JP2005278364A - Dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC motor that has field poles structured by utilizing the characteristics of magnets sufficiently. <P>SOLUTION: In the DC motor that has a yoke housing 2 that accommodates an armature rotatably and in which a plurality of field poles 1 that supply magnetic field to the armature are arranged on the inside surface along the circumferential direction, each field pole 1 is divided into a plurality of field pole pieces 1a-1d of the same polarity, and each of the field pole pieces 1a-1d is arranged on the yoke housing 2 at prescribed intervals G1 between the neighboring field pole pieces. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC motor having a yoke housing that rotatably accommodates an armature and has a plurality of field poles for supplying a magnetic field to the armature disposed on an inner surface along a circumferential direction.

  A DC motor (DC motor) is a basic motor that is driven by Fleming's left-hand rule. It has a field pole (stator), an armature (rotor), a commutator, and a brush. Iron) to form a magnetic circuit. The yoke also serves as a housing for supporting and housing an armature and the like, and is sometimes referred to as a yoke housing.

  DC motors have structural weaknesses such as mechanical loss (mechanical deterioration) caused by having a commutator or brush as a contactor, but also have ease of control such as generating torque proportional to current. Therefore, it is used in a wide range of fields, for example, for automobiles, for generating a large torque of a starter motor, and for many parts such as a drive motor for a door mirror, a wiper and a power window.

  In order for such a brushed DC motor (DC brush motor) to exhibit high torque, it is preferable that the armature has a large cross-sectional area for transmitting magnetic flux lines received from the field pole. The yoke housing that accommodates the child is also enlarged. However, for DC brush motors used in a wide range of fields, demands for high performance and miniaturization that meet these requirements are increasing day by day.

  In response to such a demand, the inventor of the present application has proposed a so-called thin DC brush motor in Patent Document 1 that reduces the size of the electric motor in the rotation axis direction. According to this, of the two bearings provided with a recess in the armature and rotatably supporting the armature, one of the bearings disposed on the side close to the brush, the brush and the commutator (commutator) are connected to the armature. By installing in this recessed part so that it may be located in the length of the axial direction of this, the size of the rotating shaft direction of an electric motor is made small.

JP 2001-86719 A (paragraph numbers 0005, 0008, 0009, 0022 to 0027, FIG. 1)

  In the invention described in Patent Document 1, miniaturization is shown by a method of reducing the size of the armature in the rotation axis direction. On the other hand, if an attempt is made to reduce the size of the electric motor in the radial direction, which is the rotation direction of the armature, it is difficult to obtain a necessary amount of magnetic flux with an inexpensive and general-purpose ferrite magnet. Therefore, there are cases where a method of miniaturizing an electric motor using, for example, a rare earth magnet as a field pole, which is excellent in magnetic characteristics such as high magnetic flux density and high coercive force, may be used.

  If a magnet with such excellent magnetic properties is used, the thickness of the field pole can be reduced, and if the armature is accommodated in a yoke housing of the same size, the diameter of the armature is increased accordingly. Can do. Conversely, the yoke housing can be made smaller if the size of the armature is maintained. However, depending on the relationship between the outer dimensions of the DC motor (yoke housing) and the diameter of the armature, the high magnetic flux density of the magnet having excellent magnetic characteristics may not be fully used. In general, a magnet having excellent magnetic characteristics is more expensive than a ferrite magnet and the cost performance is poor if the high characteristics of the magnet cannot be fully utilized. In addition, reducing the thickness of the field pole in the yoke housing diametrical direction, reducing the amount of magnets used, and reducing the magnetic field force to solve the above problem reduces the holding power of the field pole, resulting in an armature. This is not preferable because the magnetic force of the field pole is reduced by the armature magnetomotive force due to the flowing current.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a DC motor having a field pole constructed by fully utilizing the characteristics of a magnet.

  In order to achieve the above object, the first characteristic configuration of the DC motor according to the present invention is that each field pole is divided into a plurality of pole pieces of the same polarity, and each pole piece has a predetermined interval between adjacent pole pieces. It is in the point arrange | positioned in the said yoke housing with a space | interval.

  According to the first characteristic configuration, one pole of each of the plurality of field poles is divided into a plurality of pole pieces and arranged in the yoke housing at a predetermined interval. The amount of magnetic flux that is reduced and proportional to the surface area can be reduced. For example, if a magnet with a high magnetic flux density, such as a rare earth magnet, is used for the field pole, the magnetic flux density may be excessive with respect to the cross-sectional area of the armature or yoke housing. Is possible. Moreover, by dividing | segmenting and arrange | positioning separately, the quantity of the magnet to be used can be reduced and a DC motor can be comprised cheaply.

  The second characteristic configuration is that the field pole is configured by reducing the volume of the pole piece on at least one end side in the circumferential direction of the yoke housing as compared with the other part.

  According to the second characteristic configuration, for example, for the magnetic pole piece disposed at least one end in the circumferential direction of the yoke housing of one field magnetic pole made of a plurality of magnetic pole pieces of the same polarity, the amount of magnetic flux is reduced, It can be configured to reduce the strength of the magnetic field. That is, if the pole pieces have the same thickness in the radial direction, the surface area is reduced by reducing the volume, so the amount of magnetic flux is reduced, and if the surface area is the same, the volume is reduced and the thickness is reduced. The distance of becomes far and the strength of the magnetic field becomes weaker. In addition, when the magnetic pole pieces are divided and arranged in the rotation axis direction of the armature and there are a plurality of magnetic pole pieces at the circumferential ends, the total volume can be reduced. .

  In DC motors, the direction of the magnetic field changes abruptly at the part where the polarity between adjacent field poles is reversed, so that a pulsating torque called so-called cogging torque is generated, or the brush spark is caused by the so-called armature reaction. Or electrical noise due to this spark may occur. However, these can be reduced by appropriately adjusting the magnetic flux at the end of the field pole.

  According to a third characteristic configuration, the field pole has a parting line substantially parallel to the rotation axis of the armature, and the armature of the pole piece located at at least one end in the circumferential direction of the yoke housing. The length in the direction substantially parallel to the rotation axis is shorter than the other pole pieces.

  According to the third characteristic configuration, the field pole is divided substantially parallel to the rotation axis of the armature. For example, when the magnetic material is kneaded into a thermoplastic material such as plastic and integrally formed with the yoke housing. The mold can be easily formed. That is, since the field pole is divided into a plurality of magnetic pole pieces in accordance with the drawing direction of the molding die, it is possible to reduce the manufacturing cost and molding man-hour of the molding die.

  Furthermore, according to the third characteristic configuration, it is possible to reduce the amount of magnetic flux at at least one end of the field pole in the circumferential direction of the yoke housing. As already mentioned, in DC motors, the direction of the magnetic field changes abruptly at the part where the polarity between adjacent field poles is reversed, so cogging torque, brush sparks, electrical noise, etc. occur. These can be reduced by appropriately adjusting the magnetic flux.

  According to a fourth characteristic configuration, the field pole has a parting line substantially parallel to the rotation axis of the armature, and the armature of the pole piece located at at least one end in the circumferential direction of the yoke housing. The thickness in the direction substantially orthogonal to the rotation axis is that it is formed thinner than other pole pieces.

  According to the fourth feature configuration, the field pole is divided substantially parallel to the rotation axis of the armature. For example, when the magnetic material is kneaded into a thermoplastic material such as plastic and integrally formed with the yoke housing. The mold can be easily formed. That is, since the field pole is divided into a plurality of magnetic pole pieces in accordance with the drawing direction of the molding die, it is possible to reduce the manufacturing cost and molding man-hour of the molding die.

  Furthermore, according to the fourth characteristic configuration, the magnetic field strength of at least one end of the field pole in the circumferential direction of the yoke housing can be reduced. If the thickness in the direction substantially perpendicular to the rotation axis of the armature is reduced, the distance from the armature is increased, and the strength of the magnetic field at the end of the field pole is reduced. Similar to the above, problems such as cogging torque, brush sparks, and electrical noise can be reduced.

  As another configuration, the field pole may be divided into a plurality of pole pieces having the same polarity by dividing lines in at least two directions intersecting each other.

  According to this configuration, for example, the field pole is divided in two directions, ie, the circumferential direction of the armature and the rotation axis direction. Therefore, the magnetic flux distribution of the field pole can be uniformly thinned from the entire surface of the field pole before the division, and more appropriate It is possible to adjust to a proper magnetic flux density. In addition, with this proper division, a DC motor can be configured with the minimum necessary amount of magnet (magnetic material) used.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 is a perspective view showing a configuration example of the yoke housing 2 and the field pole 1 of the DC motor and a development view thereof. The armature (not shown) rotates about the center of the yoke housing 2 shown in FIG. 6 (b) is a perspective view of FIG. 6 (b) cut in half in the direction of the rotation axis, and FIG. 6 (c) is a developed view thereof.

  In the example of the DC motor shown in FIG. 6, the field pole 1 has four poles, and the field pole 1N with the N pole facing the inside of the yoke housing 2, that is, the armature side, and the field pole 1S with the S pole facing. Each has two poles. Here, one field pole 1 is provided in the circumferential direction of the yoke housing 2 with an opening angle of about 65 degrees. In addition, the field pole 1 shown in FIG. 6 represents that this area | region is the field pole 1 which has one polarity, and does not necessarily limit that the magnet as a structure exists. An example of the arrangement of magnets constituting the field pole 1 will be described below in an embodiment according to the present invention.

[First embodiment]
FIG. 1 is a perspective view showing a configuration example of a field pole of a DC motor according to a first embodiment of the present invention and a developed view thereof. As shown in FIG. 1, each field pole is divided into a plurality of magnetic pole pieces 1a, 1b, 1c and 1d (hereinafter synonymous with 1a to 1d) having the same polarity, and each magnetic pole piece 1a to 1d is an adjacent magnetic pole piece. Is disposed in the yoke housing 2 with a predetermined gap G1 therebetween.

  The amount of magnetic flux of the field pole 1 is proportional to the surface area of the field pole 1 on the armature side, that is, the inner surface side of the yoke housing 2. Therefore, if the field pole 1 is divided as shown in FIG. 1 and arranged with a predetermined gap G1 in the circumferential direction of the yoke housing 2, the surface area is reduced by the predetermined gap G1, and the amount of magnetic flux is reduced. Can be reduced. When a magnet with a high magnetic flux density such as a rare earth magnet is used for the field pole 1, the magnetic flux density may be excessive with respect to the cross-sectional area of the armature or yoke housing 2, but this should be adjusted to an appropriate magnetic flux density. Is possible. Moreover, although magnets with high magnetic flux density are generally expensive, the amount of magnets to be used can be reduced by arranging them separately and separated, and a DC motor can be constructed at low cost.

  More preferably, this division is a division into three or more pole pieces. At least one field pole 1 is divided into, for example, a magnetic pole piece 1a at one end in the circumferential direction of the yoke housing 2, a magnetic pole piece 1b and 1c at the center, and a magnetic pole piece 1d at the other end. Can be considered and practical.

  If the armature diameter and the amount of magnetic flux are adjusted to an appropriate balance, the thickness of the field pole 1 in the direction perpendicular to the rotation axis of the armature is reduced and the diameter of the armature is increased. But you can. However, if the field pole 1 is made thinner, the coercive force of the magnet constituting the field pole 1 is lowered. When the armature rotates in the magnetic field created by the field pole 1, a magnetic field in the opposite direction to the magnetic field created by the field pole 1 is generated by the armature magnetomotive force generated by the current flowing in the armature winding wound around the armature. . If the coercive force is low, there is a high possibility that a phenomenon (demagnetization) in which the magnetic force of the field pole 1 is lowered without being able to resist this counter-electromotive force is generated. The structure which does is preferable.

  In the first embodiment, the field pole 1 is divided by a dividing line L1 substantially parallel to the rotation axis of the armature. This is a particularly effective dividing method when the field pole 1 is integrally formed with the yoke housing 2. Details will be described below.

  There are various types of magnets, but most have the disadvantage of being hard and brittle. What has been developed to compensate for this drawback is called a bonded magnet. Bonded magnets are a mixture of magnetic powder, a binder such as plastic (thermoplastic resin) or rubber, and a special additive that acts as a glue, called a coupling, and is used for compression, injection, extrusion, etc. The magnet is molded and solidified into a predetermined shape. There are various names such as plastic magnets (plastic magnets), rubber magnets, and bonded magnets. In the present specification, these are hereinafter referred to as plastic magnets.

  This plastic mug is often used as a field pole 1 of a DC motor practically because it compensates the drawback of being hard and brittle and can be molded into a flexible shape. Further, since it can be formed by molding, it is technically possible to integrally mold with the yoke housing 2. When this integral molding is performed, the direction in which the mold is pulled out is the direction along the rotation axis of the armature. Therefore, if the field pole 1 is divided by a dividing line L1 that is substantially parallel to the rotation axis of the armature, the shape of the mold can be simplified, and the mold manufacturing cost can be reduced, and molding using this mold can be facilitated. Further, the amount of material used can be reduced by the division. Thus, it becomes possible to provide a DC motor having the field pole 1 adjusted to an appropriate magnetic flux density at low cost.

  In the gaps between the adjacent magnetic pole pieces 1a to 1d, another molded product that can be used as a holding means for the divided magnetic pole pieces 1a to 1d may be formed of other resin or the like. In the above description, the width of the magnetic pole pieces 1a to 1d in the circumferential direction of the yoke housing 2 and the predetermined gap G1 between the magnetic pole pieces 1a to 1d are shown to be uniform. The width may be changed for each of 1a to 1d, or the value of the predetermined interval G1 may be changed.

[Second Embodiment]
FIG. 2 is a development view showing a configuration example of the field pole of the DC motor according to the second embodiment of the present invention. According to this, the volume of the magnetic pole pieces 1f and 1g on at least one end side in the circumferential direction of the yoke housing 2 is configured to be smaller than that of the other magnetic pole pieces 1e. In particular, in the configuration example shown in FIG. 2, the field pole 1 has a parting line substantially parallel to the rotation axis of the armature, and the magnetic pole pieces 1 f and 1 g located at at least one end in the circumferential direction of the yoke housing 2. The lengths H2 and H3 in a direction substantially parallel to the rotation axis of the armature are formed shorter than the length H1 of the other pole piece 1e. In the example shown in FIG. 2, the pole pieces 1f and 1g at both ends of the yoke housing 2 in the circumferential direction of one field pole 1 are shortened in the direction of the rotation axis of the armature, It is configured to reduce the amount of magnetic flux. Here, one field pole 1 is divided into three or more pole pieces, ie, pole pieces 1f and 1g at both ends in the circumferential direction of the yoke housing 2, and a center pole piece 1e. The adjustment of the magnetic flux of 1 g can be suitably performed for each.

  In a DC motor, the direction of the magnetic field changes abruptly at a portion where the polarity between adjacent field poles 1 is reversed, so that a pulsating torque called a so-called cogging torque is generated or a brush spark is caused by a so-called armature reaction. Or electrical noise due to this spark may occur. However, these can be reduced by appropriately adjusting the magnetic flux at the end of the field pole 1.

  In the configuration example shown in FIG. 2, the volume of the magnetic pole pieces 1f and 1g on at least one end side in the circumferential direction of the yoke housing 2 is reduced as compared with the other portion 1e, and at the end of the adjacent field pole 1 The arrangement of the pole pieces 1f and 1g that reduce the volume with each other is alternately arranged up and down. As a method for reducing the volume, in the present embodiment, the arrangement of the pole pieces 1f and 1g formed short at the end portions of the adjacent field poles 1 is configured so as to be alternated vertically. With this configuration, it is possible to prevent an abrupt change in the magnetic field without excessively widening the interval between the field poles 1 for securing the rotational torque.

  The configuration example of the field pole 1 is not limited to that shown in FIG. 2, and the pole pieces are also divided and arranged in the circumferential direction end portion in the rotation axis direction of the armature. If there is a pole piece, the total length and the total volume in the direction of the rotation axis may be reduced. Further, the width and thickness of the magnetic pole pieces 1e to 1g in the circumferential direction of the yoke housing 2 and the predetermined interval between the magnetic pole pieces need not be uniform, and the values may be changed for each magnetic pole piece. Naturally, the thickness in the rotation axis direction may be changed within the same magnetic pole piece.

[Third embodiment]
3 and 4 are perspective views showing a configuration example of field poles of a DC motor according to a third embodiment of the present invention. Here, the field pole 1 has a parting line that is substantially parallel to the rotation axis of the armature, and is connected to the rotation axis of the armature of the magnetic pole piece 1i or 1j located at at least one end in the circumferential direction of the yoke housing 2. The thickness T2 or T3 in the direction substantially orthogonal to the other is formed thinner than the thickness T1 of the other pole piece 1h.

  In the configuration shown in FIG. 3, among the magnetic pole pieces 1h and 1i constituting one field pole 1, the thickness T2 of the magnetic pole piece 1i at both ends in the circumferential direction of the yoke housing 2 is set to the thickness T1 of the magnetic pole piece 1h at the central portion. It is thinner than the armature so that the distance from the armature increases. In the configuration shown in FIG. 4, among the magnetic pole pieces 1h and 1j constituting one field pole 1, the pole pieces 1j at both ends in the circumferential direction of the yoke housing 2 are moved from the thickness T1 to the thickness T3 toward the ends. The distance from the armature is increased. Both are configured such that the strength of the magnetic field exerted on the armature by both ends of one field pole 1 gradually decreases. Thereby, similarly to the second embodiment, problems such as cogging torque, brush sparks, and electric noise can be reduced.

  Note that the magnetic pole piece whose thickness is reduced has a thickness that does not cause demagnetization due to the armature magnetomotive force. Further, the width and thickness T1 (or T2 or T3) of the magnetic pole pieces 1h to 1j in the circumferential direction of the yoke housing 2 and the predetermined interval between the magnetic pole pieces do not need to be uniform, and are different for each magnetic pole piece. May be changed.

[Fourth embodiment]
FIG. 5 is a perspective view illustrating a configuration example of a field pole of a DC motor according to a fourth embodiment of the present invention and a developed view thereof. Here, the field pole 1 is divided into a plurality of magnetic pole pieces 1k having the same polarity by dividing lines L1 and L2 in at least two directions intersecting each other. In FIG. 5, as an example, the configuration having the dividing line L1 substantially parallel to the rotation axis of the armature and the dividing line L2 orthogonal to the rotation axis is shown, but the present invention is not limited to this. Both may have a dividing line that is oblique to the axis of rotation.

  Since the field pole 1 is divided into the magnetic pole pieces 1k so as to have predetermined intervals G1 and G2 in both the circumferential direction and the rotation axis direction of the armature (yoke housing 2), the magnetic flux distribution of the field pole 1 is divided before the division. It is possible to thin out the entire surface of the field pole 1 uniformly, and it is possible to adjust to a more appropriate magnetic flux density. In addition, with this proper division, a DC motor can be configured with the minimum necessary amount of magnet (magnetic material) used.

  Further, after such a division, the total volume of the pole pieces 1k on at least one end side in the circumferential direction of the yoke housing 2 may be reduced as compared with the other portions. Then, the magnetic flux distribution of the field pole 1 can be uniformly thinned out from the entire surface of the field pole 1 before division, and the magnetic flux at the end of the field pole can be adjusted appropriately. The size (volume or length) of each magnetic pole piece 1k and the predetermined intervals G1 and G2 of each magnetic pole piece 1k need not be uniform.

  By configuring as described above, it is possible to provide a DC motor having a field pole configured by fully utilizing the characteristics of the magnet.

  As described above, the configuration that makes it possible to provide a DC motor having a field pole that fully utilizes the characteristics of the magnet has been described. However, a DC motor can be similarly configured. Therefore, the present invention can also be applied to the configuration of the field pole of a DC generator.

The perspective view which shows the structural example of the field pole of the DC motor which concerns on 1st embodiment of this invention, and its expanded view The expanded view which shows the structural example of the field pole of the DC motor which concerns on 2nd embodiment of this invention. The perspective view which shows one structural example of the field pole of the DC motor which concerns on 3rd embodiment of this invention. The perspective view which shows the other structural example of the field pole of the DC motor which concerns on 3rd embodiment of this invention. The perspective view which shows the structural example of the field pole of the DC motor which concerns on 4th embodiment of this invention, and its expanded view The perspective view which shows the structural example of the yoke housing of a DC motor, and a field pole, and its expanded view

Explanation of symbols

1 Field pole 1a to 1d Pole piece 2 Yoke housing G1 Predetermined distance L1 Dividing line

Claims (4)

In a DC motor having a yoke housing that rotatably accommodates an armature and arranges a plurality of field poles for supplying a magnetic field to the armature on an inner surface along a circumferential direction,
Each field pole is divided into a plurality of pole pieces having the same polarity, and each pole piece is disposed in the yoke housing with a predetermined interval between adjacent pole pieces.   2. The DC motor according to claim 1, wherein the field pole is configured such that a volume of the pole piece on at least one end side in the circumferential direction of the yoke housing is reduced as compared with other portions.   The field pole has a parting line substantially parallel to the rotation axis of the armature, and is substantially parallel to the rotation axis of the armature of the pole piece located at at least one end in the circumferential direction of the yoke housing. The DC motor according to claim 1, wherein the direction length is shorter than that of the other magnetic pole pieces.   The field pole has a parting line substantially parallel to the rotation axis of the armature, and is substantially orthogonal to the rotation axis of the armature of the magnetic pole piece located at at least one end in the circumferential direction of the yoke housing. The DC motor according to claim 1, wherein a thickness in a direction is formed thinner than that of other pole pieces.

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