Magnetic gear, and magnetic-geared electric machine

Abstract

A pole-piece unit of a magnetic gear includes a pole-piece support body having a connection part that is connected to each end of a plurality of pole pieces, and a radially extending part that extends from the connection part toward an inner side in a radial direction. A first yoke unit includes an end plate that is disposed on an end surface of a first body part in an axial direction, and faces the radially extending part with a predetermined gap therebetween in the axial direction. The end plate has a magnetic material part that is made of a magnetic material, and a non-magnetic material part that is made of a non-magnetic material and disposed on an outer side in the radial direction relative to the magnetic material part.

Description

[0001] The present disclosure relates to a magnetic gear and a magnetic geared electrical machine. The present application claims priority based on Japanese Patent Application No. 2022-173257 filed on October 28, 2022, the entire content of which is incorporated herein by reference. BACKGROUND ART

[0002] Conventionally, magnetic gears configured to transmit magnetic torque are known. For example, Patent Document 1 discloses a magnetic geared electrical machine that incorporates a magnetic gear. This magnetic geared electrical machine includes, in order from the radially inner side, an inner rotor supporting a plurality of permanent magnets, a pole piece unit including a plurality of pole pieces, and a stator. The stator is provided with a plurality of windings and a plurality of stator magnets. The pole piece unit illustrated in this document functions as an outer rotor that rotates on the outer peripheral side of the inner rotor. When the inner rotor rotates due to a rotating magnetic field generated in response to a three-phase alternating current flowing through the windings, the pole pieces modulate a magnetic flux between the inner rotor and the stator. The pole piece unit is rotated by the modulated magnetic field and the magnetic field of the stator magnets. Citation List Patent Literature

[0003] Patent Document 1: JP5643857B SUMMARY Problems to be Solved

[0004] During operation of the magnetic gear, if an axially flowing magnetic flux passes through the pole pieces as a leakage magnetic flux, an eddy current flows through the pole pieces, resulting in eddy current loss. The leakage magnetic flux can also flow to other components that make up the pole piece unit. For example, in a configuration where the pole piece unit has an opposing member that faces the inner rotor in the axial direction, eddy current loss can occur in the opposing member when the leakage magnetic flux passes through it. In particular, in a configuration where the opposing member is connected to a rotational shaft of the magnetic gear via a bearing, there is concern that the temperature of the bearing may exceed an allowable temperature as the temperature of the opposing member rises due to the generation of eddy current. Therefore, it is desirable to reduce eddy current loss in the pole piece unit.

[0005] An object of the present disclosure is to provide a magnetic gear and a magnetic geared electrical machine with reduced eddy current loss in the pole piece unit. Solution to the Problems

[0006] A magnetic gear according to at least one embodiment of the present disclosure includes: a first yoke unit including a first body part having a plurality of first magnets arranged in a circumferential direction with respect to an axis and a first yoke supporting the plurality of first magnets; a second yoke unit including a plurality of second magnets arranged in the circumferential direction on an outer peripheral side of the first yoke unit; and a pole piece unit including a plurality of pole pieces arranged in the circumferential direction between the first yoke unit and the second yoke unit. The pole piece unit further includes a pole piece support having a connection portion connected to an end portion of each of the plurality of pole pieces, and a radial extension portion extending radially inward from the connection portion. The first yoke unit further includes an end plate disposed on an end surface of the first body part in an axial direction and facing the radial extension portion with a predetermined gap in the axial direction. The end plate has: a magnetic material part formed of a magnetic material; and a non-magnetic material part formed of a non-magnetic material and disposed radially outward of the magnetic material part.

[0007] A magnetic geared electrical machine according to at least one embodiment of the present disclosure includes: the above-described magnetic gear; a coil provided on a second yoke supporting the second magnets; and a rotational shaft for transmitting torque between an external rotating device and the magnetic gear. Advantageous Effects

[0008] The present disclosure provides a magnetic gear and a magnetic geared electrical machine with reduced eddy current loss in the pole piece unit. BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1A is a schematic diagram of a magnetic gear according to an embodiment. FIG. IB is a schematic diagram of a magnetic gear according to another embodiment. FIG. 2Ais a schematic diagram showing an example of a schematic internal structure of a magnetic gear. FIG. 2B is a schematic diagram showing another example of a schematic internal structure of a magnetic gear. FIG. 3 is a schematic diagram showing a detailed internal structure of a magnetic gear according to an embodiment. FIG. 4 is a schematic graph showing eddy current loss obtained by simulation. FIG. 5 is a schematic diagram of an end plate according to an embodiment. FIG. 6 is a schematic graph showing the relationship between dimension L and distance R and loss percentage. FIG. 7 is a schematic graph showing the relationship between dimension D and distance S and loss percentage. FIG. 8 is a schematic diagram showing one end portion of a first yoke unit in the axial direction according to an embodiment. FIG. 9 is a schematic diagram showing a steel sheet as viewed in the axial direction according to an embodiment. FIG. 10A is a schematic diagram of a magnetic geared electrical machine (magnetic geared generator) according to an embodiment. FIG. 10B is a schematic diagram of a magnetic geared electrical machine (magnetic geared generator) according to another embodiment. FIG. 10C is a schematic diagram of a magnetic geared electrical machine (magnetic geared motor) according to an embodiment. FIG. 10D is a schematic diagram of a magnetic geared electrical machine (magnetic geared motor) according to another embodiment. DETAILED DESCRIPTION

[0010] Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions, and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present disclosure.

[0011] <1. Overview of magnetic gear 5> FIGs. 1A and IB are each a schematic diagram of a magnetic gear 5 according to some embodiments of the present disclosure. In the following description, “axial direction” or “axially” refers to the direction parallel to the axis Q of the magnetic gear 5, “radial direction” or “radially” refers to the direction perpendicular to the axis Q of the magnetic gear 5, and “circumferential direction” or “circumferentially” refers to the circumferential direction with respect to the axis Q of the magnetic gear 5. The magnetic gear 5 includes a rotational shaft A for transmitting power to and from an external rotating device, which will be described below. The axis of the rotational shaft A coincides with the axis Q.

[0012] The magnetic gear 5 illustrated in FIGs. 1A and IB includes a first yoke unit 10, a pole piece unit 30, and a second yoke unit 20. All three of these units extend in the axial direction.

[0013] A first body part 11, which is a component of the first yoke unit 10, has a plurality of first magnets 19 arranged in the circumferential direction with respect to the axis Q, and a first yoke 15 supporting the plurality of first magnets 19. A second body part 21, which is a component of the second yoke unit 20, has a plurality of second magnets 29 arranged in the circumferential direction, and a second yoke 25 supporting the plurality of second magnets 29. The pole piece unit 30 includes a plurality of pole pieces 50 and a pair of pole piece supports 37. The plurality of pole pieces 50 are arranged in the circumferential direction between the first yoke unit 10 and the second yoke unit 20. The pair of pole piece supports 37 are connected to both axial ends of each of the plurality of pole pieces 50, respectively. As an example, each of the pole pieces 50 may have a plurality of electromagnetic steel sheets 150 laminated in the axial direction (see FIG. 3). The pole piece unit 30 in this example further includes a plurality of holders (not shown) for sandwiching each of the pole pieces 50 therebetween in the circumferential direction. Both axial ends of the plurality of holders are also connected to the pair of pole piece supports 37, respectively. The plurality of holders may constitute a ring member. In some embodiments, the number of second magnets 29 is greater than the number of pole pieces 50, and the number of pole pieces 50 is greater than the number of first magnets 19. Further, the circumferential length of the first magnet 19 is longer than the circumferential length of the second magnet 29.

[0014] In the magnetic gear 5 of the present disclosure, one of the first yoke unit 10, the second yoke unit 20, or the pole piece unit 30 functions as a stator, and the remaining two function as rotors. The following describes a magnetic gear 5A (5), in which the second yoke unit 20 functions as a stator, and a magnetic gear 5B (5), in which the pole piece unit 30 functions as a stator, in order.

[0015] <1-1. Magnetic gear 5A (5) according to one embodiment The magnetic gear 5A (5) illustrated in FIG. 1A includes a housing 98 that may be installed on a base 101. In the illustrated example, the second yoke unit 20 functions as a stator, and the rotational shaft A includes a first rotational shaft Al and a second rotational shaft A2 that are coaxial with each other. The housing 98 rotatably supports the first rotational shaft Al, which may function as an input shaft. One of the pair of pole piece supports 37 is connected to the first rotational shaft Al, while the other is connected via a bearing Bl to the second rotational shaft A2. Thus, the pole piece unit 30 illustrated in this figure functions as a rotor that rotates with the first rotational shaft Al. The second rotational shaft A2, which may function as an output shaft, supports the first yoke unit 10 disposed between the pair of pole piece supports 37. Thus, the first yoke unit 10 illustrated in this figure functions as a rotor that rotates with the second rotational shaft A2. The second rotational shaft A2 is rotatably supported by the housing 98 via a bearing. One end of the second rotational shaft A2 may be connected to the first rotational shaft Al via a bearing or may not be connected to the first rotational shaft Al.

[0016] The magnetic gear 5A operates as follows, for example. As the first rotational shaft Al as the input shaft rotates with the pole piece unit 30, the relative positions of the plurality of pole pieces 50, the plurality of first magnets 19, and the plurality of second magnets 29 change. This modulates a magnetic flux between the first yoke unit 10 and the second yoke unit 20, and the first magnets 19 receive a magnetic force from the modulated magnetic field, causing the first yoke unit 10 to rotate. As a result, the second rotational shaft A2 as the output shaft rotates.

[0017] In the magnetic gear 5 A, the second rotational shaft A2 may function as an input shaft, and the first rotational shaft Al may function as an output shaft. Even in this case, as the first yoke unit 10 rotates with the second rotational shaft A2, the relative positions of the plurality of pole pieces 50 and the plurality of first magnets 19 change. This modulates a magnetic flux between the first yoke unit 10 and the second yoke unit 20, and the pole pieces 50 receive a magnetic force from the modulated magnetic field, causing the pole piece unit 30 to rotate. As a result, the first rotational shaft Al as the output shaft rotates.

[0018] In the magnetic gear 5 A, NL = NH + NS holds, where NL is the number of magnetic poles of the pole pieces 50 of the pole piece unit 30, NH is the number of pairs of magnetic poles (pole pairs) of the first magnets 19 of the first yoke unit 10, and NS is the number of pairs of magnetic poles (pole pairs) of the second magnets 29 of the second yoke unit 20. If this relationship holds, the ratio of the number of rotations of the first yoke unit 10 to the pole piece unit 30 is expressed as NL / NH. In this example, NL / NH is greater than 1, meaning that the first yoke unit 10 functions as a high-speed rotor and the pole piece unit 30 functions as a low-speed rotor. The number of magnetic poles NL of the pole pieces 50 is smaller than the number of pole pairs NS of the second magnets 29.

[0019] <1-2. Magnetic gear 5B (5) according to another embodiment> In the magnetic gear 5B (5) according to another embodiment illustrated in FIG. IB, the pole piece unit 30 functions as a stator, and the first yoke unit 10 and the second yoke unit 20 function as rotors. The rotational shaft A includes a first rotational shaft Al and a second rotational shaft A2 that are coaxial with each other. The magnetic gear 5B includes a housing 96 that may be installed on a base 101, and the pole piece unit 30 is supported by the housing 96. The pair of pole piece supports 37 may be integrally formed with the housing 96. One of the pair of pole piece supports 37 in this example rotatably supports the second rotational shaft A2, which may function as an output shaft, via a bearing B1.

[0020] The first rotational shaft Al, which may function as an input shaft, is rotatably supported by a support unit (not shown) and is connected to the second yoke unit 20 via a connecting member 95. The second yoke unit 20 may be connected to the pole piece unit 30 via a bearing. The second rotational shaft A2 may be connected to the first rotational shaft Al via a bearing or may not be connected to the first rotational shaft Al.

[0021] The magnetic gear 5B operates as follows, for example. As the first rotational shaft Al as the input shaft rotates with the second yoke unit 20, the relative positions of the plurality of pole pieces 50 and the plurality of second magnets 29 change. This modulates a magnetic flux between the first yoke unit 10 and the second yoke unit 20, and the first magnets 19 receive a magnetic force from the modulated magnetic field, causing the first yoke unit 10 to rotate. As a result, the second rotational shaft A2 as the output shaft rotates.

[0022] In the magnetic gear 5B, the second rotational shaft A2 may function as an input shaft, and the first rotational shaft Al may function as an output shaft. Even in this case, as the first yoke unit 10 rotates with the second rotational shaft A2, the relative positions of the plurality of pole pieces 50 and the plurality of first magnets 19 change. This modulates a magnetic flux between the first yoke unit 10 and the second yoke unit 20, and the second magnets 29 receive a magnetic force from the modulated magnetic field, causing the second yoke unit 20 to rotate. As a result, the first rotational shaft Al as the output shaft rotates.

[0023] <1-3. Supplement to magnetic gear 5> The magnetic gears 5 illustrated in FIGs. 1A and IB may be incorporated into a magnetic geared electrical machine 1 (more specifically, magnetic geared generator 2 or magnetic geared motor 3) as will be described below (see FIGs. 10A to 10D). When the magnetic gear 5 is incorporated into the magnetic geared generator 2, the rotational shaft A does not have to include either the first rotational shaft Al or the second rotational shaft A2 that functions as an output shaft. When the magnetic gear 5 is incorporated into the magnetic geared motor 3, the rotational shaft A does not have to include either the first rotational shaft Al or the second rotational shaft A2 that functions as an input shaft. Furthermore, even when the magnetic gear 5 is incorporated into either the magnetic geared generator 2 or the magnetic geared motor 3, the rotational shaft A may consist of a single shaft member. In this embodiment, although not illustrated in detail, a single rotational shaft A may be rotatably supported by the housing 98 (see FIG. 1A) and rotatably connected to the first yoke unit 10, and the pair of pole piece supports 37 may be fixed to outer peripheral portions of the rotational shaft A. In this case, the first yoke unit 10 and the pole piece unit 30 function as rotors, and the second yoke unit 20 functions as a stator.

[0024] <2. Overview of internal structure of magnetic gear 5> FIGs. 2A and 2B are each a schematic diagram showing the internal structure of the magnetic gear 5 according to some embodiments of the present disclosure. In FIGs. 2A and 2B, which are schematic diagrams, the circumferential direction is shown linearly. In the internal structure of the magnetic gear 5, each of the axially extending pole piece 50 faces the first yoke unit 10 with a first gap G1 and faces the second yoke unit 20 with a second gap G2. In some embodiments of the present disclosure, at least one of the outer peripheral surface or inner peripheral surface of the pole pieces 50 may be covered by a pole piece cover (not shown). The material forming the pole piece cover is preferably a non-magnetic material, more preferably a non-magnetic and non-conductive material. In an embodiment where the pole piece cover includes an outer pole piece cover covering the outer peripheral surface of the pole pieces 50 and an inner pole piece cover covering the inner peripheral surface of the pole pieces 50, each pole piece 50 faces the first yoke unit 10 with the first gap G1 and the inner pole piece cover therebetween and faces the second yoke unit 20 with the second gap G2 and the outer pole piece cover therebetween. The pole piece cover may not only cover the pole pieces 50, but also at least one of the outer peripheral surface or inner peripheral surface of the abovedescribed holders.

[0025] <2-1. Example of schematic internal structure of magnetic gear 5> The first body part 11A (11) of the first yoke unit 10A (10) shown in FIG. 2A has a plurality of first magnets 19 and a first yoke 15A (15) supporting the plurality of first magnets 19. The first body part HA (11) has a structure of surface permanent magnet type (SPM) in which the plurality of first magnets 19 are disposed on the surface of the first yoke 15. Thus, the plurality of first magnets 19 face the plurality of pole pieces 50 with the first gap G1 (or with the first gap G1 and the inner pole piece cover) therebetween.

[0026] The second body part 21 of the second yoke unit 20 shown in this figure has a plurality of second magnets 29 and a second yoke 25 supporting the plurality of second magnets 29. The second yoke 25 has a stator core 27 extending in the circumferential direction and a plurality of teeth 28 protruding radially inward from the stator core 27. The plurality of teeth 28 are arranged at intervals in the circumferential direction, and the plurality of second magnets 29 are disposed on the tip side of the plurality of teeth 28. Although not illustrated in detail, the second yoke 25 may not have the plurality of teeth 28. In this case, the plurality of second magnets 29 may be attached to the inner peripheral surface of the stator core 27.

[0027] <2-2. Another example of schematic internal structure of magnetic gear 5> The first body part 1 IB (11) of the first yoke unit 10B (10) shown in FIG. 2B has a plurality of first magnets 19 and a first yoke 15B (15) supporting the plurality of first magnets 19. The first body part 11B (11) has a structure of interior permanent magnet type (IPM) in which the plurality of first magnets 19 are disposed inside the first yoke 15. Thus, the first yoke 15 faces the plurality of pole pieces 50 with the first gap G1 (or with the first gap G1 and the above-described inner pole piece cover) therebetween. The second yoke unit 20 shown in FIG. 2B is the same as the second yoke unit 20 shown in FIG. 2A. The second yoke unit 20 shown in FIG. 2B may not have the plurality of teeth 28.

[0028] <3. Detailed internal structure of magnetic gear 5> Referring to FIGs. 3 to 9, a detailed internal structure of the magnetic gear 5 according to some embodiments of the present disclosure will be described. FIG. 3 is a schematic diagram showing a detailed internal structure of the magnetic gear 5 according to an embodiment, with the first yoke 15 having the IPM structure. In the following, the configuration of the magnetic gear 5 on one side in the axial direction is mainly described.

[0029] As illustrated in FIG. 3, the pole piece support 37 of the pole piece unit 30 has a connection portion 35 connected to an end portion of each of the plurality of pole pieces 50, and a radial extension portion 36 extending radially inward from the connection portion 35. The connection portion 35 and the radial extension portion 36 may be formed of the same material or may be formed of different materials. In the illustrated example, the radially inner end of the radial extension portion 36 is connected to the first rotational shaft Al. The inner end of the radial extension portion 36 may be connected to the second rotational shaft A2 via the bearing Bl (see FIG. 1A).

[0030] The first yoke unit 10 includes an end plate 17. The end plate 17 is disposed on an end surface 11S of the first body part 11 in the axial direction. More specifically, at least a part of the end plate 17 faces and touches the end surface 11S of the first body part 11. Further, the end plate 17 faces the radial extension portion 36 with a predetermined gap G3 in the axial direction. The end plate 17 has a magnetic material part 18 formed of a magnetic material and a non-magnetic material part 16 formed of a non-magnetic material. Examples of the magnetic material include steel sheets. Examples of the non-magnetic metal include stainless steel and aluminum. The non-magnetic material is not limited to metals, but can be plastics, such as carbon fiber-reinforced plastics or glass fiber-reinforced plastics, for example. Carbon fiber-reinforced plastics and glass-fiber-reinforced plastics are both non-magnetic and non-conductive materials. That is, the non-magnetic material forming the non-magnetic material part 16 may be non-conductive. The non-magnetic material part 16 is disposed radially outward of the magnetic material part 18 and constitutes an outer end portion of the end plate 17 in the radial direction. For the sake of clarity, the end plate 17 in FIG. 3 is not hatched (the same applies to FIG. 4).

[0031] The advantages of adopting the above configuration are as follows. During operation of the magnetic gear 5, a leakage magnetic flux is generated between the first yoke unit 10 and the second yoke unit 20. The leakage magnetic flux is, for example, a magnetic flux that flows in the axial direction through an end portion of each of the plurality of pole pieces 50 (the leakage magnetic flux flows in the direction illustrated by Arrow Cl, but is not limited to the direction of this arrow). In the magnetic gear 5 of the present disclosure, at least a part of the leakage magnetic flux is directed to the magnetic material part 18 of the end plate 17 (e.g., Arrow C2). This suppresses the leakage magnetic flux flowing to the pole piece support 37 and reduces eddy current loss in the pole piece support 37. Furthermore, the non-magnetic material part 16 is disposed radially outward of the magnetic material part 18, and the non-magnetic material part 16 is in proximity to axial end portions of the pole pieces 50. Since the magnetic flux tends to flow in such a way that it avoids the non-magnetic material part 16, it is possible to reduce the generation itself of the leakage magnetic flux that passes in the axial direction through the pole pieces 50. From the above, it is possible to achieve the magnetic gear 5 with reduced eddy current loss in the pole piece unit 30 due to the generation of the leakage magnetic flux. In the embodiment where the inner end of the radial extension portion 36 is connected to the bearing Bl (see FIGs. lAand IB), the temperature rise of the radial extension portion 36 is suppressed with the reduction in eddy current loss in the pole piece unit 30, so that the temperature of the bearing Bl is prevented from exceeding an allowable temperature.

[0032] The above advantages can also be obtained for the same reason in the embodiment where the first yoke unit 10 has the SPM structure. Even in the embodiment where the radial extension portion 36 is not connected to the bearing Bl, it is possible to suppress eddy current loss in the pole piece unit 30.

[0033] It can be confirmed by simulation that the above advantages can be obtained by the configuration with the magnetic material part 18 and the non-magnetic material part 16 disposed radially outward of the magnetic material part 18. FIG. 4 shows eddy current loss in each of the magnetic gear 5 according to an embodiment, the first sample, and the second sample. The first sample is a magnetic gear in which the end plate 17 of the magnetic gear 5 is replaced by a first end plate composed solely of the material of the non-magnetic material part 16. The second sample is a magnetic gear in which the end plate 17 of the magnetic gear 5 is replaced by a second end plate including a magnetic material part and a non-magnetic material part arranged in the axial direction. In the second end plate, the magnetic material part is located closer to the pole piece support 37 than the non-magnetic material part. The first end plate and the second end plate have the same size as the end plate 17.

[0034] FIG. 4 shows the total eddy current loss, with the eddy current loss in the pole piece unit 30 indicated by hatching as a proportion of the total eddy current loss. As shown in this figure, the magnetic gear 5 according to the present embodiment can reduce the eddy current loss in the pole piece unit 30 compared to the first sample, as well as the overall eddy current loss. Further, the magnetic gear 5 according to the present embodiment can reduce the overall eddy current loss, although it increases the eddy current loss in the pole piece unit 30 compared to the second sample. Therefore, according to the simulation results, it is understood that the magnetic gear 5 can reduce both the overall eddy current loss and the eddy current loss in the pole piece unit 30 in a well-balanced manner.

[0035] As described above, the non-magnetic material forming the non-magnetic material part 16 may be non-conductive. Even if the non-magnetic material part 16 is a non-magnetic material, the leakage magnetic flux links with the non-magnetic material part 16. In this regard, with the above configuration, eddy current loss in the non-magnetic material part 16 can be suppressed by making the non-magnetic material forming the non-magnetic material part 16 non-conductive. Therefore, the magnetic gear 5 can suppress the overall eddy current loss.

[0036] FIG. 5 is a schematic diagram of the end plate 17 according to an embodiment of the present disclosure. The end plate 17 in this figure has a configuration in which the magnetic material part 18 and the non-magnetic material part 16 are in direct contact with each other. The boundary 33 between the magnetic material part 18 and the non-magnetic material part 16 is parallel to the axial direction as an example. The boundary 33 is located radially outward of an inner peripheral surface 19A of each of the plurality of first magnets 19. With the above configuration, a magnetic outer end portion 181, which is an outer end portion of the magnetic material part 18 in the radial direction, is in proximity to the pole pieces 50. This makes it easier for the leakage magnetic flux generated in the pole pieces 50 to be directed to the magnetic material part 18, further suppressing eddy current loss in the pole piece unit 30.

[0037] In another embodiment, instead of being parallel to the axial direction, the boundary 33 may be zigzag or step-like shape, for example. In this case, the entire boundary 33 is located radially outward of the inner peripheral surface 19 A. An additional member may be interposed between the magnetic material part 18 and the non-magnetic material part 16. In this case, the additional member corresponds to the boundary 33. Further, the first yoke unit 10 may have the SPM structure. In any embodiment, the above advantages can be obtained.

[0038] In some embodiments of the present disclosure, the magnetic gear 5 satisfies a relationship of R <L <6 / R, where L is the dimension of the non-magnetic material part 16 in the radial direction, and R is the distance (shortest distance) between the pole pieces 50 and the first yoke unit 10 in the radial direction. It is further preferred that the magnetic gear 5 satisfy a relationship of 2 R <L <4*R. In the embodiment of FIG. 5 in which the first yoke 15 has the IPM structure, the distance R is the shortest distance between the pole piece 50 and the first yoke 15 in the radial direction. In the embodiment of FIG. 2A in which the first yoke 15 has the SPM structure, the distance R is the shortest distance between the pole piece 50 and the first magnet 19 in the radial direction. With the above configuration, since L <6*R (preferably, L <4*R) is satisfied, the magnetic material part 18 is avoided from being too far away from the pole pieces 50, and the magnetic flux short-circuit between the pole pieces 50 and the magnetic material part 18 can be suppressed. Further, since L >R (preferably, L >2*R) is satisfied, it is possible to ensure the minimum required size of the non-magnetic material part 16 and suppress the generation itself of the leakage magnetic flux in the pole pieces 50.

[0039] The effect of reducing eddy current loss by satisfying the relationship of R <L <6*R can also be confirmed by simulation. FIG. 6 is a schematic graph showing the relationship between dimension L and distance R and loss percentage. The horizontal axis of the graph represents the ratio of dimension L of the non-magnetic material part 16 to distance R (i.e., L / R). The vertical axis of the graph represents the percentage of the overall loss in the magnetic gear 5 (more specifically, magnetic geared motor 3, which will be described below). The overall loss includes the overall iron loss in the magnetic gear 5, such as the overall eddy current loss in the magnetic gear 5. In the graph, the overall loss in a configuration where the non-magnetic material part 16 is not provided (i.e., L = 0) is 100%. In this simulation, L = 0 means an embodiment where the end plate 17 is composed only of the magnetic material part 18. In the graph, the relationship between L / R and the loss percentage predicted based on four points calculated by the simulation is shown by the thick solid line.

[0040] According to the graph, the overall loss is reduced by more than about 5% in the range of 1 <L / R <6. Therefore, it is understood that the overall loss is reduced when the magnetic gear 5 satisfies the relationship of R <L <6 / R. According to this simulation, the reduction in overall loss is due to the reduction in eddy current loss in the pole piece support 37, and it is understood that the eddy current loss in the pole piece unit 30 is reduced when the magnetic gear 5 satisfies the relationship of R <L <6*R. In addition, the overall loss is reduced by more than about 8% in the range of 2 <L / R <4. Therefore, it is understood that the eddy current loss in the pole piece unit 30 is reduced when the magnetic gear 5 satisfies the relationship of 2*R <L <4*R. In the same graph, as L / R exceeds 6, the overall loss reduction effect diminishes. This is because the non-magnetic material part 16 becomes too long in the radial direction, causing the pole pieces 50 and the magnetic material part 18 to be too far away from each other. As a result, the magnetic flux between the pole pieces 50 and the magnetic material part 18 short-circuits, leading to an increase in eddy current loss in the pole piece unit 30.

[0041] Referring to FIG. 5 again, in some embodiments of the present disclosure, the magnetic gear 5 satisfies a relationship of D >0.15 x S, where D is the dimension of the magnetic material part 18 in the axial direction, and S is the distance (shortest distance) between the radial extension portion 36 and the first body part 11 in the axial direction. As a more specific example, the magnetic gear 5 satisfies a relationship of 0.15*S <D <S. When D <S is satisfied, contact between the end plate 17 and the pole piece support 37 is avoided. With the above configuration, since D >0.15><S is satisfied, the magnetic material part 18 is avoided from being too short in the axial direction, and the magnetic flux short-circuit between the pole pieces 50 and the magnetic material part 18 can be suppressed.

[0042] The effect of reducing eddy current loss by satisfying the relationship of D >0.15 S can also be confirmed by simulation. FIG. 7 is a schematic graph showing the relationship between dimension D and distance S and loss percentage. The horizontal axis of the graph represents the ratio of dimension D of the magnetic material part 18 to distance S (i.e., D / S). The vertical axis of the graph is the same as the vertical axis in FIG. 6 and represents the percentage of the overall loss in the magnetic gear 5 (more specifically, magnetic geared motor 3, which will be described below). The overall loss in a configuration where the magnetic material part 18 is not provided (i.e., D = 0) is 100%. In this simulation, D = 0 means an embodiment where the end plate 17 is not provided. In the graph, the thick solid line connecting four points calculated by the simulation is shown for convenience. According to the graph, the overall loss is reduced by more than about 10% when D / S is equal to or greater than 0.15. According to this simulation, the reduction of more than 10% in overall loss is due to the reduction in eddy current loss in the pole piece support 37, and it is understood that the eddy current loss in the pole piece unit 30 is further reduced when the magnetic gear 5 satisfies the relationship of D >0.15 / S.

[0043] Referring to FIG. 4 again, in some embodiments of the present disclosure, the radial extension portion 36 of the pole piece unit 30 is formed of a non-magnetic material. Illustrative examples of the non-magnetic material are as previously described. With the above configuration, since the radial extension portion 36 is a non-magnetic material, it is possible to further suppress the leakage magnetic flux flowing from the pole pieces 50 to the radial extension portion 36 and reduce eddy current loss in the pole piece unit 30. The radial extension portion 36 in this example is formed of a non-magnetic and non-conductive material. Illustrative examples of the non-magnetic and non-conductive material are as previously described. With the above configuration, since the radial extension portion 36 is a nonmagnetic and non-conductive material, it is possible to further suppress the leakage magnetic flux from the pole piece 50 to the radial extension portion 36 and reduce eddy current loss in the pole piece unit 30.

[0044] FIG. 8 is a schematic diagram showing one end portion of the first yoke unit 10 in the axial direction according to an embodiment of the present disclosure. The non-magnetic material part 16 has a base portion 193 and a non-magnetic inner end portion 191 protruding radially inward from the base portion 193. The non-magnetic inner end portion 191 is an inner end portion of the non-magnetic material part 16 in the radial direction. The axial length of the non-magnetic inner end portion 191 is shorter than the axial length of the base portion 193. The magnetic material part 18 has a base portion 183 and a magnetic outer end portion 181 protruding radially outward from the base portion 183. The base portion 183 faces the first body part 11 with a gap G4 in the axial direction. In this figure, the radially outer portion of the gap G4 between the end plate 17 and the first body part 11 is closed by the non-magnetic material part 16. The magnetic outer end portion 181 is an outer end portion of the magnetic material part 18 in the radial direction. The axial length of the magnetic outer end portion 181 is shorter than the axial length of the base portion 183. The magnetic outer end portion 181 and the non-magnetic inner end portion 191 are aligned in the axial direction. More specifically, the magnetic outer end portion 181 is located on the opposite side of the nonmagnetic inner end portion 191 from the first body part 11 and is in contact with the nonmagnetic inner end portion 191. Thus, the non-magnetic inner end portion 191 faces and touches the end surface 11S of the first body part 11. With the above configuration, since the non-magnetic inner end portion 191 faces the first body part 11, it is possible to suppress the deformation of the first body part 11 (especially, a radially outer end portion of the first body part 11) toward the pole piece support 37. Instead of contacting the end surface 11S, the non-magnetic inner end portion 191 may face the end surface 11S with a gap G4. In this case, the radially outer portion of the gap G4 is open, and the distance between the non-magnetic inner end portion 191 and the end surface 11S is shorter than the distance between the magnetic material part 18 and the end surface 11S. Even in this case, the advantage of suppressing the deformation of the first body part 11 is still obtained since the non-magnetic inner end portion 191 and the first body part 11 come into contact immediately after the first body part 11 begins to deform toward the pole piece support 37.

[0045] The first yoke 15 includes a plurality of steel sheets 151 laminated in the axial direction. FIG. 9 is a schematic diagram showing a steel sheet 151 as viewed in the axial direction according to an embodiment. Each of the steel sheets 151 has a plurality of opening edge portions 153 inside which the plurality of first magnets 19 are arranged, respectively, and a covering portion 155 located radially outward of the plurality of opening edge portions 153. The covering portion 155 extends in the circumferential direction and is connected to each of the plurality of opening edge portions 153. FIG. 9 shows only one of the plurality of opening edge portions 153. Referring to FIG. 8 again, the non-magnetic material part 16 has a contact portion 196. The contact portion 196 is in contact with the covering portion 155 of the steel sheet 151 that is closest to the end plate 17.

[0046] Since a space is formed inside the opening edge portion 153 for receiving each of the plurality of first magnets 19, the covering portion 155, which is located radially outward of the opening edge portion 153, is less rigid in the axial direction. Therefore, the covering portion 155 of the one closest to the end plate 17 among the plurality of steel sheets 151 is most likely to deform toward the end plate 17 in the axial direction. In this regard, with the above configuration, since the contact portion 196 of the non-magnetic material part 16 is in contact with the covering portion 155, it is possible to suppress the deformation of the covering portion 155.

[0047] In some embodiments of the present disclosure, the contact portion 196 has an outer end 196A in the radial direction. In the radial direction, the outer end 196A is located at the same position as an outer end 155 A of the covering portion 155 or at a position inward of the outer end 155 A of the covering portion 155. With the above configuration, since the outer end 196A of the contact portion 196 is not located outward of the first body part 11 in the radial direction, the contact portion 196 is prevented from contacting the pole piece unit 30 (more specifically, the pole piece 50 or the connection portion 35). This prevents the end plate 17 or the pole piece unit 30 from being damaged during operation of the magnetic gear 5.

[0048] In some embodiments of the present disclosure, the contact portion 196 of the nonmagnetic material part 16 has a contact surface 199 in contact with the covering portion 155. The contact surface 199 is located closer to the end surface 11S of the first body part 11 than the non-magnetic material part 16 in the axial direction. With the above configuration, the contact surface 199 can actively contact the end surface US of the first body part 11 (more specifically, the end surface 11S constituting the covering portion 155). Thus, it is possible to suppress the deformation of the covering portion 155 more effectively.

[0049] <4. Magnetic geared electrical machine 1 that incorporates magnetic gear 5> Referring to FIGs. lOAto 10D, the magnetic geared electrical machine 1 that incorporates the magnetic gear 5 will be described. The magnetic geared electrical machine 1A, IB (1) illustrated in FIGs. 1 Aand IB is a magnetic geared generator 2A, 2B (2) configured to be driven by input from a prime mover 9, which is an example of the external rotating device, to generate electric power. The magnetic geared generator 2 is configured to supply electric power P generated by the power generation to a power supply destination 4 which may be, for example, a power grid. The magnetic geared electrical machine IC, ID (1) illustrated in FIGs. 10C and 10D is a magnetic geared motor 3 A, 3B (3) configured to drive a rotating machine 8, which is an example of the external rotating device, upon receiving electric power P supplied from a power supply source 6, which may be, for example, a power grid. The rotating machine 8 may be, for example, an electric vehicle driven by the magnetic geared motor 3. In this case, the rotational shaft A of the magnetic geared motor 3 may be connected to a drive shaft of the electric vehicle, which is a component of the rotating machine 8. The magnetic geared electrical machine 1A, IC illustrated in FIGs. 10A and 10C incorporate the magnetic gear 5A (see FIG. 1A), while the magnetic geared electrical machine IB, ID illustrated in FIGs. 10B and 10D incorporates the magnetic gear 5B (see FIG. IB).

[0050] <4-1. Magnetic gear generator 2A, 2B (2)> The magnetic geared generator 2A, 2B (2) is equipped with the magnetic gear 5 and a coil 99 as a stator winding (armature winding). The coil 99 of the magnetic geared generator 2A is wound on the teeth 28 of the second yoke unit 20. The coil 99 is conductive to the power supply destination 4.

[0051] The magnetic geared generator 2A illustrated in FIG. 10A operates as follows, for example. When the prime mover 9 connected to the first rotational shaft Al, which functions as the input shaft in this figure, is driven, the first yoke unit 10 rotates according to the previously described principle. As a result, a current is generated in the coil 99 by electromagnetic induction caused by rotation of the pole piece unit 30 and the first yoke unit 10. Thus, the magnetic geared generator 2A generates electric power.

[0052] The operating principle of the magnetic geared generator 2B illustrated in FIG. 10B is similar to that of the magnetic geared generator 2A. When the prime mover 9 connected to the second rotational shaft A2, which functions as the input shaft in this figure, is driven, the first yoke unit 10 rotates, and the second yoke unit 20 rotates according to the previously described principle. As a result, a current is generated in the coil 99 by electromagnetic induction caused by rotation of the first yoke unit 10 and the second yoke unit 20. Thus, the magnetic geared generator 2B generates electric power.

[0053] <4-2. Magnetic geared motor 3A, 3B (3)> The magnetic geared motor 3 A, 3B (3) is equipped with the magnetic gear 5 and a coil 99 as a stator winding (armature winding). The coil 99 of the magnetic geared motor 3A, 3B (3) is wound on the teeth 28 of the second yoke unit 20. The coil 99 is conductive to the power supply source 6.

[0054] The magnetic geared motor 3 A illustrated in FIG. 10C operates as follows, for example. The first yoke unit 10 is biased by a rotating magnetic field generated by energization of the coil 99. When the first yoke unit 10 rotates with the second rotational shaft A2, the pole piece unit 30 rotates according to the previously described principle. The first rotational shaft Al, which functions as the output shaft in the illustrated example, drives the rotating machine 8.

[0055] The operating principle of the magnetic geared motor 3B illustrated in FIG. 10D is similar to that of the magnetic geared motor 3A. The second yoke unit 20 is biased by a rotating magnetic field generated by energization of the coil 99. When the second yoke unit 20 rotates with the first rotational shaft Al, the first yoke unit 10 rotates according to the previously described principle. The second rotational shaft A2, which functions as the output shaft in the illustrated example, drives the rotating machine 8.

[0056] As previously described, the magnetic geared generator 2 does not have to include the first rotational shaft Al or the second rotational shaft A2 that functions as an output shaft, and the magnetic geared motor 3 does not have to include the first rotational shaft Al or the second rotational shaft A2 that functions as an input shaft.

[0057] <5. Conclusion> The contents described in some embodiments described above would be understood as follows, for instance.

[0058] 1) A magnetic gear (5) according to at least one embodiment of the present disclosure includes: a first yoke unit (10) including a first body part (11) having a plurality of first magnets (19) arranged in a circumferential direction with respect to an axis (Q) and a first yoke (15) supporting the plurality of first magnets; a second yoke unit (20) including a plurality of second magnets (29) arranged in the circumferential direction on an outer peripheral side of the first yoke unit; and a pole piece unit (30) including a plurality of pole pieces (50) arranged in the circumferential direction between the first yoke unit and the second yoke unit. The pole piece unit further includes a pole piece support (37) having a connection portion (35) connected to an end portion of each of the plurality of pole pieces, and a radial extension portion (36) extending radially inward from the connection portion. The first yoke unit further includes an end plate (17) disposed on an end surface of the first body part in an axial direction and facing the radial extension portion with a predetermined gap (G3) in the axial direction. The end plate has: a magnetic material part (18) formed of a magnetic material; and a non-magnetic material part (19) formed of a non-magnetic material and disposed radially outward of the magnetic material part.

[0059] With the above configuration 1), at least a part of a leakage magnetic flux generated between the first yoke unit and the second yoke unit is directed to the magnetic material part of the end plate. This suppresses the leakage magnetic flux flowing in the pole piece support and reduces eddy current loss in the pole piece support. Furthermore, the non-magnetic material part is disposed radially outward of the magnetic material part, and the non-magnetic material part is in proximity to axial end portions of the pole pieces. Since the magnetic flux tends to flow in such a way that it avoids the non-magnetic material part, it is possible to reduce the generation itself of the leakage magnetic flux that passes in the axial direction through the pole pieces. From the above, it is possible to achieve the magnetic gear with reduced eddy current loss in the pole piece unit due to the generation of the leakage magnetic flux.

[0060] 2) In some embodiments, in the magnetic gear as defined in the above 1), a boundary (33) between the magnetic material part and the non-magnetic material part is located radially outward of an inner peripheral surface (19A) of each of the first magnets.

[0061] With the above configuration 2), the magnetic material part is in proximity to the pole pieces. This makes it easier for the leakage magnetic flux generated in the pole pieces to be directed to the magnetic material part, further suppressing eddy current loss in the pole piece unit.

[0062] 3) In some embodiments, in the magnetic gear as defined in the above 1) or 2), a relationship of R <L <6*R is satisfied, where L is a dimension of the non-magnetic material part in the radial direction, and Risa distance between the pole pieces and the first yoke unit in the radial direction.

[0063] With the above configuration 3), since L <6*R is satisfied, the magnetic material part is avoided from being too far away from the pole pieces, and the magnetic flux short-circuit between the pole pieces and the magnetic material part can be suppressed. Further, since R <L is satisfied, it is possible to ensure the minimum required size of the non-magnetic material part and suppress the generation itself of the leakage magnetic flux in the pole pieces.

[0064] 4) In some embodiments, in the magnetic gear as defined in any of the above 1) to 3), a relationship of D >0.15*S is satisfied, where D is a dimension of the magnetic material part in the axial direction, and S is a distance between the radial extension portion and the first body part in the axial direction.

[0065] With the above configuration 4), since D>0.15xSis satisfied, the magnetic material part is avoided from being too short in the axial direction, and the magnetic flux short-circuit between the pole pieces and the magnetic material part can be suppressed.

[0066] 5) In some embodiments, in the magnetic gear as defined in any of the above 1) to 4), the radial extension portion is formed of a non-magnetic material.

[0067] With the above configuration 5), since the radial extension portion is a non-magnetic material, it is possible to further suppress the leakage magnetic flux flowing from the pole pieces to the radial extension portion and reduce eddy current loss in the pole piece unit.

[0068] 6) In some embodiments, in the magnetic gear as defined in the above 5), the radial extension portion is formed of a non-conductive material.

[0069] With the above configuration 6), since the radial extension portion is a non-magnetic and non-conductive material, it is possible to further suppress the leakage magnetic flux flowing from the pole pieces to the radial extension portion and reduce eddy current loss in the pole piece unit.

[0070] 7) In some embodiments, in the magnetic gear as defined in any of the above 1) to 6), the non-magnetic material part has a non-magnetic inner end portion (191) which is an inner end portion in the radial direction, and the magnetic material part has a magnetic outer end portion (181) which is an outer end portion in the radial direction, the magnetic outer end portion (181) being located on an opposite side of the non-magnetic inner end portion from the first body part and being in contact with the non-magnetic inner end portion.

[0071] With the above configuration 7), since the non-magnetic inner end portion faces the first body part, it is possible to suppress the deformation of the first body part toward the pole piece support.

[0072] 8) In some embodiments, in the magnetic gear as defined in any of the above 1) to 7), the first yoke includes a plurality of steel sheets (151) laminated in the axial direction. Each of the steel sheets has: a plurality of opening edge portions (153) inside which the plurality of first magnets are arranged, respectively; and a covering portion (155) located radially outward of each of the plurality of opening edge portions. The non-magnetic material part has a contact portion (196) in contact with the covering portion of the steel sheet that is closest to the end plate.

[0073] Since a space is formed inside the opening edge portion for receiving the first magnet, the covering portion, which is located radially outward of the opening edge portion, is less rigid in the axial direction. Therefore, the covering portion of the one closest to the end plate among the plurality of steel sheets is most likely to deform in the axial direction. In this regard, with the above configuration 8), since the contact portion of the non-magnetic material part is in contact with the covering portion, it is possible to suppress the deformation of the covering portion.

[0074] 9) In some embodiments, in the magnetic gear as defined in the above 8), in the radial direction, an outer end (196A) of the contact portion is at a same position as an outer end of the covering portion or at a position inward of the outer end of the covering portion.

[0075] With the above configuration 9), since the outer end of the contact portion is not located outward of the first body part in the radial direction, the contact portion is prevented from contacting the pole piece unit. This prevents the end plate or the pole piece unit from being damaged during operation of the magnetic gear.

[0076] 10) In some embodiments, in the magnetic gear as defined in the above 8) or 9), the contact portion of the non-magnetic material part has a contact surface (199) in contact with the covering portion and located closer to the end surface of the first body part than the magnetic material part in the axial direction.

[0077] With the above configuration 10), the contact surface can actively contact the first body part. Thus, it is possible to suppress the deformation of the covering portion more effectively.

[0078] 11) In some embodiments, in the magnetic gear as defined in any of the above 1) to 10), the non-magnetic material forming the non-magnetic material part is non-conductive.

[0079] With the above configuration 11), even if the leakage magnetic flux links with the non-magnetic material part formed of a non-magnetic material, it is possible to suppress eddy current loss in the non-magnetic material part.

[0080] 12) A magnetic geared electrical machine (1) according to at least one embodiment of the present disclosure includes: the magnetic gear (5) defined in any of the above 1) to 11); a coil (99) provided on a second yoke (25) supporting the second magnets; and a rotational shaft (A) for transmitting torque between an external rotating device (rotating machine 8, prime mover 9) and the magnetic gear.

[0081] With the above configuration 12), for the same reason described in the above 1), it is possible to achieve the magnetic geared electrical machine with reduced eddy current loss in the pole piece unit.

[0082] Embodiments of the present disclosure were described in detail above, but the present disclosure is not limited thereto, and various amendments and modifications may be implemented.

[0083] In the present specification, an expression of relative or absolute arrangement such as “in a direction”, “along a direction”, “parallel”, “orthogonal”, “centered”, “concentric” and “coaxial” shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function. For instance, an expression of an equal state such as “same”, “equal”, and “uniform” shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function. Further, an expression of a shape such as a rectangular shape or a cylindrical shape shall not be construed as only the geometrically strict shape, but also includes a shape with unevenness or chamfered comers within the range in which the same effect can be achieved. On the other hand, an expression such as “comprise”, “include”, and “have” are not intended to be exclusive of other components. Reference Signs List

[0084] 1 Magnetic geared electrical machine 5 Magnetic gear 10 First yoke unit 11 First body part 11S End surface 15 First yoke 16 Non-magnetic material part 17 End plate 18 Magneti c materi al p art 19 First magnet 19A Inner peripheral surface 20 Second yoke unit 25 Second yoke 29 Second magnet 30 Pole piece unit 33 Boundary 35 Connection portion 36 Radial extension portion 37 Pole piece support 50 Pole piece 99 Coil 151 Steel sheet 153 Opening edge portion 5 155 Covering portion 155A Outer end 181 Magnetic outer end portion 191 Non-magnetic inner end portion 196 Contact portion 10 196A Outer end 199 Contact surface D Dimension G1 First gap L Dimension 15 Q Axis R Distance S Distance

Claims

1. A magnetic gear, comprising:a first yoke unit including a first body part having a plurality of first magnets arranged in a circumferential direction with respect to an axis and a first yoke supporting the plurality of first magnets;a second yoke unit including a plurality of second magnets arranged in the circumferential direction on an outer peripheral side of the first yoke unit; anda pole piece unit including a plurality of pole pieces arranged in the circumferential direction between the first yoke unit and the second yoke unit,wherein the pole piece unit further includes a pole piece support having a connection portion connected to an end portion of each of the plurality of pole pieces, and a radial extension portion extending radially inward from the connection portion,wherein the first yoke unit further includes an end plate disposed on an end surface of the first body part in an axial direction and facing the radial extension portion with a predetermined gap in the axial direction, andwherein the end plate has:a magnetic material part formed of a magnetic material; anda non-magnetic material part formed of a non-magnetic material and disposed radially outward of the magnetic material part.

2. The magnetic gear according to claim 1,wherein a boundary between the magnetic material part and the non-magnetic material part is located radially outward of an inner peripheral surface of each of the first magnets.

3. The magnetic gear according to claim 1 or 2,wherein a relationship of R <L <6 R is satisfied, where Lisa dimension of the nonmagnetic material part in the radial direction, and R is a distance between the pole pieces andthe first yoke unit in the radial direction.

4. The magnetic gear according to claim 1 or 2,wherein a relationship of D >0.15 S is satisfied, where D is a dimension of the magnetic material part in the axial direction, and S is a distance between the radial extension portion and the first body part in the axial direction.

5. The magnetic gear according to claim 1 or 2,wherein the radial extension portion is formed of a non-magnetic material.

6. The magnetic gear according to claim 5,wherein the radial extension portion is formed of a non-conductive material.

7. The magnetic gear according to claim 1 or 2,wherein the non-magnetic material part has a non-magnetic inner end portion which is an inner end portion in the radial direction, andwherein the magnetic material part has a magnetic outer end portion which is an outer end portion in the radial direction, the magnetic outer end portion being located on an opposite side of the non-magnetic inner end portion from the first body part and being in contact with the non-magnetic inner end portion.

8. The magnetic gear according to claim 1,wherein the first yoke includes a plurality of steel sheets laminated in the axial direction, wherein each of the steel sheets has:a plurality of opening edge portions inside which the plurality of first magnets are arranged, respectively; anda covering portion located radially outward of each of the plurality of opening edge portions, andwherein the non-magnetic material part has a contact portion in contact with the covering portion of the steel sheet that is closest to the end plate.

9. The magnetic gear according to claim 8,wherein, in the radial direction, an outer end of the contact portion is at a same position as an outer end of the covering portion or at a position inward of the outer end of the covering portion.

10. The magnetic gear according to claim 8 or 9,wherein the contact portion of the non-magnetic material part has a contact surface in contact with the covering portion and located closer to the end surface of the first body part than the magnetic material part in the axial direction.

11. The magnetic gear according to claim 1 or 2,wherein the non-magnetic material forming the non-magnetic material part is non-conductive.

12. A magnetic geared electrical machine, comprising:the magnetic gear according to claim 1 or 2;a coil provided on a second yoke supporting the second magnets; anda rotational shaft for transmitting torque between an external rotating device and the magnetic gear.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2023 / 034468A. CLASSIFICATION OF SUBJECT MATTER F16H 4W0(2006.01)i; H02K 7 / 10(2006.01)1 FI: F16H49 / 00 A; H02K7 / 10 A According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) F16H49 / 00: H02K7 / 10 Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Published examined utility model applications of Japan 1922-1996 Published unexamined utility model applications of Japan 1971-2023 Registered utility model specifications of Japan 1996-2023 Published registered utility model applications of Japan 1994-2023 Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. A JP 2022-155119 A (MITSUBISHI HEAVY INDUSTRIES, LTD.) 13 October 2022 (2022-10-13) 1-12 A JP 2021-118611 A (MITSUBISHI HEAVY INDUSTRIES, LTD.) 10 August 2021 (2021-08-10) 1-12 A JP 2021-112945 A (MITSUBISHI HEAVY INDUSTRIES, LTD.) 05 August 2021 (2021-08-05) 1-12 | | Further documents are listed in the continuation of Box C. | V | See patent family annex. * Special categories of cited documents: “A” document defining the general state of the art which is not considered to be of particular relevance “E” earlier application or patent but published on or after the international filing date “L” document which may throw doubts on priority claim(s) or which is cited to establish the publication date of another citation or other special reason (as specified) “O” document referring to an oral disclosure, use, exhibition or other means “P” document published prior to the international filing date but later than the priority date claimed “T” later document published after the international filing date or priority date and not in conflict with the application but cited to understand the principle or theory underlying the invention “X” document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone “Y” document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the ait document member of the same patent family Date of the actual completion of the international search Date of mailing of the international search report 10 October 2023 24 October 2023 Name and mailing address of the ISA / JP Authorized officer Japan Patent Office (ISA / JP) 3-4-3 Kasumigaseki, Chiyoda-ku, Tokyo 100-8915 Japan Telephone No.INTERNATIONAL SEARCH REPORT Information on patent family membersInternational application No.PCT / JP2023 / 034468Patent document cited in search report Publication date (day / month / year) Patent family member)s) Publication date (day / month / year) JP 2022-155119 A 13 October 2022 WO 2022 / 210237 Al JP 2021-118611 A 10 August 2021 US 2023 / 0046567 Al WO 2021 / 149473 Al EP 4080743 Al CN 114946111 A JP 2021-112945 A 05 August 2021 US 2023 / 0047288 Al WO 2021 / 145264 Al EP 4074571 Al CN 114929546 A

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