Bearingless motor

Abstract

A bearingless motor (1) is provided with a rotor (2) and a stator (3). The stator (3) has a stator core (30) and a winding (33). The winding (33) has a motor winding (4) and a support winding (5). The motor winding (4) generates a magnetomotive force which causes the rotor (2) to generate a torque. The support winding (5) is independent of the motor winding (4) and adjusts the position of the axis (20) of the rotor (2) with respect to the stator (3). The motor winding (4) has: a main winding (41) for generating magnetomotive force; and an auxiliary winding (42) that is independent of the main winding (41). The angle around the axis (20) from the reference line (11) at an arbitrary point of the stator (3) is set to be theta (rad). F (theta) is the function of the magnetomotive force with respect to the angle (theta). The auxiliary winding (42) is configured so as to reduce the component of the order irrelevant to the torque of the rotor (2) when the Fourier series of the magnetomotive force function F (theta) is expanded.

Description

Technical Field

[0001] The present invention relates to a bearingless motor. More specifically, the present invention relates to a bearingless motor having a motor winding and a support winding. Background Art

[0002] In Patent Document 1, there is disclosed a bearingless motor in which a motor winding and a support winding are provided on a stator iron core piece disposed on the outer periphery of a rotor. The stator iron core piece has upper and lower stator teeth, is divided in the circumferential direction and provided with a plurality of them, and a motor winding and a support winding are wound around the stator iron core piece.

[0003] According to such a structure, since the motor winding and the support winding wound around the stator iron core piece expand in the radial direction, an effect such as being able to make the height of the pump chamber extremely small can be achieved.

[0004] Prior art documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-273214 Summary of the Invention

[0007] However, in the bearingless motor described in Patent Document 1, the rotor support force pulsates due to the space higher harmonic components of the magnetomotive force generated by the winding, and it is difficult to obtain a stable rotor support force.

[0008] An object of the present invention is to provide a bearingless motor in which a stable rotor support force can be easily obtained.

[0009] A bearingless motor according to an aspect of the present invention includes a rotor and a stator. The stator has: a stator core; and a winding wound around the stator core. The winding has a motor winding and a support winding. The motor winding is for generating a magnetomotive force that causes the rotor to generate a torque. The support winding is independent of the motor winding and is for adjusting the position of the axis of the rotor relative to the stator. The motor winding has: a main winding for generating a magnetomotive force; and an auxiliary winding independent of the main winding. Let the angle around the axis from a reference line at an arbitrary point of the stator when viewed from the direction extending from the axis be θ (rad). Let the function of the magnetomotive force with respect to the angle θ be F(θ). The auxiliary winding is configured to reduce the components of the order that is independent of the torque of the rotor when the function F(θ) of the magnetomotive force is expanded in a Fourier series.

[0010] In the bearingless motor of the present invention, it is easy to obtain a stable support force for the rotor. Brief Description of the Drawings

[0011] Figure 1It is a cross-sectional view of the bearingless motor according to the first embodiment of the present invention, observed from the direction extending from the axis.

[0012] Figure 2 It is a schematic side view of a part of the bearingless motor according to the first embodiment, having a cross-section.

[0013] Figure 3 It is a cross-sectional view of the bearingless motor according to the second embodiment of the present invention, observed from the direction extending from the axis.

[0014] Figure 4A It is a graph showing the relationship between the space order of the magnetomotive force and the magnetomotive force amplitude of the bearingless motor according to the second embodiment.

[0015] Figure 4B It is a graph showing the relationship between the space order of the magnetomotive force and the magnetomotive force amplitude of a conventional bearingless motor.

[0016] Figure 5A It is a graph showing the relationship between the supporting force and the angle θ of the bearingless motor according to the second embodiment.

[0017] Figure 5B It is a graph showing the relationship between the supporting force and the angle θ of a conventional bearingless motor. Detailed Embodiments

[0018] (1) Summary

[0019] The bearingless motor of the present invention will be described. The embodiments described below are only a part of the various embodiments of the present invention. In the following embodiments, various changes can be made according to design and the like as long as the object of the present invention can be achieved.

[0020] As Figure 1 shown, the bearingless motor 1 of the present invention includes a rotor 2 and a stator 3. The stator 3 has a stator core 30 and windings 33 wound around the stator core 30. The windings 33 include a motor winding 4 and a support winding 5. The motor winding 4 is used to generate a magnetomotive force that causes the rotor 2 to generate torque. The support winding 5 is independent of the motor winding 4 and is used to adjust the position of the axis 20 of the rotor 2 relative to the stator 3. The motor winding 4 has a main winding 41 for generating a magnetomotive force and an auxiliary winding 42 independent of the main winding 41. Let the angle around the axis 20 from a reference line 11 at an arbitrary point of the stator 3 when observed from the direction extending from the axis 20 be θ (rad). Let the function of the magnetomotive force with respect to the angle θ be F(θ). The auxiliary winding 42 is configured to reduce the components of the orders that are not related to the torque of the rotor 2 when the function F(θ) of the magnetomotive force is expanded in a Fourier series.

[0021] In the bearingless motor 1 of the present invention, it is easy to obtain a stable supporting force for the rotor.

[0022] (2) First Embodiment

[0023] Hereinafter, based on Figure 1 and Figure 2 the bearingless motor 1 of the first embodiment will be described. The bearingless motor 1 includes a rotor 2 and a stator 3. The bearingless motor 1 of the first embodiment is an alternating pole type motor. The bearingless motor 1 is a three-phase AC motor.

[0024] (2.1) Rotor

[0025] The rotor 2 rotates about the axis 20. The rotor 2 is integrally mounted on a rotating body (not shown) and transmits torque and power to the rotating body. The rotor 2 has an annular rotor core 21 and a plurality of magnets 22. The bearingless motor 1 of the first embodiment is an alternating pole type motor, and a plurality of (four in the illustrated example) magnets 22 are provided at intervals in the circumferential direction about the axis 20 of the rotor core 21. The plurality of magnets 22 are provided on the rotor core 21 such that the same poles (S poles in the illustrated example) are located on the side facing the axis 20. Thus, an N pole is formed in a portion of the surface of the rotor core 21 where the magnets 22 are located in the circumferential direction about the axis 20, and the portion between the magnets 22 functions like an S pole.

[0026] (2.2) Stator

[0027] The stator 3 has a stator core 30 and windings 33 wound around the stator core 30.

[0028] (2.2.1) Stator Core

[0029] The stator core 30 has a yoke 31 and a plurality of teeth 32 protruding from the inner circumferential surface of the yoke 31 toward the center of the yoke 31.

[0030] (2.2.1.1) Yoke

[0031] The yoke 31 is annular when viewed in the direction extending from the axis 20 (hereinafter referred to as the axial direction). The yoke 31 has a plurality of steel plates laminated in the axial direction. The steel plates are formed of electromagnetic steel plates such as silicon steel plates, for example.

[0032] (2.2.1.2) Teeth

[0033] A plurality of (nine in the first embodiment) teeth 32 are formed at equal intervals in the circumferential direction on the inner circumferential surface of the yoke 31. The teeth 32 are integrally formed with the yoke 31. Anti-disengagement protrusions protruding toward both sides in the circumferential direction about the axis 20 are formed at the end portion on the tip side (axis 20 side) of the teeth 32 protruding from the yoke 31.

[0034] (2.2.2) Windings

[0035] The winding 33 is wound around the stator core 30. The winding 33 has a motor winding 4 and a support winding 5.

[0036] (2.2.2.1) Motor winding

[0037] The motor winding 4 is used to generate torque on the rotor 2. The motor winding 4 is wound around each of the plurality of teeth 32. The motor winding 4 has a main winding 41 and an auxiliary winding 42.

[0038] (2.2.2.1.1) Main winding

[0039] The main winding 41 is a winding for generating torque on the rotor 2. Each main winding 41 is wound around the end portion (on the side of the axis 20) of each tooth 32 protruding from the yoke 31. In addition, each main winding 41 is wound around a portion of each tooth 32 on the base side (yoke 31 side) relative to the anti - detachment protrusion. In the first embodiment, since the bearingless motor 1 is a three - phase alternating current type, as the main winding 41, the windings of the U - phase, V - phase, and W - phase are wound around 3 teeth 32 respectively according to each phase, and are wound around a total of 9 teeth 32.

[0040] (2.2.2.1.2) Auxiliary winding

[0041] The auxiliary winding 42 is a winding independent of the main winding 41. The main purpose of providing the auxiliary winding 42 is not to increase the torque of the rotor 2, but it can increase or decrease the torque of the rotor 2 as a result. The main purpose of providing the auxiliary winding 42 is to reduce the spatial harmonic components in the magnetomotive force distribution that are unrelated to the torque of the rotor 2, which will be described in detail later.

[0042] In the first embodiment, as the auxiliary winding 42, the windings of the U - phase, V - phase, and W - phase are wound around 3 teeth 32 respectively according to each phase, and are wound around a total of 9 teeth 32. In addition, the categories of the U - phase, V - phase, and W - phase of the auxiliary winding 42 wound around the same tooth 32 may be the same as or different from the category of the main winding 41.

[0043] (2.2.2.1.3) Number of turns of the main winding and number of turns of the auxiliary winding

[0044] The number of turns of the auxiliary winding 42 wound around one of the plurality of teeth 32 is less than the number of turns of the main winding 41 wound around the same one tooth 32.

[0045] In addition, the number of turns of the motor winding 4 wound around one of the plurality of teeth 32 is the same for all teeth 32 among the plurality of teeth 32. That is, the sum of the number of turns of the main winding 41 and the number of turns of the auxiliary winding 42 wound around one tooth 32 is the same for all teeth 32.

[0046] (2.2.2.2) Support winding

[0047] The support winding 5 is a winding independent of the motor winding 4. The support winding 5 is used to generate a radial support force (a direction orthogonal to the axis 20) for supporting the rotor 2. In other words, the support winding 5 adjusts the radial position of the rotor 2 relative to the stator 3. Specifically, the support winding 5 causes the stator 3 to generate a magnetic field with two poles (spatial order of 1), and a radial force acts on the rotor 2 as the support force for the rotor 2. The rotor 2 is passively supported in the direction in which the axis 20 extends. For example, in the first embodiment, as Figure 2 shown, the rotor 2 is passively supported at a position where the gravity applied to the rotor 2 is balanced with the magnetic attraction force between the rotor 2 and the stator 3.

[0048] As Figure 1 shown, in the first embodiment, as the support winding 5, the windings of the U-phase, V-phase, and W-phase are respectively wound around 3 teeth 32 for each phase, and are wound around a total of 9 teeth 32.

[0049] (2.3) Circuit board

[0050] Although not shown, the bearingless motor 1 has a circuit board. The circuit board is disposed on the stator 3 and supplies current to the winding 33. A control unit composed of a microprocessor or the like is mounted on the circuit board. The control unit controls each current supplied to the main winding 41, the auxiliary winding 42, and the support winding 5.

[0051] (2.4) Magnetomotive force and support force

[0052] As described above, in the bearingless motor 1, the motor winding 4 is used to generate a torque for the rotor 2, and the support winding 5 is used to generate a support force for supporting the rotor 2.

[0053] The distribution of the magnetomotive force generated by the winding 33 will be described. As Figure 1 shown, when observing from the direction in which the axis 20 extends, the angle around the axis 20 from the reference line 11 at an arbitrary point on the stator 3 is set as θ (rad). At this time, the function of the magnetomotive force with respect to the angle θ is set as F(θ).

[0054] It is known that: when the component of the order unrelated to the torque of the rotor 2 is large in the Fourier series expansion of the function F(θ) of the magnetomotive force generated by the winding 33, the support force pulsation of the rotor 2 or the direction change of the support force for supporting the rotor 2 occurs. In Figure 1In the bearingless motor 1 shown, since the number of pole pairs of the rotor 2 is 4, the order related to the torque of the rotor 2 is 4, and the orders unrelated to the torque of the rotor 2 are natural numbers other than 4. That is, when the number of pole pairs of the rotor 2 is M (natural number), the order related to the torque of the rotor 2 is M, and the orders unrelated to the torque of the rotor 2 are natural numbers other than M. Therefore, in order to suppress the pulsation of the supporting force of the rotor 2 and the change in the direction in which the supporting force is generated, it is preferable that the value (absolute value) of the components of each order when the function F(θ) is expanded into a Fourier series is small for all orders other than the Mth order. Particularly preferably, the (M±1)th order components are small. In addition, in the case of an alternating pole type or single pole type motor, it is particularly preferable that the one-pole component or the two-pole component is small.

[0055] (2.5) Summary of the First Embodiment (2.5.1)

[0057] The number of turns of the auxiliary winding 42 is adjusted so as to reduce the components of the orders unrelated to the torque of the rotor 2 when the magnetomotive force function F(θ) is expanded into a Fourier series, thereby suppressing the pulsation of the supporting force of the rotor 2 and the change in the supporting force direction to a small value, and it is easy to obtain a stable supporting force.

[0058] In particular, by configuring the auxiliary winding 42 to reduce the second-order components when the magnetomotive force function F(θ) is expanded into a Fourier series, the pulsation of the supporting force of the rotor 2 and the change in the supporting force direction can be effectively suppressed to a small value. (2.5.2)

[0060] The number of turns of the auxiliary winding 42 wound around one of the plurality of teeth 32 is less than the number of turns of the main winding 41 wound around the same one tooth 32. Thereby, the number of turns of the auxiliary winding 42 with a relatively low contribution to torque generation can be suppressed to be small, and a decrease in the output (torque and power) of the bearingless motor 1 can be suppressed. (2.5.3)

[0062] The number of turns of the motor winding 4 wound around one of the plurality of teeth 32 is the same for all the teeth 32 among the plurality of teeth 32. Thereby, even in the case of the motor winding 4 in which the main winding 41 and the auxiliary winding 42 use the same wire diameter, the total cross-sectional area of the main winding 41 and the auxiliary winding 42 wound around each tooth 32 can be made the same, waste of the slot fill factor of the main winding 41 and the auxiliary winding 42 can be eliminated, and copper loss can be reduced.

[0063] (3) Second Embodiment

[0064] Next, based on Figures 3 to 5BDescribe the bearingless motor 1 of the second embodiment. In addition, since the bearingless motor 1 of the second embodiment is mostly the same as the bearingless motor 1 of the first embodiment, the same reference numerals are given to the repeated constituent elements, and the detailed description is cited.

[0065] Regarding the bearingless motor 1 of the first embodiment, which is a three-phase alternating current type with 8 poles and 9 slots, the bearingless motor 1 of the second embodiment is a three-phase alternating current type with 20 poles and 24 slots.

[0066] Define the categories and winding polarities of the U-phase, V-phase, and W-phase of the main winding 41 wound around one of the multiple teeth 32, and the categories and winding polarities of the auxiliary winding 42 wound around the same one tooth 32. Here, the winding polarity is defined according to whether the current flowing in the winding 33 wound around the tooth 32 is right-handed or left-handed when observing the tooth 32 from the axis 20.

[0067] The main winding 41 and the auxiliary winding 42 wound around each tooth 32 are represented by the bracketed writing method of (category and winding polarity of the main winding 41 / category and winding polarity of the auxiliary winding 42).

[0068] In addition, write the bracketed writing about an adjacent tooth 32 side by side. At this time, the bracketed writing of the multiple teeth 32 is configured to be

[0069] (U+ / W-)(U- / V+)(V- / U+)(V+ / W-)(W+ / V-)(W- / U+)(U- / W+)(U+ / V-)(V+ / U-)(V- / W+)(W- / V+)(W+ / U-) repetition.

[0070] And, it is configured that the ratio N of the number of turns of the auxiliary winding 42 wound around one tooth 32 to the number of turns of the main winding 41 wound around the same one tooth 32 satisfies

[0071] 0.222 ≤ N ≤ 0.511.

[0072] Thereby, the second-order component when the magnetomotive force function F(θ) is expanded into a Fourier series is reduced, and the pulsation of the supporting force of the rotor 2 and the variation of the supporting force direction are effectively suppressed to be small. And according to the analysis result, the pulsation amount of the supporting force of the rotor 2 caused by the second-order component of the magnetomotive force is suppressed to be less than 5% of the average value of the supporting force. In the case where the number of poles of the rotor is 20 (10 pole pairs), the supporting force pulsation of the rotor 2 caused by the second-order component of the magnetomotive force is a tenth-order component that pulsates 10 times when the rotor rotates one week.

[0073] Particularly preferably, it is configured that the ratio N of the number of turns satisfies

[0074] 0.322 ≤ N ≤ 0.383.

[0075] Accordingly, the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series is further reduced, and the pulsation of the supporting force of the rotor 2 and the variation of the supporting force direction are effectively suppressed to a small level. According to the analysis results, the tenth-order component of the pulsation of the supporting force is suppressed to less than 1% of the average value of the supporting force.

[0076] More preferably, at this time, the ratio N of the number of turns is one of 1 / 3, 3 / 8, 4 / 11, 5 / 14, 6 / 17, 7 / 19, 7 / 20, 8 / 21, 8 / 23, 9 / 25, 9 / 26, 10 / 27, 10 / 29, 11 / 29, 11 / 30, 11 / 31, 11 / 32, 12 / 35, 13 / 34, 13 / 35, 13 / 36, and 13 / 37. Accordingly, the ratio N of the number of turns can be set as an integer ratio, and it is easy to reduce the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series, and the pulsation of the supporting force of the rotor 2 and the variation of the supporting force direction are effectively suppressed to a small level.

[0077] (3.1) Conventional example

[0078] Figure 4B Shows the relationship between the spatial order components when the function F(θ) of the magnetomotive force of the conventional example is expanded into a Fourier series and the magnitude (amplitude) of each component. In addition, Figure 5B Shows a relationship diagram of the supporting force of the rotor 2 of the bearingless motor 1 of this conventional example with respect to the angle θ. In this conventional example, as Figure 4B shown, the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series is presented relatively large. In addition, at this time, as Figure 5B shown, it can be seen that the supporting force of the rotor 2 pulsates to a large extent.

[0079] (3.2) The present invention (second embodiment)

[0080] In the second embodiment of the present invention, the auxiliary winding 42 is configured to reduce the components of the order unrelated to the torque of the rotor 2 when the function F(θ) of the magnetomotive force is expanded into a Fourier series. Specifically, according to the winding methods (number of turns (ratio of the number of turns), combination of the categories of U-phase, V-phase, and W-phase, winding polarity, etc.) of the main winding 41 and the auxiliary winding 42 on each tooth 32 and the control unit (more specifically, the control program for controlling the control unit) of the circuit board, the reduction of the components of the order unrelated to the torque of the rotor 2 when the function F(θ) of the magnetomotive force is expanded into a Fourier series is achieved.

[0081] Figure 4A Shows the relationship between the spatial order components when the function F(θ) of the magnetomotive force of the second embodiment is expanded into a Fourier series and the magnitude (amplitude) of each component. In addition, Figure 5AA graph showing the relationship between the supporting force of the rotor 2 of the bearingless motor 1 according to the second embodiment and the angle θ. In the second embodiment, as Figure 4A shown, the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series is suppressed to approximately 0. Additionally, at this time, as Figure 5A shown, it can be seen that the pulsation of the supporting force of the rotor 2 is suppressed to a small level. In the alternating-pole type bearingless motor 1, since the second-order component has a particularly large influence on the pulsation of the supporting force, reducing the second-order component in the orders unrelated to the torque of the rotor 2 is most effective for suppressing the pulsation of the supporting force and the variation in the direction of the supporting force.

[0082] (4) Variation

[0083] The bearingless motor 1 is not limited to an alternating-pole type motor. For example, it can also be a single-pole type motor. In the single-pole type bearingless motor 1, since the second-order component has a particularly large influence on the pulsation of the supporting force, reducing the second-order component in the orders unrelated to the torque of the rotor 2 is most effective for suppressing the pulsation of the supporting force and the variation in the direction of the supporting force.

[0084] The bearingless motor 1 is not limited to a three-phase AC type motor. The bearingless motor 1 is not limited to an inner-rotor type and can also be an outer-rotor type.

[0085] The shape of the rotor core 21 is not limited to an annular shape. The rotor core 21 can also be a solid cylindrical shape. The rotor core 21 can also not be a shape that is uniform around the axis 20.

[0086] The number of poles of the rotor 2 is not limited to 20 or 28. Additionally, the number of magnets 22 provided on the rotor 2 is not limited.

[0087] The yoke 31 can also not be annular when viewed from the axial direction. That is, the yoke 31 can also not be a circular ring when viewed from the axial direction, but a non-circular ring. Additionally, the yoke 31 does not necessarily have to be formed into a ring shape.

[0088] The number of teeth 32 formed on the stator core 30 is not limited.

[0089] The teeth 32 can also be formed independently of the yoke 31 and integrally mounted on the yoke 31 by fitting, fastening, etc. In this case, the teeth 32 can also be formed of the same material as the yoke 31, such as electromagnetic steel sheets.

[0090] It is also possible that none of the multiple teeth 32 wind the motor winding 4.

[0091] The main winding 41 does not necessarily have to be wound around the (axis 20 side) end of the teeth 32.

[0092] The auxiliary winding 42 may not necessarily be wound around the portion of the tooth 32 closer to the base side (yoke 31 side) than the main winding 41, and may be wound around the portion of the tooth 32 closer to the top end side (axis 20 side) than the main winding 41. Further, even when the bearingless motor 1 is of a three-phase alternating current type, the auxiliary winding 42 does not necessarily need to be classified into the U-phase, V-phase, and W-phase.

[0093] The number of turns of the auxiliary winding 42 wound around one of the plurality of teeth 32 may be more than the number of turns of the main winding 41 wound around the same one tooth 32.

[0094] The number of turns of the motor winding 4 wound around one of the plurality of teeth 32 may not be the same for all of the plurality of teeth 32.

[0095] The support winding 5 may not necessarily be wound around the portion of the tooth 32 closer to the base side (yoke 31 side) than the auxiliary winding 42, and may be wound around the portion of the tooth 32 closer to the top end side (axis 20 side) than the auxiliary winding 42. Further, the support winding 5 may not necessarily be wound around the portion of the tooth 32 closer to the base side (yoke 31 side) than the main winding 41, and may be wound around the portion of the tooth 32 closer to the top end side (axis 20 side) than the main winding 41. Further, the support winding 5 may not be wound around the tooth 32 but may be wound around the yoke 31. The support winding 5 does not necessarily need to be classified into the U-phase, V-phase, and W-phase.

[0096] (5) Summary

[0097] As described above, the bearingless motor (1) of the first embodiment includes a rotor (2) and a stator (3). The stator (3) has: a stator core (30); and a winding (33) wound around the stator core (30). The winding (33) has a motor winding (4) and a support winding (5). The motor winding (4) is for generating a magnetomotive force that causes the rotor (2) to generate torque. The support winding (5) is independent of the motor winding (4) and is for adjusting the position of the axis (20) of the rotor (2) relative to the stator (3). The motor winding (4) has: a main winding (41) for generating a magnetomotive force; and an auxiliary winding (42) independent of the main winding (41). Let the angle around the axis (20) from a reference line (11) to an arbitrary point of the stator (3) when viewed in the direction extending from the axis (20) be θ (rad). Let the function of the magnetomotive force with respect to the angle θ be F(θ). The auxiliary winding (42) is configured to reduce the components of the orders that are independent of the torque of the rotor (2) when the function F(θ) of the magnetomotive force is expanded in a Fourier series.

[0098] In the first embodiment, the pulsation of the supporting force of the rotor (2) and the variation in the direction of the supporting force generation are suppressed to be small, and it is easy to obtain a stable supporting force for the rotor (2).

[0099] The second mode can be achieved by combination with the first mode. In the second mode, the stator core (30) has: an annular yoke (31); and a plurality of teeth (32) protruding from the inner peripheral surface of the yoke (31) toward the center of the yoke (31). A motor winding (4) is wound around the plurality of teeth (32). The number of turns of the auxiliary winding (42) wound around one of the plurality of teeth (32) is less than the number of turns of the main winding (41) wound around the same one tooth (32).

[0100] In the second mode, the number of turns of the auxiliary winding (42) that does not contribute to the magnetomotive force can be suppressed to be small, suppressing a decrease in the output (torque and power) of the bearingless motor (1).

[0101] The third mode can be achieved by combination with the first mode or the second mode. In the third mode, the bearingless motor (1) is an alternating-pole type or a single-pole type motor. The auxiliary winding (42) is configured to reduce the (2)nd order component when the magnetomotive force function F(θ) is expanded in a Fourier series.

[0102] In the third mode, the pulsation of the supporting force of the rotor (2) and the variation in the direction of the supporting force can be efficiently suppressed to be small, and it is easy to obtain a stable supporting force for the rotor (2).

[0103] The fourth mode can be achieved by combination with the second mode or the third mode. In the fourth mode, the number of turns of the motor winding (4) wound around one of the plurality of teeth (32) is the same for all of the plurality of teeth (32).

[0104] In the fourth mode, the total cross-sectional area of the main winding (41) and the auxiliary winding (42) wound around each tooth (32) can be made the same, eliminating the waste of the slot fill factor of the main winding (41) and the auxiliary winding (42), and copper loss can be reduced.

[0105] The fifth mode can be achieved by combining with any one of the second to fourth modes. In the fifth mode, the bearingless motor (1) is a three-phase alternating current type with 20 poles and 24 slots or 28 poles and 24 slots. The class and winding polarity of the U-phase, V-phase, and W-phase of the main winding (41) wound around one of the multiple teeth (32) and the class and winding polarity of the auxiliary winding (42) wound around the same one tooth (32) are represented by the bracketed writing method of (class of main winding (41) and winding polarity / class of auxiliary winding (42) and winding polarity). The bracketed writings regarding adjacent teeth (32) are written side by side. At this time, the bracketed writings of the multiple teeth (32) become a repetition of (U+ / W-)(U- / V+)(V- / U+)(V+ / W-)(W+ / V-)(W- / U+)(U- / W+)(U+ / V-)(V+ / U-)(V- / W+)(W- / V+)(W+ / U-). Moreover, the ratio N of the number of turns of the auxiliary winding (42) wound around one tooth (32) to the number of turns of the main winding (41) wound around the same one tooth (32) satisfies 0.222 ≤ N ≤ 0.511.

[0106] In the fifth mode, the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series is reduced, and the pulsation of the supporting force of the rotor (2) and the variation of the supporting force direction are effectively suppressed to be small. And the tenth-order component of the pulsation of the supporting force is suppressed below 5%.

[0107] The sixth mode can be achieved by combining with the fifth mode. In the sixth mode, the ratio N satisfies 0.322 ≤ N ≤ 0.383.

[0108] In the sixth mode, the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series is further reduced, and the pulsation of the supporting force of the rotor (2) and the variation of the supporting force direction are effectively suppressed to be small.

[0109] The seventh mode can be achieved by combining with the fifth mode. In the seventh mode, the ratio N is any one of 1 / 3, 3 / 8, 4 / 11, 5 / 14, 6 / 17, 7 / 19, 7 / 20, 8 / 21, 8 / 23, 9 / 25, 9 / 26, 10 / 27, 10 / 29, 11 / 29, 11 / 30, 11 / 31, 11 / 32, 12 / 35, 13 / 34, 13 / 35, 13 / 36, and 13 / 37.

[0110] In the seventh mode, the ratio N of the number of turns can be set as an integer ratio, and it is easy to reduce the second-order component when the function F(θ) of the magnetomotive force is expanded into a Fourier series, and the pulsation of the supporting force of the rotor (2) and the variation of the supporting force direction are effectively suppressed to be small.

[0111] Description of Reference Numerals

[0112] 1. Bearingless motor; 11. Base line; 2. Rotor; 20. Axis; 21. Rotor core; 22. Magnet; 3. Stator; 30. Stator core; 31. Yoke; 32. Teeth; 33. Winding; 4. Motor winding; 41. Main winding; 42. Auxiliary winding; 5. Support winding.

Claims

1. A bearingless motor, wherein, the bearingless motor includes a rotor and a stator, the stator has: a stator core; and a winding wound around the stator core, the winding has: a motor winding for generating a magnetomotive force that causes the rotor to generate torque; and a support winding independent of the motor winding for adjusting the position of the axis of the rotor relative to the stator, the motor winding has: a main winding for generating the magnetomotive force; and an auxiliary winding independent of the main winding, when the angle around the axis from a reference line at any point of the stator when viewed in the direction extending from the axis is set as θ (rad), and the function of the magnetomotive force with respect to the angle θ is set as F(θ), the auxiliary winding is configured to reduce the components of the order unrelated to the torque of the rotor when the function F(θ) of the magnetomotive force is expanded in a Fourier series.

2. The bearingless motor according to claim 1, wherein, the stator core has: an annular yoke; and a plurality of teeth protruding from the inner peripheral surface of the yoke toward the center of the yoke, the motor winding is wound around the plurality of teeth, the number of turns of the auxiliary winding wound around one of the plurality of teeth is less than the number of turns of the main winding wound around the same one tooth.

3. The bearingless motor according to claim 2, wherein, the bearingless motor is an alternating pole type or a single pole type motor, the auxiliary winding is configured to reduce the second-order component when the function F(θ) of the magnetomotive force is expanded in a Fourier series.

4. The bearingless motor according to claim 2 or 3, wherein, the number of turns of the motor winding wound around one of the plurality of teeth is the same in all of the plurality of teeth.

5. The bearingless motor according to claim 2 or 3, wherein, the bearingless motor is a three-phase alternating current type with 20 poles and 24 slots or 28 poles and 24 slots, when the category and winding polarity of the main winding / the category and winding polarity of the auxiliary winding are represented in such a bracketed writing manner as (the category and winding polarity of the U-phase, V-phase, and W-phase of the main winding wound around one of the plurality of teeth / the category and winding polarity of the auxiliary winding wound around the same one tooth), and the bracketed writings regarding adjacent ones of the teeth are written side by side, the bracketed writings of the plurality of teeth become a repetition of (U+ / W-)(U- / V+)(V- / U+)(V+ / W-)(W+ / V-)(W- / U+)(U- / W+)(U+ / V-)(V+ / U-)(V- / W+)(W- / V+)(W+ / U-), and the ratio N of the number of turns of the auxiliary winding wound around one tooth to the number of turns of the main winding wound around the same one tooth satisfies 0.222≤N≤0.511。 6. The bearingless motor according to claim 5, wherein, the ratio N satisfies 0.322≤N≤0.383。 7. The bearingless motor according to claim 5, wherein, The ratio N is any one of 1 / 3, 3 / 8, 4 / 11, 5 / 14, 6 / 17, 7 / 19, 7 / 20, 8 / 21, 8 / 23, 9 / 25, 9 / 26, 10 / 27, 10 / 29, 11 / 29, 11 / 30, 11 / 31, 11 / 32, 12 / 35, 13 / 34, 13 / 35, 13 / 36, and 13 / 37.

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