JP2011151919A - Power feed brush, dc motor, and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power feed brush for ensuring a high degree of silence from the beginning of use. <P>SOLUTION: A widening part 44 extended in a width direction to extend brush width W1 at the beginning of use is formed at the tip of the power feed brush 24. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power supply brush, a DC motor, and an electric power steering device.

  Generally, in a DC motor with a brush, the power supply brush is formed in a long and substantially rectangular parallelepiped shape. The power supply brush is housed in a brush holder and biased by a coil spring so that the tip thereof is in sliding contact with a plurality of segments aligned on the peripheral surface of the commutator.

  Further, in such a power supply brush, an early stabilization of the sliding contact state at the beginning of use, that is, so-called “familiarity” is one problem. Conventionally, as shown in FIG. 8, a tapered surface 53 is inclined on one side surface (upper surface in FIG. 8) of the power supply brush 50 toward the tip end side in sliding contact with each segment 52 on the commutator 51 side. Is known (for example, see Patent Document 1 (FIG. 1)). That is, by forming such a tapered surface 53, the sliding contact area of the tip portion that comes into sliding contact with each segment 52 on the commutator 51 side at the beginning of use is reduced. Then, by promoting the wear of the tip portion that becomes the initial sliding contact portion, the conformability is improved.

  Here, in the power supply brush 50 having the tapered surface 53 inclined to the tip side, the tapered surface 53 is positioned in the axial direction of the commutator 51 (in the example shown in the figure, in the axial direction upper side). Be placed. That is, as shown in FIG. 9, when the brush width (the width of the sliding contact surface) is wide (the waveform M shown by the solid line in the figure) and when the brush width is narrow (the waveform N shown by the one-dot chain line in the figure). If the brush width is narrow, the rectification is completed in a shorter time. When the rectification time is short as described above, the steep current change may cause generation of vibration and sound. For this reason, even if it is the structure which accelerates | stimulates the wear of the front-end | tip part used as an initial sliding contact part by making the sliding surface area at the time of use small by formation of the above taper surfaces 53, the brush width is before and after the wear. The tapered surface 53 is disposed in the axial direction of the commutator 51 so as not to change.

JP 2006-141200 A

  However, as shown in FIG. 10, the unused power supply brush 50 is often formed at the corners (both ends in the width direction) of the front end surface 54 due to manufacturing tolerances or subsequent wear. Since the curved portion 55 is present, the brush width W1 at the beginning of use is narrower than the original brush width W0. For this reason, at the beginning of use, regardless of the taper surface 53, the narrowness of the brush width due to the presence of the curved portion 55 is a cause of generating sound and vibration. There was still room for improvement.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a power supply brush, a DC motor, and an electric power steering device that can ensure high silence from the beginning of use. is there.

  In order to solve the above problems, the invention according to claim 1 is a power supply brush that is in sliding contact with each segment provided on the peripheral surface of the commutator, and is used at a tip portion that is in sliding contact with each segment. The gist is that a widened portion extending in the width direction is provided to expand the initial brush width.

  According to the above configuration, even when there is a curved portion formed due to tolerance at the time of manufacture, subsequent wear, or the like, at the corners (both ends in the width direction) of the tip surface that becomes the sliding contact surface at the beginning of use. A sufficient brush width can be secured from the beginning of its use. As a result, it is possible to prevent the brush width at the beginning of use from becoming narrower than the original brush width, and to suppress the generation of vibration and sound due to a sudden current change at the time of rectification. And thereby, high silence can be ensured from the beginning of use.

The gist of the invention according to claim 2 is that the widened portion is formed such that the brush width at the beginning of use is equal to or larger than the brush width after the widened portion is worn.
In other words, from the viewpoint of improving the quietness, the effect that the brush width at the beginning of use is equal to or larger than the original brush width is less affected than when it is small. Therefore, as in the above configuration, considering the existence of the curved portion formed due to manufacturing tolerances and subsequent wear, etc., the brush width at the beginning of use is set large in advance, so that the quietness from the beginning is used. A sufficient brush width can be ensured to ensure the property. In many cases, the size of such a curved portion can be predicted to some extent in advance. Therefore, in this case, the maximum width of the widened portion may be a length obtained by adding the expected size of the curved portion (length in the width direction) to the original brush width after the widened portion is worn.

The gist of the invention described in claim 3 is a DC motor provided with the power supply brush according to claim 1 or claim 2.
According to the said structure, the direct-current motor which can ensure high silence from the beginning of use can be provided.

The gist of the invention described in claim 4 is the electric power steering apparatus provided with the DC motor according to claim 3.
According to the said structure, the electric power steering apparatus which can ensure high silence from the beginning of use can be provided.

  According to the present invention, it is possible to provide a power supply brush, a DC motor, and an electric power steering device that can ensure high silence from the beginning of use.

The schematic block diagram of an electric power steering device (EPS). Sectional drawing of a motor. The perspective view of an electric power feeding brush. (A) Side view of power supply brush, (b) Front view of power supply brush. AA sectional drawing. The perspective view of the electric power feeding brush of another example. (A) Side view of another example of the power supply brush, (b) Front view of another example of the power supply brush. Explanatory drawing which shows the electric power feeding brush which slidably contacts with a commutator (each segment). Explanatory drawing which shows the relationship between brush width and rectification | straightening time. Explanatory drawing which shows the relationship between the curved part formed in the corner | angular part (width direction both ends) of a feed brush front end surface, and the brush width.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in the electric power steering apparatus (EPS) 1 of this embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 3a, an intermediate shaft 3b, and a pinion shaft 3c. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 6 connected to both ends of the rack shaft 5, whereby the steering angle of the steered wheels 7. That is, the traveling direction of the vehicle is changed.

  Further, the EPS 1 includes an EPS actuator 10 as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system, and an ECU 11 as a control unit that controls the operation of the EPS actuator 10. .

  The EPS actuator 10 of the present embodiment is configured as a so-called column-type EPS actuator in which a motor 12 that is a drive source is drivingly connected to a column shaft 3 a via a speed reduction mechanism 13. In the present embodiment, a brushed DC motor is employed as the motor 12, and the motor 12 rotates when receiving drive power from the ECU 11. The EPS actuator 10 is configured to apply the motor torque as an assist force to the steering system by decelerating the rotation of the motor 12 and transmitting it to the column shaft 3a.

  On the other hand, a torque sensor 14 and a vehicle speed sensor 15 are connected to the ECU 11, and the ECU 11 should be applied to the steering system based on the steering torque τ and the vehicle speed V detected by the torque sensor 14 and the vehicle speed sensor 15. The assist force (target assist force) is calculated. Then, in order to generate a motor torque corresponding to the target assist force, by supplying driving power to the motor 12, the operation of the EPS actuator 10 using the motor 12 as a driving source, that is, the assist applied to the steering system. It is configured to control the force.

Next, the configuration of the motor that is the drive source of the EPS of the present embodiment will be described.
As shown in FIG. 2, the motor 12 according to this embodiment includes a stator 22 formed by fixing a permanent magnet 21 to the inner periphery of a yoke 20 having a substantially bottomed cylindrical shape, and is rotatable inside the permanent magnet 21. Are configured as a DC motor with a brush including an armature 23 supported on the armature 23 and a power supply brush 24 that supplies power to the armature 23.

  More specifically, the armature 23 includes an armature core 26 and a commutator 27 that are fixed to the rotary shaft 25 and rotate together with the rotary shaft 25. In the present embodiment, the rotary shaft 25 is pivotally supported by bearings 29a and 29b provided on the housing 28 that closes the bottom 20a of the yoke 20 and the opening end 20b of the yoke 20, so that the axis of the yoke 20 is aligned. It is arranged along. As a result, the armature 23 is rotatably accommodated in the yoke 20 with the armature core 26 disposed at the axial position corresponding to the permanent magnet 21.

  More specifically, the armature core 26 has a plurality (22 in the present embodiment) of teeth 30 that extend radially outward in the radial direction. (Motor coil) 31 is wound. A plurality (four poles in this embodiment) of magnetic poles are formed along the circumferential direction of the permanent magnet 21 facing the armature core 26 on the stator 22 side.

  On the other hand, the commutator 27 is formed by fixing a plurality (22 in this embodiment) of segments 33 on the peripheral surface of the cylindrical body 32 fixed to the rotating shaft 25. Specifically, the cylindrical body 32 is arranged in the yoke 20 on the opening end 20b side (lower side in FIG. 2) from the armature core 26, and each segment 33 is arranged around the cylindrical body 32. It is aligned and arranged at predetermined intervals along the surface. Each segment 33 is connected to a part of the winding 31 wound around each of the teeth 30.

  Further, the motor 12 of the present embodiment has a plurality (four) of power supply brushes 24 arranged along the circumferential direction so as to surround the commutator 27 on the radially outer side of the commutator 27. Each of the power supply brushes 24 is housed in a brush holder 34 and is urged by a coil spring 35 as urging means, whereby the segments 33 disposed on the peripheral surface of the commutator 27 are urged. The tip is in sliding contact.

  More specifically, positive and negative voltages corresponding to the motor rotation are applied to each power supply brush 24 by the ECU 11 as a pair of two that are spaced apart in the circumferential direction at a predetermined angle. The power supply brushes 24 are in sliding contact with the segments 33 corresponding to the rotational position of the commutator 27, thereby energizing the windings 31 connected to the segments 33.

  That is, in the motor 12 of the present embodiment, which is a motor with a brush, the segment 33 that is in sliding contact with each power supply brush 24 is moved by the rotation of the armature 23, thereby switching the energization direction with respect to the winding 31 constituting the motor coil. (Rectification) is performed. The motor 12 generates a motor torque based on an electromagnetic force (electromagnetic attractive force and repulsive force) generated between the winding 31 and each magnetic pole formed on the stator 22 side when the winding 31 is energized. It has a configuration that occurs.

(Brush shape)
Next, the shape of the power supply brush used for the motor of this embodiment will be described.
FIG. 3 is a perspective view of the power supply brush, FIGS. 4A and 4B are a side view and a front view thereof, and FIG.

  As shown in FIGS. 3, 4 (a) and 4 (b), and FIG. 5, the power supply brush 24 of the present embodiment formed in a substantially rectangular parallelepiped shape is rectified with one end in the longitudinal direction as a tip as described above. It is held in a brush holder 34 provided on the radially outer side of the commutator 27 so as to be in sliding contact with the segments 33 arranged in alignment on the peripheral surface of the child 27 (see FIG. 2). The power supply brush 24 of this embodiment has a curved surface (concave surface) in which the front end surface 40 which is a sliding contact surface with each segment 33 on the commutator 27 side in the initial use is matched with the circumferential surface of the commutator 27. Is formed.

  Further, in the power supply brush 24 of the present embodiment, the one side surface (upper surface 41) arranged in the axial direction of the commutator 27 in the use state is a distal end side that is a sliding contact portion with respect to each segment 33 of the commutator 27. A tapered surface 42 that is inclined toward the right side in FIG. 4A is formed.

  That is, if the length in the direction along the axial direction of the commutator 27 in the use state is “height”, by forming such a tapered surface 42, each segment 33 on the commutator 27 side at the beginning of use. The height H1 of the front end surface 40 that becomes the sliding contact surface is lower than the height H0 of the portion where the tapered surface 42 is not formed. In the present embodiment, the sliding contact area at the beginning of use is thereby reduced, and the wear of the tip portion serving as the initial sliding contact portion is promoted, thereby achieving early stabilization of the sliding contact state. It has a configuration.

  Further, in the power supply brush 24 of the present embodiment, the tip portion that becomes the initial sliding contact portion is formed in the width direction (the width of the sliding contact surface) W1 in the width direction (in the use state of the commutator 27). A widened portion 44 extending in the direction along the circumferential direction (left and right direction in FIG. 5) is provided.

  That is, as described above, an unused power supply brush is often formed at the corners (both ends in the width direction) of the front end surface serving as the sliding contact surface due to manufacturing tolerances and subsequent wear. There is a curved portion (see FIG. 10). For this reason, the brush width W1 at the beginning of its use is narrower than the original brush width W0, and as a result, there is a risk that sound and vibration will be generated due to this.

  Considering this point, in the power supply brush 24 of the present embodiment, as described above, the widened portion 44 is formed at the tip portion, thereby ensuring a sufficient brush width from the beginning of use. This makes it possible to ensure high silence from the beginning of use.

  More specifically, in the present embodiment, the widened portion 44 is respectively provided on both side surfaces (width direction side surfaces 45 and 46) arranged in the direction along the circumferential direction of the commutator 27 in the usage state of the power supply brush 24. The protrusions 47 and 48 are formed upright in a manner continuous from the tip surface 40 that is a sliding contact surface with each segment 33 on the commutator 27 side.

  Specifically, in the present embodiment, each of the protrusions 47 and 48 constituting the widened portion 44 has a length L on the tip side in the length direction of the power supply brush 24 (vertical direction in the figure). It is formed in the range shown. The length L is set to be shorter than the length of the portion where the tip portion protrudes from the brush holder 34 when the power supply brush 24 is accommodated in the brush holder 34 at the beginning of use.

  Further, each of the protrusions 47 and 48 is along the side on the front end side (each side on the front end face 40 side) of each of the width direction side surfaces 45 and 46 where the protrusions 47 and 48 are provided. The power supply brush 24 extends in the height direction (the vertical direction in FIGS. 4A and 4B). In the present embodiment, the brush width W1 at the beginning of use is thereby extended over the entire height direction of the front end surface 40 serving as the sliding contact surface.

  Here, even when the widened portion 44 is formed in this way, curved portions are formed at the corners of the widened portion 44, that is, at both ends in the width direction of the distal end surface 40 due to manufacturing tolerances or subsequent wear. 49 is formed. Therefore, in the present embodiment, as shown in FIG. 5, the protrusion amount of each of the protrusions 47 and 48, that is, the maximum width W2 of the widened portion 44 is the brush width of the power supply brush 24 in the unused state, that is, the initial use. The brush width W1 is set to be equal to or larger than the original brush width W0 after the widened portion 44 is worn.

  In other words, from the viewpoint of improving the quietness, the influence when the initial brush width W1 is equal to or larger than the original brush width W0 (W1 ≧ W0) is smaller than that when the brush width W1 is small (W1 <W0). Therefore, in the present embodiment, in consideration of the fact that the curved portions 49 are formed at both ends in the width direction of the tip surface 40, in order to ensure the quietness by setting the brush width W1 at the beginning of use large in advance. In this configuration, a sufficient brush width is secured.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) A widened portion 44 extending in the width direction is formed at the tip of the power supply brush 24 so as to expand the brush width W1 at the beginning of use.

  According to the above configuration, even in the case where the curved portion 49 formed by the tolerance at the time of manufacture or the subsequent wear or the like exists at the corners (both ends in the width direction) of the front end surface 40 serving as the sliding contact surface. A sufficient brush width can be secured from the beginning of use. As a result, it is possible to prevent the initial brush width W1 from becoming narrower than the original brush width W0, and to suppress the generation of vibration and sound due to a sudden current change at the time of rectification. And thereby, high silence can be ensured from the beginning of use.

(2) The maximum width W2 of the widened portion 44 is set such that the brush width W1 at the beginning of use is equal to or larger than the original brush width W0 after the widened portion 44 is worn.
In other words, from the viewpoint of improving the quietness, the influence when the initial brush width W1 is equal to or larger than the original brush width W0 (W1 ≧ W0) is smaller than that when the brush width W1 is small (W1 <W0). Therefore, in consideration of the fact that the curved portions 49 are formed at both ends in the width direction of the tip surface 40 due to manufacturing tolerances and subsequent wear as in the above configuration, the brush width W1 at the beginning of use is increased in advance. By setting, it is possible to ensure a sufficient brush width from the beginning of use to ensure its quietness. In many cases, the size of the curved portions 49 formed at both ends in the width direction of the tip surface 40 can be estimated to some extent in advance. Therefore, the maximum width W2 of the widened portion 44 is preferably a length obtained by adding the expected size (length in the width direction) of the curved portion 49 to the original brush width W0.

  (3) The formation range of the widened portion 44 is longer than the length that the power supply brush 24 protrudes from the brush holder 34 when the power supply brush 24 is accommodated in the brush holder 34 at the beginning of use in the length direction of the power supply brush 24. Is set to be shorter.

According to the above configuration, there is no need to change members other than the power supply brush 24. Further, the change in motor characteristics caused by the formation of the widened portion 44 can be limited to the initial use.
In addition, you may change the said embodiment as follows.

  -In above-mentioned embodiment, although this invention was actualized to the motor 12 of EPS1, you may apply to the motor used for uses other than EPS. Also, when applied to EPS, the invention is not limited to the so-called column type such as EPS 1 of the present embodiment, but may be embodied in other types of EPS such as a so-called rack assist type or a so-called pinion type.

  -In the said embodiment, the taper surface 42 which inclines toward the front end side used as a slidable contact part is formed in one side surface (upper surface 41) arrange | positioned in the axial direction of the commutator 27 in the use condition of this invention. The power supply brush 24 is embodied. However, the present invention is not limited to this, and the present invention may be applied to a configuration that does not have such a tapered surface 42.

  In the above-described embodiment, the protrusions 47 and 48 constituting the widened portion 44 are such that the brush width W1 at the beginning of use is extended over the entire height direction of the tip surface 40 serving as the sliding contact surface. The power supply brush 24 is extended in the height direction (vertical direction in FIGS. 4A and 4B). However, not limited to this, as shown in FIGS. 6 and 7, the height H <b> 2 of the widened portion 44 may be lower than the height H <b> 1 of the distal end surface 40. That is, from the viewpoint of securing the rectification time, the sliding contact area, that is, the height of the sliding contact surface is not particularly problematic. Therefore, even with this configuration, the same effects as those of the above embodiment can be obtained.

Next, technical ideas that can be grasped from the above embodiments will be described together with effects.
(B) A brush holder that houses the power supply brush according to claim 1 or 2, and a biasing means that is provided in the brush holder and biases the power supply brush in a direction protruding from the brush holder. A brush device provided.

  (B) In the brush device according to (b), the widened portion is formed in a range in which the power supply brush is accommodated in the brush holder at the beginning of use in the length direction of the power supply brush. A brush device, wherein the brush device is set to be shorter than a length of the power supply brush protruding from the brush holder.

  According to the said structure, it is not necessary to change about members other than an electric power feeding brush. In addition, the change in motor characteristics caused by the formation of the widened portion can be limited to the beginning of use.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 2 ... Steering, 3 ... Steering shaft, 10 ... EPS actuator, 11 ... ECU, 12 ... Motor, 13 ... Deceleration mechanism, 23 ... Armature, 24 ... Feeding brush, 27 ... Rectification Child, 33 ... segment, 34 ... brush holder, 35 ... coil spring, 40 ... tip surface, 42 ... tapered surface, 44 ... widened portion, 49 ... curved portion, 50 ... feed brush, 51 ... commutator, 52 ... segment, 53: Tapered surface, 54: Tip surface, 55: Curved portion, W0, W1: Brush width, W2: Maximum width.

Claims (4)

A power supply brush that slidably contacts each segment provided on the circumferential surface of the commutator,
A power supply brush characterized in that a widening portion extending in a width direction is provided at a tip portion in sliding contact with each segment so as to expand a brush width at the time of use. The power supply brush according to claim 1,
The power supply brush, wherein the widened portion is formed such that a brush width at an initial use is equal to or greater than a brush width after the widened portion is worn.   A DC motor provided with the power supply brush according to claim 1.   An electric power steering apparatus comprising the DC motor according to claim 3.

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