Axial gap type rotating electric machine

Abstract

To provide an axial gap type rotating electric machine that can be miniaturized and thinned while maintaining performance, and can be manufactured at low cost. [Solution] An axial gap type rotating electric machine having a rotor with a disc-shaped permanent magnet and a pair of stators facing the rotor on both sides in the axial direction via an air gap, wherein the pair of stators have winding poles facing each other at the same position in the circumferential direction that are excited with the same polarity, and the disc-shaped permanent magnet has the same polarity at the same position in the circumferential direction on both sides, and the N pole and S pole are alternately magnetized to P pole in the circumferential direction.

Description

[Technical Field]

[0001] This invention relates to an axial gap type rotating electric machine used as an electric motor or generator. [Background technology]

[0002] Rotating electrical machinery is increasingly in demand for miniaturization, lightness, and thinness from the market. Recently, there has also been a growing demand for energy efficiency and higher performance as a measure against global warming. Furthermore, there is a strong demand for reduced vibration, low noise, and low cost.

[0003] A rotating electric machine comprises a stator and a rotor positioned with a gap between them. A type in which the gap is positioned radially between the stator and rotor is called a radial gap rotating electric machine, and a type in which the gap is positioned axially is called an axial gap rotating electric machine. Various forms of axial gap rotating electric machines are known, but in particular, a type having gaps on both axial sides of either the stator or the rotor allows for a larger air gap facing area than a radial gap type of the same size, thus enabling higher torque and attracting attention for applications such as electric vehicles (EVs) and robots.

[0004] Conventional brushless DC motors (hereinafter also simply referred to as "BLDCMs") use permanent magnets in the rotor and a stator core constructed from laminated silicon steel sheets, with three-phase designs being the mainstream for efficiency and low vibration. Furthermore, the coil type of conventional brushless DC motors varies; distributed windings are used for applications where low vibration is important, while concentrated windings are used when cost and efficiency are prioritized. The concentrated winding method is significantly more common in the market. The reason for this is that while distributed windings result in a sinusoidal magnetic flux distribution and thus lower vibration, the larger coil ends increase copper loss, reducing efficiency, and the winding is more complex, leading to higher costs.

[0005] Non-Patent Document 1 states that if this concentrated winding type brushless DC motor is configured with gaps on both axial sides of the rotor, the volume of the air gap can be increased compared to a radial gap type rotating electric motor of the same size, thus enabling higher torque. Non-Patent Document 1 describes an SR motor that does not use permanent magnets, but if permanent magnets are applied to the rotor and gaps are placed on both axial sides of the rotor, the same effect can be obtained, and Non-Patent Document 2 is a related document.

[0006] Furthermore, among axial gap type rotating electric machines, axial double-sided gap type rotating electric machines are particularly known, in which the stator or rotor is positioned on both sides of the rotor or stator in the axial direction. This type allows for a larger opposing air gap area than radial gap type rotating electric machines of the same size, thus enabling higher torque. For this reason, it is a type of rotating electric machine that is attracting attention for applications such as electric vehicles (EVs) and robots. Axial double-sided gap type rotating electric machines come in 1-rotor 2-stator and 1-stator 2-rotor types, but the 1-rotor 2-stator type is expected to be more suitable for use because it saves on the amount of magnets and the stators are separated.

[0007] As described above, such axial double-sided gap rotating electric machines can achieve higher torque than radial gap rotating electric machines of the same size because they have a larger air gap facing area. This is described in Non-Patent Documents 4 and 5. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Axial gap SR motor, 2013, Japan Management Association, 33rd Motor Technology Symposium, B5-3-7 [Non-Patent Document 2] Double-sided axial gap motor using ferrite magnets, 2011, Japan Management Association, 31st Motor Technology Symposium [Non-Patent Document 3] How to Use a Stepping Motor, Ohmsha, 2003, pp. 70-71 [Non-Patent Document 4] Examination of an In-Wheel Axial Gap Motor Using Ferrite Magnets for a City Commuter, The National Convention of The Institute of Electrical Engineers of Japan, 2012 [Non-Patent Document 5] Realization of a Thin and High-Torque Axial Gap Motor with a Laminated Core, SEI Technical Review, No. 192, January 2018, pp. 121, Sumitomo Metal Industries Technical Report [Non-Patent Document 6] Improvement of Characteristics of PM Type Stepping Motors, Japan Productivity Center, Motor Technology Symposium, 2-2-1, 1993 [Non-Patent Document 7] Motor Technology in Mechatronics, 26 pages, Technical Review Publishing [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] However, there is also a strong market demand for further miniaturization and thinning of conventional axial gap rotary electric machines with gaps arranged on both axial sides of the rotor. In the rotary electric machine of the method of Non-Patent Document 2, in which a rotor composed of one permanent magnet is axially sandwiched between two stators, since one magnet supplies magnetic flux to the air gaps on both sides thereof, the thickness of the magnet increases, and there are problems in realizing thinning and cost reduction.

[0010] In addition, the axial gap rotary electric machine of the one-rotor two-stator type has a problem that it is difficult to increase the torque because one magnet supplies magnetic flux to the air gaps on both sides thereof. Further, since the magnetic circuit extends between the two stators, there are problems that the magnetic resistance and iron loss increase, making it difficult to achieve high efficiency and compatibility with high-speed regions. Also, there is a problem that the linked magnetic flux waveform becomes a distorted waveform due to the influence of the magnetic fluxes generated by the currents of the two stators, making it difficult to achieve low vibration and noise.

[0011] Therefore, the present invention has been made to solve the above problems, and aims to provide an axial gap type rotating electric machine that can be made smaller and thinner while maintaining performance compared to conventional axial gap type rotating electric machines, and that can be manufactured at low cost. Furthermore, it aims to provide an axial gap type rotating electric machine that can achieve higher torque, higher efficiency, operation in high-speed ranges, and lower noise compared to conventional axial gap type rotating electric machines. [Means for solving the problem]

[0012] The axial gap type rotating electric machine according to the present invention, which solves the above problems, is an axial gap type rotating electric machine having a rotor having a disc-shaped permanent magnet and a pair of stators facing the rotor on both sides in the axial direction via an air gap, wherein the pair of stators have winding poles facing each other at the same position in the circumferential direction that are arranged to have the same excitation polarity, and the disc-shaped permanent magnet has the same magnetic polarity at the same position in the circumferential direction on both sides, and the N pole and S pole are alternately magnetized to P poles in the circumferential direction. However, P is an even number of 2 or more.

[0013] Furthermore, in the axial gap type rotating electric machine according to the present invention, the stator preferably comprises teeth made of a compacted iron core.

[0014] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the disc-shaped permanent magnet is oriented in a P set, with the circumferential orientation portion and the axial orientation portion as one set orientation, and is composed of a dipole anisotropic magnet that generates magnetic poles of the same polarity at the same position on both sides.

[0015] Furthermore, in the axial gap type rotating electric machine according to the present invention, the disc-shaped permanent magnet is preferably configured in a P set, with the spoke magnet and the axially oriented portion oriented as one set.

[0016] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the disc-shaped permanent magnet has a magnetic material in the axial orientation portion.

[0017] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the magnetic material protrudes slightly toward the center of the tooth width on the air gap side.

[0018] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the disc-shaped permanent magnet is composed of an anisotropic magnet, in which the magnetization is easily oriented between the front side N pole portion and the back side S pole portion, which are offset by 360° / P in the circumferential direction, and the same polarity magnetic poles are generated at the same position on both sides.

[0019] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that a magnetic plate member is interposed in the central part of the disc-shaped permanent magnet in the axial direction.

[0020] Furthermore, in the axial gap type rotating electric machine according to the present invention, the stator has three phase windings, each having one end and the other end, the magnetic flux on the front side of the disc-shaped permanent magnet and the magnetic flux on the back side of the stator are linked as flux links, forming independent short magnetic paths, the windings of each phase are driven by an inverter as either series-connected or parallel-connected, and it is preferable to have a connection changing means that can change the connections between the inverter and the windings of each phase.

[0021] Furthermore, in the axial gap type rotating electric machine according to the present invention, the connection changing means preferably connects the same-phase windings of a pair of stators in series, connects one end of one stator to the inverter, short-circuits one end of the series connection between the other end of one stator and one end of the other stator, and opens the other end.

[0022] Furthermore, in the axial gap type rotating electric machine according to the present invention, the connection changing means preferably connects the same-phase windings of a pair of stators in parallel, connects one end of one stator to the inverter, and short-circuits both the other end of one stator and the other stator.

[0023] Furthermore, in the axial gap type rotating electric machine according to the present invention, the connection changing means preferably connects the same-phase windings of a pair of stators in parallel, connects one end of one stator to the inverter, short-circuits one end of the other end of one stator to the other stator, and opens the other end.

[0024] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the connection changing means connects the same-phase windings of a pair of stators in series, and allows switching between a star connection and a delta connection for the connection between one stator and the other stator.

[0025] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the connection changing means connects the same-phase windings of a pair of stators in parallel, and allows switching between a star connection and a delta connection between one stator and the other stator.

[0026] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the pair of stators are each connected to an independent inverter, and that the connection changing means can switch between a star connection and a delta connection for the connection between one stator and the other stator.

[0027] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that the sum of the torques generated by each of the pair of stators be driven by synchronous operation such that T = T1 ± kT2, where T is the sum of the generated torques, T1 is the torque generated by one stator, and T2 is the torque generated by the other stator. However, k is less than 1.

[0028] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable to generate an electromagnetic braking force by controlling each switching element of the inverter to generate a regenerative circulating current, or by passing a DC current through at least one phase to generate an electromagnetic braking force for braking.

[0029] Furthermore, in the axial gap type rotating electric machine according to the present invention, it is preferable that one of the stators of the other is driven by rotational drive, which is driven by switching the phase currents of each phase, and the other is braked by controlling each switching element of the inverter to generate a regenerative circulating current or by passing a DC current through at least one phase to generate an electromagnetic braking force.

[0030] The above summary of the invention does not enumerate all the necessary features of the present invention, and subcombinations of these features may also constitute the invention. [Effects of the Invention]

[0031] According to the axial gap type rotating electric machine of the present invention, the disc-shaped permanent magnet has the same magnetic polarity at the same position in the circumferential direction on both sides, and the N pole and S pole are alternately magnetized to P poles in the circumferential direction. Therefore, while maintaining the miniaturization and thinning of conventional axial gap type rotating electric machines, the magnetic path can be shortened, making it possible to obtain an axial gap type rotating electric machine with high torque and low iron loss.

[0032] Furthermore, by constructing the stator teeth with a compacted iron core, it is possible to obtain an axial gap type rotating electric machine with reduced eddy current losses and low iron losses.

[0033] Furthermore, since the rotor is composed of dipole anisotropic magnets, high torque can be obtained without increasing the thickness of the permanent magnets that make up the rotor. In addition, because the distribution of magnetic flux density in the air gap becomes sinusoidal, a low-vibration axial-gap rotating electric machine can be obtained.

[0034] Furthermore, since the disc-shaped permanent magnet is composed of a P set with spoke magnets and an axial orientation portion as one set orientation, by using a component in which the spoke magnets are oriented and magnetized into two rectangular poles, an axial gap type rotating electric machine can be obtained with reduced manufacturing costs.

[0035] Furthermore, by constructing the axial orientation portion from a magnetic material, permanent magnets can be saved, resulting in an even cheaper axial gap type rotating electric machine. Also, since the magnetic material protrudes gradually toward the center of the tooth width on the air gap side, the magnetic flux density is maximum in the center of the tooth width, and decreases as the distance from the center increases due to the larger air gap. As a result, the distribution of magnetic flux density becomes sinusoidal, harmonics are removed, and even when using spoke magnets, the rotor rotation can be made low-vibration, low-noise rotation similar to that of a dipole anisotropic magnet.

[0036] Furthermore, because it is composed of magnets with anisotropic polarity on both sides, it is possible to obtain high torque without increasing the thickness of the permanent magnets that make up the rotor.

[0037] Furthermore, since the disc-shaped permanent magnet has a magnetic plate member interposed in the axial center, the rigidity of the rotor is improved, making it possible to obtain a robust axial gap type rotating electric machine.

[0038] Furthermore, since it is equipped with a means for changing the wiring, it is possible to control the number of turns while keeping the stators connected, or to switch the connection with the inverter, thereby realizing a multi-functional axial gap rotating electric machine with various wiring configurations.

[0039] Furthermore, if the series connection is opened and the other end of the other stator is short-circuited during driving, the stators are connected in series, resulting in a large induced voltage. In the case of a BLDCM, this makes it a rotating electric machine suitable for starting and low-speed driving. If the series connection is short-circuited and the other end of the other stator is opened during driving, the number of turns is halved, resulting in a smaller induced voltage and making it a BLDCM suitable for high-speed driving.

[0040] Furthermore, if both ends are short-circuited, the BLDCM will have up to four times the output of the series connection. If one end is short-circuited and the other is open-circuited, the input and output will be halved, resulting in a BLDCM suitable for energy saving and light load operation.

[0041] Furthermore, since it is possible to switch between star and delta connections, the output and rotational speed can be easily controlled as needed. Compared to star drive, delta drive has the windings connected in parallel, so the resistance is about 1 / 3, and even with the same voltage drive, the output increases by about 3 times and the rotational speed increases by about 1.7 times. By utilizing this difference, the rotational speed and output can be switched. On the other hand, even if the induced voltage contains a third harmonic, in a star connection the third harmonic is eliminated by the neutral point effect, but in the case of delta connection the third harmonic is not eliminated, and a third harmonic current flows inside the ring connection, increasing copper loss. The axial gap type rotating electric machine used in this invention uses polar anisotropic magnets in the rotor, so the magnetic flux distribution is sinusoidal, and therefore the induced voltage is also sinusoidal and no third harmonic is generated.

[0042] Furthermore, even when the pair of stators are connected in parallel, it is possible to switch between star and delta connections as needed, thus achieving the same effects as the configuration described above.

[0043] Furthermore, since the pair of stators are connected to independent inverters, the stators are connected in parallel, resulting in a BLDCM with four times the power output. Compared to a case where the pair of stators are connected in parallel, even with the same high power output, it becomes possible to control each stator independently, allowing for a wider range of control options.

[0044] Furthermore, the sum of the torques generated by each of the pair of stators is driven in synchronous operation where T = T1 ± kT2, where T is the sum of the generated torques, T1 is the torque generated by one stator, and T2 is the torque generated by the other stator. For example, if the power supply voltage is constant, but the PWM chopper duty cycle of the transistor in the inverter of one stator is set to 0.5, then K ≈ 0.5. By using one power supply for the two inverters and changing the duty cycle within the inverter, it is possible to produce a desired sum of torque. When driven in synchronous operation where T = T1 - kT2 is subtracted, it is a means of suppressing vibration and applies a constant brake with one stator, making it suitable for low-speed uneven driving, such as in the drive drive of a color copier.

[0045] Furthermore, by controlling each switching element of the inverter to generate a regenerative circulating current, or by flowing a DC current through at least one phase, an electromagnetic braking force is generated for braking. This electromagnetic braking force allows for instantaneous stopping of the BLDCM, shortening the stopping time and improving the accuracy of positioning control.

[0046] Furthermore, one of the stators is driven by rotation by switching the phase currents of each phase, while the other stator controls the switching elements of the inverter to generate a regenerative circulating current or to pass a DC current through at least one phase, thereby generating an electromagnetic braking force and providing braking. This allows the BLDCM to be stopped instantaneously, shortening the stopping time and improving the accuracy of positioning control. [Brief explanation of the drawing]

[0047] [Figure 1] A schematic diagram showing an axial gap type rotating electric machine according to a first embodiment of the present invention. [Figure 2] A cross-sectional view perpendicular to the axis illustrating the structure of an axial gap type rotating electric machine according to a first embodiment of the present invention. [Figure 3] A diagram illustrating the configuration of an axial gap type rotating electric machine according to a first embodiment of the present invention. [Figure 4]An explanatory diagram of a permanent magnet used in an axial gap type rotating electric machine according to the first embodiment of the present invention. [Figure 5] A diagram showing an axial gap type rotating electric machine according to a second embodiment of the present invention. [Figure 6] (A) is a diagram illustrating the configuration of a disc-shaped permanent magnet used in an axial gap type rotating electric machine according to a second embodiment of the present invention, and (B) is a diagram showing a modified example. [Figure 7] A diagram showing an axial gap type rotating electric machine according to a third embodiment of the present invention. [Figure 8] A diagram showing a magnetic piece constituting a disc-shaped permanent magnet in an axial gap type rotating electric machine according to a third embodiment of the present invention. [Figure 9] A diagram showing an axial gap type rotating electric machine according to a fourth embodiment of the present invention. [Figure 10] A diagram illustrating the orientation of a disc-shaped permanent magnet in an axial gap type rotating electric machine according to a fourth embodiment of the present invention. [Figure 11] A diagram showing a modified example of an axial gap type rotating electric machine according to a fourth embodiment of the present invention. [Figure 12] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 13] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 14] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 15] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 16] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 17] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 18] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 19] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 20]A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 21] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 22] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 23] A diagram showing an example of wiring for a wiring change means according to an embodiment of the present invention. [Figure 24] A partial cross-sectional view showing a conventional axial gap type rotating electric machine. [Figure 25] A diagram showing the conventional magnetic flux density distribution. [Figure 26] A diagram illustrating a conventional cylindrical magnet with a U-shaped magnetic path. [Modes for carrying out the invention]

[0048] Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. Note that the following embodiments are not intended to limit the invention as described in each claim, and not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention.

[0049] [First Embodiment] Figure 1 is a schematic diagram showing an axial gap type rotating electric machine according to the first embodiment of the present invention; Figure 2 is a cross-sectional view perpendicular to the axis to explain the structure of the axial gap type rotating electric machine according to the first embodiment of the present invention; Figure 3 is a diagram to explain the configuration of the axial gap type rotating electric machine according to the first embodiment of the present invention; and Figure 4 is an explanatory diagram of a permanent magnet used in the axial gap type rotating electric machine according to the first embodiment of the present invention.

[0050] As shown in Figure 1, the axial gap type rotating electric machine 10 according to this embodiment comprises a disc-shaped stator 11 and a rotor 12 that is rotatably mounted to the stator 11 with an air gap in the axial direction.

[0051] The stator 11 comprises an iron core 13 with multiple teeth 14 protruding in the axial direction (six in the case of the axial gap type rotating electric machine 10 in this embodiment), and windings 15 wound around each tooth 14 in the circumferential direction. The iron core 13 is preferably formed from a powdered iron core, as this makes it easy to form shapes such as the flange 13a formed at the tip of the tooth 14, as shown in Figure 3.

[0052] Generally, lamination of silicon steel sheets is difficult and not used in axial gap rotating electric machines. This is because when the stator is formed from silicon steel sheets, the rotor magnetic flux passes through in the axial direction. If the lamination direction is axial, the magnetic resistance increases due to the gaps between the layers and the orientation of the silicon steel sheets, negatively affecting the performance of the rotating electric machine. If the iron core 13 is formed from a powdered iron core, the magnetic orientation described above is eliminated, making it easier to use. Also, since the iron core shape has three-dimensional freedom, a so-called overhang structure that houses the windings can be easily created. In this way, the DC resistance can be reduced even with the same number of turns, reducing copper loss.

[0053] The stator 11 is positioned axially with respect to the rotor 12, with an air gap between them, so as to clamp the rotor 12. The two stators 11 are fastened together by a cylindrical housing (not shown) and are rotatably supported by bearings 18 along with the rotor shaft 19 of the rotor 12. The upper half of Figure 2 shows a cross-section of the stator 11. As shown in Figure 2, the stator 11 may be a three-phase adjacent winding system with different phases, namely U, V, and W phases, i.e., 6 windings, in the case of UVWUVW. Alternatively, in the case of an adjacent winding system with the same phase, namely 6 windings, it may be UUVVWW. It is preferable that the winding poles of the stator 11 be formed in a so-called "overhang" shape, where the windings 15 are wound and housed in teeth 14 formed in a recessed shape.

[0054] The rotor 12 comprises a disc-shaped permanent magnet 16 and a rotating shaft 19 that penetrates the central part of the disc-shaped permanent magnet 16 via a core 17.

[0055] As shown in Figure 2, the disc-shaped permanent magnets 16 are arranged so that they alternately form north and south poles in the circumferential direction. Furthermore, the disc-shaped permanent magnets 16 are oriented in the magnet thickness direction as shown in the orientation 21 of Figure 3, making each magnetic pole an anisotropic magnet. This new technology, called dipole anisotropy magnetization, is employed in which a single magnet is internally oriented in an anisotropic manner, and the magnetic poles appear in the air gap on its front and back sides. The orientation 21 in Figure 3 is a dipole anisotropy orientation shown by solid and dotted lines, and such a magnet is referred to as a dipole anisotropic magnet in this specification. Such a magnet orientation can be achieved by applying pressure pressing and appropriate temperature heat treatment in a magnetic field when forming the magnet from magnet powder.

[0056] As shown in Figure 3, the axial gap type rotating electric machine 10 according to this embodiment has a configuration in which a rotor 12 is sandwiched between two stators 11 arranged in the axial direction, and the polarity of the winding poles provided on the upper and lower stators 11 is always magnetized to the same polarity by the winding current. Therefore, the magnetic polarity of the disc-shaped permanent magnets 16 facing each other across the air gap is opposite to the polarity of the stator winding poles at the top and bottom, and the polarity is the same at the top and bottom of the magnet in the axial direction, which is the thickness direction of the disc-shaped permanent magnet 16. In this specification, the upper side of the disc-shaped permanent magnet 16 will be referred to as the front side and the lower side as the back side for the following explanation.

[0057] The orientations 25 and 26 of the disc-shaped permanent magnet 16 are curves that show the shape, direction, and length of the magnet orientation, and are in a double magnetization direction shown by solid and dotted lines. The curve length of the orientation 25 and 26 shown by the solid line or the curve length shown by the dotted line is L P If so, L P This is the effective length of the magnet in this case.

[0058] As shown in the lower half of Figure 2, the disc-shaped permanent magnet 16 is sector-shaped when viewed from the axial direction. Here, the average circumferential length of the disc-shaped permanent magnet 16 is L. R Let L be the central value in the rotor radial direction. P The axial thickness of the disc-shaped permanent magnet 16 is as shown in Figure 3. m Let's assume that.

[0059] Generally, to effectively utilize a magnet, the magnet is designed as follows. L R ≈L m (1) Also, L P >L R (2) Also, from FIG. 3 and equations (1) and (2), the following equation is obvious. L P >L m +L R >L m (3)

[0060] Also, FIG. 3 shows the magnetic fluxes 25 and 26 linked to the stator 11. In FIG. 3, if the axial thickness L m of the rotor 12 is divided into the upper side and the lower side from the central part, considering the upper half from the central part of the axial thickness L m of the upper stator 11 and the rotor 12 as one rotating electrical machine, and the remaining half of the rotor 12 and the lower stator 11 as another rotating electrical machine and controlling them, a rotating electrical machine with various unique characteristics that are not found in the prior art can be obtained. Such a specific control method will be described later.

[0061] The difference between the double-sided pole anisotropic magnet on the front and back of the disc-shaped permanent magnet 16 of the axial-gap type rotating electrical machine 10 according to the present embodiment and the pole anisotropic magnet on the surface of the conventional cylindrical magnet will be explained with reference to FIG. 26. FIG. 26 is a diagram of a rotor magnet for a PM type stepping motor proposed by one of the inventors in 1983, and similar contents are described in Non-Patent Documents 6 and 7. In FIG. 26, L2 is the effective length of the magnet oriented in pole anisotropy, and it is obvious that it is larger than the magnet thickness L1. Therefore, the magnetic flux density increases due to the pole anisotropy effect. However, in this technology, the magnet on the inner diameter side of FIG. 26 is not an oriented magnet with pole anisotropy. The reason is that since the magnet is cylindrical, the pole width and magnetic flux distribution of the magnet are not uniform on the front and back between the surface and the inside of the cylinder. On the other hand, in the configuration of the axial-gap type rotating electrical machine 10 according to the present embodiment, a disc-shaped permanent magnet 16 is used instead of a cylindrical magnet, so a double-sided pole anisotropic magnet on the front and back of the magnet becomes possible.

[0062] First, the origin, characteristics, and advantages of polar anisotropic magnet type rotating electric machines are described in Non-Patent Documents 6 and 7 as radial gap type rotating electric machines. According to these documents, polar anisotropic magnet type rotating electric machines increase torque by more than 50% in the low-speed range. Currently, most radial gap type PM-type stepping motors and claw-pole type rotating electric machines employ these polar anisotropic magnets.

[0063] Next, we will describe the features of the axial gap type rotating electric machine 10 according to this embodiment. The advantage of polar anisotropic magnets, which is that the torque is increased by more than 50%, is a known fact in radial gap type rotating electric machines, as mentioned above. However, the inventors have found that a similar effect can be obtained when this is applied to an axial gap type rotating electric machine, and in particular, this effect is greater in the axial gear-up type rotating electric machine 10, which has a structure in which one magnet supplies magnetic flux to two air gaps on the front and back. The reason for this is as follows.

[0064] Next, we will demonstrate the principle that increasing the effective length of a magnet increases the flux linkage. From Ampere's circuit law, the following equation can be derived. Air gap magnetic flux density B in Figure 3 g1 =(μ0H m / 2L g )L P (4) Here, μ0 is the permeability of vacuum, H m Magnetic field strength of the magnet, 2L g :Air gap length × 2, that is, the left side of equation (4) is L in the region where the stator core does not saturate. P It increases in proportion to [the specified value].

[0065] The flux linkage Φ to the winding pole is given by the area S of the winding pole facing the rotor pole. Φ=B g1 S (5) That is, the flux linkage in Figure 3 is L P This means that the torque can be increased in proportion to the flux linkage Φ. Since the torque of a rotating electric machine increases in proportion to the flux linkage Φ, it can be seen that the axial gap type rotating electric machine 10 according to this embodiment will have high torque.

[0066] Furthermore, the axial thickness L of the disc-shaped permanent magnet 16 m Increasing the thickness would increase the amount of magnets and thus the cost, but the axial gap type rotating electric machine 10 according to this embodiment has a thickness L m This means that high torque can be obtained without increasing the amount of L. P Since the length of the air gap is longer at the center of the magnetic pole and shorter towards the ends, the magnetic flux density distribution of the air gap becomes a sinusoidal distribution, with the density being higher at the center of the magnetic pole and lower towards the ends. This means that third, fifth, and other harmonics are not included in the magnetic flux density waveform, and the axial gap type rotating electric machine 10 according to this embodiment can achieve low vibration during rotation. The specific reasons for this are as follows.

[0067] As shown in Figure 4, of the arc-shaped effective magnetic path lengths 21a and 21b of the polar anisotropic magnet, the maximum magnetic path length L is the central magnetic path length. P The effective magnetic path length is 21a. The maximum value of the magnetic flux density in the gap in this case is given by equation (4) above. The length of this arc L P L is the thickness of the magnet in the axial direction. m It becomes longer. Therefore, from equation (4), the air gap magnetic flux density B is greater for polar anisotropic magnets than for axial anisotropic magnets. g1 This results in a larger torque. As will be described later, the magnets used in conventional 1-rotor, 2-stator axial-gap rotating electric machines are axially anisotropic, but the magnets used in the axial-gap rotating electric machine 10 according to this embodiment are polarly anisotropic, so a torque increase of about 40-50% can be expected.

[0068] Next, we will explain that the axial gap type rotating electric machine 10 according to this embodiment exhibits lower vibration than the conventional technology. In Figure 4, the effective magnetic path length L P The length is greatest at the center of the magnetic pole, but there are many arcs inside that arc. One of them is shown as orientation 21b, which is also the effective magnetic path length of the arc of the polar anisotropic magnet, and its effective length is L PIt becomes shorter. And since its effective length is shorter towards the pole ends, the magnetic flux density distribution of the air gap takes on the shape of symbol 27 or symbol 28, which is sinusoidal, with the center of the pole being higher and the ends being lower. This means that third, fifth, and other harmonics are not included in the magnetic flux density waveform, resulting in reduced vibration during rotation of the rotating electric machine. This is because vibration torque is created by third, fifth, and seventh harmonics.

[0069] In contrast, the conventional rotor magnet 112 shown in Figure 24 has axial anisotropy, meaning its magnetic orientation is anisotropic in the axial direction. As a result, the magnetic flux density distribution in the air gap is trapezoidal or rectangular, and its shape is as shown in Figure 25. This differs from the sinusoidal distribution in Figures 2 and 3. Fourier analysis of the rectangular wave distribution reveals that the rectangular wave = fundamental wave + third + fifth + seventh... harmonics are present, indicating that the vibration noise during rotation will be greater than that of the axial gap type rotating electric machine 10 according to this embodiment.

[0070] Next, in order to further clarify the operation and effects of the axial gap type rotating electric machine 10 according to this embodiment, we will explain it in comparison with the conventional technology.

[0071] Figure 24 shows a conventional double air gap type axial gap rotating electric machine equipped with a rotor in which disc-shaped permanent magnets 116 are magnetized so that they are N poles and S poles in the axial direction. The opposing view of the stator 110 and rotor 112 is the same as in Figure 2, with the stator 110 and rotor magnetic poles facing each other in a 4-way arrangement. The disc-shaped permanent magnets 116 are made of the same material as the axial gap type rotating electric machine 10 according to this embodiment, and their axial thickness is also the same Lm.

[0072] As can be seen by comparing Figure 3 with Figure 24 of the conventional technology, the magnetic poles of the disc-shaped permanent magnets 116 of the rotor 112 are magnetized with opposite polarities at the same position on both sides in the axial direction. In other words, the magnetic orientation of the disc-shaped permanent magnets 116 of the rotor 112 in the conventional technology is axial, and the effective length of the magnet is the magnet thickness L. m It is the same as this.

[0073] In this case, the following equation can be derived from Ampere's circuit law, in the same manner as in equation (4). Figure 24 shows the air gap magnetic flux density B. g2 =(μ0H m / 2L g )L m (6) From equations (3), (4), and (6), B g1 >B g2 (7) This is the result.

[0074] (7) B g1 >B g2 This shows that, compared to Figure 24 which shows the prior art, Figure 3, which shows the axial gap type rotating electric machine 10 according to this embodiment, can achieve higher torque with the same magnet material, same magnet volume, and same air gap length. Referring to Figure 3, the effective length L of the disc-shaped permanent magnet 16 of the axial gap type rotating electric machine 10 according to this embodiment. P The effective length L of conventional magnets m It can be seen that it is more than twice as long.

[0075] Since the disc-shaped permanent magnets 116 of the rotor 112 in Figure 24 have anisotropic orientation in the axial direction, the magnetic flux density distribution in the air gap is trapezoidal. This mainly contains third harmonics, indicating that the vibration noise during rotation will be greater than that of the axial gap type rotating electric machine 10 according to this embodiment.

[0076] Furthermore, the effective length and orientation direction of the magnets of the axial gap type rotating electric machine 10 according to this embodiment will be explained.

[0077] In Figure 3, the magnet orientation 21 is a curve showing the shape, direction, and length of the orientation as an easy magnetization path for the magnet, and it has a double magnetization direction shown by a solid line and a dotted line. If we represent the upper side of the disc-shaped permanent magnet 16 in Figure 3 as the front and the lower side as the back, the solid line connects the S pole on the front side to the N pole on the back side, and the dotted line connects the S pole on the back side to the N pole on the front side. In other words, when forming a magnetic path between the stator 11 on the front side and the stator 11 on the back side, the magnetic flux path shown by the solid and dotted lines is taken.

[0078] Figure 4 shows a modified example of the disc-shaped permanent magnet 16 in Figure 3. In Figure 4, the orientation 21, which shows the magnetic field orientation curve, is represented by a solid line for the front-side magnetic poles and a dotted line for the back-side magnetic poles. Even in this case, the magnet orientation position is the same as in Figure 3. This shows a double-pole anisotropy orientation in which the front-side magnet, which occupies half of the axial thickness of a single fan-shaped magnet piece 16a, creates a polar anisotropy, and at the same time, the back-side magnet, which occupies the remaining half of the axial thickness, creates another polar anisotropy. This case also corresponds to the double-pole anisotropy magnet described above.

[0079] In the case of Figure 4, the magnetic path to the stator 11 is separated into front and back sides, which shortens the magnetic path length to the stator 11 and results in advantages such as reduced magnetic resistance. In other words, in a modified example of the axial gap type rotating electric machine 10 according to this embodiment, the magnetic paths can be configured as independent magnetic paths on the front and back sides of each air gap formed at both ends of the rotor 12 in the axial direction.

[0080] Furthermore, the differences between the magnetic circuit of the axial gap type rotating electric machine 10 according to this embodiment and the conventional magnetic circuit shown in Figure 24 will be explained.

[0081] In Figure 3, the flux linkage from the permanent magnet is indicated by arrow 25 for the upper stator 11 and arrow 26 for the lower stator 11. That is, the upper stator 11 has only the flux 25 emanating from the front side of the magnet, and the lower stator 11 has the flux 26 emanating from the back side of the magnet, so the flux linkage forms a closed magnetic circuit independently for each stator.

[0082] In contrast, in the case of Figure 24, the magnetic flux 125 links with the stator 110, but this magnetic flux returns as magnetic flux 126 and enters the stator 110, forming a closed magnetic circuit with the upper and lower stators 110. This is unsuitable for use in the conventional technology because the following problems occur: (1) The magnetic circuit length is long, so the magnetic resistance is large and the magnetomotive force consumption is large, which easily leads to a decrease in efficiency. (2) The magnetic circuit is long, so the iron loss is also large, which easily leads to a decrease in efficiency. (3) The magnetic flux created by the product of the self-inductance L of stator 1 and stator 2 and their respective currents is superimposed on the magnetic flux linkage of the magnets, resulting in a combined magnetic flux linkage with large distortion, which becomes a factor in the generation of vibration torque.

[0083] In contrast, the axial gap type rotating electric machine 10 according to this embodiment has the advantage that the events described in (1), (2) and (3) above do not occur.

[0084] Thus, the axial gap type rotating electric machine 10 according to this embodiment has the excellent function of having flexibility in the magnets that can be used, by changing the disc-shaped permanent magnets used, so that the magnetic path spans both gaps or that each gap has its own pair of independent magnetic paths on the front and back. When a magnetic path spans both gaps, the flux linkage passing through the front and back stators is the same, so a low-vibration drive with no torque difference between the two stators can be obtained. When each gap has its own pair of independent magnetic paths on the front and back, the magnetic path can be made shorter, so a responsive drive with a short magnetic flux rise time and reduced iron loss can be obtained due to the shorter magnetic path.

[0085] [Second Embodiment] In the axial gap type rotating electric machine 10 according to the first embodiment described above, the case was described in which the magnetic polarity of the disc-shaped permanent magnet is the same at the same position in the circumferential direction on both the front and back sides, and the N pole and S pole are magnetized alternately in the circumferential direction. The axial gap type rotating electric machine 10a of the second embodiment, which will be described next, describes an embodiment of a disc-shaped permanent magnet having a different configuration from the first embodiment. Note that components that are the same or similar as those in the first embodiment described above are denoted by the same reference numerals and their description is omitted.

[0086] Figure 5 shows an axial gap type rotating electric machine according to a second embodiment of the present invention, Figure 6A is a diagram illustrating the configuration of a disc-shaped permanent magnet used in an axial gap type rotating electric machine according to a second embodiment of the present invention, and Figure 6B is a diagram showing a modified example of a disc-shaped permanent magnet used in an axial gap type rotating electric machine according to a second embodiment of the present invention.

[0087] In this embodiment, the axial gap type rotating electric machine 10a has fan-shaped magnet pieces 16c and spoke magnets 16b arranged alternately in the circumferential direction on the disc-shaped permanent magnet 16a of the rotor 12a. Figure 5 is a diagram illustrating the principle. The spoke magnets 16b are rectangular parallelepiped magnets arranged radially in P numbers, assuming a P-pole rotor with the disc-shaped permanent magnet 16a. They are called spoke magnets because the radially arranged rectangular parallelepiped magnets resemble the spokes of a bicycle wheel. The fan-shaped magnet pieces 16c are magnetized in two poles, circumferentially and axially, to create the magnetic poles shown in Figure 5.

[0088] As shown in Figure 6A, the disc-shaped permanent magnet 16a has horizontally and vertically oriented magnets arranged alternately in a disc shape, consisting of radially arranged spoke magnets 16b and fan-shaped magnet pieces 16c placed between the spoke magnets 16b. The spoke magnets 16b have the advantage of being rectangular parallelepipeds, easily anisotropized, readily available on the market, and inexpensive.

[0089] Furthermore, the horizontally and vertically oriented magnets of the fan-shaped magnet piece 16c may be substituted with a magnetic material of the same shape. In this case, as shown in Figure 6B, it is preferable that the magnetic material has a shape that protrudes gradually toward the center of the tooth width on the air gap side. With such a configuration, the magnetic flux generated by the spoke magnet 16b is bent in the axial direction by the fan-shaped magnetic material to form a magnetic path, and torque equivalent to that in Figure 3 can be obtained. More precisely, a higher magnetization strength can be obtained by using the fan-shaped magnet piece 16c, but if a magnetic material is used as a substitute, the axial gap type rotating electric machine 10a according to this embodiment can be obtained at a lower cost. Also, by configuring the rotor in this way, the distribution of magnetic flux density becomes sinusoidal, similar to the case of the axial gap type rotating electric machine 10 according to the first embodiment described above, resulting in a rotating electric machine with low vibration and low noise.

[0090] Furthermore, even in the case of Figure 6B, the circumferential thickness of the spoke magnet is the effective length L of the conventional magnet. m Since the length can be easily increased and the total amount of magnets used can be reduced, equation (7) is valid and inexpensive.

[0091] [Third Embodiment] In the axial gap type rotating electric machine 10a of the second embodiment described above, the case in which spoke magnets are arranged on a disc-shaped permanent magnet was explained. The axial gap type rotating electric machine 10b of the third embodiment, which will be described next, describes an embodiment of a disc-shaped permanent magnet having anisotropic magnets with oblique axial orientation, which will be described later, and is different from the first and second embodiments. Note that components that are the same or similar as those in the first and second embodiments described above are denoted by the same reference numerals and their descriptions are omitted.

[0092] Figure 7 shows an axial gap type rotating electric machine according to a third embodiment of the present invention, and Figure 8 shows the magnet pieces constituting the disc-shaped permanent magnet of the axial gap type rotating electric machine according to the third embodiment of the present invention.

[0093] As shown in Figure 7, the axial gap type rotating electric machine 10b according to this embodiment is a double-sided gap axial gap type rotating electric machine using a disc-shaped permanent magnet 16d having a magnetic path that spans both sides. The axial gap type rotating electric machine 10b according to this embodiment has a double-sided gap Although it can only be used in magnetic circuits that span across the same area, the orientation of the magnets is simpler than in the case of the axial gap type rotating electric machine 10 according to the first embodiment, making it possible to construct it at a lower cost.

[0094] In the axial gap type rotating electric machine 10 according to this embodiment, the magnetic path always spans both the front and back stators 11, resulting in a longer magnetic path and an increase in magnetic resistance, which is disadvantageous compared to the conventional disc-shaped magnet with a U-shaped magnetic path as shown in Figure 24. However, with the oblique axial orientation, the effective magnetic path length 22 is sufficiently longer than the magnet thickness Lm, making it almost equivalent to the axial gap type rotating electric machine 10 according to the first embodiment, and the front-to-back pole anisotropy effect can be obtained. For convenience, in this specification, this form is referred to as a front-to-back pole anisotropy magnet with oblique axial orientation.

[0095] In this embodiment, the disc-shaped permanent magnet 16d used in the rotor 12b of the axial gap rotating electric machine 10b is preferably constructed by combining obliquely axially oriented magnet pieces 16e having a radial cross-sectional shape perpendicular to the axis, as shown in Figure 8. Halbach magnets are a type of polar anisotropic magnet that is typically used as an anisotropic magnet by combining cubic or rectangular magnets like building blocks to approximate a desired shape. In this embodiment, the magnet shape of the magnet piece 16e used in the axial gap rotating electric machine 10b has a rhomboid cross-sectional shape in its axial direction. The magnet piece 16e has a magnet orientation direction 23 that extends from the opposing surface of one stator 11 toward the opposing surface of the other stator 11, and this is the easy magnetization axis indicating the magnet orientation direction in this case. Such magnetic pieces constitute one pole, and in the case of a P pole, P pieces are arranged circumferentially to create a disc-shaped permanent magnet 16d that is easily magnetized between the front N pole portion and the back S pole portion, which are offset by 360° / P in the circumferential direction, thereby generating magnetic poles of the same polarity at the same position on both sides.

[0096] [Fourth Embodiment] In the axial gap type rotating electric machine 10b of the third embodiment described above, the case in which a diagonally axially oriented magnet is arranged on a disc-shaped permanent magnet was described. The axial gap type rotating electric machine 10c of the fourth embodiment, which will be described next, describes an embodiment of a disc-shaped permanent magnet having a different configuration from the first to third embodiments. In addition, components that are the same or similar as those in the first to third embodiments described above are denoted by the same reference numerals and their descriptions are omitted.

[0097] Figure 9 shows an axial gap type rotating electric machine according to the fourth embodiment of the present invention, Figure 10 is a diagram illustrating the orientation of the disc-shaped permanent magnets in the axial gap type rotating electric machine according to the fourth embodiment of the present invention, and Figure 11 is a diagram showing a modified example of the axial gap type rotating electric machine according to the fourth embodiment of the present invention.

[0098] As shown in Figure 9, the axial gap type rotating electric machine 10c according to this embodiment has a rotor 12c that is practical and enhances robustness. The disc-shaped permanent magnet 16f of the axial gap type rotating electric machine 10c according to this embodiment comprises a pair of disc-shaped permanent magnet bodies 16g and a magnetic disc 30 that is sandwiched in the axial direction by the disc-shaped permanent magnet bodies 16g. The disc-shaped permanent magnet bodies 16g and the magnetic disc 30 are bonded and fixed to each other.

[0099] The pair of disc-shaped permanent magnets 16g arranged on the front and back are oriented and have the same function as the axial gap type rotating electric machine 10 according to the first embodiment. This orientation is equivalent to the configuration in which the axial thickness of the disc-shaped permanent magnet 16 in Figure 3 or Figure 4 is divided into two parts to separate it into two magnets, and a magnetic disk 30 is interposed and fixed between them. That is, Figure 10 is equivalent to the configuration in Figure 4 in which the axial thickness of the magnet is divided into two parts to separate it into two magnets, and a magnetic disk 30 is interposed and fixed between them.

[0100] As shown in Figures 9 and 10, the magnetic disk 30 is fixed to the rotating shaft 19, so The disc-shaped permanent magnet 16f becomes more robust than when the magnetic disk 30 is absent. Also, because the magnetic disk 30 is magnetic, a magnetic path can be freely formed between the front and back magnets of the pair of disc-shaped permanent magnet bodies 16g. Although not shown in the diagram, if a flange is provided on the outer circumference of the magnetic disk 30 in Figure 9 to cover the outer circumference of the two disc-shaped permanent magnet bodies 16g, the centrifugal force acting on the rotor 12c during high-speed rotation can be suppressed, preventing the magnets from scattering.

[0101] Furthermore, the rotor of the axial gap type rotating electric machine 10b according to the third embodiment can be made robust by using a magnetic disk 30, similar to the axial gap type rotating electric machine 10c according to this embodiment, and Figure 11 illustrates this configuration. In the case of Figure 11, the magnetic fields of the front and back magnet parts are oriented diagonally with respect to the axial direction, so the effective length of the magnet can be increased to more than √2 times the thickness of the magnet in the axial direction, resulting in higher torque and an advantage over conventional robust rotor types.

[0102] Next, a control method for the axial gap type rotating electric machine according to the above embodiment will be described.

[0103] Figure 12 shows an example of wiring using a wiring change mechanism. The wiring change mechanism has a configuration that allows the wiring of each coil and inverter of the axial gap type rotating electric machine according to the embodiment described above to be changed. Specifically, various conventional wiring change mechanisms can be used, for example, mechanical relay type and semiconductor switch type are preferably used. They can be appropriately selected according to the required response speed and efficiency.

[0104] First, we will explain the specific wiring method of the wiring change mechanism. In the axial gap type rotating electric machine according to the first embodiment described above, one stator M1 and the other stator M2 are connected in series as shown in Figure 12, using BLDCM. Then, the winding at one end of stator M1 is connected to the inverter, and first common terminals (C1, C2, C3) for each phase are provided at the series connection between the other end of stator M1 and one end of stator M2. Second common terminals (C4, C5, C6) for each phase are also provided at the other end of the series-connected stator M2, and the characteristics are controlled by short-circuiting or opening the first common terminals and the second common terminals.

[0105] The first and second common terminals can be opened or short-circuited by using the circuit shown in Figure 15. In Figure 15, six diodes 41 form a bridge and are connected to C1, C2, and C3 as shown. When the switching element 42 is turned on, C1, C2, and C3 are short-circuited, and when it is turned off, C1, C2, and C3 are opened. Similarly, when connected to C4, C5, and C6, the switching element 42 is short-circuited when turned on and open when turned off. For convenience, the circuit shown in Figure 15 will be called a three-terminal short-circuit bridge.

[0106] When the windings of each phase of the stator are connected in series, the magnetic path of the rotor magnets is shortened compared to conventional designs, resulting in a rotating electric machine with high torque and low iron loss. Furthermore, because the magnetic flux density distribution in the air gap becomes sinusoidal due to the use of polar anisotropic magnets, it results in a rotating electric machine with low vibration and low noise.

[0107] If the first common terminal is left open and the second common terminal is short-circuited during operation, stator M1 and stator M2 are connected in series, resulting in a large induced voltage. In the case of a BLDCM, this makes it a rotating electric machine suitable for starting and low-speed operation. Conversely, if the first common terminal is short-circuited and the second common terminal is left open during operation, the number of turns is halved, resulting in a smaller induced voltage and making it a BLDCM suitable for high-speed operation.

[0108] Furthermore, as shown in Figure 13, the connection modification means allows stator M1 and stator M2 to be connected in parallel. When the windings of each phase of the stator are connected in parallel, the magnetic path of the rotor magnets is shortened compared to the conventional type, resulting in a rotating electric machine with high torque and low iron loss. In addition, the distribution of magnetic flux density in the air gap becomes sinusoidal due to the polar anisotropic magnets, resulting in a rotating electric machine with low vibration and low noise. Furthermore, by short-circuiting the first and second common terminals and driving the machine, a circulating current flows through stator M2, generating a braking torque, which can be used to achieve instantaneous stopping or low rotational unevenness driving.

[0109] The wiring change method specifically involves connecting the windings of each phase of the inverter and stator, as shown in Figure 13. Common terminals for each phase are provided on the windings of stator M1 and stator M2, allowing them to be driven by short-circuiting both, or short-circuiting one and leaving the other open. Short-circuiting and opening the common terminals can be done using the circuit shown in Figure 15 described above.

[0110] By wiring the connection change mechanism in this way, when both common terminals are short-circuited, the BLDCM becomes up to four times more powerful than when connected in series. When one common terminal is short-circuited and the other is open-circuited, the input and output are halved, resulting in a BLDCM suitable for energy saving and light load operation.

[0111] Figure 14 is a circuit diagram showing the case where each stator M1 and M2 is connected to an independent inverter. In this connection method, each phase winding of stator M1 and stator M2 is connected to and driven by a separate, independent inverter. In this case, it is preferable to drive them in synchronous operation where the torques generated by stator M1 and stator M2 are added together as T = T1 + T2, where T1 and T2 are the respective torques.

[0112] Furthermore, the connection change mechanism allows the windings of stator M1 and stator M2 to be switched between star connection and delta connection. In this case, it is preferable that the combined torque generated by stator M1 and stator M2 is driven in synchronous operation with T = T1 ± kT2, where k is less than 1. Implementing these measures yields the following effects.

[0113] In this case, the stators are in parallel, resulting in a BLDCM with four times the output. Furthermore, compared to cases where both common terminals on each phase are short-circuited or one is short-circuited and the other is open, the output remains high, and while maintaining the same level of performance, stator M1 and stator M2 can be controlled independently, allowing for a variety of control options. For example, it is naturally possible to drive them in synchronous operation where the torques generated by each are added together as T=T1+T2.

[0114] Alternatively, the inverters can be driven in synchronous operation where their generated torques are added to or subtracted from each other as T=T1±kT2, where k is a number less than 1. For example, if the power supply voltage is constant, but the PWM chopper duty cycle of the inverter transistor in stator M2 is set to 0.5, then K≈0.5. By using one power supply for the two inverters and changing the duty cycle within the inverter, a desired combined torque can be achieved. When driven in synchronous operation where the torque is subtracted as T=T1-kT2, vibrations are suppressed and rotational unevenness is improved. This is suitable for low-speed unevenness driving, such as in the drive of a color copier.

[0115] Furthermore, rotating electric machines are sometimes required to stop instantaneously without overrun. When stator M1 and stator M2 are driven by separate inverters, it is preferable that one of stator M1 and stator M2 is driven by rotational drive by switching the currents of each phase, while the other is driven by controlling each switching element of the inverter to generate a regenerative circulating current, or by generating an electromagnetic braking force by flowing a DC current through at least one phase. The other stator is driven by controlling each switching element of the inverter to generate a regenerative circulating current.

[0116] The specific method is shown in Figure 17. The left diagram in Figure 17 illustrates short-circuit braking of the BLDCM. The 3-phase bidirectional inverter 50 is a device that generates alternating current when a DC voltage is applied and is connected to the BLDCM 51. If all three upper arm switching elements of the inverter 50 are turned off and all three lower arm switching elements are turned on, the braking current shown by the dotted line in the figure flows, and the rotation of the BLDCM is braked. In this case, the value of this braking current cannot be controlled.

[0117] The right-hand diagram in Figure 17 shows a buffer braking system. In this case, the value of the braking current is controllable, and therefore the braking force is also controllable. The circuit configuration is basically the same as the right-hand diagram in Figure 17, but a switching element 42 and a resistor 52 are added. If all six arm switching elements of the inverter 50 are turned off, a braking current as shown by the dotted line flows, but the braking current value can be controlled by the switching element 42 and the resistor 52 to achieve a buffer stop. Alternatively, by turning on the upper and lower arm elements of the inverter 50 so that a DC current flows through at least one phase, a large electromagnetic braking force can be generated.

[0118] Implementing these measures yields the following benefits: One of the stators M1 and M2 is driven by rotational drive, which is achieved by switching the phase currents of each phase. The other stator controls the switching elements of the inverter to generate a regenerative circulating current, or by supplying a DC current to at least one phase, thereby generating electromagnetic braking force to instantaneously stop the BLDCM, shortening the stopping time and improving the accuracy of positioning control. Furthermore, when driving both stators M1 and M2 with a single inverter, both stators M1 and M2 switch to braking mode simultaneously. Although Figure 17 illustrates the case with a star connection, braking is similarly possible with a delta connection.

[0119] Next, we will describe a method of controlling the stator M1 and stator M2 by switching between star and delta connections. As mentioned earlier, even with the same phase windings, switching from a star connection to a delta connection improves rotational speed and output. By utilizing this difference in characteristics, it is possible to change the speed-torque characteristics in various ways.

[0120] Figure 18 is a circuit diagram showing a three-phase bidirectional inverter used to drive an axial-gap rotating electric machine. It has three terminal outputs and can be used in a star connection where the start or end of each phase windings are short-circuited, or in a delta connection where the end of the U-phase windings is short-circuited to the start of the V-phase windings, the end of the V-phase windings is short-circuited to the start of the W-phase windings, and the end of the W-phase windings is short-circuited to the end of the U-phase windings.

[0121] As shown in Figure 12, a method is described for switching from the series star connection of stators M1 and M2 shown in Figure 19 to the series delta connection drive of stators M1 and M2 shown in Figure 20 by short-circuiting C4 to V, C5 to W, and C6 to U using the auxiliary inverter connection terminals (UVW) newly provided from the inverter output terminal section and the aforementioned second common terminals (C4, C5, C6).

[0122] In Figures 19 and 20, U1, V1, and W1 represent the phase coils of stator M1, and U2, V2, and W2 represent the phase coils of stator M2. A two-terminal short-circuit bridge as shown in Figure 16 is preferable for this switching. When the switching element 42 is turned on in Figure 16, the two terminals connected to the two-terminal diode bridge, C4 and V, C5 and W, and C6 and U in the figure, are short-circuited, resulting in a delta connection as shown in Figure 20.

[0123] To return to the star connection shown in Figure 19, simply turn off the switching element 42 in Figure 16, and in the state shown in Figure 12, turn on the switching element 42 in Figure 15 to short-circuit the second common terminals (C4, C5, C6). In other words, it is preferable to use the three-terminal short-circuit bridge shown in Figure 15 for short-circuiting and opening three terminals, and the two-terminal short-circuit bridge shown in Figure 16 for short-circuiting and opening two terminals.

[0124] Next, we will explain how to switch from the parallel star connection of stators M1 and M2 shown in Figure 21 to the parallel delta connection drive of stators M1 and M2 shown in Figure 22 by short-circuiting C1 and V, C2 and W, and C3 and U, respectively, using the auxiliary inverter connection terminals (UVW) newly provided from the inverter output terminal section and the aforementioned first common terminals (C1, C2, C3). In Figures 21 and 22, U1, V1, and W1 represent the phase coils of stator M1, and U2, V2, and W2 represent the phase coils of stator M2. For this switching, it is preferable to use the two-terminal short-circuit bridge shown in Figure 16, similar to the method described above. When the switching element 42 is turned on in Figure 16, the two terminals connected to the two-terminal diode bridge, C1 and V, C2 and W, and C3 and U, are short-circuited, resulting in a delta connection.

[0125] To revert to the star connection shown in Figure 21, simply turn off the switching element 42 in Figure 16 and turn on the switching element 42 in Figure 15 at the first common terminal (C1, C2, C3).

[0126] Furthermore, it is also possible to drive stator M1 in a star connection and stator M2 in a delta connection, as shown in Figure 23, using the three-terminal short-circuit bridge shown in Figure 15 and the two-terminal short-circuit bridge shown in Figure 16. In this case, the characteristics will be an intermediate value between the star connection and the delta connection. In terms of torque, it can be increased in the following order: two star connections, one star connection and the other delta connection, and two delta connections.

[0127] From Figure 14, it is clear that star and delta connections can be freely switched using the three-terminal short-circuit bridge in Figure 15 or the two-terminal short-circuit bridge in Figure 16, as described above, in the same manner as the previously mentioned method. This allows for switching operation as needed, with star connections to star, delta connections to delta, or one being a star connection and the other a delta connection. Similar to the case of a parallel connection of one inverter, the torque can be increased in the following order: star connections to star, one being a star connection and the other a delta connection, and then delta connections to delta. However, these are configurations that can be understood without illustrations, so they have been omitted. Since stator M1 and stator M2 use separate, independent inverters, the cost is higher, but the controllability is improved compared to the case of a single inverter, making it suitable for fine-grained control.

[0128] When a BLDCM with the same one-phase winding for stator M1 and stator M2 in each of the above-described embodiments is driven by a so-called 120° energizing method in which two of the UVW3 terminals of the inverter are sequentially energized to + and - at the same voltage, using (1) a star series connection as shown in Figure 19 and (2) a delta series connection as shown in Figure 20, the maximum torque is 1.5 times that of (1) if (2) is set to 1, the maximum speed is √3 times that of (2) if (1) is set to 1, and the maximum output is approximately 2.6 times that of (2) if (1) is set to 1. Thus, even with just star and delta switching control, the torque, speed, and output of a single rotating electric machine can be variably controlled within this range with simple control.

[0129] Figure 26 shows a conventionally known polar anisotropic magnet, but with a cylindrical magnet oriented in the direction of the arc arrow. With such a polar anisotropic magnet, the arc length L2, which is the effective length of the magnet due to the polar anisotropic orientation, can be made larger than the wall thickness L1 of the annular magnet, thereby obtaining high torque. This technology was proposed by one of the inventors of the present application at the Small Motor Technology Symposium hosted by the Japan Management Association in 1983, and an outline of it is also described in Non-Patent Literature 3. It is currently widely used in claw-pole stepping motors and the like.

[0130] The term "polar anisotropic magnet," as shown in Figure 26, was coined by the author of Non-Patent Document 3, but has since been widely used in the industry. This magnet technology is used not only in stepping motors but also in radial gap rotating electric machines, and is now widely used in brushless motors. However, this technology is limited to use in single-sided gap motors that utilize the surface of a cylindrical magnet. As shown in the first and third embodiments of the present invention, a single magnet is used polarly anisotropically on both sides, greatly improving the magnet utilization rate. Compared to conventional axial gap rotating electric machines, it is possible to miniaturize and thin the axial gap rotating electric machine while maintaining performance, and it can be manufactured at a low cost. [Industrial applicability]

[0131] The rotating electric machine according to the present invention can be used as an electric motor or generator, and is extremely practical as it is inexpensive, robust, lightweight, compact, and suitable for high torque and high efficiency. The axial double-sided gap permanent magnet type rotating electric machine has been attracting attention in recent years for its ability to increase torque because the area of ​​contact between the air gap and the stator can be increased to more than twice that of the radial gap type. The proposal to make the magnets double-pole anisotropic is expected to make a significant industrial contribution in future applications such as EVs. [Explanation of Symbols]

[0132] 10, 10a, 10b, 10c Axial gap type rotating electric machine, 11 Stator, 12, 12a, 12b, 12c Rotor, 13 Iron core, 14 Teeth, 15 Winding, 16, 16a, 16d, 16f Disc-shaped permanent magnet, 16b Spoke magnet, 16c, 16e Magnet piece, 16g Permanent magnet body, 17 Core, 18 Bearing, 19 Rotating shaft, 21 Orientation, 30 Magnetic disk, 41 Diode, 42 Switching element, 50 Inverter, 52 Resistor element.

Claims

1. A rotor having a disc-shaped permanent magnet, An axial gap type rotating electric machine having a rotor and a pair of stators facing each other on both axial sides via an air gap, The pair of stators are arranged such that the excitation polarity of the winding poles facing each other at the same position in the circumferential direction is the same. The aforementioned disc-shaped permanent magnet is characterized in that the magnetic polarity is the same at the same position in the circumferential direction on both the front and back sides, and the N pole and S pole are alternately magnetized to P poles in the circumferential direction, thus forming an axial gap type rotating electric machine. However, P is an even number greater than or equal to 2.

2. In the axial gap type rotating electric machine according to claim 1, The stator is characterized by having teeth made of a compacted iron core, forming an axial gap type rotating electric machine.

3. In the axial gap type rotating electric machine according to claim 1, The aforementioned disc-shaped permanent magnet is oriented in a P-set configuration, with the circumferential orientation portion and the axial orientation portion forming one set orientation, and is composed of a dipole anisotropic magnet that generates magnetic poles of the same polarity at the same position on both sides, characterized in that it is an axial gap type rotating electric machine.

4. In the axial gap type rotating electric machine according to claim 1, The aforementioned disc-shaped permanent magnet is configured in P sets, with spoke magnets and axially oriented portions oriented as one set, in an axial gap type rotating electric machine.

5. In the axial gap type rotating electric machine according to claim 4, The aforementioned disc-shaped permanent magnet is characterized in that the axially oriented portion is made of a magnetic material, in an axial gap type rotating electric machine.

6. In the axial gap type rotating electric machine according to claim 5, The aforementioned magnetic material is characterized by gradually protruding toward the center of the tooth width on the air gap side of the rotating electric machine.

7. In the axial gap type rotating electric machine according to claim 1, The aforementioned disc-shaped permanent magnet is composed of an anisotropic magnet, characterized in that it is magnetized by being easily oriented between the front-side N pole portion and the back-side S pole portion, which are offset by 360° / P in the circumferential direction, thereby generating magnetic poles of the same polarity at the same position on both sides.

8. In the axial gap type rotating electric machine according to claims 3 and 7, The aforementioned disc-shaped permanent magnet is characterized in that a magnetic plate member is interposed in the central part in the axial direction, forming an axial gap type rotating electric machine.

9. In the axial gap type rotating electric machine according to claim 1, The stator has a three-phase winding, each having one end and the other end. The magnetic flux on the front side of the disc-shaped permanent magnet and the magnetic flux on the back side of the stator are used as linked fluxes, and each forms an independent short magnetic path. The windings of each phase are driven by the inverter in either a series or parallel connection. An axial gap type rotating electric machine characterized by comprising a connection changing means capable of changing the connections of the inverter and the windings of each phase.

10. In the axial gap type rotating electric machine according to claim 9, The connection changing means connects the in-phase windings of the pair of stators in series, One end of the stator is connected to the inverter. An axial gap type rotating electric machine characterized by a series connection between the other end of one stator and one end of the other stator, and by short-circuiting one end of the other end of the other stator and leaving the other end open.

11. In the axial gap type rotating electric machine according to claim 9, The connection changing means connects the in-phase windings of the pair of stators in parallel. One end of the stator and one end of the other stator are connected to the inverter. An axial gap rotating electric machine characterized by short-circuiting both the other end of one stator and the other end of the other stator.

12. In the axial gap type rotating electric machine according to claim 9, The connection changing means connects the in-phase windings of the pair of stators in parallel. One end of the stator and one end of the other stator are connected to the inverter. An axial gap type rotating electric machine characterized by short-circuiting one end of one stator and the other end of the other stator, and leaving the other end open.

13. In the axial gap type rotating electric machine according to claim 9, The connection changing means connects the in-phase windings of the pair of stators in series, An axial gap rotating electric machine characterized in that the connection between one stator and the other stator can be switched between a star connection and a delta connection.

14. In the axial gap type rotating electric machine according to claim 9, The connection changing means connects the in-phase windings of the pair of stators in parallel. An axial gap rotating electric machine characterized in that the connection between one stator and the other stator can be switched between a star connection and a delta connection.

15. In the axial gap type rotating electric machine according to claim 9. The pair of stators are each connected to an independent inverter. The connection changing means is characterized in that it can switch between a star connection and a delta connection for the connection between one stator and the other stator, in an axial gap type rotating electric machine.

16. In the axial gap type rotating electric machine according to claim 15, The sum of the torques generated by each of the pair of stators is given by the sum of the generated torques, and the torque generated by one of the stators is given by T. １ The torque generated by the other stator is T ２ Therefore, T = T １ ±kT ２ An axial gap type rotating electric machine characterized by being driven by synchronous operation, wherein k is less than 1.

17. In the axial gap type rotating electric machine according to claims 9 to 12, An axial gap type rotating electric machine characterized by generating a regenerative circulating current by controlling each switching element of the inverter, or by generating an electromagnetic braking force and braking by passing a DC current through at least one phase.

18. In the axial gap type rotating electric machine according to claim 15, An axial gap type rotating electric machine characterized in that one of the stators is driven by a rotation drive that switches the phase currents of each stator, and the other controls each switching element of the inverter to generate a regenerative circulating current or to pass a DC current through at least one phase, thereby generating an electromagnetic braking force and providing braking.

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