Synchronous rotary electric machine

Abstract

This synchronous rotary electric machine (K) comprises a ring-shaped rotor (1) rotated by a rotary shaft (S), and a stator (20, 30) provided around the rotor (1). The rotor (1) comprises: magnet bodies (2) comprising a plurality of permanent magnets that are disposed at equal angular intervals with the same poles facing one another in the circumferential direction centered around the central axis of the rotary shaft (S) outward from the rotary shaft (S), and that are formed to have the same shape and the same size; and a plurality of yokes (3) that are disposed between adjacent magnet bodies (2), have side surfaces each joined to a side surface of a magnet body (2), and are all formed to have a fan shape having a prescribed central angle and to have the same shape and the same size. Where the length of the magnet bodies (2) in the axial direction is Ma, the length of the magnet bodies (2) in the radial direction is Mr, the length of the yokes (3) in the axial direction is Ya, and the length of the yokes (3) in the radial direction is Yr, Ma<Ya and Mr<Yr, and most of the magnetic flux of the magnet bodies (2) is absorbed by the yokes (3).

Description

Synchronous rotating electric motor

[0001] The present invention relates to a synchronous rotating electric machine that can be configured as an electric motor or a generator and that has a ring-shaped rotor that is rotated by a rotating shaft and a stator that is arranged around the rotor, and in particular, to a synchronous rotating electric machine that has a so-called homopolar repulsion type rotor in which permanent magnets are arranged circumferentially via independent fan-shaped yokes so that like poles face each other.

[0002] A known example of this type of synchronous rotating electric machine is disclosed in Japanese Patent Laid-Open Publication No. 6-38415 (Patent Document 1). As shown in FIG. 31 , this machine includes a ring-shaped rotor 100 rotated by a rotating shaft (not shown) and a stator (not shown) disposed around the rotor 100. The rotor 100 includes magnet bodies 101 and multiple yokes 102. The magnet bodies 101 are multiple permanent magnets formed as elongated rectangular parallelepipeds of the same shape and size, arranged at equal angular intervals (45°) around the central axis P of the rotating shaft, with like poles facing each other. The yokes 102 are disposed between adjacent magnet bodies 101, have side surfaces that join the side surfaces of the magnet bodies 101, and are formed as fan-shaped yokes of the same shape and size with a predetermined central angle (45°).

[0003] In the case of a synchronous rotating electric machine Ka, for example, a motor (electric motor), it is desirable to use magnets with high magnetic flux density, such as neodymium-based magnets, instead of ferrite-based magnets for the magnet bodies 101 of the rotor 100 in order to achieve a motor with high energy efficiency. It is desirable to inexpensively produce rotors 100 using magnet bodies 101 with high magnetic flux density. However, in a rotor 100 of the type shown in FIG. 31 in which the magnet bodies 101 are arranged circumferentially via an independent yoke 102, while ferrite-based magnets are not a problem, magnet bodies 101 with high magnetic flux density have strong magnetic force, making the assembly process difficult. For this reason, so-called IPM motors, in which the magnet bodies are embedded in the iron core, have become widespread (see, for example, Japanese Patent Application Laid-Open No. 10-66285). Meanwhile, in fields such as electric vehicles and robots, there is a demand for motors that are as light as possible, yet have high torque and high rotational speed. A rotor 100 of the type in which magnet bodies 101 are arranged in the circumferential direction via an independent yoke 102 has an excellent torque density per unit weight, and therefore it is desirable for this type to become more widespread.

[0004] Japanese Unexamined Patent Publication No. 6-38415 Japanese Unexamined Patent Publication No. 10-66285

[0005] Here, we will again look in detail at the problems associated with a rotor 100 in which magnet bodies 101 are arranged circumferentially via an independent yoke 102. This type of rotor 100 has the following problems. As shown in FIG. 31 , in this rotor 100, magnet bodies 101 are formed as elongated rectangular parallelepipeds, and the base of the sector-shaped yoke 102 is wide, resulting in magnetic flux leakage and a failure to increase the radial magnetic flux density, which is what is normally desired. This prevents effective use of the magnetic flux inherent in the magnets, resulting in poor energy efficiency. Therefore, it is conceivable to narrow the base width of the sector-shaped yoke, thereby significantly reducing the magnetic flux at the base of the yoke and increasing the radial magnetic flux density. However, this approach makes the rotor more susceptible to magnetic saturation, resulting in magnets of the same polarity repelling each other at the base of the yoke, resulting in a strong magnetic force during assembly and making the assembly process difficult.

[0006] The present invention has been made in consideration of these problems, and aims to provide the following synchronous rotating electric machine: That is, a synchronous rotating electric machine with a rotor in which permanent magnets are arranged circumferentially via independent sector-shaped yokes with like poles facing each other, which allows for easy assembly of the magnet body and yoke while counteracting repulsive forces, even when using high-performance magnets such as neodymium magnets. At the same time, the high-performance magnet and yoke are optimally structured to effectively guide the magnetic flux radiated from the magnet body to the yoke, while preventing magnetic saturation and providing a self-stable magnetic integration, allowing most of the magnetic flux density of the high-performance magnet to be absorbed by the yoke and released as magnetic flux contributing to driving force, making the most of it.

[0007] The present inventors, through many years of research into the relationship between high-performance magnet bodies with high magnetic flux density and yokes, have discovered conditions for achieving maximum efficiency without magnetic saturation, and have completed the present invention. Specifically, to solve the above-mentioned problems, the present invention provides a synchronous rotating electric machine comprising: a ring-shaped rotor rotated by a rotating shaft; and a stator disposed around the rotor; the rotor comprises magnet bodies, each of which is composed of a plurality of permanent magnets of the same shape and size, arranged circumferentially around the central axis of the rotating shaft at equal angular intervals with like poles facing each other; and a plurality of yokes, each of which is arranged between adjacent magnet bodies and has a sector-like shape and size with a predetermined central angle, and which has side surfaces that join to the side surfaces of the magnet bodies; wherein Ma is the axial length of the magnet bodies, Mr is the radial length, and Ya is the axial length of the yoke, and Yr is the radial length, so that Ma<Ya and Mr<Yr, and most of the magnetic flux from the magnet bodies is absorbed by the yoke.

[0008] More specifically, when the magnetic flux density is B, the magnet body is made of a magnetic material with 150 mT≦B; when the central angle of the yoke is θ, the relationship is set to 20°<θ<40°; when the axial length of the magnet body is Ma, the radial length is Mr, and the axial length of the yoke is Ya, the radial length is Yr, the relationship is set to Ma<Ya and Mr<Yr; when the side of the magnet body is viewed from a direction perpendicular thereto, the peripheral edge of the side of the yoke protrudes from the peripheral edge of the side of the magnet body to join the side of the magnet body and the side of the yoke; Let Ea be the protrusion dimension of the peripheral edge of the side surface of the yoke in the axial direction relative to the peripheral edge of the side surface of the magnet body on one axial side, Eb be the protrusion dimension of the peripheral edge of the side surface of the yoke on the other axial side relative to the peripheral edge of the side surface of the magnet body on the other axial side, and G be the minimum distance between adjacent magnet bodies, and the following are set: 0.5 mm≦Ea≦5 mm, 0.5 mm≦Eb≦5 mm, and 0.5 mm≦G≦5 mm.

[0009] Here, rare earth magnets can be cited as an example of a magnetic material with a resistance of 150 mT or less. Rare earth magnets are high-performance magnets made by molding and then sintering rare earth metal powder (a total of 17 elements, including neodymium, samarium, and cobalt). There are samarium-cobalt Sm-Co magnets (commonly known as samarium-cobalt magnets) and neodymium-iron-boron Nd-Fe-B magnets (commonly known as neodymium magnets).

[0010] The yoke is made of an appropriate material, such as an iron-based material with a high saturation magnetic flux density, soft magnetic iron, pressed powder iron core, electromagnetic steel sheet, low-carbon steel, silicon steel sheet, etc. If necessary, heat treatment can be performed, or anti-rust plating or painting can be applied.

[0011] As a result, when assembling the rotor, for example, the south pole side of one magnet body (one magnet body) is joined in advance to one side of one yoke, and the south pole side of another magnet body (the other magnet body) is joined to the other side of this yoke, as shown in Figure 5. Alternatively, although not shown, the north pole side of one magnet body (one magnet body) is joined in advance to one side of one yoke, and the north pole side of another magnet body (the other magnet body) is joined to the other side of this yoke.

[0012] In this case, according to the present invention, when one magnet body is brought closer to the yoke to which the other magnet body is attracted and their surfaces are joined, the other magnet body is repelled and temporarily unable to be attracted. If the other magnet body is brought even closer for surface joining, the magnetic flux of its south pole is absorbed by the yoke, allowing the other magnet body to be attracted to the yoke to which the first magnet body is attracted. The reason for this is as follows. In the present invention, as shown in FIG. 6A , the central angle θ of the yoke is set to 20°<θ<40°, and the minimum spacing G between adjacent magnet bodies is set to 0.5 mm≦G≦5 mm, thereby narrowing the base width of the sector-shaped yoke. Furthermore, as shown in FIG. 6B , when the side of the magnet body is viewed perpendicularly, the peripheral edge of the yoke protrudes from the peripheral edge of the side of the magnet body, i.e., the peripheral edge of the yoke (the entire periphery of the yoke) extends beyond the peripheral edge of the magnet body (the entire periphery of the magnet body). 6B and 7A, the periphery of the yoke protrudes 0.5 to 5 mm from the periphery of the magnet body in both the radial and axial directions. Therefore, when the other magnet body is brought even closer to the yoke and surface-joined, the magnetic flux of the south pole is absorbed by the yoke.

[0013] If the yoke does not protrude axially relative to the magnet body, that is, if the axial surfaces of the yoke perpendicular to the central axis and the axial surfaces of the magnet body perpendicular to the central axis are flush (flat), as shown in Figure 7B, the following occurs: High-performance magnets such as neodymium magnets are generally prone to chipping, so their corners are chamfered with a radius (R). As a result, magnetic flux is not absorbed by the yoke through the rounded corners, and instead leaks out. Furthermore, magnetic flux is prone to saturation near the base of the yoke. For these reasons, magnets with the same poles facing the yoke tend to repel each other. When this happens, the yoke attracts one magnet body, preventing it from absorbing all the magnetic flux generated from the south pole of the other magnet body. As a result, magnetic flux near the base of the yoke becomes magnetically saturated, repelling the south pole magnetic flux emanating from the surface of the yoke and preventing it from being attracted. In this state, even if you try to force it, for example by gluing it with an adhesive or by restraining it with a restraining means, you will not be able to use the magnetic flux effectively, and there will be little point in using a high magnetic flux density magnet. In the present invention, this phenomenon of repulsion and inability to attract can be avoided.

[0014] In this way, the magnet body and yoke are assembled sequentially to form a ring-shaped rotor. In the assembled state, the base width of the sector-shaped yoke is narrow. The periphery of the yoke protrudes 0.5 mm to 5 mm from the periphery of the magnet body in both the radial and axial directions. Therefore, even near the base of the yoke, where magnetic saturation is likely to occur, magnetic flux is absorbed by the yoke, and the magnet body is attracted to the yoke. Similarly, magnetic flux is absorbed by the yoke around the entire periphery of the yoke, and the magnet body is attracted to the yoke. In this way, the magnetic flux of the magnet can be guided to the yoke. Therefore, the total magnetic flux density in the radial direction is significantly higher than at the base of the yoke. As a result, the magnetic flux density of the magnet body can be utilized with maximum efficiency. Since magnetic flux density tends to decrease if the periphery of the yoke protrudes more than 5 mm from the periphery of the magnet body, it is desirable to set the protrusion amount to a range of 5 mm or less that allows stable attraction.

[0015] Based on the test results for yoke protrusion shown in Figure 20, it is desirable to set the protrusion amount of the yoke edge relative to the magnet body edge within a range that allows stable attraction of 3 mm or less. That is, preferably, 0.5 mm ≤ Ea ≤ 3 mm, 0.5 mm ≤ Eb ≤ 3 mm, 0.5 mm ≤ G ≤ 3 mm, and more preferably, 0.5 mm ≤ Ea ≤ 1 mm, 0.5 mm ≤ Eb ≤ 1 mm, 0.5 mm ≤ G ≤ 1 mm. Stable attraction is not possible when Ea = 0. In order to make the most of the magnetic flux density of the magnet body with maximum efficiency, it is best to keep the upper limit as small as possible. The protrusion amount can be set within a range that allows stable attraction.

[0016] 14 to 19B show that when the central angle of the yoke is less than 20°, the magnetic flux at the base end of the yoke saturates and the magnet body cannot be attracted, and therefore, in the present invention, the central angle θ of the yoke is set to 20°<θ<40°. This setting reliably avoids a situation where the magnetic flux at the base end of the yoke becomes saturated and the magnet body cannot be attracted. When θ exceeds 40°, the magnetic flux density decreases. Preferably, 20°<θ≦36°.

[0017] Therefore, in the present invention, the magnet body can be stably attached to the yoke without being pressed down by external force, so the yoke and magnet body can be stably mounted and assembled, improving productivity and reducing costs. In the assembled state, all of the magnetic flux generated from the surface of the magnet body is absorbed by the yoke, and the yoke is magnetized so that the magnetic flux can be emitted from the surface, making effective use of the magnetic flux of the high-magnetic flux density magnet. In the present invention, a motor using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more can be driven at maximum efficiency per weight, resulting in a motor that is easy to assemble, has high torque, is highly efficient, and is lightweight.

[0018] If necessary, the protrusion dimension Ec of the radially outer peripheral edge of the side surface of the yoke relative to the radially outer peripheral edge of the side surface of the magnet body is set to 0.5 mm≦Ec≦5 mm. Desirably, 0.5 mm≦Ec≦3 mm, and more desirably, 0.5 mm≦Ec≦1 mm. If Ec = 0, stable attraction is poor. In order to make the most of the magnetic flux density of the magnet body with maximum efficiency, it is better for the upper limit value to be as small as possible. Ec can be set within the range of protrusion amount that allows stable attraction.

[0019] The projection dimension Ed of the radially inner peripheral edge of the side surface of the yoke relative to the radially inner peripheral edge of the side surface of the magnet body is set to 0.5 mm≦G≦5 mm, so it does not need to be particularly specified. However, it is desirable to make the projection dimension Ed as small as possible.

[0020] Furthermore, if necessary, the yoke has an angle θ in the range of 25.7°≦θ<36°, where n is the number of yokes, and n is either n=10, n=12, or n=14, and the magnet body is formed in a substantially rectangular parallelepiped shape. n is an even integer. Examples are n=10 (θ=36°), n=12 (θ=30°), and n=14 (θ≒25.7°). When n=14, the central angle θ is not divisible, but this is within the error range in terms of the adhesion between the magnet body and the yoke, and does not affect the function or effect, causing almost no problem. If gaps are a concern, an adhesive or the like can be used. Within this range, the function and effect of the present invention can be maximized.

[0021] 19A and 19B, the total magnetic flux density cannot be used effectively when n≦8. When n≦16, the yoke becomes thin and is prone to saturation.

[0022] Furthermore, if necessary, the outer end of the side surface of the yoke may be formed with a protruding piece that protrudes in the circumferential direction and against which the outer end surface of the magnet body abuts. In the present invention, the magnet body and yoke can be stably attracted to each other without the need for an external force to press the magnet body against the yoke, so the protruding piece is not particularly necessary, but by providing the protruding piece, the magnet body can be positioned by abutting against the protruding piece during assembly, making assembly even easier. The protruding piece also reliably prevents the magnet body from shifting due to centrifugal force when the rotor rotates.

[0023] Furthermore, if necessary, the rotor may include a holder made of a non-magnetic material through which the rotating shaft is inserted and fixed, and which holds the base ends of the yokes. Since the rotating shaft can be fixed to the holder, the axes of the rotating shaft and the rotor are reliably aligned. Therefore, the rotor can be reliably and easily attached to the rotating shaft. Furthermore, when the rotating shaft is rotated, the rotor can rotate smoothly. Furthermore, since the base ends of the yoke are held by the holder during rotation, deviation of the rotor due to centrifugal force during rotation can be reliably prevented, and smooth rotation can be achieved.

[0024] Specifically, the rotor may include a ring-shaped holder, as required, through which the rotary shaft is inserted and fixed, the holder being made of a non-magnetic material and having a base end portion of each of the yokes held on its outer periphery. The yokes have inner ends provided with engaging portions that protrude circumferentially to the left and right, and the holder has outer peripheries formed with engaged portions that engage with the engaging portions when inserted from one or the other surface of the holder that is perpendicular to the central axis.

[0025] As a result, when assembling the rotor, for example, a required number of first units are prepared in advance, each having the north pole side of one magnet bonded to one side of a yoke, exposing the south pole side of the magnet, and a required number of second units are prepared in advance, each having the south pole side of one magnet bonded to one side of a yoke, exposing the north pole side of the magnet. Next, these first and second units are joined alternately in order. In this case, first, either the first or second unit is attached to the holder by engaging the engaging portion of its yoke with the engaged portion of the holder. Next, the other of the first or second unit is attached to the holder by engaging the engaging portion of its yoke with the engaged portion of the holder.

[0026] In this case, the magnet body of either the first unit or the second unit slides onto the other side of the yoke of either the first unit or the second unit and is joined. At this time, at the beginning of the sliding, they have the same polarity and repel each other, temporarily preventing them from being attracted to each other. However, as described above, as they are further slid closer together and surface-to-surface joined, the magnetic flux of the magnet body is absorbed by the yoke, allowing them to be attracted to each other. In this way, the first unit and the second unit are joined alternately in order. In this case, all that is required is to engage the engaging portion of the yoke with the engaged portion of the holder and press it in, making positioning and assembly easy.

[0027] Next, the rotor holder is attached to the rotating shaft. In this case, since the holder can be fixed to the rotating shaft, the axes of the rotating shaft and the rotor are reliably aligned. This allows the rotor to be attached to the rotating shaft reliably and easily. Furthermore, when the rotating shaft is rotated, the rotor rotates smoothly. Furthermore, since the engaging portion of the yoke engages with the engaged portion of the holder during rotation, it is possible to reliably prevent misalignment due to centrifugal force during rotor rotation, allowing for smooth rotation.

[0028] Furthermore, as necessary, the rotor may include a holder having a pair of plates made of a non-magnetic material, through which the rotating shaft is inserted and fixed, and attached to one surface and the other surface of each yoke perpendicular to the central axis, respectively, to hold the base end of each yoke. A first bolt insertion hole is formed in the base end of each yoke along the axial direction of the rotating shaft. A plurality of second bolt insertion holes corresponding to the first bolt insertion holes are formed in each plate of the holder. Bolts made of a non-magnetic material are inserted into the second bolt insertion holes of the one plate, the first bolt insertion holes of each yoke, and the second bolt insertion holes of the other plate. Nuts made of a non-magnetic material are threaded onto each bolt. Each yoke is held between the pair of plates.

[0029] As a result, when assembling the rotor, for example, a required number of first units are prepared in advance, each having a magnet body with its north pole side bonded to one side of a yoke and its south pole side exposed, and a required number of second units are prepared in advance, each having a magnet body with its south pole side bonded to one side of a yoke and its north pole side exposed. These first and second units are then joined alternately in order. In this case, bolts are inserted into the second bolt insertion holes of one plate of the holder to attach the units. Then, first, either the first or second unit is attached to one plate by inserting bolts into the first bolt insertion holes of the yoke. Next, the other of the first or second unit is attached to the one plate by inserting bolts into the first bolt insertion holes of the yoke.

[0030] In this case, the magnet body of either the first unit or the second unit slides onto the other side of the yoke of either the first unit or the second unit and is joined. At the beginning of the sliding, the magnets have the same polarity and repel each other, temporarily preventing them from adhering. However, as described above, as the magnets are further slid closer together and surface-to-surface joined, the magnetic flux of the magnet body is absorbed by the yoke, allowing them to be attracted to each other. In this manner, the first unit and the second unit are joined alternately in order. This is achieved by simply inserting a bolt into the first bolt insertion hole of the yoke and pushing it in, which allows for easy positioning and assembly. Finally, the other plate is attached by inserting a bolt into its second bolt insertion hole and screwing a nut onto the bolt. This results in each yoke being sandwiched between the pair of plates.

[0031] Next, the rotor holder is attached to the rotating shaft. In this case, since the holder can be fixed to the rotating shaft, the rotor and the rotating shaft are reliably aligned. This allows the rotor to be attached to the rotating shaft reliably and easily. Furthermore, when the rotating shaft is rotated, the rotor rotates smoothly. Furthermore, since each yoke is sandwiched between a pair of plates with a bolt inserted into its first bolt insertion hole, deviation due to centrifugal force during rotor rotation is reliably prevented, allowing for smooth rotation. Furthermore, since the first bolt insertion holes are formed at the base end of the yoke and the magnetic resistance is increased due to the use of non-magnetic bolts, the width of the base end of the yoke is effectively reduced, making it easier to guide the magnetic flux of the magnet to the yoke.

[0032] Furthermore, if necessary, the synchronous rotating electric machine may include a radial position stator as the stator, which faces the outer peripheral surface of the rotor via an air gap and has a plurality of stator coils arranged at predetermined intervals on a circumference centered on the rotation axis of the rotor.

[0033] Furthermore, if necessary, the synchronous rotating electric machine may include, as the stator, an axial position stator having a plurality of stator coils arranged at predetermined intervals on a circumference centered on the rotation axis of the rotor and facing one and / or the other side perpendicular to the central axis of the rotor via an air gap.

[0034] Furthermore, as required, the synchronous rotating electric machine may comprise, as the stators, a radial position stator having a plurality of stator coils facing the outer peripheral surface of the rotor via an air gap and arranged at predetermined intervals on a circumference centered on the rotational axis of the rotor, and an axial position stator having a plurality of stator coils facing one and / or the other surface of the rotor perpendicular to the central axis via an air gap and arranged at predetermined intervals on a circumference centered on the rotational axis of the rotor.

[0035] Because the motor has both a radial position stator and an axial position stator, the stator coil can easily capture the rotor's magnetic flux, improving the efficiency of the synchronous rotating electric machine. For example, a motor using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more can produce a highly efficient motor.

[0036] Furthermore, if necessary, the synchronous rotating electric machine may include a radial position stator as the stator, which includes a plurality of stator coils facing the outer peripheral surface of the rotor via an air gap and arranged at predetermined intervals on a circle centered on the rotation axis of the rotor, and a plurality of teeth corresponding to the plurality of stator coils and around which the stator coils are wound. The teeth of the radial position stator include a main body facing the outer peripheral surface of the rotor via an air gap, and a protruding strip that protrudes from both ends of the main body in the central axis direction toward the central axis and has facing portions that face one side and the other side of the rotor via an air gap. The stator coils are wound around the teeth with at least the facing portions of the protruding strip exposed.

[0037] The radially positioned stator teeth have a main body facing the outer peripheral surface of the rotor and a protruding strip with a facing portion facing one side and the other side of the rotor, so the stator coil can easily capture the rotor's magnetic flux. This improves the efficiency of the synchronous rotating electric machine. For example, a motor using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more can achieve a highly efficient motor.

[0038] In this case, it is effective to interpose a non-magnetic insulating member between the main body and the ridges, which balances the amount of magnetic flux density radiated from the main body facing the outer circumferential surface of the rotor and the ridges having facing portions facing one side and the other side of the rotor.

[0039] In this case, it is also effective to arrange multiple rotor-stator pairs in a row on the same rotating shaft. As a result, the magnetic flux density absorbed by the yoke from the high-performance magnet and radiated from the outer circumferential surface of the rotor and the opposing portions facing one and the other of the rotor can be guided to the stator coil to the maximum extent possible, thereby improving the efficiency of the synchronous rotating electric machine. For example, a motor using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more can provide a highly efficient motor.

[0040] According to the present invention, even when using high-performance magnets such as neodymium magnets, the magnet body and yoke can be easily assembled while counteracting repulsive forces. Furthermore, the magnetic flux radiated from the magnet body is effectively guided to the yoke, while simultaneously preventing magnetic saturation, stably integrating the high-performance magnet and yoke, and maximizing the magnetic flux density of the high-performance magnet. This allows for use as a highly efficient electric motor or generator equipped with a ring-shaped rotor and a stator surrounding the rotor. This is particularly ideal for applications requiring limited external dimensions and lightweight design, such as small, slender spindle motors, motors mounted on robot arm joints or the end of robot arms, and medical motors. These applications are extremely useful for machine tools, robots, handheld hand tools, various medical devices, drones, and other applications where compactness and light weight are desired.

[0041] FIG. 1A is an exploded perspective view of a synchronous rotating electric machine according to a first embodiment of the present invention, showing a rotor and a stator. FIG. 1B is a perspective view of a synchronous rotating electric machine according to the first embodiment of the present invention, showing the rotor and stator assembled. FIG. 2 is an exploded perspective view showing the structure of the rotor of the synchronous rotating electric machine according to the first embodiment of the present invention. FIG. 3 is a view showing the rotor of the synchronous rotating electric machine according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view showing the relationship between the rotor of the synchronous rotating electric machine according to the first embodiment of the present invention and the stator that is circumferentially surrounding the rotor via an air gap. FIG. 5 shows the basic structure and relationship between magnet bodies and a yoke in a rotor of a synchronous rotating electric machine according to the present invention. The left figure is a front view showing a state before one magnet body is attracted to the yoke to which the other magnet body is attracted, and the right figure is a front view showing a state in which the other magnet body has been attracted to the yoke to which the one magnet body has been attracted. FIG. 6A is a front view showing the basic structure and relationship between magnet bodies and a yoke in a rotor of a synchronous rotating electric machine according to the present invention, showing a state in which the other magnet body has been attracted to the yoke to which the one magnet body has been attracted. FIG. 6B is a side view of a rotor for a synchronous rotating electric machine according to the present invention, showing the basic structure of the magnet bodies and the yoke and their relationship, as viewed from a direction perpendicular to the side of the yoke. FIG. 7A is a cross-sectional view of the rotor for a synchronous rotating electric machine according to the present invention, taken along line A-A in FIG. 6A , showing the basic structure of the magnet bodies and the yoke and their relationship, in which the yoke protrudes axially relative to the magnet bodies. FIG. 7B is a cross-sectional view equivalent to FIG. 7A , showing a state in which the yoke does not protrude axially relative to the magnet bodies. FIG. 8 is a perspective view of a synchronous rotating electric machine according to a second embodiment of the present invention. FIG. 9 is a cross-sectional view of a modified example of the synchronous rotating electric machine according to the second embodiment of the present invention. FIG. 10 is a front view of a synchronous rotating electric machine according to a third embodiment of the present invention. FIG. 11A is a front view of a synchronous rotating electric machine according to a fourth embodiment of the present invention, showing a rotor and a stator. FIG. 11B is a cross-sectional view of a synchronous rotating electric machine according to the fourth embodiment of the present invention, showing one rotor and one stator assembled (single axial type).FIG. 11C is a cross-sectional view of a synchronous rotating electric machine according to a fourth embodiment of the present invention, showing two rotors and one stator assembled (double axial type). FIG. 12 is a diagram showing the relationship between the rotor and stator of a synchronous rotating electric machine according to a fifth embodiment of the present invention. FIG. 13 is an exploded perspective view showing another example of a rotor in a synchronous rotating electric machine according to each embodiment of the present invention. FIG. 14 is a diagram showing the relationship between a magnetic flux density sensor and a state in which one magnetic body is attracted to a yoke to which the other magnetic body is attracted in Test Example 1 of the present invention (a test relating to the relationship between the distance between the magnetic body and the yoke and the magnetic flux density on the yoke surface). FIG. 15 is a graph showing the measurement results of the magnetic flux density on the yoke surface in Test Example 1 of the present invention. FIG. 16 is a graph showing the measurement results of Test Example 2 of the present invention (measurement of the magnetic flux density on the yoke surface and the magnetic flux density on the surface of the magnet body). FIG. 17A is a diagram showing the state in which one magnetic body is attracted to a yoke to which another magnetic body is attracted, in relation to the measurement location of the magnetic flux density sensor (the center of the outer peripheral portion spreading in the radial direction of the sector), relating to Test Example 3 of the present invention (Test <Part 1> on the central angle θ of the yoke). FIG. 17B is a graph showing the results of measuring the magnetic flux density on the peripheral surface of the yoke for different central angles of the yoke, relating to Test Example 3 of the present invention (Test <Part 1> on the central angle θ of the yoke). FIG. 18A is a diagram showing the measurement location of the magnetic flux density sensor, relating to Test Example 4 of the present invention (Test <Part 2> on the central angle θ of the yoke). FIG. 18B is a graph showing the results of measuring the magnetic flux density for different central angles of the yoke, relating to Test Example 4 of the present invention (Test <Part 2> on the central angle θ of the yoke). 19A is a graph showing the results of calculating the total magnetic flux intensity by the number of poles (the magnetic flux strength per unit of the magnet body multiplied by the number of poles (the number of yokes) for each different central angle of the yoke in Test Example 5 of the present invention (Test <Part 3> for Central Angle θ of the yoke), and Fig. 19B is a graph showing the results of calculating the total magnetic flux intensity by the number of poles (the magnetic flux strength per unit of the magnet body multiplied by the number of poles (the number of yokes) for each different central angle of the yoke in Test Example 5 of the present invention (Test <Part 3> for Central Angle θ of the yoke),FIG. 20 is a graph showing measurement results of magnetic flux density for yokes with different axial widths relative to the magnet body (the magnetic flux density measurement locations were the same as in Test Example 1 ( FIG. 14 )) relating to Test Example 6 of the present invention (a test on the amount of protrusion of the yoke from the magnet body). FIG. 21 is a graph showing measurement results of the relationship between thickness and magnetic flux density for a neodymium magnet (a test on the thickness (circumferential length Me of the magnet body)) relating to Test Example 7 of the present invention (a test on the thickness of the magnet body (the circumferential length Me of the magnet body)). FIG. 22A is a diagram showing measurement locations of the magnetic flux density sensor relating to Test Example 8 of the present invention (a test on the material of the holder). FIG. 22B is a diagram showing measurement results for each holder material relating to Test Example 8 of the present invention (a test on the material of the holder). FIG. 23A is a graph showing measurement results of the relationship between yoke angle and magnetic flux density for different combinations of neodymium magnet size and yoke size relating to Test Example 9 of the present invention (a test on the size of the rotor). Figure 23B is a graph showing the results of measuring the relationship between the yoke angle and magnetic flux density for different combinations of neodymium magnet size and yoke size in Test Example 9 (Test on Rotor Size) of the present invention. Figure 24A is a graph showing the relationship between the yoke area ratio and the actual yoke surface area ratio (shaded area) for different combinations of neodymium magnet size and yoke size in Test Example 9 (Test on Rotor Size) of the present invention. Figure 25 is a graph visually illustrating the concept of the torque-to-weight ratio coefficient F per unit weight for the yoke and the two neodymium magnets sandwiching it in an analysis to determine the optimal rotor size for obtaining maximum torque per weight in Test Example 9 (Test on Rotor Size) of the present invention. Figure 26A is a graph showing the relationship between magnet length Mr and torque-to-weight ratio coefficient F for a radial-type synchronous rotating electric machine. Figure 26B is a graph showing the relationship between magnet length Mr and torque for a radial-type synchronous rotating electric machine. Figure 26C is a graph showing the relationship between magnet length Mr and torque-to-weight ratio coefficient F for an axial-type synchronous rotating electric machine. Fig. 26D is a graph showing the relationship between the magnet length Mr and the torque of an axial type synchronous rotating electric machine. Fig. 27 is a diagram showing a prototype of a rotor that can be used in the synchronous rotating electric machine according to each embodiment of the present invention.FIG. 28A is a perspective view of Example 1 (Prototype 1: radial gap motor) according to an embodiment of the present invention. FIG. 28B is a perspective view of Example 2 (Prototype 2: single axial gap motor) according to an embodiment of the present invention. FIG. 28C is a perspective view of Example 3 (Prototype 3: double axial gap motor) according to an embodiment of the present invention. FIG. 29A is a diagram showing test results for Examples 1 to 3 and estimated values ​​for Example 4 according to Test Example 10 (torque measurement test for Examples) of the present invention. FIG. 29B is a diagram showing data for Comparative Examples 1 to 7 (commercially available motors 1 to 7) according to Test Example 10 (torque measurement test for Examples). FIG. 30 is a diagram showing a modified example of a rotor according to an embodiment of the present invention. FIG. 31 is a diagram showing a rotor of a conventional synchronous rotating electric machine together with its problems.

[0042] A synchronous rotating electric machine according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. Figures 1A to 4 show a synchronous rotating electric machine K according to a first embodiment of the present invention. This synchronous rotating electric machine K includes a ring-shaped rotor 1 rotated by a rotating shaft S (Figure 4), and a radial position stator 20 as a stator provided around the rotor 1.

[0043] The rotor 1 includes a plurality of magnet bodies 2, a plurality of yokes 3, and a holder 10. The plurality of magnet bodies 2 are permanent magnets formed to the same shape and size. The magnet bodies 2 are arranged at equal angular intervals around the rotation axis S, with like poles facing each other in the circumferential direction around the central axis P of the rotation axis S. The yokes 3 are arranged between adjacent magnet bodies 2, have side surfaces that join to the side surfaces of the magnet bodies 2, and are formed to be sector-shaped with a predetermined central angle, the same shape, and the same size. The holder 10 is a non-magnetic material, through which the rotation axis S is inserted and fixed, and holds the base ends of the yokes 3.

[0044] The magnet body 2 is formed of a magnetic material with a magnetic flux density of 150 mT≦B, where B is its magnetic flux density. A rare earth magnet is an example of a magnetic material with a magnetic flux density of 150 mT≦B. Rare earth magnets are high-performance magnets made by molding and then sintering rare earth metal powder (a total of 17 elements, including neodymium, samarium, and cobalt). These magnets include samarium-cobalt (Sm-Co) magnets (commonly known as samarium-cobalt magnets) and neodymium-iron-boron (Nd-Fe-B) magnets (commonly known as neodymium magnets). In this embodiment, a neodymium magnet is used. The magnet body 2 is formed in a substantially rectangular parallelepiped shape.

[0045] For the yoke 3, an appropriate material is selected, such as an iron-based material with high magnetic permeability and high saturation magnetic flux density, soft electromagnetic iron, pressed powder iron core, low carbon steel, silicon steel plate, etc. If necessary, heat treatment may be performed, or plating or painting may be performed to prevent rust.

[0046] The yoke 3 has a central angle θ of 20°<θ<40°. Preferably, θ is 20°<θ≦36°. More preferably, the angle is in the range of 25.7°<θ≦36°, and the number of yokes 3 is n, where n is either n=10, n=12, or n=14. In this embodiment, n=10 (θ=36°). The outer end of the side of the yoke 3 is formed with a protrusion 4 that protrudes along the circumferential direction and abuts against the outer end surface of the magnetic body 2. The inner end of the yoke 3 is provided with an engaging portion 5 that protrudes left and right in the circumferential direction. Meanwhile, the holder 10 is formed with an engaged portion 6 that engages with the engaging portion 5 when inserted from one side or the other side perpendicular to the central axis P of the holder 10. The base end 7 of the yoke 3 and the engaging portion 5 are integrally formed in a substantially T-shape. On the other hand, the engaged portion 6 is formed in a concave shape so that the T-shaped portion consisting of the base end portion 7 of the yoke 3 and the engaging portion 5 can fit into it. In this embodiment, ten engaged portions 6 are formed at equal angular intervals, matching the number of yokes 3 (n=10).

[0047] As shown in Figures 6A and 6B, the axial length of the magnet body 2 is Ma, the radial length is Mr, and the axial length of the yoke 3 is Ya, the radial length is Yr. Ma < Ya, Mr < Yr are set. That is, when the side of the magnet body 2 is viewed from a direction perpendicular to it, the peripheral edge of the side of the yoke 3 protrudes from the peripheral edge of the side of the magnet body 2, joining the side of the magnet body 2 and the side of the yoke 3. In this embodiment, since the yoke 3 has the above-mentioned engaging portion 5, the radial length Yr of the yoke 3 is set to include the engaging portion 5. For example, the radius R of the rotor 1 (Figure 3) is approximately 20 mm ≤ R ≤ 80 mm, and the values ​​are set to 5 mm ≤ Ya ≤ 100 mm and 5 mm ≤ Yr ≤ 55 mm. The circumferential length Me (thickness) of the magnet body 2 varies depending on the radius R, but is set to 2 mm ≤ Me ≤ 20 mm. Furthermore, from Test Example 9 described later, it was found that the optimum size of the magnet body 2 is 8 mm≦Ma≦10 mm and 5 mm≦Mr≦25 mm. The dimensions of each part are not limited to these.

[0048] Furthermore, if the protrusion dimension of the peripheral edge of one side of the side of the yoke 3 in the axial direction relative to the peripheral edge of one side of the side of the magnet body 2 in the axial direction is Ea, the protrusion dimension of the peripheral edge of the other side of the side of the yoke 3 in the axial direction relative to the peripheral edge of the other side of the side of the magnet body 2 in the axial direction is Eb, and the minimum distance between adjacent magnet bodies 2 (between the adjacent inner peripheral edges of a pair of magnet bodies 2 joined to one yoke 3) is G, the following are set: 0.5 mm≦Ea≦5 mm, 0.5 mm≦Eb≦5 mm, and 0.5 mm≦G≦5 mm. Desirably, 0.5 mm≦Ea≦3 mm, 0.5 mm≦Eb≦3 mm, and 0.5 mm≦G≦3 mm, and more desirably, 0.5 mm≦Ea≦1 mm, 0.5 mm≦Eb≦1 mm, and 0.5 mm≦G≦1 mm.

[0049] Furthermore, when the protrusion dimension of the radially outer peripheral edge of the side surface of the yoke 3 relative to the radially outer peripheral edge of the side surface of the magnet body 2 is defined as Ec, it is set to 0.5 mm≦Ec≦5 mm. Preferably, 0.5 mm≦Ec≦3 mm, and more preferably, 0.5 mm≦Ec≦1 mm. If Ec = 0, stable attraction is not possible. To make the most of the magnetic flux density of the magnet body with maximum efficiency, it is better to keep the upper limit as small as possible. The protrusion amount can be set within a range that allows stable attraction.

[0050] The projection dimension Ed of the radially inner peripheral edge of the side surface of the yoke 3 relative to the radially inner peripheral edge of the side surface of the magnet body 2 is set to 0.5 mm≦G≦5 mm, so it does not need to be particularly specified. However, it is desirable to make the projection dimension Ed as small as possible. In this embodiment, since the engaging portion 5 is provided, the projection dimension Ed is set to include the engaging portion 5.

[0051] The radial position stator 20 as a stator includes a plurality of (12 in this embodiment) stator coils 21 and a plurality of (12 in this embodiment) teeth 22. The stator coils 21 face the outer peripheral surface of the rotor 1 via an air gap, and are arranged at predetermined intervals on a circumference centered on the rotation axis S of the rotor 1. The teeth 22 are provided corresponding to each of the plurality of stator coils 21, and the stator coils 21 are wound around the teeth 22. The teeth 22 are fixed to a ring-shaped frame 23 made of a non-magnetic material that surrounds the rotor 1.

[0052] As shown in Figure 4, the teeth 22 of the radial stator 20 include a body 24 facing the outer peripheral surface of the rotor 1 across an air gap, and ridges 25 protruding from both ends of the body 24 in the direction of the central axis P toward the central axis P. The ridges 25 have facing portions 25a that face one side and the other side of the rotor 1 across an air gap. A non-magnetic insulating member 26 is interposed between the body 24 and the ridges 25. The stator coils 21 are wound around the teeth 22, with at least the facing portions 25a of the ridges 25 exposed, around a radial axis Q that is perpendicular to the central axis P and passes through the body 24.

[0053] 2, when assembling the rotor 1, for example, a required number of first units U1 are prepared in advance, each having the north pole side of one magnet body 2 joined to one side of one yoke 3, exposing the south pole side of this magnet body 2, and second units U2 each having the south pole side of one magnet body 2 joined to one side of one yoke 3, exposing the north pole side of this magnet body 2. In this case, the magnet body 2 can be positioned by abutting against the protrusion 4 during assembly, making assembly even easier.

[0054] Then, the first unit U1 and the second unit U2 are alternately assembled in order to the holder 10. In this case, first, either the first unit U1 or the second unit U2 is attached to the holder 10 by engaging the engaging portion 5 of its yoke 3 with the engaged portion 6 of the holder 10. Next, the other of the first unit U1 or the second unit U2 is attached to the holder 10 by engaging the engaging portion 5 of its yoke 3 with the engaged portion 6 of the holder 10.

[0055] At this time, the magnet body 2 of either the first unit U1 or the second unit U2 slides onto the other side of the yoke 3 of either the first unit U1 or the second unit U2 and is joined. As shown in Figure 5, at the beginning of the sliding, they have the same polarity and repel each other, preventing them from attracting. However, this is only a temporary phenomenon, and as they are further slid closer together and surface-to-surface joined, the magnetic flux of the magnet body 2 is absorbed by the yoke 3, allowing them to be attracted to each other. In this way, the first unit U1 and the second unit U2 are joined alternately in order. Therefore, simply engaging and pushing the engaging portion 5 of the yoke 3 into the engaged portion 6 of the holder 10 is all that is required, making positioning and assembly easy.

[0056] Specifically, although the first unit U1 and the second unit U2 have the same polarity and repel each other, they cannot be attracted to each other if they are brought closer together and surface-joined. This is because, as shown in FIG. 6A , in this embodiment, the central angle θ of the yoke 3 is set to 20°<θ<40°, and the minimum spacing G between adjacent magnet bodies 2 is set to 0.5 mm≦G≦5 mm, thereby narrowing the base width of the sector-shaped yoke 3. Furthermore, as shown in FIG. 6B , when the side of the magnet body 2 is viewed from a direction perpendicular to the side of the magnet body 2, the periphery of the yoke 3 protrudes from the periphery of the side of the magnet body 2. In other words, the periphery of the yoke 3 (the entire periphery of the yoke 3) extends beyond the periphery of the magnet body 2 (the entire periphery of the magnet body 2). In particular, as shown in FIGS. 6B and 7A , the periphery of the yoke 3 protrudes from the periphery of the magnet body 2 by 0.5 mm to 5 mm in both the radial and axial directions. As a result, when one magnet body 2 is brought even closer to the yoke 3 to which the other magnet body 2 is attracted so as to be surface-joined, the magnetic flux of the south pole of the other magnet body 2 is absorbed by the yoke 3. Furthermore, the projection dimension Ec of the radially outer peripheral edge of the side surface of the yoke 3 relative to the radially outer peripheral edge of the side surface of the magnet body 2 is set to 0.5 mm≦Ec≦5 mm, which also ensures stable attraction.

[0057] In this way, the magnet bodies 2 and yoke 3 are assembled in order to form the ring-shaped rotor 1. In assembling this rotor 1, the magnet bodies 2 can be stably attracted to the yoke 3 without being pressed down by external force, allowing for stable mounting and assembly, improving productivity and reducing costs. Next, the holder 10 for this rotor 1 is attached to the rotating shaft S. In this case, because the holder 10 can be fixed to the rotating shaft S, the axes of the rotating shaft S and the rotor 1 are reliably aligned. This allows for reliable and easy attachment of the rotor 1 to the rotating shaft S. The rotor 1 is then assembled with the stator 20 to complete the synchronous rotating electric machine K.

[0058] In this synchronous rotating electric machine K, the base width of the sector-shaped yoke 3 in the rotor 1 is narrow, and the periphery of the yoke 3 protrudes 0.5 mm to 5 mm from the periphery of the magnet body 2 in both the radial and axial directions, enabling magnetic flux to be guided to the yoke 3. As a result, as shown in FIG. 6A , the total magnetic flux density in the radial direction is significantly higher than at the base (base end 7) of the yoke 3, thereby maximizing the magnetic flux density of the magnet body 2. In other words, in the rotor 1, all magnetic flux generated from the surface of the magnet body 2 is absorbed by the yoke 3, allowing the yoke 3 to be magnetized and the magnetic flux to be emitted from its surface, effectively utilizing the magnetic flux of high-magnetic flux density magnets. For example, a motor using a high-performance magnet, such as a neodymium magnet with a magnetic flux density of 150 mT or more, can be driven with maximum efficiency per weight, resulting in a motor that is easy to assemble, high torque, highly efficient, and lightweight.

[0059] Furthermore, the outer end of the side surface of the yoke 3 is formed with a protrusion 4 that protrudes in the circumferential direction and comes into contact with the outer end surface of the magnet body 2, thereby reliably preventing displacement of the magnet body 2 due to centrifugal force when the rotor 1 rotates. Also, the engaging portion 5 of the yoke 3 engages with the engaged portion 6 of the holder 10, reliably preventing displacement of the yoke 3 due to centrifugal force when the rotor 1 rotates, ensuring smooth rotation.

[0060] The synchronous rotating electric machine K also includes a radial position stator 20 as a stator. The teeth 22 of the radial position stator 20 include a main body 24 facing the outer peripheral surface of the rotor 1 and a protruding strip 25 having facing portions 25a facing one side and the other side of the rotor 1. Therefore, the stator coil 21 easily captures the magnetic flux of the rotor 1. This improves the efficiency of the synchronous rotating electric machine K. For example, a motor using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more can achieve a highly efficient motor. Furthermore, a non-magnetic insulating member 26 is interposed between the main body 24 and the protruding strip 25, thereby achieving a balance between the magnetic flux densities emitted from the main body 24 and the protruding strip 25.

[0061] FIG. 8 shows a synchronous rotating electric machine K according to a second embodiment. In the synchronous rotating electric machine K, a plurality of pairs of the rotor 1 and stator 20 according to the first embodiment are arranged in a row on the same rotating shaft S. This improves the efficiency of the synchronous rotating electric machine K. For example, a motor using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more can provide a highly efficient motor. This configuration is particularly effective when the motor diameter is not required to be large but high torque is desired.

[0062] Fig. 9 shows a modified example of the synchronous rotating electric machine K according to the second embodiment. In this modified example, the teeth 22 of each stator 20 shown in Fig. 8 are integrated, the ridges 25 of adjacent teeth 22 are shared, and the stator coil 21 is wound around the entire stator with the opposing portions 25a of the ridges 25 exposed. This allows the motor to effectively utilize the magnetic flux generated from both sides of the ridges 25, making it possible to effectively utilize electrical energy and increase torque per unit weight.

[0063] 10 shows a synchronous rotating electric machine K according to a third embodiment. The synchronous rotating electric machine K includes a radial position stator 20 as a stator. The radial position stator 20 faces the outer peripheral surface of the rotor 1 via an air gap and includes a plurality of stator coils 21 (12 in this embodiment) arranged at predetermined intervals on a circumference centered on the rotation axis S of the rotor 1, and a plurality of teeth 22 (12 in this embodiment) provided corresponding to the plurality of stator coils 21 and around which the stator coils 21 are wound. The teeth 22 are fixed to the inside of a ring-shaped frame 27 made of a non-magnetic material that surrounds the rotor 1.

[0064] 11A to 11C show a synchronous rotating electric machine K according to a fourth embodiment. As shown in FIG. 11A , the synchronous rotating electric machine K includes an axial position stator 30 as a stator. The axial position stator 30 includes a plurality of (12 in this embodiment) stator coils 21 and a plurality of (12 in this embodiment) teeth 22. The stator coils 21 have one and the other surfaces that face a surface perpendicular to the central axis P of the rotor 1 with an air gap between them, and are arranged at predetermined intervals on a circumference centered on the rotation axis S of the rotor 1. The teeth 22 are provided corresponding to the plurality of stator coils 21, respectively, and the stator coils 21 are wound around the teeth 22. The rotor 1 has one surface perpendicular to the central axis P of the rotor 1 and is fixed to a disk 31 centered on the central axis P. Fig. 11B shows an example (single axial type) in which the axial position stator 30 is fixed to a fixed body (not shown), and one rotor 1 is attached to the rotating shaft S, with this rotor 1 facing one side of the axial position stator 30. Fig. 11C shows an example (double axial type) in which the axial position stator 30 is fixed to a fixed body (not shown), and two rotors 1 are attached to the rotating shaft S with the axial position stator 30 sandwiched between them, with one rotor 1 facing one side of the axial position stator 30 and the other rotor 1 facing the other side of the axial position stator 30.

[0065] 12 shows a synchronous rotating electric machine K according to a fifth embodiment. The synchronous rotating electric machine K includes the radial position stator 20 of the synchronous rotating electric machine K according to the third embodiment and the axial position stator 30 of the synchronous rotating electric machine K according to the fourth embodiment. This improves the efficiency of the synchronous rotating electric machine K. For example, a highly efficient motor can be obtained by using a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more.

[0066] FIG. 13 shows another example of a rotor in the synchronous rotating electric machine according to each of the above embodiments. The rotor 1 has a different holder configuration from the rotors according to the above embodiments. Specifically, the rotor 1 includes a holder 40 having a pair of non-magnetic plates 41. A rotating shaft (not shown) is inserted through and fixed to the pair of plates 41. The pair of plates 41 are attached to one side and the other side of the rotor 1 perpendicular to the central axis P, respectively, and hold the base end of each yoke 3. The base end of each yoke 3 is formed with a first bolt insertion hole 42 that is aligned with the axial direction of the central axis P. Meanwhile, each plate 41 of the holder 40 is formed with a plurality of second bolt insertion holes 43 that correspond to the first bolt insertion holes 42. Then, bolts 44 made of a non-magnetic material are inserted into the second bolt insertion holes 43 of one plate 41, the first bolt insertion holes 42 of each yoke 3, and the second bolt insertion holes 43 of the other plate 41, and nuts (not shown) made of a non-magnetic material are screwed onto each bolt 44, so that each yoke 3 is held between the pair of plates 41.

[0067] As a result, when assembling the rotor 1, for example, a required number of first units U1 are prepared in advance, each of which has the north pole side of one magnet body 2 bonded to one side of one yoke 3, exposing the south pole side of the magnet body 2, and a required number of second units U2 are prepared in advance, each of which has the south pole side of one magnet body 2 bonded to one side of one yoke 3, exposing the north pole side of the magnet body 2. These first units U1 and second units U2 are then joined alternately in order. In this case, bolts 44 are inserted into the second bolt insertion holes 43 of one plate 41 of the holder 40 to attach the units. Then, first, either the first unit U1 or the second unit U2 is attached to one plate 41 by inserting the bolts 44 into the first bolt insertion holes 42 of the yoke 3. Next, the other of the first unit U1 or the second unit U2 is attached to the one plate 41 by inserting the corresponding bolts 44 into the first bolt insertion holes 42 of the yoke 3.

[0068] In this case, the magnet body 2 of either the first unit U1 or the second unit U2 slides onto the other side of the yoke 3 of either the first unit U1 or the second unit U2 and is joined. At the beginning of the sliding, the magnet bodies 2 are of the same polarity and repel each other, temporarily preventing them from adhering. However, as described above, as the units are further slid closer together and surface-to-surface joined, the magnetic flux of the magnet body 2 is absorbed by the yoke 3, enabling them to be attracted to each other. In this manner, the first unit U1 and the second unit U2 are joined alternately in order. This is achieved by simply inserting the bolt 44 into the first bolt insertion hole 42 of the yoke 3 and pushing it in, facilitating positioning and assembly. Finally, the other plate 41 is attached by inserting the bolt 44 into its second bolt insertion hole 43 and screwing a nut onto the bolt 44. This sandwiches each yoke 3 between the pair of plates 41.

[0069] Next, the holder 40 of the rotor 1 is attached to the rotating shaft S. In this case, because the holder 40 can be fixed to the rotating shaft S, the axes of the rotating shaft S and the rotor 1 are reliably aligned. This allows the rotor 1 to be attached to the rotating shaft S reliably and easily. Furthermore, when the rotating shaft S is rotated, the rotor 1 rotates smoothly. Furthermore, since each yoke 3 is sandwiched between the pair of plates 41 with the bolts 44 inserted into the first bolt insertion holes 42, misalignment due to centrifugal force during rotation of the rotor 1 is reliably prevented, allowing for smooth rotation. Furthermore, because the first bolt insertion holes 42 are formed at the base end of the yoke 3 and the non-magnetic bolts 44 pass through them, magnetic resistance increases. The combined effect of the through holes effectively reduces the width of the base end of the yoke 3, making it easier to guide the magnetic flux of the magnet to the yoke.

[0070] <Test Examples> Next, test examples that support the present invention are shown. (1) Test Example 1 (Test on the relationship between the distance between the magnet body 2 and the yoke 3 and the magnetic flux density on the surface of the yoke 3) Symbols shown in Figures 6A and 6B are used. The magnet body 2 was a neodymium magnet with Ma = 10 mm, Mr = 20 mm, and Me = 8 mm (B = 430 mT). The yoke 3 was made of SS400 (iron material) with Ya = 11 mm and Yr = 22 mm (without the engaging portion 5), and six types were prepared with central angles θ of 20°, 25°, 30°, 40°, 60°, and 80°.

[0071] As shown in FIG. 14 , a pair of different types of magnet bodies 2 was attached to both sides of the yoke 3 with the same poles facing each other for each yoke 3 with different central angles θ, and the magnetic flux density on the surface of the yoke 3 was measured using a magnetic flux density sensor SB. The measuring device used was the "MT-801" manufactured by Mother Tool Co., Ltd. To attach the magnet bodies 2, one of the first magnet bodies 2A was first attached to the yoke 3, and then the other, second magnet body 2B, was brought closer to the side of the yoke 3 in this state. The magnetic flux density on the surface of the yoke 3 was measured at distances d of 100 mm, 40 mm, 20 mm, 10 mm, 5 mm, and 2.5 mm. Because the thickness of the magnetic flux density sensor was approximately 2 mm, measurements were limited to distances d of 2.5 mm. Measurements were made while varying the central angle θ of the yoke 3.

[0072] The results are shown in Figure 15. When the second magnet body 2B was initially separated, the magnetic flux density of the first magnet body 2A, which had been attached to the yoke 3 earlier, was released from the surface of the yoke 3. As the second magnet body 2B approached the yoke 3, the magnetic flux density of the second magnet body 2B was effectively absorbed by the yoke 3, resulting in magnetic polarity reversal in region A in the figure. From a distance of approximately 5 mm between the yoke 3 and the second magnet body 2B, yokes 3 with a central angle θ of 25° or greater, which have a large volume and magnetic flux absorption capacity, generated a magnetic flux density that attracted the second magnet body 2B. When the distance between the yoke 3 and the second magnet body 2B was 2.5 mm, a strong magnetic attraction force was generated for yokes 3 with a central angle θ other than 20°. On the other hand, for yokes 3 with a central angle θ of 20°, magnetic saturation of the yoke 3 prevented attraction even when the magnet body approached completely.

[0073] (2) Test Example 2 (Measurement of the Magnetic Flux Density on the Surface of the Yoke 3 and the Magnetic Flux Density on the Surface of the Magnet Body 2) For the combination of the magnet body 2 and the yoke 3 of Test Example 1, the magnetic flux density on the surface of the yoke 3 and the magnetic flux density on the surface of the second magnet body 2B were measured by changing the central angle θ of the yoke 3. The results are shown in FIG. 16. From these results, it was possible to observe the details of the closest state (2.5 mm) of the second magnet body 2B for the yoke 3 with a central angle θ of 20°. That is, it was found that for the yoke 3 with a central angle θ of 20°, the magnetic flux density on the surface of the yoke 3 was 380 mT, and the magnetic flux density of 420 mT on the surface of the second magnet body 2B was not fully absorbed. The reason for this is that the yoke 3 with a central angle θ of 20° has a small volume and therefore cannot fully absorb the magnetic flux density of the combined first magnet body 2A and second magnet body 2B. Therefore, in the case of a yoke 3 with a central angle θ of 20°, the magnetic flux density of the second magnet body 2B is not induced to the opposite pole, and the magnetic force density for attraction is insufficient, resulting in repulsion by the same pole of the first magnet body 2A. On the other hand, in a yoke 3 with a central angle θ of 25° or more, the surface magnetic flux density of the second magnet body 2B flows sufficiently into the yoke 3, and the surface of the yoke 3 is induced to the opposite pole (S), allowing magnetic attraction.

[0074] (3) Test Example 3 (Test on Central Angle θ of Yoke 3 <Part 1>) Three types of magnet bodies 2 were prepared as test pieces: a neodymium magnet (B = 430 mT), a neodymium magnet (B = 153 mT), and a ferrite magnet (B = 143 mT). Using the symbols shown in FIGS. 6A and 6B , magnet bodies 2 with Ma = 10 mm, Mr = 20 mm, and Me = 8 mm were used. Nine types of yokes 3 with Ya = 11 mm and Yr = 22 mm (without engaging portion 5) and central angles θ of 20°, 25°, 30°, 35°, 40°, 50°, 60°, 70°, and 80° were prepared.

[0075] As shown in Figure 17A, for each yoke 3 with a different central angle θ, a pair of different types of magnet bodies 2 was attached to both sides of the yoke 3 with the same poles facing each other. The magnetic flux density at the center of the radially expanding fan-shaped outer periphery of the yoke 3 was measured using a magnetic flux density sensor SB. The measuring device used was an "MT-801" manufactured by Mother Tool Co., Ltd. To attach the magnet bodies 2, one magnet body 2 was first attached to the yoke 3, and then the other magnet body 2 was brought closer to the side of the yoke 3 and attached.

[0076] The measurement results are shown in Figure 17B. When the central angle θ of the yoke 3 was 20°, the ferrite magnet was attracted, but with the neodymium magnets, the magnetic flux at the base end X of the yoke 3 was saturated and attraction was not possible. However, with magnet bodies 2 with a central angle θ of 25° or more, repulsion occurred when attempting to bring them close together, temporarily preventing attraction, but they were able to be attracted when brought closer. This is because when one magnet body 2 is brought close to a yoke 3 to which another magnet body 2 is attracted, the magnetic flux of the south pole of the other magnet body 2 is absorbed by the yoke 3. Furthermore, when the central angle θ is 35° or more, the magnetic flux density tends to decrease.

[0077] (4) Test Example 4 (Test on Central Angle θ of Yoke 3 <Part 2>) As in Test Example 1, a neodymium magnet with Ma = 10 mm, Mr = 20 mm, and Me = 8 mm (B = 430 mT) was used as the magnet body 2. Five types of yokes 3 were prepared, each made of SS400 (iron material) with Ya = 11 mm and Yr = 22 mm (without engaging portion 5), with central angles θ of 20°, 25°, 30°, 40°, and 60°.

[0078] Then, as shown in FIG. 18A, the magnetic flux density on the radial surface (outer periphery) (indicated by R) of the yoke 3 and the magnetic flux density at the axial position (a point 5 mm inward from the outer periphery on one surface and the other surface perpendicular to the central axis P) (indicated by A) were measured for each yoke 3 with a different central angle θ using the same measuring device as above.

[0079] The measurement results are shown in Figure 18B. In this figure, the lower broken line appears to be a single line, but because the magnetic flux densities of the radial surface, axial surface 1 (one surface), and axial surface 2 (the other surface) are approximately the same, these broken lines are actually overlapping lines. When the central angle θ of the yoke 3 was 20°, the magnetic flux was saturated in all cases and adhesion was not possible. As a result, it can be seen that the relationship between the total magnetic flux density and the central angle θ of the yoke 3 also shows that magnet bodies 2 with central angles θ of 25° or more are good.

[0080] (5) Test Example 5 (Test on Central Angle θ of Yoke 3 <Part 3>) Using the same test specimen as in Test Example 3, the total magnetic flux intensity per unit of the magnet body 2 was calculated by multiplying it by the number of poles (number of yokes 3), and the relationship between this and the central angle θ of the yoke 3 was examined. The results are shown in Figures 19A and 19B.

[0081] Based on the results of Test Examples 3 to 5, the optimum central angle θ of the yoke 3 is considered to be in the range of 20°<θ<40°, and magnetic flux density decreases when the angle exceeds 40°. Preferably, 20°<θ≦36°. Based on the results of Test Example 5, taking into account the surface area of ​​the yoke 3 and the number of poles (number of yokes 3), it is assumed that practically, 10 poles (θ=36°), 12 poles (θ=30°), or 14 poles (θ≒25.7°) will effectively utilize the magnetic flux density of the neodymium magnet. As the central angle θ increases, the number of poles decreases, and the total magnetic flux density also decreases, resulting in lower efficiency. A central angle θ of 20° results in inefficiency because the magnetic flux saturates the yoke 3 and is not absorbed, preventing effective use of the magnetic flux density of the magnet body 2. That is, it was found that the preferable configuration is one in which the angle of the yoke 3 is in the range of 25.7°<θ≦36°, where n is the number of yokes 3, and n is an even integer, such as n=10 (θ=36°), n=12 (θ=30°), or n=14 (θ≈25.7°). When n=14, the central angle θ is not divisible, but this is within the error range in terms of the adhesion between the magnet body 2 and the yoke 3, does not affect the operation or effect, and is almost poses no problem. If gaps are a concern, an adhesive or the like can be used.

[0082] Furthermore, the results of Test Example 4 show that the magnetic flux densities of the radial surface, axial surface 1 (one surface), and axial surface 2 (the other surface) are approximately the same, and therefore, in the fifth embodiment, the radial position stator 20 and the axial position stator 30 face the radial surface, axial surface 1 (one surface), and / or axial surface 2 (the other surface), respectively, and therefore it can be seen that the fifth embodiment is extremely efficient.

[0083] (6) Test Example 6 (Test on Protrusion Amount of Yoke 3 with Respect to Magnet Body 2) A neodymium magnet (B=430 mT) with Ma=10 mm, Mr=20 mm, and Me=8 mm was used as the test piece for magnet body 2. The yoke 3 had Yr=22 mm (no engaging portion 5) and three types of central angles θ: θ=30°, θ=60°, and θ=80°. Four types with different axial widths were prepared: Ya=10 mm (Ea+Eb=0 mm), Ya=11 mm (Ea+Eb=1 mm), Ya=12 mm (Ea+Eb=2 mm), and Ya=13 mm (Ea+Eb=3 mm).

[0084] Then, for each yoke 3, a pair of magnet bodies 2 was attached to both sides of the yoke 3 with the same poles facing each other, and the magnetic flux density at the center of the outer periphery of the fan-shaped yoke 3, which spread out in the radial direction, was measured using the same measuring device as above. Note that in this test, when the side of the magnet body 2 was viewed from a direction perpendicular to it, the peripheral edge of the side of the yoke 3 protruded from the peripheral edge of the side of the magnet body 2, joining the sides of the magnet body 2 and the yoke 3.

[0085] The results are shown in Figure 20. The magnetic flux density was higher in the case where the yoke 3 did not protrude from the magnet body 2 (Ea + Eb = 0 mm total on both sides), but this was because the magnet body 2 was forcibly pressed down to be attracted, and in reality, it was not possible to attract it. The case where the yoke 3 protruded from the magnet body 2 achieved stable attraction. It was also found that the magnetic flux density decreased as the protrusion increased. If the yoke 3 protruded too much, the volume of the yoke 3 increased, increasing its surface area and decreasing the magnetic flux density. A protrusion of just 1 mm total on both sides reduced the circumferential magnetic flux density of the yoke 3 by 10%. Furthermore, a decrease in magnetic flux density was observed in the case where the central angle θ of the yoke 3 was large (θ = 60°, θ = 80°) compared to the case where the central angle θ was small (θ = 30°).

[0086] From these results, it can be said that the protrusion amount of the periphery of the yoke 3 relative to the periphery of the magnet body 2 is 0.5 mm≦Ea≦5 mm, 0.5 mm≦Eb≦5 mm, preferably 0.5 mm≦Ea≦3 mm, 0.5 mm≦Eb≦3 mm, and more preferably 0.5 mm≦Ea≦1 mm, 0.5 mm≦Eb≦1 mm.

[0087] From this, it can be said that it is also preferable to set the protrusion dimension Ec of the radially outer peripheral edge of the side surface of the yoke 3 to 0.5 mm≦Ec≦5 mm, preferably 0.5 mm≦Ec≦3 mm, and more preferably 0.5 mm≦Ec≦1 mm.

[0088] The protruding dimension Ed of the radially inner peripheral edge of the side surface of the yoke 3 is set to 0.5 mm≦G≦5 mm, so it does not need to be particularly specified. However, it is desirable to make the protruding dimension Ed as small as possible.

[0089] (7) Test Example 7 (Test on the Thickness of Magnet Body 2 (Circumferential Length Me of Magnet Body 2)) The relationship between thickness and magnetic flux density of neodymium magnets was measured. The results are shown in Figure 21. From these results, it can be seen that neodymium magnets can sometimes fall below 150 mT, but have practical value at 150 mT or higher, which is not achievable with ferrite. Increasing thickness improves magnetic flux density, but considering efficiency per weight, it is best to keep it somewhere around 6 mm≦Me≦10 mm. In other words, a magnet thickness Me of 2 mm to 20 mm can be used, but preferably it is in the range of 6 mm to 10 mm.

[0090] (8) Test Example 8 (Test on the Material of the Holder 10) As shown in FIG. 22A , the material of the holder 10 was tested for a rotor 1 (10 poles) similar to that of the first embodiment. As shown in FIG. 27( c ), which will be described later, the rotor 1 used a neodymium magnet as the magnet body 2, with Ma = 10 mm, Mr = 20 mm, and Me = 8 mm (B = 430 mT). The yoke 3 was made of SS400 (iron material), with Ya = 11 mm and Yr = 22 mm (with an engaging portion 5), and had a central angle θ of 36°. Three types of holders 10 were fabricated using the following materials: general structural rolled steel (SS400), stainless steel (SUS304), and aluminum alloy (A5052).

[0091] Then, for three types of rotors 1 (10 poles) created using each of these different types of holders 10, the magnetic flux density of the outer surface (surface A) of the yoke 3, the outer portion of one surface perpendicular to the central axis P of the yoke 3 (surface B), and the inner portion of one surface perpendicular to the central axis P of the yoke 3 (surface C) was measured using the same measuring device as above, as shown in Figure 22A.

[0092] The results are shown in Figure 22B. From these results, it can be said that by using a non-magnetic material for the holder, it is possible to prevent magnetic flux leakage from the base of the yoke, and that this has the effect of improving the magnetic flux density in the radial circumferential direction on the opposite side of the yoke, which is the most important side, and the magnetic flux density on the axial surface, by 10% or more.

[0093] (9) Test Example 9 (Test on Rotor Size) (9-1) Regarding the Radius (Ra) of the Inner Circumferential Circle of the Rotor From the results of Test Example 7, when the minimum Me = 6 mm is selected from 6 mm ≦ Me ≦ 10 mm, and the minimum G = 0.5 mm is selected from 0.5 mm ≦ G ≦ 5 mm, and these are set, the inner radius Ra of the rotor can be approximately calculated as follows: Ra ≈ (Me + G) × number of poles / 2π (Equation 1) From this Equation 1, the circumferential length of the inner circumferential circle of the rotor is approximately 65 mm (radius of approximately 10 mm) for 10 poles (θ = 36°). The maximum case is when there are 14 poles (θ ≈ 25.7°), Me is the maximum of 10 mm, and G is the maximum of 5 mm, and the circumferential length is approximately 210 mm (radius of approximately 35 mm). Therefore, in the case of a neodymium magnet, the optimum radius (Ra) of the inner circumference of the rotor is in the range of approximately 10 mm to approximately 35 mm.

[0094] (9-2) Regarding the Radius (R) of the Rotor's Outer Circumferential Circle: The diameter (radius R) of the rotor's outer circumferential circle can be determined by considering the length (Mr) of the magnet. First, as shown in Figures 23A and 23B, a neodymium magnet (2a) with Ma = 10 mm, Mr = 10 mm, and Me = 10 mm and a neodymium magnet (2b) with Ma = 10 mm, Mr = 20 mm, and Me = 10 mm were used, and the relationship between the central angle (θ) of the yoke and the magnetic flux density at the center of the radially expanding outer circumferential portion of the fan-shaped yoke was measured in the manner described above. As a result, with the neodymium magnet (2a), due to the small size of the yoke, magnetic saturation occurs easily, and adhesion becomes difficult at a yoke central angle (θ) of 20° or 25°, but adhesion becomes possible at 30°. With the neodymium magnet (2b), the yoke is larger, so magnetic saturation is less likely to occur, and adhesion does not occur at a yoke central angle (θ) of 20°, but sufficient adhesion can be obtained at 25°.

[0095] We also examined the relationship between the magnet length (Mr), the yoke, and the radial magnetic flux density. The results in Figures 23A and 23B show that the magnetic flux density decreases as the yoke angle increases and the volume increases. Furthermore, for example, when comparing a yoke (θ = 30°), as shown in Figures 24(b) and 24(c), the size (volume) of the neodymium magnet in the yoke (2a) is twice that of the neodymium magnet in the yoke (2b), but the size (volume) of the yoke is four times that of the neodymium magnet. Consequently, increasing the volume of the yoke results in a drastic decrease in efficiency. Based on actual measurements, the magnetic flux density at the center of the yoke using the neodymium magnet (2a) was 332 mT, while the magnetic flux density at the center of the yoke using the neodymium magnet (2b) was 285 mT. Despite doubling the magnet size, the magnetic flux density decreased to approximately 85% of the original value. This is because, although magnetic saturation is less likely to occur in a yoke using a neodymium magnet (2b), the magnetic flux is sufficiently absorbed within the yoke and diffused throughout, resulting in a significant reduction in the magnetic flux density appearing at the center of the yoke. From the results of Figures 23A and 23B, this reduction in magnetic flux density of approximately 85% is not limited to when the yoke central angle θ is 30°, but is common to all central angles θ. This reduction rate can be improved by using a material with good magnetic permeability. It is expected that high-permeability materials will be developed as yoke materials.

[0096] Next, we analyzed the relationships between factors that determine the optimal rotor size to obtain maximum torque per weight. We performed the analysis for (A) the case where the stator according to the embodiment shown in Fig. 1B (called a radial type) was assumed, and (B) the case where the stator according to the embodiment shown in Fig. 11A (called an axial type) was assumed.

[0097] (A) In the case of assuming a stator (radial type) according to the embodiment shown in FIG. 1B As shown in FIG. 25, the torque-to-weight ratio coefficient per unit weight of the yoke and the two neodymium magnets sandwiching it is defined as F, and this is given by F ≈ (R × B × H) ÷ (M + Y) = [(Ra + Mr) × B × H] ÷ (M + Y) (Equation 2).

[0098] where F: torque-to-weight ratio coefficient, Mr: length of the magnet body in the rotor's radial direction, Ra: radius of the rotor's inner circumferential circle. Here, the radius is assumed to be 15 mm. R (≒ Ra + Mr): radius of the rotor's outer circumferential circle, and H: surface area ratio of the actual yoke (stator-contributed surface area ratio). Here, assuming the stator according to the embodiment shown in FIG. 1B, the maximum length of the protruding stripes 25 of the teeth 22 is assumed to be approximately 10 mm. As shown in FIG. 24, the surface area of ​​the yoke (FIG. 24(b)) using neodymium magnets (2a) is set to 2 for ease of understanding by adding up the axial and radial surfaces. That is, in FIG. 24(b), the hatched portions of the yoke are on the front and back, so the hatched portions on the front and back are set to 1, and the radial circumferential surface of the yoke (not shown) is set to 1, and these are added together to get 2.

[0099] M: Weight ratio of the neodymium magnet. Here, the weight of the neodymium magnet (2a) is 2. Y: Weight ratio of the yoke. Here, the weight of the yoke using the neodymium magnet (2a) is 1. B (= 0.85n): Magnetic flux density ratio of the yoke. Based on the results of Figure 23 above, it is assumed that the magnetic flux density decreases to approximately 85% each time the length Mr of the neodymium magnet increases by 10 mm. When the neodymium magnet (2a) is used, n is set to 0 (the magnetic flux density ratio B of the yoke is set to 1), and n is increased by 1 for every 10 mm increase in length Mr. When the neodymium magnet (2b) is used, the length Mr is 20 mm, so n = 1, and therefore B = 0.85. When the length Mr is 30 mm, n = 2, so B = (0.85)2 = 0.72.

[0100] In the case of a yoke using two neodymium magnets, when the neodymium magnet length Mr is 5 mm, 10 mm (for a yoke using two neodymium magnets (2a)), 20 mm (for a yoke using two neodymium magnets (2b)), 30 mm, 40 mm, or 50 mm, and the torque weight ratio coefficients are Fa to Ff, calculations using equation 2 yield the following: In the case of a neodymium magnet with a magnet length Mr of 5 mm, since it is difficult to form teeth on the side surfaces, the specific surface area H is set to 0.5 and the magnet weight ratio M to 1.0 compared to one with a magnet length Mr of 10 mm. Fa ≒ [(15 + 5) x 1.17 x 0.5] ÷ (1.0 + 0.25) ≒ 9.4 Fb ≒ [(15 + 10) x 1 x 2] ÷ (2 + 1) ≒ 16.7 Fc ≒ [(15 + 20) x 0.85 x 5] ÷ (4 + 4) ≒ 18.6 Fd ≒ [(15 + 30) x 0.72 x 8] ÷ (6 + 9) ≒ 17.3 Fe ≒ [(15 + 40) x 0.61 x 11] ÷ (8 + 16) ≒ 15.4 Ff ≒ [(15 + 50) x 0.51 x 14] ÷ (10 + 25) ≒ 13.3

[0101] When these results are graphed, the relationship between magnet length Mr and torque-to-weight ratio coefficient is as shown in Figure 26A. Figure 26B also shows the relationship between magnet length Mr and torque (the numerator related to torque in the torque-to-weight ratio coefficient calculation formula). For example, it is assumed that the torque of a rotor using neodymium magnet (2b) increases proportionally compared to a rotor using neodymium magnet (2a), but there is no simple proportional relationship. In other words, in the torque-to-weight ratio coefficient calculation formula, each element of the numerator related to torque (torque in this case) is a linear function, and as the magnet length increases, this numerator increases linearly, as shown in Figure 26B. Because the yoke weight in the denominator is a quadratic function, the torque-to-weight ratio coefficient is maximized at a length of 10 to 20 mm as shown in Figure 26A. As the magnet size increases, the denominator increases and the torque-to-weight ratio coefficient gradually decreases.

[0102] (B) In the case of the stator (called an axial type) according to the embodiment shown in Figure 11A, the torque ratio coefficient is calculated in the same manner as above. Since the axial type stator is large in size, approximating the size of the yoke, the value of the weight ratio portion of the yoke is set to 2Y to take this into account. Also, the length of the magnet Mr is replaced by the length L to the center of gravity of the yoke where torque is generated. The actual yoke surface area H is the area of ​​the portion of the stator that actually faces the coil. The rest is the same as above.

[0103] Therefore, the torque-to-weight ratio coefficient F per unit weight of the yoke and the two neodymium magnets sandwiching it is given by: F ≒ (R × B × H) ÷ (M + 2Y) = [(Ra + L) × B × H] ÷ (M + 2Y) (Equation 3).

[0104] Similarly to the above, in the case of a yoke using two neodymium magnets, when the length Mr of the neodymium magnets is 5 mm (L = 3 mm), 10 mm (L = 7 mm), 20 mm (L = 14 mm), 30 mm (L = 20 mm), 40 mm (L = 24 mm), or 50 mm (L = 32 mm), and the torque-to-weight ratio coefficients are Fa to Ff, the calculation using Equation 2 yields the following results: Fa ≒ [(15 + 3) x 1.17 x 0.2] ÷ (1.0 + 0.5) ≒ 2.8 Fb ≒ [(15 + 7) x 1 x 0.75] ÷ (2 + 2) ≒ 4.1 Fc ≒ [(15 + 14) x 0.85 x 3.5] ÷ (4 + 8) ≒ 7.2 Fd ≒ [(15 + 20) x 0.72 x 8] ÷ (6 + 18) = 8.4 Fe ≒ [(15 + 24) x 0.61 x 15] ÷ (8 + 32) ≒ 8.9 Ff ≒ [(15 + 32) x 0.51 x 23] ÷ (10 + 50) ≒ 9.2

[0105] When these results are graphed, the relationship between magnet length Mr and torque-to-weight ratio coefficient is as shown in Figure 26C. Furthermore, Figure 26D shows the relationship between magnet length Mr and torque (the numerator related to torque in the torque-to-weight ratio coefficient calculation formula). It can be seen that in the case of the axial type (Figure 11A), the yoke area increases quadratically in relation to magnet length. For magnet lengths up to 30 mm, the radial type (Figure 1B) is advantageous, but for large-diameter motors with magnet lengths exceeding 40 mm, the axial type (Figure 11A) and double-axial type (Figure 11B) are considered effective.

[0106] (9-3) Summary To summarize the above results, under the conditions of 6 mm≦Me≦10 mm and 0.5 mm≦G≦5 mm, the radius Ra of the rotor's inner circumference can be in the range of approximately 10 mm to 35 mm, and the length Mr of the magnet body in the rotor's radial direction can be in the range of 5 mm to 50 mm. As a result, it was found that a range of 15 mm to 85 mm is preferable for the radius R of the rotor's outer circumference. Furthermore, when taking advantage of the characteristics of the elongated shape, there is an advantage to using a length Mr of 5 mm.

[0107] Next, examples are described. First, a rotor as shown in FIG. 27 was created. The rotor had the structure shown in FIGS. 2 and 3, and was made to have 10 poles using a yoke with a central angle θ of 36°. The rotor shown in FIG. 27(a) had a diameter of 40 mm, and the neodymium magnet had a length (Mr) of 5 mm, a width (Ma) of 10 mm, and a thickness (Me) of 6 mm, with a magnetic flux density of 460 mT. The rotor shown in FIG. 27(b) had a diameter of 50 mm, and the neodymium magnet had a length (Mr) of 10 mm, a width (Ma) of 10 mm, and a thickness (Me) of 8 mm. The rotor shown in FIG. 27(c) had a diameter of 70 mm, and the neodymium magnet had a length (Mr) of 20 mm, a width (Ma) of 10 mm, and a thickness (Me) of 8 mm.

[0108] Then, as shown in Fig. 28, prototype motors (Examples 1 to 3) were created using the rotors and stators according to the embodiments shown in Fig. 10 to 11C. In each example, the rotor 1 used was the rotor shown in Fig. 27(a) (diameter 40 mm, neodymium magnet length (Mr) 5 mm × width (Ma) 10 mm × thickness (Me) 6 mm, magnetic flux density 460 mT).

[0109] <Example 1 (Prototype: (Radial Gap Motor)>> The synchronous rotating electric machine K shown in Fig. 28A is of the type shown in Fig. 10. The synchronous rotating electric machine K includes a rotor 1 and a radial position stator 20. The synchronous rotating electric machine K further includes a base 50, a pair of bearing bodies 51 that support both ends of a rotating shaft S to which the rotor 1 is fixed midway in the axial direction, and a fixed body 52 that is provided on the base 50 and that fixes the radial position stator 20.

[0110] Example 2 (Prototype 2: Single Axial Gap Motor) The synchronous rotating electric machine K shown in Fig. 28B is the single axial type shown in Fig. 11B. The synchronous rotating electric machine K includes one rotor 1 and an axial position stator 30. The synchronous rotating electric machine K further includes a base 50, a pair of bearing bodies 51 that support both ends of a rotating shaft S that is provided on the base 50 and has the rotor 1 fixed midway in the axial direction, and a fixed body 52 that is provided on the base 50 and fixes the axial position stator 30. The rotor 1 is provided facing one surface of the axial position stator 30.

[0111] Example 3 (Prototype 3: Double Axial Gap Motor) The synchronous rotating electric machine K shown in FIG. 28C is the double-axial type shown in FIG. 11C . The synchronous rotating electric machine K includes two rotors 1 and an axial position stator 30. The synchronous rotating electric machine K further includes a base 50, a pair of bearing bodies 51 that support both ends of a rotating shaft S that is provided on the base 50 and has two rotors 1 fixed to its axial end, and a fixed body (not shown) that is provided on the base 50 and that fixes the axial position stator 30. The two rotors 1 are attached to the rotating shaft S with the axial position stator 30 sandwiched between them. One rotor 1 is provided facing one side of the axial position stator 30, and the other rotor 1 is provided facing the other side of the axial position stator 30.

[0112] Example 4 (Hypothetical Example) This is a hypothetical motor having the structure (single radial + double axial) shown in FIG. 1B.

[0113] Then, for Examples 1 to 3, current was passed through the stator coil, a load was applied to the rotating shaft, and the maximum torque was measured. Example 4 (hypothetical) was calculated based on the measurement results of Examples 1 to 3. The maximum torque per unit weight was also calculated. Furthermore, since the weight of the exterior and shaft is added to the mounted motor, the maximum torque per unit weight was also calculated, taking into account a 100g weight increase for (shaft + exterior) (shown in parentheses). The results are shown in Figure 29A. Furthermore, Figure 29B shows the maximum torque and maximum torque per unit weight for seven commercially available motors as comparative examples.

[0114] These results show that the motors to which the present invention is applied (Examples 1 to 4) all have a higher maximum torque per unit weight than commercially available motors (Comparative Examples 1 to 7). Furthermore, as can be seen from the results and calculations of Example 3 (Prototype 3), it was also found that high efficiency can be achieved by adopting a double axial type.

[0115] Based on the magnet length and torque ratio coefficient test in Figure 26B, it can be assumed that the simple torque value when using a neodymium magnet with a length (Mr) of 20 mm is 148. Therefore, by performing a proportional calculation based on the torque value of 12 for a 5 mm magnet, it is estimated that approximately 10 times the torque can be obtained. Therefore, based on these results, in the case of a rotor using a neodymium magnet with a length (Mr) of 20 mm as shown in Figure 27(c), for example, a motor with the structure shown in Figure 1B is expected to be able to generate a torque of approximately 10 N·m when driven at 24 V. It is also expected that the weight of the motor including the outer casing can be reduced to approximately 500 g. Furthermore, when using a dual rotor (see Figure 8), the weight including the outer casing is equivalent to approximately 1 kg, and it is believed that a torque of approximately 20 N·m can be obtained. By increasing the drive voltage, for example to 50 V, a motor weighing 1 kg can achieve a high output of 40 N·m.

[0116] Furthermore, based on the magnet length and torque-to-weight ratio coefficient in FIG. 26A, it is expected that the motor with the configuration shown in FIG. 1B will achieve the best efficiency per weight ratio when using a neodymium magnet with a magnet length (Mr) of 20 mm. If weight were not a consideration, the magnet length could be increased to 50 mm. However, considering torque buildup and maximum rotation speed, a motor using a rotor with a multi-stage rotor diameter and a magnet length (Mr) of approximately 20 mm (see FIG. 8), a combination with an axial type (see FIGS. 11A to 11C), or even a multi-stage configuration of these would be more effective. Therefore, the present invention is extremely useful for spindle motors with high torque per weight, small and slender external dimensions, and for machine tools, robots, hand tools, drones, and other applications where compactness and light weight are desired.

[0117] In the rotor 1 of the synchronous rotating electric machine K according to the above embodiment, the magnet bodies 2 are formed in a rectangular parallelepiped shape, but this is not necessarily limited to this. For example, as shown in FIG. 30, they may be fan-shaped (with a central angle α), and this shape may be modified as appropriate. The number of yokes 3 (number of poles) is also not limited to the above-described number and may be modified as appropriate. Furthermore, in the above-described embodiment, the shape of the holder 10 is not limited to the above-described embodiment and may be modified as appropriate. In short, the present invention is not limited to the above-described embodiment of the present invention. Those skilled in the art can easily make many modifications to these exemplary embodiments without substantially departing from the novel teachings and effects of the present invention, and these many modifications are within the scope of the present invention.

[0118] According to the present invention, it is possible to utilize and make use of a highly efficient electric motor (motor) or generator that has a ring-shaped rotor and a stator arranged around the rotor, and it is extremely useful for spindle motors that have high torque per weight, are small and slender in external dimensions, and for machine tools, robots, hand tools, drones, etc., where small and lightweight are desired.

Claims

1. A synchronous rotating electric machine comprising: a ring-shaped rotor rotated by a rotating shaft; and a stator arranged around the rotor; wherein the rotor comprises magnet bodies consisting of a plurality of permanent magnets of the same shape and size arranged at equal angular intervals on the outside of the rotating shaft with the same poles facing each other along a circumferential direction centered on the central axis of the rotating shaft; and a plurality of yokes arranged between adjacent magnet bodies, having sides joining to the sides of the magnet bodies and formed in a sector shape of the same shape and size with a predetermined central angle, wherein Ma<Ya, Mr<Yr are satisfied, and wherein the axial length of the magnet bodies is Ma and the radial length of the yoke is Mr, and the axial length of the yoke is Ya and the radial length is Yr, so that Ma<Ya and Mr<Yr are satisfied, and most of the magnetic flux of the magnet bodies is absorbed by the yoke.

2. A synchronous rotating electric machine as set forth in claim 1, wherein: the magnet body is formed from a magnetic material with a magnetic flux density of 150 mT≦B, where B is the magnetic flux density of the magnet body; and wherein, where θ is the central angle of the yoke, 20°<θ<40°; when the side surface of the magnet body is viewed from a direction perpendicular thereto, the peripheral edge of the side surface of the yoke protrudes from the peripheral edge of the side surface of the magnet body, and the side surface of the magnet body and the side surface of the yoke are joined together; and wherein: Ea is a protruding dimension of the peripheral edge of the side surface of the yoke in the axial direction from the peripheral edge of one side of the side surface of the magnet body in the axial direction, Eb is a protruding dimension of the peripheral edge of the side surface of the yoke in the axial direction from the peripheral edge of the side surface of the magnet body in the axial direction on the other side, and G is a minimum interval between adjacent magnet bodies; and 3. A synchronous rotating electric machine as set forth in claim 2, wherein when the projection dimension Ec of the radially outer peripheral edge of the side surface of said yoke relative to the peripheral edge on the radially outer end side of the side surface of said magnet body is set to 0.5 mm≦Ec≦5 mm.

4. A synchronous rotating electric machine as set forth in claim 3, wherein, in said yoke, θ is 25.7°<θ≦36°, and the number of said yokes is n, n=10, n=12, or n=14, and said magnet body is formed in a substantially rectangular parallelepiped shape.

5. A synchronous rotating electric machine according to claim 4, wherein a protrusion is formed on the outer end of the side surface of said yoke so as to protrude in the circumferential direction and against which the outer end surface of said magnet body abuts.

6. A synchronous rotating electric machine according to claim 5, wherein said rotor further comprises a holder made of a non-magnetic material through which said rotating shaft is inserted and fixed and which holds the base ends of said yokes.

7. A synchronous rotating electric machine as set forth in claim 5, wherein the rotor comprises a holder made of a non-magnetic material formed in a ring shape into which the rotating shaft is inserted and fixed, the holder having an outer periphery which holds the base ends of each of the yokes, the yoke having an engaging portion at its inner end which protrudes circumferentially to the left and right, and the holder having an engaged portion at its outer periphery which engages with the engaging portion when inserted from one or the other side perpendicular to the central axis of the holder.

8. The synchronous rotating electric machine according to claim 5, wherein the rotor comprises a holder having a pair of plates made of a non-magnetic material attached to one surface and the other surface of each of the yokes perpendicular to the central axis thereof, the pair of plates holding the base end of each of the yokes, a first bolt insertion hole is formed in the base end of each of the yokes along the axial direction of the rotating shaft, a plurality of second bolt insertion holes corresponding to the first bolt insertion holes are formed in each of the plates of the holder, bolts made of a non-magnetic material are inserted through the second bolt insertion holes of the one plate, the first bolt insertion holes of each of the yokes and the second bolt insertion holes of the other plate, nuts made of a non-magnetic material are screwed onto each of the bolts, and each of the yokes is held by the pair of plates.

9. A synchronous rotating electric machine as claimed in any one of claims 1 to 8, comprising as said stator a radial position stator having a plurality of stator coils arranged at predetermined intervals on a circumference centered on the rotation axis of said rotor and facing the outer peripheral surface of said rotor via an air gap.

10. A synchronous rotating electric machine as claimed in any one of claims 1 to 8, comprising an axial position stator having a plurality of stator coils arranged at predetermined intervals on a circumference centered on the rotation axis of the rotor and facing one and / or the other side perpendicular to the central axis of the rotor via an air gap.

11. A synchronous rotating electric machine as claimed in any one of claims 1 to 8, comprising as the stator: a radial position stator having a plurality of stator coils arranged across an air gap to face the outer peripheral surface of the rotor and aligned at predetermined intervals on a circumference centered on the rotational axis of the rotor; and an axial position stator having a plurality of stator coils arranged across an air gap to face one and / or the other surface perpendicular to the central axis of the rotor and aligned at predetermined intervals on a circumference centered on the rotational axis of the rotor.

12. A synchronous rotating electric machine as set forth in any one of claims 1 to 8, wherein the stator is a radial position stator having a plurality of stator coils facing the outer peripheral surface of the rotor via an air gap and arranged in a row at predetermined intervals on a circle centered on the rotation axis of the rotor, and a plurality of teeth corresponding to the plurality of stator coils and around which the stator coils are wound, the teeth of the radial position stator having a main body facing the outer peripheral surface of the rotor via an air gap, and a ridge body protruding from both ends of the main body in the central axis direction towards the central axis and having facing portions facing one side and the other side of the rotor via an air gap, respectively, the stator coils being wound around the teeth with at least the facing portions of the ridge body exposed.

13. A synchronous rotating electric machine as set forth in claim 12, wherein an insulating member is interposed between said main body and said ridges.

14. A synchronous rotating electric machine according to claim 13, wherein a plurality of said rotor / stator pairs are arranged in a row on the same rotating shaft.

Images