Motor

Abstract

To further improve torque of a motor.SOLUTION: A motor comprises a rotor core 21, in which a coil is provided, and a plurality of permanent magnets disposed around the rotor core 21. The plurality of permanent magnets includes a lower stage magnet 41, an upper stage magnet 42 and a middle stage magnet 43 which are laminated in an axial direction. The lower stage magnet 41 is positioned at a lower side of the rotor core 21 and magnetized in a first direction along the axial direction, and the upper stage magnet 42 is positioned at an upper side of the rotor core 21 and magnetized in a second direction which is a reverse direction of the first direction. The middle stage magnet 43 is positioned between the lower stage magnet 41 and the upper stage magnet 42 and magnetized in a third direction along a radial direction which is orthogonal with the axial direction. An inner side face 43a of the middle stage magnet 43 is opposed with the rotor core 21 in the radial direction, and the lower stage magnet 41 and the upper stage magnet 42 partially expand radially inward from the inner side face 43a of the middle stage magnet 43 and overlap with the rotor core 21 in the axial direction.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a motor. [Background technology]

[0002] Many motors rotate due to magnetic interaction (repulsion and attraction) between the magnetic field generated by current flowing through a coil and the magnetic field generated by a permanent magnet.

[0003] Various technologies have been proposed to realize a small motor that rotates by the above-mentioned magnetic interaction and to increase the torque. For example, Patent Document 1 discloses increasing the torque of a motor by arranging multiple magnets in a Halbach array. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-169918 A Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for motors with even higher torque. [Means for solving the problem]

[0006] A motor according to one embodiment has a core provided with a plurality of coils and a plurality of permanent magnets arranged around the core. The plurality of permanent magnets include a first permanent magnet, a second permanent magnet, and a third permanent magnet stacked in an axial direction parallel to a rotation axis of the motor. The first permanent magnet is located on one side of the core in the axial direction and is magnetized in a first direction along the axial direction, and the second permanent magnet is located on the other side of the core in the axial direction and is magnetized in a second direction opposite to the first direction. The third permanent magnet is located between the first permanent magnet and the second permanent magnet in the axial direction and is magnetized in a third direction along a radial direction perpendicular to the axial direction. An inner surface of the third permanent magnet faces the core in the radial direction. Parts of the first permanent magnet and the second permanent magnet protrude radially inward from the inner surface of the third permanent magnet and overlap with the core in the axial direction. Effect of the Invention

[0007] According to the present invention, a motor with even higher torque can be realized. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing an external appearance of a motor according to an embodiment; [Diagram 2] 1 is a cross-sectional view showing a structure of a motor according to an embodiment. [Diagram 3] 1 is a perspective view showing a structure of a motor according to an embodiment; [Figure 4] FIG. 4 is a perspective view of the rotor shown in FIG. 3 omitted. [Diagram 5] FIG. 2 is a development view of a magnet group in one embodiment. [Figure 6] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 7] FIG. 4 is a cross-sectional view taken along line BB in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings referred to in describing the embodiment, the same or substantially the same configurations and elements are designated by the same reference numerals. In addition, as a rule, once a configuration or element has been described, it will not be described repeatedly.

[0010] <Motor Overview> Fig. 1 is a perspective view showing the appearance of a motor 1A according to the present embodiment. Fig. 2 is a cross-sectional view showing the structure of the motor 1A according to the present embodiment. Fig. 3 is a perspective view showing the structure of the motor 1A according to the present embodiment. Note that some of the components shown in Figs. 1 and 2 are omitted in Fig. 3.

[0011] The motor 1A is a brushed motor. More specifically, the motor 1A is an inner rotor type brushed motor. The motor 1A has a rectangular motor case 10 that forms an outer shell. The motor case 10 is composed of a square cylindrical case body 11 having an opening at one end, and a square plate-like cover member 12 that closes the opening of the case body 11.

[0012] The rotor 20 of the motor 1A includes a core 21 and a plurality of coils 22 provided on the core 21. In the following description, the core 21 may be referred to as a "rotor core 21."

[0013] 3, a plurality of permanent magnets are arranged around rotor core 21. More specifically, a first magnet group 31, a second magnet group 32, a third magnet group 33, and a fourth magnet group 34, each of which includes a plurality of permanent magnets, are arranged around rotor core 21.

[0014] The first magnet group 31, the second magnet group 32, the third magnet group 33, and the fourth magnet group 34 are disposed at the four corners of the motor case 10 and surround the rotor 20. The first magnet group 31 and the third magnet group 33 are N-pole magnet groups, and the second magnet group 32 and the fourth magnet group 34 are S-pole magnet groups. In other words, the motor 1A is a four-pole machine.

[0015] In the following description, the first magnet group 31, the second magnet group 32, the third magnet group 33 and the fourth magnet group 34 may be collectively referred to as the "magnet group 30".

[0016] When a current flows through the coil 22, a magnetic field is generated around the rotor 20. Then, due to magnetic interaction (repulsion and attraction) between the magnetic field generated around the rotor 20 and the magnetic field generated by the magnet group 30, the rotor 20 rotates around the rotation axis R (FIG. 2).

[0017] From another perspective, torque is generated between the rotor 20 and the magnet group 30. From yet another perspective, a magnetic circuit is formed between the rotor 20 and the magnet group 30. At this time, the motor case 10 (particularly, the case body 11) functions as a yoke.

[0018] In the following description, the direction parallel to the rotation axis R of the motor 1A may be referred to as the "axial direction," and the direction perpendicular to the rotation axis R of the motor 1A may be referred to as the "radial direction." Additionally, the rotation direction of the motor 1A (rotor 20) may be referred to as the "circumferential direction."

[0019] <Rotor> Rotor core 21 is formed of a plurality of steel plates (for example, silicon steel plates) stacked in the axial direction, that is, rotor core 21 is a laminated iron core.

[0020] 3, rotor core 21 has a plurality of teeth 23 arranged at equal pitch along the circumferential direction. Although the number of teeth 23 is not particularly limited, rotor core 21 of the present embodiment has ten teeth 23. In other words, rotor core 21 of the present embodiment has ten slots.

[0021] 2, a shaft 24 which is an output shaft of the motor 1A is inserted into the rotor core 21. The central axis of the shaft 24 coincides with the rotation axis R. The shaft 24 penetrates the center of the rotor core 21 and protrudes on both axial sides of the rotor core 21.

[0022] One end of shaft 24 protruding from one side of rotor core 21 is rotatably supported by a bearing 25 held in case body 11. The other end of shaft 24 protruding from the other side of rotor core 21 is rotatably supported by a bearing 26 held in cover member 12.

[0023] In the following description, one end side of shaft 24 supported by bearing 26 will be referred to as the “upper side” or “upper end side”, and the other end side of shaft 24 supported by bearing 25 will be referred to as the “lower side” or “lower end side”.

[0024] A plurality of commutator segments 27 are provided on the upper end side of the shaft 24, and a pair of brushes 28 are provided around the commutator segments 27. Although not shown in the figure, the brushes 28 are held by a brush holder. The brushes 28 are pressed against the commutator segments 27 by the force of an urging member (e.g., a spring) built into the brush holder. As a result, a current flows through the coil 22 connected to the commutator segment 27 via the commutator segment 27 with which the brush 28 is in contact. The coil 20 and the commutator segments 27 may be connected by lap winding (parallel winding), wave winding (series winding), or another method.

[0025] 3, coils 22 are formed by a conductor wire (e.g., a copper wire or an aluminum wire) wound around rotor core 21. More specifically, each coil 22 is formed by a conductor wire wound across two circumferentially adjacent teeth 23. The winding method of the conductor wire forming coils 22 is not limited to a specific winding method, and may be distributed winding as described above, concentrated winding, or another winding method.

[0026] <Magnets> Fig. 4 is a perspective view in which the rotor 20 shown in Fig. 3 is omitted. As described above, the magnet group 30 surrounding the rotor core 21 includes a plurality of permanent magnets. More specifically, each magnet group 30 includes a first permanent magnet 41, a second permanent magnet 42, and a third permanent magnet 43.

[0027] 4 shows all of the permanent magnets constituting the first magnet group 31 and the fourth magnet group 34, while only some of the permanent magnets constituting the second magnet group 32 and the third magnet group 33. However, this is for the convenience of drawing, and each magnet group 30 has the same or substantially the same laminated structure.

[0028] More specifically, each magnet group 30 has a laminated structure consisting of a first permanent magnet 41 located at the bottom in the axial direction, a second permanent magnet 42 located at the top in the axial direction, and a third permanent magnet 43 located between the first permanent magnet 41 and the second permanent magnet 42 in the axial direction.

[0029] In the following description, the first permanent magnet 41 in each magnet group 30 may be referred to as the "lower stage magnet 41," the second permanent magnet 42 as the "upper stage magnet 42," and the third permanent magnet 43 as the "middle stage magnet 43."

[0030] 5 is a development view of the magnet group 30. The lower stage magnets 41 and upper stage magnets 42 in each magnet group 30 have the same shape. On the other hand, the middle stage magnets 43 in each magnet group 30 have a different shape from the lower stage magnets 41 and upper stage magnets 42.

[0031] More specifically, the lower stage magnet 41 and the upper stage magnet 42 have a substantially triangular planar shape. Furthermore, the inner surface 41a of the lower stage magnet 41 and the inner surface 42a of the upper stage magnet 42 are flat. Meanwhile, the middle stage magnet 43 also has a substantially triangular planar shape as a whole, but its inner surface 43a is an arcuate surface. The inner surface 43a of the middle stage magnet 43 has the same or substantially the same curvature as the outer peripheral surface 21a of the rotor core 21 (FIG. 3).

[0032] 3, the inner side surface 43a of the middle stage magnet 43 of the first magnet group 31 faces radially the outer peripheral surface 21a of the rotor core 21. Although not shown in FIG. 3, the inner side surface 43a of the middle stage magnets 43 of the other magnet groups 30 also faces radially the outer peripheral surface 21a of the rotor core 21, similar to the inner side surface 43a of the middle stage magnets 43 of the first magnet group 31. Note that an air gap exists between the inner side surface 43a of each middle stage magnet 43 and the outer peripheral surface 21a of the rotor core 21.

[0033] 4, a portion of the lower stage magnet 41 and the upper stage magnet 42 of the first magnet group 31 protrudes radially inward from the inner surface 43a of the middle stage magnet 43. Although not clearly shown in FIG. 4, a portion of the lower stage magnet 41 and the upper stage magnet 42 of the other magnet group 30 also protrudes radially inward from the inner surface 43a of the middle stage magnet 43.

[0034] Furthermore, a portion of the lower stage magnet 41 that protrudes radially inward beyond the inner surface 43a of the middle stage magnet 43 includes at least a portion of the inner surface 41a. Similarly, a portion of the upper stage magnet 42 that protrudes radially inward beyond the inner surface 43a of the middle stage magnet 43 includes at least a portion of the inner surface 42a.

[0035] In the following description, the parts of the lower stage magnet 41 and the upper stage magnet 42 that protrude radially inward beyond the inner surface 43a of the middle stage magnet 43 may be referred to as "protrusions."

[0036] Fig. 6 is a cross-sectional view taken along line AA in Fig. 3. Also, Fig. 7 is a cross-sectional view taken along line BB in Fig. 3. From another perspective, Fig. 6 is a cross-sectional view showing the positional relationship between rotor core 21 and first magnet group 31 and third magnet group 33. Also, Fig. 7 is a cross-sectional view showing the positional relationship between rotor core 21 and second magnet group 32 and fourth magnet group 34.

[0037] The lower stage magnets 41 in each magnet group 30 are located on one side (lower side) of the rotor core 21 in the axial direction. Moreover, the upper stage magnets 42 in each magnet group 30 are located on the other side (upper side) of the rotor core 21 in the axial direction.

[0038] As a result, the protruding portion of the lower stage magnet 41 protrudes below the rotor core 21 and axially overlaps with the rotor core 21 via an air gap. In addition, the protruding portion of the upper stage magnet 42 protrudes above the rotor core 21 and axially overlaps with the rotor core 21 via an air gap.

[0039] From another perspective, the outer edge (umbrella portion) of rotor core 21 is sandwiched between the protruding portion of lower stage magnet 41 and the protruding portion of upper stage magnet 42 which face each other in the axial direction.

[0040] Therefore, in addition to between rotor core 21 and middle stage magnet 43, torque is also generated between rotor core 21 and the protruding portion of lower stage magnet 41, and between rotor core 21 and the protruding portion of upper stage magnet 42. However, the torque generated between rotor core 21 and middle stage magnet 43, which have a large opposing area, is the largest.

[0041] From another perspective, in order to further increase the torque, it is desirable to suppress leakage of magnetic flux from intermediate magnet 43 as much as possible.

[0042] <Magnetization direction> The black arrows in Fig. 6 typically indicate the magnetization directions of the permanent magnets constituting the first magnet group 31 and the third magnet group 33. The black arrows in Fig. 7 typically indicate the magnetization directions of the permanent magnets constituting the second magnet group 32 and the fourth magnet group 34.

[0043] 6, the lower magnets 41 of the first magnet group 31 and the third magnet group 33 are magnetized in a first direction along the axial direction. More specifically, the lower magnets 41 of the first magnet group 31 and the third magnet group 33 have a magnetization direction that is from bottom to top along the axial direction.

[0044] On the other hand, the upper magnets 42 of the first magnet group 31 and the third magnet group 33 are magnetized in a second direction along the axial direction. More specifically, the upper magnets 42 of the first magnet group 31 and the third magnet group 33 have a magnetization direction that faces downward along the axial direction.

[0045] Furthermore, the middle magnets 43 of the first magnet group 31 and the third magnet group 33 are magnetized in a third direction along the radial direction. More specifically, the middle magnets 43 of the first magnet group 31 and the third magnet group 33 have a magnetization direction that is from the outside to the inside along the radial direction.

[0046] That is, the lower stage magnets 41 and the upper stage magnets 42 of the first magnet group 31 and the third magnet group 33 are magnetized in mutually opposite directions in the axial direction. Also, the middle stage magnets 43 of the first magnet group 31 and the third magnet group 33 are magnetized in a direction perpendicular to the magnetization direction of the lower stage magnets 41 and the upper stage magnets 42. In other words, the multiple permanent magnets constituting the first magnet group 31 and the third magnet group 33 are arranged in a Halbach configuration.

[0047] As a result, leakage of magnetic flux from the middle magnets 43 of the first magnet group 31 and the third magnet group 33 is suppressed.

[0048] 7, the lower magnets 41 of the second magnet group 32 and the fourth magnet group 34 are magnetized in a first direction along the axial direction. More specifically, the lower magnets 41 of the second magnet group 32 and the fourth magnet group 34 have a magnetization direction that runs from top to bottom along the axial direction.

[0049] On the other hand, the upper magnets 42 of the second magnet group 32 and the fourth magnet group 34 are magnetized in a second direction along the axial direction. More specifically, the upper magnets 42 of the second magnet group 32 and the fourth magnet group 34 have a magnetization direction that is from bottom to top along the axial direction.

[0050] Furthermore, the middle magnets 43 of the second magnet group 32 and the fourth magnet group 34 are magnetized in a third direction along the radial direction. More specifically, the middle magnets 43 of the second magnet group 32 and the fourth magnet group 34 have a magnetization direction that is from the inside to the outside along the radial direction.

[0051] That is, the lower stage magnets 41 and the upper stage magnets 42 of the second magnet group 32 and the fourth magnet group 34 are magnetized in mutually opposite directions in the axial direction. Also, the middle stage magnets 43 of the second magnet group 32 and the fourth magnet group 34 are magnetized in a direction perpendicular to the magnetization direction of the lower stage magnets 41 and the upper stage magnets 42. In other words, the multiple permanent magnets constituting the second magnet group 32 and the fourth magnet group 34 are arranged in a Halbach configuration.

[0052] As a result, leakage of magnetic flux from the middle magnets 43 of the second magnet group 32 and the fourth magnet group 34 is suppressed.

[0053] <Eddy current suppression> In the motor 1A of the present embodiment, high torque is realized by the above-mentioned structure. However, if the rotation speed of the motor 1A increases with the increase in torque, eddy currents may be generated in the magnet group 30. Furthermore, if eddy currents are generated in the magnet group 30, the temperature of the motor 1A may increase and the driving efficiency may decrease.

[0054] The above-mentioned eddy currents are particularly likely to occur in middle stage magnet 43, which has a large opposing area to rotor core 21. Therefore, in this embodiment, the electrical resistivity of middle stage magnet 43 is made higher than the electrical resistivity of lower stage magnet 41 and upper stage magnet 42.

[0055] Specifically, a bonded magnet is used for the middle stage magnet 43, and sintered magnets are used for the lower stage magnet 41 and the upper stage magnet 42. More specifically, the middle stage magnet 43 in this embodiment is a neodymium bonded magnet, and the lower stage magnet 41 and the upper stage magnet 42 are neodymium sintered magnets.

[0056] However, as long as the above-mentioned relationship in electrical resistivity is realized, the type and combination of magnets may be changed as appropriate. For example, the middle magnet 43 may be replaced with a ferrite bonded magnet. Also, the middle magnet 43 may be a neodymium bonded magnet, a ferrite magnet, or a ferrite bonded magnet, and the lower magnet 41 and the upper magnet 42 may be neodymium sintered magnets.

[0057] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention. For example, the motor case may be cylindrical. In this case, the permanent magnets constituting the magnet group are formed in an arc shape and arranged in an annular shape around the rotor core. However, the shapes of the motor case and the permanent magnets can be modified as appropriate.

[0058] The number of permanent magnets included in each magnet group can be changed as appropriate, and the number of poles and slots of the motor can also be changed as appropriate.

[0059] The present invention can also be applied to outer rotor motors and brushless motors, and in these cases, the same advantageous effects as those described above are achieved.

[0060] The present invention can have the following configurations.

[0061] (1) A motor having a core provided with a plurality of coils and a plurality of permanent magnets arranged around the core, The plurality of permanent magnets include a first permanent magnet, a second permanent magnet, and a third permanent magnet stacked in an axial direction parallel to a rotation shaft of the motor, The first permanent magnet is located on one side of the core in the axial direction and is magnetized in a first direction along the axial direction, the second permanent magnet is located on the other side of the core in the axial direction and is magnetized in a second direction opposite to the first direction, the third permanent magnet is located between the first permanent magnet and the second permanent magnet in the axial direction, and is magnetized in a third direction along a radial direction perpendicular to the axial direction, An inner surface of the third permanent magnet faces the core in the radial direction, A motor in which a portion of the first permanent magnet and a portion of the second permanent magnet protrude radially inward beyond the inner surface of the third permanent magnet and overlap with the core in the axial direction.

[0062] (2) The inner surface of the third permanent magnet is an arcuate surface, and the inner surfaces of the first permanent magnet and the second permanent magnet are flat surfaces, The motor described in (1), wherein the portions of the first permanent magnet and the second permanent magnet overlapping the core include at least a portion of the respective inner surfaces.

[0063] (3) a plurality of magnet groups including the first permanent magnet, the second permanent magnet, and the third permanent magnet; The motor according to (1) or (2), wherein the plurality of magnet groups are arranged around the core so as to surround the core.

[0064] (4) a rectangular motor case that houses the core and the magnet group, The motor according to (3), wherein the magnet groups are disposed at the four corners of the motor case.

[0065] (5) The motor according to any one of (1) to (4), wherein the third permanent magnet has a higher electrical resistivity than the first permanent magnet and the second permanent magnet.

[0066] (6) The motor according to (5), wherein the third permanent magnet is a bonded magnet, and the first permanent magnet and the second permanent magnet are sintered magnets.

[0067] (7) The motor according to (6), wherein the third permanent magnet is a neodymium bonded magnet or a ferrite bonded magnet, and the first permanent magnet and the second permanent magnet are neodymium sintered magnets.

[0068] (8) The motor according to (5), wherein the third permanent magnet is a neodymium bonded magnet, a ferrite magnet or a ferrite bonded magnet, and the first permanent magnet and the second permanent magnet are neodymium sintered magnets. [Explanation of symbols]

[0069] Reference Signs List 1A...motor, 10...motor case, 11...case body, 12...cover member, 20...rotor, 21...core (rotor core), 21a...outer periphery, 22...coil, 23...teeth, 24...shaft, 25, 26...bearing, 27...commutator, 28...brush, 30...magnet group, 31...first magnet group, 32...second magnet group, 33...third magnet group, 34...fourth magnet group, 41...first permanent magnet (lower magnet), 41a...inner surface, 42...second permanent magnet (upper magnet), 42a...inner surface, 43...third permanent magnet (middle magnet), 43a...inner surface, R...rotating shaft

Claims

1. A motor having a core provided with a plurality of coils and a plurality of permanent magnets arranged around the core, the plurality of permanent magnets include a first permanent magnet, a second permanent magnet, and a third permanent magnet stacked in an axial direction parallel to a rotation shaft of the motor, The first permanent magnet is located on one side of the core in the axial direction and is magnetized in a first direction along the axial direction, the second permanent magnet is located on the other side of the core in the axial direction and is magnetized in a second direction opposite to the first direction, the third permanent magnet is located between the first permanent magnet and the second permanent magnet in the axial direction, and is magnetized in a third direction along a radial direction perpendicular to the axial direction, An inner surface of the third permanent magnet faces the core in the radial direction, A motor in which a portion of the first permanent magnet and a portion of the second permanent magnet protrude radially inward beyond the inner surface of the third permanent magnet and overlap with the core in the axial direction.

2. the inner surface of the third permanent magnet is an arcuate surface, and the inner surfaces of the first permanent magnet and the second permanent magnet are flat surfaces; The motor of claim 1 , wherein the portions of the first permanent magnet and the second permanent magnet overlapping the core include at least a portion of the respective inner surfaces.

3. a plurality of magnet groups including the first permanent magnet, the second permanent magnet, and the third permanent magnet; The motor according to claim 1 , wherein the magnet group is arranged around the core so as to surround the core.

4. a rectangular motor case that houses the core and the magnet group, The motor according to claim 3 , wherein the magnet groups are disposed at four corners of the motor case.

5. The motor according to claim 1 , wherein the third permanent magnet has a higher electrical resistivity than the first permanent magnet and the second permanent magnet.

6. 6. The motor according to claim 5, wherein the third permanent magnet is a bonded magnet, and the first permanent magnet and the second permanent magnet are sintered magnets.

7. 7. The motor according to claim 6, wherein the third permanent magnet is a neodymium bonded magnet or a ferrite bonded magnet, and the first permanent magnet and the second permanent magnet are neodymium sintered magnets.

8. 6. The motor according to claim 5, wherein the third permanent magnet is a neodymium bonded magnet, a ferrite magnet or a ferrite bonded magnet, and the first permanent magnet and the second permanent magnet are neodymium sintered magnets.

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