Motors for drones

Abstract

The objective is to prevent the magnets from falling radially inward while improving the suppression of magnetic flux leakage between the rotor's magnetic poles. [Solution] The first core has a combination of a first magnet and a second magnet adjacent to the other side of the first magnet in the circumferential direction, between the second core and the second core adjacent to the second core in the circumferential direction, the first core has a first protrusion on one side of the first magnet in the circumferential direction and radially inward for positioning the first magnet, the first core does not have a protrusion on the other side of the first magnet in the circumferential direction and radially inward for positioning the first magnet, the first core has a second protrusion on the other side of the second magnet in the circumferential direction and radially inward for positioning the second magnet, and the first core does not have a protrusion on one side of the second magnet in the circumferential direction and radially inward for positioning the second magnet.

Description

[Technical Field]

[0001] The present invention relates to a motor for drones. [Background Art]

[0002] Conventionally, drone motors that rotate propellers of a drone are known. As a drone motor, for example, an inner-rotor motor in which a rotor is disposed radially inward of a stator is known.

[0003] Patent Document 1 discloses a structure in which an air gap is provided radially inward of a magnet and the outer peripheral portion and inner peripheral portion of a core are connected by a bridge in a rotor, in order to suppress magnetic flux leakage between adjacent magnetic poles. Further, Patent Document 2 discloses that magnetic flux leakage between magnetic poles of a rotor is suppressed by a structure in which a bridge is disposed between an outer peripheral portion and an inner peripheral portion of a core sandwiched between either two adjacent N poles or two adjacent S poles of permanent magnets. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. WO 2019 / 066003 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2024-082188 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] However, in the structures disclosed in Patent Document 1 and Patent Document 2, no consideration is given to preventing magnets from falling off radially inward, and the suppression of magnetic flux leakage between the magnetic poles of the rotor is insufficient, resulting in the problem that torque decreases.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the suppression of magnetic flux leakage between magnetic poles of a rotor while preventing magnets from falling off radially inward. [Means for solving the problem]

[0007] A drone motor according to one aspect of the present invention comprises a stator, a rotor disposed radially inward of the stator with a gap between them, and a shaft fixed to the rotor, wherein the stator comprises a stator core and stator coils wound around the stator core, the rotor comprises a rotor core and rotor magnets fixed to the rotor core, the rotor core comprises an annular first core whose radially outer end faces the radially inner end of the stator core with a gap between it, a plurality of spoke-shaped second cores extending radially inward from the radially inner end of the first core, and a third core connected to the radially inner end of the second core to which the shaft is fixed radially inward, and the rotor magnet comprises a plurality of first magnets provided on the first core and arranged circumferentially, and a plurality of second magnets adjacent to the first magnets in the circumferential direction and arranged circumferentially The first magnet is made of stone and has a north pole on one side in the circumferential direction and a south pole on the other side in the circumferential direction, the second magnet has a south pole on one side in the circumferential direction and a north pole on the other side in the circumferential direction, the first core is arranged in the circumferential direction between the second core and the second core adjacent to the second core, the first magnet and the second magnet adjacent to the other side in the circumferential direction of the first magnet are arranged, the first core has a first protrusion on one side in the circumferential direction and radially inward of the first magnet for positioning the first magnet, the first core does not have a protrusion on the other side in the circumferential direction and radially inward of the first magnet for positioning the first magnet, the first core has a second protrusion on the other side in the circumferential direction and radially inward of the second magnet for positioning the second magnet, and the first core does not have a protrusion on one side in the circumferential direction and radially inward of the second magnet for positioning the second magnet. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to improve the suppression of magnetic flux leakage between the magnetic poles of the rotor while preventing the magnet from falling radially inward. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of the drone 100 according to Embodiment 1 of the present invention. [Figure 2] This is a perspective view of a motor 110 according to Embodiment 1 of the present invention. [Figure 3] This is a plan cross-sectional view of a motor 110 according to Embodiment 1 of the present invention. [Figure 4] This is a plan view showing an enlarged view of the vicinity of magnets 132a and 132b in the rotor 130 according to Embodiment 1 of the present invention. [Figure 5] (A) is a diagram showing the magnetic flux density distribution in a conventional configuration, and (B) is a diagram showing the magnetic flux density distribution near magnets 132a and 132b in the rotor 130 according to Embodiment 1 of the present invention. [Figure 6] This is a plan view showing an enlarged view of the vicinity of magnets 132a and 132b in the rotor 130 according to Embodiment 2 of the present invention. [Figure 7] This figure shows the magnetic flux density distribution near magnets 132a and 132b in the rotor 130 according to Embodiment 2 of the present invention. [Figure 8] This is a plan view showing an enlarged view of the vicinity of magnets 132a and 132b in the rotor 130 according to Embodiment 3 of the present invention. [Figure 9] This figure shows the magnetic flux density distribution near magnets 132a and 132b in the rotor 130 according to Embodiment 3 of the present invention. [Modes for carrying out the invention]

[0010] The following description of a rotating electric machine according to an embodiment of the present invention will be made with reference to the drawings. Note that in the following drawings, the scale and number of components in each structure may differ from the actual structure in order to make the components easier to understand.

[0011] <Embodiment 1> Figure 1 is a perspective view of a drone 100 according to Embodiment 1 of the present invention. The drone 100 is driven by the rotation of a motor 110, which causes a propeller 180 to rotate. Figure 2 is a perspective view of a motor 110 according to Embodiment 1 of the present invention. Figure 2 shows the drone 100 with the propeller 180 removed. Motor 100 is an example of an inner rotor type motor for drones. Motor 110 rotates around a shaft 140 that extends along the central axis J. The center of the propeller 180 is fixed to the shaft 140.

[0012] Furthermore, in the drawings, the XYZ coordinate system is shown as a three-dimensional Cartesian coordinate system where appropriate. In the XYZ coordinate system, the Z-axis direction is parallel to the axis direction of the central axis J shown in Figure 1. The X-axis direction is the radial direction relative to the central axis J as shown in the illustration. The Y-axis direction is perpendicular to both the X-axis and Z-axis directions. In all of the X-axis, Y-axis, and Z-axis directions, the side indicated by the arrow in the figure is the + side, and the opposite side is the - side.

[0013] Furthermore, in the following explanation, the positive side in the Z-axis direction (+Z side) will be referred to as "one side," and the negative side in the Z-axis direction (-Z side) will be referred to as "the other side." Note that "one side" and "the other side" are merely names used for explanatory purposes and do not limit the actual positional relationship or direction. Unless otherwise specified, the direction parallel to the central axis J (Z-axis direction) will be simply referred to as the "axis direction," the radial direction centered on the central axis J will be simply referred to as the "radial direction," and the circumferential direction centered on the central axis J, i.e., around the axis of the central axis J, will be simply referred to as the "circumferential direction." In the radial direction, the side approaching the central axis J will be referred to as the "inside radial direction," and the side moving away from the central axis J will be referred to as the "outside radial direction." In the circumferential direction, the clockwise side when viewed from the +Z side to the -Z side will be referred to as the "one side circumferential," and the counterclockwise side will be referred to as the "other side circumferential."

[0014] In the present specification, the expression "extend in the axial direction" includes not only the case of extending strictly in the axial direction, but also the case of extending in a direction inclined at an angle of less than 45° with respect to the axial direction. Further, in the present specification, the expression "extend in the radial direction" includes not only the case of extending strictly in the radial direction, that is, in a direction perpendicular to the axial direction, but also the case of extending in a direction inclined at an angle of less than 45° with respect to the radial direction. In addition, the term "parallel" includes not only the case of being strictly parallel, but also the case where the angle formed between the two is inclined within a range of less than 45°. Further, the expression "spread in a direction orthogonal to the axial direction" includes not only the case of spreading strictly in a direction orthogonal to the axial direction, but also the case of spreading in a direction inclined at an angle of less than 45° with respect to the direction orthogonal to the axial direction.

[0015] As shown in FIG. 1, the drone 100 includes a propeller 180 that drives the drone 100 by rotation, and a motor 110 that rotates the propeller 180. The motor 110 includes a stator 120, a rotor 130 (see FIG. 3) disposed radially inward of the stator 120 with a gap therebetween, and a shaft 140 fixed to the rotor 130. Further, the motor 110 includes a first case 150 that accommodates the stator 120, the rotor 130 and the shaft 140 from one axial side, and a second case 160 that accommodates the stator 120, the rotor 130 and the shaft 140 from the other axial side. The other axial end of the first case 150 is spaced apart from the one axial end of the second case 160, and the radially outer side of the stator 120 is exposed through the gap.

[0016] FIG. 3 is a plan cross-sectional view of the motor 110 according to Embodiment 1 of the present invention. FIG. 3 shows the motor 110 cut at an axial position between the other axial end of the first case 150 and the one axial end of the second case 160.

[0017] The stator 120 includes a stator core 121 and a stator coil 122 wound around the stator core 121. The rotor 130 includes a rotor core 131 and magnets 132a and 132b fixed to the rotor core 131.

[0018] The rotor core 131 includes: an annular first core 131a whose radially outer end faces the radially inner end of the stator core 121 via a gap; a plurality of spoke-shaped second cores 131b extending radially inward from the radially inner end of the first core 131a; and a third core 131c connected to the radially inner end of the second core 131b, to which the shaft 140 is fixed radially inward. The second core 131b functions as a bridge connecting the first core 131a and the third core 131c. Magnets 132a and 132b are fixed to the first core 131a.

[0019] Magnets 132a and 132b are magnets contributing to the torque of the motor 110 and have specific polarities. In the present embodiment, one circumferential side of the magnet 132a is an N pole side, and the other circumferential side is an S pole side; while one circumferential side of the magnet 132b is an S pole side, and the other circumferential side is an N pole side. The present invention does not exclude the case where the polarities are reversed.

[0020] FIG. 4 is an enlarged plan view showing the vicinity of the magnet 132a and the magnet 132b in the rotor 130 according to Embodiment 1 of the present invention. The first core 131a has a through-hole 131d into which the magnet 132a is inserted and fixed. The through-hole 131d is a hole penetrating the first core 131a in the axial direction. The first core 131a has a through-hole 131e into which the magnet 132b is inserted and fixed. The through-hole 131e is a hole penetrating the first core 131a in the axial direction. The through-hole 131d is provided on one circumferential side of the through-hole 131e.

[0021] The first core 131a has a protrusion 131da for positioning the magnet 132a inserted into the through-hole 131d, the protrusion 131da being located on the N pole side (one circumferential side) of the magnet 132a and radially inward of the magnet 132a. In a portion 131db on the S pole side (the other circumferential side) of the magnet 132a, the first core 131a does not have a protrusion for positioning the magnet 132a inserted into the through-hole 131d. The protrusion 131da prevents the magnet 132a from falling off radially inward.

[0022] The first core 131a has a protrusion 131ea on the north pole side (the other side in the circumferential direction) and radially inward of the magnet 132b, which positions the magnet 132b inserted into the through hole 131e. The first core 131a does not have a protrusion on the south pole side (one side in the circumferential direction) of the magnet 132b (the portion 131eb) which positions the magnet 132b inserted into the through hole 131e. The protrusion 131ea prevents the magnet 132b from falling out radially inward.

[0023] The first core 131a has one combination of through holes 131d and 131e between a certain second core 131b and an adjacent second core 131b in the circumferential direction.

[0024] Figure 5(A) shows the magnetic flux density distribution in a conventional configuration. Figure 5(B) shows the magnetic flux density distribution near magnets 132a and 132b in a rotor 130 according to Embodiment 1 of the present invention. Figure 5(A) shows the magnetic flux density distribution in a configuration in which the first core 131a has a protrusion 131g for positioning magnet 132a in portion 131db and a protrusion 131h for positioning magnet 132a in portion 131eb. Figure 5(B) shows the magnetic flux density distribution in the configuration shown in the plan view of Figure 4.

[0025] Comparing the conventional configuration in Figure 5(A) with the configuration of Embodiment 1 in Figure 5(B), it can be confirmed that Embodiment 1, by not having the protrusions 131g and 131h, reduces the leakage flux between the magnetic poles. As a result, the amount of magnetic flux directed toward the stator core increases, improving torque.

[0026] <Embodiment 2> Next, Embodiment 2 of the present invention will be described. In the description of Embodiment 2, components similar to those in Embodiment 1 will be denoted by the same reference numerals and their descriptions will be omitted, and only the differences from Embodiment 1 will be described.

[0027] Figure 6 is an enlarged plan view showing the vicinity of magnets 132a and 132b in the rotor 130 according to Embodiment 2 of the present invention. The first core 131a of the rotor 130 according to Embodiment 2 has a through hole 131j in addition to the configuration of Embodiment 1. The through hole 131j is a hole that penetrates the first core 131a in the axial direction. The first core 131a has the through hole 131j between the north pole side of magnet 132a and the north pole side of the adjacent magnet 132b. Furthermore, the first core 131a has the through hole 131j radially outward from the position where the second core 131b is arranged in the circumferential direction. In this embodiment, the cross-sectional shape of the through hole 131j in a plane perpendicular to the axial direction is a triangle with a base on the radially inward side and rounded corners.

[0028] Figure 7 shows the magnetic flux density distribution near magnets 132a and 132b in the rotor 130 according to Embodiment 2 of the present invention. Figure 7 shows the magnetic flux density distribution in the configuration shown in the plan view of Figure 6.

[0029] As shown in Figure 7, according to Embodiment 2, by having a through hole 131j radially outward from the position where the second core 131b is positioned in the circumferential direction, sandwiched between the N poles, the magnetic resistance around it is increased, and the leakage flux can be reduced even further than in Embodiment 1.

[0030] <Embodiment 3> Next, Embodiment 3 of the present invention will be described. In the description of Embodiment 3, components similar to those in Embodiment 1 will be denoted by the same reference numerals and their descriptions will be omitted, and only the differences from Embodiment 1 will be described.

[0031] Figure 8 is an enlarged plan view showing the vicinity of magnets 132a and 132b in the rotor 130 according to Embodiment 3 of the present invention. The first core 131a of the rotor 130 according to Embodiment 3 has a recess 131k in addition to the configuration of Embodiment 1. The recess 131k is a recess that extends radially inward to radially outward along the entire axial length of the first core 131a. The first core 131a has a recess 131k between the south pole side of magnet 132a and the south pole side of the adjacent magnet 132b. Furthermore, the first core 131a has a recess 131k in the circumferential direction at a position where the second core 131b is not located.

[0032] Figure 9 shows the magnetic flux density distribution near magnets 132a and 132b in the rotor 130 according to Embodiment 3 of the present invention. Figure 9 shows the magnetic flux density distribution in the configuration shown in the plan view of Figure 8.

[0033] As shown in Figure 9, according to Embodiment 3, by providing a recess 131k on the radially inner side of the second core 131b, at a position sandwiched between the S poles, the magnetic resistance of the leakage magnetic path is further increased, and the leakage magnetic flux can be reduced even further than in Embodiment 1.

[0034] Furthermore, the present invention also includes a configuration in which the configuration of Embodiment 2 is added to the configuration of Embodiment 3. In this case, leakage flux can be reduced even further.

[0035] According to the present invention described above, leakage flux between magnetic poles can be reduced by changing the shape of the air gap on the radial side of the rotor core. Furthermore, the bridge and magnet retainer (protrusions for positioning the magnet), which were excessive in light of ensuring strength, can be omitted, thereby achieving weight reduction. For this reason, the present invention is particularly suitable for drone applications where small size and limited output capacity are required.

[0036] The present invention is not limited to the embodiments described above, and various improvements and design modifications may be made without departing from the spirit of the invention. In addition, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the above description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0037] 100... Drones 110...motor 120...Stata 130... Rotor 140... Shaft 150…Case 1 160…Case 2

Claims

1. It comprises a stator, a rotor disposed radially inward of the stator with a gap between them, and a shaft fixed to the rotor. The stator comprises a stator core and stator coils wound around the stator core. The rotor comprises a rotor core and rotor magnets fixed to the rotor core. The rotor core comprises an annular first core whose radially outer end faces the radially inner end of the stator core via a gap, a plurality of spoke-shaped second cores extending radially inward from the radially inner end of the first core, and a third core connected to the radially inner end of the second core, to which the shaft is fixed radially inward. The rotor magnet consists of a plurality of first magnets provided on the first core and arranged in the circumferential direction, and a plurality of second magnets adjacent to the first magnets in the circumferential direction and arranged in the circumferential direction. The first magnet has one side in the circumferential direction as the north pole and the other side in the circumferential direction as the south pole. The second magnet has one side in the circumferential direction as the south pole and the other side in the circumferential direction as the north pole. The first core is arranged in the circumferential direction between the second core and the second core adjacent to the first core, and a combination of the first magnet and the second magnet adjacent to the first magnet on the other side in the circumferential direction. The first core has a first protrusion on one side of the first magnet in the circumferential direction and radially inward, which positions the first magnet. The first core does not have a protrusion on the other circumferential side and radially inward side of the first magnet for positioning the first magnet. The first core has a second protrusion on the other side in the circumferential direction and radially inward of the second magnet, which positions the second magnet. The first core does not have a protrusion on one side of the second magnet in the circumferential direction and radially inward for positioning the second magnet. A motor for drones characterized by the following features.

2. The first core has a through hole that penetrates the first core axially, located radially outward from the position where the second core is positioned in the circumferential direction. A motor for a drone according to feature 1.

3. The first core has a recess extending along its entire axial length, between the other circumferential side of the first magnet and one circumferential side of the second magnet, which extends from the radially inward to the radially outward direction. A motor for a drone according to feature 1.

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