JP2017175770A - motor - Google Patents

Abstract

A motor capable of suppressing variations in pressing force applied to each of a plurality of brushes is provided. A motor 10 includes a motor case 2 in which a permanent magnet 20 is disposed, a rotor 34 having a shaft 34 and a commutator 33 that are rotatably supported by the motor case 2, and a sliding contact that is in sliding contact with the commutator 33. A plurality of brushes 4 having a surface 4a, a base member 5 made of an insulator accommodated in the motor case 2, and a plurality of guides fixed to the base member 5 and slidably held in the radial direction of the shaft 34 A member 6 and an urging member 7 for applying a pressing force toward the commutator 33 side to the back surface 4 b opposite to the sliding contact surface 4 a of the brush 4 are provided. The urging member 7 is arranged so as to surround the plurality of brushes 4 in an extended state from the natural length, and from an annular elastic body that applies a pressing force toward the commutator 33 side to the plurality of brushes 4 by its restoring force. Thus, the motor case 2 is provided with support portions 25 that support the biasing member 7 at a plurality of locations. [Selection] Figure 4

Description

  The present invention relates to a motor having a brush that is elastically pressed against a commutator of a rotor.

  Conventionally, a motor having a permanent magnet fixed to a case, a rotor rotatably supported in the case, and a plurality of brushes for elastically contacting the commutator and supplying current to the coils of the rotor It is used for various applications (see, for example, Patent Document 1).

  In the motor described in Patent Document 1, four brushes and four torsion springs are supported by a base plate made of resin. Each brush is held by a brush holder fixed to the base plate so as to be movable back and forth, and is connected to a pigtail made of a stranded wire having conductivity and flexibility. The torsion spring includes a coil portion wound in a spiral shape and a pair of arm portions extending from both ends of the coil portion. The coil portion is supported by a support shaft of the base plate, one arm portion is locked by a locking piece provided on the base plate, and the other arm portion is locked by a brush. Each brush is elastically pressed against the commutator by the restoring force of the torsion spring.

  The base plate is accommodated in a holder accommodating portion that is integrally formed with a gear housing that accommodates a speed reduction mechanism that decelerates rotation of the motor. The holder accommodating portion has a bottomed cylindrical shape and closes an opening of a case (motor housing) to which a permanent magnet is attached.

  When electric current is supplied from the pigtail to the rotor coil through the brush, an attractive force and a repulsive force are generated between the magnetic pole generated in the core around which the coil is wound and the magnetic pole of the permanent magnet. Rotate against.

JP 2014-39378 A

  Since the brush is pressed against and in contact with the commutator, a contact resistance is generated between the brush and the commutator. This contact resistance decreases as the pressing force that presses the brush against the commutator increases. Therefore, if the pressing force of the brush on the commutator side varies due to individual differences in the spring constant of the torsion spring that presses the brush or the misalignment of the base plate that supports the brush, the contact between the brush and the commutator Resistance varies. If the contact resistance between the brush and the commutator varies, feedback control based on the motor current may not be performed with high accuracy. This is because the controller that controls the motor cannot distinguish the resistance component due to the counter electromotive force accompanying the rotation of the rotor and the contact resistance between the brush and the commutator. Due to the decrease in controllability of the motor, there is a risk that vibration and noise may occur in the motor itself or in the equipment driven by the motor.

  This invention is made | formed in view of said situation, The objective is to provide the motor which can suppress the dispersion | variation in the pressing force provided to each of several brush.

  In order to achieve the above object, the present invention provides a case in which a permanent magnet is disposed, a core facing the permanent magnet, a coil that generates a magnetic field in the core, a commutator connected to the coil, and A rotor having a shaft rotatably supported by the case, a plurality of brushes having a sliding contact surface slidingly contacting the commutator, a base member made of an insulator housed in the case, and fixed to the base member A plurality of guide members that hold the brush slidably in the radial direction of the shaft, and a biasing member that applies a pressing force to the commutator side on the back surface of the brush opposite to the sliding contact surface. And the urging member is disposed so as to surround the plurality of brushes in a state of being extended from a natural length, and an annular elastic body that applies the pressing force to the plurality of brushes by a restoring force thereof Rannahli, the said casing, the support portion for supporting the biasing member at a plurality of positions are provided, to provide a motor.

  According to the present invention, in a motor in which a plurality of brushes are elastically pressed against a commutator of a rotor, variation in pressing force applied to each of the plurality of brushes can be suppressed.

1 is a cross-sectional view illustrating a schematic configuration of an electric power steering apparatus to which a motor according to an embodiment of the present invention is applied. It is a fragmentary sectional view which shows the internal structure of a motor with the gear mechanism of an electric power steering apparatus. FIG. 3 is a configuration diagram illustrating a plurality of brushes, a base member, a plurality of guide members, a biasing member, and the like in the cross section taken along line AA of FIG. It is the perspective view which looked at each member shown in FIG. 3 from the diagonal direction. (A) is an exploded view of a base member and a guide member. (B) And (c) is a perspective view of a brush. FIG. 4 is a sectional view taken along line BB in FIG. 3. It is a block diagram which shows the structure of a modification.

[Embodiment]
Embodiments of the present invention will be described with reference to FIGS. In addition, although embodiment described below is shown as a suitable specific example in implementing this invention, although there are some parts which have illustrated various technical matters that are technically preferable. The technical scope of the present invention is not limited to this specific embodiment.

(Overall configuration of electric power steering device)
FIG. 1 is a cross-sectional view showing a schematic configuration of an electric power steering apparatus to which a motor according to an embodiment of the present invention is applied. FIG. 2 is a partial cross-sectional view showing the internal structure of the motor together with the gear mechanism of the electric power steering apparatus. 1 corresponds to the front of the vehicle on which the electric power steering device is mounted, and the upper side in FIG. 1 corresponds to the upper side in the vertical direction.

  The electric power steering apparatus 1 includes a steering shaft 11 that rotates together with a steering wheel 100, a cylindrical column housing 12 that accommodates the steering shaft 11, a support mechanism 13 that supports the column housing 12 with respect to the vehicle body, and the steering shaft 11. 2 includes a gear mechanism 14 (shown in FIG. 2) for applying a steering assist force, a gear housing 15 that houses the gear mechanism 14, and a motor 10 that drives the gear mechanism 14.

  The steering shaft 11 includes an upper shaft 111 having a steering wheel 100 fixed to one end thereof, and a lower shaft 112 coupled to the upper shaft 111 so as not to be relatively rotatable and to be movable in the axial direction. In FIG. 1, an end portion of the lower shaft 112 protruding from the gear housing 15 toward the front of the vehicle is illustrated.

  The rotation of the lower shaft 112 is transmitted to a steering device having a rack and pinion mechanism via an intermediate shaft and a pinion shaft (not shown) to move the rack shaft of the steering device in the vehicle width direction. By this movement of the rack shaft, the left and right steered wheels (front wheels) are steered via tie rods. FIG. 1 illustrates a part of the cross joint 16 that connects the lower shaft 112 and the intermediate shaft.

  The column housing 12 includes an outer tube 121 and an inner tube 122, and the outer tube 121 is relatively movable along the axial direction with respect to the inner tube 122. A bearing 17 is disposed between the outer tube 121 and the upper shaft 111.

  The support mechanism 13 has a lock state in which the outer tube 121 is locked (fixed in position) with respect to the vehicle body by a cam mechanism that is operated by the operation of the operation lever 131 by the driver of the vehicle, and the outer tube 121 can be moved in the vertical direction. The unlocked state in which the inner tube 122 can move in the axial direction can be switched. In this unlocked state, the driver can perform tilt adjustment and telescopic adjustment.

  The gear mechanism 14 is a worm gear mechanism including a worm 141 that receives the rotational force of the motor 10 and a worm wheel 142 that rotates together with the lower shaft 112. The gear mechanism 14 decelerates the rotation of the motor 10 and transmits it to the lower shaft 112 as a steering assist force. A motor current corresponding to the steering force of the steering wheel 100 detected by the torque sensor is supplied to the motor 10 from a controller (not shown).

  The gear housing 15 includes a worm housing 151 in which a worm 141 and a worm wheel 142 are disposed, and a sensor housing 152 that houses a torque sensor. The worm housing 151 and the sensor housing 152 are fastened by a plurality of bolts 153. Has been. In FIG. 2, illustration of the sensor housing 152 is omitted, and the worm wheel 142 accommodated in the worm housing 151 is illustrated. In FIG. 2, the worm 141 in the worm housing 151 is indicated by a broken line.

  As shown in FIG. 1, the worm housing 151 includes a sensor connector 18 to which a wire harness that sends an output signal of the torque sensor to the controller is connected, and a power supply connector 19 to which an electric wire that supplies a motor current to the motor 10 is connected. It is attached.

  The motor 10 is a DC motor with a brush, and includes a motor case 2 in which a plurality of permanent magnets 20 are disposed, and a rotor 3 that is connected so as to rotate integrally with a worm 141. The rotor 3 includes a core 31 facing the permanent magnet 20, a coil 32 that generates a magnetic field in the core 31, a commutator 33 connected to the coil 32, and a shaft 34 that is rotatably supported by the motor case 2. Have. A worm 141 is connected to the tip of the shaft 34 so as not to be relatively rotatable.

  The motor 10 includes a plurality of brushes 4 having a sliding contact surface 4 a that is in sliding contact with the commutator 33, a base member 5 made of an insulator housed in the motor case 2, and a base member 5 fixed to the brush 4. A plurality of guide members 6 that are slidably held in the radial direction of the shaft 34, and an annular urging member 7 that applies a pressing force toward the commutator 33 to the back surface 4 b opposite to the sliding contact surface 4 a of the brush 4. And a shock-absorbing material 8 disposed between the base member 5 and the first case member 21, and a flexible conductive wire 90 connected to the brush 4.

  The motor case 2 includes a first case member 21 fixed to the worm housing 151 by a plurality of bolts 154, and a bottomed cylindrical second case member 22 that covers an upper portion of the first case member 21. The first case member 21 and the second case member 22 are made of, for example, an aluminum alloy. The second case member 22 is fixed to the first case member 21 with a plurality of bolts 23.

  The first case member 21 includes a cylindrical cylindrical portion 211, an inward protruding portion 212 that protrudes inward from one end of the cylindrical portion 211, and a flange portion 213 for fixing the worm housing 151. Have. The bolt 154 is screwed into a screw hole formed in the worm housing 151 through a bolt insertion hole formed in the flange portion 213 of the first case member 21.

  The second case member 22 is fixed to the first case member 21 by projecting outward from the cylindrical portion 221 having a cylindrical shape, a bottom portion 222 that closes one end portion of the cylindrical portion 221, and the other end portion of the cylindrical portion 221. The flange portion 223 is integrally provided. The bolt 23 is screwed into a screw hole formed in the cylindrical portion 211 of the first case member 21 through a bolt insertion hole formed in the flange portion 223 of the second case member 22.

  The cylindrical portion 221 of the second case member 22 has an annular magnet holder 200 made of a nonmagnetic material attached to the inner peripheral surface 221a. In the magnet holder 200, a plurality of permanent magnets 20 whose S poles face the core 31 and a plurality of permanent magnets 20 whose N poles face the core 31 are alternately held in the circumferential direction. These permanent magnets 20 are fixed to the second case member 22 via a magnet holder 200. A recess 222 a that houses the bearing 24 is formed in the bottom 222 of the second case member 22. The bearing 24 rotatably supports the rear end portion of the shaft 34.

  In the rotor 3, the outer peripheral surface of a commutator 33 configured in a cylindrical shape is in contact with the sliding contact surface 4 a of the brush 4, and current is supplied to a coil 32 wound around a core 31 made of a soft magnetic material. A terminal of the power supply connector 19 and the conductive wire 90 are electrically connected by a power supply member 91. The power supply member 91 includes a terminal 911 to which the conductive wire 90 is fixed and an electric wire 912 having one end connected to the terminal 911. The other end of the electric wire 912 is connected to a terminal of the power supply connector 19.

  The conductive wire 90 is a braided wire formed by braiding strands made of copper, for example, in a lattice shape, and has flexibility capable of following the movement of the brush 4 in the radial direction of the shaft 34. . The other end of the conductive wire 90 is fixed to the terminal 911 by, for example, soldering or caulking, and is electrically connected to the power supply member 91.

  In addition, in this Embodiment, although the electric power feeding member 91 is comprised by the terminal 911 and the electric wire 912, you may comprise the electric power feeding member 91 by the bus bar which consists of not only this but a plate-shaped electroconductive metal, for example.

  Hereinafter, the configuration of the plurality of brushes 4, the base member 5, the plurality of guide members 6, and the biasing member 7 and the support structure thereof will be described in detail with reference to FIGS.

  FIG. 3 is a configuration diagram showing a plurality of brushes 4, a base member 5, a plurality of guide members 6, a biasing member 7 and the like in the cross section taken along line AA of FIG. FIG. 4 is a perspective view of these members as viewed obliquely. FIG. 5A is an exploded view of the base member 5 and the guide member 6. FIGS. 5B and 5C are perspective views of the brush 4. 6 is a cross-sectional view taken along line BB in FIG. In FIG. 3, illustration of the commutator 33 and the shaft 34 is omitted, but each brush 4 shows a state in which the sliding contact surface 4 a is in a position in contact with the commutator 33.

  In the present embodiment, four brushes 4 are arranged around the commutator 33 at equal intervals. Each brush 4 is guided by the guide member 6 and can move forward and backward in the radial direction of the shaft 34. Among the four brushes 4, a voltage having the same polarity is applied to a pair of brushes 4 at positions facing each other across the commutator 33. For example, a positive voltage is applied to the pair of brushes 4 arranged in the vertical direction in FIG. 3, and a negative voltage is applied to the pair of brushes 4 arranged in the horizontal direction.

  The brush 4 is made of a conductor mainly composed of copper and graphite, for example. Further, the brush 4 has a rectangular parallelepiped shape in which one end portion on the sliding contact surface 4 a side is obliquely cut out, and the longitudinal direction thereof is arranged along the radial direction of the shaft 34.

  The base member 5 is made of, for example, an injection-molded resin, and has a disc portion 51 in which a shaft insertion hole 50 through which the shaft 34 is inserted is formed in the center portion, and an annular standing on an outer peripheral side end portion of the disc portion 51. The wall portion 52 is integrally formed. The outer peripheral surface 52a of the annular wall portion 52 and the inner peripheral surface 211a of the cylindrical portion 211 of the first case member 21 face each other with a gap S therebetween. The gap S is formed over the entire circumference between the outer peripheral surface 52 a of the annular wall portion 52 and the inner peripheral surface 211 a of the cylindrical portion 211 of the first case member 21.

  The plurality of brushes 4 slide on the upper surface 51a of the disk portion 51 (the surface on the side where the plurality of brushes 4 are disposed) and move forward and backward in the radial direction of the shaft 34. The lower surface 51 b of the disk part 51 faces the inward protruding part 212 of the first case member 21. The cushioning material 8 is disposed between the lower surface 51 b of the disk portion 51 and the inward protruding portion 212 of the first case member 21. The buffer material 8 is made of, for example, porous sponge-like rubber or resin.

  The guide member 6 is a metal member formed so as to surround a part in the longitudinal direction of the brush 4 from three directions, and is fixed to the base member 5. As shown in FIG. 5A, the guide member 6 integrally includes an upper wall 61 facing the upper surface 4c of the brush 4 (surface opposite to the base member 5) and a pair of side walls 62. Yes. The upper wall 61 is formed with a notch 610 for leading out the conductive wire 90. One end of the conductive wire 90 is fitted and fixed in a connection hole 40 formed in the upper surface 4 c of the brush 4 through a notch 610.

  The pair of side walls 62 of the guide member 6 faces the side surface 4d of the brush 4 and sandwiches the brush 4 in the short direction perpendicular to the moving direction (longitudinal direction). Each side wall 62 is provided with first to third projecting pieces 621 to 623 projecting on the opposite side to the upper wall 61. The first to third projecting pieces 621 to 623 are arranged along the longitudinal direction of the brush 4, and a second projecting piece 622 is formed between the first projecting piece 621 and the third projecting piece 623. Yes.

  An inclined surface 4e that is inclined with respect to the longitudinal direction of the brush 4 is formed between the upper surface 4c of the brush 4 and the sliding contact surface 4a. The inclined surface 4e is inclined with an obtuse angle with respect to the sliding contact surface 4a and the upper surface 4c.

  First to third fitting holes 511 to 513 through which the first to third protruding pieces 621 to 623 are inserted are formed in the disk portion 51 of the base member 5. The first to third fitting holes 511 to 513 penetrate between the upper surface 51 a and the lower surface 51 b of the base member 5. The guide member 6 is positioned on the base member 5 by fitting the first protrusion 621 into the first fitting hole 511 and fitting the third protrusion 623 into the third fitting hole 513. Is done. Further, the guide member 6 is fixed to the base member 5 by bending the tip end portion of the second protruding piece 622 that protrudes toward the lower surface 51 b side of the base member 5.

  The disk portion 51 of the base member 5 includes a plurality of conductive wire insertion holes 514 through which the plurality of conductive wires 90 are respectively inserted, and a plurality of protrusions 251 that are erected on the inward protruding portion 212 of the first case member 21. A plurality of through holes 515 to be inserted are formed. The protrusion 251 passes through the through hole 515 and protrudes from the upper surface 51 a of the base member 5. The conductive wire 90 inserted through the conductive wire insertion hole 514 is connected to the power supply member 91 on the lower surface 5 b side of the base member 5.

  The protrusion 251 has a cylindrical shape, and one end thereof is press-fitted into a press-fitting hole 210 formed in the inward protruding portion 212 of the first case member 21 (see FIG. 6). The central axis of the protrusion 251 is parallel to the rotation axis of the shaft 34. The protrusion 251 may be fixed to the inward protruding portion 212 of the first case member 21 by welding. In the present embodiment, eight protrusions 251 are erected on the inward projecting portion 212 of the first case member 21, and eight through holes 515 are similarly formed in the disk portion 51 of the base member 5. These eight protrusions 251 constitute a support portion 25 that supports the biasing member 7 at a plurality of locations.

  In the support portion 25, four of the eight protrusions 251 are arranged inside the urging member 7, and the other four protrusions 251 are arranged outside the urging member 7. The urging member 7 is sandwiched between the four protrusions 251 disposed on the inner side and the four protrusions 251 disposed on the outer side. That is, the projection 251 disposed inside the biasing member 7 and the projection 251 disposed outside form a pair, and the biasing member 7 is sandwiched between the two projections 251 forming a pair. In the present embodiment, the support portion 25 has four pairs of protrusions 251 and the biasing member 7 is supported at four locations.

  The two protrusions 251 forming a pair are aligned in the radial direction of the shaft 34. The location where the biasing member 7 is supported by the pair of protrusions 251 is between two adjacent brushes 4 when the base member 5 is viewed in the circumferential direction.

  The plurality of protrusions 251 are arranged with reference to the central axis (rotary axis) of the shaft 34 that is rotatably supported by the motor case 2. In other words, the center of the support portion 25 coincides with the central axis of the shaft 34. Specifically, the four protrusions 251 disposed inside the biasing member 7 and the four protrusions 251 disposed inside the biasing member 7 have the same circumference around the central axis of the shaft 34. Is placed on top. Here, the center of the support portion 25 is a polygonal (rectangular) center formed by connecting the center positions of the four protrusions 251 disposed inside the urging member 7, and is disposed outside the urging member 7. This is the center of a polygon (rectangle) formed by connecting the center positions of the four protrusions 251 formed.

  The base member 5 is positioned with respect to the motor case 2 by closely fitting the protrusions 251 into the through holes 515. In other words, the movement of the base member 5 relative to the motor case 2 is restricted by the outer peripheral surface 251a of the protrusion 251 and the inner peripheral surface 515a of the through hole 515 being in close contact with each other without a gap.

  The base member 5 may be positioned with respect to the motor case 2 by closely fitting the protrusions 251 into some of the eight through holes 515. That is, among the eight through holes 515, the inner diameter of some of the through holes 515 into which the protrusions 251 are closely fitted is equal to the outer diameter of the protrusions 251, and the inner diameters of the other through holes 515 are larger than the outer diameters of the protrusions 251. May be formed larger. However, it is desirable that there are two or more through holes 515 into which the protrusions 251 are closely fitted. Fixing the base member 5 to the motor case 2 by closely fitting the protrusions 251 to some of the through-holes 515 as compared with the case of closely fitting the protrusions 251 to all the through-holes 515. Is facilitated.

  The biasing member 7 is made of, for example, a synthetic rubber and is an annular elastic body having elasticity. The urging member 7 is disposed so as to surround the four brushes 4 in a state of being extended from the natural length, and applies a pressing force toward the commutator 33 to each brush 4 by its restoring force.

  In the present embodiment, the urging member 7 has a band shape, and the inner peripheral surface 7 a is in contact with the back surface 4 b of the brush 4. The outer peripheral surface 7 b of the urging member 7 faces the annular wall portion 52 of the base member 5. The thickness between the inner peripheral surface 7a and the outer peripheral surface 7b in the natural state of the urging member 7 (a state in which no external force is applied) is larger than the distance d between the two protrusions 251 forming a pair (see FIG. 6). thick.

  The procedure for assembling the motor 10 is, for example, as follows. That is, a plurality of guide members 6 are fixed to the base member 5, and the brush 4 in which one end portion of the conductive wire 90 is connected in advance to each guide member 6 is inserted from the shaft insertion hole 50 side. Next, the urging member 7 is disposed so that the inner peripheral surface 7 a faces the back surface 4 b of each brush 4, and the other end portion of the conductive wire 90 is inserted into the conductive wire insertion hole 514 to be connected to the power supply member 91. .

  Next, the lower surface 51b of the base member 5 to which the plurality of guide members 6 are fixed is opposed to the inward projecting portion 212 of the first case member 21, and the base member 5 is moved to the inward projecting portion 212 side to penetrate. The protrusion 251 is inserted into the hole 515. At this time, the cushioning material 8 is sandwiched between the base member 5 and the inward protruding portion 212 of the first case member 21. The buffer material 8 is preferably fixed to the lower surface 51b of the base member 5 in advance by bonding or the like. Further, an adhesive may be applied between the periphery of the through hole 515 on the upper surface 51 a and the outer peripheral surface 251 a of the protrusion 251 in order to ensure the fixing of the base member 5.

  Next, the urging member 7 is supported by the support portion 25 including the eight protrusions 251 protruding to the upper surface 51a side of the base member 5 in a state where the urging member 7 is extended beyond the natural length. Specifically, the urging member 7 is sandwiched at four positions between the two protrusions 251 forming a pair.

  Thereafter, the shaft 34 of the rotor 3 is inserted into the shaft insertion hole 50, and the commutator 33 is disposed between the four brushes 4. At this time, the end of the commutator 33 in the axial direction abuts on the inclined surface 4 e of each brush 4, and the interval between the brushes 4 facing the radial direction of the shaft 34 is increased. Thereby, the urging member 7 further extends.

  And the 2nd case member 22 with which the magnet holder 200 with which the some permanent magnet 20 was hold | maintained previously and the bearing 24 were assembled | attached is fixed to the 1st case member 21 with the some volt | bolt 23. FIG. As described above, the motor 10 is assembled.

(Effect of embodiment)
According to the embodiment described above, each brush 4 is pressed against the commutator 33 by one urging member 7 arranged so as to surround the plurality of brushes 4, so that the pressing force applied to each brush 4 is reduced. Variation is suppressed. Further, since the biasing member 7 is supported not by the base member 5 but by the support portion 25 including a plurality of protrusions 251 provided on the motor case 2, the biasing member 7 is not concerned regardless of the processing accuracy of the base member 5. Can be made to coincide with the rotational axis of the shaft 34 with high accuracy. Thereby, the dispersion | variation in the pressing force provided to each brush 4 is suppressed more reliably.

  The base member 5 is positioned with high accuracy with respect to the motor case 2 because the protrusion 251 provided on the motor case 2 is closely fitted in the through hole 515. That is, if the base member 5 is positioned with respect to the motor case 2 by fitting the annular wall portion 52 of the base member 5 into the cylindrical portion 211 of the first case member 21, the base member 5 or the first case When the outer diameter of the annular wall 52 is larger than the allowable value than the inner diameter of the cylindrical portion 211 due to a processing error of the member 21, or the trueness of the outer peripheral surface 52 a of the annular wall 52 or the inner peripheral surface 211 a of the cylindrical portion 211. If the circularity is bad, assembly cannot be performed. On the other hand, if the outer diameter of the annular wall portion 52 is made smaller than the inner diameter of the cylindrical portion 211, the positioning accuracy of the base member 5 is lowered by the play. On the other hand, in the present embodiment, the base member 5 is positioned with high accuracy with respect to the motor case 2 by tightly fitting the protrusions 251 into the through holes 515. For this reason, the center positions of the plurality of brushes 4 (positions where the central axes along the longitudinal direction of the respective brushes 4 intersect) and the rotation axis of the shaft 34 coincide with each other with high accuracy, and the brushes 4 are smooth in the radial direction of the shaft 34 Move forward and backward.

  Further, since the urging member 7 is sandwiched between the protrusion 251 facing the inner peripheral surface 7a and the protrusion 251 facing the outer peripheral surface 7b, the position with respect to the base member 5 is stabilized at the time of assembly, and the assembly work can be performed. It becomes easy. Further, since the plurality of projections 251 have both functions of the positioning function of the base member 5 and the support function of the biasing member 7, the number of parts and Manufacturing costs can be reduced.

(Modification)
FIG. 7 is a configuration diagram illustrating a modification of the embodiment. In the above embodiment, the case where the support portion 25 that supports the urging member 7 includes the eight protrusions 251 and the urging member 7 is sandwiched between the two protrusions 251 that are paired at four locations has been described. In the modification shown in FIG. 7, the support portion 25 includes four protrusions 251, and the outer peripheral surface 7 b of the biasing member 7 is in contact with the protrusions 251 at four locations. Further, the position where the urging member 7 contacts the protrusion 251 is between two brushes 4 adjacent to each other in the circumferential direction of the base member 5 and connects the corners of the back surface 4b of the two brushes 4 to each other. Inside the imaginary line L (on the shaft insertion hole 50 side).

  The four protrusions 251 are arranged with reference to the center axis (rotation axis) of the shaft 34 rotatably supported by the motor case 2, and the center of the support portion 25 formed by these four protrusions 251 is the center axis of the shaft 34. Is consistent with Specifically, the four protrusions 251 are arranged on the same circumference with the central axis of the shaft 34 as the center.

  The other configurations are the same as the configurations of the embodiment described with reference to FIGS. 1 to 6, and thus the same reference numerals as those used in FIGS. To do. This modification can also provide the same effects as described above.

(Appendix)
Although the present invention has been described based on the above embodiments, the present invention is not limited to these embodiments, and can be appropriately modified and implemented without departing from the spirit of the present invention. It is. For example, in the above embodiment, the case where the motor is applied to the electric power steering apparatus has been described. However, the present invention is not limited to this, and the motor according to the present invention can be used for various applications. Moreover, although the said embodiment demonstrated the case where the urging | biasing member 7 was a cyclic | annular elastic body with a rectangular cross section, not only this but the urging member 7 may be a cyclic | annular elastic body with a circular cross section. . Furthermore, although the case where the motor 10 has four brushes 4 has been described in the above embodiment, the number of brushes 4 is not limited to this. However, the present invention can be particularly preferably applied to a motor having three or more brushes in which the biasing member has a polygonal shape.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus 10 ... Motor 2 ... Motor case (case) 20 ... Permanent magnet 200 ... Magnet holder 25 ... Supporting part 251 ... Protrusion 3 ... Rotor 31 ... Core 32 ... Coil 33 ... Commutator 34 ... Shaft 4 ... Brush 4a ... sliding surface 4b ... back surface 5 ... base member 6 ... guide member 7 ... biasing member

Claims (3)

A case with a permanent magnet inside,
A core that faces the permanent magnet, a coil that generates a magnetic field in the core, a commutator connected to the coil, and a rotor that is rotatably supported by the case;
A plurality of brushes having a sliding contact surface in sliding contact with the commutator;
A base member made of an insulator housed in the case;
A plurality of guide members fixed to the base member and holding the brush slidably in the radial direction of the shaft;
An urging member for applying a pressing force to the commutator side on the back surface of the brush opposite to the sliding contact surface;
The urging member is arranged so as to surround the plurality of brushes in an extended state from a natural length, and is composed of an annular elastic body that applies the pressing force to the plurality of brushes by its restoring force,
The case is provided with a support portion that supports the biasing member at a plurality of locations.
motor. The support portion includes a plurality of protrusions that protrude through a surface of the base member on which the plurality of brushes are disposed, through a through hole formed in the base member.
The base member is positioned with respect to the case by tightly fitting the protrusions into the through holes.
The motor according to claim 1. In the support portion, a part of the plurality of protrusions is disposed inside the biasing member, and the other protrusion is disposed outside the biasing member.
The biasing member is sandwiched between the part of the protrusions disposed on the inside and the other protrusions disposed on the outside.
The motor according to claim 2.

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