JP2015220773A - Bearingless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearingless motor capable of being applied to a location with a small installation space by achieving miniaturization in a rotation shaft direction while miniaturizing a device including a drive circuit.SOLUTION: A bearingless motor 1 comprises: a rotor 2 that can rotate around a rotation shaft; and a stator 3 that supports only one end side of both ends in a rotation shaft direction of the rotor 2, by a magnetic force. The rotor 2 has: a shaft member 24 magnetized in the rotation shaft direction; and a plurality of motor magnets 25 arranged along an outer periphery of the shaft member 24. The stator 3 has: a shaft member 32 that is a hollow-shaped member magnetized in the rotation shaft direction, and that houses at least a part of the shaft member 24 therein; and a plurality of coils 33 opposed to the motor magnets 25 in the rotation shaft direction, and divided and provided along the outer periphery of the shaft member 32.

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, various pumps used in the semiconductor manufacturing process and medical field, reaction wheels built into satellites, and cooling. Application to fans 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 shaft member. 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 five-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 size of the apparatus tends to increase. In addition, the size of the bearingless motor itself, particularly the size in the direction of the rotation axis, becomes a barrier, and the device may not be applied to a place where the installation space is relatively small.

  Therefore, the present invention has been made in view of such problems, and it is possible to reduce the size of the device including the drive circuit, and to realize the downsizing in the direction of the rotation axis, thereby reducing the installation space. An object of the present invention is to provide a bearingless motor that can be applied to a small space.

  In order to solve the above problems, a bearingless motor of the present invention includes a rotor that can rotate around a rotation axis, and a stator that supports only one end side by magnetic force among both ends in the rotation axis direction of the rotor, And the rotor includes a first shaft member magnetized in the direction of the rotation axis, and a plurality of permanent magnets arranged along the outer periphery of the first shaft member, and the stator is in the direction of the rotation axis. A hollow shaft member magnetized to the second shaft member, the second shaft member accommodating at least a part of the first shaft member therein, and the permanent magnet facing the permanent magnet in the direction of the rotation axis, And a coil provided by being divided into a plurality along the outer periphery.

  In such a bearingless motor, only one end side of the rotor is supported by the stator. Therefore, for example, compared with the structure which a stator supports the both ends of a rotor, it can be made small in a rotating shaft direction. Further, when the rotation axis direction 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 θx direction centered on the X-axis, and the Y-axis are The four-degree-of-freedom motion of the rotor in the θy direction at the center is a portion in which the first shaft member is accommodated in the second shaft member (the first shaft member is surrounded by the second shaft member). This is passively suppressed by the magnetic coupling between the first shaft member and the second shaft member. For example, in a configuration in which only one end of the rotor is supported by the stator, the movement of the rotor is controlled by magnetic coupling between the rotor-side shaft member and the stator-side shaft member that are opposed in the rotation axis direction. The rotor displacement and the stator side shaft member have different outer diameters, etc., so that the rotor displacement (X-axis direction and Y-axis direction) and inclination (θx direction and θy direction) interact with each other. As the amount of displacement and the amount of tilt increase, passive suppression of the 4-degree-of-freedom movement of the rotor may not be sufficiently achieved. In this regard, in the configuration in which the first shaft member is accommodated (enclosed) in the second shaft member, an increase in the displacement amount and the inclination amount due to the above-described mismatch in the outer diameter of the shaft member is less likely to be a problem. The four-degree-of-freedom motion of the rotor can be appropriately suppressed by the magnetic coupling between the first shaft member and the second shaft member. At the same time, the movement of the rotor in the direction of the rotation axis is actively controlled by adjusting the excitation current flowing through the plurality of coils facing the permanent magnet, and at the same time, by controlling the excitation current of the plurality of coils. The rotor is driven to rotate. As a result, the direction of motion of the object 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 and the number of built-in displacement sensors can be reduced. As described above, according to the present invention, it is possible to reduce the size of the device including the drive circuit, and to apply to a place where the installation space is small by realizing the size reduction in the rotation axis direction. It is possible to provide a bearingless motor capable of achieving the above.

  In the bearingless motor of the present invention, the stator may support the lower end of the rotor in the direction of the rotation axis in a non-contact manner. When the stator supports the rotor from the lower side, the rotor can be appropriately supported in the direction of the rotation axis by the support force based on the Lorentz force generated between the permanent magnet and the coil.

  In the bearingless motor of the present invention, the first shaft member may be composed of a rod-shaped magnet, and the second shaft member may be composed of a cylindrical magnet. With such a configuration, the first shaft member can be reliably and easily accommodated in the second shaft member.

  In the bearingless motor of the present invention, the permanent magnet may have 6 poles and the coil may have 9 slots. By adopting the 6-pole 9-slot configuration, it is possible to more reliably control the movement and rotational driving of the rotor in the rotational axis direction.

  In the bearingless motor of the present invention, a hall element may be disposed in the coil. With such a Hall element, the magnetic field generated by the permanent magnet can be output as a voltage, and the movement and rotational driving of the rotor in the Z-axis direction can be reliably and easily controlled.

  According to the present invention, it is possible to reduce the size of a device including a drive circuit, and also to apply to a place where installation space is small by realizing size reduction in the direction of the rotation axis. A bearingless motor can be provided.

FIG. 1 is a perspective view showing a bearingless motor which is a preferred embodiment of the present invention. FIG. 2 is an exploded view showing a cross section taken along line II-II of the bearingless motor of FIG. 3 is a partially enlarged view of a cross section taken along line II-II of the bearingless motor of FIG. FIG. 4 is a plan view of a motor magnet included in the rotor. FIG. 5 is a plan view of a coil included in the stator. FIG. 6 is a view for explaining the support principle in the Z-axis direction. FIG. 7 is a diagram for explaining the rotation principle. FIG. 8 is a diagram for explaining the principle of passive support. It is a block diagram which shows schematic structure of the control circuit used for the bearingless motor of FIG. It is a figure which shows the vibration amplitude measurement result of the rotating shaft direction which concerns on an Example. It is a figure which shows the vibration amplitude measurement result of the radial direction which concerns on an Example. It is a figure which shows the vibration amplitude measurement result of the inclination direction which concerns on an Example.

  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 on the stator by the magnetic levitation of the rotor.

(Configuration of bearingless motor)
FIG. 1 is a perspective view showing a bearingless motor 1 according to a preferred embodiment of the present invention, and FIG. 2 is an exploded view showing a section along the line II-II of the bearingless motor 1 of FIG. 3 is a partially enlarged view of a section along the line II-II of the bearingless motor 1 of FIG. 1, FIG. 4 is a plan view of a motor magnet 25 included in the rotor 2, and FIG. It is a top view of the coil 33 contained in. As shown in these drawings, the bearingless motor 1 is configured such that only one end side of the rotor 2 is supported by a single stator 3 fixed by a fixing member (not shown). The bearingless motor 1 is a one-degree-of-freedom control-type bearingless motor. A repulsive passive magnetic bearing (PMB) is disposed in the center of the bearingless motor 1 and an axial gap coreless motor is disposed on the outer periphery of the PMB. (Details will be described later). The bearingless motor 1 preferably has a configuration in which elements that cause vibration are eliminated as much as possible, and a coreless motor (for example, an axial gap type coreless motor) that does not generate cogging torque that causes vibration is employed. The bearingless motor 1 is applied to a cooling fan for a computer such as a personal computer.

  A plurality of rotors 2 are arranged along the outer periphery of the substantially disc-shaped frame portion 21, the sensor target 23 provided at the center of the frame portion 21, the shaft member 24 (first shaft member), and the shaft member 24. And a yoke 26 disposed between the motor magnet 25 and the frame portion 21 so as to overlap the motor magnet 25. For example, the rotor 2 can have a diameter of about 49 mm and a height (a height including the length of the sensor target 23) of about 26 mm, but is not limited thereto. The frame portion 21 and the sensor target 23 may be made of a non-magnetic material so as not to affect a magnetic circuit such as a motor. A blade portion may be attached to the outer side of the frame portion 21. In this case, the bearingless motor 1 can be easily applied to a cooling fan. The sensor target 23 is provided with a displacement sensor (not shown) for detecting the displacement of the rotor 2 in the direction of the rotation axis. In the present embodiment, the non-magnetic sensor target 23 is described as a displacement sensor target. However, the present invention is not limited to this. For example, an eddy current displacement sensor is used as the displacement sensor, and the shaft is made of metal. The member 24 may be targeted. Further, a Hall element may be disposed below the magnet such as the shaft member 24 and the Hall element may be used as a displacement sensor. In this case, the Hall element detects the magnetic flux density that changes as the rotor 2 moves up and down, and detects the displacement of the rotor 2 in the direction of the rotation axis. Since the hall element 41 is disposed in the coil 33 of the stator 3 to be described later, the hall element is used to detect the displacement of the rotor 2 in the direction of the rotation axis in accordance with the change in the magnetic flux density. Also good. In the following description, the rotation axis direction along the central axis of the shaft member 24 is set as the Z axis, and the X axis and the Y axis are set perpendicular to the Z axis.

  The shaft member 24 is a shaft member that is magnetized in the Z-axis direction and extends in the Z-axis direction on the central axis of the rotor 2. The shaft member 24 constitutes a PMB together with a shaft member 32 of the stator 3 described later. The shaft member 24 is a rod-shaped magnet made of a permanent magnet such as a neodymium magnet. The shaft member 24 is fixed to the frame portion 21 by being bonded to the frame portion 21.

  The motor magnet 25 is a ring-shaped magnet provided so as to cover the outer periphery of the shaft member 24, and is configured by a permanent magnet such as a neodymium magnet. The bearingless motor 1 of the present embodiment has a 6-pole 9-slot configuration. That is, the number of poles of the motor magnet 25 is 6 (divided into 6 segments), and the number of slots of the coil 33 of the stator 3 described later is 9 slots. As shown in FIG. 4, the motor magnet 25 includes six poles (N / S is three sets) magnets magnetized in the Z-axis direction and arranged along the outer periphery of the shaft member 24. The motor magnet 25 is bonded to a yoke 26 that is press-fitted into the frame portion 21. The yoke 26 is a ring-shaped soft iron plate provided to amplify the attractive force of the motor magnet 25, and the shape of the yoke 26 is substantially the same. The motor magnet 25 and the yoke 26 constitute an axial gap type coreless motor together with a coil 33 of the stator 3 described later.

  The stator 3 supports one end side, more specifically, only the lower end side of the both ends of the rotor 2 in the Z-axis direction by magnetic force. A plurality of stators 3 are provided so as to cover the outer periphery of the shaft member 32 (second shaft member) magnetized in the Z-axis direction, extending in the Z-axis direction, and the motor magnet 25 and the Z-axis direction. And a coil 33 facing each other. The stator 3 has a shape that is substantially smaller than the rotor 2 in both diameter and height. For example, the stator 3 has a diameter of about 43.8 mm and a height (a height that takes into account the length of the shaft member 32 extending in the Z-axis direction). Although it can be set to about 5 mm, it is not limited to this. In the rotor 2 supported by the stator 3, the movable range MS (X, Y) (FIG. 3) in the X-axis direction and the Y-axis direction is, for example, about 0.3 mm. Further, the movable range MS (θx, θy) (FIG. 3) of the rotational motion in the θx, θy directions of the rotor 2 with the X axis or the Y axis as the rotation axis is set to 17 mrad, for example. In the state where the rotor 2 is supported by the stator 3, the gap G between the motor magnet 25 and the coil 33 is, for example, about 0.2 mm.

  The shaft member 32 is a hollow cylindrical magnet made of a permanent magnet such as a neodymium magnet, for example, and at least a part of the end of the shaft member 24 of the rotor 2 on the shaft member 32 side is provided inside the hollow shape. Contained. In other words, the shaft member 32 is disposed so as to surround the periphery of the shaft member 24 (so as to sandwich both sides of the shaft member 24 in the cross section of FIG. 2).

  The coil 33 is provided to rotationally drive the rotor 2 and stably support the rotor 2, and generates a magnetic field with the motor magnet 25. The coil 33 is divided into a plurality of pieces along the outer periphery of the shaft member 32 and faces the motor magnet 25 in the Z-axis direction. The coil 33 and the motor magnet 25 have substantially the same length in the width direction (radial direction). As described above, the bearingless motor 1 has a 6-pole 9-slot configuration, and the coil 33 has 9 slots. As shown in FIG. 5, the coil 33 is a coreless coil in which a three-phase winding (U / V / W phase) is applied in the winding direction TD, and a Hall element 41 is disposed at the center thereof. The rotation angle is detected by using the output voltages of three of the hall elements 41 (details will be described later). Further, the Hall element 41 detects the displacement of the rotor 2 in the Z-axis direction. Of the nine Hall elements 41 corresponding to the number of coils 33, three are Hall elements used for detecting the rotation angle and the other six are spare Hall elements.

(Z-axis direction support principle)
In the bearingless motor 1, the Z-axis direction is magnetically unstable, and the rotor 2 needs to be actively supported. Hereinafter, the support principle in the Z-axis direction will be described with reference to FIG. FIG. 6 is a view for explaining the support principle in the Z-axis direction.

  As shown in FIG. 6, when focusing on the coil Cu1 (FIG. 6B) which is a U-phase coil, the air core of the coil Cu1 faces the magnet M1 (FIG. 6A) in the Z-axis direction. think of. In this case, as shown in FIG. 6C, the magnetic flux mf1 passing through the Y-axis direction of the coil Cu1 and the current I1 of the circumferential component of the coil Cu1 interact with each other in the Z-axis direction of the coil Cu1. Lorentz force Fl1 is generated. Since the coil Cu1 (coil 33) has the configuration of the stator 3 and is fixed, the support force Fb1 acts on the rotor 2 in the Z-axis direction as a reaction of the Lorentz force Fl1. As shown in FIG. 6D, when attention is paid to the YZ section of the coil Cu1, due to the interaction between the magnetic flux mf2 passing through the Z-axis direction of the coil Cu1 and the current I2 of the radial component of the coil Cu1, A Lorentz force Fl2 is generated in two directions in the circumferential direction of the coil Cu1, but they cancel each other, so that no torque is generated. From the above, the rotor 2 can be actively supported in the bearingless motor 1 by the support force Fb1 in the Z-axis direction, which is the reaction of the Lorentz force Fl1. Active support in the Z-axis direction is realized by specifying a d-axis current described later. That is, magnetic levitation is controlled by the d-axis current.

(Rotation principle)
FIG. 7 is a diagram for explaining the rotation principle. As shown in FIG. 7, paying attention to the coil Cu2 (FIG. 7B), which is a U-phase coil, consider the case where the air core of the coil Cu2 faces the magnetic field boundary Mb of the magnet. In this case, as shown in FIG. 7C, Lorentz in the circumferential direction of the coil Cu2 due to the interaction of the magnetic flux mf3 passing through the Z-axis direction of the coil Cu2 and the current I3 of the radial component of the coil Cu2. A force Fl3 is generated. Since the coil Cu2 (coil 33) has the configuration of the stator 3 and is fixed, the rotor 2 is torqued in the circumferential direction of the coil Cu2 (that is, the circumferential direction of the rotor 2) as a reaction of the Lorentz force Fl3. Tr1 acts. As shown in FIG. 7D, when attention is paid to the YZ section of the coil Cu2, due to the interaction between the magnetic flux mf4 passing through the Y-axis direction of the coil Cu2 and the current I4 of the circumferential component of the coil Cu2, The Lorentz force Fl5 in the Z-axis positive direction is generated on the right side (refer to the cross section dB) of the coil Cu2, and the Lorentz force Fl4 in the Z-axis negative direction is generated on the left side (refer to the cross section dA). Does not occur. From the above, the rotor 2 can be rotated in the bearingless motor 1 by the circumferential torque Tr1 which is the reaction of the Lorentz force Fl3. The rotation of the rotor 2 around the Z axis is realized by designating a q-axis current to be described later.

(Principles of freedom passive support)
In the bearingless motor 1, the four-degree-of-freedom motion of the rotor 2 (the four-degree-of-freedom motion in the X-axis direction, the Y-axis direction, the θx direction centered on the X-axis, and the θy direction centered on the Y-axis) is passive. It is possible to stabilize (suppress). In the following, the principle of freedom passive support will be described with reference to FIG. FIG. 8 is a diagram for explaining the principle of passive support.

As described above, in a state where the rotor 2 is supported by the stator 3, the shaft member 32 magnetized in the Z-axis direction is arranged so as to surround the periphery of the shaft member 24 magnetized in the Z-axis direction. Has been. Therefore, a repulsive force is generated in the radial direction (X, Y) of the rotor 2 between the shaft member 24 and the shaft member 32. For example, as shown in FIG. 8A, when the rotor 2 (more specifically, the shaft member 24) is displaced in the radial direction (X-axis direction in the drawing), the shaft member 24 is displaced. A restoring force FR acts in the opposite direction, and the displacement of the shaft member 24 is automatically corrected. The ratio of the restoring force FR against radial displacement amount is defined as radial rigidity Kr (N / m), can be considered as radial stiffness K _r can be positive if the passive support has.

Further, as shown in FIG. 8B, when the rotor 2 (more specifically, the shaft member 24) is tilted in the tilt directions (θx, θy), the shaft member 24 has a direction opposite to the tilt. The restoring torque TR acts on the tilt, and the tilt is passively corrected. The ratio of the restoring torque TR to the tilt amount of the shaft member 24 is defined as tilt stiffness K _θ (Nm / rad). If the tilt stiffness K _θ is positive, it can be considered that passive support is possible. As described above, the four-degree-of-freedom motion in the X-axis direction, the Y-axis direction, the θx direction around the X-axis, and the θy direction around the Y-axis can be passively stabilized (suppressed). .

(Rotation angle detection process)
As shown in FIG. 5, Hall elements 41 are arranged in the U / V / W phase coils 33, respectively, and the Hall elements 41 output a magnetic field generated by the motor magnet 25 as a voltage. If the voltages output from the U / V / W phase Hall element 41 are V _u , V _v , and V _w , the Hall elements 41 are arranged at intervals of 40 ° (120 ° in electrical angle). Assuming that the amplitude of V is V and the rotation angle of the rotor 2 is ωt, each output waveform is expressed as follows.

When the above formulas (1) and (2) are expanded using the addition theorem, the following formulas (4) and (5) are derived.

Furthermore, when the difference between the above equations (4) and (5) is obtained, the following equation (6) is derived.

このようにして検出・導出された回転角度ωｔは、後述するｄ軸電流及びｑ軸電流の調整に用いられる。 From the above, the rotation angle ωt can be expressed as follows.

The rotation angle ωt detected and derived in this way is used for adjusting a d-axis current and a q-axis current described later.

(Configuration of control circuit for bearingless motor)
Next, the configuration of the control circuit 50 including an inverter used in the bearingless motor 1 will be described with reference to FIG. FIG. 9 is a block diagram showing a schematic configuration of the control circuit 50.

  The current of the bearingless motor 1 is classified into a d-axis current that is a field adjustment component of the motor magnet 25 and a q-axis current that is a torque component, and by specifying these currents, the Z-axis of the rotor 2 is specified. Provides directional support and rotation around the Z axis.

  As shown in FIG. 9, the rotation angle ωt of the rotor 2 and the position Z1 in the Z-axis direction are input to the control circuit 50 by the Hall element 41 and the displacement sensor 52 attached to the bearingless motor 1. The difference from the preset target value Z0 based on the input position Z1 is acquired and input to the PID controller 53. Based on this difference value, the PID controller 53 calculates a d-axis current command value id 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 54. Also, the rotational speed ω is acquired from the input rotational angle ωt by the differentiator 55, and the difference between the rotational speed ω and a preset target value ω 0 is acquired and input to the PI controller 56. Based on this difference value, the PI controller 56 calculates a q-axis current command value iq corresponding to the q-axis component of the magnetic field vector by PI control, and outputs it to the converter 54.

同時に、変換器５７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（９）参照）。

変換器５４から出力されたＸ軸電流目標値ｉｘ及びＹ軸電流目標値ｉｙをもとにして、変換器５７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５８，５９にそれぞれ入力される。 The converter 54 converts the d-axis current command value id and the q-axis current command value iq from the X-axis current target value ix corresponding to the X-axis component of the magnetic field vector and the Y-axis of the magnetic field vector by coordinate conversion with reference to the rotation angle ωt. It converts into the Y-axis electric current target value iy corresponding to a component (refer following formula (8)).

At the same time, the converter 57 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 (9)).

Based on the X-axis current target value ix and the Y-axis current target value iy output from the converter 54, a difference between the X-axis component value and the Y-axis component value output from the converter 57 is calculated, The difference values are input to the PI controllers 58 and 59, respectively.

そして、インバータ６１（一台の三相インバータ）が、変換器６０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３３に供給する。 The PI controllers 58 and 59 determine the increase / decrease value vx of the X-axis current and the increase / decrease value vy of the X-axis current and the Y-axis current based on the input difference, respectively, and output these values to the converter 60. The converter 60 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 vx of the X-axis current and increase / decrease value vy of the Y-axis current (see below). (Refer Formula (10)).

Then, the inverter 61 (one three-phase inverter) generates three-phase alternating currents I _u , I _v , I _w according to the set values input from the converter 60, and the coil of the bearingless motor 1. 33.

  Next, the operation and effect of the bearingless motor 1 according to this embodiment will be described.

  In the bearingless motor 1 described above, only one end side (more specifically, the lower end side) of the rotor 2 is supported by the stator 3. Therefore, for example, as compared with the configuration in which the stator 3 supports both ends of the rotor 2, the size can be reduced in the direction of the rotation axis. Further, when the rotation axis direction 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 θx direction centered on the X-axis, and the Y-axis are In the four-degree-of-freedom movement of the rotor in the θy direction centered, the shaft member 24 of the rotor 2 is accommodated inside the shaft member 32 of the stator 3 (the shaft member 24 is surrounded by the shaft member 32). Due to the magnetic coupling between the shaft member 24 and the shaft member 32 of the portion, it is passively suppressed.

  For example, in a configuration in which only one end of the rotor is supported by the stator, the movement of the rotor is controlled by magnetic coupling between the rotor-side shaft portion and the stator-side shaft portion facing each other in the rotation axis direction. The rotor displacement (X axis direction and Y axis direction) and inclination (θx direction and θy direction) interact with each other because of a mismatch in the outer diameters of the shaft portions on the rotor side and the stator side. (Coupled motion is performed), and the displacement amount and the tilt amount are increased, and thus there is a possibility that passive suppression of the 4-degree-of-freedom motion of the rotor cannot be sufficiently achieved.

  In this regard, in the configuration in which the shaft member 24 is accommodated (enclosed) in the shaft member 32, an increase in the amount of displacement and the amount of inclination is a problem due to a mismatch in the outer diameters of the shaft portions of the rotor and the stator described above. It ’s hard to be. For this reason, the four-degree-of-freedom motion of the rotor 2 can be appropriately suppressed by the magnetic coupling between the shaft member 24 and the shaft member 32. At the same time, the movement of the rotor 2 in the Z-axis direction is actively controlled by adjusting the excitation current flowing through the plurality of coils 33 facing the motor magnet 25, and at the same time, the excitation current of the plurality of coils 33 is adjusted. The rotor 2 is rotationally driven by the control. Thereby, the direction of movement of the object 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. As described above, according to the present invention, it is possible to reduce the size of the device including the drive circuit, and to apply to a place where the installation space is small by realizing the size reduction in the rotation axis direction. It is possible to provide a bearingless motor capable of achieving the above. Note that a general fan motor has a configuration with six transistors. However, when the bearingless motor 1 according to the present embodiment is applied to a fan, the configuration can be similarly configured with six transistors.

  In the bearingless motor 1, the stator 3 supports the lower end of the rotor 2 in the Z-axis direction in a non-contact manner. When the stator 3 supports the rotor 2 from the lower side, the rotor 2 is appropriately supported in the Z-axis direction by the support force based on the Lorentz force generated between the motor magnet 25 and the coil 33. Can do.

  Moreover, in the bearingless motor 1, the shaft member 24 is comprised from the rod-shaped magnet, and the shaft member 32 is comprised from the cylindrical magnet. With such a configuration, the shaft member 24 can be reliably and easily accommodated in the shaft member 32.

  Further, the number of poles of the motor magnet 25 of the bearingless motor 1 is 6, and the number of slots of the coil 33 is 9 slots. Thereby, the movement of the rotor in the Z-axis direction and the rotational drive can be controlled more reliably.

  In the bearingless motor 1, the Hall element 41 is disposed in the coil 33, and the Hall element 41 can output a magnetic field generated by the motor magnet 25 as a voltage. Axial motion and rotational drive can be reliably and easily controlled.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, it has been described that the shaft member 24 of the rotor 2 is composed of a rod-shaped magnet and the shaft member 32 of the stator 3 is composed of a cylindrical magnet. However, the shape of the magnet is not limited to this. As long as the shaft member 24 of the rotor 2 can be accommodated (enclosed) in the shaft member 32 of the stator 3, each shape may be other shapes. Further, the shaft members 24 and 32 may be configured by combining a plurality of magnets. For example, the shaft member 24 may be configured by combining a rod-shaped magnet and a ring-shaped magnet.

  In addition, the motor magnet 25 has 6 poles and the coil 33 has 9 slots. However, the present invention is not limited to this. For example, the motor magnet has 2 poles corresponding to NS. Any of multiples, and the number of slots in the coil may be any multiple of 3 corresponding to the three-phase inverter.

[Example]
Hereinafter, although the vibration performance of the bearingless motor which concerns on one form of this invention is demonstrated based on an Example, a bearingless motor is not limited to the following Example.

  When the vibration performance is low, the vibration in the radial direction / inclination direction of the rotor increases, and the rotor and the stator may come into contact with each other. Therefore, vibration performance is important in operating a bearingless motor that is downsized as in the present invention. The rotor radial direction and the tilt direction are passively supported by the PMB, and it is necessary to increase the radial rigidity (N / m) and the tilt rigidity (Nm / rad) in order to reduce vibration. In order to improve the radial rigidity and the inclination rigidity, a magnet that generates a strong magnetic field is used for the shaft member of the rotor, or the outer diameter of the shaft member of the rotor is increased to increase the space between the magnets (rotor It is conceivable to increase the repulsive force acting between the shaft member and the shaft member of the stator.

Prepare two rotor shaft members with different magnet types and outer diameter conditions, and evaluate the vibration performance in the same way for the rotor (the rotor structure excluding the shaft member) and the stator structure. It was. The shaft member of the rotor according to Example 1 has a neodymium magnet type of N35 and an outer diameter of 6.0 mm. The shaft member of the rotor according to Example 2 has a neoaxial magnet type of N48 and an outer diameter of 6.5 mm. Moreover, the shaft member of the rotor according to Example 1 has a radial rigidity of 1.73 × 10 ³ N / m and an inclination rigidity of 0.11 Nm / rad, and the shaft member of the rotor according to Example 2 is The radial rigidity is 2.76 × 10 ³ N / m, and the inclination rigidity is 0.18 Nm / rad. The vibration performance was evaluated by measuring the vibration amplitude in the radial direction and the tilt direction when the rotation speed of the rotor was changed. The rotational speed measurement range was 0 to 4000 rpm, and the measurement interval was 250 rpm. The vibration amplitude was evaluated at 3 times the standard deviation (3σ). FIG. 10 shows the vibration amplitude measurement result in the rotation axis (Z-axis) direction, FIG. 11 shows the vibration amplitude measurement result in the radial direction, and FIG. 12 shows the vibration amplitude measurement result in the tilt direction.

  As shown in FIG. 10, when the shaft member of Example 1 and Example 2 was used at each rotation speed of 0 to 4000 rpm, the vibration amplitude in the rotation axis direction could be suppressed to 40 μm or less. In particular, when the shaft member of Example 1 and Example 2 was used at a rotation speed of 1500 rpm, the vibration amplitude in the direction of the rotation axis could be suppressed to 15 μm or less. For example, the rotational speed of a bearingless motor applied to a cooling fan for a computer is about 1500 rpm. However, the bearingless motor using the shaft member of the embodiment has excellent vibration characteristics when applied to a cooling fan for a computer. It was shown to show.

  As shown in FIG. 11, when the shaft member of Example 1 and Example 2 was used at each of the rotational speeds of 0 to 4000 rpm, the vibration amplitude in the radial direction could be suppressed to 0.7 mm or less. . In particular, in the shaft member of Example 2, the vibration amplitude could be suppressed to 0.1 mm when the rotation speed was 1500 rpm. For example, the rotational speed of a bearingless motor applied to a computer cooling fan is about 1500 rpm. The bearingless motor using the shaft member of Example 2 has excellent vibration characteristics when applied to a computer cooling fan. It was shown to show.

  As shown in FIG. 12, when the shaft member of Example 1 and Example 2 was used at each rotation speed of 0 to 4000 rpm, the vibration amplitude in the tilt direction could be suppressed to 30 rad or less. In particular, in the shaft member of Example 2, the vibration amplitude could be suppressed to 4.3 rad when the rotation speed was 1500 rpm. For example, the rotational speed of a bearingless motor applied to a computer cooling fan is about 1500 rpm. The bearingless motor using the shaft member of Example 2 has excellent vibration characteristics when applied to a computer cooling fan. It was shown to show.

DESCRIPTION OF SYMBOLS 1 ... Bearingless motor, 2 ... Rotor, 3 ... Stator, 24, 32 ... Shaft member, 25 ... Motor magnet, 33 ... Coil, 41 ... Hall element.

Claims (5)

A rotor that can rotate around a rotation axis;
A stator that supports only one end side by magnetic force among both ends of the rotor in the direction of the rotation axis;
The rotor is
A first shaft member magnetized in the rotation axis direction;
A plurality of permanent magnets arranged along the outer periphery of the first shaft member,
The stator is
A hollow member magnetized in the direction of the rotation axis, the second shaft member accommodating at least a part of the first shaft member therein;
A bearingless motor, comprising: a coil that is opposed to the permanent magnet in the direction of the rotation axis and is divided into a plurality of coils along an outer periphery of the second shaft member.   The bearingless motor according to claim 1, wherein the stator supports a lower end of the rotor in the rotation axis direction in a non-contact manner. The first shaft member is composed of a rod-shaped magnet,
The bearingless motor according to claim 1, wherein the second shaft member is formed of a cylindrical magnet. The number of poles of the permanent magnet is 6,
The bearingless motor according to any one of claims 1 to 3, wherein the coil has nine slots. The bearingless motor according to claim 1, wherein a hall element is disposed in the coil.

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