JP2004364414A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor which can reduce magnetic sound. <P>SOLUTION: This motor is provided with brushes 51a-51d, with the centrifugal centers of brushes 51c and 51d on negative load side being slid x° counterclockwise from the circumferential centers of gaps G, that is, from a virtual line R extending at right angles from the center O of a commutator 6, when the centrifugal centers of brushes 51a and 51b on positive electrode side face the centrifugal centers of segments 61. Furthermore, they are provided, being slid x° counterclockwise within the range until the centrifugal centers of the brushes 51c and 51d on negative load side face the centrifugal centers of the segments 61. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric motor of an electric power steering device for assisting a steering force of a steering, for example.
[0002]
[Prior art]
BACKGROUND ART Conventionally, an electric motor of an electric power steering device for assisting a steering force of a steering includes an armature core having a coil wound thereon, a commutator having a plurality of segments electrically connected to the coil, and a commutator having the commutator. And a magnetic pole provided on the outer peripheral side of the armature core. In addition, the plurality of segments are provided with a fixed gap over the entire circumference, and when the circumferential center of the positive brush is opposed to the gap between the adjacent segments, the brush of the negative brush is It is arranged so that the circumferential center coincides with the circumferential center of the segment (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-62-230340 (page 11, lower left column, line 11 to page 4, lower right column, line 5, FIGS. 1 to 11)
[0004]
[Problems to be solved by the invention]
In the electric motor of the electric power steering apparatus described above, when a current flows from the battery to the coil wound around the armature core via the brush, the armature core and the commutator rotate together. However, experiments have shown that magnetic noise is generated when the armature core and the commutator rotate at high speed.
[0005]
The present invention has been made in view of the above problems, and has as its object to provide an electric motor that can reduce magnetic noise.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, in claim 1, an armature core on which a coil is wound, and a plurality of segments that are electrically connected to the coil and that are provided with a constant gap over the entire circumference. A commutator and a brush on the positive electrode side and a brush on the negative electrode side slidably provided on the outer periphery of the segment. When the circumferential center of the brush on the positive electrode faces the circumferential center of the segment, the brush on the negative electrode side It is characterized in that it is provided so as to be opposed and the circumferential center is shifted in the circumferential direction from a virtual line extending from the center of the commutator from the circumferential center of the gap.
[0007]
With this configuration, when the circumferential center of the brush on the positive electrode side faces the circumferential center of the segment, the brush on the negative electrode side faces the gap, and the circumferential center extends from the center of the commutator from the circumferential center of the gap. It has been clarified by experiments that the magnetic noise generated from the electric motor can be reduced by rotating the armature core and the commutator by displacing the wire in the circumferential direction with respect to the wire.
[0008]
According to the second aspect, the four brushes are provided at intervals of approximately 90 degrees in the circumferential direction with respect to the center of the commutator, and the first brush and the second brush on the positive electrode side are positioned with respect to the center of the commutator. The third brush and the fourth brush on the negative electrode side are provided to face the center of the commutator. The number of segments is 22, and the number of segments is 22. The circumferential width of the sliding contact with the segment is almost the same as the circumferential distance from the circumferential center of the gap to the circumferential center of the adjacent gap, and the magnet provided on the outer peripheral side of the armature core is positioned with respect to the center of the commutator. Four brushes are provided at substantially 90-degree intervals in the circumferential direction, and when the circumferential centers of the first and second brushes face the circumferential centers of the segments, the third and fourth brushes face the gap, and The center in the circumferential direction is Is characterized in that it is provided displaced only circumferentially x ° represented by the following relation with respect to the virtual line from the axial center.
[0009]
3.2 ≦ x ≦ 6.4
According to the third aspect, the four brushes are provided at intervals of approximately 90 degrees in the circumferential direction with respect to the center of the commutator, and the first brush and the second brush on the positive electrode side are positioned with respect to the center of the commutator. The third brush and the fourth brush on the negative electrode side are provided to face the center of the commutator. The number of segments is 22, and the number of segments is 22. The circumferential width in sliding contact with the segment is approximately half the circumferential distance from the circumferential center of the gap to the circumferential center of the adjacent gap, and the magnetic pole provided on the outer peripheral side of the armature core is Four brushes are provided at substantially 90-degree intervals in the circumferential direction, and when the circumferential centers of the first and second brushes face the circumferential centers of the segments, the third and fourth brushes face the gap, and The circumferential center is the circumferential direction of the gap It is characterized in that it is provided offset sincerely x ° only circumferential direction represented by the following relation with respect to the virtual line.
[0010]
4.0 ≦ x ≦ 5.2
With these configurations, when the circumferential centers of the first and second brushes face the circumferential center of the segment, the third and fourth brushes face the gap, and the circumferential center is the circumferential center of the gap. From the imaginary line in the circumferential direction by x ° represented by the above relation, the magnitude of the audible frequency component of the magnetic sound generated from the electric motor becomes larger than when x is 0 ° as in the related art. It was clarified by an experiment that it was possible to reduce the amount of water.
[0011]
According to a fourth aspect of the present invention, the width in the circumferential direction of the first to fourth brushes in sliding contact with the segments is approximately 4.0 mm.
[0012]
It has been clarified by an experiment that this configuration makes it possible to reduce the magnitude of the audible frequency component of the magnetic sound generated from the electric motor most when the circumferential width of the brush contacting the first to fourth brush segments is approximately 4.0 mm. did it.
[0013]
Further, the present invention is characterized in that the present invention is used for an electric power steering device for assisting the steering force of the steering.
[0014]
According to this configuration, since the electric power steering device is provided near the driver of the vehicle, the use of the electric motor of the present invention in the electric power steering device reduces magnetic noise generated from the electric motor. It is possible to suppress the driver from feeling uncomfortable. Furthermore, since the size of the audible frequency component of the magnetic sound generated from the electric motor is reduced, the size of the resonance frequency component of the audible frequency component of the magnetic sound generated from the commut axis of the electric power steering device can be reduced.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments shown in the drawings will be described.
[0016]
FIG. 1 is a front view of the brush device 5 according to the present embodiment viewed from an axial direction. FIG. 2 is a sectional view taken along the line II-II in FIG. FIG. 3 is a diagram showing the positional relationship of the brush 51. 4A is an axial perspective view of the brush 51, and FIG. 4B is a cross-sectional view taken along the line IV-IV of FIG. FIG. 5 is an enlarged view of a part of the commutator 6.
[0017]
The electric motor 1 in the present embodiment is used in an electric power steering device for assisting the steering force of the steering. As shown in FIGS. 1 and 2, the electric motor 1 includes an armature including an armature core 2, a shaft 3, and a commutator 6. , Magnet 4, brush device 5, yoke 7, housing 8, and end frame 9.
[0018]
The armature core 2 is cylindrical and has a coil (not shown) wound inside.
[0019]
The shaft 3 extends through the commutator 6 and the armature core 2 and extends in the axial direction. Further, the shaft 3 rotates in the circumferential direction together with the armature core 2, and a tip portion at one axial end is connected to a joint 10, and the rotation of the shaft 3 is controlled via the joint 10 in an electric power steering device (not shown). It is configured to be transmitted to a power transmission device.
[0020]
The magnet 4 is fixed to the outer periphery of the armature core 2 with a certain gap and fixed to the inner periphery of the yoke 7, and is arranged at an interval of about 90 degrees in the circumferential direction so that N poles and S poles are alternately arranged. Four are provided.
[0021]
The brush device 5 is provided on the outer peripheral side of the commutator 6, and includes a brush 51, a brush holder 52, a spring 53, and a pigtail 54.
[0022]
The brush 51 is made of carbon whose copper content is 60% or less, and as shown in FIG. 1, the positive brushes 51a and 51b and the negative brushes 51c and 51d are arranged at substantially 90-degree intervals in the circumferential direction. Four are provided facing each other. As shown in FIG. 4, the brush 51 is a substantially rectangular parallelepiped, the longitudinal direction of which is provided in parallel with the axial direction of the shaft 3, and the sliding contact surface 51 e is in sliding contact with the outer periphery of the commutator 6. Further, by grinding both ends of the sliding contact surface 51e in the longitudinal direction, a grinding portion 51f is formed so that the sliding contact width h in the longitudinal direction of the sliding contact surface 51e is smaller than the brush width 1 in the longitudinal direction of the brush 51. ing. In this embodiment, the brush width 1 is about 6 mm, and the grinding portions 51f are shaved by 1 mm so that the sliding contact width h is about 4 mm.
[0023]
The brush holder 52 is made of resin, and houses the brush 51 therein. The spring 53 is provided in the brush holder 52 and urges the surface of the brush 51 facing the sliding contact surface 51 e toward the commutator 6. One end of the two pigtails 54 provided to face each other is electrically connected to a battery (not shown), and the other end is electrically connected to the positive brushes 51a and 51b. One end of the remaining two pigtails 54 is grounded, and the other end is electrically connected to the negative brushes 51c and 51d.
[0024]
The commutator 6 is provided on one end side of the armature core 2 in the axial direction, and has a columnar shape smaller in diameter than the armature core 2. As shown in FIG. 3, the commutator 6 has a segment 61 on the outer periphery of which the sliding surface 51 e of the brush 51 slides. 22 segments 61 are provided over the entire circumference with a fixed gap G therebetween. Further, the segment 61 is electrically connected to a coil wound inside the armature core 2, and the sliding contact surface 51 e of the brush 51 slides on the outer periphery of the segment 61, so that the current from the battery is brushed. The power is supplied to a coil wound inside the armature core 2 through a center 51. Further, as shown in FIG. 5, the circumferential width n of one segment 61 in the present embodiment is about 3.6 mm, and the circumferential distance k of the gap G is about 0.4 mm. From this, the circumferential distance m from the circumferential center of the gap G to the circumferential center of the circumferentially adjacent gap G is about 4 mm.
[0025]
The yoke 7 has a bowl shape, and a bearing 12 for axially supporting the other end of the shaft 3 in the axial direction is provided on the inner periphery of one end in the axial direction on the closed side. The opening side of the yoke 7 protrudes radially outward, and the protruding portion is fixed to the housing 8 by bolts 13.
[0026]
The housing 8 is provided on the outer peripheral side of the brush device 5, and the holder 15 and the end frame 9 are fixed by bolts 14.
[0027]
The end frame 9 is provided with a hole in which the tip of one end in the axial direction of the shaft 3 protrudes outside, and a bearing 11 for axially supporting one end of the shaft 3 in the axial direction is formed in the inner periphery of the hole. Is provided.
[0028]
Next, the positional relationship between the four brushes 51a to 51d provided on the outer periphery of the 22 segments 61 in the present embodiment will be described with reference to FIG.
[0029]
The brushes 51a to 51d are arranged such that when the circumferential centers of the positive brushes 51a and 51b face the circumferential center of the segment 61, the circumferential centers of the negative brushes 51c and 51d extend from the circumferential center of the gap G to the center of the commutator 6. It is provided x ° counterclockwise with respect to a virtual line R extending from O. The negative brushes 51c and 51d are provided at a position deviated by x ° counterclockwise with respect to the virtual line R within a range until the center in the circumferential direction faces the center in the circumferential direction of the segment 61.
[0030]
In the present embodiment, the center of the negative brushes 51c and 51d in the circumferential direction is provided to be displaced in the counterclockwise direction with respect to the virtual line R within a range represented by the following relational expression (1).
[0031]
0 <x <8.0 (1)
Next, regarding the magnetic noise generated from the electric motor 1 when the circumferential centers of the negative brushes 51c and 51d are displaced in the counterclockwise direction with respect to the imaginary line R within the range shown by the above relational expression (1), A description will be given based on experimental data. Note that shifting the circumferential center of the negative brushes 51c and 51d by 0.5 mm in the counterclockwise direction with respect to the virtual line R in the present embodiment is equivalent to shifting the circumferential center of the negative brushes 51c and 51d to the virtual line R. This is the same as shifting 2 ° counterclockwise.
[0032]
When the electric motor 1 is rotated at a low speed, the frequency component of the magnetic sound generated from the electric motor 1 is divided into first to fourth order components A to D. The primary component A is around 25 Hz, the secondary component B is around 50 Hz, the tertiary component C is around 75 Hz, and the quaternary component D is around 100 Hz. The audible frequency components that can be heard by human ears are the second-order component B, the third-order component, and the fourth-order component D.
[0033]
First, when the circumferential centers of the negative brushes 51c and 51d are shifted counterclockwise by 0 to 2 mm (0 to 8 °) with respect to the imaginary line R, the electric motor 1 of the first to fourth order components A to D is used. FIG. 6 shows the total resistance variation.
[0034]
As shown in FIG. 6, by shifting the circumferential centers of the negative brushes 51 c and 51 d in the counterclockwise direction with respect to the imaginary line R, the resistance fluctuation of the entire electric motor 1 of the primary component A which is not an audible frequency component. The amount is increasing.
[0035]
Here, based on the experimental data of the second-order component B to the fourth-order component D shown in FIG. 6, the audible frequency at the amount of shift of the center of the negative brushes 51c and 51d in the circumferential direction is calculated from the following equation (2). The index value S was calculated.
[0036]
S = B + C × 1.5 + D × 2 (2)
The index value S is an index that can be heard by an occupant in the vehicle when the electric motor 1 of the present invention is used in an electric power steering device. As the rotation of the electric motor 1 increases, the tertiary component C is increased. And the fourth-order component D tends to coincide with the resonance frequency (about 1 kHz) of the magnetic sound generated from the column shaft of the electric power steering apparatus. Therefore, the experimental data shown in FIG. The next component C and fourth order component D are multiplied by a constant. The index value S indicates the magnitude of the audible frequency component of the magnetic sound generated by the electric motor 1 of the electric power steering device that can be heard by a passenger in the vehicle.
[0037]
FIG. 7 shows the index value S calculated from the above equation (2). As shown in FIG. 7, the index value S is smaller than the conventional value of 0 mm when the amount of shift of the circumferential center of the negative brushes 51c and 51d in the counterclockwise direction is within a range of 0.8 mm to 1.6 mm. In other words, the index value S is smaller than the conventional value of 0 ° when the shift amount of the circumferential center of the negative brushes 51c and 51d in the counterclockwise direction is in the range of 3.2 ° to 6.4 °.
[0038]
From this, the fact that the index value S becomes smaller means that the audible frequency component of the magnetic sound generated from the electric motor 1 is reduced, and therefore, for example, the electric power steering device for assisting the steering force of the steering In this case, it is possible to make it difficult for the occupant to hear the magnetic noise generated from the electric motor 1, and it is possible to suppress the occupant from feeling uncomfortable.
[0039]
Further, according to the present invention, since the audible frequency component of the magnetic sound generated from the electric motor 1 can be reduced, resonance with the audible frequency component of the magnetic sound generated from the column shaft of the electric power steering device can be avoided. Therefore, it is possible to further suppress discomfort to the occupant.
[0040]
[Other Examples]
The sliding width h of the brush 51 described above is 4.0 mm. The magnetic sound generated from the electric motor 1 when the sliding width h of the brush 51 is 2.0 mm will be described based on experimental data.
[0041]
Similarly to the case where the sliding width h is 4.0 mm, when the circumferential centers of the negative brushes 51 c and 51 d are shifted counterclockwise by 0 to 2 mm (0 to 8 °) with respect to the imaginary line R, 1 FIG. 8 shows the resistance fluctuation amount of the entire electric motor 1 of the next component A to the fourth component D.
[0042]
As shown in FIG. 8, by shifting the circumferential centers of the negative brushes 51 c and 51 d in the counterclockwise direction with respect to the imaginary line R, the resistance variation of the entire electric motor 1 of the primary component A which is not an audible frequency component is obtained. The amount is increasing.
[0043]
Here, based on the experimental data of the second-order component B to the fourth-order component D shown in FIG. 8, the audible frequency at the shift amount in the circumferential direction of the circumferential center of the negative brushes 51c and 51d is calculated from the above equation (2). The index value S was calculated.
[0044]
FIG. 9 shows the index value S calculated from the above equation (2). As shown in FIG. 9, the index value S is smaller than the conventional value of 0 mm when the amount of shift of the circumferential center of the negative brushes 51c and 51d in the counterclockwise direction is in the range of 1.0 mm to 1.3 mm. In other words, the index value S becomes smaller than the conventional value of 0 ° when the amount of shift of the circumferential center of the negative brushes 51c and 51d in the counterclockwise direction is in the range of 4.0 ° to 5.2 °.
[0045]
From this, the fact that the index value S becomes smaller means that the audible frequency component of the magnetic sound generated from the electric motor 1 is reduced, and thus the same effect as when the sliding contact width h is 4.0 mm. Can be obtained.
[0046]
Note that when the sliding contact width h of the brush 51 is 2 to 6 mm when the circumferential centers of the negative brushes 51 c and 51 d are shifted counterclockwise by 1 mm (4 °) with respect to the virtual line R, the electric motor of the present invention is used. When the index value S of the audible frequency component of the magnetic sound that can be heard by the occupant in the vehicle when 1 is used in the electric power steering device is calculated, a graph shown in FIG. 10 is obtained.
[0047]
As shown in FIG. 10, when the sliding width h of the brush 51 is 4.0 mm, the index value S becomes the smallest.
[Brief description of the drawings]
FIG. 1 is a front view of a brush device viewed from an axial direction of an electric motor according to an embodiment.
FIG. 2 is a sectional view taken along the line II-II of FIG.
FIG. 3 is a diagram showing a positional relationship between brushes.
4A is an axial perspective view of the brush, and FIG. 4B is a cross-sectional view taken along the line IV-IV of FIG.
FIG. 5 is an enlarged view of a part of the commutator.
FIG. 6 is a graph showing the amount of change in resistance for each frequency of magnetic noise generated from an electric motor with respect to the amount of brush displacement when the brush sliding width is 4 mm.
7 is a graph showing an index value of an audible frequency component of a magnetic sound generated from the electric motor based on the graph of FIG. 6;
FIG. 8 is a graph showing the amount of resistance change for each frequency of magnetic sound generated from the electric motor with respect to the amount of brush displacement when the brush sliding width is 2 mm.
9 is a graph showing an index value of an audible frequency component of a magnetic sound generated from the electric motor based on the graph of FIG.
FIG. 10 is a graph showing an index value of a variation amount of a current flowing through an electric motor when a sliding contact width of a brush is changed.
[Explanation of symbols]
1. Electric motor,
2. Armature core,
3 ... shaft,
4 ... magnet,
5 brush device,
6 ... commutator,
7 ... York,
8 ... housing,
51 ... brush,
52: brush holder,
53 ... Spring,
61 ... segment.

Claims (5)

An armature core wound with coils,
A commutator having a plurality of segments that are electrically connected to the coil, and are provided with a constant gap over the entire circumference;
A brush on the positive electrode side and a brush on the negative electrode side slidably provided on the outer periphery of the segment,
When the circumferential center of the brush on the positive side faces the circumferential center of the segment, the brush on the negative side faces the gap, and the circumferential center extends from the center of the commutator from the circumferential center of the gap. An electric motor, which is provided so as to be circumferentially offset from a line. The four brushes are provided at substantially 90-degree intervals in the circumferential direction with respect to the center of the commutator,
A first brush and a second brush on the positive electrode side are provided to face the center of the commutator;
A third brush and a fourth brush on the negative electrode side are provided to face the center of the commutator,
The number of segments is 22,
The circumferential width of the first to fourth brushes in sliding contact with the segment is substantially the same as the circumferential distance from the circumferential center of the gap to the circumferential center of the adjacent gap,
Four magnets provided on the outer peripheral side of the armature core are provided at intervals of approximately 90 degrees in the circumferential direction with respect to the center of the commutator,
When the circumferential center of the first and second brushes faces the circumferential center of the segment, the third and fourth brushes face the gap, and the circumferential center is the circumferential center of the gap. 2. The electric motor according to claim 1, wherein the electric motor is provided at a distance from the imaginary line by x ° expressed by the following relationship in the circumferential direction.
3.2 ≦ x ≦ 6.4 The four brushes are provided at substantially 90-degree intervals in the circumferential direction with respect to the center of the commutator,
A first brush and a second brush on the positive electrode side are provided to face the center of the commutator;
A third brush and a fourth brush on the negative electrode side are provided to face the center of the commutator,
The number of segments is 22,
The circumferential width of the first to fourth brushes in sliding contact with the segment is substantially half the circumferential distance from the circumferential center of the gap to the circumferential center of the adjacent gap,
Four magnetic poles provided on the outer peripheral side of the armature core are provided at substantially 90-degree intervals in the circumferential direction with respect to the center of the commutator,
When the circumferential center of the first and second brushes faces the circumferential center of the segment, the third and fourth brushes face the gap, and the circumferential center is the circumferential center of the gap. 2. The electric motor according to claim 1, wherein the electric motor is provided at a distance from the imaginary line by x ° expressed by the following relationship in the circumferential direction.
4.0 ≦ x ≦ 5.2 3. The electric motor according to claim 2, wherein a circumferential width of the first to fourth brushes in sliding contact with the segment is approximately 4.0 mm. The electric motor according to any one of claims 1 to 4, wherein the electric motor is used in an electric power steering device for assisting a steering force of a steering.

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