JPH08237905A - Miniature motor - Google Patents

Abstract

PURPOSE: To provide a miniature motor which has stable performance by suppressing vibrations between a shaft and a bearing to prevent the generation of mechanical noise. CONSTITUTION: In a miniature motor which is provided with a rotor rotatably supported through the respective bearings 3 in a housing comprising a case 1 and a bracket 2 and always energized to the bracket 2 side and is constituted so that the base end part of the shaft 4 of the rotor is supported by thrust bearings 10, 11 disposed on the bracket 2 side, a hollow hole is provided in the thrust bearing 10 and the like and a part of the base end part is received by the circumferential edge of the hollow hole. Therefore, the shaft 4 is energized in the lateral direction by utilizing the energizing force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor used in various electronic devices and the like, and particularly to a small motor for suppressing mechanical vibration by suppressing vibration between a shaft and a bearing. Regarding motors.

[0002]

2. Description of the Related Art Conventionally, there is known a motor having a rotor, which is rotatably supported by bearings in a housing consisting of a case and a bracket. FIG. 5 shows the conventionally used motor. In FIG. 5, M is a motor, which is a partial sectional view of the motor M. This motor M
Is a bottomed cylindrical case 21 having an opening at one end,
The bracket 22 arranged in the opening of the case 21 constitutes a housing. A shaft 24 is rotatably supported in each of the housings via bearings 23. A core 25 provided by laminating a plurality of thin plates such as silicon steel plates on the shaft 24, and a core 25 provided on the core 25. A rotor including the wound armature coil 26 is provided. A magnetic thrust attracting force is exerted on this rotor by making the center of the core 25 and the center of a magnet 27, which will be described later, different from each other in the axial direction, and the attracting force biases the rotor toward the bracket 2. ing.

On the other hand, an annular magnet 27 is provided on the inner periphery of the case 21, and the magnet 27 is arranged in the core 25 with a gap. Also, in the figure, axis 2
A commutator 28 is inserted below 4 and an open end of a brush 29 having elasticity is arranged in sliding contact with the commutator 28. Further, the base end of the brush 29 is fixed to the bracket 22. Further, in the bracket 22, a thrust bearing 30 is arranged at a portion with which the shaft 24 abuts in order to regulate the position of the rotor biased to the bracket side.

[0004]

However, when the motor M having the above-described structure is driven, the shaft 2 may be slightly unbalanced or cogging by the rotor itself.
4, vibration due to the clearance between the bearings 23 occurs, and mechanical noise occurs due to the vibration. This significantly impairs the performance of the motor. Further, in order to eliminate this clearance, there is a technical proposal previously disclosed in Japanese Patent Application Laid-Open No. 3-234915, but in this case, in order to obtain plastic deformation of the bearing, a considerable load is also applied to the shaft itself. As a result, the shaft itself may be deformed, and the lubrication action of the bearing is also reduced.

Therefore, the present invention solves the above problems, suppresses the vibration between the shaft and the bearing, prevents the occurrence of mechanical noise, and provides a small motor having stable performance. is there.

[0006]

The small motor of the present invention comprises:
A rotor, which is rotatably supported via bearings in a housing composed of a case and a bracket, and is always biased to the bracket side, has a base end portion of a shaft of the rotor on the bracket side. In the small motor configured to be supported by the thrust bearings arranged, a hollow hole is provided in the thrust bearing, and the biasing force is utilized by receiving a part of the base end portion at the peripheral edge of the hollow hole. The shaft is biased laterally.

[0007]

The thrust bearing is provided with a hollow hole, and a force for urging the shaft in the lateral direction is generated by receiving a part of the base end portion at the peripheral edge of the hollow hole. It can be kept in contact with the inner surface.

[0008]

[First Embodiment] FIG. 1 is a partial sectional view showing the structure of a small motor according to a first embodiment of the present invention. 2 is an enlarged view of a main part of the small motor in FIG. 1, and FIG. 3 is frequency analysis data comparing noise occurrence states of the small motor in the same embodiment. In FIG. 1, a housing is formed by a case 1 formed in a bottomed cylindrical shape having an opening at one end and a bracket 2 made of resin or metal and arranged in the opening of the case 1. And
A shaft 4 is rotatably supported in the housing via bearings 3, and a core 5 provided by laminating a plurality of thin plates such as silicon steel plates on the shaft 4,
A rotor including an armature coil 6 wound around the core 5 is provided.

On the other hand, an annular magnet 7 is provided on the inner circumference of the case 1, and the magnet 7 is arranged in the core 5 with a gap. Further, in the figure, a commutator 8 is inserted below the shaft 4, and an open end of a brush 9 having elasticity is arranged so as to be in sliding contact with the commutator 8. Further, the base end of the brush 9 is fixed to the bracket 2. In such a motor M, a magnetic thrust attraction force acts on the rotor by making the center of the core 5 and the center of the magnet 7 different in the axial direction, and is urged toward the bracket 2 side by the attraction force. It will be. In order to receive this urging force, a thrust bearing 10 is arranged on the bracket 2 to regulate the position of the rotor.

Now, the thrust bearing 10 will be described. In FIG. 2, between the bracket 2 and the bearing 3,
A thrust bearing 10 having the same width as the bearing 3 is interposed. As the thrust bearing 10, it is preferable to use an elastic hollow disk-shaped washer or spring washer. In this case, the thrust bearing 10
The shape is such that the inner circle and the outer circle are non-concentrically arranged.
The thrust bearing 10 as described above is mounted on the bracket 2 and the bearing 3.
, The thrust bearing 10 is arranged so that the outer circle of the thrust bearing 10 is concentric with the shaft 4.
The thrust bearing 1 so that the
Shaft 4 on the periphery of the inner circle eccentrically arranged with respect to the outer circle of 0
A part of the base end of the abut. With this configuration,
As indicated by an arrow in the figure, a force F1 for axially pressing the thrust bearing 10 acts due to the influence of the thrust suction force, and a force F2 of the radial component of the motor M acts. Since the shaft 4 is urged in the lateral direction by the action of this force F2, it is possible to suppress the vibration caused by the clearance between the shaft 4 and the bearing 3.

Next, the situation of noise generation using the motor of this embodiment will be described in comparison with the conventional one. FIG.
(A) to (c) show the frequency of noise on the horizontal axis and the noise level on the vertical axis, and show the noise generation state by FFT (frequency analysis). First, FIG. 3 (a) shows a state in which the motor is off. In the graph, the level sharply increases near 280 Hz and 840 Hz, but these level peaks A are fan noises of the apparatus itself. . Based on this, FIG. 3 (b) shows the state in which the conventional motor is rotated, but from this graph, in addition to the level peak A, 470 Hz, 600 H
It can be seen that peaks exist around z and 940 Hz, respectively, and these level peaks B are due to mechanical noise generated by the clearance between the shaft 4 and the bearing 3. On the other hand, FIG. 3C shows the case where the motor according to the present embodiment is used, but it is clear that the level peak B disappears, as is clear from comparison with FIG. 3B. , A graph close to the state of FIG. From this, it is understood that the use of this embodiment can prevent mechanical noise due to the clearance between the shaft 4 and the bearing 3.

[0012]

[Second Embodiment] FIG. 4 is an enlarged view of an essential part of a motor according to a second embodiment of the present invention. The thrust bearing 11 in this embodiment is a hollow disk in which the inner circle and the outer circle are concentrically arranged, and is configured to be slightly narrower than the bearing 3. Along with this, the bracket 2 has a thrust bearing 1
In order to hold 1 in a stable state, the convex portion 2a is formed so that a part of the housing portion thereof is projected. In this way, even when the thrust bearing 11 formed in the concentric hollow disk shape is used, the force F2 acts in the radial direction of the motor M and the shaft 4 can be urged laterally. Therefore, it is possible to prevent the occurrence of mechanical noise due to the clearance between the shaft 4 and the bearing 3, and to obtain the same effect as that of the first embodiment. In each of the above-mentioned embodiments, the thrust bearings 10 and 11 are configured as hollow discs, but they may be recessed instead of hollow, and can be implemented by appropriately changing them. Further, in the above embodiment, the cored type motor is exemplified, but needless to say, it can be applied to various motors such as a flat coreless motor.

[0013]

As described above, according to the present invention, the thrust bearing is provided with the hollow hole, and the peripheral edge of the hollow hole receives a part of the base end portion of the shaft, whereby the thrust bearing is urged toward the bracket side. Since it is configured to urge the shaft in the lateral direction by utilizing the urging force of the rotor, it is possible to keep the shaft in contact with the inner surface of the bearing at all times and to prevent vibration between the shaft and the bearing. It is possible to suppress the occurrence of mechanical noise due to the suppression, and to provide a small motor having stable performance.

[0014]

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of a small motor according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the small motor in FIG.

FIG. 3 is frequency analysis data comparing noise occurrence states of small motors in the same embodiment.

FIG. 4 is an enlarged view of an essential part of a small motor according to a second embodiment of the present invention.

FIG. 5 is a partial cross-sectional view showing the configuration of a conventional small motor.

[Explanation of symbols]

 M: Motors 1, 21 ... Cases 2, 22 ... Brackets 3, 23 ... Bearings 4, 24 ... Shafts 10, 11 ... Thrust bearings

Claims (1)

[Claims] 1. A rotor, which is rotatably supported via bearings in a housing composed of a case and a bracket, and is constantly biased toward the bracket,
In a small motor configured such that the base end of the shaft of the rotor is supported by a thrust bearing arranged on the bracket side, a hollow hole is provided in the thrust bearing, and the base end is formed around the hollow hole. A small motor characterized in that the shaft is urged laterally by utilizing a part of the urging force.