JP2008228479A - Dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC motor which can prolong the lifetime by reducing brush spark while suppressing motor loss by rationalizing the brush shift angle thereby enhancing the commutation characteristics. <P>SOLUTION: Field pole of a stator is eight poles (eight permanent magnets 16), the armature of a rotor is provided with 32 tees 33c, and a coil 35 is wound at a short-pitch across three tees 33c and connected with a commutator (segment 42). A power supply brush 19 is arranged while being shifted from a normal position to the anti-rotational direction side and the shift angle α is set at a predetermined value within a range of θ/4-θ/2 (θ is a commutation zone or an angular period where the power supply brush 19 performs commutation substantially). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an outer rotor type DC motor configured to supply power by bringing a power supply brush arranged in a circumferential direction into contact with a commutator of a rotor in which a coil is wound by distributed winding.

Conventionally, an outer rotor type DC motor in which a rotor having a plurality of coils that rotate integrally with a rotating shaft is arranged on the outer periphery of a stator having a permanent magnet as a field magnet is described in Patent Document 1. It has been known. The outer rotor type DC motor disclosed in Patent Document 1 is a coreless one that reduces the weight of the rotor. However, even when a coil is wound around a core, the coil interlinkage magnetic flux is increased to achieve a small size and high output. For this purpose, full-pitch winding is adopted in which the magnetic pole pitch of the magnet on the stator side and the coil pitch on the rotor side are the same.
JP-A-6-261502

  However, when full-pitch winding is adopted as described above, the no-spark zone during rectification (the period in which no spark discharge occurs between the commutator and the power supply brush) is reduced, so that the power supply brush is damaged by the brush spark. There is a problem that the service life is shortened and the life is reduced.

  In order to reduce the brush spark during commutation, a brush shift in which the power supply brush is shifted from the normal position on the magnetic pole center line of the permanent magnet to one side in the rotational direction is effective. However, if the shift angle is increased, the stator side Over-rectification is likely to occur due to the induced voltage generated in the coil by the permanent magnet. In particular, when a rare earth magnet is used for the permanent magnet and the magnetic flux density is increased to achieve a small size and high output, over-rectification becomes more prominent. Since this overcommutation generates brake torque, there is a problem that motor loss increases.

  The present invention has been made in view of such circumstances, and its purpose is to optimize the brush shift angle to improve the rectification characteristics, and to extend the life and reduce motor loss by reducing brush sparks. It is to provide a DC motor.

  In order to solve the above-mentioned problems, the invention according to claim 1 is configured such that a stator having a field and a periphery of the field are rotatably arranged, and a coil is wound around a tooth of an armature core. And a rotor integrally provided with a commutator having a segment to which the coil is connected, and a power supply brush that contacts the segment of the commutator, and rotates from the power supply brush to the coil via the commutator. An outer rotor type DC motor provided with a power supply device for supplying power for driving, wherein the stator has eight magnetic poles, and the armature core of the rotor is provided with 32 teeth. In addition, the coil is wound with a short-pitch winding across three teeth, and the power supply brush is shifted from the normal position on the magnetic pole center line of the field pole to one direction of rotation. Is, the gist of the brush shift angle is set within a range of θ / 4~θ / 2 when the rectified band was theta.

  In this invention, the stator has 8 field poles, and the rotor has 32 teeth on the armature core, and the coil is wound with a short-pitch winding across the 3 teeth and connected to the commutator. Thus, the power supply brush that contacts the commutator is shifted from the normal position to one side in the rotational direction, and the shift angle is θ / 4 to θ / 2 (θ is a commutation band, and the angle period during which the power supply brush performs substantial commutation). Is set within the range. As a result, the rectification characteristics are improved (see FIG. 5), and good results can be obtained in terms of both brush sparks and motor loss.

  According to the present invention, it is possible to provide a direct current motor capable of improving the commutation characteristics by optimizing the brush shift angle, extending the life by reducing the brush spark, and suppressing the motor loss.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 shows a DC motor 1 of the present embodiment. The DC motor 1 is composed of an outer rotor type DC motor in which a rotor 3 having a coil 35 is disposed on the outer periphery of a stator 2 having a permanent magnet 16 as a field.

  The stator housing 11 constituting the stator 2 has a substantially circular dish shape, and a support member 12 is fixed inside an annular protrusion 11a provided at the bottom. The support member 12 includes a cylindrical support member main body 12b in which a through hole 12a is formed, a holding portion 12c formed at a base end portion of the support member main body 12b, and a substantially axial center of the support member main body 12b. And a flange 12d formed. The support member 12 has a base end holding portion 12c positioned at the protruding portion 11a of the stator housing 11 and fixed to the housing 11, and a bearing 13 fixed to the inner peripheral portion of the holding portion 12c. Has been.

  A substantially cylindrical field core 15 in which a fixing hole 15a is formed is disposed on the outer periphery of the support member main body 12b on the front end side of the flange portion 12d. The field core 15 is fixed so that the support member main body 12b is fitted into the fixing hole 15a and the base end surface of the core 15 is in contact with the flange 12d, and protrudes from the distal end of the support member main body 12b in the fixed state. Attached. A bearing 14 that is paired with the bearing 13 is fixed to the inner peripheral portion of the fixing hole 15a in the protruding portion. On the outer peripheral surface of such a field core 15, as shown in FIG. 2, eight permanent magnets 16 having an arc shape and the same shape are alternately arranged with N and S poles in the circumferential direction. Arranged and fixed. That is, the stator 2 has eight poles at regular angular intervals.

  The outer surface 16a of each permanent magnet 16 has an arcuate surface portion 16b having the same circumference in the circumferential central region (magnetic pole central region), and on both sides of the arcuate surface portion 16b, the radially inner side is directed toward the circumferential end. It has a pair of inclined surface parts 16c which incline to each other. That is, in the circular arc surface portion 16b of the outer surface 16a of the permanent magnet 16, the gap with the inner peripheral surface 33e of the inner annular portion 33d of the armature core 33 to be described later is equally spaced in the circumferential direction, and in the inclined surface portion 16c, the end portion The gap with the inner peripheral surface 33e increases as it goes toward the center. In the present embodiment, since eight permanent magnets 16 are arranged in the circumferential direction, each angle range is 45 °, and the arcuate surface portion 16b in the central region is about 23 ° (22.5 which is half of 45 °). It corresponds to an angle range a1 between the center lines of the teeth 33c on both sides around which the coil 35 is wound over three teeth 33c. Further, the inclined surface portions 16c on both sides are each set to about 11 ° (11.25 ° which is 1/4 of 45 °), and corresponds to the angle range a2 between the center lines of the adjacent teeth 33c.

  As shown in FIG. 1, a holding plate 17 fixed to the bottom of the stator housing 11 is disposed on the outer periphery of the holding portion 12 c of the support member 12, and the holding plate 17 has a square cylindrical shape 6. The individual brush holders 18 are provided at equiangular intervals. FIG. 1 is a cross-sectional view of a portion where the brush holder 18 is present and a portion where the brush holder 18 is absent, and only one brush holder 18 is illustrated. Each brush holder 18 is inserted with a substantially square pole-shaped power supply brush 19 so as to be movable in the axial direction. Incidentally, the brush width (circumferential width) of each power supply brush 19 is set to be substantially the same as the circumferential width of the segment 42. Each power supply brush 19 is pressed into contact with a commutator 41 (segment 42) described later by a compression coil spring 20 accommodated in the brush holder 18. Each power supply brush 19 is electrically connected to a lead wire 21 drawn out of the stator housing 11, and power is supplied for rotation of the rotor 3 from the outside through the lead wire 21. . In the power supply brush 19, positive side power supply and negative side power supply are alternately arranged in the circumferential direction.

  The rotor housing 31 constituting the rotor 3 is formed integrally with a cylindrical core fixing portion 31a and a bottom portion 31b that closes one end of the core fixing portion 31a, and has a bottomed cylindrical shape. . The core fixing portion 31a has an outer diameter equal to the outer diameter of the stator housing 11, and a cylindrical support portion 31c is integrally provided at the center of the bottom portion 31b. A press-fit hole 31d penetrating in the axial direction is formed inside the cylindrical support portion 31c, and the rotary shaft 32 is fixed to the press-fit hole 31d by press-fitting. Predetermined portions of the rotary shaft 32 are pivotally supported by the bearings 13 and 14, respectively, whereby the rotor 3 is rotatably supported with respect to the support member 12.

  As shown in FIGS. 1 and 2, an annular armature core 33 is fixed to the inner peripheral surface of the core fixing portion 31 a and is disposed on the outer periphery of the permanent magnet 16 of the stator 2. The armature core 33 includes an annular outer core 33a that is press-fitted into the inner peripheral surface of the core fixing portion 31a, and an inner core 33b that is assembled to the inner peripheral portion of the outer core 33a. The inner core 33b has 32 teeth 33c extending radially from the inner peripheral portion of the outer core 33a toward the central portion at equal angular intervals, and inner end portions of adjacent teeth 33c are annularly formed by an inner annular portion 33d. Are integrally formed. An inner circumferential surface 33e of the inner annular portion 33d is formed with a circumferential surface having the same circumference and faces the outer surface 16a of the permanent magnet 16 of the stator 2.

  The armature core 33 includes a plurality of coils 35 in which a conductive wire is wound around the teeth 33c in distributed winding from above the insulator 34 made of an insulating resin. Incidentally, the coil 35 is wound around the teeth 33c of the inner core 33b before being assembled to the outer core 33a, and the inner core 33b is assembled to the outer core 33a after the winding. The armature core 33 in which the coil 35 is wound and the inner core 33b is assembled to the outer core 33a is fixed to the inner peripheral surface of the core fixing portion 31a of the rotor housing 31 by press fitting. Ends 35 a and 35 b of each coil 35 (winding start end and winding end end in each coil 35) are drawn to the opening 31 e side of the rotor housing 31.

  An annular fixing member 36 is fixed to the opening 31 e of the rotor housing 31, and a commutator 41 is fixed on the fixing member 36. The commutator 41 includes 32 segments 42 arranged radially in the radial direction, an annular holding portion 43 made of an insulating resin material that holds the segments 42, and a short-circuit wire that short-circuits the predetermined segments 42. 44.

  As shown in FIGS. 1 and 3, each segment 42 has a substantially fan shape in which the width in the circumferential direction becomes wider as the shape viewed from the axial direction moves toward the outer peripheral side, and the axial direction of each segment 42 is also increased. One end surface (surface opposite to the armature core 33) is a slidable contact surface 42a made of an axis orthogonal to the power supply brush 19 in slidable contact. Each segment 42 is arranged at equal angular intervals in the circumferential direction by the holding portion 43 so that the sliding contact surface 42a is flush and a gap (slit) is provided between the segments 42 adjacent in the circumferential direction. . In addition, a pair of inner peripheral side connection pins 42b arranged in the circumferential direction is formed at the radially inner end of each segment 42, and the radially outer end of each segment 42 protrudes radially outward. In addition, an outer peripheral side connection pin 42c having a shape bent in the circumferential direction is formed.

  FIG. 3 is a plan view of the commutator 41 as viewed from the back side (the anti-sliding contact surface 42a side). In FIG. 3, only the segment 42 and the short-circuit line 44 are shown. As shown in FIG. 3, 32 short-circuit wires 44 are provided in the same number as the segment 42, and one end is connected to the inner peripheral side connection pin 42 b of the predetermined segment 42 and the other end is 90. It is connected to the outer peripheral side connection pin 42c of the segment 42 which is at a position shifted by [deg.] (Every seven pieces). As a result, the segments 42 are set to the same potential at every 90 ° by the short-circuit wire 44.

  The corresponding end portions 35a and 35b of the coil 35 are electrically connected to the segment 42 of the commutator 41, respectively. In this case, the end portion 35a drawn out radially inward in each coil 35 is connected to the inner peripheral side connection pin 42b of the corresponding segment 42, and the end portion 35b drawn out radially outward is the corresponding segment 42. Connected to the outer peripheral side connection pin 42c.

  The specific connection of the present embodiment is as shown in FIG. 4. The coil 35 is wound around the three teeth 33 c and connected to the next segment 42, and then the three teeth shifted by one are next. Each coil 35 and the commutator 41 are connected by repeating this so that the coil 35 is wound over 33c and further connected to the next segment 42. In this case, since the coil 35 is wound over the three teeth 33c, as shown in FIG. 2, the magnetic pole pitch of the permanent magnet 16 on the stator 2 side (angle range A1 between both ends in the circumferential direction). In other words, the winding of the coil 3 on the rotor 3 side (angle range A2 between both ends in the circumferential direction) is short winding. Incidentally, the magnetic pole pitch (angle range A1) of the permanent magnet 16 is 45 ° in the present embodiment as described above, whereas the pitch (angle range A2) of the coil 35 is about 34 in the present embodiment. This is an angle (interval 33.75 ° between three teeth 33c).

  Further, with respect to such a connection, each power supply brush 19 is shifted by an angle α from the normal position on the magnetic pole center line of the permanent magnet 16 to one side in the rotation direction (shown by a solid line from the position indicated by a two-dot chain line in FIG. 4). The position is shifted to the position). Here, the DC motor 1 of the present embodiment is a motor for one-way rotation driving, and each power supply brush 19 is arranged to be shifted to the opposite side to the rotation direction. The shift angle α of each power supply brush 19 is represented by the present embodiment, where θ is a rectification band in the rectification period (an angle period in which the width of the power supply brush 19 is removed from the circumferential width of the power supply brush 19 is substantially rectified). In the embodiment, it is set to a predetermined value within the range of θ / 4 to θ / 2.

  As shown in FIGS. 5A and 5B, the motor loss increases as the shift angle α of the power supply brush 19 increases from the normal position (shift angle zero), whereas the shift angle α of the power supply brush 19 is normal. The brush spark decreases as it increases from the position (zero shift angle), and the brush spark becomes substantially zero when θ / 2 is slightly exceeded. Note that the change shown by the solid line in FIG. 5 is due to the motor 1 of the present embodiment adopting short-pitch winding, and the change shown by the broken line in FIG. 5 is the whole-pitch winding (winding over four teeth). ). In other words, the motor 1 of the present embodiment that employs short-pitch winding has a greater improvement in commutation characteristics, and is excellent in terms of motor loss and brush sparks. Then, in the motor 1 of this embodiment that employs such short winding, when considering from both aspects of motor loss and brush spark, the shift angle α of the power supply brush 19 is θ as shown in FIG. It was found that a good range including a minimum value was obtained between / 4 and θ / 2. Therefore, in the present embodiment, the shift angle α of the power supply brush 19 is set to a predetermined value within the range of θ / 4 to θ / 2, for example, θ / 3 which is the minimum value, and the life is extended by reducing the brush sparks. In this way, the motor loss is suppressed.

As described above, the present embodiment has the following effects.
(1) In the direct current motor 1 of the present embodiment, the stator 2 has eight field poles (eight permanent magnets 16). In the rotor 3, the armature core 33 is provided with 32 teeth 33c, and the coil 35 Is wound by a short-pitch winding across the three teeth 33c and connected to the commutator 41 (segment 42). Then, the power supply brush 19 in contact with the commutator 41 is shifted from the normal position to the counter-rotation direction, and the shift angle α is set to θ / 4 to θ / 2 (θ is a rectification band, and the power supply brush 19 performs substantial rectification. Set to a predetermined value within the range of the angle period to be performed. As a result, the rectification characteristics are improved (see FIG. 5), and both the brush spark and the motor loss are satisfactory, and the life can be extended and the motor loss can be suppressed by reducing the brush spark.

The embodiment of the present invention may be modified as follows.
In the above embodiment, eight permanent magnets 16 independent for each magnetic pole are used, but one permanent magnet with a plurality of magnetic poles or one annular permanent magnet may be used. Moreover, although the permanent magnet 16 which has the circular arc surface part 16b and the inclined surface part 16c was used for the outer surface 16a, you may use the permanent magnet which abbreviate | omitted the inclined surface part 16c and formed the outer surface 16a whole on the same periphery.

  In the above-described embodiment, the commutator 41 is configured using the short-circuit wire 44 having the same potential between the predetermined segments 42. However, the short-circuit wire 44 may be omitted. In this case, six power supply brushes 19 are essential. In addition, since the commutator 41 is configured using the short-circuit wire 44, the number of the power supply brushes 19 can be two or four, for example. Moreover, although all the power supply brushes 19 are shifted and arranged, at least one of them may be shifted and arranged. In addition, the power supply brush 19 and the commutator 41 are configured to contact in the axial direction, but may be configured to contact in the radial direction.

  In the above embodiment, the teeth 33c are integrated with the inner annular portion 33d in the armature core 33, but the inner annular portion 33d may not be formed, and the inner portion of the teeth 33c may be made independent. In this case, it is preferable to integrally form the teeth 33c on the outer annular portion corresponding to the outer core 33a, and in this case, the outer annular portion is rotatably connected so that the inner ends of the teeth 33c expand. It is good.

It is a longitudinal cross-sectional view of the DC motor in this Embodiment. It is a cross-sectional view of the DC motor in the present embodiment. It is a top view of the commutator in this Embodiment. It is a connection diagram of the DC motor in the present embodiment. It is a figure for demonstrating the relationship between the motor loss with respect to the brush shift angle in this Embodiment, and the generation level of a brush spark.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... DC motor, 2 ... Stator, 3 ... Rotor, 16 ... Permanent magnet as field magnet, 19 ... Feeding brush which comprises power feeding apparatus, 33 ... Armature core, 33c ... Teeth, 35 ... Coil, 41 ... Commutator , 42 ... segment, α ... shift angle.

Claims (1)

A stator having a field,
A rotor that is rotatably arranged on the outer periphery of the field, is configured by winding a coil around a tooth of an armature core, and integrally includes a commutator having a segment to which the coil is connected;
An outer rotor type direct current motor having a power supply brush that contacts a segment of the commutator, and a power supply device that supplies power to the coil from the power supply brush via the commutator for rotational driving. ,
The field pole of the stator is 8 poles,
In the rotor, the armature core is provided with 32 teeth, and the coil is wound with a short-pitch winding over three teeth,
The power supply brush is shifted from the normal position on the magnetic pole center line of the field magnetic pole to one direction of rotation, and the brush shift angle is set within the range of θ / 4 to θ / 2 when the rectification band is θ. DC motor characterized by

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