JP2011019382A - Motor with brush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC motor capable of reducing commutator noises.SOLUTION: An armature coil wound around the rotor core of the DC motor with brushes includes phase coils 31, 32 and 33, and secondary coils 31A, 32A and 33A. The phase coils 31, 32 and 33 are delta-connected, and the secondary coils 31A, 32A and 33A are delta-connected. Commutation sparks can be reduced by transformer action between the phase coils 31, 32, and 33 and the secondary coils 31A, 32A and 33A. Furthermore, at least either the front ends or the rear ends of segments 51, 52 and 53 of the commutator 5 and brushes are formed into a saw-tooth shape. As a result, an electrical resistance just before separation of the segments 51, 52 and 53 from the brushes is increased, thereby suppressing the commutation sparks.

Description

  The present invention relates to a brushed motor having a rotor having a commutator, and more particularly to a brushed motor capable of reducing commutation noise and extending brush life. The brushed motor includes a brushed DC motor and a universal motor.

  A DC motor with a brush or a universal motor has a rotor coil (armature winding) that is energized by contact between the brush and the commutator. The commutator has segments arranged at a predetermined pitch in the circumferential direction. Energization of the armature winding is performed when the brush contacts and separates from the segment. When the brush contacts two adjacent segments, one partial coil (hereinafter also referred to as a phase coil) of the armature winding whose both ends are connected to the two segments is short-circuited. Due to this short circuit, the residual magnetic energy of this phase coil is consumed by the resistance of the brush.

  When one of these two segments moves away from the brush, the energization of this phase coil is interrupted. At this time, if the phase coil has residual magnetic energy, a spark is generated. This spark is called a rectifying spark. It is known that most brush wear is caused by rectifying sparks. Furthermore, the electromagnetic noise generated by this rectifying spark requires countermeasures.

  Related prior art is described below. In the following, the front end of the brush and the segment means the front end in the rotational direction, and the rear end of the brush and the segment means the front end in the counter-rotating direction.

Patent Document 1 proposes to provide a high resistance portion at the rear end portion of the segment. Patent document 2 has proposed providing a high resistance part in the rear-end part of a brush. These high resistance parts generate large power consumption in the period immediately before the brush leaves the high resistance part. As a result, sparks and noise are suppressed.
However, providing the high resistance portion in the segment reduces the substantial segment density of the commutator. This method generates an effective area of the segments arranged at high density, and this method generates a brush temperature rise and wasteful power consumption. Further, if the brush has a high resistance layer, this high resistance layer has a different coefficient of thermal expansion than the low resistance body of the brush. As a result, the reliability of the brush decreases. It is not easy to provide a high resistance layer at the rear end of the segment.

  Patent Document 3 proposes a commutator having a structure in which a main segment and an auxiliary segment (conductive piece) adjacent to each other in the axial direction are connected through a high resistance body. The main and auxiliary segments leave the brush at different times. This timing difference is realized by changing the circumferential width between the brush portion in contact with the main segment and the brush portion in contact with the auxiliary segment. However, the added segments and brushes increase the axial length of the DC motor.

JP 2001-126838 A JP 02-86081 JP 2001-286102 A

(Object of invention)
The present invention has been made in view of the above problems, and an object thereof is to provide a brushed motor capable of reducing commutation sparks and brush wear. Another object of the present invention is to effectively recover the residual magnetic energy generated during rectification.

(Characteristics of the invention)
The brushed motor of the present invention that achieves this object has a commutator and at least a pair of brushes in contact with the commutator. The brush has a plurality of segments fixed to the rotating shaft at a predetermined pitch in the circumferential direction. The segment is connected to an armature winding wound around the rotor core.
Since this type of brushed motor and its rectifying mechanism have a well-known structure, description thereof is omitted. The present invention can be applied to both brushed DC motors and universal motors.

  In the first aspect of the present invention, the brush includes a conductive main brush portion that contacts the segment, a conductive auxiliary brush portion that contacts the segment, and a high-resistance insulating layer. The auxiliary brush portion is joined to the side surface on the rear side in the rotation direction of the main brush portion via an insulating layer. The auxiliary brush portion is connected to a diode for recovering the residual magnetic energy of the armature winding, a capacitor for storing the residual magnetic energy, or a resistor for consuming the residual magnetic energy. Connected to a diode or capacitor or resistor. According to this invention, the heat generation of the brush can be suppressed, and the rectifying spark and electromagnetic noise can be reduced.

In a preferred aspect, it has a second auxiliary brush portion joined to the side surface on the front side in the rotation direction of the main brush portion via a high-resistance second insulating layer,
The second auxiliary brush unit includes a diode for recovering the residual magnetic energy of the armature winding, a capacitor for storing the residual magnetic energy, or a resistor for consuming the residual magnetic energy. Connected to the body. According to this aspect, heat generation of the brush can be suppressed, and rectifying sparks and electromagnetic noise can be reduced.

In a preferred aspect, the resistor connects the auxiliary brush portion and the main brush portion. Thereby, with a simple structure, the heat generation of the brush can be suppressed and the rectifying spark can be suppressed.
In a preferred aspect, the diode connected to the auxiliary brush portion is connected to a power supply terminal different from the power supply terminal connected to the main brush portion adjacent to the auxiliary brush portion. Thereby, with a simple structure, the heat generation of the brush can be suppressed and the rectifying spark can be suppressed.

  In a preferred embodiment, the diode connects the auxiliary brush portions of a pair of brushes to which different potentials are applied from a DC power source. Thereby, with a simple structure, the heat generation of the brush can be suppressed and the rectifying spark can be suppressed.

  In the second aspect of the present invention, at least one of the contact portion of the brush and the contact portion of the segment has a plurality of convex portions protruding outward in the circumferential direction. The plurality of convex portions are distributed in a sawtooth shape in a substantially axial direction or a substantially radial direction. In addition, the aspect by which the some convex part is distributedly arranged in an axial direction is applied to the cylindrical commutator in which each segment extends in the axial direction. The aspect in which the plurality of convex portions are distributed in the radial direction is applied to a ring-shaped commutator in which each segment extends in the warp direction.

  That is, according to the present invention, the front end or the rear end of the segment and the brush has a plurality of convex portions arranged at a predetermined pitch in a direction different from the rotation direction (preferably in a direction substantially perpendicular to the rotation direction). As a result, the front end or the rear end of the contact area passes through the convex portion at the beginning of a short circuit in which the segment contacts the brush or immediately before the shut-off period in which the segment leaves the brush. As a result, the contact area between the segment and the brush decreases during this period and the electrical resistance increases.

  For example, when the segment contacts the brush, the convex portion at the front end of the segment first contacts the brush. Thereafter, the contact area between the convex portion and the brush increases. Finally, the brush reaches the rear end of the recess. As a result, the contact resistance between the segment and the brush at the beginning of the contact period between the segment and the brush decreases more slowly and earlier than when the front end portion of the segment does not have unevenness. For this reason, it is suppressed that the short circuit current of the partial coil produced by the contact of this segment increases rapidly. Since it is proportional to the square of the current, the resistance loss of the short-circuit current at the time of contact is reduced.

  Next, when the segment moves away from the brush, first, the root of the convex portion at the rear end of the segment moves away from the brush. Thereafter, the contact area between the convex portion and the brush decreases. Finally, the brush moves away from the tip of the convex portion. As a result, the contact resistance between the segment and the brush increases before the segment leaves the brush. As a result, the current flowing in the partial coil from the brush through the segment is reduced by the increase in the contact resistance, so that the surge voltage immediately after the segment leaves the brush can be reduced.

  Since the effect of suppressing the rectifying spark is relatively important, the convex portion at the initial stage of the short circuit period can be omitted when the segment contacts the brush. That is, the convex part provided in the front-end part of the rotation direction (circumferential direction) of a segment and the rear-end part of the rotation direction (circumferential direction) of a brush can be abbreviate | omitted. Thereby, while simplifying the segment shape and the brush shape, rectifying sparks and noise can be suppressed, and the wear of the brush can be reduced.

  Further, in the present invention, since a plurality of convex portions separated by a predetermined pitch in the axial direction are formed, it is possible to prevent the current from being concentrated locally on the segment and the brush. As a result, the local temperature rise of the segments and brushes can be suppressed, and the local wear thereof can be suppressed.

  In a preferred aspect, the convex portion has a width in the axial direction (or substantially in the radial direction) that gradually decreases toward the distal end side in the circumferential direction. Thereby, the mechanical strength of a convex part can be improved, slowing down the electric current change of a partial coil.

  In a preferred aspect, at least one of the contact portion of the brush and the contact portion of the segment has a plurality of convex portions at both the circumferential front end and the circumferential rear end. Thereby, noise can be reduced both at the time of short circuit and at the time of interruption.

  In a preferred aspect, the convex portion at the front end in the circumferential direction of the segment is arranged so as to be shifted from the convex portion at the rear end in the circumferential direction by a half pitch in the axial direction (or substantially radial direction). Thereby, it can prevent that the abrasion of a brush and a segment concentrates locally. Furthermore, the convex part at the circumferential front end and the convex part at the circumferential rear end of the segment can overlap when viewed in the axial direction (or substantially radial direction), and thus the commutator can be miniaturized. . Moreover, since the variation of the segment contact time of each part of an axial direction of a brush can be reduced, it can suppress that a brush wears locally.

  In addition, since the convexity of one segment and the resistance increase period of the adjacent segment overlap well with the resistance decrease period of the other segment, smooth current switching between two adjacent segments is possible. It becomes.

In a preferred embodiment, the contact portion of the segment has a plurality of protrusions, and the contact portion of the brush does not have a plurality of protrusions. Thereby, the increase in the manufacturing man-hour of a brush can be prevented.
In a preferred embodiment, the contact portion of the brush has a plurality of convex portions, and the contact portion of the segment does not have a plurality of convex portions. Thereby, it can prevent that the manufacturing man-hour of a segment increases.

  In a preferred embodiment, both the contact portion of the brush and the contact portion of the segment have a plurality of convex portions at both the circumferential front end and the circumferential rear end. The convex part of the brush and the convex part of the segment are arranged at substantially the same position in the substantially axial direction (or substantially radial direction). Thereby, the resistance change in the initial stage of the short circuit period and the initial period of the cutoff period can be slowed down while reducing the circumferential length of the convex part of the brush and the circumferential length of the convex part of the segment.

In a preferred embodiment, the brush comprises a metal spring plate in which a contact portion that contacts the segment protrudes toward the segment side, and the convex portion is formed on the contact portion. Thereby, the said convex part can be easily provided in the brush of a metal spring board structure.
In a preferred embodiment, the contact portion protrudes by plastic deformation of the metal spring plate toward the thickness direction segment side. Thereby, the contact part which has a convex part can be formed easily.

In the third aspect of the present invention, there are provided a plurality of secondary coils wound around the rotor core together with each phase coil and magnetically coupled separately from each phase coil. The plurality of secondary coils are connected in order to form a short-circuit closed circuit.
That is, since the phase coil of the armature winding also serves as the primary coil of the transformer, the phase coil generates an induced voltage in the secondary coil. One secondary coil passes an induced current through the closed circuit. As a result, the closed circuit consumes electric power generated by this induced voltage, or transmits electric power to other phase coils through other secondary coils.

  Since the voltage induced in the secondary coil is proportional to the frequency of the current flowing in the phase coil that is magnetically coupled, the high frequency component of the alternating current flowing in the phase coil is selectively absorbed by the secondary coil. For example, the harmonic voltage component that is five times higher than the basic AC voltage component generated in each phase coil of the armature winding is five times the basic AC voltage component. If the short-circuit closed circuit including the secondary coil has a relatively small inductance, much of the high-frequency power generated in the phase coil can be consumed by this short-circuit closed circuit.

  For example, when the current of the phase coil suddenly decreases due to the segment being separated from the brush, the secondary coil passes an induced current in an attempt to suppress a change in magnetic flux due to this sudden decrease in current. As a result, the magnetic flux change rate of the magnetic circuit around which the phase coil and the secondary coil are wound is reduced. As a result, the induced voltage of the partial coil is reduced and the rectifying spark is suppressed.

  Each secondary coil is connected in series. Each secondary coil is connected in series in such a direction that the sum of their EMF voltages (generated voltage due to the field flux) becomes zero. Moreover, it is preferable that the electric current which flows into a 1st secondary coil is connected in the direction which accelerates | stimulates the magnetic flux change which the electric current of the phase coil magnetically coupled with a 2nd secondary coil forms. The phase coil is preferably electromagnetically coupled with the secondary coil as well as possible. Thereby, the leakage inductance of a short circuit closed circuit can be reduced. As a result, it is possible to prevent a change in the induced current flowing through the short circuit closed circuit from being suppressed by this leakage inductance.

  In the fourth aspect of the present invention, the gap between the segments is obliquely provided with a predetermined skew angle. The brush has a plurality of brush arms arranged with a predetermined gap in the axial direction. The brush arm on the end side has a higher electrical resistance than the brush arm on the center side and is connected to a power source. Thereby, rectification sparks and noise can be reduced for the reason described above.

2 is a schematic diagram illustrating a rectifying structure and a circuit according to Embodiment 1. FIG. It is a schematic diagram which shows the rectification structure and circuit of a deformation | transformation aspect. It is a schematic diagram which shows the rectification structure and circuit of a deformation | transformation aspect. FIG. 3A is a schematic diagram showing a rectifying structure and a circuit showing an example in which auxiliary brush portions are provided on both sides of the main brush. FIG. 3B is a schematic diagram illustrating an example in which the capacitor is omitted in FIG. 6 is a schematic diagram illustrating a rectifying structure and a circuit of Example 2. FIG. FIG. 4A is a schematic diagram showing a rectifying structure and a circuit showing a point in time when a segment contacts the auxiliary brush portion of the positive brush. FIG. 4B is a schematic diagram showing a rectifying structure and a circuit showing a point in time when the segment leaves the main brush portion of the positive brush. FIG. 4C is a schematic diagram showing a rectifying structure and a circuit showing a point in time when the segment leaves the auxiliary brush portion of the positive brush. 6 is a schematic diagram illustrating a rectifying structure and a circuit of Example 2. FIG. FIG. 5A is a schematic diagram showing a rectifying structure and a circuit showing a point in time when a segment contacts the auxiliary brush portion of the negative brush. FIG. 5B is a schematic diagram showing a rectifying structure and a circuit showing a point in time when the segment leaves the main brush portion of the negative brush. FIG. 5C is a schematic diagram showing a rectifying structure and a circuit showing a point in time when the segment leaves the auxiliary brush portion of the negative brush. 6 is a schematic radial cross-sectional view showing a rectifying structure of Example 3. FIG. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. FIG. 7 is a schematic circumferential sectional view showing an example of FIG. 6. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. FIG. 7 is a schematic partial radial cross-sectional view illustrating an example of FIG. 6. 10 is a schematic radial cross-sectional view showing a rectifying structure of Example 4. FIG. FIG. 3 is a circumferential partial development view showing the shape of a segment of a commutator 5. FIG. 6 is a schematic plan view of a brush according to modification 1; It is the fragmentary sectional view which looked at the brush of FIG. 17 in radial direction. It is a partial top view of the brush of the modification 2. FIG. 20 is a partial side view of the brush of FIG. 19. It is a partial side view of the brush of the modification 3. It is a front view of the commutator of the modification 4. FIG. 10 is a schematic plan view illustrating the vicinity of a brush of a rectifying mechanism according to a fifth embodiment. It is a side view of the rectification | straightening mechanism of FIG. It is a front view which shows the base of a brush. It is a model partial top view which shows a deformation | transformation aspect. FIG. 10 is a schematic radial cross-sectional view showing the overall structure of a DC motor of Example 6. It is a simple equivalent circuit diagram of the rotor coil of FIG. FIG. 28 is a detailed equivalent circuit diagram of the motor of FIG. 27. It is a timing chart which shows the rectification operation | movement of the motor of FIG.

Example 1
A first embodiment will be described with reference to FIG. FIG. 1 is a schematic radial sectional view showing a rectifying mechanism of a DC motor having a pair of brushes.
(Constitution)
This DC motor has an armature winding 3, a commutator 5, a positive brush 700A, and a negative brush 700B. The armature winding 3 has six phase coils (31 to 36). The commutator 5 has six segments (51 to 56). The segments (51 to 56) are connected to the connection points of the phase coils (31 to 36).

  The commutator 5 is a normal cylindrical commutator configured by a number of segments (not shown) arranged in a cylindrical shape. It is easy to make the commutator 5 a disk-type commutator. Each segment is arranged in the circumferential direction across a gap. Each segment is made of graphite and / or copper alloy material. Each segment is supported by a cylindrical resin holder (not shown). The resin holder is fixed to a rotating shaft (not shown) of the DC motor.

The rectifying mechanism includes a positive brush 700 </ b> A and a negative brush 700 </ b> B that are in contact with the outer peripheral surface of the commutator 5. Each of the positive brush 700A and the negative brush 700B includes a low-resistance main brush portion 710, a high-resistance insulating layer 715, and a low-resistance auxiliary brush portion 713.
The main brush portion 710, the insulating layer 715, and the auxiliary brush portion 713 are arranged in the circumferential direction in close contact with each other. The main brush part 710, the insulating layer 715, and the auxiliary brush part 713 are integrated.

  The main component of the main brush part 710 and the auxiliary brush part 713 is graphite mixed with copper powder. The main brush part 710 and the auxiliary brush part 713 have a large specific resistance and a small circumferential thickness. The main component of the insulating layer 715 is a resin material or an inorganic material. The insulating layer 715 has a large specific resistance and a small circumferential thickness. The main brush portion 710 has a greater circumferential thickness than the auxiliary brush portion 713 disposed at the rear end portion of the pair of brushes (700A and 700B).

  The thickness of the insulating layer 715 is made as small as possible within a range in which current leakage between the main brush portion 710 and the auxiliary brush portion 713 can be suppressed. The circumferential width of the auxiliary brush portion 713 is preferably substantially equal to the circumferential width of the gap between the segments (51 to 56).

  The main brush portion 710 of the positive brush 700 </ b> A is connected to the + terminal of the battery 100. The main brush portion 710 of the negative brush 700B is connected to the negative terminal of the battery 100. The auxiliary brush portion 713 of the positive brush 700A is connected to the cathode of the diode 200. The anode of the diode 200 is connected to the negative terminal of the battery 100. The auxiliary brush portion 713 of the negative brush 700B is connected to the anode of the diode 201. The cathode of the diode 201 is connected to the + terminal of the battery 100. The capacitor 400 connects two auxiliary brush portions 713 in an alternating manner. This rectifying mechanism has the following characteristics.

(1) Each of the positive brush 700A and the negative brush 700B has an auxiliary brush portion 713 formed integrally with the insulating layer 715 sandwiched between the rear end portions of the main brush portion 710.
(2) The pair of auxiliary brush portions 713 are individually connected to both ends of the battery 100 through the diode 200 and the diode 300 for power regeneration.
(3) The pair of auxiliary brush portions 713 are connected by the capacitor 400. The capacitor 400 is a circuit element for suppressing the potential change of the auxiliary brush unit 713.

  In a modified embodiment, the other end of the capacitor 400 whose one end is connected to the auxiliary brush part 713 can be connected to another part. For example, the capacitor 400 can be replaced with a capacitor connected in parallel with the diode 200 and a capacitor connected in parallel with the diode 300.

(Rectifying operation)
The rectifying operation of this rectifying mechanism will be described below.
(1) Resistance short-circuit operation When both the first segment and the second segment adjacent to each other in the circumferential direction are short-circuited by the main brush portion 710 of the positive brush 700A or the main brush portion 710 of the negative brush 700B, both ends thereof are the first. The phase coils individually connected to the segment and the second segment are short-circuited. Due to this short circuit, the residual magnetic energy of this phase coil is consumed by the resistance of the brush.

(2) Power regeneration operation In FIG. 1, a current i indicated by an arrow indicates a direction of a current in which residual magnetic energy is generated when the segment is separated from the main brush portion 710.
From the state in which the first segment is in contact with both the main brush portion 710 and the auxiliary brush portion 713 and the second segment existing on the rear side of the first segment is in contact with the main brush portion 710, the first segment When the rear end moves away from the front end of the main brush portion 710, the residual magnetic energy of the phase coil connected to the first segment and the second segment absorbs current from the auxiliary brush portion 713 of the positive brush 700A. Then, a current is supplied to the auxiliary brush portion 713 of the negative brush 700B.

The auxiliary brush portion 713 of the positive brush 700A absorbs current from the negative electrode end of the battery 100 through the diode 200, and flows current from the main brush portion 710 of the positive brush 700A to the positive electrode end of the battery 100. That is, the residual magnetic energy of the phase coil charges the battery 100.
Similarly, the auxiliary brush part 713 of the negative brush 700B flows current to the positive terminal of the battery 100 through the diode 300, and absorbs current from the negative terminal of the battery 100 through the main brush part 710 of the negative brush 700B. That is, the residual magnetic energy of the phase coil charges the battery 100.

This power regeneration operation is ended when the first segment on the front side moves away from the auxiliary brush portion 713 or when the second segment on the rear side contacts the auxiliary brush portion 713. The residual magnetic energy of the phase coil is rapidly attenuated by the charging operation of the battery 100 having a large voltage.
When the second segment on the rear side is in contact with the auxiliary brush portion 713, if the first segment is in contact with the auxiliary brush portion 713, after the power regeneration operation, the resistance short-circuit operation by the auxiliary brush portion 713 is performed. To be implemented.

(3) Operation of Capacitor 400 At the moment when the rear end of the segment 51 moves away from the front end of the main brush portion 710 of the positive brush 700A, the residual magnetic energy of the phase coil 31 rapidly decreases the potential of the segment 51. Similarly, at the moment when the rear end of the segment 54 moves away from the front end of the main brush portion 710 of the negative brush 700B, the residual magnetic energy of the phase coil 34 rapidly increases the potential of the segment 54.

  Capacitor 400 has a rapid change in the potential of segment 51 or segment 54 when segment 51 is away from main brush portion 710 of positive brush 700A and when segment 54 is away from main brush portion 710 of negative brush 700B. Suppress. The charge stored in the capacitor 400 immediately after the rear end of the segment leaves the front end of the main brush portion 710 is discharged after the front end of the next segment contacts the auxiliary brush portion 713.

  In this embodiment, when the auxiliary brush part 713 is formed of a low resistance body having the same specific resistance as the main brush part 710, the auxiliary brush part 713 and the main brush part 710 may be formed of the same material. it can. Since there is no difference in coefficient of thermal expansion between the auxiliary brush part 713 and the main brush part 710, the mechanical joint strength of the positive brush 700A and the negative brush 700B is improved. Furthermore, since the resistance heat generation of the positive brush 700A and the negative brush 700B is reduced, the brush temperature is reduced.

(Production method)
The main brush part 710, the auxiliary brush part 713, and the insulating layer 715 can be manufactured integrally. For example, the positive brush 700A and the negative brush 700B can be manufactured by filling graphite particles on both sides of the insulating layer 715 manufactured in advance and then molding them.
It is also possible to manufacture the positive brush 700A and the negative brush 700B by bonding the positive brush 700A and the negative brush 700B separately manufactured with the insulating layer 715 interposed therebetween.

(Modification 1)
The auxiliary brush part 713 can have a specific resistance larger than that of the main brush part 710. As a result, the residual magnetic energy of the segment is rapidly attenuated by both power consumption due to the electric resistance of the auxiliary brush portion 713 and power recovery by the battery.

(Modification 2)
A resistance element may be connected in series with the diode 200 or the diode 300. As a result, the residual magnetic energy of the segment rapidly decays due to both power consumption due to the electrical resistance of the resistive element and power recovery by the battery.

(Modification 3)
The capacitor 400 can be omitted.
(Modification 4)
FIG. 1 shows a DC motor having a pair of brushes. The rectifying mechanism of this embodiment can also be applied to a DC motor having many pairs of brushes. FIG. 2 shows a rectifying mechanism employed in a DC motor having two pairs of brushes. Two positive brushes 700A and two negative brushes 700B are in contact with the commutator 5. The brush interval is 90 degrees. The capacitor 400, the diode 200, and the diode 300 are shared. The commutator 5 is fixed to the rotating shaft 2 via an electrically insulating brush holder (not shown).

(Modification 5)
The auxiliary brush part 713 for power regeneration can be provided on the front end side of the main brush part 710. FIG. 3A is a schematic radial sectional view showing a rectifying mechanism having a first auxiliary brush portion 713 and a second auxiliary brush portion 712. The auxiliary brush portion 713 is joined to the rear rear end side in the circumferential direction of the main brush portion 710 via the insulating layer 715. The second auxiliary brush portion 712 is joined to the front end side in the circumferential direction of the main brush portion 710 with the insulating layer 715 interposed therebetween.

The diode pair and the capacitor for supplying current to the second auxiliary brush unit 712 are provided separately from the diode pair and the capacitor for supplying current to the first auxiliary brush unit 713. As a result, the DC motor can regenerate the residual magnetic energy of the phase coil when rotating in the opposite direction.
A modification of the rectifying mechanism of FIG. 3A is shown in FIG. In FIG. 3 (B), the capacitor of the rectifying mechanism of FIG. 3 (A) is omitted.

(Example 2)
The rectifying mechanism of Embodiment 2 will be described with reference to FIGS. 4 (A), 4 (B), and 4 (C). The commutator 5 has three segments 5A, 5B and 5C. The diode 200 and the diode 300 shown in the first embodiment (FIG. 1) are omitted. The capacitor 400 connects the auxiliary brush portion 713 of the positive brush 700A and the auxiliary brush portion 713 of the negative brush 700B.

(Operation of the capacitor 400)
FIG. 4A shows a moment when the front end of the segment 5A comes into contact with the auxiliary brush portion 713 of the positive brush 700A. The main brush portion 710 of the positive brush 700A charges the capacitor 400 through the auxiliary brush portion 713.
FIG. 4B shows a moment when the rear end of the segment 5A leaves the main brush portion 710 of the positive brush 700A. The capacitor 400 discharges to the segment 5A through the auxiliary brush part 713 of the positive brush 700A. Thereafter, the capacitor 400 is charged in the reverse direction.
This reverse charging continues until the rear end of the segment 5 (A) is separated from the auxiliary brush portion 713 of the normal brush 700A (FIG. 4C). This reverse charging is eliminated when the front end of the next segment 5C contacts the auxiliary brush portion 713 of the normal brush 700A.

  FIGS. 5A, 5B, and 5C show a state where the capacitor 400 is charged and discharged by contact between the segment 5A and the negative brush 700B. FIG. 5A corresponds to FIG. FIG. 5B corresponds to FIG. FIG. 5C corresponds to FIG.

(Example 3)
A rectifying mechanism of Embodiment 3 will be described with reference to FIG. FIG. 6 is a schematic radial cross-sectional view showing the rectifying mechanism.

  The commutator 5 is composed of a number of segments arranged in a cylindrical shape. Each segment is made of copper powder including graphite powder. A small circumferential gap (segment gap) is provided between each segment. Each segment is mechanically supported by a cylindrical resin holder 50. The resin holder 50 is fitted on the rotary shaft 2 of the DC motor.

  The rectifying mechanism has a brush device 7A and a brush device 7B. The brush device 7A and the brush device 7B are 180 degrees apart from each other in the circumferential direction. Each of the brush device 7A and the brush device 7B includes a brush 700, a brush holder 701, and a spring 702. A brush 700 made of graphite material is housed in a resin brush holder 701. The spring 702 presses the brush 700 against the commutator 5. The brush 700 of the brush device 7A is connected to the positive terminal of the power source. The brush 700 of the brush device 7B is connected to the negative terminal of the power source. The brush device 7A and the brush device 7B are basically the same as a normal brush device.

(Brush 700 structure)
The brush 700 includes a low-resistance auxiliary brush portion 712, a high-resistance insulating layer 714, a low-resistance main brush portion 710, a high-resistance insulating layer 715, and a low-resistance layer that are sequentially stacked in the circumferential direction (referred to as a tangential direction). An auxiliary brush portion 713 is provided.

  The auxiliary brush part 712, the main brush part 710, and the auxiliary brush part 713 are configured by increasing the content of copper powder mixed in the sintered graphite. The insulating layer 714 and the insulating layer 715 are configured by greatly increasing the content of the electric insulating powder mixed in the sintered graphite. Nitride and oxide can be adopted as the electrically insulating powder. As the electrically insulating powder, fine powder of alumina or silica can be adopted. The insulating layer 714 and the insulating layer 715 can be formed of an organic insulating material.

  The main brush portion 710 disposed at the center portion in the circumferential direction has a larger circumferential thickness than the auxiliary brush portions 712 and the auxiliary brush portions 713 on both sides in the circumferential direction. The insulating layer is formed as thin as possible within a range in which a larger electric resistance than the auxiliary brush portion and the main brush portion can be secured. For example, the circumferential thickness of one auxiliary brush portion is 20% of the total circumferential thickness of the brush 700.

  For example, the circumferential thickness of the insulating layer 715 is 55% or more of the entire circumferential thickness of the brush 700. For example, the circumferential thickness of the insulating layer is 2.5% or less of the total circumferential thickness of the brush 700. For example, the insulating layer has a specific resistance that is 10 times or more, more preferably 20 times or more larger than that of the auxiliary brush portion and the main brush portion.

  The main brush portion and the auxiliary brush portion preferably have equal specific resistance. The upper end surface of the main brush portion 710 is connected to a power source by a pigtail (not shown). The upper end surface of the auxiliary brush part is connected to the upper end surface of the central low resistance layer 710 or a power source through a resistance element r (not shown).

The operation of this rectifying mechanism will be described below with reference to FIG.
A segment 52 of the commutator 5 is in contact with the main brush portion 710. After the segment 51 of the commutator 5 starts to contact the auxiliary brush portion 712, the phase coil L1 whose both ends are connected to the segments 51 and 52 includes the main brush portion 710, the segment 52, the phase coil L1, the segment 51, and the auxiliary brush. Shorted by the portion 712 and the resistance element r.

  Since the resistance value of the insulating layer 714 is high, the short circuit current in the brush 700 flowing through the insulating layer 714 is sufficiently small. As a result, most of the stored energy of the phase coil L1 is consumed by the resistance element r. This power consumption prevents the occurrence of sparks. Furthermore, the temperature rise of the brush 700 is reduced.

  After the segment 52 comes into contact with the main brush portion 710 and the segment 53 leaves the auxiliary brush portion 713, the phase coil L2 includes the auxiliary brush portion 713, the segment 53, the phase coil L2, the segment 52, the main brush portion 710, and the resistance element. Shorted by r. Since the resistance value of the insulating layer 715 is high, the short circuit current in the brush 700 flowing through the insulating layer 715 is sufficiently small. As a result, the residual magnetic energy of the phase coil L2 is consumed by power consumption by the resistance element r. This power consumption prevents the occurrence of sparks. Furthermore, the temperature rise of the brush 700 is reduced.

  The formation of the main brush portion 710, the insulating layer 715, and the auxiliary brush portion 713 can be realized by changing the components in the brush powder deposition step that is sequentially performed. In addition, after forming the insulating layer 715 on at least one surface of the two low-resistance brushes, they can be bonded to each other.

(Modification 1)
The resistance element r can be fixed to the upper end surface of the brush 700. In FIG. 8, a resistance element r formed by a ring-shaped medium resistance layer 716 is provided on the upper end surface of the brush 700. The middle resistance layer 716 has a higher electrical resistance than the low resistance layers 710, 712 and 713 and lower than the high resistance layers 714 and 715. The heat resistance of the middle resistance layer 716 is excellent. The middle resistance layer 716 reduces internal heat generation of the brush 700. The medium resistance layer 716 can be formed by mixing electric insulating powder with graphite particles, and can also be formed by applying and baking a resistance powder solution.

(Modification 2)
FIG. 9 shows an example in which a minimum resistance layer 718 having a very small resistance value is provided on the front side surface of the auxiliary brush portion 712 and the rear side surface of the auxiliary brush portion 713. This minimal resistance layer 718 is made of, for example, copper foil. These minimum resistance layers 718 reduce heat generation in the auxiliary brush part 712 and the auxiliary brush part 713.

(Modification 3)
FIG. 10 shows an example in which a resistance element r composed of a ring-shaped medium resistance layer 716 is brought into contact with the upper end surface of the brush 700. The middle resistance layer 716 has an electric resistance higher than that of the main brush portion 710 and the auxiliary brush portion and lower than that of the insulating layer. The middle resistance layer 716 is in contact with the pigtail 717.

(Modification 4)
FIG. 11 shows an example in which a medium resistance phase 716 is provided on all sides of the brush 700.
(Modification 5)
FIG. 12 shows an example in which the front auxiliary brush portion 712, the insulating layer 714, and the resistance element r are omitted. A pigtail 717 that energizes the main brush portion 710 extends in the upstream direction of the rotation direction. A middle resistance layer 716 constituting the resistance element r is fixed to the upper end surface of the brush 700.

(Deformation mode 6)
FIG. 13 shows an example in which the downstream resistance element r is changed to a diode D. The main brush portion 710 is connected to the + terminal of the DC power source. The anode of the diode D is connected to the negative terminal of the DC power supply. The cathode of the diode D is connected to the upper part of the auxiliary brush part 713.
When the segment 53 begins to move away from the main brush portion 710, the potential of the auxiliary brush portion 713 that contacts the segment 53 decreases. Due to this potential drop, the rotor coil is energized through the diode D, auxiliary brush part 713 and segment 53 from the negative terminal of the DC power supply. Thereby, electric power is collected.

(Deformation mode 7)
FIG. 14 shows an example in which the downstream resistance element r is changed to a diode D. The main brush portion 710 is connected to the negative terminal of the DC power source. The cathode of the diode D is connected to the + terminal of the DC power supply. The anode of the diode D is connected to the upper part of the auxiliary brush part 713.
When the segment 53 begins to move away from the main brush portion 710, the potential of the auxiliary brush portion 713 that contacts the segment 53 increases. Due to this potential increase, the residual magnetic energy of the rotor coil is recovered to the positive terminal of the DC power source through the segment 53, the auxiliary brush portion 713, and the diode D.

Example 4
A rectifying mechanism of Embodiment 4 will be described with reference to FIGS. 15 and 16. FIG. 15 is a schematic radial cross-sectional view showing the rectifying mechanism. FIG. 16 is a circumferential partial development view showing the shape of the segment of the commutator 5.
A commutator holder 50 made of a resin cylinder is fitted to the rotary shaft 2. The segments (51, 52 and 53) are fixed to the outer peripheral surface of the commutator holder 50. In FIG. 5, the segment 53 is not shown.

  The commutator 5 includes a commutator holder 50 and segments (51, 52, and 53). The brush 7 has a conductor spring plate 71 and a contact portion 72 made of a noble metal joined to the conductor spring plate 71. The brush 7 is fixed to a brush holder (not shown). The front ends and rear ends of the segments (51, 52 and 53) are formed in a sawtooth shape and extend in the axial direction (AX). PH is the circumferential direction.

  Reference numeral 511 denotes the rear end of the segment 51. Reference numeral 512 denotes a front end of the segment 51. Reference numeral 522 denotes the front end of the segment 552. Reference numeral 531 denotes the rear end of the segment 53. Wb is the axial width of the contact portion 72 of the brush 7. The front end 511 of the segment 51 has four convex portions 54 arranged at a predetermined pitch in the axial direction. Each protrusion 54 protrudes forward in the circumferential direction at a predetermined pitch. R indicates the direction of rotation. The rear end 512 of the segment 51 has four convex portions 54. The four protrusions 54 arranged in the axial direction at a predetermined pitch protrude rearward in the circumferential direction at a predetermined pitch.

  The rear end 522 of the segment 52 has four convex portions 54. The four protrusions 54 arranged in the axial direction at a predetermined pitch protrude rearward in the circumferential direction at a predetermined pitch. The front end 531 of the segment 53 has four convex portions 54 arranged at a predetermined pitch in the axial direction. Each protrusion 54 protrudes forward in the circumferential direction at a predetermined pitch. The front end and the rear end of each segment 51, 52 and 53 have serrated edges.

  The convex portions 54 of two segments adjacent to each other are arranged with a half-pitch shift in the axial direction. As a result, the convex portions 54 of two segments adjacent to each other overlap when viewed in the axial direction. That is, they mesh with each other with a predetermined gap. The convex portion 54 has a tapered shape toward the distal end side in the circumferential direction.

(Convex part 54)
The function of the convex part 54 is demonstrated below. At the timing when the segments 51, 52, and 53 come into contact with the contact portion 72 of the brush 7, and at the timing when the segments 51, 52, and 53 are separated from the contact portion 72 of the brush 7, resistance loss due to the electric resistance value Δr of the convex portion 54 occurs. For this reason, rectification sparks and noise can be reduced.

(Modification 1)
Modification 1 will be described with reference to FIGS. 17 and 18. FIG. 17 is a schematic plan view of the brush 7. FIG. 18 is a partial radial cross-sectional view of the brush 7. The brush 7 is made of block-like graphite. The brush 7 has a block-shaped central portion 73. The front end portion in the circumferential direction of the brush 7 has three convex portions 74 protruding forward in the circumferential direction. The three convex portions 74 are arranged at a predetermined pitch in the axial direction AX. The rear end portion in the circumferential direction of the brush 7 has three convex portions 75 protruding forward in the circumferential direction. The three convex portions 75 are arranged at a predetermined pitch in the axial direction AX. That is, the front end portion and the rear end portion of the brush 7 are formed in a sawtooth shape and extend in the axial direction.

  The convex portion 74 and the convex portion 75 of the brush 7 are disposed at the same position as the convex portion 54 of the segment 51 in the axial direction. Similarly, the convex portions 54 of the segments 52 and 53 are arranged at positions overlapping the convex portions 74 and the convex portions 75 of the brush 7. Therefore, when the segment comes into contact with and separates from the brush 7, the electrical resistance of the convex portions 74 and 75 and the electrical resistance of the convex portion 54 are added, so that the resistance loss increases. As a result, rectifying sparks and noise are reduced.

(Modification 2)
The deformation | transformation aspect 2 is demonstrated with reference to FIG.19 and FIG.20. FIG. 19 is a partial plan view of the lead-shaped brush 7. FIG. 20 is a side view of the lead-shaped brush 7. The convex portion 74 and the convex portion 75 of the brush 7 are configured by a contact portion 72 fixed to the metal spring plate 71 of the brush 7. The contact portion 72 is joined to the metal spring plate 71. A convex portion 74 is provided at the front end in the circumferential direction of the contact portion 72 made of a noble metal material. Similarly, a convex portion 75 is provided on the circumferential rear end of the contact portion 72. In this way, the convex portions 74 and 75 can be easily formed on the spring-plate-shaped brush 7.

(Modification 3)
The modification 3 is demonstrated with reference to FIG. This deformation mode is characterized in that the convex portions 74 and 75 of the brush 7 are formed by stamping and molding the metal spring plate 71. The metal spring plate 71 is a copper alloy and can be plastically deformed relatively easily.

(Modification 4)
Variation 4 will be described with reference to FIG. FIG. 22 is a front view of the commutator 5. In this modification, the commutator 8 is formed in a ring plate shape. The commutator 8 is fitted and fixed to the rotating shaft 2. The commutator 8 has fan-shaped segments 51, 52, and 53 arranged in a rotationally symmetrical manner. The + brush 91 and the −brush 92 are formed of a graphite block. The + brush 91 and the −brush 92 are in contact with the segments 51, 52, and 53. The front end portion in the circumferential direction of the + brush 91 and the −brush 92 has two convex portions 74. The rear end portions in the circumferential direction of the + brush 91 and the −brush 92 have two convex portions 75. Thereby, the rectification spark suppression effect by the convex parts 74 and 75 mentioned above is realizable.

  In FIG. 22, it is natural that the segments 51, 52 and 53 can have a convex portion 54. The circumferential front end and the circumferential rear end of the segments 51, 52, and 53 in FIG. 22 extend in the radial direction, but may extend obliquely.

(Example 5)
A rectifying mechanism according to the fifth embodiment will be described with reference to FIGS. FIG. 23 is a schematic plan view showing the vicinity of the brush 7 of the rectifying mechanism. FIG. 24 is a side view of the brush 7 of the rectifying mechanism. FIG. 25 is a front view showing the base of the brush 7. The brush 7 is one of a pair of brushes of a brushed DC motor. For example, the brush 7 which is a + brush is configured by joining an unillustrated contact portion to an L-shaped copper alloy plate. In FIG. 23, a part of the rotating shaft 2, the commutator 5, and the segments 51 and 52 are illustrated. The segment 53 is hidden in FIG.

  The brush 7 includes a brush arm (7X, 7Y, and 7Z), a base arm (79X, 79Y, and 79Z), and a base plate 700. The brush arms (7X, 7Y, and 7Z) extend parallel to each other in a direction substantially perpendicular to the rotation shaft 2 (see FIG. 23). The flat brush arms (7X, 7Y, and 7Z) are in sliding contact with the segments (51, 52, and 53), respectively. The brush arm 7X extends perpendicularly from the tip of the flat base arm 79X.

  The brush arm 7Y extends perpendicularly from the tip of the flat base arm 79Y. The brush arm 7Z extends perpendicularly from the tip of the flat base arm 79Z. The base arms (79X, 79Y and 79Z) extend from a wide flat base plate 700. This type of 3-arm type metal plate brush has a well-known structure. Narrow base arms (79X and 79Z are supported by the brush holder 78). The unillustrated brush has the same structure as described above.

  The feature of this embodiment is that the base arms 79X and 79Z on both sides are formed narrower than the base arm 79Y at the center. Therefore, the base arms (79X and 79Z) on both sides have a larger electric resistance value than the base arm 79Y at the center. This is characterized in that the gap g between the segments (51, 52 and 53) extends obliquely with respect to the axial direction (that is, has a skew angle).

  The effect of the rectifying structure of this embodiment will be described below. In this embodiment, the circumferential positions of the front and rear ends of the segments (51, 52 and 53) are shifted. Therefore, the timing at which the brush arms (7X, 7Y and 7Z) of the brush 7 are connected to the segment and the timing at which the brush arm is separated from the segment are different. For example, in FIG. 23, when it is assumed that the rotating shaft 2 is rotating in the CCW direction, the brush arm 7Z moves away from the segment 51 later than the brush arm 7Y. Similarly, the brush arm 7X contacts the segment 552 earlier than the brush arm 7Y.

  Base arms (79X and 79Z) connected to the brush arms (7X and 7Z) are formed narrower than the brush arm 77Y. Of course, the brush arms (7X and 7Z) may have a narrower width than the brush arm 7Y. Accordingly, the electrical resistance of the brush 7 increases immediately before the segment 51 moves away from the brush 7.

  Similarly, immediately after the segment 52 contacts the brush 7, the electrical resistance of the brush 7 increases. The magnetic energy of the partial coils connected between the segments (51, 52 and 53) is rapidly consumed by the large electrical resistance of the brush. As a result, the current change of the partial coil at the time of contact and separation between the brush and the segment is suppressed, and rectification sparks and noise are suppressed.

(Modification 1)
The brush arm 7X and the base arm 79X (referred to as the front arm), and the brush arm 7Z and the base arm 79Z (referred to as the rear arm) are made thinner than the brush arm 7Y and the base arm 79Y (referred to as the central arm), It can be formed using a material having a large specific resistance (specific resistance).

(Modification 2)
Either the front arm or the rear arm may be omitted, or a plurality of front arms and rear arms may be provided.
(Modification 3)
In the above embodiment, the front arm and the rear arm of the brush 7 are narrower than the central arm, and the resistance values of the front arm and the rear arm are increased. In this variation shown in FIG. 26, a square hole 701 is provided in the base arms 79X and 79Z. As a result, the resistance value of the base arms (79X, 79Y and 79Z) increases. The square hole 701 may be provided in the brush arms 7X and 7Z.

(Example 6)
A rectifying mechanism of a brushed motor according to Embodiment 6 will be described with reference to the drawings.
(Overall structure)
FIG. 27 is a schematic radial cross-sectional view showing the overall structure of the DC motor of this embodiment. The brush and the motor housing are not shown.

  A rotor core 1 made of a laminated soft magnetic steel plate is fixed to a rotating shaft 2. The rotating shaft 2 is rotatably supported by a motor housing (not shown) through a bearing. The rotor core 1 has three magnetic pole portions (11A, 12A and 13A). The magnetic pole portions (11A, 12A, and 13A) protrude in a rotationally symmetric manner in the radially outward direction. The phase coils (31, 32 and 33) are separately concentrated and wound around the magnetic pole portions (11A, 12A and 13A).

  The phase coils (31, 32 and 33) constitute the armature winding 3. The three-phase magnetic pole portions (11A, 12A, and 13A) face the tip portions of the field magnetic poles (41 and 42) in the radial direction. The base portions of the field poles (41 and 42) are magnetically connected by a cylindrical yoke portion 43. The field poles (41 and 42) constitute the stator 4 together with the yoke portion 43. In this embodiment, the field poles (41 and 42) are composed of permanent magnets. Of course, the field poles (41 and 42) can be constituted by a magnetic member excited by a field coil.

  The commutator 5 has three segments (51, 52 and 53) arranged rotationally symmetrically. The segments (51, 52 and 53) are fixed to the outer peripheral surface of a resin cylindrical commutator holder (not shown). The commutator holder is fitted and fixed to the rotating shaft 2. The segments (51, 52 and 53) are arranged rotationally symmetrical. The three connection points of the three Δ-connected phase coils (31, 32 and 33) are separately connected to the segments (51, 52 and 53). Since the above-described two-pole three-phase brushed DC motor is well known, further explanation is omitted.

  This embodiment is characterized in that the secondary coils (31A, 32A and 33A) are wound on the phase coils (31, 32 and 33). The secondary coils (31A, 32A and 33A) are composed of sheet-like copper plates. The number of turns of the secondary coils (31A, 32A and 33A) is larger than 1, but smaller than that of the phase coils (31, 32 and 33). However, the cross-sectional areas of the secondary coils (31A, 32A, and 33A) are much larger than the cross-sectional areas of the phase coils (31, 32, and 33).

(Rotor circuit)
The secondary coils (31A, 32A, and 33A) are Δ-connected as shown in FIG. 28 to form a short-circuit closed circuit. FIG. 28 is an equivalent circuit showing the armature winding and the short-circuit closed circuit of FIG. U is a phase coil 31. V is a phase coil 32. W is a phase coil 33. US is the secondary coil 31A. VS is the secondary coil 32A. WS is the secondary coil 33A. Terminal a is connected to segment 53. Terminal b is connected to segment 51. Terminal c is connected to segment 52.

  The operation of the secondary coils (31A, 32A and 33A) will be described in detail with reference to FIG. FIG. 29 is an equivalent circuit diagram of the secondary coil (31A, 32A and 33A) and the phase coil (31, 32 and 33). The phase coil U and the secondary coil US constitute a U-phase transformer. The phase coil V and the secondary coil VS constitute a V-phase transformer. The phase coil W and the secondary coil WS constitute a W-phase transformer.

  By interlinking with the field flux, the phase coil U generates a voltage EmfU1. Similarly, phase coil V generates voltage EmfV1, and phase coil W generates voltage EmfW1. Similarly, the secondary coil US generates the voltage EmfU2, the secondary coil VS generates the voltage EmfV2, and the secondary coil WS generates the voltage EmfW2. The total voltage (EmfU1 + EmfV1 + EmfW1) is considered to be approximately zero. Similarly, the sum of the voltages (EmfU2 + EmfV2 + EmfW2) is considered to be approximately zero.

  The contact / separation between the pair of + brush and −brush and the segments 51, 52 and 53 is equivalent by a three-phase inverter composed of three half-bridge circuits 61, 62 and 63. The electrical resistance between the brush and the segment is equivalent by the variable resistance elements r1, r2 and r3. Secondary coil US (secondary coil 33A), secondary coil VS (secondary coil 31A) and secondary coil WS (secondary coil 32A) are composed of phase coils 31, 32 and 33 and magnetic pole portions 11A, 12A and 13A. It can also be wound between.

  The operation of this DC motor will be described. FIG. 29 shows the timing at which the segment 53 moves away from the + brush. During the period in which the segment 53 moves away from the + brush, the W-phase current flowing in the phase coil W rapidly decreases. As a result, an induced voltage Vi is generated in the secondary coil WS. As a result, the induced current, that is, the secondary current flows in a direction to suppress the magnetic flux change of the magnetic pole portion 13A around which the secondary coil WS is wound. As a result, the magnetic energy accumulated in the phase coil W is rapidly consumed, and rectification sparks and noise can be suppressed.

  Furthermore, the current flowing through the secondary coil WS circulates through the secondary coils US and VS. Secondary coils US and VS constitute a transformer by magnetically coupling with phase coils U and V. Therefore, if this transformer is regarded as an ideal transformer, the currents of the phase coils U and V change according to the currents of the secondary coils US and VS.

  In this embodiment, the magnetic flux formation of the magnetic pole around which the phase coil U is wound is promoted by the induced voltage of the secondary coil WS. That is, before the segment 53 leaves the + brush, both ends of the phase coil U are + V and the current is 0. When the segment 53 moves away from the + brush, the potential of the segment 53 decreases, and the current of the phase coil U increases.

  The current increase in the phase coil U is delayed by the inductance of the phase coil U. Since this delay is compensated by the current flowing through the secondary coil US, the current increase in the phase coil U is promoted.

That is, the induced current flowing in the secondary coil wound together with this phase coil during the period when the magnetic energy of one phase coil is extinguished promotes the current disappearance of this one phase coil and increases the current of the other phase coil. To accelerate. Eventually, the secondary coils (US, VS and WS) suppress rectifying sparks.
The transformer action will be described in more detail with reference to the timing chart shown in FIG. In FIG. 30, a time point (t18 to t18) indicates one rotation period of the rotor. During this period, alternating voltages (Va, Vb, Vc) are applied to the three terminals of the three-phase armature coil.

  The AC voltage Va has a positive potential during the period (t2 to t9) and a negative potential during the period (t11 to t18). The period (t18 to t2) and the period (t9 to t11) are periods in which no potential is applied to the terminal a. The period in which the potential is not applied to the terminal a is, for example, a period in which a segment connected to the terminal a in a normal DC motor is not in contact with either the + potential brush or the −potential brush.

  Similarly, the AC voltage Vb becomes a positive potential during the period (t8 to t15) and becomes a negative potential during the period (t17 to t6). The periods (t6 to t8) and the periods (t15 to t17) are periods in which no potential is applied to the terminal b. Similarly, the AC voltage Vc becomes a positive potential during the period (t14 to t3) and becomes a negative potential during the period (t5 to t12). The periods (t3 to t5) and the periods (t12 to t14) are periods in which no potential is applied to the terminal c.

  As a result, the phase voltages (Vu, Vv, and Vw) applied to the phase coils U, V, and W have the waveforms shown in FIG. In period D, the power supply voltage is applied to the entire phase coil. In the period E, the power supply voltage is equally applied to the two phase coils connected in series. The period (X and Y) is a period in which one phase coil is short-circuited by the brush.

  In period X, magnetic energy stored in the positive direction in the phase coil is released. Current flows in the positive direction through a coil of a short circuit coil wound around the same rotor pole as this phase coil. In period Y, the magnetic energy accumulated in the negative direction of the phase coil is released. Current flows in the negative direction through a coil of a short circuit coil wound around the same rotor pole as this phase coil. Since the coils (Us, Vs, and Ws) constituting the short-circuited coil are formed in a ring shape, the total of the back electromotive force with respect to the voltage applied from the outside is zero. The same applies to the period (X, Y).

  For example, in the period X, during the period in which the current flows in the positive direction to the secondary coil WS (period t2 to t3) due to the disappearance of the magnetic energy of the phase coil W, this current flows in the positive direction in the secondary coil US. Assist in increasing the positive current of the phase coil U. In addition, it flows to the secondary coil VS in the positive direction and assists in reducing the negative direction current of the phase coil V.

  As a result, the positive current increases in the initial period of the positive current conduction period of the phase coil U. Further, at the end of the negative current decrease period of the phase coil V, the negative current is attenuated. Eventually, in the period (t2 to t3), the magnetic energy of the W-phase magnetic pole portion causes a positive current to flow through the secondary coil WS. Further, this positive current assists in increasing the amount of magnetic flux in the U-phase magnetic pole portion and decreasing the amount of magnetic flux in the V-phase magnetic pole portion.

(Relationship between each example)
In the first embodiment shown in FIGS. 1 to 3, the auxiliary brush part joined to the rear end side of the main brush part with a high resistance layer (insulating layer) interposed therebetween is connected to a power source through a diode, whereby a phase coil is obtained. Discloses a technique for recovering the residual magnetic energy when leaving the main brush portion to the power source.

  In the second embodiment shown in FIGS. 4 to 5, the auxiliary brush part joined with the high resistance layer (insulating layer) sandwiched between the rear end side of the main brush part is connected to the capacitor, so that the phase coil is the main one. Disclosed is a technique for recovering residual magnetic energy in a capacitor when moving away from a brush portion.

  In the third embodiment shown in FIG. 6 to FIG. 14, by connecting the auxiliary brush portion joined with the high resistance layer (insulating layer) sandwiched between the rear end side or the front end side of the main brush portion to the resistor, Disclosed is a technique for consuming residual magnetic energy by a resistor when a phase coil leaves a main brush portion.

  The resistor can be connected to the power supply line (FIGS. 7, 9, 10, and 12). The resistor can be connected to the main brush portion (FIGS. 8 and 11). The resistor can also be constituted by an auxiliary brush part. By connecting the auxiliary brush part, which is joined to the front end side of the main brush part with a high resistance layer (insulating layer) sandwiched between the resistors, the brush heat generated by the segment voltage change when the segment contacts the main brush part Can be suppressed.

  The fourth embodiment shown in FIGS. 15 to 22 has a very simple configuration in which the shape of the brush or segment is changed, so that the residual magnetic energy when the phase coil moves away from the main brush portion is increased. Consume at the resistance part.

  The fifth embodiment shown in FIGS. 23 to 26 has a very simple configuration in which the shape of the brush constituted by the metal lead piece is changed, and thereby the residual magnetic energy when the phase coil is separated from the main brush portion, It is consumed at the high resistance part of this lead type brush.

In the sixth embodiment shown in FIGS. 27 to 30, a secondary coil is magnetically coupled to each phase coil of a rotor coil of a brushed motor, and each secondary coil is connected in series to constitute a short circuit.
When the residual magnetic energy when leaving the main brush portion generates an induced voltage in one phase coil of the short circuit, this induced voltage promotes a current change in the other phase coil.
The above embodiments can be implemented together or used for a universal motor.

  3 is an armature winding, 5 is a commutator, 100 is a battery, 200 is a diode, 300 is a diode, and 400 is a capacitor.

Claims (12)

A commutator and at least a pair of brushes in contact with the commutator;
The brush has a plurality of segments fixed to the rotating shaft at a predetermined pitch in the circumferential direction,
The segment is a brushed motor connected to an armature winding wound around a rotor core.
The brush has a conductive main brush portion that contacts the segment, a conductive auxiliary brush portion that contacts the segment, and a high-resistance insulating layer,
The auxiliary brush portion is joined to the side surface on the rear side in the rotation direction of the main brush portion via the insulating layer,
The auxiliary brush part is connected to a diode for recovering the residual magnetic energy of the armature winding, a capacitor for storing the residual magnetic energy, or a resistor for consuming the residual magnetic energy. A motor with a brush. A second auxiliary brush portion joined to the side surface of the main brush portion in the rotational direction front side through a high-resistance second insulating layer;
The second auxiliary brush unit includes a diode for recovering the residual magnetic energy of the armature winding, a capacitor for storing the residual magnetic energy, or a resistor for consuming the residual magnetic energy. The brushed motor according to claim 1 connected to a body. A commutator and at least a pair of brushes in contact with the commutator;
The brush has a plurality of segments fixed to the rotating shaft at a predetermined pitch in the circumferential direction,
The segment is a brushed motor connected to an armature winding wound around a rotor core.
At least one of the contact portion of the brush and the contact portion of the segment has a plurality of convex portions protruding outward in the circumferential direction,
The motor with brush, wherein the plurality of convex portions are arranged in a sawtooth shape in a substantially axial direction (or a substantially radial direction).   The brushed motor according to claim 3, wherein the convex portion has an axial width or a radial width that gradually decreases toward a distal end side in the circumferential direction.   4. The motor with brush according to claim 3, wherein at least one of the contact portion of the brush and the contact portion of the segment has the plurality of convex portions at both a circumferential front end and a circumferential rear end. The contact portion of the segment has the plurality of convex portions,
The brushed motor according to claim 3, wherein a contact portion of the brush does not have the plurality of convex portions. The contact portion of the brush has the plurality of convex portions,
The brushed motor according to claim 3, wherein the contact portion of the segment does not have the plurality of convex portions. Both the contact portion of the brush and the contact portion of the segment have the plurality of convex portions,
The brushed motor according to claim 3, wherein the convex part of the brush and the convex part of the segment are arranged at substantially the same position in the axial direction or the radial direction. The brush comprises a metal spring plate with a contact portion that contacts the segment protruding toward the segment side,
The brush motor according to claim 3, wherein the convex portion is formed at the contact portion.   4. The brush motor according to claim 3, wherein the contact portion protrudes by plastic deformation of the metal spring plate toward the thickness direction segment side. A commutator and at least a pair of brushes in contact with the commutator;
The brush has a plurality of segments fixed to the rotating shaft at a predetermined pitch in the circumferential direction,
The segment is a brushed motor connected to an armature winding wound around a rotor core.
A plurality of secondary coils wound around the rotor core together with a plurality of phase coils constituting the armature winding and magnetically coupled separately from the respective phase coils,
The brush motor, wherein the plurality of secondary coils are connected in order to form a short-circuit closed circuit.   The brushed motor according to claim 11, wherein the secondary coil has a smaller number of turns than the phase coil and a larger cross-sectional area than the phase coil.

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