JP2579099B2 - Small DC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to audio equipment, video equipment,
This is related to small DC motors used in precision equipment, etc., especially to prevent abnormal wear and polymer from being generated on the sliding surface of the commutator due to sliding with the brush, and to exhibit stable performance. The present invention relates to a small DC motor which has been improved.

[0002]

2. Description of the Related Art FIG. 1 is a longitudinal sectional front view of an essential part showing an example of a small DC motor to which the present invention is applied. In FIG.
Reference numeral 1 denotes a case, which is formed of a metal material such as soft iron in a hollow cylindrical shape with a bottom, and has a permanent magnet 2 formed, for example, in the form of an arc segment fixed to the inner peripheral surface. An armature 3 and a commutator 4 facing the permanent magnet 2 are provided in the case 1.
And the rotor 5 composed of the following. Next, reference numeral 6 denotes a case cap, which is formed of, for example, a synthetic resin or another insulating material so as to fit into the opening of the case 1. Reference numeral 7 denotes a brush arm, which is provided so as to be slidably engaged with the commutator 4, and is provided on the case cap 6 together with an input terminal 8 electrically connected to the brush arm 7. Bearings 9 and 10 are fixed to the bottom of the case 1 and the center of the case cap 6, respectively, and rotatably support a shaft 11 constituting the rotor 5.

[0003] With the above configuration, current is supplied from the input terminal 8 to the armature 3 via the commutator 4 constituting the rotor 5 via the brush arm 7, thereby fixing the current to the inner peripheral surface of the case 1. The rotating force is applied to the armature 3 existing in the magnetic field formed by the permanent magnet 2
Can be rotated, and an external device (not shown) can be driven via the output-side shaft 11.

[0004]

In the conventional small DC motor having the above-mentioned structure, arc discharge or the like occurs at the sliding portion between the brush (not shown) provided at the end of the brush arm 7 and the commutator 4. Joule heat, or brush and commutator 4
Brush and commutator 4 due to metal contact between
Abrasion occurs within a short period of time.
When such abnormal wear occurs, the electrical connection between the brush and the commutator 4 is not ensured, so that the stability of the initial motor performance is impaired and the motor life is shortened.

When the brush is used in an atmosphere containing an organic gas in the atmosphere, a black insulating polymer is generated at a sliding portion between the brush and the commutator 4 due to the arc discharge and Joule heat. I do. When such an insulating polymer is generated, there is a problem that the contact state between the brush and the commutator 4 becomes unstable, and the contact resistance is increased, so that the life of the motor is shortened.

In order to solve the above problems, there has been proposed a configuration in which a polyhydric alcohol or the like is sealed in a case and the inside of the case is made of an atmosphere of the polyhydric alcohol or the like (for example, Japanese Patent Application Laid-Open No. 60-162449). reference). However, in the small DC motor having the configuration shown in FIG. 1, the clearance between the shaft 11 and the bearing 9 is required, so that the inside of the case 1 cannot be hermetically sealed and the inside of the case 1 is exposed to the atmosphere. It is in a state of communication.

When the small DC motor is aged, the temperature inside the case 1 rises due to frictional heat and heat generated by the electric resistance of the coil forming the armature 3, and the internal pressure inside the case 1 rises. I do. For this reason, Case 1
Even if the internal atmosphere is made of polyhydric alcohol or the like as described above, the difference between the internal pressure of the case 1 and the atmospheric pressure causes
There is a problem in that the atmosphere components of Case 1 flow out to the outside and are not effective means.

An object of the present invention is to solve the problems existing in the prior art and to provide a small DC motor capable of exhibiting stable performance by preventing abnormal wear and polymer occurring on a sliding surface of a commutator. Aim.

[0009]

In order to achieve the above object, the present invention relates to 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 fitted into the opening of the case and slidably engaged with the commutator; and an input terminal electrically connected to the brush. A small DC motor comprising a case cap comprising: a rotor provided rotatably via a bearing provided at the bottom of the case and the case cap. The technical means of applying a thin film made of polybutene having a thickness of 1 μm or less was employed.

In the present invention, polybutene is a material having electrical insulation properties. However, if it is a thin film having a thickness of 1 μm or less, it is a layer of several molecules. It has no effect on the stability of the contact resistance between them.

Means for applying the above-mentioned polybutene thin film on the sliding surface of the commutator include the following. (1) After the rotor is formed, the rotor is rotated about an axis, and a paper tape or a cloth tape impregnated with polybutene is rubbed on the outer peripheral surface of the commutator to form a thin film.

(2) After the commutator portion is immersed in a dilute solution of polybutene, the solvent is evaporated to dryness to form a thin film. (3) Each component other than the commutator is masked, and placed or passed in a polybutene vapor atmosphere to form a thin film.

[0013]

According to the above configuration, the sliding surface of the commutator is protected, and the motor characteristics can be improved. That is,
Polybutene is hardly decomposed, oxidized and evaporated at room temperature, is stable to light and heat, and has excellent weather resistance and aging resistance. In addition, since it acts as a synthetic non-drying oil, abnormal wear of the sliding surface and generation of polymer can be prevented.

[0014]

FIG. 2 is a longitudinal sectional view of a main part showing the vicinity of a commutator according to an embodiment of the present invention, and the same parts are denoted by the same reference numerals as in FIG. In FIG. 2, reference numeral 4a denotes a thin film made of polybutene, which is formed by being attached to the outer peripheral surface of the commutator 4. In order to form such a thin film 4a, the rotor 5 incorporating the commutator 4 is rotated around the axis 11 and, for example, a cloth tape impregnated with polybutene is rubbed against the outer peripheral surface of the commutator 4. I just need.

A 100-hour aging test was performed on the small DC motor formed by applying the thin film 4a having a thickness of about 0.7 μm to the outer peripheral surface of the commutator 4 as described above. As a comparative example, a similar aging test was performed on a conventional configuration lacking the thin film 4a.

FIG. 3 is a view showing the state of wear of the outer peripheral surface of the commutator before and after the aging test in the atmosphere. As is clear from FIG. 3, in the conventional device, after 100 hours of the aging test, the wear amount locally reached 4 μm or more, whereas the wear of the present invention hardly progressed. It can be seen that it is reduced to about 1/10 of the conventional one. This is considered to be the effect of applying the thin film 4a made of polybutene on the sliding surface of the commutator 4 (see FIG. 2).

FIG. 4 is a view showing a state of wear of the outer peripheral surface of the commutator before and after the aging test in an organic gas atmosphere.
In this case, as an organic gas source, for example, Diamond Bond DN83
K (rubber-based adhesive) was used. Therefore, the generated organic gas is methyl ethyl ketone, nitrile rubber constituting the adhesive, additives, and the like. As is clear from FIG. 4, the wear on the outer peripheral surface of the commutator has not progressed much even in the conventional device and after the aging test. However, due to the presence of the organic gas, generation of an insulating polymer has been observed on the surface of the commutator, and the insulating polymer has prevented metal contact between the brush and the commutator. Therefore, energization between the two may be hindered and the motor may eventually stop. On the other hand, in the case of the present invention, generation of such an insulating polymer was not recognized at all.

FIG. 5 shows current waveforms before and after the aging test in the atmosphere. As is clear from FIG.
There is no change or difference in the current waveform before and after the test between the present invention and the conventional one. This is because, since the atmosphere is the atmosphere, there is no or very little insulating polymer due to the organic gas, and the metal contact between the brush and the commutator is maintained. However, in the conventional device, as shown in FIG. 3, the amount of wear on the sliding surface of the commutator is large.

FIG. 6 shows current waveforms before and after an aging test in an organic gas atmosphere. The organic gas source is the same as that in FIG. As is apparent from FIG. 6, in the conventional device, the current waveform after 100 hours is greatly disturbed, and the level of the current value is reduced. This is because, due to the presence of the organic gas, an insulating polymer is generated on the sliding surface of the commutator, and the contact resistance between the commutator and the brush becomes unstable as described later. On the other hand, in the case of the present invention, it was confirmed that the above-mentioned polymer was not generated, and the same good current waveform as that at the initial stage was maintained even after 100 hours.

FIG. 7 is a diagram showing the contact resistance before and after the aging test in the atmosphere, and FIG. 8 is a diagram showing the contact resistance before and after the aging test in the organic gas. First, in FIG. 7, since the test was performed in the atmosphere, no insulating polymer was generated on the sliding surface of the commutator as described above. No change is observed. However, in FIG. 8, the conventional one shows a large disturbance in the contact resistance after the test.
This is because an insulating polymer is generated on the sliding surface of the commutator due to the presence of the organic gas. Since the contact resistance becomes unstable and large, the current waveform shown in FIG. It appears as a disorder. On the other hand, in the case of the present invention, the generation of the polymer was not recognized, and it was recognized that the contact resistance maintained a stable state.

[0021]

According to the present invention, the sliding surface of the commutator is protected by a thin film made of polybutene to prevent initial abrasion, and has an insulating polymer even in an organic gas atmosphere. Can be prevented from occurring. Therefore, there is an effect that the contact resistance is reduced and stabilized, and the motor performance is stabilized and the life is extended.

[Brief description of the drawings]

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

FIG. 2 is a vertical sectional view of a main part showing the vicinity of a commutator in the embodiment of the present invention.

FIG. 3 is a diagram showing a state of wear of a commutator outer peripheral surface before and after an aging test in the atmosphere.

FIG. 4 is a view showing a state of wear of a commutator outer peripheral surface before and after an aging test in an organic gas atmosphere.

FIG. 5 is a diagram showing current waveforms before and after an aging test in the atmosphere.

FIG. 6 is a diagram showing current waveforms before and after an aging test in an organic gas atmosphere.

FIG. 7 is a diagram showing contact resistance before and after an aging test in the atmosphere.

FIG. 8 is a diagram showing contact resistance before and after an aging test in an organic gas atmosphere.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 4 Commutator 4a Thin film 5 Rotor

Claims (1)

(57) [Claims] 1. A case formed of a metal material in a hollow cylindrical shape with a bottom and having a permanent magnet fixed to an inner peripheral surface thereof, a rotor comprising an armature and a commutator facing the permanent magnet,
A brush fitted to the opening of the case and slidably engaged with the commutator, and a case cap provided with an input terminal electrically connected to the brush; and a bottom portion of the case. In a small DC motor in which the rotor is rotatably supported via a bearing provided on a case cap, a thin film made of polybutene having a thickness of 1 μm or less is applied to a sliding surface of the commutator. Features a small DC motor.