JP5545053B2 - Bearingless motor - Google Patents

Description

  The present invention relates to a bearingless motor that is supported in a non-contact manner by a magnetic levitation of a rotor.

  Conventionally, a bearingless motor that is supported in a non-contact manner by a magnetic levitation of a rotor is known. Many bearingless motors are provided with a magnetic levitation coil in addition to a rotation control coil applied to the stator. When a current is passed through the magnetic levitation coil, a magnetic force is applied in the radial direction of the rotor by making the magnetic flux density in the gap between the rotor and the stator unbalanced. Further, the displacement in the radial direction of the rotor is measured by a sensor, and the magnetic force is adjusted based on the measurement result, whereby the two-degree-of-freedom motion in the radial direction of the rotor is actively controlled. Such a bearingless motor has advantages such as no frictional force and less generation of wear powder. It can be applied to various pumps used in semiconductor manufacturing processes and medical fields, and reaction wheels built into satellites. Application is expected.

  The following Patent Document 1 describes an example of a configuration of an electromagnetic machine using a bearingless motor. This electromagnetic machine is a combination of two conventional bearingless motors and a thrust magnetic bearing. When the z axis is set along the main axis of the rotor and the x and y axes are set along the direction perpendicular to the main axis, In addition, it has a configuration capable of controlling a 5-degree-of-freedom motion in the directions of x, y, z, θx, and θy.

JP 2009-192041 A

  In the conventional 5-degree-of-freedom control type electromagnetic machine described above, 4 inverters are required for 5-degree-of-freedom control and rotation control, and at least 5 displacement sensors are required to detect the displacement of the rotor for feedback control of magnetic force. It is. As a result, the power consumption is increased and the size of the apparatus is easily increased.

  Therefore, the present invention has been made in view of such problems, and an object thereof is to provide a bearingless motor capable of reducing the size and power consumption of a device including a drive circuit.

  In order to solve the above-mentioned problems, a bearingless motor according to the present invention is a rotor in which two rotating members each having a plane parallel to each other are connected by a connecting member extending along an axial direction perpendicular to the plane. And a plurality of first permanent magnets provided on the surface of one rotating member of the two rotating members, and a plurality of the permanent magnets arranged along the circumference on the surface of the other rotating member of the two rotating members. A first stator including a second permanent magnet, a magnetic material provided so as to face the surface of one rotating member, and a magnetic material provided so as to face the surface of the other rotating member. A second stator including a coil wound around the second stator in a plurality of divided directions in the arrangement direction of the second permanent magnets and generating a magnetic field toward the surface of the other rotating member. Prepare.

  According to such a bearingless motor, when the direction along the main axis of the rotor is the Z-axis direction and the directions perpendicular to the Z-axis are the X-axis direction and the Y-axis direction, the X-axis direction, the Y-axis direction, The four-degree-of-freedom motion of the rotor in the θx direction centered on the X axis and the θy direction centered on the Y axis is the magnetic force between the permanent magnets provided on the surfaces of the two rotating members and the two stators. By binding, it is suppressed passively. At the same time, the movement of the rotor in the Z-axis direction is actively controlled by adjusting the excitation current flowing through the plurality of coils wound around the second stator facing the permanent magnet of one of the rotating members. At the same time, the rotor is driven to rotate by controlling the excitation currents of the plurality of coils of the second stator. As a result, the direction of movement of the object to be actively controlled can be reduced to a minimum of one degree of freedom, the number of inverters connected to the bearingless motor and the number of built-in displacement sensors can be reduced, and the drive circuit is included. The device can be reduced in size and power consumption.

  The rotor is preferably formed by connecting two disk-shaped rotating members by columnar connecting members extending in the axial direction. In this case, when the length of the rotor in the main axis direction becomes large, the processing becomes easy and the work of attaching the permanent magnet to the surface of the rotor becomes easy.

  The first permanent magnet is provided in a ring shape along the edge of the surface of one rotating member, and the second permanent magnet is arranged in a ring shape along the edge of the surface of the other rotating member. The first stator has a protrusion that extends toward the first permanent magnet, and the second stator has a plurality of protrusions that extend toward the second permanent magnet. And it is also preferable that the coil is wound around the several projection part of the 2nd stator. In this way, the magnetic coupling between the permanent magnets of the two rotating members and the two stators is evenly formed on the surface, so that the four-degree-of-freedom motion of the rotor can be efficiently suppressed. At the same time, the moment acting on the rotor at the time of rotational driving can be increased.

Furthermore, the length L along the axial direction of the rotor and the width D in the direction perpendicular to the axial direction of the surface of the rotor are represented by the following formula:
2 x D <L
It is also preferable to have the following relationship. By adopting such a configuration, it is possible to further strengthen the passive suppression effect of the four-degree-of-freedom movement of the rotor.

  According to the bearingless motor of the present invention, it is possible to reduce the size and power consumption of the device including the drive circuit.

It is a perspective view showing a bearingless motor which is a preferred embodiment of the present invention. It is a disassembled perspective view of the bearingless motor of FIG. It is a top view which shows the structure of the both end surfaces of the rotor of FIG. It is a figure which shows the structure of one stator of FIG. 2, (a) is a side view of a stator, (b) is a top view of a stator. FIG. 3 is a plan view of the other stator of FIG. 2. FIG. 3 is a side view showing a state where the rotor of FIG. 2 is held by a stator. FIG. 3 is a side view showing a state where the rotor of FIG. 2 is held by a stator. FIG. 3 is a side view showing a state where the rotor of FIG. 2 is held by a stator. FIG. 3 is a side view showing a state where the rotor of FIG. 2 is held by a stator. It is a figure which shows the time waveform of the electric current supplied to the coil of FIG. It is a figure which shows the positional relationship of the d-axis and q axis | shaft fixed with respect to the rotor, and the X-axis and Y-axis fixed with respect to the stator. It is a block diagram which shows schematic structure of the control circuit used for the bearingless motor of FIG. It is sectional drawing which shows the structure of the stator of the modification of this invention.

  Hereinafter, preferred embodiments of a bearingless motor according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  First, the structure of the bearingless motor according to the present invention will be described with reference to the drawings. The bearingless motor of the present invention is a motor that is supported in a non-contact manner by a stator by the magnetic levitation of a rotor.

(Configuration of bearingless motor)
1 is a perspective view showing a bearingless motor 1 according to a preferred embodiment of the present invention, FIG. 2 is an exploded perspective view of the bearingless motor 1 of FIG. 1, and FIG. 3 is a view of the rotor 4 of FIG. 4A and 4B are a side view and a plan view of one stator 2 in FIG. 1, respectively, and FIG. 5 is the other stator in FIG. 3 is a plan view of FIG. As shown in these drawings, the bearingless motor 1 includes a rotor 4 supported by a magnetic force between two stators 2 and 3 fixed by a fixing member (not shown). The bearingless motor 1 applies a rotational force to the rotor, and the rotational force of the rotor is provided with a through hole at the center of the stator and is coupled with the rotor through the through hole. It is used by providing a shaft and rotating a rotating plate attached to the end opposite to the coupling portion of the shaft. It is also conceivable that the rotational force of the rotor is used by a method of attaching an impeller to the rotor shaft and driving a fluid.

  The rotor 4 is formed in a substantially cylindrical shape with circular flat surfaces 7A and 7B on both ends of a connecting shaft (connecting member) 5 extending between the two stators 2 and 3, respectively. Two disk-shaped rotating plates (rotating members) 6A and 6B on the side are connected to each other. Specifically, in the rotor 4, the centers of the flat surfaces 7 </ b> A and 7 </ b> B of the rotating plates 6 </ b> A and 6 </ b> B are located on the central axis of the connecting shaft 5, and the two flat surfaces 7 </ b> A and 7 </ b> B In other words, the two flat surfaces 7A and 7B are configured to be parallel to each other.

  Two permanent magnets 9 and 10 are arranged and fixed on the flat surfaces 7A and 7B of the rotating plates 6A and 6B of the rotor 4 along the circular peripheral edges 8A and 8B of the flat surfaces 7A and 7B, respectively. Has been. These two permanent magnets 9 and 10 are permanent magnets such as a plate-like neodymium magnet having a shape obtained by dividing the ring shape into two, and are respectively opposite to each other in a direction perpendicular to the flat surfaces 7A and 7B. Magnetized. As a result, the permanent magnets 9 and 10 are arranged and fixed on the flat surfaces 7A and 7B, thereby forming a ring shape along the peripheral portions 8A and 8B of the flat surfaces 7A and 7B as a whole. Furthermore, different magnetic poles are alternately arranged along the peripheral portions 8A and 8B on the flat surfaces 7A and 7B.

Here, from the viewpoint of stabilizing the position between the stators 2 and 3 of the rotor 4, the length L along the central axis of the connecting shaft 5 between the flat surfaces 7A and 7B of the rotor 4 and the rotating plate The width (diameter) D in the direction perpendicular to the central axis of the connecting shaft 5 of the flat surfaces 7A and 7B of 6A and 6B is the following formula (1);
2 × D <L (1)
It is preferable to set so as to have the following relationship. By setting in this way, the position of the rotor 4 is reliably stabilized by magnetic coupling with respect to the four-degree-of-freedom movement of the rotor 4. For example, the diameters D of the stators 2 and 3 and the rotor 4 are 25 mm, the length L of the rotor 4 is 75 mm, the thicknesses of the permanent magnets 9 and 10 are 5 mm, the left and right stators 2 and 3 and the rotor 4 The gap is designed to be 0.6mm.

  The stator 2 has substantially the same shape as the flat surface 7A of the rotating plate 6A, and is arranged at equal intervals along the peripheral edge of the bottom plate 11 and the bottom plate 11 disposed so as to face the flat surface 7A. And six protrusions 12 extending from the bottom plate 11 toward the permanent magnets 9 and 10 on the flat surface 7A. In this stator 2, at least a portion of the protrusion 12 is made of a magnetic material such as electromagnetic soft iron, carbon steel, or a dust core so that an attractive force acts between the permanent magnets 9 and 10 of the rotating plate 6A. Has been.

  The stator 3 has substantially the same shape as the flat surface 7B of the rotating plate 6B, and is arranged at equal intervals along the peripheral edge of the bottom plate 13 and the bottom plate 13 arranged to face the flat surface 7B. And six protrusions 14 extending from the bottom plate 13 toward the permanent magnets 9 and 10 on the flat surface 7B. Furthermore, a plurality of coils 15 are wound around each protrusion 14 of the stator 3 along the arrangement direction of the permanent magnets 9 and 10 of the rotating plate 6B. These coils 15 are provided for rotationally driving the rotor 4 and stably holding it between the stators 2 and 3 in a non-contact manner, and apply a magnetic field toward the flat surface 7B of the rotating plate 6B. Have a role to generate. The stator 3 functions as an electromagnet together with the coil 15, and at least the portion of the protrusion 14 is made of a magnetic material such as electromagnetic soft iron, carbon steel, or a dust core.

(Mechanism of rotor magnetic levitation and drive)
In the bearingless motor 1 configured as described above, the motion of the four degrees of freedom of the rotor 4 can be passively stabilized (suppressed). That is, a magnetic field is generated with a predetermined magnetic flux density between the protrusion 12 of the stator 2 and the permanent magnets 9 and 10 of the rotor 4, and magnetic coupling is formed by this magnetic field. At the same time, between the protrusion 14 of the stator 3 and the permanent magnets 9 and 10 of the rotor 4, a current corresponding to the position of the permanent magnets 9 and 10 is passed through the plurality of coils 15 to rotate with the stator 2. A magnetic coupling that generates an attraction force that balances the attraction force in the central axis direction with the child 4 is formed (details will be described later). Here, when the Z axis is set along the central axis of the rotor 4 and the X axis and the Y axis are set perpendicular to the Z axis (FIG. 2), the X axis direction or the Y axis direction of the rotor 4 is set. for translation, the restoring force _{F R} is exerted between the stator 2 and the rotor 4 (Fig. 6). Further, the rotational movement in the θx and θy directions of the rotor 4 with the center point of the rotor 4 as the rotation center and the X axis or the Y axis as the rotation axis is also between the stators 2 and 3 and the rotor 4. restoring torque _{T R} acting on (Figure 7). As a result, the four-degree-of-freedom motion of the rotor 4 in X, Y, θx, and θy is passively stabilized by the magnetic coupling between the rotor 4 and the two stators 2 and 3.

On the other hand, the translational motion along the Z-axis direction of the rotor 4 is directed to the direction in which the rotor 4 moves when the rotor 4 moves from the neutral position even if the current supplied to the coil 15 is not controlled. As a result, a suction force is generated, resulting in instability. Therefore, the current supplied to the plurality of coils 15 is feedback-controlled in the coil 15 of the bearingless motor 1 along with the translational motion of the rotor 4 along the Z-axis direction. That is, when the rotor 4 moves from the neutral position along the Z-axis direction, the displacement is detected by the displacement sensor, and the current of the coil 15 is adjusted according to the detection result, so that the rotor 4 The magnetic flux density in the gap with the stator 3 is increased or decreased. For example, when the rotor 4 moves in the + Z-axis direction, the magnetic flux density in the gap between the rotor 4 and the stator 3 is increased, so that the attractive force F in the −Z direction with respect to the rotor 4 is increased. _-Z acts to actively stabilize the position (FIG. 8; strong field). On the other hand, when the rotor 4 moves in the −Z-axis direction, the magnetic flux density in the gap between the rotor 4 and the stator 3 is weakened, so that the attractive force F in the + Z direction with respect to the rotor 4 is reduced. _{+ Z} acts to actively stabilize the position (FIG. 9; field weakening).

FIG. 10 shows an example of a time waveform of the current supplied to the six coils 15. As shown in the figure, the coil 15 is supplied with three-phase alternating currents I _U , I _V , and I _W from the inverter, and with respect to the two coils 15 positioned on opposite sides of the center of the bottom plate 13. Thus, a current that generates a magnetic field in the opposite direction with the same current value is supplied.

At the time of feedback control of the three-phase alternating currents I _U , I _V , and I _W , the origin is set at the center on the flat surface 7B of the rotating plate 6B, and the magnetic field generated by the permanent magnets 9 and 10 along the flat surface 7B. The d axis is set in the direction, and the q axis is set in the direction perpendicular to the d axis along the flat surface 7B. Then, the three-phase alternating currents I _U , I _V , and I _W are controlled so as to adjust the magnitudes of the d-axis component and the q-axis component of the magnetic field vector generated by the stator 3. This d-axis component corresponds to the magnetic flux density between the rotor 4 and the stator 3, and the q-axis component corresponds to the torque acting on the rotor 4. FIG. 11 shows the positional relationship between the d-axis and q-axis fixed to the rotor 4 and the X-axis and Y-axis fixed to the stator 3. As shown in the figure, when the d-axis direction and the q-axis component of the magnetic field vector are adjusted by feedback control, the X-axis component and the Y-axis component of the magnetic field vector according to the adjustment value and the rotation angle θ of the rotor 4. Is determined. Accordingly, the X-axis component and the Y-axis component of the magnetic field vector are converted into set values for the three-phase alternating currents I _U , I _V , I _W. For example, when a strong field is required, the d-axis component of the magnetic field vector is increased, and when a weak field is required, the d-axis component of the magnetic field vector is decreased. Further, the q-axis component of the magnetic field vector is adjusted so as to maintain the rotational speed of the rotor 4 at a predetermined value.

(Configuration of control circuit for bearingless motor)
Next, the configuration of the control circuit 20 including an inverter used for the bearingless motor 1 will be described. FIG. 12 is a block diagram illustrating a schematic configuration of the control circuit 20.

The rotation angle θ of the rotor 4 and the position Z _{1 in the} Z-axis direction are input to the control circuit 20 by the angle sensor 21 and the displacement sensor 22 attached to the bearingless motor 1. A difference from the preset target value Z ₀ based on the input position Z ₁ is acquired and input to the PID controller 23. Based on this difference value, the PID controller 23 calculates a d-axis current target value corresponding to the d-axis component of the magnetic field vector generated in the stator 3 by PID control, and outputs it to the converter 24. Also, the rotational speed ω is acquired by the differentiator 25 from the input rotational angle θ, and the difference between the rotational speed ω and a preset target value ω ₀ is acquired and input to the PI controller 26. . Based on this difference value, the PI controller 26 calculates a q-axis current target value corresponding to the q-axis component of the magnetic field vector by PI control, and outputs it to the converter 24.

同時に、変換器２７は、現在ベアリングレスモータ１に供給されている三相交流電流Ｉ_Ｕ，Ｉ_Ｖ，Ｉ_Ｗをモニタし、それらの値をＸ軸成分値及びＹ軸成分値に変換する（下記式（２）参照）。

変換器２４から出力されたＸ軸電流目標値及びＹ軸電流目標値をもとにして、変換器２７から出力されたＸ軸成分値及びＹ軸成分値との差分が算出されて、それらの差分値はＰＩ制御器２８，２９にそれぞれ入力される。 The converter 24 converts the d-axis current target value and the q-axis current target value into an X-axis current target value and a Y-axis current target value corresponding to the X-axis component of the magnetic field vector by coordinate conversion with reference to the angle θ ( (See the following formula (1)).

At the same time, the converter 27 monitors the three-phase AC currents I _U , I _V and I _W currently supplied to the bearingless motor 1 and converts these values into X-axis component values and Y-axis component values ( (See the following formula (2)).

Based on the X-axis current target value and the Y-axis current target value output from the converter 24, a difference between the X-axis component value and the Y-axis component value output from the converter 27 is calculated, and those differences are calculated. The difference values are input to the PI controllers 28 and 29, respectively.

そして、インバータ３１が、変換器３０から入力された設定値に応じて、三相交流電流Ｉ_Ｕ，Ｉ_Ｖ，Ｉ_Ｗを生成して、ベアリングレスモータ１のコイル１５に供給する。 Based on the input difference, the PI controllers 28 and 29 determine the increase / decrease value of the X-axis current and the increase / decrease value of the Y-axis current, respectively, by PI control, and output these values to the converter 30. The converter 30 determines the phase relationship and current amplitude of the three-phase alternating currents I _U , I _V , I _W based on the input increase / decrease value of the X-axis current and the increase / decrease value of the Y-axis current (the following formula ( 3)).

Then, the inverter 31 generates three-phase alternating currents I _U , I _V , I _W according to the set values input from the converter 30 and supplies them to the coil 15 of the bearingless motor 1.

  According to the bearingless motor 1 described above, the four-degree-of-freedom motion of the rotor 4 in the X-axis direction, the Y-axis direction, the θx direction, and the θy direction is applied to the flat surfaces 7A and 7B of the two rotary plates 6A and 6B. It is passively suppressed by the magnetic coupling between the provided permanent magnets 9 and 10 and the two stators 2 and 3. At the same time, the movement of the rotor 4 in the Z-axis direction is actively performed by adjusting the excitation current flowing through the coils 15 wound around the stator 3 facing the permanent magnets 9 and 10 of the rotating plate 6B. Simultaneously with the control, the rotor 4 is driven to rotate by controlling the excitation currents of the plurality of coils 15 of the stator 3. As a result, the direction of motion of the rotor 4 to be actively controlled can be reduced to a minimum of one degree of freedom, and the number of inverters connected to the bearingless motor 1 and the number of built-in displacement sensors can be reduced. Thus, it is possible to reduce the size and power consumption of the device including the drive circuit.

  Further, since the rotor 4 has two disk-shaped rotating plates 6A and 6B connected by a columnar connecting shaft 5 extending along the Z-axis direction, the length of the rotor 4 in the Z-axis direction is long. When the thickness increases, the processing becomes easy, and the attachment work of the permanent magnet to the flat surfaces 7A and 7B becomes easy.

  Further, the permanent magnets 9 and 10 of the rotating plates 6A and 6B are arranged in a ring shape along the edges of the flat surfaces 7A and 7B, and the stator 2 has protrusions 12 extending toward the flat surface 7A. The stator 3 has a protrusion 14 around which a plurality of coils 15 extending toward the flat surface 7B are wound. With such a structure, the magnetic coupling between the permanent magnets 9 and 10 of the two rotating plates 6A and 6B and the two stators 2 and 3 is evenly formed along the peripheral edges of the flat surfaces 7A and 7B. Thus, the four-degree-of-freedom motion of the rotor 4 can be efficiently suppressed, and the moment acting on the rotor 4 at the time of rotational driving can be increased.

  Furthermore, when the length L along the Z-axis direction of the rotor 4 and the width D of the rotor 4 in the direction perpendicular to the Z-axis direction satisfy the relationship of the above formula (1), the rotor Thus, it is possible to further strengthen the passive suppression effect of the four-degree-of-freedom motion.

  In addition, this invention is not limited to embodiment mentioned above. For example, the permanent magnet on the rotating plate 6A may be divided into an arbitrary number. Conversely, the permanent magnet on the rotating plate 6A may not be divided, and the magnetization direction may be the same direction throughout. Further, the number of the protrusions 12 of the stator 2 may be changed to an arbitrary number, or may be integrally formed in a cylindrical shape along the peripheral edge of the bottom plate 11.

  Further, the permanent magnets on the rotating plate 6B may be divided into an arbitrary number as long as they are evenly arranged along the peripheral edge of the flat surface 7B. At this time, any number of permanent magnets may be alternately arranged so that the number of poles of the magnetic field generated by the stator 3 is the same and different magnetic poles are arranged along the peripheral edge 8B of the flat surface 7B. . Further, the number of the projecting portions 12 of the stator 2 may be changed to an arbitrary number so as to be evenly arranged along the peripheral edge portion of the bottom plate 13 so as to face the permanent magnets on the rotating plate 6B.

  Further, the shape of the two rotating plates constituting the rotor is not limited to the disc shape, and other shapes as shown in FIG. 13 are adopted as long as the shape has a surface to which the permanent magnet is attached. May be. A rotating plate 106B, which is a modification of the present invention shown in the figure, has a substantially hemispherical shape, and a flat portion 107B for disposing the permanent magnets 9 and 10 is formed on the peripheral edge thereof.

  DESCRIPTION OF SYMBOLS 1 ... Bearingless motor, 2, 3 ... Stator, 4 ... Rotor, 5 ... Connecting shaft (connecting member), 6A, 6B ... Rotating plate (rotating member), 7A, 7B ... Flat surface, 9, 10 ... Permanent Magnet, 12, 14 ... protrusion, 15 ... coil.

Claims (4)

A rotor formed by connecting two rotating members each having a plane parallel to each other by a connecting member extending along an axial direction perpendicular to the plane;
A first permanent magnet provided on the surface of one of the two rotating members;
A plurality of second permanent magnets arranged along a circumference on the surface of the other rotating member of the two rotating members;
A first stator including a magnetic material provided to face the surface of the one rotating member;
A second stator including a magnetic material provided to face the surface of the other rotating member;
A coil that is divided into a plurality of portions in the arrangement direction of the second permanent magnet and wound around the second stator and generates a magnetic field toward the surface of the other rotating member;
A bearingless motor comprising: The rotor is formed by connecting the two disk-shaped rotating members by the columnar connecting members extending along the axial direction.
The bearingless motor according to claim 1. The first permanent magnet is provided in a ring shape along an edge of the surface of the one rotating member,
A plurality of the second permanent magnets are provided so as to be arranged in a ring shape along the edge of the surface of the other rotating member,
The first stator has a protrusion extending toward the first permanent magnet,
The second stator has a plurality of protrusions extending toward the second permanent magnet,
The coil is wound around the plurality of protrusions of the second stator.
The bearingless motor according to claim 2. A length L along the axial direction of the rotor and a width D in a direction perpendicular to the axial direction of the surface of the rotor are represented by the following formula:
2 x D <L
Having a relationship
The bearingless motor according to any one of claims 1 to 3, wherein the bearingless motor is provided.

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