JP2008017657A - Dc motor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC motor easily enabling a further decrease in cogging torque by a simple configuration. <P>SOLUTION: The DC motor is provided with a stator 102 having planar permanent magnets 105 fixed on each of flat surfaces of the internal circumferential wall of a polygonally cylindrical yoke 104, and an armature provided rotatably inside the yoke 104. Each permanent magnet 105 having a rectangular flat surface is disposed so that its rectangular side is inclined with respect the axial direction of the yoke 104 so as not to be line-symmetric with respect to a symmetrical line passing through the center X of the symmetry along the axial direction of the yoke 104. Thus, the length of the axial direction is shortened toward the end of the circumferential direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a DC motor and a manufacturing method thereof.

2. Description of the Related Art Conventionally, there is a DC motor including a stator in which a permanent magnet is fixed to each plane on the inner peripheral surface of a substantially polygonal cylindrical yoke (yoke housing) (see, for example, Patent Document 1). In such a DC motor, deformation of the yoke due to magnetic fluctuation during rotation of the armature hardly occurs, and vibration of the motor due to deformation of the yoke is suppressed. In this DC motor, in the arc shape of the inner surface of the permanent magnet (surface facing the armature), the radius of curvature of the arc is set larger than the radius of curvature of the outer peripheral surface of the armature, and the circumferential direction of the permanent magnet The distance (air gap) in the radial direction from the armature gradually increases from the center toward both ends in the circumferential direction. As a result, a sudden change in magnetic flux with the armature at the circumferential end of the permanent magnet is reduced to reduce the cogging torque, which also suppresses vibration of the motor.
JP 2005-20914 A

However, the cogging torque is not lost even in the DC motor as described above, and it is desired to further reduce the cogging torque easily with a simple configuration.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a DC motor capable of easily further reducing the cogging torque with a simple configuration and a method for manufacturing the same. It is in.

According to the first aspect of the present invention, there is provided a stator in which a flat permanent magnet is fixed to each plane on the inner peripheral surface of a polygonal cylindrical yoke, and an armature that is rotatably provided inside the yoke. In the direct-current motor provided, the permanent magnet is disposed such that its axial length becomes shorter toward the circumferential end.

  According to this configuration, the stator is formed by fixing a plate-like permanent magnet to each plane on the inner circumferential surface of the polygonal cylindrical yoke, and the radial direction from the armature toward the circumferential end of the permanent magnet. Since the distance gradually increases, a sudden change in magnetic flux with the armature at the circumferential end of the permanent magnet is reduced, thereby reducing the cogging torque. In addition, the permanent magnet has a flat plate shape and is arranged so that its axial length becomes shorter toward the circumferential end, so that it can be easily arranged at the circumferential end of the permanent magnet. The rapid change in magnetic flux with the armature is further reduced, and the cogging torque can be further reduced.

In the invention according to claim 2, a stator in which a flat permanent magnet is fixed to each plane on the inner peripheral surface of a polygonal cylindrical yoke, and an armature that is rotatably provided inside the yoke. The permanent magnet has a plane with point symmetry and a non-circular shape, and a line along the axial direction of the yoke passing through the center of symmetry is a line of symmetry. Arranged so as not to be symmetrical.

  According to this configuration, the stator is formed by fixing a flat permanent magnet to each plane on the inner peripheral surface of the polygonal cylindrical yoke, and the radial direction of the armature increases toward the circumferential end of the permanent magnet. Since the distance gradually increases, a sudden change in magnetic flux with the armature at the circumferential end of the permanent magnet is reduced, thereby reducing the cogging torque. In addition, the permanent magnet has a flat plate shape, and its plane is a point-symmetrical shape and a non-circular shape, and the line-symmetrical line is a line along the axial direction of the yoke passing through the center of symmetry. Therefore, the axial length becomes shorter toward the end in the circumferential direction. Therefore, a sudden change in magnetic flux with the armature at the circumferential end of the permanent magnet can be further reduced with a simple configuration, and the cogging torque can be further reduced. Further, in this configuration, since the motor characteristics including the cogging torque can be changed by rotating the permanent magnet around the symmetry center, the motor characteristics can be easily adjusted. .

  According to a third aspect of the present invention, in the DC motor according to the second aspect, the permanent magnet has a rectangular or square plane and its side is inclined with respect to the axial direction of the yoke. In addition, the north pole and the south pole alternately arranged in the circumferential direction have the same inclination angle and the inclination directions are reversed.

  According to the same configuration, the permanent magnet has a rectangular or square plane and is arranged so that its side is inclined with respect to the axial direction of the yoke. It becomes. In addition, since the permanent magnet is disposed with the same inclination angle and the opposite inclination direction between the N pole and the S pole arranged alternately in the circumferential direction, for example, the permanent magnet is applied to the armature when the armature rotates. Good balance of axial force.

  According to a fourth aspect of the present invention, in the DC motor according to the second or third aspect, the yoke has a hexagonal cylindrical shape, and six permanent magnets are provided at equiangular intervals, and the plane is rectangular. It is a shape or a square shape, and its side is disposed so as to be inclined with respect to the axial direction of the yoke, and the central angle between both ends in the width direction with respect to the motor shaft center is 34.5 ° to 52 °. Was set.

  According to this configuration, the permanent magnet has a center angle between both ends in the width direction with respect to the motor shaft center (hereinafter referred to as a permanent magnet opening angle) set to 34.5 ° to 52 °. As a result of studying the relationship with the cogging torque (see FIG. 4), the cogging torque is reduced as compared with the case where the permanent magnet opening angle is 60 ° (permanent magnets are disposed without gaps in the circumferential direction).

  According to a fifth aspect of the present invention, in the DC motor according to the fourth aspect, the permanent magnet further has a center angle between both ends in the width direction with respect to the motor shaft center set to 44 ° to 46.5 °. .

  According to the same configuration, the permanent magnet has a center angle between both ends in the width direction with respect to the motor shaft center (hereinafter referred to as a permanent magnet opening angle) set to 44 ° to 46.5 °. As a result of studying the relationship with the cogging torque (see FIG. 4), the cogging torque is significantly reduced, and a sufficient amount of magnetic flux can be obtained at a high level close to the maximum value.

  According to a sixth aspect of the present invention, there is provided a DC motor manufacturing method according to the second to fifth aspects, wherein the permanent magnetized magnet is temporarily fixed to the yoke by its own magnetic force, After the temporary fixing step, a measuring step for measuring motor characteristics including cogging torque, and when the measured motor characteristics do not satisfy a preset value, the permanent magnet is rotated about its symmetrical center. And an adjusting step for fixing the permanent magnet to the yoke with an adhesive after the adjusting step or the adjusting step.

  According to the invention, the motor characteristics including the cogging torque are measured in the measurement process, and if the measured motor characteristics do not satisfy the preset value, the permanent magnet is rotated around the symmetrical center in the adjustment process. Therefore, a DC motor with good motor characteristics including cogging torque can be obtained. Note that this method can be adopted because it is based on the premise that the flat permanent magnet is fixed to the plane of the yoke as described in claim 2.

  ADVANTAGE OF THE INVENTION According to this invention, the direct current motor which can aim at the further reduction of cogging torque easily with a simple structure, and its manufacturing method can be provided.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the DC motor 101 of this embodiment includes a stator 102 and an armature 103 that rotates with respect to the stator 102. The stator 102 has a polygonal cylindrical shape, and in this embodiment, a hexagonal cylindrical yoke 104 and six flat plates fixed to each plane on the inner peripheral surface of the yoke 104 and arranged in parallel at equal angular intervals. Shaped permanent magnet 105. The permanent magnet 105 of the present embodiment is formed of a neodymium magnet, and as shown in FIG. 3, a magnetic flux is generated in a vertical direction on a plane 105 a facing the armature 103 (in FIG. (See arrow) Magnetized. An armature 103 is rotatably accommodated inside the yoke 104 (permanent magnet 105) of the stator 102.

  The armature 103 is wound around the rotating shaft 106, the armature core 107 having eight teeth T1 to T8 extending radially and fixed to the rotating shaft 106, and the teeth T1 to T8 by concentrated winding. Eight windings M1 to M8 are provided. Incidentally, slots S1 to S8 are formed between the teeth T1 to T8.

  Further, the armature 103 is provided with a commutator 108 in which 24 segments 1 to 24 are arranged in parallel in the circumferential direction on the outer peripheral surface and fixed to the rotating shaft 106. The segments 1 to 24 of the commutator 108 are short-circuited between segments arranged at intervals of 120 ° (every seven), such as a set of segments 1, 9, 17 and a set of segments 5, 13, 21. Are at the same potential. The windings M1 to M8 are connected so as to form one closed loop (with two windings connected in the circumferential direction). In addition, the segments 1 to 24 of the commutator 108 can be slidably contacted with anode-side and cathode-side power supply brushes (not shown) arranged at intervals of 180 °, and each power supply brush is rectified based on external power supply. Power is supplied to the armature 103 (windings M1 to M8) through the child 108, and the DC motor 101 (rotary shaft 106) is rotationally driven.

  Here, each permanent magnet 105 of the present embodiment is arranged so that its axial length becomes shorter toward the circumferential end. Specifically, the permanent magnet 105 has a flat plate shape, and its plane is a point-symmetrical shape and a non-circular shape, and is formed in a rectangular shape (see FIG. 2) in the present embodiment. The permanent magnet 105 is not line-symmetric with respect to a line along the axial direction of the yoke 104 passing through the symmetry center X, that is, in this embodiment, the side of the rectangular shape is the yoke. By being disposed so as to be inclined with respect to the axial direction of 104, the axial length is shortened toward the circumferential end. In addition, the permanent magnet 105 of this embodiment is arranged with the same inclination angle and the same inclination direction between the N pole and the S pole arranged alternately in the circumferential direction.

  Here, in the DC motor 101 having the above-described configuration, the width of the flat permanent magnet whose side of the rectangular shape is not inclined with respect to the axial direction of the yoke 104, more specifically, the motor axis center O The central angle θ between the both ends in the width direction of the permanent magnet with respect to (referred to as the permanent magnet opening angle θ in the present embodiment, see FIGS. 1 and 3). Incidentally, since there are six permanent magnets 105 used in the present embodiment, the maximum value of the permanent magnet opening angle θ in each permanent magnet 105 is 60 °. Therefore, when the permanent magnet opening angle θ is changed to a maximum of 60 °, the amount of magnetic flux and the cogging torque at the maximum 60 ° (permanent magnets arranged without gaps in the circumferential direction) are assumed to be 100%. The amount of magnetic flux and the cogging torque at the magnet opening angle θ change as shown in FIG.

  More specifically, when the permanent magnet opening angle θ is increased from around 34 °, the cogging torque decreases with the increase, becoming 100% or less at 34.5 °, and a minimum value of 30% at 36 °. When the permanent magnet opening angle θ exceeds 36 °, the cogging torque temporarily increases to 40 °, and reaches a maximum value of 80% at 40 °. When the permanent magnet opening angle θ exceeds 40 °, the cogging torque decreases again to 45 °.

  When the permanent magnet opening angle θ becomes 45 °, the cogging torque reaches a minimum value of 10%, and when the angle exceeds 45 °, the cogging torque increases again. At this time, when the permanent magnet opening angle θ is in the range of 44 ° to 46.5 °, the cogging torque is 30% or less, which is the minimum value. Further, when the permanent magnet opening angle θ is 52 °, the cogging torque exceeds 100%, and then reaches the maximum value, and at 60 °, the cogging torque becomes 100%.

  On the other hand, with respect to the amount of magnetic flux, when the permanent magnet opening angle θ is increased from around 34 °, the amount of magnetic flux increases with the increase, and the amount of magnetic flux exceeds 100% at 35.5 °. When the permanent magnet opening angle θ reaches 48 °, the magnetic flux amount reaches a maximum value of 105%, and starts to decrease at the boundary of 48 °. When the permanent magnet opening angle θ is 60 °, the amount of magnetic flux is 100%.

  Based on such examination results, it was found that the cogging torque was reduced to 100% or less when the permanent magnet opening angle θ of the permanent magnet 105 was in the range of 34.5 ° to 52 °. .

Further, it was found that when the permanent magnet opening angle θ is in the range of 35.5 ° to 52 °, the cogging torque is reduced and the magnetic flux amount is in a better range exceeding 100%.
Further, it was found that when the permanent magnet opening angle θ is in the range of 40 ° to 52 °, the cogging torque is reduced and the magnetic flux amount is sufficiently better than a high level including the maximum value. .

  Within this range, when the permanent magnet opening angle θ is in the range of 44 ° to 46.5 °, the amount of magnetic flux can be sufficiently obtained at a high level close to the maximum value, but the cogging torque is greatly increased (mostly From the viewpoint of reducing the cogging torque, it was found that this is a desirable range.

  In consideration of these, in the DC motor 101 of the present embodiment, the width dimension and the inclination angle of the permanent magnet 105 are set from the above-described permanent magnet opening angle θ, thereby reducing the cogging torque and increasing the amount of magnetic flux. Thereby, in the present embodiment, low vibration and high output of the DC motor 101 are achieved. In the permanent magnet 105 of the present embodiment, the central angle (permanent magnet open angle) θ between the width direction both ends with respect to the motor shaft center O is set to 44 ° to 46.5 °.

  The method for manufacturing the DC motor 101 includes a “temporary fixing step”, a “measurement step”, an “adjustment step”, and a “main fixing step”. Specifically, in the “temporary fixing step”, the magnetized permanent magnet 105 is temporarily fixed to the yoke 104 with its own magnetic force. Next, in the “measurement step”, motor characteristics including cogging torque are measured. Next, in the “adjustment step”, when the measured motor characteristics do not satisfy a preset value, the permanent magnet 105 is rotated about the symmetrical center X (the tilt angle is changed). In the measured motor characteristics, for example, when the cogging torque does not satisfy a preset value (becomes larger than the value), the permanent magnet 105 is symmetric so that the tilt angle becomes large. Is rotated around the center X of the axis. Further, when the measured motor characteristics satisfy a preset value, the “adjustment step” is not performed. Next, after the “measuring step” or the “adjusting step”, that is, the permanent magnet 105 is fixed (fixed) to the yoke 104 with an adhesive so that the motor characteristics satisfy a preset value. In this way, the stator 102 of the DC motor 101 is manufactured.

Next, characteristic effects of the above embodiment will be described below.
(1) The stator 102 has a plate-like permanent magnet 105 fixed to each plane on the inner peripheral surface of the polygonal cylindrical yoke 104, and the diameter of the stator 102 with the armature 103 increases toward the circumferential end of the permanent magnet 105. Since the direction distance gradually increases, a sudden change in magnetic flux with the armature 103 at the circumferential end of the permanent magnet 105 is reduced, and the cogging torque is reduced. Moreover, the permanent magnet 105 has a flat plate shape and is arranged so that its axial length becomes shorter toward the circumferential end, so that the circumferential end of the permanent magnet 105 can be easily formed with a simple configuration. The sudden change in magnetic flux with the armature 103 is further reduced, and the cogging torque can be further reduced.

  (2) The permanent magnet 105 has a point-symmetrical and non-circular shape (rectangular shape in the present embodiment) and a line along the axial direction of the yoke 104 passing through the symmetrical center X. Since it arrange | positions so that it may not become line symmetry which makes a symmetrical axis | shaft, axial direction length becomes short, so that it goes to the circumferential direction edge part. Therefore, the effect described in (1) can be easily obtained with a simple configuration. Further, in this configuration, the motor characteristics including the cogging torque can be changed by rotating the permanent magnet 105 around the symmetrical center X, so that the motor characteristics can be easily adjusted. It becomes.

  (3) Six permanent magnets 105 are provided at equiangular intervals, the plane thereof is rectangular, the sides thereof are disposed so as to be inclined with respect to the axial direction of the yoke 104, and the motor shaft center A central angle (permanent magnet opening angle) θ between both end portions in the width direction with respect to O is set to 34.5 ° to 52 °. Then, as a result of examining the relationship between the permanent magnet opening angle θ and the cogging torque (see FIG. 4), the permanent magnet opening angle θ is 60 ° (the permanent magnets are arranged without gaps in the circumferential direction). Compared to the cogging torque, the cogging torque is reduced. Further, since the permanent magnet opening angle θ of the permanent magnet 105 is set to 44 ° to 46.5 °, the result of studying the relationship between the permanent magnet opening angle θ and the cogging torque (see FIG. 4). The cogging torque is greatly reduced, and a sufficient amount of magnetic flux can be obtained at a high level close to the maximum value.

  (4) In the method for manufacturing the DC motor 101, when the motor characteristics including the cogging torque are measured in the “measuring step” and the measured motor characteristics do not satisfy a preset value, the permanent magnet 105 is obtained in the “adjusting step”. Is rotated about the symmetrical center X, so that the DC motor 101 having good motor characteristics including cogging torque can be obtained.

The above embodiment may be modified as follows.
In the above embodiment, the permanent magnet 105 is arranged with the same inclination angle and the same inclination direction between the N pole and the S pole arranged alternately in the circumferential direction, but is not limited thereto. Instead, as shown in FIG. 5, the N poles and S poles alternately arranged in the circumferential direction may have the same inclination angle and the opposite inclination directions. FIG. 5 is a schematic diagram in which the plane of the yoke 104 arranged in the circumferential direction and the permanent magnet 105 (that is, the stator) are developed. In this way, for example, the balance of the axial force applied to the armature 103 during rotation of the armature 103 is improved.

  In the above embodiment, the permanent magnet 105 is disposed so that the plane thereof is rectangular and its side is inclined with respect to the axial direction of the yoke 104. However, the permanent magnet 105 is disposed on the yoke 104. If the axial length becomes shorter toward the circumferential end in the state, the shape and the like may be changed to other modes.

  For example, you may change as shown in FIG. The permanent magnet 201 in this example (see FIG. 6) is a flat plate and has a parallelogram shape having two sets of sides with different lengths on the plane. The permanent magnet 201 is arranged along a direction in which two sides of one pair (short sides) opposite to each other (parallel) are orthogonal to the axial direction of the yoke 104 (vertical direction in FIG. 6). At the same time, the other (long side) pair of opposite (parallel) two sides is disposed so as to be inclined with respect to the axial direction of the yoke 104. Even in this case, the cogging torque can be further reduced. Needless to say, the permanent magnet 201 of this example (see FIG. 6) may be rotated (tilted) around the center of symmetry.

  Further, for example, it may be changed as shown in FIG. The permanent magnet 202 in this example (see FIG. 7) has a flat plate shape, and its plane has a hexagonal shape. The permanent magnet 202 is disposed along a direction in which two sides of one pair (parallel) facing each other are orthogonal to the axial direction (vertical direction in FIG. 7) of the yoke 104. Even in this case, the cogging torque can be further reduced. Needless to say, the permanent magnet 202 of this example (see FIG. 7) may be rotated (tilted) around the center of symmetry.

  Further, for example, it may be changed as shown in FIG. The permanent magnet 203 in this example (see FIG. 8) has a flat plate shape and a parallelogram shape (that is, a rhombus shape) whose planes all have sides having the same length. The permanent magnet 203 is arranged such that one (shorter) diagonal line is disposed along a direction orthogonal to the axial direction (vertical direction in FIG. 8) of the yoke 104 and the other (longer) diagonal line. Are arranged along the axial direction of the yoke 104. Even in this case, the cogging torque can be further reduced. Needless to say, the permanent magnet 203 of this example (see FIG. 8) may be rotated (tilted) around the center of symmetry.

  Further, for example, it may be changed as shown in FIG. The permanent magnet 204 in this example (see FIG. 9) has a flat plate shape, and has a substantially rectangular shape on the plane and a chamfered corner (that is, an octagonal shape). In the permanent magnet 204, except for the chamfered sides, the two sides of one (short side) pair facing each other (parallel) are perpendicular to the axial direction of the yoke 104 (vertical direction in FIG. 9). And the other two (long side) sets opposite to each other (parallel) are arranged along the axial direction of the yoke 104. Even in this case, the cogging torque can be further reduced. Needless to say, the permanent magnet 204 of this example (see FIG. 9) may be rotated (tilted) around the center of symmetry.

  Further, for example, it may be changed as shown in FIG. The permanent magnet 205 in this example (see FIG. 10) has a flat plate shape and a substantially elliptical plane. The permanent magnet 205 is disposed along the direction in which the short axis is orthogonal to the axial direction of the yoke 104 (the vertical direction in FIG. 8), and the long axis is disposed along the axial direction of the yoke 104. ing. Even in this case, the cogging torque can be further reduced. Needless to say, the permanent magnet 205 of this example (see FIG. 10) may be rotated (tilted) around the center of symmetry.

  In the above embodiment, the yoke 104 has a hexagonal cylinder shape, and six permanent magnets 105 are provided at equiangular intervals. However, the present invention is not limited to this, and the yoke 104 has other polygonal cylinder shapes ( That is, the number of planes on the inner peripheral surface may be a number other than 6), and the number of permanent magnets 105 may be changed accordingly. In this case, of course, it is necessary to change the permanent magnet opening angle θ (44 ° to 46.5 °) so that at least the permanent magnets can be arranged in the circumferential direction.

  In the above embodiment, the permanent magnet 105 has the permanent magnet opening angle θ set to 44 ° to 46.5 °, but is not limited thereto, and the permanent magnet opening angle θ is set to another angle. It may be changed. For example, the permanent magnet opening angle θ may be changed to 34.5 ° to 52 ° excluding 44 ° to 46.5 °. Even in this case, from the result of studying the relationship between the permanent magnet opening angle θ and the cogging torque (see FIG. 4), the permanent magnet opening angle θ is 60 ° (the permanent magnets are arranged without gaps in the circumferential direction). The cogging torque is reduced compared to

  -Although the manufacturing method of the DC motor 101 in the said embodiment was provided with the "temporary fixing process", the "measurement process", the "adjustment process", and the "main fixing process", it is not limited to this, The DC motor 101 may be manufactured by a method. For example, the “temporary fixing step”, “measuring step”, and “adjustment step” are omitted, and the permanent magnet 105 is fixed (fixed) to the yoke 104 with an adhesive so that the inclination angle is designed in advance. It may be.

  In the above embodiment, the permanent magnet 105 is formed of a neodymium magnet, but may be formed of other magnets such as a ferrite magnet.

Sectional drawing which looked at the DC motor in this Embodiment from the axial direction. Sectional drawing which looked at the stator in this Embodiment from the axis orthogonal direction. Explanatory drawing for demonstrating the permanent magnet in this Embodiment. Explanatory drawing for demonstrating the relationship between a permanent magnet opening angle, cogging torque, and the amount of magnetic flux. The schematic diagram which expand | deployed the stator in another example. Sectional drawing which looked at the stator in another example from the axial orthogonal direction. Sectional drawing which looked at the stator in another example from the axial orthogonal direction. Sectional drawing which looked at the stator in another example from the axial orthogonal direction. Sectional drawing which looked at the stator in another example from the axial orthogonal direction. Sectional drawing which looked at the stator in another example from the axial orthogonal direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 102 ... Stator, 103 ... Armature, 104 ... Yoke, 105, 201-205 ... Permanent magnet, X ... Symmetric center, (theta) ... Center angle.

Claims (6)

A stator in which a flat permanent magnet is fixed to each plane on the inner peripheral surface of the polygonal cylindrical yoke;
A DC motor including an armature rotatably provided inside the yoke,
The direct current motor according to claim 1, wherein the permanent magnet is disposed such that an axial length thereof decreases toward a circumferential end. A stator in which a flat permanent magnet is fixed to each plane on the inner peripheral surface of the polygonal cylindrical yoke;
A DC motor including an armature rotatably provided inside the yoke,
The permanent magnet has a plane that is point-symmetric and non-circular, and is arranged so as not to be line-symmetric with respect to a line along the axial direction of the yoke that passes through the center of symmetry. DC motor characterized by that. The DC motor according to claim 2,
The permanent magnet has a rectangular or square plane and is arranged such that its side is inclined with respect to the axial direction of the yoke, and N poles are alternately arranged in the circumferential direction. A direct-current motor characterized in that the inclination angle is the same as that of the south pole and the inclination direction is reversed. In the DC motor according to claim 2 or 3,
The yoke has a hexagonal cylindrical shape,
Six of the permanent magnets are provided at equiangular intervals, the plane thereof is rectangular or square, the sides thereof are disposed so as to be inclined with respect to the axial direction of the yoke, and the motor shaft center A direct current motor characterized in that the center angle between both ends in the width direction is set to 34.5 ° to 52 °. The DC motor according to claim 4, wherein
The permanent magnet further has a central angle between 44 ° and 46.5 ° between both ends in the width direction with respect to the motor shaft center. It is a manufacturing method of the direct current motor according to claim 2 thru / or 5,
A temporary fixing step of temporarily fixing the magnetized permanent magnet to the yoke with its own magnetic force;
After the temporary fixing step, a measuring step for measuring motor characteristics including cogging torque,
When the measured motor characteristics do not satisfy a preset value, the adjusting step of rotating the permanent magnet about its symmetrical center;
A DC motor manufacturing method comprising: a main fixing step of fixing the permanent magnet to the yoke with an adhesive after the measuring step or the adjusting step.

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