JP2010028917A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor for prolonging the service life of a carbon brush by inexpensively suppressing the wobbling of a brush holder and highly precisely controlling a clearance between the brush holder and the carbon brush. <P>SOLUTION: The electric motor includes: a carbon brush 22 slidably contacting a commutator and feeding power; a brush holder 21 for housing the carbon brush 22 so as to freely move forward and backward for the commutator; and a holder stay 20 for fixing the brush holder 21. In the electric motor, the holder stay 20 includes a convex portion 57 for blocking the displacement of the brush holder 21 to the outside of a sidewall 52, and a clearance C is set to meet formula: A=5.3±1.8% when the clearance C between the carbon brush 22 and the sidewall 52 of the brush holder 21 is C (C=C1+C2) and a proportion A between a width Lb of the carbon brush 22 and the clearance C is A=(C/Lb)×100%, where Lb is the width of the carbon brush 22. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric motor including a carbon brush for supplying power to an armature commutator.

Generally, an electric motor with a brush often has a configuration in which an armature around which an armature coil is wound is rotatably disposed inside a cylindrical yoke having a permanent magnet attached to an inner peripheral surface. The armature has an armature core that is externally fixed to the rotating shaft. A plurality of teeth that are long in the axial direction are formed on the armature core, and a coil is wound around the teeth.
Each coil is connected to a plurality of segments of a commutator attached to the rotating shaft. The commutator is for supplying current to the coil and performing rectification, and the plurality of segments and the carbon brush are in sliding contact with each other.

The carbon brush is electrically connected to an external power source and applies a voltage to the segment. The carbon brush is housed in the brush holder so as to be movable back and forth with respect to the commutator (segment). The brush holder is fixed to a bracket that covers the opening of the yoke via a holder stay.
When the carbon brush applies a voltage to the segment, a current is supplied to the coil, and a magnetic field is formed in the armature core. And a rotating shaft rotates by the magnetic attractive force and repulsive force which arise between this magnetic field and a permanent magnet. This rotation sequentially changes the segments in which the carbon brush is in sliding contact with each other, mechanically rectifies, and the armature core continuously rotates.

Here, in the electric motor with a brush, as the armature rotates, the carbon brush repeatedly contacts and separates from the segment. For this reason, when the inter-segment voltage is large, when the carbon brush is separated from the segment, the electromagnetic energy stored in the coil is released, so that discharge may occur between the carbon brush and the segment.
If a discharge occurs between the carbon brush and the segment, the carbon brush and the segment may be subjected to discharge wear, which may cause poor electrical contact between the carbon brush and the segment, and may shorten the life of the carbon brush. is there.

For this reason, various techniques for reducing the voltage between segments have been proposed. For example, the coil wound around the teeth has a five-phase (U, V, W, X, Y phase) structure, so that it is more segmented than an electric motor having a three-phase (U, V, W phase) coil. A technique for reducing the inter-voltage is known (see, for example, Patent Document 1).
JP 2008-136343 A

By the way, if the brush holder attached to the holder stay is loose, the vibration of the carbon brush increases when the armature rotates. When the vibration of the carbon brush increases, the impact applied to the carbon brush increases and the life of the carbon brush is shortened.
Here, the brush holder is often formed by bending a metal plate, while the holder stay is often formed of resin. For this reason, in order to fix the brush holder to the holder stay without rattling, the number of parts increases, such as fastening with bolts, and the cost increases. Moreover, even if the clearance between the brush holder and the carbon brush is accurately controlled to suppress the backlash of the carbon brush, the manufacturing cost for manufacturing the brush holder with high accuracy increases.

  Therefore, the present invention has been made in view of the above-described circumstances, and can control rattling of the brush holder at a low cost and manage the clearance between the brush holder and the carbon brush with high accuracy. Thus, an electric motor capable of extending the life of a carbon brush is provided.

  In order to solve the above-described problems, the invention described in claim 1 includes a carbon brush that is slidably brought into contact with a commutator provided in an armature to supply power, and the carbon brush is housed in a retractable manner with respect to the commutator. In the electric motor having a brush holder and a holder stay for fixing the brush holder, the holder stay is provided with a displacement prevention portion for preventing displacement to the outside of the side wall of the brush holder, and the width of the carbon brush is set to Lb, When the clearance between the carbon brush and the side wall of the brush holder is C, and the ratio A between the carbon brush width Lb and the clearance C is A = (C / Lb) × 100%, A = 5.3 The clearance C is set so as to satisfy ± 1.8%.

  According to a second aspect of the present invention, the brush holder is formed in a U-shaped cross section in which the surface on the holder stay side is opened, and the side wall extends toward the holder stay side and engages with the holder stay. While the claw portion is provided, the holder stay is formed with an insertion hole through which the claw portion of the brush holder can be inserted, and the displacement prevention portion is a convex portion provided along the side wall of the brush holder. It is characterized by being.

  According to a third aspect of the present invention, 20 segments are arranged in the commutator, and 10 teeth are formed between the teeth for winding a coil conducting to the segment on the armature. Ten slots are provided, and eight permanent magnets are provided on the yoke.

According to the present invention, it is possible to securely and inexpensively fix the brush holder to the holder stay without preparing a separate mounting part, and to suppress the backlash of the brush holder.
Further, since the side wall of the brush holder can be pressed by the displacement prevention portion provided in the holder stay, the clearance between the carbon brush and the brush holder can be easily managed with high accuracy. At this time, by setting the clearance C so that the ratio A between the width Lb of the carbon brush and the clearance C satisfies A = 5.3 ± 1.8%, the backlash of the carbon brush, the carbon brush and the brush holder The clearance C can be optimized in consideration of sliding friction. For this reason, it becomes possible to extend the life of the carbon brush.
Furthermore, by providing the holder stay with a convex portion along the side wall of the brush holder and configuring the convex portion as a displacement preventing portion, the displacement preventing portion can be simplified, and the manufacturing cost can be further reduced. It becomes possible.

Next, embodiments of the present invention will be described with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each part recognizable.
As shown in FIGS. 1 and 2, the brushed electric motor 1 is a so-called DC brush motor, and is used, for example, as a drive source for an electrical component (for example, a radiator fan) mounted on a vehicle. The electric motor 1 includes an armature 3 that is rotatably provided in a bottomed cylindrical yoke 2 and covers an opening 2 c of the yoke 2 with an end bracket 17.
Eight permanent magnets 4 are arranged on the inner surface of the circumferential wall 2a of the yoke 2 along the circumferential direction. Further, a boss portion 10 is formed in the end portion (bottom portion) 2b of the yoke 2 at a substantially radial center. The boss portion 10 is formed with an insertion hole 11 for inserting the rotation shaft 5 of the armature 3 and a bearing 12 for rotatably supporting one end side of the rotation shaft 5.

  The armature 3 includes an armature core 6 that is externally fitted and fixed to the rotating shaft 5, an armature coil 7 that is wound around the armature core 6, and a commutator 13 that is disposed on the other end side of the rotating shaft 5. . The armature core 6 is formed by laminating a plurality of metal plates in the axial direction or press-molding soft magnetic powder.

  The armature core 6 has a substantially annular rotary shaft fixing portion 61 that is fitted and fixed to the rotary shaft 5. The rotary shaft 5 is press-fitted and fixed in an insertion hole 61 a formed in the rotary shaft fixing portion 61. An outer annular portion 62 formed concentrically with the rotation shaft fixing portion 61 is provided on the outer side in the radial direction of the rotation shaft fixing portion 61. Between the rotary shaft fixing portion 61 and the outer annular portion 62, five spoke portions 63 are provided at equal intervals in the circumferential direction so as to extend over both the portions 61 and 62. That is, the armature core 6 is formed with five through-holes 64 penetrating in the axial direction and substantially fan-shaped in a plan view in the axial direction by the rotating shaft fixing portion 61, the outer annular portion 62, and the spoke portion 63. become.

  On the radially outer side of the outer annular portion 62, ten teeth 36 that are substantially T-shaped in plan view in the axial direction are radially formed at equal intervals along the circumferential direction. Between adjacent teeth 36, a dovetail slot 37 is formed. Ten slots 37 extend along the axial direction, and are formed at equal intervals along the circumferential direction. An enamel-coated winding 38 is passed through the slot 37, and the winding 38 is wound around the tooth 36 by concentrated winding via an insulator (not shown). As a result, a plurality of armature coils 7 are formed on the outer periphery of the armature core 6.

  The armature core 6 is formed with substantially circular recesses 30 in the axial center in the radial center. Of these recesses 30, 30, a ring-shaped guide portion 66 is fitted into the recess 30 formed on the commutator 13 side. The guide portion 66 is for preventing the crossover portion of the winding 38 routed between the teeth 36 from interfering with the riser 43 of the commutator 13 described later.

The commutator 13 includes a resin mold body 40 that is externally fixed to the rotary shaft 5 and formed in a columnar shape, 20 segments 41 that are exposed on the outer peripheral surface of the resin mold body 40, and the resin mold body 40. And the short-circuit member 42 that short-circuits the same potential segments of the 20 segments 41.
The segment 41 is made of a plate-like metal piece that is long in the axial direction, and is fixed in parallel at equal intervals along the circumferential direction while being insulated from each other. Among these segments 41, five segments 41 that are present at equal intervals in the circumferential direction are integrally formed with a riser 43 that is folded back to the outer diameter side at the end on the armature core 6 side.

The riser 43 is for connecting the armature coil 7 to the segment 41. The winding start end and the winding end end of the winding 38 drawn from the armature coil 7 are respectively wound around and fixed by fusing. It has become so. Thereby, the segment 41 and the armature coil 7 corresponding to this are electrically connected.
The short-circuit member 42 is formed by laminating a plurality of short-circuit rings 46 at intervals in the axial direction.
That is, the same potential segments are short-circuited by one short ring 46.

  Here, the electric motor 1 of the present embodiment has eight permanent magnets 4 (magnetic poles), ten slots 37, and twenty segments 41, and windings 38 are concentrated on the teeth 36 of the armature core 6. It is an 8-pole 10-slot 20-segment 5-phase direct current motor wound around. Therefore, every fourth segment 41 is the same potential segment. Accordingly, since five sets of equipotential segments are formed, the short-circuit member 42 is composed of five short-circuit rings 46.

The end bracket 17 is made of a metal and is formed in a substantially disc shape, and has a boss portion 18 projectingly formed at a substantially radial center. A bearing 19 for rotatably supporting the other end side of the rotating shaft 5 is press-fitted and fixed to the boss portion 18.
A stay 9 is provided on the outer peripheral side of the end bracket 17 and extends outward. This stay 9 is used when fixing the electric motor 1, and is provided with a bolt hole 9 a that is formed by burring and projects toward the side opposite to the yoke 2.

  A holder stay 20 is attached to the inside of the end bracket 17. The holder stay 20 is made of resin and formed in a substantially disc shape, and four brush holders 21 are fixed to the inner surface.

  As shown in FIG. 3, each brush holder 21 is provided with a carbon brush 22 urged via a coil spring 23 so as to be able to advance and retreat relative to the commutator 13. Since the tip portions of the carbon brushes 22 are urged by the coil springs 23, they are in sliding contact with the segments 41 of the commutator 13.

  The carbon brush 22 is configured to include two sets of an anode side brush 22a and a cathode side brush 22b. The anode-side brush 22a and the cathode-side brush 22b are arranged in a state where the carbon brushes 22 on the same polarity side are spaced apart in the circumferential direction by a mechanical angle of 90 °. On the one hand, the mechanical angle is 135 °, and on the other hand, the mechanical angle is 45 °.

  That is, in this embodiment, the eight permanent magnets 4 are arranged at equal intervals in the circumferential direction, so that the carbon brushes 22 on the same pole side are arranged at an electrical angle of 360 ° in the circumferential direction. The carbon brushes 22 on the opposite pole sides are arranged with an electrical angle of 180 ° in the circumferential direction. And the brushes of the same polarity side are in a state of being concentrated at one place. That is, the anode side brushes 22a and 22a are arranged in the right half of the holder stay 20 (the right half of the paper surface in FIG. 3), while the cathode side brushes 22b and 22b are the left half of the holder stay 20 (the paper surface in FIG. 3). The left half) is placed.

  In addition, the holder stay 20 is provided with a power feeding unit 70 at the approximate center between the anode-side brush 22a and the cathode-side brush 22b that are spaced apart from each other by a mechanical angle of 135 °. The power supply unit 70 supplies power to the anode side brush 22a and the cathode side brush 22b, and is electrically connected to an external power source (not shown). Furthermore, one end of an anode-side terminal 71 and a cathode-side terminal 72 that are insert-molded in the holder stay 20 are connected to the power supply unit 70.

  The anode-side terminal 71 is for connecting the power feeding unit 70 and the anode-side brushes 22a and 22a, and has an exposed portion 74 in the vicinity of the two anode-side brushes 22a and 22a. The pigtail 73 of the anode-side brush 22a is connected to the exposed portion 74 of the anode-side terminal 71, thereby being electrically connected to the power feeding portion 70.

On the other hand, the cathode side terminal 72 is for connecting the power supply unit 70 and the cathode side brushes 22b and 22b, and has an exposed portion 75 in the vicinity of the two cathode side brushes 22b and 22b. The pigtail 73 of the cathode-side brush 22b is connected to the exposed portion 75 of the cathode-side terminal 72, thereby being electrically connected to the power feeding portion 70.
Under such a configuration, the electric power of the external power source is supplied to the armature coil 7 via the power feeding unit 70, the terminals 71 and 72, the pigtail 73, the carbon brush 22, and the segment 41.

  Here, as shown in FIGS. 3 to 7, the brush holder 21 is made of a metal plate such as a cast metal and is press-formed long in the radial direction in a substantially U-shaped cross section. The wall 51 has a pair of side walls 52 and 52 extending from both ends in the short direction toward the holder stay 20 side. That is, the brush holder 21 is in a state in which the openings 58 are formed on both end surfaces in the radial direction and the surface on the holder stay 20 side. The holder stay 20 is provided with a pressing plate 59 that closes the opening 58 at the radially outer end (rear end) of the brush holder 21, whereby the coil spring 23 built in the brush holder 21 falls off. Is regulated.

The side wall 52 of the brush holder 21 is formed with a bulging portion 53 that bulges outward at the approximate center in the height direction. The bulging portion 53 is for avoiding interference between the coil spring 23 and the brush holder 21, and is formed to correspond to the shape of the coil spring 23.
In addition, a slit 54 is formed in one of the pair of side walls 52, 52 for drawing the pigtail 73 connected to the carbon brush 22 outward. The slit 54 is formed from the front end of one side wall 52 on the side of the commutator 13 to slightly closer to the rear end than the center in the longitudinal direction (see FIG. 6).

  Furthermore, the latching claw 55 is integrally formed by four places from the longitudinal direction both ends at the holder stay 20 side end of the pair of side walls 52 and 52. The locking claw 55 is for fixing the brush holder 21 to the holder stay 20. The locking claw 55 is bent and extended from the side wall 52 along the attachment surface 20a of the holder stay 20 to the outside, and bent and extended from the tip of the first bent portion 55a toward the holder stay 20 side. The second bent portion 55b bent in a shape that is folded back is integrally formed.

  On the other hand, the holder stay 20 is formed with four slits 56 through which the second bent portion 55b can be inserted at positions corresponding to the joint portion between the first bent portion 55a and the second bent portion 55b of the locking claw 55. . That is, the second bent portion 55b extends along the vertical direction (vertical direction in FIG. 6) until the brush holder 21 is fixed to the holder stay 20, but after being inserted through the slit 56 of the holder stay 20, (See FIGS. 6 and 7). The size of the slit 56 is set to be large enough to pass through the second bent portion 55 b of the locking claw 55.

Further, the holder stay 20 is integrally formed with a pair of convex portions 57, 57 between the two slits 56, 56 outside the side walls 52, 52 of the brush holder 21.
The convex portion 57 is a displacement prevention portion for preventing the side walls 52 and 52 from being displaced outward when the brush holder 21 is attached to the holder stay 20. The convex portion 57 is formed long in the radial direction along the side walls 52 and 52 of the brush holder 21 so as to contact the side walls 52 and 52.

That is, the length Lh between the side walls 52 and 52 whose outward displacement is prevented by the convex portion 57 is determined by the convex portion 57. The two convex portions 57 determine the distance L1 between the pair of convex portions 57 so that the length Lh between the side walls 52, 52 of the brush holder 21 has a desired dimension, and are located at positions based on the distance L1. Is formed.
The desired dimension of the length Lh is a value obtained by adding the width Lb of the carbon brush 22 and the clearances C1 and C2 between the carbon brush 22 and the side wall 52 of the brush holder 21 determined based on the width Lb. (See FIG. 5).

More specifically, the value obtained by adding the clearance C1 and the clearance C2 is the total clearance C, and the ratio A between the total clearance C and the width Lb of the carbon brush 22 is A = (C / Lb) × 100%.
When
Total clearance C is
A = 5.3 ± 1.8%
It is set to satisfy.

For example, when the width Lb of the carbon brush 22 is 5.45 mm, it is desirable to set the total clearance C to 0.29 mm.
here,
A = (C / Lb) × 100 = (0.29 / 5.45) × 100≈5.32%
So,
A = 5.3 ± 1.8%
Will be satisfied.
Since the total clearance C is a value obtained by adding the clearance C1 and the clearance C2, the clearance C1 and the clearance C2 are respectively
C1 = C2 = C / 2 = 0.145 mm
It becomes.

Next, a procedure for assembling the brush holder 21 to the holder stay 20 will be described with reference to FIGS.
As shown in FIG. 6, the locking claw 55 of the brush holder 21 has the second bent portion 55 b extending along the vertical direction before being assembled to the holder stay 20. Then, the second bent portion 55 b is directed toward the holder stay 20, and the second bent portion 55 b is inserted into the slit 56 of the holder stay 20. At this time, the brush holder 21 is slightly deformed so that the width L2 of the brush holder 21 is slightly larger than the distance L1 between the pair of convex portions 57 formed integrally with the holder stay 20. Then, the operator inserts the second bent portion 55 b into the slit 56 of the holder stay 20 while narrowing the both side walls 52, 52 of the brush holder 21 inward.

  After inserting the second bent portion 55 b into the slit 56, the brush holder 21 is pushed into the holder stay 20 until the side wall 52 of the brush holder 21 comes into contact with the mounting surface 20 a of the holder stay 20. After the brush holder 21 is completely brought into contact with the mounting surface 20a of the holder stay 20, when the operator removes his / her hand from the brush holder 21, a restoring force acts on the brush holder 21, and both side walls 52, 52 are displaced outward. try to.

  At this time, since the convex portions 57 and 57 are integrally formed on the holder stay 20, the side walls 52 and 52 of the brush holder 21 abut against the convex portions 57 and 57, and the side walls 52 and 52 are formed by the convex portions 57 and 57. Is prevented from moving outward. That is, the side walls 52 and 52 of the brush holder 21 are pressed by the convex portions 57 and 57. As a result, the brush holder 21 does not rattle with respect to the holder stay 20, and the length Lh (see FIG. 5) between the side walls 52, 52 is set to a desired length.

  As shown in FIG. 7, after the brush holder 21 is placed on the mounting surface 20 a of the holder stay 20, the second bent portion 55 b of the locking claw 55 protruding from the surface of the holder stay 20 opposite to the brush holder 21 is provided. Bend inward (see arrow in FIG. 7). Thereby, the assembly | attachment to the holder stay 20 of the brush holder 21 is completed.

  Therefore, according to the above-described embodiment, the brush holder 21 can be fixed to the holder stay 20 at low cost without rattling. Further, the side walls 52 and 52 of the brush holder 21 can be pressed by the convex portion 57 formed integrally with the holder stay 20, so that the clearances C 1 and C 2 (total clearance) between the carbon brush 22 and the side wall 52 of the brush holder 21 are provided. C) can be easily managed with high accuracy. At this time, by setting the total clearance C so that the ratio A between the width Lb of the carbon brush and the total clearance C satisfies A = 5.3 ± 1.8%, the backlash of the carbon brush 22 occurs. The total clearance C can be optimized in consideration of the sliding friction between the brush holder 21 and the brush holder 21. For this reason, it is possible to extend the life of the carbon brush 22.

This will be described in more detail with reference to FIGS.
FIG. 8 is a graph showing changes in the amplitude of the carbon brush 22 when the electric motor 1 is driven, where the vertical axis is the displacement (μm) of the carbon brush 22 and the horizontal axis is the drive time (ms) of the electric motor 1. (A) shows the case where the total clearance C is 0.22 mm, and (b) shows the case where the total clearance C is 0.29 mm.
In FIG. 8, the width Lb of the carbon brush 22 is set to 5.45 mm. That is, (a) shows that the ratio A between the total clearance C and the width Lb of the carbon brush 22 is A = (C / Lb) × 100 = (0.22 / 5.45) × 100≈4.04%
Thus, A = 5.3 ± 1.8% is not satisfied.

  According to FIG. 8A and FIG. 8B, when the brush holder 21 satisfying A = 5.3 ± 1.8% is used (FIG. 8B), A = 5.3 ± 1. It can be confirmed that the amount of displacement (amplitude) is smaller than when the brush holder 21 that does not satisfy 8% is used (FIG. 8A). For this reason, the brush life and rectification of the electric motor 1 are reduced.

FIG. 9 is a graph showing changes in the life of the carbon brush 22 when the use environment temperature of the electric motor 1 is 25 ° C. and 90 ° C., and FIG. 9A shows the total clearance C and the width Lb of the carbon brush 22. The ratio A of A does not satisfy A = 5.3 ± 1.8%, that is, shows the life of the carbon brush 22 when the total clearance C is 0.22 mm, and (b) shows that the total clearance C is 0.29 mm. In this case, the lifetime of the carbon brush 22 is shown.
As shown in the figure, when the brush holder 21 that satisfies A = 5.3 ± 1.8% is used (FIG. 9B), the brush holder that does not satisfy A = 5.3 ± 1.8%. It can be confirmed that the life of the carbon brush 22 is extended as compared with the case of using 21 (FIG. 9A).

  Furthermore, according to the above-described embodiment, the convex portions 57 and 57 are formed in the holder stay 20 so as to be long in the radial direction so as to contact the side walls 52 and 52 along the side walls 52 and 52 of the brush holder 21. The part 57 is made to function as a displacement prevention part for preventing the displacement to the outside of the side wall 52 of the brush holder 21. Therefore, in order to prevent the displacement to the outside of the side wall 52, it is not necessary to assemble a large part on the holder stay 20, and the manufacturing cost of the holder stay 20 can be reduced.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention.
In the above-described embodiment, the case where the width Lb of the carbon brush 22 is set to 5.45 mm and the total clearance C between the carbon brush 22 and the side wall 52 of the brush holder 21 is set to 0.29 mm has been described. . However, the present invention is not limited to this. When the ratio A between the total clearance C and the width Lb of the carbon brush 22 is A = (C / Lb) × 100%, the total clearance C is A = 5.3 ± 1. It suffices if it is set to satisfy 8%.

Furthermore, in the above-described embodiment, the case where the convex portion 57 is formed integrally with the holder stay 20 and the displacement of the brush holder 21 to the outside of the side walls 52 and 52 is prevented by the convex portion 57 has been described. However, the shape is not limited to this, and any shape that can prevent the outward displacement of the side walls 52 and 52 of the brush holder 21 may be used.
In the above-described embodiment, the holder stay 20 is provided with four carbon brushes 22, that is, the carbon brush 22 includes two sets of the anode side brush 22 a and the cathode side brush 22 b. I explained the case. However, the present invention is not limited to this, and the carbon brush 22 can be increased to the same number as the number of magnetic poles in the holder stay 20.

It is a longitudinal section showing the composition of the electric motor in the embodiment of the present invention. It is a top view of the electric motor of the state which removed the end bracket in embodiment of this invention. It is a layout drawing of the brush in the embodiment of the present invention. It is A arrow directional view of FIG. It is sectional drawing which follows the BB line of FIG. It is a perspective view of the brush holder in the embodiment of the present invention. It is explanatory drawing which shows the assembly | attachment procedure of the brush holder in embodiment of this invention. It is a graph which shows the amplitude change of the carbon brush in embodiment of this invention, Comprising: (a) shows the case where a total clearance is 0.22 mm, (b) shows the case where a total clearance is 0.29 mm. It is a graph which shows the change of the lifetime of the carbon brush in embodiment of this invention, Comprising: (a) shows the case where total clearance is 0.22 mm, (b) shows the case where total clearance is 0.29 mm. .

Explanation of symbols

1 Electric motor 2 Yoke 3 Armature 4 Permanent magnet 7 Armature coil (coil)
13 Commutator 20 Holder stay 21 Brush holder 22 Carbon brush 22a Anode side brush 22b Cathode side brush 36 Teeth 37 Slot 38 Winding (coil)
41 segment 55 locking claw 55a first bent portion 55b second bent portion 56 slit 57 convex portion (displacement preventing portion)
58 Opening Lb Width C Total clearance (clearance)

Claims (3)

A carbon brush that slidably contacts a commutator provided in the armature to supply power;
A brush holder for storing the carbon brush with respect to the commutator so as to freely advance and retract;
In an electric motor having a holder stay for fixing the brush holder,
The holder stay is provided with a displacement prevention portion for preventing displacement of the brush holder to the outside of the side wall,
The width of the carbon brush is Lb, the clearance between the carbon brush and the side wall of the brush holder is C, and the ratio A between the width Lb of the carbon brush and the clearance C is A = (C / Lb) × 100%
When
A = 5.3 ± 1.8%
An electric motor characterized in that the clearance C is set so as to satisfy The brush holder is formed in a U-shaped cross-section with an open surface on the holder stay side,
The side wall is provided with a claw portion that extends toward the holder stay side and engages with the holder stay, while the holder stay is formed with an insertion hole through which the claw portion of the brush holder can be inserted,
The electric motor according to claim 1, wherein the displacement prevention portion is a convex portion provided along a side wall of the brush holder. 20 segments are arranged in the commutator,
The armature is provided with 10 teeth for winding a coil conducting to the segment, and 10 slots formed between the teeth,
The electric motor according to claim 1, wherein eight permanent magnets are provided on the yoke.

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