Baking type ultrahigh vacuum low-temperature vacuum pump and control method

Abstract

The invention discloses a baking type ultrahigh vacuum low-temperature vacuum pump and a control method. The vacuum pump comprises a vacuum cover, an anti-radiation screen, a baffle and a condensation plate set. The device further comprises a heater, a cover body temperature sensor and a pump-out valve. The refrigerating machine is provided with a first-stage refrigerating section and a second-stage refrigerating section which extend into the cover body and are communicated with each other; the primary refrigeration section and the secondary refrigeration section are respectively provided with a primary temperature sensor and a secondary temperature sensor; the heater, the cover body temperature sensor, the pump-out valve, the refrigerating machine, the first-stage temperature sensor and the second-stage temperature sensor are respectively connected with the controller. The vacuum cover is automatically heated through the controller, the inner wall face of the vacuum cover is heated for degassing, the temperature of the refrigerating machine is increased due to the influence of heat radiation in the process, the refrigerating machine is controlled to start to reduce the temperature and keep the temperature within a certain range at the moment, heating is stopped when the vacuum in the pump is reduced to a certain pressure value or below, and the refrigerating machine starts to be cooled to the working temperature. By means of the structure and the control method, the pre-vacuumizing treatment time before the cooling stage is shortened, and the ultrahigh vacuum state below 10 <-9 > torr is achieved.

Description

Technical Field

[0001] The present invention relates to a vacuum pump and a control method, and in particular to a baking type ultra-high vacuum low temperature vacuum pump and a control method. Background Art

[0002] A cryogenic vacuum pump is a vacuum pump that uses an ultra-low temperature cryopanel and activated carbon attached to the cryopanel to condense or adsorb gas. In this way, the cryogenic vacuum pump evacuates the chamber connected to the cryogenic vacuum pump to achieve a vacuum state.

[0003] Ultra-high vacuum refers to pressure below 10 -9 The vacuum state of Torr (a unit of pressure). At present, the vacuum that can be achieved by cryogenic vacuum pumps is generally around 10 -7 Support up to 10 -9 Although the cryogenic vacuum pump can continuously extract gas molecules from the vacuum chamber, the inner wall surface of the vacuum chamber will continuously desorb gas molecules from the metal surface, and gas molecules outside the vacuum chamber will also continuously penetrate the chamber wall into the chamber. The lower the pressure inside the chamber, the stronger the molecular desorption and molecular penetration outside the chamber. Therefore, it is difficult for the vacuum chamber pressure after the cryogenic vacuum pump is pumped to be lower than 10 -9 Entrust. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a method for reducing the pre-evacuation time before the cooling stage and achieving 10 -9 A baking type ultra-high vacuum cryogenic vacuum pump in an ultra-high vacuum state below 1000 torr;

[0005] The second object of the present invention is to provide a control method for full-process automatic control of the above-mentioned baking type ultra-high vacuum low-temperature vacuum pump.

[0006] Technical solution: The baking type ultra-high vacuum low-temperature vacuum pump described in the present invention includes a vacuum cover and a radiation shield, a baffle and a condensation plate group contained in the vacuum cover; the baffle covers the top of the radiation shield, and the radiation shield and the baffle together form a radiation shield cavity; the condensation plate group is contained in the radiation shield cavity; the condensation plate group is connected to a refrigerator; it also includes a heater for heating the vacuum cover, a cover body temperature sensor for detecting the temperature of the vacuum cover, and an evacuation valve connected to the inner cavity of the vacuum cover for extracting the gas in the vacuum cover; the refrigerator is provided with a first-level refrigeration section and a second-level refrigeration section that are connected; the first-level refrigeration section and the second-level refrigeration section both extend into the cover body, the first-level refrigeration section is connected to the radiation shield, the second-level refrigeration section is connected to the condensation plate group, the first-level refrigeration section is connected to a first-level temperature sensor, and the second-level refrigeration section is connected to a second-level temperature sensor; the heater, the cover body temperature sensor, the evacuation valve, the refrigerator, the first-level temperature sensor, and the second-level temperature sensor are respectively connected to the controller.

[0007] Wherein, the inner cavity of the vacuum cover is connected to a pressure sensor for detecting the pressure inside the vacuum cover.

[0008] Wherein, the heater is arranged on the outer wall surface of the vacuum cover.

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

[0010] The invention comprises a motor arranged outside the vacuum cover, and the motor is connected with a primary refrigeration section and a secondary refrigeration section arranged in the cavity of the radiation protection screen in sequence.

[0011] Wherein, the vacuum cover comprises a cover body, the upper end of the cover body is connected to the cover body upper flange, and the lower end of the cover body is connected to the cover body lower flange.

[0012] The control method of the above-mentioned baking type ultra-high vacuum low-temperature vacuum pump is as follows: the controller controls the evacuation valve to open, and the front pump connected to the evacuation valve interface extracts the gas molecules in the vacuum cover. The controller collects the pressure sensor and turns on the heater when it drops below 1 torr, and collects the temperature value T of the cover body temperature sensor. The heating power of the heater is controlled according to the temperature value T to keep the temperature of the vacuum cover stable. After the vacuum cover is heated and the temperature rises, it radiates heat to the inside, and the first-stage refrigeration section and the second-stage refrigeration section of the refrigerator are heated and the temperature rises. The controller collects the temperature value T1 of the first-stage temperature sensor and the temperature value T2 of the second-stage temperature sensor. When the temperature of T1 or T2 exceeds 320K, the controller controls the operation of the refrigerator to reduce T1 and T2, and keep T1 and T2 below 320K and not less than 290K; after heating and evacuating for a period of time, when the pressure collected by the pressure sensor drops to a certain pressure value P, the heater is turned off, and the controller starts the refrigerator to cool down to the working temperature.

[0013] The controller turns on the refrigerator to cool down normally to the working temperature. For example, the temperature of the first-stage refrigeration section is controlled to be maintained at 100K, while the temperature of the second-stage refrigeration section is about 10K.

[0014] Among them, the front pump is prepared by the user.

[0015] The heating temperature T is 100-250℃; the pressure value P is less than 10 -4 Torr, preferably less than 10 -5 Torr, and the heating temperature T and 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) The present invention provides a heater and a housing temperature sensor for the vacuum housing, and connects the heater, the housing temperature sensor, the evacuation valve, the refrigerator, the primary temperature sensor and the secondary temperature sensor to the controller respectively, so that when the vacuum housing is evacuated by the front pump and the pressure drops below 1 torr, the controller controls the heater to heat the vacuum housing, so that the inner wall of the vacuum housing, the wall of the radiation shield and other walls of the internal components of the vacuum housing continuously desorb gas molecules at high temperature, thereby preventing the wall from continuously releasing gas molecules after the low-temperature vacuum pump drops to a low temperature, making it difficult to reduce the pressure to 10 -9 Torr or less, and the present invention can eventually reduce the pressure to 10 -9 (2) The low-temperature vacuum pump of the present invention can automatically heat the pump, cool it down to maintain the temperature of the refrigerator, stop heating, cool it down, etc. through the controller, thus reducing the pre-evacuation time before the cooling stage and achieving 10 -9 Ultra-high vacuum state below Torr. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 2 for Figure 1 Sectional view along line AA;

[0020] Figure 3 A top view of a baking type ultra-high vacuum low temperature vacuum pump of the present invention;

[0021] Figure 4 This is a flow chart of the control method of the baking type ultra-high vacuum low-temperature vacuum pump of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with 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 comprises: a vacuum cover 20, a cover body 21, a cover body upper flange 22, a cover body lower flange 28, a heater 23, a cover body temperature sensor 24, an evacuation valve 25, an evacuation 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 condensation plate group 43. The specific structure is as follows:

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

[0025] The refrigerator 10 includes a refrigerator flange 11, a primary refrigeration section 12, a secondary refrigeration section 13 and a refrigerator motor 14. The refrigerator flange 11 is arranged on the upper end of the refrigerator motor 14, and the primary refrigeration section 12 and the secondary refrigeration section 13 are arranged on the upper end of the refrigerator flange 11. The refrigerator flange 11 is connected to the lower flange 28 of the cover body 21, and the connection method generally uses a metal gasket. The primary refrigeration section 12 and the secondary refrigeration section 13 penetrate into the inside of the cover body 21 through the lower flange 28 of the cover body 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, and the upper end surface of the primary refrigeration section 12 is connected to the lower end surface of the radiation protection screen 41, the upper end of the radiation protection screen 41 is connected to the baffle 42, the secondary refrigeration section 13 is connected to the condensation plate group 43, the secondary refrigeration section 13 and the condensation plate group 43 are contained in the space enclosed by the radiation protection screen 41 and the baffle 42, and the radiation protection screen 41 and the baffle 42 are contained in the cover body 21. Activated carbon for adsorbing gas molecules is bonded to the surface of the condensation plate group 43 .

[0026] The heater 23, the housing temperature sensor 24, the evacuation valve 25 and the pressure sensor 27 are all connected to the controller 30 by 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 housing temperature sensor 24, and control the heating power of the heater 23.

[0027] In this embodiment, the controller 30 can be Figure 4The displayed process automatically completes the evacuation and cooling processes of the cryogenic vacuum pump. The fore-stage pump is connected to the evacuation valve interface 26 on the evacuation valve 25, wherein the fore-stage pump is provided and opened by the user, and it is necessary to ensure that the fore-stage pump is always turned on during the implementation process; the controller 30 opens the evacuation valve 25, at which time the fore-stage pump evacuates most of the gas in the cryogenic vacuum pump, and the remaining small amount of gas molecules are continuously evacuated, and the inner wall surface of the cover body 21, the wall surface of the radiation shield 41 and other walls of the internal components of the cover body 21 will continuously desorb gas molecules. At room temperature, the process of desorbing gas molecules from the metal wall is very slow, usually taking 24-72 hours. The low-temperature vacuum pump of the present invention, after the controller 30 opens the evacuation valve 25, the controller 30 continuously collects pressure values ​​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 the cover body 21 to a higher temperature, such as 200°C. The cover body 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 body 21 stable and prevent the heating temperature from being too high or too low.

[0028] After the heater 23 is turned on, the vacuum cover 20 is heated to the controlled temperature value T. At this time, affected by the heat radiation and heat conduction of the vacuum cover 20, the temperature of the radiation shield 41, the first-stage refrigeration section 12, the second-stage refrigeration section 13 and the condensation plate group 43 contained in the vacuum cover 20 increases. However, affected by the material of the refrigerator 10, the refrigeration section is not easily 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 the temperature values ​​T1 and T2 fed back by the primary temperature sensor 15 and the secondary temperature sensor 16, and determines whether T1 and T2 are higher than 320K. If neither T1 nor T2 is 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 refrigerator 10 to start the normal cooling stage until the primary refrigeration section 12 and the secondary refrigeration section 13 are reduced to the operating temperature. The automatic process ends, and the user waits for the pressure value to drop to 10 -9 Torr or less. Usually measured to 10 -7 The pressure sensor used for pressure values ​​below Torr is prepared by the user and mounted on the vacuum chamber that needs to be evacuated and is connected to the pump.

[0030] During the heating and evacuation process, if T1 or T2 is higher than 320K, the controller 30 will preferentially start the refrigerator 10 to start cooling, and control T1 and T2 to remain between 290K-320K. In this way, 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 refrigerator 10 to start the normal cooling stage until the first refrigeration section 12 and the second refrigeration section 13 are reduced to the operating temperature, and the automatic process ends.

[0031] The operating temperature of the cryogenic vacuum pump, for example, the controller 30 controls the temperature T1 of the first refrigeration section 12 to be reduced to 100K and maintained at this temperature, and at this time, the temperature T2 of the second refrigeration section 13 is generally reduced to 10K. After the cryogenic vacuum pump is reduced to the operating temperature, the pressure value will continue to decrease to 10 -9 Note: The general way of cooling by the controller is: after cooling to low temperature, control T1, not T2. Generally, T1 is set at 65-100K, and T2 is kept at 8-12K.

[0032] At high temperatures, gas molecules will accelerate the desorption rate from the metal wall. In this way, the desorbed gas molecules will be pumped away by the foreline pump, which speeds up the pumping time of the foreline pump. If the gas molecules adsorbed on the wall are not desorbed during the early stage of the pumping process, after the cryogenic vacuum pump is lowered to a low temperature, the wall will continue to release gas molecules, and it will be difficult to reduce the pressure to 10 -9 Support below.

[0033] In this embodiment, the higher the heating temperature of the vacuum cover 20 is, the faster the gas is desorbed from the wall, and the faster the pressure value decreases to P. However, at the same time, the more heat is received by the refrigerator 10, and a higher frequency of cooling is required to maintain T1 and T2.

Claims

1. A baking type ultra-high vacuum low temperature vacuum pump, comprising a vacuum cover (20) and a radiation shield (41), a baffle (42) and a condensation plate group (33) contained in the vacuum cover (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 condensation plate group (33) is contained in the radiation shield cavity (36); the condensation plate group (33) is connected to a refrigerator (10); characterized in that, The refrigerator (10) further comprises a heater (23) for heating the vacuum cover (20), a cover body temperature sensor (24) for detecting the temperature of the vacuum cover (20), and an evacuation valve (25) which is in communication with the inner cavity of the vacuum cover (20) and is used to extract gas from the vacuum cover (20); the refrigerator (10) is provided with a primary refrigeration section (12) and a secondary refrigeration section (13) which are in communication with each other; the primary refrigeration section (12) and the secondary refrigeration section (13) both extend into the interior of the vacuum cover (20), the primary refrigeration section 12 is connected to a radiation protection screen (41), and the secondary refrigeration section (13) is connected to a condensation 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 cover body 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 a controller (30).

2. The baking type ultra-high vacuum low temperature vacuum pump according to claim 1, characterized in that: The inner cavity of the vacuum cover (20) is connected to a pressure sensor (27) for detecting the pressure inside the vacuum cover (20).

3. The baking type ultra-high vacuum low temperature vacuum pump according to claim 1, characterized in that: The heater (23) is arranged on the outer wall surface of the vacuum cover (20).

4. The baking type ultra-high vacuum low temperature vacuum pump according to claim 1, characterized in that: The heater (23) is arranged on the outer wall surface of the vacuum cover (20) in a ring-shaped winding manner, or is wrapped on the outer wall surface of the vacuum cover (20) in the form of a sheet heater.

5. The baking type ultra-high vacuum low temperature vacuum pump according to claim 1, characterized in that: The refrigerator (10) comprises a motor (14) arranged outside the vacuum cover (20), and the motor (14) is sequentially connected to a primary refrigeration section (12) and a secondary refrigeration section (13) arranged in the cavity of the radiation protection screen.

6. The baking type ultra-high vacuum low temperature vacuum pump according to claim 1, characterized in that: The vacuum cover (20) comprises a cover body (21), the upper end of the cover body (21) is connected to a cover body upper flange (22), and the lower end of the cover body (21) is connected to a cover body lower flange (28).

7. A control method for a baking type ultra-high vacuum cryogenic vacuum pump according to claim 1, characterized in that: The controller controls the vacuum valve (25) to open, and the front pump connected to the vacuum valve interface (26) extracts gas molecules in the vacuum cover (20). The controller (30) detects that the pressure sensor drops below 1 torr and turns on the heater, collects the temperature value T of the cover body 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 cover (20) stable. After the vacuum cover (20) is heated and the temperature rises, it radiates heat to the inside, and the first refrigeration section (12) and the second refrigeration section (13) of the refrigerator (10) are heated. When the radiation temperature rises, the controller (30) collects the temperature value T1 of the primary temperature sensor (15) and the temperature value T2 of the secondary temperature sensor (16). When the temperature of T1 or T2 exceeds 320K, the controller (30) controls the operation of the refrigerator (10) to reduce T1 and T2, and keep T1 and T2 below 320K and not below 290K. After heating and evacuating for a period of time, when 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) starts the refrigerator (10) to cool down to the working temperature.

8. The control method of the baking type ultra-high vacuum low temperature vacuum pump according to claim 7, characterized in that: The temperature T of the heated vacuum cover (20) is 100-250°C, and the pressure value P is less than 10 -4 Torr.

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