A bearingless motor

Abstract

A bearingless motor (1) has a rotor (2), a stator (3) for giving a supporting force and a torque to the rotor (2), a first displacement sensor (4) and a second displacement sensor (5) for detecting a radial direction position of the rotor (2), an arithmetic unit (10) for calculating a tilt direction displacement of the rotor (2) based on detection results obtained by the first displacement sensor (4) and the second displacement sensor (5), and a tilt direction position controller (11) for receiving the tilt direction displacement obtained by the arithmetic unit (10), removing at least a part of a frequency band not including an inherent angular vibration frequency of the tilt of the rotor (2), and outputting a current command. The stator (3) has a motor winding (32) for generating a magnetic flux of a pole number p to generate a torque and a supporting winding (33) for generating a magnetic flux of a pole number p±2 or 2 to generate a supporting force. The first displacement sensor (4) and the second displacement sensor (5) are arranged at different positions in an axial direction.

Description

Technical Field

[0001] The present invention relates to a bearingless electric motor that supports the rotor non-contactly and rotates the rotor by magnetically levitizing the rotor. Background Technology

[0002] A bearingless motor functions as both a torque-generating motor and a magnetic bearing in a magnetic circuit, providing the supporting force to levitate the rotor without contact. To levitate the rotor, active control is required for the five degrees of freedom (excluding the rotational axis), or a portion of these five degrees of freedom must be passively stabilized without active control.

[0003] A 2-axis controlled bearingless motor detects the rotor's position only in the radial direction using sensors, adjusting the support force to match the detected position with the target position. In other words, the 2-axis controlled bearingless motor actively controls only the radial direction, which includes both the X-axis and Y-axis directions.

[0004] Two-axis controlled bearingless motors typically do not perform active control in the axial and tilt directions of the rotor, exhibiting a passively stable structure. The axial direction is the Z-axis, and the tilt direction is θ. x and θ y The direction that is controlled is then called the control direction. On the other hand, the direction that becomes stable passively without being controlled is called the passively stable direction.

[0005] To passively stabilize the rotor, the attractive force between the rotor's permanent magnets and the stator's iron core is utilized. For example, when the rotor is tilted, the attractive force between the rotor's permanent magnets and the stator's iron core acts to restore the rotor's tilt. As a result, without control, a restoring torque is generated in the opposite direction to the rotor's tilt. Similarly, when the rotor is moving axially, a restoring force acts in the opposite direction to the rotor's movement. The attractive force acting between the permanent magnets and the iron core is proportional to the distance and can therefore be considered as a spring force. Hereinafter, the ratio of the restoring torque to the tilt angle is called the restoring torque coefficient k. θ .

[0006] In the tilt direction, which serves as a passive stabilization direction, stability is ensured solely by the restoring torque, thus lacking stability compared to the control direction. The restoring torque does not dampen vibrations. Damping forces that are proportional to velocity and dampen vibrations are not generated in principle in the passive stabilization direction. Therefore, vibrations in the passive stabilization direction may be continuous or divergent, sometimes causing the rotor to become unstable.

[0007] Furthermore, it has been reported that the radial direction control of a 2-axis controlled bearingless motor sometimes affects the stability of the rotor's tilt direction (see, for example, Non-Patent Literature 1). The line of action of the radial support force of the rotor does not pass through the rotor's center of gravity; therefore, the radial support force also acts as a torque that tilts the rotor. Through tilting motion, the output of the displacement sensor used for radial position detection sometimes changes. Ideally, radial motion and control are independent of tilting motion, but in reality, the radial and tilting directions interfere with each other and become connected.

[0008] A method is proposed that improves the structure by changing the position of the displacement sensor, thereby solving the problem of instability caused by the aforementioned interference (see, for example, Patent Document 1). For the purpose of detecting the tilt direction of the rotor, a control region occupying the upper or lower magnetic plane of the rotor within the measurement area, although comprising at least 50% of the signal from the first displacement sensor, is used. The tilting motion generates a damping force via the differential term of the radial direction position controller. As a result, the radial direction position controller not only stabilizes the radial direction but also suppresses vibrations during the tilting motion.

[0009] Patent Document 1: US Patent No. 8,729,758

[0010] Non-patent document 1: H.Sugimoto and A.Chiba, "Stability Consideration of Magnetic Suspension in Two-Axis Actively Positioned Bearingless Motor WithCollocation Problem," IEEE Transactions on Industry Applications, vol.50, no.1, Jan.-Feb.2014.pp.338-345 Summary of the Invention

[0011] Previously, as mentioned above, the stability of the rotor in the tilt direction depended solely on the restoring torque, which was proportional to the tilt amount. This resulted in weak stability in the rotor's tilt direction. The radial suspension and tilting motions of the rotor interfered with each other, causing the rotor to become unstable, and in the worst case, the rotor's vibration diverged.

[0012] In the method of Patent Document 1, by shifting the position of the displacement sensor above or below the magnetic plane of the rotor, information including the rotor's tilt direction position information is fed back from the displacement sensor to control and stabilize the rotor. That is, in the method of Patent Document 1, the tilt direction position information and the radial direction position information are not detected as separate independent state variables. In the method of Patent Document 1, while the radial direction position controller sometimes helps generate damping force in the tilt direction, it cannot suppress radial and tilt direction vibrations in advance and appropriately.

[0013] At dangerous speeds where the natural angular vibration frequency in the tilt direction of the rotor coincides with the rotational angular velocity, the periodic disturbances generated by rotation amplify the vibration in the tilt direction. As a result, the vibration intensity can easily increase significantly. The same problem occurs when the natural angular vibration frequency in the tilt direction is a multiple of the rotational angular velocity. Therefore, without properly suppressing vibration, it is difficult to sustain rotation at speeds where the natural angular vibration frequency in the tilt direction coincides with the rotational angular velocity, or at speeds where the natural angular vibration frequency in the tilt direction is a multiple of the rotational angular velocity.

[0014] The present invention is proposed in view of the above circumstances, and its purpose is to provide a bearingless motor that improves the stability of the rotor in the tilt direction.

[0015] To address the aforementioned issues and achieve the objectives, the bearingless motor disclosed in this invention is a two-axis controlled bearingless motor, comprising: a rotor; a stator for imparting support force and torque to the rotor; a first displacement sensor and a second displacement sensor for detecting the radial position of the rotor; an arithmetic unit for calculating the displacement in the tilt direction of the rotor based on the detection results obtained from the first and second displacement sensors; and a tilt direction position controller that receives the displacement in the tilt direction obtained from the arithmetic unit, removes at least a portion of the frequency band that does not include the inherent angular vibration frequency of the rotor's tilt, and outputs a current command. The stator comprises: a motor winding that generates a magnetic flux with a pole number p to produce torque; and a support winding that generates a magnetic flux with a pole number p ± 2 or 2 to produce support force. At least a portion of the magnetic circuit for the magnetic flux with a pole number p used to generate torque and at least a portion of the magnetic circuit for the magnetic flux with a pole number p ± 2 or 2 used to generate support force are shared. The support force is generated by superimposing a magnetic flux with a pole number p ± 2 or 2 into the magnetic flux with a pole number p. p is a natural number. The first displacement sensor and the second displacement sensor are configured at different positions along the axial direction.

[0016] The effects of the invention

[0017] The bearingless electric motor of the present invention has the effect of improving the stability of the rotor in the tilt direction. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the bearingless electric motor according to Embodiment 1.

[0019] Figure 2 This is a cross-sectional view of the bearingless motor according to Embodiment 1, in which the position of the second displacement sensor is configured at the same angular position as that of the first displacement sensor.

[0020] Figure 3 This is a wireframe diagram showing, in Embodiment 1, structural elements for supporting and controlling the rotor using the detected radial position and tilt direction.

[0021] Figure 4 This is a diagram showing the structure of a tilt direction position controller that outputs a current command in Embodiment 2, except for at least a portion of the frequency band that does not include the inherent angular vibration frequency of the tilt.

[0022] Figure 5 This diagram shows the situation where accessories are added to the rotor of the bearingless electric motor according to Embodiment 2.

[0023] Figure 6 This is a cross-sectional view of a bearingless motor with a non-magnetic sensor target that does not contribute to the generation of supporting force and torque installed at the bottom of the rotor.

[0024] Figure 7 This is a cross-sectional view of a bearingless motor with a non-magnetic sensor target that does not contribute to the generation of supporting force and torque installed at the bottom of the rotor.

[0025] Figure 8 This is a cross-sectional view of a bearingless motor with a non-magnetic sensor target that does not contribute to the generation of supporting force and torque mounted on the upper part of the rotor.

[0026] Figure 9 This is a cross-sectional view of a bearingless motor with a non-magnetic sensor target that does not contribute to the generation of supporting force and torque mounted on the upper part of the rotor.

[0027] Figure 10 This is a diagram showing the processor in the case where the tilt direction position controller of the bearingless motor according to Embodiment 1 is implemented by a processor.

[0028] Figure 11This is a diagram showing the processing circuit when the tilt direction position controller of the bearingless motor according to Embodiment 1 is implemented by the processing circuit. Detailed Implementation

[0029] The bearingless motor according to the embodiments will now be described in detail with reference to the accompanying drawings.

[0030] Implementation method 1.

[0031] Figure 1 This is a cross-sectional view of the bearingless electric motor 1 according to Embodiment 1. Figure 1 The diagram also shows the X-axis, Y-axis, and Z-axis. The X-axis is orthogonal to both the Y-axis and Z-axis, and the Y-axis is orthogonal to the Z-axis. Figure 1 A cross-section of the bearingless motor 1 is shown in a plane parallel to the plane containing the X-axis and Z-axis.

[0032] The bearingless motor 1 is a 2-axis controlled bearingless motor, having a rotor 2 and a stator 3 for providing support force and torque to the rotor 2. The stator 3 has a stator core 31 with slots. The stator 3 also has motor windings 32 and support windings 33 disposed in the slots formed in the stator core 31. The motor windings 32 generate a magnetic flux with a pole number p, thereby producing torque. p is a natural number. Torque is generated by generating a magnetic flux with a pole number p by flowing current in the motor windings 32.

[0033] The support winding 33 generates a magnetic flux with a pole number of p±2 or 2, thereby producing a support force. A radial support force is generated in the rotor 2 by flowing current through the support winding 33, thereby generating a magnetic flux with a pole number of p±2 or 2. For example, in a typical electric motor including a surface magnet type motor, the support force is generated by a magnetic field with a pole number of p±2 generated by the support winding; in a commutated pole type motor or a single-pole type motor, the support force is generated by a magnetic field with a pole number of 2 generated by the support winding.

[0034] At least a portion of the magnetic circuit for generating torque with pole number p and at least a portion of the magnetic circuit for generating support force with pole number p ± 2 or 2 are shared. The support force is generated by superimposing magnetic flux with pole number p ± 2 or 2 into the magnetic flux with pole number p. As described above, at least a portion of the two magnetic circuits are shared, and magnetic flux with pole number p ± 2 or 2 is superimposed into the magnetic flux with pole number p, thereby creating a density variation in the magnetic flux density. Therefore, by adjusting the magnitude and phase of the support current, the magnitude and orientation of the support force in the radial direction of the rotor 2 can be controlled.

[0035] Regarding rotor 2, its own weight A acts downwards, but due to the upward axial restoring force acting from stator 3, rotor 2 is suspended at the position where its own weight A and the restoring force are balanced. A displacement sensor is used to detect the position x of rotor 2 in the X-axis direction. The displacement sensor can be an eddy current sensor or an optical sensor.

[0036] To detect the position of the rotor 2 in the X-axis direction, at least one displacement sensor is required, but the bearingless motor 1 has two displacement sensors: a first displacement sensor 4 and a second displacement sensor 5. The first displacement sensor 4 and the second displacement sensor 5 detect the radial position of the rotor 2. The first displacement sensor 4 and the second displacement sensor 5 are positioned at different axial positions of the rotor 2. In Embodiment 1, the second displacement sensor 5 is positioned at a position offset from the first displacement sensor 4 in the circumferential direction by a mechanical angle of 0°. Alternatively, the second displacement sensor 5 may be positioned at a position offset from the first displacement sensor 4 in the circumferential direction by a mechanical angle of 180°.

[0037] Figure 2 This is a cross-sectional view of the bearingless motor 1 according to Embodiment 1, in which the position of the second displacement sensor 5 is configured at the same angular position as that of the first displacement sensor 4. Figure 2 A cross-section of the bearingless motor 1 is shown in a plane parallel to the plane containing the X and Z axes. Figure 2 In this context, the second displacement sensor 5 is positioned at a location offset from the first displacement sensor 4 by a mechanical angle of 180° in the circumferential direction. Hereinafter, the signal of the displacement sensor when the second displacement sensor 5 is positioned at a location offset from the first displacement sensor 4 by a mechanical angle of 180° in the circumferential direction will be described. Figure 1 In the case of, Figure 2 In this case, the sign of the signal from the second displacement sensor 5 in the formula can be reversed.

[0038] Using the center of gravity B of rotor 2 as a reference, the axial position of the first displacement sensor 4 is set as L1, and the axial position of the second displacement sensor 5 is set as L2. Furthermore, Figure 1 The "L" indicates the stacking length of rotor 2. The surface of rotor 2 serves as the sensor target. If rotor 2 moves in the X-axis direction, the distance between the surface of rotor 2 and the displacement sensor changes. This is indicated by the tilt θ of rotor 2 about the Y-axis. y The distance between the surface of rotor 2 and the displacement sensor changes. The signal x1 of the first displacement sensor 4 is represented by the following equation (1), and the signal x2 of the second displacement sensor 5 is represented by the following equation (2).

[0039] Formula 1

[0040]

[0041] Formula 2

[0042]

[0043] Figure 2 The diagram shows the case where the center of gravity B of rotor 2 is located between the first displacement sensor 4 and the second displacement sensor 5. However, if the center of gravity B is lower than the second displacement sensor 5, the sign of the axial position L2 of the second displacement sensor 5 can be reversed. L2 is the distance between the center of gravity B and the axial position of the second displacement sensor 5.

[0044] The bearingless motor 1 can obtain information about the position x of the rotor 2 in the X-axis direction and the tilt θ about the Y-axis by effectively using both the signal x1 from the first displacement sensor 4 and the signal x2 from the second displacement sensor 5. y The information. The position x of rotor 2 in the X-axis direction is represented by the following equation (3), and the tilt θ about the Y-axis. y This is expressed by the following equation (4).

[0045]

Formula 3

[0046]

[0047]

Formula 4

[0048]

[0049] The stacked length L of rotor 2 is less than or equal to the radius of rotor 2. That is, rotor 2 has a flat structure.

[0050] When rotor 2 is displaced in the axial or tilting direction, a restoring force and a restoring torque are generated to recover the displacement. That is, a positive spring force is generated, which acts in a way that passively stabilizes rotor 2 in the axial and tilting directions. However, in other words, there is a limitation that the stacked length L of rotor 2 cannot be made longer than the radius of rotor 2.

[0051] The tilt angle θ of rotor 2 around the Y-axis y The difference x1 - x2 between the signal x1 from the first displacement sensor 4 and the signal x2 from the second displacement sensor 5 is calculated by dividing the axial distance L1 + L2 between the first displacement sensor 4 and the second displacement sensor 5. This difference x1 - x2 is proportional to the distance L1 + L2. However, the distance L1 + L2 cannot be longer than the stacking length L of the flat rotor 2.

[0052] If the rotor 2, which is the target of the displacement sensor, moves axially or tilted, and the detection range of the displacement sensor includes a portion where the rotor 2 is not present, then errors may be included in the detection value of the displacement sensor. Due to axial or tilted vibration of the rotor 2 or steady-state sinking of the rotor 2 caused by its own weight A, the positions of the upper and lower ends of the rotor 2 will change. To avoid the influence of this phenomenon, the aforementioned distance L1+L2 needs to be shorter than the stacking length L of the rotor 2.

[0053] Let Δz be the amplitude of the axial variation of the upper and lower ends of rotor 2 caused by vibration or sinking of rotor 2, and let D be the outer diameter of the displacement sensor. If it is an eddy current method, the displacement sensor needs to be placed between the upper and lower ends of rotor 2, which is the object to be measured by the displacement sensor. The sensor is set as a circle with an outer diameter of 3 times the outer diameter of the sensor, that is, a circle with a radius of 3 / 2 times D. Therefore, the distance between the upper end of the rotor and the center of the displacement sensor and the distance between the lower end of the rotor and the center of the displacement sensor are preferably more than 3 / 2 times D. If the vibration of the object to be measured is considered, the axial distance L1+L2 between the first displacement sensor 4 and the second displacement sensor 5 needs to satisfy the following equation (5).

[0054]

Formula 5

[0055] L1+L2 <L-2Δz-3D…(5)

[0056] As a result, the difference x1-x2 between the signal x1 from the first displacement sensor 4 and the signal x2 from the second displacement sensor 5 decreases, which occurs with respect to the tilt θ of the rotor 2 around the Y-axis. y The problem is that the amount of interference or noise involved in the calculation becomes relatively large.

[0057] Figure 3 This is a wireframe diagram in Embodiment 1, including structural elements for supporting the rotor 2 using the detected radial position and tilt direction. The deviation is calculated based on the difference between the command value x* in the radial direction and the detected value x. The detected value x is the position x of the rotor 2 in the X-axis direction. The bearingless motor 1 has a command value i that outputs a support current i for supporting the rotor 2 in the radial direction based on the deviation. x0 The radial direction position controller 6. The radial direction position controller 6 will assign the command value i x0 * Input is sent to the current controller 7. The current controller 7 outputs a voltage command value, and based on its signal, the inverter 8 applies voltage to the motor section 9, thereby causing current to flow in the motor section 9. The motor section 9 has a rotor 2 and a stator 3. The bearingless motor 1 effectively utilizes displacement in the tilt direction while performing radial support control.

[0058] The bearingless motor 1 also includes: a calculation unit 10, which calculates the tilt angle θ of the rotor 2 about the Y-axis based on the detection results obtained by the first displacement sensor 4 and the second displacement sensor 5. y The calculation is performed; and the tilt direction position controller 11 receives the tilt angle θ of the rotor 2 about the Y-axis obtained by the calculation unit 10. y Based on tilt θ y Except for at least a portion of the frequency band that does not include the inherent angular vibration frequency of rotor 2, the output current command i θy * The tilt angle θ of rotor 2 about the Y-axis y It is the displacement in the tilt direction of rotor 2.

[0059] Therefore, the bearingless motor 1 can detect the tilt direction position information of the rotor 2 by removing unwanted signals or noise. By removing at least a portion of the frequency band that does not contain the natural angular vibration frequency of the tilt, the bearingless motor 1 eliminates interference and noise components, and can detect the desired tilt angle θ of the rotor 2 around the Y-axis. y Extraction is performed. The vibration at the natural angular frequency along the tilt direction is the primary component, and it is necessary to attenuate the vibration caused by this natural angular frequency. The natural angular frequency ω along the tilt direction... n This is expressed by the following equation (6).

[0060]

Formula 6

[0061]

[0062] I is the moment of inertia of rotor 2 in the tilt direction. This tilt direction is the tilt direction about the X and Y axes. z ω is the moment of inertia of rotor 2 about the Z-axis. ω is the rotational angular velocity of rotor 2, k θ It is the recovery torque coefficient.

[0063] like Figure 2 As shown, the force generated by the support winding 33 primarily functions as a support force to move the rotor 2 in the X-axis direction. However, since the line of action of this force does not pass through the center of gravity B, it also functions as a torque to tilt the rotor 2 about the Y-axis. Therefore, the bearingless motor 1 will use the current command i generated by the tilt direction position controller 11 to... θy * Command value i for the support current used to support the radial direction x0 * Superimpose the command value i of the supporting current. x * Set as i x0 * and i θy The sum of * allows for the early and appropriate suppression of vibrations in both the radial and tilt directions.

[0064] Just as the X-axis direction and the tilt direction about the Y-axis of rotor 2 interfere with each other as described above, the Y-axis direction and the tilt direction about the X-axis of rotor 2 also interfere with each other. To detect the position in the Y-axis direction and the tilt direction about the X-axis, the bearingless motor 1 also uses two displacement sensors: a first displacement sensor 4 and a second displacement sensor 5. Figure 3 The structural elements shown are used for vibration suppression control in the Y-axis direction and the tilt direction around the X-axis.

[0065] As described above, the bearingless motor 1 according to Embodiment 1 will adjust the tilt angle θ of the rotor 2 about the Y-axis. y The positions in the radial and tilt directions are obtained as independent state variables. The radial position controller 6 and the tilt position controller 11 can suppress the vibration of the rotor 2 in the tilt and radial directions in advance and appropriately. As a result, even when disturbances are applied to the rotor 2 or the rotor 2 rotates at a dangerous speed, the bearingless motor 1 can suppress the vibration of the rotor 2, enabling the rotor 2 to rotate more stably while suspended. That is, the bearingless motor 1 can improve the stability of the rotor 2 in the tilt direction.

[0066] Implementation method 2.

[0067] Figure 4 This indicates that in Embodiment 2, except for at least a portion of the frequency band that does not include the tilted natural angular vibration frequency, the current command i θy * A diagram showing the structure of the tilt direction position controller 40 that outputs the signal. Specifically, it can be configured such that the tilt direction position controller 11 of Embodiment 1 is replaced by the tilt direction position controller 40. The tilt direction position controller 40 has an inherent angular vibration frequency calculation unit 41 that calculates the inherent angular vibration frequency using rotational angular velocity and moment of inertia. In Embodiment 2, the calculation unit 10 of Embodiment 1 is replaced by the inherent angular vibration frequency calculation unit 41. The inherent angular vibration frequency calculation unit 41 has the function of calculating the inherent angular vibration frequency of the rotor 2 in the tilt direction by taking at least one of the rotational speed of the rotor 2 and the moment of inertia as input.

[0068] The tilt position controller 40 also includes a changing unit 42 that modifies the gain and phase of the signal inside the tilt position controller 40. The tilt position controller 40 further includes a reverse notch filter 43 that removes frequency components other than the natural angular vibration frequency. That is, the tilt position controller 40 performs filtering processing that passes through the frequency band of the natural angular vibration frequency of the rotor 2 in the tilt direction, removing at least a portion of the frequency band components other than the natural angular vibration frequency in the tilt direction. The transfer function G of the reverse notch filter 43 is... S (S) is expressed by the following formula (7).

[0069]

Formula 7

[0070]

[0071] In equation (7), a is a coefficient that determines the gain of the reverse notch filter 43, and Q is a coefficient that determines the frequency band of the reverse notch filter.

[0072] In embodiment 2, when the moment of inertia or rotational speed changes, the tilt direction position controller 40 can update the natural angular vibration frequency by changing its internal parameters. Therefore, there is no need to change the placement of the displacement sensor. Alternatively, a conventional bandpass filter can be used, or a Discrete Fourier Transform (DFT) can be used, which averages specific trigonometric functions and signals.

[0073] like Figure 4 As shown, the tilt direction position controller 40 also has a gain-phase adjuster 44 that takes the output of the reverse notch filter 43 as input and adjusts the gain and phase of the input.

[0074] The bearingless motor described in Embodiment 2 can still respond to current commands i used to suppress vibrations in the tilt direction of the rotor 2, even when the structure of the rotor 2 and the surrounding environment of the rotor 2 change, resulting in partial or complete changes in the suspension position, center of gravity, moment of inertia, rotational speed, and the angle at which the entire device is configured. θy * Adjustments will be made.

[0075] Conventionally, when stability is achieved by shifting the position of the displacement sensor upwards or downwards towards the magnetic plane of the rotor, changes in the rotor's structure can sometimes cause instability due to the sensor's position, which had previously stabilized the rotor. In such cases, it is necessary to change the position of the displacement sensor. In Embodiment 2, the gain and phase of the signal inside the tilt direction position controller 40, i.e., the signal obtained by the gain-phase adjuster 44, are changed by the adjustment unit 42, thus eliminating the need to change the position of the displacement sensor. The tilt direction position controller 40 of Embodiment 2 also has a function to correct for phase shifts caused by the reverse notch filter 43.

[0076] The inverse notch filter 43 causes a phase shift as the frequency moves away from the center frequency. To suppress this effect, the phase can be corrected in the gain-phase adjuster 44, for example, by connecting delay phase compensators in series. Alternatively, the input can be temporarily stored in a memory, causing the output to be delayed relative to the input to adjust the phase.

[0077] Figure 5This diagram illustrates the situation where an accessory 51 is added to the rotor 2 of the bearingless electric motor 1A according to Embodiment 2. For example, the accessory 51 may be a fan or a support. By adding the accessory 51, the center of gravity of the rotor 2 and the accessory 51 as a whole changes from center of gravity B to center of gravity C. In the case where the accessory 51 is a fan, the thrust changes due to the reaction force of the fan, and the suspension position of the rotor 2 changes. When the center of gravity of the rotor 2 and the accessory 51 changes to center of gravity C due to the mass and reaction force of the accessory 51, if there is only one displacement sensor, the interference effect in the radial and tilt directions changes, and sometimes the rotor 2 becomes unstable.

[0078] However, in the case of the influence of the accessory 51, the bearingless motor 1A according to embodiment 2 can ensure the stability of the rotor 2 by adjusting the gain phase adjuster 44 without changing the position of the displacement sensor.

[0079] Implementation method 3.

[0080] Figure 6 This is a cross-sectional view of a bearingless motor 1B with a non-magnetic sensor target 60, which does not contribute to the generation of supporting force and torque, installed at the lower part of the rotor 2. Figure 7 This is a cross-sectional view of a bearingless motor 1C with a non-magnetic sensor target 60, which does not contribute to the generation of supporting force and torque, installed at the lower part of the rotor 2. Figure 8 This is a cross-sectional view of a bearingless motor 1D in which a non-magnetic sensor target 60, which does not contribute to the generation of supporting force and torque, is mounted on the upper part of the rotor 2. Figure 9 This is a cross-sectional view of a bearingless motor 1E with a non-magnetic sensor target 60, which does not contribute to the generation of supporting force and torque, mounted on the upper part of the rotor 2. Figures 6 to 9 Each one shows the X-axis, Y-axis, and Z-axis. Figures 6 to 9 Cross-sections of bearingless motors 1B, 1C, 1D, and 1E are shown in a plane parallel to the plane containing the X and Z axes.

[0081] If the displacement sensor is an eddy current type sensor, then the sensor target 60 needs to be metallic. If the displacement sensor is an optical type sensor, then the sensor target 60 needs to be a material that reflects light. Figure 6 and Figure 8 In this case, the first displacement sensor 4 and the second displacement sensor 5 are both positioned at different locations between the upper and lower ends of the stator 3. One or both of the first displacement sensor 4 and the second displacement sensor 5 detect the position of the rotor 2 according to the sensor target 60.

[0082] exist Figure 7 and Figure 9 In this case, one of the first displacement sensor 4 and the second displacement sensor 5 is positioned at a different location from the upper and lower ends of the stator 3, while the other of the first displacement sensor 4 and the second displacement sensor 5 is positioned between the upper and lower ends of the stator 3. The aforementioned first displacement sensor 4 and the second displacement sensor 5 detect the position of the rotor 2 based on the sensor target 60. The aforementioned other first displacement sensor 4 and the second displacement sensor 5 detect the position of the rotor 2 based on the rotor 2 itself.

[0083] Figure 6 and Figure 8 Even when it is difficult to position the displacement sensor in the same axial position as the stator 3, such as inside a slot, the bearingless motors 1B and 1D can detect the position of the rotor 2 based on the sensor target 60. Figure 7 and Figure 9 In the bearingless motors 1C and 1E, the distance L1+L2 between the first displacement sensor 4 and the second displacement sensor 5 can be made larger than the stacked length L of the rotor 2. As a result, the bearingless motors 1C and 1E can make the difference x1-x2 between the signal x1 of the first displacement sensor 4 and the signal x2 of the second displacement sensor 5 larger compared with interference or noise.

[0084] Figure 10 This diagram illustrates the processor 91 in the case where the tilt direction position controller 11 of the bearingless motor 1 according to Embodiment 1 is implemented by the processor 91. That is, the function of the tilt direction position controller 11 can be implemented by the processor 91 executing a program stored in the memory 92. The processor 91 can be a CPU (Central Processing Unit), a processing device, an arithmetic unit, a microprocessor, or a DSP (Digital Signal Processor). Figure 10 The memory 92 is also shown.

[0085] When the function of the tilt position controller 11 is implemented by the processor 91, this function is implemented by the processor 91 and software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the memory 92. The processor 91 reads the program stored in the memory 92 and executes it, thereby implementing the function of the tilt position controller 11.

[0086] With the functions of the tilt position controller 11 implemented by the processor 91, the bearingless motor 1 has a memory 92 for storing the program that is ultimately executed by the program steps performed by the tilt position controller 11. The program stored in the memory 92 enables the computer to execute the tilt position controller 11.

[0087] Memory 92 includes, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), disks, floppy disks, optical disks, compact disks, mini disks, or DVDs (Digital Versatile Disk).

[0088] Figure 11 This diagram illustrates the processing circuit 93 in the case where the tilt direction position controller 11 of the bearingless motor 1 according to Embodiment 1 is implemented by the processing circuit 93. That is, the tilt direction position controller 11 can be implemented by the processing circuit 93. The processing circuit 93 is dedicated hardware. The processing circuit 93 can be, for example, a single circuit, a composite circuit, a programmable processor, a parallel-programmable processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. A portion of the tilt direction position controller 11 can be implemented by dedicated hardware different from the remainder.

[0089] Regarding the various functions of the tilt position controller 11, some of these functions may be implemented by software or firmware, while the remainder may be implemented by dedicated hardware. As described above, the various functions of the tilt position controller 11 can be implemented by hardware, software, firmware, or a combination thereof.

[0090] The radial position controller 6 of the bearingless motor 1 according to Embodiment 1 can be implemented by a processor or by a processing circuit. The arithmetic unit 10 of the bearingless motor 1 according to Embodiment 1 can be implemented by a processor or by a processing circuit. The processor is the same as the processor 91 described above. The processing circuit is the same as the processing circuit 93 described above.

[0091] The tilt direction position controller 40 of the bearingless motor according to Embodiment 2 can be partially or entirely implemented by a processor or by a processing circuit. The processor is the same as the processor 91 described above. The processing circuit is the same as the processing circuit 93 described above.

[0092] The structure shown in the above embodiments is an example and can be combined with other known technologies. The embodiments can also be combined with each other, and parts of the structure can be omitted or changed without departing from the main idea.

[0093] Explanation of the label

[0094] 1. Bearingless motors 1A, 1B, 1C, 1D, 1E; 2. Rotor; 3. Stator; 4. First displacement sensor; 5. Second displacement sensor; 6. Radial position controller; 7. Current controller; 8. Inverter; 9. Motor section; 10. Calculation section; 11. Tilt position controller; 40. Stator core; 31. Motor winding; 33. Support winding; 41. Natural angle vibration frequency calculation section; 42. Modulation section; 43. Reverse notch filter; 44. Gain and phase adjuster; 51. Accessories; 60. Sensor target; 91. Processor; 92. Memory; 93. Processing circuit.

Claims

1. A bearingless electric motor, which is a 2-axis controlled bearingless electric motor, characterized in that, have: Rotor; Stator, which provides supporting force and torque to the rotor; and The first displacement sensor and the second displacement sensor detect the radial position of the rotor. The stator has: The motor windings generate the torque by producing a magnetic flux with pole number p; and The supporting winding generates the supporting force by producing a magnetic flux with a pole number of p±2 or 2. At least a portion of the magnetic circuit for the magnetic flux with the number of poles p used to generate the torque, and at least a portion of the magnetic circuit for the magnetic flux with the number of poles p ± 2 or 2 used to generate the supporting force, are shared. The supporting force is generated by superimposing magnetic flux of pole number p ± 2 or 2 into the magnetic flux of pole number p. p is a natural number. The first displacement sensor and the second displacement sensor are configured at different positions along the axial direction. The bearingless motor also has a calculation unit that takes at least one of the rotor's rotational speed and moment of inertia as input and calculates the natural angular vibration frequency of the rotor in the tilt direction.

2. The bearingless electric motor according to claim 1, characterized in that: The calculation unit calculates the displacement of the rotor in the tilt direction based on the detection results obtained from the first displacement sensor and the second displacement sensor. It also has a tilt direction position controller, which receives the displacement in the tilt direction obtained by the calculation unit, removes at least a portion of the frequency band that does not include the inherent angular vibration frequency of the tilt of the rotor, and outputs a current command.

3. The bearingless electric motor according to claim 2, characterized in that, The tilt direction position controller also has a modification unit that modifies the magnitude and phase of the gain of the signal inside the tilt direction position controller.

4. The bearingless electric motor according to claim 1 or 2, characterized in that, The stacked length of the rotor is less than or equal to the radius of the rotor.

5. The bearingless electric motor according to claim 1 or 2, characterized in that, The second displacement sensor is positioned relative to the first displacement sensor at a position offset in the circumferential direction by a mechanical angle of 0° or 180°.

6. The bearingless electric motor according to claim 1 or 2, characterized in that, When a non-magnetic sensor target that does not contribute to the generation of the torque and the support force is mounted on the upper or lower part of the rotor, One or both of the first displacement sensor and the second displacement sensor are configured to detect the position of the rotor based on the sensor target.

7. The bearingless electric motor according to claim 2, characterized in that, The tilt direction position controller performs filtering processing that passes through the frequency band of the natural angular vibration frequency of the tilt direction of the rotor and removes at least a portion of the frequency band components other than the natural angular vibration frequency of the tilt direction.

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