JP5693114B2 - DC motor - Google Patents

Description

  The present invention relates to a DC motor.

  DC motors (hereinafter also simply referred to as “motors”) are used in a variety of fields and applications, ranging from electrical equipment such as automobiles, audio / video equipment, or home appliances to toys, models, and electric tools.

  Since such a motor is required to reduce electric noise generated during operation, a motor in which an electric element such as a capacitor or a choke coil is connected to a circuit constituting the motor is known. Patent Document 1 discloses an electric motor in which an end portion of a winding electrically connected to a carbon brush is passed through an insulating tube, and the insulating tube is disposed so as to pass through a ferrite ring. . In this electric motor, a plurality of ferrite rings are fixed to a brush holding substrate.

Japanese Utility Model Publication No. 57-201063

  However, in the above-described electric motor, since the windings penetrating the ferrite ring are covered with the insulating tube, the diameter of the ferrite ring becomes large if an attempt is made to achieve sufficient electrical noise prevention performance. On the other hand, if an attempt is made to achieve electrical noise prevention performance by providing a plurality of ferrite rings without increasing the diameter, the size of the electric motor will be increased.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a small DC motor in which measures against electric noise are taken.

  In order to solve the above problems, a DC motor according to an aspect of the present invention includes a yoke, a magnet that is provided along the inner surface of the yoke and has a plurality of magnetic poles in the circumferential direction, and an armature that is disposed to face the magnet. , A shaft inserted and fixed on the rotation shaft of the armature, a commutator attached to the shaft so as to be coaxial with the armature, a pair of brushes slidably in contact with the commutator, and wiring used for power supply to the pair of brushes And an annular member made of a ferromagnetic material made of a metal oxide. The annular member is provided so that the exposed conductor portion of the wiring is located at the center thereof.

  According to this aspect, the annular member made of the ferromagnetic material made of the metal oxide is provided so that the exposed conductor portion of the wiring is located at the center thereof. Therefore, the inner peripheral part of the annular member can be brought closer to the outer peripheral part of the conductor part, and the effect of noise suppression is enhanced. Moreover, since the inner peripheral part of the annular member is reduced in diameter, the outer peripheral part of the annular member can also be reduced in diameter, and the annular member can be reduced in size. As a result, the DC motor itself is also reduced in size.

  A resin brush holder connected to the yoke and supporting the brush may be further provided. The annular member and the wiring may be disposed on the brush holder. Thereby, an annular member and wiring can be stored in a DC motor.

  The magnet may have four magnetic poles in the circumferential direction. The pair of brushes are arranged so that the longitudinal directions thereof are orthogonal to each other, and the annular member is on a support surface on which the annular member is supported by the brush holder and other than the region sandwiched between the pair of brushes. It may be disposed on the region. Since the pair of brushes are arranged so that their longitudinal directions are orthogonal to each other, the region between them is relatively narrow. Therefore, by arranging the annular member in a region other than the region sandwiched between the pair of brushes, the pair of brushes and the annular member can be laid out effectively using the region on the support surface of the brush holder.

  The wiring is composed of a first wiring that is electrically connected to one of the pair of brushes, and a second wiring that is electrically connected to the other of the pair of brushes. You may be comprised from the 1st cyclic | annular member which has passed through, and the 2nd cyclic | annular member in which the conductor part which the 2nd wiring exposed passes the center part. Thereby, since a separate annular member can be provided for every wiring, each annular member can be reduced in size. Moreover, compared with the case where a plurality of wires are passed through the central portion of one annular member, the inner peripheral portion of the annular member can be brought closer to the outer peripheral portion of the conductor portion, and the effect of noise suppression is enhanced.

  A capacitor connected to the wiring may be provided. One end of the capacitor may be connected to the exposed conductor portion of the wiring at a position away from the annular member with respect to the brush. As a result, the capacitor can be housed in the DC motor, and the effect of noise suppression is further enhanced.

  The annular member may be a ferrite core. Thereby, cost can be reduced compared with the case where a choke coil is used as a noise countermeasure component. The arrangement of the ferrite core does not require a time-consuming process such as soldering like a choke coil, and contributes to a reduction in manufacturing cost.

  The inner diameter of the annular member is equal to or greater than the outer diameter of the conductor portion of the wiring, the inner diameter of the annular member is 0.5 to 6 [mm], and the outer diameter of the conductor portion is 0.5 to 3.0 [mm]. ].

  The wiring may have an exposed portion where the conductor portion is exposed and a coating portion where the conductor portion is covered with an insulating material. The outer diameter of the coating portion is larger than the outer diameter of the exposed portion. Thereby, the case where the annular member is arranged so as to surround the exposed portion is closer to the outer peripheral portion of the conductor portion than the case where the annular member is arranged so as to surround the coating portion. The noise suppression effect is enhanced.

  ADVANTAGE OF THE INVENTION According to this invention, the small DC motor by which the countermeasure against the electrical noise was taken can be provided.

It is a front view of the DC motor which concerns on embodiment. FIG. 2 is a side view of the DC motor viewed from the direction A in FIG. 1. FIG. 2 is a side view of the DC motor viewed from a direction B in FIG. 1. FIG. 4 is a cross-sectional view taken along the line C-C ′ of FIG. 3. It is a top view of a commutator. It is the side view which looked at the metal case with which the magnet was fixed inside from the opening side. It is the side view which looked at the metal case with which the magnet was fixed inside and the armature was accommodated from the opening side. It is a top view which shows the state which mounted each component in the brush holder which concerns on embodiment. It is a top view of the brush holder which concerns on embodiment. It is a perspective view of the brush holder which concerns on embodiment. FIG. 11A is a cross-sectional view of the ferrite core according to the embodiment. It is an enlarged view of the area | region D shown in FIG. It is EE sectional drawing of FIG. FIG. 14A, FIG. 14B, and FIG. 14C are diagrams for explaining the layout of each component on the brush holder in the motor of the modified example. FIG. 15A and FIG. 15B are diagrams for explaining the layout of each component on the brush holder in the two-pole motor according to the modification. FIG. 16A and FIG. 16B are diagrams for explaining the layout of each component on the brush holder in the two-pole motor according to the modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. Moreover, the structure described below is an illustration and does not limit the scope of the present invention at all.

  Conventionally, depending on the application of a motor, a prescribed measure against electric noise has been required. There are also fields where electric noise countermeasures will be required in the future, such as electric tools. As a countermeasure against electric noise of a motor, there is a built-in ceramic capacitor or choke coil. A choke coil generally has a high component cost. In addition, when the choke coil is built in the motor, the number of parts is increased due to electrical connection, and the number of man-hours is required for connection, resulting in an increase in manufacturing cost.

  On the other hand, as a countermeasure against electric noise, there is a method using a ferrite core. Since the ferrite core is relatively inexpensive, it is preferable from the viewpoint of cost reduction. However, when a ferrite core is used, it is often used through a lead wire drawn out from the motor. Therefore, it is disadvantageous for downsizing the mechanism on which the motor is mounted.

  As a result of intensive studies based on such knowledge, the present inventor has devised a technique that can achieve both a reduction in the size of a motor and measures against electric noise. This technology employs a configuration that can reduce the size of the ferrite core while satisfying the electrical noise suppression performance. In addition, the ferrite core can be miniaturized so that it can be built into the motor. In addition, a structure has been devised to securely fix the ferrite core to the motor without cracks.

  FIG. 1 is a front view of a DC motor according to an embodiment. FIG. 2 is a side view of the DC motor as viewed from the direction A in FIG. FIG. 3 is a side view of the DC motor viewed from the direction B of FIG. 4 is a cross-sectional view taken along the line C-C ′ of FIG. 3.

  As shown in FIGS. 1 to 3, a DC motor (simply referred to as “motor”) 10 is configured by a rotor (rotor) 14 housed in a cylindrical housing 12. The housing 12 is constructed by assembling a bottomed cylindrical metal case 16 that also functions as a yoke and a cylindrical resin brush holder 18. An annular auxiliary yoke 19 is fixed to the outer periphery of the metal case 16. The auxiliary yoke 19 is a steel plate that is supplementarily wound around the metal case 16 in order to reduce the leakage magnetic flux from the housing 12.

  The metal case 16 and the auxiliary yoke 19 also function as a yoke that forms a magnetic circuit. A cylindrical field magnet (simply referred to as “magnet”) 20 is fixed to the inner peripheral surface of the metal case 16, and both are stators. Is configured. A boss 17 is formed at the center of the bottom of the metal case 16 so as to protrude slightly outward and accommodates a bearing described later.

  The rotor 14 is configured by providing an armature 24, a commutator 26, and the like on a shaft 22 serving as a rotation axis. The shaft 22 is inserted along the axis of the housing 12 and is inserted along the rotation axis of the armature 24 and is fixed to the armature 24. The armature 24 is disposed so as to face the magnet 20. The brush holder 18 is provided with a pair of carbon brushes 30 arranged to face the commutator 26. The pair of carbon brushes 30 are arranged so that their longitudinal directions intersect each other. In the present embodiment, the pair of carbon brushes 30 are arranged so that their longitudinal directions intersect at approximately 90 °. A lead wire 32 for electrical connection with an electrical component (not shown) is attached to the brush holder 18 in series with the carbon brush 30. The lead wire 32 functions as a wiring used for power feeding to the pair of carbon brushes 30.

  The brush holder 18 is assembled so as to be inserted into the metal case 16 in the state of the brush holder assembly to which the lead wire 32 is attached. After assembling the brush holder assembly in this manner, the brush holder assembly is fixed to the opening of the metal case 16. The brush holder 18 has an outer shape substantially the same shape as the opening of the metal case 16 and is inserted and fitted into the opening. The end plate 36 is fixed to the metal case 16 so as to cover the carbon holder 31 and the lead wire 32 provided in the brush holder 18.

  A boss 39 is formed in the center of the end plate 36 so as to protrude slightly outward, and a slide bearing 37 made of a so-called oilless metal which is ring-shaped and impregnated with lubricating oil is press-fitted. An insertion hole is provided at the bottom of the boss portion 39 coaxially with the sliding bearing 37. One end side of the shaft 22 passes through the insertion hole and is exposed to the outside. Although the sliding bearing 37 can be provided in the brush holder 18 instead of the end plate 36, the configuration of the present embodiment, which is held by the end plate 36 made of metal, is more resistant to changes in temperature and humidity than the resin, and the motor. Since the expansion and contraction of the volume due to changes in the operating temperature and humidity environment are small, the coaxiality of the shaft 22 can be improved, and the rotor 14 can be maintained in a highly accurate and stable rotational state.

  As shown in FIG. 4, the internal space of the housing 12 is formed so as to be surrounded by the metal case 16 and the brush holder 18. On the other hand, the sliding bearing 41 is also press-fitted into the boss portion 17 of the metal case 16. The sliding bearing 41 is inserted through the end of the shaft 22 and supports the shaft 22 rotatably. The boss portion 17 has an opening at the center so that one end of the shaft 22 can protrude.

  The armature 24 includes a core 46 press-fitted into the shaft 22 and a winding 48 wound around the core 46, and the outer peripheral surface of the core 46 is separated from the inner peripheral surface of the magnet 20 with a predetermined clearance ( They are arranged opposite each other with a magnetic gap. Details of the magnetic pole configuration by the magnet 20 and the core 46 will be described later.

  The commutator 26 has a cylindrical shape and is press-fitted into the shaft 22 at a position facing the carbon brush 30 when the brush holder 18 is assembled to the metal case 16, and is coaxial with the armature 24. Is attached. A cylindrical carbon holder 31 (see FIG. 3) is fixed to the brush holder 18, and the carbon brush 30 is inserted into and supported by the carbon holder 31. Further, the carbon brush 30 is positioned so as to be in sliding contact with the outer peripheral surface of the commutator 26 in this state.

  FIG. 5 is a top view of the commutator 26. The commutator 26 has ten commutator pieces 26a. Each commutator piece 26a made of a conductor is divided by a slit 26c on the circumference of a commutator core 26b made of an insulator, and ends thereof are bent to form an electric wire connection portion 26d. .

  FIG. 6 is a side view of the metal case 16 in which the magnet 20 is fixed as viewed from the opening side. FIG. 7 is a side view of the metal case 16 in which the magnet 20 is fixed and the armature 24 is accommodated as viewed from the opening side. In FIG. 6, other parts are omitted for explaining the magnetic poles of the magnet 20. FIG. 7 shows a state in which the armature is inserted into the metal case, and the winding is omitted.

  The outer surface of the magnet 20 is fixed to the inner surface of the metal case 16 with an adhesive. The magnet 20 is composed of four arc-shaped members 20a, and each member 20a is disposed at a predetermined position at intervals in the circumferential direction. The magnet 20 is configured such that the center of an imaginary circle formed by the inner peripheral surfaces of the four arc-shaped members 20a coincides with the axial center of the armature 24, and each magnetic pole is formed on each member 20a. ing.

  That is, the magnet 20 is a four-pole field cylindrical tube in which a magnetic pole 60 (N pole), a magnetic pole 61 (S pole), a magnetic pole 62 (N pole), and a magnetic pole 63 (S pole) are provided at equal intervals in the circumferential direction. Consists of the body. The magnet 20 can be formed by fixing it to the metal case 16 and then magnetizing it from the outside of the metal case 16 by a magnetic field generator. However, since the magnetization technique is known, detailed description thereof will be omitted. The magnet 20 may be a single annular member.

The magnet 20 according to the present embodiment is made of a material having a maximum energy product BHmax of ^{3 to} 6 MGOe (23.9 to 47.8 kJ / m ³ ). Examples of such a material include a sintered body of ferrite, a material in which ferrite is dispersed in plastic, and a material in which a plurality of types of magnetic materials are dispersed in plastic. A magnet having the maximum energy product as described above can be manufactured with a low-cost material.

  On the other hand, as shown in FIG. 7, the core 46 has five magnetic poles 64 to 68 extending radially from the central cylindrical portion press-fitted into the shaft 22, and a winding is wound around each magnetic pole. An insulating coating powder is applied between the core 46 and the winding.

  Next, the configuration and arrangement of the ferrite core, the capacitor, the carbon brush 30, the carbon holder 31, the lead wire 32, and the like mounted on the brush holder 18 will be described in detail. FIG. 8 is a top view showing a state in which each component is mounted on the brush holder 18 according to the embodiment. FIG. 9 is a top view of the brush holder 18 according to the embodiment. FIG. 10 is a perspective view of the brush holder 18 according to the embodiment.

  The brush holder 18 has a bottomed cylindrical shape and is formed in a circular shape like the metal case 16. An opening 66 through which the commutator 26 and the shaft 22 can be inserted is formed in the center of the brush holder 18 in the axial direction, and various functional parts are optimally disposed around the opening 66 so as to effectively use the space. The axial direction of the brush holder 18 is the length direction of the shaft 22 inserted through the brush holder 18.

  A pair of cylindrical carbon holders 31a and 31b (hereinafter referred to as “carbon holder 31” as appropriate) are fixed to the left region (see FIG. 8) of the brush holder 18 so as to form 90 degrees in the circumferential direction. Carbon brushes 30a and 30b (hereinafter referred to as “carbon brushes” as appropriate) are slidably accommodated inside. Each of the carbon holders 31a and 31b is formed of a long cylindrical body having a quadrangular cross section made of a conductive metal, and is disposed so as to extend along the radial direction from the axial center of the brush holder 18.

  The carbon brush 30 has a long prismatic shape having a rectangular cross section, and is slidably inserted into and supported by the carbon holder 31. Thereby, when the metal case 16, the rotor 14, and the brush holder assembly are assembled, the carbon brush 30 is disposed so as to extend on a line connecting the peripheral portion of the brush holder 18 and the axial center of the commutator 26. Become so. In the present embodiment, the line connecting the axis center and the peripheral portion is also on the diagonal line of the brush holder 18.

  A torsion spring 70 is disposed at the periphery of the brush holder 18 and beside the carbon holder 31. The torsion spring 70 is supported by the winding portion 71 being inserted into and supported by a boss portion 68 disposed close to the side surface portion of the brush holder 18, and one end portion 72 extending from the winding portion 71 is disposed behind the carbon brush 30. It abuts on the end face. The other end portion 73 extending from the winding portion 71 is fixed to the bottom portion of the brush holder 18. The torsion spring 70 accumulates an urging force at the winding portion 71, and the one end portion 72 transmits the urging force to the carbon brush 30 and urges the commutator 26.

  A slit (not shown) along the stroke direction of the carbon brush 30 is provided on the surface of the carbon holder 31 facing the torsion spring 70. Thereby, even if the carbon brush 30 is stroked toward the commutator 26, the one end portion 72 of the torsion spring 70 is displaced through the slit, and an urging force can always be applied to the carbon brush 30. That is, even if the carbon brush 30 is worn and shortened with aging, a stable contact state with the commutator 26 can be maintained. On the other hand, by providing the winding portion 71 of the torsion spring 70 at a position off the extended line of the stroke range of the carbon brush 30, it is possible to select the carbon brush 30 as long as possible in advance, and the carbon brush 30 itself. As a result, the life of the motor 10 can be increased.

  In the interior space of the brush holder 18, two ferrite cores 76, two capacitors 78, and the like are further disposed. The two ferrite cores 76 that are annular members are electrical noise erasing members, and are respectively disposed in regions between the holding portion 80 and the carbon holder 31 that are fitted and held in the middle of the lead wires 32. As described above, the ferrite core 76 and a part of the lead wire 32 according to the present embodiment are disposed on the brush holder 18. Thereby, a part of ferrite core 76 and lead wire 32 can be stored in a DC motor. Further, by employing the ferrite core 76, the cost can be reduced as compared with the case where a choke coil is used as a noise countermeasure component. Further, the arrangement of the ferrite core 76 does not require a time-consuming process such as soldering like a choke coil, and contributes to a reduction in manufacturing cost. The electric noise eliminating member is not limited to the ferrite core 76, and may be made of a ferromagnetic material made of a metal oxide. The capacitor 78 is made of a known material such as a ceramic capacitor, and contributes to suppression of electrical noise together with the ferrite core 76.

  One wiring 32a of the lead wire 32 passes through the center of one ferrite core 76 and is electrically connected to one carbon brush 30a. The wiring 32a has an exposed portion 32a1 in which the conductor portion is exposed, and a coating portion 32a2 in which the conductor portion is covered with an insulating material. The coating portion 32a2 is a portion from the outside of the motor to the holding portion 80, and the tip is an exposed portion 32a1. The other wiring 32b of the lead wire 32 passes through the center portion of the other ferrite core 76 and is electrically connected to the other carbon brush 30b. The wiring 32b has an exposed portion 32b1 in which the conductor portion is exposed, and a coating portion 32b2 in which the conductor portion is covered with an insulating material. The coating portion 32b2 is a portion from the outside of the motor to the holding portion 80, and the tip is an exposed portion 32b1.

  The capacitor 78 described above is connected between the wiring 32 a (32 b) and the metal case 16. Specifically, one end of the capacitor 78 is connected to the exposed portion 32a1 (32b1) of the wiring by the solder 82 at a position away from the ferrite core 76 with respect to the carbon brush 30a (30b). As described above, by disposing the capacitor 78 in the brush holder 18, the capacitor can be accommodated in the DC motor, and the effect of noise suppression is further enhanced. The capacitor may be provided in an electrical component to which the motor is attached without being provided in the motor body.

  FIG. 11A is a cross-sectional view of the ferrite core according to the embodiment. FIG.11 (b) is sectional drawing of the modification of a ferrite core. The ferrite core 76 according to the present embodiment has an outer diameter D1 of 1.5 [mm] to 15 [mm], an inner diameter d1 of 0.5 [mm] to 6 [mm], and a thickness t1 of 0.5 [mm]. ] To 5 [mm], and the total length L is appropriately set in the range of 1 [mm] to 20 [mm]. The optimum value can be obtained by experiment or simulation in consideration of the configuration (thickness, material, etc.) of the wiring passing through the center of the ferrite core 76. Further, as shown in FIG. 11B, the ferrite core may have a racetrack shape (a shape in which two semicircles are connected by a straight line).

In the wires 32a and 32b constituting the lead wire 32 according to the present embodiment, the thickness t2 of the coating made of an insulating material is 1.0 mm or less, and the outer diameter D2 of the core wire as the conductor portion is 0.5 [mm] to 3 0.0 [mm] and the maximum outer diameter D3 including the coating is appropriately set in the range of 0.5 [mm] to 5.0 [mm]. The optimum value can be obtained by experiment or simulation in consideration of the configuration (shape, material, etc.) of the ferrite core 76 through which the wiring penetrates. In addition, the conductor part of wiring can employ | adopt not only the case of a single wire but a strand, a pigtail wire, a brass component, etc. In addition, when a conductor part is not one line, it is good in the cross-sectional area of the whole conductor part being 0.2 [mm < ² >]-8.0 [mm < ² >].

The impedance Z of the ferrite core is expressed by the following formulas (1) and (2).
Z∝ (A _e / L _e ) × N ² (1)
A _e / L _e = (H / 2π) log _e (D1 / d1) (2)
Here, A _e is the average cross-sectional area of the ferrite core, L _e is the mean magnetic path length of the ferrite core, N is the number of turns, H is the ferrite core height, D1 is the outer diameter of the ferrite core, d1 is the ferrite core The inner diameter.

  As shown in the equations (1) and (2), the impedance Z of the ferrite core is highly influenced by the inner diameter d1 of the ferrite core. Further, the electrical noise can be eliminated (suppressed) by increasing the impedance Z of the ferrite core. Specifically, the impedance Z can be increased as the inner diameter d1 is reduced.

  In the lead wire 32, the outer diameters of the coating portions 32a2 and 32b2 are larger than the outer diameters of the exposed portions 32a1 and 32b1. Therefore, the ferrite core 76 according to the present embodiment is provided so that the exposed portions (conductor portions) 32a1 and 32b1 of the wiring are located at the center thereof. That is, when the ferrite core 76 is disposed so as to surround the exposed portions 32a1 and 32b1, rather than when the ferrite core 76 is disposed so as to surround the coating portions 32a2 and 32b2, the ferrite core 76 is disposed on the outer peripheral portion of the conductor portion. The inner periphery of the can be brought closer. For this reason, the inner diameter d1 of the ferrite core 76 is reduced, and the noise suppression effect of the ferrite core is enhanced. Further, if D1 / d1 is constant, the impedance Z is also constant. Therefore, by reducing the inner diameter d1 of the ferrite core 76, the outer diameter D1 of the ferrite core 76 can be reduced proportionally, and the ferrite core 76 76 can be downsized. That is, by setting the shape within the above numerical range, the ferrite core can be reduced in size while suppressing electrical noise. As a result, the DC motor itself is also reduced in size. Also, the downsizing of the ferrite core leads to a reduction in material costs.

  Also, as shown in FIG. 8, the ferrite core 76 is disposed on the support surface of the brush holder 18 and on a region other than the region sandwiched between the pair of carbon brushes 30. Here, the region sandwiched between the pair of carbon brushes 30 refers to a sector region R in the case of the circular brush holder 18 shown in FIG. Since the pair of carbon brushes 30 are arranged so that their longitudinal directions are orthogonal (intersect), the region between them (the region where the torsion spring 70 that biases the carbon brush 30a shown in FIG. 8 is supported) Is relatively narrow. Therefore, the ferrite core 76 according to the present embodiment is disposed not in a region sandwiched between the pair of carbon brushes 30 but in a region between the pair of carbon brushes 30 and the holding portion 80. Thereby, a pair of carbon brush 30 and the ferrite core 76 can be laid out effectively using the region on the support surface of the brush holder 18.

  Further, when a plurality of wires are passed through the central portion of one ferrite core, the inner diameter of the ferrite core is increased. In addition, when a plurality of wires are passed through the central portion of one ferrite core, the coating film portion of the wires is positioned at least inside the ferrite core so that the wires do not short-circuit. For this reason, the inner diameter of the ferrite core is further increased in consideration of the coating portion. However, in the motor 10 according to the present embodiment, since the lead wires 32 are provided with the separate ferrite cores 76 in the wirings 32a and 32b, the individual ferrite cores 76 can be reduced in size. Further, in the present embodiment, the inner peripheral portion of the ferrite core 76 can be brought closer to the outer peripheral portion of the conductor portion, compared with a case where a plurality of wires are passed through one ferrite core, and the noise suppression effect is enhanced. .

  Next, a method for fixing the ferrite core 76 to the brush holder 18 will be described. FIG. 12 is an enlarged view of a region D shown in FIG. 13 is a cross-sectional view taken along line EE in FIG. Hereinafter, the fixing unit will be described with reference to FIGS. 8 to 10, 12, and 13.

  Two fixing portions 90 for fixing the ferrite core 76 are provided on the brush holder 18. As shown in FIG. 12, FIG. 13, etc., the fixing portion 90 includes a bending portion 92 and a mounting portion 94. The bending portion 92 includes two leg portions 96 extending from the brush holder 18 in the vertical direction, and a bar plate-like connecting portion 98 that connects the upper ends of the leg portions 96. At least the leg portion 96 of the bent portion 92 is made of a flexible material such as a resin material. The mounting portion 94 is formed with a bottom portion 100 formed with a curved surface according to the peripheral surface of the ferrite core 76 to be mounted, and a back portion 102 extending vertically upward from the end of the bottom portion 100. The back portion 102 has a substantially flat back surface 102a. Further, a bent portion 104 is formed at the end portion of the back portion 102 on the side close to the holding portion 80.

  The distance between the two legs 96 is substantially equal to the entire length of the ferrite core 76. The distance F between the connecting portion 98 and the back surface 102a is set to be smaller than the outer diameter D1 of the ferrite core 76 when the ferrite core 76 is not fixed. When fixing the ferrite core 76 to the fixing portion 90, the ferrite core 76 is pushed along the back portion 102 from above the fixing portion 90. At this time, when the peripheral surface of the ferrite core 76 contacts the connecting portion 98, the connecting portion 98 supported by the two leg portions 96 bends away from the back portion 102. When the ferrite core 76 is further pushed in, the widest portion of the ferrite core 76 passes through the connecting portion 98. Here, the width of the ferrite core 76 is the width in the direction of the arrow G shown in FIG. Since ferrite core 76 according to the present embodiment has a cylindrical shape, the widest portion of ferrite core 76 corresponds to the diameter of the ferrite core. When the ferrite core has a polygonal cylindrical shape, the widest portion of the ferrite core corresponds to the widest portion in the direction orthogonal to the direction in which the ferrite core is pushed. Finally, the ferrite core 76 is seated on the bottom 100 of the fixed portion 90, and the widest portion of the ferrite core 76 enters between the two legs 96.

  In this state, the connecting portion 98 that has been bent until then returns to the original position, and the peripheral surface of the ferrite core 76 is pressed toward the back portion 102 and the bottom portion 100, and the ferrite core 76 is fixed to the fixing portion 90. The By such fixing, the ferrite core 76 is positioned in the radial direction of the brush holder 18 on the brush holder 18. Further, the ferrite core 76 is restricted from moving in the cylindrical axis direction of the ferrite core 76 on the bottom 100 by the two leg portions 96 and the bent portion 104. As described above, the fixing portion 90 according to the present embodiment reliably fixes the ferrite core 76 at a desired position by incorporating from one direction (upward in the present embodiment) by the action of the bending portion 92 and the bending portion 104. can do. Moreover, since the bending part 92 functions like an elastic body, the ferrite core 76 is prevented from being cracked or chipped.

  In the motor 10 according to the present embodiment, the outer diameter D of the metal case 16 (or the auxiliary yoke 19) is 30 to 55 [mm]. Thereby, even if it is a motor small to some extent, the full length of a motor can be shortened, maintaining a desired motor characteristic. In the motor 10, the distance between the two plain bearings 37 and 41 (hereinafter referred to as “full length” as appropriate) is 35 to 70 [mm]. As a result, the overall length of the electric tool using such a motor can be shortened. In addition, the motor 10 achieves a performance of about 100 to 1500 [mN · m], which is suitable for a power tool.

A part of the effects of the motor 10 according to the above-described embodiment are listed as follows.
(1) By using the portion where the core wire without the coating is exposed directly through the ferrite core, the effect of suppressing electrical noise by the ferrite core can be improved, and the physique (outer diameter and overall length) of the ferrite core can be reduced.
(2) Since one end of the capacitor can be connected to the exposed core wire, and the core wire can be connected to the brush through the ferrite core, workability can be improved, and the motor can be reduced in cost and size. Figured.
(3) By adopting a structure in which the ferrite core is fixed using the elasticity of the fixing part of the brush holder, it can be easily assembled, and can be fixed inexpensively and safely without using other parts or adhesives. It becomes possible.

  The present invention is not limited to the above-described embodiments and examples, and various modifications such as design changes can be added to the embodiments and examples based on the knowledge of those skilled in the art. There are also modifications to which such modifications are added and can be included in the scope of the present invention. Hereinafter, modified examples will be described.

  FIG. 14A, FIG. 14B, and FIG. 14C are diagrams for explaining the layout of each component on the brush holder in the motor of the modified example. In the following description, the layout of each component will be mainly described, and members similar to those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The brush holder 110 shown in FIG. 14A is greatly different from the brush holder 18 according to the above-described embodiment in that two torsion springs 70 are disposed between the pair of carbon brushes 30a and 30b. Such a layout eliminates the need to prevent the wires 32a and 32b and the torsion spring 70 from interfering when connecting the pair of carbon brushes 30a and 30b and the wires 32a and 32b. Workability at the time of placing is improved.

  The brush holder 112 shown in FIG. 14B is characterized in that the member that urges the carbon brush is the arm 114. Thereby, the above-mentioned torsion spring can be omitted. In addition, since the carbon brush is supplied with power through the arm, it is not necessary to consider interference with the wiring unlike a torsion spring.

  The brush holder 116 shown in FIG. 14C is characterized in that power supply from the outside is performed from the terminal 118 rather than through the lead wire. In the configuration employing the terminal 118 as described above, since the wires 32a and 32b are all accommodated in the brush holder 116, the coating is not necessarily required. That is, all of the wirings 32a and 32b may be exposed portions where the conductor portions are exposed.

  In the above-described embodiment, the magnetic pole of the magnet is described as four poles, but the magnetic pole of the magnet may be other than four poles. For example, a motor having two magnetic poles may be used. FIG. 15A and FIG. 15B are diagrams for explaining the layout of each component on the brush holder in the two-pole motor according to the modification.

  The brush holder 120 shown in FIG. 15A is arranged so that the tip of the carbon brush 30a and the tip of the carbon brush 30b face each other. In the brush holder 120, two torsion springs 70 are disposed in the left semicircular region with the pair of opposed carbon brushes 30a and 30b interposed therebetween, and two ferrite cores 76 are disposed in the right semicircular region. ing. Thereby, the two wirings 32a and 32b can be drawn out of the motor as lead wires 32 from the same place.

  The brush holder 122 shown in FIG. 15B is arranged so that the tip of the carbon brush 30a and the tip of the carbon brush 30b face each other. The brush holder 122 is provided with a torsion spring 70 on the left side of the carbon brush 30a and a ferrite core 76 on the right side. The brush holder 122 has a torsion spring 70 on the right side of the carbon brush 30b and a ferrite core 76 on the left side. As a result, the two wires 32a and 32b can be drawn out of the motor from locations opposite to each other across the center of the brush holder 122.

  FIG. 16A and FIG. 16B are diagrams for explaining the layout of each component on the brush holder in the two-pole motor according to the modification.

  The brush holder 124 shown in FIG. 16A is characterized in that power is supplied from the outside through the terminal 118 instead of through the lead wire. In the configuration employing the terminal 118 as described above, since the wires 32a and 32b are all accommodated in the brush holder 124, the coating is not necessarily required. That is, all of the wirings 32a and 32b may be exposed portions where the conductor portions are exposed. The brush holder 124 is disposed so that the tip of the carbon brush 30a and the tip of the carbon brush 30b face each other. The brush holder 124 has a torsion spring 70 on the left side of the carbon brush 30a and a ferrite core 76 on the right side. The brush holder 124 is provided with a torsion spring 70 on the right side of the carbon brush 30b and a ferrite core 76 on the left side. As a result, the two wires 32a and 32b are supplied with power from the terminals 118 located on opposite sides of the center of the brush holder 124.

  The brush holder 126 shown in FIG. 16 (b) is the same as the brush holder 120 shown in FIG. 15 (a) except that power is supplied from the outside from the terminal 118, not through the lead wire.

  The brush holder 128 shown in FIG. 16C is arranged so that the tip of the carbon brush 30a and the tip of the carbon brush 30b face each other. The brush holder 128 is an arm 114 that biases the carbon brushes 30a and 30b. Thereby, the above-mentioned torsion spring can be omitted. Further, since power is supplied to the carbon brushes 30a and 30b via the arm 114, it is not necessary to consider interference with the wirings 32a and 32b like a torsion spring.

  10 motor, 12 housing, 14 rotor, 18 brush holder, 20 magnet, 22 shaft, 24 armature, 26 commutator, 30 carbon brush, 31 carbon holder, 32 lead wire, 32a, 32b wiring, 76 ferrite core, 78 capacitor 80 holding part, 90 fixing part, 92 flexing part, 94 mounting part, 96 leg part, 98 connecting part, 100 bottom part, 102 back part, 104 bending part.

Claims (7)

York,
A magnet provided along the inner surface of the yoke and having a plurality of magnetic poles in the circumferential direction;
An armature disposed opposite to the magnet;
A shaft inserted through and fixed to the rotating shaft of the armature;
A commutator attached to the shaft to be coaxial with the armature;
A pair of brushes in sliding contact with the commutator;
A wiring having a conductor portion used for power feeding to the pair of brushes;
An annular member made of a ferromagnetic material made of a metal oxide,
The wiring has an exposed portion where the conductor portion is exposed, and a coating portion where the conductor portion is covered with an insulating material,
The DC motor according to claim 1, wherein the annular member is provided so that the exposed portion is positioned at a central portion thereof. A resin brush holder connected to the yoke and supporting the brush;
The DC motor according to claim 1, wherein the annular member and the wiring are disposed on the brush holder. The magnet has four magnetic poles in the circumferential direction,
The pair of brushes are arranged so that their longitudinal directions are orthogonal to each other,
The annular member is disposed on a support surface on which the annular member is supported by the brush holder and on a region other than a region sandwiched between the pair of brushes. The DC motor described in 1. Comprising a capacitor connected to the wiring;
4. The capacitor according to claim 1, wherein one end of the capacitor is connected to the exposed conductor portion of the wiring at a position away from the annular member with respect to the brush. DC motor.   The DC motor according to claim 1, wherein the annular member is a ferrite core. The inner diameter of the annular member is equal to or greater than the outer diameter of the conductor portion of the wiring,
The inner diameter of the annular member is 0.5 to 6 [mm],
6. The DC motor according to claim 1, wherein an outer diameter of the conductor portion is 0.5 to 3.0 [mm]. The inner diameter of the front Symbol annular member, DC motor according to claim 6, characterized in that it is less than the outer diameter of the coating portion.

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