JPS59185140A - Contact structure of motor - Google Patents

Abstract

PURPOSE:To always maintain preferable contacting state of a contact structure for a motor by constructing a structure that a contact unit of a plurality of brush pieces are not simultaneously existed on the end face of one segment when the brush pieces are contacted with commutator segments and the motor is energized. CONSTITUTION:A brush unit which has brush pieces 42, 43 and a brush spring 41 is contacted with a commutator segment 44 of a coreless motor or the like, and the motor is energized. At this time the length of the brush spring 41 of a tuning fork shape is altered to mount the pieces 42, 43 so as to contact with the segment 4, or the width of brush pieces 62, 63 is altered to mount on a brush spring 61. Accordingly, the difference of deflection amounts is provided at the pieces 42, 43 or 62, 63, improper contact can be liminated as a whole even if silicon oxide is produced on the surface of the segment 4 without simultaneously breaking the end face of the segment 44 by both, thereby obtaining a preferable commutating state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the reliability of contacts of a brush motor.

[Prior art]

FIG. 1 is a perspective view of a flat four-pole three-coil coreless motor. 1 is a stator magnet magnetized in the direction of the rotor shaft 7; 2.9 is a bearing for the rotor shaft 7; 3 is a brush; 4
is a rotor, 5 is a coil, 6 is a commutator, and 8 is a housing. FIGS. 2 and 3 are a plan view and a side view of the brush and commutator portions. Here, for convenience of explanation, only one of the two brushes is shown. The brush 6 is
Furthermore, brush piece 11. Brush spring 12. It is composed of vibration-proof rubber 13 that suppresses the vibration of the brush. 14
is a commutator piece, and the commutator 6 is composed of six commutator pieces. The brush piece is usually composed of a plurality of brush pieces to increase the reliability of the contact. The contact points that are electrically connected are the brush piece 11 and the commutator piece 14. Further, the commutator piece 14 is made of silver thread, and the brush piece 11 is made of gold thread.

Conventionally, such motors were kept in a certain environment, for example at 25°C.
When the motor is operated continuously at 50% humidity and the current waveform of the motor is observed, the waveform as shown in FIG. 4 will be shown after 50 to 200 hours. A portion A surrounded by a dotted line is a waveform that appears due to an increase in the contact resistance between the brush piece 11 and the commutator piece 14, and in this case, the resistance value is several hundred ohms or more. Normally, this resistance is 0.1 ohm or less. If such a contact failure occurs when the motor is used in a tape recorder, for example, the tape running speed may change, the signal may undergo frequency modulation, or the current of several tens of milliamps or more may be intermittent. If the rotor stops in a place where noise is generated from the speaker through the power line or there is a large contact resistance when the motor is stopped, the next time the motor is started, sufficient current will not flow to the motor and the motor will start. This will cause a serious problem of not doing so.

[Purpose of the invention]

The present invention was made in order to improve such poor contact of a motor, and an object of the present invention is to provide a contact structure for a motor that has good contact resistance even after long-term operation.

[Structure of the invention]

Next, the content of the present invention will be explained in detail.When the vicinity of the sliding surface where the commutator piece 14 contacts the brush piece 11 was analyzed using an X-ray microanalyzer, the results shown in FIG. 5 were obtained. One commutator piece 14 has sliding surfaces for four brush pieces, but here, a case will be described in which the four sliding surfaces do not overlap but are in contact with each other. Sliding surface S1-+
``'8 is the sliding surface of the negative brush piece, S, S4 is the sliding surface of the positive brush piece.In addition, in this figure, the commutator is oriented from the bottom to the top of the page, in the direction of the arrow in the figure. Move to.

21 and 22 in FIG. 5 represent the distribution of silicon obtained as a result of analysis with an X-ray microanalyzer. The direct cause of a contact failure as shown by the dotted line A in FIG. 4 is the formation of a silicon oxide film on the surface of the commutator piece 14. Silicon oxide film Sin,
If such an insulating film is formed on a contact, as used in the protective film of the first method, a serious contact failure will occur at the contact.

After analyzing many commutator pieces, it was found that silicon oxide is often formed on the sliding surface of the minus brush, on the side where the current breaks (hereinafter referred to as the break side).

Next, let's consider the reason for this.

Figures 6α, 7α, and 8α are brush B+.

B-, commutator piece α1 #α2 *hl *b2
*'1 Diagrammatically represents the positional relationship between tC2 and coils α, h, and c. By moving brushes B+ and B- clockwise, the relative positional relationship between the brush and commutator is shown. . Brushes B+ and B- are mechanically placed at positions shifted by 90 degrees. There are 6 commutator pieces, so
When the rotor rotates once, the commutator and brushes switch 12 times. That is, when 12 convex parabolas appear at the bottom of FIG. 4, it means that the rotor has made one revolution.

FIG. 6α shows the state immediately before the contact of the brush B- is switched from the commutator piece α1 to the commutator piece C6. Chapter 6b
The figure is a circuit diagram at that time. Figure 7α shows the brush B-
is in contact with both the commutator bar α and the commutator bar C3, and the seventh blil is the circuit diagram thereof. At this time, coil b is short-circuited by brush B-. The spike at point 1w portion A' in FIG. 4 is a waveform that appears at the time of this short circuit.

FIG. 8α is a diagram showing the state immediately after the brush B- transfers the contact point from the short-circuited state of the commutator segments α1 and c2 to the commutator segment 02, and FIG. 8b is a circuit diagram thereof. Brush B-
When moving from Fig. 7b to Fig. 8b, commutator piece α1
It can be seen that the current flowing to the brush B- suddenly becomes zero. FIG. 9 is a sectional view showing the state when the contacts between the brush 31 (B-) and the commutator piece 32 (α, )s34 (Ct) are switched. Immediately before the brush 31 separates from the commutator piece 32, the contact becomes a point contact as shown at 32, and a current expressed by the voltage between the brushes B+ and B- divided by the resistance of the coil α is generated at the minute contact point. is concentrated and Joule heat is generated, causing high heat and, in some cases, electrical discharge. This heat decomposes the silicon-containing organic gas contained in the atmosphere around the contacts, and silicon oxide is formed on the commutator pieces. 21 in FIG. 5 shows the results of analyzing the silicon distribution using an xm microanalyzer. When silicon oxide is formed as shown at 21, no current flows there, so the gap between the commutator pieces 32 and 34 is widened, and the brush 31 and the commutator piece 52 are separated. .5'I switching timing becomes earlier. This situation is shown in FIG. 10, where the current in the contact piece 32 is switched at the position 65, and heat is generated here.

For this reason, the silicon oxide expands toward the center of the commutator piece 62. FIG. 5 22 shows this situation, and shows the newly expanded distribution range of silicon oxide. In this way, silicon oxide gradually spreads over the sliding surface as long as there is silicon-containing gas in the surrounding atmosphere, expanding the range that causes contact failure.

Eliminating the influence of contact failure caused by silicon oxide can be achieved by not switching the contacts of the two brush pieces at the same time, but by slightly shifting the timing. That is, since the contacts 51 and 52 of the two brush pieces 46 and 47 can be present at the same time on the end face 50 of the commutator piece, silicon oxide is applied to the sliding surfaces S1 and S, as shown in FIG. This is possible. Therefore, as shown in FIG. 12, the contact points 53.5 of the two brush pieces 46.47 in one brush
4 does not exist on the break side end surface 50 of the commutator piece 45 at the same time, the brush piece 46 and the commutator piece 45
When the contact formed at the end face 50 of (C1) breaks,
Even if silicon oxide forms in the vicinity and a contact failure occurs, the contact point of the brush piece 47 is already connected to the next commutator piece (C1).
is moving to. For this reason, there is no apparent contact failure in the motor as a whole, and no spikes like the dotted line A in FIG. 4 occur.

FIG. 13 shows an embodiment that applies the above idea, and satisfies the above conditions by changing the length of the arm of the tuning fork-shaped brush spring 41. FIG. 14 is a side view of the brush shown in FIG. 16 when it is brought into contact with the commutator 44. FIG. 15 shows another embodiment in which the width of the brush pieces 62, 65 is changed to create a difference in the amount of deflection of the two brush pieces 62, 63 when they come into contact with the commutator piece. This prevents two contacts from existing at the same time. FIG. 17 shows a current waveform of a motor using the above contacts. The dotted line indicates when the contacts are switching, and even if a contact failure occurs in one brush piece during the flat waveform portion of the dotted line, the motor current waveform will hardly change.

Fig. 16 shows a brush piece that is pressed from a single plate material and designed to have multiple contact points.
By changing the width of 5, 66, and 67, the amount of deflection of each brush piece is changed.

Although the present specification has been described using a cylindrical commutator, it goes without saying that the effects of the present invention are not impaired even when a disc-shaped commutator is used.

〔Effect of the invention〕

As described above, the contact structure of the present invention makes it possible to manufacture highly reliable brush motor contacts by only slightly modifying the conventional contact structure, thereby making a significant contribution to industry.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a flat brush motor, Fig. 2 is a plan view of the contacts of a conventional brush motor, Fig. 3 is a side view thereof, and Fig. 4 is a diagram showing the current waveform of the motor. Figure 5 is a diagram showing the sliding movement of commutator pieces, Figure 6 (α), Figure 7
Figures (α) and 8 (α) are diagrams showing the positional relationship between brush pieces, commutator pieces, and coils, and Figures 6 (b) and 7 (b).
, Figure 8Cb) are the respective circuit diagrams, Figures 9 and 10.
The figure is a cross-sectional view showing the state when the brush pieces and commutator pieces are switched, FIG. 11 is a diagram showing the positional relationship between the contacts of the conventional brush and the commutator end face, and FIG. 12 is the brush of the present invention. 16 is a plan view of one embodiment of the present invention, FIG. 14 is a side view thereof, and FIG. 15 is a diagram showing the positional relationship of commutator end faces.
FIG. 6 is a plan view of another embodiment, and FIG. 17 is a current waveform diagram of a motor using the contacts of the present invention. 45... Commutator piece 42.43-. 46, 47, 62, 63, 65°66.
67... Brush piece 53.54... Contact point between brush piece and commutator piece Applicant Daini Seiko Co., Ltd. Figure 1 Figure 2 Figure 5 5θ Figure 6 (( 1) Figure 6 (b) Figure 7 (θ)
Figure 8 (a) Figure 7 (b) Figure S (1,) Figure 9
1/ I2I Male/θ Figure 72 Figure 73 Figure 74 Figure 75 Dark Resistance

Claims (1)

[Claims] In a motor contact structure having a plurality of commutator pieces, a plurality of brush pieces, and a plurality of contact points between one commutator piece and the plurality of brush pieces, the plurality of contacts are simultaneously connected to one commutator piece. A motor contact structure characterized in that it does not exist on the end face of the motor.