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CN-121976951-A - Device and method for balancing thermal expansion gap of vacuum pump

CN121976951ACN 121976951 ACN121976951 ACN 121976951ACN-121976951-A

Abstract

The invention provides a device and a method for balancing a thermal expansion gap of a vacuum pump, and belongs to the technical field of multistage vacuum pumps. The rotor-shell material and structure of the multistage Roots vacuum pump are subjected to fine design, the thermal expansion difference between the shell and the rotor is accurately calculated, and differential gap design is performed based on the ratio of the temperature variation, so that equivalent reverse compensation is realized for the thermal expansion deformation generated by the multistage pump set during high-speed operation, and the axial gap between the rotor and the pump shell is automatically maintained in a preset design interval on the premise that a hydraulic compensation mechanism or a temperature sensing assembly and a temperature control system are not required to be additionally arranged, and serious faults such as rotor blocking, friction and even locking caused by uneven thermal expansion are effectively avoided.

Inventors

  • Zou Wangjiang
  • CHEN FENG
  • LI ZIMU

Assignees

  • 陕西光德星锐科技有限公司

Dates

Publication Date
20260505
Application Date
20260121

Claims (10)

  1. 1. The device for balancing the thermal expansion gap of the vacuum pump is characterized by comprising a clamshell type shell (1) with a multi-stage separation plate, a rotor (2) with multi-stage rotor blades and a thrust bearing for positioning the rotor (2), wherein the rotor (2) is provided with a theoretical zero point, the theoretical zero point is a fixed point between the shell (1) and the rotor (2), and the rotor (2) and the shell (1) can generate axial gap change during operation.
  2. 2. Device for balancing the thermal expansion gap of a vacuum pump according to claim 1, characterized in that the factor of the variation of the axial gap of the rotor (2) with the housing (1) is mainly thermal expansion deformation, the thermal expansion deformation formula being as follows: (1) Wherein DeltaL is the length variation, L 0 is the initial length; The rotor (2) and each stage of the shell (1) have the same initial length L 0 .
  3. 3. The device for balancing the thermal expansion gap of the vacuum pump according to claim 1, wherein the rotor (2) and the housing (1) are required to be provided with a gap between each stage during installation, and the gap between each stage is indirectly ensured by providing a reference initial gap, wherein the reference initial gap is a gap of a blade stage where the air inlet is located, the reference initial gap is a reference stage fixed end gap if the thermal expansion of the vacuum pump is forward expansion, and the reference initial gap is a reference stage floating end gap if the thermal expansion of the vacuum pump is reverse expansion.
  4. 4. A device for balancing thermal expansion gap of vacuum pump according to claim 3, wherein the forward expansion is that the expansion amount of rotor (2) is larger than the expansion amount of shell (1), at this time, the gap of fixed end is increased, the collision between the blade of rotor (2) and the partition plate of shell (1) will not happen to the fixed end, the fixed end does not need to reserve thermal expansion gap, the gap of free end is reduced, and the thermal expansion gap when rotor reaches preset limit temperature is reserved at the free end; The reverse expansion means that the expansion amount of the shell (1) is larger than that of the rotor (2), at the moment, the clearance of the movable end is continuously increased, the rotor blade and the shell partition plate cannot collide with each other at the movable end, the movable end does not need to reserve a thermal expansion clearance, the clearance of the fixed end is reduced, the rotor blade and the shell partition plate collide at the fixed end, and the thermal expansion clearance when the vacuum pump reaches a preset limit temperature is reserved at the fixed end.
  5. 5. A method for balancing thermal expansion gap of vacuum pump based on the device of any one of claims 1-4, comprising the following steps: acquiring structural parameters and material parameters of a vacuum pump, including a first thermal expansion coefficient of a vacuum pump housing material Second coefficient of thermal expansion of rotor material And a temperature variation ratio n, n=Δt 2 /ΔT 1 , of each stage rotor to the case, wherein And Determining the axial distance from each stage to an axial theoretical zero point; Calculating a thermal expansion gap between the fixed end and the movable end based on the acquired structural parameters and material parameters of the vacuum pump; determining a safety gap between the fixed end and the movable end; Calculating gaps of the fixed end and the movable end based on the thermal expansion gap and the safety gap, respectively; based on the gap between the fixed end and the movable end, the actual gap of each stage is determined by combining the actual temperature distribution of each stage and the distance from the theoretical zero point.
  6. 6. The method for balancing thermal expansion gap of vacuum pump according to claim 5, wherein the method for calculating thermal expansion gap of fixed end based on the obtained structural parameters and material parameters of vacuum pump is as follows, wherein the fixed end thermal expansion gap delta Heat of the body is the difference between the variation of the length of the rotor and the variation of the length of the housing of the stage: Wherein, the For the thermal expansion gap of the fixed end, In order to obtain the thermal expansion coefficient of the first material constituting the housing (1), For the temperature variation of the housing (1), A coefficient of thermal expansion of a second material constituting the rotor (2); Is the temperature variation of the rotor (2), n is And (3) with The ratio of the two is L 0 , which is the distance from the position of each stage to the theoretical zero point; the method for calculating the thermal expansion gap of the free end is as follows: Wherein, the Is the free end thermal expansion gap.
  7. 7. The method of claim 6, wherein the fixed end safety gap is a minimum gap at which the vane and the housing divider plate do not collide at the fixed end due to axial movement caused by pump system load variation, bearing settling, initial error accumulation factors.
  8. 8. A method of balancing a thermal expansion gap of a vacuum pump according to claim 7, wherein the running end safety gap is a minimum gap where dynamic mechanical stress, axial force fluctuations, initial error accumulation and load changes cause axial movement such that rotor blades do not collide with the housing divider plate at the running end.
  9. 9. The method of balancing thermal expansion gap of vacuum pump according to claim 8, wherein the method of calculating the gap of fixed end and free end based on thermal expansion gap and safety gap respectively is as follows: the gap at the fixed end is calculated as follows: Wherein, the Is a gap between the fixed ends, Is a fixed end safety gap; the clearance of the free end is calculated as follows: Wherein, the For the clearance of the free ends, Is a swimming end safety gap.
  10. 10. The method of claim 9, wherein, in the calculation of the fixed end gap, if the relationship between the coefficients of thermal expansion of the first material and the second material is selected to be For forward expansion, fixing end gap With increasing temperature, if the relationship between the coefficients of thermal expansion of the first material and the second material is that For reverse expansion, the gap delta between the fixed ends is continuously reduced along with the temperature rise; in the calculation of the free end gap, if the relation between the thermal expansion coefficients of the first material and the second material is selected as For reverse expansion, running end gap With increasing temperature, if the relationship between the coefficients of thermal expansion of the first material and the second material is that For forward expansion, clearance between free ends Continuously decreasing with increasing temperature; When (when) And during the process, the matching optimization of the vacuum pump structure and the gap is carried out, so that the dynamic balance is realized.

Description

Device and method for balancing thermal expansion gap of vacuum pump Technical Field The invention belongs to the technical field of multistage vacuum pumps, and particularly relates to a device and a method for balancing thermal expansion gaps of a vacuum pump. Background With the continuous emergence of new materials and new processes, vacuum technology will develop deeply in the fields of high speed, high vacuum degree, high precision and the like, and in the fields of semiconductor manufacturing, chemical industry, medical treatment, aerospace and the like, dry vacuum pumps are required to match with the rapid development of vacuum technology with higher requirements in the aspects of performance, adaptability, reliability and the like. The core principle of the multistage vacuum pump is that the pressure of the pumped gas is gradually reduced through the series connection of a plurality of pump stages, such as Roots pumps or claw pumps, so as to achieve higher vacuum degree, and the multistage vacuum pump realizes high vacuum degree and strong air pumping capability through a multistage structure, so that the multistage vacuum pump is the most prominent in the field of vacuum pumps. The excellent performance of the rotor is not separated from the strictly controlled axial clearance, the axial clearance (the distance between the end face of the rotor blade and the separation plate of the shell) is usually required to be controlled to be 0.05-0.3 mm, the clearance deviation of the rotor at the same stage is less than or equal to 0.05mm, and the axial position deviation of any stage can influence the clearance of the adjacent stages, so that the performance of the vacuum pump is influenced. The axial position of the rotor is usually fixed by a thrust bearing (such as an angular contact ball bearing, the axial play is less than or equal to 0.02 mm) and a positioning end plate, so that the thermal expansion gap between the rotor and the shell becomes a main factor affecting the gaps of all stages of the dry vacuum pump. In the running process of the vacuum pump, if the gap is reduced, the rotor and the shell can be possibly rubbed and collided, even equipment is blocked when serious, the normal running of the vacuum pump is affected, the service life of the equipment is reduced, the maintenance cost is increased, and the tightness of the vacuum pump is reduced, the air extraction efficiency is affected and the expected vacuum degree requirement cannot be met when the gap is increased. At present, in order to solve the problem of thermal expansion gap of a vacuum pump, engineering technicians in different fields are started from various aspects, for example, in the field of materials, new materials with small thermal expansion coefficients suitable for the application environment of the vacuum pump are constantly explored, such as the existing materials of titanium, nickel alloy, silicon carbide, silicon nitride, aluminum oxide ceramics and the like, all have lower thermal expansion coefficients and higher corrosion resistance, but all have the problems of high price, high processing difficulty, high use cost and the like, for example, in the field of electronic information, the gap change generated by continuously adjusting the thermal expansion by adopting the measures such as tip detection, calculation, feedback mechanism, displacement compensation and the like is gradually applied to the design of the vacuum pump, but the introduction of the mechanism increases the complexity of the vacuum pump, increases potential leakage sources, also increases the unreliability of a system, and in the field of vacuum mechanical design, metal sheets (copper sheets) with higher thermal expansion coefficients, for example, embedded in a shell, have been proposed in the field of highest attention, the expansion amount of a rotor is pushed by the deformation of the shell, the material with low thermal expansion coefficients is coated on the rotor, for example, the most practical and the method such as the method of realizing the thermal expansion coefficient is realized, and the most widely-used dynamic expansion control is realized. The results prove that the former two schemes have more manufacturing difficulty and limited control effect on the thermal expansion gap, and the latter method has more difficulty in realizing the cooling of the rotor with concentrated temperature, and the heating of the shell can bring the problems of energy loss, part performance degradation and the like. Disclosure of Invention The invention aims to overcome the defects and provide a device and a method for balancing a thermal expansion gap of a vacuum pump. In order to achieve the above purpose, the invention adopts the following technical scheme: In a first aspect, the invention provides a device for balancing thermal expansion gap of a vacuum pump, comprising a clamshell type shell with a multi-stage separation plate, a rotor with multi-