacuum chamber along the cold screen (2) and opened on the side of the cold screen (2). The other side of the cold screen (2) opposite to the long strip groove (21) is connected to the first heat transfer mechanism (6).

6. The cryogenic vacuum pump according to claim 5, characterized in that, The baffle (5) is set along the long strip groove (21) and connected to the side wall of the cold screen (2). The baffle (5) has multiple sets of blades (51) arranged in a louver or herringbone pattern. A tortuous channel for gas molecules to pass through is formed between any two adjacent sets of blades (51).

7. The cryogenic vacuum pump according to claim 6, characterized in that, Multiple sets of blades (51) all use rotatable airflow regulating vanes to adjust the air intake area of ​​the intake channel.

8. The cryogenic vacuum pump according to claim 5, characterized in that, The adsorption array (3) includes a central support (31) and a multi-layer condenser plate (32). The central support (31) is set perpendicular to the elongated through groove (21). The end of the central support (31) away from the elongated through groove (21) is connected to the second heat transfer mechanism (7). The multi-layer condenser plate (32) is set at intervals along the axial direction of the central support (31).

9. The cryogenic vacuum pump according to claim 8, characterized in that, A layer of activated carbon is evenly distributed on the surface of the condenser plate (32).

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