Method for testing stiffness reduction of a magnetic levitation molecular pump turbine rotor and application

Abstract

The application discloses a magnetic suspension molecular pump turbine rotor stiffness reduction test method and application, and belongs to the field of molecular pump testing. The technical key points are as follows: S100, acquiring a temperature-radial displacement vibration value curve of a magnetic suspension molecular pump turbine rotor at a rated rotating speed; S200, determining a starting linear section and a tail linear section of the temperature-radial displacement vibration value curve; S300, solving a temperature-radial displacement vibration value curve of the turbine rotor at T max Compared with the turbine rotor stiffness reduction value u of the temperature at T min ~T1: u=1-[δ Tmin +a1(T2-T min )) / δ T2 , wherein δ Tmin , δ T2 represent radial displacement vibration values corresponding to T min , T2. By using the technical scheme, whether the rotor stiffness reduction amplitude of the turbine rotor at 120-160 ° temperature meets the requirements can be tested.

Description

Technical Field

[0001] This application relates to the field of molecular pump testing, and more specifically, to a method and application for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor. Background Technology

[0002] In semiconductor etching processes, magnetically levitated molecular pumps require active heating of the turbine to maintain the rotor temperature between 90°C and 100°C, preventing byproduct condensation and ensuring normal pump operation. However, considering potential abnormal operating conditions, the rotor turbine temperature may rise to 140°C.

[0003] Once the turbine temperature exceeds 100°C, the following problems will arise: (1) The elastic modulus E of the rotor material will decrease significantly after a certain temperature. In terms of rotor structure, this means that the stiffness K will also decrease significantly after a certain temperature.

[0004] (2) A decrease in rotor stiffness will lead to a decrease in the first-order mode, which in turn will cause a decrease in the critical speed (the critical speed at which the first-order mode is entered earlier). The second-order speed may drop below the rated speed, and the molecular pump will have an additional resonance point during speed-up. All of these will greatly increase the risk of severe vibration of the rotor at the operating speed.

[0005] Therefore, it is necessary to test the decrease in stiffness of the turbine rotor of the magnetic levitation molecular pump. Summary of the Invention

[0006] The purpose of this application is to address the shortcomings of the prior art by providing a method and application for testing the decrease in stiffness of a magnetic levitation molecular pump turbine rotor.

[0007] The technical solution of this application is as follows: A method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor includes the following steps: S100, obtain the temperature-radial displacement vibration curve of the magnetic levitation molecular pump turbine rotor at rated speed, where the temperature range is T min ~T max Among them, T min T max These represent the temperature start and end points of the temperature-radial displacement vibration curve, respectively; T min The selection range is [20°C~30°C], T max The selection range is [150°C~160°C]; S200, determine the initial and final linear segments of the temperature-radial displacement vibration value curve; The temperature range of the initial linear segment is T. min~T1, with a slope of a1; the temperature range of the final linear segment, T2~T max Where T1 is the temperature value corresponding to the end point of the initial linear segment, and T2 is the temperature value corresponding to the start point of the final linear segment. S300, solve for temperatures in the range T2~T max Compared to temperature at T min ~T1 turbine rotor stiffness reduction value u: u=1-[δ Tmin +a1(T2-T min )] / δ T2 , where δ Tmin δ T2 T represents min The radial displacement vibration value corresponding to T2.

[0008] Furthermore, the range of T2-T1 is [4°C, 6°C].

[0009] Furthermore, T1 = 115°C, T2 = 120°C.

[0010] A method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor includes the following steps: S100, acquire the temperature-radial displacement vibration data sequence L of the magnetic levitation molecular pump turbine rotor at rated speed; L={(T) D1 δ TD1 )……(T) Di δ TDi )……(T) Dn δ TDn )}, where T Di For any i-th temperature point, δ TDi It is T Di The corresponding radial displacement vibration value; T Di < T Di+1 T D1 T Dn These represent the temperature start and end points of the temperature-radial displacement vibration curve, respectively; T D1 The selection range is [20°C~30°C], T Dn The selection range is [150°C~160°C]; S200, the temperature-radial displacement vibration data sequence L is divided into two line segments for fitting, and the temperature range of the initial linear segment and the last linear segment is determined; Initial linear segment: (T) D1 δ TD1 )……(T) Dj δ TDj The data is fitted according to a linear relationship, and its slope is a1; The final linear segment: will (T) Dk δ TDk )……(T) Dn δ TDn Fitting according to a linear relationship; Among them, T Dj T represents the temperature value corresponding to the end point of the initial linear segment. Dk This is the temperature value corresponding to the starting point of the last linear segment; S300, calculate the decrease in turbine rotor stiffness u in the final linear segment of temperature compared to the initial linear segment of temperature: u=1-[δ TD1 +a1(T Dk -T D1 )] / δ TDk , where δ TDk δ TD1 T represents Dk T D1 The corresponding radial displacement vibration value.

[0011] Furthermore, the temperature interval T between any two data points Di+1- T Di The range is less than or equal to 5°C.

[0012] Furthermore, T Dk -T Dj The range is [4°C, 6°C].

[0013] Furthermore, T Dj =115°C, T Dk =120°C.

[0014] An application of a test method for the stiffness reduction of a magnetic levitation molecular pump turbine rotor is disclosed, which is used to determine whether the stiffness reduction value of the turbine rotor meets the requirements. The aforementioned test method for the stiffness reduction of a magnetic levitation molecular pump turbine rotor is used to test the stiffness reduction value u of the turbine rotor: if u is greater than or equal to the reduction threshold [u], it does not meet the requirements for the stiffness reduction of the turbine rotor; otherwise, it meets the requirements.

[0015] Furthermore, [u] = 30%.

[0016] The beneficial effects of this application are as follows: (1) This application develops a test method for the decrease in stiffness of a magnetic levitation molecular pump turbine rotor, which uses temperature-radial displacement vibration curves or datasets to solve the decrease in rotor stiffness at extreme temperatures relative to rotor stiffness at normal temperatures.

[0017] (2) This application uses temperature-radial displacement vibration data to quantitatively solve for the "stiffness reduction value". The theoretical solution is: u=1-[δ TD1+a1(T Dk -T D1 )] / δ TDk , where δ TDk δ TD1 T represents Dk T D1 The corresponding radial displacement vibration value. From the actual test results of the magnetic levitation molecular pump, it can be seen that the temperature-radial displacement vibration value relationship curve shows a clear linear relationship in the initial and final segments (this indicates that the turbine rotor stiffness remains constant within these two linear segments). From the above temperature-radial displacement vibration values, the slope a1 of the initial linear segment and the temperature T corresponding to the starting point of the final linear segment can be obtained. Dk。 TD1 is the starting temperature of the test data, δ TD1 δ TDk It is TD1, T Dk The corresponding radial displacement vibration value. Attached Figure Description

[0018] The present application will be further described in detail below with reference to the embodiments in the accompanying drawings, but this does not constitute any limitation on the present application.

[0019] Figure 1 It is a testing fixture for radial displacement vibration of a molecular pump at different temperatures.

[0020] Figure 2 It is a curve of measured temperature-radial displacement vibration values. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] <Experimental Instructions> Test subject: Magnetic levitation molecular pump.

[0023] Test parameters: Test temperature - radial displacement vibration value.

[0024] Test fixtures: such as Figure 1As shown, its dynamic balancing test fixture is similar to that of CN119063986B. Sensor components: turbine upper end face vibration sensor, lower end face vibration sensor, turbine temperature sensor. Heating section: An inlet pipe is connected to the opening of the molecular pump, and a flow meter is installed on the inlet pipe to control the gas flow rate entering the molecular pump between 500 scm and 1000 scm (the inlet flow rate remains constant after the test begins). Starting pressure: The starting pressure is provided to the molecular pump through a backing pump. Dynamic balancing test results: The dynamic balancing instrument monitoring cabinet is connected to the turbine upper end face vibration sensor and the turbine temperature sensor. The radial displacement vibration value of the turbine rotor is measured by the turbine upper end face vibration sensor.

[0025] Test steps: First, stress relief is performed on the magnetic levitation molecular pump to be tested. The fore-pump is turned on, and the molecular pump is run after the starting pressure is reached. Then, a certain flow rate of air is introduced into the molecular pump, and the turbine temperature is allowed to rise. The turbine rotor temperature is kept at 90°C and then run continuously for 24 hours (i.e., the timing starts when the temperature first reaches 90°C). During this process, dynamic balance testing is continuously performed. If the difference between the vibration values ​​of the upper end face and the vibration values ​​of the lower end face are less than 0.01μm after 24 hours and 20 hours respectively, it indicates that the stress has been relieved. Second, after the turbine stress is released, turn off the flow meter and the molecular pump. After the turbine temperature is reduced to room temperature, restart the molecular pump to start the high-temperature vibration test. Third, after the molecular pump reaches full speed, open the fine-tuning valve and control the flow rate to 1000 sccm ± 50 sccm using the flow meter. At this time, the turbine temperature T will gradually increase over time, and the unbalance X on the upper end face of the turbine will... a Vibration value, lower end face A a The vibration value also increases with the increase of turbine temperature T (X). a Greater than A a Only set X a This is also feasible. Generally speaking, the unbalance of the upper end face is taken as X. a The vibration value is analyzed as the radial displacement vibration value δ.

[0026] In other words, the vibration test of the turbine at high temperature can be carried out in conjunction with the stress removal process.

[0027] <Experimental Phenomena and Theoretical Analysis> like Figure 2 The figure shows the measured turbine temperature T-radial displacement vibration value δ curve of the CAS Instrument CXF320 / 3001CV magnetic levitation molecular pump. It exhibits the following characteristics: (1) Stage 1: The temperature-radial displacement vibration values ​​are linearly related from 30°C to 115°C.

[0028] (2) Stage 2: The radial displacement vibration value "jumps" between 115°C and 120°C.

[0029] (3) Stage 3: The temperature-radial displacement vibration value is linearly related between 120°C and 160°C.

[0030] Regarding the above phenomenon, parameters such as mass m and rotational speed ω remained constant during the experiment. The influencing factors on the vibration value are mainly considered in the following two aspects: (1) The influence of mass eccentricity e, δ is directly proportional to e.

[0031] (2) The influence of turbine rotor stiffness K, δ is inversely proportional to K.

[0032] That is, it can be expressed as: δ∝e / K.

[0033] <Example 1> A method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor includes the following steps: S100, obtain the temperature-radial displacement vibration curve of the magnetic levitation molecular pump turbine rotor at rated speed, where the temperature range is T min ~T max Among them, T min T max These represent the temperature start and end points of the temperature-radial displacement vibration curve, respectively; T min The selection range is [20°C~30°C], T max The selection range is [150°C~160°C]; S200 divides the temperature-radial displacement vibration curve into two linear relationships: the initial linear segment's temperature range is T. min ~T1, with a slope of a1; the temperature range of the final linear segment, T2~T max Where T1 is the temperature value corresponding to the end point of the initial linear segment, and T2 is the temperature value corresponding to the start point of the final linear segment (the rotor stiffness change is completed between T1 and T2). S300, solve for the stiffness reduction value u: u=1-[δ Tmin +a1(T2-T min )] / δ T2 , where δ Tmin δ T2 T represents min The radial displacement vibration value corresponding to T2.

[0034] <Example 2> A method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor includes the following steps: S100, acquire the temperature-radial displacement vibration data sequence L of the magnetic levitation molecular pump turbine rotor at rated speed; L={(T) D1 δ TD1 )……(T) Di δ TDi )……(T) Dn δ TDn )}, where T Di For any i-th temperature point, δ TDi It is T Di The corresponding radial displacement vibration value; T Di < T Di+1 T D1 T Dn These represent the temperature start and end points of the temperature-radial displacement vibration curve, respectively; T D1 The selection range is [20°C~30°C], T Dn The selection range is [150°C~160°C]; S200, the temperature-radial displacement vibration data sequence L is divided into two line segments for fitting, and the temperature range of the initial linear segment and the last linear segment is determined; Initial linear segment: (T) D1 δ TD1 )……(T) Dj δ TDj The data is fitted according to a linear relationship, and its slope is a1; The final linear segment: will (T) Dk δ TDk )……(T) Dn δ TDn Fitting according to a linear relationship; Among them, T Dj T represents the temperature value corresponding to the end point of the initial linear segment. Dk This is the temperature value corresponding to the starting point of the last linear segment; S300, calculate the decrease in turbine rotor stiffness u in the final linear segment of temperature compared to the initial linear segment of temperature: u=1-[δ TD1 +a1(T Dk -T D1 )] / δ TDk , where δ TDk δ TD1 T represents Dk T D1 The corresponding radial displacement vibration value.

[0035] It should be noted that the temperature step size of the data acquisition points for the temperature-radial displacement vibration value curve described in this application is 5°C.

[0036] It should be noted that T in Example 2 Dk It is not necessarily equal to T Dj ,for example Figure 2 In the middle, T Dj =115°C, T Dk =120°C. If the curve also contains the radial displacement vibration value corresponding to 118°C, this data is not needed.

[0037] like Figure 2 The example shown has δ Tmin =0.015μm, T2=120°C, T min =30°C, δ T2 =0.079μm, a1=0.464×10-3μm / °C, and the calculated stiffness reduction value u=28.1%.

[0038] The above-described embodiments are preferred embodiments of this application and are only used to facilitate the illustration of this application. They are not intended to limit this application in any way. Any person with ordinary knowledge in the art can make equivalent embodiments by making partial modifications or alterations to the technical content disclosed in this application without departing from the scope of the technical features of this application. Such equivalent embodiments are still within the scope of the technical features of this application.

Claims

1. A method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor, characterized in that, Includes the following steps: S100, obtain the temperature-radial displacement vibration curve of the magnetic levitation molecular pump turbine rotor at rated speed, where the temperature range is T min ~T max Among them, T min T max These represent the temperature start and end points of the temperature-radial displacement vibration curve, respectively; T min The selection range is [20°C~30°C], T max The selection range is [150°C~160°C]; S200, determine the initial and final linear segments of the temperature-radial displacement vibration value curve; The temperature range of the initial linear segment is T. min ~T1, with a slope of a1; the temperature range of the final linear segment, T2~T max Where T1 is the temperature value corresponding to the end point of the initial linear segment, and T2 is the temperature value corresponding to the start point of the final linear segment. S300, solve for temperatures in the range T2~T max Compared to temperature at T min ~T1 turbine rotor stiffness reduction value u: u=1-[δ Tmin +a1(T2-T min )] / δ T2 , where δ Tmin δ T2 T represents min The radial displacement vibration value corresponding to T2.

2. The method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor as described in claim 1, characterized in that, The range of T2-T1 is [4°C, 6°C].

3. The method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor as described in claim 1, characterized in that, T1=115°C, T2=120°C.

4. A method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor, characterized in that, Includes the following steps: S100, acquire the temperature-radial displacement vibration data sequence L of the magnetic levitation molecular pump turbine rotor at rated speed; L={(T) D1 δ TD1 )……(T) Di δ TDi )……(T) Dn δ TDn )}, where T Di For any i-th temperature point, δ TDi It is T Di The corresponding radial displacement vibration value; T Di < T Di+1 T D1 T Dn These represent the temperature start and end points of the temperature-radial displacement vibration curve, respectively; T D1 The selection range is [20°C~30°C], T Dn The selection range is [150°C~160°C]; S200, the temperature-radial displacement vibration data sequence L is divided into two line segments for fitting, and the temperature range of the initial linear segment and the last linear segment is determined; Initial linear segment: (T) D1 δ TD1 )……(T) Dj δ TDj The data is fitted according to a linear relationship, and its slope is a1; The final linear segment: will (T) Dk δ TDk )……(T) Dn δ TDn Fitting according to a linear relationship; Among them, T Dj T represents the temperature value corresponding to the end point of the initial linear segment. Dk This is the temperature value corresponding to the starting point of the last linear segment; S300, calculate the decrease in turbine rotor stiffness u in the final linear segment of temperature compared to the initial linear segment of temperature: u=1-[δ TD1 +a1(T Dk -T D1 )] / δ TDk , where δ TDk δ TD1 T represents Dk T D1 The corresponding radial displacement vibration value.

5. The method for testing the decrease in stiffness of a magnetically levitated molecular pump turbine rotor as described in claim 4, characterized in that, Temperature interval T between any two data points Di+1- T Di The range is less than or equal to 5°C.

6. The method for testing the decrease in stiffness of a magnetic levitation molecular pump turbine rotor as described in claim 4, T Dk -T Dj The range is [4°C, 6°C].

7. The method for testing the decrease in stiffness of a magnetic levitation molecular pump turbine rotor as described in claim 4, T Dj =115°C, T Dk =120°C.

8. The application of the test method for the decrease in stiffness of the turbine rotor of the magnetic levitation molecular pump as described in any one of claims 1 to 7, which is used to determine whether the decrease in stiffness of the turbine rotor meets the requirements; Its features are, The turbine rotor stiffness reduction value u is tested using the aforementioned magnetic levitation molecular pump turbine rotor stiffness reduction test method: if u is greater than or equal to the reduction threshold [u], it does not meet the turbine rotor stiffness reduction requirement; otherwise, it meets the requirement.

9. The application as described in claim 8, characterized in that, [u]=30%。

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