JP2003250255A - Dc machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC machine which is capable of eliminating commutating fault by means of a third brush, and achieving reduction in the number of parts and costs. <P>SOLUTION: A salient-pole portion 16 which generates flux in the direction opposite to a magnet 3 is provided at the end of the magnet 3. The salient-pole portion 16 is arranged at a location where, when a third brush 8 begins to short-circuit both segments 12a, 12b during rotation of an armature 4, teeth bar rear end 10b located at five teeth 10a to which an armature coil 11 connected to the both segments 12a, 12b will be wound, is designed to overlap to the salient-pole portion 16. In addition, the salient-pole portion 16 is formed with such width that corresponds to an angle θ1 in the rotating direction where the third brush 8 short-circuits the both segments 12a, 12b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC machine equipped with an armature, a magnet, a brush and the like.

[0002]

2. Description of the Related Art Conventionally, a DC motor having a brush has been adopted as an automobile wiper motor. Among these, there is a three-brush motor, that is, a motor using a so-called third brush.
In this type of motor, the third brush is used for the purpose of changing the rotation speed of the motor. The main principle is to increase the rotation speed of the motor by reducing the magnetic flux used. Specifically, it has been easily realized by providing brushes at different installation positions and changing the energization range of the armature coil by selecting (combining) the brushes.

[0003]

However, in the above configuration, in the normal operation (low speed specification) of the motor, each time the high speed brush (third brush) straddles the adjacent commutator piece, the brush ( Due to the induced voltage generated in the armature coil short-circuited by the third brush), a large current instantaneously flows in the opposite direction to the energization direction. In FIG. 12, peaks A2 and B2 indicate instantaneous changes in the coil current flowing in the armature coil. As a result, spark discharge occurs in the third brush, which causes electrical noise and brush wear, and causes so-called rectification failure by the so-called third brush. As a countermeasure against this, a noise prevention circuit in which a plurality of coils (inductors), capacitors and the like are combined is provided in a motor drive circuit. This has been a problem in reducing the number of parts and cost of the motor.

The present invention has been made to solve the above problems, and an object thereof is to eliminate the so-called third brush, which is a commutation obstacle, and to reduce the number of parts and the cost. To provide a DC machine.

[0005]

According to a first aspect of the present invention, an armature in which an armature coil is wound around an armature core having a plurality of teeth, and the armature coil is connected to a commutator; A pair of magnets that are arranged to face each other with the child sandwiched therebetween; first and second brushes that are arranged at a position that faces the central axis of the armature and that come into contact with the segments of the commutator; and the first and second brushes. In a direct current machine, which is arranged at a predetermined angle from the facing position of the brushes and has at least one third brush that comes into contact with the segment. The special pole portion for suppressing the change in the interlinkage magnetic flux of the armature coil connected to both of the adjacent segments of the brush is short-circuited between the adjacent segments.

According to a second aspect of the present invention, in the DC machine according to the first aspect, the special pole portion is in a state in which the armature is powered by the first brush and the second brush and is rotated. When the third brush starts to short-circuit both adjacent segments, the rear end of the teeth bar on the opposite side in the direction of rotation of the plurality of teeth around which the armature coils connected to the two segments are wound is the special pole portion. The third brush is provided at a position where it comes to the start, and is formed with a width corresponding to the angle in the rotation direction, which is a period in which both segments are short-circuited.

According to a third aspect of the present invention, in the DC machine according to the first aspect, the special pole portion is in a state in which the armature is powered by the first brush and the second brush and rotates. When the third brush starts to short-circuit both adjacent segments, the tips of the teeth bars on the rotation direction side of the plurality of teeth around which the armature coils connected to the two segments are wound approach the special pole portion. The third brush is formed with a width corresponding to an angle in the rotation direction, which is a period in which both segments are short-circuited.

According to a fourth aspect of the present invention, in the DC machine according to any one of the first to third aspects, the special pole portion is
It is a reverse magnetic flux portion that generates a magnetic flux in the opposite direction to the adjacent magnet.

According to a fifth aspect of the present invention, in the DC machine according to any one of the first to third aspects, the special pole portion is
The magnet is made of a ferromagnetic material and is provided at the end of the magnet on the rotation direction side.

According to a sixth aspect of the present invention, in the DC machine according to any one of the first to third aspects, the special pole portion is
It is a weak magnetic flux part in which the magnetic flux is weaker than the adjacent magnets. According to a seventh aspect of the present invention, in the DC machine according to any one of the first to sixth aspects, the other magnet on the opposite side of the one magnet provided with the special pole portion is the magnet in the magnet. A weak magnetic flux portion is formed in which the magnetic flux is weaker than the other portions, and the weak magnetic flux portion, when one of the teeth bar ends of the plurality of teeth around which the armature coil is wound reaches the special pole portion, It is provided at the place where the opposite end of the teeth bar comes into contact.

(Operation) According to the invention described in claims 1 to 3, a chain of armature coils, in which a special pole portion is provided at one magnet end of the pair of magnets and is short-circuited by the third brush. The change amount of the magnetic flux is suppressed. In this case, when the armature is powered by the first brush and the second brush and rotates, the induced voltage (voltage opposite to the coil energization direction) generated in the armature coil short-circuited by the third brush is generated. It is reduced and the commutation obstacle by the 3rd brush is suppressed. Also,
Since the special pole portion is provided at the end portion of the magnet, reduction in magnetic force of the magnet serving as the rotation drive source is suppressed as compared with the case where the special pole portion is provided at the center of the magnet.

According to the fourth aspect of the invention, the special pole portion generates a magnetic flux in the opposite direction to the adjacent magnet and has the same polarity as the other magnet on the opposite side of the adjacent magnet. Here, when the third brush starts to short-circuit both adjacent segments, the tooth bar ends (tips or rear ends) of the plurality of teeth around which the armature coils connected to the segments are wound are the special pole parts. Approach.
On the other hand, the end of the teeth bar on the side opposite to the direction toward the special pole portion is located on the magnet on the opposite side of the magnet to which the special pole portion is adjacent. That is, in the short circuit period by the third brush, the polarities of the special pole portion where the tooth bar front and rear ends are located and the magnet are the same. Therefore, the interlinkage magnetic flux of the armature coil during the short circuit period is canceled by the front end side and the rear end side of the teeth bar, and the interlinkage magnetic flux can be made substantially constant. Therefore, the induced voltage generated in the armature coil (voltage opposite to the coil energization direction) is further reduced.

According to the fifth aspect of the invention, the special pole portion made of a ferromagnetic material is provided at the end of the magnet on the rotation direction side. In this case, when the DC machine is driven, the special pole portion is magnetized by the magnetic field generated by the armature to have the opposite polarity of the adjacent magnet. Therefore, similarly to the invention described in claim 4, the interlinkage magnetic flux of the armature coil during the short-circuit period of the third brush is canceled by the tooth bar front end side and the tooth bar end side, and the same interlinkage magnetic flux becomes substantially constant. It becomes possible to do.
Therefore, the induced voltage generated in the armature coil (voltage opposite to the coil energization direction) is further reduced.

According to the invention described in claim 6, the special pole portion is a weak magnetic flux portion having a weaker magnetic flux than the adjacent magnets. In this case, as in claim 4 or claim 5,
It is not possible to cancel the interlinkage magnetic flux between the tip side and the rear end side of the teeth bar, but the amount of change in the interlinkage flux is suppressed, and the induced voltage generated in the armature coil (voltage opposite to the coil energization direction). Can be reduced.

According to the seventh aspect of the invention, a weak magnetic flux portion having a weaker magnetic flux than other portions is formed in the other magnet on the opposite side of the one magnet provided with the special pole portion. There is. This weak magnetic flux portion is the other tooth bar end portion on the opposite side when one tooth bar end portion (front end or rear end) of the plurality of teeth around which the armature coil is wound approaches the special pole portion. It is placed in such a place that it can be touched. With this configuration, the special pole portion formed on one magnet end portion and the weak magnetic flux portion formed on the other magnet reliably suppress the change in the interlinkage magnetic flux of the armature coil, and The induced voltage (voltage in the direction opposite to the coil energization direction) that occurs is further reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is embodied in a DC motor (for example, a wiper motor) as a DC machine will be described below with reference to the drawings. Figure 1
FIG. 3 is a partial cross-sectional view showing the schematic structure of the wiper motor 1 of the present embodiment. The wiper motor 1 includes magnets 2, 3,
It has an armature 4, a commutator 5, and a plurality of brushes 6-8.

More specifically, the wiper motor 1 of this embodiment
Is a two-pole DC motor in which two magnets 2 and 3 forming an N-pole and an S-pole are arranged to face each other with an armature 4 sandwiched therebetween in a yoke (motor housing) 9. The armature 4 has an armature core 10 and an armature coil 11 wound around the core 10, and is rotationally driven by supplying a direct current.

The armature core 10 includes a plurality of teeth 10
a is formed, and the armature coil 11 is wound around a predetermined number (five in the embodiment) of adjacent teeth 10a. In the present embodiment, the number of teeth 10a is 12, and the teeth 10a are arranged every 30 ° along the circumferential direction of the armature 4. Therefore, the angle formed by the center lines of the adjacent teeth 10a, that is, the array pitch or the motor armature slot angle θ is 30 ° (= 360 ° / 12).
Although not shown, a plurality of armature coils 11
Are similarly wound around every five teeth 10a. That is, the winding method of the winding is distributed winding.

The commutator 5 is arranged at one end of the armature 4 and has a plurality of segments 12. In this embodiment, twelve segments 12 are provided every 30 ° in the circumferential direction. The armature coil 11 wound around the five teeth 10a has two segments 12 (for example, the segment 12) on the side substantially facing the five teeth 10a.
a, 12b).

Further, the plurality of brushes 6 to 8 are arranged in a biased state so as to come into sliding contact with the commutator 5. In this embodiment, three brushes 6 to 8 are arranged. Among them, the first and second brushes 6 and 7 as the first and second brushes are arranged in a relationship of being 180 degrees apart (opposing), and the third brush 8 as the third brush is
It is disposed so as to form a predetermined angle δ with the first brush 6. In the present embodiment, the angle δ is set to be an acute angle formed by the first brush 6 in the rotation direction. Further, the brushes 6 to 8 are connected to the DC power supply circuit 13 via the respective terminals 6a to 8a.

More specifically, the DC power supply circuit 13 includes a DC power supply 14 and a changeover switch 15, and the brushes 6, 8 are provided.
Are terminals 6a and 8a and a selector switch 15 respectively.
The second brush 7 is connected to the positive electrode of the DC power source 14 via the terminal 7a, and is connected to the negative electrode of the DC power source 14 via the terminal 7a. That is, the changeover switch 15 is switched depending on the driving condition to supply power to the motor 1 via the brushes 6 and 7, or the motor 1 is supplied via the brushes 7 and 8.
Select whether to feed power to.

In the present embodiment, in the normal operation (low speed specification), the changeover switch 15 is switched so that the motor 1 is supplied with power via the brushes 6 and 7, and in the high speed operation, the motor 1 is supplied via the brushes 7 and 8. The change-over switch 15 is switched so that the power is supplied to. That is, the brushes 6 and 7 are arranged in the first position which is low speed rotation, and the brushes 7 and 8 are arranged in the second position which is high speed rotation.

When the change-over switch 15 is switched, the DC current supplied from the DC power supply 14 flows through the brushes 6 and 7 or the brushes 7 and 8 and the segment 12 of the commutator 5 to the armature coil 11. As a result, the armature 4 rotates in the clockwise direction (X arrow direction in the figure).

The magnets 2 and 3 are connected to each other by an armature 4
Are arranged so that they are point-symmetric with respect to the central axis of
As shown in FIGS. 1 and 2, a special pole portion 16 is provided at the end of the magnet 3 (the end on the rotation direction side of the armature 4). The special pole portion 16 is a reverse magnetic flux portion that generates a reverse magnetic flux with respect to the magnet 3. That is, in the present embodiment, the polarity of the magnet 3 is the S pole, and the polarity of the special pole portion 16 is the N pole having the same pole as the magnet 2. The special pole portion 16 is formed integrally with the magnet 3, and is magnetized by applying a magnetic field in the opposite direction of the magnetizing process after the magnet 3 is magnetized.

As shown in FIG. 1, in the special pole portion 16, when the armature 4 is rotating, the third brush 8 has both segments 12a and 12b.
When short-circuiting b is started, the tooth bar rear end 10b on the opposite side in the rotational direction of the five teeth 10a around which the armature coil 11 connected to both segments 12a, 12b is wound.
Is provided at a position where it reaches the special pole portion 16. Further, the special pole portion 16 is formed with a width corresponding to an angle θ1 in the rotation direction, which is a period (short-circuit period) in which the third brush 8 short-circuits both segments 12a and 12b.

Segments 12a, 1 by the third brush 8
During the short-circuit period of 2b, the five teeth 10 around which the armature coil 11 connected to the segments 12a and 12b is wound.
The tooth bar tip 10c on the rotation direction side in a passes through the substantially central portion (a portion having a width corresponding to the angle θ1 in the rotation direction) 2a of the magnet 2. In the present embodiment, the magnetic flux density in the special pole portion 16 is formed so that the tooth bar tip 10c has the same pole and strength as the predetermined portion 2a of the magnet 2 facing during the short circuit period.

In this case, the interlinkage magnetic flux of the armature coil 11 connected to both the segments 12a and 12b becomes substantially constant during the short circuit period of both the segments 12a and 12b. That is, when the armature 4 rotates from the state of FIG. 1 by the angle θ1 (short-circuit period), magnetic flux is added on the tooth bar tip 10c side and magnetic flux is reduced on the tooth bar rear end 10b side. At this time, since the predetermined portion 2a of the magnet 2 facing the tooth bar tip 10c and the special pole portion 16 facing the tooth bar rear end 10b have the same pole and the same strength, the addition is made on the tooth bar tip side. The magnetic flux and the magnetic flux subtracted on the rear end side of the teeth bar are the same (cancelled out). Therefore, the interlinkage magnetic flux of the armature coil 11 during the short-circuit period is constant, so that the armature coil 11 that is short-circuited by the brush 8 in the state where the brushes 6 and 7 supply power (normal operation)
The induced voltage of is suppressed.

FIG. 3 shows changes in the current flowing through the armature coil 11 when the brushes 6 and 7 supply power (normal operation). In the present embodiment, as described above, the induced voltage generated in the armature coil 11 during the short circuit period by the brush 8 is suppressed. Therefore, the peak A1 and the peak B1 of the coil current flowing in the armature coil 11
Is smaller than the conventional peak A2 and peak B2 shown in FIG. 12, and a sharp reverse current change is suppressed.

As described in detail above, this embodiment has the following features. (1) The special pole portion 16 is provided at the end of the magnet 3 to suppress the amount of change in the interlinkage magnetic flux of the armature coil 11 that is short-circuited by the third brush 8. In this case, the armature coil 11
Induced voltage (voltage in the opposite direction of the coil energization direction)
Is reduced, and a reverse current change can be suppressed.
Therefore, spark discharge in the third brush 8 is prevented, and electric noise of the motor 1 and brush wear can be reduced.

Further, since the spark discharge at the third brush 8 is prevented, circuit parts (inductor, capacitor, etc.) for noise prevention are unnecessary, and the parts cost of the motor 1 can be reduced.

Further, since the special pole portion 16 is provided at the end portion of the magnet 3, compared with the case where the special pole portion 16 is provided at the center of the magnet 3, a decrease in the magnetic force of the magnet 3 serving as a rotation drive source is suppressed. be able to.

(2) Since the special pole portion 16 of this embodiment is a reverse magnetic flux portion that generates a magnetic flux in the opposite direction to the adjacent magnet 3, the interlinkage of the armature coil 11 during the short-circuiting period of the third brush 8. The magnetic flux is on the tooth bar tip 10c side and the rear end 1
The 0b side cancels each other out, and the same interlinkage magnetic flux can be made substantially constant.

(Second Embodiment) The second embodiment of the present invention will be described below. FIG. 4 shows a schematic configuration of the wiper motor 21 in this embodiment. In addition,
The same components as those in the first embodiment are designated by the same reference numerals in the drawings, and detailed description thereof will be omitted.
Then, the differences from the first embodiment will be mainly described below.

That is, in this embodiment, the special pole portion 16a provided at the end of the magnet 3 is made of a ferromagnetic material (high magnetic permeability material), for example, soft iron. The special pole portion 16a is also provided at the same position as the special pole portion 16 of the first embodiment. That is, the special pole portion 16a is
When the third brush 8 starts to short-circuit both segments 12a and 12b, the tooth bar rear end 10b on the opposite side in the rotational direction of the five teeth 10a around which the armature coil 11 connected to both segments 12a and 12b is wound is the Special pole section 1
It is provided at a place where it reaches to 6a. Also,
The special pole portion 16a is also formed with a width corresponding to the angle θ1 in the rotation direction during the short circuit period by the third brush 8.

On the other hand, in the magnet 22 arranged so as to face the magnet 3, the portion 22a where the tooth bar tip 10c faces during the short circuit period is cut out along the axial direction as shown in FIGS. 4 and 5. , Its thickness is thinner than other parts. Therefore, the magnetic flux in the portion 22a is weaker than the magnetic flux in other portions of the magnet 22, and the portion 22a corresponds to the weak magnetic flux portion.

In this embodiment, since the special pole portion 16a at the end of the magnet 3 is made of a ferromagnetic material, it is magnetized by the magnetic field generated by the armature 4 when the motor 21 is operating. Specifically, the special pole portion 16a is located at the end of the magnet 3 on the rotation direction side, and the polarity of the magnetic field of the portion of the armature 4 facing the special pole portion 16a is the S pole. Therefore, the special pole portion 16a has the polarity of the magnet 3 (S pole).
It is magnetized to the N pole which has the opposite polarity with respect to. In the present embodiment, the thickness (depth of the cutout) of the weak magnetic flux portion 22a in the magnet 2 is set based on the magnetic flux density of the special pole portion 16a. That is, the thickness of the weak magnetic flux portion 22a is set so that the magnetic flux of the special pole portion 16a during the normal operation of supplying power via the brushes 6 and 7 and the magnetic flux of the weak magnetic flux portion 22a of the magnet 22 are substantially the same. .

When the wiper motor 21 is constructed as described above, both the segments 12a,
In the short circuit period of 12b, both segments 12a, 12
The interlinkage magnetic flux of the armature coil 11 connected to b becomes substantially constant, and the induced voltage generated in the armature coil 11 is suppressed. Therefore, the spark discharge in the third brush 8 is prevented,
It is possible to reduce electric noise and brush wear of the motor 21.

(Third Embodiment) A third embodiment of the present invention will be described below. FIG. 6 shows a schematic configuration of the wiper motor 31 in this embodiment. In FIG. 6, the same components as those in the first embodiment are designated by the same reference numerals.

In this embodiment, the teeth bar tips 10c of the five teeth 10a around which the armature coil 11 is short-circuited by the third brush 8 are wound.
The magnetic poles are not provided in the section through which the tooth bar rear end 10b passes (section in the rotational position indicated by the angle θ1 in FIG. 6).

More specifically, the magnet 32 arranged to face the magnet 3 is composed of two divided pieces 32a and 32b. Then, in the yoke 9, the divided pieces 32a, 32b are separated by a width corresponding to the angle θ1, and a gap 32c is formed between the divided pieces 32a, 32b. The gap 32c is such that when the third brush 8 starts short-circuiting the segments 12a and 12b,
The teeth bar tips 10c on the rotation direction side of the five teeth 10a around which the armature coils 11 connected to the segments 12a and 12b are wound are provided at positions where they approach the gap 32c. The gap 32c
Angle θ1 of the segment 12a by the third brush 8,
The angle corresponds to the short circuit period 12b.

Further, the third brush 8 has the segments 12a,
The magnet 3 is arranged so that the rear end 10b of the teeth bar reaches the end of the magnet 3 when the short circuit of 12b starts. Then, during the short-circuit period, the teeth bar rear end 10b is moved to the magnet 3 and the magnet 32.
It is located in the space (gap) formed between them. In the present embodiment, the space having an angle θ1 from the end of the magnet 3 toward the rotation direction serves as a special pole portion.

When the wiper motor 31 is constructed in this manner, as in the first and second embodiments, both segments 12a and 12b are short-circuited during the short-circuiting period.
The interlinkage magnetic flux of the armature coil 11 connected to a and 12b becomes substantially constant, and the induced voltage generated in the armature coil 11 is suppressed. Therefore, spark discharge in the third brush 8 is suppressed, and electric noise of the motor 31 and brush wear can be reduced.

Further, in this embodiment, the gap 32c of the magnet 32 is divided into the divided pieces 3 of the magnet 32 which are divided.
It is formed by arranging 2a and 32b apart.
Further, unlike the above-described embodiment, it is not necessary to dispose the special pole portion 16 that is a magnetic pole of opposite polarity or the special pole portion 16a that is made of a ferromagnetic material at the end of the magnet 3. Therefore, the wiper motor 3
1 is easy to manufacture and is advantageous in terms of cost.

(Fourth Embodiment) The fourth embodiment of the present invention will be described below. FIG. 7 shows a schematic configuration of the wiper motor 41 in this embodiment. In FIG. 7, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. Then, the differences from the first embodiment will be mainly described below.

In the first embodiment, the armature coil 11 wound around the five teeth 10a is connected to the two segments 12 (for example, the segments 12a and 12b) on the side substantially facing the five teeth 10a. There is. On the other hand, in the present embodiment, the armature coil 11 wound around the five teeth 10a is connected to the two segments 12 (for example, the segments 12c and 12d) located substantially in the center in the same direction as the five teeth 10a. is doing. Also,
The third brush 8 is arranged so as to form a predetermined angle δ1 with the first brush 6. In this embodiment, the angle δ1 is set to be approximately 90 ° from the first brush 6 in the rotation direction (X arrow direction).

In the present embodiment, at the end portion of the magnet 3 (the end portion on the rotating direction side of the armature 4), a special pole for generating a magnetic flux in the opposite direction to the magnet 3 is formed, as in the first embodiment. A section 16 is provided. This special pole portion 16 is the third
When the brush 8 starts to short-circuit both the segments 12a and 12b, the tooth bar tips 10c on the rotational direction side of the five teeth 10a around which the armature coil 11 connected to the segments 12a and 12b is wound are the special pole portions 16. It will be installed in a place where it will be exposed.

Even if the wiper motor 41 is configured as described above, during the short-circuit period of both the segments 12a and 12b,
Armature coil 1 connected to both segments 12a, 12b
The induced voltage (voltage opposite to the coil energization direction) generated in 1 is suppressed. Therefore, spark discharge at the third brush 8 is prevented, and electric noise of the motor 21 and brush wear can be reduced.

In addition to the above, the present invention can be embodied in the following forms. In the first embodiment, the special pole portion 16 at the end of the magnet 3 generates the magnetic flux in the opposite direction of the magnet 3, but the invention is not limited to this, and the magnetic flux is generated more than the magnet 3. The weak magnetic flux portion may be weakened. Specifically, as shown in FIG. 8, the special pole portion (weak magnetic flux portion) 16b may be formed by thinly notching the end portion of the magnet 51, or as shown in FIG. Special pole part (weak magnetic flux part) by weakening the magnetization at the end 1
6c may be formed. In this case, unlike the first embodiment, the interlinkage magnetic flux of the armature coil 11 cannot be made substantially constant, but since the change amount of the interlinkage magnetic flux can be suppressed, it is generated in the armature coil 11. The induced voltage that occurs can be suppressed.

Of course, the special pole portion 1 in the fourth embodiment described above.
6 may be embodied in place of the special pole portion 16b of FIG. 8 and the special pole portion 16c of FIG. Also in this case, the induced voltage generated in the armature coil 11 can be suppressed.

In the second embodiment, the magnet 22 is used.
Although the weak magnetic flux portion 22a is formed by cutting out the inner peripheral surface of the above, the invention is not limited to this. For example, in FIG.
Like the magnet 53, the weak magnetic flux portion 54 having a weaker magnetic flux than other portions may be provided in the cutout portion 53a extending from the axial end portion to the central portion. Further, as shown in FIG. 11, a weak magnetic flux portion 56 having a weaker magnetic flux than other portions may be formed in the through hole 55a penetrating the magnet 55. The weak magnetic flux portion 54 of the magnet 53 and the magnet 55
The weak magnetic flux portion 56 is formed by using different magnetic materials.

The present invention may be embodied in a motor provided with a plurality of teeth other than twelve. Further, the same armature coil may be wound around the motor with n teeth other than five. Further, it may be embodied as a motor provided with a plurality of third brushes 8.

In each of the above embodiments, the wiper motor 1 is embodied as a DC machine, but it may be embodied as another DC motor or a DC generator. The technical idea that can be understood from the above-described embodiment will be described along with its effects.

(A) An armature in which an armature coil is wound around an armature core having a plurality of teeth, and the armature coil is connected to a commutator; and a pair of magnets arranged to face each other with the armature interposed therebetween. , The first and second brushes arranged at a position facing the central axis of the armature and contacting the segment of the commutator, and arranged at a predetermined angle from the facing position of the first and second brushes Is
In a DC machine including at least one third brush that contacts the segment, one magnet of the pair of magnets is composed of divided pieces, and the divided pieces have a predetermined angle between the divided pieces. One of a plurality of teeth in which armature coils connected to both segments are wound in a short-circuit period in which the third brush short-circuits both adjacent segments so as to form a gap having a gap. A DC machine, characterized in that an end of the teeth bar is located in the gap, and an end of the other teeth bar is located in a gap formed between the pair of magnets. Even in this case, the change in the interlinkage magnetic flux of the armature coil can be reliably suppressed, and the induced voltage (voltage opposite to the coil energization direction) generated in the armature coil can be reduced.

[0054]

As described in detail above, according to the present invention,
The rectification obstacle due to the third brush can be removed, and the cost of the DC machine can be reduced.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a schematic configuration of a DC motor according to a first embodiment.

FIG. 2 is a perspective view of a magnet provided with a special pole portion.

FIG. 3 is a graph showing changes in coil current flowing in the armature coil.

FIG. 4 is a partial cross-sectional view showing a schematic configuration of a DC motor according to a second embodiment.

FIG. 5 is a perspective view of a magnet provided with a weak magnetic flux portion.

FIG. 6 is a partial cross-sectional view showing a schematic configuration of a DC motor according to a third embodiment.

FIG. 7 is a partial cross-sectional view showing a schematic configuration of a DC motor according to a fourth embodiment.

FIG. 8 is an explanatory view showing a special pole portion of a magnet of another example.

FIG. 9 is an explanatory view showing a special pole portion of a magnet of another example.

FIG. 10 is a perspective view of a magnet provided with another weak magnetic flux portion.

FIG. 11 is a perspective view of a magnet provided with another weak magnetic flux portion.

FIG. 12 is a graph showing changes in coil current flowing in a conventional armature coil.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wiper motor as a DC machine, 2, 3 ... Magnet, 4 ... Armature, 5 ... Commutator, 6 ... 1st brush as a 1st brush, 7 ... 2nd brush as a 2nd brush, 8 ... A third brush as a brush of No. 3, 10 ... Armature core, 10a ... Teeth, 10b ... Teeth bar rear end, 10c ... Teeth bar tip, 11 ... Armature coil,
12, 12a, 12b, 12c, 12d ... Segment,
16, 16a, 16b, 16c ... Special pole portion, 21 ... Wiper motor as DC machine, 22 ... Magnet, 22a ... Weak magnetic flux section, 31 ... Wiper motor as DC machine, 32 ... Magnet, 41 ... Wiper motor as DC machine, 51 ...
Magnet, 52 ... Magnet, 53 ... Magnet, 5
4 ... Weak magnetic flux part, 55 ... Magnet, 56 ... Weak magnetic flux part.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H613 AA03 BB04 BB14 BB35 GA02                 5H622 AA03 CA02 CA05 CB04                 5H623 AA03 BB07 GG11 GG13 GG16                       JJ01

Claims (7)

[Claims] 1. An armature in which an armature coil is wound around an armature core having a plurality of teeth, and the armature coil is connected to a commutator; and a pair of magnets arranged to face each other with the armature interposed therebetween. The first and second brushes, which are arranged at a position opposed to the central axis of the armature and are in contact with the segments of the commutator, and the first and second brushes are arranged at a predetermined angle from the opposed position. A DC machine comprising at least one third brush in contact with the segment, wherein one magnet end of the pair of magnets short-circuits both adjacent segments of the third brush. A direct current machine comprising a special pole portion for suppressing a change in interlinkage magnetic flux of an armature coil connected to the both segments. 2. The DC machine according to claim 1, wherein the special pole portion is configured such that the third brush is in a state in which the armature is powered by the first brush and the second brush and is rotated. Provided at a place where the rear end of the teeth bar on the opposite side in the direction of rotation of the plurality of teeth around which the armature coils connected to the two adjacent segments start is short-circuited when starting to short-circuit both adjacent segments. The DC machine is characterized in that the third brush is formed with a width corresponding to an angle in the rotation direction that is a period in which both segments are short-circuited. 3. The DC machine according to claim 1, wherein, in the special pole portion, the third brush is in a state in which the armature is powered by the first brush and the second brush and is rotated. When short-circuiting both adjacent segments, the teeth bar tips on the rotation direction side of the plurality of teeth around which the armature coils connected to the both segments are wound are provided at a position where they come to the special pole portion. In addition, the DC brush is characterized in that the third brush is formed with a width corresponding to an angle in a rotation direction that is a period in which both segments are short-circuited. 4. The direct current machine according to claim 1, wherein the special pole portion is a reverse magnetic flux portion that generates a magnetic flux in a direction opposite to that of an adjacent magnet. Machine. 5. The DC machine according to claim 1, wherein the special pole portion is made of a ferromagnetic material, and is provided at an end portion of the magnet on a rotation direction side. DC machine to do. 6. The DC machine according to claim 1, wherein the special pole section is a weak magnetic flux section having a weaker magnetic flux than an adjacent magnet. 7. The DC machine according to claim 1, wherein the other magnet on the opposite side of the one magnet provided with the special pole portion is provided with a portion other than the other portion of the magnet. A weak magnetic flux portion is also formed by weakening the magnetic flux, and the weak magnetic flux portion, when one of the teeth bar ends of the plurality of teeth around which the armature coil is wound reaches the special pole portion, A DC machine characterized in that it is provided at a place where the ends of the teeth bars come into contact with each other.