JP2000110777A - Turbo molecular pump and protective operating method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To guarantee rotation of a turbo molecular pump while eliminating a possible danger of breakdown when an abnormal vibration of a rotor that comprises dynamic blades and a rotary shaft or an erratic operation of an energization control unit of a magnetic bearing is detected, by forcing to move the rotary shaft to one side and supporting rotatably through contact the rotary shaft with a support portion located on that side. SOLUTION: A rotary shaft is given an aerial support by an electromagnetic portion on one side of an upper magnetic bearing and an electromagnetic portion on one side of a lower magnetic bearing in a longitudinal and crosswise direction, and by an electromagnetic portion on one side of a thrust magnetic bearing in an axial direction. Evaluation means 33B determines that a broken dynamic blade will result if a comparison output provided by a comparator 31, i.e., a detected amplitude is 125 μm or more. In this case, a drive control circuit 37 that controls energization of a drive power source 36 of each magnetic bearing changes from inverter control, with which the rotary shaft is normally held in an aerial position, to a rectifier circuit. This results in the rotary shaft being forced to move to the right by a magnetic attraction, thus allowing the rotary shaft to come into contact with a protective bearing to eliminate a danger of breakdown. At the same time, it guarantees good rotation of a turbo molecular pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in a semiconductor manufacturing apparatus or the like, and includes a moving and stationary blade stage composed of a stationary blade provided in an upper casing and a moving blade provided on a rotating shaft. The present invention relates to a turbo-molecular pump that evacuates the gas to an exhaust port, particularly when an abnormal vibration of a rotor composed of the rotor blades and a rotating shaft or an abnormality of an energization control unit of a magnetic bearing that maintains the rotating shaft in the air occurs. The present invention relates to a turbo-molecular pump capable of effectively preventing the rotor blade from contacting a stationary blade and being damaged due to the abnormality, and a method of operating the turbo-molecular pump.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a turbo molecular pump applied to the present invention. In FIG. 5, reference numerals 1 and 16 denote an upper part integrally assembled via an O-ring 15 by bolts 21. A casing and a lower casing. The upper opening of the upper casing 1 serves as a gas intake port 2, and a plurality of spacers 13 are provided in the inside thereof in the axial direction via a ring-shaped gap. The upper end of the spacer 13 is in contact with the inner end surface of the upper casing 1, and the lower end is fitted into the upper end of the lower casing 16. It is clamped and fixed and provided in a multi-stage shape.

[0003] Reference numeral 6 denotes a rotor. The rotor 6 is provided with a plurality of moving blades 5 in a multi-stage manner, and the moving blades 5 and the stationary blades 4 are provided so as to mesh with each other alternately to form a blade stage. A thread groove pump stage 8 is provided below the rotor 6. 14 is
A seal ring fixed to the upper surface of the lower casing 16 by bolts 18 is disposed opposite to the outer periphery of the thread groove pump stage 8 with a small gap therebetween, thereby increasing the compression effect.

[0004] An exhaust port 3 is opened at the lower side of the lower casing 16, and the fluid that has passed through the thread groove pump stage 8 is sent out from the exhaust port 3 to the outside. Reference numeral 17 denotes a cylindrical support cylinder fixed to the lower casing 16 and protruding upward. The upper protection bearing 1 made of a radial ball bearing is arranged on the inner periphery of the support cylinder 17 in order from the top.
9, upper magnetic bearing 9 as a radial bearing, stator portion 12a of motor 12, lower magnetic bearing 1 as a radial bearing
0, a lower protection bearing 20 composed of a radial ball bearing, and a thrust magnetic bearing 11 provided with a thrust disk 7a at the lower end of the rotating shaft 7 described later interposed therebetween.

Reference numeral 7 denotes a rotating shaft fixed to the center of the upper portion of the rotor 6. The rotating shaft 7 is suspended in the axial direction from a portion fixed to the rotor 6, and the upper magnetic bearing 9 and the lower magnetic bearing 9 are arranged in order from the upper portion. A radial load is supported by the bearing 10, and a thrust disk 7 a made of a disk-shaped magnetic plate provided at the lower end is sandwiched by the thrust magnetic bearing 11.
Aerial maintenance control in the thrust direction (axial direction) is performed.

A rotor 12b is fixed to the rotor 6 and the rotating shaft 7 so as to face a stator 12a of the motor 12 provided between the upper magnetic bearing 9 and the lower magnetic bearing 10.

An upper protection bearing 19 is provided above the upper magnetic bearing 9 of the rotary shaft 7, and a radial interval between the rotary shaft 7 and the upper protection bearing 19 is set to a required value. I have. Further, the lower protective bearing 20 is provided below the lower magnetic bearing 10 of the rotating shaft 7, and the radial and thrust intervals between the rotating shaft 7 and the lower protective bearing 20 are set to required values. ing.

Next, an upper magnetic bearing 9 and a lower magnetic bearing 10
Is in a plane orthogonal to the axis (Z-axis) of the rotating shaft 7,
A pair is provided in each of the left-right (X-axis) and front-rear (Y-axis) directions, so that the rotary shaft 7 can be maintained in the air on the center axis without falling down (see FIG. 5B). .
Therefore, the rotating shaft 7 is moved in the left-right (X-axis) and front-rear (Y-axis) directions by the upper magnetic bearing 9 and the lower magnetic bearing 10.
The axial center (Z axis) direction is set by the thrust magnetic bearing 11,
That is, the five axis directions are supported in the air, and the rotation is controlled.

During operation of the turbo molecular pump constructed as described above, the magnetic bearings 9, 10, and 11 are energized to keep the pump rotating parts such as the rotary shaft 7 and the rotor 6 having the moving blades 5 in the air. In this state, the motor 12 is driven to rotate the pump rotating unit at a high speed of, for example, 10,000 to 100,000 rpm. Due to the high speed rotation of the pump rotating part, the moving blade 5
And the thread pump stage 8 is
After the gas to be evacuated is compressed in the first stage between the moving blades 5 and the stationary blades 4 from the upper gas inlet 2 by rotating while facing the inner peripheral surface of the screw groove 4, the screw groove is formed. The second stage compression takes place in the spiral groove passage of the pump stage 8 and flows in the direction of the outlet 3 via the gas passage in the pump,
The gas inlet 2 side is maintained at a high vacuum.

When the magnetic control of the upper and lower magnetic bearings 9 and 10 and the thrust magnetic bearing 11 becomes abnormal and the rotary shaft 7 is eccentric to one side, the upper protection bearing 19 and the lower protection bearing 20 When the outer periphery of the rotating shaft 7 abuts (touch-down), the rotating shaft 7 and the rotor 6
To compensate for rotation.

[0011]

The magnetic bearing 9,
Abnormalities in the magnetic controls 10 and 11 include, for example, control circuit failure, cable disconnection, poor connector contact, and the like.
In other words, the clearance between the protective bearings 19, 20 and the rotating shaft 7 is normally maintained in the air by the magnetic bearings 9, 10, 11 and within the range of variation, the rotating shaft 7
The design gap is set such that the rotor blades 5 do not contact the stationary blades 4 even when the rotating shaft 7 contacts the protective bearings 19 and 20 due to the magnetic control abnormality without contacting the protective bearings 19 and 20. Is done.

However, the protection bearing has a configuration in which the rotating shaft 7 is supported at two points vertically by the upper protecting bearing 19 and the lower protecting bearing 20, but the rotor blade 5 is large at the upper end of the rotating shaft 7 as described above. Since the center of gravity of the rotating shaft 7 is on the upper end side, the magnetic bearings 9, 10, 1
When the magnetic restraining force is released, the rotating shaft 7 randomly swings in the clearance, and rotates while repeatedly colliding with the inner periphery of the protective bearing.

With the repetition of the impact, the vibration of the rotary shaft 7 is repeated, and the moving blade 5 fitted in the comb-like shape in the stationary blade 4 vibrates and resonates following the vibration, and The run-out of the moving blade 5 is a clearance (compression space) between the stationary blade moving blades.
The blade 5 and the stationary blade 4 come into contact with each other,
There is a risk of damage. Also, on the protective bearing side, the bearing is deformed by the collision of the rotating shaft 7 to cause backlash (increase in the clearance). As a result, the design gap between the moving blades 5 and the stationary blades 4 cannot be guaranteed. The moving blades 5 and the stationary blades 4 may come into contact with each other, leading to breakage.

The present invention has been made in view of the above-mentioned technical problems, and even when abnormal vibration of a rotor including a moving blade and a rotating shaft or abnormality of a power supply control unit of a magnetic bearing occurs, the moving blade and the stationary blade come into contact with each other. An object of the present invention is to provide a turbo molecular pump protection operation method capable of guaranteeing rotation of the turbo molecular pump while eliminating the possibility of breakage.

[0015]

In order to solve the above-mentioned problem, the invention according to the first aspect of the present invention is to provide a rotary shaft having a moving blade at one end while maintaining the rotary shaft in the air by controlling the energization of a magnetic bearing. In the method of protecting a turbo-molecular pump for rotating and moving a moving blade and exhausting and compressing a gas between the moving blade and a stationary blade, an abnormal vibration of a rotor including the moving blade and a rotating shaft or an energization control unit of a magnetic bearing. An abnormality is detected, and the rotary shaft is forcibly moved to one side in the radial or / and thrust direction based on the detection signal, and the rotary shaft is rotatably contacted and supported by a support located on the one side. And

That is, according to the present invention, in the case of abnormal vibration of the rotor including the rotor blades and the rotating shaft or abnormality of the power supply control section of the magnetic bearing, the rotating shaft randomly fluctuates in the clearance between the rotating shaft and the protective bearing. In order to prevent movement, the rotary shaft is forcibly moved to one side in the radial or / and thrust direction based on the abnormality detection signal, and the rotary shaft is rotatably supported by a support located on the one side. Is to let
The forcible moving means may use a magnetic attraction force as described in claim 4, or may use an elastic force such as a spring. Further, the one-side supporting portion may use a protective bearing as described in claim 4, or the surface of the electromagnet constituting the magnetic bearing may be processed by a fluororesin to support the surface.

The forcible movement may be performed only in the radial direction. However, if there is play in the thrust direction, the moving blades and the stationary blades are arranged in a comb-teeth shape, so that they come close to each other. Even if the positions are fixed, there is a risk that they will come into contact with each other. In such a case, as described in claim 3, the rotation shaft is supported by one point in the thrust direction and two points above and below the rotation axis in the radial direction, and is supported by a so-called three-point support. The disadvantage can be eliminated.

A fourth aspect of the present invention relates to an apparatus for effectively implementing the first aspect of the present invention.
In the turbo-molecular pump having the above-described configuration, means for detecting abnormal vibration of the rotor including the rotor blades and the rotating shaft or abnormality of the power supply control unit of the magnetic bearing, and a protective bearing loosely fitted with a predetermined clearance to the rotating shaft. Voltage switching means for supplying an energizing voltage to the magnetic bearing based on the detection signal from a system different from the energizing control unit, and protecting the rotating shaft by a magnetic attraction of the magnetic bearing by the switching means. It is characterized in that it is forcibly moved to one side of the bearing, and the rotating shaft is rotatably contacted and supported by the protective bearing.

According to a second aspect of the present invention, in the method for protecting the turbo-molecular pump, the abnormal vibration of the rotor including the rotor blades and the rotating shaft or the abnormality of the power supply control unit of the magnetic bearing is related to the relationship between the amount of vibration and time. In the first abnormality and the second abnormality is detected and determined, and in the first abnormality detection, an alarm is sounded or displayed while the rotation of the rotating shaft in the air-maintaining state is continued, and in the second abnormality detection, The rotary shaft is forcibly moved to one side in a radial or / and thrust direction based on the second abnormality detection signal, and the rotary shaft is rotatably contacted and supported by a support portion located on the one side. The protective operation method of the turbo molecular pump described above.

According to this invention, when the air bearing is stopped immediately by the magnetic bearing when the abnormal signal is detected and the bearing is supported by the contact support by a mechanical bearing such as a radial ball bearing, the number of rotations is greatly increased. In particular, if a rapid rotation down occurs during the formation of an oxide film or a CVD film while flowing a reaction gas such as silane through a wafer in a semiconductor manufacturing apparatus, the wafer in the batch process becomes defective. If the pump is left as it is without taking the protective action described in claim 1, the destruction of the pump not only leads to damage to other semiconductor equipment, but also toxic gas such as silane flows to the outside, which is dangerous. . Furthermore, when a light abnormality signal is issued, an instantaneous abnormality may necessarily occur due to external noise, and it is necessary to eliminate such a malfunction. On the other hand, in the case of a heavy abnormality, unless the protection operation is immediately started, the moving blades and the stationary blades may come into contact with each other and may be damaged.

Therefore, the present invention classifies the abnormalities into light abnormalities in which the moving blade and the stationary blade do not come into contact with each other and heavy abnormalities in which the moving blades and the stationary blade may come into contact with each other. In the case where the first abnormality (light abnormality) and the second abnormality (heavy abnormality) are discriminated and detected and a light abnormality signal is issued, an instantaneous abnormality may necessarily be caused by external noise. In order to eliminate a malfunction, for example, it is determined whether or not the light abnormal signal continues for about 2 seconds, and if it continues, an alarm is sounded or displayed to alert the operator,
At that time, take measures such as lowering the pressure or switching to a backup pump.

Even if the above countermeasures are taken, if a serious abnormality occurs before taking the countermeasures, unless the protection operation is immediately started, the moving blades and the stationary blades may come into contact with each other, possibly leading to breakage. Therefore, in the case of a serious abnormality, the abnormality is immediately determined to be abnormal, and the rotary shaft is forcibly moved to one side in the radial or / and thrust direction based on the second abnormality detection signal, and is rotated by the support portion located on the one side. By rotatably contacting the shaft, the rotating blade and the stationary blade come into contact with each other, and rotation of the turbo-molecular pump can be guaranteed while eliminating the possibility of damage.

A fifth aspect of the present invention relates to an apparatus for effectively implementing the first aspect of the present invention.
In the turbo-molecular pump having the above-described configuration, abnormal vibration of the rotor including the rotor blade and the rotating shaft or abnormality of the power supply control unit of the magnetic bearing is determined as a first abnormality and a second abnormality in relation to the amount of vibration and time. Means for detecting, means for sounding or displaying an alarm, a protective bearing loosely fitted with a predetermined clearance to the rotating shaft, and an energizing control unit for applying an energizing voltage to the magnetic bearing based on the detection signal. A voltage switching unit supplied from another system, wherein in the first abnormality detection, an alarm is sounded or displayed while the rotation of the rotary shaft in the air-maintaining state is continued, and in the second abnormality detection, the second abnormality is detected. The switching means is operated on the basis of the abnormality detection signal, and the rotating shaft is forcibly moved to one side of the protection bearing by the magnetic attraction force of the magnetic bearing by the switching means, and is rotated by the protection bearing. And characterized in that rotatably contact support the shaft.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

FIG. 1 shows a block diagram of a main part of a pump unit A and a power supply unit B of a turbo-molecular pump according to an embodiment of the present invention, in which an alarm display based on vibration detection and a protection operation of a rotating shaft are set. It is a block diagram. FIG.
FIG. 2 is a cross-sectional view illustrating a main part configuration of the turbo-molecular pump according to the embodiment of the present invention, showing a state before abnormality detection. FIG. 3A is an enlarged view of a main part of the protection operation of the rotating shaft after the abnormality is detected, and is a corresponding view of FIG. 2, FIG. 3B is a view of FIG.
(A) is an enlarged view of a circle portion. FIG. 4 is a block diagram showing a flow of an alarm display based on vibration detection and a protection operation of the rotating shaft. FIG. 5 is an overall sectional view of a turbo-molecular pump to which the present invention is applied.

First, in order to facilitate understanding of this embodiment,
Protective bearing for the rotating shaft 7 and the support cylinder 17 according to FIGS.
19, 20 and magnetic bearings 9, 10, 11
This will be briefly described. 17 is fixed to the lower casing 16
And a cylindrical support cylinder projecting upward,
In the inner circumference of the upper part, in order from the top,
Protection bearing 19, position sensor 24, upper part which is a radial bearing
One side left and right electromagnet part 9R of the magnetic bearing 9 ₁, 9L₁, Motor 1
2 and a radial bearing (not shown).
Left and right electromagnets 10R on one side of the lower magnetic bearing 10₁, 10
L₁, Lower protective bearing 20 consisting of a radial ball bearing,
Provided with a thrust disk 7a at the lower end of the rotating shaft 7
Upper and lower electromagnet portions 11U, 1 of the separated thrust magnetic bearing 11
1L is provided.

On the other hand, the rotating shaft 7 is provided on the other left and right electromagnet portions 9R ₂ and 9L ₂ on the other side of the upper magnetic bearing 9, the other left and right electromagnet portions 10R ₂ and 10L ₂ on the other side of the lower magnetic bearing 10 and the lower end in order from the top. Thrust disk 7a made of a disk-shaped magnetic plate
The thrust disk 7a is sandwiched between the upper and lower electromagnets 11U and 11L of the thrust magnetic bearing 11 to perform aerial maintenance control in the thrust direction (axial direction).

As shown in FIGS. 1 and 5, the upper magnetic bearing 9 and the lower magnetic bearing 10 are provided with an axis (Z
Axis), a pair is provided in each of the left-right (X-axis) and front-rear (Y-axis) directions, so that the rotating shaft 7 can be maintained in the air on the center axis without falling down. I have. Therefore, the rotating shaft 7 is moved in the left-right (X-axis) and front-rear (Y-axis) directions by the one-side electromagnet portion 9 of the upper magnetic bearing and the one-side electromagnet portion 10 of the lower magnetic bearing. The electromagnet section 11 supports the axis (Z axis) direction, that is, the five axis directions, in the air, and rotates in a controlled manner.

Returning to the original, the upper magnetic bearing 9 of the rotating shaft 7
The upper protection bearings 19 are provided above the one-side electromagnet portions 9R ₂ and 9L ₂ , and the distance between the rotary shaft 7 and the upper protection bearings 19 is set to a required value α ₁ . Further, the rotating shaft 7
The lower protective bearing 20 is provided below the one-side electromagnet section 10 of the lower magnetic bearing 10, and the interval between the rotating shaft 7 and the lower protective bearing 20 is set to a required value α ₁ .

The electromagnet portions 9R ₁ and 9R ₂ , 9L ₁ and 9L ₂ , 10R ₁ and 10R ₂ , 1 located between the support cylinder 17 and the rotating shaft 7
The clearance β ₁ between 0L ₁ and 10L ₂ is increased
Than the distance alpha ₁ between 9,20 and set to a large (β _{1> α 1),} as shown in FIG. 3, when the rotary shaft 7 is in contact with the protection bearings 19 and 20, the electromagnet portion 9R ₁ 9R ₂ , 10R ₁ and 10
R ₂ is set so spaced (β ₁ -α _1).

As shown in FIG. 3, the distance α ₂ between the upper surface of the protection bearing 20 located at the small diameter portion 7b of the rotary shaft 7 and the upper step surface 7c of the small diameter portion 7b is set at the lower end of the rotary shaft 7. The clearance (β ₂ −α ₂ ) is set to be smaller than the clearance β ₂ between the lower surface of the thrust disk 7 a formed of a disk-shaped magnetic plate and the lower electromagnet portion 11 L of the thrust magnetic bearing.

According to this embodiment, as will be described later in detail, when the amplitude of the rotating shaft or the moving blade portion detected by the position displacement sensor or the like is 125 μm and continues for 0.5 seconds or more, 9R ₁ and 10R _{1 of} the electromagnet portion of the magnetic bearing located between the support cylinder 17 and the rotating shaft 7 attract 9R ₂ and 10R ₂ , and 9L ₁ and 9L ₂ , 10L ₁ and 10L ₂
As shown in FIG. 3, the rotating shaft is forcibly moved to the right in the radial direction by magnetic attraction force to reduce the attraction of the electromagnets 9R ₁ and 9R.
For clearance beta ₁ of R _2, 10R ₁ and 10R ₂ is set to a large (β _{1> α 1)} than the distance alpha ₁ between the protective bearings 19 and 20, the electromagnet portion 9R ₁ and 9R _2, 10R ₁ and 1
In a state where 0R ₂ is separated (β ₁ -α _1), to the rotating shaft 7 is in contact with the protection bearings 19 and 20, the rotation of the rotary shaft 7 is smoothly ensured by protective bearings 19, 20 .

As shown in FIG. 3, by energizing only the lower electromagnet portion 11L of the thrust magnetic bearing 7a and deenergizing the upper electromagnet portion 11U, the rotating shaft 7 is moved downward by magnetic attraction. Side, thereby maintaining a clearance (β ₂ −α ₂ ) between the lower surface of the thrust disk 7a and the lower electromagnet portion 11L of the thrust magnetic bearing, while protecting the rotary shaft 7 at the small diameter portion 7b. The upper surface of the bearing 20 and the upper step surface 7c of the small diameter portion 7b are engaged, and the position of the rotating shaft 7 is fixed while being smoothly assured by the protective bearing 20. As a result, the rotation shaft 7 is supported at one point in the thrust direction and at two points above and below the rotation shaft in the radial direction, and the position of the rotation shaft 7 is fixed while so-called three-point support ensures rotation of the rotation shaft 7. .

FIG. 1 is a block diagram of such a point as a circuit configuration, and FIG. 4 is a flowchart illustrating the operation thereof. First, the amplitude amount detected by the position displacement sensor or the independent vibration sensor 30 from the pump main body A side is input to the comparators 31A and 31B.

The comparator 31A compares the signal with a signal from the reference voltage generator 32A corresponding to the reference amplitude of 50 μm, and sends a comparison output to the judging means 33A when the detected amplitude is 50 μm or more. (S1)

On the other hand, the comparator 31B has a reference amplitude of 125 μm.
The signal is compared with a signal from the reference voltage generator 32B corresponding to m, and when the detected amplitude is 125 μm or more, a comparison output is sent to the judgment means 33B. (S2) The reference amplitude of the comparator 31B is set to 125 μm in correspondence with the interval α ₁ between the rotating shaft 7 and the protective bearings 19 and 20 (α ₁ : 125 μm).

In the determination means 33A, if the comparison output from the comparator 31A, in other words, the detected amplitude amount of 50 μm or more continues for 2 seconds or more (S4), it is determined that the magnetic bearing power supply control circuit or the like is faulty. Judgment is made to sound an alarm or display 35 is performed (S5). 34A is a timer.

In the judgment means 33B, the comparator 31B
The comparison output, in other words, the detected amplitude amount 125 μm
In the above case, more specifically, when the operation continues for 0.5 seconds (S6), it is determined that the rotor blade 5 is damaged, and the energization control of the drive power supply 36 of the magnetic bearings 9, 10, 11 is performed. In the drive control circuit 37 that performs the operation, the inverter control that normally maintains the rotary shaft 7 in the air is switched to the rectifier circuit (S
7), to cut the power in the Y-axis direction side of the electromagnet 9YU ₁ ~9YL ₂ for magnetic bearing of the radial direction, of the electromagnet of the Χ axis side, and 9Kaiaru _1, so 9Kaiaru ₂ with each other by suction, by also applying a current to the suction of 9 L ₁ and 9 L ₂ decreases (as well as the lower magnetic bearings), the rotary shaft is moved forcibly in the drawing the right direction in the radial direction by the magnetic attraction force, the electromagnet portion 9R ₁ and in a state where 9R ₂ is separated (β ₁ -α _1), to the rotating shaft 7 is in contact with the protection bearings 19 and 20, the rotation of the rotary shaft 7 is smoothly ensured by protective bearings 19, 20 You. 34B is a timer.

In the thrust magnetic bearing 11, only the lower electromagnet portion 11L is energized, and the upper electromagnet portion 11U
, The rotating shaft 7 is forcibly moved downward by the magnetic attraction force, thereby maintaining the clearance (β ₂ −α ₂ ) while maintaining the clearance (β ₂ −α ₂ ) at the small diameter portion 7 b of the rotating shaft 7. The upper surface of the protective bearing 20 and the upper step surface 7c of the small-diameter portion 7b engage with each other, and the rotation of the rotating shaft 7 is fixed by the protective bearing 20 while being smoothly assured.

As a result, the rotation shaft is supported at one point in the thrust direction and at two points above and below the rotation shaft in the radial direction. Becomes

[0041]

As described above, according to the first and third aspects of the present invention, the rotary shaft is forcibly moved to one side in the radial or / and thrust direction based on the abnormal vibration detection signal of the rotor. In order to rotatably support the rotating shaft with the support located on one side, even if abnormal vibration of the rotor including the moving blade and the rotating shaft or abnormality of the power supply control unit of the magnetic bearing occurs, the moving blade and the stationary blade Contact with each other to ensure the rotation of the turbo-molecular pump while eliminating the risk of breakage.

The forcible movement may be performed only in the radial direction. However, if there is backlash in the thrust direction, the moving blades and the stationary blades are arranged in a comb shape, so that they come close to each other. Even if the positions are fixed, there is a risk that they will come into contact with each other. In such a case, as described in claim 3, the rotation shaft is supported by one point in the thrust direction and two points above and below the rotation axis in the radial direction, and is supported by a so-called three-point support. The disadvantage can be eliminated.

According to the second and fifth aspects of the present invention, the present invention classifies the abnormalities into light abnormalities in which the moving blade and the stationary blade do not come into contact with each other and heavy abnormalities in which the moving blade and the stationary blade may come into contact with each other. In the case of, the vibration detection time is discriminated and detected as a first abnormality (light abnormality) and a second abnormality (heavy abnormality) in relation to time, and when a light abnormality signal is issued, it is not necessarily instantaneous due to external noise. In order to eliminate such a malfunction, it is determined whether or not the light abnormality signal continues for about 2 seconds, and if so, an alarm is sounded or displayed, and attention is paid to the operator. In the case of a heavy abnormality, the abnormality is immediately judged to be abnormal, and the rotary shaft is forcibly moved to one side in the radial or / and thrust direction based on the second abnormality detection signal, and the support located on the one side is The rotation of the rotating shaft is supported by the And stationary vanes in contact, may guarantee the rotation of the turbo-molecular pump while eliminating the risk to failure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part block configuration of a pump unit A and a power supply unit B of a turbo-molecular pump according to an embodiment of the present invention, in which an alarm display based on vibration detection and a rotation axis protection operation are set. is there.

FIG. 2 is a cross-sectional view showing a configuration of a main part of the turbo-molecular pump according to the embodiment of the present invention, showing a state before abnormality detection.

3A is an enlarged view of a main part of the operation of protecting the rotating shaft after detecting an abnormality, and is a corresponding view of FIG. 2, FIG. 3B is a view of FIG. 2A as viewed from above, and FIG. It is an enlarged view of the circle part of ().

FIG. 4 is a block diagram showing a flow of an alarm display based on vibration detection and a protection operation of a rotating shaft.

FIG. 5 is an overall sectional view of a turbo-molecular pump to which the present invention is applied.

[Explanation of symbols]

 Reference Signs List A pump main body B power supply unit 5 rotor blade 7 rotating shaft 7b small-diameter portion of rotating shaft 7c upper step surface of small-diameter portion 9 upper magnetic bearing 10 lower magnetic bearing 11 thrust magnetic bearing (electromagnet) 19, 20 protective bearing 30 vibration sensor 31A, 31B Comparator 32A, 32B Reference voltage generator 33A, 33B Judging means 36 Drive power supply 37 Drive control circuit

Claims (5)

[Claims] In a state where a rotating shaft having a moving blade at one end is maintained in the air by energizing control of a magnetic bearing, the moving blade is rotated through the rotating shaft to exhaust and compress gas with the stationary blade. In the method for performing a protective operation of a turbo-molecular pump to be performed, abnormal vibration of a rotor including the rotor blades and the rotating shaft or abnormality of a power supply control unit of a magnetic bearing is detected, and the rotating shaft is radially and / or thrusted based on the detection signal. A protective operation method for a turbo-molecular pump, comprising: forcibly moving the rotary shaft in one side in the direction, and rotatably contacting and supporting the rotation shaft by a support portion located on the one side. In a state where a rotating shaft having a moving blade at one end is maintained in the air by energizing control of a magnetic bearing, the moving blade is rotated through the rotating shaft to exhaust and compress gas with the stationary blade. In the protection operation method of the turbo-molecular pump to be performed, the abnormal vibration of the rotor including the rotor blade and the rotating shaft or the abnormality of the power supply control unit of the magnetic bearing, the first abnormality and the second abnormality in relation to the amount of vibration and time. In the first abnormality detection, an alarm is sounded or displayed while the rotation shaft keeps rotating in the air-maintaining state, and the second abnormality detection is performed based on the second abnormality detection signal. Wherein the rotating shaft is forcibly moved to one side in a radial or / and thrust direction, and the rotating shaft is rotatably contacted and supported by a support located on the one side. 3. The method according to claim 1, wherein the rotary shaft is supported at one point in the thrust direction and at two points above and below the rotary shaft in the radial direction. 4. A rotating shaft having a moving blade at one end thereof is maintained in the air by energizing control of a magnetic bearing, and the moving blade is rotated via the rotating shaft to exhaust and compress gas with the stationary blade. In the turbo-molecular pump to be performed, means for detecting abnormal vibration of the rotor including the rotor blades and the rotating shaft or abnormality of the power supply control unit of the magnetic bearing; and a protective bearing loosely fitted with a predetermined clearance to the rotating shaft; A voltage switching means for supplying an energizing voltage to the magnetic bearing based on a detection signal from a different system from the energizing control unit, and a magnetic attraction force of the magnetic bearing by the switching means.
A turbo-molecular pump wherein a rotating shaft is forcibly moved to one side of a protective bearing, and the rotating shaft is rotatably contacted and supported by the protective bearing. 5. A rotating shaft having a moving blade at one end is maintained in the air by energization control of a magnetic bearing, and the moving blade is rotated via the rotating shaft to exhaust and compress gas with the stationary blade. In the turbo molecular pump to be performed, abnormal vibration of the rotor including the rotor blade and the rotating shaft or abnormality of the power supply control unit of the magnetic bearing is discriminated and detected as a first abnormality and a second abnormality in relation to the amount of vibration and time. Means, a means for sounding or displaying an alarm, a protection bearing loosely fitted with a predetermined clearance to the rotating shaft, and a system different from the conduction control unit for supplying an energizing voltage to the magnetic bearing based on the detection signal. And a voltage switching means supplied from the controller. In the first abnormality detection, an alarm is sounded or displayed while the rotation of the rotary shaft in the air-maintenance state is continued, and the second abnormality is detected in the second abnormality detection. The switching means is operated based on the normal detection signal, and the rotating shaft is forcibly moved to one side of the protection bearing by the magnetic attraction of the magnetic bearing by the switching means, and the rotating shaft is rotatably contacted by the protection bearing. A turbo-molecular pump characterized by being supported.