JP7471619B1 - Synchronous rotating motor - Google Patents

Abstract

To easily assemble a magnet body and a yoke while counteracting a repulsive force, and to stably integrate the magnet body and the yoke while preventing magnetic saturation.
[Solution] In a rotor in which magnet bodies 2 are arranged at equal angular intervals via a sector-shaped yoke 3, with like poles facing each other, neodymium magnets with a magnetic flux density B of 150 mT≦B are used as the magnet bodies 2, and the central angle θ of the yoke 3 is set to 20°<θ<40°. 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 to join the side of the magnet body 2 and the side of the yoke 3. The relationship between the axial protrusion dimension Ea of the yoke 3, the protrusion dimension Eb on the other axial side and the minimum gap G between adjacent magnet bodies 2 are set to 0.5 mm≦Ea≦5 mm, 0.5 mm≦Eb≦5 mm and 0.5 mm≦G≦5 mm.
[Selected Figure] Figure 6

Description

The present invention relates to a synchronous rotating electric machine that can be configured as an electric motor or 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 sector-shaped yokes so that like poles face each other.

Conventionally, as an example of this type of synchronous rotating electric machine, one that is disclosed in JP Patent Publication 6-38415 (Patent Document 1) is known, which, as shown in FIG. 31, comprises a ring-shaped rotor 100 that is rotated by a rotating shaft (not shown) and a stator (not shown) that is provided around the rotor 100. The rotor 100 is configured with magnet bodies 101 consisting of multiple permanent magnets that are arranged on the outside of the rotating shaft along a circumferential direction centered on the central axis P of the rotating shaft with the same poles facing each other at equal angular intervals (45°) and are formed into elongated rectangular parallelepipeds of the same shape and size, and multiple yokes 102 that are arranged between adjacent magnet bodies 101, have sides that join the sides of the magnet bodies 101, and are formed into sectors of the same shape and size with a predetermined central angle (45°).

Now, in the case of a synchronous rotating electric machine Ka, for example, a motor (electric motor), in order to obtain a motor with high energy efficiency, it is desirable to use, for example, a neodymium-based magnet with high magnetic flux density, instead of a ferrite-based magnet, as the magnet body 101 of the rotor 100. However, when designing and inexpensively producing a rotor 100 using this high-magnetic-flux-density magnet body 101, in a type of rotor 100 in which the magnet body 101 shown in FIG. 31 is arranged in the circumferential direction via an independent yoke 102, there is no problem with the magnet body being a ferrite-based magnet, but in the case of a magnet body 101 with high magnetic flux density, the magnetic force is strong and the assembly and mounting process is difficult. For this reason, so-called IPM motors in which the magnet body is embedded in the iron core as the rotor have been popular (for example, see JP-A-10-66285, etc.). However, for example, in fields such as EVs and robots, there is a demand for motors that are as light as possible and have high torque and high rotation speeds, and the rotor 100 type in which the magnet body 101 is arranged circumferentially via an independent yoke 102 has excellent torque density per unit weight, so it is desirable for it to become more widespread.

Japanese Patent Application Laid-Open No. 6-38415 Japanese Patent Application Laid-Open No. 10-66285

Here, we will go into more detail about the problems with the rotor 100 in which the magnet body 101 is arranged in the circumferential direction via an independent yoke 102. As shown in FIG. 31, in this rotor 100, the magnet body 101 is formed as an elongated rectangular parallelepiped, and the base of the sector-shaped yoke 102 is wide, so there is a problem that the magnetic flux leaks and the magnetic flux density in the radial direction, where it is originally desired to increase the magnetic flux density, does not increase, and the magnetic flux that the magnet originally possesses cannot be effectively utilized, resulting in poor energy efficiency. For this reason, it is possible to narrow the base width of the sector-shaped yoke and extremely reduce the magnetic flux at the base of the yoke to increase the magnetic flux density in the radial direction, but on the other hand, this makes it easier to become magnetically saturated, and magnets of the same polarity will repel from this part, so when mounting as described above, the magnetic force is strong and the assembly mounting process becomes difficult.

The present invention was made in consideration of these problems, and aims to provide a synchronous rotating electric machine that has a rotor in which permanent magnets are arranged circumferentially with the same poles facing each other via independent sector-shaped yokes, and that, even when using high-performance magnets such as neodymium magnets, allows the magnet body and yoke to be easily assembled while counteracting repulsive forces, effectively directs the magnetic flux emitted from the magnet body to the yoke, while at the same time preventing magnetic saturation, achieving an optimal structure for the high-performance magnet and yoke, automatically stabilizing the magnets and integrating them, and maximizing the use of most of the magnetic flux density possessed by the high-performance magnets, which are absorbed by the yoke and released as magnetic flux that contributes to the driving force.

The inventors of the present application conducted research for many years and investigated the relationship between high-performance magnets with high magnetic flux density and the yoke, and as a result discovered the conditions for achieving maximum efficiency without magnetic saturation, thereby completing the present invention.
That is, the synchronous rotating electric machine of the present invention for solving the above-mentioned problems includes a ring-shaped rotor rotated by a rotating shaft, and a stator provided around the rotor, the rotor being configured with magnet bodies made of a plurality of permanent magnets formed with the same shape and size and arranged at equal angular intervals with the same poles facing each other along a circumferential direction centered on the central axis of the rotating shaft on the outside of the rotating shaft, and a plurality of yokes arranged between adjacent magnet bodies, having side surfaces joining to side surfaces of the magnet bodies, and formed with the same shape and size in a sector shape with a predetermined central angle,
When the axial length of the magnet body is Ma and the radial length is Mr, and the axial length of the yoke is Ya and the radial length is Yr, the relationships Ma<Ya and Mr<Yr are set so that most of the magnetic flux of the magnet body is absorbed by the yoke.
More specifically, the magnet body is made of a magnet material having a magnetic flux density of 150 mT≦B, where B is the magnetic flux density of the magnet body;
When the central angle of the yoke is θ, the central angle is set to 20°<θ<40°.
Let Ma be the axial length of the magnet body, Mr be the radial length thereof, and Ya be the axial length of the yoke, Yr be the radial length thereof, so that Ma<Ya and Mr<Yr are satisfied;
when the side surface of the magnet body is viewed in a direction perpendicular to the side surface of the magnet body, the peripheral edge of the side surface of the yoke is caused to protrude 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;
Let Ea be the protruding 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 in the axial direction on one side, Eb be the protruding dimension of the peripheral edge of the side surface of the yoke in the axial direction on the other side relative to the peripheral edge of the side surface of the magnet body in the axial direction on the other side, and G be the minimum distance between adjacent magnet bodies,
The configuration is set to 0.5 mm≦Ea≦5 mm, 0.5 mm≦Eb≦5 mm, and 0.5 mm≦G≦5 mm.

Here, rare earth magnets can be cited as examples of magnet materials with a magnetic field strength of 150 mT or less (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). 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).
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 core, magnetic steel sheet, low carbon steel, silicon steel sheet, etc. If necessary, heat treatment may be performed, or anti-rust plating or painting may be performed.

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

In this case, according to the present invention, even if one magnet body is temporarily unable to be attracted to another magnet body due to repulsion when the two magnet bodies are brought close to the yoke to which the other magnet body is attracted in order to join their surfaces, if the other magnet body is brought even closer to join the surfaces, the magnetic flux of its south pole will be absorbed by the yoke, and the magnets will be able to be attracted to each other. The reason for this is that in the present invention, as shown in FIG. 6, the central angle θ of the yoke is set to 20°<θ<40°, and the minimum gap G between adjacent magnet bodies is set to 0.5 mm≦G≦5 mm, thereby narrowing the base width of the sector-shaped yoke, and furthermore, when the side of the magnet body is viewed in a direction perpendicular to it, the periphery of the side of the yoke protrudes from the periphery of the side of the magnet body, i.e., the periphery of the yoke (the entire periphery of the yoke) protrudes beyond the periphery of the magnet body (the entire periphery of the magnet body). In particular, as shown in FIG. 6(b) and FIG. 7(a), the periphery of the yoke protrudes from the periphery of the magnet body by 0.5 mm to 5 mm in both the radial direction and the axial direction. Therefore, when the other magnet body is brought even closer to the yoke and surface-joined, the magnetic flux of the S pole is absorbed by the yoke.

If there is no axial protrusion of the yoke relative to the magnet body, that is, as shown in FIG. 7(b), in the axial direction, one and the other faces of the yoke perpendicular to the central axis direction and one and the other faces of the magnet body perpendicular to the central axis direction are flush (flat), generally, high-performance magnets such as neodymium magnets are easily chipped, and the corners are chamfered in an R shape, so the magnetic flux is not absorbed by the yoke and leaks out from the corners, and the magnetic flux is easily saturated near the base of the yoke, so the same poles of the magnet body facing the yoke tend to repel each other. Therefore, the yoke to which one magnet body is attracted does not absorb the entire magnetic flux generated from the S pole of the other magnet body, and as a result, the magnetic flux is magnetically saturated near the base of the yoke, and it cannot be attracted by repelling the S pole magnetic flux emitted from the yoke surface. In this state, even if it is forcibly attached with, for example, an adhesive or restrained by a restraining means, the magnetic flux cannot be used effectively, and there is little point in using a high magnetic flux density magnet. In the present invention, this phenomenon of repulsion and inability to adhere can be avoided.

In this way, the magnet body and the yoke are assembled in order to form a ring-shaped rotor. In the assembled state, the base width of the sector-shaped yoke is narrow, and the periphery of the yoke protrudes from the periphery of the magnet body by 0.5 mm to 5 mm in both the radial and axial directions, so that the magnetic flux is absorbed and attracted by the yoke near the base of the yoke, which is prone to magnetic saturation, and similarly, the magnetic flux is absorbed and attracted by the yoke at the periphery of the entire yoke, making it possible to guide the magnetic flux of the magnet to the yoke. For this reason, the total magnetic flux density in the radial direction is much higher than the base of the yoke, and as a result, the magnetic flux density of the magnet body can be utilized with maximum efficiency. If it exceeds 5 mm, the magnetic flux density tends to decrease, so it is desirable to set it to a range of 5 mm or less where stable attraction is possible.

The protrusion amount of the periphery of the yoke relative to the periphery of the magnet body is desirably set to a range of 3 mm or less that allows stable adsorption, based on the test results for the protrusion amount of the yoke shown in Figure 20. That is, preferably, 0.5 mm ≤ Ea ≤ 3 mm, 0.5 mm ≤ Eb ≤ 3 mm, 0.5 mm ≤ G ≤ 3 mm, and more desirably, 0.5 mm ≤ Ea ≤ 1 mm, 0.5 mm ≤ Eb ≤ 1 mm, 0.5 mm ≤ G ≤ 1 mm. Stable adsorption is not possible when Ea = 0. In order to utilize 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, but it can be set within the protrusion amount range that allows stable adsorption.

In addition, from the test results shown in Figures 14 to 19, it is known that when the central angle of the yoke is less than 20°, the magnetic flux at the base end of the yoke becomes saturated and cannot be attracted. In the present invention, the central angle θ of the yoke is set to 20°<θ<40°, so that it is possible to reliably avoid a state in which the magnetic flux at the base end of the yoke becomes saturated and cannot be attracted. If it exceeds 40°, the magnetic flux density decreases. It is preferable that 20°<θ≦36°.

Therefore, in the present invention, the magnet body can be stably attached to the yoke without being pressed down by an external force, allowing for stable mounting and assembly, improving productivity and reducing costs. In the assembled state, all of the magnetic flux generated from the surface of the magnet body can be absorbed by the yoke, and the yoke can be magnetized to release the magnetic flux 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 with maximum efficiency per weight, resulting in a motor that is easy to assemble, has high torque, is highly efficient, and is lightweight.

If necessary, the protruding dimension Ec of the radially outer periphery of the side surface of the yoke relative to the radially outer periphery 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. When Ec=0, stable adhesion is poor. In order to utilize 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, but it can be set within the range of protrusion amount that allows stable adhesion.
The projection dimension Ed of the radially inner periphery of the side surface of the yoke relative to the radially inner periphery of the side surface of the magnet body is set to 0.5 mm≦G≦5 mm, so it does not need to be specified in particular. However, it is preferable to make the projection dimension Ed as small as possible.

In addition, if necessary, the yoke is in the range of 25.7°≦θ<36°, and the number of the yokes is n, n=10, n=12, or n=14, and the magnet body is formed into a substantially rectangular parallelepiped shape. n is an even integer. n=10 (θ=36°), n=12 (θ=30°), or n=14 (θ≒25.7°). In the case of n=14, the central angle θ is not divisible, but this is within the error range in the adhesion between the magnet body and the yoke, and there is no effect on the action and effect, so there is almost no problem. If the gap is a concern, an adhesive or the like can be inserted. Within this range, the action and effect of the present invention can be maximized.
As can be seen from the test example in FIG. 19, when n≦8, the total magnetic flux density cannot be used effectively.
If n is 16 or less, the yoke becomes thin and is prone to saturation.

Furthermore, if necessary, a protrusion is formed on the outer end of the side surface of the yoke, protruding in the circumferential direction, against which the outer end surface of the magnet body abuts. In the present invention, the magnet body and the yoke can be stably attracted to each other without pressing the magnet body against the yoke with an external force, so the protrusion is not particularly necessary, but the magnet body can be positioned by abutting against the protrusion during assembly, making assembly even easier. Also, it is possible to reliably prevent misalignment due to centrifugal force when the rotor rotates.

Furthermore, if necessary, the rotor is configured with 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 axis alignment between the rotating shaft and the rotor is ensured. Therefore, the rotor can be attached to the rotating shaft reliably and easily. When the rotating shaft is rotated, the rotor can rotate smoothly. Also, since the base ends of the yoke are held by the rotor during rotation, it is possible to reliably prevent misalignment due to centrifugal force when the rotor rotates, and rotation can be performed smoothly.

Specifically, if necessary, the rotor is configured to include a holder made of a non-magnetic material that is formed in a ring shape through which the rotating shaft is inserted and fixed, and that holds the base ends of the yokes on its outer periphery. The inner end of the yoke is provided with an engaging portion that protrudes circumferentially to the left and right, and the outer periphery of the holder is configured to have an engaged portion that engages with the engaging portion when inserted from one side or the other side perpendicular to the central axis of the holder.

As a result, when assembling the rotor, for example, a required number of first units are prepared in advance, in which the north pole side of one magnet body is joined to one side of one yoke to expose the south pole side of the magnet body, and a required number of second units are prepared in advance, in which the south pole side of one magnet body is joined to one side of one yoke to expose the north pole side of the magnet body, and these first and second units are joined in alternating order. In this case, first, either the first or second unit is attached to the holder by engaging the engaging portion of the 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 the yoke with the engaged portion of the holder.

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 to join them. At the beginning of the slide, they are of the same polarity and repel each other, temporarily preventing them from being attracted to each other. However, as described above, if they are further slid closer together and joined by surface bonding, the magnetic flux of the magnet body is absorbed by the yoke, and they can be attracted to each other. In this way, the first unit and the second unit are joined in alternating order. At this time, it is only necessary to engage the engaging portion of the yoke with the engaged portion of the holder and push it in, so positioning can be easily performed and assembly can be easily performed.

Next, the rotor holder is attached to the rotating shaft. In this case, the holder can be fixed to the rotating shaft, so the axis alignment between the rotating shaft and the rotor is ensured. This allows the rotor to be attached to the rotating shaft reliably and easily. When the rotating shaft is rotated, the rotor can rotate 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 when the rotor rotates, and rotation can be performed smoothly.

If necessary, the rotor may be configured with a holder having a pair of plates made of a non-magnetic material, through which the rotating shaft is inserted and fixed, and which are attached to one side and the other side of each yoke perpendicular to the central axis 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, and nuts made of a non-magnetic material are screwed onto each bolt, so that each yoke is held between the pair of plates.

As a result, when assembling the rotor, for example, a required number of first units are prepared in advance, in which the north pole side of one magnet body is joined to one side of one yoke to expose the south pole side of the magnet body, and a required number of second units are prepared in advance, in which the south pole side of one magnet body is joined to one side of one yoke to expose the north pole side of the magnet body, and these first and second units are joined in alternating order. In this case, the holder is attached by inserting bolts into each of the second bolt insertion holes of one plate. Then, first, either the first unit or the second unit is attached to one plate by inserting a bolt into the first bolt insertion hole of the yoke. Next, the other of the first unit or the second unit is attached to one plate by inserting a bolt into the first bolt insertion hole of the yoke.

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 to join them. At the beginning of the slide, they are of the same polarity and repel each other, temporarily preventing them from being attracted to each other. However, as described above, if they are further slid closer together and joined to each other by surface bonding, the magnetic flux of the magnet body is absorbed by the yoke, and they can be attracted to each other. In this way, the first unit and the second unit are joined in alternating order. At this time, it is only necessary to insert the bolt into the first bolt insertion hole of the yoke and push it in, so that the positioning can be easily performed and the assembly can be easily performed. Finally, the other plate is attached by inserting the bolt into its second bolt insertion hole and screwing a nut onto the bolt. In this way, each yoke is sandwiched between a pair of plates.

Next, the rotor holder is attached to the rotating shaft. In this case, since the holder can be fixed to the rotating shaft, the axis alignment between the rotating shaft and the rotor is ensured. Therefore, the rotor can be attached to the rotating shaft reliably and easily. And, when the rotating shaft is rotated, the rotor can rotate smoothly. Also, during rotation, each yoke is sandwiched between a pair of plates with a bolt inserted into its first bolt insertion hole, so that deviation due to centrifugal force during rotation of the rotor can be reliably prevented, and rotation can be performed smoothly. Also, since the first bolt insertion hole is formed at the base end of the yoke, and the width of the base end of the yoke is effectively reduced due to the increase in magnetic resistance caused by the use of a non-magnetic bolt, the magnetic flux of the magnet can be easily guided to the yoke.

If necessary, the stator may be a radially positioned stator that faces the outer peripheral surface of the rotor via an air gap and has multiple stator coils arranged at predetermined intervals on a circle centered on the rotation axis of the rotor.

If necessary, the stator may be configured to include 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 side and/or the other side perpendicular to the central axis of the rotor via an air gap.

Furthermore, as required, the stator may be configured to include a radial 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 the outer peripheral surface of the rotor via an air gap, and 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 side and/or the other side perpendicular to the central axis of the rotor via an air gap.

As a result, by having a radial position stator and an axial position stator, the stator coil can easily capture the magnetic flux of the rotor, thereby improving the efficiency of the synchronous rotating electric machine. For example, if a motor uses a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more, a highly efficient motor can be obtained.

Furthermore, as required, the stator may be a radial position stator including a plurality of stator coils arranged at predetermined intervals on a circumference centered on the rotation axis of the rotor and facing the outer circumferential surface of the rotor via an air gap, and a plurality of teeth provided corresponding to the plurality of stator coils, respectively, around which the stator coils are wound,
The teeth of the radial position stator are configured to include a main body facing the outer peripheral surface of the rotor via an air gap, and a convex strip protruding from both ends of the main body in the central axial direction toward the central axis and having facing portions facing one side and the other side of the rotor via an air gap, and the stator coil is wound around the teeth with at least the facing portions of the convex strip exposed.

As a result, the teeth of the radial position stator are configured with a main body facing the outer peripheral surface of the rotor and a convex strip having a facing portion facing one side and the other side of the rotor, so that the stator coil can easily capture the magnetic flux of the rotor, thereby improving the efficiency of the synchronous rotating electric machine. For example, if a motor uses a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more, a highly efficient motor can be obtained.

In this case, it is effective to interpose a non-magnetic insulating material between the main body and the protruding strip. This allows for a balance in the amount of magnetic flux density radiated from the main body facing the outer circumferential surface of the rotor and the protruding strip having a facing portion facing one side and the other side of the rotor.

In this case, it is also effective to arrange multiple sets of rotors and stators in a row on the same rotating shaft. As a result, the magnetic flux density that is 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 side and the other side of the rotor can be guided to the stator coil to the maximum extent, improving the efficiency of the synchronous rotating electric machine. For example, if a motor uses a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more, a highly efficient motor can be obtained.

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 the repulsive force. In addition, the magnetic flux radiated from the magnet body can be effectively guided to the yoke, and at the same time, magnetic saturation can be prevented, stably integrating the high-performance magnet and the yoke, and the magnetic flux density of the high-performance magnet can be maximized. This allows the motor to be used as a highly efficient electric motor (motor) or generator equipped with a ring-shaped rotor and a stator provided around the rotor. In particular, it is ideal for applications where the external dimensions are limited and weight reduction is required, such as small and slender spindle motors, motors mounted on the arm joints or the tips of robot arms, medical motors, etc., and by using these, it becomes extremely useful for machine tools, robots, handy manual tools, various medical devices, drones, etc., where small and lightweight are desired.

1A is an exploded perspective view showing a rotor and a stator in a synchronous rotating electric machine according to a first embodiment of the present invention, and FIG. 1B is a perspective view showing the rotor and the stator in an assembled state. 1 is an exploded perspective view showing a structure of a rotor of a synchronous rotating electric machine according to a first embodiment of the present invention; 1 is a diagram showing a rotor of a synchronous rotating electric machine according to a first embodiment of the present invention; 1 is a cross-sectional view showing a relationship between a rotor of a synchronous rotating electric machine according to a first embodiment of the present invention and a stator that is circumferentially surrounding the rotor via an air gap. FIG. 2 shows the basic structure of the magnet bodies and yokes and their relationship in the rotor of a synchronous rotating electric machine of the present invention, where (a) 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 (b) is a front view showing a state in which one magnet body has been attracted to the yoke to which the other magnet body is attracted. FIG. 2 shows the basic structure of the magnet bodies and yoke and their relationship in the rotor of a synchronous rotating electric machine of the present invention, where (a) is a front view showing a state in which one magnet body is attracted to a yoke to which the other magnet body is attracted, and (b) is a side view seen from a direction perpendicular to the side of the yoke. FIG. 6A shows the basic structure of the magnet body and yoke and their relationship in the rotor of a synchronous rotating electric machine of the present invention, with (a) being a cross-sectional view taken along line A-A in FIG. 6A showing the present invention in which the yoke protrudes axially from the magnet body, and (b) being a cross-sectional view equivalent to FIG. 7A showing the state in which the yoke does not protrude axially from the magnet body. FIG. 4 is a perspective view showing a synchronous rotating electric machine according to a second embodiment of the present invention. FIG. 11 is a cross-sectional view showing a modified example of a synchronous rotating electric machine according to the second embodiment of the present invention. FIG. 11 is a front view showing a synchronous rotating electric machine according to a third embodiment of the present invention. 10A shows a synchronous rotating electric machine according to a fourth embodiment of the present invention, in which (a) is a front view showing a rotor and a stator, (b) is a cross-sectional view showing a state in which one rotor and one stator are assembled (single axial type), and (c) is a cross-sectional view showing a state in which two rotors and one stator are assembled (double axial type). FIG. 13 is a diagram showing a synchronous rotating electric machine according to a fifth embodiment of the present invention, and illustrating the relationship between a rotor and a stator. FIG. 4 is an exploded perspective view showing another example of the rotor in the synchronous rotating electric machine according to each embodiment of the present invention. FIG. 13 is a diagram showing a state in which one magnet body is attracted to a yoke to which the other magnet body is attracted, in relation to the magnetic flux density sensor, in Test Example 1 of the present invention (a test relating to the relationship between the distance between the magnet body and the yoke and the magnetic flux density on the yoke surface). FIG. 2 is a graph showing the measurement results of Test Example 1 of the present invention. FIG. 11 is a graph showing the measurement results of Test Example 2 of the present invention (measurement of magnetic flux density on the surface of a yoke and on the surface of a magnet body). FIG. 11A is a diagram showing a state in which one magnetic body is attracted to a yoke to which another magnetic body is attracted, in relation to the measurement site of the magnetic flux density sensor (the center of the outer circumferential part spreading in the radial direction of the sector), relating to Test Example 3 of the present invention (Test <Part 1> for the central angle θ of the yoke), and FIG. 11B is a graph showing the results of measuring the magnetic flux density for different central angles of the yoke. FIG. 11A is a diagram showing measurement locations of a magnetic flux density sensor, and FIG. 11B is a graph showing the results of measuring the magnetic flux density for different central angles of the yoke, relating to Test Example 4 (Test <Part 2> for central angle θ of the yoke) of the present invention. FIG. 11 is a graph showing the results of calculating the total magnetic flux intensity for the number of magnetic poles by multiplying the magnetic flux intensity per unit of the magnet body 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 the central angle θ of the yoke). FIG. 14 is a graph showing the measurement results of magnetic flux density for yokes having different axial widths relative to the magnet body (the magnetic flux density was measured at the same positions 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 relative to the magnet body). FIG. 13 is a graph showing the results of measuring the relationship between thickness and magnetic flux density of a neodymium magnet, relating to Test Example 7 of the present invention (test on the thickness of the magnet body (the circumferential length Me of the magnet body)). FIG. 13A is a diagram showing measurement sites of a magnetic flux density sensor, and FIG. 13B is a graph showing measurement results for each holder material, relating to Test Example 8 of the present invention (test on holder material). FIG. 13A 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 of the present invention (test on rotor size), and FIG. 13B is a table showing the underlying data. FIG. 13 is a diagram showing different combinations (a), (b), (c), and (d) of the size of the neodymium magnet and the size of the yoke in relation to the area ratio of the yoke and the surface area ratio of the actual yoke (shaded area) in Test Example 9 (test on rotor size) of the present invention. FIG. 13 is a diagram visually illustrating the concept of torque-to-weight ratio coefficient F per unit weight for a yoke and two neodymium magnets sandwiching the yoke in an analysis for determining the optimal rotor size for obtaining maximum torque per weight, relating to Test Example 9 (Test on rotor size) of the present invention. FIG. 11 is a graph showing the relationship between magnet length Mr and torque-to-weight ratio coefficient F. 1A, 1B, and 1C show a prototype of a rotor that can be used in a synchronous rotating electric machine according to each embodiment of the present invention. 1A is a perspective view showing a first embodiment (prototype 1: radial gap motor), FIG. 1B is a perspective view showing a second embodiment (prototype 2: single axial gap motor), and FIG. 1C is a perspective view showing a third embodiment (prototype 3: double axial gap motor) of the present invention. FIG. 10 is a table showing the test results of Examples 1 to 3 and the estimated values of Example 4 in accordance with Test Example 10 (torque measurement test for the embodiments), and FIG. 10 is a table showing the data of Comparative Examples 1 to 7 (commercially available motors 1 to 7). FIG. 13 is a diagram showing a modified example of a rotor according to an embodiment of the present invention. 1 is a diagram showing a rotor of a conventional synchronous rotating electric machine together with problems associated therewith.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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.
1 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 (FIG. 4) and a radial position stator 20 as a stator provided around the rotor 1.

The rotor 1 is composed of a magnet body 2 made of multiple permanent magnets of the same shape and size arranged at equal angular intervals with the same poles facing each other along the circumferential direction centered on the central axis P of the rotation shaft S on the outside of the rotation shaft S, multiple yokes 3 arranged between adjacent magnet bodies 2, each having a side that joins with the side of the magnet body 2 and formed in a sector shape with a predetermined central angle, and a holder 10 made of a non-magnetic material through which the rotation shaft S is inserted and fixed, and which holds the base end of each yoke 3.

The magnet body 2 is made of a magnet material with a magnetic flux density of 150 mT or less, where B is the magnetic flux density. An example of a magnet material with a magnetic flux density of 150 mT or less is a rare earth magnet. A rare earth magnet is a high-performance magnet 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). In the embodiment, a neodymium magnet is used. The magnet body 2 is formed in an approximately rectangular parallelepiped shape.

The yoke 3 is made of an appropriate material, such as an iron-based material with high magnetic permeability and high saturation magnetic flux density, soft magnetic iron, pressed powder core, low carbon steel, silicon steel plate, etc. If necessary, it can be heat-treated or plated or painted to prevent rust.

The yoke 3 is set to 20°<θ<40° when its central angle is θ. Preferably, 20°<θ≦36°. More preferably, the range is 25.7°<θ≦36°, and when the number of yokes 3 is n, n=10, n=12, or n=14. In the embodiment, n=10 (θ=36°). At the outer end of the side surface of the yoke 3, a protruding piece 4 is formed to protrude along the circumferential direction and to abut against the outer end surface of the magnet body 2. At the inner end of the yoke 3, an engaging portion 5 is provided that protrudes left and right in the circumferential direction, while the holder 10 is formed with an engaged portion 6 that engages with the engaging portion 5 by inserting it 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 formed integrally and are formed in an approximately 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 7 of the yoke 3 and the engaging portion 5 fits into it. In this embodiment, ten engaged portions 6 are formed at equal angular intervals, matching the number of yokes 3 (n=10).

As shown in FIG. 6, the axial length of the magnet body 2 is Ma, the radial length is Mr, the axial length of the yoke 3 is Ya, and the radial length is Yr. Ma<Ya, Mr<Yr are set, and when the side of the magnet body 2 is viewed from a direction perpendicular to it, the periphery of the side of the yoke 3 protrudes from the periphery of the side of the magnet body 2 to join the side of the magnet body 2 and the side of the yoke 3. In the embodiment, since the yoke 3 has the above-mentioned engagement portion 5, the radial length Yr of the yoke 3 is set including the engagement portion 5. For example, the radius R (FIG. 3) of the rotor 1 is about 20 mm≦R≦80 mm, and is set to 5 mm≦Ya≦100 mm, 5 mm≦Yr≦55 mm. The circumferential length Me (thickness) of the magnet body 2 varies depending on the size of the radius R, but is set to 2 mm≦Me≦20 mm. Furthermore, from Test Example 9 described below, the optimal size of the magnet body 2 is 8 mm≦Ma≦10 mm, 5 mm≦Mr≦25 mm. The dimensions of each part are not limited to these.

In addition, when the projection dimension of the periphery of one side of the side of the yoke 3 in the axial direction relative to the periphery of the side of the magnet body 2 in the axial direction is Ea, the projection dimension of the periphery of the other side of the side of the yoke 3 in the axial direction relative to the periphery 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 peripheries of a pair of magnet bodies 2 joined to one yoke 3) is G, the values are set to 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.

In addition, when the protruding dimension of the radially outer periphery of the side surface of the yoke 3 relative to the radially outer periphery of the side surface of the magnet body 2 is Ec, it is configured to be set to 0.5 mm ≦ Ec ≦ 5 mm. Preferably, 0.5 mm ≦ Ec ≦ 3 mm, and more preferably, 0.5 mm ≦ Ec ≦ 1 mm. Stable adhesion is not possible when Ec = 0. In order to utilize 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, but it can be set within the range of protruding amount that allows stable adhesion.

The protruding dimension Ed of the radially inner periphery of the side surface of the yoke 3 relative to the radially inner periphery 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 specified in particular. However, it is desirable to make the protruding dimension Ed as small as possible. In the embodiment, since the engaging portion 5 is provided, the protruding dimension Ed is set to include the engaging portion 5.

The radial position stator 20 as a stator is configured with a plurality of (12 in the embodiment) stator coils 21 arranged at a predetermined interval on a circumference centered on the rotation axis S of the rotor 1 and facing the outer peripheral surface of the rotor 1 via an air gap, and a plurality of (12 in the embodiment) teeth 22 provided corresponding to the plurality of stator coils 21, respectively, around which the stator coils 21 are wound. The teeth 22 are fixed to a frame 23 made of a non-magnetic material formed in a ring shape surrounding the rotor 1.

As shown in FIG. 4, the teeth 22 of the radial position stator 20 are configured to include a main body 24 that faces the outer peripheral surface of the rotor 1 via an air gap, and a convex strip 25 that protrudes from both ends of the main body 24 in the direction of the central axis P toward the central axis P and has a facing portion 25a that faces one side and the other side of the rotor 1 via an air gap. A non-magnetic insulating member 26 is interposed between the main body 24 and the convex strip 25. The stator coil 21 is wound around a radial axis Q that is perpendicular to the central axis P and passes through the main body 24, with at least the facing portion 25a of the convex strip 25 exposed to the teeth 22.

Therefore, when assembling the rotor 1 in the synchronous rotating electric machine K according to this embodiment, as shown in FIG. 2, for example, a required number of first units U1 are prepared in advance, in which the N pole side of one magnet body 2 is joined to one side of one yoke 3, exposing the S pole side of the magnet body 2, and a required number of second units U2 are prepared in which the S pole side of one magnet body 2 is joined to one side of one yoke 3, exposing the N pole side of the magnet body 2. In this case, the magnet body 2 can be positioned by impacting against the protrusion 4 during assembly, making assembly even easier.

Then, the first unit U1 and the second unit U2 are assembled alternately 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.

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 to join, but at the beginning of the slide, they are of the same polarity and repel each other, making it impossible to attract them. However, this is only a temporary occurrence, and if they are further slid closer together and joined by surface bonding, the magnetic flux of the magnet body 2 is absorbed by the yoke 3, making it possible to attract them. In this way, the first unit U1 and the second unit U2 are joined in alternating order. Therefore, it is easy to position and assemble the units, as it is only necessary to engage and push the engaging portion 5 of the yoke 3 into the engaged portion 6 of the holder 10.

In more detail, although there is a state where the magnets cannot be attracted due to repulsion between the same poles, they can be attracted by bringing them even closer together and joining them by surface contact, as shown in FIG. 6. In this embodiment, the central angle θ of the yoke 3 is set to 20°<θ<40°, and the minimum gap 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, and further, 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. That is, the periphery of the yoke 3 (the entire periphery of the yoke 3) is configured to protrude from the periphery of the magnet body 2 (the entire periphery of the magnet body 2), and as shown in particular in FIG. 6(b) and FIG. 7(a), 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 direction and the axial direction. Therefore, when one magnet body 2 is brought even closer to the yoke 3 to which the other magnet body 2 is attracted and surface-joined, the magnetic flux of the S pole of the other magnet body 2 is absorbed by the yoke 3. In addition, the protruding dimension Ec of the radially outer periphery of the side of the yoke 3 relative to the radially outer periphery of the side of the magnet body 2 is set to 0.5 mm≦Ec≦5 mm, so that stable attraction can also be achieved in this respect.

In this way, the magnet body 2 and the yoke 3 are assembled in order to form the ring-shaped rotor 1. In assembling this rotor 1, the magnet body 2 can be stably attached to the yoke 3 without being pressed down by an external force, so it can be stably mounted and assembled, improving productivity and reducing costs. Then, the holder 10 of this rotor 1 is attached to the rotating shaft S. In this case, the holder 10 can be fixed to the rotating shaft S, so the axial alignment of the rotating shaft S and the rotor 1 is ensured. Therefore, the rotor 1 can be attached to the rotating shaft S reliably and easily. The rotor 1 is then assembled with the stator 20 to complete the synchronous rotating electric machine K.

In this synchronous rotating electric machine K, the root 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 direction and the axial direction, so that the magnetic flux can be guided to the yoke 3. Therefore, as shown in FIG. 6, the total magnetic flux density in the radial direction is significantly higher than that at the root (base end 7) of the yoke 3, and as a result, the magnetic flux density of the magnet body 2 can be utilized with maximum efficiency. In other words, in the rotor 1, the entire magnetic flux generated from the surface of the magnet body 2 can be absorbed by the yoke 3, and the yoke 3 can be magnetized to release the magnetic flux from the surface, so that the magnetic flux of the high magnetic flux density magnet can be effectively utilized. 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, and a motor that is easy to assemble, has high torque, is highly efficient, and is lightweight can be obtained.

Furthermore, the outer end of the side of the yoke 3 is formed with a protrusion 4 that protrudes in the circumferential direction and abuts against the outer end surface of the magnet body 2, so that the magnet body 2 can be reliably prevented from shifting due to the 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, so that the yoke 3 can be reliably prevented from shifting due to the centrifugal force when the rotor 1 rotates, allowing for smooth rotation.

Furthermore, the stator is provided with a radial position stator 20, and the teeth 22 of this radial position stator 20 are configured with a main body 24 facing the outer peripheral surface of the rotor 1 and a convex strip 25 having a facing portion 25a facing one side and the other side of the rotor 1, so that the stator coil 21 can easily capture the magnetic flux of the rotor 1, thereby improving the efficiency of the synchronous rotating electric machine K. For example, if a motor uses a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more, a highly efficient motor can be obtained. In addition, since a non-magnetic insulating member 26 is interposed between the main body 24 and the convex strip 25, the magnetic flux density radiated from the main body 24 and the convex strip 25 can be balanced.

Figure 8 shows a synchronous rotating electric machine K according to the second embodiment. This is configured by arranging multiple sets of the rotor 1 and stator 20 according to the first embodiment in a row on the same rotating shaft S. This improves the efficiency of the synchronous rotating electric machine K. For example, if a motor uses a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more, a highly efficient motor can be obtained. This is a particularly effective configuration when the motor diameter is not to be increased but high torque is desired.

Figure 9 shows a modified example of a synchronous rotating electric machine K according to the second embodiment. In this, the teeth 22 of each stator 20 shown in Figure 8 are integrated, the ridges 25 of adjacent teeth 22 are shared, and the stator coil 21 is wound around the entire ridges 25 with the opposing portions 25a of the ridges 25 exposed. In the case of a motor, this allows the magnetic flux generated from both sides of the ridges 25 to be effectively utilized, making effective use of electrical energy and increasing the torque per unit weight.

Figure 10 shows a synchronous rotating electric machine K according to a third embodiment. This machine is equipped with a radial position stator 20 as a stator. This radial position stator 20 faces the outer peripheral surface of the rotor 1 via an air gap and is configured with a plurality of stator coils 21 (12 in this embodiment) arranged at a predetermined interval 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 frame 27 made of a non-magnetic material formed in a ring shape surrounding the rotor 1.

Figure 11 shows a synchronous rotating electric machine K according to a fourth embodiment. As shown in Figure 11 (a), this includes an axial position stator 30 as a stator, which has one side and the other side facing a surface perpendicular to the central axis P of the rotor 1 via an air gap, and is configured with a plurality of (12 in the embodiment) stator coils 21 arranged at a predetermined interval on a circumference centered on the rotation axis S of the rotor 1, and a plurality of (12 in the embodiment) teeth 22 around which the stator coils 21 are wound, which are provided corresponding to the plurality of stator coils 21. The rotor 1 is fixed to a disk 31 centered on the central axis P, with one side perpendicular to the central axis P of the rotor 1. Figure 11 (b) shows an example (single axial type) in which the axial position stator 30 is fixed to a fixed body (not shown), one rotor 1 is attached to the rotation axis S, and the rotor 1 is arranged to face one side of the axial position stator 30. FIG. 11(c) 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.

Figure 12 shows a synchronous rotating electric machine K according to the fifth embodiment. This is configured with 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, if a motor uses a high-performance magnet such as a neodymium magnet with a magnetic flux density of 150 mT or more, a highly efficient motor can be obtained.

Figure 13 shows another example of a rotor in the synchronous rotating electric machine according to each of the above embodiments. In this rotor 1, the shape of the holder is different from that of the rotor in each of the above embodiments. In detail, this rotor 1 is configured with a holder 40 having a pair of plates 41 made of a non-magnetic material, which are inserted and fixed by a rotating shaft (not shown) and are attached to one side and the other side of the rotor 1 perpendicular to the central axis P to hold the base end of each yoke 3. A first bolt insertion hole 42 is formed in the base end of each yoke 3 along the axial direction of the rotating shaft P, while each plate of the holder 40 has a plurality of second bolt insertion holes 43 corresponding to the first bolt insertion holes 42. Then, a bolt 44 made of a non-magnetic material is inserted into the second bolt insertion hole 43 of one plate 41, the first bolt insertion hole 42 of each yoke 3, and the second bolt insertion hole 43 of the other plate 41, and a nut (not shown) made of a non-magnetic material is screwed onto each bolt 44, and each yoke 3 is sandwiched between the pair of plates 41.

In this way, when assembling the rotor 1, for example, a first unit U1 in which the N-pole side of one magnet body 2 is joined to one side of one yoke 3 to expose the S-pole side of the magnet body 2 and a second unit U2 in which the S-pole side of one magnet body 2 is joined to one side of one yoke 3 to expose the N-pole side of the magnet body are prepared in advance as many times as necessary, and the first unit U1 and the second unit U2 are joined in turn. In this case, the bolts 44 are inserted into the second bolt insertion holes 43 of one plate 41 of the holder 41 to attach them. Then, first, either the first unit U1 or the second unit U2 is attached to one plate 41 by inserting the bolt 44 into the first bolt insertion hole 42 of the yoke 3. Next, the other of the first unit U1 or the second unit U2 is attached to one plate 41 by inserting the corresponding bolt 44 into the first bolt insertion hole 42 of the yoke 3.

In this case, the magnet body 2 of either the first unit U1 or the second unit U2 slides and joins to the other side of the yoke 3 of either the first unit U1 or the second unit U2. At the beginning of the slide, they are of the same polarity and repel each other, temporarily preventing them from being attracted to each other. However, as described above, if they are further slid and brought closer together for surface joining, the magnetic flux of the magnet body 2 is absorbed by the yoke 3, and they can be attracted to each other. In this way, the first unit U1 and the second unit U2 are joined in turn. At this time, it is only necessary to insert the bolt 44 into the first bolt insertion hole 42 of the yoke 3 and push it in, so that the positioning can be easily performed and the assembly can be easily performed. 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. As a result, each yoke 3 is sandwiched between the pair of plates 41.

Next, the holder 40 of the rotor 1 is attached to the rotating shaft S. In this case, since the holder 40 can be fixed to the rotating shaft S, the axis alignment between the rotating shaft S and the rotor 1 is ensured. Therefore, the rotor 1 can be attached to the rotating shaft S reliably and easily. Then, when the rotating shaft S is rotated, the rotor 1 can rotate smoothly. Also, during rotation, each yoke 3 is sandwiched between a pair of plates 41 with a bolt 44 inserted into its first bolt insertion hole 42, so that deviation due to centrifugal force during rotation of the rotor 1 can be reliably prevented, and rotation can be performed smoothly. Also, since the first bolt insertion hole 42 is formed at the base end of the yoke 3, the non-magnetic bolt 44 penetrates it, so that the magnetic resistance increases, and the effect of the through hole is multiplied, and the width of the base end of the yoke 3 is effectively reduced, making it easier to guide the magnetic flux of the magnet to the yoke.

<Test Example>
Next, test examples supporting the present invention will be described.
(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)
6, a neodymium magnet with Ma = 10 mm, Mr = 20 mm, Me = 8 mm (B = 430 mT) was used as the magnet body 2. Six types of yokes 3 were prepared (without engaging portion 5) made of SS400 (iron material) with Ya = 11 mm, Yr = 22 mm, with central angles θ of 20°, 25°, 30°, 40°, 60°, and 80° (FIG. 15).

As shown in Figure 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. The measuring device used was the "MT-801" manufactured by Mother Tool Co., Ltd. In attaching the magnet bodies 2, one magnet body 2 was first attached to the yoke 3, and in this state the other magnet body 2 was brought closer to the side of the yoke 3, and the magnetic flux density on the surface of the yoke 3 was measured when the distance was 100 mm, 40 mm, 20 mm, 10 mm, 5 mm, and 2.5 mm. As the magnetic flux density sensor was approximately 2 mm thick, a gap of 2.5 mm was left and measurements were taken while changing the central angle θ of the yoke 3.

The results are shown in Figure 15. Initially, the magnetic flux density of one magnet body 2 (A) that was attached to the yoke 3 first was emitted from the surface of the yoke 3, but as the other magnet body 2 (B) approached, the magnetic flux density of magnet body 2 (B) began to be effectively absorbed by the yoke 3, resulting in a reversal. From around 5 mm, a yoke 3 with a central angle θ of 25° or more, which has a large volume and magnetic flux absorption capacity, will have a magnetic flux density that attracts magnet body 2 (B). At a distance of 2.5 mm, yokes 3 with central angles θ other than 20° generate a strong attraction force, but a yoke 3 with a central angle θ of 20° will not attract even when completely close due to magnetic saturation of the yoke 3.

(2) Test Example 2 (Measurement of magnetic flux density on the surface of the yoke 3 and the surface of the magnet body 2)
In the combination of the magnet body 2 and the yoke 3 in the test example 1, the magnetic flux density on the surface of the yoke 3 and the magnetic flux density on the surface of the magnet body 2 (B) 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 magnet body 2 (B) for the yoke 3 with a central angle θ of 20°. That is, it was found that in 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 the surface of the magnet body 2 (B), 420 mT, could not be completely absorbed. The reason for this is that the yoke 3 with a central angle θ of 20° has a small volume, so it cannot completely absorb the magnetic flux density of the combined magnet body 2 (A) and magnet body 2 (B). Therefore, in the case of the yoke 3 with a central angle θ of 20°, the magnetic flux density of the magnet body 2 (B) is not induced to the opposite pole, and the magnetic force density to be attracted is insufficient, so it is repelled by the same pole of the magnet body 2 (A). On the other hand, in a yoke 3 with a central angle θ of 25° or more, the surface magnetic flux density of the magnet body 2 (B) flows sufficiently into the yoke 3, and the surface of the yoke 3 is induced to the opposite pole (S), allowing magnetic attraction.

(3) Test Example 3 (Test on the central angle θ of the yoke 3 <Part 1>)
Three types of magnet bodies 2 were prepared as test pieces: a neodymium magnet (B=430mT), a neodymium magnet (B=153mT), and a ferrite magnet (B=143mT). Using the symbols shown in Fig. 6, magnet bodies 2 with Ma=10mm, Mr=20mm, and Me=8mm were used. Nine types of yokes 3 with Ya=11mm, Yr=22mm (without engaging portion 5) and central angles θ ranging from 20° to 80° and differing in increments of 5° were prepared (Fig. 17(b)).

As shown in Figure 17(a), 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, and the magnetic flux density was measured at the center of the radially spreading sector-shaped outer periphery of the yoke 3. The measuring device used was the "MT-801" manufactured by Mother Tool Co., Ltd. When attaching the magnet bodies 2, one magnet body 2 was first attached to the yoke 3, and in this state the other magnet body 2 was brought close to the side of the yoke 3 and attached.

The measurement results are shown in Figure 17 (b). When the central angle θ of the yoke 3 was 20°, the ferrite magnet was attracted, but in the case of neodymium magnets, the magnetic flux at the base end X of the yoke 3 was saturated and attraction was not possible. However, when the magnet bodies 2 had a central angle θ of 25° or more, they were temporarily unable to be attracted when they were brought close together due to repulsion, but were able to be attracted when brought even closer. This is because when one magnet body 2 is brought close to the yoke 3 to which the other magnet body 2 is attracted, the magnetic flux of the S 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.

(4) Test Example 4 (Test on the central angle θ of the yoke 3 <part 2>)
As the test specimens, similar to Test Example 1, a neodymium magnet with Ma = 10 mm, Mr = 20 mm, Me = 8 mm (B = 430 mT) was used as the magnet body 2. Five types of yokes 3 (without engaging portion 5) made of SS400 (iron material) with Ya = 11 mm, Yr = 22 mm were prepared with central angles θ of 20°, 25°, 30°, 40°, and 60° ( FIG. 18( b )).

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

The measurement results are shown in Figure 18 (b). In this figure, there is only one broken line at the bottom, but because the magnetic flux density is approximately the same on the radial surface, axial surface 1 (one surface), and axial surface 2 (the other surface), these broken lines overlap. 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.

(5) Test Example 5 (Test on the central angle θ of the yoke 3 <part 3>)
Using the same test specimen as in Test Example 3, the magnetic flux intensity per unit of the magnet body 2 was multiplied by the number of poles (the number of yokes 3) to calculate the total magnetic flux intensity for the number of magnetic poles, and the relationship between this and the central angle θ of the yoke 3 was examined. The results are shown in Fig. 19.

From the results of test examples 3 to 5, the central angle θ of the yoke 3 is considered to be appropriate in the range of 20°<θ<40°, and if it exceeds 40°, the magnetic flux density decreases. Preferably, it is 20°<θ≦36°. In practice, from 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 can be assumed that 10 poles (θ=36°), 12 poles (θ=30°), and 14 poles (θ≒25.7°) can effectively use the magnetic flux density of the neodymium magnet. If the central angle θ is widened, the number of poles decreases and the total magnetic flux density decreases at the same time, resulting in a decrease in efficiency. If the central angle θ is 20°, the magnetic flux saturates the yoke 3 and is not absorbed, and the magnetic flux density of the magnet body 2 cannot be effectively used, resulting in inefficiency. That is, it was found that the yoke 3 has a range of 25.7°<θ≦36°, and when the number of yokes 3 is n, n is an even integer, and a configuration in which n=10 (θ=36°), n=12 (θ=30°), or n=14 (θ≒25.7°) is preferable. When n=14, the central angle θ is not divisible, but this is within the margin of error in the adhesion between the magnet body 2 and the yoke 3, and does not affect the action or effect, so there is almost no problem. If the gap is a concern, an adhesive or similar can be used.

In addition, 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.

(6) Test Example 6 (Test on the amount of protrusion of the yoke 3 from the 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 the magnet body 2. The yoke 3 had Yr=22 mm (no engaging portion 5) and three types of central angles θ of θ=30°, θ=60°, and θ=80°, and 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) ( FIG. 20 ).

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 radially spreading outer periphery of the sector of the yoke 3 was measured using the same measuring device as above. Note that in this test, when the side of the magnet body 2 is viewed from a direction perpendicular to it, the periphery of the side of the yoke 3 protrudes from the periphery of the side of the magnet body 2 to join the side of the magnet body 2 and the side of the yoke 3.

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 in total on both sides) than in the case where the magnet body 2 was forcibly pressed down and attracted, but in reality it was not possible to attract it. The case where the yoke 3 protruded from the magnet body 2 was able to be stably attracted. It was also found that the magnetic flux density decreased as the protrusion amount increased. If the yoke 3 protrudes too much, the volume of the yoke 3 increases, increasing the surface area and decreasing the magnetic flux density. The magnetic flux density in the circumferential direction of the yoke 3 decreased by 10% with only a 1 mm protrusion on both sides in total. 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 was small (θ = 30°).

From these results, it can be said that the amount of protrusion 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.

Furthermore, from this, it can be said that it is preferable to set the protruding dimension Ec of the radially outer peripheral edge of the side surface of the yoke 3 to 0.5 mm ≤ Ec ≤ 5 mm. Desirably, 0.5 mm ≤ Ec ≤ 3 mm, and more desirably, 0.5 mm ≤ Ec ≤ 1 mm.

The protruding dimension Ed of the radially inner periphery of the side of the yoke 3 is set to 0.5 mm ≤ G ≤ 5 mm, so it does not need to be specified. However, it is desirable to make the protruding dimension Ed as small as possible.

(7) Test Example 7 (Test on the Thickness of the Magnet Body 2 (the Circumferential Length Me of the 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 with neodymium magnets, although they can fall below 150 mT, there is practical value in a magnet exceeding 150 mT, which cannot be achieved with ferrite. Magnetic flux density improves by increasing thickness, but considering efficiency per weight, it is best to keep it in the range of 6 mm≦Me≦10 mm. In other words, magnet thicknesses Me between 2 mm and 20 mm can be used, but a thickness between 6 mm and 10 mm is preferable.

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

Then, for three types of rotors 1 (10 poles) created using different types of holders 10, the magnetic flux density of the outer peripheral 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 22 (a).

The results are shown in Figure 22 (b). 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 most important opposite side of the yoke, and the magnetic flux density on the axial surface, by more than 10%.

(9) Test Example 9 (Test on Rotor Size)
(9-1) Regarding the radius (Ra) of the inner circumference 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, the inner radius Ra of the rotor is approximately
Ra ≒ (Me + G) × number of poles / 2π (Equation 1)
Because it is okay to
From this formula 1, the circumferential length of the inner circumference of the rotor is approximately 65 mm (radius approximately 10 mm) for 10 poles (θ=36°).
The maximum case is when there are 14 poles (θ≈25.7°), Me is at its maximum of 10 mm, and G is at its maximum of 5 mm, resulting in a circumferential length of approximately 210 mm (radius of approximately 35 mm). Therefore, in the case of neodymium magnets, the optimum range for the radius (Ra) of the rotor's inner circumference is approximately 10 mm to approximately 35 mm.

(9-2) Regarding the radius (R) of the rotor's outer circumference The diameter (radius R) of the rotor's outer circumference can be determined by considering the length (Mr) of the magnet. First, as shown in FIG. 23, a neodymium magnet (2a) with Ma=10mm, Mr=10mm, Me=10mm and a neodymium magnet (2b) with Ma=10mm, Mr=20mm, Me=10mm were used to measure the relationship between the yoke angle (θ) and the magnetic flux density at the center of the radially spreading outer circumference of the sector of the yoke in the above manner. As a result, the neodymium magnet (2a) is easily magnetically saturated because the size of the yoke is small, and it is difficult to attract the magnet when the yoke angle (θ) is 20° or 25°, and it is possible to attract the magnet from 30°. The neodymium magnet (2b) is large in size, so it is difficult to cause magnetic saturation, and it is not attracted when the yoke angle (θ) is 20°, but it can obtain sufficient attractive force at 25°.

We also confirmed the relationship between the length of the magnet (Mr), the yoke, and the radial magnetic flux density. From the results in Figure 23, it can be seen that the magnetic flux density decreases as the angle of the yoke increases and the volume increases. Also, for example, when comparing the yoke (θ = 30°), referring to Figures 24 (b) and (c), the size (volume) of the neodymium magnet is twice as large as that of the yoke of the neodymium magnet (2a) and the yoke of the neodymium magnet (2b), but the size (volume) of the yoke is four times as large. Therefore, as a result, the efficiency decreases drastically when the volume of the yoke increases. Looking at the actual measured values, the magnetic flux density at the center of the yoke using the neodymium magnet (2a) is 332 mT, and the magnetic flux density at the center of the yoke using the neodymium magnet (2b) is 285 mT, and the magnetic flux density decreases to about 85% despite the size of the magnet being doubled. This is because, although magnetic saturation is less likely to occur in a yoke using a neodymium magnet (2b), the magnetic flux is fully absorbed within the yoke and diffuses throughout, resulting in a significant reduction in the magnetic flux density that appears at the center of the yoke. From the results in Figure 23, this reduction in magnetic flux density of approximately 85% is not limited to when the yoke angle θ is 30°, but is common to all angles θ. This rate of reduction can be changed in a positive direction by using a material with good magnetic permeability. It is hoped that high-permeability materials will be developed as yoke materials.

Next, we analyzed the factor relationships that determine the optimal rotor size to obtain maximum torque per weight. We performed the analysis assuming (A) a stator (called a radial type) according to the embodiment shown in Figure 1, and (B) a stator (called an axial type) according to the embodiment shown in Figure 11(a).

(A) In the case of assuming the stator (radial type) according to the embodiment shown in FIG. 1, 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 F, and this is expressed as follows:
F ≒ (R × B × H) ÷ (M + Y) = [(Ra + Mr) × B × H] ÷ (M + Y)
... (Equation 2)
It was defined as:

here,
F: torque-to-weight ratio coefficient Mr: length of the magnet body in the radial direction of the rotor Ra: radius of the inner circumferential circle of the rotor Here, the radius is set to 15 mm.
R (≈Ra+Mr): radius of rotor outer circumferential circle H: surface area ratio of actual yoke (surface area ratio contributed by stator). Here, assuming the stator according to the embodiment shown in Fig. 1, the maximum length of the convex stripes 25 of the teeth 22 is about 10 mm, and as shown in Fig. 24, the surface area of the yoke using neodymium magnets (2a) (Fig. 24(b)) is set to 2 for easy understanding by adding up the axial surface and radial surface. That is, in Fig. 24(b), since the hatched parts of the yoke are on the front and back, the hatched parts 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.

M: weight ratio of neodymium magnet. Here, the weight of the neodymium magnet (2a) was set to 2.
Y: weight ratio of the yoke. Here, the weight of the yoke using the neodymium magnet (2a) was set to 1.
B (= ^0.85n ): magnetic flux density ratio of the yoke. Here, based on the results of Figure 23 above, it is assumed that the magnetic flux density drops to approximately 85% each time the length Mr of the neodymium magnet increases by 10 mm, and n is set to 0 when a neodymium magnet (2a) is used (magnetic flux density ratio B of the yoke is set to 1), and 1 is added to n for each 10 mm increase in length Mr. When a 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, and therefore B = (0.85) ² = 0.72.

In the case of a yoke using two neodymium magnets, when the length Mr of the neodymium magnets is 5 mm, 10 mm (in the case of a yoke using two neodymium magnets (2a)), 20 mm (in the case of a yoke using two neodymium magnets (2b)), 30 mm, 40 mm, or 50 mm, and the torque-to-weight ratio coefficients are respectively set to Fa to Ff, the calculation results are as follows using Equation 2:
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 surface, the specific surface area H is set to 0.5 and the magnet weight ratio M is set to 1.0 compared to one with a magnet length Mr of 10 mm.
Fa ≒ [(15 + 5) × 1.17 × 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

When these results are graphed, the relationship between magnet length Mr and torque weight ratio coefficient is as shown in Figure 26(a). Figure 26(b) shows the relationship between magnet length Mr and torque (the numerator part related to torque in the calculation formula for torque weight ratio coefficient). For example, it is expected that the torque of a rotor using neodymium magnet (2b) will increase proportionally compared to a rotor using neodymium magnet (2a), but there is no simple proportional relationship.
That is, in the torque 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 26(b). Since the yoke weight in the denominator is a quadratic function, the torque weight ratio coefficient is maximum for a length of 10 to 20 mm as shown in Figure 26(a), and as the magnet size increases, the denominator increases and gradually decreases.

(B) In the case of the stator (called axial type) according to the embodiment shown in Fig. 11(a), the torque ratio coefficient is calculated in the same manner as above, but since the axial type stator is large in size to approximate the size of the yoke, the value of the weight ratio portion of the yoke is set to 2Y to take this into consideration. 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.

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

Similarly, 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), and 50 mm (L = 32 mm), the torque-to-weight ratio coefficients are Fa to Ff, and the calculation using Equation 2 yields the following results.
Fa ≒ [(15 + 3) × 1.17 × 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

When these results are graphed, the relationship between magnet length Mr and torque-to-weight ratio coefficient is as shown in Figure 26(c). Figure 26(d) shows the relationship between magnet length Mr and torque (the numerator involved in torque in the torque-to-weight ratio coefficient calculation formula). In the case of the axial type (Figure 11(a)), it can be seen that the yoke area increases quadratically in relation to the magnet length. For magnet lengths up to 30 mm, the radial type (Figure 1) is advantageous, but for large-diameter motors with magnet lengths exceeding 40 mm, the axial type (Figure 11(a)) and double axial type (Figure 11(b)) are effective.

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

Next, an example will be described.
First, a rotor as shown in FIG. 27 was created. The rotor has the structure shown in FIG. 2 and FIG. 3, and has 10 poles using a yoke with a central angle θ of 36°. The rotor shown in FIG. 27(a) has a diameter of 40 mm, the neodymium magnet has a length (Mr) of 5 mm, a width (Ma) of 10 mm, and a thickness (Me) of 6 mm, and a magnetic flux density of 460 mT. The rotor shown in FIG. 27(b) has a diameter of 50 mm, the neodymium magnet has 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) has a diameter of 70 mm, and the neodymium magnet has a length (Mr) of 20 mm, a width (Ma) of 10 mm, and a thickness (Me) of 8 mm.

As shown in Fig. 28, motor prototypes (Examples 1 to 3) were created using the rotor and stator according to the embodiment shown in Fig. 10 and Fig. 11. In each example, the rotor 1 used was the rotor shown in Fig. 27(a) (diameter R is 40 mm, neodymium magnet length (Mr) 5 mm × width (Ma) 10 mm × thickness (Me) 6 mm, magnetic flux density 460 mT).

Example 1 (Prototype: (Radial Gap Motor))
As shown in Figure 28 (a), this is of the type shown in Figure 10, and is equipped with a rotor 1 and a radial position stator 20, as well as 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 halfway in the axial direction, and a fixed body 52 that is provided on the base 50 and fixes the radial position stator 20.

<Example 2 (Prototype 2: Single Axial Gap Motor)>
28(b), this is a single axial type shown in Fig. 11(b), and is equipped with one rotor 1 and axial position stator 30, as well as a base 50, a pair of bearing bodies 51 that are provided on the base 50 and 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 fixes the axial position stator 30. The rotor 1 is provided facing one surface of the axial position stator 30.

<Example 3 (Prototype 3: Double Axial Gap Motor)>
28(c), this is a double axial type shown in Fig. 11(c), and includes two rotors 1 and an axial position stator 30, 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 midway in the axial direction, and a fixed body (not shown) that is provided on the base 50 and 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, 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.

Example 4 (hypothetical example)
This is a hypothetical motor with the structure shown in Figure 1 (single radial + double axial).

In these 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 from 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 weight increase of 100 g for (shaft + exterior) (shown in parentheses). The results are shown in Figure 29 (a). Also, Figure 29 (b) shows the maximum torque and maximum torque per unit weight for seven types of commercially available motors as comparative examples.

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). In addition, as can be seen from the results and calculations of Example 3 (Test Machine 3), it was also found that high efficiency can be achieved by adopting a double axial type.

From these results, in the case of a rotor using a neodymium magnet with a length (Mr) of 20 mm shown in FIG. 27(c), it is assumed from the magnet length and torque ratio coefficient test in FIG. 26(b) that the simple torque value when using a neodymium magnet with a length (Mr) of 20 mm is 148, so if a proportional calculation is performed from the torque value of 12 for a magnet with a length (Mr) of 5 mm, it is assumed that about 10 times the torque can be obtained. Therefore, for example, with a motor with the structure shown in FIG. 1, it is assumed that a torque of about 10 N.m can be generated when driven at 24 V, and the weight of the motor with the exterior can be about 500 g. Furthermore, in the case of a double rotor (see FIG. 8), it is thought that a torque of about 20 N.m can be obtained with a weight of about 1 kg including the exterior. If the driving voltage is increased, for example to 50 V, a high output of 40 N.m can be obtained with a motor weighing 1 kg.

In addition, based on the magnet length and torque-to-weight ratio coefficient in FIG. 26(a), it is assumed that in the motor with the configuration shown in FIG. 1, the best efficiency per weight ratio is achieved when a neodymium magnet with a magnet length (Mr) of 20 mm is used. If weight is not a consideration, the magnet length can be further increased to 50 mm. However, considering the torque rise and maximum rotation speed, a motor using a rotor (see FIG. 8) with a rotor diameter of about 20 mm in magnet length (Mr) combined in multiple stages, a combination with an axial type (see FIG. 11), or a configuration with multiple stages of this is considered to be effective. For this reason, the present invention can be said to be extremely useful for spindle motors with large torque per weight, small and slender external shapes, and machine tools, robots, hand tools, drones, etc., where small and lightweight are desired.

In the rotor 1 of the synchronous rotating electric machine K according to the above embodiment, the magnet body 2 is formed in a rectangular parallelepiped shape, but this is not necessarily limited to this, and for example, as shown in FIG. 30, it may be sector-shaped (with a central angle α) and may be modified as appropriate. The number of yokes 3 (number of poles) is also not limited to the above number and may be modified as appropriate. Furthermore, in the above embodiment, the shape of the holder 10 is not limited to the above and may be modified as appropriate. In short, the present invention is not limited to the above-described embodiment of the present invention, and 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 included in the scope of the present invention.

The present invention can be used and utilized as a highly efficient electric motor (motor) or generator equipped with a ring-shaped rotor and a stator arranged around the rotor, and is extremely useful for spindle motors with large torque per weight, small and slender external shapes, and for machine tools, robots, hand tools, drones, etc. where small and lightweight are desired.

K synchronous rotating electric machine S rotating shaft 1 rotor P central axis 2 magnet body 3 yoke θ central angle 4 protrusion 5 engaging portion 6 engaged portion 7 base end portion 10 holder 20 radial position stator 21 stator coil 22 teeth 23 frame body 24 main body 25 convex strip body 25a facing portion 26 non-magnetic insulating member U1 first unit U2 second unit 27 frame body 30 axial position stator 31 disk 40 holder 41 plate 42 first bolt insertion hole 43 second bolt insertion hole 44 bolt 50 base 51 bearing body 52 fixed body

Claims (14)

A synchronous rotating electric machine comprising a ring-shaped rotor rotated by a rotating shaft and a stator provided around the rotor, the rotor being configured with magnet bodies made of a plurality of permanent magnets of the same shape and size arranged at equal angular intervals with like poles facing each other along a circumferential direction centered on the central axis of the rotating shaft on the outside of the rotating shaft, and a plurality of yokes arranged between adjacent magnet bodies, having side surfaces joining to side surfaces of the magnet bodies, and formed in a sector shape with a predetermined central angle, the same shape and the same size ,
A synchronous rotating electric machine characterized in that , when the axial length of the magnet body is Ma, the radial length of the magnet body is Mr, the axial length of the yoke is Ya, and the radial length of the yoke is Yr, Ma<Ya and Mr<Yr are set, and most of the magnetic flux of the magnet body is absorbed by the yoke . The magnet body is made of a magnet material having a magnetic flux density of 150 mT or less, where B is the magnetic flux density of the magnet body;
When the central angle of the yoke is θ, the central angle is set to 20°<θ<40°.
when the side surface of the magnet body is viewed in a direction perpendicular to the side surface of the magnet body, the peripheral edge of the side surface of the yoke is caused to protrude 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;
Let Ea be the protruding 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 in the axial direction on one side, Eb be the protruding dimension of the peripheral edge of the side surface of the yoke in the axial direction on the other side relative to the peripheral edge of the side surface of the magnet body in the axial direction on the other side, and G be the minimum distance between adjacent magnet bodies.
2. The synchronous rotating electric machine according to claim 1, wherein the following are set: 0.5 mm≦Ea≦5 mm, 0.5 mm≦Eb≦5 mm, and 0.5 mm≦G≦5 mm.. 3. A synchronous rotating electric machine according to claim 2 , characterized in that, when a protruding dimension Ec of the radially outer peripheral edge of the side surface of the yoke relative to a peripheral edge on the radially outer end side of the side surface of the magnet body is set to 0.5 mm≦Ec≦5 mm. 4. The synchronous rotating electric machine according to claim 3, wherein the yoke has an angle θ in the range of 25.7°< θ≦36 °, the number of the yokes being n, and n being any one of n=10, n=12, and n=14, and the 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 a side surface of said yoke, said protruding piece being formed along the circumferential direction and adapted to abut against the outer end surface of said magnet body. 6. The 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. 6. The synchronous rotating motor according to claim 5, wherein the rotor is configured to include a holder made of a non-magnetic material formed in a ring shape through 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 inner ends of the yokes being provided with engaging portions which protrude circumferentially to the left and right, and the outer periphery of the holder is formed with engaged portions which engage with the engaging portions when inserted from one or the other side of the holder perpendicular to the central axis. 6. The synchronous rotating electric machine according to claim 5, wherein the rotor is configured to include a holder having a pair of plates made of a non-magnetic material, into which the rotating shaft is inserted and fixed, and which are attached to one and the other faces of each of the yokes perpendicular to the central axis, respectively, to hold a 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 into 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, and nuts made of a non-magnetic material are screwed onto each bolt, so that each of the yokes is held by the pair of plates. 9. A synchronous rotating electric machine according to claim 1, further comprising a radial position stator, the stator being provided with a plurality of stator coils arranged at predetermined intervals on a circumference centered on the rotation axis of the rotor and facing the outer circumferential surface of the rotor via an air gap . 9. A synchronous rotating electric machine according to claim 1, further 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 surface perpendicular to the central axis of the rotor via an air gap. 9. The synchronous rotating electric machine according to claim 1, further comprising: a radial position stator having a plurality of stator coils arranged in a row at predetermined intervals on a circumference centered on the rotational axis of the rotor and facing an outer peripheral surface of the rotor via an air gap; and an axial position stator having a plurality of stator coils arranged in a row at predetermined intervals on a circumference centered on the rotational axis of the rotor and facing one side and/or the other side perpendicular to the central axis of the rotor via an air gap. The stator is a radial position stator including a plurality of stator coils arranged at predetermined intervals on a circumference centered on a rotation axis of the rotor and facing an outer circumferential surface of the rotor via an air gap, and a plurality of teeth provided corresponding to the plurality of stator coils, respectively, around which the stator coils are wound,
9. A synchronous rotating electric machine as claimed in any one of claims 1 to 8, characterized in that the teeth of the radial position stator are configured to include a main body facing the outer peripheral surface of the rotor via an air gap, and a convex strip protruding from both ends of the main body in the central axial direction towards the central axis and having facing portions facing one side and the other side of the rotor via an air gap, and the stator coil is wound around the teeth with at least the facing portions of the convex strip exposed. 13. The synchronous rotating electric machine according to claim 12, further comprising an insulating member interposed between said main body and said ridges. 14. The synchronous rotating electric machine according to claim 13, wherein a plurality of said rotor/stator pairs are arranged in line on the same rotating shaft.

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