JPH08107655A - Compact motor - Google Patents

Abstract

PURPOSE: To prolong the life of a motor by suppressing the vibration of a brush by applying a vibration-damping material at a proper position on the brush and suppressing a resonance frequency also to a constant and low value. CONSTITUTION: A vibration-damping material 5 is applied to the middle point among a brush 1, a contact point 7 of a commutator piece 4, and a brush support point 3 so that a middle point 10 in longer direction of the vibration- damping material 5 matches and a length 9 of the vibration-sampling material is set to a range of 17.9-75.0% of a length 12 of the brush or the vibration- damping material for suppressing the vibration of the brush is applied to the brush by matching a middle point in longer direction of the vibration-damping material within a range of 7.1% of the length between the contact point and a brush support point at the contact point or the brush support point side from the middle point between the contact point of the brush and the commutator and the brush support point of the brush and setting the length of the vibration- damping material to a range of 17.9-64.3% of the length between the contact point and the brush-supporting point.

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 in office automation equipment, audiovisual equipment and the like.

[0002]

2. Description of the Related Art In a small motor used for OA equipment, audiovisual equipment, etc., a metal brush is brought into sliding contact with a commutator (commutator element), and a current is applied to a winding coil wound around a rotor. The motor is rotating at. This type of motor is cheaper than a brushless motor, and contributes to the cost reduction of OA equipment and the like.

However, during the sliding contact, the brush vibrates greatly due to sparks due to the rectifying action, or the step or contact resistance of the commutator, and the contact pressure between the brush and the commutator increases. For this reason, the contact portion between the brush and the commutator is abnormally worn, and the performance is inferior in terms of life compared to the brushless motor.

Therefore, conventionally, a vibration damping material is attached to the brush to reduce vibration of the brush and suppress wear. FIG. 10 shows a state in which the damping material is attached to the brush.

In the figure, reference numeral 30 is a commutator piece integrally formed with a motor shaft 31, and 32 is a brush which is in contact with the commutator piece 30 from a brush holder 33 with a brush support portion 34 as a fulcrum. Further, the damping material 60 is attached on the longitudinal direction of the brush 32 so that the longitudinal direction of the damping material 60 is aligned. Although not shown in the figure, the tip of the brush is branched into 3 to 6 pieces.

Since the brush is very small in a small motor, the damping material 60 is designed in consideration of the problems of the electrical conductivity of the contact portion between the brush and the commutator and the adhesiveness of the damping material and the brush due to abrasion powder. As described above, the vibration is suppressed by being attached near the brush holder 33 and changing the structure or material of the vibration damping material.

[0007]

However, the resonance frequency of the brush to which the damping material is attached changes, and the contact pressure between the brush and the commutator piece also changes, even if the position where the damping material is attached is slightly deviated. Change. Therefore, wear of the commutator pieces and brushes was not uniform, and the life of the motor varied depending on the product. Further, as the proportion of the damping material increases, the vibration of the brush itself is suppressed, but on the other hand, the resonance frequency of the brush increases and the contact pressure between the brush and the commutator increases. Therefore, the brush and the commutator are abnormally worn, and the life of the motor is shortened.

Further, as a result of analyzing the vibration mode of the brush without the damping material attached, as shown in FIG.
6 and the intermediate point 40 between the contact point 39 of the brush 37 and the commutator 38 were found to change most. Here, 1 is the length of the contact point 38 and the brush support point 41. From this result, it was found that when the damping material was attached around the midpoint 40, the vibration of the brush was suppressed and the sufficient damping effect was not obtained at the pasting position.

The present invention solves the above problems by preventing the brush and the commutator from being abnormally worn by improving the vibration damping effect of the brush and keeping the resonance frequency of the brush constant at a low value. It is intended to extend the life of a small brush motor.

[0010]

In order to achieve the above object, the present invention is based on the above analysis results, and when a damping material for suppressing the vibration of the brush is attached on the brush, The contact point between the brush and the commutator, and the midpoint of the brush support point of the brush are made to coincide with each other, and the length of the damping material is set to the length of the contact point and the brush support point. Apply within the range of 17.9 to 75.0%.

Alternatively, a damping material for suppressing the vibration of the brush is provided on the brush on the brush supporting point side from the midpoint between the contact point of the brush and the commutator and the brush supporting point of the brush.
Within the range of 0 to 10.7% of the length between the contact point and the brush support point, the midpoint in the longitudinal direction of the damping material is matched, and the length of the damping material is the contact point and the brush. Attach within the range of 26.8 to 60.7% of the length with the supporting point.

Alternatively, a damping material for suppressing the vibration of the brush is provided on the brush on the contact point side from the midpoint between the contact point of the brush and the commutator and the brush support point of the brush. Within the range of 0 to 12.5% of the length between the support points, the midpoint in the longitudinal direction of the damping material is matched, and the length of the damping material is the length of the contact point and the brush support point. of
Apply within the range of 26.8 to 57.1%.

Alternatively, a damping material for suppressing the vibration of the brush is provided on the brush at the contact point from the midpoint between the contact point of the brush and the commutator and the brush support point of the brush, or at the brush support point side. Within the range of 7.1% of the length between the contact point and the brush support point, the midpoint in the longitudinal direction of the damping material is matched, and the length of the damping material is the contact point and the brush support point. Apply within the range of 17.9 to 64.3% of the length of.

[0014]

[Function] The vibration of the brush is suppressed most efficiently by attaching a damping material around the midpoint between the contact point between the brush and the commutator and the brush support point. At the same time, the resonance frequency of the brush can be kept low and constant.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a state in which a damping material is attached to the center of a brush in this embodiment.

The brush 1 is supported by a brush holder 2,
In addition, it is installed so as to contact the commutator piece 4 provided on the motor shaft 11. The damping material 5 has a contact point 7 between the brush 1 and the commutator piece 4 and an intermediate point 8 between the brush support point 3 as shown in the figure.
The intermediate point 10 in the longitudinal direction of the damping material 5 (hereinafter, referred to as the intermediate point 8 of the brush) (hereinafter, referred to as the intermediate point 10 of the damping material) was attached so as to coincide with it.

Reference numeral 12 denotes a length between the contact point 7 and the brush support point 3, which will be referred to as a brush length hereinafter. Further, 9 indicates the length of the damping material 5 in the longitudinal direction, which will be referred to as the damping material length hereinafter.
Further, thereafter, 1 indicates the length of the damping material.

FIG. 2 shows a measuring device used in this embodiment. Reference numeral 13 is a motor having a CD-ROM disk as a load. A part of the motor is cut to measure the vibration state of the brush. Lacking. Further, the motor 13 is connected to the DC power supply 14. Reference numeral 15 is a laser Doppler vibrometer for measuring the vibration state of the brush, and the measurement value amplified by the amplifier 16 is read by the oscilloscope 17.

Using the above measuring device, a width of 0.8 mm and a length of 8.5
Fig. 1 shows a vibration damping material 5 made of foamed rubber with a width of 0.8 mm, a length of 2.8 mm and a thickness of 1.0 mm on a brush made of phosphor bronze with a thickness of 0.1 mm and a thickness of 0.1 mm.
The vibration state at the intermediate point 8 of the brush having the brush length 12 of 5.6 mm was measured in the direction of arrow A in FIG.
FIG. 3 (c) shows a case where the midpoint 8 of the brush and the midpoint 10 of the damping material correspond to the present invention.

Further, in this embodiment, in order to know the damping effect depending on the sticking position of the damping material 5, as a comparative example, the sticking position of the damping material 5 is shown in FIGS. (D),
It moved to the position of (e) and measured. 3 (a), 3 (e)
Shows the case where the damping material 5 is moved 1.0 mm toward the brush support point 3 side or the contact point 7 side with reference to FIG. 3 (c), and the same figures (b) and (d) are moved 0.5 mm in both directions. This is a comparative example.

FIG. 4 shows the measurement result of the brush in FIG. Here, FIG. 4A shows the vibration measurement result of the brush in FIG. 3A, and FIG. 3E shows the same tendency. Further, FIG. 4B shows the vibration measurement result of the brush of FIG. 3B, and FIG. 4D shows the same tendency. Further, FIG. 4C shows the vibration measurement result of the brush of FIG. 3C.

From FIG. 4, the vibration of the brush is suppressed most when the midpoint 10 of the damping material and the midpoint 8 of the brush match as shown in FIG. 3C. As shown, the vibration of the brush cannot be suppressed so much that the midpoint 10 of the vibration damping material deviates from the midpoint 8 of the brush.

Next, the time until the motor stopped due to wear was measured at the position where the damping material was attached as shown in FIG. 3, and the life of the motor was examined. This time, the motor drive of 1100-2000 rpm was repeated. FIG. 5 shows the result, and FIG.
Is the life of the brush in FIG. 3 (a), and FIG.
Also had almost the same life time. FIG. 5B shows FIG.
It is the life of the brush of (b), and the life time of FIG. Further, FIG. 5 (c) shows the life of the brush of FIG. 3 (c).

As shown in FIG. 3, the vibration of the brush is most suppressed.
It has been found that when the damping material is attached to the position (c), the life of the motor is also improved as compared with the pasting position of the conventional motor shown in FIG. 3 (a).

Next, for the brush to which the damping material shown in FIG. 1 is attached, the damping material 5 is moved from position I to position I as shown in FIG.
After moving to I, the vibration damping characteristics of the brush 1 were examined. In the figure, 7 is a contact point, 4 is a commutator, and 2 is a brush support.

FIG. 7 shows the measuring apparatus used in this embodiment,
The brush 18 is mounted on an impedance head 19 that emits a basic signal that serves as a reference for a resonance frequency and a vibration level, and is in contact with a commutator 21. Impedance Head 19
Is equipped with a shaker 20. Micrometer 25
Adjusts the contact pressure between the brush 18 and the commutator 21. The laser 22 measures the resonance frequency and vibration level of the brush 18 and has a Fourier transform (FF) having a two-channel input.
The frequency response function is obtained by T) 23. Incidentally, 24 is an amplifier.

In the above apparatus, the vibrator 18 vibrates the brush 18, the resonance frequency and vibration level of the brush 18 are detected by the laser 22, and a Fourier transformer (FFT) is used.
The frequency response function is obtained from 23.

Note that the measuring apparatus of FIG. 7 vibrates the brush by the vibrator, and the brush vibrated by the actual motor drive as shown in FIG. 2 is not measured, but the vibrating state of the brush is the same.

FIG. 8 shows a frequency response function measured using the measuring device. Where f0 is the resonance frequency and Δ
f is the frequency width of the vibration level which is 3 dB lower than the vibration level of the resonance frequency f0.

As a method of expressing the damping characteristic in this embodiment, the ratio of the frequency width Δf to the resonance frequency f0 shown in FIG. 8 was taken.

[0032]

[Equation 1]

The loss coefficient η expressed by Here, (Equation 1) indicates that the larger the loss coefficient η, the greater the vibration damping. Generally, if the loss coefficient η is 0.1 or more, the damping effect is obtained.

[0034]

[Table 1]

Table 1 shows the loss coefficient η and the resonance frequency f0 with respect to the position where the damping material is attached on the brush. FIG.
When the midpoint of the damping material shown in (c) is aligned with the midpoint of the brush, 0 is set, and the relative position where the damping material is moved to the brush support point side is set to +, and conversely, the contact between the brush and the commutator. The relative position moved to the point is represented as −. Also, (a) to
(E) has shown the sticking position of the damping material of (a)-(e) in FIG.

From the table, it was found that the brush damping effect was greatest when the location of FIG. 3 (c), that is, the midpoint of the brush and the midpoint of the damping material coincided. Also, FIG.
At the location of (c), the resonance frequency of the brush is also the minimum.

As described above, when the midpoints of the brush and the damping material are the same, the vibration of the brush itself can be suppressed most and the resonance frequency of the brush can be minimized.

However, as the length of the vibration damping material increases, the resonance frequency of the brush increases accordingly, and the wear due to the resonance frequency becoming larger than the vibration damping effect of the vibration damping material has a greater effect, so that it is appropriate. It is necessary to consider the length of the damping material.

In this embodiment, by using the measuring device shown in FIG. 7, the damping material 26 is extended evenly from the midpoint 8 of the brush in the direction of arrow B shown in FIG. I checked the frequency. Here, the measured brushes and measurement points are the same as those in the above-described examples.

[0040]

[Table 2]

Table 2 shows the relationship between the loss coefficient η and the resonance frequency f0 with respect to the length of the damping material.

Since the vibration damping effect is obtained when the loss coefficient η is 0.10 or more, the vibration damping effect is obtained when the length of the damping material is 1.0 mm or more, that is, 17.9% or more of the brush length 5.6 mm from the table.

Further, when the motor was driven so that a constant resonance frequency was generated in the brush, the life of the motor with respect to the resonance frequency was about 2500 hours at the resonance frequencies of 3500 and 3800 Hz, which was almost unchanged. On the other hand, 1000 at 4000 Hz
It was 800 hours at 4300Hz.

From this, in order to extend the life of the motor, the length of the damping material should be 4.2 mm or less so that the resonance frequency is 3800 Hz or less, that is, 75.0% or less of the brush length of 5.6 mm. There was a need.

From the above measurement results, the vibration of the brush is suppressed within the range of 17.9 to 75.0% of the length of the brush, and the resonance frequency of the brush does not reduce the life of the motor due to wear. It can be suppressed to a value (hereinafter referred to as an appropriate value).

(Embodiment 2) One of the features of the present invention is that the midpoint of the damping material and the midpoint of the brush match.
Actually, as described above, it is not easy to match the two intermediate points because the brush is small. Therefore, it is necessary to find out how much the damping material is displaced from the brush even if it has a damping effect, that is, the range of deviation between the midpoint of the damping material and the midpoint of the brush, which produces an effective damping effect. is there.

Here, the following can be said from the measurement results of Table 1 in Example 1. If the midpoint of the damping material is displaced within ± 1.4 mm from the midpoint of the brush at the relative position, the loss coefficient η is 0.10 or more and there is a sufficient damping effect, but the displacement is +0.6 to − at the relative position. If the deviation is within 0.7 mm, that is, outside the range of +10.7 to -12.5% of the brush length of 5.6 mm, the resonance frequency exceeds 3800 Hz and the life of the motor is affected.

As described above, if the midpoint of the damping material deviates from the midpoint of the brush within +10.7 to -12.5% of the brush length, the damping effect and resonance frequency substantially similar to those of the first embodiment can be obtained. To be

Next, the midpoint of the damping material is extended +10.7 and -12.5% from the midpoint of the brush, and the damping material is extended evenly to the left and right. I checked.

The measuring apparatus used in this example is the same as that shown in FIG. The measured brushes and measurement points are the same as those in the above-described examples.

[0051]

[Table 3]

Table 3 shows the relationship between the damping characteristic and the resonance frequency with respect to the length of the damping material when the distance is -12.5%.

Also in this embodiment, as described in the first embodiment, the loss coefficient η is set to 0.1 or more and the resonance frequency is set to 3800 (Hz) or less.

First, from Table 3, the length of the damping material is 1.5 mm or more,
That is, if the brush length is 5.6 mm and 26.8% or more, the loss coefficient η is 0.10 or more, and a sufficient vibration damping effect is obtained.

On the other hand, if the length of the damping material is 3.2 mm or less, that is, 57.1% or less of the brush length of 5.6 mm, the resonance frequency can be suppressed to 3800 (Hz) or less. However, the length of the damping material is
When it exceeds 3.2 mm, the resonance frequency rapidly increases.

From the above measurement results, when the length of the damping material is within the range of 26.8 to 57.1% of the length of the brush, the damping effect of the brush can be obtained, and the resonance frequency of the brush can be suppressed to an appropriate value. it can.

[0057]

[Table 4]

Next, Table 4 shows the measurement results when the distance is + 10.7%. From the table, it is possible to suppress the vibration of the brush within the range of 1.5 mm to 3.4 mm, that is, within the range of 26.8 to 60.7% of the brush length, and to suppress the resonance frequency of the brush to an appropriate value. it can.

Further, from Table 1, if the midpoint of the damping material is displaced within ± 0.4 mm in relative position from the midpoint of the brush, that is, within ± 7.1% of the brush length of 5.6 mm, the loss factor is
There is 0.18 or more, and there is a damping effect of 90% or more of the loss coefficient value of 0.20 when the center positions described in Example 1 match.

The resonance frequency is also in the range of 3500 to 3570 Hz, and the change in the resonance frequency is small. From this, the above ±
A more effective vibration damping effect can be obtained within the range of deviation of 7.1% or less.

Table 5 shows the results of measuring the vibration damping effect and the resonance frequency of the brush by the same method as in the above example, by extending the vibration damping material evenly in the left and right direction with the deviation of the intermediate point of ± 0.4 mm. .

[0062]

[Table 5]

The table shows the measurement results shifted to the brush side.
The same tendency was observed when the point was shifted to the supporting point side.

From the figure, the length of the damping material is 1.0 to 3.6 mm, that is, there is a damping effect in the range of 17.9 to 64.3% of the brush length,
Moreover, the resonance frequency can be set to an appropriate value, and the life of the motor can be extended. For each of the above examples, the width of the damping material was 0.4 mm.
However, the loss coefficient and the resonance frequency did not change at all. Therefore, it can be seen that the width of the damping material is hardly affected. However, in practice, making the brush so small makes it difficult to work.

Although foam rubber is used as the material of the damping material in each of the above embodiments, it is needless to say that a similar effect can be obtained with a general viscoelastic body such as urethane rubber (Young's modulus of elastic constant is 0.1 to 30 GPa). Yes.

[0066]

From the above results, it is possible to suppress the vibration of the brush itself and to keep the resonance frequency of the brush at an appropriate value by applying the damping material within the range specified by the present invention. Abnormal wear of the contact part between the brush and commutator can be prevented, and the life of the motor can be extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a damping material is attached to the center of the brush in Example 1.

FIG. 2 is an overall configuration diagram of an apparatus for measuring a vibration state of a brush in the embodiment.

FIG. 3 is a diagram showing a position where a damping material is attached in the same embodiment.

FIG. 4 is a diagram showing a vibration state of a brush in the example.

FIG. 5 is a diagram showing the life of the brush in the example.

FIG. 6 is a diagram showing a change in the attachment position of the damping material in the example.

FIG. 7 is an overall configuration diagram of a brush resonance frequency measuring device in the embodiment.

FIG. 8 is a diagram showing a frequency response function of a brush.

FIG. 9 is a diagram showing a change in length of the damping material in the same example.

FIG. 10 is a diagram showing a pasting position of a damping material of a conventional small motor.

FIG. 11 is a diagram showing a vibration mode analysis result of a brush to which a damping material is not attached.

[Explanation of symbols]

1 brush 2 brush holder 3 brush support point 4 commutator 5, 26, 60 damping material 7 contact point between brush and commutator 8 intermediate point between brush support point and contact point between brush and commutator 9 damping material length 10 damping Midpoint in the longitudinal direction of the vibration material 11 Motor shaft 12 Brush length

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minami Banmitsu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A small motor in which a damping material for suppressing vibration of the brush is attached on a brush, wherein a midpoint in the longitudinal direction of the damping material is defined as a contact point between the brush and a commutator, and a brush support of the brush. A small motor in which the length of the damping material is set to be 17.9 to 75.0% of the length between the contact point and the brush support point, which coincides with the midpoint between the point and the point. 2. A small motor in which a vibration damping material for suppressing brush vibration is attached to a brush, wherein the brush support point is located at an intermediate point between a contact point of the brush and the commutator and a brush support point of the brush. On the side, the middle point in the longitudinal direction of the damping material is made to coincide within the range of 0 to 10.7% of the length between the contact point and the brush supporting point, and the length of the damping material is set to the contact point. A small motor in which the damping material is attached onto the brush so that the length is 26.8 to 60.7% of the length of the brush supporting point. 3. A small motor in which a vibration damping material for suppressing brush vibration is attached on a brush, wherein a contact point side is located from an intermediate point between a contact point of the brush and the commutator and a brush support point of the brush. In the range of 0 to 12.5% of the length between the contact point and the brush support point, the midpoint in the longitudinal direction of the damping material is matched, and the length of the damping material is set to the contact point and the brush. A small motor in which the damping material is attached onto the brush so that the length is 26.8 to 57.1% of the length of the support point. 4. A small motor in which a vibration damping material for suppressing vibration of the brush is attached on the brush, wherein a contact point side is located from an intermediate point between a contact point of the brush and the commutator and a brush support point of the brush. Or, on the brush support point side, the midpoint in the longitudinal direction of the damping material is made to coincide within the range of 7.1% of the length between the contact point and the brush supporting point, and the length of the damping material is A small motor in which the vibration damping material is attached on the brush so that the length is within the range of 17.9 to 64.3% of the length between the contact point and the brush support point. 5. A foamed rubber is used as a damping material.
The small motor according to any one of to 4.