Rotor weight reduction structure, control system and molecular pump

Abstract

The invention discloses a rotor weight reduction structure, a control system and a molecular pump, and relates to the field of non-variable-capacity pumps, the rotor weight reduction structure comprises an outer cylinder, a rotor, a thrust disc and a thrust device, a bearing seat is arranged in the center of the bearing beam at the inlet end of the outer cylinder, a bearing groove is formed in the upper surface of the bearing seat, and a through hole is formed in the center of the bearing seat and used for allowing the convex column to penetrate into the bearing groove from bottom to top; the thrust disc is located in the bearing groove and detachably connected to the upper portion of the protruding column. The magnetic device is arranged above the thrust disc and is detachably connected to the bearing beam; the magnetic device is used for generating a magnetic field to generate attraction force to the thrust disc, and a stress sensor is further arranged in the bearing groove and used for measuring the pressure between the magnetic device and the bearing groove. According to the invention, the molecular pump capable of bearing a large impeller is prepared by using a mechanical bearing, and the mechanical bearing has longer service life.

Description

Technical Field

[0001] The present invention relates to the technical field of non-variable displacement pumps, and in particular to a rotor weight reduction structure, a control system and a molecular pump. Background Art

[0002] With the emergence of emerging industries such as semiconductor manufacturing, vacuum coating, and aerospace, high vacuum environment is crucial. A non-variable displacement pump is a pump that uses the kinetic energy, momentum transfer, or other physical principles of the fluid to transport the fluid, and does not rely on changing the volume of the working chamber to achieve fluid transportation during operation. Since there is no volume change, the flow rate of the pump is relatively stable, and the continuity of fluid transportation is good. It can provide a reliable fluid supply for systems that require a stable flow rate, which is very important for some application scenarios that require high flow stability. A molecular pump is a non-variable displacement pump that uses a high-speed rotating rotor to transfer momentum to gas molecules, allowing them to obtain a directional speed, so that they are compressed and driven to the exhaust port and then pumped away by the front stage. It is one of the key equipment for achieving high vacuum and has undergone continuous development and change.

[0003] Traditional molecular pumps usually use mechanical bearings to support and rotate the impeller. However, with the increase in the size of the vacuum chamber and the continuous increase in the pumping speed requirements, the limitations of mechanical bearings have gradually become apparent. Generally speaking, a large vacuum chamber requires a larger impeller to improve the pumping efficiency and speed, but the increase in impeller size is not unlimited. The increase in impeller size means an increase in weight, which will put forward requirements on the load capacity of the bearing. When the load is large and the rotation is high, the mechanical bearing will produce greater friction and wear, which not only reduces the efficiency and service life of the molecular pump, but also pollutes the vacuum environment due to the heat and wear particles generated by friction.

[0004] In order to overcome these problems, magnetic levitation technology is introduced into the design of molecular pumps, and magnetic bearings are used to support and drive impellers, etc., to achieve contactless and low-friction operation, thereby reducing wear and improving operating efficiency. However, the introduction of this technology makes the structure of the molecular pump more complicated, and the requirements for the design of magnetic bearings, algorithm design, dynamic adjustment, and impact resistance (which are very demanding and seriously hinder the promotion) are very high. First of all, the manufacturing cost of the molecular pump is increased. In addition, during the operation of the molecular pump, the concentric state of the main shaft and the bearing seat needs to be included. However, since there is no contact between the main shaft and the bearing, when the main shaft rotates at high speed, when the molecular pump is impacted by a large airflow or fails, the main shaft falls on the bearing. The instantaneous collision impact energy is very large, which will cause serious loss of the bearing and affect the life of the bearing. Therefore, the maintenance cost is also very high. The current caliber of this type of molecular pump is limited to 500 mm, and there are no larger products available. Not only because of the high price, but also because of the stability and safety of the product at a larger caliber, there are great challenges. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a rotor weight reduction structure, a control system and a molecular pump. The technical problem to be solved is how to use mechanical bearings to prepare a molecular pump that can carry a large impeller, and the mechanical bearings have a better life and a lower production cost, which is suitable for industrial promotion.

[0006] The objective of the present invention is achieved through the following technical solutions: The present invention provides a rotor weight reduction structure, comprising: an outer cylinder, a rotor, a thrust plate and a magnetic device, wherein: The rotor is provided with a convex column; A bearing seat is provided at the center of the bearing beam at the inlet end of the outer cylinder, a bearing groove is provided on the upper surface of the bearing seat, and a through hole is opened at the center of the bearing seat for the boss to penetrate into the bearing groove from bottom to top; The thrust plate is located in the bearing groove and is detachably connected to the upper part of the boss; the magnetic device is arranged above the thrust plate and is detachably connected to the bearing beam; The magnetic device is used to generate a magnetic field to generate an attractive force on the thrust plate. A force sensor is also provided in the bearing slot to measure the pressure between the magnetic device and the bearing slot.

[0007] Preferably, the rotor comprises a main shaft and an impeller, the impeller comprises a center seat located at the center of the impeller, and the bottom of the center seat is detachably connected to the main shaft.

[0008] Further preferably, a circular rotation groove is provided on the upper surface of the center seat for accommodating the bearing groove.

[0009] Preferably, a groove is provided on a side edge of the magnetic device for accommodating one end of the load-bearing beam.

[0010] Further preferably, the magnetic device is provided with grooves which are symmetrically distributed around the circumference.

[0011] Further preferably, the groove on the magnetic device is in a shape with an opening on the top and an opening on the outer side.

[0012] Further preferably, when the groove on the magnetic device is in a shape with an opening on the outer side, the height of the groove is greater than the height of the inner end portion of the load-bearing beam.

[0013] Preferably, a gap is left between the thrust plate and the bearing groove.

[0014] Preferably, a spacer ring is provided at the bottom of the bearing groove and is arranged between the force sensor and the bearing groove.

[0015] Preferably, the boss has two optional structures, as shown below: The first structure is: the boss is arranged at the top of the spindle, and a through hole is opened on the center seat, so that the boss passes through the through hole of the center seat and the through hole of the bearing groove from bottom to top in sequence; The second structure is: the convex column is arranged at the center position of the central seat and passes through the through hole of the bearing groove from bottom to top.

[0016] Preferably, the thrust plate is made of ferromagnetic material.

[0017] Preferably, the magnetic device is a magnetic coil.

[0018] The present invention provides a molecular pump, comprising the rotor weight reduction structure, wherein the caliber range of the molecular pump is between 700 and 1200 mm.

[0019] The present invention provides a control system for a rotor weight reduction structure, comprising: Detection end: device used to detect pressure; Actuator: used to generate magnetic force and adjust the magnetic force by adjusting the current. Analysis end: used to receive the signal from the detection end, determine the instantaneous pressure value, analyze it in combination with the preset pressure value, and output a signal for regulating the current size of the execution end; Control end: used to receive the signal from the analysis end and adjust the current of the execution end; When the instantaneous pressure value is greater than the preset pressure value, the current of the execution end is reduced, otherwise, the current of the execution end is increased.

[0020] Preferably, the preset pressure value is a range value, and both ends of the range are the first threshold value, including two positive and negative values.

[0021] Further preferably, the first threshold is determined based on a preset pressure value when the bearing has a longer life according to experiments and / or experience.

[0022] Further preferably, the analysis end also includes a second threshold value, the range of which is greater than the range of the first threshold value, for early warning.

[0023] Further preferably, the analysis end further includes a third threshold value, the range of which is larger than the range of the second threshold value, and is used for fault shutdown.

[0024] The control system of the rotor weight reduction structure provided by the present invention is applied to the rotor weight reduction structure.

[0025] The control system of the rotor weight reduction structure provided by the present invention is applied to a molecular pump including the rotor weight reduction structure.

[0026] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a rotor weight reduction structure in a molecular pump. By adopting a semi-magnetic levitation structure and using a magnetic device to generate magnetic force on a thrust plate, the load on the bearing is reduced, and the problem that high speed, heavy load and large pumping speed of a rolling bearing cannot be achieved at the same time is solved. The purpose of using a large bearing to achieve high speed and heavy load is achieved, thereby realizing the functions of a molecular pump with large diameter, large pumping speed, energy saving and environmental protection, ultra-long life, and improved production efficiency.

[0027] The present invention provides a rotor weight reduction system in a molecular pump. By calculating the instantaneous load of the bearing and judging the load between the instantaneous load and the optimal load of the bearing, the current of the magnetic device is adjusted so that the molecular pump is always kept in the optimal load state during operation, which can better extend the service life of the bearing, reduce frictional heat and improve efficiency.

[0028] The present invention provides a molecular pump using the rotor weight reduction structure and weight reduction system in the molecular pump, thereby realizing the functions of the molecular pump such as large caliber, high pumping speed, energy saving and environmental protection, ultra-long life, and improved production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 It is a three-dimensional schematic diagram of a molecular pump; Figure 2 It is a schematic diagram of a longitudinal section of a molecular pump rotor weight reduction structure according to Embodiment 1 of the present invention; Figure 3 It is a schematic longitudinal section diagram of the molecular pump rotor weight reduction structure according to Example 1 of the present invention; Figure 4 for Figure 3 A partial enlarged view of part A; Figure 5 It is a schematic diagram of a longitudinal section of a molecular pump rotor weight reduction structure according to Embodiment 2 of the present invention; Figure 6 It is a schematic longitudinal section diagram of a molecular pump rotor weight reduction structure according to Embodiment 2 of the present invention; Figure 7 for Figure 6 A partial enlarged view of part B; Figure 8 This is a flowchart of the molecular pump rotor weight reduction system of Example 3 of the present invention.

[0030] In the figure, 1, main shaft; 11, boss A; 2, impeller; 21, center seat; 22, rotating groove; 23, through hole A; 24, boss B; 3, outer cylinder; 31, bearing beam; 32, bearing seat; 33, bearing groove; 34, through hole B; 4, thrust plate; 5, magnetic device; 6, force sensor; 7, spacer ring; 8, rolling bearing; 9, motor; 10, stator; 12, spiral guide groove; 13, traction wheel; 14, exhaust port. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, some adjustments and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0032] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "up, down, left, right", "horizontal, vertical" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0033] This specific embodiment provides a rotor weight reduction structure, which is improved on the basis of the molecular pump using rolling bearings in the prior art. The bearing load is reduced by structural improvement to further achieve the purpose of expanding the caliber of the molecular pump. Figure 1 As shown, the invention is specifically introduced through Example 1 and Example 2.

[0034] Example 1 like Figures 2 to 4 As shown, this embodiment introduces a rotor weight reduction structure in a molecular pump, including a rotor, an outer cylinder 3, a thrust plate 4, and a magnetic device 5, wherein: The rotor includes a main shaft 1 and an impeller 2. The main shaft 1 is controlled to rotate by a motor 9. A boss A11 is provided at the top of the main shaft 1. The impeller 2 includes a center seat 21. The bottom of the center seat 21 is detachably connected to the main shaft 1 and rotates synchronously with the main shaft 1. A circular rotation groove 22 is provided on the upper surface of the center seat 21 with the rotation center line of the impeller 2 as the center. A through hole A23 is provided at the center of the rotation groove 22 for the boss A11 to penetrate the rotation groove 22 from bottom to top. The bearing seat 32 is arranged at the center of the bearing beam 31 at the entrance end of the outer tube 3, and a bearing groove 33 is provided on the upper surface. A through hole B34 is provided at the center of the bearing groove 33 for the boss A11 to penetrate into the bearing groove 33 from bottom to top; Thrust plate 4: located inside the bearing groove 33 and detachably connected to the upper part of the boss A11; Magnetic device 5: arranged above the thrust plate 4 and detachably connected to the load-bearing beam 31.

[0035] In this embodiment, a blind hole is provided on the thrust plate 4 for connecting the boss A11.

[0036] Furthermore, a groove is provided on the side edge of the magnetic device 5 for accommodating one end of the load-bearing beam.

[0037] In this embodiment, three symmetrical grooves are provided on the magnetic device 5 . The grooves are open at the top and at the outer side. The magnetic device 5 is supported by the force sensor 6 . The inner end of the load-bearing beam 31 is accommodated in the grooves.

[0038] It should be noted that, if the groove on the magnetic device 5 is only open on the side and not on the top, a gap must be left between the top surface of the groove and the upper surface of the inner end of the load-bearing beam 31 to prevent the load-bearing beam 31 from generating a supporting force on the magnetic device 5 and affecting the force measurement between it and the thrust plate 4.

[0039] When the magnetic device 5 is energized to generate a magnetic field and generate an attractive force on the thrust plate 4, it is equivalent to generating an upward pulling force on the main shaft 1 and the impeller 2, thereby achieving the purpose of reducing the weight of the rotor and further reducing the load on the rolling bearing 8.

[0040] Furthermore, the thrust plate 4 is made of ferromagnetic material.

[0041] Furthermore, a force sensor 6 is provided in the bearing groove 33 for measuring the pressure between the magnetic device 5 and the bearing groove 33 .

[0042] Specifically, a spacer ring 7 is provided inside the bearing groove 33 and is disposed below the force sensor 6 . The upper surface of the spacer ring 7 contacts the lower surface of the force sensor 6 , and the lower surface contacts the inner bottom surface of the bearing groove 33 .

[0043] Furthermore, a gap is left between the thrust plate 4 and the bearing groove 33 .

[0044] Furthermore, the magnetic device 5 is a magnetic coil.

[0045] Specifically, in the present embodiment, the circuit of the force sensor 6 may be arranged in the load-bearing beam 31 , for example, a penetrating hollow cavity may be arranged in one or more load-bearing beams 31 .

[0046] By adjusting the current, the attraction of the magnetic device 5 to the thrust plate 4 is controlled. When the suction force is large, the pressure value measured by the force sensor 6 is also large. Therefore, in actual use, the required attraction force can be predicted according to the optimal load of the rolling bearing 8, and the current can be adjusted through the feedback of the force sensor 6.

[0047] When in use, after the motor 9 is started, torque is applied to the main shaft 1, and the main shaft 1 drives the impeller 2 to rotate. The moving blades of the impeller 2 and the corresponding static blades 10 work together to compress the gas molecules layer by layer. After several layers of compression, the gas molecules are sent to the traction wheels 13 of the spiral guide groove 12, and spirally compressed again, and finally discharged from the molecular pump through the exhaust port 14 to achieve the purpose of exhausting gas.

[0048] Example 2 like Figures 5 to 7 As shown, this embodiment introduces a rotor weight reduction structure in a molecular pump, which is a variation of the structure of embodiment 1. The connection position of the thrust plate 4 is changed, as follows: A rotor weight reduction structure in a molecular pump, comprising: Spindle 1: controlled by motor 9 for rotation; Impeller 2: includes a center seat 21, the lower part of which is detachably connected to the main shaft 1 and rotates synchronously with the main shaft 1. A circular rotation groove 22 is opened on the upper surface of the center seat 21 with the rotation center line of the impeller 2 as the center, and a convex column B24 is set at the center of the rotation groove 22; The bearing seat 32 is connected to the bearing beam 31 at the inlet end of the outer tube 3, and a bearing groove 33 is provided on the upper surface. A through hole B34 is provided in the center of the bearing groove 33 for the boss B24 to penetrate into the bearing groove 33 of the bearing seat 32 from bottom to top; Thrust plate 4: located inside the bearing groove 33 and detachably connected to the upper part of the boss B24; Magnetic device 5: arranged above the thrust plate 4 and detachably connected to the load-bearing beam 31.

[0049] In this embodiment, a through hole is provided on the thrust plate 4 for connection with the boss B24.

[0050] The following describes a control system suitable for the above-mentioned rotor weight reduction structure.

[0051] Example 3 like Figure 8 As shown, a rotor weight reduction control system in a molecular pump is applied to a molecular pump having the above-mentioned rotor weight reduction structure, comprising: a control end, a detection end, an analysis end and an execution end, wherein: Detection end: a force sensor 6, used to detect the instantaneous pressure value; Execution end: the magnetic device 5, the magnetic force of the magnetic device 5 is regulated by the current; Analysis end: used to receive the signal of the force sensor 6 and determine the instantaneous pressure value F t , by combining and analyzing with the preset pressure value F0, a signal for regulating the current size of the magnetic device 5 is output; Control end: used to receive the signal from the analysis end and adjust the current of the magnetic device 5.

[0052] set up: , but: When , it means that the instantaneous pressure value of the force sensor 6 is large, the suction force generated by the magnetic device 5 is large, and it is inferred that the current is large, and the current of the magnetic device 5 needs to be reduced; on the contrary, , it is necessary to increase the current of the magnetic device 5.

[0053] However, in practice, the optimal load of the bearing is a range value, not a fixed value. Therefore, the first threshold , contains positive and negative values, defined here is a positive value, when , reduce the current of the magnetic device 5; when , increase the current of the magnetic device 5.

[0054] Of course, the analysis end can also add a second threshold , when the detected Exceeding the threshold Upper limit, or below threshold When the limit is reached, the analysis end will issue an early warning, which can provide timely reminders and shut down the machine for maintenance to avoid larger failures.

[0055] Furthermore, the analysis end can also add a third threshold , when the detected Exceeding the threshold Above or below threshold When the lower limit is reached, the analysis end issues a shutdown command and shuts down the machine immediately to avoid production accidents.

[0056] It should be noted that the preset pressure value F0 is set based on the rotor deadweight m and the optimal load N of the bearing, and the formula is: .

[0057] The optimum load of a bearing is generally a range value, where N can take any value within the range, preferably the middle value. .

[0058] In practical engineering applications, it can be approximated by Perform simple calculations.

[0059] The following is a reference for setting several thresholds.

[0060] Assuming that the optimum load N of the bearing is in the range of [N1, N2], the set So The first threshold is set based on the endpoint values ​​N1 and N2, that is: .

[0061] Furthermore, the second threshold is generally set when the bearing load exceeds 20%. For example, the formula for setting it at 10% is: , lower limit ; Or the formula is: Upper limit , the lower limit is the upper limit The opposite number of .

[0062] Furthermore, the third threshold is generally set when the bearing load exceeds the third threshold by at least 20%. For example, the formula for setting the third threshold at 20% is: , lower limit ; Or the formula is: Upper limit , the lower limit is the upper limit The opposite number of .

[0063] Such a design can keep the operation of the molecular pump basically within the optimal load range of the bearing, with stable operation and extended service life.

[0064] Example 4 The above rotor weight reduction structure can increase the caliber of the molecular pump. For example, the molecular pumps shown in the following table are several examples of molecular pumps determined after experiments.

[0065]

[0066] It should be noted that since the weight of molecular pumps with smaller diameters decreases exponentially, the bearings used are sufficient to support their weight and maintain a sufficient service life, so it is not necessary to adopt this weight-reducing structure. Considering the complexity and economy of the weight-reducing structure, there is currently no need for such applications in molecular pumps with a diameter of less than 400mm. Another prerequisite is the progress and development of bearing technology. If the bearing technology and performance are strong enough, even large-diameter molecular pumps can do without this structure, but this performance and requirement have not yet been achieved. In essence, whether to adopt a weight-reducing structure depends on whether the load, life and maximum speed of the bearing meet the standards.

[0067] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A rotor weight reduction structure, characterized in that: include: An outer cylinder, a rotor, a thrust plate and a magnetic device, wherein: The rotor is provided with a convex column; A bearing seat is provided at the center of the bearing beam at the inlet end of the outer cylinder, a bearing groove is provided on the upper surface of the bearing seat, and a through hole is opened at the center of the bearing seat for the boss to penetrate into the bearing groove from bottom to top; The thrust plate is located in the bearing groove and is detachably connected to the upper part of the boss; the magnetic device is arranged above the thrust plate and is detachably connected to the bearing beam; The magnetic device is used to generate a magnetic field to generate an attractive force on the thrust plate. A force sensor is also provided in the bearing slot to measure the pressure between the magnetic device and the bearing slot.

2. The rotor weight reduction structure according to claim 1, characterized in that: The rotor comprises a main shaft and an impeller. The impeller comprises a center seat located at the center of the impeller. The bottom of the center seat is detachably connected to the main shaft.

3. The rotor weight reduction structure according to claim 2, characterized in that: A circular rotating groove is formed on the upper surface of the center seat for accommodating the bearing groove.

4. The rotor weight reduction structure according to claim 2, characterized in that: The side edge of the magnetic device is provided with a groove for accommodating one end of the load-bearing beam, and also includes one or more of the following technical features: A. The magnetic device is provided with grooves symmetrically distributed around the circumference; B. The groove on the magnetic device is open at the top and open on the outer side; C. When the groove on the magnetic device is in a shape with an outer side opening, the height of the groove is greater than the height of the inner end of the load-bearing beam.

5. The rotor weight reduction structure according to claim 2, characterized in that: It also includes one or more of the following technical features: A. A gap is left between the thrust plate and the bearing groove; B. A spacer ring is provided at the bottom of the bearing groove, and is arranged between the force sensor and the bearing groove.

6. The rotor weight reduction structure according to any one of claims 2 to 5, characterized in that: It also includes one or more of the following technical features: A. The boss is arranged at the top of the spindle, and a through hole is opened on the center seat, so that the boss can pass through the through hole of the center seat and the through hole of the bearing groove from bottom to top in sequence; B. The protruding column is arranged at the center position of the center seat and passes through the through hole of the bearing groove from bottom to top.

7. The rotor weight reduction structure according to claim 6, characterized in that: It also includes one or more of the following technical features: A. The thrust plate is made of ferromagnetic material; B. The magnetic device is a magnetic coil.

8. A molecular pump, characterized in that: Comprising the rotor weight reduction structure according to any one of claims 1 to 7, the caliber range of the molecular pump is between 700 and 1200 mm.

9. A control system for a rotor weight reduction structure, characterized in that: The control system is applied to the rotor weight reduction structure described in any one of claims 1 to 7 or to a molecular pump including the rotor weight reduction structure described in any one of claims 1 to 7, and includes: a detection end, an execution end, an analysis end and a control end, wherein the detection end is a device for detecting pressure, the execution end is used to generate magnetic force, and the magnitude of the magnetic force is regulated by the magnitude of the current, the analysis end is used to receive the signal from the detection end, determine the instantaneous pressure value, and combine and analyze it with the preset pressure value, and output a signal for regulating the magnitude of the current at the execution end, and the control end is used to receive the signal from the analysis end and regulate the magnitude of the current at the execution end, and when the instantaneous pressure value is greater than the preset pressure value, the current at the execution end is reduced, and vice versa, the current at the execution end is increased.

10. The control system of the rotor weight reduction structure according to claim 9, characterized in that: The preset pressure value is a range value, and both ends of the range are the first threshold value, including positive and negative values.

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