Low-temperature vacuum pump and using method thereof

Abstract

The invention discloses a low-temperature vacuum pump and a using method thereof. The low-temperature vacuum pump comprises a vacuum cover, a refrigerator and a control box. The vacuum cover is provided with a purging valve; the refrigerating machine performs forward rotation cooling and reverse rotation cooling, and a first-stage temperature sensor and a second-stage temperature sensor are arranged on the refrigerating machine; the control box collects data of the first-stage temperature sensor and the second-stage temperature sensor, controls opening of the purging valve and controls opening and operation frequency of the refrigerating machine. According to the invention, rewarming is carried out by reverse heating of the refrigerating machine and room-temperature dry nitrogen purging, so that the rewarming process of the low-temperature vacuum pump can be automatically completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cryogenic vacuum pumps, in particular to a cryogenic vacuum pump and a method for using the same. BACKGROUND

[0002] A cryogenic vacuum pump uses a refrigerator to reduce the temperature of a condensing assembly and activated carbon attached to the condensing assembly to a working temperature, such as 10K, to condense or adsorb gases inside the pump to achieve a vacuum state. Thus, the cryogenic vacuum pump is connected to a chamber that needs to be pumped. During operation, the gases in the chamber are frozen into solid condensate by the condensing assembly. A cryogenic vacuum pump that is pumped for a long time cannot maintain the vacuum degree. Therefore, the pump needs to be separated from the chamber and the solid condensate needs to be gasified and discharged out of the pump by rewarming. Subsequently, the pump is cooled to the working temperature again to continue pumping. The process of increasing the temperature of the cryogenic vacuum pump from low temperature to room temperature and then cooling it to low temperature is called the rewarming process.

[0003] Currently, a common way to increase the temperature of a cryogenic vacuum pump is to install a heater in the pump. However, this method can cause heat from the high-temperature area to be continuously conducted from the heater to the condensing assembly, thereby increasing the temperature of the condensing assembly and affecting the pumping efficiency. In addition, turning on the heater at a relatively low vacuum degree can easily cause vacuum breakdown and damage the control components.

[0004] Therefore, it is necessary to develop a new type of cryogenic vacuum pump and a method for using the same to overcome the above problems. SUMMARY

[0005] The present application provides a cryogenic vacuum pump and a method for using the same, which can automatically complete the rewarming process by relying on the reverse heating of the refrigerator and the room temperature drying nitrogen purge.

[0006] Technical scheme: The cryogenic vacuum pump of the present application comprises a vacuum cover, a refrigerator and a control box. The vacuum cover is provided with a purge valve. The refrigerator is capable of positive rotation and reverse rotation. A first temperature sensor and a second temperature sensor are arranged on the refrigerator. The control box collects data from the first temperature sensor and the second temperature sensor, controls the opening of the purge valve, and controls the opening and operating frequency of the refrigerator.

[0007] The vacuum cover comprises a cover body. A purge line is arranged on the side of the cover body, and a purge valve is arranged on the purge line. The refrigerator is arranged on the side of the cover body, and the control box is arranged on the side of the refrigerator. A radiation shielding screen is arranged inside the cover body, and a baffle is arranged on the top of the radiation shielding screen.

[0008] The condensing plate group is arranged at the end of the refrigerating machine horizontally, the refrigerating machine is provided with a first refrigeration section and a second refrigeration section, the first refrigeration section and the second refrigeration section are provided with temperature sensors, and the two temperature sensors are connected with the temperature connector arranged on the cover body.

[0009] The refrigerating machine is controlled to rotate forward to reduce temperature and to rotate reversely to increase temperature, the control box is connected with the temperature connector and the refrigerating machine, the control box collects the temperature signal transmitted by the temperature sensor, that is, the temperature of the refrigerating machine, and controls the forward rotation, the reverse rotation and the operation frequency of the refrigerating machine.

[0010] The use method of the low-temperature vacuum pump is characterized in that: the first refrigeration section, the radiation-proof screen and the baffle are reduced in temperature to a first working temperature T1 by forward rotation of the refrigerating machine, the second refrigeration section and the condensing plate group are reduced in temperature to a second working temperature T2, when the rewarming starts, the refrigerating machine stops running, the purge valve is opened, the room-temperature dry nitrogen gas flows through the purge valve and the purge pipeline into the low-temperature vacuum pump, exchanges heat with the low-temperature radiation-proof screen, the baffle and the condensing plate group, and is heated to a reverse rotation temperature; at this time, the refrigerating machine starts to rotate reversely, the heat generated by the reverse rotation accelerates the temperature rise of the above-mentioned components, the control box adjusts the operation frequency according to the collected temperature, so as to control the temperature difference between the first refrigeration section and the second refrigeration section, and the temperature is increased to room temperature.

[0011] The use method of the low-temperature vacuum pump is characterized in that: the use method comprises the following steps:

[0012] 1) the rewarming process is started, the control box opens the purge valve and collects the temperature value T1 of the first temperature sensor and the temperature value T2 of the second temperature sensor;

[0013] 2) the control box collects and judges whether the temperature value T2 of the second temperature sensor is higher than a set reverse rotation starting temperature Ts, if T2 is not higher than Ts, the action of step 1) is kept unchanged, if T2 is higher than Ts, the action of step 1) is kept and the control box controls the refrigerating machine to start full-frequency reverse rotation;

[0014] 3) the control box collects and judges whether the temperature value T1 of the first temperature sensor is higher than a variable-frequency temperature Tb, if T1 is not higher than Tb, the refrigerating machine keeps full-frequency reverse rotation, if T1 is higher than Tb, the control box controls the reverse rotation frequency of the refrigerating machine to be reduced;

[0015] 4) The control box collects and judges whether the value of the first temperature sensor T1 is higher than the first temperature limit point Tg1, if T1 is not higher than Tg1, the refrigerator keeps low frequency inversion, if T1 is higher than Tg1, the control box controls the refrigerator to stop running, waits for T1 to drop to not higher than Tg1-10 K, the control box controls the refrigerator to low frequency inversion, until T1 is higher than Tg1 again, the refrigerator stops; in the above process, the control box collects and judges whether the value of the second temperature sensor T2 is higher than the second temperature limit point Tg2, if T2 is not higher than Tg2, the above process is kept, if T2 is higher than Tg2, the refrigerator stops running, the control box does not control the refrigerator to invert again.

[0016] Wherein, the vacuum cover includes cover body, pump port flange and lower flange, the outer wall of the vacuum cover is provided with exhaust valve, temperature connector and purge valve; the exhaust valve, temperature connector and purge valve are connected with the control box through cable.

[0017] Wherein, the refrigerator includes refrigerator flange, first refrigeration section and second refrigeration section, the refrigerator flange is connected with the lower flange, the first refrigeration section and the second refrigeration section pass through the lower flange to enter the inside of the cover body; the upper end surface of the first refrigeration section is connected with the lower end surface of the radiation shielding screen.

[0018] Wherein, the upper end of the radiation shielding screen is connected with the baffle, the second refrigeration section is connected with the condensing plate group, the second refrigeration section and the condensing plate group are located in the space enclosed by the radiation shielding screen and the baffle, and the radiation shielding screen and the baffle are located in the inside of the cover body; the surface of the condensing plate group is bonded with activated carbon for adsorbing gas molecules.

[0019] Wherein, the first refrigeration section is provided with a first piston, and the second refrigeration section is provided with a second piston.

[0020] Beneficial effects: compared with the prior art, the present application has the following remarkable advantages: the present application relies on the heating of the refrigerator inversion and the drying nitrogen gas blowing to perform rewarming, so that the low temperature vacuum pump can automatically complete the rewarming process. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a front view structural schematic diagram of the low temperature vacuum pump of the present application;

[0022] Figure 2 It is a side view structural schematic diagram of the low temperature vacuum pump of the present application;

[0023] Figure 3 It is a sectional view of A-A section of Figure 1

[0024] Figure 4 It is a flow chart of the rewarming method of the present application;

[0025] ​In the diagram, 10 is the vacuum chamber; 11 is the pump port flange; 12 is the lower flange; 13 is the exhaust valve; 14 is the temperature connector; 15 is the purge valve; 16 is the enclosure; 20 is the refrigerator; 21 is the primary refrigeration section; 22 is the secondary refrigeration section; 23 is the primary temperature sensor; 24 is the secondary temperature sensor; 25 is the refrigerator flange; 26 is the primary piston; 27 is the secondary piston; 30 is the control box; 41 is the radiation shield; 42 is the baffle; and 43 is the condenser plate assembly. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] The cryogenic vacuum pump of the present invention is connected to the chamber to be evacuated during use, and a backing pump is also required. The backing pump is not included in the cryogenic vacuum pump of this embodiment and is provided by the user.

[0028] like Figures 1 to 3 As shown, the cryogenic vacuum pump rewarming method of the present invention involves a cryogenic vacuum pump comprising: a vacuum hood 10, an exhaust valve 13, a temperature connector 14, a purge valve 15, a refrigerator 20, a primary temperature sensor 23, a secondary temperature sensor 24, a control box 30, a radiation shield 41, a baffle 42, and a condenser plate assembly 43. The specific configuration is as follows:

[0029] The vacuum chamber 10 includes a chamber body 16, a pump port flange 11, and a lower flange 12. The chamber body 16 is connected to the pump port flange 11 and the lower flange 12 by welding. An exhaust valve 13, a temperature connector 14, and a purge valve 15 are provided on the outer wall of the vacuum chamber 10. The exhaust valve 13 is used to discharge gas from the pump. The temperature connector 14, exhaust valve 13, and purge valve 15 are all connected to the control box 30 via cables. The control box 30 can control the opening and closing of the exhaust valve 13 and the purge valve 15. The exhaust valve 13 will also open when the internal pressure of the cryogenic vacuum pump exceeds a certain value, i.e., it will be forced open by the internal gas pressure.

[0030] The refrigeration unit 20 includes a refrigeration unit flange 25, a primary refrigeration section 21, and a secondary refrigeration section 22. The refrigeration unit 20 is equipped with the refrigeration unit flange 25, with the primary refrigeration section 21 and the secondary refrigeration section 22 located at the upper end of the flange 25. The refrigeration unit flange 25 is connected to the lower flange 12, typically using a metal gasket. The primary refrigeration section 21 and the secondary refrigeration section 22 pass through the lower flange 12 of the enclosure 16 and extend into the interior of the enclosure 16. The upper end face of the primary refrigeration section 21 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 22. The secondary refrigeration section 22 and the condenser plate assembly 43 are contained within the space enclosed by the radiation shield 41 and the baffle 42, which are also contained within the enclosure 16. Activated carbon for adsorbing gas molecules is adhered to the surface of the condenser plate assembly 43.

[0031] The primary refrigeration section 21 contains a primary piston 26, and the secondary refrigeration section 22 contains a secondary piston 27. The refrigerator 20 has both forward and reverse rotation functions. The pistons move inside the refrigerator 20. When rotating forward, the temperature of the primary refrigeration section 21 and the secondary refrigeration section 22 decreases, and when rotating in reverse, the temperature increases.

[0032] The cryogenic vacuum pump is connected to the chamber to be evacuated via the pump port flange 11. During operation, the refrigerator 20 lowers the temperature T1 of the primary refrigeration section 21 to the primary operating temperature Tt1, for example, 65-100K, and lowers the temperature T2 of the secondary refrigeration section 22 to the secondary operating temperature Tt2, for example, 10K. At the same time, the condenser plate assembly 43, which is thermally connected to the secondary refrigeration section 22, is lowered to Tt2, and the radiation shield 41, which is thermally connected to the primary refrigeration section 21, and the baffle 42, which is thermally connected to the radiation shield 41, are lowered to Tt1.

[0033] The refrigeration unit 20 is connected to the control box 30. This connection is generally made by screws. The first-stage refrigeration section 21 of the refrigeration unit 20 is equipped with a first-stage temperature sensor 23, and the second-stage refrigeration section 22 is equipped with a second-stage temperature sensor 24. Both temperature sensors are connected to the temperature connector 14 via cables. The control box 30 is connected to the thermometer connector 14 to collect two temperatures T1 and T2.

[0034] The gas inside the chamber flows through baffle 42 into the space enclosed by the radiation shield 41 and baffle 42, and is frozen on the surface of the condenser plate assembly 43 at temperature Tt2, forming a solid condensation layer. This creates a vacuum environment inside the cryogenic vacuum pump. The solid condensation layer thickens as more frozen gas is added, until it contacts the radiation shield 41 or baffle 42 at temperature Tt1. Since Tt1 exceeds the freezing point of the gas, it is not effectively frozen, meaning the internal pressure of the cryogenic vacuum pump increases. At this point, the pump needs to heat up to expel the frozen gas and then cool down again before it can continue operating.

[0035] This invention discloses a method for rewarming a cryogenic vacuum pump, specifically a process for raising the pump from cryogenic to ambient temperature. This process is implemented via a control box 30. At the start of rewarming, the control box 30 opens the purge valve 15, allowing a large amount of room-temperature dry nitrogen gas to enter the pump. This causes the primary refrigeration section 21 and its connected radiation shield 41, baffle 42, and the secondary refrigeration section 22 and its connected condenser plate assembly 43 to heat up. The condensate layer frozen on the condenser plate assembly 43 rapidly heats up, transforming into a liquid state and evaporating into a gaseous state. Once the internal pressure reaches a certain value, the gas is discharged from the exhaust valve 13. The control box 30, through the secondary temperature sensor 24, detects that the temperature T2 of the secondary refrigeration section 22 has risen to the reverse start temperature Ts. Then, it controls the refrigerator 20 to start full-frequency reverse operation (operating at 100% of the rated frequency) to accelerate the heating of the pump's internal components. The reverse start temperature Ts is, for example, 80K. During this period, the purge valve 15 remains open to maintain nitrogen gas flow.

[0036] When the condenser plate assembly 43 has a thick condensate layer, if the reverse rotation is initiated when the secondary refrigeration section is below temperature Ts, the primary piston 26 and secondary piston 27 inside the refrigerator 20 will expand due to the increased temperature during the reverse rotation. Meanwhile, the secondary refrigeration section 22 will remain under contraction due to the condensate layer. Because the pistons and refrigeration sections are tightly fitted during refrigerator operation, the expansion of the secondary piston 27 and the contraction of the secondary refrigeration section 22 below Ts cause severe friction between them, shortening the lifespan of the refrigerator 20. Therefore, purging the secondary refrigeration section 22 to raise its temperature T2 to Ts before initiating the reverse rotation can extend the lifespan of the refrigerator 20.

[0037] The refrigerator 20 is a two-stage refrigerator, consisting of a primary refrigeration section 21 and a secondary refrigeration section 22. The cooling capacity of the primary refrigeration section 21 is greater than that of the secondary refrigeration section 22. In reverse operation, the heating capacity of the primary refrigeration section 21 is greater than that of the secondary refrigeration section 22. During the reverse operation, the temperature of the primary refrigeration section 21 is higher than that of the secondary refrigeration section, and the temperature difference between the two increases with the increase of the reverse operation time. After the primary refrigeration section 21 heats up to the variable frequency temperature Tb, for example, 250K, the control box 30 controls the refrigerator 20 (reverse operation) to reduce the operating frequency. At this time, the purge valve 15 remains open, that is, room temperature dry nitrogen is continuously introduced, which can reduce the temperature difference between the primary refrigeration section 21 and the secondary refrigeration section 22, ensuring that the two temperatures can reach room temperature similarly for subsequent processes, and shortening the waiting time of the rewarming process.

[0038] The piston temperature should not be too high, generally not exceeding 320K. If the refrigerator 20 operates at full frequency during the reverse rotation, the first-stage refrigeration section 21 will reach the first-stage temperature limit point Tg1 (generally set to 320K) first. At this point, the refrigerator 20 will stop operating to prevent overheating and will only resume reverse operation after the temperature drops, continuing to heat the second-stage refrigeration section 22 to reach the second-stage temperature limit point Tg2. If the first-stage refrigeration section 21 reaches the temperature limit point Tg1 again during this process, it will stop operating again to wait for cooling, and then cool down again, repeating the above process until the temperature of the second-stage refrigeration section 22 reaches the second-stage temperature limit point Tg2. If the refrigerator 20 operates at full frequency during the reverse rotation, the waiting time for cooling down after the first-stage refrigeration section 21 reaches 320K will be too long. Reducing the frequency during the reverse rotation can reduce the temperature difference between the first-stage refrigeration section 21 and the second-stage refrigeration section 22, reduce the cooling waiting time, shorten the time required for the rewarming process, and improve working efficiency.

Claims

1. A cryogenic vacuum pump, characterized in that: The system includes a vacuum chamber (10), a refrigerator (20), and a control box (30). The vacuum chamber (10) is equipped with a purge valve (15). The refrigerator (20) performs forward and reverse cooling. The refrigerator (20) is equipped with a primary temperature sensor (23) and a secondary temperature sensor (24). The control box (30) collects data from the primary temperature sensor (23) and the secondary temperature sensor (24), controls the opening of the purge valve (15), and controls the start-up and operating frequency of the refrigerator (20).

2. The cryogenic vacuum pump according to claim 1, characterized in that: The vacuum hood (10) includes a hood body (16), a purge pipe is provided on the side of the hood body (16) and a purge valve (15) is provided on the purge pipe, a refrigerator (20) is provided on the side of the hood body (16) and a control box (30) is provided on the side of the refrigerator (20), and radiation shields (41) are provided at intervals inside the hood body (16), and a baffle (42) is provided on the top of the radiation shields (41).

3. The cryogenic vacuum pump according to claim 2, characterized in that: The refrigeration unit (20) extends into the radiation shield (41). A condenser plate group (43) is horizontally arranged at the end of the refrigeration unit (20). The refrigeration unit (20) is provided with a primary refrigeration section (21) and a secondary refrigeration section (22). Both the primary refrigeration section (21) and the secondary refrigeration section (22) are provided with temperature sensors. The two temperature sensors are connected to the temperature connector (14) arranged on the cover (16).

4. The cryogenic vacuum pump according to claim 3, characterized in that: The refrigeration unit (20) cools down by rotating forward and heats up by rotating in reverse. The control box (30) connects the temperature connector (14) to the refrigeration unit (20). The control box (30) collects the temperature signal transmitted by the temperature sensor, that is, collects the temperature of the refrigeration unit (20). The control box (30) controls the forward and reverse rotation and the operating frequency of the refrigeration unit (20).

5. The method of using the cryogenic vacuum pump according to any one of claims 1-4, characterized in that: The refrigerator (20) rotates forward to lower the temperature of the first-stage refrigeration section (21), the radiation shield (41), and the baffle (42) to the first working temperature T1, and lower the temperature of the second-stage refrigeration section (22) and the condenser plate group (43) to the second working temperature T2. When the rewarming begins, the refrigerator (20) stops running, the purge valve (15) opens, and the room temperature dry nitrogen gas flows through the purge valve (15) and the purge pipeline into the low-temperature vacuum pump. It exchanges heat with the low-temperature radiation shield (41), the baffle (42), and the condenser plate group (43) to heat the temperature to the reverse temperature. At this time, the refrigerator (20) starts to reverse. The heat generated by the reverse rotation accelerates the heating of the above components. The control box (30) adjusts the operating frequency according to the collected temperature to control the temperature difference between the first-stage refrigeration section (21) and the second-stage refrigeration section (22) and raise the temperature to the room temperature.

6. The method of using the cryogenic vacuum pump according to claim 5, characterized in that: Includes the following steps: 1) Start the rewarming process. The control box (30) opens the purge valve (15) and simultaneously collects the temperature value T1 of the first-level temperature sensor (23) and the temperature value T2 of the second-level temperature sensor (24). 2) The control box (30) collects and judges whether the value T2 of the secondary temperature sensor (24) is higher than the set reverse start temperature Ts. If T2 is not higher than Ts, the action of step 1) remains unchanged. If T2 is higher than Ts, the action of step 1) remains unchanged and the control box (30) controls the refrigerator (20) to start full-frequency reverse. 3) The control box (30) collects and judges whether the value T1 of the first-level temperature sensor (23) is higher than the frequency conversion temperature Tb. If T1 is not higher than Tb, the refrigerator (20) is kept in full-frequency reverse rotation. If T1 is higher than Tb, the control box (30) controls the reverse rotation frequency of the refrigerator (20) to decrease. 4) The control box (30) collects and judges whether the value T1 of the primary temperature sensor (23) is higher than the primary temperature limit point Tg1. If T1 is not higher than Tg1, the refrigerator (20) will continue to reverse at a low frequency. If T1 is higher than Tg1, the control box (30) will control the refrigerator (20) to stop running. When T1 drops to no higher than Tg1-10 K, the control box (30) will control the refrigerator (20) to reverse at a low frequency until T1 is higher than Tg1 again, and the refrigerator (20) will stop. During the above process, the control box (30) collects and judges whether the value T2 of the secondary temperature sensor (24) is higher than the secondary temperature limit point Tg2. If T2 is not higher than Tg2, the above process will continue. If T2 is higher than Tg2, the refrigerator (20) will stop running and the control box (30) will no longer control the refrigerator (20) to reverse.

7. The cryogenic vacuum pump according to any one of claims 1-4, characterized in that: The vacuum hood (10) includes a hood body (16), a pump port flange (11) and a lower flange (12). The outer wall of the vacuum hood (10) is provided with an exhaust valve (13), a temperature connector (14) and a purge valve (15). The exhaust valve (13), the temperature connector (14) and the purge valve (15) are all connected to the control box (30) via cables.

8. The cryogenic vacuum pump according to claim 7, characterized in that: The refrigeration unit (20) includes a refrigeration unit flange (25), a primary refrigeration section (21) and a secondary refrigeration section (22). The refrigeration unit flange (25) is connected to the lower flange (12). The primary refrigeration section (21) and the secondary refrigeration section (22) pass through the lower flange (12) and enter the interior of the enclosure (16). The upper end face of the primary refrigeration section (21) is connected to the lower end face of the radiation shield (41).

9. The cryogenic vacuum pump according to claim 8, characterized in that: The upper end of the radiation shield (41) is connected to the baffle (42), the secondary cooling section (22) is connected to the condenser plate group (43), the secondary cooling section (22) and the condenser plate group (43) are located in the space enclosed by the radiation shield (41) and the baffle (42), and the radiation shield (41) and the baffle (42) are located inside the cover (16); the surface of the condenser plate group (43) is coated with activated carbon that adsorbs gas molecules.

10. The cryogenic vacuum pump according to claim 9, characterized in that: The first-stage refrigeration section (21) is equipped with a first-stage piston (26), and the second-stage refrigeration section (22) is equipped with a second-stage piston (27).

Images