JP2010043684A - Magnetic bearing displacement detecting method and detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a thermal problem and reduction in detection accuracy by an eddy current, in a magnetic bearing displacement measuring device. <P>SOLUTION: In a rotator position detecting method, permanent magnets 15 are provided while facing both ends of a main shaft 1 of a rotary body 21 supported contactlessly by magnetic bearings 4, and position detection sensors 3 are provided while being separated on a side face in the vicinity of both ends of the rotary body 21, and a displacement of the rotary body 21 is detected by detecting a static magnetic field of the permanent magnet 15 by a position detection sensor 3. An axial displacement of the rotary body 21 can also be detected by symmetrically preparing the permanent magnets 15 and the position detection sensors 3 in the vicinity of both ends of the main shaft 1 of the rotary body 21 via the main shaft 1. The generation of eddy current can be restrained on a can 7 or a target 5 since the static magnetic field is used. In particular, reduction in position detection accuracy by the eddy current and a problem of heat generation are solved in a case that the metallic can 7 is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a position detection method and a detection device for detecting a position of an axis of a rotating body in a magnetic bearing that supports the rotating body in a non-contact manner by magnetism. More specifically, the present invention relates to a displacement measuring method for detecting a gap between an electromagnet and a rotating body and a shaft position detecting apparatus in a magnetic bearing device (canned motor) in which the rotating body is provided in a sealed metal container.

The control type magnetic bearing device that actively controls the position of the rotating body using an electromagnet controls the rotating shaft in a non-contact manner, and therefore is suitable for high-speed rotation with low torque and low noise because no lubricant is required. . (Patent Document 1, Patent Document 2)
Usually, in a control type magnetic bearing device, when detecting the position of a rotating body, a detection method using a Hall element as shown in Patent Document 3, or an eddy current type or differential transformer as shown in Patent Document 4 is used. There is an inductive detection method.

  FIG. 6 is a cross-sectional view of the main part of a magnetic bearing device 12 having a can structure according to the prior art. In FIG. 6, the electromagnet 2 and the position detection sensor 13 are disposed so as to face the side surface of the main shaft 1 including the rotor 9. The electromagnet 2 and the position detection sensor 13 form a magnetic bearing 24. Is configured. A target 18 corresponding to the electromagnet 2 and a target 5 corresponding to the position detection sensor 13 are attached to the main shaft 1 (hereinafter, the main shaft 1 including the rotor 9 and the targets 5 and 13 are provided. It is called a rotating body 21).

  The position detection sensor 13 detects the gap 6 between the target 5 and the position detection sensor 13, and the magnetic force of the electromagnet 2 is controlled by a controller (not shown) based on the detection output signal. The rotating body 21 is magnetically levitated, and the rotating body 21 is supported without contact. A can 7 is disposed between the rotating body 21, the electromagnet 2, and the position detection sensor 13. That is, the rotating body 21 is provided in the can 7. And since the stator 8 gives a rotational drive force to the rotor 9, the rotary body 21 rotates. Here, a floating electromagnet that controls the rotating body 21 in the axial direction (z-axis direction) and a displacement detector that detects the displacement of the gap 6 by the output of the position detection sensor 13 are not shown.

  As described above, in a canned motor or the like having a metal hermetic container (that is, the can 7) between the stator 8 and the rotating body 21 as shown in FIG. 6, the radial direction is set so that the rotating body 21 does not contact the container. Axis control is performed in the direction (x-axis direction or y-axis direction) and in the axial direction (z-axis direction). As the position detection sensor 3, an inexpensive eddy current type displacement detector or an induction type using a differential transformer which is not easily affected by the hermetically sealed container is employed.

In the differential transformer type, position detection is performed by converting the differential voltage e ₃ of the secondary coil into a position using the electromagnetic induction action of the primary coil and the secondary coil as shown in FIG.

  That is, the inductive sensor has a configuration in which a sensor coil is wound around a sensor core. Here, a position detection method in the case where an inductive sensor is used as the position detection sensor 13 will be described with reference to the control type bearing device 12 shown in FIG.

  When an excitation voltage of several tens of kHz or less is applied to the sensor coil of the position detection sensor 13 from the oscillator, the magnetic flux generated in the sensor core (that is, the magnetic flux generated from the position detection sensor 13) penetrates the can 7 and the gap 6, and the target A magnetic loop that passes through the magnetic material in 5 and returns to the sensor core (that is, the position detection sensor 13) is formed. The distance between the position detection sensor 13 and the target 5 can be detected by a change in inductance of the sensor coil (Patent Document 4).

  On the other hand, an eddy current sensor uses a non-metallic material or an air core as a sensor core, and a sensor coil is wound around the sensor core to constitute an eddy current sensor. Here, a position detection method when an eddy current sensor is used as the position detection sensor 13 will be described with reference to the control type bearing device 12 shown in FIG.

An excitation voltage of about several MHz is supplied from the oscillator to the sensor core of the position detection sensor 13, and a magnetic flux is generated in the sensor core by this excitation voltage (that is, a magnetic flux is generated from the position detection sensor 13). The sensor target 5 is reached. At this time, magnetic flux is generated by eddy current generated on the surface of the sensor target 5. This magnetic flux is opposite to the magnetic flux generated in the sensor core. The inductance of the sensor coil changes due to the magnetic flux generated by the eddy current. The distance between the position detection sensor 13 and the sensor target 5 can be detected from this inductance change amount (Patent Document 4).
JP 58-61324 A Japanese Patent Laid-Open No. 2-297012 Japanese Patent Laid-Open No. 7-98015 JP 2003-106333 A

  However, in the canned motor according to the above prior art, an eddy current is generated in the core and the metallic can due to the AC voltage of the primary coil. For this reason, the detection error accompanying the increase in the AC voltage, the heat generation accompanying the increase in the rotation speed of the rotating body, the rotation loss, and the like become problems. In particular, since the canned motor is hermetically sealed, it is preferable that heat generation is small.

  As shown in FIG. 8, in the eddy current type, since the eddy current 14 flows through the can 7, the position detection sensor 13 detects the can 7 itself, and it is difficult to accurately detect the displacement of the rotating body. It is.

  Further, when the magnetic bearing device as in Patent Document 3 includes a can, the permanent magnet that is a target rotates in synchronization with the rotation of the rotating body, so that an eddy current may be generated on the can and the detection accuracy may be reduced. . That is, even when a Hall element is used for the position detection sensor 13 of the canned motor 12 shown in FIG. 6, if a can is provided, the detection accuracy may be reduced due to the influence of eddy current.

  Therefore, the present invention is a magnetic bearing device that performs radial (x-axis direction or y-axis direction) and axial axis (z-axis direction) control of a rotating body, and the rotating body that suppresses generation of eddy currents on a can and a target. It is an object of the present invention to provide an axial position measuring method and measuring apparatus.

  Therefore, the magnetic bearing displacement detection method according to claim 1 includes first permanent magnets opposed to both ends of the shaft of the rotating body that is supported in a non-contact manner by the magnetic bearing, in the vicinity of both ends of the shaft of the rotating body. A position detection sensor is provided apart from the side surface, and the sensor detects a displacement of the rotating body by detecting a static magnetic field of the first permanent magnet.

  The magnetic bearing displacement detection method according to claim 2 is the magnetic bearing displacement detection method according to claim 1, wherein the first permanent magnet and the sensor are provided symmetrically via an axis of the rotating body, A displacement in a radial direction and an axial direction of the shaft is detected.

  The magnetic bearing displacement detection method according to claim 3 is the magnetic bearing displacement detection method according to claim 1, wherein the same magnetic pole as that of the first permanent magnet faces the end of the shaft of the rotating body. Each includes a second permanent magnet, and the sensor detects a displacement of the rotating body by detecting a static magnetic field of the second permanent magnet.

  The magnetic bearing displacement detection device according to claim 4 is provided with first permanent magnets facing both ends of the shaft of the rotating body supported in a non-contact manner by the magnetic bearing, on side surfaces near both ends of the shaft of the rotating body. A position detection sensor is provided at a distance, and the sensor detects a displacement of the rotating body by detecting a static magnetic field of the first permanent magnet.

  The magnetic bearing displacement detection device according to claim 5 is the magnetic bearing displacement detection device according to claim 4, wherein the first permanent magnet and the sensor are provided symmetrically via an axis of the rotating body, A displacement in a radial direction and an axial direction of the shaft is detected.

  The magnetic bearing displacement detection device according to claim 6 is the magnetic bearing displacement detection device according to claim 4, wherein the same magnetic pole as that of the first permanent magnet faces the end of the shaft of the rotating body. Each includes a second permanent magnet, and the sensor detects a displacement of the rotating body by detecting a static magnetic field of the second permanent magnet.

  A magnetic bearing displacement detection device according to a seventh aspect is the magnetic bearing displacement detection device according to the fourth to sixth aspects, wherein the rotor is provided in a metal hermetic container.

  According to the magnetic bearing displacement detection method described in claims 1 to 3 and the magnetic bearing displacement detection device described in claims 4 to 7, generation of eddy current can be suppressed.

  In particular, according to the magnetic bearing displacement detection method of the second aspect, in addition to the effect of the first aspect, since the displacement of the rotor in the axial direction (z-axis direction) can be detected, a new axial direction ( There is no need to provide a position detection sensor for detecting displacement in the z-axis direction).

  According to the magnetic bearing displacement detection method of the third aspect, in addition to the effect of the first aspect, the displacement of the rotor in the axial direction (z-axis direction) can be suppressed.

  Further, the magnetic bearing displacement detection device according to claim 1 can be realized by the magnetic bearing displacement detection device according to claim 4.

  Furthermore, the magnetic bearing displacement detection device according to claim 2 can be realized by the magnetic bearing displacement detection device according to claim 5.

  Then, the magnetic bearing displacement detection device according to claim 3 can be realized by the magnetic bearing displacement detection device according to claim 6.

  In particular, in the magnetic bearing displacement detection device according to the seventh aspect, when the magnetic bearing includes a metal sealed container (can), generation of eddy current on the sealed container can be suppressed.

  Therefore, according to the above invention, it is possible to solve a decrease in detection accuracy due to eddy currents and a thermal problem.

(Embodiment 1)
The shaft position measuring apparatus according to the first embodiment of the present invention will be described in detail with reference to FIG. The same parts as those in the apparatus shown in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a cross-sectional view of a main part of a canned motor 10 according to the first embodiment of the present invention. The canned motor 10 includes a rotating body 21. The rotating body 21 includes a stator 9, a main shaft 1, a target 18 corresponding to the electromagnet 2, and a target 5 corresponding to the position detection sensor 3.

  As shown in FIG. 1, an electromagnet 2 and a position detection sensor 3 are arranged so as to face a main shaft 1 having a rotor 9, and a magnetic bearing 4 is constituted by these electromagnets 2 and the position detection sensor 3. Has been. A target 18 corresponding to the electromagnet 2 and a target 5 corresponding to the position detection sensor 3 are attached to the main shaft 1.

  A can 7 is inserted between the rotating body 21 and the magnetic bearing 4. That is, the rotating body 21 is provided in the can 7. Then, when the stator 8 gives a rotational driving force to the rotor 9, the rotating body 21 rotates. Electromagnetic steel members 16 are provided at both ends on the axis of the rotating body 21 so as to be separated from the rotating body 21. A position detection sensor 3 is provided near the end of the electromagnetic steel member 16, and a permanent magnet 15 is provided at the center of the electromagnetic steel member 16. At this time, the permanent magnet 15 is arranged so as to be positioned on an extension line of the axis of the rotating body 21. The position detection sensor 3 detects the static magnetic field of the permanent magnet 15. An example of the position detection sensor 3 is a hall element.

  As indicated by a broken line in FIG. 1, the magnetic flux generated by the permanent magnet 15 passes through the can 7, the target 5, the can 7, the position detection sensor 3, and the electromagnetic steel member 16 radially about the main shaft 1 of the rotating body 21. Since this magnetic flux is a static magnetic field, no change in magnetic flux occurs in the can 7 or the target 5 when the gap 6 is balanced. That is, even if the target 21 rotates at a high speed, the magnetic flux does not change due to the rotation. Therefore, even if the rotating body 21 rotates, no eddy current is generated in the can 7 or the like.

  If the position of the rotator 21 deviates from the center position for some reason, the gap 6 increases or decreases. Then, since the magnetic flux changes in proportion to the reciprocal of the displacement of the gap 6, the position detection sensor 3 detects the displacement of the rotating body 21 in the radial direction (x-axis direction or y-axis direction) and the axial direction (z-axis direction). can do.

  In this case, the magnetic flux changes due to the non-uniformity of the gap 6. However, since it is very small, there is no problem with a decrease in gap detection accuracy compared to the eddy current type and inductance type.

  Next, referring to FIGS. 2 and 3, an example of detecting the gap between the magnetic bearing 4 and the rotating body 21 by the position detection sensor 3 will be described. 2A is a cross-sectional view taken along the line AA of the axial position measuring apparatus according to the first embodiment shown in FIG. 1, and FIG. 2B is an axial position measuring apparatus according to the first embodiment shown in FIG. FIG. 3 is a flowchart showing the flow of detection control.

  As shown in FIGS. 2A and 2B, the two position detection sensors 3 arranged symmetrically with respect to the target 5 detect the position of the target 5. A difference between these detected values can be detected as a displacement of the main shaft 1 in the radial direction (x-axis direction or y-axis direction).

  Further, in the two position detection sensors 3 on the x axis arranged symmetrically with respect to the target 5, when the detected magnetic fluxes both increase (or decrease both), the axial direction (z-axis direction) is increased. It can be determined that there was a displacement. Similarly, the displacement in the axial direction (z-axis direction) can be similarly detected for the position detection sensor 3 provided on the y-axis. And the displacement detection precision to an axial direction (z-axis direction) can be improved from the information of each position detection sensor 3 provided in the both ends of the main axis | shaft 1. FIG.

  That is, as shown in FIG. 2 (a), the position detection sensor 3 is arranged symmetrically with respect to the x axis (or y axis symmetrical) via the main axis 1 to separately provide position detection in the axial direction (z axis direction). Even without this, displacement of the axial axis (z-axis direction) can be detected.

  Furthermore, the flow of detection control will be described with reference to FIG. An example in which a Hall element is used as the position detection sensor 3 will be described. The position detection sensor 3 includes a controller 19 that supplies power to the position detection sensor 3 and receives an electrical signal output from the position detection sensor 3. And the control part 19 is equipped with the arithmetic processing part 20 which detects the position of the rotary body 21 from the received electrical signal.

  First, the power source of the control unit 19 is turned on, and a constant current or a constant voltage is supplied to the drive terminal of the position detection sensor 3 (Hall element). The position detection sensor 3 outputs a signal corresponding to the magnetic field applied to the position detection sensor 3 from the output terminal to the control unit 19. The control unit 19 adjusts the gain and offset of the output signal, and outputs the output signal to the arithmetic processing unit 20 through a filter. The arithmetic processing unit 20 corrects the position based on the signal from the control unit 19 and detects the position of the rotating body 21.

  With the above flow, the position detection sensor 3 can detect the magnetic field of the permanent magnet 15, and the change in the position of the rotating body 21 can be detected by the change in the magnetic field. Note that the position detection sensor 3 is not limited to a Hall element, and a sensor that can detect a static magnetic field may be used as appropriate.

(Embodiment 2)
FIG. 4 describes in detail an axial position measuring apparatus according to the second embodiment of the present invention with reference to FIG.

  In the first embodiment, a pair of sensors for detecting displacement in the x-axis direction and sensors for detecting displacement in the y-axis direction are provided as the position detection sensor 3 for detecting the gap 6. On the other hand, in the second embodiment, as shown in FIG. 4, as the position detection sensor 3 for detecting the gap 6, a sensor for detecting the displacement in the x-axis direction and a sensor for detecting the displacement in the y-axis direction are each one. It is provided one by one. In this way, the cost can be reduced by reducing the number of position detection sensors 3.

  As described above, the number of position detection sensors 3 is different in the second embodiment as compared to the first embodiment. Therefore, the detailed configuration is the same as in FIG. 1, and a detailed description thereof is omitted. The control flow is also performed by the same method as in FIG. 3, and detailed description thereof is omitted.

(Embodiment 3)
The shaft position measuring device 11 according to the third embodiment of the present invention will be described in detail with reference to FIG. The same parts as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

  FIG. 5 is a cross-sectional view of a main part of a canned motor 11 according to the third embodiment of the present invention. The canned motor 11 includes a rotating body 22. The rotating body 22 includes a stator 9, a main shaft 1, a target 5 corresponding to the position detection sensor 3, a target 18 corresponding to the electromagnet 2, and a permanent magnet 17 provided on the main shaft 1.

  As shown in FIG. 5, in the shaft position measuring device 11 according to the third embodiment of the present invention, the permanent magnet 17 has a main shaft so that the same magnetic pole as the permanent magnet 15 provided at both ends of the main shaft 1 is opposed. 1 is provided at both ends. That is, by providing the permanent magnet 17 at both ends of the main shaft 1, a magnetic repulsive force acts between the permanent magnet 17 and the permanent magnet 15 and suppresses displacement of the rotating body 22 in the axial direction (z-axis direction). can do.

  The position detection sensor 3 detects the position of the rotating body 22 by detecting the static magnetic field of the permanent magnet 17. In FIG. 5, the arrangement of the position detection sensors 3 is the same as that in the second embodiment, but a pair may be provided in each of the x-axis direction and the y-axis direction as in the first embodiment.

  As described above, according to the axial position measurement apparatus 11 having the configuration as in the third embodiment, in addition to the effect of suppressing the eddy current of the first embodiment, the axial direction (z-axis) of the rotating body 22 Direction) can be suppressed. Then, the position detection sensor 3 detects the static magnetic field of the permanent magnet 17 provided to suppress the displacement in the axial direction (z-axis direction), so that the radial direction (x-axis direction or y-axis direction) of the main shaft 1 is increased. Displacement can be detected.

  As described above, according to the axial position measuring method and measuring apparatus of the first to third embodiments according to the present invention, the displacement of the rotating body can be detected using the static magnetic field of the permanent magnet. . And since a static magnetic field is utilized in order to detect the displacement of a rotary body, it can suppress that an eddy current generate | occur | produces on a can and a target.

  That is, by suppressing the generation of eddy currents, heat generation can be reduced and a decrease in shaft position detection accuracy due to eddy currents can be prevented. In particular, in a canned motor equipped with a metallic can, by suppressing the generation of eddy current, the problem of heat generation can be solved and the position of the rotating body can be detected with high accuracy.

The principal part sectional view of the canned motor concerning a 1st embodiment of the present invention. (A) AA sectional view of a canned motor concerning a 1st embodiment, (b) BB sectional view of a canned motor concerning a 1st embodiment. The position detection control flowchart of the canned motor which concerns on 1st Embodiment of this invention. (A) Position detection sensor part (left side) sectional view of the canned motor according to the second embodiment of the present invention, (b) Position detection sensor part (right side) sectional view of the canned motor according to the second embodiment of the present invention. Sectional drawing of the principal part of the canned motor which concerns on 3rd Embodiment of this invention. Sectional drawing of the principal part of the canned motor which concerns on a prior art. Example of eddy current displacement detection. An example of eddy current generated by a position detection sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main shaft 3, 13 ... Position detection sensor 5 ... Target 6 ... Gap 7 ... Can 9 ... Rotor 10, 11, 12 ... Shaft position measuring device 14 ... Eddy current 15, 17 ... Permanent magnet 16 ... Electromagnetic steel member 19 ... Control unit 20 ... arithmetic processing units 21 and 22 ... rotating body

Claims (7)

A first permanent magnet is provided opposite to both ends of the shaft of the rotating body supported in a non-contact manner by the magnetic bearing,
A position detection sensor is provided apart from the side surfaces near both ends of the shaft of the rotating body,
The sensor detects a static magnetic field of the first permanent magnet,
A magnetic bearing displacement detection method, wherein the displacement of the rotating body is detected. The first permanent magnet and the sensor are provided symmetrically via an axis of the rotating body;
The magnetic bearing displacement detection method according to claim 1, wherein a displacement in a radial direction and an axial direction of the shaft is detected. A second permanent magnet is provided at each end of the shaft of the rotating body so that the same magnetic poles as the first permanent magnet face each other;
The sensor detects a static magnetic field of the second permanent magnet,
The magnetic bearing displacement detection method according to claim 1, wherein the displacement of the rotating body is detected. A first permanent magnet is provided opposite to both ends of the shaft of the rotating body supported in a non-contact manner by the magnetic bearing,
A position detection sensor is provided apart from the side surfaces near both ends of the shaft of the rotating body,
The sensor detects a static magnetic field of the first permanent magnet,
A magnetic bearing displacement detecting device for detecting a displacement of the rotating body. The first permanent magnet and the sensor are provided symmetrically via an axis of the rotating body;
The magnetic bearing displacement detection device according to claim 4, wherein a displacement in a radial direction and an axial direction of the shaft is detected. A second permanent magnet is provided at each end of the shaft of the rotating body so that the same magnetic poles as the first permanent magnet face each other;
The sensor detects a static magnetic field of the second permanent magnet,
The magnetic bearing displacement detection device according to claim 4, wherein the displacement of the rotating body is detected. The magnetic bearing displacement detection device according to claim 4, wherein the rotating body is provided in a metal hermetic container.

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