JPH10299688A - Turbo molecular drag pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective function capable of stopping operation so that the creep rupture of moving blade can be prevented if a moving blade temperature exceeds an allowable limit by accurately measuring the temperature of the moving blade irrespective of the differences of gas conditions (type of gas, flow, temperature) and environmental conditions (ambient temperature, cooling conditions). SOLUTION: The shaft 4a of a rotor 4 to which a moving blade is installed is supported rotatably inside a rotor chamber 2, and rotated at high speed by a motor 11 installed inside the rotor chamber 2. Also gas molecules inside a vacuum container are exhausted from a suction port 1c to an exhaust port 1d side by a compressive action caused by rotating the moving blade 5 at high speed by the rotor shaft 4a. In addition, a temperature detector 12 for always detecting the temperature of the moving blade 5 during operation is installed in the rotor chamber 2 and, if the temperature of the moving blade 5 detected exceeds a set value, the rotor 4 is stopped or alarm is given.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo-molecular pump provided with a protection function (interlock) for preventing breakage of a high-speed rotating part.

[0002]

2. Description of the Related Art A turbo molecular pump will be described with reference to FIG. 5. In FIG. 5, reference numeral 1 denotes a turbo molecular pump casing composed of an upper half 1a and a lower half 1b, and 1c denotes an upper half of the casing.
a, an exhaust port provided in the lower casing half 1b, a rotor chamber 2 in the casing 1,
Reference numeral 4 denotes a stationary blade fixed to the upper half 1a of the casing, and reference numeral 4 denotes a rotor disposed in the rotor chamber 2. Reference numeral 5 denotes a rotor blade provided on the rotor 4, and reference numeral 4a denotes a rotor shaft. The rotor blade 5 and the rotor shaft 4a constitute the rotor 4.

Reference numeral 6 denotes a thrust magnetic disk provided at the lower end of the rotor shaft 4a, upper and lower radial magnetic bearings 7a and 7b provided on a surface facing the rotor shaft 4a and the lower casing half 1b, and 8 denotes a thrust magnetic disk 6 Thrust magnetic bearings provided opposite the upper and lower surfaces of the rotor shaft, ball bearings 9 provided as upper protection bearings for the radial direction at the upper end of the rotor shaft 4a, and radial and lower thrusts provided at the lower neck portion of the rotor shaft 4a. It is a protection bearing (ball bearing). Reference numeral 11 denotes a rotor drive rotation motor provided in the lower half portion 1b of the casing.

FIG. 5 shows an example of a turbo-molecular pump having an active magnetic bearing as a bearing. However, a turbo-molecular pump or the like using a ball bearing type and other bearings differs only in the mechanism of the bearing. The content is the same. This is the same in the turbo molecular pump according to the embodiment of the present invention shown in FIG. 1 described later.

[0005] Further, the moving blade in the turbo-molecular pump referred to in the present specification is configured to perform a compressing action by rotating at a high speed.
It is a composite rotor composed of turbine blades and screw grooves, a screw groove rotor, and the like.

[0006] In using the turbo molecular pump, a blade material (generally, an aluminum alloy that is lightweight and has a high stress strength is used) with respect to a temperature rise of the blade 5 provided on the rotor 4
In consideration of the destruction life due to the decrease in creep strength of the gas turbine, a restriction is imposed on the flow rate of gas exhausted by the turbo molecular pump or the pressure at the intake port. Therefore, the process conditions (inlet pressure, gas flow rate, etc.) are set on the user side to satisfy these restrictions.

[0007] The turbo molecular pump itself is also provided with the rotor blade 5.
In order to prevent destruction due to a decrease in creep strength due to a rise in temperature, a protection function (interlock) for a gas load (flow rate) that exhausts gas so that operation is stopped when the above limit is exceeded. The operation is stopped when it becomes necessary to use.

This conventional protection function utilizes the fact that the windage loss of the rotor blades 5 caused by the gas load is reflected on the input current value of the motor 11 for rotating the rotor 4 at high speed, and the current value increases as the gas load increases. Then, by monitoring this current value and comparing it with a specified current value (trip value), it is determined that the operation state is within the limit.

The specified current value is determined in advance by a limited number of types of gas (specifically, nitrogen gas,
Using a test of the maximum allowable gas load (flow rate) using argon gas or the like, the gas flow conditions under which the temperature of the moving blade 5 can allow the creep life are measured, and the maximum gas load (flow rate) at the maximum gas load (flow rate) is measured. The input current value to the motor 11 is set as a specified value. By monitoring the input current to the motor 11 during the rated operation of the turbo molecular pump with the specified current value, the operation can be performed within the limit.

[0010]

Generally, a rotor blade 5 in a turbo-molecular pump is made of an aluminum alloy which is a lightweight and high-strength material, but is exposed to a gas load exceeding the use condition of the turbo-molecular pump. In such a case, the temperature of the moving blade 5 rises due to windage loss and heat of gas compression due to an excessive gas load, resulting in destruction due to a decrease in creep strength.

Conventionally, in order to prevent creep destruction of the rotor blade 5, a limited number of gases (specifically, nitrogen gas, argon gas, etc.) previously used in the turbo molecular pump alone are used as described above. The temperature of the moving blade 5 has determined the gas flow conditions under which the creep life can be tolerated by testing the maximum allowable gas load (flow rate).

Then, an input current value to the motor 11 at the maximum gas load (flow rate) is measured, and this value is set as a specified current value (trip value). The specified current value is used during rated operation of the turbo-molecular pump. When the motor current value exceeds the specified current value as compared with the input current value to the motor 11, the protection function is provided to stop the operation of the turbo molecular pump.

However, the type of process gas used by the user who actually uses the turbo-molecular pump is the gas used for measuring a specified current value (trip value) of the motor current determined by a test using the turbo-molecular pump alone. Since it is different from nitrogen gas, argon gas and the like, gas characteristics such as molecular weight and specific heat of the gas are different.

For this reason, the motor input current value and the moving blade temperature with respect to the load by the actual process gas cannot be uniquely determined (even if the motor input current value is the same, the moving blade temperature differs depending on the type of gas). However, there has been a problem that the object of preventing creep destruction of the moving blade 5 due to the temperature rise of the moving blade 5 due to the actual process gas load cannot be completely achieved.

Further, the temperature of the rotor blade 5 varies depending on the environmental temperature and the cooling conditions, and the motor input current value and the rotor blade temperature cannot be uniquely determined from these conditions. There is a problem that reliability is inferior in prevention of the problem.

The present invention accurately measures the temperature of the moving blade under any gas conditions (gas type, flow rate, temperature, etc.) and environmental conditions (environmental temperature, cooling conditions), and if the temperature exceeds the allowable moving blade temperature, the moving blade It is an object of the present invention to provide a turbo-molecular pump having a protection function capable of stopping the operation of the turbo-molecular pump so as to prevent creep destruction of the turbo-molecular pump.

[0017]

SUMMARY OF THE INVENTION The present invention provides a rotor chamber,
A stator provided in the rotor chamber, a rotor having a rotor shaft and a rotor blade rotatably supported in the rotor chamber, and a motor provided in the rotor chamber for rotating the rotor shaft at high speed. In order to solve the above-described problem in the turbo molecular pump in which the motor blade is rotated at high speed through the rotor shaft by the same motor to exhaust gas molecules in the vacuum vessel from the suction side to the exhaust side. Adopt configuration.

That is, in the turbo-molecular pump according to the present invention, in order to solve the above-mentioned problem, means for detecting the temperature of the moving blade provided in the rotor chamber and the detected temperature of the moving blade exceed a set value. In such a case, means is provided for performing at least one of stopping the rotor and generating an alarm.

As means for detecting the temperature of the moving blade in the turbo-molecular pump according to the present invention, a displacement sensor for detecting the temperature expansion of the moving blade is provided, and the temperature of the moving blade is calculated from the detected displacement. It may be configured.

In the turbo-molecular pump according to the present invention, by providing a means for detecting the temperature of the moving blade in the rotor chamber, it is possible to accurately detect that the temperature of the moving blade has increased and the material strength has become dangerous. Then, the motor was switched to the deceleration mode to stop the operation or generate an alarm, so that the rotor blades could be used for any gas conditions (gas type, flow rate, temperature, etc.) and environmental conditions (environmental temperature, cooling conditions). Creep destruction can be prevented in advance.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a turbo molecular pump according to the present invention will be specifically described based on an embodiment shown in FIG. In the following embodiments, the same components as those of the related art shown in FIG. 5 are denoted by the same reference numerals for the sake of simplicity of description, and redundant description thereof will be omitted.

In FIG. 1, reference numeral 12 denotes a temperature detector, which is provided in the lower half 1b of the casing in the rotor chamber 2 and constantly directly measures the surface temperature of the moving blade 5 during rated rotation. And configure it so that it can be monitored in real time. The temperature detector 12 can detect the surface temperature of the moving blade 5 rotating at a high speed in a non-contact manner.

The temperature detector 12 is selected so as not to be affected by the environment in the rotor chamber 2, for example, the type of process gas, pressure, the temperature of the mounting portion, or a mechanism for correcting the influence. In addition, those which are installed in a vacuum environment and which do not cause destruction such as expansion and discharge, and those which do not cause corrosion and deterioration of insulation by a process gas are selected.

Further, in order to avoid contact with the rotating blade 5, the temperature detector 12 needs a sufficient gap for the vibration and inclination of the rotor 4. Can be secured. Various non-contact thermometers such as a radiation thermometer and an infrared camera can be applied to the temperature detector 12 satisfying these conditions.

(First Embodiment) As a first embodiment, a case where a radiation thermometer is employed for the temperature detector 12 will be described below. Due to the specifications of the radiation thermometer, the measurement value fluctuates depending on the environment in which the detection unit is mounted, specifically, the type and pressure of the gas surrounding the radiation thermometer. Therefore, it is necessary to correct the influence of the usage environment.

FIG. 2 shows a method of correcting the influence of the environment. The correction method shown in FIG. 2 is as follows. First,
The measurement value from the temperature detector 12 is taken into a microprocessor capable of performing a numerical operation or an operation unit (controller) incorporating an operation circuit using electronic components.

It should be noted that temperature correction data is collected by measuring in advance the temperature change of each process gas evacuated by the turbo molecular pump due to each pressure of the radiation thermometer, and the data is used as a table as a microprocessor or the like in the arithmetic unit. To be stored.

Therefore, during the operation of the turbo molecular pump, the temperature correction value is interpolated from the data table by inputting information on the type of the process gas (process gas A in FIG. 2) and the pressure (P in FIG. 2). The temperature of the moving blade 5 can be calculated by multiplying the output value of the radiation thermometer by the temperature correction value.

With respect to the temperature of the moving blade 5 measured in real time during the rated operation of the turbo-molecular pump in this way, the relationship between the moving blade temperature and the creep life was previously calculated or experimentally determined. With the specified value (trip value).

When the temperature of the rotor blade 5 becomes higher than the prescribed temperature, the power supply for driving the turbo molecular pump is stopped by the interlock signal of the arithmetic unit (controller), and the operation of the turbo molecular pump is stopped or Generate an alarm.

As described above, the flowchart of the control of the operation / stop of the turbo molecular pump based on the interpolation of the measured value (T) by the radiation thermometer based on the type and pressure of the process gas and the comparison with the trip set temperature is shown in FIG. It is shown in

(Second Embodiment) Next, the temperature detector 12
A case where a non-contact displacement sensor is employed in the first embodiment will be described below as a second embodiment. In the second embodiment of the present invention, the temperature detector (displacement sensor) 12 and the moving
It is detected from the size of the gap, in other words, the temperature expansion of the cylindrical portion of the moving blade 5 that
The temperature of the moving blade 5 is calculated.

However, in order to use a displacement sensor for the temperature detector 12, the temperature deviation of the displacement sensor due to the temperature change of the moving blade 5, the deformation due to the centrifugal force of the moving blade 5, and the temperature detector 12 must be used. A calculation for subtracting the temperature expansion of the lower half 1b of the attached casing is required.

In order to improve the accuracy of displacement measurement (rotor blade temperature), it is preferable to measure two points at an axially symmetric position of the rotor 4 having a phase difference of 180 degrees and average the measured values.

FIG. 4 shows a flowchart of an arithmetic system for subtracting the above-mentioned temperature deviation and the like and measuring two points when a displacement sensor is used as a temperature detector. Less than,
The operation will be described with reference to this.

The measured value of the displacement sensor used as the temperature detector 12 during the rated operation of the turbo-molecular pump includes not only the thermal expansion due to the temperature change of the moving blade 5 as a measurement item, but also the measured value of the moving blade 5 during the rated rotation. The imbalance component, the thermal expansion of the lower casing half 1b in which the temperature detector 12 is installed, the deformation of the moving blade 5 due to the centrifugal force, and the temperature deviation of the displacement sensor are included.

First, the displacement output value of the temperature detector 12 is passed through a low-pass filter set at a frequency lower than the rotation speed to remove the unbalance component (AC component) and extract only the DC component. On the other hand, the temperature near the temperature detector 12 attached to the casing lower half 1b is measured with a thermocouple or the like, and the temperature is multiplied by the radius of the casing lower half 1b and the coefficient of linear expansion. The temperature displacement is calculated and added to the value.

Further, the initial displacement amount at the time of reaching the rated value (centrifugal force displacement of the moving blade 5) is subtracted, and the temperature deviation amount of the displacement sensor is corrected to this value to calculate the moving blade displacement change amount due to the temperature. Further, the temperature of the moving blade 5 is calculated by dividing the above value by the value obtained by multiplying the inner diameter of the opposed portion of the moving blade 5 of the temperature detector 12 by the linear expansion coefficient.

The temperature value of the moving blade 5 calculated as described above is compared with the trip set temperature value, and if the temperature exceeds the set temperature, an interlock for stopping the operation is operated. Note that an eddy current type, a laser type, a capacitance type, or the like can be used as the non-contact displacement sensor in the second embodiment.

As described above, the present invention has been specifically described based on the illustrated embodiments. However, the present invention is not limited to these embodiments, and specific structures within the scope of the present invention shown in the claims are set forth. Needless to say, various changes may be made to the configuration. For example, in the above embodiment, a method of measuring the temperature expansion of the rotor blade 5 in the radial direction and detecting the temperature of the rotor blade has been described. Can be

[0041]

The present invention relates to a turbo molecular pump,
A mechanism that detects the temperature of the rotor blades is provided in the rotor chamber, and accurately detects that the temperature of the rotor blades rises to a dangerous state in terms of material strength, and switches the motor that drives and rotates the rotor to the deceleration mode. Since the operation is stopped or an alarm is issued, creep destruction of the rotor blade can be prevented in advance under any gas conditions (gas type, flow rate, temperature, etc.) and environmental conditions (environmental temperature, cooling conditions). Thus, the effect of improving the reliability with respect to the safety of the turbo molecular pump against destruction was obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a turbo-molecular pump according to an embodiment of the present invention.

FIG. 2 is a diagram showing a correction method of a radiation thermometer used in the turbo molecular pump according to the first embodiment of the present invention.

FIG. 3 is a flowchart of operation control in the turbo-molecular pump according to the first embodiment of the present invention.

FIG. 4 is a flowchart of operation control in a turbo-molecular pump according to a second embodiment of the present invention.

FIG. 5 is a side view showing the basic structure of a turbo-molecular pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 1a Upper casing half 1b Lower casing 1c Inlet 1d Exhaust port 2 Rotor chamber 3 Stator blade 4 Rotor 4a Rotor shaft 5 Moving blade 6 Thrust magnetic disk 7a Upper magnetic bearing 7b Lower magnetic bearing 8 Thrust magnetic bearing 9 Upper part Protective bearing 10 Lower protective bearing 11 Motor 12 Temperature detector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaharu Mizu 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi Hiroshima Works, Mitsubishi Heavy Industries, Ltd. Tokyo Electron Yamanashi Co., Ltd.

Claims (2)

[Claims] A rotor having a rotor chamber, a stationary blade provided in the rotor chamber, a rotor shaft and a rotor blade rotatably supported in the rotor chamber, and the rotor chamber rotating the rotor shaft at high speed. A turbo-molecular pump that exhausts gas molecules in a vacuum vessel from an intake side to an exhaust side by rotating the rotor blades at a high speed through the rotor shaft by the motor. A means provided in the rotor chamber for detecting the temperature of the moving blade, and means for performing at least one of stopping the rotor and generating an alarm when the detected temperature of the moving blade exceeds a set value. A turbo-molecular pump characterized in that: 2. A method according to claim 1, wherein the means for detecting the temperature of the moving blade has a displacement sensor, detects a temperature expansion of the moving blade by the displacement sensor, and calculates the temperature of the moving blade from the detected displacement amount. The turbo-molecular pump according to claim 1, wherein