JP2601485Y2 - Magnetic bearing device - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to a magnetic bearing device,
For example, the present invention relates to a magnetic bearing device used for a turbo molecular pump, a spindle, and the like.

[0002]

2. Description of the Related Art In recent years, for example, in a turbo molecular pump or the like which is used in a place where a high clean environment is required such as IC manufacturing, a rotor is levitated by the magnetic force of an electromagnet,
A magnetic bearing device that holds this in a non-contact manner is used.

FIG. 4 shows a schematic configuration of a magnetic bearing device. In this magnetic bearing device, the rotor 10 is magnetically levitated by the magnetic force generated by the electromagnets 11a, 11b and 12a, 12b. The position of the rotor 10 is detected by position sensors 14a, 14b, 15a, and 15b, and the detected value is supplied to a control circuit (not shown). The floating position of the rotor 10 is determined by the electromagnets 11 a and 11
By controlling the exciting currents b, 12a, and 12b, a predetermined position (control center) is maintained.

The electromagnets 11a and 11b and the electromagnets 12a and
2b, the electromagnets 11a, 11b and 12a, 1
Protective bearings 16 and 17 each having an inner diameter smaller than 2b and an inner diameter larger than the rotor 10 are provided, and the rotor 10 is directly connected to the electromagnets 11a, 11b and 12a and 12a.
b. The rotor 10 magnetically levitated at a predetermined position is rotated at a high speed by a motor 18.

In such a magnetic bearing device, the rotor 10
If a failure occurs in the control circuit during rotation of
When excessive vibration, impact, or the like is applied from the outside, the control becomes impossible and the rotor 10 may swing largely. Also, when the rotor 10 is rotated from the stop state to the rated rotation speed, the rotor 10 must pass through the resonance point in the process, so that the rotor 10 may swing largely.

By the way, the whirling of the rotor 10 includes a whirling in a cylindrical mode and a whirling in a conical mode. Must pass through the resonance point of the mode.

FIGS. 5 and 6 show whirling of the rotor 10 in the cylindrical mode and the conical mode, respectively. In the figure, x _Ph and x _Pb are:
The displacement of the center of the rotor 10 from the control center O at the mounting position of the protective bearings 16 and 17 is represented by x _Sh ,
x _Sb is the position sensors 14a and 14b and the position sensor 15
The displacement of the center of the rotor 10 from the control center O at the mounting positions of a and 15b is shown.

In the cylindrical mode shown in FIG. 5, the rotor 10 oscillates as indicated by arrows A and A 'with substantially equal amplitudes (rotational radii) at respective portions thereof. That is, it oscillates in a relationship of x _Ph ≒ x _Sh ≒ x _Sb ≒ x _Pb . On the other hand, in the conical mode of FIG. 6, the rotor 10 increases the amplitude of the whirling (rotation radius) at both ends of the rotor 10 with a certain point C as a fixed point, as indicated by arrows B and B '. Swing around. That is, [x _Ph ]>
It swings in the relationship of [x _Sh ], [x _Pb ]> [x _Sb ].

However, the displacements x _Ph , x _Pb and x _Sh , x _Sb are:
When the rotor 10 swings upward from the control center O, it takes a positive value, and when it swings downward, it takes a negative value.
In this specification, [n] represents the absolute value of n. In the whirling as described above, when the amplitude is further increased, the rotor 10 is moved to the protective bearings 16 and 1.
7 comes into contact. Protective bearings 16, 17
Is provided in consideration of such a case. However, if the rotor 10 rotates at a high speed at the time of contact, or if such a contact state continues for a long time even at a low speed, protection is provided. The bearings 16 and 17 are significantly worn. Finally, the protective bearings 16, 1
There is a possibility that the rotor 7 itself may be damaged due to galling.

Therefore, in order to prevent such damage to the rotor 10, in the magnetic bearing device, when the amplitude of the whirling becomes larger as the rotor 10 comes into contact with the protective bearings 16 and 17, this is judged as a large disturbance. Thus, the rotation of the rotor 10 is immediately stopped.

However, the determination of the disturbance is made by each position sensor 14.
By monitoring the amplitude of the whirling of the rotor 10 by a, 14b and 15a, 15b, the detection is performed based on the displacements x _Sh , x _Sb which are the detected values. That is, displacement x _Sh ,
Whether or not x _Sb is larger than a predetermined amplitude value (threshold value) is determined as a large disturbance.

However, due to structural limitations of the magnetic bearing device, the position sensors 14a, 14b and 15a, 15b
In the conical mode as shown in FIG. 6, the displacement x
_Sh and _xSb are smaller than the actual whirling amplitudes near the protective bearings 16 and 17, that is, smaller than the displacements _xPh and _xPb .

Therefore, the rotor 10 is mounted on the protective bearing 1.
In order to judge a large disturbance based on the displacements x _Sh and x _{Sb on} the condition that the displacements x _Sh and x _Sb do not come into contact with the contact points 6 and 17, the displacement x when the displacements x _Ph and x _Pb take the maximum value in the conical mode.
It is necessary to set _Sh and x _Sb as threshold values. Conventionally, a large disturbance is determined based on the threshold value set based on the whirling in the conical mode.

[0014]

However, when a large disturbance is determined on the basis of the conical mode as described above, the width of the threshold value is narrow. Therefore, when the rotor 10 swings in the cylindrical mode, the swing Although the rotation amplitude is not large enough to contact the protective bearings 16 and 17,
We judge that it is a great disturbance.

Therefore, in the prior art, the rotation of the rotor 10 was stopped even though no large disturbance actually occurred, so that the number of stops was large and efficiency in operating the apparatus was poor. Therefore, an object of the present invention is to provide a magnetic bearing device that can detect only whirling that may actually cause the rotor to come into contact with the protective bearing as a large disturbance, and can reduce the number of stops of the rotating body. is there.

[0016]

According to the present invention, magnetic generating means for magnetically levitating a cylindrical rotary body rotating about an axis to a predetermined position, and the rotary body levitated to a predetermined position by the magnetic generating means. A protection bearing disposed concentrically with the center of the shaft, position detection means for juxtaposing the protection bearing in the axial direction of the rotating body for detecting the position of the rotating body, and detection by the position detecting means. Distance calculating means for calculating a distance between the protective bearing and the rotating body from the detected value, and the distance between the protective bearing and the rotating body calculated by the distance calculating means is equal to or less than a predetermined value. The above object is achieved by providing a magnetic bearing device with stop command means for commanding the rotation of the rotating body to stop.

[0017]

In the magnetic bearing device described above, when the rotating body is magnetically levitated to a predetermined position by the magnetism generating means, the position detecting means detects the position of the rotating body, and based on the detected value, the distance calculating means determines the distance between the bearing and the bearing. Calculate the distance to the rotating body. When the calculated distance becomes equal to or less than a predetermined value, the stop command means issues a command to stop the rotation of the rotating body.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic bearing device according to the present invention will be described below in detail with reference to FIGS. In addition,
The same components as those in the conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

FIG. 1 shows a part of the configuration of a magnetic bearing device according to an embodiment of the present invention. However, this magnetic bearing device controls the rotor 10 in four axes in the radial direction. However, since each shaft has the same configuration,
Only the configuration relating to single-axis control (for example, control in the X-axis direction) is illustrated, and the following description will focus on this configuration.

The magnetic bearing device includes position detection circuits 20a and 20b, an operation circuit 21, a protection sequence circuit 22, and an abnormality display circuit 23. Position detection circuits 20a, 20
b are position sensors 14a, 14b and 15a, respectively.
15b. The position detection circuit 20a detects a displacement x _{Sh of the} rotor 10 from output signals of the position sensors 14a and 14b. Position detection circuit 20
“b” detects the displacement x _Sb from the output signals of the position sensors 15a and 15b. This position detection circuit 2
Reference numerals 0a and 20b are connected to a control circuit (not shown) for controlling the position of the rotor 10, and the detected displacements x _Sh and x _Sb
Is supplied to a control circuit (not shown).

On the other hand, the displacements x _Sh and x _Sb are also supplied to the arithmetic circuit 21 as displacement signals. , The displacements x _Ph and x _Pb of the rotor 10 are calculated. The calculated values of the displacements x _Ph and x _Pb are sent to the protection sequence circuit 22.

The protection sequence circuit 22 monitors the whirling of the rotor 10 based on the displacements x _Ph and x _Pb from the arithmetic circuit 21 and performs a predetermined sequence control when it is determined that a large disturbance has occurred. It is. The protection sequence circuit 22 has a memory (not shown). This memory contains the protective bearing 1 when the rotor 10 swings around.
Under the condition that the rotor 10 does not come into contact with
The maximum amplitude value that can be taken (the maximum value that can be taken by the displacements x _Ph and x _Pb ) is stored as a threshold value. The determination as to whether or not a large disturbance has occurred is made based on the threshold value and the arithmetic circuit 21.
The comparison is made by comparing the actual displacements x _Ph and x _Pb calculated in the above.

Although not shown, the protection sequence circuit 22 is connected to a drive control system of the motor 18.
When a large disturbance is detected, a control signal for instructing the stop of the motor 18 is sent to this. On the other hand, the protection sequence circuit 22 is also connected to the abnormality display circuit 23, and when a large disturbance is detected, supplies a signal notifying the detection of the large disturbance to the abnormality display circuit 23.
Thus, the abnormality display circuit 23 informs the operator of the abnormality, for example, by turning on a warning lamp.

FIG. 2 shows the displacements x _Ph , x _Pb and x _Sh , x _Sb.
Represents the distance from the center line O 'of the position where the occurrence occurs. However, the center line O 'represents a position equidistant from the position sensors 14a and 14b and the position sensors 15a and 15b, l _Ph represents the distance from the protection bearing 16 to the center line O', and l _Pb represents the protection bearing. 17 represents the distance from the center line O ′. l _S is the position sensor 14a, 14b
And the distance between the position sensors 15a and 15b.

When the distance from the center line O 'at each position is determined as described above, these relationships are as follows. _{x Ph = (x Sh + x} Sb) / 2 + (x Sh -x Sb) l Ph / l S ... (1) x Pb = (x Sh + x Sb) / 2- (x Sh -x Sb) l Pb / l _S ... (2) The arithmetic circuit 21 calculates, based on the above equations (1) and (2),
The value x _Sh of the displacement signal from the position detection circuits 20a and 20b,
By calculating x _Sb , displacements x _Ph and x _Pb of the rotor 10 at the mounting positions of the protective bearings 16 and 17 are obtained.

FIG. 3 shows an operation circuit 2 for performing such an operation.
1 shows a detailed configuration. That is, the arithmetic circuit 21
Are arithmetic units 30 and 35 for performing addition processing, and arithmetic units 32 and 36 for performing subtraction processing, respectively, １ ／, l _Ph / l _S ,
Computing units 31, 33, and 34 for multiplying the value of l _Pb / l _S are provided.

Next, the operation of the embodiment configured as described above will be described. As is well known, the rotor 10 is connected to the electromagnet 11
When magnetically levitated by a, 11b and 12a, 12b, etc., and rotated by the motor 18, the rotor 10 may swing largely at the resonance point. The whirling of the rotor 10 at this time is caused by the position sensors 14a, 14b and 1
5a, 15b, and the position detection circuit 20a,
At 20b, they are detected as displacements x _Sh and x _Sb respectively. Then, the displacements x _Sh and x _Sb are supplied to an arithmetic circuit 21, and the arithmetic circuit 21 performs the calculations of Expressions (1) and (2).

That is, the displacements x _Sh and x _Sb from the position detection circuits 20 a and 20 b are added by the computing unit 30 and subtracted by the computing unit 32. The addition value (x _Sh + x _Sb ) in the arithmetic unit 30 is 1 by the arithmetic unit 31.
/ 2. On the other hand, the subtraction value (x _Sh
−x _Sb ) is multiplied by a value of l _Ph / l _S in a computing unit 33 and is also multiplied by a value of l _Pb / l _{S in} a computing unit 34. The value calculated by the calculator 31 ((x _Sh + x _Sb ) /
2) and the value calculated by the calculator 33 ((x _Sh -x _Sb ) l _Ph
/ L _s ) is added by the computing unit 35 to obtain a displacement x _Ph .
On the other hand, the arithmetic unit 36 subtracts the computed value calculator _{31 ((x Sh + x Sb} ) / 2) values calculated by the calculator 34 from _{((x Sh -x Sb) x} Pb / l S) An operation is performed to obtain a displacement _xPb .

[0029] by the arithmetic circuit 21, the displacement x _Ph, when x _Pb is obtained, protection sequence circuit 22, the displacement x _Ph,
It is determined whether or not x _Pb is larger than a threshold value stored in a memory (not shown). If smaller than the threshold value, monitoring of the whirling is continued.

On the other hand, if it is equal to or greater than the threshold value, it is determined that a large disturbance has occurred, and the protection sequence circuit 22
A control signal for instructing the control circuit 8 to stop the rotation of the motor 18 is transmitted. Further, a signal is sent to the abnormality display circuit 23 to turn on a warning lamp or the like. As a result, the motor 18 is stopped, and the rotor 10 is prevented from coming into contact with the protective bearings 16 and 17 due to a large disturbance. On the other hand, the operator knows the abnormality by watching the lighting of the warning lamp.

As described above, in the magnetic bearing device according to the present embodiment, the protection bearings 16, 1 and 2 are subjected to the arithmetic processing represented by the equations (1) and (2) on the displacements x _Sh and x _Sb.
Since the amplitude of whirling of the rotating body at the mounting position of 7 is detected, the maximum whirling amplitude can be allowed within a range where the rotor 10 does not contact the protective bearings 16 and 17. That is, the threshold value for detecting a large disturbance can be set to be larger than in the related art regardless of the whirling mode.

This makes it easier to pass the resonance point when the rotor 10 is in rated operation from the stopped state, and reduces the number of times the rotating body is stopped by detecting a large disturbance, so that the apparatus can be operated efficiently. The magnetic bearing device according to the embodiment of the present invention has been described above.
The present invention is not limited to this, and various modifications are possible based on the technical idea of the present invention.

For example, in the above embodiment, the magnetic bearing device
Although the rotor 10 is controlled by four axes in the radial direction, a magnetic bearing device of a type by which two axes are controlled may be used. Also, the electromagnets 11a, 11b and 12a, 1
The present invention is applicable to a case where a permanent magnet is used instead of 2b.

Also, in the above embodiment, the protection sequence circuit 22 determines a large disturbance by the arithmetic circuit 21 _obtaining the displacements x _Ph and x _Pb from the displacements x _Sh and x _{Sb of the} rotor 10. The arithmetic circuit 21 calculates the distance between the rotor 10 and the protective bearings 16 and 17 from the displacements x _Sh and x _Sb , and when this distance becomes equal to a predetermined value (substantially 0), it is determined that a large disturbance has occurred. May be.

In the above embodiment, the position sensor 14
a, 14b and 15a, 15b are protective bearings 16,
Although attached to the inside of 17, it may be attached to the outside.

[0036]

According to the magnetic bearing device of the present invention, large disturbance detection is determined based on the distance between the bearing and the rotating body obtained by performing a predetermined operation on the detection value of the position detecting means. It is possible to detect only whirling that may actually cause the rotating body to come into contact with the bearing as a large disturbance,
The number of stops of the rotating body due to the protection sequence at the time of detecting a large disturbance can be reduced, and the apparatus can be operated efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a magnetic bearing device according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing the amplitude of whirling in each part of a rotor of the magnetic bearing device and a positional relationship between the amplitudes.

FIG. 3 is an explanatory diagram showing details of an arithmetic circuit of the magnetic bearing device.

FIG. 4 is a sectional view schematically showing a conventional magnetic bearing device.

FIG. 5 is an explanatory diagram showing whirling of a rotor of the magnetic bearing device in a cylindrical mode.

FIG. 6 is an explanatory diagram showing whirling of the rotor of the magnetic bearing device in a conical mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotor 11a, 11b, 12a, 12b Electromagnet 14a, 14b, 15a, 15b Position sensor 16, 17 Protection bearing 20a 20b Position detection circuit 21 Operation circuit 22 Protection sequence circuit 30, 31, 32, 33, 34, 35, 36 Operation vessel

Claims (1)

(57) [Scope of request for utility model registration] 1. A magnetism generating means for magnetically levitating a cylindrical rotating body rotating about an axis to a predetermined position, and being arranged concentrically with an axis center of the rotating body levitated to a predetermined position by the magnetic generating means. A protective bearing provided, position detecting means for juxtaposing the protective bearing in the axial direction of the rotating body, and detecting a position of the rotating body; and a protective bearing based on a detection value detected by the position detecting means. Distance calculating means for calculating the distance between the rotating body and the rotating body; and when the distance between the protective bearing and the rotating body calculated by the distance calculating means becomes a predetermined value or less, the rotation of the rotating body is stopped. And a stop instruction means for instructing the magnetic bearing device.