Magnetic Gear Unit

Abstract

To provide a magnetic gear device which has less torque ripples while maintaining large transmission torque in a non-contact manner.SOLUTION: A magnetic gear device 100 has two rotators (rotors) each having a plurality of permanent magnets, and a magnetic piece body having a plurality of magnetic pieces formed of soft magnetic materials between the two rotators, such that the magnetic gear device transmits rotation by modulating magnetic fluxes of magnet pole number ratios via the magnetic pieces. For securing a change gear ratio with less torque ripple of transmission torque, torque ripples become large at a change gear ratio of an integer multiple, which results in the magnetic gear device being subject to restrictions such as being extremely disadvantageous as a product. In the present invention, by combining irregularly-shaped magnetic body pieces which are individually set in the shapes of the magnetic pieces of the magnetic piece body arranged between the rotators, the torque ripples of the magnetic gear device can be reduced. It is therefore possible to provide a magnetic gear device that is not restricted by the change gear ratio.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic gear mechanism that transmits power in a non-contact manner by utilizing the magnetism of a magnet. [Background technology]

[0002] In recent years, magnetic gear devices have been attracting attention as a means of transmitting power between rotating shafts. The magnetic gear device is configured by supporting an inner magnet cylinder, an outer magnet cylinder, and a magnetic material cylinder, all of which are cylindrical, on the same axis with the magnetic material cylinder interposed between the two magnet cylinders. A plurality of rod-shaped magnets extending in the axial direction are arranged on the outer periphery of the inner magnet cylinder and the inner periphery of the outer magnet cylinder. The magnetic material cylinder is configured by arranging a plurality of rod-shaped magnetic bodies at equal intervals in the circumferential direction and holding them with a non-magnetic holder arranged between them. The number of magnets arranged in the inner magnet cylinder and the outer magnet cylinder is different from each other, and each magnet is magnetized so that different magnetic poles are adjacent to each other in the circumferential direction. In addition, the number of magnetic bodies arranged in parallel in the magnetic material cylinder is different from the number of magnets in both magnet cylinders.

[0003] A magnetic gear device is used, for example, in which an inner magnet cylinder and an outer magnet cylinder are used as a rotor that is supported so as to be freely rotatable, and a magnetic material cylinder provided between the two rotors is used as a stator that is supported so as not to be rotatable, and the magnetomotive force of one of the inner rotor or the outer rotor is modulated by a magnetic material provided in the stator, thereby applying a magnetomotive force of a different waveform to the other rotor, thereby transmitting power (rotational torque) under speed change (deceleration, acceleration) between both rotors and the rotating shafts that rotate integrally with each of them.

[0004] Magnetic gear devices have the advantages of being able to transmit power without contact, suppressing vibration and noise during operation, and being easy to maintain as they do not require lubrication. In addition, the gear ratio and direction of rotation can be appropriately set by selecting the number of magnets in the inner and outer rotors and the magnetic bodies in the stator arranged in parallel. Furthermore, in recent years, it has become possible to obtain high torque density (maximum transmission torque per size) by applying strong magnetic forces such as rare earth iron boron magnets. For these reasons, there is a strong demand for magnetic gear devices to be used as a replacement for various gear devices that achieve variable speed transmission using multiple gears that mesh mechanically.

[0005] However, in torque transmission of a magnetic gear device, the attraction force between the magnets of the inner rotor and the outer rotor as magnet cylinders changes successively with the relative rotation of the two rotors, generating a cogging torque, which causes the torque transmitted between the rotating shafts to fluctuate periodically. This torque fluctuation is an undesirable phenomenon for a power transmission means, and therefore reducing the cogging torque and the torque ripple caused by the cogging torque is an important issue in the practical application of magnetic gear devices.

[0006] Patent Document 1 discloses that the cogging torque can be reduced by providing the magnetic body (magnetic teeth) of a stator configured as a magnetic cylinder in a state where it is skewed with respect to the axial length direction of the stator.

[0007] Furthermore, Patent Document 2 discloses that the cogging torque is reduced by providing a skew between the inner magnet cylinder and the outer magnet cylinder. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2013-47546 A [Patent Document 2] International Publication No. WO 2015 / 053005 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the disclosure of Patent Document 1 only deals with skewing the magnetic teeth, and makes no mention of how much skew (amount, angle, etc.) is required to effectively reduce the cogging torque.

[0010] Furthermore, Patent Document 2 discloses a case in which the magnetic part of the magnetic body located in the middle of the inner and outer rotors is skewed, and a case in which the magnets of the inner and outer rotors are skewed to reduce cogging torque.

[0011] However, these methods for reducing cogging torque and torque ripple all involve skew in either the magnetic material portion or the magnet tube portion. In these skewed structures, it is usually difficult to process a magnetic material that is approximately rectangular parallelepiped shaped into a skewed structure, and it is difficult to ensure a uniform gap between the magnet of the rotating body, which determines the transmission characteristics and quality of a magnetic gear, and the magnetic material located in between, over the entire axial length of the magnetic gear, which can lead to deterioration and instability of the transmission characteristics.

[0012] On the other hand, it is known that cogging is reduced when the least common multiple (Nc) of the number of magnet pair poles (Ph) of the inner magnet cylinder of the two rotating bodies that make up the magnetic gear, 2Ph, and the number of magnetic poles (Np) of the intermediate magnetic cylinder, Np, is larger. Therefore, the least common multiple (Nc) is large when setting the speed ratio of the magnetic gear, and the speed ratio is set to a fraction. In this way, the speed ratio of the magnetic gear device that takes cogging torque and torque ripple into consideration is restricted to being set to a fraction, which is disadvantageous in developing new applications for the magnetic gear. In particular, in small magnetic gears, the number of pairs of poles is reduced, making it even more difficult to set the speed ratio of the magnetic gears. The present invention has been made in view of the above-mentioned problems, and has an object to provide a magnetic gear device that has less torque ripple while maintaining transmittable torque. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems and achieve the object, the magnetic gear device of the present invention has two rotors with multi-pole permanent magnets and a plurality of magnetic pieces made of soft magnetic material between the rotors, and the magnetic pieces transmit rotation by modulating the magnetic flux of the pole number ratio of each magnet, wherein the plurality of magnetic pieces are magnetic piece bodies made up of several magnetic pieces each having different circumferential widths between adjacent magnetic pieces, and the magnetic gear device is characterized in that the magnetic pieces are arranged at an equal pitch.

[0014] In claim 2, the magnetic gear device according to claim 1, characterized in that the magnetic pieces have circumferential width ratios of 0.7 pitch width, 0.8 pitch width, and 0.3 pitch width in one set.

[0015] In a third aspect of the present invention, there is provided the magnetic gear device according to the first and second aspects, wherein a magnet-to-pole number ratio of the permanent magnets arranged on the two rotors is an integer multiple.

[0016] In a fourth aspect of the present invention, there is provided the magnetic gear device according to any one of the first to third aspects, wherein the two rotors and the magnetic piece are disk-shaped and arranged to face each other.

[0017] In a fifth aspect of the present invention, there is provided the magnetic gear device according to any one of the first to third aspects, wherein the two rotors and the magnetic piece are cylindrical and disposed opposite each other, with their respective centers of rotation being concentric.

[0018] In a sixth aspect of the present invention, the magnetic gear device according to any one of the first to fifth aspects is characterized in that the magnetic pieces are made of soft magnetic material such as a laminate, a powder magnetic core, or an amorphous body.

[0019] In a seventh aspect of the present invention, the magnetic gear device according to any one of the first to sixth aspects is characterized in that the magnetic pole piece is embedded in a magnetic piece holder made of a non-magnetic or non-metallic material, one side of which is substantially flush with the surface of the magnetic pole piece. Effect of the Invention

[0020] According to the present invention, the magnetic pieces of the intermediate stator, which is located between two rotating bodies and is an important component of the transmission characteristics of the magnetic gear device, have conventionally been composed of multiple magnetic pieces of the same shape arranged evenly around a circle.However, by changing the structure to one in which multiple magnetic pieces with different circumferential width ratios are combined and arranged at equal intervals, it is possible to realize a magnetic gear device that significantly reduces the torque ripple of the transmitted torque. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 shows a magnetic gear device according to a first embodiment of the present invention, with FIG. 1a being a cross-sectional view and FIG. 1b being a side view thereof. [Diagram 2] FIG. 2 is an exploded view of FIG. 1, with FIG. 2a being a front view of the low-speed rotor, FIG. 2b being a front view of the disk-shaped stator, and FIG. 2c being a front view of the high-speed rotor. [Diagram 3] 3 is a front view of the magnetic piece portion of the disk-shaped stator of FIG. 2b, FIG. 3a is an overall view of the magnetic piece portion of the intermediate stator with the magnetic pieces attached, and FIG. 3b is a diagram showing the relevant dimensions of the arrangement shape of the magnetic pieces. [Figure 4] 1 is a table summarizing examples of magnetic gear speed ratio settings and torque ripple values ​​for a typical magnetic gear device. [Diagram 5] 4 is a table showing the transition of design specifications leading to the improvement of torque ripple according to the present invention and the improvement effect. [Figure 6] FIG. 4 is a cross-sectional view of a cylindrical portion of a cylindrical magnetic gear device according to a second embodiment of the present invention, cut in a central portion. [Figure 7] FIG. 7 is a side cross-sectional view of the cylindrical magnetic gear device of FIG. 6. [Figure 8] 1 is a table showing an embodiment in which the torque ripple reduction method according to the present invention is applied to magnetic gear devices having gear ratios of integers 9 and 11. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of a magnetic gear device according to the present invention will be described in detail with reference to the drawings. In addition, the same reference numerals are used for common members in each drawing. Furthermore, all bolts are referred to as bolts B regardless of their size and type. However, the present invention is not limited to the following embodiment.

[0023] A magnetic gear device according to a first embodiment of the present invention will be described with reference to Figures 1, 2, and 3. The magnetic gear device 1 has a first rotating body 2, a second rotating body 3, an intermediate stator 4, a shaft 10 of the first rotating body, and a shaft 50 of the second rotating body.

[0024] The first rotating body 2 has a yoke holder 21, a magnet yoke 22, and a magnet 23. The second rotating body 3 has a yoke holder 31, a magnet yoke 32, and a magnet 33. In addition, the intermediate stator 4 has a magnetic piece holder 41 and a magnetic piece 42, and the intermediate stator 4 is connected to stator frames 5 and 6 to form the outer frame of the main body of the magnetic gear device 1. Each configuration will be described in detail below.

[0025] The yoke holder 21 of the first rotor 2 is disk-shaped and made of a non-magnetic material as shown in Fig. 2(a), and the magnet yoke 22 is fixed to one side of the yoke holder 21 by screwing or the like, and its inner diameter side is fixed to the rotating shaft 10 by a screw B, so that it can rotate freely with respect to the stator frame 5. The magnet yoke 22 is formed in a laminated shape from a soft magnetic material such as silicon steel plate, and magnets 23 are attached to one side of the magnet yoke 22 by adhesive or the like. The magnets 23 are attached at equal intervals around the circumference so that the magnetization direction is N pole, S pole, and adjacent magnets have opposite poles as shown in Fig. 2(a). The magnets 23 have more poles than the number of magnets of the second rotor shown in Fig. 2(c).

[0026] The second rotor 3 will be described. Its basic structure is the same as that of the first rotor, but the number of magnet poles is less than that of the first rotor 2. The yoke holder 31 is a non-magnetic disk-shaped body, and the magnet yoke 32 is fixed to one side of the yoke holder 31 by screwing or the like. The inner diameter side of the magnet yoke 32 is fixed to the rotating shaft 50 by a screw B, and the rotating shaft 50 is rotatable relative to the stator frame 6. The magnet yoke 32 is formed in a laminated shape from a soft magnetic material such as silicon steel plate, and the magnet 33 is attached to one side of the magnet yoke 32 by an adhesive or the like. The magnet 23 is attached circumferentially in such a manner that the magnetization direction is the N pole, the S pole, and the adjacent magnet has a different pole, as shown in FIG. 2(c). The number of magnets 33 is less than that of the first rotor shown in FIG. 2(a), and in the figure, there are six magnets, forming three pole pairs.

[0027] The intermediate stator 4 will be described. As shown in FIG. 2(b), the intermediate stator 4 is a rectangular plate made of a nonmetallic material such as CFRP, and magnetic pieces 42 made of, for example, a powder magnetic core material are embedded in a magnetic piece holder 41 located in the center of the intermediate stator 4 at equal intervals on one side of the magnetic piece holder 41 with an adhesive or the like. The magnetic pieces 42 are each made up of a set of magnetic pieces 42a, 42b, and 42c each having a different shape, and there are 11 sets of magnetic pieces in total, making a total of 33 magnetic pieces. As shown in FIG. 3(b), the individual shapes of the magnetic pieces 42a, 42b, and 42c are fan-shaped, and the circumferential width ratios are 0.7 (magnetic piece 42a), 0.8 (magnetic piece 42b), and 0.3 (magnetic piece 42c) in the circumferential direction in sequence. Here, the circumferential width ratio is a value obtained by dividing the circumference (360°) by the number of magnetic pieces, 33, to obtain 10.9°, with the circumferential width ratio being 1. By using magnetic pieces of different shapes in this way, a magnetic gear device with less torque ripple can be realized. The reduction of torque ripple will be described later. As shown in Figures 1(a) and 1(b), the intermediate stator 4 is fixed at its four corners to stator frames 5 and 6 with screws B, and is fixed to multiple bearing holders 7 that incorporate bearings 8. The rotors 1 and 2 are rotatable relative to the intermediate stator 4.

[0028] The above-described magnet 23 of the first rotating body 2, magnet 33 of the second rotating body 3, and magnetic body 42 of the intermediate stator 4 are arranged in a disk-like, non-contacting, opposing manner to form a magnetic gear device. As a result, the magnetic gear device of the present invention has a gear ratio of 10 (30 / 3) due to the relationship between the number of pairs of poles of the magnet 23 of the first rotating body 2 (30 pieces) and the number of pairs of magnet poles of the magnet 33 of the second rotating body 3 (3 pieces).

[0029] Next, a method for reducing torque ripple in a magnetic gear device, which is the basis for the above-mentioned embodiment of the present invention, will be described based on the results of magnetic field analysis calculated using a three-dimensional magnetic field analysis simulation using the finite element method.

[0030] As a condition for determining the gear ratio of the magnetic gear device, the number of paired poles of the magnets of the first rotor (Ph), the number of paired poles of the magnets of the second rotor (Pl), and the number of magnetic poles of the intermediate body (Np) are set so that Np = Ph + Pl holds. It is known that magnetic gears usually have less torque ripple when the least common multiple (Nc) of the number of paired poles (Ph) of the magnets of the first rotor (2Ph) and the number of magnetic poles (Np) of the intermediate body is larger. If the gear ratio is set taking this into consideration, as shown in the table in Figure 4 described later, gear ratios that are integer multiples will have larger torque ripple, and gear ratios that are fractional multiples will have smaller torque ripple.

[0031] For example, in the case of a magnetic gear device with a target gear ratio (Gr) of around 10, a combination of Gr (gear ratio) = 10.33, which has little torque ripple, is generally selected. As an example, the transmission torque and torque ripple rate for four patterns of gear ratios were obtained by magnetic field analysis, and the results are summarized in the table of Figure 4. In the figure, magnetic field analysis was performed for four patterns of gear ratios, 10, 10.5, 10.33, and 10.25, and the transmission torque and torque ripple rate (%) were calculated and listed in the table. The symbols in the table of Figure 4 are: Gr is the gear ratio between the two rotors, Ph is the number of paired poles of the magnet of the first rotor (high speed side), Np is the number of magnetic poles of the magnetic piece of the intermediate stator, P is the number of paired poles of the magnet of the second rotor (low speed side), Nc is the least common multiple of 2Ph of the Ph and the Np, and Tr is the torque ripple rate (%) of the first rotor. The torque ripple rate (%) is the torque transmitted by the magnetic gear device and the torque fluctuation value expressed as a percentage. In addition, in Fig. 4, the number of pole pairs Ph of the magnet of the high-speed rotor is shown as Ph=2, Ph=3, and Ph=4, and the gear ratio Gr is shown as Gr=10.5, Gr=10.33, and Gr=10.25 in comparison with Gr=10. As a result, it can be seen that the least common multiple is generally larger and the torque ripple is smaller for the magnetic gear devices with fractional gear ratios of Gr=10.5, Gr=10.33, and Gr=10.25 than for the gear ratio Gr=10, which is an integer. From this result, Gr=10.33 is selected as the gear ratio for magnetic gear devices with a gear ratio of around 10. Although details are omitted, in other cases such as gear ratios of 4, 5, and 6, the magnetic gear devices with fractional gear ratios with smaller torque ripple are generally selected. Therefore, in the magnetic gear device of the present invention, a method has been devised that makes it possible to realize a magnetic gear device with little torque ripple, even when the speed change ratio is required to be an integer multiple.

[0032] In order to address the above-mentioned issues, it has been discovered that in the magnetic gear device according to the present invention, the torque ripple can be reduced by combining a plurality of magnetic pieces having different shapes for the magnetic pieces of the intermediate stator that constitute the magnetic gear device. An example of this is described below with reference to the drawings.

[0033] Fig. 5 shows an example of a selection method when the speed ratio Gr of the magnetic gear device is selected to be an integer multiple of 10. The vertical columns of the table shown in Fig. 5 represent the number of paired poles of the magnet in the high-speed rotating body 1 Ph, the number of poles of the magnetic body of the intermediate stator Np, the number of paired poles of the magnet in the low-speed rotating body 2 P, the circumferential width ratio Np of the magnetic piece 42 of the intermediate stator (42a, 42b, 42c shown in Fig. 3), the transmission torque (N m) of the magnetic gear device, and the torque ripple rate (%), while the horizontal columns represent the transmission torque and torque ripple rate for the above-mentioned respective specification values ​​when the speed ratio is 10.33 and 10. In the case where the gear ratio in the table is 10.33, that is, the Ph=3 and the Np=34, When the Np width ratio was 0.5, 0.5, and 0.5 at Pl = 31 mentioned above, the transmitted torque of the magnetic gear device was 28.7 N m, and the torque ripple (%) was 2.5% on the low-speed side and 2.7% on the high-speed side. Next, when the speed change ratio was changed to 10 while keeping the Np width ratio the same (second line of the table), the transmitted torque was 28.4 N m, and the torque ripple rate (%) was 2.8% on the low-speed side and 33.3% on the high-speed side, meaning that the torque ripple on the high-speed side had deteriorated significantly. Therefore, in the present invention, as a method for reducing torque ripple when the speed ratio of the magnetic gear device is 10, the Np width ratio of the magnetic pieces of the intermediate stator of the magnetic gear device with the above-mentioned speed ratio of 10 is set to 0.7, 0.8, and 0.3 (third row of the table). By setting this Np width ratio, the torque ripple rate on the high speed side was significantly reduced to 3.8%. The details of the setting of this Np width are omitted, but magnetic field analysis was performed with various Np widths, and the optimum conditions were derived and the above Np width was set. As explained above, it has been found that a method of reducing torque ripple in a magnetic gear device that requires a gear ratio that is an integer multiple can be achieved by combining the magnetic pieces of the intermediate stator with different circumferential width ratios, making it possible to realize a magnetic gear device with a gear ratio that is an integer multiple. Furthermore, it goes without saying that this method can further reduce torque ripple even in magnetic gear devices with fractional gear ratios, by appropriately optimizing the circumferential width ratio of the magnetic pieces, regardless of whether the gear ratio of the magnetic gear device is an integer multiple.

[0034] Next, a second embodiment of the present invention will be described with reference to FIGS. Fig. 6 is a cross-sectional view of the structure of the rotor of the magnetic gear device of the present invention, and Fig. 7 is a cross-sectional side view of the magnetic gear device. In the figure, reference numeral 100 denotes a cylindrical magnetic gear device, which has a first rotor 60, a second rotor 70, an intermediate stator 80, a rotor shaft 99 of the first rotor, and a shaft 90 of the second rotor.

[0035] The first rotating body 60 has a yoke holder 61, a magnet yoke 62, and a magnet 63. The second rotating body 70 has a yoke holder 71, a magnet yoke 72, and a magnet 73. The intermediate stator 80 has a magnetic piece holder 81 and a magnetic piece 82, and the intermediate stator 80 is a cylinder connected to a stator frame 83, and is connected to a fixing part (not shown) by screwing through an external connection screw hole 96 provided on the side of the stator frame 83. Each configuration will be described in detail below.

[0036] 6, the yoke holder 61 of the first rotor 60 is cylindrical and made of a non-magnetic material, and a cylindrical magnet yoke 62 is fixed to the inner peripheral surface of the yoke holder 61 with an adhesive or the like, and one outer peripheral side surface is fixed to the first rotor frame 65 with screws B. The inner diameter side of the first rotor frame 65 is connected to the rotating shaft 99 with screws B, and is rotatably attached to the rotating shaft 90 and intermediate stator 80 by bearings 93, 94, and 95. The magnet yoke 62 is formed in a laminated shape from soft magnetic material such as silicon steel plate, and magnets 63 are attached to its inner periphery with adhesive or the like. The magnets 63 are magnetized in the radial direction as shown in Fig. 6, and are attached at equal intervals in a circumferential shape with adjacent magnets having opposite poles. The magnets 63 have more poles than the number of magnets in the second rotor described later.

[0037] Next, the rotor 70 will be described. Its basic structure is the same as that of the first rotor, but the number of poles of the magnet is less than that of the magnets of the first rotor 2. In the figure, the yoke holder 71 is a cylindrical non-magnetic material, and a magnet yoke 72 is fixed to the outer circumferential surface of the yoke holder 71 by adhesion or the like, and a rotating shaft 90 is inserted into its inner diameter side, and the rotating shaft 90 is freely rotatable about the rotating shaft 99 and intermediate stator 80 by a key groove 91, a key 92, and two bearings 93 of the rotating shaft 90. The magnet yoke 72 is formed in a laminated shape from soft magnetic material such as silicon steel plate, and magnets 73 are attached to its outer circumferential surface with an adhesive or the like. Furthermore, the magnets 73 are magnetized in the radial direction as shown in Fig. 6, and are attached at equal intervals in a circumferential shape with adjacent magnets having opposite poles. The number of poles of the magnets 73 is less than the number of magnets in the first rotor.

[0038] The intermediate stator 80 will be described. As shown in FIG. 6, the intermediate stator 80 is cylindrical and made of a non-metallic material such as CFRP. In the magnetic holder 81 at the center of the cylinder, magnetic pieces 82 made of, for example, a powder magnetic core material are embedded in a circular shape with adhesive or the like. The magnetic pieces 82 are arranged in a circular shape with equal pitches, with magnetic pieces 82a, 82b, and 82c each having a different shape as one set. There are 11 sets in total, which means 33 magnetic pieces. The individual shapes of the magnetic pieces 82a, 82b, and 82c are, for example, fan-shaped segments, and the circumferential width ratios are 0.7 (magnetic piece 82a), 0.8 (magnetic piece 82b), and 0.3 (magnetic piece 82c) in the same order as in the first embodiment. The circumferential width ratio is 10.9°, which is the circumference (360°) divided by the number of magnetic pieces, 33, and the circumferential width ratio is 1. As shown in FIG. 7, the intermediate stator 80 is fixed to a magnetic gear device mounting base (not shown) by screws through external mounting screw holes in a stator frame 83 provided on the side of the rotor 80, and the rotating shaft 90 and the rotating shaft 99 are allowed to rotate freely relative to the intermediate stator 80 by bearings 93, 94, and 95.

[0039] The specifications of the magnetic gear device are the same as in Example 1, with the number of paired poles of the magnets of the first rotor 60 being 30, the number of paired poles of the magnets of the second rotor being 3, the number of magnetic poles of the intermediate stator 80 being 33, and the gear ratio being 10 (30:3). It has been confirmed that this magnetic gear device 100 has a torque ripple rate approximately the same as in Example 1, with the shape of the magnetic pieces of the magnetic piece body of the intermediate stator 80 having the same circumferential width ratio as in the first example, and that a torque ripple reduction effect can be obtained.

[0040] Also, in the case of a magnetic gear device with a gear ratio of an integer ratio of around 10, the results of confirming the improvement effect using the torque ripple reduction method applied in the first embodiment will be described with reference to Fig. 8. The table in Fig. 8 shows various specifications of the magnetic gear device when the gear ratio is 9 and 11, and the transmission torque and torque ripple rate of the magnetic gear device calculated using the above-mentioned magnetic field analysis simulation with those specifications. The table shows, from the left, the speed ratio of the magnetic gear device, Gr, the number of paired poles of the magnet of the high-speed rotating body of the magnetic gear device, Ph, the number of poles of the magnetic body of the intermediate body, Np, the number of paired poles of the magnet of the low-speed rotating body, the circumferential width ratio of the magnetic pieces of the intermediate body stator, the Np width ratio, the transmission torque of the magnetic gear device, and the torque ripple rate (%) of the magnetic gear device. In the table of Fig. 8, the magnetic gear establishment conditions for a speed ratio of 9 are Ph = 3, Pl = 27, and Np = 30 (Np = 3 + 27), and the transmission torque and torque ripple rate (%) for the cases of Np width ratios of 0.5, 0.5, and 0.5 and Np width ratios of 0.7, 0.8, and 0.3 were calculated by magnetic field analysis and are shown in the table of Fig. 8. As shown in the table, when the magnetic piece shapes have the same Np width ratios of 0.5, 0.5, and 0.5, the torque ripple on the high-speed side is 37.5%, whereas when the magnetic piece shapes have different Np width ratios of 0.7, 0.8, and 0.3, the torque ripple rate on the high-speed side is significantly reduced to 2.9%, confirming the effectiveness of the torque ripple reduction method according to the present invention.

[0041] Similarly, a magnetic field analysis example for a magnetic gear device with a speed ratio of 11 is shown in the second row at the bottom of the table in Fig. 8. As shown in the table, the specification settings for a speed ratio of 11 are Ph = 3, Pl = 33, and Np = 36 (3 + 33). In the table, when the circumferential width ratios Np width ratios are 0.5, 0.5, and 0.5 are compared with the cases where the Np width ratios are 0.7, 0.8, and 0.3, in the case of the magnetic body shapes with the same Np width ratios of 0.5, 0.5, and 0.5, the torque ripple rate on the high-speed side is 31.6%, whereas in the case of the magnetic piece shapes with different Np width ratios of 0.7, 0.8, and 0.3, the torque ripple rate on the high-speed side is 2.7%, which is a significant reduction, and the effectiveness of the torque ripple reduction method according to the present invention was confirmed, as in the case of a speed ratio of 9.

[0042] The method for reducing torque ripple in the transmission torque of a magnetic gear device according to the present invention has been described above in terms of Example 1 and Example 2. However, the present invention is not limited to the above-described embodiments, and can of course be freely modified without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0043] 1, 100 Magnetic gear device 2, 60 First rotating body 3, 70 Second rotating body 4, 80 Intermediate stator 5, 6, 83 Stator frame 7 Bearing holder 8, 93, 94, 95 Bearings 9 Retaining ring 10, 50, 90, 99 Rotation Axis 21, 31, 61, 71 Yoke holder 22, 32, 62, 72 Magnet Yoke 23, 33, 63, 73 Magnets 41, 81 Magnetic single body holder 42, 82 magnetic piece 42a, 42b, 42c, 82a, 82b, 82c magnetic piece 65 First rotor frame 91 Keyway 92 Keys 96 Screw holes for external mounting base B Screw

Claims

1. A magnetic gear device has two rotors each having a multi-pole permanent magnet and a plurality of magnetic pieces made of a soft magnetic material between the rotors, and transmits rotation by modulating the magnetic flux of the respective magnet pole ratios using the magnetic pieces. A magnetic gear device characterized in that the multiple magnetic pieces are magnetic pieces formed by groups of several magnetic pieces in which adjacent magnetic pieces have different circumferential widths, and the magnetic pieces are arranged at an equal pitch.

2. 2. The magnetic gear device according to claim 1, wherein the magnetic pieces have circumferential width ratios of 0.7 pitch width, 0.8 pitch width, and 0.3 pitch width in one set.

3. 3. The magnetic gear device according to claim 1, wherein a magnet-to-pole number ratio of the permanent magnets arranged on the two rotors is an integer multiple.

4. 4. The magnetic gear device according to claim 1, wherein the two rotors and the magnetic piece are disk-shaped and arranged to face each other.

5. 4. The magnetic gear device according to claim 1, wherein the two rotors and the magnetic piece are cylindrical and disposed opposite each other, with their respective centers of rotation being concentric.

6. 6. The magnetic gear device according to claim 1, wherein the magnetic pieces are made of soft magnetic material such as a laminate, a powder magnetic core, or an amorphous material.

7. 7. The magnetic gear device according to claim 1, wherein the magnetic piece is embedded in a magnetic piece holder made of a non-magnetic or non-metallic material so that one side of the magnetic piece is substantially flush with the other side of the magnetic piece holder.

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