JPH05276713A - Small-sized dc motor - Google Patents

Abstract

PURPOSE:To provide a small-sized DC motor which can exhibit stable performance by preventing abnormal abrasion of the sliding surface of the armature and production of polymers on the surface. CONSTITUTION:This motor comprises a case, which is made in the shape of a bottomed hollow cylinder out of metallic material and besides which has a permanent magnet fixed to the inside surface, a rotor 5, which consists of an armature opposed to the permanent magnet and a commutator 4, and a case cap, which is provided with a brush fit in the opening of the case and engaging slidably with the commutator 4 and an input terminal electrically connected to this brush. In a small-sized DC motor in which the rotor 5 is supported rotatably through the bearings provided on the bottom of the case and the case cap, the sliding face of the commutator 4 is coated with a film 4a 1mum or less in thickness consisting of polybutene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to audio equipment, video equipment,
The present invention relates to small DC motors used in precision equipment, etc., in particular, to prevent abnormal wear and polymer generation on the sliding surface of the commutator due to sliding with a brush and to ensure stable performance. The present invention relates to an improved small DC motor.

[0002]

2. Description of the Related Art FIG. 1 is a vertical sectional front view of an essential part showing an example of a small direct current motor which is an object of the present invention. In FIG.
Reference numeral 1 denotes a case, which is formed of a metal material such as soft iron into a hollow cylindrical shape with a bottom, and has an inner peripheral surface to which a permanent magnet 2 formed in, for example, an arc segment shape is fixed. In this case 1, an armature 3 and a commutator 4 facing the permanent magnet 2 are provided.
The rotor 5 composed of is configured so that it can be interposed. Next, 6 is a case cap, which is made of, for example, a synthetic resin or other insulating material so that it can be fitted 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. Reference numerals 9 and 10 denote bearings, which are fixed to the bottom portion of the case 1 and the central portion of the case cap 6, respectively, and rotatably support the shaft 11 constituting the rotor 5.

With the above structure, the current is supplied from the input terminal 8 to the armature 3 via the brush arm 7 and the commutator 4 forming the rotor 5, so that the case 1 is fixed 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 generated permanent magnet 2, and the rotor 5
Can be rotated, and an external device (not shown) can be driven through the output side shaft 11.

[0004]

In the conventional small direct current motor having the above-described structure, arc discharge or a discharge is generated at the sliding portion between the brush (not shown) provided at the tip of the brush arm 7 and the commutator 4. Joule heat, or brush and commutator 4
Brush and commutator 4 due to metal contact with
Abnormal wear occurs, which is caused by wear within a short period of time.
When such abnormal wear occurs, the electrical connection between the brush and the commutator 4 cannot be secured, the stability of the initial motor performance is impaired, and the motor life is shortened.

When used in an atmosphere containing organic gas in the atmosphere, black insulating polymer is generated at the sliding portion between the brush and the commutator 4 due to the arc discharge and Joule heat. To 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 contact resistance increases, resulting in shortening the motor life.

In order to solve the above problems, there has been proposed a structure in which a polyhydric alcohol or the like is enclosed in a case and the inside of the case is made to have an atmosphere of the polyhydric alcohol or the like (for example, JP-A-60-162449). reference). However, in the small DC motor having the configuration shown in FIG. 1, since a clearance is required between the shaft 11 and the bearing 9, the inside of the case 1 cannot be sealed and the inside of the case 1 is not exposed to the atmosphere. It is in a state of communication.

When the small DC motor is aged, the internal temperature of 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 of the case 1 also rises. To do. For this reason case 1
Even if the internal atmosphere of is made into an atmosphere of polyhydric alcohol as described above, due to the difference between the internal pressure of the case 1 and the atmospheric pressure,
There is a problem in that the atmosphere components of Case 1 flow out to the outside, which is not an effective means.

SUMMARY OF THE INVENTION The present invention solves the above problems existing in the prior art and provides a small direct current motor capable of preventing abnormal wear and polymer generated on the sliding surface of a commutator and exhibiting stable performance. To aim.

[0009]

In order to achieve the above object, in the present invention, a case formed of a metallic material in a hollow cylindrical shape with a bottom and a permanent magnet fixed to the inner peripheral surface thereof, A rotor including an armature facing the magnet and a commutator, a brush fitted into the opening of the case and slidably engaged with the commutator, and an input terminal electrically connected to the brush. In a small direct current motor comprising a case cap provided with, and rotatably supporting the rotor through a bearing provided on the bottom of the case and the case cap, the sliding surface of the commutator is A technical means of depositing a thin film of polybutene having a thickness of 1 μm or less was adopted.

In the present invention, polybutene is a material having an electric insulating property, but if it is a thin film having a thickness of 1 μm or less, it is a layer of several molecules, and therefore it is a layer of several molecules. It has no effect on the stability of the contact resistance between them.

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

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

[0013]

With the above construction, the sliding surface of the commutator is protected and the motor characteristics can be improved. That is,
Polybutene does not easily decompose, oxidize or evaporate at room temperature, is stable to light and heat, and has excellent weather resistance and aging resistance. Further, since it also functions as a synthetic non-drying oil, it is possible to prevent abnormal wear of the sliding surface and generation of polymer.

[0014]

FIG. 2 is a longitudinal sectional view showing the vicinity of a commutator according to an embodiment of the present invention, and the same parts are designated by the same reference numerals as those in FIG. In FIG. 2, 4a is 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 shaft 11 and, for example, a cloth tape impregnated with polybutene is rubbed on the outer peripheral surface of the commutator 4. Good.

A 100-hour aging test was carried out on the small DC motor formed by depositing the thin film 4a having a thickness of about 0.7 μm on the outer peripheral surface of the commutator 4 as described above. As a comparative example, the same aging test was performed for the conventional structure lacking the thin film 4a.

FIG. 3 is a diagram showing the state of wear of the commutator outer peripheral surface before and after the aging test in the atmosphere. As is apparent from FIG. 3, in the conventional case, the abrasion amount locally reaches 4 μm or more after 100 hours of the aging test, whereas in the case of the present invention, the abrasion hardly progresses, It is recognized that the amount is reduced to about 1/10 of the conventional one. This is considered to be the effect of depositing the thin film 4a made of polybutene on the sliding surface of the commutator 4 (see FIG. 2).

FIG. 4 is a diagram showing the state of wear of the commutator outer peripheral surface 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 adhesive) was used. Therefore, the generated organic gas is methyl ethyl ketone, nitrile rubber constituting the adhesive, additives, and the like. As is apparent from FIG. 4, the wear on the outer peripheral surface of the commutator did not progress so much even in the conventional case and after the aging test. However, due to the presence of the organic gas, generation of an insulating polymer is recognized on the surface of the commutator, and this insulating polymer prevents metal contact between the brush and the commutator. Therefore, there is a risk that the power supply between the two will be obstructed and eventually the motor will stop. On the other hand, in the case of the present invention, generation of such an insulating polymer is not observed at all.

FIG. 5 is a diagram showing 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, the insulating polymer is not generated by the organic gas, or if any, it is extremely small, and the metal contact between the brush and the commutator is maintained. However, in the conventional case, as shown in FIG. 3, the amount of wear on the sliding surface of the commutator is large.

FIG. 6 is a diagram showing current waveforms before and after an aging test in an organic gas atmosphere. The organic gas source is the same as that shown in FIG. As is clear from FIG. 6, in the conventional device, the current waveform after 100 hours is greatly disturbed and the level of the current value is lowered. This is because the presence of the organic gas causes an insulating polymer to be generated on the sliding surface of the commutator, which makes the contact resistance between the commutator and the brush unstable as described later. On the other hand, in the case of the present invention, it is recognized that the above-mentioned polymer is not generated and the good current waveform similar to the initial state is 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, there was no generation of an insulating polymer 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 the insulating polymer is generated on the sliding surface of the commutator due to the presence of the organic gas, and the contact resistance becomes unstable and large as described above, and thus the current waveform shown in FIG. It appears as a disturbance of. On the other hand, in the case of the present invention, generation of the above-mentioned polymer is not recognized, and it is recognized that the contact resistance maintains a stable state.

[0021]

EFFECTS OF THE INVENTION Since the present invention has the constitution and operation as described above, the sliding surface of the commutator is protected by the thin film made of polybutene, the initial wear is prevented, and the polymer is insulative even in the organic gas atmosphere. Can be prevented. Therefore, the contact resistance can be reduced and stabilized, and the motor performance can be stabilized and the service life can be extended.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an example of a small direct current motor which is an object of the present invention.

FIG. 2 is a longitudinal sectional view of an essential part showing the vicinity of a commutator in an example of the present invention.

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

FIG. 4 is a diagram showing a wear state 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]

 1 case 4 commutator 4a thin film 5 rotor

Claims (1)

[Claims] 1. A case formed of a metallic material in the shape of a hollow cylinder with a bottom and having a permanent magnet fixed to the inner peripheral surface thereof, and a rotor composed of an armature and a commutator facing the permanent magnet.
The bottom of the case comprises a brush fitted into 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. In a small direct current motor in which the rotor is rotatably supported through a bearing provided on the case cap, a thin film of polybutene having a thickness of 1 μm or less is deposited on the sliding surface of the commutator. Characteristic small DC motor.