Baking type ultra-high vacuum low-temperature vacuum pump and control method

Abstract

The application discloses a baking type ultra-high vacuum low-temperature vacuum pump and a control method thereof, and relates to the field of vacuum pumps.The vacuum pump comprises a vacuum cover, a radiation-proof screen, a baffle and a condenser plate group; further comprises a heater, a cover temperature sensor and an evacuation valve; the refrigerating machine is provided with a first-stage refrigeration section and a second-stage refrigeration section which are connected and extend into the cover; the first-stage and second-stage refrigeration sections are respectively provided with first-stage and second-stage temperature sensors; the heater, the cover temperature sensor, the evacuation valve, the refrigerating machine and the first-stage and second-stage temperature sensors are connected with a controller. The application automatically heats the vacuum cover through the controller, the inner wall surface is heated to remove gas, the temperature of the refrigerating machine is increased due to the influence of heat radiation during the process, the refrigerating machine is controlled to start to reduce the temperature at this time, and the temperature is kept within a certain range, the heating is stopped when the vacuum in the pump is reduced to below a certain pressure value, and the refrigerating machine starts to reduce the temperature to the working temperature. The structure and the control method reduce the pre-evacuation processing time before the temperature reduction stage, and realize the ultra-high vacuum state below 10 ‑9

Description

Technical Field

[0001] This invention relates to a vacuum pump and a control method, and more particularly to a baking-type ultra-high vacuum cryogenic vacuum pump and a control method. Background Technology

[0002] A cryogenic vacuum pump is a vacuum pump that utilizes an ultra-low temperature plate and activated carbon adhered to the plate to condense or adsorb gases. In this way, the cryogenic vacuum pump evacuates the chamber connected to it to achieve a vacuum state.

[0003] Ultra-high vacuum refers to pressures below 10. -9 A vacuum in Torr (a unit of pressure). Currently, cryogenic vacuum pumps can generally achieve a vacuum of around 10... -7 Up to 10 -9 During the process, although the cryogenic vacuum pump can continuously extract gas molecules from the vacuum chamber, the inner wall surface of the vacuum chamber continuously desorbs gas molecules from the metal surface, and gas molecules from outside the vacuum chamber also continuously permeate into the chamber through the chamber wall. The lower the pressure inside the chamber, the stronger the molecular desorption and molecular permeation from outside the chamber. Therefore, it is difficult to reduce the pressure of the vacuum chamber after evacuation by the cryogenic vacuum pump to below 10. -9 Entrust. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method that reduces the pre-evacuation time before the cooling stage, and can achieve 10 -9 Baking-type ultra-high vacuum cryogenic vacuum pumps with ultra-high vacuum conditions below Torr;

[0005] The second objective of this invention is to provide a control method for the fully automated control of the above-mentioned baking-type ultra-high vacuum cryogenic vacuum pump.

[0006] Technical Solution: The baking-type ultra-high vacuum low-temperature vacuum pump of the present invention includes a vacuum hood and a radiation shield, baffle, and condenser plate assembly housed within the vacuum hood; the baffle covers the top of the radiation shield, and the radiation shield and baffle together form a radiation shield cavity; the condenser plate assembly is housed within the radiation shield cavity; the condenser plate assembly is connected to a refrigerator; it also includes a heater for heating the vacuum hood, a hood temperature sensor for detecting the temperature of the vacuum hood, and an evacuation valve communicating with the inner cavity of the vacuum hood for extracting gas from the vacuum hood; the refrigerator has a primary refrigeration section and a secondary refrigeration section connected to each other; both the primary and secondary refrigeration sections extend into the hood, the primary refrigeration section is connected to the radiation shield, the secondary refrigeration section is connected to the condenser plate assembly, the primary refrigeration section is connected to a primary temperature sensor, and the secondary refrigeration section is connected to a secondary temperature sensor; the heater, hood temperature sensor, evacuation valve, refrigerator, primary temperature sensor, and secondary temperature sensor are respectively connected to a controller.

[0007] The vacuum chamber is connected to a pressure sensor for detecting the pressure inside the vacuum chamber.

[0008] The heater is located on the outer wall of the vacuum chamber.

[0009] The heater is arranged in a ring-shaped manner on the outer wall of the vacuum hood, or wrapped around the outer wall of the hood in the form of a sheet heater.

[0010] This includes a motor located outside the vacuum enclosure, which is sequentially connected to a primary cooling section and a secondary cooling section located inside the radiation shield cavity.

[0011] The vacuum hood includes a hood body, the upper end of which is connected to an upper flange, and the lower end of which is connected to a lower flange.

[0012] The control method of the baking-type ultra-high vacuum cryogenic vacuum pump described above involves the controller opening the evacuation valve, allowing the pre-pump connected to the evacuation valve to extract gas molecules from the vacuum chamber. When the pressure sensor detects a drop below 1 torr, the controller activates the heater and collects the temperature value T from the chamber temperature sensor. Based on this temperature value T, the controller controls the heating power of the heater to maintain a stable vacuum chamber temperature. As the vacuum chamber heats up, it radiates heat into the interior, causing the primary and secondary cooling sections of the refrigerator to heat up. The controller collects the temperature values ​​T1 from the primary temperature sensor and T2 from the secondary temperature sensor. If either T1 or T2 exceeds 320K, the controller controls the refrigerator to operate, lowering T1 and T2 to maintain them below 320K and not below 290K. After heating and evacuating for a period of time, once the pressure sensor detects a drop to a certain pressure value P, the heater is turned off, and the controller activates the refrigerator to cool down to the operating temperature.

[0013] The controller turns on the refrigeration unit to cool the temperature to the operating temperature. For example, it controls the temperature of the first-stage refrigeration section to be kept at 100K, while the temperature of the second-stage refrigeration section is around 10K.

[0014] The back pump is to be provided by the user.

[0015] The heating temperature T is 100-250℃; the pressure value P is less than 10. -4 Torr, preferably below 10 -5 Torr, and both the heating temperature T and the pressure value P can be set by the user.

[0016] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0017] (1) This invention, by equipping the vacuum chamber with a heater and a chamber temperature sensor, and connecting the heater, chamber temperature sensor, evacuation valve, refrigerator, primary temperature sensor, and secondary temperature sensor to a controller, allows the controller to heat the vacuum chamber when the pressure drops below 1 torr during the evacuation process by the pre-pump. This causes the inner wall of the vacuum chamber, the wall of the radiation shield, and other walls of components inside the vacuum chamber to continuously desorb gas molecules at high temperatures. This prevents the walls from continuing to release gas molecules after the cryogenic vacuum pump has lowered the temperature, making it difficult to reduce the pressure to 10. -9 In the following situations, the present invention can ultimately reduce the pressure to 10. -9 (2) The cryogenic vacuum pump of the present invention can automatically perform processes such as heating, cooling, maintaining the temperature of the refrigerator, stopping heating, and cooling through the controller, thereby reducing the pre-evacuation time before the cooling stage and achieving 10 -9 The ultra-high vacuum state below Torr. Attached Figure Description

[0018] Figure 1 This is a front view of the baking-type ultra-high vacuum cryogenic vacuum pump of the present invention;

[0019] Figure 2 for Figure 1 Cross-sectional view of line AA in the middle;

[0020] Figure 3 This is a top view of the baking-type ultra-high vacuum cryogenic vacuum pump of the present invention;

[0021] Figure 4 This is a flowchart of the control method for the baking-type ultra-high vacuum cryogenic vacuum pump of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings.

[0023] like Figures 1 to 3 As shown, the baking-type ultra-high vacuum low-temperature vacuum pump of the present invention includes: a vacuum hood 20, a hood body 21, an upper flange 22 of the hood body, a lower flange 28 of the hood body, a heater 23, a hood body temperature sensor 24, a vacuum valve 25, a vacuum valve interface 26, a pressure sensor 27, a refrigerator 10, a refrigerator flange 11, a primary refrigeration section 12, a secondary refrigeration section 13, a controller 30, a baffle 42, and a condenser plate assembly 43. The specific configuration is as follows:

[0024] The vacuum chamber 20 includes a chamber body 21, an upper flange 22, and a lower flange 28. The upper end of the chamber body 21 is connected to the upper flange 22, and the lower end of the chamber body 21 is connected to the lower flange 28 by welding. A heater 23 is provided on the outer wall of the chamber body 21. The heater 23 can be wrapped around the chamber body 21 in a ring as shown in the figure, or a sheet heater can be directly wrapped around the outer wall of the chamber body 21. A temperature sensor 24 is attached to the chamber body 21 to detect the temperature of the chamber body 21. The chamber body 21 is connected to a vacuum valve 25 and a pressure sensor 27, which are used to extract gas from the chamber body and detect the pressure inside the chamber body, respectively.

[0025] The refrigeration unit 10 includes a refrigeration unit flange 11, a primary refrigeration section 12, a secondary refrigeration section 13, and a refrigeration unit motor 14. The refrigeration unit flange 11 is located at the upper end of the refrigeration unit motor 14, and the primary refrigeration section 12 and the secondary refrigeration section 13 are located at the upper end of the refrigeration unit flange 11. The refrigeration unit flange 11 is connected to the lower flange 28 of the enclosure 21, typically using a metal gasket. The primary refrigeration section 12 and the secondary refrigeration section 13 pass through the lower flange 28 of the enclosure 21 and extend into the interior of the enclosure 21. A primary temperature sensor 15 is arranged on the primary refrigeration section 12, and a secondary temperature sensor 16 is arranged on the secondary refrigeration section. The upper end face of the primary refrigeration section 12 is connected to the lower end face of the radiation shield 41. A baffle 42 is connected to the upper end of the radiation shield 41. A condenser plate assembly 43 is connected to the secondary refrigeration section 13. The secondary refrigeration section 13 and the condenser plate assembly 43 are contained within the space enclosed by the radiation shield 41 and the baffle 42, and the radiation shield 41 and the baffle 42 are contained within the enclosure 21. The surface of the condenser plate assembly 43 is coated with activated carbon that adsorbs gas molecules.

[0026] The heater 23, the enclosure temperature sensor 24, the evacuation valve 25, and the pressure sensor 27 are all connected to the controller 30 via cables (the connecting cables are not shown in the figure). The controller 30 can control the opening and closing of the evacuation valve 25, collect the pressure value measured by the pressure sensor 27, collect the temperature values ​​measured by the primary temperature sensor 15, the secondary temperature sensor 16, and the enclosure temperature sensor 24, and control the heating power of the heater 23.

[0027] In this embodiment, the controller 30 can follow Figure 4The demonstrated process automatically completes the evacuation and cooling processes of the cryogenic vacuum pump. The fore-pump is connected to the evacuation valve interface 26 on the evacuation valve 25. The fore-pump is provided and opened by the user and must be kept open throughout this implementation. The controller 30 opens the evacuation valve 25, at which point the fore-pump evacuates most of the gas in the cryogenic vacuum pump. The remaining small amount of gas molecules are continuously evacuated, and the inner wall of the enclosure 21, the wall of the radiation shield 41, and the walls of other components inside the enclosure 21 continuously desorb gas molecules. At room temperature, the desorption of gas molecules by the metal walls is very slow, typically requiring 24-72 hours. In the cryogenic vacuum pump of the present invention, after the controller 30 opens the evacuation valve 25, the controller 30 continuously collects the pressure value and determines whether the pressure value drops below 1 torr. When the pressure value drops below 1 torr, the heater 23 is turned on. The heater 23 heats and bakes the cover 21 to a certain high temperature, such as 200°C. The cover temperature sensor 24 collects the temperature value T and feeds it back to the controller 30. The controller 30 controls the heating power of the heater 23 according to the temperature value T to keep the temperature of the cover 21 stable and prevent the heating temperature from being too high or too low.

[0028] After the heater 23 is turned on, the vacuum chamber 20 is heated to the controlled temperature value T. At this time, due to the heat radiation and heat conduction of the vacuum chamber 20, the temperature of components such as the radiation shield 41, the first-stage refrigeration section 12, the second-stage refrigeration section 13 and the condenser plate group 43 contained inside the vacuum chamber 20 rises. However, due to the influence of the material of the refrigerator 10, the refrigeration section is not easy to be baked at high temperature for a long time, otherwise it will affect the performance of the refrigerator 10.

[0029] During the heating and evacuation process, the controller 30 continuously collects temperature values ​​T1 and T2 from the primary temperature sensor 15 and the secondary temperature sensor 16, and determines whether T1 and T2 are higher than 320K. If T1 and T2 are not higher than 320K during the heating and evacuation process, the controller 30 determines whether the pressure value is less than P. If the pressure value is less than P, the controller 30 closes the evacuation valve 25 and the heater 23, and starts the refrigeration unit 10 to begin the normal cooling phase until the primary refrigeration section 12 and the secondary refrigeration section 13 reduce the temperature to the operating temperature. The automatic process ends, and the user waits for the pressure value to drop to 10. -9 Torr below. Generally measured up to 10. -7 Pressure values ​​below Torr require a user-supplied pressure sensor, which is mounted on the vacuum chamber that needs to be evacuated and connected to the pump.

[0030] During the heating and evacuation process, if T1 or T2 is higher than 320K, the controller 30 will prioritize starting the refrigeration unit 10 to begin cooling, and control T1 and T2 to be maintained between 290K and 320K. Then, the controller 30 will determine whether the pressure value is less than P. If the pressure value is less than P, the controller 30 will close the evacuation valve 25 and the heater 23, and start the refrigeration unit 10 to begin the normal cooling phase, until the primary refrigeration section 12 and the secondary refrigeration section 13 are cooled to the working temperature, and the automatic process ends.

[0031] The operating temperature of this cryogenic vacuum pump is, for example, controlled by controller 30, to decrease the temperature T1 of the first-stage cooling section 12 to 100K and maintain that temperature. At this time, the temperature T2 of the second-stage cooling section 13 typically decreases to 10K. After the cryogenic vacuum pump reaches its operating temperature, the pressure will continue to decrease to 10K. -9 Below Torr, it generally takes more than 6 hours. Note: The general way the controller controls the cooling is as follows: after cooling to a low temperature, control T1, but do not control T2. Generally, T1 is set at 65-100K, and T2 will be kept at 8-12K.

[0032] At high temperatures, gas molecules desorb from metal walls more rapidly. These desorbed gas molecules are then drawn away by the backing pump, accelerating the evacuation time. If the gas molecules adsorbed on the wall are not desorbed during the initial evacuation process, the wall will continue to release gas molecules after the cryogenic vacuum pump lowers the temperature, making it difficult to reduce the pressure to 10. -9 The following is a request.

[0033] In this embodiment, the higher the heating temperature of the vacuum hood 20, the faster the gas desorbed from the wall surface, and the faster the pressure value drops to P. However, at the same time, the more heat the refrigerator 10 receives, the more frequently it needs to run to cool down in order to maintain T1 and T2.

Claims

1. A control method for a baking-type ultra-high vacuum cryogenic vacuum pump, characterized in that, The baking-type ultra-high vacuum low-temperature vacuum pump includes a vacuum hood (20) and a radiation shield (41), a baffle (42), and a condenser plate assembly (43) housed within the vacuum hood (20). The baffle (42) covers the top of the radiation shield (41), and the radiation shield (41) and the baffle (42) together form a radiation shield cavity. The condenser plate assembly (43) is housed within the radiation shield cavity (36). The condenser plate assembly (43) is connected to a refrigerator (10). The pump also includes a heater (23) for heating the vacuum hood (20), a hood temperature sensor (24) for detecting the temperature of the vacuum hood (20), and an evacuation valve (25) connected to the inner cavity of the vacuum hood (20) for extracting gas from the vacuum hood (20). The refrigerator (10) is provided with a primary refrigeration section (12) and a secondary refrigeration section (13) connected to each other; the primary refrigeration section (12) and the secondary refrigeration section (13) both extend into the vacuum chamber (20), the primary refrigeration section (12) is connected to the radiation shield (41), and the secondary refrigeration section (13) is connected to the condenser plate group (43); a primary temperature sensor (15) is arranged on the primary refrigeration section (12), and a secondary temperature sensor (16) is arranged on the secondary refrigeration section (13); the heater (23), the chamber temperature sensor (24), the evacuation valve (25), the refrigerator (10), the primary temperature sensor (15), and the secondary temperature sensor (16) are respectively connected to the controller (30); The controller controls the evacuation valve (25) to open, and the pre-pump connected to the evacuation valve interface (26) extracts gas molecules from the vacuum chamber (20). When the controller (30) detects that the pressure sensor has dropped below 1 Torr, it turns on the heater, collects the temperature value T from the chamber temperature sensor (24), and controls the heating power of the heater (23) according to the temperature value T to keep the temperature of the vacuum chamber (20) stable. After the vacuum chamber (20) is heated and its temperature rises, it radiates heat into the interior, and the primary refrigeration section (12) and the secondary refrigeration section (13) of the refrigerator (10) are heated. When the radiation temperature rises, the controller (30) collects the temperature value T1 from the primary temperature sensor (15) and the temperature value T2 from the secondary temperature sensor (16). If the temperature of T1 or T2 exceeds 320K, the controller (30) controls the refrigerator (10) to run, reducing T1 and T2, keeping T1 and T2 below 320K and not below 290K. After heating and evacuating for a period of time, once the pressure collected by the pressure sensor (27) drops to a certain pressure value P, the heater (23) is turned off, and the controller (30) turns on the refrigerator (10) to cool down to the working temperature.

2. The control method for the baking-type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that, The temperature T of the heated vacuum chamber (20) is 100-250℃, and the pressure P is less than 10. -4 Torr.

3. The control method for the baking-type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that, The vacuum chamber (20) is connected to a pressure sensor (27) for detecting the pressure inside the vacuum chamber (20).

4. The control method for the baking-type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that, The heater (23) is located on the outer wall of the vacuum shroud (20).

5. The control method for the baking-type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that, The heater (23) is arranged in a ring-wound manner on the outer wall of the vacuum shroud (20).

6. The control method for the baking-type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that, The refrigeration unit (10) includes a motor (14) located outside the vacuum chamber (20), and the motor (14) is sequentially connected to the primary refrigeration section (12) and the secondary refrigeration section (13) located inside the radiation shield cavity.

7. The control method for the baking-type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that, The vacuum hood (20) includes a hood body (21), the upper end of which is connected to the upper flange (22) of the hood body (21), and the lower end of which is connected to the lower flange (28) of the hood body (21).

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