Magnetic gear device

Abstract

This magnetic gear device (1) is provided with: a first magnet (11) in which a plurality of first magnetic poles (111) are disposed in the circumferential direction; a second magnet (12) in which a plurality of second magnetic poles (121) are disposed in the circumferential direction; and a pole piece (13) that is positioned between the first magnet (11) and the second magnet (12) and magnetically connects the first magnet (11) and the second magnet (12). One of the plurality of first magnetic poles (111) of the first magnet (11) and the plurality of second magnetic poles (121) of the second magnet (12) has a ring shape formed integrally. The first magnetic poles (111) of the first magnet (11) are more in number than the second magnetic poles (121) of the second magnet (12).

Description

magnetic gear device

[0001] The present invention relates to a magnetic gear device.

[0002] Conventionally, a magnetic gear device has been known that includes an inner magnet in which multiple magnets are arranged in a circumferential direction, and an outer magnet in which multiple magnets are arranged in a circumferential direction, with the outer magnet arranged radially outside the inner magnet (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-150601

[0004] However, the technology described in Patent Document 1 has room for improvement in terms of simplifying the structure.

[0005] The present invention has been made in view of the above, and has as its object to provide a magnetic gear device that can be simplified in structure.

[0006] In order to solve the above-mentioned problems and achieve the object, the magnetic gear device of the present invention comprises a first magnet having a plurality of first magnetic poles arranged circumferentially, a second magnet having a plurality of second magnetic poles arranged circumferentially, and a pole piece located between the first magnet and the second magnet and magnetically connecting the first magnet and the second magnet, wherein either the plurality of first magnetic poles of the first magnet or the plurality of second magnetic poles of the second magnet are integrally formed in a ring shape, and the number of the first magnetic poles of the first magnet is greater than the number of the second magnetic poles of the second magnet.

[0007] According to one aspect of the magnetic gear device of the present invention, the structure can be simplified.

[0008] FIG. 1 is a plan view of a power transmission device including a magnetic gear device according to a first embodiment. FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1. FIG. 3 is a perspective view of the magnetic gear device shown in FIG. 1. FIG. 4 is a perspective view of a magnetic gear device according to a first modified example of the first embodiment. FIG. 5 is a perspective view of a magnetic gear device according to a second modified example of the first embodiment. FIG. 6 is a plan view of a power transmission device according to a second modified example of the first embodiment. FIG. 7 is a cross-sectional view of a power transmission device according to a third embodiment. FIG. 8 is a front view of an intermediate transmission mechanism included in the power transmission device shown in FIG. 7. FIG. 9 is a cross-sectional view of a power transmission device according to a first modified example of the third embodiment. FIG. 10 is a cross-sectional view of a power transmission device according to a second modified example of the third embodiment. FIG. 11 is a cross-sectional view of a power transmission device according to a third modified example of the third embodiment. FIG. 12 is a front view of the intermediate transmission mechanism included in the power transmission device shown in FIG. 11. FIG. 13 is a cross-sectional view of a power transmission device according to a fourth embodiment. FIG. 14 is a cross-sectional view of a power transmission device according to a fifth embodiment.

[0009] Magnetic gear devices according to embodiments will be described in detail below with reference to the drawings. Note that the dimensional relationships and ratios of elements in the drawings may differ from the actual situation. The dimensional relationships and ratios may also differ between the drawings.

[0010] [First embodiment] Fig. 1 is a plan view of a power transmission device 100 including a magnetic gear device 1 according to a first embodiment. Fig. 2 is a cross-sectional view taken along the arrows A-A in Fig. 1. Fig. 3 is a perspective view of the magnetic gear device 1 shown in Fig. 1. For ease of explanation, back yokes 112, 122 are omitted from Fig. 2, and the motor 2, intermediate transmission mechanism 3, and second shaft 14 are omitted from Fig. 3.

[0011] In describing the power transmission device 100 including the magnetic gear device 1 shown in Figures 1, 2, and 3 according to the embodiment, in order to facilitate understanding of directions, the direction in which the second shaft 14 extends will be referred to as the axial direction A, the direction in which the first magnet 11 and the second magnet 12 rotate will be referred to as the circumferential direction C, and the direction that is included in a plane perpendicular to the axial direction A, passes through the axes 22o and 14o, and is perpendicular to the circumferential direction C will be referred to as the radial direction R.

[0012] 1 and 2 according to this embodiment transmits torque from a first shaft 22, which is an input shaft, to a second shaft 14, which is an output shaft. In the power transmission device 100 according to this embodiment, the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are disposed in a skewed position. In other words, the power transmission device 100 according to this embodiment is a device with skewed shafts, in which the axis 22o of the input shaft and the axis 14o of the output shaft are disposed in a skewed position. The power transmission device 100 includes, for example, a magnetic gear device 1, a motor 2, and an intermediate transmission mechanism 3.

[0013] The power transmission device 100 according to the first embodiment amplifies the torque of the first shaft 22 of the motor 2, which is the input shaft, at the second shaft 14, which is the output shaft, and outputs the amplified torque. The power transmission device 100 is housed in a frame (not shown), for example.

[0014] The motor 2 includes, for example, a main body 21 and a first shaft 22 serving as an input shaft. The motor 2 is an electric motor that converts electrical energy supplied from a power source into mechanical energy, which is the rotation of the first shaft 22.

[0015] The main body 21 is fixed to a frame. Inside the main body 21, devices such as a rotor and a stator are housed.

[0016] The first shaft 22 is a so-called shaft, and is formed, for example, from a metal member in a columnar or cylindrical shape. The first shaft 22 has an axis 22o and is provided rotatably about the axis 22o relative to the frame and the main body 21. The axis 22o of the first shaft 22 is disposed in a twisted position with respect to the axis 14o of the second shaft 14. The first shaft 22 extends along a first direction D.

[0017] The intermediate transmission mechanism 3 transmits the driving force from the motor 2 to the magnetic gear device 1. The intermediate transmission mechanism 3 includes, for example, a first gear 31 and a second gear 32.

[0018] The first gear 31 is, for example, a worm. The first gear 31 is fixed to the tip of the first shaft 22 in the first direction D and rotates together with the rotation of the first shaft 22.

[0019] The second gear 32 is, for example, a worm wheel formed to rotate in the circumferential direction C together with the second magnet 12 in the magnetic gear device 1. The second gear 32 meshes with the first gear 31, which is a worm. The intermediate transmission mechanism 3 according to this embodiment is composed of the mechanical first gear 31 and second gear 32. The first gear 31 and second gear 32 are examples of mechanical gears.

[0020] When the intermediate transmission mechanism 3 and motor 2 having the above configuration are driven, the first shaft 22 rotates about the axis 22o, and in response to this rotation, the first gear 31 rotates about the axis 22o. Then, in response to the rotation of the first gear 31, the second gear 32 meshing with the first gear 31 rotates together with the second magnet 12 in the circumferential direction C about the axis 14o.

[0021] The magnetic gear device 1 includes a first magnet 11, a second magnet 12, a pole piece 13, and a second shaft 14. The magnetic gear device 1 according to this embodiment is a so-called flux modulation type magnetic gear (harmonic type magnetic gear) in that, when the second magnet 12 connected to the driving side rotates about the axis 14o, the change in magnetic flux of the multiple second magnetic poles 121 is modulated by the pole piece 13 and transmitted to the first magnetic pole 111 of the first magnet 11 connected to the driven side, causing the first magnet 11 to rotate about the axis 14o. Furthermore, in the magnetic gear device 1 according to this embodiment, the first magnet 11, the second magnet 12, and the pole piece 13 are formed separately.

[0022] The first magnet 11 is provided to be rotatable about the axis 14o relative to the frame and the pole piece 13. The first magnet 11 has a plurality of (e.g., 52) first magnetic poles 111 arranged in the circumferential direction C, and the plurality of first magnetic poles 111 are integrally formed in a ring shape. The first magnet 11 is provided to be rotatable about the axis 14o relative to the frame and the pole piece 13. Furthermore, a first space S1 is formed between the first magnet 11 and the pole piece 13 in the radial direction R. In other words, the first magnet 11 is provided to be rotatable about the axis 14o without contacting the pole piece 13. Note that the first space S1 may be filled with a non-magnetic material such as a resin sliding material, as long as it allows rotation of the first magnet 11 and the pole piece 13 in a vacuum state or when a fluid such as air, water, or oil is present.

[0023] The multiple first magnetic poles 111 are arranged such that north poles and south poles alternate in the circumferential direction C. The multiple first magnetic poles 111 of the first magnet 11 are formed by magnetizing a magnetic body as described below. The first magnet 11 has, for example, 52 first magnetic poles 111, so the number of pole pairs of the first magnet 11 is 26.

[0024] The number of first magnetic poles 111 of the first magnet 11 is greater than the number of second magnetic poles 121 of the second magnet 12. In addition, the first magnet 11 is provided with a first back yoke 112, for example, on the inner side in the radial direction R. In the magnetic gear device 1 according to this embodiment, the first magnet 11 and the second magnet 12 are arranged so as to be rotatable about a common axis 14o.

[0025] 2 and 3, the first magnet 11 is formed in a ring shape and has a downward side surface 11a and an upward side surface 11b. The first magnet 11 also has a through hole 11c and an outer peripheral surface 11d. The first magnet 11 is a rare earth iron-based magnet, and in this embodiment, is formed by mixing magnetic powder containing neodymium (Nd—Fe—B), a magnetically isotropic rare earth iron-based magnet, with a thermosetting resin, such as epoxy resin, in a predetermined ratio.

[0026] The rare earth iron-based magnet before magnetization that is the material for the first magnet 11 is preferably an anisotropic rare earth iron-based magnet with an average crystal grain size of 10 nm or more and 10,000 nm or less, and more preferably an anisotropic rare earth iron-based magnet with an average crystal grain size of 10 nm or more and 6,600 nm or less.

[0027] The first magnet 11 is formed by magnetizing the object to be magnetized, which is the rare earth iron-based magnet described above before magnetization, by raising the temperature of the object to be magnetized from below the Curie point to above the Curie point, and then lowering the temperature from above the Curie point to below the Curie point while a magnetizing magnetic field is applied by the field magnet section.

[0028] Furthermore, in response to the miniaturization and high-resolution of devices (e.g., magnetic encoders) used, if the permanent magnet to be magnetized is composed of a rare-earth magnet with high magnetic properties (e.g., a Nd bonded magnet), the conventional pulse current coil current method requires a larger current to be passed, which can lead to problems such as larger and more expensive magnetization devices.In contrast, the first magnet 11 shown in this embodiment is formed from the object to be magnetized by heating the object to be magnetized using a heating unit and lowering the temperature from a temperature above the Curie point of the magnetic powder that makes up the object to be magnetized to a temperature below the Curie point, while continuing to generate a magnetic field using the permanent magnet in the field magnet unit, thereby performing multi-pole magnetization (see, for example, JP 2021-93521 A).

[0029] Forming the first magnet 11 in this manner makes it possible to achieve uniformity in the magnetization characteristics of the object to be magnetized. Furthermore, forming the first magnet 11 in the above manner makes it possible to narrow the pitch of the multiple first magnetic poles 111 in the circumferential direction C (for example, 3 mm or less in the circumferential direction C). In particular, when the first magnet 11 with a large number of first magnetic poles is arranged inside in the radial direction R relative to the second magnet 12 with a small number of second magnetic poles 121, as in this embodiment, the pitch of the first magnetic poles 111 needs to be narrower. Note that the pitch of the first magnetic poles 111 is measured on the outer periphery of the first magnet 11.

[0030] The second magnet 12 is rotatable about the axis 14o relative to the frame and the pole piece 13. Furthermore, a second space S2 is formed between the second magnet 12 and the pole piece 13 in the radial direction R. In other words, the second magnet 12 is rotatable about the axis 14o without contacting the pole piece 13. The second magnet 12 is formed in the same manner as the first magnet 11. That is, the second magnet 12 has multiple (six) second magnetic poles 121 arranged in the circumferential direction C, and the multiple second magnetic poles 121 are formed integrally in a ring shape. Furthermore, the multiple second magnetic poles 121 are arranged so that north poles and south poles alternate in the circumferential direction C. Since the second magnet 12 has, for example, six second magnetic poles 121, the number of pole pairs of the second magnet 12 is three. Furthermore, the second magnet 12 has, for example, a second back yoke 122 arranged on the outer side in the radial direction R. The second space S2 may be filled with a non-magnetic material such as a resin sliding material, as long as it allows the second magnet 12 and the pole piece 13 to rotate when in a vacuum state or when a fluid such as air, water, or oil is present.

[0031] The pole piece 13 is composed of a plurality of (e.g., 29) modulation pieces 131 and modulates the magnetic flux of the magnets 11, 12. The pole piece 13 is located between the first magnet 11 and the second magnet 12 in the radial direction R, and magnetically connects the first magnet 11 and the second magnet 12. The modulation pieces 131 are formed, for example, from a magnetic material, are arranged at equal intervals along the circumferential direction C, and are fixed to a frame (not shown).

[0032] In the magnetic gear device 1 according to this embodiment, the number of pole pairs 11M of the first magnet 11 is 26, the number of pole pairs 12M of the second magnet 12 is 3, and the number of modulation pieces 131 of the pole piece 13 is 29. Therefore, when the second magnet 12 on the outside in the radial direction R is used as the input, the first magnet 11 on the inside in the radial direction R is used as the output, and the pole piece 13 is fixed, the reduction ratio X1 can be calculated as follows: X1 = 11M ÷ 12M = 26 ÷ 3 = 8.67

[0033] Alternatively, when the second magnet 12 is the input, the pole piece 13 is the output, the first magnet 11 is fixed, and the second magnet 12 is placed on the input side, the reduction ratio X2 can be calculated as follows: X2 = 13M ÷ 12M = 29 ÷ 3 = 9.67

[0034] The second shaft 14 is a so-called shaft and is formed, for example, from a metal member in a columnar or cylindrical shape. The second shaft 14 has an axis 14o and is provided to be rotatable about the axis 14o relative to the frame. The second shaft 14 is fixed to the inner circumferential surface of the first back yoke 112 of the first magnet 11 in the radial direction R and rotates in the circumferential direction C together with the first magnet 11. The magnetic gear device 1 outputs torque to the outside as the second shaft 14 rotates in the circumferential direction C about the axis 14o.

[0035] In the power transmission device 100 according to this embodiment, when the motor 2 is driven to rotate the second gear 32 in the circumferential direction C, the second back yoke 122 and the second magnet 12 fixed to the second gear 32 rotate in the circumferential direction C together with the second gear 32. The change in magnetic flux of the second magnetic pole 121 in the second magnet 12 is modulated by the pole piece 13 and transmitted to the first magnetic pole 111 of the first magnet 11 connected to the driven side. In this case, in the magnetic gear device 1 according to this embodiment, the number of first magnetic poles 111 of the first magnet 11 arranged inside the second magnet 12 in the radial direction R is greater than the number of second magnetic poles 121 of the second magnet 12. Therefore, although the rotation speed in the circumferential direction C decreases, the torque can be increased. Furthermore, in the magnetic gear device 1 according to this embodiment, the first magnet 11 has a ring shape in which multiple first magnetic poles 111 are arranged in the circumferential direction C and are integrally formed. Therefore, the magnetic gear device 1 of this embodiment can increase torque because the pitch of the multiple first magnetic poles 111 in the circumferential direction C can be narrowed compared to, for example, a magnetic gear device having a ring-shaped first magnet formed by connecting multiple individually formed magnets (for example, the device described in JP 2022-150601 A).

[0036] In the magnetic gear device 1 according to this embodiment, the first magnet 11 and the pole piece 13 are not in contact with each other in the radial direction R, and the pole piece 13 and the second magnet 12 are not in contact with each other in the radial direction R. Furthermore, in the magnetic gear device 1, the pole piece 13 is disposed between the first magnet 11 and the second magnet 12 in the radial direction R, and the first magnet 11 and the second magnet 12 are magnetically coupled by this pole piece 13. Therefore, when a torque equal to or greater than the maximum transmission torque set by the magnetic force of the second magnetic pole 121 and the gap between the second magnet 12 and the pole piece 13 in the radial direction R is applied to the magnetic gear device 1, the magnetic gear device 1 functions as a torque limiter, and rotation of the first magnet 11 in the circumferential direction C is stopped even when the second magnet 12 is rotating in the circumferential direction C. Therefore, the magnetic gear device 1 according to this embodiment can protect the motor 2 by separating the drive side from the driven side during an overload. Alternatively, if unintended torque is generated by the motor 2, the magnetic gear device 1 functions as a torque limiter, separating the drive side from the driven side to protect the load side. Furthermore, if the magnetic gear device 1 is used in an electric opening and closing mechanism for a home appliance, it can cut off torque from the drive side when a member on the load side comes into contact with the human body, and therefore can also function as a safety device that minimizes the impact on the human body.

[0037] As described above, the magnetic gear device 1 according to this embodiment includes a first magnet 11 having a plurality of first magnetic poles 111 arranged in the circumferential direction C, a second magnet 12 having a plurality of second magnetic poles 121 arranged in the circumferential direction C, and a pole piece 13 located between the first magnet 11 and the second magnet 12 and magnetically connecting the first magnet 11 and the second magnet 12. Either the plurality of first magnetic poles 111 of the first magnet 11 or the plurality of second magnetic poles 121 of the second magnet 12 are integrally formed in a ring shape, and the number of first magnetic poles 111 of the first magnet is greater than the number of second magnetic poles 121 of the second magnet. This allows for increased torque density, as described below. Furthermore, the magnetic gear device 1 according to this embodiment allows for increased torque (output torque) of the second shaft 14 connected to the first magnet 11 of the magnetic gear compared to the torque (input torque) of the first shaft 22 of the motor 2. Furthermore, in the magnetic gear device 1 according to this embodiment, the first magnet 11 and the pole piece 13 are not in contact with each other in the radial direction R, and the pole piece 13 and the second magnet 12 are not in contact with each other in the radial direction R. This reduces noise during operation, prevents dust generation during use, and eliminates the need for lubricating oil. Furthermore, since the magnetic gear device 1 does not generate dust during use and does not require lubricating oil for use, it does not require maintenance. Furthermore, compared to a magnetic gear device in which the outer circumferential surfaces of the ring-shaped first magnet and the ring-shaped second magnet are opposed to each other and magnetically coupled only by the opposed magnets, the magnetic gear device 1 according to this embodiment magnetically couples the first magnetic poles 111 of the multiple first magnets 11 to the second magnetic poles 121 of the multiple second magnets 12 via the pole piece 13 in the radial direction R, thereby increasing torque density. Furthermore, since the magnetic gear device 1 according to this embodiment includes at least the first magnet 11 having the above-described configuration, it can be made smaller and lighter than a magnetic gear device including a first magnet formed by connecting individually formed magnets in the circumferential direction C.Furthermore, because the magnetic gear device 1 includes the first magnet 11 having the above configuration, it is possible to reduce the number of parts, simplify the shape of the back yoke 112 and / or the frame, and eliminate the need to provide a cover to prevent the first magnetic poles 111 from falling off. Furthermore, in the first magnet 11, the pitch of the multiple first magnetic poles 111 in the circumferential direction C is narrow, which makes it possible to reduce torque ripple.

[0038] Because the magnetic gear device 1 according to this embodiment has the above-mentioned functions and effects, it can be applied, for example, to devices used in clean rooms where dust generation is undesirable, devices used in special environments such as marine or aerospace environments, residential equipment and home appliances that require safety measures against contact with the human body and measures against overload, and, taking advantage of its high efficiency, to generators, etc. More specifically, the magnetic gear device 1 can be applied to robot arms, semiconductor manufacturing equipment, electric opening and closing mechanisms and electronic locks of home appliances, cooling pumps and cooling fans for air conditioners, etc.

[0039] Furthermore, since the intermediate transmission mechanism 3 according to this embodiment is composed of the first gear 31, which is a worm, and the second gear 32, which is a worm wheel, it is possible to reduce the noise generated when the motor 2 is driven.

[0040] The first gear 31 is, for example, a worm. The first gear 31 is fixed to the tip of the first shaft 22 in the first direction D and rotates together with the rotation of the first shaft 22.

[0041] In the magnetic gear device 1 according to this embodiment, the first magnet 11 has a plurality of first magnetic poles 111 integrally formed into a ring shape, and the second magnet has a plurality of second magnetic poles 121 integrally formed into a ring shape.

[0042] In the magnetic gear device 1 according to this embodiment, the pole piece 13 is located between the first magnet 11 and the second magnet 12 in the radial direction R.

[0043] In the magnetic gear device 1 according to this embodiment, the first magnet 11 is arranged inside the second magnet 12 in the radial direction R. In the magnetic gear device 1 according to this embodiment, the ring-shaped first magnet 11 is formed by integrally forming a plurality of first magnetic poles 111 by magnetizing the magnetic material as described above, so the ring-shaped first magnets 11 can be arranged even at a narrow pitch inside in the radial direction R.

[0044] In the magnetic gear device 1 according to the embodiment described above, the pole piece 13 is fixed, the first magnet 11 arranged on the inside in the radial direction R is non-fixed and rotates together with the second shaft 14, and the second magnet 12 arranged on the outside in the radial direction R is non-fixed and rotates together with the second gear 32. However, the magnetic gear device 1 according to this embodiment is not limited to this. For example, as shown in Table 1, it is also possible for one of the first magnet 11, the second magnet 12, and the pole piece 13 to be fixed and the remaining two to be non-fixed. Furthermore, it is also possible for one of the first magnet 11 and the second magnet 12 to be arranged on the inside in the radial direction R, and the other to be arranged on the outside in the radial direction R.

[0045] In the above-described embodiment, the power transmission device 100 is described as including the magnetic gear device 1, the motor 2, and the intermediate transmission mechanism 3. However, the power transmission device 100 according to this embodiment is not limited to this. For example, the driving force of the motor 2 may be input directly to the magnetic gear device 1 without the intermediate transmission mechanism 3. Furthermore, the motor 2 may be replaced with a generator.

[0046] Furthermore, the magnets 11 and 12 are described as being provided with back yokes 112 and 122. However, the back yokes 112 and 122 do not necessarily have to function as back yokes, as long as they can connect (fix) the magnets 11 and 12 to other components.

[0047] In the magnetic gear device 1 according to the embodiment described above, the first magnet 11 has been described as having 52 (26 pole pairs) first magnetic poles 111. However, the number of first magnetic poles 111 of the first magnet 11 according to this embodiment is not limited to this and can be set to any number.

[0048] Furthermore, in the magnetic gear device 1 according to the above embodiment, the second magnet 12 has been described as having six (three pole pairs) second magnetic poles 121. However, the number of second magnetic poles 121 of the second magnet 12 according to this embodiment is not limited to this and can be set to any number.

[0049] Furthermore, in the magnetic gear device 1 according to the embodiment described above, the pole piece 13 has been described as being composed of 29 modulation pieces 131. However, the number of modulation pieces 131 constituting the pole piece 13 according to this embodiment is not limited to this and can be set to any number. Note that, if any two of the numbers of the first magnetic poles 111 of the first magnet, the second magnetic poles 121 of the second magnet, and the number of modulation pieces 131 of the pole piece 13 are determined, the number of the remaining one can be set appropriately depending on the numbers of the other two.

[0050] Furthermore, in the power transmission device 100 according to the above embodiment, the intermediate transmission mechanism 3 has been described as including the first gear 31, which is a worm, and the second gear 32, which is a worm wheel. However, the intermediate transmission mechanism 3 according to the present embodiment is not limited to this. For example, the intermediate transmission mechanism 3 may include a first gear, which is a screw gear, and a second gear 32, which meshes with the first gear and is also a screw gear. Of course, the intermediate transmission mechanism 3 is not limited to this, and may be configured with a plurality of meshing gears, or may be configured using other gears. For example, a helical gear or the like may be used as the other gear.

[0051] Furthermore, in the magnetic gear device 1 according to the above-described embodiment, the second magnet 12 has been described as having a plurality of second magnetic poles 121 arranged in the circumferential direction C, and the plurality of second magnetic poles 121 formed integrally in a ring shape. However, the second magnet 12 according to this embodiment can also be formed by joining a plurality of magnets each formed in an arc shape and having two second magnetic poles 121. Similarly, the first magnet 11 can also be formed by joining a plurality of magnets each having two first magnetic poles 111.

[0052] Furthermore, in the magnetic gear device 1 according to the embodiment described above, the input and output shafts can be interchanged, for example by connecting the first shaft 22 of the motor 2 to the first magnet 11 to serve as the input shaft and the second magnet 12 to serve as the output shaft. In this case, torque decreases, but speed can be improved. In this case, if the first magnet 11 on the inside in the radial direction R serves as the input, the second magnet 12 on the outside in the radial direction R serves as the output, and the pole piece 13 is fixed, the speed increase ratio X3 can be calculated as follows: X3 = 11M ÷ 12M = 26 ÷ 3 = 8.67

[0053] Alternatively, when the pole piece 13 is the output, the first magnet 11 is the input, and the second magnet 12 is fixed, the speed increase ratio X4 can be calculated as follows: X4 = 13M ÷ 12M = 29 ÷ 3 = 9.67

[0054] Furthermore, for example, in the magnetic gear device 1 according to the above embodiment, if the first magnet 11 and the second magnet 12 are interchanged, with the first magnet 11 on the outside in the radial direction R and the second magnet 12 on the inside in the radial direction R, the first shaft 22 of the motor 2 is connected to the second magnet 12 to serve as the input shaft, the first magnet 11 is the output shaft, and the pole piece 13 is fixed, the reduction ratio X5 can be calculated as follows: X5 = 11M ÷ 12M = 26 ÷ 3 = 8.67

[0055] Alternatively, when the pole piece 13 is the output, the first magnet 11 is fixed, and the second magnet 12 is the input, the reduction ratio X6 can be calculated as follows: X6 = 13M ÷ 12M = 29 ÷ 3 = 9.67

[0056] Furthermore, the power transmission device 100 according to the above embodiment has been described as being provided with an intermediate transmission mechanism 3 between the motor 2 and the magnetic gear device 1. However, the power transmission device according to this embodiment is not limited to this, and the intermediate transmission mechanism 3 does not have to be provided. In other words, the magnetic gear device 1 according to this embodiment is a device that receives power directly or indirectly from the motor 2, which is the drive source. Furthermore, the drive source may be something other than the motor 2.

[0057] [First Modification of First Embodiment] Next, a magnetic gear device 1A according to a first modification of the first embodiment will be described using Fig. 4. Fig. 4 is a plan view of the magnetic gear device 1A according to the first modification of the first embodiment. Note that in the configuration of the magnetic gear device 1A according to the first modification of the first embodiment, the same components as those in the magnetic gear device 1 according to the first embodiment are given the same reference numerals and description thereof will be omitted. Furthermore, although not shown, a motor 2 and an intermediate transmission mechanism 3 similar to those in the power transmission device 100 according to the first embodiment are arranged on the radially outer side R of the magnetic gear device 1A.

[0058] The magnetic gear device 1A according to this embodiment has a first magnet 11, a second magnet 12, and a pole piece 13.

[0059] In the magnetic gear device 1A, the first magnet 11 is disposed outside the second magnet 12 in the radial direction R, and the first back yoke 112 is fixed to the inner circumferential surface of the second gear 32. The first magnet 11 according to this modification is disposed on the input side (drive side) of the second magnet 12.

[0060] In the magnetic gear device 1A, the second magnet 12 is disposed radially inward of the first magnet 11 in the radial direction R, and the second back yoke 122 is fixed to the outer peripheral surface of the second shaft 14. The second magnet 12 according to this modification is disposed on the output side (driven side) of the first magnet 11.

[0061] In the power transmission device according to this modification, when the motor 2 is driven to rotate the second gear 32 in the circumferential direction C, the first back yoke 112 and the first magnet 11 fixed to the second gear 32 rotate in the circumferential direction C together with the second gear 32. Then, changes in the magnetic flux of the first magnetic poles 111 in the first magnet 11 are modulated by the pole piece 13 and transmitted to the second magnetic poles 121 of the second magnet 12 connected to the driven side. In this case, in the magnetic gear device 1 according to this modification, the number of second magnetic poles 121 of the second magnet 12 arranged inward of the first magnet 11 in the radial direction R is fewer than the number of first magnetic poles 111 of the first magnet 11. Therefore, although torque decreases, the rotation speed in the circumferential direction C can be increased. Furthermore, in the magnetic gear device 1A according to this modification, the first magnet 11 has a ring shape in which multiple first magnetic poles 111 are arranged in the circumferential direction C and are integrally formed. Therefore, the magnetic gear device 1A of this modified example can increase speed because the pitch of the multiple first magnetic poles 111 in the circumferential direction C can be narrowed compared to, for example, a magnetic gear device having a ring-shaped first magnet formed by connecting multiple individually formed magnets (for example, the device described in JP 2022-150601 A).

[0062] As described above, in the magnetic gear device 1A according to this modification, the first magnet 11 is disposed outside the second magnet 12 in the radial direction R, and the number of first magnetic poles 111 of the first magnet 11 is greater than the number of second magnetic poles 121 of the second magnet 12. Therefore, the magnetic gear device 1A according to this embodiment can increase the speed of the second shaft 14 (rotational speed on the output side) of the magnetic gear device 1A more than the speed of the first shaft 22 of the motor 2 (rotational speed on the input side). Furthermore, the magnetic gear device 1A according to this modification achieves the same functions and effects as the magnetic gear device 1 according to the first embodiment.

[0063] In the magnetic gear device 1A according to this modification, the second magnet 12 is disposed inside the first magnet 11 in the radial direction R.

[0064] [Second Modification of First Embodiment] Next, a magnetic gear device 1B according to a second modification of the first embodiment will be described using Fig. 5. Fig. 5 is a perspective view of the magnetic gear device 1B according to the second modification of the first embodiment. Note that in the configuration of the magnetic gear device 1B according to the second modification of the first embodiment, the same components as those in the magnetic gear device 1 according to the first embodiment are given the same reference numerals and their description will be omitted. Furthermore, although not shown, a motor 2 and an intermediate transmission mechanism 3 similar to those in the power transmission device 100 according to the first embodiment are arranged on the outside of the magnetic gear device 1B.

[0065] The magnetic gear device 1B according to this embodiment has a first magnet 11, a second magnet 12, and a pole piece 13, and the first magnet 11 and the second magnet 12 face each other in the axial direction A with the pole piece 13 interposed therebetween.

[0066] The first back yoke 112 of the first magnet 11 is fixed to the outer peripheral surface of the second shaft 14. In other words, the first magnet 11 according to this modification is disposed on the output side (driven side) of the second magnet 12.

[0067] The second back yoke 122 of the second magnet 12 is fixed to the inner circumferential surface of the second gear 32. In other words, the second magnet 12 according to this modification is disposed on the input side (drive side) relative to the first magnet 11.

[0068] As described above, in the magnetic gear device 1B according to this modified example, the first magnet 11 and the second magnet 12 face each other in the axial direction A with the pole piece 13 interposed therebetween.

[0069] Furthermore, in the magnetic gear device 1B according to this embodiment, the axis of the first magnet 11 and the axis of the second magnet 12 can be arranged coaxially, which facilitates modularization and improves the degree of freedom in layout. Furthermore, the magnetic gear device 1B according to this modification achieves the same actions and effects as the magnetic gear device 1 according to the first embodiment.

[0070] Second Embodiment Next, a power transmission device 100C according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a plan view of the power transmission device 100C according to the second embodiment. Note that in the configuration of the power transmission device 100C according to the second embodiment, the same components as those in the power transmission device 100 according to the first embodiment are designated by the same reference numerals, and description thereof will be omitted.

[0071] The power transmission device 100C according to this embodiment includes a magnetic gear device 1, a motor 2, and an intermediate transmission mechanism 3. The power transmission device 100C according to this embodiment is arranged so that the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are parallel to each other. In other words, the power transmission device 100C according to this embodiment is a parallel-axis device in which the axis 22o of the input shaft and the axis 14o of the output shaft are parallel to each other.

[0072] As described above, in the power transmission device 100C according to this embodiment, the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are arranged to be parallel to each other. Therefore, the power transmission device 100C according to this embodiment can be easily modularized and can improve the degree of freedom in layout.

[0073] Third Embodiment Next, a power transmission device 100D according to a third embodiment will be described with reference to Figures 7 and 8. Figure 7 is a cross-sectional view of the power transmission device 100D according to the third embodiment. Figure 8 is a front view of an intermediate transmission mechanism 3D included in the power transmission device 100D shown in Figure 7. Note that in the configuration of the power transmission device 100D according to the third embodiment, the same components as those in the power transmission device 100 according to the first embodiment are designated by the same reference numerals, and description thereof will be omitted.

[0074] The power transmission device 100D according to this embodiment includes a magnetic gear device 1, a motor 2, and an intermediate transmission mechanism 3D. The power transmission device 100C according to this embodiment is arranged so that the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are coaxial. In other words, the power transmission device 100D according to this embodiment is a device in which the axis 22o of the input shaft and the axis 14o of the output shaft are coaxial.

[0075] The intermediate transmission mechanism 3D shown in this embodiment is a planetary gear mechanism, and includes a sun gear 301, a ring gear 302, a plurality of (three in this embodiment) planetary gears 303, and a planet carrier 304.

[0076] The sun gear 301 is formed, for example, in a cylindrical shape and has teeth on its outer circumferential surface. The teeth of the sun gear 301 mesh with the teeth of the planetary gears 303. The sun gear 301 is fixed to the outer circumferential surface of the first shaft 22 of the motor 2.

[0077] The ring gear 302 is formed in an annular shape and has teeth on its inner circumferential surface. The ring gear 302 is fixed to a frame (not shown). In other words, the planetary gear mechanism of the intermediate transmission mechanism 3D according to this embodiment is a planetary type in which the ring gear 302 is fixed to a frame.

[0078] Each of the planetary gears 303 is formed, for example, in a cylindrical shape and has teeth formed on its outer circumferential surface and a planetary shaft 303 a. The planetary gears 303 are provided in the intermediate transmission mechanism 3D so as to be rotatable around an axis 303 o of the planetary shaft 303 a. The teeth of the planetary gears 303 mesh with the teeth of the ring gear 302 and the sun gear 301.

[0079] The planetary carrier 304 is coupled to each of the planetary shafts 303 a of the multiple planetary gears 303. The planetary carrier 304 is provided in the intermediate transmission mechanism 3D so as to be rotatable about the axis 22 o in accordance with the revolution of the planetary gears 303. Furthermore, in the intermediate transmission mechanism 3D according to this embodiment, the planetary carrier 304 is coupled to the back yoke 122 of the second magnet 12.

[0080] Next, a description will be given of the power transmission device 100D according to this embodiment when the motor 2 is driven. When the motor 2 is driven in the power transmission device 100D, the sun gear 301 rotates about the axis 22o together with the rotation of the first shaft 22.

[0081] As the sun gear 301 rotates, the multiple planetary gears 303 rotate around the axis 303o of the planetary shafts 303a while meshing with the ring gear 302, and also revolve around the sun gear 301. When the planetary gears 303 revolve, because the planetary shafts 303a are connected to the planetary carrier 304, the planetary carrier 304 rotates around the axis 22o in conjunction with the revolution of the planetary gears 303.

[0082] Furthermore, since the planetary carrier 304 is connected to the second back yoke 122 of the second magnet 12, the second magnet 12 rotates about the axis 14o as the planetary carrier 304 rotates about the axis 22o. Therefore, similar to the power transmission device 100 according to the first embodiment, the first magnet 11 and the second shaft 14 rotate as the second magnet 12 rotates.

[0083] As described above, in the power transmission device 100D according to this embodiment, the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are arranged so as to be coaxial. Therefore, the power transmission device 100D according to this embodiment can be easily modularized and can improve the degree of freedom in layout. Furthermore, this power transmission device 100D can also increase torque in the intermediate transmission mechanism 3D, which is a planetary gear mechanism, thereby further increasing torque.

[0084] [First Modification of Third Embodiment] Next, a power transmission device 100E according to a first modification of the third embodiment will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the power transmission device 100E according to the first modification of the third embodiment. Note that in the configuration of the power transmission device 100E according to the first modification of the third embodiment, the same components as those of the above-described power transmission device 100 or magnetic gear device 1A are assigned the same reference numerals and description thereof will be omitted.

[0085] A power transmission device 100E according to this modified example includes a magnetic gear device 1A, a motor 2, and an intermediate transmission mechanism 3E.

[0086] The intermediate transmission mechanism 3E shown in this embodiment is a planetary gear mechanism, and includes a sun gear 301, a ring gear 302, a plurality of planet gears 303, and a planet carrier 304.

[0087] In the intermediate transmission mechanism 3E according to this modified example, the planetary carrier 304 is connected to the second shaft 14. Furthermore, the first back yoke 112 of the first magnet 11 is connected to an output shaft (not shown).

[0088] Next, a description will be given of the power transmission device 100E according to this embodiment when the motor 2 is driven. When the motor 2 is driven in the power transmission device 100E, the sun gear 301 rotates about the axis 22o together with the rotation of the first shaft 22.

[0089] As the sun gear 301 rotates, the multiple planetary gears 303 rotate around the axis 303o of the planetary shafts 303a while meshing with the ring gear 302, and also revolve around the sun gear 301. When the planetary gears 303 revolve, because the planetary shafts 303a are connected to the planetary carrier 304, the planetary carrier 304 rotates around the axis 22o in conjunction with the revolution of the planetary gears 303.

[0090] Furthermore, because the planet carrier 304 is connected to the second shaft 14 of the magnetic gear device 1, the second shaft 14 rotates about the axis 14o as the planet carrier 304 rotates about the axis 22o. Therefore, the second magnet 12 rotates together with the second shaft 14, and the first magnet 11 rotates in conjunction with the rotation of the second magnet 12. As a result, the rotation of the first magnet 11 rotates the output shaft (not shown).

[0091] As described above, in the power transmission device 100E according to this modification, the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are arranged so as to be coaxial. Therefore, the power transmission device 100E according to this embodiment can be easily modularized and can improve the degree of freedom in layout. Furthermore, this power transmission device 100E can increase torque in the intermediate transmission mechanism 3E, which is a planetary gear mechanism. Therefore, when the above-described magnetic gear device 1A is applied to the power transmission device 100E, torque can be further increased.

[0092] [Second Modification of Third Embodiment] Next, a power transmission device 100F according to a second modification of the third embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view of the power transmission device 100F according to the second modification of the third embodiment. Note that in the configuration of the power transmission device 100F according to the second modification of the third embodiment, the same components as those in the power transmission device 100 according to the first embodiment and the power transmission device 100D according to the third embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

[0093] A power transmission device 100F according to this modified example includes a magnetic gear device 1, a motor 2, and an intermediate transmission mechanism 3F.

[0094] The intermediate transmission mechanism 3F shown in this embodiment is a planetary gear mechanism. The intermediate transmission mechanism 3F, which is a planetary gear mechanism, includes a sun gear 301, a ring gear 302, a plurality of planet gears 303, and a planet carrier 304.

[0095] In the intermediate transmission mechanism 3F according to this modification, the ring gear 302 is connected to the back yoke 122 of the second magnet 12. The planetary carrier 304 is fixed to a frame (not shown). In other words, the planetary gear mechanism of the intermediate transmission mechanism 3F according to this embodiment is a star type in which the planetary carrier is fixed to the frame.

[0096] Next, a description will be given of the power transmission device 100F according to this embodiment when the motor 2 is driven. When the motor 2 is driven in the power transmission device 100F, the sun gear 301 rotates about the axis 22o together with the rotation of the first shaft 22.

[0097] The plurality of planetary gears 303 rotate around the axis 303o of the planetary shaft 303a while meshing with the ring gear 302 due to the rotation of the sun gear 301. Since the planetary carrier 304 is fixed to the frame, when the planetary gears 303 rotate, the ring gear 302 rotates around the axis 303o.

[0098] Furthermore, because the ring gear 302 is connected to the second back yoke 122, the second magnet 12 rotates about the axis 14o together with the rotation of the ring gear 302 and the second back yoke 122. Therefore, together with the rotation of the second magnet 12, the first magnet 11 and the second shaft 14 rotate about the axis 14o.

[0099] As described above, in the power transmission device 100F according to this embodiment, the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are arranged so as to be coaxial. Therefore, the power transmission device 100F according to this embodiment can be easily modularized and can improve the degree of freedom in layout. Furthermore, this power transmission device 100F can also increase torque in the intermediate transmission mechanism 3F, which is a planetary gear mechanism, thereby further increasing torque.

[0100] [Third Modification of Third Embodiment] Next, a power transmission device 100G according to a third modification of the third embodiment will be described with reference to Figures 11 and 12. Figure 11 is a cross-sectional view of the power transmission device 100G according to the third modification of the third embodiment. Figure 12 is a front view of an intermediate transmission mechanism 3G included in the power transmission device 100G shown in Figure 11. Note that in the configuration of the power transmission device 100G according to the third modification of the third embodiment, the same components as those of the power transmission devices 100, 100D or magnetic gear device 1A described above will be assigned the same reference numerals and descriptions thereof will be omitted.

[0101] The power transmission device 100G according to this modification includes a magnetic gear device 1A, a motor 2, and an intermediate transmission mechanism 3G.

[0102] The intermediate transmission mechanism 3G shown in this embodiment is a planetary gear mechanism. The intermediate transmission mechanism 3G, which is a planetary gear mechanism, includes a sun gear 301, a ring gear 302, a plurality of planet gears 303, and a planet carrier 304.

[0103] In the intermediate transmission mechanism 3G according to this modification, the first shaft 22 is connected to the planet carrier 304. The sun gear 301 is connected to the second shaft 14 via a shaft 305. The back yoke 122 of the second magnet 12 is connected to an output shaft (not shown). The ring gear 302 is fixed to a frame (not shown).

[0104] Next, a description will be given of the power transmission device 100G according to this embodiment when the motor 2 is driven. When the motor 2 is driven in the power transmission device 100G, the planet carrier 304 rotates about the axis 22o.

[0105] The planetary gears 303 rotate about the axis 303o of the planet shafts 303a while meshing with the ring gear 302 due to the rotation of the planet carrier 304, and also revolve around the sun gear 301. When the planetary gears 303 revolve, the sun gear 301 rotates about the axis 14o. The sun gear 301 according to this modification is connected to the second shaft 14 via the axis 305, so that as the sun gear 301 rotates, the second shaft 14 rotates about the axis 14o.

[0106] Therefore, the first magnet 11 rotates together with the rotation of the second shaft 14, and the second magnet 12 rotates in conjunction with the rotation of the first magnet 11. As a result, the rotation of the second magnet 12 rotates the output shaft (not shown).

[0107] As described above, in the power transmission device 100G according to this modification, the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are arranged so as to be coaxial. Therefore, the power transmission device 100G according to this embodiment can be easily modularized and can improve the degree of freedom in layout. Furthermore, this power transmission device 100G can increase the rotational speed of the intermediate transmission mechanism 3G, which is a planetary gear mechanism. Therefore, when the above-described magnetic gear device 1A is applied to the power transmission device 100G, the rotational speed can be further increased.

[0108] The intermediate transmission mechanisms 3D, 3E, and 3G according to the third embodiment and the modified examples have been described as planetary types in which the ring gear 302 is fixed to the frame, and the intermediate transmission mechanism 3F has been described as a star type in which the planet carrier 304 is fixed to the frame. However, the intermediate transmission mechanisms 3D, 3E, 3F, and 3G according to the present embodiment and the modified examples are not limited to these. For example, the intermediate transmission mechanisms can be applied to solar-type planetary gear mechanisms in which the sun gear 301 is fixed.

[0109] [Fourth Embodiment] Next, a power transmission device 100H according to a fourth embodiment will be described with reference to Fig. 13. Fig. 13 is a cross-sectional view of the power transmission device 100H according to the fourth embodiment. Note that in the configuration of the power transmission device 100H according to the fourth embodiment, the same components as those of the power transmission device 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0110] 13, the power transmission device 100H according to this embodiment includes a magnetic gear device 1, a motor 2 (not shown), and a transmission mechanism 3H. In the power transmission device 100H according to this embodiment, the motor 2 is connected to an axis 14o of the input shaft, which is disposed perpendicular to the output shaft of the transmission mechanism 3H. In other words, the power transmission device 100H according to this embodiment is an orthogonal-axis device in which the axis 14o of the input shaft and the output shaft of the transmission mechanism 3H are disposed perpendicular to each other.

[0111] The transmission mechanism 3H includes a pinion gear 313 and a rack gear 312. The pinion gear 313 is, for example, cylindrical and has a plurality of teeth. The inner peripheral surface of the pinion gear 313 is fixed to the outer peripheral surface of the second back yoke 122.

[0112] The rack gear 312 extends, for example, perpendicular to the direction in which the axis 14o extends. The rack gear 312 has a plurality of teeth. In the transmission mechanism 3H, the teeth of the rack gear 312 mesh with the teeth of the pinion gear 311.

[0113] The output shaft (not shown) of the motor is fixed to the axis 14o. Therefore, when the motor of this power transmission mechanism 1H is driven, the first magnet 11 is driven, which causes the second magnet 12 to rotate in the circumferential direction C via the pole piece 13. This causes the pinion gear 313 to rotate in the circumferential direction C together with the second magnet 12 and the second back yoke 122. This causes the rack gear 312, which meshes with the teeth of the pinion gear 313, to move in a direction perpendicular to the axial direction A and the radial direction R. The moving direction of the rack gear 312 at this time is the output axial direction of the power transmission mechanism 1H. In other words, the rack gear 312 is the output shaft of the transmission mechanism 3H. In this embodiment, the magnetic gear device 1 serves as an intermediate transmission mechanism.

[0114] Fifth Embodiment Next, a power transmission device 100I according to a fifth embodiment will be described with reference to Fig. 14. Fig. 14 is a cross-sectional view of the power transmission device 100I according to the fifth embodiment. Note that in the configuration of the power transmission device 100I according to the fifth embodiment, the same components as those in the power transmission device 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0115] The power transmission device 100I according to this embodiment includes a magnetic gear device 1, a motor 2, and an intermediate transmission mechanism 3I. The power transmission device 100I according to this embodiment is arranged so that the axis 22o of the first shaft 22, which is the input shaft, and the axis 14o of the second shaft 14, which is the output shaft, are perpendicular to each other. In other words, the power transmission device 100I according to this embodiment is an orthogonal-axis device in which the axis 22o of the input shaft and the axis 14o of the output shaft are perpendicular to each other.

[0116] The intermediate transmission mechanism 3I includes a first bevel gear 321 and a second bevel gear 322. The first bevel gear 321 is fixed to the first shaft 22 and has a plurality of teeth.

[0117] The second bevel gear 322 has a plurality of teeth. The second bevel gear 322 is fixed to the outer peripheral surface of the second back yoke 122 of the second magnet 12 in the radial direction R. In the intermediate transmission mechanism 3I, the teeth of the first bevel gear 321 and the teeth of the second bevel gear 322 mesh with each other.

[0118] The above has been a description of the embodiments and modifications of the magnetic gear devices 1, 1A, and 1B according to the present invention, and the embodiments and modifications of the power transmission devices 100, 100C, 100D, 100E, 100G, 100H, and 100I. However, the present invention is not limited to the embodiments and modifications, and various modifications are possible without departing from the spirit of the present invention. The present invention also includes configurations in which the components of the above-described embodiments and modifications are appropriately combined. Such various modifications without departing from the spirit of the present invention are also included within the technical scope of the present invention, and this will be clear to those skilled in the art from the claims.

[0119] REFERENCE SIGNS LIST 1, 1A, 1B magnetic gear device, 11 first magnet, 111 first magnetic pole, 12 second magnet, 121 second magnetic pole, 13 pole piece, A axial direction, C circumferential direction

Claims

1. A magnetic gear device comprising: a first magnet having a plurality of first magnetic poles arranged in the circumferential direction; a second magnet having a plurality of second magnetic poles arranged in the circumferential direction; and a pole piece located between the first magnet and the second magnet and magnetically connecting the first magnet and the second magnet; wherein either the plurality of first magnetic poles of the first magnet or the plurality of second magnetic poles of the second magnet are integrally formed in a ring shape; and the number of the first magnetic poles of the first magnet is greater than the number of the second magnetic poles of the second magnet.

2. A magnetic gear device according to claim 1, wherein the first magnet has a plurality of first magnetic poles integrally formed in a ring shape, and the second magnet has a plurality of second magnetic poles integrally formed in a ring shape.

3. A magnetic gear device according to claim 1 or 2, wherein the pole piece is located between the first magnet and the second magnet in the radial direction.

4. A magnetic gear device according to claim 1 or 2, wherein the pole piece is located axially between the first magnet and the second magnet.

5. The magnetic gear device according to claim 3, wherein the first magnet is disposed radially inward of the second magnet.

6. The magnetic gear device according to claim 3, wherein the second magnet is disposed radially inward of the first magnet.

7. A magnetic gear device according to claim 4, wherein the first magnet and the second magnet face each other in the axial direction with the pole piece interposed therebetween.

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