JPH10248228A - Dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent permanent demagnetization of a magnet and to reduce the weight by arranging a pair of magnets face-to-face without contact at outer side of an armature and by arranging a pair of yokes separately and oppositely in a direction perpendicular to the opposite direction of these magnets. SOLUTION: At the outer side of an armature core 9, a pair of a first magnet 3 and a second magnet 4 are arranged without contact, each of these first and second magnets 3 and 4 is a permanent magnet having a shape of a cylinder split into half, and its length is measured along the axial direction of the armature shaft 10. The first magnet 3 abuts the first yoke 5 at the outer side of a first yoke contact portion 3a, and a second yoke 6 abuts the second yoke contact portion 3c at its outer side. Also for the second magnet 4, the first yoke 5 abuts the outer side of the first yoke contact portion 4b, and the second yoke 6 abuts outside the second yoke abutting portion 4c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor used for a vehicle power window, power seat, sunroof, and the like.

[0002]

2. Description of the Related Art Power windows for vehicles, power seats,
As shown in FIG. 6, as a DC motor used for a sunroof or the like, magnets 71 and 72 are mounted inside a cylindrical yoke 70 so as to face each other.
An armature 73 rotatably supported by a yoke 70 is disposed inside the armatures 1 and 72. In such a DC motor, when an armature coil wound around an armature core included in the armature 73 is energized, the armature coil is excited, and as shown by a broken line in the drawing, one of the armatures 73 is turned off. While the magnetic flux flows through the magnet 71, the yoke 70, the one magnet 71, and the armature 73, the magnetic flux flows from the armature 73 to the other magnet 72, the yoke 70, the other magnet 72, and the armature 73.

[0003]

In the above-described DC motor, the flow of the magnetic flux without exciting the armature 73 passes through the one magnet 71, the yoke 70 and the other magnet 72. In the radial direction, and otherwise pass through the inside of the yoke 70 having high magnetic permeability. On the other hand, the flow of magnetic flux from the armature 73 by exciting the armature coil causes the armature 73, one magnet 71,
Yoke 70, one magnet 71, armature 73
And the armature 73, the other magnet 72, the yoke 70, the other magnet 72, and the armature 73. Most of the magnetic flux from the armature 73 passes through both magnets 71, 72, and the yoke 70 having a high magnetic permeability.
Through the interior of For this reason, the demagnetizing magnetomotive force generated by the armature 73 due to the large current flowing at the time of high load or low temperature passes through the inside of the yoke 70 outside the two magnets 71 and 72, and the magnet 7
Permanent demagnetization of 1, 72 easily occurs. Therefore, in such a DC motor, demagnetization is dealt with by increasing the thickness of the magnets 71 and 72, and as a result, the magnets 71 and 72 having a large thickness are used.
Thus, there is a problem that the motor weight increases.

[0004]

SUMMARY OF THE INVENTION A DC motor according to the present invention provides a DC motor that can be reduced in weight by preventing permanent demagnetization of the magnet without affecting the motor characteristics and without using a magnet having a large thickness. It is intended to be.

[0005]

Configuration of the Invention

[0006]

According to a first aspect of the present invention, there is provided a DC motor, comprising: a case; an armature rotatably supported by the case; and a pair of magnets which are arranged outside of the armature so as to face each other in a non-contact manner. And a pair of yokes spaced apart and opposed to each other in a direction perpendicular to the facing direction of the pair of magnets.

In the DC motor according to a second aspect of the present invention, the case has a low magnetic permeability portion capable of reducing the amount of magnetic flux applied from the armature to the pair of magnets to the pair of yokes. It is characterized in that it is configured to be formed between a pair of yokes.

In the DC motor according to a third aspect of the present invention, the magnet is formed so as to have a length in the axial direction of the armature shaft, and the low magnetic permeability portion is formed along the axial direction of the armature shaft. It is characterized by having the configuration described above.

In the DC motor according to a fourth aspect of the present invention, the magnet is provided with an outer edge formed in a planar shape on the case side, and the low magnetic permeability portion of the case extends along the outer edge of the magnet. Is formed on a flat surface.

According to a fifth aspect of the present invention, there is provided a DC motor, wherein the case has a structure in which a fixed portion capable of mounting a pair of yokes and a pair of magnets inside is integrally formed. .

In the DC motor according to claim 6 of the present invention, the case, the armature shaft rotatably supported by the case, the commutator mounted on the armature shaft, and a slidable contact with the commutator for electrical connection. A brush, an armature core attached to the armature shaft, an armature coil wound on the armature core and electrically connected to the commutator, and a first diameter of the armature core outside the armature core. The first and second magnets are separated from each other in a direction and are arranged in a pair without contact with the armature core, and in the second radial direction of the armature core orthogonal to the first radial direction of the armature core, respectively. The first and second magnets are separated from each other and arranged outside the first and second magnets. It is characterized in that it has a configuration in which a second yoke.

In the DC motor according to a seventh aspect of the present invention, the first yoke is provided with a magnet contact portion that contacts only one end of the first magnet and one end of the second magnet, The second yoke is characterized in that a magnet contact portion that is in contact with only the other end of the first magnet and the other end of the second magnet is formed.

[0013]

In the DC motor according to the first aspect of the present invention, the pair of yokes are opposed to each other in a direction perpendicular to the direction in which the pair of magnets face each other. It is difficult for the magnetic flux to pass between the ends. Therefore, most of the magnetic flux from the pair of magnets without the magnetic flux from the armature passes through the pair of yokes, but the amount of magnetic flux from the armature that passes through the pair of magnets with the magnetic flux from the armature decreases, and Permanent demagnetization of the magnet due to demagnetizing magnetomotive force is unlikely to occur.

In the DC motor according to the second aspect of the present invention, the amount of magnetic flux from the armature passing through the pair of magnets by the low-permeability portion and being given to the pair of yokes is reduced, whereby the demagnetizing magnetomotive force is reduced. Hardly cause permanent demagnetization of the magnet.

In the DC motor according to a third aspect of the present invention, the magnetic flux is formed between the pair of yokes along the axial direction of the armature shaft by the low magnetic permeability portion formed in the case along the axial direction of the armature shaft. A gap that is difficult to pass is formed. Therefore, most of the magnetic flux from the pair of magnets without the magnetic flux from the armature passes through the pair of yokes without passing through the low magnetic permeability part, but in the state with the magnetic flux from the armature, the axial direction of the armature shaft The low magnetic permeability portion along the line makes it difficult for the pair of yokes to flow through the pair of yokes, so that the amount of the magnet passing through the pair of magnets is reduced, and permanent demagnetization of the magnet due to demagnetizing magnetomotive force is unlikely to occur.

In the DC motor according to a fourth aspect of the present invention, the low magnetic permeability portion of the case is formed flat between the pair of yokes along the planar outer edge of the magnet. The thickness of the center portion of the magnet is smaller than that of the magnet having a curved outer edge. This is because, when there is no magnetic flux from the armature, the magnetic flux flowing through the central portion of the magnet decreases, and the magnetic flux tends to collect on both end surfaces of the magnet as the shortest path of the magnetic circuit. Therefore, by guiding the central portion of the magnet that does not contribute to the effective magnetic flux, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur.

In the DC motor according to the fifth aspect of the present invention, the pair of yokes and the pair of magnets are mounted inside the case by fixed portions. Therefore, in addition to the operation of the first aspect, it is not necessary to use a separate mounting member when fixing the pair of yokes and the pair of magnets to the case.

According to a sixth aspect of the present invention, in the DC motor, the first and second yokes are provided on the armature core orthogonal to the first and second magnets spaced apart from each other in the first radial direction of the armature core. Since it is arranged apart in the second radial direction, it is difficult for the magnetic flux to pass between the first and second yokes. Therefore, most of the magnetic flux from the first and second magnets in the state where the armature coil is not excited and there is no magnetic flux from the armature core passes through the first and second yokes, but the armature coil is excited. As a result, the amount of magnetic flux from the armature core that passes through the first and second magnets is reduced, and permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur.

In the DC motor according to a seventh aspect of the present invention, the first yoke has a magnet abutting portion which abuts only on one end of the first magnet and one end of the second magnet, and , The magnet contact portion contacts only the other end of the first magnet and the other end of the second magnet. Therefore, most of the magnetic flux from the first and second magnets in the state where the armature coil is not excited and there is no magnetic flux from the armature core is the first,
Although passing through the second yoke, when the armature coil is excited, the amount of magnetic flux from the armature core that passes through the first and second magnets is reduced, and the magnet is permanently demagnetized by the demagnetizing magnetomotive force. Is unlikely to occur.

[0020]

1 to 4 show a first embodiment of a DC motor according to the present invention.

The illustrated DC motor 1 mainly includes an armature 2, a first magnet (magnet) 3, a second magnet (magnet) 4, a first yoke (yoke) 5, and a second yoke (yoke). 6, the first brush 7,
It comprises a second brush 8 and a case 9.

The armature 2 includes an armature shaft 10, an armature core 11, a commutator 12,
An armature coil 13 is provided.

The armature shaft 10 is made of an iron material formed in a round bar shape, and one end on the left side in FIG. 1 is inserted into a first bearing 15 attached to the center of an end bracket 14 described later. In addition, the other end on the right side in FIG. 1 is inserted into a second bearing 16 attached to a closed end of a case 9 described later. The armature shaft 10 is rotatably supported on the case 9 by first and second bearings 15 and 16. The armature shaft 10 has one end coupled to a load.

At the approximate center of the armature shaft 10, a projecting portion 10a is formed along the axial direction, and the armature core 11 is fixed to the projecting portion 10a.
The armature core 11 is formed by laminating a plurality of thin iron plates, has a winding portion 11a having a predetermined number of slots on an outer peripheral portion, and has an inner peripheral portion formed on a projecting portion 10a of the armature shaft 10. It is press-fitted.

A commutator 12 is attached to the armature shaft 10 near the armature core 11. The commutator 12 has the same number of commutator pieces 1 on the outer peripheral portion of the cylindrical commutator body 12a as the winding portion 11a of the armature core 11 described above.
2b are provided in the circumferential direction so as to be insulated from each other.
The armature coil 13 wound around the winding portion 11a of the armature core 11 is electrically connected to the commutator piece 12b.

Outside the commutator 12, first and second brushes 7, 8 are arranged. The first and second brushes 7 and 8 are held by a brush holder 17. The brush holder 17 is fixed near the open end of the case 9 described later, and first and second brush springs 18 and 19 are provided in brush boxes 17 a and 17 b formed to face the outside of the commutator 12. The first and second brushes 7 and 8 are accommodated through the first and second brushes, respectively. The first and second brushes 7 and 8 are electrically connected to each other by sliding contact with the commutator pieces 12b of the commutator 12 by the first and second brush springs 18 and 19. The first and second brushes 7, 8 are electrically connected to an external control circuit.

On the other hand, a pair of first and second magnets 3 and 4 are arranged outside the armature core 9.
Each of the first and second magnets 3 and 4 is a permanent magnet having a shape obtained by cutting a cylinder in half, and has a length along the axial direction of the armature shaft 10.

As shown in FIG. 2, the first magnet 3 has a first armature core 11 extending in the vertical direction in the drawing.
The second magnet 4 is disposed on the upper side in the radial direction of FIG.
Is disposed below the armature core 11 in the first radial direction in the drawing. The first and second magnets 3, 4 are opposed to each other outside the armature core 11 at positions separated from each other.

The first magnet 3 has a first fixed portion 9 having a curved outer edge 3d formed in a case 9 described later.
a, the second magnet 4 is fixed to the top plate 9e side of the case 9 by the third fixing portion 9c, and the second magnet 4 has a second fixing portion 9b having a curved outer edge 4d formed in the case 9 described later;
It is fixed to the bottom plate 9f side of the case 9 by the fourth fixing portion 9d.

The first magnet 3 has an N pole magnetized on the inner peripheral side which is the armature core 11 side, and an S pole opposite to the N pole magnetized on the outer peripheral side. In contrast to this, the second magnet 4 has an S pole magnetized on the inner peripheral side which is the armature core 11 side, and an N pole opposite to the S pole magnetized on the outer peripheral side.

As shown in FIG. 2, the first magnet 3 has a first yoke contact portion 3b on the left side of a semi-cylindrical first magnet main body 3a in the drawing, and a first yoke contact portion 3b. The right side of the first magnet body 3a in the drawing is a second yoke contact portion 3c.

The first magnet 3 has a first yoke 5 to be described later abutting on the outside of the first yoke abutting portion 3b, and
A second yoke 6 described later is in contact with the outside of the yoke contact portion 3c.

As shown in FIG. 2, the second magnet 4 has a first yoke contact portion 4b on the left side of a semi-cylindrical second magnet main body 4a in the drawing, and a second magnet main body 4a. The right side in the figure of the second magnet body 4a is a second yoke contact portion 4c.

The second magnet 4 has a first yoke 5 which will be described later abut on the outside of the first yoke abutment portion 4b.
A second yoke 6 described below is in contact with the outside of the yoke contact portion 4c.

First and second yokes 5 and 6 are arranged outside the first and second magnets 3 and 4. As shown in FIG. 3, each of the first and second yokes 5 and 6 has a shape obtained by cutting a square tube into a half shape, and has a length along the axial direction of the armature shaft 10.

As shown in FIG. 2, the first yoke 5 is located on the left side in the second radial direction of the armature core 11 perpendicular to the first radial direction of the armature core 11 described above. The second yoke 6 is disposed on the right side of the armature core 11 in the second radial direction in the drawing.
Away from the first yoke 5.

The first yoke 5 has a first half-cylindrical first shape.
A first magnet contact portion 5b that can contact the first yoke contact portion 3b of the first magnet 3 is formed on the upper side of the yoke main body 5a in FIG. A second magnet contact portion 5c that can contact the first yoke contact portion 4b of the second magnet 4 is formed below the main body 5a in FIG.

The first yoke 5 has a structure in which the first magnet contact portion 5b is formed by the first yoke contact portion 3b of the first magnet 3.
, And the second magnet contact portion 5c is in contact with the first yoke contact portion 4b of the second magnet 4.

The second yoke 6 has a second half-cylindrical cylindrical shape.
A first magnet contact portion 6b that can contact the second yoke contact portion 3c of the first magnet 3 is formed above the yoke main body 6a in FIG. A second magnet contact portion 6c that can contact the second yoke contact portion 4c of the second magnet 4 is formed below the main body 6a in FIG.

In the second yoke 6, the first magnet contact portion 6b is formed by the second yoke contact portion 3c of the first magnet 3.
, And the second magnet contact portion 6c is in contact with the second yoke contact portion 4c of the second magnet 4.

The first and second yokes 5 and 6 are arranged such that the first magnet contact portion 5b of the first yoke 5 contacts the first yoke contact portion 3b of the first magnet 3, Yoke 6
The first magnet contact portion 6b of the first magnet 3 is in contact with the second yoke contact portion 3c of the first magnet 3, but the first magnet contact portion 5b of the first yoke 5 is in contact with the second magnet contact portion 5b. York 6
The first gap portion 21 is formed between the first magnet contact portion 6b and the first magnet contact portion 6b.

The first and second yokes 5 and 6 are arranged such that the second magnet contact portion 5c of the first yoke 5 contacts the first yoke contact portion 4b of the second magnet 4, Although the second magnet contact portion 6c of the second yoke 6 is in contact with the second yoke contact portion 4c of the second magnet 4,
Since the second magnet contact portion 5c of the first yoke 5 and the second magnet contact portion 6c of the second yoke 6 are arranged apart, the second gap 22 is formed between them. Is formed.

The first yoke 5 has a structure in which the first magnet contact portion 5b is formed by the first yoke contact portion 3b of the first magnet 3.
And the second magnet contact portion 5c
Is in contact with the first yoke contact portion 4 b of the second magnet 4, so that there is no magnetic flux from the armature core 11.
Applied to the first yoke contact portion 4b of the second magnet 4, the second magnet contact portion 5c of the first yoke 5, the first yoke main body 5a, and the first yoke 5 First
Most of the magnetic flux passes through the first yoke 5 through a magnetic circuit including the magnet contact portion 5b, the first yoke contact portion 3b of the first magnet 3, and the second magnet 4.

In the second yoke 6, the first magnet contact portion 6b is connected to the second yoke contact portion 3c of the first magnet 3.
And the second magnet contact portion 6c
Is in contact with the second yoke contact portion 4 c of the second magnet 4, so that there is no magnetic flux from the armature core 11.
Is applied to the second yoke contact portion 4c of the second magnet 4, the second magnet contact portion 6c of the second yoke 6, the second yoke main body 6a, and the second yoke 6 First
Most of the magnetic flux passes through the second yoke 6 through a magnetic circuit including the magnet contact portion 6b, the second yoke contact portion 3c of the first magnet 3, and the second magnet 4.

The first gap portion 21 is provided in the armature core 1
When there is a magnetic flux from 1, as shown by the broken line in FIG.
The armature core 11, the second yoke contact portion 3 c of the first magnet 3, the first magnet contact portion 6 b of the second yoke 6, the first gap 21, and the first of the first yoke 5 In the magnetic circuit leading to the magnet contact portion 5b, the first yoke contact portion 3b of the first magnet 3, and the armature core 11, the first magnet contact portion 6b of the second yoke 6 and the first yoke 5 first magnet contact portion 5b
Armature core 1 because it is located between
By preventing a part of the magnetic flux from 1 from being given to the first magnet contact portion 6b of the second yoke 6, most of the magnetic flux does not pass through the inside of the first magnet 3.
It has a function of reducing the demagnetizing magnetomotive force acting on the first magnet 3.

When a magnetic flux from the armature core 11 is present, the second gap portion 22 is contacted with the armature core 11 and the second yoke of the second magnet 4 as shown by a broken line in FIG. 4c, the second magnet contact portion 6c of the second yoke 6, the second gap portion 22, the second magnet contact portion 5c of the first yoke 5, and the first magnet 4
Between the second magnet contact portion 6c of the second yoke 6 and the second magnet contact portion 5c of the first yoke 5 in the magnetic circuit leading to the yoke contact portion 4b and the armature core 11. Due to the arrangement, a part of the magnetic flux from the armature core 11 is not given to the second magnet contact portion 6c of the second yoke 6, and most of the magnetic flux is
Has a function of reducing the demagnetizing magnetomotive force acting on the second magnet 4 by preventing the magnet from passing through the inside of the magnet 4.

The first and second yokes 5 and 6 are accommodated in a case 9. The case 9 includes a cylindrical case body 9g made of resin and a case body 9g shown in FIG.
An end bracket 14 is fixed to an open end on the left side of the case body 9g in FIG. 1 of the case main body 9g. As described above, the first bearing 15 is attached to the end bracket 14.
Is mounted, and the second bearing 1 is provided at the center of the case end 9h.
6 are attached. The above-mentioned brush holder 17 is fixed near the open end of the case body 9g.

Then, as shown in FIG. 2, a first fixing portion 9a and a second fixing portion 9b are formed near the first side plate 9i disposed on the left side of the case body 9g in the drawing, respectively. A third fixing portion 9c and a fourth fixing portion 9d are formed near the second side plate 9j disposed on the right side of the case body 9g in the drawing.

First, second, third and fourth fixing parts 9a, 9
b, 9c, 9d are respectively formed as rod-like protrusions from the case end 9h along the cylinder direction of the case body 9g, and include a first fixing portion 9a, a second fixing portion 9b, and a first side plate 9i.
The first yoke main body 5a of the first yoke 5 is sandwiched between the first yoke 5 and the second yoke main body 6 of the second yoke 6 between the third fixing portion 9c and the fourth fixing portion 9d.
a is pinched. In the first yoke 5, the first magnet contact portion 5b is disposed on the top plate 9e side of the case 9, and the second magnet contact portion 5c is disposed on the bottom plate 9f side of the case 9. In the second yoke 6, the first magnet contact portion 6b is arranged on the top plate 9e side of the case 9, and the second magnet contact portion 6c is arranged on the bottom plate 9f side of the case 9.

Then, in the case 9, the first fixing portion 9a,
The first magnet 3 is fixed between the third fixing portion 9 c, the first magnet contact portion 5 b of the first yoke 5, and the first magnet contact portion 6 b of the second yoke 6, 2
The fixing part 9b, the fourth fixing part 9d, and the second part of the first yoke 5
The second magnet 4 is fixed between the second magnet contact portion 5c and the second magnet contact portion 6c of the second yoke 6.

In the top plate 9e of the case 9, the first
A first low magnetic permeability portion 23 is provided in a first gap portion 21 disposed between the first magnet contact portion 5b of the yoke 5 and the first magnet contact portion 6b of the second yoke 6. In contrast to this, on the bottom plate 9f of the case 9, the second magnet contact portion 5c of the first yoke 5 and the second magnet contact portion 6c of the second yoke 6 are arranged. A second low magnetic permeability portion 24 is formed in the second gap portion 22. First low magnetic permeability part 23 and second low magnetic permeability part 2
4 is formed of the same resin as the case 9.

In the DC motor 1 having such a structure, one end of the armature shaft 10 is connected to a load, and the first and second brushes 7 and 8 are connected to a control circuit.

When a high level is applied to the first brush 7 from the control circuit and the second brush 8 goes to a low level,
One commutator piece 12b in contact with the first brush 7, an armature coil 13 electrically connected to the commutator piece 12b, and another one commutator piece electrically connected to the armature coil 13 Since an electric current flows through 12b and the second brush 8, the armature coil 13 is excited, and a magnetic force is generated from the armature core 11 toward each of the first and second magnets 3, 4.

The first magnet 3 has an N-pole magnetized on the inner circumference side, and the second magnet 4 has an S-pole magnetized on the inner circumference side, so that the magnetic field generated by the armature core 11 is reduced. Armature core 11 according to the right-handed screw rule caused by the magnetic field generated by first, second and third magnets 3, 4.
Starts spinning.

When the armature core 11 starts rotating, the commutator 12 also rotates, the first and second brushes 7 and 8 are electrically connected to the adjacent commutator 12b sequentially, and the armature coil 13 is excited for each slot. As a result, magnetic force is sequentially generated from the armature core 11, so that the armature shaft 10 continues to rotate together with the armature core 11, and the armature shaft 10.
Activate the load coupled to.

The magnetic flux generated from the armature core 11 is supplied to the first magnet 3 side by the armature core 11, the second yoke contact portion 3 c of the first magnet 3,
The first magnet contact portion 6b of the second yoke 6, the first gap portion 21, the first magnet contact portion 5b of the first yoke 5, and the first yoke contact portion of the first magnet 3. 3b,
In the magnetic circuit leading to the armature core 11, the first magnet contact portion 6b of the second yoke 6 and the first magnet contact portion 5b of the first yoke 5
Of the magnetic flux from the armature core 11 is not provided to the first magnet contact portion 6b of the second yoke 6, and most of the magnetic flux is It does not pass through the magnet 3.

The magnetic flux generated from the armature core 11 is supplied to the second magnet 4 side by the armature core 11 and the second yoke contact portion 4 of the second magnet 4.
c, the second magnet contact portion 6c of the second yoke 6, the second gap portion 22, the second magnet contact portion 5c of the first yoke 5, and the first yoke contact of the second magnet 4. Contact 4
b, disposed between the second magnet contact portion 6c of the second yoke 6 and the second magnet contact portion 5c of the first yoke 5 in the magnetic circuit leading to the armature core 11; By armature core 11
A part of the magnetic flux from the second magnet 4 is not provided to the second magnet contact portion 6c of the second yoke 6, and most of the magnetic flux does not pass through the inside of the second magnet 4.

FIG. 5 shows a second embodiment of the DC motor according to the present invention.

In this case, the outer edge 3d of the first magnet 3 has a planar shape, and the first fixing portion 9a and the third fixing portion 9c formed on the case 9 are on the top plate 9e side of the case 9. It is fixed to.

The second magnet 4 also has an outer edge 4
d is planar, and the bottom plate 9f of the case 9 is formed by the second fixing portion 9b and the fourth fixing portion 9d formed on the case 9.
Fixed on the side.

In this case, the thickness of the first and second magnets 3 and 4 at the central portion thereof is smaller than that of the first embodiment by the outer edges 3d and 4d which are flat. On the other hand, the top plate 9e and the bottom plate 9f of the case 9
Since the outer edges 3d, 4d of the first and second magnets 3, 4 are planar, the thickness dimension corresponding to the outer edges 3d, 4d is increased, whereby the first and second low-profile portions are formed. The thickness of the magnetically permeable portions 23 and 24 is also increased.

The DC motor 1 in this case also operates in the same manner as in the first embodiment, and a part of the magnetic flux from the armature core 11 is used for the first magnet contact portion 6b of the second yoke 6 and the second yoke. 6 is not applied to the second magnet contact portion 6c, and most of the magnetic flux is not applied to the first magnet 3 and the second magnet contact portion 6c.
Does not pass through the inside of the magnet 4.

[0063]

As described above, according to the DC motor according to the first aspect of the present invention, the pair of yokes includes:
Since the pair of magnets are disposed so as to face each other in a direction orthogonal to the direction in which the pair of magnets face each other, it is difficult for the magnetic flux to pass between the ends of the pair of yokes. Therefore, most of the magnetic flux from the pair of magnets passes through the pair of yokes when there is no magnetic flux from the armature, but the amount of magnetic flux from the pair of magnets that passes through the pair of magnets decreases when the magnetic flux from the armature exists. Therefore, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur.
By using a magnet having a small thickness dimension, there is an excellent effect that the weight can be reduced by preventing permanent demagnetization of the magnet without affecting the motor characteristics.

According to the DC motor according to the second aspect of the present invention, a small amount of magnetic flux from the armature passes through the pair of magnets and is provided to the pair of yokes by the low magnetic permeability portion. Therefore, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur, so using a magnet with a small thickness dimension does not affect the motor characteristics,
There is an excellent effect that the weight can be reduced by preventing permanent demagnetization of the magnet.

According to the DC motor according to the third aspect of the present invention, the low magnetic permeability formed in the case along the axial direction of the armature shaft causes the low magnetic permeability portion between the pair of yokes to extend along the axial direction of the armature shaft. A gap through which the magnetic flux is difficult to pass is formed. Therefore, most of the magnetic flux from the pair of magnets without the magnetic flux from the armature passes through the pair of yokes without passing through the low magnetic permeability part, but in the state with the magnetic flux from the armature, the axial direction of the armature shaft The low magnetic permeability along the pair makes it difficult for the pair of yokes to flow, thereby reducing the amount of passage through the pair of magnets. Therefore, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur. Therefore, by using a magnet having a small thickness, the permanent magnet demagnetization of the magnet is prevented without affecting the motor characteristics, thereby reducing the weight. It has an excellent effect that it can be performed.

According to the DC motor according to the fourth aspect of the present invention, the low magnetic permeability portion of the case is formed between the pair of yokes in a plane along the planar outer edge of the magnet. The thickness of the central portion of the magnet is smaller than that formed when the magnet is formed in a curved shape along the curved outer edge. This is because when there is no magnetic flux from the armature, the magnetic flux flowing through the central portion of the magnet decreases, and the magnetic flux tends to collect on both end surfaces of the magnet as the shortest path of the magnetic circuit. Therefore, by guiding the central portion of the magnet that does not contribute to the effective magnetic flux, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is less likely to occur, so using a magnet having a small thickness dimension does not affect the motor characteristics. In addition, there is an excellent effect that the weight can be reduced by preventing permanent demagnetization of the magnet.

According to the DC motor according to the fifth aspect of the present invention, the pair of yokes and the pair of magnets are attached to the inside of the case by the fixing portions. Therefore, in addition to the effect of the first aspect, there is an excellent effect that it is not necessary to use a separate mounting member when fixing the pair of yokes and the pair of magnets to the case. .

According to the DC motor according to the sixth aspect of the present invention, the first and second yokes are orthogonal to the first and second magnets spaced apart in the first radial direction of the armature core. Since the cores are spaced apart in the second radial direction, it is difficult for the magnetic flux to pass between the first and second yokes. Therefore, most of the magnetic flux from the first and second magnets in the state where the armature coil is not excited and there is no magnetic flux from the armature core passes through the first and second yokes, but the armature coil is excited. As a result, the amount of magnetic flux from the armature core that passes through the first and second magnets is reduced. Therefore, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur. Therefore, by using a magnet having a small thickness, the permanent magnet demagnetization of the magnet is prevented without affecting the motor characteristics, thereby reducing the weight. It has an excellent effect that it can be performed.

According to the DC motor according to claim 7 of the present invention, the first yoke is such that the magnet contact portion contacts only one end of the first magnet and one end of the second magnet, , The magnet contact portion contacts only the other end of the first magnet and the other end of the second magnet. Therefore, most of the magnetic flux from the first and second magnets in the state where the armature coil is not excited and there is no magnetic flux from the armature core is the first,
Although passing through the second yoke, the amount of magnetic flux from the armature core due to the excitation of the armature coil decreases through the first and second magnets. Therefore, permanent demagnetization of the magnet due to the demagnetizing magnetomotive force is unlikely to occur. Therefore, by using a magnet having a small thickness, the permanent magnet demagnetization of the magnet is prevented without affecting the motor characteristics, thereby reducing the weight. It has an excellent effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of a first embodiment of a DC motor according to the present invention.

FIG. 2 is a vertical sectional side view of the DC motor shown in FIG.

FIG. 3 is an external perspective view illustrating an assembling relationship between a magnet and a yoke in the DC motor shown in FIG. 1;

FIG. 4 is an explanatory diagram showing a flow of a magnetic flux by an armature coil in the DC motor according to the present invention.

FIG. 5 is a vertical sectional side view of a second embodiment of the DC motor according to the present invention.

FIG. 6 is an explanatory diagram showing a flow of a magnetic flux by an armature coil in a conventional DC motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC motor 2 Armature 3 (Magnet) 1st magnet 3d Outer edge 4 (Magnet) 2nd magnet 4d Outer edge 5 (Yoke) 1st yoke 5b (Magnet contact part) 1st magnet contact Part 5c (Magnet contact part) Second magnet contact part 6 (Yoke) Second yoke 6b (Magnet contact part) First magnet contact part 6c (Magnet contact part) Second magnet contact Part 7 (brush) first brush 8 (brush) second brush 9 case 9a (fixed part) first fixed part 9b (fixed part) second fixed part 9c (fixed part) third fixed part 9d (fixed part ) Fourth fixed part 10 Armature shaft 11 Armature core 12 Commutator 13 Armature coil 23 (Low magnetic permeability part) First low magnetic permeability part 24 (Low magnetic permeability part) Second Low magnetic permeability

Claims (7)

[Claims] 1. A case, an armature rotatably supported by the case, a pair of magnets disposed outside of the armature in a non-contact manner and opposed to each other, and orthogonal to a facing direction of the pair of magnets. A DC motor, comprising: a pair of yokes spaced from each other in opposite directions. 2. The case has a low magnetic permeability portion formed between the pair of yokes, the amount of magnetic flux given to the pair of magnets from the armature being reduced by the pair of yokes. The direct-current motor according to claim 1, wherein: 3. The magnet according to claim 2, wherein the magnet has a length direction in the axial direction of the armature shaft, and the low magnetic permeability portion is formed along the axial direction of the armature shaft. A DC motor according to claim 1. 4. The magnet has an outer edge formed in a planar shape on the case side, and the low magnetic permeability portion of the case is formed on a plane along the outer edge of the magnet. The DC motor according to claim 3, wherein the DC motor is a motor. 5. The direct-current motor according to claim 4, wherein the case is integrally formed with a fixing portion to which a pair of yokes and a pair of magnets can be attached inside. 6. A case, an armature shaft rotatably supported by the case, a commutator attached to the armature shaft, a brush slidably contacting the commutator and electrically connected thereto, and the armature. An armature core attached to a shaft; an armature coil wound around the armature core and electrically connected to the commutator; a first radial direction of the armature core outside the armature core. First and second magnets, which are separated from each other and are arranged in a non-contact manner with the armature core, and are separated from each other in a second radial direction of the armature core orthogonal to the first radial direction of the armature core; do it,
A DC motor comprising a pair of first and second yokes arranged outside the first and second magnets. 7. A first yoke is provided with a magnet contact portion which is in contact with only one end of the first magnet and one end of the second magnet, and the second yoke is provided with a first magnet.
7. The DC motor according to claim 6, wherein a magnet contact portion is formed which contacts only the other end of the magnet and the other end of the second magnet.