JP3183757B2 - Small motor - Google Patents

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 for, for example, audio equipment, precision equipment, electric equipment for automobiles, industrial equipment, and the like. The present invention relates to a small-sized motor capable of preventing noise caused by sliding between the brushes and secondary vibration of a brush arm holding a brush, and reducing so-called mechanical noise.

[0002]

2. Description of the Related Art FIG. 1 is a longitudinal sectional view of an essential part showing an example of a small motor to which the present invention is applied, and FIG. 2 is a sectional view taken along line AA in FIG. 1 and 2, reference numeral 1 denotes a case, which includes a permanent magnet 2 which is formed of a ferromagnetic metal material such as soft iron and has a hollow cylindrical shape with a bottom and an inner peripheral surface formed of, for example, an arc segment. Stick. The case 1 is configured so that a rotor 5 including an armature 3 and a commutator 4 facing the permanent magnet 2 can be interposed. Next, reference numeral 6 denotes a case cap, which is formed of, for example, a synthetic resin or another insulating material, and is fitted into the opening of the case 1.

[0003] 7 is a brush arm is formed of a conductive material, the brush 14 made of, for example, carbon on the tip provided with so as engaged the commutator 4 and the sliding engagement, the brush arms 7 and the electrical It is provided on the case cap 6 together with the input terminal 8 which is connected to the main body.
Reference numerals 9 and 10 denote bearings, respectively, which are fixed to the bottom of the case 1 and the center of the case cap 6 and constitute the rotor 5.
1 is rotatably supported. 13 is an oil stopper washer.

[0004] With the above configuration, current is supplied from the input terminal 8 to the armature 3 via the brush arm 7 and the brush 14 via the commutator 4 constituting the rotor 5, so that the case 1 A rotating force is applied to the armature 3 existing in the magnetic field formed by the permanent magnet 2 fixed to the peripheral surface, and the rotor 5 can be rotated. (Not shown) can be driven.

[0005]

In the small motor having the above structure, the sliding portion between the brush 14 and the commutator 4 is a portion for supplying power, so that lubricating oil cannot be generally used, and the dry contact is not possible. Therefore, the frictional force between the two fluctuates,
Causes abnormal stick-slip phenomenon. The abnormal stick-slip phenomenon caused by such a change in frictional force
There is also a problem that secondary vibration of the brush arm 7 holding the brush 14 is developed, generating an unpleasant abnormal sound and increasing noise or mechanical noise.

On the other hand, in a small motor in which a brush made of a metal material is slid on the sliding surface of the commutator 4, the purpose is to improve the stability of contact between the two, improve the life, and prevent the generation of an insulating substance. The use of abrasives or the like has been proposed to regulate the surface roughness of the sliding surface of the commutator 4 to, for example, 0.2 to 0.4 μm (for example, Japanese Patent Publication No. 57-43990;
No. 60-34345).

However, even if the above-mentioned proposal is applied to a small motor to which the present invention is applied in which the brush 14 made of carbon and the commutator 4 are slid in contact with each other as shown in FIG. It was found that prevention and reduction of mechanical noise did not occur.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems existing in the prior art and to provide a small motor capable of preventing abnormal noise and reducing mechanical noise.

[0009]

In order to achieve the above object, in the present invention, there is provided a case formed of a metal material into a hollow cylindrical shape having a bottom and having a permanent magnet fixed to an inner peripheral surface thereof; A rotor comprising an armature and a commutator facing the magnet, a brush arm having a brush fitted at an opening of the case and slidably engaged with the commutator at a distal end thereof; A small motor comprising a case cap having an input terminal electrically connected thereto and rotatably supporting the rotor via a bearing provided on the bottom of the case and the case cap. And the brush arm (7) is formed in an L-shape, and the sliding surface around the commutator (4) is formed with an abrasive to a 10-point average surface roughness Rz = 2.0 to 5.5 μm. did.

[0010]

[0011]

With the above arrangement, the sliding engagement between the brush and the commutator can be made smooth, so-called stick-slip phenomenon can be eliminated, and abnormal noise can be prevented and mechanical noise can be reduced. can do.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The outer peripheral sliding surface of the commutator 4 shown in FIGS. 1 and 2 was polished with abrasives having grain sizes of 3, 12, 30, 40, and 60 μm, respectively. (JIS Rz 10-point average roughness). In this case, in order to stabilize the processing conditions, polishing was performed using a wrapping tape in which the abrasives of the above-mentioned respective particle sizes were bonded to a polyester film, and the surface roughness was measured by a contact type roughness meter. As a comparative example, a conventional one without the above-mentioned polishing was prepared.

[0013]

[Table 1]

The above-mentioned small motor was rotated at 4,000 rpm, and the sound pressure level (noise level) of the A characteristic was measured using a sound pressure meter equipped with a 1/2 inch microphone. The above sound pressure measuring instrument is generally called a sound level meter, and incorporates a frequency correction circuit with a frequency response that is the inverse of the loudness curve so that the frequency sensitivity is approximately equal to 40 phon. It is.

[0015]

[Table 2]

FIG. 3 is a diagram showing the measurement results shown in Table 2 in relation to mechanical noise and abrasive particle size. As can be seen from FIG.
Although 7.8 dB is shown, it can be seen that the mechanical noise is reduced by polishing the sliding surface of the commutator.
The mechanical noise gradually decreases as the abrasive particle size increases, and by setting the abrasive particle size to 30 μm or more,
The level of mechanical noise 34 dB required in recent years can be reduced.

FIG. 4 shows a fast Fourier transform (F) of mechanical noise.
7A and 7B are diagrams showing the results of frequency analysis by FT), wherein FIG. 7A shows a conventional one and FIG. As is clear from FIG. 4, the abnormal sound of 45 dB at 10.4 kHz was recognized in FIG. 4A, while the abnormal sound of 35 dB was recognized in FIG.
Has been reduced to

FIG. 5 and FIG. 6 show the results of measuring the vibration of the brush arm and the results of frequency analysis by Fast Fourier Transform (FFT), respectively.
(B) shows that of the present invention. A non-contact vibrometer (Ono Sokki Co., Ltd., Laser Doppler) was used for measuring the vibration of the brush arm. First, as is clear from FIG. 5, a comparison between (a) showing the conventional one and (b) showing the present invention shows that the vibration is greatly reduced. Also in the frequency analysis results shown in FIG. 6, the peak existing near 10.4 kHz in (a) showing the conventional one is almost disappeared in (b) showing the present invention. It can be seen that the cause of the unpleasant abnormal sound can be eradicated.

[0019]

As described above, the present invention has the above-described structure and operation. As a result, the sliding engagement relationship between the brush and the commutator becomes smooth, so that the frictional force between the brushes and the commutator is stabilized, and The occurrence of the stick-slip phenomenon can be prevented. As a result, secondary vibration of the brush and the brush arm holding the brush is eliminated, so that an unpleasant abnormal sound is prevented from being generated, and the overall noise, that is, the mechanical noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a main part showing an example of a small motor to which the present invention is applied.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a diagram showing a relationship between mechanical noise and abrasive particle size.

FIGS. 4A and 4B are diagrams showing the results of frequency analysis of mechanical noise by fast Fourier transform (FFT), wherein FIG. 4A shows a conventional one and FIG.

FIG. 5 is a diagram showing a measurement result of vibration of a brush arm;
(A) shows the conventional one and (b) shows the one of the present invention.

FIGS. 6A and 6B are diagrams showing a frequency analysis result of a brush arm by fast Fourier transform (FFT), wherein FIG. 6A shows a conventional one and FIG.

[Explanation of symbols]

 4 commutator 7 brush arm 14 brush

Continuation of the front page (72) Inventor Yoshinori Toda 280 Ryugoji Temple, Motono-mura, Inba-gun, Chiba Prefecture Mabuchi Motor Co., Ltd. Technical Center (56) References JP-A-2-106150 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02K 13/00

Claims (1)

(57) [Claims] 1. A case (1) formed of a metal material in a hollow cylindrical shape with a bottom and having a permanent magnet (2) fixed to an inner peripheral surface thereof, and an armature (3) facing the permanent magnet (2). )
And a brush (14) fitted to the opening of the case (1) and slidably engaged with the commutator (4) at its tip. A case cap (6) provided with a provided brush arm (7) and an input terminal (8) electrically connected to the brush arm (7), and a bottom portion of the case (1) and a case In a small motor in which the rotor (5) is rotatably supported via bearings (9) and (10) provided on the cap (6), the brush arm (7) is formed in an L-shape. And a commutator (4) in which a sliding surface on an outer periphery is formed with an abrasive to a 10-point average surface roughness Rz = 2.0 to 5.5 μm.