JP2004120886A - Bearing-less motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing-less motor capable of largely generating a radial direction force by constituting so that a position control flux of a rotor may not pass through a permanent magnet. <P>SOLUTION: This bearing-less motor 10 is provided with a cylindrical rotor 12 on an inner side and a cylindrical stator 14 on an outer side which face each other with cylindrical surfaces through a gap. The rotor 12 has the permanent magnet 22 with two poles, and the stator 14 has motor windings Nd, Nq with two poles and positioning control windings Nx, Nx, Ny, Ny with four poles. The permanent magnet 22 is separated from the facing surfaces of the stator 12, and deeply buried in the rotor 12. In this rotor 12, the part on the more facing surface side than the permanent magnet 22 functions as a yoke in which fluxes pass. Therefore, the positioning control fluxes Ψx, Ψy do not pierce through the permanent magnet with large magnetic resistance, and generate the large radial direction force. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bearingless motor having both the function of driving the rotor to rotate and the function of a magnetic bearing for controlling the radial position of the rotor. In more detail, a permanent magnet is embedded deeply into the rotor from the surface of the rotor facing the stator, and has a bearingless function that has both the function of driving the rotor to rotate and the function of a magnetic bearing that controls the radial position of the rotor. Motor related.
[0002]
[Prior art]
The spindle of a machine tool is rotated at high speed for precise machining in a short time, and the turbine of a vacuum pump is tens to hundreds of thousands of revolutions per minute to obtain a high vacuum with accelerators and semiconductor manufacturing equipment. It is necessary to rotate at ultra-high speed. In order to realize such an ultra-high-speed rotation motor, not only the structure of the motor itself and the control device are improved, but also a bearing that can withstand ultra-high-speed rotation is indispensable.
Magnetic bearings have been used as such for a long time. Further, as a further improvement, a bearingless motor having both the function of rotating the rotor and the function of a magnetic bearing for controlling the radial position of the rotor by integrating the motor and the magnetic circuit of the magnetic bearing. There is. In a bearingless motor, the size of the motor can be reduced by using a magnetic field that rotationally drives the rotor as an exciting magnetic field of the magnetic bearing. Such bearingless motors are characterized by non-contact, lubrication-free, maintenance-free, and miniaturization, and research and development is progressing into applications to canned pumps and artificial hearts, and to pumps and motor-integrated pumps. I have.
[0003]
Generally, such a bearingless motor includes an inner rotor and an outer stator facing each other. A gap is formed between the rotor and the stator so as to maintain non-contact.
However, a bearingless motor used for a small pump such as a canned pump or an artificial heart requires a gap of 2 to 3 mm or more so that, for example, fluid can flow into the gap even when the rotor rotates. . In the case of a large-capacity motor, even if there is a gap length of 2 to 3 mm, the performance is hardly affected. However, in a small-capacity motor of 1 kW or less, the gap length of 2 to 3 mm is a very large value. is there. In the induction motor type or reluctance type bearingless motor, the magnetic flux decreases in inverse proportion to the gap length, so that the radial force decreases in inverse proportion to the square of the gap length. Therefore, with a relatively large gap length, it is difficult to sufficiently generate a radial force necessary for magnetically supporting the rotor main shaft. For this reason, a permanent magnet type bearingless motor is generally employed instead of an induction machine type or a reluctance type (see Patent Documents 1 and 2).
[0004]
[Patent Document 1]
JP-A-10-150755
[Patent Document 2]
JP 2001-339979 A
[0005]
A permanent magnet type bearingless motor is described in, for example, Japanese Patent Application Laid-Open No. 2001-339979. Referring to FIGS. 25 and 26, the bearingless motor 410 includes an inner rotor 412 and an outer stator 414 facing each other, and a thrust bearing 416 provided in the axial direction of the rotor 412. The rotor 412 includes a divided permanent magnet 422 having an arc-shaped cross section attached along the facing surface, and the stator 414 determines a motor winding for driving the rotor 412 and a radial position of the rotor 412. And a position control winding for controlling. Such a bearingless motor 410 is called an SPM type.
Other permanent magnet type bearingless motors include an Inset type in which salient poles are formed between the poles of the permanent magnet, and an embedded permanent magnet type (shallowly-Buried Permanent Magnet Type) in which a permanent magnet is embedded shallowly in the rotor surface. There is.
Some types of bearingless motors include a rotor on the outside and a stator on the inside.
[0006]
The conventional bearingless motor shown in FIG. 26 has a four-pole motor / two-pole position control structure, that is, an n-pole motor / n-2 pole position control structure. This is because the efficiency of the electric motor is emphasized. In addition, a bearingless motor having a 6-pole motor / 4-pole position control structure is also common.
The principle of generating a radial force in the positive x-axis direction at the time of no load in the bearingless motor of FIG. 26 will be described. When a current Ix is applied to the position control winding Nx, a two-pole position control magnetic flux Ψx is generated. Due to the position control magnetic flux Ψx and the field magnetic flux Ψm generated by the four-pole permanent magnet, the magnetic fluxes strengthen each other in the positive x-axis direction and weaken each other in the negative x-axis direction. Due to the strength of the magnetic flux, a radial force Fx is generated in the positive x-axis direction where the magnetic flux is strengthened.
[0007]
[Problems to be solved by the invention]
However, in the bearingless motor 410 having the n-pole motor / n-2 pole position control structure as described above, since the permanent magnet 422 is provided along the facing surface of the rotor 412, the position control magnetic flux is the same as that of the vacuum. It must penetrate the permanent magnet 422 having a high magnetic resistance and a high magnetic resistance. Therefore, the position control magnetic flux cannot be generated effectively with respect to the magnetomotive force of the position control winding, and the radial force cannot be sufficiently generated.
As one method, the field magnetic flux can be increased by increasing the thickness of the magnet. However, since the magnetic resistance of the permanent magnet increases as the magnet thickness increases, there is a problem that the position control magnetic flux decreases more than the increase of the field magnetic flux, and the radial force decreases.
[0008]
An object of the present invention is to provide a bearingless motor capable of generating a large radial force by configuring a rotor so that a position control magnetic flux does not pass through a permanent magnet.
It is another object of the present invention to provide a bearingless motor capable of obtaining a larger radial force by effectively utilizing the magnetic flux of a permanent magnet as a position control magnetic flux.
[0009]
[Means for Solving the Problems]
Therefore, the present invention provides a bearingless motor in which a rotor and a stator face each other via a gap, the rotor including an n-pole permanent magnet buried separately from a surface facing the stator, The above object has been solved by a bearingless motor in which the stator includes an n-pole motor winding and an n + 2 pole position control winding.
[0010]
The present invention also provides a bearingless motor in which the rotor includes an interpole magnet between adjacent permanent magnets of different polarities. It is preferable that the pole magnets protrude more toward the rotor than the permanent magnets.
[0011]
By making the number of poles of the position control winding larger than the number of poles of the motor winding, that is, by providing an n-pole motor winding and an n + 2 pole position control winding, the position control magnetic flux is larger than that of the n-pole motor. Close in a small area. Here, “n” is a positive number that is a multiple of two. That is, the position control magnetic flux is closed in a range smaller than the magnetic flux of the electric motor.
Furthermore, since the permanent magnet of the rotor is buried so as to be immersed deeper than the surface facing the stator, the position control magnetic flux can pass through the portion facing the permanent magnet. In other words, the magnetic material on the side of the rotor facing the opposite surface can be used as a passage (yoke) for the position control magnetic flux. Thereby, the position control magnetic flux is configured not to pass through the permanent magnet having a large magnetic resistance, and a large radial force is generated.
Since the area through which the position control magnetic flux passes is ensured on the side facing the permanent magnet, even if the magnet thickness is increased, the position control magnetic flux does not decrease, so that a large rotating torque can be output.
[0012]
The radial force is further increased by providing an interpole magnet projecting from the permanent magnet to the facing surface between the adjacent permanent magnets having different polarities. That is, adjacent permanent magnets of different polarities do not form a closed magnetic circuit between the permanent magnets, and the magnetic flux of the permanent magnet passes through the facing surface side of the rotor. Large radial forces are generated.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically illustrates one embodiment of a bearingless motor 10 used in combination with a compressor, blower, fan, pump, and centrifugal pump for water purification. In addition, bearingless motors include disk drive units, powdering machines, canned pumps, artificial heart pumps, gas transfer machines, semiconductor manufacturing equipment, flywheels, rotary stages for monitor devices, spindles, multi-stage generators, centrifugal separators, etc. Used in combination.
[0014]
The bearingless motor of FIG. 1 has a structure in which a rotor is arranged inside and a stator is arranged outside, but there is also a structure in which a stator is arranged inside and a rotor is arranged outside. Will be described later.
[0015]
As shown in FIG. 1, the bearingless motor 10 is spaced apart from the inner rotors 12, 12 and the outer stators 14, 14 facing each other via a gap in the axial direction of the rotor 12 and the stator 14. And a thrust bearing 16 provided. The rotors 12, 12 and the thrust bearing 16 are provided on one shaft, and the shaft is connected to the impeller 20 of the pump 18. Although the rotor and the stator according to the present embodiment have a tandem structure including the unit 1 and the unit 2, a combination of one unit or three or more units may be used.
[0016]
FIG. 2 shows a cross-sectional view of the rotor 12 and the stator 14. The bearingless motor 10 of the present embodiment has a two-pole motor and a four-pole position control structure as one form of an n-pole motor and an (n + 2) -pole position control structure. Here, “n” is a positive number that is a multiple of two. The bearingless motor in which “n” is another even number will be described later.
[0017]
The rotor 12 has a two-pole permanent magnet 22, and the stator 14 has two-pole motor windings Nd and Nq and four-pole position control windings Nx, Nx, Ny and Ny. Further, the rotor 12 is provided with a pole magnet 24 at a portion between the poles of the permanent magnet.
[0018]
The permanent magnet 22 is buried deep in the rotor 12 at a distance from the facing surface of the rotor 12. The permanent magnets 22 are provided with a phase of 180 ° and include arc-shaped permanent magnets 22a, 22a having a surface S pole on the left side in the figure and arc-shaped permanent magnets 22b, 22b having a surface N pole on the right side in the figure. Each of the permanent magnets 22a, 22a, 22b, 22b forms an annular permanent magnet on a concentric circle. The rotor 12 itself is made of a magnetic material, and the opposing surface of the permanent magnet 22 divided by the pole magnet 24 functions as a yoke through which magnetic flux passes. The pole magnet 24 prevents the field magnetic flux from forming a closed magnetic path between the adjacent permanent magnets 22a and 22b having different polarities. As a result, the field magnetic flux passes through the rotor 12 on the side facing the permanent magnet 22.
[0019]
Next, the operating principle of the bearingless motor 10 will be described with reference to FIGS.
FIG. 3 illustrates the principle of generation of a radial force in the x-axis direction when no load is applied. A position control magnetic flux Ψx is generated by flowing a position control current through the four-pole position control winding Nx in the illustrated direction. Due to the field magnetic flux Ψm generated by the two-pole permanent magnet, the magnetic fluxes reinforce each other in the positive x-axis direction and weaken each other in the negative x-axis direction. Thus, the radial force Fx is generated in the positive x-axis direction depending on the strength of the magnetic flux. The radial force in the negative x-axis direction is generated by flowing the position control current in the opposite direction.
[0020]
FIG. 4 shows the principle of generation of a radial force in the y-axis direction when no load is applied. A position control magnetic flux Ψy is generated by passing a position control current through the four-pole position control winding Ny in the illustrated direction. Due to the field magnetic flux Δm generated by the two-pole permanent magnet, the magnetic fluxes reinforce each other in the positive y-axis direction, and weaken each other in the negative y-axis direction. Thus, a radial force Fy is generated in the positive y-axis direction depending on the strength of the magnetic flux. The radial force in the negative x-axis direction is generated by flowing the position control current in the opposite direction.
[0021]
FIG. 5 shows the radial force generated by the interference between the torque magnetic flux Ψq and the position control current Ψx when the torque current flows through the motor winding Nq. In the positive y-axis direction, the respective magnetic fluxes weaken each other, and in the y-axis negative direction, the respective magnetic fluxes strengthen each other. As a result, a radial force Fy is generated in the negative y-axis direction.
[0022]
FIG. 6 shows a radial force generated by the interference between the torque magnetic flux Ψq and the position control current Ψy when a torque current flows through the motor winding Nq. In the positive x-axis direction, the magnetic fluxes reinforce each other, and in the negative x-axis direction, the magnetic fluxes weaken each other. As a result, a radial force Fx is generated in the positive x-axis direction.
[0023]
In the bearingless motor 10 of the present invention, the number of poles of the position control structure winding is larger than the number of poles of the motor winding, and the permanent magnet 22 of the rotor 12 is buried deeply so as to be immersed from the facing surface. In the rotor 12, a portion on the side facing the permanent magnet 22 functions as a yoke through which magnetic flux passes. As shown in FIGS. 3 to 6, each magnetic flux passes on the side facing the permanent magnet. As a result, at least the position control magnetic fluxes Ψx and こ と が y do not penetrate through the permanent magnet having a high magnetic resistance, and these magnetic fluxes generate a large radial force.
Further, since the radial force generated in this way has no relation to the thickness of the permanent magnet, the bearingless motor of the present invention is also applicable to increasing the thickness of the permanent magnet according to the radial force required for the bearingless motor. Can respond.
[0024]
In the present embodiment, the pole magnet 24 is provided between the permanent magnets 22a and 22b having different polarities. The pole magnet 24 extends in the normal direction to a position closer to the facing surface of the rotor 12 and the stator 14 than the surface of the permanent magnet 22. With this configuration, the field magnetic flux of the permanent magnet does not close to the adjacent permanent magnet of the different polarity, and accordingly, the position control magnetic fluxes Ψx, Ψy and the torque magnetic flux Ψq that pass through the surface side of the permanent magnet 22. In conjunction with this, the radial force and the rotational torque also increase.
In particular, in the case of a bearingless motor having a large gap length such as a canned pump or a pump for an artificial heart, it is preferable to insert an interpole magnet between permanent magnets having different polarities. The reason is that, as described above, the field magnetic flux flowing from the rotor to the stator can be increased, and the magnetic flux of the permanent magnet can be effectively used for generating a radial force and a rotational torque. .
[0025]
FIG. 7 shows another embodiment of a rotor in a bearingless motor having a two-pole motor and a four-pole position control structure. The rotor 30 shown in FIG. 1 includes a two-pole permanent magnet 32. The stator (not shown) is substantially the same as the stator shown in FIG. Further, the rotor 30 is provided with a pole magnet 34 at a portion between the permanent magnets.
[0026]
The permanent magnet 32 is buried deep in the rotor 30 at a distance from the surface of the rotor 30 facing the stator. The permanent magnets 32 are provided with a phase of 180 ° and include flat permanent magnets 32a, 32a having a surface S pole on the left side in the figure and flat permanent magnets 32b, 32b having a surface N pole on the right side in the figure.
Each of the permanent magnets 32a, 32a, 32b, 32b is inserted into a groove penetrating the rotor 30 in the longitudinal direction. Further, the pole magnet 34 is also inserted into a groove penetrating the rotor 30 in the longitudinal direction.
Each of the plate-like permanent magnets 32 has a polygonal structure so as to surround the shaft or the hole for inserting the shaft when viewed in cross section, and the magnetic flux is generated substantially in the normal direction of the rotor 30. The pole magnet 34 prevents the field magnetic flux from forming a closed magnetic path between adjacent permanent magnets 32a and 32b having different poles. As a result, the field magnetic flux passes through the side of the rotor 30 facing the permanent magnet 32.
The grooves are wider than the permanent magnets 32, and gaps are formed between the permanent magnets and between the permanent magnets and the pole magnets. Due to this gap, the magnetic material portion remaining in the rotor 30 is narrowed, so that it is possible to avoid forming a closed magnetic path by each permanent magnet itself, and it is also easy to insert the permanent magnet 32 into the rotor 30. It becomes.
[0027]
FIG. 8 shows still another embodiment of the rotor of the two-pole motor, the four-pole position control structure of the bearingless motor. The rotor 40 shown in the figure has a two-pole permanent magnet 42. The stator (not shown) is substantially the same as the stator shown in FIG. Further, the rotor 40 is provided with a pole magnet 44 at a portion between poles of the permanent magnet.
[0028]
The rotor 40 shown in FIG. 8 includes three plate-shaped permanent magnets 42a and 42a having three S poles on the left side in the figure and three plate-shaped permanent magnets 42b and 42b having three N poles on the right side in the drawing. I have.
Each permanent magnet 42 is inserted in a groove that penetrates the rotor 40 in the longitudinal direction. The pole magnet 44 is also inserted in a groove penetrating the rotor 40 in the longitudinal direction. Each of the plate-shaped permanent magnets 42 has a polygonal structure surrounding the shaft or the hole for inserting the shaft in cross section, and is formed between the permanent magnet and the permanent magnet and between the permanent magnet and the pole magnet. Creates a void.
Similarly to rotor 30 shown in FIG. 7, rotor 40 shown in FIG. 8 narrows the remaining portion of the rotor functioning as a yoke, so that the field magnetic flux moves from rotor 40 to the stator. It is formed.
[0029]
9 and 10 show another embodiment of the bearingless motor according to the present invention. The bearingless motor 110 is used, for example, in a disk drive unit, and has a structure in which a stator 114 is disposed inside and a rotor 112 is disposed outside.
[0030]
As shown in detail in FIG. 10, the bearingless motor 110 includes outer rotors 112 and 112 and inner stators 114 and 114 facing each other via a gap. In FIG. 10, the winding of the stator 114 is omitted, but the bearingless motor 110 of the present embodiment also has a two-pole electric motor and four-pole position control structure.
[0031]
The rotor 112 includes a two-pole permanent magnet 122 immersed and buried from a surface facing the stator 114. Also. The rotor 112 includes a pole magnet 124 at a portion between poles of the permanent magnet 122. The rotor 112 itself is made of a magnetic material, and the opposing surface of the permanent magnet 122 divided by the pole magnet 124 functions as a yoke through which magnetic flux passes.
The pole magnet 124 prevents the field magnetic flux from forming a closed magnetic path between adjacent permanent magnets of different polarities. Therefore, the pole magnet 124 extends closer to the facing surface than the permanent magnet 122. As a result, the field magnetic flux passes through the rotor 112 on the side facing the permanent magnet 122.
[0032]
FIG. 11 shows an embodiment in which n = 4 in an n-pole motor, n + 2 pole position control structure.
The bearingless motor 210 of this embodiment includes an inner rotor 212 and an outer stator 214 that face each other via a gap. The rotor 212 has four-pole permanent magnets 222, and the stator 214 has four-pole motor windings Nd, Nq and six-pole position control windings Nx, Nx, Nx, Ny, Ny, Ny. I have. In addition, the rotor 212 includes a pole magnet 224 at a portion between poles of the permanent magnet.
[0033]
The permanent magnet 222 is buried deep in the rotor 212 at a distance from the facing surface of the rotor 212. The permanent magnets 222 are provided with a phase of 90 °, and each permanent magnet is arranged in an annular shape. The rotor 212 itself is made of a magnetic material, and the opposing surface side of the permanent magnet 222 defined by the pole magnet 224 functions as a yoke through which magnetic flux passes. The pole magnet 224 prevents a field magnetic flux from forming a closed magnetic path between adjacent permanent magnets 222 of different poles. As a result, the field magnetic flux passes through the rotor 212 on the side facing the permanent magnet 222.
[0034]
12 to 20 show an application example of the bearingless motor according to the present invention, that is, applications.
FIG. 12 shows an application example of the bearingless motor 301 to applications such as a pump, an implantable artificial heart, a fan, a compressor, and a dangerous gas transfer device. The pump 300 includes an impeller 303 in a partition 302, and pumps fluid from an inlet 304 to an outlet 305. The rotor 306 of the bearingless motor 300 is attached to the impeller 302, and the stator 307 is attached to the outside of the partition 302. The partition 302 extends the gap between the rotor 306 and the stator 307, and such a bearingless motor 301 is suitable for pumping a fluid in an airtight environment.
[0035]
FIG. 13 shows an example in which the bearingless motor 311 is applied to a powdering machine. The powdering machine 310 includes a transfer pipe 313 that can rotate inside the housing 312. The distal end of the transfer tube 313 branches into a plurality of discharge tubes extending radially in the housing 312. Each rotor 316 of the tandem type bearingless motor 311 is attached to the transfer pipe 313, and each stator 317 is attached to the inner wall of the housing 312. When the bearingless motor 311 is started, the transfer tube 313 rotates together with the rotor 316, and the liquid is ejected from the opening of the discharge tube to be powdered, and the powder is discharged from the lower opening of the housing 312.
[0036]
FIG. 14 shows an example of application of the bearingless motor 321 to a use of a semiconductor manufacturing apparatus. The semiconductor manufacturing apparatus 320 includes a plate 323 on which a semiconductor wafer can be placed or attached in a case 322. The rotor 326 of the bearingless motor 321 is attached to the plate 323, and the stator 327 is attached to the outside of the case 322. The case 322 extends the gap between the rotor 326 and the stator 327, and such a bearingless motor 321 is suitable for handling a workpiece in an environment requiring extremely high cleanliness.
[0037]
FIG. 15 shows an example of the application of the bearingless motor 331 to the use of the flywheel 330. A rotor 336 is attached to the hollow cylindrical inner wall of the rim 332 of the flywheel 310 so as to face each stator 337 of the tandem type bearingless motor 331. A thrust bearing 334 is disposed between the base 333 and the rim 332, and the flyhole 330 is supported in a floating state. When the bearingless motor 331 is started, the rim 332 rotates together with the rotor 336.
[0038]
FIG. 16 shows an example of application to a flyhole in which another configuration is adopted for the configuration facing the gap. The rotor 346 is attached to the flywheel 340, and the stator 337 is attached to the base 343. The tandem-type bearingless motor 341 has a tapered shape in which each rotor 346 expands outward in the axial direction, and a pair of stators 347 has a V-shape following the shape of the rotor 346. .
The rotor and the stator may be configured in an inverse relationship, and the respective rotor and stator may be configured in a mirror-image symmetrical step shape. In the example shown in FIG. 16, the flywheel rotates in a floating state without the thrust bearing.
[0039]
FIG. 17 shows an example of application of the bearingless motor 351 to the use of the monitor device 350. A rotor 356 is attached to a cylindrical inner wall of a cap-shaped housing 352 that supports the monitor device 350 so as to face each stator 357 of the tandem type bearingless motor 351. A thrust bearing 354 is disposed between a tip of a shaft 355 protruding from the base 353 and the housing 352, and the housing 352 is supported in a floating state. When the bearingless motor 351 is started, the housing 352 rotates together with the rotor 356, and controls the visual field of the monitor device 350.
[0040]
FIG. 18 shows an example of application of the bearingless motor 361 to the use of the spindle unit 360. Each rotor 366 of the tandem type bearingless motor 361 is mounted on a spindle 363, and each stator 367 is mounted on an inner wall of the housing 362. A chuck 365 is attached to one end of the spindle 363, and a cutting tool such as a reamer or a grinding tool is detachable. The other end of the spindle 362 is provided with a thrust bearing 364. Note that the bearingless motor of the present invention may be employed only in one of the unit 1 and the unit 2.
[0041]
FIG. 19 shows an example of application of the bearingless motor 371 to the use of the centrifuge 370. Each rotor 376 of the tandem type bearingless motor 371 is attached to a spindle shaft 373, and each stator 377 surrounds the rotor 376. At one end of the spindle shaft 373, a receiving member 374 for accommodating an object to be centrifuged is provided. Thrust bearings are provided as needed.
[0042]
Next, in order to confirm the effectiveness of the bearingless motor according to the present invention, a static magnetic field analysis was performed by a finite element method, and a comparative test was performed with a conventional bearingless motor. Further, a comparative example was manufactured, and the comparative example was subjected to a comparative test.
As the analysis model, (1) the conventional product shown in FIG. 26, (2) the comparative product, and (3) the invention product shown in FIG. 2 were used. Although not shown, the comparative product is a bearingless motor having a two-pole motor / four-pole position control structure and having a permanent magnet embedded shallowly from the facing surface. In order to equalize the conditions, a pole-to-pole magnet was inserted between permanent magnets having different polarities in the conventional product.
[0043]
20 and 21 show the specifications of the conventional product, the comparative product, and the invention product, respectively. The lower table of FIG. 20 shows the parameters of the rotor. In the conventional product, the comparative product, and the invention product, since the embedded depth d and the magnet thickness t of the permanent magnet cannot be increased without limit, the test was performed with d + t ≦ 11.
[0044]
In the comparative test, each of the position control windings Nx and Ny was supplied with a half of the rated current of 8 A, that is, a position control current of 4 A was passed through the position control winding Nx, and a position control current of 4 A was passed through the position control winding Ny.
FIG. 22 shows the change in the magnet thickness t and the radial force at that time. FIG. 23 shows the change in the magnet thickness t and the torque when a rated value of 8 A flows in the torque current. In FIGS. 22 and 23, A, A ′, and A ″ are limits on the rotor structure where d + t = 11.
[0045]
As shown in FIG. 22, the radial force of the conventional product was maximum at point B, and the radial force of the comparative product was maximum at point C. In the comparative product, the decrease in the radial force due to the increase in the magnet thickness is smaller than that of the conventional product. The reason is that, in the comparative product, a part of the position control magnetic flux can pass through the rotor yoke having a thickness of d = 1 mm, whereas in the conventional product, all the position control magnetic fluxes are reduced by the magnetic saturation in the gap between the poles. Therefore, it cannot be passed through the rotor yoke, and must pass directly through the permanent magnet. Therefore, in the conventional product, when the magnet thickness t is increased, the position control magnetic flux is reduced, and the radial force is rapidly reduced, which is not practical.
[0046]
In the invention product, since the permanent magnet is buried deeply from the facing surface, a sufficient rotor yoke width is secured as compared with the comparative product. Thereby, almost all the position control magnetic flux passes through the rotor yoke, and as the magnet thickness t increases, the radial force increases accordingly. Then, the radial force becomes maximum at point A, which is the limit of the structure in which the thickness of the permanent magnet is set to 5 mm, which is almost the same as the embedded depth. 47
[0047]
However, in FIG. 23, it is recognized that the rotational torque gradually decreases in the order of the conventional product, the comparative product, and the inventive product in the case of the same magnet thickness contrary to the radial force. From FIG. 23, it cannot be determined which bearingless motor can generate the radial force more effectively.
Therefore, when the magnetic field analysis is performed as shown in the upper table of FIG. 20, the motor winding and the position control winding have the same cross-sectional area, and the number of turns is Nm = 20 turns and Ns = 10 turns. The number of turns Nm of the motor winding was converted so that Nm + Ns = 30 turns per slot, and then the torque analysis results of the conventional product, the comparative product, and the invention product were all 1 Newton meter. Then, the number of windings of the position control winding was set to Ns = 30-Nm, and was changed so that the total per slot was always 30 turns.
[0048]
FIG. 24 shows the radial force generated when the number of turns is changed and the magnitude of the torque is made equal by 1 Newton meter. When the magnet thickness t is less than 1.3 mm, a torque of 1 Newton meter cannot be generated even if Nm is 30 turns, so that the radial force cannot be converted.
Comparing the conventional product, the comparative product, and the invention product, the invention product has the maximum radial force of 52.5 N at point A. The conventional product has the maximum at point D, and the comparative product has the maximum at point E. The radial force of the invention is increased by 87.6% over the conventional product and by 25.4% over the comparison product.
As can be seen from the above comparative test, in a bearingless motor having an n-pole electric motor and an n + 2 position control structure and a structure in which a permanent magnet is buried deeply, the position control magnetic flux passes through the opposing surface of the permanent magnet, which is extremely effective. A large rotational torque can be obtained.
[0049]
【The invention's effect】
In the bearingless motor of the present invention, since the permanent magnet of the rotor is embedded so as to be immersed deeper than the surface facing the stator, the position control magnetic flux passes through the portion on the side facing the permanent magnet. Since the magnetic body on the side of the rotor facing the side of the rotor passes the position control magnetic flux, the position control magnetic flux does not pass through the permanent magnet having a large magnetic resistance, and a large radial force is generated.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an application example of a bearingless motor according to the present invention.
FIG. 2 is a sectional view of one embodiment of a bearingless motor according to the present invention.
FIG. 3 is a cross-sectional view illustrating the principle that a radial force acts in the x direction when no load is applied to the bearingless motor according to the present invention.
FIG. 4 is a cross-sectional view illustrating the principle that a radial force acts in the y-direction when there is no load in the bearingless motor according to the present invention.
FIG. 5 is a cross-sectional view illustrating a principle in which a radial force is applied by a torque current and a position control current in a bearingless motor according to the present invention.
FIG. 6 is a cross-sectional view illustrating a principle in which a radial force is applied by a torque current and a position control current in a bearingless motor according to the present invention.
FIG. 7 is a sectional view of another embodiment of the rotor in the bearingless motor of FIG. 2;
FIG. 8 is a sectional view of still another embodiment of the rotor in the bearingless motor of FIG. 2;
FIG. 9 is a schematic view showing another application example of the bearingless motor according to the present invention.
FIG. 10 is a sectional view of another embodiment of the bearingless motor according to the present invention.
FIG. 11 is a sectional view of still another embodiment of the bearingless motor according to the present invention.
FIG. 12 is a schematic view showing an example in which a bearingless motor according to the present invention is applied to a pump.
FIG. 13 is a schematic view showing an application example of a bearingless motor according to the present invention to a powdering machine.
FIG. 14 is a schematic view showing an example in which a bearingless motor according to the present invention is applied to a semiconductor manufacturing apparatus.
FIG. 15 is a schematic view showing an example in which the bearingless motor according to the present invention is applied to a flywheel.
FIG. 16 is a schematic view showing another application example of the bearingless motor according to the present invention to a flywheel.
FIG. 17 is a schematic view showing an example in which a bearingless motor according to the present invention is applied to a monitor device.
FIG. 18 is a schematic view showing an example in which a bearingless motor according to the present invention is applied to a spindle unit.
FIG. 19 is a schematic view showing an example in which a bearingless motor according to the present invention is applied to a centrifuge.
FIG. 20 shows a specification table of a comparative test.
FIG. 21 is a sectional view showing conditions of a comparative test.
FIG. 22 is a graph showing the radial force of a comparative test.
FIG. 23 is a graph showing torque in a comparative test.
FIG. 24 is a graph showing the radial force when the torque is converted to 1 Newton meter.
FIG. 25 is a perspective view showing the whole of a general bearingless motor.
FIG. 26 is a sectional view showing the arrangement and operation of a permanent magnet, a motor winding, and a position control winding of a conventional bearingless motor.
[Explanation of symbols]
10,110,210 Bearingless motor
12,112,212 rotor
14,114,214 Stator
16 Thrust bearing 18 Pump
20 Impeller
22,212,222 permanent magnet
24,124,224 Interpole magnet

Claims (3)

In a bearingless motor in which a rotor and a stator face each other via a gap,
The rotor includes an n-pole permanent magnet buried away from a surface facing the stator, and the stator includes an n-pole motor winding and an n + 2 pole position control winding. A bearingless motor. The bearingless motor according to claim 1, wherein the rotor includes an interpole magnet between adjacent permanent magnets having different polarities. The bearingless motor according to claim 1, wherein the interpole magnet protrudes toward the stator from the permanent magnet.

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