JPH11113209A - Bearing structure of small-sized motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce rotating vibration sound, especially in a sintered oil retaining bearing structure, regarding the bearing structure for a small-sized DC motor. SOLUTION: In the bearing structure of a motor equipped with a sintered oil retaining bearing 5 rotatably supporting a rotary shaft 7, and a motor frame 10 holding the sintered oil retaining bearing 5, a fixed magnet 14 and a movable magnet 15 are fixed on the inside of the sintered oil retaining bearing 5 and on the end surface 12 facing the inside of the bearing 5, in such a manner that the same polarities face each other in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure for a small motor, and more particularly to a method for reducing abnormal rotational vibration and vibration noise of a sintered oil-impregnated bearing.

[0002]

2. Description of the Related Art FIG. 5 shows a general structure of a small DC motor having a conventional sintered oil-impregnated bearing structure. In FIG. 5, the motor shaft 7 is connected to the motor shaft 7 from the terminal 2 held by the bracket 1 via the brush 4 which comes into contact with the commutator 3 and the commutator 3 fixed to the motor shaft 7 supported by the bearings 5 and 6. When a current is supplied to the rotor coil 9 wound around the fixed rotor core 8, the rotor 1 existing in the magnetic field formed by the magnet 11 fixed to the inner peripheral surface of the motor frame 10 is provided.
2 is configured to rotate.

Generally, the clearance between the bearings 5 and 6 and the motor shaft is at least 10 μm or more in order to sufficiently operate the self-lubrication function and to reduce bearing loss. FIG. 6 is an enlarged cross-sectional view of the bearing 5 and the motor shaft 7.

[0004]

However, when a small DC motor is used in such a manner that no lateral pressure is applied to the load, vibrations caused by the clearance between the bearing and the motor shaft, and the resulting rattling noise occur. . FIG.
5 is a view of the bearing 5 in FIG. 5 as viewed from the tip of the motor shaft 7. 6 and 7, the mechanism of generating the vibration and roaring sound will be described. When the motor shaft 7 starts rotating, the magnetic and mechanical unbalance of the rotor fixed to the motor shaft 7 causes the motor shaft 7 to rotate. Radial vibration of the arrow is generated. Also, this vibration causes the motor shaft 7
Will hit the inside of the bearing 5. At this time, a sound is generated. This is the grunt sound. In other words, the roaring noise is mechanical noise generated by rotation of the motor shaft 7 in the radial direction due to the rotation of the motor shaft 7 and hitting the inside of the bearing 5 with the vibration.

[0005] Generally, as for the rotational vibration and the rattling noise, the larger the clearance between the motor shaft and the bearing is, the larger the amplitude of the motor shaft vibration becomes. Therefore, as a method for reducing the vibration and the rattling noise, the bearing is decentered, or the magnetic force balance of the NS pole of the stator magnet is broken, and the motor shaft is biased and biased to the bearing, or There is a method for making the clearance as small as possible. However,
The above-described method of biasing the motor shaft toward the bearing may cause a one-sided contact state of the bearing, which may lead to deterioration of the life of the bearing and a complicated structure. On the other hand, the method of reducing the clearance is that if the clearance is reduced, the self-lubrication of the sintered oil-impregnated bearing will be incomplete, or the bearing loss will increase due to the bending of the motor shaft. Since there is a possibility of causing a problem of an increase in the value and a deterioration of the bearing life, the clearance cannot be reduced unnecessarily.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the radial vibration and gurgling of a shaft with a simple structure without reducing the clearance.

[0007]

According to the present invention, radial vibrations caused by the rotation of the motor shaft, which are factors of the above-mentioned rotational vibrations and rattling, are interposed between the thrust of the rotor and the motor frame with the same poles facing each other. Rotational vibration and rattling are prevented or reduced by the repulsive force of the magnet.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION
A small motor comprising: a rotor that rotates by a stator and electromagnetic interaction; a sintered oil-impregnated bearing rotatably supporting a rotating shaft of the rotor; and a motor frame that holds the sintered oil-impregnated bearing. A bearing structure for a small motor, characterized in that a magnet is fixed in a thrust direction of a rotating shaft, and the magnet is fixed to the sintered oil-impregnated bearing so as to face a surface of the same polarity as a magnet fixed to the thrust direction side.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a small DC motor according to a first embodiment of the present invention. FIG. 2 is a sectional view of a main part in FIG. 1 and 2, reference numeral 14 denotes a ring-shaped fixed magnet which is fixed to the motor frame 10 and N and S are magnetized in the axial direction, respectively. 15 is N, S in the axial direction
Are ring-shaped movable magnets respectively magnetized, and the rotor 12 is arranged such that the same pole faces the fixed magnet A in parallel.
It is stuck to.

FIG. 4 shows the relationship between the gap and the repulsive force when the same pole faces of the magnet face each other in parallel. FIG. 4 shows that a larger repulsive force is generated as the gap is smaller.

Here, when the fixed magnet 14 and the movable magnet 15 face each other in parallel with a gap a, the motor shaft 7 is always at the center of the bearing 5 because an equal force acts on the circumferential surface. Will be kept. Next, when the rotor 12 is tilted due to magnetic and mechanical imbalance at the time of energization rotation, it becomes as shown in FIG. Assuming that the gap between the fixed magnet 14 and the movable magnet 15 in this case is b and c, the relationship is b>a> c. As can be seen from FIG. 4, when the fixed magnet 14 and the movable magnet 15 are kept parallel to the c side. A large force acts.

As described above, when the rotor 12 is tilted due to magnetic and mechanical imbalance and the shaft 7 is tilted to hit the inner surface of the bearing 5, a force for rapidly returning the tilt is applied. 7 is always kept at the center of the bearing 5 without hitting the inner surface of the bearing. As a result, no vibration is generated, and it is possible to prevent the squealing noise accompanying the vibration.

[0013]

As described above, according to the present invention, the rotation of the motor shaft is achieved by fixing the magnets facing the same polarity buds in parallel to the inner surface of the bearing portion of the motor housing and the rotor side facing the bearing. The effect of promptly preventing or reducing the vibration that occurs at times and the squeaking noise accompanying the vibration can be obtained without increasing the bearing loss.

[Brief description of the drawings]

FIG. 1 is a sectional view of a small DC motor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation principle of the present invention.

FIG. 4 is a characteristic diagram of the magnet of the present invention.

FIG. 5 is a sectional view of a conventional small DC motor.

FIG. 6 is a bearing structure diagram of a conventional small motor.

FIG. 7 is an explanatory diagram of generation of a roaring sound.

[Explanation of symbols]

1 ‥‥ Bracket 2 ‥‥ Terminal 3 ‥‥ Commutator 4 軸 受 Brush 5 ‥‥ (Load side) Bearing 6 ‥‥ (Commutator side) Bearing 7 ‥‥ Motor shaft 8 ‥‥ Rotor core 9 ‥‥ Rotor coil 10 ‥ Motor frame 11 field magnet 12 rotor 13 thrust washer 14 fixed magnet 15 movable magnet a, b, c gap between fixed magnet and movable magnet

Claims (1)

[Claims] 1. A small motor comprising: a rotor that rotates by electromagnetic interaction with a stator; a sintered oil-impregnated bearing rotatably supporting a rotating shaft of the rotor; and a motor frame that holds the sintered oil-impregnated bearing. A magnet fixed to the rotor in the thrust direction of the rotating shaft, and disposed on the sintered oil-impregnated bearing side so as to face the same pole as the magnet fixed to the thrust direction side. Construction.