JP5764393B2 - DC motor - Google Patents

Description

  The present invention relates to a DC motor, and more particularly, to a brushed DC motor having a multi-pole multi-slot structure.

  Increasing the number of poles and the number of slots is already known as a measure to reduce cogging torque and suppress rotation unevenness (rotation ripple) in a DC motor using a permanent magnet or the like as a stator. Further, as the number of slots increases, the number of commutator pieces (segments) constituting the commutator also increases, so the width of each commutator piece (the length in the rotational direction of the rotor) becomes shorter. Here, the shorter the width of the commutator pieces, the easier the short circuit between the commutator pieces caused by the power supply brush abutting simultaneously on the plurality of commutator pieces, and the coils connected to the commutator pieces. The number of so-called short-circuit coils will also increase. Such an increase in the number of short-circuited coils may disturb the rectification, and the effect of suppressing rotation unevenness by increasing the number of poles or the number of slots may not be effectively achieved.

  Measures have already been taken for the above problems (see, for example, Patent Document 1). In the motor described in Patent Document 1, the width of the brush (more specifically, rotation that contacts the commutator). The occurrence of a short-circuited coil is avoided by setting the direction arc length) to 1/20 or less of the outer peripheral length of the commutator.

JP 2002-209362 A

However, in the technique disclosed in Patent Document 1, as the width of the brush is narrowed, the area of the contact surface with the commutator is reduced and the current density is increased. Life expectancy will be shortened.
Accordingly, an object of the present invention is to provide a DC motor capable of suppressing rotational ripple without shortening the life of the brush.

According to the DC motor of the present invention, the problem is that an armature that rotates in the rotation direction and a plurality of commutator pieces that are provided in the armature and are arranged at equal intervals along the rotation direction. A magnetic flux wound around the core of the armature and the coil connected to the commutator piece, and arranged so that the magnetic poles change at regular intervals along the rotation direction. A field body for generating, and an anode having a contact surface that contacts each of the plurality of commutator pieces for flowing an exciting current through the coil, and arranged so as to be arranged at equal intervals along the rotation direction A direct current motor comprising a brush and a cathode brush, wherein the contact surfaces of both the anode brush and the cathode brush are curved in an arc shape along the rotation direction, and one of the two In the rotation direction of the contact surface Width, widely than a width in the rotational direction of the other of said abutment surface, the outer peripheral length of the commutator segments is d, the width of the gap of the commutator segments and t, the equivalent of the anode brush When the width of the contact surface in the rotation direction is b1, and the width of the contact surface of the cathode brush in the rotation direction is b2, the following equation (1) is satisfied .
(D−b1) / 2 + t = (b2−t) / 2 (1)
If the width of the brush is set wide, the area of the contact surface of the brush is expanded by the amount corresponding to the wide width, the current density is reduced, and shortening of the life of the brush can be prevented. However, on the other hand, if the width of the brush is set wide, a short circuit coil is likely to be generated. In other words, the generation of short-circuited coils and the life of the brush are in a trade-off relationship, and in consideration of such a relationship, in the DC motor of the present invention, the width of one brush of the anode brush and the cathode brush is set to the other brush. It is wider than the width. Therefore, with the DC motor of the present invention, the deterioration of the brush (specifically, the brush with the wider width) is suppressed while minimizing the occurrence of short-circuit coils, and the motor life is shortened. It becomes possible to prevent. In addition, the difference in width between the anode brush and the cathode brush causes the brush rectification timing to become unequal pitches, and regular vibrations due to the motor structure are dispersed. Leading to a reduction in
Furthermore, by forming the anode brush and the cathode brush with the width of the contact surface satisfying the above formula (1), it is possible to suppress the number of short-circuited coils during motor rotation. In other words, even if the width of one brush is made wider than the width of the other brush, it is possible to keep the decrease in the utilization factor of the coil to a minimum.

In the DC motor, a curve indicating a change in the magnetic flux density of the field magnetic flux with respect to the rotation angle of the armature is a first curve, and the coil is formed inside the field body with the rotation of the armature. When the second curve showing the change with respect to the rotation angle of the magnetic flux density of the combined magnetic flux obtained by combining the magnetic flux generated by the rotation of the magnetic field and the field magnetic flux, the one contact surface with respect to the rotation angle It is more preferable that the difference between the width in the rotation direction and the width of the other contact surface in the rotation direction is a length corresponding to the phase difference between the first curve and the second curve. is there.
With such a configuration, it is possible to obtain the above-described effects (effects obtained by making the width of one brush wider than the width of the other brush) without reducing motor performance. More specifically, as the armature rotates, the coil rotates inside the field body to generate magnetic flux (hereinafter also referred to as inhibition magnetic flux), and the motor output decreases due to the inhibition magnetic flux. Here, if the relative position of each brush with respect to the field body is shifted by an amount corresponding to the deviation due to the inhibition magnetic flux (that is, the above phase difference), it is possible to suppress a decrease in motor output caused by the inhibition magnetic flux. On the other hand, instead of shifting the relative position, the reduction in motor output can be suppressed even when the width of the brush is increased by the amount of the shift. However, as described above, if the widths of both the anode brush and the cathode brush are set wide, a short-circuit coil is likely to be generated. Therefore, by reducing only the width of one of the brushes, the reduction in motor output is suppressed. It is possible to extend the life of the brush.

  In the DC motor, the field body includes a plurality of N-pole magnet pieces and the same number of S-pole magnet pieces as the N-pole magnet pieces, and each of the N-pole magnet pieces and the S-pole magnet pieces. Are arranged at equal intervals along the rotation direction, and arranged so that the N-pole magnet pieces and the S-pole magnet pieces are arranged alternately along the rotation direction. A plurality of sets are provided, and each of the anode brush and the cathode brush has a central position in the rotation direction that is closest to the plurality of N-pole magnet pieces and the plurality of S-pole magnet pieces. It is even more preferable that the magnet pieces are arranged so as to overlap the center position in the rotation direction.

In addition, a winding is formed by forming a plurality of the coils on the core, and the winding has a pressure equalizing line that connects points of the winding that should have the same potential. And more preferred.
With such a configuration, since the number of brushes can be reduced in a motor having a multi-pole multi-slot structure, it is possible to reduce the number of parts and the sliding loss of the brush.

If the width of the brush is set wider, the area of the contact surface of the brush will be increased by the width, and the current density will be reduced, preventing the shortening of the life of the brush. If the width of is set wide, a short-circuit coil is likely to be generated. That is, there is a trade-off between the occurrence of a short-circuit coil and the life of the brush. Considering such a relationship, in the DC motor of the present invention, the width of one brush of the anode brush and the cathode brush is made wider than the width of the other brush, thereby minimizing the occurrence of a short-circuit coil. , It becomes possible to extend the life of the brush (specifically, the brush with the wider width). Furthermore, since the widths of the anode brush and the cathode brush are different, the rectification timing of the brush becomes unequal pitch, the regular vibration caused by the motor structure is dispersed, and the motor vibration is reduced. Furthermore, even if the width of one brush is made wider than the width of the other brush, it is possible to keep the reduction in the coil utilization rate to a minimum.

It is a schematic cross section of the DC motor according to the present embodiment. It is a figure which shows the core of an armature. It is a figure which shows the positional relationship of a field body, a commutator, and a brush. It is a development view of a winding structure. It is a related figure of the rotation angle of an armature and magnetic flux density. It is a figure which shows the precondition at the time of setting the width | variety of a brush.

  Hereinafter, a DC motor according to an embodiment of the present invention (hereinafter, this embodiment) will be described with reference to FIGS. 1A to 5. FIG. 1A is a schematic cross-sectional view of a DC motor according to the present embodiment. FIG. 1B is a diagram illustrating an armature core. FIG. 2 is a diagram illustrating a positional relationship among the field body, the commutator, and the brush. FIG. 3 is a development view of the winding structure. FIG. 4 is a relationship diagram between the rotation angle of the armature and the magnetic flux density. FIG. 5 is a diagram showing preconditions for setting the brush width.

  The DC motor according to the present embodiment (hereinafter simply referred to as “motor 1”) is a motor having a multi-pole multi-slot structure (in the following description, a 4-pole 10-slot structure), as shown in FIG. 1A. The housing 2 has a bottom cylindrical housing 2, and the housing 2 includes an armature 3 (rotor), a substantially annular field body 4 (stator), and two sets of power supply brushes 20 and 21.

  The armature 3 is accommodated in the housing 2 so as to be rotatable about the shaft 5 by supporting the shaft 5 forming the rotation axis thereof on the housing 2 via the bearings 10a and 10b. In particular, the armature 3 of the present embodiment can rotate in both forward and reverse directions.

  As shown in FIGS. 1A and 1B, the armature 3 has a core 6 made of a plurality of electromagnetic steel plates laminated through the shaft 5, and an outer periphery of the core 6 is provided around the core 6. A field body 4 is arranged so as to surround it. Ten slots 7a to 7j are provided at equal intervals along the circumferential direction on the outer peripheral portion of the core 6, and teeth 8a to 8j are formed between the slots. A coil C made of a conductive wire is wound around each of the teeth 8 a to 8 j, and a plurality of coils C are formed on the core 6 to form a winding WL. In this embodiment, as shown in FIG. 3, each coil C is wound between two teeth (so-called distributed winding).

  The armature 3 (more specifically, one end portion of the shaft 5) is also provided with a commutator 11 composed of a plurality (10 in this embodiment) of commutator pieces 9a to 9j. The plurality of commutator pieces 9 a to 9 j are arranged so as to be arranged at equal intervals along the outer circumferential direction of the shaft 5, in other words, along the rotation direction of the armature 3. Moreover, the terminal of the above-mentioned coil C is connected to each commutator piece 9a-9j. As a result, when the power supply brushes 20 and 21 are in sliding contact with the commutator pieces 9a to 9j, an exciting current flows through the coil C.

  Note that predetermined commutator pieces 9a to 9j (specifically, commutator pieces 9a to 9j having an interval of 216 degrees from each other) are short-circuited by a short-circuit line SL. As a result, each of the power supply brushes 20 and 21 rectifies the same coil C, and is the same as when there are two sets of two types of power supply brushes 20 and 21 (that is, when there are four power supply brushes). Acts.

  The field body 4 is for generating a field magnetic flux, and includes a plurality of N-pole magnet pieces 12 and the same number of S-pole magnet pieces 13 as the N-pole magnet pieces 12. More specifically, in the present embodiment, the number of magnetic poles of the motor 1 is four, and two N-pole magnet pieces 12 and two S-pole magnet pieces 13 are provided. Each of the N-pole magnet pieces 12 and the S-pole magnet pieces 13 is arranged at equal intervals (90-degree intervals) along the inner circumferential direction of the housing 2, in other words, the rotation direction of the armature 3, and in the same direction. The N-pole magnet pieces 12 and the S-pole magnet pieces 13 are alternately arranged along the inner peripheral surface of the housing 2. That is, the field body 4 is arranged so that the magnetic poles change at regular intervals along the rotation direction of the armature 3.

  The power supply brushes 20 and 21 are arranged around the commutator 3 and abut against each of the plurality of commutator pieces 9a to 9j in order to cause an exciting current to flow through the coil C. That is, each of the power supply brushes 20, 21 includes a contact surface TS at an end (tip) on the side facing the commutator 3 in the radial direction of the commutator 3. The commutator pieces 9a to 9j are brought into sliding contact. Here, the contact surface TS is curved in an arc shape along the outer periphery of the commutator 3, that is, the rotation direction of the armature 3, so as to match the outer peripheral surface of each commutator piece 9 a to 9 j. On the other hand, lead wires (not shown) are connected to the power supply brushes 20 and 21. As a result, an exciting current flows through each coil C from the external power source (not shown) through the lead wire, the power supply brushes 20 and 21 and the commutator 3.

  The power supply brushes 20 and 21 according to the present embodiment will be described in detail. In the present embodiment, one set of a combination of an anode brush and a cathode brush is provided, and equidistant (90 degree intervals) along the rotation direction of the armature 3. It is arranged to line up. In the case shown in FIG. 2, the power supply brush 20 corresponds to an anode brush, and the power supply brush 21 corresponds to a cathode brush.

  Further, in the present embodiment, as shown in FIG. 2, each power supply brush 20, 21 has a central position (correctly, the central position in the rotation direction of the armature 3, and the same applies hereinafter). Of the pole magnet piece 12 and the plurality of S pole magnet pieces 13, they are arranged so as to overlap the center position of the nearest magnet piece. For example, the center position of the power supply brush 20 overlaps the center position of the nearest N-pole magnet piece 12.

  And in this embodiment, the width | variety of one brush is larger than the width | variety of the other brush among an anode brush and a cathode brush. Here, the width of the brush means the arc length (width in the rotation direction of the armature 3) of the contact surface TS of each of the power supply brushes 20 and 21. As described above, since the width of one brush is wider than the width of the other brush, uneven rotation (ripple) during motor rotation can be suppressed without shortening the life of the brush.

More specifically, if the width of the brush is increased, the area of the contact surface TS is increased correspondingly, the current density is reduced, and the shortening of the life of the brush can be prevented. However, on the other hand, if the width of the brush is set wide, a short circuit coil is likely to be generated. In other words, the generation of short-circuited coils and the life of the brush are in a trade-off relationship, and in consideration of such a relationship, in the DC motor of the present invention, the width of one brush of the anode brush and the cathode brush is set to the other brush. It is wider than the width. Thereby, in the motor 1 according to the present embodiment, it is possible to extend the life of the brush having a wider width while minimizing the occurrence of short-circuit coils.
Further, since the widths of the anode brush and the cathode brush are different, the brush rectification timing becomes unequal pitch, the regular vibration caused by the motor structure is dispersed, and the motor vibration is reduced.

  The above effect will be described in detail below, taking as an example a case where the width of the anode brush is wider than the width of the cathode brush. However, the following case is only an example, and a configuration in which the width of the cathode brush is wider than the width of the anode brush may be employed. In the following description, the length (arc length) along the rotation direction of the armature 3 including the width of the brush is expressed by an angle (size of the central angle) corresponding to the length. To do.

  In this case, as described above, the width of the anode brush is wider than the width of the cathode brush. In the configuration shown in FIG. 2, the width of the power supply brush 20 corresponding to the anode brush is the power supply corresponding to the cathode brush. It is narrower than the width of the brush 21.

First, the procedure for determining the difference in brush width will be described with reference to FIG.
In FIG. 4, a curve indicated by a solid line is a curve indicating a change in the magnetic flux density of the field magnetic flux with respect to the rotation angle (electrical angle) of the armature 3. Equivalent). In FIG. 4, a curve indicated by a broken line indicates a magnetic flux (inhibition magnetic flux) generated by the rotation of the coil C inside the field body 4 with the rotation of the armature 3 with respect to the rotation angle of the armature 3. It is a curve showing a change in magnetic field strength, and is hereinafter referred to as an inhibition magnetic flux curve. Further, in FIG. 4, a curve indicated by a thick solid line is a curve indicating a change in the magnetic flux density of the combined magnetic flux obtained by combining the inhibition magnetic flux and the field magnetic flux with respect to the rotation angle of the armature 3. It is called a curve (corresponding to the second curve).

  Referring to FIG. 4, the field magnetic flux curve is obtained, for example, by effective magnetic flux calculation, and is expressed as a sin function with the magnetic flux density of the gap magnetic flux as a maximum value. On the other hand, the inhibition magnetic flux curve is obtained, for example, by demagnetization analysis, and is expressed as a cos function with the maximum value of the magnetic field strength corresponding to the magnetomotive force when the rated excitation current flows through the coil C. The magnetic flux curve is shifted by about 90 degrees. Further, the composite magnetic flux curve reflects that the field magnetic flux is affected by the inhibition magnetic flux, and is shifted by a predetermined angle (hereinafter referred to as a shift angle) with respect to the field magnetic flux curve. This shift angle corresponds to the phase difference between the field magnetic flux curve and the composite magnetic flux curve. In the motor 1 with 4 poles and 10 slots, the electrical angle is about 6 degrees (that is, the mechanical angle is 3 degrees on one side). .

  Then, the shift angle obtained as described above is adopted as the difference in brush width. By determining the difference in the width of the brush by this procedure and adopting the difference, the width of one power supply brush 20 can be made wider than the width of the other power supply brush 21 without deteriorating the motor performance. .

This makes it possible to extend the life of the brush having a wide width while suppressing an increase in current density. Note that, by widening the width of one of the brushes, the coil C that is the source of the inhibition magnetic flux is short-circuited, and the effect of suppressing the reduction in motor output is more effectively achieved.
Next, a procedure for determining the width of each of the anode brush and the cathode brush will be described.

  In the 4-pole 10-slit structure, the outer diameter of the commutator 11, the outer peripheral length (arc length) of the commutator pieces 9a to 9j, the width of the gap between the commutator pieces, and the pitch between the commutator pieces are determined in advance. The values are as shown in FIG. On the other hand, as described above, the difference between the difference between the anode brush and the width of the cathode brush corresponds to the shift angle. The interval between the anode brush and the cathode brush (more specifically, the length between the central positions of the brushes) is 90 degrees. Further, the center position of each brush overlaps the center position of the magnet pieces 12 and 13.

Here, the condition for determining the width of each of the anode brush and the cathode brush is to minimize the number of short-circuited coils, and the configuration of the present embodiment (the configuration including two anode brushes and two cathode brushes). ), It is limited to two coils. In other words, the condition is that the four coils do not short-circuit at the same time. When the widths of the anode brush and the cathode brush are determined under such conditions, the following equations are established for the widths of the anode brush and the cathode brush.
(Peripheral length of commutator piece−width of anode brush) / 2 + width of gap between commutator pieces = (width of cathode brush−width of gap between commutator pieces) / 2 (1)

  Substituting the values shown in FIG. 5 into the above equation (1) and considering that the width of the anode brush is wider than the width of the cathode brush by the shift angle, the widths of the anode brush and the cathode brush are calculated. It becomes like this. More specifically, 24.3 degrees are obtained as the solution of the width of the anode brush, and 18.3 degrees are obtained as the solution of the width of the cathode brush.

Then, by forming the anode brush and the cathode brush with a width corresponding to the calculation result, it is possible to suppress the number of short-circuited coils during motor rotation. In other words, by adopting the above calculation result, even if one brush width is made wider than the other brush width, it is possible to keep the decrease in the coil utilization factor to a minimum.
<< Other Embodiments >>
The embodiments described above are for facilitating the understanding of the present invention, and do not limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof.

  In the above embodiment, the armature 3 rotates in both forward and reverse directions. However, the present invention is not limited to this, and the armature 3 may rotate only in the forward rotation direction (one direction). .

  Further, in the above embodiment, the anode brush and the cathode brush are arranged at substantially the center position of the field body 4. However, the present invention is not limited to this, and the coil C (winding WL) and the commutator are not limited thereto. It is good also as changing the arrangement position of each brush suitably according to the connection position.

  In the above embodiment, two power supply brushes 20 and 21 are provided. However, the present invention is not limited to this, and the number of anode brushes and cathode brushes to be provided can be set to (number of magnetic poles / 2) or less.

  More specifically, when the points that should theoretically have the same potential among the windings WL wound around the core 6 of the armature 3 are connected by a pressure equalizing line (not shown), the anode to be provided The number of brushes and cathode brushes can be set to (number of magnetic poles / 2) or less. By using pressure equalization lines in this way, the number of brushes can be reduced in a motor with a multi-pole multi-slot structure. As a result, it is possible to reduce the number of parts and the sliding loss of the brush. become.

  Note that the pressure equalizing line may be formed by extending a part of the winding WL. In other words, the winding WL itself may have a pressure equalizing line that connects points of the winding WL that should have the same potential. However, the present invention is not limited to this, and the pressure equalizing line may be formed by a conductor different from the winding WL. Further, commutator pieces 9a to 9j to which the winding WL is connected are included at the points where the winding WL should have the same potential. That is, the commutator pieces 9a to 9j may be connected to each other by a pressure equalizing line.

  In the above embodiment, a DC motor having a 4-pole 10-slot structure has been described as an example. However, the present invention is not limited to this, and the number of magnetic poles and the number of slots are different from those in the above embodiment. Basically, the number of magnetic poles is preferably 2n (n is a natural number) and the number of slots is 4m + 2 (m is a natural number). Note that the effect of the present invention becomes more significant as the number of slots (in other words, the number of commutator pieces) increases.

In the above-described embodiment, the method for obtaining the width of each brush has been described in a configuration in which two sets of anode brushes and cathode brushes are provided. That is, in the case of the motor 1 having a 4-pole 10-slot structure, the case where the widths of both the anode brush and the cathode brush are obtained by substituting values such as the outer peripheral length of the commutator piece into the above formula (1) has been described. .
On the other hand, in the case where three or more sets of anode brushes and cathode brushes are provided, a relational expression related to the width of the anode brush and the width of the cathode brush is obtained in the same relational expression as in the above formula (1). Various values may be input to obtain the widths of both the anode brush and the cathode brush. Note that the above relational expression can be derived by numerical analysis or the like.

1 motor, 2 housing, 3 armature, 4 field body,
5 shafts, 6 cores, 7a-7j slots,
8a-8j teeth, 9a-9j commutator pieces,
10a, 10b bearing, 11 commutator,
12 N-pole magnet pieces, 13 S-pole magnet pieces,
20, 21 Power supply brush,
C coil, SL short-circuit wire, TS contact surface, WL winding

Claims (4)

An armature that rotates in the direction of rotation;
A commutator comprising a plurality of commutator pieces provided in the armature and arranged so as to be arranged at equal intervals along the rotation direction;
A coil wound around the core of the armature and connected to the commutator piece;
A field body for generating a field magnetic flux, arranged such that the magnetic poles change at regular intervals along the rotation direction;
An anode brush and a cathode brush provided with contact surfaces that contact each of the plurality of commutator pieces for flowing an exciting current through the coil, and arranged at equal intervals along the rotation direction; A direct current motor,
The contact surfaces of both the anode brush and the cathode brush are curved in an arc shape along the rotation direction, and the width of one of the contact surfaces in the rotation direction is the other of the both. the widely than a width in the rotational direction of the abutment surface,
The outer peripheral length of the commutator pieces is d, the width of the gap between the commutator pieces is t, the width of the contact surface of the anode brush in the rotational direction is b1, and the contact surface of the cathode brush The following formula (1) is materialized when the width in the said rotation direction is set to b2 .
(D−b1) / 2 + t = (b2−t) / 2 (1) A curve indicating a change in the magnetic flux density of the field magnetic flux with respect to the rotation angle of the armature is a first curve
A second change of the magnetic flux density of the combined magnetic flux generated by the magnetic field generated by the rotation of the coil inside the field body as the armature rotates and the field magnetic flux with respect to the rotation angle. When it is a curve
The difference between the width of one contact surface in the rotation direction and the width of the other contact surface in the rotation direction with respect to the rotation angle is a phase difference between the first curve and the second curve. The DC motor according to claim 1, wherein the DC motor has a corresponding length. The field body includes a plurality of N-pole magnet pieces and the same number of S-pole magnet pieces as the N-pole magnet pieces,
Each of the N-pole magnet pieces and the S-pole magnet pieces is arranged at equal intervals along the rotation direction, and the N-pole magnet pieces and the S-pole magnet pieces are arranged alternately along the rotation direction. Arranged as
A plurality of sets of the anode brush and the cathode brush are provided,
In each of the anode brush and the cathode brush, the center position in the rotation direction of each of the plurality of N-pole magnet pieces and the plurality of S-pole magnet pieces is closest to the rotation of the magnet piece. The direct current motor according to claim 2, wherein the direct current motor is disposed so as to overlap a central position in the direction. A winding is formed by forming a plurality of the coils in the core,
4. The DC motor according to claim 3, wherein the winding includes a pressure equalizing line that connects points of the winding that should have the same potential.

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