JPH0458752A - Rotary yoke type brushless motor subjected to noise reduction - Google Patents

Abstract

PURPOSE:To suppress noise by arranging a high density metallic member closely to the free end of stator, i.e., a through-hole. CONSTITUTION:A stator has a central through-hole 11a and comprises a thick film fine pattern board printed with a plurality of armature coils and the stator 11 is secured to a stator holding section 9a having outer circumference molded integrally with a bracket 9. The through-hole 11a is set as a pattern for arranging the routing lead of armature coil at the inside of the inner diameter 2b of a magnet 2, and a high density metallic member 12 comprising a brass ring is bonded through an acrylic bond in a space delimited by a magnet case 2a, the magnet 2 and the step part 4a of a rotor holder 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a low-noise rotary yoke type brushless motor suitable for use in portable audio equipment.

(Prior Art) Conventionally, a flat rotary yoke type brushless motor mounted on an audio device such as a headphone stereo has a basic structure as shown in FIG.

That is, a rotor R is made up of a thin stator L having a plurality of armature coils, a magnet 2 and a rotating yoke 3, each of which has the stator 1 interposed therebetween, and
A shaft 5 supports this rotor R via a rotor holder 4 passed through a through hole 11a of the stator 1, and this shaft 5 is rotatable via a bearing 6.7 and a metal holder 8 that supports this bearing 6.7. The shaft 50 is supported by a bracket 9 which holds the outer circumferential portion of the stator. In the figure, reference numeral 10 denotes a receiving plate disposed on a metal holder, which pivotally supports the base end of the shaft 50.

<Fill to be Solved by the Invention) With the recent trend toward thinner portable audio equipment such as headphone stereo players, the rotating yoke type brushless motor as described above is also required to be as thin as 3IllI in thickness. Therefore, for the stator 1, a printed wiring board such as a thick film fine pattern coil is often used rather than a partially molded winding coil.

However, since the stator l made of thick-film fine pattern coils is only about 0.4 mm thick, the entire stator vibrates when energized and acts as a speaker, generating relatively large acoustic noise. . A part of this vibration vibrates the rotary yoke 3 through the gap and is radiated to the outside as mechanical noise. As can be seen from the drawings, brushless motors with rotating yoke are oven-type, so this mechanical noise cannot be contained, and this has been highlighted as one of the major problems. In order to prevent this mechanical noise from leaking outward, it is necessary to cover the entire motor with a cover, but it is not completely covered and is disadvantageous in terms of height.

The second invention aims to solve the above problems with a simple structure and provide a rotating yoke type brushless motor with extremely low noise.

(Means for Solving the Problems) This invention focuses on the fact that the through holes of the stator can be placed further inward than the inner diameter of the magnet without reducing efficiency due to the routing of thick film fine pattern coil glue. In other words, in the rotary yoke type brushless motor having the conventional structure described above, a high-density metal member is arranged near the through hole at the free end of the stator.

(Function) When configured as described above, the high-density metal member has a function of damping vibrations caused by energization of the stator.

(Example) Hereinafter, an example of the present invention will be described based on FIG. 1, and the same reference numerals are used to indicate the same parts as those in FIG. 4, which is a conventional example.

In FIG. 1, the stator 11 has a through hole 11a in the center and is formed of a thick film fine pattern board on which a plurality of armature coils are printed and wired, and the outer peripheral portion is formed by a bracket 9.
It is fixed to a stator holding portion 9a which is partially molded. A brass metal holder 8 fitted with an oil-impregnated bearing 6.7 is fixed to the center of the bracket by caulking or other means. A shaft 5 is rotatably supported by this oil-impregnated bearing 6.7, and a rotor holder 4 having an output portion formed as a pulley is attached to the shaft 5 through the through hole 11a of the stator 11.
The stepped portion 4 of the rotor holder 4 is press-fitted through the rotor holder 4.
A rare earth magnet 2 is attached via a magnet case 2a, and a rotating yoke 3 made of a silicon steel plate is attached to the magnet case 2a with a gap therebetween, with the stator 11 in between.

The through hole 11a of the stator 11 is set so as to be inside the inner diameter 2b of the magnet 2 for the armature coil routing lead arrangement pattern. A high-density metal member 12 made of a brass ring is fixed with an acrylic adhesive material 13 in the space surrounded by the stepped portion 4a of the rotor holder 4.

FIG. 2 shows the noise characteristics of the motor of the above embodiment, and it can be seen that a significant reduction in noise has been obtained compared to the noise characteristics of the conventional motor shown in FIG.

The high-density metal member is not limited to brass, but may also be made of 5US304 class non-magnetic stainless steel, lead, tungsten, etc.

(Effects of the Invention) As described above, this invention has a simple configuration in which a high-density metal member is placed near the through hole of the stator made of thick-film fine pattern coils, thereby reducing the mechanical noise caused by the vibration of the stator when the rotor is energized. This means that noise can be reduced even in oven-type rotary yoke-type brushless motors.

Note that the high-density metal member is not placed in a portion that contributes to the generation of torque in the armature coil, so it does not pose any particular problem in terms of performance.

[Brief explanation of drawings]

1st I! I is a cross-sectional view of the main parts of the rotating yoke type brushless motor of the present invention, FIG. 2 is a noise characteristic diagram of the same motor of the present invention,
FIG. 3 is a noise characteristic diagram of the conventional motor, and FIG. 4 is a sectional view of the main part of the conventional motor. 2 is a magnet 3 is a rotating yoke 4 is a rotor holder 5 is a shaft 6. 7 is a bearing 8 is a metal holder 9 is a bracket 11 is a stator 12 is a high-density metal member Patent applicant Tokyo Parts Kogyo Co., Ltd. Reprint of drawings (no changes to the content) ) Diagram diagram procedural correction sound (method) procedural correction sound

Claims (1)

[Claims] (1) A stator consisting of a thick film fine pattern formed by printing and wiring a plurality of armature coils, a rotor consisting of a magnet with the stator arranged with a gap in between, and a rotating yoke, and this rotor. A shaft supported via a rotor holder passed through a through hole provided in the stator, and a bracket rotatably supporting this shaft via a bearing and a metal holder supporting the bearing, and holding an outer peripheral portion of the stator. 1. A rotary yoke type brushless motor with reduced noise, characterized in that a high-density metal member is arranged near the through hole at the free end of the stator.