JP2010004727A - Brush-holding device and direct current motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brush-holding device which avoids the vibration of a brush due to the resonance of coil spring, while simplifying the construction and reducing the cost. <P>SOLUTION: The brush-holding device is provide with a brush 22 for slidably contacting a commutator 20, a coil spring 28 for activating the brush 22 to the commutator 20 side, and a brush holder 24 for housing the brushing 22 and the coil spring 28. The brush 22 has a pressing surface 22a, which is to be pressed against one side of the coil spring 28. The brush holder 24 has a bottom surface 24a to be pressed against the other side of the coil spring 28. The pressing surface 22a and the bottom surface 24a are respectively inclined in the rotation direction of the commutator 20. Consequently, the vibration of the brush 22 to the rotation direction of the commutator 20 can be suppressed, by pushing the brush 22 onto one side surface of the brush holder 24, and the vibration in the pressing direction of the brush 22 can also be suppressed, by regulating the direction of curvature of the coil spring 28, to thereby avoid variations in the natural frequency. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brush holding structure for a DC motor, and more particularly to a brush holding structure for preventing brush vibration.

In a DC motor, a brush and a commutator are generally used to obtain a rectifying action. As a brush holding device, for example, a brush holder in which a brush is housed in a brush holder that elastically presses the brush against a commutator is known.
In such a brush and brush holder, since the predetermined clearance is provided between the brush side and the brush holder, the brush may vibrate in the brush holder due to sliding friction during rotation of the commutator. It is known that when the brush vibrates greatly in the brush holder, the rectifying action is deteriorated, and when it is remarkable, the rectifying spark is generated and the brush life is extremely shortened.

  As a countermeasure against the above problem, the technique of Patent Document 1 or Patent Document 2 is disclosed. According to these techniques, the brush is pressed to one side of the brush holder by inclining the rear end surface of the brush pressed by the coil spring. By setting it as such a structure, the vibration of the brush by the sliding contact friction with a commutator can be suppressed.

JP 2006-340474 A Japanese Patent Laid-Open No. 10-146025

  According to the technique of the above-mentioned patent document 1, the brush vibrates in the rotation direction of the commutator by providing a spacer having an inclination at the rear end portion of the brush and pressing the brush toward one side of the brush holder via the spacer. To suppress. At this time, the coil spring in the brush holder is bent at the end along the inclination direction of the rear end surface of the spacer, and the coil spring is also bent and held in the brush holder from the end as a spiral. . In particular, when a coil spring having a small coil outer diameter with respect to the space in the brush holder is used, the coil spring is bent into various shapes in the brush holder.

  Thus, since the coil spring is curved and held in a spiral shape in the brush holder, when the wear of the brush advances and the space in the length direction in the brush holder increases, the coil spring becomes in the brush holder. The curved state changes to take an arbitrary arrangement according to the space. Due to the change in the bending state of the coil spring, the apparent spring constant changes, so that the natural frequency of the coil spring varies. When the excitation frequency from the commutator side matches this natural frequency, the coil spring resonates and the brush vibrates greatly in the urging direction. For this reason, there existed a problem that a commutation spark arises and a brush lifetime becomes extremely short. In addition, since the spacers are provided, the number of parts and the number of assembling steps are increased, which makes it difficult to reduce costs.

  On the other hand, according to the technique of Patent Document 2, as shown in FIG. 9, the brush 102 is pressed against one side of the brush holder 104 to suppress the vibration of the brush 102 in the rotational direction of the commutator 100. Yes. Since the configuration is such that the spacer 102 is omitted and the brush 102 is pressed directly by the coil spring 108, an increase in the number of parts and assembly cost can be suppressed. However, also in this case, the coil spring 108 in the brush holder 104 is curved and held spirally in the brush holder 104. For this reason, as in the technique of Patent Document 1, when the wear of the brush 102 progresses and the space in the length direction in the brush holder 104 increases, the brush life becomes extremely long when a rectifying spark occurs with the commutator 100. It has the problem of shortening.

In view of the above problems, an object of the present invention is to provide a brush holding structure that avoids resonance of a coil spring.
Another object of the present invention is to provide a brush holding structure that avoids large vibrations of the brush while simplifying the structure and reducing the cost.

  According to the brush holding device of the first aspect, the problem is that the brush is in sliding contact with the outer peripheral side of the commutator, the urging means for urging the brush toward the commutator side, and the brush and the urging means are advanced and retracted. A brush holder for a DC motor comprising a movably stored brush holder, wherein the brush has a brush pressing surface in contact with one end side of the urging means, and the brush holder is This is solved by having a holder pressing surface that comes into contact with the other end side of the biasing means, and the brush pressing surface and the holder pressing surface have inclination angles opposite to each other.

  In this way, the curved shape of the urging means can be limited by having the brush pressing surface and the holder pressing surface with which both ends of the urging means abut have mutually opposite inclination angles. For this reason, even if the wear of the brush progresses and the space in the length direction in the brush holder increases, the curved shape of the urging means changes only slightly, and the natural frequency fluctuates little. A brush holding structure that can avoid resonance with the excitation frequency from the commutator side is obtained regardless of the state of wear of the brush.

Specifically, as in claim 2, it is preferable that the brush pressing surface and the holder pressing surface each have an inclination angle with respect to the rotation direction of the commutator.
With the above configuration, the urging means can be bent in the rotation direction of the commutator, and the brush can be pressed against the inner side surface of the brush holder located on the rotation direction side of the commutator. Therefore, even if the brush wear progresses and the space in the length direction in the brush holder increases, the curved shape of the biasing means changes only slightly, and the natural frequency changes only slightly. Regardless of the state of wear, resonance with the excitation frequency from the commutator side can be avoided, and furthermore, brush contact with the commutator can prevent the brush from vibrating greatly in the direction of rotation of the commutator. A structure is obtained.

As in claim 3, it is preferable that the brush pressing surface and the holder pressing surface each have an inclination angle with respect to the thickness direction of the commutator.
With the above configuration, the biasing means can be curved in the thickness direction of the commutator, and the brush can be pressed against the inner side surface of the brush holder located on the thickness direction side of the commutator. Therefore, even if the brush wear progresses and the space in the length direction in the brush holder increases, the curved shape of the biasing means changes only slightly, and the natural frequency changes only slightly. Regardless of the state of wear, the brush can avoid resonance with the excitation frequency from the commutator side, and can also prevent the brush from vibrating greatly in the thickness direction of the commutator due to sliding contact with the commutator. A holding structure is obtained.

According to a fourth aspect of the present invention, the brush pressing surface and the holder pressing surface may have a tilt angle with respect to both the rotational direction and the thickness direction of the commutator.
With the above configuration, the brush and the urging means can be held in a state where they are always in contact with the two surfaces. It is possible to suppress the brush from vibrating in either the thickness direction or the rotation direction of the commutator. In addition, the effect of suppressing the change in the bending state of the urging means accompanying the wear of the brush is high, and the range of resonating frequencies can be narrowed. Therefore, a brush holding structure that can effectively avoid resonance regardless of the amount of wear of the brush can be obtained.

Specifically, as in claim 5, the magnitudes of the inclination angles of the brush pressing surface and the holder pressing surface are approximately in both directions with respect to a surface perpendicular to the urging direction by the urging means. It is preferable that they are configured in the same manner.
With the above configuration, the curved shape of the urging means can be maintained in a bilaterally symmetric shape in which the natural frequency is less likely to fluctuate. Therefore, resonance between the excitation frequency from the commutator side and the urging means is more effectively avoided. A brush holding structure is obtained.

On the other hand, as in claim 6, the brush against the surface perpendicular to the urging direction by the urging means as compared to the inclination angle of the holder pressing surface with respect to the surface perpendicular to the urging direction by the urging means. It is preferable that the inclination angle of the pressing surface is configured to be larger.
With the above configuration, since the inclination of the holder pressing surface and the brush pressing surface that sandwich the urging means is different, the urging means can be curved asymmetrically. By making the curved shape of the urging means asymmetric, the natural frequency of the urging means can be slightly changed, and the range of the excitation frequency that causes resonance in the urging means can be further narrowed. That is, a brush holding structure that can more effectively avoid resonance between the excitation frequency from the commutator side and the urging means is obtained.

Specifically, as in claim 7, the surface perpendicular to the urging direction by the urging means with respect to the inclination angle of the holder pressing surface with respect to the surface perpendicular to the urging direction by the urging means. More preferably, the angle of inclination of the brush pressing surface with respect to the angle is approximately doubled.
With the above configuration, by setting the inclination angle of the brush pressing surface with respect to the inclination angle of the holder pressing surface to almost double, the curved shape of the biasing means can be designed with regular specifications while being asymmetrical. A brush holding structure capable of preventing complications and reducing costs can be obtained.

More specifically, as in claim 8, it is preferable that the brush pressing surface is formed with a brush protrusion that locks one end side of the urging means.
Due to the upper structure, the one end portion of the urging means is fixed to the brush side, thereby suppressing vibration of one end portion of the urging means on the brush pressing surface and accompanying the wear of the brush. Variations in the bending state of the urging means can be suppressed. Therefore, a brush holding structure that can more effectively avoid resonance between the excitation frequency from the commutator side and the urging means is obtained.

According to a DC motor according to a ninth aspect, the problem is solved by including the brush holding device according to any one of the first to eighth aspects.
Thus, the DC motor of the present invention can be obtained with the features of claims 1 to 8.

According to the brush holding device of the first aspect, a brush structure capable of avoiding resonance between the excitation frequency from the commutator side and the urging means regardless of the wear of the brush can be obtained.
According to the brush holding device of the second to fourth aspects, vibration in the biasing direction of the brush due to resonance between the excitation frequency from the commutator side and the biasing means, and vibration of the brush due to sliding contact with the commutator are provided. A brush structure that can be avoided is obtained.
According to the brush holding device of the fifth to eighth aspects, a brush structure that can more effectively avoid resonance between the excitation frequency from the commutator side and the urging means is obtained.
According to the DC motor of the ninth aspect, a DC motor having the features of the first to eighth aspects can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the members, arrangements, and the like described below do not limit the present invention, and can be variously modified within the scope of the gist of the present invention.
In the following description of the embodiments, the brush pressing surface corresponds to the pressing surface 22a, the holder pressing surface corresponds to the bottom surface 24a, and the biasing means corresponds to the coil spring 28.

(First embodiment)
1 to 3 show a first embodiment of the present invention, FIG. 1 is a schematic explanatory view of a DC motor, FIG. 2 is a cross-sectional explanatory view of a brush holding device, and FIG. 3 is an explanatory view showing a vibration waveform of the brush. is there.

First, based on FIG. 1, the structure of the DC motor 1 which concerns on embodiment of this invention is demonstrated.
The DC motor 1 according to the present embodiment includes a rotating shaft 10, a rotor 11 formed integrally with the rotating shaft 10, a stator 12, and a housing 13 for housing them.
Further, a commutator 20 is provided integrally with the rotor 11 in a part of the rotor 11, and a brush 22 attached to the housing 13 so as to be able to advance and retreat toward the commutator 20 is urged by a coil spring 28. Are held by the brush holder 24.

  Next, as shown in FIG. 2, the brush holding device according to the present embodiment holds the brush 22 while pressing it against the commutator 20. The brush holder 24 holds the brush 22 so as to be able to advance and retreat, and the brush. A coil spring 28 that urges 22 toward the commutator 20 and a brush 22 are provided. In addition, a conductor (not shown) for energization is connected to the brush 22.

  The brush 22 is a member that slidably contacts the commutator 20 and energizes, and is formed in a prismatic shape having a substantially rectangular cross section. It is comprised by the same member conventionally used with this kind of apparatus. The brush 22 is constantly urged toward the commutator 20 by pressing the pressing surface 22a, which is the surface opposite to the sliding contact surface 22b with the commutator 20, by the coil spring 28.

  The brush holder 24 is a resin or metal member that is fixed to the housing 13 side and accommodates the brush 22 so as to be able to move forward and backward. One end on the side of the commutator 20 is opened, and the other end is formed in a substantially rectangular tube shape having a bottom surface 24a. In a state where the brush 22 is housed in the brush holder 24, a gap 26 (clearance) is formed between the outer surface of the brush 22 and the inner surface of the brush holder 24. The gap 26 is a slight interval for fitting the brush 24 so that the brush 24 can move forward and backward in the brush holder 24.

  The coil spring 28 is a compression coil spring, and is housed inside the brush holder 24 in a state in which both ends are in contact with the bottom surface 24 a opposite to the commutator 20 side of the brush holder 24 and the pressing surface 22 a of the brush 22. Has been. The brush 22 is constantly urged toward the commutator 20 with the pressing surface 22 a being pressed by the coil spring 28.

Here, the bottom surface 24 a of the brush holder 24 and the pressing surface 22 a of the brush 22 are formed with an inclination angle with respect to the biasing direction of the coil spring 28. The bottom surface 24 a has an inclination angle α with respect to the rotation direction of the commutator 20, while the pressing surface 22 a has an inclination angle β with respect to the rotation direction of the commutator 20. The inclination angle β is inclined in the direction opposite to the inclination direction of the bottom surface 24a. That is, the inclination directions of the bottom surface 24a and the pressing surface 22a are opposite to each other (relatively spaced directions).
Since both ends of the coil spring 28 are supported by contact surfaces inclined in opposite directions, the coil spring 28 is arranged in an arc shape inside the brush holder 24.
Note that the bottom surface 24 a may be configured by bending one surface continuous with the side surface portion of the brush holder 24. In this case, it is preferable in terms of workability to provide a connecting portion between the bottom surface 24a and the side surface of the brush holder 24 so that the portion to be bent is obtuse.

  In addition, the inclination angle α of the bottom surface 24a and the inclination angle β of the pressing surface 22a are configured to have the same angle although the inclination direction is opposite. It has become a relationship. Since the inclination angle α of the bottom surface 24a and the inclination angle β of the pressing surface 22a have the same inclination amount, the coil spring 28 held between these surfaces is curved in a bilaterally symmetrical shape.

  The brush holding device according to the present embodiment can be assembled by storing the coil spring 28 in the brush holder 24 and storing it in the brush holder 24 while pressing the pressing surface 22 a of the brush 24 against the coil spring 28. At this time, by making the inclination directions of the pressing surface 22a and the bottom surface 24a reverse, the curved shape of the coil spring 28 can be made symmetrical, and no special treatment or handling is required for the coil spring 28. Therefore, it has a good assembly property.

The operation of the brush holding mechanism having such a configuration will be described.
Both ends of the coil spring 28 are sandwiched between a bottom surface 24 a and a pressing surface 22 a inclined in opposite directions, and are curved in an arc shape in the brush holder 24. Therefore, even when the wear of the brush 22 proceeds and the space in the length direction in the brush holder 24 increases, the bending direction of the coil spring 28 does not change. That is, the change in the direction of the force applied to the coil spring 28 is small, the change in the apparent spring constant caused by the change in the inclination with respect to the biasing direction of the effective coil portion is less likely to occur, and the change in the natural frequency can be prevented. it can. By reducing the fluctuation of the natural frequency, the range of the frequency at which the coil spring 28 resonates can be narrowed. Therefore, regardless of the wear of the brush 22, a brush structure that can avoid resonance with the excitation frequency from the commutator 20 side is obtained.

Further, the pressing surface 22 a of the brush 22 is inclined with respect to the rotation direction (circumferential direction) of the commutator 20, so that the brush 22 is pressed by the coil spring 28 on one side surface (the commutator 20) in the brush holder 24. The side surface located on the rotational direction side of the brush can be pressed. Therefore, the vibration of the brush 22 in the brush holder 24 in the rotation direction of the commutator 20 due to sliding friction during rotation of the commutator 20 can also be reduced.
That is, according to the brush holding device according to the present embodiment, vibration in the rotational direction of the commutator 20 of the brush 22 due to sliding friction during rotation of the commutator 20 is suppressed, and vibration from the commutator 20 side is performed as described above. Resonance with the frequency can also be avoided.

  Furthermore, when the coil outer diameter of the coil spring 28 is extremely small with respect to the space in the width direction inside the brush holder 24, the coil spring 28 is also included in the brush holder 24 in the brush holding device according to the present embodiment. Although curved in a complicated manner, both the bottom surface 24a and the pressing surface 22a with which the end portions of the coil spring 28 are in contact with each other are inclined, so that the bending directions on both ends are fixed. Therefore, even if the space in the length direction in the brush holder 24 increases due to the progress of wear of the brush 22, the curved state that the coil spring 28 can take is limited as compared with the conventional brush holding device. Therefore, the variation amount of the natural frequency can be reduced, and a brush structure that can avoid resonance is obtained.

FIG. 3 shows a vibration waveform of the brush 22 according to the present embodiment.
For comparison, FIG. 10 shows a vibration waveform of the brush 102 that may occur in the conventional brush holding device.
The brush 22 according to the brush holding mechanism of the present embodiment has a reduced peak value and undulation of the vibration waveform of the brush as compared with the brush 102 according to the conventional brush holding device.
As described above, the brush holding mechanism according to the present embodiment has a simple structure, but can effectively suppress vibration of the brush 22 due to resonance of the coil spring 28. Therefore, the DC motor including the brush holding mechanism according to the present embodiment can prevent the brush life from being reduced due to vibration of the brush 22.

(Second Embodiment)
FIG. 4 is a cross-sectional explanatory view of a brush holding device according to a second embodiment of the present invention.
In each of the following embodiments, the same reference numerals are assigned to the same members and arrangements as those in the first embodiment, and detailed description thereof is omitted.
The brush holding device according to the present embodiment is different in the inclination direction of the bottom surface 34a and the pressing surface 32a as compared to the first embodiment.

In the brush holding device according to the present embodiment, the bottom surface 34 a has an inclination angle α ₂ with respect to the thickness direction of the commutator 20. On the other hand, the pressing surface 32a, relative to the thickness direction of the commutator 20, and the angle beta ₂ inclined in opposite direction to the inclination direction of the bottom surface 34a. That is, the inclination directions of the bottom surface 34a and the pressing surface 32a are opposite to each other (relatively spaced directions). Further, the inclination angle beta ₂ of the inclination angle alpha ₂ and the pressing surface 32a of the bottom surface 34a is inclined direction is reversed is set at the same angle.
For this reason, the coil spring 28 is arranged in an arc shape projecting in the thickness direction of the commutator 20 inside the brush holder 34.

According to this embodiment, since the pressing surface 32a of the brush 32 is inclined with respect to the thickness direction of the commutator 20, the brush 32 is pressed toward the commutator 20 side and at the same time in the thickness direction of the commutator 20. Is also pressed. Unlike the first embodiment, when the commutator 20 is pressed in the thickness direction, the brush 32 can weaken vibration in the thickness direction of the commutator 20 in the brush holder 34.
Of course, since it also has the effect of suppressing fluctuations in the natural frequency of the coil spring 28, the excitation frequency from the commutator 20 side, regardless of the wear of the brush 32, as in the brush holding device according to the first embodiment. Can be avoided.

In the first embodiment and the second embodiment described above is configured bottom surface 24a, 34a inclination angle alpha of alpha ₂ and the pressing surface 22a, 32a inclination angle beta of the beta ₂ as the same value However, it is not necessarily limited to the same angle. For example, the pressing surface 22a, 32a inclination angle beta of the beta _2, bottom 24a, 34a inclination angle alpha of the may be larger than alpha _2. By increasing the inclination angles β and β ₂ , the coil spring 28 can be brought into contact with the inside of the brush holders 24 and 34 with a larger force, and vibration transmitted from the commutator 20 is reduced before being transmitted to the entire coil spring 28. can do.

Further, the inclination directions of the bottom surfaces 24a and 34a and the pressing surfaces 22a and 32a are not limited to the above-described embodiments. For example, the bottom surfaces 24a and 34a and the pressing surfaces 22a and 32a are inclined in opposite directions in the diagonal direction inside the substantially rectangular cross section of the brush holders 24 and 34, so that the brushes 22 and 32 are inside the brush holders 24 and 34, respectively. Since it can press in the diagonal direction of a cross section, the brush holding | maintenance apparatus which has both the effect of 1st Embodiment and 2nd Embodiment can be obtained.
Configuration examples in which the inclination directions of the bottom surfaces 24a and 34a and the pressing surfaces 22a and 32a are changed will be described below as third to fifth embodiments.

(Third embodiment)
In the first embodiment and the second embodiment described above, the inclination direction of the bottom surfaces 24a, 34a and the pressing surfaces 22a, 32a is configured as the rotational direction or thickness direction of the commutator 20. However, the inclination directions of the bottom surfaces 24a and 34a and the pressing surfaces 22a and 32a are not limited to this, and the following configuration can be adopted.
FIG. 5 is a cross-sectional explanatory view of a brush holding device according to a third embodiment of the present invention, FIG. 5 (a) is a transverse cross-sectional view, and FIG. 5 (b) is a cross-sectional view taken along line AA in FIG. FIG. 5 (c) is a longitudinal sectional view, and FIG. 5 (d) is a BB sectional view of FIG. 5 (c).
The brush holding device according to the present embodiment is different in the inclination directions of the bottom surface 44a and the pressing surface 42a as compared to the first and second embodiments.
In each of the following embodiments, the same reference numerals are assigned to the same members and arrangements as those in the first embodiment, and detailed description thereof is omitted.

The bottom surface 44 a has an inclination angle α ₃₁ with respect to the rotation direction of the commutator 20 and an inclination angle α ₃₂ in the thickness direction of the commutator 20, while the pressing surface 42 a has an inclination angle α ₃₂ with respect to the rotation direction of the commutator 20. It has an inclined angle beta ₃₂ in the thickness direction of the commutator 20 and having an inclination angle beta ₃₁ Te. The bottom surface 44a and the pressing surface 42a are inclined in opposite directions (relatively spaced directions).

  By being configured as described above, the brush 42 is always held in contact with the two surfaces. Therefore, since the brush 42 can weaken both vibrations in the rotational direction and the thickness direction of the commutator 20, resonance with the excitation frequency from the commutator 20 side can be avoided regardless of wear of the brush 42. it can. That is, a brush holding device having both the effects of the first embodiment and the second embodiment can be obtained.

  The effect of suppressing the change in the bending state of the coil spring 28 due to wear of the brush 44 is also high, and the fluctuation of the natural frequency of the coil spring 28 can be effectively suppressed. That is, when the coil spring 28 continues to contact the two surfaces inside the brush holder 44, the curved state is further stabilized, and the range of resonating frequencies can be narrowed.

Note that α ₃₁ , α ₃₂ , β ₃₁ , and β ₃₂ are all preferably in the range of 15 to 45 °. By setting the inclination angle to 15 ° or more, it is possible to give an inclination that the coil spring 28 contacts (or slides) with the inner surface of the brush holder 44 with a predetermined load or more. On the other hand, by setting the inclination angle to 45 ° or less, it is possible to prevent unnecessary bending from occurring in the coil spring 28 by the coil spring 28 coming into contact with the inner surface of the brush holder 44 with a large angle. .

With respect to the diagonal direction of the inner cross section of the brush holder 44 whose cross-sectional shape is formed on a substantially rectangular shape, the bottom surface 44a and the pressing surface 42a are inclined at substantially the same angle in opposite directions so as to draw a letter C. Therefore, the coil spring 28 is disposed in contact with the two surfaces inside the brush holder 44 so as to be curved in an arc shape in the diagonal direction, and the variation in the curved state can be effectively suppressed.
At the same time, the brush 42 is pressed in the diagonal direction of the inner cross section of the brush holder 44 by the coil spring 28, so that the brush 42 is held in a pressed state by the urging forces from the two directions. For this reason, the brush 42 can prevent excessive vibration in any of the rotational direction / thickness direction of the commutator 20.

Further, even if the brush 42 is worn, the fluctuation of the bending state of the coil spring 28 is small, so the fluctuation of the urging force (brush load P) pressing the brush 42 is small and stable. Therefore, it is possible to approach an ideal brush load characteristic in which the lower limit value of the urging force is constant.
FIG. 6 is a graph plotting changes in the brush load P with respect to the brush wear amount L in the present embodiment. According to FIG. 6, it can be seen that the lower limit value of the brush load P is not different from the conventional value, but the difference between the initial value and the lower limit value before the brush wear is small. That is, it has a good brush load characteristic.

(Fourth embodiment)
7A and 7B are cross-sectional explanatory views of a brush holding device according to a fourth embodiment of the present invention. FIG. 7A is a cross-sectional view, and FIG. 7B is a cross-sectional view taken along the line CC in FIG. FIG. 7 (c) is a longitudinal sectional view, and FIG. 7 (d) is a DD sectional view of FIG. 7 (c).
In the brush holding device according to the present embodiment, the bottom surface 54a and the pressing surface 52a are inclined in both the rotational direction and the thickness direction of the commutator 20 as in the third embodiment. However, the inclination angles of the bottom surface 54a and the pressing surface 52a are different.
In each of the following embodiments, the same reference numerals are assigned to the same members and arrangements as those in the first embodiment, and detailed description thereof is omitted.

The bottom surface 54 a has an inclination angle α _{41 with} respect to the rotation direction of the commutator 20, and an inclination angle α ₄₂ with respect to the thickness direction of the commutator 20, while the pressing surface 52 a has an inclination angle α ₄₂ with respect to the rotation direction of the commutator 20. An inclination angle β _{41 is} provided, and an inclination angle β ₄₂ is provided in the thickness direction of the commutator 20. The bottom surface 54a and the pressing surface 52a are inclined in opposite directions (relatively spaced directions).

  The bottom surface 54a and the pressing surface 52a are inclined in opposite directions with respect to the diagonal direction of the inner cross section of the brush holder 54 having a substantially rectangular cross section. For this reason, the coil spring 28 is arranged so as to be curved in an arcuate shape in a diagonal direction in contact with the two surfaces inside the brush holder 54, and at the same time, the brush 52 is arranged in the diagonal direction of the inner cross section of the brush holder 54 by the coil spring 28. Since it is pressed, it is held in contact with the two surfaces.

Further, if the inclination angle β ₄₁ (and β ₄₂ ) is formed larger than the inclination angle α ₄₁ (and α ₄₂ ), the bottom surface 54a and the pressing surface 52a have different inclinations, so that the coil spring 28 is curved asymmetrically. It will be. Further, since the inclination angle α ₄₁ (α ₄₂ ) of the bottom surface 54 a is large, the coil spring 28 comes into contact with the inner wall (C-C cross-sectional line) of the brush holder 54 close to the commutator 20.

In this embodiment, twice the angular inclination angle beta ₄₁ (and beta ₄₂₎ and approximately equal (2α ₄₁ = β _41, and a 2α ₄₂ = _{β 42)} of the inclination angle alpha ₄₁ (and alpha ₄₂₎ configured Has been. At this time, the inclination of the annular coil portions caused by the bending of the coil spring 28 is asymmetric, but the inclination angle is regular. Also in this embodiment, it is desirable that α ₄₁ , α ₄₂ , β ₄₁ , and β ₄₂ are all in the range of 15 to 45 °.

According to the present embodiment, the natural frequency of the coil spring 28 can be slightly changed by making the curved shape of the coil spring 28 in the brush holder 54 asymmetric. That is, the apparent spring constant changes due to the difference in the coil shape between the portion where the curvature curvature of the coil spring 28 is large and the portion where the curvature is small, and a slight difference also occurs in the natural frequency. In other words, the natural frequency for resonating the entire coil spring 28 needs to be a frequency that resonates both of the two regions having different curvatures of the coil spring 28. Therefore, the vibration that generates resonance in the entire coil spring 28 is required. The frequency range can be further narrowed. In the first embodiment and the second embodiment, the same effect as described above can be obtained by increasing the inclination angle on the brush 22 and 32 side.
Of course, the brush holding device according to the present embodiment also has the functions and effects described in the third embodiment.

Note that α ₄₁ (β ₄₁ ) and α ₄₂ (β ₄₂ ) can be configured as different angles. The direction in which the brush 54 is pressed and the pressing force can be adjusted by appropriately changing the angle of inclination of the commutator 20 in the thickness direction and the rotation direction. For example, by increasing the inclination angle α ₄₂ (β ₄₂ ) in the rotation direction more than the inclination angle α ₄₁ (β ₄₁ ) in the thickness direction of the commutator 20, it is possible to effectively suppress vibration in the rotation direction of the commutator 20. it can.
In addition, when a rectangular columnar (rectangular cross-section) compression coil spring having an aspect ratio of less than 1 is used instead of the coil spring 28 that is a cylindrical (circular cross-section) compression coil spring, the inclination angle α ₄₁ (β ₄₁ ) and α ₄₂ (β ₄₂ ) can be adjusted to correct the difference in pressing force (biasing force) depending on the bending direction.
In this case as well, the above-described effects can be obtained by forming the inclination angle α ₄₁ (α ₄₂ ) larger than the inclination angle β ₄₁ (β ₄₂ ).

(Fifth embodiment)
FIG. 8 is an explanatory cross-sectional view of a brush holding device according to a fifth embodiment of the present invention. 8A is a cross-sectional view, FIG. 8B is an EE cross-sectional view of FIG. 8A, FIG. 8C is a vertical cross-sectional view, and FIG. 8D is FIG. 8C. It is FF sectional drawing.
As in the third embodiment, in the brush holding device according to the present embodiment, the bottom surface 64a and the pressing surface 62a are inclined in both the rotational direction and the thickness direction of the commutator 20, and the bottom surface 64a and the pressing surface 62a. Are inclined by substantially the same angle in opposite directions. However, the pressing surface 62a is different from the third embodiment in that a brush protrusion 63 is provided on the pressing surface 62a.
In each of the following embodiments, the same reference numerals are assigned to the same members and arrangements as those in the first embodiment, and detailed description thereof is omitted.

  The brush protrusion 63 is a protrusion provided on the pressing surface 62 a and is formed in a substantially cylindrical shape having a diameter smaller than the inner diameter of the end of the coil spring 28. By inserting the brush protrusion 63 inside the coil at the end of the coil spring 28, the coil spring 28 can be bent in a predetermined direction and locked so that the end does not move.

By fixing one end of the coil spring 28 to the brush 62 side, vibration of the end of the coil spring 28 on the pressing surface 62a can be suppressed. Accordingly, since the coil spring 28 is less likely to resonate, it is effective in avoiding resonance with the excitation frequency from the commutator 20 side.
In addition, since the coil spring 28 has an effect of preventing a change in the bending state of the coil spring 28 due to wear of the brush 64, fluctuations in the natural frequency of the coil spring 28 can be suppressed. That is, by fixing one end side, the curved state of the coil spring 28 is further stabilized, and the range of the resonance frequency can be narrowed.
Of course, the brush holding device according to the present embodiment also has the functions and effects described in the third embodiment.
The brush protrusion 63 according to the present embodiment can also be applied to the brushes 22, 32, 42, and 52.

  The brush protrusion 63 may be configured to have a diameter slightly larger than the inner diameter of the end of the coil spring 28. Since the coil spring 28 can be fixed while receiving a pressing force from the inside of the coil, the coil spring 28 can be locked in a state in which the rotation of the coil spring 28 is suppressed. By providing such a protruding portion that can be locked while suppressing the rotation of the coil spring 28 on both the pressing surface 62a and the bottom surface 64a, the coil spring 28 can be held with a torsional stress applied. . The curved shape that can be taken by the coil spring 28 can be further limited by fixing the both ends of the coil spring 28 in a state where torsional stress is applied to both ends of the coil spring 28. At the same time, since the brush 62 can be slidably contacted with the inner surface of the brush holder 64 at all times, abnormal wear of the brush 64 can be prevented. Note that the protrusion that can be locked while suppressing the rotation of the coil spring 28 can be applied to any of the embodiments according to the present invention described above. Moreover, it is good also as a structure which can be fixed firmly by latching the edge part side of the coil spring 28 to a projection part with a screw | thread etc. FIG.

1 is a schematic explanatory diagram of a DC motor according to a first embodiment of the present invention. It is a section explanatory view of the brush holding device concerning a 1st embodiment of the present invention. It is explanatory drawing which shows the vibration waveform of the brush which concerns on the 1st Embodiment of this invention. It is a section explanatory view of the brush holding device concerning a 2nd embodiment of the present invention. It is a section explanatory view of the brush holding device concerning a 3rd embodiment of the present invention. It is the figure which plotted the change of the brush load with respect to the brush wear amount which concerns on the 3rd Embodiment of this invention. It is a section explanatory view of the brush holding device concerning a 4th embodiment of the present invention. It is a section explanatory view of the brush holding device concerning a 5th embodiment of the present invention. It is explanatory drawing of the conventional brush holding | maintenance apparatus. It is explanatory drawing which shows the vibration waveform of the brush which may generate | occur | produce with the conventional brush holding | maintenance apparatus.

Explanation of symbols

α Inclination angle of the bottom surface, β Inclination angle of the pressing surface, 1 DC motor, 10 rotating shaft, 11 rotor, 12 stator, 13 housing, 20, 100 commutator, 22, 32, 42, 52, 62, 102 brush, 22a, 32a, 42a, 52a, 62a Press surface, 22b Sliding surface, 24, 34, 44, 54, 64, 104 Brush holder, 24a, 34a, 44a, 54a, 64a Bottom surface, 26 Clearance, 28, 108 Coil spring, 63 Brush protrusion

Claims (9)

A brush that is in sliding contact with the outer periphery of the commutator;
Biasing means for biasing the brush toward the commutator;
A brush holder for a DC motor comprising: the brush and a brush holder that accommodates the urging means so as to be movable forward and backward,
The brush has a brush pressing surface that comes into contact with one end side of the biasing means,
The brush holder has a holder pressing surface that comes into contact with the other end side of the biasing means,
The brush holding device, wherein the brush pressing surface and the holder pressing surface have inclination angles opposite to each other.   The brush holding device according to claim 1, wherein the brush pressing surface and the holder pressing surface each have an inclination angle with respect to a rotation direction of the commutator.   The brush holding device according to claim 1, wherein the brush pressing surface and the holder pressing surface each have an inclination angle with respect to the thickness direction of the commutator.   The brush holding device according to claim 1, wherein the brush pressing surface and the holder pressing surface have an inclination angle with respect to both a rotation direction and a thickness direction of the commutator.   The inclination angle of the brush pressing surface and the holder pressing surface is configured to be substantially the same in both side directions with respect to a surface perpendicular to the urging direction by the urging means. The brush holding device according to any one of 1 to 4. Compared to the inclination angle of the holder pressing surface with respect to the surface perpendicular to the urging direction by the urging means,
5. The brush holding device according to claim 1, wherein an inclination angle of the brush pressing surface with respect to a surface perpendicular to an urging direction by the urging unit is configured to be larger. For the inclination angle of the holder pressing surface with respect to the surface perpendicular to the urging direction by the urging means,
The brush holding device according to claim 6, wherein an inclination angle of the brush pressing surface with respect to a surface perpendicular to an urging direction by the urging unit is approximately doubled.   The brush holding device according to any one of claims 1 to 7, wherein the brush pressing surface is formed with a brush protrusion that locks one end side of the biasing means.   A direct current motor comprising the brush holding device according to claim 1.

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