JP4153468B2 - Magnetic levitation motor and turbo pump - Google Patents

Description

  The present invention relates to a magnetic levitation motor that rotates while supporting a rotor in a non-contact state by a magnetic force, and more particularly to a magnetic levitation motor suitable for miniaturization and a turbo pump using the same.

  The magnetic levitation type motor has an advantage that there is no wear on the bearing portion because the rotor is rotationally driven in a state of being supported in a non-contact manner by a magnetic bearing. However, a magnetic levitation motor that uses an electromagnet as a magnetic bearing requires a large current to levitate the rotor. In order to increase the magnetic force with a small current, it is required that the gap between the rotor and the stator be small, and high machining accuracy is required.

  As an effective method for solving these problems, a hybrid type magnetic levitation motor that uses a magnetic flux generated from a permanent magnet as a bias magnetic flux of a magnetic bearing has been used (Patent Document 1). The most popular type of this hybrid type magnetic levitation type motor is that a permanent magnet magnetized in the axial direction is sandwiched between two radial magnetic bearings spaced apart in the rotational axis direction of the rotor, The radial attraction is controlled by biasing the radial bearing to the N pole and biasing the other radial bearing to the S pole, and strengthening the bias magnetic flux in the radial direction by the exciting coil and weakening the other in the other direction. .

In addition, the present inventors have proposed a small axial flow pump used in an artificial heart or the like to which such a magnetic levitation motor is applied (Non-patent Document 1). In this axial flow pump, two magnetic bearings are arranged at both ends of the rotor in the axial direction. Each magnetic bearing is composed of four electromagnets, and each of the four electromagnets at both ends controls the position of the rotor in the radial direction, axial direction, and tilt direction. Between these magnetic bearings, a stator for a motor is disposed so as to surround the central portion in the axial direction of the rotor, and the rotor is driven to rotate by a rotating magnetic field from the stator.
JP 2003-021140 A (paragraphs 0053 to 0056, FIG. 6) “Development of magnetic levitation system for axial flow pump” (Kojima et al., May 16, 2003, Japan Society for Life Support Engineering, p29)

  In the conventional magnetic levitation motor described above, when the rotor is displaced from the center, an attractive force acts in a direction that causes the magnetic levitation to fail by the rotating permanent magnet of the rotor. For this reason, in the magnetic levitation motor of the type which arrange | positions a rotor between magnetic bearings, there exists a problem that position control of a rotor is difficult.

  The present invention has been made in view of such problems, and an object thereof is to provide a magnetic levitation motor and a turbo pump that are excellent in controllability and can be further reduced in size and weight. .

A first magnetically levitated motor according to the present invention is a magnet composed of a rotor and an electromagnet which is disposed at both ends of the rotor in the rotation axis direction and supports the rotor in a non-contact manner by a magnetic force in the rotation axis direction and radial direction. A bearing, a stator arranged between the magnetic bearings so as to surround a central portion in the rotation axis direction of the rotor, and a rotational driving force applied to the rotor, and different poles face each other between the magnetic bearing and the stator. And a permanent magnet for supplying a bias magnetic flux to the magnetic bearing, the diameter of the central portion of the rotor to which a rotational driving force is applied by the stator is supported by the magnetic bearing. It is set smaller than the diameter of the both ends of the rotor.

A second magnetic levitation motor according to the present invention is a magnet comprising a rotor and electromagnets arranged at both ends in the rotation axis direction of the rotor and supporting the rotor in a non-contact manner by a magnetic force in the rotation axis direction and the radial direction. A bearing, a stator arranged between the magnetic bearings so as to surround a central portion in the rotation axis direction of the rotor, and a rotational driving force applied to the rotor, and different poles face each other between the magnetic bearing and the stator. in the magnetic levitation type motor is inserted and a permanent magnet for supplying a bias flux to said magnetic bearing as the magnetic attraction force between the said stator rotor, than the magnetic attraction force between the said magnetic bearing rotor It is characterized by being set small.

Further, the turbo pump according to the present invention has a rotor in which the diameter of the central part is set smaller than the diameters of both end parts and an impeller is formed on the outer peripheral surface of the central part, and the rotor can be rotated without contact inside. A cylindrical casing having a transfer fluid inlet at one end and a discharge outlet of the transfer fluid at the other end; and the rotor disposed at both ends of the rotor in the rotation axis direction. A magnetic bearing composed of an electromagnet that is supported in a non-contact manner by a magnetic force in the direction of the rotation axis and in the radial direction, and disposed between the magnetic bearings so as to surround a central portion in the direction of the rotation axis of the rotor. And a permanent magnet that is inserted so that different poles face each other between the magnetic bearing and the stator and supplies a bias magnetic flux to the magnetic bearing.

  According to the present invention, since the magnetic attractive force between the stator and the rotor is set to be smaller than the magnetic attractive force between the magnetic bearing and the rotor, the position control of the rotor by the magnetic bearing is performed even when the rotor is displaced. The controllability is good, and further reduction in size and weight can be achieved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a perspective view in which a part of a magnetic levitation motor according to a first embodiment of the present invention is cut away, FIG. 2 is a cross-sectional view taken along a rotation axis, and FIG. It is a cross-sectional view.

  This magnetic levitation motor includes a cylindrical rotor 1, magnetic bearings 2 and 3 that support both ends of the rotation axis direction (Z-axis direction) of the rotor 1 in a non-contact manner, and between these magnetic bearings 2 and 3. An annular stator 4 that is disposed at a position and applies a rotational driving force to the central portion in the rotational axis direction of the rotor 1, and is disposed at four positions in the circumferential direction between the magnetic bearings 2, 3 and the stator 4. The bias permanent magnets 5 and 6 to be supplied and a gap such as an eddy current sensor for detecting displacement in the rotation axis direction (Z-axis direction) and radial direction (X and Y-axis directions) of the rotor 1 on one end side of the rotor 1. Gap sensors 10, 11 such as eddy current sensors for detecting displacement in the radial direction (X, Y axis direction) of the rotor 1 on the other end side of the sensors 7, 8, 9 and the rotor 1, the magnetic bearings 2, 3 and the stator Cases 12 and 13 covering the outer periphery of each It is constituted by a 14.

  The rotor 1 is made of a ferromagnetic material such as magnetic stainless steel, and both end portions are large diameter portions 16a and 16b supported by the magnetic bearings 2 and 3, and the axial central portion facing the stator 4 is smaller in diameter than both end portions. The rotor main body 16 has a small diameter portion 16c, and four rotor permanent magnets 17 are mounted on the small diameter portion 16c of the rotor main body 16. The permanent magnet 17 has an outer shape in which a cylindrical body is divided into four in the circumferential direction, is attached in the thickness direction, and is mounted on the rotor 1 so that the south pole and the north pole are alternately arranged in the circumferential direction.

  The magnetic bearings 2 and 3 include, for example, electromagnet cores 21 and 31 made of a ferromagnetic material such as magnetic stainless steel, and four electromagnet coils 22 and 32 wound around the electromagnet cores 21 and 31. . The electromagnet cores 21 and 31 are cylindrical axial salient poles 21a and 31a that extend in the rotation axis direction of the rotor 1 and that have one end opposed to both ends of the rotation axis direction (Z-axis direction) of the rotor 1 via a predetermined gap. The four first yokes 21b, 31b extending radially from the four circumferential positions on the base end side of the axial salient poles 21a, 31a and the axial directions from the tips of the first yokes 21b, 31b 4 second yokes 21c and 31c extending to the biasing permanent magnets 5 and 6, respectively, and projecting in the radial direction from the tips of the second yokes 21c and 31c toward the large diameter portions 16a and 16b of the rotor 1. It is provided with four radial salient poles 21d and 31d that are provided and face the rotor 1 via a predetermined gap. The electromagnet coils 22 and 32 are wound around the four second yokes 21c and 31c of the electromagnet cores 21 and 31, respectively. A central hole is formed in the axial salient poles 21a and 31a, and a gap sensor 7 that detects displacement in the rotational axis direction (Z-axis direction) of the rotor 1 in the central hole of at least one of the axial salient poles 21a. Is installed.

  As shown in FIG. 3, the stator 4 is a six salient pole type stator driven by, for example, three phases, and an annular stator core 41 made of a laminated body of ferromagnetic materials such as laminated silicon steel plates in order to prevent generation of eddy current. And six stator coils 42 wound around the stator core 41. The stator core 41 is divided into six parts for each pole. The stator core 41 extends in the radial direction from the inner periphery every 60 ° of the annular yoke 41 a and the annular yoke 41 a, and the tip extends along the circumferential surface of the rotor 1. It has six salient poles 41b that widen.

  FIG. 4 is a circuit diagram showing a magnetic bearing control circuit of the magnetically levitated motor.

  The output of the gap sensor 7 that detects the displacement of the rotor 1 in the rotation axis direction is input to the axial direction controller 51, and the outputs of the gap sensors 8 and 9 are input to the first radial direction controller 52, 11 is input to the second radial direction controller 53. The axial direction controller 51 outputs a PID control signal for correcting the difference from the axial target gap based on the output of the gap sensor 7 that detects the displacement of the rotor 1 in the rotational axis direction. The first radial direction controller 52 is based on the outputs of the gap sensors 8 and 9 that detect the radial gap on the large diameter portion 16a side of the rotor 1 and the difference from the radial target gap on the large diameter portion 16a side. A PID control signal for correcting the error is output. Further, the second radial direction controller 53 determines the radial target gap on the large diameter portion 16b side based on the outputs of the gap sensors 8 and 9 that detect the radial gap on the large diameter portion 16b side of the rotor 1. A PID control signal for correcting the difference is output. The PID control signals output from these controllers 51, 52, and 53 are appropriately added and subtracted by adders 54a to 54d and 55a to 55d, and electromagnet coils 22a to 22d and 32a to 32d via amplifiers 56a to 56d and 57a to 57d. Drive.

  Next, the operation of the magnetic levitation motor according to the present embodiment configured as described above will be described.

  FIG. 5 shows the magnetic flux formed in the magnetic circuit of the motor and its direction. In the figure, the dotted line arrows indicate the bias magnetic flux B generated by the biasing permanent magnets 5 and 6, and the solid line arrows indicate the control magnetic fluxes C1 and C2 generated by the electromagnet coils 22 and 32. The bias magnetic flux B is formed so as to extend from the north pole side to the south pole side of the permanent magnets 5 and 6, and flows inside the rotor 1 from the magnetic bearing 3 side to the magnetic bearing 2 side. In the outer peripheral side formed by 31c and the stator 4, it flows from the magnetic bearing 2 side to the magnetic bearing 3 side. On the way, there also exists a bypass route via the radial salient poles 21d and 31d. As a result of the formation of the bias magnetic flux B, the electromagnet coils 22 and 32 need only supply a magnetic flux corresponding to the position correction of the rotor 1, and the power consumption can be reduced.

  Assuming that the axial gap between the rotor 1 and the axial salient pole 21a has increased, the controller 51 increases the axial magnetic flux on the magnetic bearing 2 side as shown in FIG. The control magnetic fluxes C1 and C2 are controlled so as to weaken the directional magnetic flux. Since the control magnetic fluxes C1 and C2 act equally in the radial direction, the rotor 1 moves to the axial salient pole 21a side of the magnetic bearing 2 as a whole along the axial direction. It becomes possible to return to the direction position.

  In addition, when the rotor 1 is displaced in the radial direction, the first and second radial direction controllers 52 and 53 are arranged in the radial direction in the magnetic bearings 2 and 3 based on the outputs of the gap sensors 8 to 11. The electromagnetic coils 22 and 32 are controlled so that the control magnetic fluxes C1 and C2 are strengthened in the radial direction and the other control magnetic fluxes C1 and C2 in the radial direction are weakened in the radial direction. Thereby, the rotor 1 moves in the radial direction in which the magnetic flux is strengthened, and the rotor 1 can be returned to the normal radial direction position.

  When the rotor 1 is tilted with respect to the central axis, the rotor 1 can be tilted in either direction by moving the rotor 1 in the different radial directions with the magnetic bearings 2 and 3. 1 tilt correction is also possible.

  Thus, the rotor 1 supported in a non-contact manner by the magnetic bearings 2 and 3 constitutes a synchronous motor in which the motor permanent magnet 17 on the rotor 1 side follows the three-phase AC rotating magnetic field supplied from the stator 4 and rotates. . When the rotor 1 is displaced in the radial direction during rotation, the magnetic attractive force between the motor permanent magnet 17 mounted on the small diameter portion 16 c of the rotor 1 and the stator 4 increases. For this reason, the attitude control of the rotor 1 in the magnetic bearings 2 and 3 is affected.

  Therefore, in the present embodiment, both end portions of the rotor 1 supported in a non-contact manner by the magnetic bearings 2 and 3 are the large diameter portions 16a and 16b, and the central portion of the rotor 1 to which the rotating magnetic field is applied is the small diameter portion 16c. Thus, the gap between the radial salient poles 21d and 31d and the large diameter portions 16a and 16b is made smaller than the gap between the motor permanent magnet 17 of the rotor 1 and the salient pole 41b of the stator 4.

  FIG. 6 is a graph showing changes in magnetic attractive force in the magnetic bearing and the motor with respect to the radial displacement of the rotor 1 for the experimental machines I and II.

  In both the experimental machines I and II, the diameter of the radial salient poles 21d and 31d of the magnetic bearings 2 and 3 was set to 22 mm, and the diameter of the salient pole 41b of the stator 4 was set to 22 mm.

  In the rotor of the experimental machine I, the diameters of the large diameter portions 16a and 16b were φ20 mm, and the surface diameter of the permanent magnet 17 was φ15 mm.

  Further, in the rotor (1) of the experimental machine II, the diameters of the large diameter portions 16a and 16b were set to φ20 mm, and the diameter of the surface of the permanent magnet 17 was set to φ14 mm.

  Further, in the rotor (2) of the experimental machine II, the diameters of the large diameter portions 16a and 16b were φ20 mm, and the diameter of the surface of the permanent magnet 17 was φ13 mm.

  As is clear from FIG. 6, the experimental machines I and II both have a radial magnetic force between the magnetic bearings 2 and 3 and the rotor 1 even when the radial displacement of the rotor 1 reaches 0.5 mm. Since the attractive force (dotted line in the figure) exceeds the radial magnetic attractive force between the stator 4 and the rotor 1 (solid line in the figure), the magnetic levitation of the rotor is less affected by the magnetic attractive force by the motor. Control could be done.

  FIG. 7 is a sectional view showing a magnetic levitation motor according to another embodiment of the present invention.

  In the previous embodiment, the outer diameters of the second yokes 21c and 31c of the magnetic bearings 2 and 3 and the outer diameter of the stator 4 are substantially the same, but in this embodiment, the second yokes of the magnetic bearings 2 and 3 are the same. The outer diameter of the stator 61 is made larger than the outer diameters of the irons 21c and 31c. For this reason, the width | variety of the permanent magnet 62 for bias inserted between the 2nd yokes 21c and 31c and the stator 61 is also large.

  According to this embodiment, since the number of windings of the stator coil 63 can be increased by an amount corresponding to the increase in the diameter of the stator 61, the generated torque can be increased.

  FIG. 8 is a cross-sectional view showing an embodiment of an axial flow pump as an example of a turbo pump to which the present invention is applied.

  In the rotor 71, a plurality of holes 71c and 71d penetrating in the axial direction are formed in a plurality of locations in the circumferential direction in the large diameter portions 71a and 71b at both ends, and the impeller is disposed on the rotor permanent magnet 72 of the middle small diameter portion 71e. 73 is formed. The rotor 71 is housed inside a non-magnetic cylindrical casing 74. Four inlets 75 are connected to the magnetic bearing 2 side of the casing 74 using four empty spaces. In addition, four outlets 76 are connected to the magnetic bearing 3 side of the casing 74 using four empty spaces.

  According to this axial flow pump, the transfer fluid introduced from the inlet 75 into the casing 74 is introduced to the impeller 73 side through the hole 71c of the rotor 71, and the kinetic energy is generated by the rotation of the rotor 71 to which the impeller 73 is attached. After being applied, it is discharged through the hole 71d and further discharged from the outlet 76 to the outside.

  According to this embodiment, since the impeller 73 is provided in the small diameter portion 71e, the diameter of the rotor 71 does not increase, and a small axial flow pump can be realized. This axial flow pump is particularly suitable as a pump for an artificial heart. That is, since the turbo pump of the present invention uses a floating rotor, the bearing portion has good durability and does not cause problems such as thrombus formation.

  In the present invention, the magnetic attraction force between the stator and the rotor is set smaller than the magnetic attraction force between the magnetic bearing and the rotor. The diameter of the part was made smaller than the diameters of both ends constituting the magnetic bearing. However, the present invention is not limited to this, and the attractive force adjustment based on the geometrical shape can also reduce the attractive force by reducing the motor magnet itself. A method of reducing the attractive force by taking a distance from the magnet for use is conceivable. Further, not only the geometric shape but also the magnetic characteristics of the permanent magnet 17 may be set to an appropriate one so as to satisfy the above-described relationship.

  In the above embodiment, an axial flow pump is illustrated as an example of a turbo pump. However, it goes without saying that the present invention can also be applied to turbo pumps such as a centrifugal pump and a mixed flow pump. As for the stator of the motor, the present invention can also be applied to a motor using a type of stator that does not have a core (a salient pole 41b) around which a coil is wound.

It is the perspective view which notched some magnetic levitation type motors concerning a 1st embodiment of the present invention. It is a longitudinal cross-sectional view of the same magnetic levitation type motor. It is AA 'sectional drawing in FIG. 2 of the magnetic levitation type motor. It is a circuit diagram which shows the control circuit of the bearing of the same magnetic levitation type motor. It is a perspective view for demonstrating the magnetic flux for the magnetic bearing in which the same magnetic levitation type motor is formed. It is a graph which shows the radial direction displacement of the rotor of the same magnetic levitation type motor, and the magnetic attraction force change in a magnetic bearing and a motor. It is sectional drawing of the magnetic levitation type motor which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the axial flow pump which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,71 ... Rotor, 2, 3 ... Magnetic bearing, 4, 61 ... Stator, 5, 6, 62 ... Permanent magnet for bias, 7-11 ... Gap sensor, 12-14 ... Case, 16 ... Rotor main body, 16a, 16b: Large diameter portion, 16c: Small diameter portion, 17, 72 ... Permanent magnet for rotor, 21, 31 ... Electromagnetic core, 22, 32 ... Electromagnetic coil, 41 ... Stator core, 42, 63 ... Stator coil, 51 ... Axial direction controller 52 ... 1st radial direction controller, 53 ... 2nd radial direction controller, 73 ... Impeller, 74 ... Casing, 75 ... Inlet, 76 ... Outlet.

Claims (6)

A rotor,
A magnetic bearing comprising electromagnets arranged at both ends in the rotation axis direction of the rotor and supporting the rotor in a non-contact manner by a magnetic force in the rotation axis direction and the radial direction;
A stator that is disposed between these magnetic bearings so as to surround a central portion in the rotation axis direction of the rotor, and applies a rotational driving force to the rotor;
A magnetic levitation type motor having a permanent magnet inserted between the magnetic bearing and the stator so that different poles face each other and supplying a bias magnetic flux to the magnetic bearing;
A magnetic levitation type motor, wherein a diameter of a central portion of the rotor to which a rotational driving force is applied by the stator is set smaller than a diameter of both end portions of the rotor supported by the magnetic bearing. A rotor,
A magnetic bearing comprising electromagnets arranged at both ends in the rotation axis direction of the rotor and supporting the rotor in a non-contact manner by a magnetic force in the rotation axis direction and the radial direction;
A stator that is disposed between these magnetic bearings so as to surround a central portion in the rotation axis direction of the rotor, and applies a rotational driving force to the rotor;
A magnetic levitation type motor having a permanent magnet inserted between the magnetic bearing and the stator so that different poles face each other and supplying a bias magnetic flux to the magnetic bearing;
A magnetic levitation type motor, wherein a magnetic attraction force between the stator and the rotor is set smaller than a magnetic attraction force between the magnetic bearing and the rotor.   3. The magnetically levitated motor according to claim 1, wherein the stator forms a magnetic path for bias magnetic flux of the magnetic bearing. The magnetic bearing is
One end protrudes in the rotation axis direction toward both ends of the rotor in the rotation axis direction to form an axial salient pole facing the rotor via a predetermined gap, and the other end faces the rotor. An electromagnet core projecting in a radial direction to form a radial salient pole facing the rotor via a predetermined gap;
The magnetic levitation motor according to claim 1, further comprising: an electromagnet coil wound around the electromagnet core. The rotor includes a permanent magnet for a rotor magnetized in a radial direction at a central portion in a rotation axis direction,
The stator is
An annular stator core having a plurality of motor salient poles projecting toward the rotor projecting from the inner circumference;
The magnetic levitation type motor according to claim 1, comprising a motor coil wound around each of the motor salient poles. A rotor in which the diameter of the central portion is set smaller than the diameter of both end portions, and an impeller is formed on the outer peripheral surface of the central portion;
A cylindrical casing in which the rotor is rotatably accommodated in a non-contact manner and has a transfer fluid inlet at one end and a discharge outlet for the transfer fluid at the other end;
A magnetic bearing comprising electromagnets arranged at both ends of the rotation axis of the rotor and supporting the rotor in a non-contact manner by a magnetic force in the rotation axis and radial direction;
A stator that is disposed between these magnetic bearings so as to surround a central portion in the rotation axis direction of the rotor, and applies a rotational driving force to the rotor;
A turbo pump comprising: a permanent magnet that is inserted so that different poles face each other between the magnetic bearing and the stator and supplies a bias magnetic flux to the magnetic bearing.

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