JP3716068B2 - Turbo molecular pump and vacuum vessel having the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a turbo molecular pump having a protection function (interlock) for preventing destruction of a high-speed rotating part.
[0002]
[Prior art]
The turbo molecular pump will be described with reference to FIG. 5. 1 in FIG. 5 is a casing of a turbo molecular pump comprising an upper half 1a and a lower half 1b, 1c is an intake port provided in the upper half 1a of the casing, and 1d is a casing. An exhaust port provided in the lower half 1b, 2 is a rotor chamber in the casing 1, 3 is a stationary blade fixed to the casing upper half 1a, and 4 is a rotor disposed in the rotor chamber 2. 5 is a rotor blade provided on the rotor 4, 4 a is a rotor shaft, and the rotor blade 5 and the rotor shaft 4 a constitute the rotor 4.
[0003]
6 is a thrust magnetic disk provided at the lower end of the rotor shaft 4a, 7a and 7b are upper and lower radial magnetic bearings provided on the opposed surfaces of the rotor shaft 4a and the casing lower half 1b, and 8 is the upper and lower surfaces of the thrust magnetic disk 6. A thrust magnetic bearing provided opposite to the ball bearing, 9 a ball bearing provided as a radial upper protective bearing at the upper end of the rotor shaft 4a, and 10 a radial and thrust lower protective bearing provided at the lower neck of the rotor shaft 4a ( Ball bearing). Reference numeral 11 denotes a rotor driving rotation motor provided in the casing lower half 1b.
[0004]
FIG. 5 shows an example of a turbo molecular pump having an active magnetic bearing as a bearing. However, in a turbo molecular pump using a ball bearing type and other bearings, only the mechanism of the bearing is different. It is the same. This also applies to the turbo molecular pump according to the embodiment of the present invention shown in FIG.
[0005]
In addition, the moving blade in the turbo molecular pump referred to in this specification is configured to perform a compression action by rotating at a high speed, and is a composite composed of a turbine blade rotor, a turbine blade and a screw groove. A rotor, a threaded rotor, and the like.
[0006]
When using the turbo molecular pump, considering the fracture life due to the decrease in creep strength of the blade material (generally using a light weight and high stress strength aluminum alloy) against the temperature rise of the blade 5 provided on the rotor 4, the turbo There is a limit on the gas flow rate or the inlet pressure exhausted by the molecular pump. Therefore, process conditions (inlet pressure, gas flow rate, etc.) are set on the user side so as to satisfy these restrictions.
[0007]
In addition, the turbo molecular pump itself also prevents a damage due to a decrease in creep strength caused by a rise in the temperature of the moving blade 5, so that when the limit is exceeded, a protection function (interflow) against the gas load (flow rate) that exhausts to stop the operation. If it is used outside the limit, the operation is stopped.
[0008]
This conventional protection function utilizes the fact that the windage loss of the rotor blade 5 caused by the gas load is reflected in the input current value of the motor 11 that rotates the rotor 4 at a high speed, and the current value increases as the gas load increases. By monitoring the current value and comparing it with the specified current value (trip value), it is determined that the operating state is within the limits.
[0009]
This specified current value is determined by testing the maximum allowable gas load (flow rate) using a limited number of gases (specifically nitrogen gas, argon gas, etc.) that are limited to a single turbo molecular pump. A gas flow rate condition in which the temperature of the blade 5 allows the creep life is measured, and an input current value to the motor 11 at the maximum gas load (flow rate) 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 this specified current value, it can be operated within the limits.
[0010]
[Problems to be solved by the invention]
In general, the rotor blade 5 in the turbo molecular pump is made of an aluminum alloy that is a lightweight and high strength material. However, when exposed to a gas load exceeding the usage conditions of the turbo molecular pump, the wind due to an excessive gas load is generated. The temperature of the rotor blade 5 rises due to the loss and heat of compression of the gas, and causes destruction due to a decrease in creep strength.
[0011]
In order to prevent creep destruction of the moving blade 5, conventionally, as described above, several kinds of gases (specifically, nitrogen gas, argon gas, etc.) limited in advance by a single turbo molecular pump are used. The test of the maximum allowable gas load (flow rate) determined the gas flow rate condition in which the temperature of the moving blade 5 can allow the creep life.
[0012]
Then, the 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), and this specified current value is used for the motor 11 during the rated operation of the turbo molecular pump. Compared with the input current value of, when the motor current value exceeded the specified current value, it was a protective function to stop the operation of the turbo molecular pump.
[0013]
However, the type of process gas in the user who actually uses the turbo molecular pump is nitrogen gas, which is the gas used for the specified current value (trip value) measurement of the motor current determined by the test with the turbo molecular pump alone, Since it is different from argon gas etc., gas characteristics such as gas molecular weight and specific heat are different.
[0014]
For this reason, the motor input current value and the blade temperature for the load due to the actual process gas cannot be uniquely determined (even if the motor input current value is the same, the blade temperature varies depending on the type of gas). There was 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 gas load could not be achieved completely.
[0015]
In addition, 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 was a problem of poor reliability.
[0016]
The present invention accurately measures the blade temperature under any gas condition (gas type, flow rate, temperature, etc.) and environmental condition (environment temperature, cooling condition). If the temperature exceeds the allowable blade temperature, creep destruction of the 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 the above and a vacuum vessel having the turbo molecular pump.
[0017]
[Means for Solving the Problems]
The present invention includes a rotor chamber, a stationary blade provided in the rotor chamber, a rotor having a rotor shaft and a moving blade rotatably supported in the rotor chamber, and a rotor chamber that rotates the rotor shaft at a high speed. A turbo molecular pump comprising: a motor provided therein, wherein gas molecules in a vacuum vessel are exhausted from an intake side to an exhaust side by rotating the rotor blade at high speed via the rotor shaft by the motor. In order to solve the above problems, the following configuration is adopted.
[0018]
That is, in the turbo molecular pump according to the present invention, in order to solve the above problem, a radiation thermometer provided in the rotor chamber for detecting the temperature of the moving blade, and a detected temperature change of the radiation thermometer due to the exhausted process gas and pressure a calculator that stores a data table of an amount, the stop of the rotor when the temperature of the rotor blade resulting et a corrected were detected by a radiation thermometer said data table by the computing unit exceeds a set value and a structure in which a means for performing one either at a minimum of alarm.
[0019]
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. Is switched to the deceleration mode to stop the operation or generate an alarm, so that the creeping destruction of the rotor blades under any gas conditions (gas type, flow rate, temperature, etc.) and environmental conditions (environment temperature, cooling conditions) Can be prevented in advance. Moreover, according to this invention, the vacuum vessel which has a turbo-molecular pump with the above-mentioned characteristic is provided.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a turbo molecular pump according to the present invention will be described in detail based on the embodiment shown in FIG. Note that, in the following embodiment, the same reference numerals are given to the same components as those of the conventional one shown in FIG. 5 for the sake of simplicity, and duplicate descriptions thereof will be omitted.
[0021]
In FIG. 1, 12 is a temperature detector, and the temperature detector (sensor) 12 is provided in the lower half 1b of the casing in the rotor chamber 2 to always directly measure the surface temperature of the moving blade 5 during rated rotation, and in real time. Configure to be able to monitor. The temperature detector 12 can detect the surface temperature of the moving blade 5 rotating at high speed without contact.
[0022]
Further, the temperature detector 12 is selected so as not to be affected by the environment in the rotor chamber 2, for example, the process gas type, the pressure, the temperature of the mounting portion, etc., or a mechanism for correcting the influence. In addition, since they are installed in a vacuum environment, those that do not cause destruction such as expansion and discharge, and those that do not cause corrosion or decrease in insulation due to process gas are selected.
[0023]
Further, the temperature detector 12 needs to have a sufficient gap with respect to the vibration and inclination of the rotor 4 in order to avoid contact with the rotating rotor blade 5. Even with this necessary gap, temperature detection accuracy can be ensured. It is like that. The temperature detector 12 which satisfies these conditions can be applied radiation thermometer.
[0024]
(First embodiment)
The case where a radiation thermometer is employ | adopted for the temperature detector 12 as 1st Embodiment is demonstrated below. Radiation thermometers need to be corrected for the influence of the usage environment because the measured values vary depending on the environment in which the detection unit is installed, specifically, the type and pressure of the gas surrounding the radiation thermometer.
[0025]
FIG. 2 shows a method for correcting the influence of this environment. The correction method shown in FIG. 2 is as follows. First, the measurement value from the temperature detector 12 is incorporated into a microprocessor that can numerically calculate or an arithmetic unit (controller) incorporating an arithmetic circuit using electronic components.
[0026]
Note that temperature correction data is collected by measuring the amount of temperature change due to each pressure of the radiation thermometer for each process gas exhausted by the turbo molecular pump in advance, and the data is stored as a table in a microprocessor or the like inside the arithmetic unit. Keep it.
[0027]
Accordingly, the temperature correction value is interpolated from the data table (K in FIG. 2) by inputting information on the type of process gas (process gas A in FIG. 2) and pressure (P in FIG. 2) at all times during operation of the turbo molecular pump. The temperature of the moving blade 5 can be calculated by multiplying the output value of the radiation thermometer by the temperature correction value.
[0028]
In this way, the relationship between the blade temperature and the creep life was calculated in advance or calculated for the temperature of the blade 5 measured in real time during the rated operation of the turbo molecular pump. Compare with (trip value).
[0029]
When the temperature of the moving blade 5 becomes higher than the specified temperature, the turbo molecular pump drive power supply is stopped by the interlock signal of the computing unit (controller), and the operation of the turbo molecular pump is stopped or an alarm is generated. Let
[0030]
As described above, FIG. 3 shows a flowchart of the operation / stop control of the turbo molecular pump by the interpolation of the measured value (T) of the radiation thermometer based on the process gas type and pressure information, and the comparison with the trip set temperature. is there.
[0031]
The present invention has been specifically described above based on the illustrated embodiments. However, the present invention is not limited to these embodiments, and the specific structure and configuration are within the scope of the present invention shown in the claims. Needless to say, various changes may be made. For example, in the above embodiment, the method of measuring the temperature expansion in the radial direction of the moving blade 5 and detecting the temperature of the moving blade has been shown, but various ideas such as a method of measuring the temperature expansion in the axial direction of the rotor 4 are presented. It is done.
[0032]
【The invention's effect】
In the turbo molecular pump, a mechanism for detecting the temperature of the moving blade is provided in the rotor chamber, and it is accurately detected that the temperature of the moving blade is increased and the material strength becomes dangerous. Since the driving and rotating motor is switched to the deceleration mode and the operation is stopped or an alarm is generated, it can operate under any gas conditions (gas type, flow rate, temperature, etc.) and environmental conditions (environment temperature, cooling conditions). It was possible to prevent the wing from creeping in advance and to improve the reliability of the turbo molecular pump against safety.
Moreover, according to this invention, the vacuum vessel which has a turbo-molecular pump with an above-described effect is provided.
[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 view 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 side view showing a basic structure of a turbo molecular pump.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Casing 1a Casing upper half 1b Casing lower half 1c Intake port 1d Exhaust port 2 Rotor chamber 3 Stator blade 4 Rotor 4a Rotor shaft 5 Rotor 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

Claims (2)

A rotor chamber, a stationary blade provided in the rotor chamber, a rotor having a rotor shaft and a moving blade rotatably supported in the rotor chamber, and a motor provided in the rotor chamber for rotating the rotor shaft at a high speed And a turbo molecular pump that exhausts gas molecules in the vacuum vessel from the intake side to the exhaust side by rotating the moving blades at high speed via the rotor shaft by the same motor. A radiation thermometer that detects the temperature of the blade, a calculator that stores a data table of a detected temperature change amount of the radiation thermometer according to exhausted process gas and pressure, and a detector that is detected by the radiation thermometer and wherein either the at least of the rotor stop and alarm when corrected by the data table the temperature of the rotor blade resulting et al was in exceeds the set value one Turbomolecular pump characterized by comprising a means for performing. A rotor chamber, a stationary blade provided in the rotor chamber, a rotor having a rotor shaft and a moving blade rotatably supported in the rotor chamber, and a motor provided in the rotor chamber for rotating the rotor shaft at a high speed A vacuum vessel having a turbo molecular pump that exhausts gas molecules in the vacuum vessel from the intake side to the exhaust side by rotating the moving blade at high speed via the rotor shaft by the same motor. A radiation thermometer provided in the room for detecting the temperature of the moving blade, a calculator storing a data table of a detected temperature change amount of the radiation thermometer according to the exhausted process gas and pressure, and detected by the radiation thermometer small of the arithmetic unit at the stop of the rotor when the temperature of the rotor blade resulting et a corrected by the data table has exceeded the set value and alarm Vacuum vessel, characterized in that it comprises a turbo molecular pump provided with a means for performing one either also.

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