JPH0678624U - Magnetic bearing device - Google Patents

Abstract

(57) [Summary] [Purpose] To detect the actual large disturbance only, reduce the number of times of rotation stop of the rotor due to the large disturbance detection, and operate the device efficiently. [Structure] Position sensors 14a, 14b and 15a, 15
The position detection circuits 20a and 20b obtain the displacements x _Sh and x _Sb of the rotor 10 at the mounting positions of the position sensors 14a, 14b and 15a, 15b from the detection signal of b. The arithmetic circuit 21 is adapted to obtain the displacements x _Ph and x _Pb of the rotor 10 at the mounting positions of the protective bearings by subjecting the displacements x _Sh and x _Sb to predetermined arithmetic processing. The protection sequence circuit 22 determines the displacement x _Ph ,
A large disturbance is judged based on x _Pb , and when it is judged that a large disturbance has occurred, a control signal for instructing rotation stop of the rotor 10 is output.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

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

[0002]

[Prior art]

 2. Description of the Related Art In recent years, in a place where a highly clean environment such as IC manufacturing is required, for example, in a turbo molecular pump, a magnetic bearing device that floats a rotor by the magnetic force of an electromagnet and holds it in a non-contact manner is used. Has been.

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, 15b, and the detected value is supplied to a control circuit (not shown). The floating position of the rotor 10 is maintained at a predetermined position (center of control) by controlling the exciting current of the electromagnets 11a, 11b and 12a, 12b by a control circuit (not shown).

Outside the electromagnets 11a and 11b and the electromagnets 12a and 12b, there are provided protective bearings 16 and 17 each having an inner diameter smaller than that of the electromagnets 11a, 11b and 12a and 12b, and larger than that of the rotor 10. The rotor 10 does not come into direct contact with the electromagnets 11a, 11b and 12a, 12b. The rotor 10 magnetically levitated at a predetermined position is rotated at high speed by a motor 18.

In such a magnetic bearing device, if a failure occurs in the control circuit or the like when the rotor 10 rotates, or if excessive vibration or shock is applied from the outside, the control becomes impossible and the rotor 10 is There may be large swings. Also, when the rotor 10 is rotated from the stopped state to the rated speed, the rotor 10 must pass through the resonance point in the process, so that the rotor 10 may swing around greatly.

By the way, whirling of the rotor 10 includes whirling in a cylindrical mode and whirling in a conical mode, and in a magnetic bearing device, these two conditions are required until the rotor 10 reaches a rated speed from a stopped state. It must pass through the resonance points of one 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 represent displacements of the center of the rotor 10 from the control center O at the mounting positions of the protective bearings 16 and 17, and x _Sh and x _Sb represent position sensors 14a and 14b. The displacement of the center of the rotor 10 from the control center O at the mounting position of the position sensors 15a and 15b is shown.

In the cylindrical mode shown in FIG. 5, the rotor 10 oscillates as indicated by arrows A and A ′ with the amplitudes (rotation radii) of the respective parts being substantially equal. That is, it swings around in the relationship of x _Ph ≈x _Sh ≈x _Sb ≈x _Pb . On the other hand, in the conical mode of FIG. 6, the rotor 10 has a certain point C as a fixed point as shown by arrows B and B ′, and the swinging amplitude (rotation radius) is increased at both ends of the rotor 10. Swing around. That is, it swings around in the relation of [x _Ph ]> [x _Sh ], [x _Pb ]> [x _Sb ].

However, the displacements x _Ph , x _Pb and x _Sh , x _Sb take a positive value when the rotor 10 swings above the control center O, and a negative value when it swings below. Let's take. Moreover, in this specification, [n] represents the absolute value of n. When the amplitude further increases in the above-described whirling, the rotor 10 comes into contact with the protective bearings 16 and 17. Although the protective bearings 16 and 17 are provided for such a case, even if the rotor 10 rotates at high speed or low speed at the time of contact, such contact state is not provided. If it lasts for a long time, the protective bearings 16 and 17 will be consumed significantly. Finally, there is a risk that the protective bearings 16 and 17 will bite and damage the rotor 10 itself.

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

However, the large disturbance is determined by monitoring the amplitude of the whirling of the rotor 10 by each of the position sensors 14a, 14b and 15a, 15b, and detecting the displacements x _Sh , x _Sb which are the detected values. It is done based on. That is, the large disturbance is determined by whether or not the displacements x _Sh and x _Sb are larger than a predetermined amplitude value (threshold value) set in advance.

However, because of the structural limitation of the magnetic bearing device, the position sensors 14a, 14b and 15a, 15b are mounted inside the protective bearings 16, 17, so that the conical mode as shown in FIG. Then, the displacements x _Sh and x _Sb are smaller than the actual whirling amplitudes in the vicinity of the protective bearings 16 and 17, that is, the displacements x _Ph and x _Pb .

Therefore, in order to judge the large disturbance by the displacements x _Sh , x _Sb under the condition that the rotor 10 does not contact the protective bearings 16, 17, the displacements x _Ph , x _{Pb in the} conical mode are It is necessary to set the displacement x _Sh , x _Sb when the maximum value is taken as a threshold value. Conventionally, the large disturbance is judged based on the threshold value that is set based on the whirling in this conical mode. I was going.

[0014]

[Problems to be solved by the device]

 However, when a large disturbance is judged based on the conical mode in this way, the width of the threshold is narrow, so when the rotor 10 swings around in the cylindrical mode, the swinging amplitude of the rotor 10 is Although it is not big enough to come into contact with, it is judged to be a large disturbance.

Therefore, in the related art, the rotation of the rotor 10 is stopped in spite of the fact that no large disturbance actually occurs, so the number of times of stop is large and the efficiency of the operation of the device is 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 reduce the number of times the rotor stops. It is in.

[0016]

[Means for Solving the Problems]

 In the present invention, a magnetic generating means for magnetically levitating a cylindrical rotating body rotating about an axis to a predetermined position, and a magnetic generating means levitated to a predetermined position by the magnetic generating means are arranged concentrically with the axis center of the rotating body. A protective bearing provided, position detecting means arranged in parallel to the protective bearing in the axial direction of the rotating body to detect the position of the rotating body, and the 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 rotation of the rotating body is stopped when the distance between the protective bearing and the rotating body calculated by the distance calculating means becomes a predetermined value or less. The magnetic bearing device is equipped with a stop command means for instructing the above purpose.

[0017]

[Action]

 In the above magnetic bearing device, 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 the distance calculating means detects the position of the bearing and the rotating body from the detected value. Calculate the distance between. The stop command means commands the stop of the rotation of the rotating body when the calculated distance becomes equal to or less than a predetermined value.

[0018]

【Example】

 Hereinafter, an embodiment of the magnetic bearing device of the present invention will be described in detail with reference to FIGS. The same components as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be appropriately omitted.

FIG. 1 shows a part of the configuration of a magnetic bearing device according to an embodiment of the present invention. However, although this magnetic bearing device is configured to control the rotor 10 in the radial direction by four axes, since each shaft has the same configuration, two-axis control (for example, control in the X-axis direction) is performed. ) Is shown, and the description will be centered on this.

The magnetic bearing device includes position detection circuits 20 a and 20 b, an arithmetic circuit 21, a protection sequence circuit 22, and an abnormality display circuit 23. The position detection circuits 20a and 20b are connected to the position sensors 14a, 14b and 15a, 15b, respectively. The position detection circuit 20a is adapted to detect the displacement x _{Sh of the} rotor 10 from the output signals of the position sensors 14a and 14b. The position detection circuit 20b is _adapted to detect the displacement x _Sb from the output signals of the position sensors 15a and 15b. The position detection circuits 20a and 20b are connected to a control circuit (not shown) that controls the position of the rotor 10, and supply the detected displacements x _Sh and x _Sb to the 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, and by performing a predetermined arithmetic processing described later, the mounting positions of the protective bearings 16 and 17 are set. The displacements x _Ph and x _Pb of the rotor 10 at 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 on the basis of the displacements x _Ph and x _Pb from this arithmetic circuit 21, and when it judges that a large disturbance has occurred, a predetermined sequence control is performed. Is to do. The protection sequence circuit 22 has a memory (not shown). In this memory, the maximum amplitude value that the rotor 10 can take (maximum value that the displacements x _Ph and x _Pb can take) under the condition that the rotor 10 does not come into contact with the protective bearings 16 and 17 when it swings, Stored as a threshold. The determination as to whether or not a large disturbance has occurred is made by comparing this threshold value with the actual displacements x _Ph and x _Pb calculated by the calculation circuit 21.

Although not shown, the protection sequence circuit 22 is connected to the drive control system of the motor 18, and when a large disturbance is detected, it sends a control signal for instructing the motor 18 to stop. ing. On the other hand, the protection sequence circuit 22 is also connected to the abnormality display circuit 23, and when detecting a large disturbance, it supplies a signal notifying the abnormality display circuit 23 of the detection of the large disturbance. Accordingly, the abnormality display circuit 23 is configured to notify the operator of the abnormality by, for example, turning on a warning lamp.

FIG. 2 shows the distances from the center line O ′ at the positions where the displacements x _Ph , x _Pb and x _Sh , x _Sb occur. However, the center line O'represents a position equidistant from the position sensors 14a, 14b and the position sensors 15a, 15b, l _Ph is the distance from the protective bearing 16 to the center line O ', and l _Pb is the protection line. It represents the distance from the bearing 17 to the center line O '. l _S represents the distance between the position sensors 14a and 14b and the position sensors 15a and 15b.

When the distance from the center line O ′ at each position is determined in this way, the relationship between them is 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 the displacement signal values x _Sh , x _Sb from the position detection circuits 20 a, 20 b based on the above equations (1), (2), and the protective bearings 16, 17 The displacements x _Ph and x _Pb of the rotor 10 at the mounting position are determined.

FIG. 3 shows a detailed configuration of the arithmetic circuit 21 that performs such an arithmetic operation. That is, the arithmetic circuit 21 multiplies the arithmetic units 30 and 35 that perform addition processing and the arithmetic units 32 and 36 that performs subtraction processing by the values of 1/2, l _Ph / l _S , and l _Pb / l _S , respectively. The calculators 31, 33, and 34 are provided.

Next, the operation of the embodiment thus configured will be described. As is well known, when the rotor 10 is magnetically levitated by the electromagnets 11a, 11b and 12a, 12b, and rotated by the motor 18, the rotor 10 may oscillate greatly at the resonance point. The whirling of the rotor 10 at this time is detected by the position sensors 14a, 14b and 15a, 15b, and detected by the position detection circuits 20a, 20b as displacements x _Sh , x _Sb , respectively. Then, the displacements x _Sh and x _Sb are supplied to the arithmetic circuit 21, and the arithmetic circuit 21 performs the arithmetic operations of the 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 calculator 30 and subtracted by the calculator 32. The added value (x _Sh + x _Sb ) in the calculator 30 is halved by the calculator 31. On the other hand, the subtracted value (x _Sh −x _Sb ) in the arithmetic unit 32 is multiplied by the value of l _Ph / l _S in the arithmetic unit 33, and also multiplied by the value of l _Pb / l _{S in} the arithmetic unit 34. To be done. 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 ) are added by the calculator 35, Obtain the displacement x _Ph . On the other hand, in the calculator 36, the value calculated by the calculator 31 ((x _Sh + x _Sb ) / 2) is calculated by the calculator 34 ((x _Sh −x _Sb ) x _Pb / l _S ). Is calculated to obtain the displacement x _Pb .

When the displacement x _Ph , x _Pb is obtained by the arithmetic circuit 21, the protection sequence circuit 22 determines whether or not the displacement x _Ph , x _Pb is larger than a threshold value stored in a memory (not shown). However, if it is smaller than the threshold value, the whirling is continuously monitored.

On the other hand, if it is equal to or more than the threshold value, it is judged as a large disturbance, and the protection sequence circuit 22 sends a control signal for instructing the control circuit of the motor 18 (not shown) to stop the rotation of the motor 18. 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 contact with the protective bearings 16 and 17 of the rotor 10 due to a large disturbance is prevented, while the operator knows the abnormality by observing the lighting of the warning lamp.

As described above, in the magnetic bearing device according to the present embodiment, the mounting positions of the protective bearings 16 and 17 are obtained by performing the arithmetic processing shown in the equations (1) and (2) on the displacements x _Sh and x _Sb. Since the amplitude of the whirling of the rotating body is detected, it is possible to allow the maximum whirling amplitude within the range in which the rotor 10 does not contact the protective bearings 16 and 17. That is, regardless of the whirling mode, it is possible to set a larger threshold value for detecting large disturbance than before.

As a result, when the rotor 10 is in the rated operation from the stopped state, passage of the resonance point is facilitated, and the number of times the rotor is stopped due to large disturbance detection is reduced, so that the device can be operated efficiently. . The magnetic bearing device according to the embodiment of the present invention has been described above. However, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in the above-described embodiments, the magnetic bearing device controls the rotor 10 by four axes in the radial direction, but of course, a magnetic bearing device of a two-axis control type may be used. The present invention is also applicable to the case where permanent magnets are used instead of the electromagnets 11a, 11b and 12a, 12b.

Further, in the above embodiment, the protection circuit 22 determines the large disturbance by calculating the displacements x _Ph and x _Pb from the displacements x _Sh and x _{Sb of the} rotor 10 by the arithmetic circuit 21. However, the calculation 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 (almost 0), a large disturbance occurs. You may judge that.

Further, although the position sensors 14a, 14b and 15a, 15b are mounted inside the protective bearings 16, 17 in the above-mentioned embodiments, they may be mounted outside.

[0036]

[Effect of device]

 Since the magnetic bearing device of the present invention determines the large disturbance detection based on the distance between the bearing and the rotating body obtained by performing a predetermined calculation on the detection value of the position detecting means, Only the whirling that may cause the rotating body to actually contact the bearing can be detected as a large disturbance, and the number of times the rotating body is stopped by the protection sequence at the time of detecting a large disturbance can be reduced to operate the device efficiently can do.

[Brief description of 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 diagram showing an amplitude of whirling in each part of the rotor of the magnetic bearing device and a positional relationship thereof.

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 a rotor of the magnetic bearing device in a conical mode.

[Explanation of symbols]

 10 rotors 11a, 11b, 12a, 12b electromagnets 14a, 14b, 15a, 15b position sensor 16, 17 protective bearing 20a 20b position detection circuit 21 arithmetic circuit 22 protective sequence circuit 30, 31, 32, 33, 34, 35, 36 arithmetic vessel

Claims (1)

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