Permanent magnet motor and motor system

Abstract

To provide an electrical motor capable of achieving high-speed rotation and miniaturization.SOLUTION: A permanent magnet motor 1 comprises: a motor rotor 6 having a plurality of permanent magnets 5; and a motor stator 7 adjacent to the motor rotor 6. The permanent magnets 5 each have a plurality of easy axes of magnetization that are inclined with respect to the d-axis and the q-axis. The easy axes of magnetization include a first easy axis of magnetization M1 close to the d-axis, and a second easy axis of magnetization M2 close to the q-axis. The angle of the second easy axis of magnetization M2 relative to the q-axis is larger than the angle of the first easy axis of magnetization M1 relative to the d-axis. The motor stator 7 has amorphous teeth 20 and windings 23 wound around the teeth 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a permanent magnet motor having a permanent magnet in a motor rotor, and more particularly to a permanent magnet motor capable of rotating at high frequency, and a driver or inverter for driving such a permanent magnet motor. [Background technology]

[0002] Motors are used in a wide range of fields, from household appliances to toys, and electrical and drive equipment for mobility. In recent years, the electrification of devices has been promoted against the backdrop of CO2 countermeasures. For example, in aerospace equipment and land mobility, which are seen as promising CO2 countermeasures, there is a demand for small, high-efficiency, high-output motors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-120399 Summary of the Invention [Problem to be solved by the invention]

[0004] In particular, permanent magnet motor technology has evolved with the advent of neodymium magnets and the development of improved BH products (energy products), as well as miniaturization, oxygen-free processing, Halbach arrays, and low-vibration orientation, all of which have promoted the miniaturization and high efficiency of permanent magnet motors. In this patent specification, miniaturization technology is essentially equivalent to high-efficiency technology. This is because achieving a 2x miniaturization requires both a √2x miniaturization and a √2x higher efficiency before the heat balance can be achieved.

[0005] One approach to miniaturization is to miniaturize the motor system as a whole, rather than the motor itself. In other words, the size of the motor itself is kept the same, and high efficiency is achieved by changing the rotational speed using a transmission mechanism such as a mechanical gear using planetary gears or helical gears, a magnetic gear, or an electric gear.

[0006] For example, when transmitting power to the drive wheels of electric mobility vehicles, the motor operates at low torque and high rotation speed, and the gears are tasked with deceleration and increasing torque, thereby reducing the current to the motor and reducing copper loss. In this case, rather than using a powerful magnet in the motor, bonded magnets, which have weaker magnetic force than sintered magnets, are used to reduce iron loss, or coreless motors, which have very little iron loss, are used. In some cases, motors are designed with six poles or less.

[0007] Conversely, there are also motors that reduce iron loss by using gears to increase speed and reduce torque, and rotating the motor at a low speed with high torque. In this case, a multi-pole motor with at least six poles is often used to increase the motor frequency, and by reducing the protrusion of the coil from the core, the motor can be made smaller and lighter.

[0008] In both cases, we search for optimal calculation results based on calculations such as copper loss and iron loss for heat balance, and the high-frequency capability of the motor driver.

[0009] The present invention provides an electric motor capable of high-speed rotation and miniaturization, and related techniques. [Means for solving the problem]

[0010] In one aspect, a permanent magnet motor is provided, comprising: a motor rotor having a plurality of permanent magnets; and a motor stator adjacent to the motor rotor, each of the plurality of permanent magnets having a plurality of magnetic easy axes tilted with respect to a d-axis and a q-axis, the plurality of magnetic easy axes including a first magnetic easy axis close to the d-axis and a second magnetic easy axis close to the q-axis, the angle of the second magnetic easy axis relative to the q-axis being greater than the angle of the first magnetic easy axis relative to the d-axis, and the motor stator having teeth formed from a plurality of stacked amorphous plates and windings wound around the teeth.

[0011] In one embodiment, each of the plurality of permanent magnets has a coercive force of 450 kA / m or more, a residual magnetic flux density of 0.7 T or more, and an energy product of 13 MGOe or more. In one embodiment, the winding includes a bundle of multiple wires and an outer coating covering the bundle of multiple wires, each of the multiple wires includes a conductor and an inner coating covering the conductor, and each of the multiple wires has a cross-sectional area corresponding to a circular diameter of 0.71 mm or less. In one embodiment, the thickness of the inner coating is 5 μm or less. In one embodiment, the thickness of each of the plurality of amorphous plates is less than 0.3 mm. In one embodiment, the motor stator has an annular core positioned outside the teeth, and the annular core is made of an electromagnetic steel plate. In one embodiment, the motor rotor has an outer cylinder surrounding the multiple permanent magnets, and the outer surface of the outer cylinder is formed with at least one of grooves extending in the axial direction of the outer cylinder, grooves extending in the circumferential direction of the outer cylinder, and grooves extending obliquely relative to the circumferential direction of the outer cylinder.

[0012] In one aspect, a motor system is provided that includes the permanent magnet motor, a plurality of inverters that supply variable frequency power to the permanent magnet motor, and a plurality of DC power supplies that apply voltages to the plurality of inverters, respectively. [Effects of the Invention]

[0013] The permanent magnet has magnetic lines of force (axis of easy magnetization) longer than its radial width, and the motor stator teeth have a laminated structure made of amorphous material with high magnetic flux density. The combination of this permanent magnet and amorphous teeth makes it possible to realize a permanent magnet motor that is compact yet achieves high output. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing an embodiment of a permanent magnet motor. [Figure 2] FIG. 2 is a cross-sectional view showing a part of the motor rotor as viewed from the axial direction of the rotating shaft. [Figure 3] FIG. 2 illustrates one embodiment of an easy axis of a permanent magnet. [Figure 4] 10A and 10B are diagrams illustrating other embodiments of the easy axis of magnetization of a permanent magnet. [Figure 5] FIG. 10 is a diagram showing yet another embodiment of the easy axis of magnetization of a permanent magnet. [Figure 6] FIG. 10 is a diagram showing yet another embodiment of the easy axis of magnetization of a permanent magnet. [Figure 7] FIG. 10 is a diagram showing yet another embodiment of the easy axis of magnetization of a permanent magnet. [Figure 8] FIG. 10 is a diagram showing yet another embodiment of the easy axis of magnetization of a permanent magnet. [Figure 9] FIG. 10 is a diagram showing yet another embodiment of the easy axis of magnetization of a permanent magnet. [Figure 10] FIG. 10 is a diagram showing yet another embodiment of the easy axis of magnetization of a permanent magnet. [Figure 11] 10A and 10B are diagrams showing an embodiment of grooves formed on the outer peripheral surface of an outer cylinder. [Figure 12] 10A and 10B are diagrams showing an embodiment of grooves formed on the outer peripheral surface of an outer cylinder. [Figure 13] 10A and 10B are diagrams showing an embodiment of grooves formed on the outer peripheral surface of an outer cylinder. [Figure 14] FIG. 1 is a cross-sectional view illustrating an embodiment of a motor stator. [Figure 15] FIG. 1 is a cross-sectional view illustrating one embodiment of a winding. [Figure 16] FIG. 2 is a cross-sectional view showing one embodiment of a wire. [Figure 17] 1 is a graph showing the relationship between the diameter of a conductor and the loss caused by heat generated by electrical resistance when a direct current flows through the conductor, and the relationship between the diameter of the conductor and the loss caused by eddy currents generated when an alternating current flows through the conductor. [Figure 18] 1 is a graph showing the relationship between the diameter of a wire and the loss of the wire. [Figure 19] FIG. 10 is a schematic diagram showing one embodiment of how to wind a winding around a tooth. [Figure 20] 10A and 10B are schematic diagrams showing another embodiment of a method of winding a winding around a tooth. [Figure 21] FIG. 10 is a schematic diagram showing yet another embodiment of how to wind a winding around teeth. [Figure 22] 10A-10C illustrate an embodiment of a method for creating multiple teeth from a flat plate by a stamping process. [Figure 23] 10A and 10B are diagrams illustrating an embodiment in which a stator core having a plurality of teeth formed by a punching process is bent to form a plurality of teeth arranged in an annular shape. [Figure 24] Figures 24(a) and 24(b) are BMD diagrams. [Figure 25] FIG. 1 is a cross-sectional view showing an embodiment of a dual radial type permanent magnet motor. [Figure 26] FIG. 1 is a cross-sectional view showing an embodiment of an axial gap motor. [Figure 27] FIG. 1 is a cross-sectional view showing an embodiment of an axial gap motor. [Figure 28] 1 is a cross-sectional view showing an embodiment of a coreless motor. [Figure 29] 1 is a view showing an embodiment of a hollow coreless motor as viewed from the axial direction; [Figure 30] FIG. 10 is a view of another embodiment of a hollow coreless motor as viewed from the axial direction. [Figure 31] 1 is a cross-sectional view illustrating an embodiment of an outer rotor permanent magnet motor. FIG. [Figure 32]10A and 10B are schematic diagrams showing other embodiments of permanent magnets of a motor rotor. [Figure 33] 10 is a graph showing an example of the relationship between the torque ratio of a permanent magnet motor and the number of permanent magnets that make up one group. [Figure 34] This is an enlarged view of five permanent magnets that make up one group. [Figure 35] 33 is a diagram showing an embodiment of a cylindrical magnetic body that covers the outer peripheral surface of the permanent magnet shown in FIG. 32. [Figure 36] 10A and 10B are diagrams illustrating an embodiment in which gaps between two or more permanent magnets that make up a magnet block are filled with a filler material such as resin. [Figure 37] FIG. 33 is a cross-sectional view showing an embodiment of a motor rotor equipped with the permanent magnet shown in FIG. 32. [Figure 38] 1A and 1B illustrate an embodiment of a method for manufacturing (creating) a barrel. [Figure 39] FIG. 1 is a schematic diagram showing an embodiment of a motor system including a permanent magnet motor, two inverters for driving the permanent magnet motor, and two DC power supplies for supplying power to the two inverters. [Figure 40] FIG. 10 is a schematic diagram showing another embodiment of a motor system including two inverters and two DC power supplies. [Figure 41] FIG. 10 illustrates an embodiment in which a chopper circuit is disposed between a power supply and an inverter. [Figure 42] 4 is a graph illustrating an embodiment of a control operation of an inverter. [Figure 43] FIG. 1 is a schematic diagram showing an embodiment in which a permanent magnet motor is used as a drive source for a liquid fuel pump. [Figure 44] FIG. 1 is a diagram showing an embodiment in which a permanent magnet motor is applied to a dry motor. [Figure 45] FIG. 1 is a diagram showing an embodiment in which a permanent magnet motor is applied to a wet motor. DETAILED DESCRIPTION OF THE INVENTION

[0015] Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a permanent magnet motor. As shown in FIG. 1, the permanent magnet motor 1 includes a rotating shaft 2, a motor rotor 6 having a plurality of permanent magnets 5, and a motor stator 7 for generating a rotating magnetic field. The plurality of permanent magnets 5 are fixed to a rotor core 9 of the motor rotor 6. The motor rotor 6, including the plurality of permanent magnets 5 and the rotor core 9, is fixed to the rotating shaft 2 and rotates integrally with the rotating shaft 2. The permanent magnet motor 1 of this embodiment is a multi-pole electric motor with four or more poles.

[0016] The permanent magnet motor 1 further includes bearings 11 and 12 that rotatably support the rotating shaft 2, and a motor housing 15 to which the bearings 11 and 12 are fixed. The bearings 11 and 12 are arranged on both sides of the motor rotor 6 in the axial direction of the rotating shaft 2. The motor rotor 6, motor stator 7, and bearings 11 and 12 are arranged within the motor housing 15. The bearings 11 and 12 are ball bearings, and conductive oil is used to lubricate the balls of the bearings 11 and 12. In one embodiment, the balls of the bearings 11 and 12 are made of ceramic. The use of conductive oil or ceramic balls prevents electrolytic corrosion.

[0017] The motor stator 7 is disposed adjacent to the motor rotor 6. The motor stator 7 includes a plurality of teeth (or pole teeth) 20, windings 23 wound around the teeth 20, and an annular core 24 disposed outside the plurality of teeth 20. The windings 23 are wound around the plurality of teeth 20 to form a plurality of coils. In the embodiment shown in FIG. 1, the motor stator 7 is disposed radially outside the motor rotor 6 and surrounds the motor rotor 6. There is a radial gap between the motor rotor 6 and the motor stator 7. Such an electric motor is a radial gap type electric motor.

[0018] The permanent magnets 5 are covered by an outer cylinder 30, which prevents the permanent magnets 5 from flying out due to centrifugal force when the motor rotor 6 is rotating at high speed. To more firmly secure the outer cylinder 30 and prevent the permanent magnets 5 from flying away in the axial direction, end plates 31 are arranged on both sides of the permanent magnets 5 in the axial direction of the rotating shaft 2. The permanent magnets 5 are arranged between the end plates 31 of the motor rotor 6. The outer cylinder 30 is fixed to the outer peripheral surface of the end plates 31.

[0019] 2 is a cross-sectional view showing a portion of the motor rotor 6 as viewed from the axial direction of the rotating shaft 2. The multiple permanent magnets 5 are arranged along the circumferential direction of the motor rotor 6 so that the north and south poles are arranged alternately. In one embodiment, the multiple permanent magnets 5 are arranged without gaps along the circumferential direction of the motor rotor 6. Gaps of about 1 mm for manufacturing purposes, application of adhesive, etc. are included in the category of being without gaps.

[0020] Each permanent magnet 5 has a coercive force of 450 kA / m or more, a residual magnetic flux density of 0.7 T or more (preferably 0.9 T or more), and an energy product (B×H, where B is magnetic flux density and H is magnetic field) of 13 MGOe or more. In one embodiment, the permanent magnets 5 are rare earth magnets containing samarium (Sm), neodymium (Nd), praseodymium (Pr), cerium (Ce), didymium, or the like. For example, the permanent magnets 5 are made of samarium cobalt and produced by a sintering method. In another embodiment, the permanent magnets 5 are iron nitride (FeN) magnets with an L10 structure.

[0021] Each permanent magnet 5 has different crystal orientations in the d-axis and q-axis. More specifically, the permanent magnet 5 has multiple easy axes of magnetization M1, M2 that are inclined at different angles relative to the radial direction of the motor rotor 6. Here, the d-axis is a virtual radial axis that passes through the magnetic pole center of each permanent magnet 5, and the q-axis is a virtual radial axis that passes through the magnetic pole inflection point. The q-axis extends along both ends of each permanent magnet 5.

[0022] As shown in FIG. 2, each permanent magnet 5 has multiple easy axes M1 and M2 tilted toward the d-axis and q-axis. The multiple easy axes M1 and M2 include a first easy axis M1 close to the d-axis and a second easy axis M2 close to the q-axis. Here, "close" does not mean absolutely close, but rather relatively close. That is, the first easy axis M1 is closer to the d-axis than the second easy axis M2, and the second easy axis M2 is closer to the q-axis than the first easy axis M1. The first easy axis M1 and the second easy axis M2 are tilted toward the d-axis.

[0023] The angle of the second easy axis M2 with respect to the q axis is larger than the angle of the first easy axis M1 with respect to the d axis. In addition, the second easy axis M2 is inclined more to the d axis than the first easy axis M1. That is, the angle of the second easy axis M2 with respect to the d axis is larger than the angle of the first easy axis M1 with respect to the d axis. The first easy axis M1 may be approximately parallel to the d axis. The second easy axis M2 is inclined in a direction away from the q axis. Such easy axes M1 and M2 can be achieved by controlling the crystal orientation when forming the magnetic powder by sintering.

[0024] As can be seen from Figure 2, the permanent magnet 5 has magnetic lines of force (easy axis of magnetization) longer than its radial width, which allows the permeance Pc to be increased. The effective magnetic flux density Bd of the magnet is calculated using the following formula: Bd=Br / (1+1 / Pc) where Br is the residual magnetic flux density. The above formula shows that as the permeance coefficient approaches infinity, the effective magnetic flux density Bd approaches Br. The permeance coefficient is a value proportional to the thickness of the magnet, that is, a value proportional to the length of the easy axis of magnetization. Therefore, the magnetic flux can be increased by lengthening the easy axis of magnetization. In other words, this embodiment improves the coercivity of the magnet by increasing the denominator m of the unit [A / m] relative to the performance value of the magnet's coercivity [A / m], enabling the permanent magnet to operate without irreversible demagnetization even in areas with strong magnetic fields.

[0025] The permanent magnet 5 of this embodiment, which has such easy axes of magnetization M1, M2, can make the magnetic lines of force that traverse its thickness direction longer than the radial thickness of the permanent magnet 5. In other words, even a permanent magnet of the same size can generate longer magnetic lines of force. As a result, the permanent magnet motor 1 can generate high torque, and the permanent magnet motor 1 can be made smaller.

[0026] 3 to 10 are diagrams showing various embodiments of the easy axis of magnetization of the permanent magnet 5. FIG. 3, the easy axes M1 and M2 are curved, tilting at different angles toward the d-axis and away from the q-axis. In FIG. 4, the easy axes M1 and M2 extend linearly, but the easy axis M2 extends toward the easy axis M1. In Figure 5, both ends of the permanent magnet 5 are inclined with respect to the q-axis. More specifically, both ends 5a, 5a of the permanent magnet 5 are inclined in a direction away from the q-axis toward the radially outer side of the permanent magnet 5. Therefore, there is an air gap between two adjacent permanent magnets 5. Since the corners of the permanent magnets 5, where the magnetic flux lines are short, are cut off, it is possible to prevent demagnetization.

[0027] In Figure 6, there is a recess 5b in the center of the inner edge of permanent magnet 5. Recess 5b is on the d-axis and has a wedge shape. This recess 5b prevents magnetic flux lines on both sides of the center of permanent magnet 5 from colliding with each other, making it possible to prevent demagnetization. FIG. 7 shows an example similar to FIG. 5, but outer portions 5c, 5c of both side ends 5a, 5a of the permanent magnet 5 are inclined inward of the permanent magnet 5. In Fig. 8, the inner portions 5d, 5d between both end portions 5a, 5a of the permanent magnet 5 are inclined inward of the permanent magnet 5. The inwardly inclined inner portions 5d, 5d can make the lengths of the magnetic flux lines closer to equal.

[0028] Fig. 9 is a modification of Fig. 8. That is, a magnetic material (for example, metal) 35 is attached to the inner portions 5d, 5d that are inclined inward. In Figure 10, the permanent magnet 5 has a shape divided along the d-axis. In this example, the permanent magnet 5 is composed of two divided bodies, but it may be composed of three or more divided bodies. For example, if it is composed of ten divided bodies, a curved easy axis of magnetization can be formed, which allows for a smooth change in magnetic flux and effectively prevents demagnetization.

[0029] Furthermore, for the gap between the magnets created by the q-axis line and symbol 5a in Figure 5, the gap formed by symbol 5b in Figure 6, the gap formed by the q-axis and symbol 5c in Figure 7, the gap formed by the q-axis and symbol 5d in Figure 8, and the gap near the d-axis in Figure 10, by installing wedges in the axial direction to prevent the permanent magnets 5 from flying away or by filling the gaps with a resin adhesive or the like, a circular magnet set can be formed, which will improve manufacturability and make it easier to handle.

[0030] In summary, the permanent magnet 5 of this embodiment is characterized by having fewer higher-order components, such as third-order components, and a magnetic flux waveform closer to a SIN wave than conventional radially aligned or linearly aligned sintered magnets. In other words, the permanent magnet 5 of this embodiment has a magnetic flux waveform that enhances the magnetic flux linking the motor coil in accordance with the Biot-Savart equation. In Halbach-arranged or linearly aligned magnet arrangements, the dq-axis orientation angle is set to suppress the phenomenon of a magnetic flux waveform becoming nearly rectangular at the end of the magnet oriented furthest toward the stator in the arrangement, and to increase the primary component of the magnetic flux that responds more effectively to the primary current waveform. Specifically, if the entire range of the outflow surface of the magnetic flux of one magnet pole pair is defined as 360 degrees in order to avoid tertiary waveforms, it is possible to reduce low-order harmonic magnetic flux waveforms such as a 120-degree 3rd-order magnetic flux waveform, a 72-degree 5th-order magnetic flux waveform, a 51.4-degree 7th-order magnetic flux waveform, and an 11th-order magnetic flux waveform of approximately 32.7 degrees and a 13th-order magnetic flux waveform of approximately 27.7 degrees, which tend to occur as orders twice the number of stator pole teeth.

[0031] When the q-axis portion is cut into by a curved surface of the permanent magnet 5 facing the stator (see symbol 5e in FIG. 7) as shown in FIG. 7, the central angle determined by the arc of the curved surface 5e of the permanent magnet 5 with the stator is preferably 120 degrees, 72 degrees, 51.4 degrees, 32.7 degrees, 27.7 degrees, or 144 degrees, 102.8 degrees, 65.4 degrees, or 55.4 degrees which are twice the high-order frequency, or 154.2 degrees, 98.1 degrees, or 83.1 degrees which are three times the high-order frequency, or 130.8 degrees or 110.8 degrees which are four times the high-order frequency, or 163.5 degrees or 138.5 degrees which are five times the high-order frequency, or 166.2 degrees which is six times the high-order frequency, and further preferably these angles are ±1 degree in consideration of manufacturing precision. If the permanent magnet 5 is manufactured with the above angle, the permanent magnet motor 1 does not need to have any of the high-harmonic frequency elements of the 3rd, 5th, 7th, 11th, or 13th orders. In particular, when configured with a 120-degree angle in a three-phase motor, it is possible to effectively suppress the circulating current caused by the 3rd-order electromotive force that occurs when the permanent magnet motor 1 is delta-connected. If the permanent magnet 5 is divided into multiple pieces, it is preferable that the angle range occupied by magnets such as M1 that are relatively strongly angularly oriented in the d-axis direction is the above angle.

[0032] As shown in FIG. 2, the permanent magnets 5 are covered by an outer cylinder 30 made of carbon fiber reinforced plastic (CFRP). In one embodiment, the thickness of the outer cylinder 30 is 1 mm or less, and the stress generated in the outer cylinder 30 is 0.2% proof stress or less. To withstand low temperatures, the resin to be compounded is preferably thermoplastic. The multiple permanent magnets 5 are fixed to the outer peripheral surface of the rotor core 9 with an adhesive to form a ring-shaped magnet. If the permanent magnets 5 were fixed with adhesive alone, they may come off when the motor rotor 6 rotates at high speed, so the permanent magnets 5 are covered by the outer cylinder 30. The ring-shaped permanent magnets 5 are press-fitted into the outer cylinder 30.

[0033] The pressure applied during this press-fitting is preferably higher than the stress caused by centrifugal force on the outer casing 30 within the rated rotational speed range of the motor rotor 6. The centrifugal force can be calculated based on the expected rotational speed of the motor rotor 6 and the structure of the motor rotor 6. For example, for a vehicle motor, the press-fitting pressure should be equal to or greater than the stress generated in the outer casing 30 due to centrifugal force at the rotational speeds output by cluster analysis of WLTC cycle driving at 5 to 10 points. This prevents the outer casing 30 of an inner rotor type rotor from expanding theoretically even when subjected to centrifugal force, thereby minimizing protrusion of the outer casing 30 into the air gap between the rotor and stator, which affects motor quality. As a secondary effect, for IPM rotors with magnets embedded in electromagnetic steel sheets, the inductance and magnetic flux obtained at low speeds can change by tens of microns due to the protrusion of the laminated steel sheets into the air gap at high speeds. This suppresses this phenomenon. This allows for good proportional control without changes in gain when performing PI control at low speeds or at an arbitrary rated rotation speed, making it possible to use cheaper and simpler control, or even to operate the motor using a microcomputer.

[0034] The outer cylinder 30 is made of a non-magnetic, high-strength material such as a fiber material made of carbon fiber reinforced plastic (CFRP), glass fiber reinforced plastic (GFRP), titanium, or austenitic stainless steel, a metal, or a combination of these. The outer cylinder 30 prevents the magnetic flux loop of the permanent magnet 5 from completing within the motor rotor 6, while suppressing eddy current loss due to the AC magnetic field generated by the motor stator 7, thereby achieving high reliability. When the outer cylinder 30 is made of the above-mentioned fiber material, the fibers are oriented in the circumferential direction of the motor rotor 6. This orientation increases the strength of the outer cylinder 30. The outer cylinder 30 prevents the outer diameter of the motor rotor 6 from changing due to centrifugal force and prevents slippage of the permanent magnets.

[0035] If sufficient magnetic force can be obtained without suppressing magnetic flux leakage, the outer casing 30 may be made of a martensitic stainless steel or iron-based alloy. In this case, the outer casing 30 is easy to manufacture. Furthermore, if the eddy current generated in the motor rotor 6 is negligible, the outer casing 30 may be made of a conductive material such as copper or iron. In this case, grooves may be cut, or the outer circumferential surface of the outer casing 30 may be knurled or grooved to reduce eddy current loss. In one embodiment, the outer casing 30 may be made of a composite material of carbon fiber reinforced plastic (CFRP) and metal.

[0036] Examples of grooves formed on the outer peripheral surface of the outer tube 30 include grooves extending in the axial direction of the outer tube 30, grooves extending in the circumferential direction of the outer tube 30, grooves extending obliquely relative to the circumferential direction of the outer tube 30, and combinations thereof. FIGS. 11 to 13 are diagrams showing an embodiment of grooves formed on the outer peripheral surface of the outer tube 30. In the embodiment shown in FIG. 11, the grooves 150 formed on the outer peripheral surface of the outer tube 30 extend in the axial direction of the outer tube 30. In the embodiment shown in FIG. 12, the grooves 150 formed on the outer peripheral surface of the outer tube 30 extend in the circumferential direction of the outer tube 30. In the embodiment shown in FIG. 12, the grooves 150 formed on the outer peripheral surface of the outer tube 30 extend obliquely relative to the circumferential direction of the outer tube 30. The grooves 150 may be lattice-shaped grooves or spiral grooves. In one example, the depth of the grooves 150 is within a range of 0.3 mm to 0.5 mm. The grooves 150 formed on the outer peripheral surface of the outer cylinder 30 can reduce eddy currents that occur on the outer peripheral surface of the outer cylinder 30 .

[0037] FIG. 14 is a cross-sectional view showing one embodiment of a motor stator 7. As shown in FIG. 14, the motor stator 7 has T-shaped teeth 20 (also called pole teeth) that form slots 21 for winding the windings 23. These teeth 20 serve to more effectively circulate magnetic flux from the motor rotor 6. The motor stator 7 has an annular core 24 arranged outside the teeth 20. The windings 23 are wound around the teeth 20 to form multiple coils. The motor stator 7 and windings 23 in FIG. 14 employ a so-called concentrated winding configuration. In an inner rotor type radial gap electric motor, the annular core 24 is arranged radially outside the teeth 20.

[0038] In this embodiment, the tooth 20 is made up of a plurality of stacked amorphous plates, each of which has a thickness of less than 0.3 mm (preferably 0.2 mm or less, more preferably 0.1 mm or less). In one embodiment, the thickness of each of the plurality of amorphous plates is 0.025 mm to 0.035 mm.

[0039] The annular core 24 is formed of a laminated structure of multiple electromagnetic steel plates made of alloy steel containing silicon. The thickness of the electromagnetic steel plates is greater than the thickness of the amorphous plates, for example, 0.35 mm. In one embodiment, the teeth 20 and the annular core 24 may be integrally formed to form a stator core. In this case, the stator core including the multiple teeth 20 has a laminated structure of multiple amorphous plates.

[0040] The tooth 20 made of amorphous has a configuration that satisfies the relationship B50×Ast>Br×Am, where B50 represents the magnetic flux density when the magnetizing force is 5000 A / mm, Ast represents the product of the width of the stator pole tooth 20 that faces the permanent magnet 5 within an electrical angle of 180 and the core axial length, Br represents the residual magnetic flux density, and Am represents the product of Ast and the surface of the permanent magnet 5 that faces it.

[0041] In one embodiment, the thickness of each of the stacked amorphous plates is less than 0.2 mm, and the magnetic flux density B50 is 1.5 T (Tesla) or more. In another embodiment, the thickness of each of the stacked amorphous plates is 0.1 mm or less, and the magnetic flux density B50 is 2.0 T (Tesla) or more.

[0042] When the magnetic flux generated by the motor rotor 6 is φm [Wb], it is appropriate to satisfy B50×Ast≧φm [Wb]. Alternatively, if the motor system is an axial gap system or the material is a powder magnetic core, it is appropriate to satisfy B100×Ast≧φm [Wb].

[0043] Amorphous materials have high magnetic permeability and a saturation magnetic flux density (Bs) that is approximately 20% lower than that of conventional soft magnetic iron. SST (Single Sheet Magnetic Measurement Test) and Single Sheet Magnetic Measurement Test (JIS C 2556) were conducted on samples of such amorphous materials measuring 30 mm wide x 120 mm long x 35 μm thick. When measuring B50 for such materials, magnetic flux values ​​exceed Bs. This is because Bs is reached below B50, and then the magnetic flux increases with the magnetic permeability of air, similar to that of a coreless motor. The preferred material in this invention is such an amorphous material. It is desirable to use an amorphous material that reaches Bs below B50, then increases with the magnetic permeability of air, and measures B50 ≥ 1.7 [T] as a test result. This means that magnetic flux densities exceeding those of magnetic steel sheets can be achieved in the magnetic flux range handled by typical permanent magnet motors of approximately 400 kW or less.

[0044] The windings 23 are wound in a distributed manner in the slots 21 of the motor stator 7. As a result, the winding factor of the motor is high because it is a full-pitch winding, which reduces the harmonic magnetic flux imparted to the motor rotor 6 and reduces losses in the motor components as a whole.

[0045] Figure 15 is a cross-sectional view showing one embodiment of the winding 23. As shown in Figure 15, the winding 23 is configured by twisting together a plurality of strands 40. The plurality of strands 40 are compressed to form a single bundle. Each of the plurality of strands 40 has a rectangular or square cross section, so there are almost no gaps between the strands 40.

[0046] The bundle of multiple wires 40 is covered with an insulating outer coating 42. The outer coating 42 is made of glass fiber or engineering plastic (e.g., PEEK or PPS). Because the winding 23 is made up of an assembly of multiple wires 40, the generation of eddy currents in each wire 40 is suppressed, making it possible to reduce eddy currents in the winding 23. Furthermore, because the multiple wires 40 are twisted, parasitic inductance components can be minimized and stray capacitance between adjacent wires 40 can be canceled out.

[0047] As shown in FIG. 15 , the winding 23 has a rectangular cross section. Because the winding 23 can be treated as a rectangular wire, the space factor of the winding 23 in the slot 21 can be increased. In one embodiment, the space factor of the winding 23, excluding the outer coating 42, is 90% or more, where the cross-sectional area of ​​the winding 23 including its four corners is defined as 100%. In this embodiment, the motor stator 7 has a three-phase winding structure, but the winding structure is not limited to this embodiment. For example, the motor stator 7 may have a two-phase winding structure, a five-phase winding structure, or a seven-phase winding structure, or any number of phases, as long as it is a commercially available motor.

[0048] Fig. 16 is a cross-sectional view showing one embodiment of wire 40. As shown in Fig. 16, wire 40 has a quadrilateral cross section such as a rectangle or a square. Wire 40 has a conductor 45 and an inner coating 48, which is an insulating film that covers conductor 45. Conductor 45 is made of a low-resistance material, and examples of the material for conductor 45 include aluminum, aluminum alloy, copper, and carbon nanotubes (CNTs).

[0049] The inner coating 48 covers the entire outer surface of the conductor 45. Materials for the inner coating 48 include oxide insulating materials, enamel resins made of polyamide-imide, polyimide, etc. Oxide insulating materials are preferred because they allow the inner coating 48 to be made thin. The inner coating 48 may have an air insulating layer with partial voids.

[0050] The thickness of the inner coating 48 of each wire 40 is 5 μm or less. When the inner coating 48 is made of enamel resin, the thickness of the inner coating 48 can be controlled to 1 to 3 μm, 3 to 5 μm, or the like, by adjusting the number of times the enamel resin is applied during the wire 40 manufacturing process. The wire 40 has a cross-sectional area equivalent to the cross-sectional area of ​​a circle with a diameter of 0.71 mm or less. The cross-sectional area of ​​the wire 40 is the overall cross-sectional area of ​​the wire 40, including the conductor wire 45 and the inner coating 48. In particular, as described below, the wire 40 has a cross-sectional area equivalent to the cross-sectional area of ​​a circle with a diameter of 0.126 mm to 0.71 mm.

[0051] 17 is a graph showing the relationship between the loss caused by heat generated by electrical resistance when a DC current flows through the wire 40 (hereinafter referred to as DC loss) and the cross-sectional area of ​​the wire 40, and the relationship between the loss caused by eddy current generated when an AC current flows through the wire 40 (hereinafter referred to as AC loss) and the cross-sectional area of ​​the wire 40. As can be seen from this graph, the larger the cross-sectional area of ​​the wire 40, the smaller the DC loss, while the larger the cross-sectional area of ​​the wire 40, the larger the AC loss. Therefore, there is a trade-off between DC loss and AC loss.

[0052] Therefore, in this embodiment, a wire 40 having a cross-sectional area that can reduce the total DC loss and AC loss is used. Fig. 18 is a graph showing the relationship between the diameter of a circle with a cross-sectional area equal to the cross-sectional area of ​​the wire 40 and the loss of the wire 40. The vertical axis represents the total DC loss and AC loss, and the horizontal axis represents the diameter of a circle with a cross-sectional area equal to the cross-sectional area of ​​the wire 40 including the conductor 45 and inner coating 48.

[0053] In this graph, the strand 40 has an inner coating 48 with a thickness of 5 μm or less, which is a reliable and manufacturable insulating coating. The range of 0.126 mm to 0.71 mm is an effective size range for reducing total loss when subtracting the reduction in AC loss (loss due to eddy current) of the strand 40 from the increase in DC loss (loss due to heat generated by electrical resistance) of the strand 40. In one embodiment, the diameter of a circle with a cross-sectional area equal to the cross-sectional area of ​​the strand 40 is within the range of 0.2 mm to 0.71 mm.

[0054] The windings 23 are fixed in place with varnish or the like to prevent movement within the slots 21. In this embodiment, the windings 23 are fixed to the slots 21 with epoxy resin. The linear expansion coefficient relationship between the varnish, the inner coating 48 of the wires 40, and the outer coating 42 of the windings 23 is varnish > outer coating 42 > inner coating 48. This linear expansion coefficient relationship results in a gradual change in the linear expansion coefficient in the direction of transmission of heat generated by the motor rotor 6 or motor stator 7 or heat generated within the windings 23. This prevents dimensional changes due to sudden temperature changes, thereby preventing cracks and chips in the varnish, outer coating 42, inner coating 48, and motor stator 7.

[0055] The configuration using the amorphous teeth 20 and windings 23 described above controls the d-axis and q-axis, making it possible to increase the magnetic flux of the primary component. The low-loss amorphous teeth 20 minimize high-frequency loss caused by excessively large magnetic flux, thereby minimizing iron loss. The eddy current loss generated within the windings 23 due to the larger magnetic flux than before leaking into the windings 23 caused by excessively large magnetic flux can be reduced compared to conventional conductors. As a result, it is possible to select a larger number of poles and an inverter that operates at a higher frequency, achieving a smaller and lighter system overall.

[0056] FIG. 19 is a schematic diagram showing one embodiment of how the windings 23 are wound around the teeth 20. This embodiment shows how the windings 23 are wound for a 2-pole, 6-slot, full-pitch motor. This embodiment allows for good core material yield and an increased space factor. The teeth 20 may be separated from one another, or only the outer edges of the teeth 20 may be connected to one another. If only the outer edges of the teeth 20 are connected to one another, the structure of the teeth 20 is bent inward to form a cylindrical shape. If the teeth 20 are separated from one another, the teeth 20 are arranged in a circular pattern to form a cylindrical shape, and the teeth 20 are fixed in place using a jig (not shown) or an adhesive (e.g., varnish).

[0057] The width of the slots between the linearly arranged teeth 20 is larger than the width of the slots between the cylindrically arranged teeth 20, making it easy to arrange the windings 23. Pre-molded resin insulators or paper insulators may be placed between the windings 23, and an adhesive such as varnish may also be placed between the windings 23 to secure the windings 23 to the teeth 20. This protects the insulating coating on the surface of the windings 23 while ensuring insulation of the windings 23. Each slot is filled with a conductor or various insulating materials, mainly resin, which can produce various desirable effects such as improved thermal conductivity and conductor space factor (increased efficiency).

[0058] The symbols S1 to S7 (S1) in Figure 19 represent slot numbers. The winding 23 extends through the first layer of slot S1 and the second layer of slot S4, in that order, and then through the second layer of slot S7 (S1) and the second layer of slot S4, in that order. By connecting the wires in this manner, it is possible to make the current flow in the same direction within the same slot.

[0059] FIG. 20 is a schematic diagram showing one embodiment of how the winding 23 is wound around the teeth 20. This embodiment shows how the winding 23 is wound for a 4-pole, 12-slot full-pitch motor. The symbols S1 to S13 (S1) represent the slot numbers. The winding 23 extends through the first layer of slot S1, the second layer of slot S4, the first layer of slot S7, and the second layer of slot S10, in that order, and further through the second layer of slot S13 (S1), the first layer of slot S10, the second layer of slot S7, and the first layer of slot S4, in that order. Slots S10 to S13 (S1) may be connected by a bus bar.

[0060] In the embodiments shown in Figures 19 and 20, two turns are wound in each slot, but multiple turns, such as 4, 6, or 8 turns, can also be wound in each slot in a similar manner. Figure 21 is a schematic diagram showing yet another embodiment of how the winding 23 is wound around the teeth 20. In this embodiment, there are four turns of the winding 23 per slot. As shown in Figure 21, two layers are created at a time. To create two layers of the winding 23 at a time, in a winding with a number of layers that is a multiple of two, the 2n+1 layer and the 2n layer are connected. Current in and out appear in two layers.

[0061] 22 is a diagram illustrating one embodiment of a method for creating a plurality of teeth 20 from a flat plate by a punching process. In this punching process, a strip-shaped flat plate 36 is prepared, and two stator cores 37 are created from the flat plate 36, and each of the stator cores 37 has a plurality of teeth 20 connected linearly.

[0062] 23 is a diagram illustrating an embodiment in which a plurality of teeth 20 arranged in an annular shape are created by bending a stator core 37 having a plurality of teeth 20 created by a punching process. The stator core 37 having a plurality of linearly connected teeth 20 is sent to a spiral processing unit 38, which deforms the stator core 37 into a spiral shape. In this way, a stator core 37 having a plurality of annular teeth 20 is created.

[0063] In one embodiment, the thin plate constituting the stator core 37 has a thickness of 0.3 mm or less. The thin plate material is either a material with a silicon content of 6.5% or an amorphous material with a Vickers hardness exceeding 1000. For this reason, conventional die designs are expected to be unable to punch through many plate materials properly, significantly shortening the die's lifespan. Furthermore, the stress distribution in the plate material may cause cracks or chips in the plate material. Therefore, in the die used in this embodiment, the clearance between the punch and die during punching is set to less than 2 μm, and strict tolerances and temperature settings are set to concentrate the shear force.

[0064] 24(a) and 24(b) show BMD diagrams (Bending Moment Diagrams). In FIG. 24(a), the clearance between the punch 200 and the die 201 is greater than 2 μm. In this case, the shear force generated in the thin plate 202 is widely distributed. As a result, the thin plate 202 is prone to cracking rather than being cut. Alternatively, sagging and burrs are likely to occur. In contrast, in FIG. 24(b), the clearance between the punch 200 and the die 201 is less than 2 μm. In this case, the shear force generated in the thin plate 202 is concentrated at one point, allowing the punch 200 to cut the thin plate 202.

[0065] The above-described embodiments can also be applied to a dual-radial type permanent magnet motor shown in FIG. 25. One embodiment shown in FIG. 25 has two motor rotors 6 arranged radially inside and outside a motor stator 7. The multiple permanent magnets 5 of the motor rotor 6 arranged radially inside the motor stator 7 are fixed to the outer circumferential surface of a rotor core 9. The multiple permanent magnets 5 of the motor rotor 6 arranged radially outside the motor stator 7 are fixed to the inner circumferential surface of a rotor housing 16. These two motor rotors 6 are connected to a rotating shaft 2 (see FIG. 1) and rotate together. In one embodiment, the permanent magnets 5 are arranged in a Halbach array.

[0066] The above-described embodiments can be applied not only to the radial gap motor shown in Fig. 1, but also to the axial gap motor shown in Figs. 26 and 27 and the coreless motor shown in Fig. 28. The embodiment shown in Fig. 26 has two motor stators 7 arranged on both sides of the motor rotor 6 in the axial direction. The embodiment shown in Fig. 27 has two motor rotors 6 arranged on both sides of the motor stator 7 in the axial direction.

[0067] Figure 29 is a view of one embodiment of a hollow-type coreless motor as seen from the axial direction. Configurations not specifically described are the same as those in the above-described embodiments, and therefore redundant explanations will be omitted. The permanent magnet motor 1 serving as a coreless motor of the embodiment shown in Figure 29 has an annular motor rotor 6 and an annular motor stator 7 surrounding the motor rotor 6. Multiple permanent magnets 5 are fixed to the outer peripheral surface of a rotor core 9. The annular motor rotor 6 is positioned radially inward of the motor stator 7.

[0068] Figure 30 is a view of another embodiment of a hollow-type coreless motor as seen from the axial direction. Configurations not specifically described are the same as those of the above-described embodiments, and therefore redundant explanations will be omitted. The permanent magnet motor 1 serving as a coreless motor of the embodiment shown in Figure 30 has an annular motor rotor 6 and an annular motor stator 7 disposed radially inside the motor rotor 6. Multiple permanent magnets 5 are fixed to the inner circumferential surface of a rotor housing 16. The annular motor rotor 6 is disposed radially outside the motor stator 7 and surrounds it.

[0069] The above-described embodiment can also be applied to an outer rotor type permanent magnet motor described below. FIG. 31 is a cross-sectional view illustrating one embodiment of an outer rotor type permanent magnet motor. Configurations not specifically described are the same as those in the above-described embodiments, and therefore redundant description will be omitted. In the embodiment shown in FIG. 31, the motor rotor 6 is disposed radially outside the motor stator 7. That is, the multiple permanent magnets 5 of the motor rotor 6 are arranged radially outside the multiple teeth 20 of the motor stator 7, and the multiple permanent magnets 5 are fixed to the inner circumferential surface of the rotor housing 16. The annular core 24 is disposed radially inside the multiple teeth 20.

[0070] The rotor housing 16 is fixed to the rotating shaft 2. Therefore, the rotor housing 16, the multiple permanent magnets 5, and the rotating shaft 2 can rotate together. The motor stator 7 is fixed to a stator holder 17, which is fixed to the motor housing 15. The rotating shaft 2 extends through the stator holder 17.

[0071] Fig. 32 is a schematic diagram showing another embodiment of the permanent magnets 5 of the motor rotor 6 used in the permanent magnet motor 1 of each of the above-mentioned embodiments. In the embodiment shown in Fig. 32, five permanent magnets 5 form one group, and a plurality of permanent magnets 5 (40 in this embodiment) consisting of multiple groups are arranged on the outer circumferential surface of the rotor core 9.

[0072] As shown in Figure 32, the five permanent magnets 5 in each group have different magnetization directions. The magnetization direction is the direction of the magnetic flux inside each permanent magnet 5. The magnetization directions of the five permanent magnets 5 that make up each group change slightly clockwise or counterclockwise, so that one group consisting of five permanent magnets 5 forms circular magnetic field lines ML on the outside of the motor rotor 6, as shown in Figure 32.

[0073] In the embodiment shown in Figure 32, the magnetization direction of the leftmost permanent magnet 5 is opposite to that of the rightmost permanent magnet 5. The magnetization direction of the permanent magnet 5 adjacent to the leftmost permanent magnet 5 is oblique to the d-axis of that permanent magnet 5. The magnetization direction of the permanent magnet 5 adjacent to the rightmost permanent magnet 5 is oblique to the d-axis of that permanent magnet 5. The magnetization direction of the permanent magnet 5 located in the middle is perpendicular to the d-axis of that permanent magnet 5. In one embodiment, the magnetization directions of the five permanent magnets 5 gradually change counterclockwise (or clockwise) in increments of 36 degrees.

[0074] By configuring each group with five permanent magnets 5 in this way, the torque of the permanent magnet motor 1 can be improved. FIG. 33 is a graph showing an example of the relationship between the torque ratio of the permanent magnet motor 1 and the number of permanent magnets 5 constituting one group. The torque ratio is a relative value based on the torque of the permanent magnet motor 1 when one permanent magnet 5 constitutes one group. As can be seen from the graph in FIG. 33, the torque ratio increases as the number of permanent magnets 5 constituting each group increases. However, considering the increased cost associated with increasing the number of permanent magnets 5, there is no significant difference between the torque ratio of 1.50 for five permanent magnets 5 and the torque ratio of 1.53 for seven permanent magnets 5. In other words, when considering both torque ratio and cost, the significant number of permanent magnets 5 per group saturates at five. Therefore, in this embodiment, each group contains five permanent magnets 5.

[0075] Each of the five permanent magnets 5 constituting each group has a sector shape. Ideally, these permanent magnets 5 have the same shape and dimensions, but slight differences in dimensions exist. In one embodiment, the variation in the radial positions of the inner circumferential surfaces of the five permanent magnets 5 constituting each group is greater than the variation in the radial positions of the outer circumferential surfaces of the five permanent magnets 5.

[0076] FIG. 34 is an enlarged view of five permanent magnets 5 constituting one group. As shown in FIG. 34, the radial positions of the outer peripheral surfaces of the five permanent magnets 5 constituting one group are almost uniform, and the outer peripheral surfaces of the five permanent magnets 5 are smoothly connected. As a result, the five permanent magnets 5 can provide magnetic force with little uniformity on the outer peripheral side of the motor rotor 6. On the other hand, the radial positions of the inner peripheral surfaces of the five permanent magnets 5 vary more than the outer peripheral surfaces. This uniformity in the radial positions of the inner peripheral surfaces of the permanent magnets 5 can provide an excellent anti-slip effect on the outer peripheral surface of the rotor core 9. Note that in FIG. 34, the uniformity in the radial positions of the inner peripheral surfaces of the permanent magnets 5 is exaggerated.

[0077] FIG. 35 is a diagram showing an embodiment of a cylindrical magnetic body 160 covering the outer circumferential surface of the permanent magnets 5 shown in FIG. 32. The cylindrical magnetic body 160 has a cylindrical shape and is made of a magnetic material. The five permanent magnets 5 constituting each group have a circular magnetic flux, forming a strong magnetic field around the permanent magnets 5. The outer circumferential surfaces of the multiple permanent magnets 5 (40 in this embodiment) in the multiple groups constituting the motor rotor 6 are in close contact with the inner circumferential surface of the cylindrical magnetic body 160. That is, during the manufacture of the motor rotor 6, the multiple permanent magnets 5 are arranged while their outer circumferential surfaces are in close contact with (pressed against) the inner circumferential surface of the cylindrical magnetic body 160, thereby achieving the arrangement of the permanent magnets 5 shown in FIG. 34. The grooves 150 described with reference to FIGS. 11 to 13 may also be applied to the outer circumferential surface of the cylindrical magnetic body 160.

[0078] Of the five permanent magnets 5 that make up each group, two adjacent ones attract each other due to the magnetic force between their north and south poles. For this reason, in manufacturing the motor rotor 6, it is easy to create a magnet block, which is an assembly of two or more permanent magnets 5, before attaching the multiple permanent magnets 5 to the outer circumferential surface of the rotor core 9. That is, a magnet block is created by causing two or more permanent magnets 5 to attract each other using their magnetic force, and the motor rotor 6 is created by arranging multiple magnet blocks created in the same way on the outer circumferential surface of the rotor core 9. This manufacturing method makes it possible to reduce the number of steps in the attachment work for the motor rotor 6.

[0079] In one embodiment, before bonding the magnet block to the rotor core 9, as shown in FIG. 36 , the gaps between the two or more permanent magnets 5 that make up the magnet block are filled with a filler 170 such as resin to correct the circumferential dimension of the magnet block so that the circumferential dimension of the magnet block falls within a predetermined range. As shown in FIG. 36 , the gaps between two adjacent permanent magnets 5 are filled with the filler 170. If dimensional correction is not required, filling with the filler 170 is not necessary. By correcting the circumferential dimension of each magnet block when assembling them in this way, the multiple permanent magnets 5 can be distributed evenly in the circumferential direction when the multiple magnet blocks are attached to the outer circumferential surface of the rotor core 9.

[0080] FIG. 37 is a cross-sectional view showing one embodiment of the motor rotor 6 equipped with the permanent magnet 5 shown in FIG. 32. As shown in FIG. 37, the permanent magnet 5 is covered by the outer cylinder 30 described with reference to FIG. 2. In one embodiment, the thickness of the outer cylinder 30 is 1 mm or less, and the stress generated in the outer cylinder 30 is 0.2% proof stress or less. The permanent magnet 5 is press-fitted into the outer cylinder 30. The pressure applied by this press-fitting is desirably higher than the stress caused by centrifugal force that the outer cylinder 30 experiences within the rated rotational speed range of the motor rotor 6. The centrifugal force can be calculated from the expected rotational speed of the motor rotor 6 and the structure of the motor rotor 6. The grooves 150 described with reference to FIGS. 11 to 13 may be applied to the outer peripheral surface of the outer cylinder 30.

[0081] Any two of the permanent magnets 5 constituting the magnet blocks are in contact with each other or with the filler 170 filled between the two adjacent permanent magnets 5. Therefore, the relative positions of all the permanent magnets 5 are constrained to each other, dispersing stress generated in the outer cylinder 30. Furthermore, the absence of gaps prevents stress concentration.

[0082] The end plates 31 are disposed on both sides of the permanent magnets 5. An annular seal 180 such as an O-ring is disposed between the outer cylinder 30 and the end plate 31. More specifically, the annular seal 180 is disposed between the inner peripheral surface of the outer cylinder 30 and the outer peripheral surface of the end plate 31. The annular seal 180 closes the gap between the outer cylinder 30 and the end plate 31, thereby preventing gas or liquid from coming into contact with the permanent magnets 5. The annular seal 180 is particularly suitable when the liquid handled by the permanent magnet motor 1 is liquid hydrogen. That is, since the permanent magnets 5 are vulnerable to liquid hydrogen, the annular seal 180 can prevent the permanent magnets 5 from being damaged by contact with liquid hydrogen. The annular seal 180 can also be applied to the other embodiments described above.

[0083] In an embodiment in which the outer cylinder 30 is made of carbon fiber reinforced plastic (CFRP), the outer cylinder 30 can be manufactured (created) according to the method shown in Figure 38. As shown in Figure 38, the permanent magnet 5 and rotor core 9 are rotated by a rotating device (not shown), and a sheet-like or string-like fiber material 200 of a certain width is pulled and wound around the outer surface of the permanent magnet 5. The fiber material 200 is wound around a reel 201. The tension applied to the fiber material 200 at this time is a tension that applies a higher stress to the permanent magnet 5 than the stress caused by the centrifugal force that the outer cylinder 30 experiences within the rated rotational speed range of the motor rotor 6. The centrifugal force can be calculated from the expected rotational speed of the motor rotor 6 and the structure of the motor rotor 6.

[0084] In one embodiment, during the manufacture of the motor rotor 6, the permanent magnets 5 are press-fitted at a pressure lower than the centrifugal force to which the outer cylinder 30 is subjected. The stress (MPa) generated by the centrifugal force is concentrated at the position between two adjacent permanent magnets 5. The cross-sectional area of ​​the outer cylinder 30 subjected to this stress is the area of ​​an elongated rectangular cross section extending in the axial direction of the outer cylinder 30. Since the stress is applied to this cross section, in one example, stress calculation is performed using 0.2% yield strength against the centrifugal force and the cross-sectional area.

[0085] In contrast, in this embodiment, by setting the pressure applied during press-fitting to be lower than the stress caused by centrifugal force, it is possible to reduce the cross-sectional area of ​​the outer cylinder 30, i.e., preferably make the outer cylinder 30 thinner. For example, if the stress caused by centrifugal force at the rated rotation speed is 100 MPa and the pressure during press-fitting is 50 MPa, the stress in the outer cylinder 30 when the stress caused by centrifugal force is 50 MPa will be 0 MPa, and the stress in the outer cylinder 30 when the stress caused by centrifugal force is 100 MPa will be 50 MPa. Ideally, by press-fitting the permanent magnet 5 into the outer cylinder 30 with a pressure half the stress caused by centrifugal force, it is possible to halve the thickness of the outer cylinder 30. This reduces the distance between the motor rotor 6 and the motor stator 7, thereby increasing permeance, which also has secondary effects such as a shorter axial length and improved efficiency due to increased torque.

[0086] Next, an embodiment of an inverter and DC power supply that can operate the permanent magnet motor 1 of the above-mentioned embodiment with low loss will be described. Fig. 39 is a schematic diagram showing an embodiment of a motor system that includes the permanent magnet motor 1 of the above-mentioned embodiment, two inverters 51, 52 that supply variable frequency power to the permanent magnet motor 1, and two DC power supplies 55, 56 that supply power to the two inverters 51, 52.

[0087] 39, the motor system includes two inverters 51, 52 for driving the permanent magnet motor 1, and two DC power supplies 55, 56 electrically connected to the two inverters 51, 52 and applying voltage to the inverters 51, 52. The DC power supplies 55, 56 may be batteries. The inverters 51, 52 are provided with six semiconductor elements (or power elements) 58 on the positive side and six semiconductor elements (or power elements) 58 on the negative side to supply positive and negative currents to the U-, V-, and W-phase windings 23 of the permanent magnet motor 1.

[0088] The DC power supply 55 is connected to the inverter 51. More specifically, the positive electrode of the DC power supply 55 is connected to three semiconductor elements 58 on the positive electrode side of the inverter 51, and the negative electrode of the DC power supply 55 is connected to three semiconductor elements 58 on the negative electrode side of the inverter 51. The DC power supply 56 is connected to the inverter 52. More specifically, the positive electrode of the DC power supply 56 is connected to three semiconductor elements 58 on the positive electrode side of the inverter 52, and the negative electrode of the DC power supply 56 is connected to three semiconductor elements 58 on the negative electrode side of the inverter 52. A capacitor 61 for smoothing current is connected in parallel to the DC power supply 55, and a capacitor 62 for smoothing current is connected in parallel to the DC power supply 56.

[0089] The two DC power supplies 55, 56 have the same capacity [V]. For example, when a voltage of 800 V is applied to the permanent magnet motor 1, the two DC power supplies 55, 56 each have a capacity of 400 V. The semiconductor element 58 on the positive side of the inverter 51 is connected to the U-, V-, and W-phase windings of the permanent magnet motor 1. The semiconductor element 58 on the negative side of the inverter 51 is also connected to the U-, V-, and W-phase windings of the permanent magnet motor 1. Similarly, the semiconductor element 58 on the positive side of the inverter 52 is connected to the U-, V-, and W-phase windings 23 of the permanent magnet motor 1. The semiconductor element 58 on the negative side of the inverter 52 is also connected to the U-, V-, and W-phase windings 23 of the permanent magnet motor 1.

[0090] Three electric wires extending from the three output terminals of inverter 51 are joined with three electric wires extending from the three output terminals of inverter 52 to form three output electric wires 64, 65, and 66, respectively, and these three output electric wires 64, 65, and 66 are connected to the U-, V-, and W-phase windings 23 of permanent magnet motor 1, respectively. More specifically, a U-phase electric wire extending from the U-phase output terminal of inverter 51 and a U-phase electric wire extending from the U-phase output terminal of inverter 52 are joined to form U-phase output electric wire 64. A V-phase electric wire extending from the V-phase output terminal of inverter 51 and a V-phase electric wire extending from the V-phase output terminal of inverter 52 are joined to form V-phase output electric wire 65. A W-phase electric wire extending from the W-phase output terminal of inverter 51 and a W-phase electric wire extending from the W-phase output terminal of inverter 52 are joined to form W-phase output electric wire 66. The U-phase output wire 64, the V-phase output wire 65, and the W-phase output wire 66 are connected to the U-phase winding 23, the V-phase winding 23, and the W-phase winding 23, respectively, of the permanent magnet motor 1. Therefore, the combined power of the two inverters 51, 52 is supplied to the permanent magnet motor 1.

[0091] Hereinafter, the three semiconductor elements 58 on the positive side and the three semiconductor elements 58 on the negative side of each of the inverters 51 and 52 are each provided with a switching element 68 that can be turned on and off. The switching elements 68 are basically kept OFF. In this embodiment, taking into consideration the number of switching times, the switching elements 68 are configured from SiC semiconductor elements rather than relays.

[0092] In this way, even if the inverter 51 becomes inoperable, voltages from the two DC power supplies 55, 56 can be supplied to the inverter 52, and the inverter 52 can apply a high voltage to the permanent magnet motor 1. For this reason, the semiconductor elements 58 of each of the inverters 51, 52 have the voltage resistance required to withstand the total voltage of the two DC power supplies 55, 56. In addition, each semiconductor element 58 is equipped with the same number of gate drivers as the number of semiconductor elements 58. The bus bars from the DC power supplies 55, 56 to each terminal have a multi-layer structure to reduce their parasitic impedance.

[0093] By using inverters 51 and 52 configured in this manner, the low inductance of the wiring, including the bus bars, reduces the dV / dt characteristics, enabling operation with a short dead time and achieving a high carrier frequency. In one embodiment, the carrier frequency of each of inverters 51 and 52 is 20 kHz or higher. By employing such a high carrier frequency, each of inverters 51 and 52 can output smooth AC power.

[0094] Next, we will discuss the control of this motor system. The motor system is equipped with a control device 70 that controls the operation of inverters 51 and 52. This control device 70 controls the operation of inverters 51 and 52 using current sensors installed in inverters 51 and 52 and a rotation sensor mounted on rotating shaft 2 (see Figure 1). That is, the control device 70 generates current commands using space vector control based on the d-axis, q-axis, and phase angle, and sends these current commands to inverters 51 and 52. The control device 70 generates the current commands using torque control that uses so-called PI control. PI control serves to correct for changes in conditions such as temperature.

[0095] A specific example of such correction is the correction of the difference in gain between the normal temperature and the current temperature when the temperature of the permanent magnet motor 1 rises from normal temperature to 100°C, causing a decrease in back electromotive force due to a decrease in the magnetic flux of the magnet. Furthermore, in order to drive the permanent magnet motor 1 even when it faces a temporary loss of control due to a current sensor failing to read the current or a rotation sensor failing to read the rotation speed, the control device 70 has a function to ensure control using a pre-prepared map based on the current command and operating conditions immediately prior to the incident.

[0096] The two inverters 51, 52 and two DC power supplies 55, 56 having the configuration shown in Fig. 39 are capable of controlling voltage. That is, if the current to the permanent magnet motor 1 can be supplied by one of the two DC power supplies 55, 56, only one of the two DC power supplies 55, 56 operates, but if one of the two DC power supplies 55, 56 cannot supply the current, both DC power supplies 55, 56 operate.

[0097] By doing this, the voltage is changed in stages during high current operation, when iron loss is particularly large, or during rated operation, when permanent magnet motor 1 is required to operate, and voltage fluctuations are reduced, thereby reducing eddy current loss that occurs in the amorphous material and wire 40 of permanent magnet motor 1 (see Figures 15 and 16).

[0098] In the embodiment shown in FIG. 39, two inverters 51, 52 and two DC power supplies 55, 56 are provided, but three or more inverters and corresponding three or more DC power supplies may be provided.

[0099] 40, two switches 73, 74 may be provided to electrically connect and disconnect the two inverters 51, 52. According to this configuration, when one of the two inverters 51, 52 fails, the voltages of both DC power supplies 55, 56 can be applied to the other of the inverters 51, 52, thereby providing redundancy to the motor system.

[0100] In one embodiment, as shown in FIG. 41 , a chopper circuit 71 may be disposed between a DC power supply 55 and an inverter 51, and a chopper circuit 72 may be disposed between a DC power supply 56 and an inverter 52. The chopper circuits 71 and 72 are configured to control the DC voltage by switching (on / off) DC power using power semiconductor elements. The configurations of the chopper circuits 71 and 72 themselves are well known, so detailed description thereof will be omitted. The chopper circuits 71 and 72 aim to operate the inverters 51 and 52 at an optimal voltage. Specifically, the chopper circuits 71 and 72 provide a high voltage when the rotational frequency is high, thereby setting up a mode in which losses due to the rotational frequency and voltage alternating amplitude are high. In addition, the chopper circuits 71 and 72 provide a low voltage when the rotational frequency is low, thereby setting up a mode in which losses due to the rotational frequency and voltage alternating amplitude are low.

[0101] The magnitude of the voltage causes fluctuations in losses due to the high switching voltage for the inverter. The lower the voltage, the more it can suppress current fluctuations. For example, when generating a current of 150 Arms by alternating between 100A and 200A, the DC copper loss at 1Ω is 30,000W. In contrast, when controlling a current of 150 Arms at 150A, the DC copper loss is 22,500W. As can be seen from this example, suppressing current alternation at a lower voltage reduces copper loss in the inverter, motor, harness, etc., and can be expected to increase overall efficiency.

[0102] Iron loss and eddy current loss also occur depending on the magnitude of the magnetic flux. For example, when controlling a current fluctuating between 200A and 100A to create 150 Arms, if the winding inductance is 1 [H] = 1 [Wb / A], Δφ [Wb] is 100 [Wb], resulting in hysteresis loss from the energy change in the hysteresis curve, or eddy current loss caused by a 100 Wb change in magnetic flux. If control can be maintained at 150A without fluctuation, Δφ [Wb] is 0, and there is no change in magnetic flux, so no loss due to magnetic flux alternation occurs. In this way, operating the system at the optimal voltage and with as little voltage alternation as possible will lead to overall loss improvement.

[0103] 42 is a graph showing one embodiment of the control operation of the inverters 51 and 52. In one embodiment, the inverters 51 and 52 are configured to perform one-pulse control operation. One-pulse control operation is a control operation that outputs a voltage with a pulse waveform that occurs once per sine wave period. The pulse control operation can maximize the voltage utilization rate of the inverters 51 and 52.

[0104] FIG. 43 is a schematic diagram showing an embodiment in which a permanent magnet motor 1 is used as a drive source for a liquid fuel pump 80. The permanent magnet motor 1 is connected to the liquid fuel pump 80. An inverter 81 is located at a distance from the permanent magnet motor 1. As mentioned above, the permanent magnet motor 1 has a configuration that tends to have low inductance. This is due to the use of electromagnets made of superconductors with large magnetic flux and powerful permanent magnets such as SmCo, NdFeB, and FeNi. Using a strong magnet and operating with a high power factor and low impedance reduces AC resistance, enabling the motor to produce large outputs of several hundred kilowatts or more at voltages of around 100 to 1,000 V. This configuration inevitably reduces the number of turns in the windings of the permanent magnet motor 1, lowering the electrical time constant and necessitating an increase in the carrier frequency for control.

[0105] In infrastructure pumps that require large output and mobility pumps that reach temperatures below -30°C, the inverter 81, battery 82, and permanent magnet motor 1 must operate in temperature environments that are harsh for the operation of the power elements of the battery 82 and inverter 81. For this reason, insulation must be provided between the inverter 81 and the permanent magnet motor 1, which can operate in low-temperature or high-temperature environments.

[0106] Therefore, in the embodiment shown in FIG. 43 , a harness or electric wires 89 is arranged between the inverter 81 and the permanent magnet motor 1 to connect them. That is, the battery 82 and the inverter 81 are arranged in an electric room 85 separated from the permanent magnet motor 1. The permanent magnet motor 1 is connected to the inverter 81 by a harness or electric wires 89. In one embodiment, the inverter 81 may be a multi-inverter or dual inverter described with reference to FIGS. 39 to 41 . The permanent magnet motor 1 and the pump 80 are arranged in an explosion-proof area 86 that is independent from the electric room 85. The electric room 85 and the explosion-proof area 86 are located within a plant boundary 87. The permanent magnet motor 1 is connected to the pump 80 to drive it.

[0107] With this structure, the battery 82 and inverter 81 can be cooled separately from the permanent magnet motor 1, and the temperature control of the battery 82 and inverter 81 can be performed independently from the temperature control of the permanent magnet motor 1. Furthermore, the distance between the inverter 81 and the permanent magnet motor 1 makes it easy to control the inverter 81 using the inductance of the electric wires 89. For example, for infrastructure motor control, by placing the electric wires 89 preferably 80 m or more, an inductance of approximately 80 μH or more can be ensured, making it easy to control the inverter 81 using PWM of approximately 1000 V or less.

[0108] FIG. 44 shows an embodiment in which the permanent magnet motor 1 is applied to a dry motor. The pump device shown in FIG. 44 includes the permanent magnet motor 1, a liquid pump 90 connected to the permanent magnet motor 1, and a shaft seal device 91 disposed between the permanent magnet motor 1 and the liquid pump 90. The liquid pump 90 includes a pump casing 92 and an impeller 93 disposed within the pump casing 92. The impeller 93 is connected to the rotating shaft 2 of the permanent magnet motor 1 and is rotated by the permanent magnet motor 1. The pump casing 92 has a liquid suction port 94 and a liquid discharge port 95. The liquid pump suction port 94 is immersed in the liquid, while the permanent magnet motor 1 is disposed above the liquid surface. Therefore, the permanent magnet motor 1 functions as a dry motor.

[0109] Figure 45 is a diagram showing an embodiment in which the permanent magnet motor 1 is applied to a wet motor. The pump device shown in Figure 45 is suitable for transporting liquefied gas. Examples of liquefied gas include liquid hydrogen, liquid helium, liquid methane, liquefied natural gas, liquefied ammonia, liquid nitrogen, liquefied ethylene gas, and liquefied petroleum gas.

[0110] The pump device includes a suction vessel 109, which is a fluid vessel, and a permanent magnet motor 1 and a pump 110 disposed in the suction vessel 109. A small amount of heat from the ambient atmosphere around the pump device is transferred to the liquefied gas in the suction vessel 109. As a result, a portion of the liquefied gas is gasified, forming boil-off gas (BOG) in the suction vessel 109. Therefore, the liquefied gas transfer system includes a boil-off gas discharge pipe 115 that discharges the boil-off gas from the suction vessel 109.

[0111] The pump device further includes a discharge pipe 116 connected to the discharge port of the pump 110 and extending to the outside of the suction vessel 109. The suction vessel 109 has a suction port 117 connected to its side wall. Liquefied gas is introduced into the suction vessel 109 through the suction port 117. During operation of the pump 110, the permanent magnet motor 1 and the entire pump 110 are immersed in the liquefied gas. Therefore, the permanent magnet motor 1 is a wet motor, and the pump 110 is a submersible pump that can operate in liquefied gas.

[0112] The pump 110 has a pump-side rotating shaft 120 connected to the rotating shaft 2, a bearing 121 that rotatably supports the pump-side rotating shaft 120, a plurality of impellers 125 fixed to the pump-side rotating shaft 120, and a pump casing 126 that houses the plurality of impellers 125. In one embodiment, the pump 110 may be provided with a single impeller 125.

[0113] When power is supplied to the permanent magnet motor 1 through a power cable (not shown), the permanent magnet motor 1 rotates the pump-side rotating shaft 120 and the impeller 125 together. As the impeller 125 rotates, the liquefied gas in the suction container 109 is sucked into the pump 110 through the suction port 127 of the pump 110 and is discharged into the discharge pipe 116.

[0114] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0115] 1. Permanent magnet motor 2 rotation axes 5. Permanent magnets 6 Motor rotor 7 Motor Stator 9. Rotor core 11,12 Bearings 15 Motor housing 16 rotor housing 17 Stator holder 20 teeth 23 windings 24 Annular Core 30 outer cylinder 31 End plate M1,M2 Easy magnetization axis 35 Magnetic materials 37 stator core 40 wire 42 Outer coat 45 Conductor 48 Inner membrane 51,52 Inverter 55,56 DC power supply 58 Semiconductor elements 61,62 Capacitor 64, 65, 66 Output wires 68 Switching element 70 Control device 71,72 Chopper circuit 73,74 Switch 80 Liquid fuel pump 81 Inverter 82 Battery 85 Electrical Room 86 Explosion-proof area 87 Plant Boundary 89 Electric wire 90 Liquid Pump 91 Shaft sealing device 92 Pump casing 93 Impeller 94 Intake port 95 Discharge port 109 Suction vessel 110 Pump 115 Boil-off gas discharge pipe 116 Discharge pipe 117 Suction port 120 Pump side rotating shaft 121 Bearings 125 Impeller 126 Pump casing 127 Intake port 150 groove 160 Cylindrical magnetic body 170 Filling material 180 Ring Sticker 200 Fiber 201 reels

Claims

1. A permanent magnet motor, a motor rotor having a plurality of permanent magnets; a motor stator adjacent to the motor rotor; each of the plurality of permanent magnets has a plurality of easy axes of magnetization tilted with respect to the d-axis and the q-axis; the plurality of easy axes include a first easy axis close to the d-axis and a second easy axis close to the q-axis, and an angle of the second easy axis with respect to the q-axis is larger than an angle of the first easy axis with respect to the d-axis; The motor stator is a permanent magnet motor having teeth formed by a plurality of laminated amorphous plates and windings wound around the teeth.

2. 2. The permanent magnet motor according to claim 1, wherein each of the plurality of permanent magnets has a coercive force of 450 kA / m or more, a residual magnetic flux density of 0.7 T or more, and an energy product of 13 MGOe or more.

3. the winding includes a bundle of a plurality of wires and an outer coating covering the bundle of the plurality of wires, Each of the plurality of wires has a conductor and an inner coating covering the conductor, 2. The permanent magnet motor according to claim 1, wherein each of the plurality of wires has a cross-sectional area corresponding to a circular diameter of 0.71 mm or less.

4. 4. The permanent magnet motor according to claim 3, wherein the inner coating has a thickness of 5 μm or less.

5. 2. The permanent magnet motor according to claim 1, wherein each of the plurality of amorphous plates has a thickness of less than 0.3 mm.

6. 2. The permanent magnet motor according to claim 1, wherein the motor stator has an annular core positioned outside the teeth, the annular core being made of an electromagnetic steel sheet.

7. the motor rotor has an outer cylinder surrounding the plurality of permanent magnets, 2. The permanent magnet motor according to claim 1, wherein the outer peripheral surface of the outer cylinder is formed with at least one of grooves extending in the axial direction of the outer cylinder, grooves extending in the circumferential direction of the outer cylinder, and grooves extending obliquely with respect to the circumferential direction of the outer cylinder.

8. A permanent magnet motor according to any one of claims 1 to 7; a plurality of inverters that supply variable frequency power to the permanent magnet motor; A motor system comprising a plurality of DC power supplies that apply voltages to the plurality of inverters, respectively.

Images