JP2017028757A - Dc motor, resin composition, and protective member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce manufacturing cost of a DC motor.SOLUTION: A DC motor includes a stator and a rotor 1. The stator includes a brush to which a DC voltage is applied from an external power supply. The rotor 1 includes an armature coil 3 as a winding for generating a magnetic force by a current, a commutator 5 for supplying a current to the armature coil 3 when in contact with the brush, and a protective element 61 for protecting the commutator 5. The commutator 5 has a plurality of commutator pieces 6, and a plurality of commutator risers 7 associated, respectively, with the plurality of commutator pieces 6 and connected with the armature coil 3. The protective element 61 is molded of a resin composition containing a thermosetting resin and formed so that the cured product exhibits nonlinearity not following the Ohm's law, and connected electrically with to the commutator risers 7, respectively.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a DC motor, a resin composition, and a protective member.

  Conventionally, DC motors have been used as drive sources for various devices. For example, DC motors are used as drive sources for office equipment such as printers and copiers, home appliances such as electric shavers, and various electric parts of automobiles.

Many of the DC motors are provided with brushes, and the brushes are brought into sliding contact with a rotating commutator, and the direction is switched while current is passed through the rotor windings.
In such a brushed DC motor, sparks are generated by a high voltage induced by the intermittent commutator during rotation. Due to the occurrence of this spark, the brush and commutator are consumed and noise is generated.
Therefore, a DC motor equipped with a ring varistor for suppressing this spark has become widespread (see Patent Document 1).

JP 2007-300705 A

  However, in recent years, there has been a demand for downsizing of a DC motor as the driving target of the DC motor is downsized. However, the presence of a ring varistor has been a factor that hinders downsizing of a DC motor.

In addition, in a conventional DC motor using such a ring varistor, it is necessary to fix the ring varistor to the rotor, and to electrically connect each commutator piece and the ring varistor using solder or the like. Become. As a result, the number of man-hours for assembling the DC motor was large.
Furthermore, in a DC motor with a large number of poles, the number of commutator pieces provided on the commutator increases, and the space for mounting the ring varistor is limited, so each commutator piece is connected to the ring varistor. The work to do becomes difficult.
Such a large number of assembling man-hours and difficulty in work have been factors that increase the manufacturing cost of the DC motor.

  The present invention has been made in view of such a situation, and an object of the present invention is to realize downsizing of a DC motor and to reduce manufacturing cost.

In order to achieve the above object, a DC motor according to an aspect of the present invention is provided.
A DC motor comprising a stator and a rotor,
The stator includes a brush to which a DC voltage is applied from an external power source,
The rotor is
A rotation axis;
A barrel formed in a cylindrical shape and fixed to the rotating shaft;
A winding that generates a magnetic force by an electric current;
A commutator for passing the current through the windings by contact of the brush;
With
The commutator has a plurality of commutator pieces, each disposed with a predetermined gap in the circumferential direction on the outer peripheral surface of the body portion,
At least a part of a portion of the body portion that comes into contact with the plurality of commutator pieces is molded from a protective member that exhibits nonlinearity in which voltage-current characteristics do not follow Ohm's law.
It is characterized by that.

Here, the protection member may be a member formed in an annular shape, disposed inside the commutator piece, and in contact with the inner side surface of each commutator piece on the outer peripheral surface.
Furthermore, the voltage-current characteristic may be a member formed by laminating a varistor part exhibiting nonlinearity that does not follow Ohm's law and a conductive electrode part.

Alternatively,
The trunk is
A cylindrical first portion that is formed of a non-conductor and covers the rotating shaft;
A cylindrical second portion that is molded with the protective member, covers the insulating portion, and contacts the inner surface of each commutator piece on the outer peripheral surface;
It can be made to have.

One aspect of the present invention is a resin composition,
Including a thermosetting resin and semiconductor ceramic particles;
The semiconductor ceramic particles have a grain boundary part and a plurality of crystal parts separated by the grain boundary part,
The cured product of the resin composition exhibits non-linearity in which voltage-current characteristics do not follow Ohm's law,
A plurality of rectifiers each provided with a predetermined gap in the circumferential direction on a rotating shaft, a cylindrically formed barrel portion fixed to the rotating shaft, a brush, a winding, and an outer circumferential surface of the barrel portion In a direct-current motor including a commutator having a piece, the resin composition is used to be formed on at least a part of a portion of the body portion that comes into contact with the plurality of commutator pieces.

One aspect of the present invention is a protective member that is molded from a resin composition and protects a transient voltage for a circuit to be protected,
The resin composition is
Including a thermosetting resin and semiconductor ceramic particles;
The semiconductor ceramic particles have a grain boundary part and a plurality of crystal parts separated by the grain boundary part,
The protective member exhibits non-linearity in which the voltage-current characteristic does not follow Ohm's law,
A plurality of rectifiers each provided with a predetermined gap in the circumferential direction on a rotating shaft, a cylindrically formed barrel portion fixed to the rotating shaft, a brush, a winding, and an outer circumferential surface of the barrel portion A protective member for a DC motor comprising a commutator having a child piece,
It is a protection member used as at least a part of the part which contacts the plurality of commutator pieces of the trunk part.

  ADVANTAGE OF THE INVENTION According to this invention, size reduction of a DC motor can be implement | achieved and manufacturing cost can be reduced.

It is a partially broken sectional view showing an example of a DC motor according to an embodiment of the present invention. It is a perspective view which shows the detail of a commutator among the DC motors concerning 1st Embodiment. It is sectional drawing of the commutator shown in FIG. It is sectional drawing which follows the AA line among the commutators shown in FIG. It is a perspective view which shows the protection part arrange | positioned in the commutator of the DC motor of 1st Embodiment shown in FIG. 2 thru | or FIG. It is a figure explaining the process of forming a commutator piece raw material among the manufacturing methods of the trunk | drum which has a commutator and the protection part of the DC motor of 1st Embodiment shown in FIG. 2 thru | or FIG. It is a figure explaining the process of arrange | positioning the protection part 81 to a commutator piece raw material among the manufacturing methods of the trunk | drum which has the commutator and protection part of the direct current motor of 1st Embodiment shown in FIG. 2 thru | or FIG. It is a figure explaining the process which molds a trunk | drum to a commutator piece raw material among the manufacturing methods of the trunk | drum which has a commutator and the protection part of the direct-current motor of 1st Embodiment shown in FIG. It is a figure explaining the process of shape | molding a commutator piece raw material among the manufacturing methods of the trunk | drum which has a commutator and the protection part of the direct-current motor of 1st Embodiment shown in FIG. It is sectional drawing of a commutator among the DC motors concerning 2nd Embodiment. It is sectional drawing which follows the AA line among the commutators shown in FIG. It is an expanded sectional view of the semiconductor ceramic particle concerning this embodiment. It is a schematic diagram which shows an example of the structure which concerns on this embodiment. It is a schematic diagram which shows an example of the structure which concerns on this embodiment.

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

[First Embodiment]
FIG. 1 is a partially broken sectional view showing an example of a DC motor according to the first embodiment of the present invention.
In the present embodiment, the DC motor 30 has a specification that can handle, for example, 0.4 W to 15 W output, and has a diameter of 24 mm and a length of 38 mm. Note that the size is merely an example, and various sizes of semiconductor elements can be provided depending on specifications and the like.
In the DC motor 30, one or a plurality of magnets 42 are arranged on the inner wall of a cylindrical housing 41. The magnet 42 is arranged so that the magnetic poles (N pole and S pole) are located inside, and the N pole and the S pole are alternately arranged along the circumferential direction of the inner wall of the housing 41.
That is, the housing 41 and the magnet 42 are one component of the stator of the DC motor 30.

A rotor 43 is disposed at the center of the housing 41.
The rotor 43 includes a shaft 44, a core 45, a winding 46, and a commutator 47.

The shaft 44 functions as a rotating shaft that supports the rotor 43 via the bearings 49a and 49b, and also functions as an output shaft.
The core 45 is configured by laminating a plurality of steel plates. In the center of the core 45, the shaft 44 is fixed in a penetrating manner.
The winding 46 is wound around the groove 45a of the core 45, and generates a magnetic force when a current flows.

  The commutator 47 is fixed to the shaft 44 together with the core 45, and functions as a contact that allows current to flow through the winding 46 at an appropriate timing via the brush 48 that contacts the commutator 47. The sliding part (commutator piece 71 of FIG. 2 mentioned later) with the brush 48 among the commutators 47 is comprised, for example with a silver containing metal.

The brush 48 is fixed to the brush holder 52 while being connected to a brush base 51 serving as a terminal. The brush holder 52 is mounted in the housing 41. Then, the opening of the housing 41 is covered with the end bell 50.
That is, the brush 48, the brush base 51, and the brush holder 52 are one component of the stator of the DC motor 30.
In the present embodiment, a fork-shaped metal brush mainly composed of a noble metal or the like is employed as the brush 48. The brush 48 may be a carbon brush.

Conventionally, a ring varistor is disposed between the core 45 and the commutator 47. However, in the present embodiment, such a ring varistor is not necessary.
However, since it is necessary to suppress the occurrence of sparks between the commutator 47 and the brush 48, in this embodiment, a protection unit having the same function as the conventional ring varistor is provided inside the commutator 47 (described later). It is provided in one part of the trunk 72 in FIG.
That is, the DC motor 30 according to the present embodiment does not require a ring varistor to be disposed outside the commutator 47, and thus can be reduced in size as compared with a conventional DC motor.

  In the following, the commutator 47 having a protective part inside will be described with reference to FIGS.

FIG. 2 is a perspective view showing details of the commutator 47 in the DC motor of FIG.
FIG. 3 is a cross-sectional view of the commutator 47 shown in FIG.
4 is a cross-sectional view taken along the line AA of the commutator 47 shown in FIG.

Inside the commutator 47 is provided a barrel 72 formed in a cylindrical shape by a resin material which is a nonconductor in the first embodiment. Here, the non-conductor is a non-conductive member, that is, a member having electrical insulation.
An attachment hole 75 is formed in the axial center of the trunk portion 72, and the commutator 47 is fixed to the shaft 44 via the trunk portion 72 by press-fitting the shaft 44 into the attachment hole 75.

The commutator 47 has eight commutator pieces 71 in this embodiment.
These commutator pieces 71 are each formed of a copper plate as a conductor, and as shown in FIG. 4, two anchors 96 are formed on the inner surface of each commutator piece 71.
Two anchors 96 formed on one commutator piece 71 project toward the body 72 while being inclined in opposite directions in the circumferential direction. As a result, these anchors 96 engage with the body portion 72, and the commutator pieces 71 are fixed to the outer peripheral surface of the body portion 72. As a result, even if the DC motor 30 (FIG. 1) rotates, each commutator piece 71 is difficult to come off from the trunk portion 72.
A slit 73 is provided between the commutator pieces 71. Due to these slits 73, the commutator pieces 71 are arranged on the outer peripheral surface of the body portion 72 side by side with a predetermined interval in the circumferential direction. As a result, the commutator pieces 71 are electrically insulated from each other.
Further, each commutator piece 71 is provided with a hook portion 74. Corresponding windings 46 (FIG. 1) are electrically connected to these hook portions 74.

The brush 48 (FIG. 1) is in sliding contact with the outer peripheral surface of each commutator piece 71.
When a DC voltage is applied from an external power source to the brush 48, a current flows from the brush 48 to each winding 46 via the commutator piece 71.
Further, when the rotor 43 (FIG. 1) rotates together with the shaft 44, the commutator piece 71 in contact with the brush 48 is switched. Thereby, the winding 46 through which the current flows and the energization direction to the winding 46 are sequentially switched.
That is, a current commutated at a timing corresponding to the magnetic field generated by the magnet 42 (FIG. 1) flows through each winding 46. As a result, an electromagnetic force in a predetermined rotational direction is generated in each winding 46 located in the magnetic field, and the rotor 43 rotates.

  Here, in order to suppress the occurrence of sparks between the commutator 47 and the brush 48, in the present embodiment, a protection unit 81 shown in FIG. 3 is employed instead of the conventional ring varistor.

FIG. 5 is a perspective view showing the protection part 81 of FIG.
The protective part 81 of FIG. 5 is a thin circle so as to cover the outer periphery of the varistor part 81a formed in a thin annular shape by a protective member exhibiting non-linearity in which the voltage-current characteristic does not follow Ohm's law. A conductive electrode portion 81b formed in an annular shape is integrally formed. That is, the protection part 81 has a double ring structure with different diameters, in which the varistor part 81a is arranged on the inner peripheral side and the electrode part 81b is arranged on the outer peripheral side.

In this specification, “a protective member exhibiting non-linearity in which voltage-current characteristics do not follow Ohm's law” is also referred to as “insulating material with varistor function”.
The insulating material with a varistor function functions as an insulating material until a voltage equal to or lower than a predetermined voltage is applied, but functions as a conductive material when a voltage exceeding the predetermined voltage is applied. Details of the insulating material with a varistor function will be described later with reference to FIGS.
Here, “connected” means electrically connected when a voltage exceeding the predetermined voltage is applied.

  As shown in FIG. 3, the protection part 81 is provided as a part of the body part 72, that is, inside the commutator 47. Thereby, since it becomes unnecessary to arrange | position a ring varistor outside the commutator 47, the direct current motor 30 of this embodiment can be reduced in size compared with the conventional direct current motor.

More specifically, as shown in FIG. 3, a notch 93 is formed on one end side in the axial direction of the inner surface of each commutator piece 71.
In a state in which the protection part 81 is disposed in the notch part 93, the side surface of the protection part 81 abuts on the contact surface 94 that is perpendicular to the axial direction constituting the notch part 93 and the outer peripheral surface of the protection part 81 is The inner surface of each commutator piece 71 comes into contact.
In this state, one end portion of each commutator piece 71 in the axial direction is caulked, so that the protection portion 81 is formed between the caulking portion 95 formed at the axial end portion of each commutator piece 71 and the contact surface 94. It is sandwiched between and fixed.
Further, the protection unit 81 is electrically connected to each commutator piece 71 by contacting the inner surface of each commutator piece 71. Thereby, since a high voltage generated in the brush 48 is applied to the protection unit 81 via each commutator piece 71, the generation of sparks between the commutator 47 and the brush 48 can be suppressed.
Further, a conductive electrode portion 81 b is attached to the protection portion 81 in advance. Thereby, the electrical contact property with each commutator piece 71 when caulked by the caulking portion 95 can be improved, and cracking of the varistor portion 81a during caulking can be prevented.

An escape hole 92 is formed on the inner peripheral surface of the body portion 72 inside the protection portion 81 so as to be aligned with the mounting hole 91.
The escape hole 92 is formed to have a larger diameter than the inner diameter of the mounting hole 91, that is, the outer diameter of the shaft 44. When the shaft 44 is press-fitted into the mounting hole 91 of the trunk portion 72 in order to fix the commutator 47 to the shaft 44, a gap is generated between the escape hole 92 and the shaft 44. Thereby, when the commutator 47 is fixed to the shaft 44 by press fitting, a large load is not applied to the protection part 81, and damage to the protection part 81 can be prevented.

In addition, in order to prevent the load due to caulking from being applied to the protective portion 81 and damaging the protective portion 81, a load reducing member such as solder or a conductive adhesive is provided between the contact surface 94 and the protective portion 81. May be inserted.
That is, when a load relaxation member is sandwiched between the contact surface 94 and the protection portion 81, even if a load is applied to the protection portion 81 during caulking, the load relaxation member is deformed by the load. Thereby, the load added to the protection part 81 can reduce, and the damage of the protection part 81 at the time of crimping can be prevented.
Further, by employing a conductive member such as solder or a conductive adhesive as the load relaxation member, the protection part 81 and each commutator piece 71 can be reliably electrically connected.
The location of the load relaxation member is not particularly limited between the abutment surface 94 and the protection part 81, and the load applied to the protection part 81 such as between the inner surface of each commutator piece 71 and the protection part 81. As long as it is a part to receive, it may be arbitrary.

(Manufacturing method of body part having commutator and protection part)
Next, the manufacturing method of the trunk | drum 72 which has the commutator 47 and the protection part 81 is demonstrated with reference to FIG.
FIG. 6 is a diagram illustrating a process of forming a commutator piece material (hereinafter referred to as a “commutator piece material forming process”).
FIG. 7 is a diagram for explaining a process of arranging the protective part 81 on the commutator piece material (hereinafter referred to as “protective part arranging process”).
FIG. 8 is a diagram for explaining a process of molding the body 72 on the commutator piece material (hereinafter referred to as “body forming process”).
FIG. 9 is a diagram illustrating a process of forming a commutator piece material (hereinafter referred to as a “commutator piece material forming process”).

First, the commutator piece material forming step shown in FIG. 6 is performed.
Specifically, a conductive plate material (copper plate) is stamped by a press to form a blank material 101 that is the basis of the commutator piece material.
As shown in FIG. 6A, the blank 101 is formed in a substantially rectangular shape, and eight hook portions 74 are formed on one side thereof at regular intervals.

  Next, in the commutator piece material forming step, the blank material 101 is rounded so that both sides in the longitudinal direction face each other, and a cylindrical commutator piece material 102 is formed as shown in FIG. Each hook portion 74 is bent into a hook shape.

Next, in the commutator piece material forming step, an anchor 96 is formed on the inner peripheral surface of the commutator piece material 102 by shaving.
The shaving process is performed by inserting a die having a predetermined outer shape into the commutator piece material 102 to cut the inner peripheral surface of the commutator piece material 102. The number of anchors 96 corresponding to each hook part 74 is formed by this cutting process.
An annular notch 93 is formed on one end side in the axial direction of the inner peripheral surface of the commutator piece material 102. The notch 93 has a contact surface 94 perpendicular to the axial direction and is formed so as to open to one end side in the axial direction.

After the commutator piece material forming step shown in FIG. 6 is performed in this way, the protective part arranging step shown in FIG. 7 is performed.
Specifically, the protection part 81 formed in the cylindrical shape is generated by the insulating material with a varistor function. In addition, the generation | occurrence | production timing of the protection part 81 should just be before the protection part arrangement | positioning process is started, and may be before or after the above-mentioned commutator piece raw material formation process.
As shown in FIG. 5, the protector 81 has a varistor part 81a and an electrode part 81b integrally formed in advance. As shown in FIGS. 7 (a) and 7 (b), the commutator piece material 102 is notched. Inserted into the section 93. At this time, the protection portion 81 has a notch portion 93 (inside the commutator piece material 102 so that its side surface abuts on the contact surface 94 and its outer peripheral surface contacts the inner peripheral surface of the commutator piece material 102. ).
As described above, a load relaxation member such as solder may be inserted between the contact surface 94 and the side surface of the protection portion 81.

Thus, in the DC motor 30 of this embodiment, the notch 93 is formed on one end side in the axial direction of the inner peripheral surface of the commutator piece material 102. And the protection part 81 is arrange | positioned at this notch part 93. FIG.
As a result, the positioning of the protection part 81 is facilitated, and the attaching operation of the protection part 81 to the commutator piece material 102 is facilitated.

Next, in the protective part arranging step, as shown in FIGS. 7C and 7D, one end in the axial direction of the commutator piece material 102 on which the protective part 81 is arranged is caulked by the punch die 103.
That is, the protective portion 81 is sandwiched between the crimping portion 95 formed at the axial end portion of the commutator piece material 102 and the contact surface 94 by the punch die 103. As a result, the protection part 81 is fixed to the commutator piece material 102.
Here, as described above, the load relaxation member may be sandwiched between the contact surface 94 and the protection portion 81. In this case, even if a load is applied to the protection part 81 during caulking, the load relaxation member is deformed by the load. As a result, the load applied to the protection part 81 is reduced, so that the protection part 81 can be prevented from being damaged.

  As described above, when the DC motor 30 according to this embodiment is manufactured, as a work for fixing the protection unit 81 to the commutator piece material 102, one end portion of the commutator piece material 102 in the axial direction is caulked so that the protection unit 81 is rectified. An easy operation such as fixing to the child piece material 102 can be employed.

Thus, after the protection part arrangement | positioning process shown in FIG. 7 is performed, the trunk | drum shaping | molding process shown in FIG. 8 is performed.
Specifically, as shown in FIGS. 8A and 8B, a cylindrical body 72 provided with a mounting hole 91 is formed inside the commutator piece material 102 by a non-conductive resin material. Molding is performed using a mold (not shown).
At this time, the body portion 72 is formed so as to hold the protection portion 81, whereby the protection portion 81 is disposed inside the body portion 72. That is, the trunk | drum 72 is formed by insert molding so that the protection part 81 may be embedded inside.
Further, at the time of molding of the barrel portion 72, each anchor 96 formed on the commutator piece material 102 is also filled with the resin material, whereby each anchor 96 is fixed to the barrel portion 72 when the resin material is cured. The

Thus, after the trunk | body part shaping | molding process shown in FIG. 8 is performed, the commutator piece raw material shaping | molding process shown in FIG. 9 is performed.
Specifically, the commutator piece material 102 is undercut in the axial direction, and as shown in FIG. 9, eight slits 73 are formed in this embodiment. Thereby, the commutator piece material 102 is divided into eight commutator pieces 71.
At this time, as can be seen from FIG. 4, the slit 73 is formed with a depth reaching the body portion 72 from the outer peripheral surface of the commutator piece material 102. Each commutator piece 71 is in a state of being fixed to the outer periphery of the trunk portion 72 by a corresponding anchor 96 and is divided from each other.
In this way, the divided commutator pieces 71 are fixed to the outer peripheral surface of the body portion 72 side by side with a predetermined interval in the circumferential direction and are electrically insulated from each other.
In addition, the electrode 81b of the protection part 81 is also divided | segmented by the slit 73 corresponding to each commutator piece 71, and will be in the state electrically insulated from each other.

  When each commutator piece 71 is formed, a post-process such as an after-curing process for heating the body 72 to increase heat resistance is performed, and the body 72 having the commutator 47 and the protection unit 81 is completed.

As described above, in the DC motor 30 according to the present embodiment, the protection unit 81 is disposed inside the commutator 47 (one part of the body 72), and the inner side surface of each commutator piece 71 and the protection unit 81 are connected. Is done.
This eliminates the conventionally required work of connecting each commutator piece 71 and the ring varistor using wiring, connecting members, or the like. That is, as the work for attaching the protection part 81 to the rotor 43 (FIG. 1), the above-described easy work is sufficient. As a result, in the DC motor 30 of the present embodiment, the number of assembling steps is reduced as compared with the conventional one, so that the manufacturing cost can be reduced.
In addition, by using an insulating material with a varistor function that is excellent in formability, the operation of manufacturing or attaching the protection part 81 becomes very easy. In other words, since an insulating material with a varistor function having excellent formability can be used, various design requirements can be met, and as a result, the design freedom of the DC motor 30 is increased.

[Second Embodiment]
Heretofore, the DC motor according to the first embodiment of the present invention has been described.
Next, a DC motor according to a second embodiment of the present invention will be described.

In the first embodiment described above, the protection portion 81 is formed in an annular shape, and is disposed inside the commutator piece 71 and contacts the inner side surface of each commutator piece 71 on the outer peripheral surface (see FIG. 5). )Met.
However, the protection part 81 is not particularly limited to the configuration of the first embodiment as described above, and is a part that contacts at least a part of the plurality of commutator pieces 71 in the body part 72, and is an insulating material with a varistor function. If it is formed from, it is enough.
Therefore, a DC motor in which the protection unit 81 having a configuration different from that of the first embodiment is employed will be described as a DC motor according to the second embodiment with reference to FIGS. 10 and 11 as appropriate.
Note that the configuration of the DC motor according to the second embodiment is basically the same as the configuration of the first embodiment (FIG. 1), and therefore the description thereof is omitted here.

FIG. 10 is a cross-sectional view of the commutator 47 of the DC motor according to the second embodiment.
11 is a cross-sectional view taken along line AA of commutator 47 shown in FIG.

As shown in FIG.10 and FIG.11, the trunk | drum 72 is arrange | positioned inside the commutator 47 of the DC motor 30 which concerns on 2nd Embodiment. The body portion 72 includes a protection portion 81 and an insulating portion 82.
The insulating part 82 has a cylindrical configuration covering the shaft 44 (FIG. 1) and is formed of a nonconductor.
The protection part 81 has a cylindrical configuration that covers the insulating part 82 and contacts the inner side surface of each commutator piece 71 on the outer peripheral surface, and is formed of an insulating material with a varistor function.

  As described above, in the DC motor 30 according to the second embodiment, the protection part 81 is provided as one part of the trunk part 72 as in the first embodiment. That is, the protection part 81 is provided inside the commutator 47. As a result, the DC motor 30 of the second embodiment is also reduced in size as compared with the conventional DC motor because it is not necessary to arrange a ring varistor outside the commutator 47 as in the first embodiment. be able to.

The protection part 81 of the DC motor 30 according to the second embodiment is electrically connected to each commutator piece 71 by contacting the inner surface of each commutator piece 71 as in the first embodiment. Thereby, since a high voltage generated in the brush 48 is applied to the protection unit 81 via each commutator piece 71, the generation of sparks between the commutator 47 and the brush 48 can be suppressed.
Here, due to the high voltage generated in the brush 48 via each commutator piece 71, a current flows through the protection unit 81, but no current flows through the insulating unit 82. As a result, no current flows through the shaft 44 (FIG. 1). Thus, in the second embodiment, since the insulating portion 82 is provided between the protection portion 81 and the shaft 44, the shaft 44 can be protected without an unnecessary current flowing through the shaft 44.

(Manufacturing method of body part having commutator and protection part)
Next, the manufacturing method of the trunk | drum 72 which has the commutator 47 and the protection part 81 in the DC motor 30 which concerns on 2nd Embodiment is demonstrated.
First, as in the first embodiment, a commutator piece material forming step (see FIG. 6) is performed.
Here, in the first embodiment, the protection unit 81 is separately prepared and inserted into the commutator piece material 102. For this reason, a notch portion 93 for inserting the protection portion 81 is formed in the commutator piece material 102.
However, in the second embodiment, the cylindrical protective portion 81 provided with the hollow portion is formed by using a molding die (not shown) with an insulating material having a varistor function. Therefore, in the second embodiment, it is not necessary to form the notch 93 in the commutator piece material 102.
Accordingly, the protective part arranging step (see FIG. 7) required in the first embodiment becomes unnecessary.

That is, in 2nd Embodiment, after a commutator piece raw material formation process (refer FIG. 6) is performed, a trunk | drum formation process is performed, without performing a protection part arrangement | positioning process (refer FIG. 7).
Specifically, although not shown, a cylindrical protective portion 81 having a hollow portion is formed inside the commutator piece material 102 with a varistor function insulating material using a molding die (not shown). . Further, a cylindrical insulating portion 82 having a mounting hole 91 is formed on the inner side of the protective portion 81 using a non-conductive resin material using a molding die (not shown).
Here, at the time of molding the body portion 72 (protection portion 81), each anchor 96 formed on the commutator piece material 102 is also filled with an insulating material with a varistor function, whereby each anchor 96 has an insulating material with a varistor function. Is fixed to the body portion 72 when it is cured.

As described above, in the DC motor 30 according to the second embodiment, the protective part arranging step (see FIG. 7) required in the first embodiment is not necessary, and the assembly is compared with the first embodiment. The number of steps can be reduced, and as a result, the manufacturing cost can be further reduced.
In addition, by using an insulating material with a varistor function that is excellent in formability, the operation of manufacturing the protection part 81 becomes very easy. In other words, since an insulating material with a varistor function having excellent formability can be used, various design requirements can be met, and as a result, the design freedom of the DC motor 30 is increased.

  Here, the DC motor to which the present invention is applied is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.

For example, in the above-described embodiment, eight commutator pieces 71 are employed. That is, in the above-described embodiment, the 8-pole DC motor 30 is employed. However, the number of poles of the DC motor 30 (the number of commutator pieces 71) is not particularly limited to this.
That is, the DC motor to which the present invention is applied only needs to have the following configuration, and can take various embodiments.

The DC motor to which the present invention is applied is
A DC motor comprising a stator and a rotor,
The stator includes a brush to which a DC voltage is applied from an external power source,
The rotor is
A rotation axis;
A barrel formed in a cylindrical shape and fixed to the rotating shaft;
A winding that generates a magnetic force by an electric current;
A commutator for passing the current through the windings by contact of the brush;
With
The commutator has a plurality of commutator pieces, each disposed with a predetermined gap in the circumferential direction on the outer peripheral surface of the body portion,
At least a part of a portion of the body portion that comes into contact with the plurality of commutator pieces is formed of a protective member that exhibits nonlinearity in which voltage-current characteristics do not follow Ohm's law.
DC motor.

Thus, the protective member for suppressing generation | occurrence | production of the spark between a commutator and a brush is provided as a site | part of the trunk | drum inside a commutator. As a result, it is not necessary to arrange a conventional ring varistor between the core and the commutator.
Thereby, the DC motor to which the present invention is applied can be reduced in size as compared with the conventional DC motor.
Further, the conventionally required work of connecting each commutator piece and the ring varistor using wiring, a connecting member, or the like is unnecessary. As a result, in the DC motor to which the present invention is applied, the assembly man-hour is reduced as compared with the conventional one, and thus the manufacturing cost can be reduced.
Furthermore, by using an insulating material with a varistor function that is excellent in formability, the operation of manufacturing the protective member becomes very easy. In other words, since an insulating material with a varistor function that is excellent in formability can be used, various design requirements can be met, and as a result, the degree of freedom in designing a DC motor is increased.

The protective member formed from the insulating material with a varistor function may be any resin composition as follows.
That is, the resin composition according to the present invention includes a thermosetting resin, and semiconductor ceramic particles having a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and the cured product has voltage-current characteristics. Is a resin composition that exhibits non-linearity that does not follow Ohm's law, and includes a rotating shaft, a cylindrical portion that is formed in a cylindrical shape and fixed to the rotating shaft, a brush, a winding, and the body portion. In a DC motor comprising a commutator having a plurality of commutator pieces that are respectively arranged with a predetermined gap in the circumferential direction on the outer peripheral surface, at least one of the portions of the body that contact the plurality of commutator pieces. Used to form the part. The resin composition corresponds to the insulating material with a varistor function shown as an example above.

  By using the resin composition adopting such a configuration, it becomes possible to provide a protective member in the commutator with a high yield, so that a ring varistor is provided between the core and the commutator in a DC motor as in the past. As a result, it is possible to reduce the size of the DC motor. In addition, the work conventionally required to connect each commutator piece and the ring varistor using wiring, connection members, etc. is unnecessary, and as a result, the assembly man-hour is reduced compared to the conventional, Manufacturing cost can be reduced.

Here, the non-linearity (varistor characteristic) that the voltage-current characteristic does not follow Ohm's law of the structure obtained by the manufacturing method according to this embodiment is an electronic component that includes at least two commutator pieces. When a voltage that gradually increases is applied, the current flowing through an overvoltage protection element, generally called a varistor element, increases non-linearly. In the present embodiment, the structure having the varistor characteristics is specifically a structure that is mounted on an electronic component having a first terminal and a second terminal, and the structure is attached to the electronic component. When mounted, if the voltage between the first terminal and the second terminal is less than the withstand voltage of the device, it exhibits insulation and the voltage between the first terminal and the second terminal When the voltage is higher than the driving voltage of the device, it indicates the one showing conductivity. In addition, the voltage which the characteristic which the structure which concerns on this embodiment has is converted from insulation to electroconductivity as mentioned above, or the voltage converted from electroconductivity to insulation is hereafter called a varistor voltage. .

  Hereinafter, the resin composition according to the present embodiment will be described in detail.

  Conventionally, as described in the section of the problem to be solved by the invention, it has been usual to employ a configuration in which a ring varistor is arranged in a DC motor as a countermeasure for suppressing the occurrence of sparks. Therefore, conventionally, it has been necessary to secure a space for disposing the spark generation suppressing element. Conventionally, it has been necessary to connect each commutator piece and the ring varistor using wiring, a connecting member, or the like. Therefore, there has been a limit to the miniaturization of DC motors and the reduction of manufacturing costs. In view of such circumstances, the present inventor considered that if a protective member can be provided in the commutator, the DC motor can be reduced in size and the manufacturing cost can be reduced. Specifically, the present inventor has a rotating shaft, a cylindrical portion formed in a cylindrical shape and fixed to the rotating shaft, a brush, a winding, and a predetermined gap in the circumferential direction on the outer peripheral surface of the barrel portion. In a DC motor comprising a commutator having a plurality of commutator pieces arranged respectively, it is possible to arrange at a portion that contacts at least a part of the plurality of commutator pieces in the body portion. For example, it has been found that it is effective as a design guideline to realize a member having a flake shape and exhibiting varistor characteristics.

  However, in order to produce a member (structure) exhibiting the above-described varistor characteristics, it was necessary to produce a resin composition having the following three characteristics. The first characteristic required of the resin composition is such that the shape of the member can be controlled so as to correspond to the shape of the commutator piece mounted in the commutator that is a target of use of the member exhibiting varistor characteristics. Excellent moldability. The second characteristic required for the resin composition is the function of the sealing material used for protecting the commutator piece in the conventional electronic component, that is, heat resistance, temperature cycle resistance, insulation reliability. The required properties such as durability, adhesion, and dimensional stability. The 3rd characteristic requested | required of the said resin composition is that the said resin composition can express sufficient varistor characteristic.

  In view of such circumstances, as a result of intensive studies on design guidelines for producing a resin material that satisfies the above three required characteristics, the present inventor has obtained semiconductor ceramic particles 100 having varistor characteristics (see FIG. 12). When blended in the resin composition, a member capable of having a structure having a function of protecting the commutator from an external load of a stress applied from a spark or an external environment in the commutator is manufactured with a high yield. The knowledge that it is possible was obtained. In addition, the present inventor employs a transfer molding method as a method for producing a member exhibiting the above-described varistor characteristics from the viewpoint of satisfying the above-described first characteristics, that is, from the viewpoint of realizing sufficient moldability. I also found it desirable. Therefore, the present resin composition is desirably processed into a tablet-like form.

<Thermosetting resin>
Specific examples of the thermosetting resin contained in the resin composition according to the present invention include novolak type phenol resins such as phenol novolak resin, cresol novolak resin, bisphenol A novolak resin, and triazine skeleton-containing phenol novolak resin; Phenolic resins such as phenolic resins, tung oil, linseed oil, walnut oil, and other resol type phenolic resins such as oil-modified resol phenolic resins; bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol E Type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, bisphenol Z type epoxy resin and other bisphenol type epoxy resins; phenol novolac type epoxy resin, Novolec type epoxy resins such as resole novolac type epoxy resins; biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, arylalkylene type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, phenoxy type epoxy resins, dicyclopentadiene type epoxy resins , Epoxy resin such as norbornene type epoxy resin, adamantane type epoxy resin, fluorene type epoxy resin; resin having triazine ring such as urea (urea) resin, melamine resin; unsaturated polyester resin; maleimide resin such as bismaleimide compound; polyurethane Resin; diallyl phthalate resin; silicone resin; benzoxazine resin; cyanate ester resin; polyimide resin; polyamideimide resin; Resin, a novolac type cyanate resin, bisphenol A type cyanate resin, bisphenol E type cyanate resin, bisphenol type cyanate resin such as tetramethyl bisphenol F type cyanate resins. One of these may be used alone, two or more having different weight average molecular weights may be used in combination, and one or two or more thereof and a prepolymer thereof may be used in combination.

  The content of the thermosetting resin is preferably 1% by mass or more and 38% by mass or less, and more preferably 1.5% by mass or more and 35% by mass or less with respect to the total amount of the resin composition according to the present invention. Yes, more preferably 2% by mass or more and 30% by mass or less, and most preferably 3% by mass or more and 25% by mass or less. By making content of a thermosetting resin more than the said numerical range, the fluidity | liquidity of a resin composition can be improved. In addition, by making the content of the thermosetting resin not more than the above numerical range, the heat dissipating property of the resin composition can be improved, and the varistor characteristics provided in the structure composed of the resin composition according to the present invention can be improved. It is possible to improve.

  As the thermosetting resin contained in the resin composition according to the present invention, an epoxy resin is preferably used. As said epoxy resin, it is possible to use the monomer, oligomer, and polymer in general which have 2 or more of epoxy groups in 1 molecule irrespective of the molecular weight and molecular structure. Specific examples of such epoxy resins include biphenyl type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, stilbene type epoxy resins, hydroquinone type epoxy resins and the like; cresol novolac type epoxy resins, Novolak type epoxy resins such as phenol novolac type epoxy resin and naphthol novolak type epoxy resin; Phenol aralkyl type epoxy such as phenylene skeleton-containing phenol aralkyl type epoxy resin, biphenylene skeleton containing phenol aralkyl type epoxy resin, phenylene skeleton containing naphthol aralkyl type epoxy resin Resin; Trifunctional epoxy resin such as triphenolmethane type epoxy resin and alkyl-modified triphenolmethane type epoxy resin; Examples include modified phenolic epoxy resins such as diene-modified phenolic epoxy resins and terpene-modified phenolic epoxy resins; and heterocyclic-containing epoxy resins such as triazine nucleus-containing epoxy resins. These can be used alone or in two types. A combination of the above may also be used.

The present resin composition may contain a release agent. By doing so, a member (structure 300) exhibiting varistor characteristics can be manufactured with higher yield. The reason for this is as follows. As described above, this resin composition is preferably assumed to be used as a raw material for producing a member (structure 300) exhibiting varistor characteristics by a transfer molding method. When the transfer molding method is employed, the member (structure 300) is manufactured using a resin mold. In this case, after molding the member (structure 300) using the resin composition, it is necessary to release the molded product from the mold. And when the mold release force at the time of releasing a molding from a molding die becomes strong, there exists a tendency for the inconvenience that the obtained molding is damaged easily arises. Therefore, when a resin composition containing a release agent is used, it is possible to suppress the above-described inconvenience, and as a result, a member (structure 300) exhibiting varistor characteristics is manufactured with high yield. It becomes possible.

  Specific examples of the release agent according to this embodiment include natural wax, synthetic wax, higher fatty acid or metal salt thereof, paraffin, polyethylene oxide and the like. The content of the release agent is preferably 0.01% by mass or more and 1% by mass or less, and more preferably 0.03% by mass or more and 0.8% by mass or less, based on the total amount of the resin composition. .

The resin material 200 according to the present invention (see FIGS. 13 and 14) may contain a curing agent. The curing agent only needs to be cured by reacting with a thermosetting resin. Specific examples of curing agents that can be used when an epoxy resin is used as the thermosetting resin include ethylenediamine and trimethylene. C2-C20 linear aliphatic diamine such as diamine, tetramethylenediamine, hexamethylenediamine, metaphenylenediamine, paraphenylenediamine, paraxylenediamine, 4,4 ■ -diaminodiphenylmethane, 4,4 ■ -diaminodiphenyl Propane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodicyclohexane, bis (4-aminophenyl) phenylmethane, 1,5-diaminonaphthalene, metaxylenediamine, para Xylenediamine, 1,1-bis (4-a Nophenyl) aminos such as cyclohexane and dicyanodiamide; resol type phenol resins such as aniline-modified resole resin and dimethyl ether resole resin; novolac type phenol resins such as phenol novolac resin, cresol novolac resin, tert-butylphenol novolac resin, nonylphenol novolac resin; Phenol aralkyl resins such as phenylene skeleton-containing phenol aralkyl resins and biphenylene skeleton-containing phenol aralkyl resins; phenol resins having a condensed polycyclic structure such as naphthalene skeleton and anthracene skeleton; polyoxystyrenes such as polyparaoxystyrene; hexahydrophthalic anhydride ( HHPA), alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride (MTHPA), trimellitic anhydride (T A), acid anhydrides including aromatic acid anhydrides such as pyromellitic anhydride (PMDA), benzophenone tetracarboxylic acid (BTDA), etc .; polymercaptan compounds such as polysulfide, thioester, thioether; isocyanate prepolymer, blocked Isocyanate compounds such as isocyanate; organic acids such as carboxylic acid-containing polyester resins. These may be used alone or in combination of two or more. Among them, from the viewpoint of improving the moisture resistance and reliability of the structure 300, a compound having at least two phenolic hydroxyl groups in one molecule is preferable, and specific examples thereof include phenol novolac resin, cresol novolac resin, tert-butylphenol. Novolak type phenol resins such as novolak resins and nonylphenol novolak resins; resol type phenol resins; polyoxystyrenes such as polyparaoxystyrene; phenylene skeleton-containing phenol aralkyl resins, biphenylene skeleton-containing phenol aralkyl resins, phenylene skeleton-containing naphthol aralkyl type phenol resins Is mentioned.

The resin material 200 included in the resin composition may contain a curing accelerator. The curing accelerator is not particularly limited as long as it accelerates the curing reaction between a functional group such as an epoxy group and the curing agent. Specific examples thereof include 1,8-diazabicyclo (5,4,0) undecene- Diazabicycloalkenes and derivatives thereof such as 7; amine compounds such as tributylamine and benzyldimethylamine; imidazole compounds such as 2-methylimidazole; organic phosphines such as triphenylphosphine and methyldiphenylphosphine; tetraphenylphosphonium tetra Phenylborate, tetraphenylphosphonium / tetrabenzoic acid borate, tetraphenylphosphonium / tetranaphthoic acid borate, tetraphenylphosphonium / tetranaphthoyloxyborate, tetraphenylphosphonium / tetranaphthyloxyborate Triphenylphosphine and the like that adduct benzoquinone; tetra-substituted phosphonium tetra-substituted borate over bets like. These may be used alone or in combination of two or more.

  In addition to the above-described components, the resin material 200 contained in the resin composition includes a coupling agent such as γ-glycidoxypropyltrimethoxysilane; a colorant such as carbon black; Mold release agents such as waxes, synthetic waxes, higher fatty acids or metal salts thereof, paraffin and polyethylene oxide; low stress agents such as silicone oil and silicone rubber; ion scavengers such as hydrotalcite; flame retardants such as aluminum hydroxide; You may mix | blend various additives, such as antioxidant.

<Semiconductor ceramic particles>
FIG. 12 is an enlarged cross-sectional view of semiconductor ceramic particles according to the present embodiment.
As shown in FIG. 12, the semiconductor ceramic particle 100 according to the present embodiment is a particle having a grain boundary part 120 and a plurality of crystal parts 110 separated by the grain boundary part 120. In other words, in the semiconductor ceramic particle 100 according to the present embodiment, a plurality of crystals composed of the grain boundary part 120 and two or more crystal parts 110 arranged so as to be separated from each other via the grain boundary part 120 are aggregated. It can be said that it is a particle. When a voltage lower than the varistor voltage is applied to the particle, the semiconductor ceramic particle 100 does not pass a current because the grain boundary 120 acts as a resistance, but a voltage higher than the varistor voltage is applied. In some cases, the particles have a characteristic that a tunnel effect occurs and current flows as shown by an arrow in FIG. In addition, about the member provided with the varistor characteristic like the semiconductor ceramic particle 100 according to the present embodiment, it is included in a withstand voltage protection element (varistor element or the like) to be mounted on the same circuit together with the electronic element in the conventional electronic component. It was. However, a method for producing a member made of the resin composition containing the semiconductor ceramic particles 100 satisfying the following two required characteristics with high yield has not been reported so far. The first required characteristic described above is that it can be provided inside the electronic element itself mounted in the circuit mounted in the electronic component. The second required characteristic described above has a function of protecting the electronic element from stress applied from the external environment in addition to overvoltage such as static electricity when the member is provided inside the electronic element itself. That is.

  The average particle diameter D50 of the semiconductor ceramic particle 100 is, for example, 0.01 μm or more and 1500 μm or less, preferably 0.1 μm or more and 1000 μm or less, more preferably 1 μm or more and 500 μm or less, and particularly preferably. It is 5 μm or more and 150 μm or less. By doing so, it becomes possible to develop varistor characteristics without depending on the shape of the structure 300 formed of the resin composition including the semiconductor ceramic particles 100.

  The semiconductor ceramic particles 100 are preferably spherical particles. Thereby, it is possible to easily control the varistor characteristics.

  In the semiconductor ceramic particle 100, the crystal part 110 is preferably formed of a material including at least one selected from the group consisting of zinc oxide, silicon carbide, strontium titanate, and barium titanate. Especially, the material which contains zinc oxide as a main component is preferable from a viewpoint of improving the nonlinear coefficient and energy tolerance of the semiconductor ceramic particle 100 itself. Since a material containing silicon carbide as a main component has a high dielectric breakdown voltage, it is suitable when the varistor voltage is set to a high voltage. A material containing strontium titanate as a main component is preferable in terms of absorption and suppression of high voltage / high frequency noise.

In the semiconductor ceramic particle 100, the grain boundary part 120 is preferably formed of a material containing at least one selected from the group consisting of bismuth, praseodymium, antimony, manganese, cobalt and nickel, or a compound thereof. Among these, the grain boundary portion 120 is preferably formed of a material containing at least one selected from the group consisting of bismuth, praseodymium, and these compounds from the viewpoint of good non-linear resistance characteristics. . Examples of these compounds include oxides, nitrides, organic compounds, and other inorganic compounds, but oxides are preferable from the viewpoint of satisfactorily expressing varistor characteristics.

  The content of the semiconductor ceramic particles 100 is preferably 60% by mass or more and 97% by mass or less, and more preferably 70% by mass with respect to the total amount of the resin composition, from the viewpoint of surely expressing the varistor characteristics of the structure 300. It is not less than 95% by mass and particularly preferably not less than 75% by mass and not more than 95% by mass. By controlling the content of the semiconductor ceramic particles 100 to be within the above numerical range, a plurality of spaces between the two conductor portions 130 (for example, the commutator piece 71 in FIG. 3 and the like) are provided as shown in the schematic diagram of FIG. The structure 300 filled with the semiconductor ceramic particles 100 so that the particles can be in contact with each other can be realized. That is, when the content of the semiconductor ceramic particles 100 is controlled to be within the above numerical range, the varistor characteristics of the structure can be surely expressed.

  The resin composition preferably contains conductive particles. Thus, when a high voltage exceeding the varistor voltage is applied to the commutator including the structure 300 formed of the present resin composition, the electric conductivity of the structure 300 is further improved. Can be. Specifically, as shown in FIG. 14, the conductive particles 150 can enter the gap region between the plurality of semiconductor ceramic particles 100 arranged so as to fill the gap between the two conductor portions 130. Thereby, the varistor characteristic of the structure 300 can be further improved.

  The content of the conductive particles 150 is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass with respect to the total amount of the resin composition, from the viewpoint of surely expressing the varistor characteristics of the structure 300. The content is from 15% to 15% by mass, and most preferably from 2% to 10% by mass. By controlling the content of the conductive particles 150 to be within the above numerical range, the plurality of semiconductor ceramic particles 100 arranged so as to fill the space between the two conductor portions 130 as shown in the schematic diagram of FIG. It becomes possible to allow the conductive particles 150 to enter the gap region evenly.

  The average particle diameter D50 of the conductive particles 150 is, for example, 0.01 μm or more and 500 μm or less, preferably 0.02 μm or more and 300 μm or less, more preferably, from the viewpoint of surely expressing the varistor characteristics of the structure. Is 0.05 μm or more and 200 μm or less, and particularly preferably 0.1 μm or more and 100 μm or less.

  Specific examples of the material forming the conductive particles 150 are selected from the group consisting of nickel, carbon black, aluminum, silver, gold, copper, graphite, zinc, iron, stainless steel, tin, brass, and alloys thereof. And a semiconductive material selected from the group consisting of zinc oxide, silicon carbide, strontium titanate, and barium titanate.

Moreover, it is preferable that the magnitude | size of the semiconductor ceramic particle 100 contained in this resin composition and the electrically-conductive particle 150 satisfy | fills the following conditions. Specifically, when the average particle diameter D50 of the semiconductor ceramic particles 100 is X and the average particle diameter D50 of the conductive particles 150 is Y, the value of Y / X is preferably 0.05 or more and less than 1. More preferably, it is 0.1 or more and 0.8 or less. By doing so, as shown in the schematic diagram of FIG. 14, the conductive particles 150 can easily enter the gap regions of the plurality of semiconductor ceramic particles 100 arranged so as to fill the gap between the two conductor portions 130.

  The resin composition according to the present embodiment employs a configuration including semiconductor ceramic particles exhibiting a specific amount of varistor characteristics together with a thermosetting resin. By using the resin composition adopting such a configuration, it is possible to provide the commutator with a configuration having a function of protecting the commutator from an external load of stress applied from a spark or an external environment. Thus, unlike the conventional DC motor, there is no need to arrange a ring varistor between the core and the commutator, and as a result, the DC motor can be reduced in size and manufacturing cost can be reduced.

  Hereinafter, a method for producing a protective member (hereinafter, also referred to as “member showing varistor characteristics” and / or “structure 300”) in the commutator using the resin composition according to the present embodiment will be described. .

  When the resin composition according to this embodiment is used, a member (structure 300) exhibiting varistor characteristics can be produced in the commutator with a high yield by using a transfer molding method as a resin molding method. Therefore, the structure 300 corresponding to the shape of the electrode terminal can be manufactured. Here, in the case of adopting a transfer molding method of the resin composition in order to produce the structure 300, the resin composition is preferably processed into a tablet shape.

  As an example of a method for producing a member (structure 300) exhibiting varistor characteristics in a commutator, for example, a rotating shaft, a body formed in a cylindrical shape and fixed to the rotating shaft, a brush, and a winding And a commutator having a plurality of commutator pieces arranged in the circumferential direction on the outer peripheral surface of the body part, in a DC motor, the plurality of commutator pieces of the body part Examples include a method including a step of forming the structure 300 (high voltage protection member) by transfer molding the resin composition at least at a part in contact with the resin composition.

  Hereinafter, an example of a method for mounting the structure 300 according to the present embodiment in a commutator will be described by taking as an example a case where the structure 300 is manufactured by transfer molding using a tablet-like resin composition. .

  First, a molding die provided with a commutator piece material is prepared. The molding die prepared here was melted with a pot charged with a tablet-shaped resin composition, and then a plunger with an auxiliary ram inserted into the pot to melt the resin composition by applying pressure. A sprue for feeding the resin composition into the molding space is provided.

  Next, the tablet-shaped resin composition is charged into the pot with the molding die closed. Here, the form of the resin composition charged in the pot may be in a semi-molten state by preheating with a preheater or the like in advance. Next, in order to melt the resin composition charged in the pot, a plunger having an auxiliary ram is inserted into the pot to apply pressure to the resin composition. Thereafter, the molten resin composition is introduced into the molding space through a sprue. Next, the resin composition filled in the molding space is cured by being heated and pressurized. After the resin composition is cured, the commutator including the structure 300 in which the resin composition surely exhibits the varistor characteristics can be obtained by opening the molding die.

  The molding temperature in transfer molding is not particularly limited, but is preferably 50 to 250 ° C, more preferably 50 to 200 ° C, and particularly preferably 80 to 180 ° C. By setting the molding temperature within the above range, it is possible to prevent both the occurrence of a portion not filled with the molten resin composition and the displacement of the commutator piece material.

  The protective member according to the present invention is molded from a thermosetting resin and a resin composition containing semiconductor ceramic particles having a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a voltage-current The characteristic is non-linearity that does not follow Ohm's law, the rotating shaft, the cylindrical portion formed in a cylindrical shape, fixed to the rotating shaft, the brush, the winding, the circumferential direction on the outer peripheral surface of the barrel portion And a commutator having a plurality of commutator pieces disposed with a predetermined gap therebetween, and a protection member for a DC motor, wherein at least one of the portions of the body portion that contacts the plurality of commutator pieces. Used as a part. As the resin composition, the resin composition according to the present invention can be used.

  The protective member according to the present invention can be manufactured using the resin composition according to the present embodiment in the same manner as described above for producing a protective member in a commutator.

DESCRIPTION OF SYMBOLS 30 ... DC motor 41 ... Housing 42 ... Magnet 43 ... Rotor 44 ... Shaft 45 ... Core 46 ... Winding 47 ... Commutator 48 ... Brush 49 ... Bearing 50 ... Endbell 51 ... Brush base 52 ... Brush holder 71 ... Commutator piece 72 ... Body 73 ... Slit 74 ... Hook 75 ... Installation Hole 81 ... Protection part 81a ... Varistor part 81b ... Electrode part 82 ... Insulation part 91 ... Mounting hole 92 ... Escape hole 93 ... Notch part 94 ... Contact Surface 95 ... Caulking part 96 ... Anchor 100 ... Semiconductor ceramic particle 101 ... Blank material 102 ... Commutator piece material 103 ... Punch mold 110 ... Crystal part 120 ... Grain Boundary 130 ... conductor Part 150 ... Conductive particles 200 ... Resin material 300 ... Member showing varistor characteristics (structure)

Claims (6)

A DC motor comprising a stator and a rotor,
The stator includes a brush to which a DC voltage is applied from an external power source,
The rotor is
A rotation axis;
A barrel formed in a cylindrical shape and fixed to the rotating shaft;
A winding that generates a magnetic force by an electric current;
A commutator for passing the current through the windings by contact of the brush;
With
The commutator has a plurality of commutator pieces, each disposed with a predetermined gap in the circumferential direction on the outer peripheral surface of the body portion,
At least a part of a portion of the body portion that comes into contact with the plurality of commutator pieces is formed of a protective member that exhibits nonlinearity in which voltage-current characteristics do not follow Ohm's law.
DC motor. The protective member is a member formed in an annular shape, disposed inside the commutator piece, and in contact with the inner surface of each commutator piece on the outer peripheral surface.
The DC motor according to claim 1. The protective member is a member formed by laminating a varistor portion showing non-linearity in which the voltage-current characteristic does not follow Ohm's law, and a conductive electrode portion.
The DC motor according to claim 2. The trunk is
A cylindrical first portion that is formed of a non-conductor and covers the rotating shaft;
A cylindrical second part that is molded with the protective member, covers the first part, and contacts the inner surface of each commutator piece on the outer peripheral surface;
The DC motor according to claim 1, wherein A resin composition comprising:
Including a thermosetting resin and semiconductor ceramic particles;
The semiconductor ceramic particles have a grain boundary part and a plurality of crystal parts separated by the grain boundary part,
The cured product of the resin composition exhibits non-linearity in which voltage-current characteristics do not follow Ohm's law,
A plurality of rectifiers each provided with a predetermined gap in the circumferential direction on a rotating shaft, a cylindrically formed barrel portion fixed to the rotating shaft, a brush, a winding, and an outer circumferential surface of the barrel portion The resin composition used in order to form in at least one part of the site | part which contacts the said several commutator piece among the said trunk | drum in a direct current motor provided with the commutator which has a piece. A protective member that is molded from a resin composition and protects a transient voltage for a circuit to be protected,
The resin composition is
Including a thermosetting resin and semiconductor ceramic particles;
The semiconductor ceramic particles have a grain boundary part and a plurality of crystal parts separated by the grain boundary part,
The protective member exhibits non-linearity in which the voltage-current characteristic does not follow Ohm's law,
A plurality of rectifiers each provided with a predetermined gap in the circumferential direction on a rotating shaft, a cylindrically formed barrel portion fixed to the rotating shaft, a brush, a winding, and an outer circumferential surface of the barrel portion A member for a DC motor comprising a commutator having a child piece,
A protective member used as at least a part of a portion of the body portion that comes into contact with the plurality of commutator pieces.

Images