JP2012130090A - Apparatus for magnetizing motor rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for magnetizing a motor rotor which implements low cogging and low torque rippling while ensuring complete magnetization in the vicinity of center regions of rotor poles.SOLUTION: The motor rotor magnetization apparatus for magnetizing a circumferential surface of a brushless motor rotor in circumferentially alternate magnetic poles of different polarities includes a magnetization yoke 1 having a required number of teeth 12 opposite the circumferential surface of the rotor. The teeth 12 are delimited by slots 11 on an inner circumferential surface 1a of the magnetization yoke 1 opposite the rotor, the slots 11 are circumferentially curved elongated holes parallel to the inner circumferential surface 1a of the magnetization yoke 1, and magnetizing coils 15 are housed in associated slots 11 and wound on the respective teeth 12 in a plurality of turns.

Description

  The present invention relates to a magnetizing device for a motor rotor, and more particularly to a structure improvement of a magnetizing device for realizing a brushless motor with low cogging and low torque ripple.

  In the brushless motor, the magnetic peripheral surface of the rotor is alternately magnetized to magnetic poles having different polarities in the circumferential direction, and a rotating magnetic field is applied to the rotor to rotate it. In this case, as shown in FIG. 5, the magnetic flux density in the radial direction (radial direction) of the magnetic field with respect to the circumferential surface of the rotor is sufficient for each magnetic pole portion (V region in the figure) in the circumferential direction of the rotor. In addition to ensuring the size, it is necessary to provide a magnetic flux change angle that provides an optimum magnetization inclination in order to realize low cogging and low torque ripple in the portion between the magnetic poles (W region in the figure).

  An example of a conventional magnetizing apparatus is shown in FIG. In FIG. 6, the magnetizing yoke 2 has an annular shape in which a circular inner space 23 for accommodating a rotor (not shown) is formed. Then, on the inner peripheral part of the magnetized yoke 2 facing the magnetic outer peripheral surface of the magnetized rotor, teeth 22 equally spaced in the circumferential direction by slots 21 correspond to the number of magnetic poles formed on the rotor. A necessary number (four in FIG. 6) is provided, and a magnetizing coil 25 is wound around the teeth 22.

  FIG. 7 shows a state of the magnetizing coil 25 wound around the teeth 22 to form one magnetic pole of the rotor. The slot 21 of the magnetized yoke 2 is formed in the shape of a long hole whose inner peripheral end opens to the inner space 23 of the yoke 2 through a small gap 24 and extends in the radial direction of the yoke 2. Then, on the outer periphery of the teeth 22 defined by the slots 21, the magnetizing coil 25 has three steps (three turns) in the inner and outer directions perpendicular to the inner peripheral surface 2a of the magnetizing yoke 2, that is, the outer peripheral surface of the rotor. It is wound so as to be laminated. In FIG. 7, the first winding portion of the magnetized coil is x ′, the second winding portion is y ′, and the third winding portion is z ′.

  Patent Document 1 discloses a magnetized yoke including a slot formed in the shape of a long hole extending in the radial direction.

JP2008-35636

  However, the radial magnetic flux density distribution of the magnetizing magnetic field realized by the conventional magnetizing apparatus, as shown conceptually in FIG. 8, shows the trapezoidal distribution of the same shape (thin solid line in the figure). A trapezoidal shape having steep angles at both ends indicated by thick solid lines in FIG. Actually, when the magnetic flux density distribution of the magnetizing magnetic field formed by such a conventional magnetizing apparatus is actually measured, it is substantially trapezoidal with sharp angles at both ends as indicated by A ′, B ′, and C ′ in FIG. Become. The magnetic flux density distributions indicated by A ′, B ′, and C ′ are those when the magnetizing coil has 3 turns and the magnetizing currents are 10 kA, 15 kA, and 20 kA, respectively.

  With the magnetic flux density distribution of such a conventional magnetizing device, an attempt is made to obtain a magnetic flux density that is equal to or higher than the critical amount (line L in FIG. 4) necessary for complete magnetization at the magnetic pole portion of the rotor (the central portion of the magnetic flux density). As a result, the magnetization gradient at the portion between the magnetic poles (both sides of the magnetic flux density) is often steeper than the optimum one, and it is difficult to sufficiently reduce the cogging and torque ripple of the motor. .

  Accordingly, the present invention is to solve such problems, and an object thereof is to provide a magnetizing device for a motor rotor capable of realizing low cogging and low torque ripple while ensuring complete magnetization near the center of the rotor magnetic pole. To do.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a motor rotor magnetizing apparatus for alternately magnetizing magnetic poles having different polarities in the circumferential direction on the rotor peripheral surface of the brushless motor, A magnetizing yoke (1) provided with a necessary number of teeth (12) facing each other is provided, and a magnetizing coil (15) is wound around each of the teeth (12) a plurality of times in a plane extending along the circumferential surface of the rotor. It is turned.

  In the first invention, the magnetic flux density distribution at the time of magnetization can be made to be a substantially mountain shape with a sufficient height at the center portion, instead of a substantially trapezoidal shape where the angles at both ends are steep as in the prior art. Therefore, even if a magnetic flux density higher than the critical amount necessary for complete magnetization is secured in the rotor magnetic pole part, the change in the degree of magnetization in the part between the magnetic poles can be made gradual. And torque ripple can be made sufficiently small.

  In the second aspect of the invention, the teeth (12) are defined by slots (11) on the circumferential surface (1a) of the magnetizing yoke (1) facing the rotor, and the slots (11) are magnetized. Each of the teeth is accommodated in the slot (11) by accommodating the magnetizing coil (15) as a curved long hole extending in the circumferential direction along the circumferential surface (1a) of the yoke (1). It is wound around (12).

  The reference numerals in the parentheses indicate the correspondence with specific means described in the embodiments described later.

  As described above, according to the magnetizing device for a motor rotor of the present invention, low cogging and low torque ripple can be realized while ensuring complete magnetization near the center of the rotor magnetic pole.

It is sectional drawing of the magnetizing yoke of the magnetizing apparatus which shows one Embodiment of this invention. It is an expanded sectional view of the quarter part of the magnetizing yoke shown in FIG. It is a conceptual diagram of magnetic flux density distribution formed with the magnetizing apparatus of this invention. It is an actual measurement figure which compared the magnetic flux density distribution for magnetization formed with the magnetizing apparatus of this invention with the magnetic flux density distribution for magnetizing formed with the conventional apparatus. It is a figure explaining magnetic flux density distribution in the rotor peripheral surface direction formed of a magnetizing apparatus. It is sectional drawing of the magnetizing yoke of the magnetizing apparatus which shows a prior art example. It is an expanded sectional view of the quarter part of the magnetizing yoke shown in FIG. It is a conceptual diagram of the magnetic flux density distribution formed with the conventional magnetizing apparatus.

  FIG. 1 shows a magnetizing yoke of a magnetizing device. In FIG. 1, the magnetizing yoke 1 has an annular shape having a circular inner space 13 for accommodating a rotor (not shown). Then, on the inner peripheral surface 1a of the magnetized yoke 1 facing the magnetic outer peripheral surface of the magnetized rotor, teeth 12 divided at equal intervals in the circumferential direction by slots 11 correspond to the number of magnetic poles formed on the rotor. The required number (four in FIG. 1) is provided.

  Each slot 11 has a curved long hole shape extending in the circumferential direction along the inner peripheral surface 1 a of the magnetizing yoke 1, and the width of each slot 11 is larger than the outer diameter of the magnetizing coil 15. It is somewhat large and is open to the inner space 13 of the magnetized yoke 1 by a gap 14 at the central portion on the inner peripheral side. A magnetizing coil 15 is wound around the outer periphery of the teeth 12 defined by the slots 11.

  FIG. 2 shows a state of the magnetizing coil 15 wound around the teeth 12 to form one magnetic pole of the rotor. The magnetizing coil 15 is an inner peripheral surface 1a of the magnetizing yoke 1, that is, It is wound so as to be stacked in three steps (three turns) within a curved surface extending in parallel along the outer peripheral surface of the rotor. In FIG. 2, the first winding portion of the magnetizing coil 15 is x, the second winding portion is y, and the third winding portion is z.

  FIG. 3 conceptually shows the radial magnetic flux density distribution realized by the magnetizing apparatus of this embodiment. In this case, the magnetic flux density distribution is obtained by adding the magnetic flux density that is generated by the coil winding portions x, y, and z in each stage and becomes a trapezoidal distribution having different widths in the circumferential direction. As shown in the figure, the central part is high, and on both sides thereof, it becomes a mountain shape that is low in two steps.

  Actually, the magnetic flux density distribution at the magnet insertion position formed by the magnetizing apparatus of the present embodiment was measured (only the shaft was put in the yoke, the probe was installed at the position where the magnet was originally located, and the magnetic flux density at that point was measured. Measurement), the central portion has a sufficient height as shown by A, B, and C in FIG. 4 and has a substantially mountain shape with gentle ends at both ends compared to the conventional A ′, B ′, and C ′. The magnetic flux density distributions indicated by A, B, and C are obtained when the magnetizing coil has three turns and the magnetizing currents are 10 kA, 15 kA, and 20 kA, respectively.

  In the magnetizing apparatus of the present embodiment that realizes such magnetic flux density distributions A, B, and C, the critical amount (line L in FIG. 4) necessary for complete magnetization at the rotor magnetic pole portion (the center portion of the magnetic flux density). Even if the above magnetic flux density is secured, the change in the degree of magnetization at the part between the magnetic poles (both sides of the magnetic flux density) can be made gradual, so the cogging and torque ripple of the motor must be made sufficiently small. Is possible.

  In the above embodiment, the case of magnetizing the outer peripheral surface of the inner rotor of the motor has been described. However, the present invention can be applied to the case of magnetizing the inner peripheral surface of the outer rotor of the motor.

DESCRIPTION OF SYMBOLS 1 ... Magnetization yoke, 1a ... Inner peripheral surface (peripheral surface), 11 ... Slot, 12 ... Teeth, 15 ... Magnetization coil.

Claims (2)

A motor rotor magnetizing device for alternately magnetizing magnetic poles having different polarities in the circumferential direction on a rotor circumferential surface of a brushless motor, comprising a magnetizing yoke provided with a necessary number of teeth facing the rotor circumferential surface A magnetizing device for a motor rotor, wherein a magnetizing coil is wound around each tooth a plurality of times in a plane extending along the circumferential surface of the rotor. The teeth are defined by slots on the circumferential surface of the magnetizing yoke facing the rotor, and the slots are formed in the shape of curved long holes extending in the circumferential direction along the circumferential surface of the magnetizing yoke. The magnetizing device for a motor rotor according to claim 1, wherein the magnetizing coil is accommodated in the slot and wound around each of the teeth.

Images