JP2007300704A - Electric motor and method of manufacturing commutator used therefor - Google Patents

Abstract

An object of the present invention is to reduce the man-hours for assembling an electric motor and reduce its cost.
A commutator 31 used in an electric motor has a body 64 formed in a cylindrical shape by a nonconductor, and a plurality of commutations fixed to the outer peripheral surface of the body 64 side by side with a predetermined interval in the circumferential direction. A child piece 34 is provided. A varistor material made of a pulverized product of a thermosetting resin and a semiconductor ceramic is molded inside each commutator piece 34 to form a varistor 71, and the varistor 71 is placed inside the body 64 by insert molding. Further, anchors are formed on the inner surface of each commutator piece 34, and these anchors are connected to the outer periphery of the varistor 71 to electrically connect each commutator piece 34 to the varistor 71. Thereby, the surge voltage generated at the sliding contact portion between the brush and the commutator 31 is absorbed by the varistor 71 to reduce the electromagnetic noise of the electric motor, and the number of steps for assembling the electric motor provided with the varistor 71 can be reduced. .
[Selection] Figure 5

Description

  The present invention includes an electric motor including a motor yoke provided with a field portion on an inner surface, an armature including a rotating shaft and a plurality of armature windings and rotatably accommodated in the motor yoke; The present invention relates to a method of manufacturing a commutator used in the electric motor.

  Vehicles such as automobiles are provided with electrical components such as a front wiper device, a rear wiper device, a power window device, and the like, and an electric motor with a brush is often used as a drive source for these electrical components.

  Such an electric motor with a brush has a motor yoke having a magnet mounted on the inner surface, and an armature is rotatably accommodated in the motor yoke. An armature core is fixed to the rotating shaft of the armature. A plurality of slots are formed in the armature core, and a plurality of armature windings are wound around the slots. In addition, the rotating shaft is fixed with a commutator including a resin body portion and a plurality of commutator pieces fixed to the outer peripheral surface of the body portion at predetermined intervals in the circumferential direction. Each commutator piece is connected to a corresponding armature winding. Further, the electric motor is provided with a plurality of power supply brushes to which a drive current is supplied from a power source, and these brushes are in sliding contact with the outer peripheral surface of the commutator while being urged by a spring. . As a result, when a drive current is supplied from the power source to the brush, the drive current is commutated by the commutator and supplied to each armature winding, and a rotational force is generated in the armature winding. Rotate.

  In such an electric motor with a brush, a drive current is supplied to each armature winding via the brush and the commutator, so that the brush contacts the armature due to the influence of the inductance of the armature winding. When the commutator piece is switched, a pulse-like abnormal voltage called a surge voltage is generated between the brushes. Since this surge voltage causes electromagnetic noise, if the electric motor is used as a drive source for an electrical component mounted on a vehicle, this electromagnetic noise may cause radio noise or malfunction of other electronic devices.

Therefore, for example, in the electric motor shown in Patent Document 1, a varistor that is a voltage stabilizing element is attached to a commutator, and the surge voltage and abnormal voltage generated between the brush and the commutator are absorbed by the varistor, thereby Electromagnetic noise generated by the motor is reduced.
Japanese Utility Model Publication No. 6-88176

  However, in the method of reducing the surge voltage using such a varistor, it is necessary to fix the varistor to the armature and to electrically connect each commutator piece and the varistor using solder or the like. As a result, the number of assembling steps for the electric motor increases. In particular, in an electric motor with a large number of poles, the number of commutator pieces provided on the commutator increases, and the space for installing the varistors is limited. It becomes difficult, and the assembly man-hour increases and becomes the factor which raises the cost of the electric motor.

  An object of the present invention is to reduce the number of man-hours for assembling an electric motor and reduce its cost.

  An electric motor according to the present invention includes a motor yoke provided with a field portion on an inner surface, and an armature that includes a rotating shaft and a plurality of armature windings and is rotatably accommodated in the motor yoke. A motor, which is formed in a cylindrical shape by a non-conductor and is fixed to the rotating shaft, and is fixed to the outer peripheral surface of the body with a predetermined interval in the circumferential direction. A commutator including a plurality of commutator pieces to be connected to each other and connected to a power source and in sliding contact with the outer peripheral surface of the commutator to supply a drive current to the armature winding through the commutator pieces A plurality of brushes, and a varistor formed in an annular shape and disposed inside the commutator piece, and connected to an anchor formed on an inner surface of each commutator piece at an outer periphery. And

  The electric motor of the present invention is characterized in that the anchor is formed in a rail shape extending along the axial direction of the commutator piece.

  The electric motor of the present invention is characterized in that a relief hole having a diameter larger than the outer diameter of the rotary shaft is formed on the inner peripheral surface of the body portion inside the varistor.

  The electric motor of the present invention includes a power supply circuit that supplies power to the brush, and the power supply circuit is provided with a capacitor that absorbs an abnormal voltage generated in the brush.

  The commutator manufacturing method of the present invention is a commutator manufacturing method used for an electric motor, and includes a commutator piece material forming step of forming a cylindrical commutator piece material from a conductive plate material, and thermosetting. A varistor material is mixed with a conductive resin to perform mold forming, and a varistor molding step of forming an annular varistor inside the commutator piece material, and holding the varistor formed inside the commutator piece material The body forming step of molding a cylindrical body portion with a nonconductor inside the commutator piece material, and the commutator piece material with the body portion formed on the inside is cut in the axial direction in the circumferential direction And a commutator piece forming step of forming a plurality of commutator pieces arranged at predetermined intervals.

  In the method of manufacturing a commutator according to the present invention, the varistor material is a material in which a thermosetting resin such as a phenol resin or an epoxy resin is mixed with a pulverized product of a semiconductor ceramic such as barium titanate or strontium titanate. Features.

  In the commutator manufacturing method of the present invention, an anchor formed in a rail shape extending in the axial direction is provided on the inner peripheral surface of the commutator piece material, and the varistor material is molded so as to cover the anchor. It is characterized by.

  According to the present invention, the varistor is arranged inside the commutator and connected to the commutator piece by being connected to the anchor of each commutator piece. The operation of connecting the piece and the varistor is unnecessary, and the operation of attaching the varistor to the armature can be facilitated. Thereby, the assembly man-hour of an electric motor can be reduced and the cost of this electric motor can be reduced. Further, since the varistor is provided in the commutator, the electric motor provided with the varistor can be reduced in size to reduce electromagnetic noise. Furthermore, since each commutator piece is fixed to the body part and is also connected to a varistor disposed inside the commutator piece, the strength of fixing each commutator piece to the body part can be increased.

  Further, according to the present invention, since the escape hole having a diameter larger than that of the rotating shaft is formed on the inner peripheral surface of the body portion inside the varistor, when the commutator is fixed to the rotating shaft by press fitting, the press-fitting is performed. It is possible to make it difficult to apply the load due to the varistor. Thereby, the load applied to the varistor during press-fitting can be suppressed, and damage to the varistor can be prevented.

  Furthermore, according to the present invention, the varistor is provided with a varistor, and the power supply circuit that supplies power to the brush is provided with a capacitor that absorbs the abnormal voltage of the brush. The noise of the frequency can be reduced by the capacitor, and the electromagnetic noise of the electric motor can be reduced in a wide frequency range.

  Furthermore, according to the present invention, since the varistor material mixed with the thermosetting resin is molded to form an annular varistor inside the commutator, each commutator piece The varistor can be easily connected to the anchor. Further, by forming each anchor into a rail shape extending along the axial direction of the commutator piece, a mold for forming the varistor material is inserted inside the commutator piece material so as to be movable along the anchor. This makes it easy to mold the varistor.

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

  FIG. 1 is a front view showing a wiper drive device including an electric motor according to an embodiment of the present invention. The wiper drive device 11 is attached to a vehicle (not shown) via a bracket 12 and is used to drive a rear wiper of the vehicle, and includes an electric motor 13 and a speed reducer 14.

  FIG. 2 is a cross-sectional view showing the internal structure of the wiper driving device shown in FIG. 1, and the electric motor 13 used in the wiper driving device 11 is a so-called brushed motor. And an armature 16 accommodated in the yoke 15. The motor yoke 15 is formed by drawing a steel plate with a press, and has a bottomed cylindrical shape with an oval cross section. A pair of magnets 17 (field portions) are fixed to the inner surface of the motor yoke 15 so that different magnetic poles face each other, and a magnetic field is formed inside the motor yoke 15 by these magnets 17. It has become.

  The armature 16 has a rotating shaft 18 and an armature core 21 fixed to the rotating shaft 18. The rotating shaft 18 is provided at the bottom of the motor yoke 15. As a result, the armature 16 is rotatable inside the motor yoke 15. The armature core 21 is disposed so as to be located in the magnetic field of the motor yoke 15, and 12 slots 23 extending in the axial direction are formed on the outer circumferential surface of the armature core 21. A child winding (an amateur coil) 24 is attached.

  The electric motor 13 is provided with a commutator (commutator) 31 and a pair of brushes 32 and 33 in order to supply a drive current to each armature winding 24. The commutator 31 is fixed to the rotary shaft 18 adjacent to the armature core 21, and each armature winding 24 is connected to a plurality of commutator pieces (segments) 34 constituting the commutator 31. . On the other hand, the brushes 32 and 33 are held by a brush holder 35 fixed to the motor yoke 15 while being biased toward the commutator 31 by a spring 36, and come into sliding contact with the outer peripheral surface of the commutator 31. Yes. Details of the commutator 31 will be described later.

  FIG. 3 is a circuit diagram showing a power feeding circuit of the electric motor shown in FIG. 1. The wiper driving device 11 is provided with a connector unit 41, and the brush unit 32, 33 is supplied with electric power inside the connector unit 41. A power feeding circuit 42 for supplying is provided. As shown in FIG. 2, the connector unit 41 is provided with a connection connector 44 connected to the wiper control device 43. The connection connector 44 includes a power input terminal 44a connected to the wiper control device 43, and A ground terminal 44b that is grounded to the vehicle body and an auto stop signal output terminal 44c that is connected to the wiper control device 43 are provided. One brush 32 of the electric motor 13 is connected to the power input terminal 44a, and the other brush 33 is connected to the ground terminal 44b. A wiper switch (not shown) is operated to drive the wiper control device 43 to the power input terminal 44a. When a current is supplied, this drive current is supplied to the brushes 32 and 33 so that the electric motor 13 operates. Further, a stop position detection switch 45 is provided between the brush 33 and the auto stop signal output terminal 44c. When the rear wiper arm driven by the wiper driving device 11 reaches the stop position, the stop position detection switch 45 is closed. Thus, a detection signal is output from the auto stop signal output terminal 44c. As a result, the wiper control device 43 can detect that the rear wiper arm is in the stop position, and when the wiper switch is stopped during the wiper operation, the electric motor is operated when the rear wiper arm is in the lower reverse position. 13 is stopped. Further, a capacitor 46 is connected between the power input terminal 44a and the ground terminal 44b, and a surge voltage or the like generated in the brushes 32, 33 due to the sliding contact between the brushes 32, 33 and the commutator 31 by the capacitor 46. The electromagnetic noise of the electric motor 13 is reduced by absorbing the low frequency component of the abnormal voltage. Reference numeral 47 represents a choke coil, and reference numeral 48 represents a circuit breaker.

  As shown in FIG. 2, the speed reducer 14 has a gear case 52 fixed to the electric motor 13 by a fastening member 51, and has a structure in which a worm gear mechanism 53 and a power conversion mechanism 54 are accommodated in the gear case 52. It has become. The worm gear mechanism 53 includes a worm 53a and a worm wheel 53b that meshes with the worm 53a. The worm 53a is integrally formed on the outer peripheral surface of the rotary shaft 18 protruding inside the gear case 52, and the worm wheel 53b is attached to the support shaft 55. The gear case 52 is supported so as to be rotatable. As a result, when the electric motor 13 is operated and the rotary shaft 18 rotates, the rotation is decelerated to a predetermined rotational speed and transmitted to the worm wheel 53b.

  As shown in FIG. 1, the gear case 52 is provided with a boss portion 52a protruding in a direction parallel to the support shaft 55, and an output shaft 56 is rotatably supported by the boss portion 52a. One end of the output shaft 56 protrudes to the outside from the boss portion 52a, and a rear wiper arm is attached to the tip of the output shaft 56. The other end of the output shaft 56 protrudes into the gear case 52, and an output gear 57 is fixed to the tip thereof.

  The power conversion mechanism 54 includes a power conversion member 58 that couples the worm wheel 53b and the output gear 57. The power conversion member 58 converts the rotational motion of the worm wheel 53b into a swinging motion and outputs it to the output shaft 56. To communicate. The power conversion member 58 is formed in the shape of a plate having an arm portion 58a and a sector gear portion 58b, and the tip of the arm portion 58a rotates on a connecting shaft 61 provided on the worm wheel 53b and shifted in the radial direction from the support shaft 55. It is connected freely. Further, the sector gear portion 58b of the power conversion member 58 is meshed with the output gear 57, and in order to maintain the meshing between the sector gear portion 58b and the output gear 57, a gear shaft 62 provided at the shaft center of the sector gear portion 58b and the output. The shaft 56 is connected to a swing plate 63 so as to be swingable. As a result, when the worm wheel 53b rotates, the power conversion member 58 reciprocates due to the rotational motion, and the reciprocating motion is converted into a swing motion by the sector gear portion 58b and the output gear 57 and output from the output shaft 56. . When the output shaft 56 swings, the rear wiper arm attached to the output shaft 56 swings between an upper reversing position and a lower reversing position on the rear glass, thereby performing a wiping operation of the rear wiper. Become.

  4 is a perspective view showing details of the commutator shown in FIG. 2, FIG. 5 is a cross-sectional view of the commutator shown in FIG. 4, and FIG. 6 is a cross-sectional view taken along line AA in FIG. Next, based on FIGS. 4-6, the detail of the commutator used for the electric motor of this invention is demonstrated.

  The commutator 31 used in the electric motor 13 includes a body portion 64 formed in a cylindrical shape from a resin material that is a nonconductor. An attachment hole 65 is formed in the shaft center of the body portion 64, and the body portion 64, that is, the commutator 31 is fixed to the rotation shaft 18 by press-fitting the rotation shaft 18 into the attachment hole 65. Yes. Here, the non-conductor is a non-conductive member, that is, a member having electrical insulation.

  Further, as described above, the commutator 31 has twelve commutator pieces 34, and these commutator pieces 34 are each formed of a copper plate as a conductor, and as shown in FIG. Two anchors 66 are formed on the inner surface of the child piece 34. These anchors 66 are formed in the shape of rails that extend along the axial direction of the rotary shaft 18 and project toward the body 64, and each commutator piece 34 has a projecting direction opposite to the circumferential direction. Two anchors 66 are provided. Each anchor 66 protruding in the opposite direction protrudes toward the trunk portion 64, whereby a part of the trunk portion 64 is sandwiched between the anchors 66, whereby the anchor 66 is engaged with the trunk portion 64. Each commutator piece 34 is fixed to the outer peripheral surface of the body portion 64. Thereby, even if the electric motor 13 rotates, each commutator piece 34 is not easily detached from the body portion 64. In addition, slits 67 are provided between the respective commutator pieces 34, and the respective commutator pieces 34 are arranged on the outer peripheral surface of the body portion 64 at predetermined intervals in the circumferential direction by the slits 67. As a result, the commutator pieces 34 are electrically insulated from each other. Further, each commutator piece 34 is provided with a hook portion 68, and the corresponding armature winding 24 is electrically connected to these hook portions 68.

  Although a plurality of commutator pieces 34, anchors 66, slits 67, and hook portions 68 are provided, only one of them is provided with a reference numeral in the drawing.

  The brushes 32, 33 are in sliding contact with the outer peripheral surface of each commutator piece 34, and when the drive current from the wiper control device 43 is supplied to the brushes 32, 33, the brushes 32, 33 rectify. A drive current is supplied to each armature winding 24 via the piece 34. Further, when the armature 16 rotates together with the rotating shaft 18, the commutator piece 34 that is in contact with the brushes 32 and 33 is switched, whereby the armature winding 24 to which the drive current is supplied and the energization to the armature winding 24. The direction is switched sequentially. That is, a drive current commutated at a timing corresponding to the magnetic field generated by the magnet 17 is supplied to each armature winding 24. As a result, an electromagnetic force in a predetermined rotation direction is generated in each armature winding 24 located in the magnetic field, and the armature 16 rotates. The wiper control device 43 includes a CPU and a memory (not shown) and functions as a microcomputer. The wiper control device 43 outputs a driving current in response to a command signal of a wiper switch (not shown) to operate the electric motor 13. It comes to control.

  FIG. 7 is a cross-sectional view taken along line B-B in FIG. 5. The commutator 31 includes a varistor 71 in order to reduce electromagnetic noise generated from a sliding contact portion between the brushes 32 and 33 and the commutator 31. It is installed.

  The varistor 71 is formed in an annular shape by molding a varistor material that is mixed with a thermosetting resin and is plasticized by heat, for example, compression molding. It is arranged inside the commutator 31, that is, the body portion 64 so as to be located inside.

  Here, the varistor material is a mixture of 200 to 1000 parts by weight of a pulverized semiconductor ceramic such as barium titanate or strontium titanate with respect to 100 parts of thermosetting resin such as phenol resin or epoxy resin. More preferably, it is preferable to mix 300 to 500 parts by weight of a pulverized semiconductor ceramic. In addition, the thermosetting resin forming the varistor material has plasticity at room temperature, and thus the varistor material also has plasticity at room temperature. On the other hand, the thermosetting resin has a property of being cured by being heated, and as a result, the molded varistor material is cured by heat at the time of being insert-molded into the body portion 64 as described later. It becomes a varistor 71.

  The varistor 71 is partly sandwiched between the anchors 66 in the same manner as the body 64, so that the varistor 71 is connected to the anchors 66, that is, the commutator pieces 34 at the outer periphery. ing. Accordingly, each commutator piece 34 is fixed to the body portion 64 and also connected to the varistor 71 disposed inside the body portion 64, so that the strength of fixing each commutator piece 34 to the body portion 64 is increased. be able to. The varistor 71 is electrically connected to each commutator piece 34 by being connected to the anchor 66 so that the voltage of the brushes 32 and 33 is applied via the commutator piece 34. It has become.

  An escape hole 72 is formed on the inner peripheral surface of the body portion 64 on the inner side of the varistor 71 so as to be aligned with the mounting hole 65. The escape hole 72 is formed to have a larger diameter than the inner diameter of the mounting hole 65, that is, the outer diameter of the rotating shaft 18, and the rotating shaft 18 is inserted into the mounting hole 65 of the trunk portion 64 in order to fix the commutator 31 to the rotating shaft 18. Even if press-fitted, a gap is formed between the escape hole 72 and the rotary shaft 18. Therefore, even if the commutator 31 is fixed to the rotary shaft 18 by press-fitting, a large load is not applied to the varistor 71, and damage to the varistor 71 can be prevented.

  As described above, in the electric motor 13, the escape hole 72 having a diameter larger than that of the rotary shaft 18 is formed on the inner peripheral surface of the body portion 64 inside the varistor 71. The load applied to the varistor 71 when it is fixed to 18 can be suppressed, and the varistor 71 can be prevented from being damaged.

  The varistor 71 has a function as a voltage stabilizing element. When an abnormal voltage such as a surge voltage is generated in the brushes 32 and 33 due to the sliding contact between the brushes 32 and 33 and the commutator 31, a high frequency of the abnormal voltage is generated. The component is applied to the varistor 71 through each commutator piece 34 and absorbed by the varistor 71. Thereby, the electromagnetic noise which this electric motor 13 emits can be reduced. That is, in the electric motor 13, the low frequency component of the electromagnetic noise is absorbed by the capacitor 46, and the high frequency component of the electromagnetic noise is absorbed by the varistor 71 to suppress the electromagnetic noise of each frequency.

  Thus, in this electric motor 13, since the varistor 71 is provided inside the commutator 31, the electric motor 13 can be reduced in size even if the varistor 71 for reducing electromagnetic noise is provided. it can.

  In the electric motor 13, the commutator 31 is provided with the varistor 71 and the power supply circuit 42 that supplies power to the brushes 32 and 33 is provided with the capacitor 46. Therefore, the high-frequency electromagnetic noise is reduced by the varistor 71. At the same time, low frequency electromagnetic noise can be reduced by the capacitor 46, and electromagnetic noise generated by the electric motor 13 can be reduced in a wide frequency range.

  FIGS. 8A to 8C are perspective views showing a procedure for forming a commutator piece material, and FIGS. 9A to 9C show a procedure for molding a varistor inside the commutator piece material. FIGS. 10A and 10B are cross-sectional views showing a procedure for molding a body portion on a commutator piece material, and FIG. 11 is a front view showing a state where the commutator piece material is divided. is there. Next, a method for manufacturing the commutator 31 will be described with reference to FIGS.

  First, a conductive plate material (copper plate) is stamped by a press to form a blank material 81 that is the basis of the commutator piece material. As shown in FIG. 8A, the blank 81 is formed in a substantially rectangular shape, and twelve hook portions 68 are arranged at equal intervals on one side.

  Next, in the commutator piece material forming step, the blank material 81 is rounded so that both sides in the longitudinal direction face each other, and a cylindrical commutator piece material 82 is formed as shown in FIG. Each hook portion 68 is bent into a hook shape.

  Next, as shown in FIG. 8C, the anchor 66 is formed on the inner peripheral surface of the commutator piece material 82 by shaving. The shaving process is performed by inserting a die having a predetermined outer shape into the commutator piece material 82 to cut the inner peripheral surface of the commutator piece material 82. The number of anchors 66 corresponding to each hook portion 68 is formed by this shaving process.

  Next, as shown in FIGS. 9A to 9C, in the varistor molding process, the varistor material mixed with the thermosetting resin and in a plastic state is molded by compression molding and commutator piece material 82 is obtained. An annular varistor 71 is formed inside.

  That is, as shown in FIG. 9A, first, the first molding die 83 inserted from one side in the axial direction is disposed inside the commutator piece material 82. The first mold 83 is formed in an outer shape having grooves (not shown) corresponding to the anchors 66 on the outer peripheral surface, and is axially along the inner peripheral surface of the commutator piece material 82 and the anchors 66. It is possible to move to.

  Next, as described above, the inside of the commutator piece material 82 is formed so that the varistor materials 84 formed by mixing the thermosetting resin and the pulverized semiconductor ceramic are gathered into an annular shape and come into contact with the first mold 83. Set to 9B, the second mold 85 is inserted into the commutator piece material 82 from the other side in the axial direction, and between the first mold 83 and the second mold 85. The varistor material 84 is compression-molded by sandwiching the annular varistor material 84. At this time, the varistor material 84 is compressed and formed so as to cover each anchor 66 and fill the inside of each anchor 66. As with the first molding die 83, the second molding die 85 is also formed in an outer shape having grooves (not shown) corresponding to the anchors 66 on the outer peripheral surface. It is possible to move in the axial direction along the peripheral surface and each anchor 66.

  Next, as shown in FIG. 9C, the respective molds 83, 85 are removed from the commutator piece material 82, and an annular varistor 71 is formed inside the commutator piece material 82. The varistor 71 formed in this way is formed into a shape in which the outer peripheral portion of the varistor material 84 is engaged with and connected to the anchor 66 when the varistor material 84 is also filled inside each anchor 66.

  When the varistor 71 is formed inside the commutator piece material 82, next, as shown in FIGS. 10A and 10B, in the body forming process, the combustor piece material 82 is formed inside the commutator piece material 82 by injection molding. A cylindrical body 64 having a mounting hole 65 is formed from a resin material which is a nonconductor using a molding die (not shown). The body portion 64 is formed so as to hold the varistor 71, and the varistor 71 is disposed inside the body portion 64, that is, inside each commutator piece 34. That is, the body 64 is formed by insert molding so as to embed the varistor 71 therein. Further, the thermosetting resin constituting the varistor 71 is cured by the heated resin material, and the varistor 71 is cured in a predetermined shape. Further, when the body 64 is molded, each anchor 66 formed on the commutator piece material 82 is also filled with the resin material, whereby each anchor 66 is fixed to the body 64 when the resin material is cured. It is like that.

  When the body 64 is formed, the commutator piece material 82 is then undercut in the axial direction by the commutator piece forming step, and twelve slits 67 are formed as shown in FIG. As a result, the commutator piece material 82 is divided into twelve commutator pieces 34. At this time, as can be seen from FIG. 6, the slit 67 is formed at a depth reaching the body portion 64 from the outer peripheral surface of the commutator piece material 82, and each commutator piece 34 is formed on the body portion 64 by the anchor 66 corresponding thereto. It becomes a state fixed to the outer periphery and is divided into each other. Thus, the divided commutator pieces 34 are fixed to the outer peripheral surface of the body portion 64 side by side with a predetermined interval in the circumferential direction, and are electrically insulated from each other. Further, as shown in FIG. 7, each commutator piece 34 is connected to the outer peripheral portion of the varistor 71 by an anchor 66 corresponding to the commutator piece 34, thereby increasing the fixing strength to the trunk portion 64.

  When each commutator piece 34 is formed, a post-process such as an after-curing process for heating the body portion 64 to increase heat resistance is performed, and the commutator 31 shown in FIG. 4 is completed.

  As described above, in this electric motor 13, the varistor material is molded to form the annular varistor 71 inside the commutator 31, so that the varistor 71 connected to the anchor 66 of each commutator piece 34. Can be easily formed. Further, since each anchor 66 formed inside the commutator piece material 82 is formed in a rail shape extending in the axial direction, each molding die 83, with an outer shape provided with a groove corresponding to these anchors 66 is provided. By forming 85, each mold 83, 85 can be moved in the axial direction along the inner peripheral surface of each commutator piece material 82 and each anchor 66. Thereby, the molding of the varistor 71 can be facilitated.

  Further, in this electric motor 13, by arranging the varistor 71 inside the commutator 31, the inner surface of each commutator piece 34 and the varistor 71 can be connected, so that wiring, connecting members, etc. are used. Thus, the work of connecting each commutator piece 34 and the varistor 71 becomes unnecessary, and the work of attaching the varistor 71 to the armature 16 can be facilitated. Therefore, the number of assembling steps for the electric motor 13 can be reduced, and the cost of the electric motor 13 can be reduced.

  Further, each commutator piece 34 is fixed to the body portion 64 and also connected to the varistor 71 disposed inside the body portion 64, so that the strength of fixing each commutator piece 34 to the body portion 64 is increased. be able to.

  FIG. 12 is a cross-sectional view showing a fan motor according to another embodiment of the present invention. In FIG. 12, the members corresponding to the members described above are denoted by the same reference numerals.

  In the case shown in FIG. 1, the electric motor 13 of the present invention is used as a drive source of the wiper drive device 11. However, as shown in FIG. 12, the electric motor of the present invention is used as a fan motor 91. Also good. The fan motor 91 drives a cooling fan (not shown) for cooling a radiator or the like provided in the vehicle, and is disposed in the engine room of the vehicle. Therefore, by providing the varistor 71 in the commutator 31 of the fan motor 91, electromagnetic noise generated from the fan motor 91 is reduced, and malfunction of electronic equipment or the like disposed in the engine room or in the vicinity thereof is prevented. can do.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the present embodiment, the electric motor 13 to which the commutator 31 of the present invention is applied is used for the wiper driving device 11 and the fan motor 91 of the vehicle, but is not limited to this, for example, a power window device. It may also be used for other purposes such as driving sources such as sunroof devices and sliding door opening and closing devices.

  Further, in this embodiment, the commutator 31 is provided with twelve commutator pieces 34, but the number is not limited to this, and the number can be variously changed according to the specification of the electric motor 13 to be applied. It is.

It is a front view which shows the wiper drive device provided with the electric motor which is one embodiment of this invention. It is sectional drawing which shows the internal structure of the wiper drive device shown in FIG. It is a circuit diagram which shows the electric power feeding circuit of the electric motor shown in FIG. It is a perspective view which shows the detail of the commutator shown in FIG. It is sectional drawing of the commutator shown in FIG. It is sectional drawing which follows the AA line in FIG. It is sectional drawing which follows the BB line in FIG. (A)-(c) is a perspective view which shows the procedure which forms a commutator piece raw material. (A)-(c) is sectional drawing which shows the procedure which molds a varistor inside the commutator piece raw material. (A), (b) is sectional drawing which shows the procedure which molds a trunk | drum to a commutator piece raw material. It is a front view which shows the state which divided | segmented the commutator piece raw material. It is sectional drawing which shows the fan motor which is other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Wiper drive device 12 Bracket 13 Electric motor 14 Reduction gear 15 Motor yoke 16 Armature 17 Magnet 18 Rotating shaft 21 Armature core 22 Bearing 23 Slot 24 Armature winding 31 Commutator 32, 33 Brush 34 Commutator piece 35 Brush holder 36 Spring 41 Connector unit 42 Power supply circuit 43 Wiper control device 44 Connection connector 44a Power input terminal 44b Ground terminal 44c Auto stop signal output terminal 45 Stop position detection switch 46 Capacitor 47 Choke coil 48 Circuit breaker 51 Fastening member 52 Gear case 52a Boss part 53 Warm gear Mechanism 53a Worm 53b Worm wheel 54 Power conversion mechanism 55 Support shaft 56 Output shaft 57 Output gear 58 Power conversion member 58a Arm portion 58b Sector gear portion DESCRIPTION OF SYMBOLS 1 Connection shaft 62 Gear shaft 63 Oscillation plate 64 Body part 65 Mounting hole 66 Anchor 67 Slit 68 Hook part 71 Varistor 72 Escape hole 81 Blank material 82 Commutator piece material 83 1st shaping | molding die 84 Varistor material 85 2nd shaping | molding die 91 Fan motor

Claims (7)

An electric motor comprising a motor yoke provided with a field part on the inner surface, and an armature that includes a rotating shaft and a plurality of armature windings and is rotatably accommodated inside the motor yoke,
A cylindrical portion formed of a non-conductor and fixed to the rotating shaft, and a plurality of portions that are fixed to the outer peripheral surface of the barrel portion in a circumferential direction with a predetermined interval and are connected to the armature windings. A commutator with a commutator piece;
A plurality of brushes each connected to a power source and in sliding contact with the outer peripheral surface of the commutator, and supplying a drive current to the armature winding via the commutator piece;
An electric motor comprising: a varistor formed in an annular shape, disposed inside the commutator piece, and connected to an anchor formed on an inner surface of each commutator piece at an outer peripheral portion.   The electric motor according to claim 1, wherein the anchor is formed in a rail shape extending along an axial direction of the commutator piece.   The electric motor according to claim 2, wherein an escape hole having a diameter larger than the outer diameter of the rotating shaft is formed on an inner peripheral surface of the body portion inside the varistor.   The electric motor according to claim 1, further comprising a power supply circuit that supplies power to the brush, wherein the power supply circuit is provided with a capacitor that absorbs an abnormal voltage generated in the brush. Electric motor. A method of manufacturing a commutator used in an electric motor,
A commutator piece material forming step of forming a cylindrical commutator piece material from a conductive plate material;
A varistor molding process in which a varistor material is mixed with a thermosetting resin to perform molding, and an annular varistor is formed inside the commutator piece material;
A body forming step of molding a cylindrical body with a nonconductor inside the commutator piece material so as to hold the varistor formed inside the commutator piece material;
And a commutator piece forming step of forming a plurality of commutator pieces arranged in the circumferential direction at predetermined intervals by cutting the commutator piece material having a body portion formed therein in an axial direction. A method for manufacturing a commutator.   6. The commutator manufacturing method according to claim 5, wherein the varistor material is a material in which a thermosetting resin such as a phenol resin or an epoxy resin is mixed with a pulverized product of a semiconductor ceramic such as barium titanate or strontium titanate. A method of manufacturing a commutator characterized by the above.   The commutator manufacturing method according to claim 5 or 6, wherein an anchor formed in a rail shape extending along an axial direction is provided on an inner peripheral surface of the commutator piece material, and the varistor material is disposed so as to cover the anchor. A method of manufacturing a commutator, characterized by molding.

Images