JPH09247917A - Brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress vibration and noise by separating a ring-shaped flange formed along the periphery of a rotor yoke, with an end face of the flange being located in a different level with an end face of a magnetic pole of a rotor magnet. SOLUTION: On an lower face of a rotor yoke 1 which constitutes a rotor assembly A, a ring-shaped rotor magnet 2 is adhered through an elastic member 11. On an upper face of a stator yoke 4 which constitutes a stator assembly B, a plurality of armature coils 7 are so adhered through an elastic member 12 in the circumferential direction as to face the rotor magnet 2. Furthermore, a ring-shaped flange is formed in the periphery of the rotor yoke 1, with an end face 1b being positioned in a different level with an end face of a magnetic pole of the rotor magnet 2 and also being away from it. Due to this structure, magnetic flux from the rotor magnet 2 is not leaked in the end face 1b of the ring-shaped flange and no excitation force in the thrust direction appears between the rotor magnet 2 and the armature coil 7 and thereby the production of noise can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial type brushless DC motor used as a disk drive motor in OA equipment such as personal computers and word processors.

[0002]

2. Description of the Related Art FIG. 10 is a half-cut longitudinal sectional view showing the structure of a conventional three-phase axial type brushless DC motor. In the figure, reference numeral 1 denotes a rotor yoke, an annular rotor magnet 2 is adhered to the lower surface thereof, and a rotary shaft 3 is press-fitted and fixed in an orthogonal posture at a central portion of the shaft center so that the rotary shaft 3 is interposed via a radial bearing 5. It is rotatably supported by the bearing housing 6 and constitutes a rotor assembly A. Reference numeral 4 denotes a stator yoke. As clearly shown in FIG. 11, a plurality of amateur coils 7 are bonded to the upper surface of the stator yoke 4 so as to face the rotor magnet 2 in the circumferential direction (direction of arrow a). And a copper foil pattern (not shown) fixed to the bearing housing 6 and connected to each of the amateur coils 7, and three holes for detecting the magnetic position of the rotor magnet 2. The element 8 is fixed to form a stator assembly B.

In a three-phase axial type brushless DC motor having the rotor assembly A and the stator assembly B as a basic structure, the rotor magnet 2 has an N-pole portion 2n with a magnetization distribution as shown in FIG.
And S pole portions 2s are alternately magnetized in the circumferential direction and equally arranged, and the magnetizing boundary line L is arranged along the radiation x from the rotation center O. On the other hand, in order to effectively generate a torque in the circumferential direction, each of the amateur coils 7 has an outer shape spirally formed along a line segment substantially parallel to the radiation x from the rotation center O, and As shown in FIG. 13, the vertical cross-sectional shape is the coil wire 7.
It is formed in a rectangular shape in which the number of turns of a in the thrust direction (direction of arrow b) is uniform over the inner and outer circumferences.

In the brushless DC motor having the above structure, a signal from the Hall element 8 is input to a drive circuit (not shown), and a current I is sequentially applied to each armature coil 7, so that the rotor magnet 2 and the stator yoke 4 are connected. Magnetic flux Φ in the thrust direction (direction of arrow b) generated between
n, Φs (FIG. 14) and the current I are linked to generate a rotational force based on Fleming's left-hand rule, and the rotor assembly A is rotationally driven in the direction of arrow a, for example.

[0005]

By the way, according to the above-mentioned structure, since the ring-shaped collar portion 1a is formed on the outer peripheral portion of the rotor yoke 1 to house and hold the rotor magnet 2, the ring-shaped collar is formed. The end surface 1b of the portion 1a and the magnetic pole end surface 2a of the rotor magnet 2 are close to each other, and the magnetic flux Φ (Φn, Φs) from the rotor magnet 2 leaks to the end surface 1b of the annular collar portion 1a, and the leakage magnetic flux Φr. Has a magnetic component .PHI.r1 in the radial direction (direction of arrow c), the magnetic component .PHI.r1 in the radial direction is sequentially linked to the current I of each of the amateur coils 7, and the magnetic component .PHI.r1 between the rotor magnet 2 and the stator yoke 4. Is generated in the thrust direction (direction of arrow b) based on Fleming's left-hand rule, vibrating the rotor yoke 1 and the stator yoke 4 to generate noise. To produce.

Further, since the N pole portion 2n and the S pole portion 2s are arranged close to each other in the rotor magnet 2, the leakage magnetic flux Φt is also circumferentially (arrow) between the both magnetic pole portions 2n and 2s. The leakage magnetic flux Φt has a magnetic component Φt1 in the circumferential direction. Therefore, the magnetic flux Φt1 in the circumferential direction is generated.
Sequentially interlinks with the current I of each of the above amateur coils 7,
Excitation force F in the thrust direction (direction of arrow b) is generated between the rotor magnet 2 and the stator yoke 4, causing the rotor yoke 1 and the stator yoke 4 to vibrate and generate noise.

Further, the magnetic flux distribution between the rotor magnet 2 and the stator yoke 4 is as shown in FIG.
Since the magnetic fluxes Φn and Φs having a uniform density are generated from the N pole portion 2n and the S pole portion 2s, each time the energization direction of the current I is switched with the rotation of the rotor magnet 2, the armature is switched. The coil 7 has a steep torque change having a rectangular wave characteristic, and the rotor yoke 1 and the rotor assembly vibrate due to a large impact force based on the steep torque ripple, which causes noise. Moreover, since the stator yoke 4 has a flat plate shape and the supporting structure is relatively simple, there is a problem that the exciting force F in the thrust direction is generated and the stator yoke 4 is more likely to vibrate.

The present invention has been made to solve the above problems, and an object thereof is to provide a brushless DC motor capable of suppressing the generation of vibration and noise.

[0009]

In order to achieve the above object, the brushless DC motor according to the invention of claim 1 has a rotor assembly in which a rotor magnet is bonded to a rotor yoke having a rotating shaft fixed to the center of the shaft center. A stator assembly fixed to a bearing housing that rotatably supports the rotary shaft, and a stator assembly in which a plurality of armature coils facing the rotor magnet are bonded in a circumferential direction, and the armature coils are sequentially energized. And a drive circuit for rotationally driving the rotor assembly, the rotor magnet and the armature coil are bonded to the rotor yoke and the stator yoke via elastic members, and are formed on the outer peripheral portion of the rotor yoke. The end face of the annular collar part Characterized in that the magnetic pole end face of the motor magnets were spaced with a step.

A brushless DC motor according to a second aspect of the present invention includes a rotor assembly in which a rotor magnet is adhered to a rotor yoke having a rotating shaft fixed to a central portion of a shaft, and a bearing housing which rotatably supports the rotating shaft. The stator assembly is provided with a stator assembly in which a plurality of amateur coils facing the rotor magnet are bonded to a fixed stator yoke in the circumferential direction, and a drive circuit for rotating the rotor assembly by sequentially energizing the amateur coils. In the brushless DC motor, a non-magnetic portion is radially arranged along each magnetizing boundary line between the N pole portion and the S pole portion formed on the rotor magnet.
It is characterized in that the magnetic flux leaking across the magnetized boundary line between the pole portion and the S pole portion is cut off by the non-magnetic portions.

A brushless DC motor according to a third aspect of the present invention includes a rotor assembly in which a rotor magnet is bonded to a rotor yoke having a rotating shaft fixed to a central portion of a shaft, and a bearing housing which rotatably supports the rotating shaft. The stator assembly is provided with a stator assembly in which a plurality of amateur coils facing the rotor magnet are bonded to a fixed stator yoke in the circumferential direction, and a drive circuit for rotating the rotor assembly by sequentially energizing the amateur coils. In the present brushless DC motor, recesses are radially formed along the magnetizing boundary lines between the N pole portion and the S pole portion formed on the rotor magnet, so that the N pole portion and the S pole portion are attached to each other. It is characterized in that the magnetic flux leaking across the magnetic boundary line is cut off by the recess.

[0012]

According to the first aspect of the present invention, since the end surface of the annular collar portion is disposed with a step from the magnetic pole end surface of the rotor magnet, the magnetic flux from the rotor magnet is applied to the end surface of the annular collar portion. Therefore, the magnetic flux in the magnetic flux in the radial direction is eliminated, and the exciting force in the thrust direction is not generated between the rotor magnet and the stator yoke. It is possible to prevent the generation of noise based on.

Further, even if some leakage magnetic flux is generated from the rotor magnet and an exciting force in the thrust direction is generated between the rotor magnet and the stator yoke, elastic members are provided on the rotor yoke and the stator yoke. The rotor magnet and the armature coil are adhered to each other via the, so that the vibration of the rotor yoke and the stator yoke can be absorbed to effectively prevent the generation of noise.

According to the second aspect of the present invention, since the magnetic flux leaking across the magnetized boundary lines of the N pole portion and the S pole portion formed on the rotor magnet can be blocked by the nonmagnetic portion. The magnetic flux from the rotor magnet has no magnetic component in the circumferential direction, and no thrust force is generated between the rotor magnet and the armature coil.
It is possible to prevent the generation of noise due to the vibration of the rotor yoke and the stator yoke.

According to the third aspect of the present invention, the recesses are radially formed along the magnetization boundary lines of the N pole portion and the S pole portion formed on the rotor magnet, and the N pole portion and the S pole are formed. The magnetic flux leaking across the respective magnetizing boundary lines with the portion can be blocked by the recess, and the generation of noise due to the vibration of the rotor yoke and the stator yoke can be prevented almost in the same manner as in the invention of claim 2. be able to.

Further, according to the inventions of claims 2 and 3, the magnetic flux density in the circumferential direction becomes coarser in the vicinity of the magnetizing boundary line, and the torque change at the time of switching the energized phase of the armature coil becomes gentle. As a result, the impact force acting on the rotor assembly at the time of switching the energized phase is alleviated, and it is possible to reduce vibration and noise.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a half-cut vertical sectional view showing the structure of a three-phase axial type brushless DC motor according to the present invention. As shown in the figure, an annular rotor magnet 2 is adhered to the lower surface of the rotor yoke 1 which constitutes the rotor assembly A via an elastic member 11, and an upper surface of a stator yoke 4 which constitutes the stator assembly B. Includes a plurality of armature coils 7 (FIG. 2) that face the rotor magnet 2 in the circumferential direction and are elastic members 12.
3, the end surface 1b of the annular flange portion 1a formed on the outer peripheral portion of the rotor yoke 1 is set apart from the magnetic pole end surface 2a of the rotor magnet 2 with a step d as shown in FIG. Has been done. Since other configurations are almost the same as those of the conventional example shown in FIGS. 10 and 11, the same reference numerals are given to corresponding portions and detailed description thereof will be omitted.

According to the above construction, since the end surface 1b of the annular flange portion 1a is arranged with the step d from the magnetic pole end surface 2a of the rotor magnet 2, the magnetic flux Φ (Φn, Φs from the rotor magnet 2 is set. ) Does not leak to the end face 1b of the annular collar portion 1a, so that the magnetic flux Φ (Φn, Φs) has no magnetic component in the radial direction (arrow c direction), and the rotor magnet 2 and the amateur coil Since the exciting force F in the thrust direction (direction of arrow b) is not generated between the rotor yoke 1 and the rotor 7, it is possible to prevent generation of noise due to the vibration of the rotor yoke 1 and the stator yoke 4.

Further, some leakage magnetic flux Φr is generated from the rotor magnet 2 to cause a thrust direction (direction of arrow b) between the rotor magnet 2 and the armature coil 7.
Even if the exciting force F is generated, the rotor magnet 2 and the armature coil 7 are attached to the rotor yoke 1 and the stator yoke 4 via elastic members 11 and 12 made of, for example, flexible synthetic resin or elastic rubber. Since they are bonded, the vibrations of the rotor magnet 2 and the amateur coil 7 can be absorbed by the elastic members 11 and 12, and the generation of noise due to the vibrations of the rotor yoke 1 and the stator yoke 4 can be effectively prevented. it can. In particular, the adhesive surface 1 between the elastic member 11 and the rotor magnet 2
By exposing 3 to the stator yoke 4 side from the end surface 1b of the annular collar portion 1a, the magnetic flux leakage Φr from the rotor magnet 2 can be blocked by the elastic member 11.

In the above embodiment, the rotor magnet 2 is formed by mixing magnetic powder with elastic material powder made of, for example, flexible synthetic resin or elastic rubber. The vibration of the rotor yoke 1 can be absorbed. Further, by inserting a diamagnetic material 13 such as glass or a copper plate into the hollow portion 7a of the amateur coil 7 and adhering the diamagnetic material 13 to the stator yoke 4, the hollow portion 7a is energized when the amateur coil 7 is energized. It is possible to suppress the generated vertical magnetic flux and suppress the vibration of the stator yoke 4. Further, as shown in FIG. 4, the rotor yoke 1 and the stator yoke 4 are, for example, two rope plates 14,
By using a vibration damping steel plate in which an elastic material layer 16 such as a synthetic resin is interposed between the two, the vibration of the rotor yoke 1 and the stator yoke 4 can be absorbed by itself, and the rotor yoke 1 Since the gap between the stator yoke 4 and the stator yoke 4 does not change, there is no fear of adverse effects on motor characteristics.

Embodiment 2 FIG. 5 is a plan view of the essential portion showing another example of the brushless DC motor according to the present invention. As shown in the figure, a non-magnetic portion 17 made of, for example, a synthetic resin is radially arranged along each magnetization boundary line x of the N pole portion 2n and the S pole portion 2s formed on the rotor magnet 2. ,
The magnetic flux Φt that leaks across each of the magnetized boundary lines x of the N pole portion 2n and the S pole portion 2s can be blocked by the nonmagnetic portions 17. Therefore, the rotor magnet 2
The magnetic flux Φ (Φn, Φs) from the magnetic flux Φt in the circumferential direction (direction of arrow a) shown in FIG. 6 disappears, and the magnetic flux Φt in the thrust direction (direction of arrow b) between the rotor magnet 2 and the amateur coil 7 is removed. Since the exciting force F is not generated, it is possible to prevent the generation of noise due to the vibration of the rotor yoke 1 and the stator yoke 4.

Further, as shown in FIG. 6, the magnetic flux density in the circumferential direction (direction of arrow a) becomes coarser in the vicinity of the magnetizing boundary line x, and the torque change at the time of switching the energized phase of the amateur coil 7 is gentle. Which reduces the impact force acting on the rotor assembly A when switching the energized phase,
It is possible to reduce vibration and noise.

Embodiment 3 FIG. 7 is a plan view of the essential portion showing another example of a brushless DC motor according to the present invention. As shown in the figure, the recesses 18 are radially formed along each magnetizing boundary line x of the N pole portion 2n and the S pole portion 2s formed on the rotor magnet 2 to form the N pole portion 2n and the S pole portion 2n. Pole 2
The magnetic flux Φt leaking across each magnetization boundary line x with s can be blocked by the recess 18. Therefore, the magnetic flux Φ (Φn, Φs) from the rotor magnet 2 has no magnetic component Φt in the circumferential direction (arrow a direction) shown in FIG. 8, and the rotor magnet 2 and the amateur coil 7 are removed.
Since the exciting force F in the thrust direction (direction of arrow b) is not generated between and, it is possible to prevent the generation of noise due to the vibration of the rotor yoke 1 and the stator yoke 4.

In each of the above embodiments, a large number of small holes 4a are formed in the stator yoke 4 as shown in FIG.
It is possible to reduce the surface area where the stator yoke 4 vibrates the air, reduce the generation of eddy current, and suppress the generation of noise.

[0025]

As described above, according to the invention of claim 1, since the end face of the annular flange portion of the rotor yoke is disposed with a step from the magnetic pole end face of the rotor magnet, the magnetic flux from the rotor magnet is Does not leak to the end face of the annular flange, eliminates the magnetic component in the radial direction, and bonds the rotor magnet and the amateur coil to the rotor yoke and the stator yoke via the elastic member. It is possible to absorb the vibration and effectively prevent the generation of noise.

According to the second and third aspects of the present invention, the magnetic flux leaking across the magnetized boundary lines of the N pole portion and the S pole portion formed on the rotor magnet is blocked by the nonmagnetic portion or the recess. At the same time, the magnetic flux density in the circumferential direction becomes coarser near the magnetizing boundary line, the torque change at the time of switching the energized phase of the amateur coil becomes gradual, and the impact force acting on the rotor assembly at the time of switching the energized phase is reduced. It is alleviated and vibration and noise can be reduced.

[Brief description of drawings]

FIG. 1 is a semi-longitudinal side view showing a configuration of a three-phase axial type brushless DC motor according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway plan view of the DC motor.

FIG. 3 is an enlarged cross-sectional view of a main part of the same DC motor.

FIG. 4 is a semi-longitudinal side view showing another example of the same DC motor.

FIG. 5 is an enlarged plan view of a main part showing an example of a magnetization distribution in a rotor magnet of the same DC motor according to a second embodiment of the present invention.

FIG. 6 is an enlarged side view of a main part showing an example of magnetic flux distribution of a rotor magnet in the same DC motor.

7A and 7B are an enlarged plan view and a sectional view of a main part showing another example of the magnetization distribution in the rotor magnet of the same DC motor according to the third embodiment of the present invention.

FIG. 8 is an enlarged side view of a main part showing an example of magnetic flux distribution of a rotor magnet in the same DC motor.

FIG. 9 is a plan view showing another example of a rotor yoke in the same DC motor.

FIG. 10 is a semi-longitudinal side view showing the configuration of a conventional three-phase axial type brushless DC motor.

FIG. 11 is a partially cutaway plan view of the conventional DC motor.

FIG. 12 is a plan view showing an example of a magnetization distribution of a rotor magnet in the conventional DC motor.

FIG. 13 is an enlarged vertical sectional view of an amateur coil in the conventional direct-current motor.

FIG. 14 is an enlarged side view of a main part showing an example of magnetic flux distribution in the rotor magnet of the same DC motor.

[Explanation of symbols]

 A rotor assembly B stator assembly 1 rotor yoke 2 rotor magnet 2n N pole part 2s S pole part 3 rotating shaft 4 stator yoke 6 bearing housing 7 amateur coil 11 elastic member 12 elastic member 17 non-magnetic part 18 recess x magnetized boundary line Φr Leakage magnetic flux Φt Leakage magnetic flux

Claims (3)

[Claims] 1. A rotor assembly in which a rotor magnet is adhered to a rotor yoke having a rotating shaft fixed to a central portion of an axial center, and a rotor yoke fixed to a bearing housing which rotatably supports the rotating shaft. A brushless DC motor comprising: a stator assembly formed by bonding a plurality of amateur coils facing each other in the circumferential direction; and a drive circuit for sequentially energizing the amateur coils to rotationally drive the rotor assembly. Also, the armature coil is bonded to the rotor yoke and the stator yoke via an elastic member, and the end face of the annular flange formed on the outer peripheral portion of the rotor yoke is separated from the magnetic pole end face of the rotor magnet by a step. Brushless DC mode . 2. A rotor assembly in which a rotor magnet is adhered to a rotor yoke having a rotating shaft fixed to the center of the shaft center, and the rotor magnet is attached to a stator yoke fixed to a bearing housing rotatably supporting the rotating shaft. A brushless DC motor comprising: a stator assembly formed by bonding a plurality of amateur coils facing each other in the circumferential direction; and a drive circuit for sequentially energizing the amateur coils to rotationally drive the rotor assembly. A non-magnetic portion is radially arranged along each magnetized boundary line between the N pole portion and the S pole portion, and leakage occurs across each magnetized boundary line between the N pole portion and the S pole portion. A brushless DC motor characterized in that the magnetic flux that is generated is cut off by each of the non-magnetic portions. 3. A rotor assembly in which a rotor magnet is adhered to a rotor yoke having a rotating shaft fixed to the central portion of an axis, and a rotor yoke fixed to a bearing housing which rotatably supports the rotating shaft. A brushless DC motor comprising: a stator assembly formed by bonding a plurality of amateur coils facing each other in the circumferential direction; and a drive circuit for sequentially energizing the amateur coils to rotationally drive the rotor assembly. A magnetic flux which is formed by radially forming a recess along each magnetizing boundary line between the N pole portion and the S pole portion, and which leaks across each magnetizing boundary line between the N pole portion and the S pole portion. A brushless DC motor, characterized in that it is configured to be cut off by the recess.