JP2006187075A - Brushless dc motor and blower fan using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-output efficient brushless DC motor which enables the board thickness in the centrifugal direction of a magnetic pole part to be thickened without being subjected to restriction on board thickness in the bending processing of a yoke thereby being able to easily increase the sectional area for guiding magnetic flux and easily increase the number of pieces of magnetic flux of the magnetic pole part of a yoke facing a rotor magnet, in a simple constitution of stator, and can get sufficient rotating torque even if it is downsized. <P>SOLUTION: This brushless DC motor has a magnetic conduction part 16 where at least one hand of a pair of yokes 15 is arranged substantially vertically to the spool of a coil 14, and a magnetic part 18 which is extended from the end of the magnetic conduction part 16, in substantially parallel with the spool of the coil 14 and in opposition to the rotor magnet 9, and the board thickness of the magnetic pole part 18 is made thicker than the board thickness of the magnetic conduction part 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a brushless DC motor and a blower fan using the brushless DC motor which are widely used in general, and more particularly to a motor yoke structure capable of increasing rotational torque.

  In recent years, brushless DC motors are used in a wide range of fields such as fans, blowers, AV equipment, information equipment, home appliances, and medical equipment. With the miniaturization and high performance of these devices, there is a demand for a brushless DC motor that is small and has a large rotational torque.

  (Patent Document 1) states that “at least two magnetic pole pieces are fitted into both end faces of the bobbin, and the magnetic pole pieces are respectively formed with magnetic pole faces and magnetic conducting pieces. The pieces are installed so as to be offset from each other, and the magnetic pole surfaces of the magnetic pole pieces are fitted into the center holes of the bobbins, and the coupling members are closely attached to the inner peripheral walls of the magnetic conductive pieces provided around the magnetic pole pieces. A combined brushless DC motor stator "is disclosed. In addition, a configuration is also disclosed in which two magnetic pole pieces are fitted to both ends of the bobbin, and the magnetic pole surfaces formed on the two magnetic pole pieces on one side of the bobbin are adjacent to each other, overlapped or locally overlapped. Yes.

In addition, (Patent Document 2) states that, in a fan motor in which a ring-shaped magnet is attached to the inside of a fan portion of a rotor and a magnetic circuit formed by a yoke and a coil facing the inside of the magnet is provided in the stator, Has a hole for coupling to the outer frame side in the center, an upper yoke part having one polarity, a lower yoke part having the other polarity, and a coil winding part for coupling the upper yoke part and the lower yoke part The upper yoke portion and the lower yoke portion form a rotationally symmetric system around the rotation axis, and the upper yoke portion and the lower yoke portion are arranged in the axial direction with the coil winding portion interposed therebetween. There is disclosed a "yoke structure in a fan motor" characterized in that a coil is wound in a circumferential direction around a rotation axis at a coil winding portion, which is at an upper and lower position and has an angle difference by a predetermined angle. Yes.
JP 2003-61271 A JP 2000-245079 A

  However, the above conventional techniques have the following problems.

  In (Patent Document 1) and (Patent Document 2), in order to obtain a motor having a stable quality, which is easy to bend and form a yoke, a relatively thin plate before forming the yoke is selected. There is a need to. However, if the plate thickness is thin, the number of magnetic fluxes cannot be increased because the cross-sectional area that induces magnetic flux is small, so in order to increase the rotational torque of the rotor, the stator diameter or height is increased to face the rotor magnet. The surface area of the magnetic pole portion to be increased has to be increased, and there is a problem that it is not suitable for reducing the size and weight of a brushless DC motor.

  In addition, two magnetic pole pieces are fitted to both ends of the bobbin in (Patent Document 1), and the magnetic pole surfaces formed on the two magnetic pole pieces on one side of the bobbin are attached adjacently, overlapped or locally. In the configuration, since the number of parts increases, there is a problem that the number of assembling steps increases, productivity is poor, and practicality is lacking.

  The present invention solves the above-described conventional problems, and easily increases the cross-sectional area for inducing magnetic flux by increasing the thickness of the magnetic pole portion in the centrifugal direction without being restricted by the thickness of the bending process of the yoke. The number of magnetic fluxes of the magnetic pole part of the yoke facing the rotor magnet can be easily increased with a simple stator, and high output and efficiency can be obtained even if the size and weight are reduced. An object is to provide an excellent brushless DC motor.

  The present invention solves the above-described conventional problems, and can increase the thickness of the magnetic pole portion in the centrifugal direction without being restricted by the thickness of the yoke, and easily increase the cross-sectional area for inducing magnetic flux. By using a brushless DC motor that has a simple configuration and increases the number of magnetic fluxes of the magnetic pole part of the yoke facing the rotor magnet, and can obtain a sufficient rotational torque with a small size and light weight, it is small and space-saving. An object of the present invention is to provide a blower fan that is excellent and practical in terms of high blowing efficiency.

  In order to solve the above-mentioned problems, a brushless DC motor of the present invention comprises a coil, a pair of yokes disposed on both end surfaces of the coil and mutually forming a counter electrode, and an outer peripheral surface of the yoke opposed to each other via a gap and freely rotatable. A brushless DC motor including a rotor magnet disposed on the magnetic yoke, wherein at least one of the pair of yokes is disposed substantially perpendicular to the coil winding axis, and the coil winding axis; And a magnetic pole part extending from the end of the magnetic conduction part so as to face the rotor magnet, and the thickness of the magnetic pole part is greater than the thickness of the magnetic conduction part. ing.

  As a result, the plate thickness in the centrifugal direction of the magnetic pole portion can be increased without being restricted by the plate thickness in the bending process of the yoke, so that the cross-sectional area for inducing magnetic flux can be easily increased, and the rotor magnet can be realized with a simple configuration. It is possible to easily increase the number of magnetic fluxes of the magnetic pole portion of the yoke facing the motor, and to provide a brushless DC motor with high output and excellent efficiency that can obtain sufficient rotational torque even if it is reduced in size and weight. .

  In order to solve the above-mentioned problems, the blower fan of the present invention comprises a coil, a pair of yokes that are disposed on both end surfaces of the coil and that mutually form counter electrodes, and an outer peripheral surface of the yoke that is opposed to each other via a gap and is rotatable. And at least one of the pair of yokes, a magnetic conduction portion disposed substantially perpendicular to the coil winding axis, and substantially parallel to the coil winding axis and facing the rotor magnet And a magnetic pole portion extending from the end of the magnetic conduction portion, and a configuration including a brushless DC motor in which the magnetic pole portion is thicker than the magnetic conduction portion. .

  As a result, the thickness of the magnetic pole portion in the centrifugal direction can be increased without being restricted by the thickness of the yoke, and the cross-sectional area for inducing magnetic flux can be easily increased. By using a brushless DC motor that can increase the number of magnetic fluxes of the magnetic poles of the opposing yokes and obtain a sufficient rotational torque with a small size and light weight, it is small and excellent in space saving and practicality with high blowing efficiency. A blower fan can be provided.

  As described above, according to the brushless DC motor of the present invention and the blower fan using the same, the following advantageous effects can be obtained.

According to the invention of claim 1,
At least one of the pair of yokes has a magnetic conduction portion disposed substantially perpendicular to the winding axis of the coil, and is substantially parallel to the winding axis of the coil and from the end of the magnetic conduction portion facing the rotor magnet. And the magnetic pole portion is thicker than the magnetic conductive portion, so that the magnetic pole portion of the magnetic pole portion is not restricted by the bending thickness of the yoke. The plate thickness in the centrifugal direction can be increased, the cross-sectional area for inducing magnetic flux can be easily increased, and the number of magnetic fluxes in the magnetic pole part of the yoke facing the rotor magnet can be easily increased with a simple configuration, making it compact and lightweight. It is possible to provide a brushless DC motor with high output and excellent efficiency that can obtain a sufficient rotational torque even if it is made.

  Since the magnetic pole portion is thicker than the magnetic conducting portion, the leakage flux of the coil from the magnetic pole portion can be reduced, and the magnetic pole number that induces the magnetic flux is large, so the number of magnetic fluxes is large. It is possible to provide a brushless DC motor that increases and can suppress saturation of the magnetic circuit and obtain a sufficient rotational torque of the rotor.

According to invention of Claim 2, in addition to the effect of Claim 1,
Since the width of the magnetic pole part is narrower from the magnetic conduction part toward the tip of the magnetic pole part, adjusting the magnetic circuit can improve the rotational performance of the rotor and suppress noise and vibration The brushless DC motor which can be provided can be provided.

According to invention of Claim 3,
The plate thickness in the centrifugal direction of the magnetic pole part can be increased without being restricted by the plate thickness in the bending process of the yoke, the cross-sectional area for inducing magnetic flux can be easily increased, and the rotor is opposed to the rotor magnet with a simple configuration. By using a brushless DC motor that can increase the number of magnetic fluxes of the magnetic pole part of the yoke and obtain a sufficient rotational torque with a small size and light weight, it is small and excellent in space-saving and practical in terms of air blowing efficiency and high practicality Can be provided.

  The present invention increases the sectional thickness of the magnetic pole portion in the centrifugal direction without being restricted by the thickness of the yoke in the bending forming process, thereby easily increasing the cross-sectional area for inducing magnetic flux, and the stator with a simple configuration. An object of the present invention is to provide a brushless DC motor which can easily increase the number of magnetic fluxes of the magnetic pole portion of the yoke facing the magnet, and can obtain a sufficient rotational torque even if it is reduced in size and weight, and is excellent in efficiency. A magnetic conducting portion in which at least one of the pair of yokes is disposed substantially perpendicular to the winding axis of the coil, and an end portion of the magnetic conducting portion that is substantially parallel to the winding axis of the coil and faces the rotor magnet. And the magnetic pole portion is formed so that the thickness of the magnetic pole portion is larger than the thickness of the magnetic conduction portion.

  An object of the present invention is to provide a blower fan that is small in size, excellent in space saving, and has high blowing efficiency and high practicality. At least one of a pair of yokes is disposed substantially perpendicular to a winding axis of a coil. And a magnetic pole portion that is substantially parallel to the winding axis of the coil and that faces the rotor magnet and extends from the end of the magnetic conduction portion. This was realized by using a brushless DC motor formed thicker than the plate thickness.

  A first invention made to solve the above-mentioned problems is a coil, a pair of yokes disposed on both end surfaces of the coil and forming a counter electrode with each other, and an outer peripheral surface of the yoke opposed to each other via a gap so as to be rotatable. A brushless DC motor including a rotor magnet disposed on the magnetic yoke, wherein at least one of the pair of yokes is disposed substantially perpendicular to the coil winding axis, and the coil winding axis; And a magnetic pole portion extending from the end of the magnetic conduction portion so as to face the rotor magnet, and the thickness of the magnetic pole portion is greater than the thickness of the magnetic conduction portion. have.

  This configuration has the following effects.

  At least one of the pair of yokes has a magnetic conduction portion disposed substantially perpendicular to the winding axis of the coil, and is substantially parallel to the winding axis of the coil and from the end of the magnetic conduction portion facing the rotor magnet. And the magnetic pole portion is thicker than the magnetic conductive portion, so that the magnetic pole portion of the magnetic pole portion is not restricted by the bending thickness of the yoke. The plate thickness in the centrifugal direction can be increased, the cross-sectional area for inducing magnetic flux can be easily increased, and the number of magnetic fluxes in the magnetic pole part of the yoke facing the rotor magnet can be easily increased with a simple configuration, making it compact and lightweight. A sufficient rotational torque can be obtained even if the speed is increased.

  Since the magnetic pole portion is thicker than the magnetic conducting portion, the leakage flux of the coil from the magnetic pole portion can be reduced, and the magnetic pole number that induces the magnetic flux is large, so the number of magnetic fluxes is large. The saturation of the magnetic circuit can be suppressed and a sufficient rotor rotational torque can be obtained.

  Here, the coil can be formed through winding, immersion plating, insulation layer coating, and the like. When the coil is wound around the outer periphery of the insulating member, the insulation of the coil can be improved, and the step of forming an insulating layer by immersion plating or the like or covering with an insulating layer can be omitted, Excellent in assembly workability and preferable.

  As the rotor magnet, a magnet having a multipolar configuration on the inner peripheral surface of a rotor formed in a cup shape, a magnet formed in a cylindrical shape and having a plurality of magnetic poles formed in the circumferential direction, or the like is used. As the magnet, a radial anisotropy or polar anisotropy ring magnet (cylindrical magnet), a bond magnet formed by compression molding or injection molding, or the like is used.

  The pair of yokes can be coupled by the coupling member so that the magnetic pole portions are alternately meshed with each other. Further, without using a coupling member, a convex portion formed on one yoke may be coupled by being fitted or inserted into a concave portion or a hole formed on the other yoke.

  The magnetic conduction part and the magnetic pole part are formed of a magnetic member such as iron, cobalt, nickel, soft iron, or electromagnetic steel.

  It is preferable that the thickness of a portion of the yoke corresponding to the magnetic conductive portion is reduced by a method such as pressing, cutting, or punching before bending. As a result, the magnetic pole portion can be easily bent, and the thickness of the magnetic pole portion can be increased without being restricted by the thickness of the bent portion. In addition, it is possible to improve the degree of design freedom for obtaining desired performance.

  In addition, when the magnetic pole part is formed in an arc shape, it is preferable that the magnetic pole part can be arranged with high density along the curved surface of the coil, and the leakage magnetic flux can be reduced.

  When a plurality of magnetic members are laminated on the outer surface or inner surface or both surfaces of the magnetic pole portion by a laminating method such as pack (half press), caulking, welding, adhesion, etc. It is preferable because the plate thickness can be adjusted, and the degree of freedom in design for obtaining desired performance can be improved. Further, the number of magnetic pole portions can be appropriately selected depending on the application, desired performance, and the like.

  In addition, the magnetic pole portion can change the thickness in the winding axis direction and the circumferential direction, and can change the width in the winding axis direction. As a result, the rotational performance of the rotor can be adjusted by adjusting the magnetic circuit. Depending on the characteristics of the motor, part or all of the magnetic pole portions of the pair of yokes, and part or all of the magnetic pole portions of one of the yokes are appropriately selected to change the width and thickness of the magnetic pole portions. The magnetic circuit can be adjusted.

  A second invention made to solve the above-described problem is the brushless DC motor according to the first invention, wherein the width of the magnetic pole portion is narrower from the magnetic conduction portion toward the tip of the magnetic pole portion. It has the structure formed in.

  With this configuration, in addition to the operation of the first invention, the following operation is provided.

  Since the width of the magnetic pole part is narrower from the magnetic conduction part toward the tip of the magnetic pole part, adjusting the magnetic circuit can improve the rotational performance of the rotor and suppress noise and vibration it can.

  Here, the width of the magnetic pole part may be any shape as long as it is formed narrower from the magnetic conduction part toward the tip of the magnetic pole part, for example, one side of the magnetic pole part from the magnetic conduction part toward the tip. It can also be formed in a staircase shape with a narrow width.

  3rd invention made | formed in order to solve the said subject is a ventilation fan, Comprising: It has the structure provided with the brushless DC motor of Claim 1 or 2.

  This configuration has the following effects.

  The brushless DC motor can increase the thickness of the magnetic pole part in the centrifugal direction without being restricted by the thickness of the bending process of the yoke. Since the number of magnetic fluxes of the magnetic pole part of the yoke facing the rotor magnet can be increased and sufficient rotational torque can be obtained with a small size and light weight, it is possible to improve the space-saving performance with a small size, and to increase the blowing efficiency of the blower fan The practicality can be improved.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the main cross section of the blower fan provided with the brushless DC motor according to the first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the main portion of the stator of the brushless DC motor according to the first embodiment of the present invention. FIG. 3 is an end view taken along line AA of the yoke of the brushless DC motor according to the first embodiment of the present invention, and FIG. 4 is a B direction arrow of the yoke of the brushless DC motor according to the first embodiment of the present invention. FIG.

  In FIG. 1, 1 is a blower fan in the first embodiment, 2 is a brushless DC motor disposed in the blower fan 1, 3 is a fan case of the blower fan 1, and 4 is disposed in a predetermined portion of the fan case 3. Base portion 5 is a bearing housing erected on the base portion 4, 6 is a cylindrical bearing fitted inside the bearing housing 5, 7 is a shaft rotatably supported by the bearing 6, and 8 is a shaft 7 is a cup-shaped rotor whose center is fixed to one end, 9 is a cylindrical rotor magnet having a plurality of magnetic poles in the circumferential direction and press-fitted into the inner peripheral surface of the rotor 8, and 10 is an outer peripheral surface of the rotor 8 The disposed blade portion, 11 is a circuit board mounted on the fan case 3 on which electronic components such as rotational position detecting elements are mounted, and 12 is a lead connected to the circuit board 11 to apply the driving voltage of the brushless DC motor 2. Is a line Circuit board 11 to which the drive voltage is applied in the direction by the output signal of the rotor rotation detecting element such as a Hall element (not shown) to generate a coil energizing current is controlled.

  In FIGS. 1 and 2, 13 is a cylindrical insulating member having ridges formed at both ends, 13a is a central hole formed at the center of the insulating member 13, and 14 is wound around the outer periphery of the insulating member 13. 15 is a pair of yokes disposed at both ends of the coil 14, and 16 is a disk made of a magnetic member such as iron, cobalt, nickel, soft iron, electromagnetic steel, and the winding axis of the coil 14. The magnetic conduction portion of the yoke 15 arranged substantially vertically, 16a is a central hole formed in the approximate center of the magnetic conduction portion 16, and 17 is an extension of the magnetic conduction portion 16 extending from the magnetic conduction portion 16 in all directions. And 18 are formed of a magnetic member such as iron, cobalt, nickel, soft iron, and electromagnetic steel, and extend from the end of the extending portion 17 of the magnetic conducting portion 16 so as to be substantially parallel to the winding axis of the coil 14 and the rotor magnet. 9 is a magnetic pole portion bent so as to face 9. As shown in FIG. 3, the plate thickness tb of the magnetic pole portion 18 in the centrifugal direction of the winding axis of the coil 14 is formed to be thicker than the plate thickness ta of the magnetic conduction portion 16. Further, as shown in FIG. 4, the width wa of the base portion on the magnetic conduction portion 16 side of the magnetic pole portion 18 and the width wb of the tip are formed substantially the same. Further, in the present embodiment, as shown in FIG. 2, the magnetic pole portion 18 is formed in a gentle arc shape along the circumferential direction.

  A coupling member 19 is a magnetic member formed in a cylindrical shape. The coupling member 19 is fitted into the central hole 16a of the magnetic conduction portion 16 and the central hole 13a of the insulating member 13 to couple the pair of yokes 15 with the coil 14 interposed therebetween and a bearing. A housing 5 is fitted and fixed to the fan case 3. The magnetic conducting portions 16 of the yoke 15 are disposed at both ends of the coil 14 substantially perpendicular to the winding shaft, and the yoke 15 is coupled by a coupling member 19 so that the four magnetic pole portions 18 are alternately meshed with each other.

  The operation of the brushless DC motor and the blower fan using the brushless DC motor according to Embodiment 1 configured as described above will be described below.

  When a drive voltage is applied to the circuit board 11 through the lead wire 12 and electric power is supplied to the brushless DC motor 2, a current flows through the coil 14 to generate a magnetic force. The energizing current of the coil 14 is controlled by the circuit board 11, and a pair of energizing currents is controlled by the direction of the energizing current of the coil 14 controlled by the output signal of the rotational position detecting element of the rotor 8 such as a Hall element (not shown). The yokes 15 periodically perform magnetic pole conversion while mutually forming counter electrodes. The magnetic flux generated by the coil 14 is guided to the magnetic circuit of the magnetic conducting portion 16, the extending portion 17 and the magnetic pole portion 18 of the yoke 15. The four magnetic pole portions 18 (four poles) arranged in the circumferential direction of the upper yoke 15 repeat attraction and repulsion with the opposing rotor magnet 9 to generate rotational torque of the rotor 8. Similarly, the lower yoke 15 has four magnetic pole portions 18 arranged in the circumferential direction (four poles), and repeats attraction and repulsion with the opposing rotor magnet 9 to generate rotational torque of the rotor 8. Let In other words, a total of eight magnetic pole portions 18 are formed on the pair of yokes 15 while being adjacent to each other in the circumferential direction, and a rotational torque is generated in the rotor magnet 9 having eight poles, so that the rotor 8 and the blade portion 10 rotate. To do.

  Here, in the present embodiment, before bending the pair of yokes 15, the magnetic conductive portion 16 and the extending portion 17 are formed thin by a method such as press working, cutting, or punching. Thereby, the bending molding process can be easily performed, and the plate thickness of the magnetic pole portion 18 can be increased without being restricted by the plate thickness in the bending process. In addition, it is possible to improve the degree of design freedom for obtaining desired performance.

  Here, in the present embodiment, the case where the extending portion 17 extending in the four directions of the magnetic conducting portion 16 is described, but the disc-like magnetic conducting portion 16 is not formed without forming the extending portion 17. In some cases, the magnetic pole portion 18 may be extended. Further, instead of the coil 14 formed by winding around the outer periphery of the insulating member 13, an air core coil formed through winding, immersion plating, or coating of an insulating layer may be used.

  As described above, the brushless DC motor and the blower fan using the brushless DC motor according to Embodiment 1 of the present invention are configured, and thus have the following operations.

  A pair of yokes 15 includes a magnetic conduction portion 16 disposed substantially perpendicular to the winding axis of the coil 14, and a winding axis of the coil 14 from the end of the extension portion 17 extending to the magnetic conduction portion 16. A magnetic pole portion 18 that is substantially parallel and extends opposite to the rotor magnet 9, and the magnetic pole portion 18 has a thickness greater than that of the magnetic conduction portion 16. The thickness of the magnetic pole portion 18 in the centrifugal direction can be increased without being restricted by the plate thickness in the molding process, the cross-sectional area for inducing magnetic flux can be easily increased, and the magnetic pole portion facing the rotor magnet 9 with a simple configuration stator. The number of magnetic fluxes of 18 can be easily increased, and sufficient rotational torque can be obtained even if the size and weight are reduced.

  Since the coil 14 is wound around the outer periphery of the insulating member 13, the insulation of the coil 14 can be improved, and an insulating layer is formed by immersion plating or the step of covering with the insulating layer is omitted. Can be assembled and has excellent assembly workability.

  Since the plate thickness tb in the centrifugal direction of the winding axis of the coil 14 of the magnetic pole portion 18 is formed to be thicker than the plate thickness ta of the magnetic conduction portion 16, the leakage magnetic flux of the coil 14 from the magnetic pole portion 18 can be reduced. Since the magnetic pole part 18 for inducing magnetic flux has a large cross-sectional area, the number of magnetic fluxes increases, saturation of the magnetic circuit can be suppressed, and sufficient rotor rotational torque can be obtained.

  Since the magnetic pole portion 18 is formed in an arc shape, the magnetic pole portion 18 can be disposed at a high density along the curved surface of the coil, and the leakage magnetic flux can be reduced.

  By using the brushless DC motor 2 that is small and light and can obtain a sufficient rotational torque, the blower fan 1 can be reduced in size, space saving can be improved, and the blowing efficiency becomes higher and practicality. Can be improved.

(Embodiment 2)
FIG. 5A is a front view of the yoke of the brushless DC motor according to the second embodiment of the present invention, and FIG. 5B is a front view showing a modification of the yoke. In addition, the same thing as having demonstrated in Embodiment 1 attaches | subjects the same code | symbol, and abbreviate | omits description.

  In FIG. 5A, 15a is the yoke of the brushless DC motor according to the second embodiment, 18a is extended to the extension part 17 of the magnetic conduction part 16, and is bent substantially perpendicular to the magnetic conduction part 16 and the extension part 17. It is the made magnetic pole part. The difference between the yoke 15a in the second embodiment and the yoke 15 of the brushless DC motor in the first embodiment is that the magnetic pole portion 18a of the yoke 15a has a narrower width wb at the tip than the width wa on the magnetic conduction portion 16 side. One side of the magnetic pole part 18a is formed in a stepped manner from the magnetic conduction part 16 toward the tip.

  In FIG. 5B, 15 b is a yoke of a modified example of the brushless DC motor in the second embodiment, 18 b is extended to the extending portion 17 of the magnetic conducting portion 16, and is substantially perpendicular to the magnetic conducting portion 16 and the extending portion 17. It is a magnetic pole part bent in a circle. The yoke 15b of the modified example of the brushless DC motor in the second embodiment is different from the yoke 15 of the brushless DC motor in the second embodiment in that the yoke 15b of the modified example has two sides of the magnetic pole portion 18b from the magnetic conducting portion 16. The width is smoothly narrowed toward the tip, and the tip width wb is narrower than the width wa on the magnetic conduction part 16 side.

  Here, the magnetic pole portions 18a and 18b only need to be formed narrower from the magnetic conduction portion 16 toward the tip of the magnetic pole portion, and the shape is not limited to the above. Further, the magnetic pole portions of the pair of yokes may be formed as described above, or only one of the yokes may be formed as described above. Further, it is not necessary to form all of the plurality of magnetic pole portions as described above, and they may be appropriately formed depending on the application, desired performance, and the like.

  As described above, since the brushless DC motor and the blower fan according to the second embodiment are configured, in addition to the functions of the first embodiment, the following actions are provided.

  By adjusting the magnetic circuit by forming the width of the magnetic pole portions 18a and 18b narrower from the magnetic conduction portion 16 toward the tip of the magnetic pole portion, the rotational performance of the rotor can be improved, and noise and vibration can be suppressed. Can do.

  The present invention relates to a brushless DC motor and a blower fan using the brushless DC motor, and the thickness of the magnetic pole portion in the centrifugal direction can be increased without being restricted by the thickness of the yoke in the bending process. Easily increased, the number of magnetic fluxes of the magnetic pole part of the yoke facing the rotor magnet can be increased easily with a stator with a simple configuration, and high output and efficiency that can provide sufficient rotational torque even if it is reduced in size and weight A brushless DC motor excellent in performance can be provided. In addition, the present invention can increase the thickness of the magnetic pole portion in the centrifugal direction without being restricted by the thickness of the bending process of the yoke, and can easily increase the cross-sectional area for inducing magnetic flux. By using a brushless DC motor that increases the number of magnetic fluxes of the magnetic pole part of the yoke facing the rotor magnet and can obtain a sufficient rotational torque with a small size and light weight, it is small and excellent in space saving and practicality with high blowing efficiency. It is possible to provide an excellent blower fan.

Sectional cross-sectional view of the central cross section of the blower fan provided with the brushless DC motor in Embodiment 1 of the present invention The principal part disassembled perspective view of the stator of the brushless DC motor in Embodiment 1 of this invention AA line end view of the yoke of the brushless DC motor according to Embodiment 1 of the present invention B direction arrow view of the yoke of the brushless DC motor in Embodiment 1 of the present invention (A) Front view of a yoke of a brushless DC motor in Embodiment 2 of the present invention, (b) Front view showing a modification of the yoke

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blower fan 2 Brushless DC motor 3 Fan case 4 Base part 5 Bearing housing 6 Bearing 7 Shaft 8 Rotor 9 Rotor magnet 10 Blade part 11 Circuit board 12 Lead wire 13 Insulating member 13a Center hole 14, 14a Coil 15, 15a, 15b Yoke 16 Magnetic conduction part 16a Center hole 17 Extension part 18, 18a, 18b Magnetic pole part 19 Coupling member

Claims (3)

Brushless DC comprising: a coil; a pair of yokes disposed on both end surfaces of the coil and forming a counter electrode; and a rotor magnet rotatably disposed opposite the outer peripheral surface of the yoke with a gap. A motor, wherein at least one of the pair of yokes is disposed substantially perpendicular to the winding axis of the coil, is substantially parallel to the winding axis of the coil, and faces the rotor magnet. And a magnetic pole portion extending from an end portion of the magnetic conduction portion, and the thickness of the magnetic pole portion is larger than the thickness of the magnetic conduction portion. 2. The brushless DC motor according to claim 1, wherein a width of the magnetic pole portion is narrower from the magnetic conduction portion toward a tip of the magnetic pole portion. A blower fan comprising the brushless DC motor according to claim 1.

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