JP6692870B2 - Outer rotor type rotor for electric motor - Google Patents

Description

  According to the present invention, a bottomed cylindrical rotor case having a cylindrical side wall, a magnetic metal ring-shaped yoke fixed to the inner periphery of the side wall, and an inner surface of the yoke are injection-molded and coupled to each other. To a rotor for an outer rotor type electric motor including a resin-bonded permanent magnet.

  The relative rotation of the rotor case and the yoke is restricted by the engagement of the projections provided on the outer circumference of the yoke with the recesses provided at the multiple locations on the inner circumference of the rotor case, and the plurality of protrusions provided on the inner circumference of the yoke Patent Document 1 discloses an outer rotor type electric motor rotor in which the relative rotation of the yoke and the resin-bonded permanent magnet is regulated by cutting into the outer periphery of the resin-bonded permanent magnet.

JP, 2016-111738, A

  However, in the technique disclosed in Patent Document 1, a step of forming a resin bonded permanent magnet on the inner circumference of the yoke to obtain a yoke assembly and a step of fixing the yoke assembly to the inner circumference of the rotor case are performed. Since they are separated from each other, the manufacturing process is complicated.

  The present invention has been made in view of such circumstances, and a rotor is obtained by assembling a rotor case, a yoke, and a resin-bonded permanent magnet so as to prevent their relative rotation in one step of molding the resin-bonded permanent magnet. An object of the present invention is to provide a rotor for an outer rotor type electric motor as described above.

  To achieve the above object, the present invention provides a bottomed cylindrical rotor case having a cylindrical side wall, a magnetic metal ring-shaped yoke fixed to the inner periphery of the side wall, and injection molding. In an outer rotor type electric motor rotor including a resin-bonded permanent magnet that is mold-bonded to the inner surface of the yoke, axial grooves extending in the axial direction of the rotor are provided at a plurality of locations on the inner surface of the side wall at intervals in the circumferential direction. A first feature is that the yoke is formed with through holes arranged at a plurality of positions corresponding to the axial groove in the circumferential direction of the yoke.

  Further, in addition to the configuration of the first feature, the present invention is characterized in that, in the inner surface of the side wall, a circumferential groove extending in the circumferential direction in common with the axial groove is formed over the entire circumference. Characterize.

  In addition to the configuration of the first characteristic, the present invention has a third characteristic that the yoke is entirely or partially fitted in a concave portion formed over the entire inner circumference of the side wall.

  Further, in addition to any one of the constitutions of the first to third characteristics, the present invention has a fourth characteristic that the axial groove is formed over the entire axial length of the side wall.

  According to the first aspect of the present invention, when the resin-bonded permanent magnet is injection-molded with the yoke positioned with respect to the rotor case, the molding material for molding the resin-bonded permanent magnet is the yoke. The resin-bonded permanent magnet is prevented from flowing through the through hole into the axial groove on the side wall of the rotor case, which prevents the relative rotation of the yoke with respect to the rotor case and the relative rotation of the resin-bonded permanent magnet with respect to the yoke. In one molding step, the rotor case, the yoke, and the resin-bonded permanent magnet can be assembled to prevent their relative rotation, and the rotor can be obtained, so that the manufacturing process can be reduced and the cost can be reduced.

  According to the second feature of the present invention, the molding material for molding the resin-bonded permanent magnet also flows into the circumferential groove, so that the axial relative movement of the resin-bonded permanent magnet with respect to the rotor case is prevented. In addition, since the molding material stays in the through hole of the yoke, the axial relative movement of the resin-bonded permanent magnet with respect to the yoke is prevented, and the yoke and the resin-bonded permanent magnet are prevented from being separated from the rotor case. You can

  According to the third feature of the present invention, by fitting all or part of the yoke in the recess on the inner periphery of the side wall, relative movement of the yoke in the axial direction with respect to the rotor case is prevented, and the yoke is transparent. Since the molding material for molding the resin-bonded permanent magnet stays in the hole, the axial relative movement of the resin-bonded permanent magnet with respect to the yoke is blocked, and the yoke and the resin-bonded permanent magnet are separated from the rotor case. Can be prevented.

  Further, according to the fourth aspect of the present invention, since the axial groove is formed over the entire axial length of the side wall, the axial groove can be easily formed.

FIG. 1 is a cross-sectional view of a rotor for an outer rotor type electric motor according to a first embodiment and an outer rotor type electric motor using the rotor. It is the perspective view which looked at the rotor case from the open end side. It is a perspective view of a yoke. It is a longitudinal section of an injection molding device for a resin bond permanent magnet. It is a longitudinal cross-sectional view of the rotor for outer rotor type electric motors of 2nd Embodiment. It is the perspective view which looked at the rotor case from the open end side. It is a perspective view of a yoke.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  A first embodiment of the present invention will be described with reference to FIGS. 1 to 4. First, in FIG. 1, the outer rotor type electric motor is used for, for example, a drone, and is fixed to a casing 11. 12 and a rotor 13 that covers the stator 12, and the rotor 13 is fastened to one end of a rotary shaft 14 that is arranged coaxially with the stator 12 and is rotatably supported by the casing 11.

  The stator 12 includes a ring-shaped stator core 17 formed by laminating and joining a plurality of magnetic steel sheets, a synthetic resin bobbin 18 mounted on the stator core 17, and a coil 19 wound around the bobbin 18. And the stator 12 is fixed to the casing 11 by screwing the first bolts 21 inserted into the insertion holes 20 provided at a plurality of positions spaced apart in the circumferential direction of the stator core 17 into the casing 11 and tightening the same. Fixed to.

  The rotor 13 includes a rotor case 23A made of light metal or synthetic resin that is fastened to the rotating shaft 14, a ring-shaped yoke 24A made of magnetic metal fixed to the inner surface of the rotor case 23A, and an inner surface of the yoke 24A. And the resin-bonded permanent magnet 25 provided in, the light metal is, for example, aluminum, magnesium, titanium, or the like.

  A supporting hole 26 extending coaxially with the rotating shaft 14 is provided in the center of the casing 11, and first and second supporting holes 26 facing the opposite sides are provided at an intermediate portion and one end portion of the supporting hole 26. Annular steps 26a and 26b are formed. The rotary shaft 14 is inserted through the support hole 26, and the other end of the rotary shaft 14 is rotatably supported by the casing 11 via a first ball bearing 27. Is rotatably supported by the casing 11 via a second ball bearing 28.

  That is, the inner race 27a of the first ball bearing 27 is press-fitted into the other end of the rotary shaft 14, and the outer race 27b of the first ball bearing 27 is formed into the first annular step 26a of the support hole 26. And the outer peripheral portion of a disk-shaped plate 30 fastened to the other end of the rotary shaft 14 by a plurality of second bolts 29. The inner race 28a of the second ball bearing 28 is press-fitted into the rotary shaft 14 so as to correspond to the third annular stepped portion 14a formed in the intermediate portion of the rotary shaft 14, and the second race 28a The outer race 28b of the ball bearing 28 is press-fitted into the support hole 26, or fitted into the support hole 26 so as to come close to, face, or abut the second annular step 26b.

  Referring also to FIG. 2, the rotor case 23A includes a cylindrical side wall 31A and a dish-shaped end wall continuously provided at one end of the side wall 31A so as to close an opening at one end of the side wall 31A. 32 is integrally formed with a bottomed cylindrical shape, and a plurality of cooling air discharge holes 33 are formed in the end wall 32. Further, as shown in FIG. 1, a cover 15 for covering the casing 11 from the side opposite to the end wall 32 is attached to the casing 11, and a plurality of covers for circulating cooling air are attached to the cover 15. Cooling air introduction holes 16 are formed.

  A flange 14b having four screw holes 34 at equal intervals in the circumferential direction is integrally formed at one end of the rotary shaft 14, and is formed at the end wall 32 at equal intervals in the circumferential direction. One end of the rotary shaft 14 is attached to the center of the end wall 32 of the rotor case 23A by screwing the third bolt 36 inserted into the four insertion holes 35 into the screw hole 34 and tightening the third bolt 36. It is concluded.

  In the rotor case 23A, a plurality of positions are formed at intervals in the circumferential direction of the inner surface of the side wall 31A, and in the first embodiment, 16 positions are equally spaced in the circumferential direction of the inner surface of the side wall 31A. An axial groove 37 extending in the axial direction of the case 23A is formed over the entire axial length of the side wall 31A. Further, a circumferential groove 38, which is connected to the axial groove 37 in common, is formed over the entire circumference on the inner surface of the side wall 31A near the end opposite to the end wall 32. Further, injection holes for injecting a molding material 53 (see FIG. 4 described later) at the time of injection molding of the resin bond permanent magnet 25 are provided at a plurality of positions in the rotor case 23A near the outer periphery of the end wall 32 in the circumferential direction. 40 is drilled.

  Focusing on FIG. 3, the ring-shaped yoke 24A is formed with through holes 39 arranged at a plurality of positions corresponding to the axial grooves 37 in the circumferential direction of the yoke 24A. In the above embodiment, two through-holes 39 are formed at 16 locations at equal intervals in the circumferential direction of the yoke 24A and two at intervals in the axial direction of the yoke 24A.

  The resin-bonded permanent magnet 25 is injection-molded and mold-bonded to the inner surface of the yoke 24A. At this time, the resin-bonded permanent magnet 25 is magnetized into a plurality of N poles and S poles on the outer peripheral side and the inner peripheral side, and the polarities of the magnetized poles are adjacent to each other in the circumferential direction of the yoke 24A. There is a case where the poles are so-called radial magnetized so that they are different from each other on the outer peripheral side and the inner peripheral side and have a ring shape as a whole, and are mold-bonded to the inner surface of the yoke 24A. In addition, there are various other magnetization patterns, for example, a so-called polar anisotropic magnetization in which the N pole and the S pole are adjacent to each other in the circumferential direction only on the inner peripheral surface side or the outer peripheral surface side of the ring shape. There is also a porcelain.

  When anisotropic magnet powder is used, magnetic field orientation treatment for aligning the easy axis of magnetization of each magnet powder in the orientation magnetic field in the molten resin is performed in advance. This makes it possible to obtain an anisotropic resin-bonded magnet having magnetic properties superior to those obtained by using isotropic magnet powder. A magnetic field orientation treatment and a magnetizing treatment are required to manufacture an anisotropic resin-bonded magnet.

  The anisotropic magnet powder includes ferrite magnet powder and rare earth magnet powder, and examples of the rare earth magnet powder include Nd-Fe-B system magnet powder, Sm-Co system magnet powder, and Sm-Fe-N system magnet powder. Etc.

  The axial groove 37 of the rotor case 23A and the through hole 39 of the yoke 24A are arranged at the center of the N pole and the S pole of the resin bond permanent magnet 25. Thereby, the leakage of the magnetic flux from the through hole 39 can be minimized, and the influence on the deterioration of the output performance of the outer rotor type electric motor can be minimized.

  In injection molding of the resin bond permanent magnet 25, an injection molding device 41 shown in FIG. 4 is used, and the injection molding device 41 includes a mold device 42 and an injection machine 43.

  The mold device 42 includes a first mold 44, and a second mold that clamps the rotor case 23A in a state where the rotary shaft 14 is fastened and the yoke 24A is assembled between the first mold 44 and the first mold 44. A mold 45 and a ring-shaped magnetic field orientation magnet 46 attached to the first mold 44 are provided. Moreover, when assembling the yoke 24A to the rotor case 23A, the yoke 24A with respect to the side wall 31A is positioned so that the through hole 39 is located at the axial groove 37 on the inner surface of the side wall 31A of the rotor case 23A. With the positioning performed, the yoke 24A is pressed into the side wall 31A, or the yoke 24A fitted in the side wall 31A is temporarily fixed to the side wall 31A with an adhesive.

  A cavity 47 corresponding to the resin bond permanent magnet 25 is formed in the mold device 42 by the first mold 44, the second mold 45, the magnetic field orientation magnet 46, the rotor case 23A and the yoke 24A. To be done. That is, in injection molding of the resin bond permanent magnet 25, the rotor case 23A is set in the mold device 42 with the yoke 24A fixed in the circumferential position and the rotary shaft 14 fastened. Will be done.

  In the second mold 45, a sprue 50 connected to the nozzle 49 at the tip of the injector 43, a plurality of gates 51 connected to the injection hole 40, and the gate 51 and the sprue 50 are connected to each other. A runner 52 to tie is formed. In the case of using anisotropic magnet powder, a powdery molding material (compound) 53 in which magnetic powder is covered with a resin to be coated is melted by heating and injected from the nozzle 49 of the injector 43. It is injected from the nozzle 49 into the cavity 47 through the sprue 50, the runner 52, the gate 51 and the injection hole 40. The heat-melted molding material 53 is oriented and magnetized by the magnetic field orientation magnet 46 simultaneously with the molding in the cavity 47, and a resin-bonded permanent magnet 25 integrated in a ring shape is molded on the inner surface of the yoke 24A. After being coupled, they are mold-bonded to the inner surface of the yoke 24A (by fixing resin by molding and magnetic attraction between the resin-bonded permanent magnet 25 and the yoke 24A). In the case of this molding, it may not be possible to complete the magnetization to the required magnetic characteristics by the orientation magnetic field, and in that case, the ring-shaped resin bond magnet will be magnetized again.

  Moreover, the molding material 53 flows from the through hole 39 of the yoke 24A into the axial groove 37 and the circumferential groove 38 of the side wall 31A of the rotor case 23A, and in the injection molding completed state, the through hole 39 and the shaft. The molding material 53 remains in the directional groove 37 and the circumferential groove 38.

  Next, the operation of the first embodiment will be described. The rotor case 23A is provided at a plurality of circumferentially spaced locations on the inner surface of the cylindrical side wall 31A of the bottomed cylindrical rotor case 23A. Since an axial groove 37 extending in the axial direction is formed and through holes 39 are formed in the yoke 24A at a plurality of positions corresponding to the axial groove 37 in the circumferential direction of the yoke 24A, the rotor 24 is formed. When the resin-bonded permanent magnet 25 is injection-molded with the yoke 24A positioned with respect to the case 23A, the molding material 53 forming the resin-bonded permanent magnet 25 is passed through the through hole 39 of the yoke 24A to the rotor. When it flows into the axial groove 37 of the side wall 31A of the case 23A and the relative rotation of the yoke 24A with respect to the rotor case 23A is blocked. Therefore, the relative rotation of the resin bond permanent magnet 25 with respect to the yoke 24A is blocked, and the rotor case 23A, the yoke 24A, and the resin bond permanent magnet 25 can be separated from each other in one step of molding the resin bond permanent magnet 25. The relative rotation can be prevented and the rotor 13 can be assembled to obtain the rotor 13, and the cost can be reduced by reducing the manufacturing process.

  Further, since the molding material 53 remains in the plurality of injection holes 40 of the rotor case 23A after the injection molding of the resin bond permanent magnet 25, the resin bond permanent magnet 25 with respect to the rotor case 23A is also thereby retained. And the relative rotation of the yoke 24A is prevented.

  Further, since the circumferential groove 38, which is commonly connected to the axial groove 37, is formed on the inner surface of the side wall 31A over the entire circumference, the molding material 53 forming the resin bond permanent magnet 25 is removed from the axial groove 37. Since the resin-bonded permanent magnet 25 is prevented from moving in the axial direction relative to the rotor case 23A, the molding material 53 remains in the through hole 38 of the yoke 24A. Thus, the axial relative movement of the yoke 24A with respect to the resin bond permanent magnet 25 is prevented, and the yoke 24A and the resin bond permanent magnet 25 can be prevented from being separated from the rotor case 23A.

  Moreover, since the axial groove 37 is formed over the entire axial length of the side wall 31A, the axial groove 37 can be easily formed.

  The second embodiment of the present invention will be described with reference to FIGS. 5 and 6, but the portions corresponding to those of the first embodiment will be designated by the same reference numerals and will only be illustrated. Detailed description is omitted.

  The rotor case 23B integrally includes a cylindrical side wall 31B and a dish-shaped end wall 32 that is connected to one end of the side wall 31B so as to close the one end opening of the side wall 31B. The bottom has a cylindrical shape.

  A recess 56 is formed on the inner circumference of the side wall 31B over the entire circumference. In addition, at a plurality of locations spaced apart in the circumferential direction of the inner surface of the side wall 31B, in this embodiment, at 16 locations equally spaced in the circumferential direction of the inner surface of the side wall 31B, the same as in the first embodiment. The axial groove 57 extending in the axial direction of the rotor case 23B is formed over the entire axial length of the side wall 31B.

  In FIG. 7, in the ring-shaped yoke 24B, two through holes 39 are arranged at a plurality of positions circumferentially corresponding to the axial groove 57 on the inner surface of the side wall 31B of the rotor case 23B. Is formed.

  The axial groove 57 of the rotor case 23B and the through hole 39 of the yoke 24B are arranged at the pole centers of the N pole and the S pole of the resin bonded permanent magnet 25 (see the first embodiment). Thereby, the leakage of the magnetic flux from the through hole 39 can be minimized, and the influence on the deterioration of the output performance of the outer rotor type motor can be minimized.

  A slit 58 extending in the axial direction is formed at one location in the circumferential direction of the yoke 24B, and the slit 58 is arranged at a position different from the axial groove 57 of the side wall 31B in the circumferential direction. As a result, a decrease in strength caused by disposing the axial groove 57 and the slit slit 58 at the same position in the circumferential direction is avoided.

  All or a part of the yoke 24B is fitted in the recess 56 of the side wall 31B. In the second embodiment, the diameter of the yoke 24B having the slit 58 is reduced, Of the overall axial length of the yoke 24B, a half portion on the radially outer side is fitted into the recess 56.

  According to the second embodiment, the axial grooves 57 are formed in the inner surface of the side wall 31B at a plurality of circumferentially spaced intervals, and the yokes 24B are arranged at a plurality of positions corresponding to the axial grooves 57. Since the through hole 39 is formed, the relative rotation of the yoke 24B with respect to the rotor case 23B is blocked and the relative rotation of the resin bond permanent magnet 25 with respect to the yoke 24B is blocked, as in the first embodiment. Therefore, the cost can be reduced by reducing the number of manufacturing steps, and all or part of the yoke 24B is fitted in the recess 56 formed over the entire inner circumference of the side wall 31B of the rotor case 23B. Therefore, the relative movement of the yoke 24B in the axial direction with respect to the rotor case 23B is prevented, and the molding material 53 is formed in the through hole 39 of the yoke 24B. (Refer to the first embodiment) prevents the resin bond permanent magnet 25 from moving relative to the yoke 24B in the axial direction, so that the yoke 24B and the resin bond permanent magnet 25 are separated from the rotor case 23B. Can be prevented.

  In the second embodiment described above, the rotor case 23B is made of a light metal, and the whole or a part of the yoke 24B having no slit 58 is fitted into the recess 56 of the rotor case 23B by shrink fitting. May be.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

13 ... Rotors 23A, 23B ... Rotor cases 24A, 24B ... Yoke 25 ... Resin bond permanent magnets 31A, 31B ... Side walls 37, 57 ... Axial groove 38 ... Circumferential direction Groove 39 ... Through hole 56 ... Recess

Claims (4)

  A bottomed cylindrical rotor case (23A, 23B) having a cylindrical side wall (31A, 31B), and a magnetic metal ring-shaped yoke (24A) fixed to the inner circumference of the side wall (31A, 31B). , 24B) and a resin-bonded permanent magnet (25) mold-bonded to the inner peripheral surface of the yoke (24A, 24B) by injection molding, the rotor case (23A, 23B) Axial grooves (37, 57) extending in the axial direction of the yoke (24A, 24B) are formed at a plurality of positions on the inner surface of the side wall (31A, 31B) circumferentially spaced from each other. , 24B), through holes (39) arranged at a plurality of positions corresponding to the axial grooves (37, 57) in the circumferential direction of the outer rotor type electric motor rotor.   The circumferential groove (38) extending in the circumferential direction in common with the axial groove (37) is formed on the inner surface of the side wall (31A) over the entire circumference. Outer rotor type rotor for electric motor.   The outer rotor type according to claim 1, wherein all or part of the yoke (24B) is fitted in a recess (56) formed over the entire inner circumference of the side wall (31B). Rotor for electric motor.   The rotor for an outer rotor type electric motor according to any one of claims 1 to 3, wherein the axial groove (37, 57) is formed over the entire axial length of the side wall (31A, 31B). ..

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