Motor with brush

Abstract

In order to prevent or suppress damage to a bent portion of a brush formed by bending in a motor with a brush, this motor (100) with a brush comprises: a commutator (60) fixed to a rotary shaft (40); and a brush (80) in which one end-side portion (81) is pivotally supported, the other end-side portion (82) is in contact with the commutator (60), and a bent portion (85) is provided between the one end-side portion (81) and the other end-side portion (82). A recess (88) for increasing the density of the bent portion (85) is formed in the range of the bent portion (85) on a surface (86) of the brush (80).

Description

Brushed motor

[0001] The present invention relates to a brushed motor.

[0002] A brush motor has a configuration in which brushes, made of, for example, sintered carbon powder, are pressed against a commutator fixed to a rotating shaft by a biasing means. The brushes are formed, for example, in a roughly U-shape (which also includes a roughly V-shape and a roughly L-shape; hereinafter, referred to as a U-shape, etc.), with one end of the U-shape supported and the other end bent so that it contacts the commutator (see, for example, Patent Document 1).

[0003] Patent No. 3898942

[0004] In this way, brushes that are bent, for example, in a U-shape, tend to be subject to large stresses at the bend between the supported end and the other end that contacts the commutator, making them prone to cracks and other damage at the bend.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a brushed motor that can prevent or suppress breakage at the bent portions of bent brushes.

[0006] The present invention is a brush motor comprising a commutator fixed to a rotating shaft, and a brush whose one end is supported by a shaft and whose other end is in contact with the commutator, and which has a bent portion between the one end and the other end, wherein the brush has a recess formed in the area of ​​the bent portion on at least one of its front and back surfaces to increase the density of the bent portion.

[0007] The brushed motor according to the present invention can prevent or suppress breakage at the bent portions of the bent brushes.

[0008] 1 is a cross-sectional view showing a longitudinal section of a brush motor including the center C of the rotating shaft. FIG. 2 is a perspective view of the brush of the brush motor shown in FIG. 1, seen from the cap side. FIG. 3 is a perspective view showing the brush supported by the cap. FIG. 4 is a perspective view showing the spring groove and pin hole formed on the support surface of the cap, and the torsion spring and support pin. FIG. 5 is a perspective view showing the brush in detail. FIG. 6 is a perspective view showing the brush, in which the support hole extending along the axis C2 is formed by two holes with different inner diameters connected along the axis C2 direction, and the support pin, in which two shaft portions with different outer diameters are connected along the axis C2 direction. FIG. 7 is a plan view of the surface of the brush, seen from the front.

[0009] An embodiment of a brushed motor according to the present invention will be described below with reference to the drawings.

[0010] Fig. 1 is a cross-sectional view showing a longitudinal section of a brushed motor 100 including the center of a rotating shaft 40, Fig. 2 is a perspective view of a brush 80 of the brushed motor 100 shown in Fig. 1 as seen from the cap 20 side (as viewed from arrow A in Fig. 1), and Fig. 3 is a perspective view showing the brush 80 in a state supported by the cap 20. However, Fig. 3 shows only one supported brush 80, and the other brush 80 is not shown. The brushed motor 100 is a brushed coreless motor that is one embodiment of a brushed motor according to the present invention.

[0011] As shown in FIG. 1, the brushed motor 100 (hereinafter simply referred to as the motor 100) includes a housing 10, a cap 20, a magnet 30, a rotating shaft 40, a coil 50, a commutator 60, and brushes 80.

[0012] The housing 10 is formed by closing one end face of a cylindrical tube portion 11 extending parallel to the axis C1 with an end wall 12. The other open end face of the tube portion 11 is closed by attaching a cap 20 formed in a substantially disk shape. The cap 20 not only serves to close the other open end face of the tube portion 11, but also serves as a brush base that supports the brush 80. In other words, the cap 20 is an example of a brush base that supports the brush 80. Furthermore, a sleeve portion 13 extending parallel to the axis C1 is formed inside the housing 10. A cylindrical magnet 30 is fixed to the outer circumferential surface of the sleeve portion 13.

[0013] The rotating shaft 40 has a shaft portion 41 extending along the axis C1, a flange portion 42 having a diameter larger than that of the shaft portion 41, and a boss portion 43 protruding along the axis C1 on the opposite side of the flange portion 42 from the shaft portion 41. The shaft portion 41 of the rotating shaft 40 is inserted into the inside of the sleeve portion 13.

[0014] The rotating shaft 40 is supported so as to be rotatable about the axis C1 by a bearing 14 provided on the end wall 12 and a bearing 15 provided on the sleeve portion 13. One end of the rotating shaft 40 supported by the bearing 14 protrudes outward from the bearing 14, while the other end on the bearing 15 side is disposed inside the housing 10.

[0015] The coil 50 is formed in a cylindrical shape centered on the shaft 41 and extending parallel to the shaft 41, and is disposed in the space between the magnet 30 and the cylindrical portion 11 of the housing 10, away from the magnet 30 and the cylindrical portion 11. The coil 50 is fixed to the outer periphery of the flange portion 42 of the rotating shaft 40, and rotates integrally with the rotating shaft 40.

[0016] The commutator 60 is fixed to the boss portion 43 and rotates integrally with the rotary shaft 40 .

[0017] The brushes 80 are carbon brushes formed by, for example, sintering. Two brushes 80 are provided, and the two brushes 80 are arranged opposite each other with the commutator 60 in between, as shown in Fig. 2. The brushes 80 are supported on the cap 20 by support pins 70, as shown in Fig. 3. As shown in Figs. 2 and 3, the brushes 80 are formed in a substantially U-shape in plan view (as viewed in the direction of the axes C1 and C2).

[0018] Specifically, the brush 80 has a one-end portion 81 including one end of the approximately U-shape, an other-end portion 82 including the other end of the approximately U-shape, and an intermediate portion 83 which is the middle portion connecting the one-end portion 81 and the other-end portion 82, and a bent portion 85 which is the bent portion of the approximately U-shape is formed in the intermediate portion 83.

[0019] FIG. 4 is a perspective view showing the spring groove 23 and pin hole 24 formed in the support surface 21 of the cap 20, the torsion spring 90, and the support pin 70, and FIG. 5 is a perspective view showing the brush 80 in detail.

[0020] 3 and 5, a support hole 84 (through hole) through which the support pin 70 is passed is formed in the one end portion 81. An end surface 82a of the other end portion 82 is a surface that contacts the peripheral surface of the commutator 60. The brush 80 is journaled to the cap 20 by the support pin 70 that is passed through the support hole 84, and is supported so as to be swingable (rotatable) about an axis C2 of the support pin 70.

[0021] The bent portion 85 is, for example, a portion of the intermediate portion 83 that connects the portion extending radially outward from the one end portion 81 to the portion extending radially outward from the other end portion 82 at the outermost radial circumference, and is a portion where the portion extending radially outward from the one end portion 81 and the portion extending radially outward from the other end portion 82 intersect, for example, at an acute angle.

[0022] The brush 80 is supported on a surface 21 (hereinafter referred to as the support surface 21) of the cap 20 that faces the inside of the housing 10 when the cap 20 is attached to the housing 10. As shown in Fig. 4, the support surface 21 is formed with a spring groove 23 in which a torsion spring 90 (described later) is disposed, and a pin hole 24 in which a support pin 70 is disposed.

[0023] As shown in Figure 4, the support pin 70 has a fixed shaft portion 71 that fits into the pin hole 24 of the cap 20, a flange portion 73 that presses the winding portion 92 of the torsion spring 90 described later, and a support shaft portion 72 that passes through the support shaft hole 84 of the brush 80, and the fixed shaft portion 71, flange portion 73 and support shaft portion 72 are formed in a straight line along the axis C2 direction.

[0024] As shown in FIG. 5, of the surfaces 86 and 87 of the brush 80 in a plan view (as viewed along the axis C1), the surface 86 (the lower surface in FIG. 2 and the upper surface in FIG. 3; hereinafter referred to as the front surface 86) facing the flange portion 42 of the rotating shaft 40 has a spring groove 89 formed in an intermediate portion 83 thereof, into which a straight portion 95 of a torsion spring 90 (described later) is hooked.

[0025] The torsion spring 90 is a spring member that applies a biasing force to press the end surface 82a of the brush 80 against the peripheral surface of the commutator 60. As shown in Figure 4, the torsion spring 90 has a straight portion 91 at one end, a straight portion 95 at the other end, and a spiral winding portion 92 formed between the straight portions 91, 95, and generates a torque (biasing force) between the two straight portions 91, 95 around the axis C2 of the winding portion 92.

[0026] Specifically, the straight portion 91 and the winding portion 92 of the torsion spring 90 are inserted into the spring groove 23 of the cap 20, as shown in Fig. 4. Meanwhile, the straight portion 95 of the torsion spring 90 is hooked into the spring groove 89 formed in the surface 86 of the brush 80, as shown in Fig. 3. At this time, one straight portion 91 is prevented from rotating around the axis C2 by the spring groove 23, and the other straight portion 95 is hooked into the spring groove 89 of the brush 80 in a state in which the winding portion 92 is twisted in a direction that makes the diameter of the winding portion 92 smaller than in its natural state.

[0027] As a result, a torque is generated in the winding portion 92 in a direction that restores it to its natural state, and this torque acts on the brush 80 via the straight portion 95 of the torsion spring 90, becoming a biasing force that presses the end face 82a of the other end portion 82 of the brush 80 against the peripheral surface of the commutator 60.

[0028] The torsion spring 90 is arranged with the straight portion 91 and the winding portion 92 inserted into the spring groove 23 of the cap 20, and the winding portion 92 is pressed from above by the flange portion 73 of the support pin 70 fixed in the pin hole 24, as shown in Figure 3.

[0029] In addition, the torsion spring 90 of this embodiment has a radial extension portion 93 extending radially outward and an axial extension portion 94 extending in the direction of the axis C2 formed between the winding portion 92 and the straight portion 95 at the other end, and the straight portion 95 is offset from the back surface 87 to the front surface 86 of the brush 80.

[0030] Furthermore, a depression 88 is formed on the surface 86 of the brush 80 in the range of the bent portion 85. The depression 88 has a generally arc-shaped outline when viewed from above and a generally U-shaped outline in a cross section (longitudinal cross section) cut in the depth direction. The depression 88 is not formed over the entire area in the width direction W from the inner peripheral edge to the outer peripheral edge of the bent portion 85 on the surface 86, but is formed only in a portion in the width direction W.

[0031] 5, the recess 88 is formed in approximately the center of the bent portion 85 in the width direction W. In other words, the recess 88 is formed only in a range that is outer than the inner peripheral edge of the bent portion 85 and inner than the outer peripheral edge of the bent portion 85, and the portions of the surface 86 that are outer than the recess 88 and inner than the recess 88 are formed as flat surfaces. In addition, the center of the bottom surface of the recess 88 is formed as a flat surface.

[0032] However, the recess 88 is not limited to that shown in Fig. 5. For example, the recess 88 may be formed in the range from the inner peripheral edge to the outer peripheral edge of the bent portion 85 in the width direction W (the range including the inner peripheral edge and the outer peripheral edge).

[0033] The depressions 88 are formed by protrusions provided on a mold that forms the surface 86 of the brush 80 during the sintering process used to manufacture the brush 80 .

[0034] In other words, the portions of the surface 86 of the brush 80 other than the depressions 88 are formed as flat surfaces, and the depressions 88 are formed as convex portions. Therefore, the convex portions of the mold have a longer dimension for pressing into the material of the brush 80 (e.g., carbon powder) than the other portions (flat surfaces) other than the convex portions. The convex portions of the mold apply stronger pressure to the material of the brush 80 by the amount of their longer dimension, so the depressions 88 of the brush 80 are denser than the portions other than the depressions 88. As a result, the depressions 88 of the brush 80 formed by sintering are formed with greater strength than the portions other than the depressions 88.

[0035] Therefore, the motor 100 can prevent or suppress damage to the bent portion 85 of the brush 80 .

[0036] In the motor 100 of this embodiment, the spring groove 89 into which the straight portion 95 of the torsion spring 90 is hooked is also formed to be recessed from the other portions of the surface 86, similar to the recess 88. Therefore, the portion of the intermediate portion 83 where the spring groove 89 is formed is formed to be denser and stronger than the other portions, similar to the bent portion 85 where the recess 88 is formed. The recess 88 is connected to the spring groove 89, and the recess 88 and the spring groove 89 are formed as a continuous, integrated unit.

[0037] Therefore, the range where the strength is increased by the recess 88 extends to the range where the strength is increased by the spring groove 89, and further, because the recess 88 and the spring groove 89 are continuous, the motor 100 can ensure continuity of the portion where the strength of the brush 80 is increased. Furthermore, because the recess 88 and the spring groove 89 are continuous, the motor 100 can discharge friction powder of the brush 80 that has accumulated inside the recess 88 to the outside of the recess 88 via the spring groove 89. In other words, if friction powder of the brush 80 accumulates in the recess 88, the mechanical and electrical characteristics of the brush 80 may deteriorate, but the motor 100 can prevent this from happening.

[0038] In motor 100, recess 88 and spring groove 89 are formed on the same surface 86, but the surface on which recess 88 is formed and the surface on which spring groove 89 is formed may be separate surfaces. Therefore, motor 100 may have recess 88 formed on surface 86 and spring groove 89 formed on back surface 87, or may have recess 88 formed on back surface 87 and spring groove 89 formed on surface 86.

[0039] In particular, in the latter case where the recess 88 is formed on the back surface 87 and the spring groove 89 is formed on the front surface 86, the recess 88 faces the cap 20, making it difficult for the sliding powder of the brush 80 to reach the recess 88, and the spring groove 89 is located on the opposite side from the cap 20, making it easier for the straight portion 95 of the torsion spring 90 to become caught in the spring groove 89. Therefore, the motor 100 can prevent the sliding powder of the brush 80 from accumulating in the recess 88 while also preventing the straight portion 95 of the torsion spring 90 from coming out of the spring groove 89.

[0040] Furthermore, in this case, the flange portion 73 of the support pin 70 may cover at least a portion (preferably the entirety) of the recess 88 of the brush 80 from the rear surface 87 of the brush 80. Specifically, for example, the entire outer diameter of the flange portion 73 may be increased, or a portion of the flange portion 73 may be protruded so that the flange portion 73 covers at least a portion of the recess 88. When configured in this manner, the motor 100 can more effectively prevent the accumulation of sliding powder of the brush 80 in the recess 88.

[0041] However, when the brush 80 is formed by sintering, it is preferable that the recess 88 and the spring groove 89 are formed on the same surface, since this makes it easier to manufacture the mold.

[0042] Furthermore, motor 100 does not need to have spring grooves 89 on front surface 86 or rear surface 87 of brush 80. In other words, motor 100 only needs to have a portion on brush 80 where one end of torsion spring 90 (the portion corresponding to straight portion 95) is hooked, and the portion where torsion spring 90 is hooked does not need to be front surface 86 or rear surface 87 of brush 80. Therefore, motor 100 may have a portion where torsion spring 90 is hooked formed on the side surface of brush 80.

[0043] In addition, the motor 100 may have the recesses 88 formed on both the front surface 86 and the back surface 87 of the brush 80. In other words, the motor 100 may have the recesses 88 formed on at least one of the front surface 86 and the back surface 87 of the brush 80.

[0044] Furthermore, the recess 88 in the motor 100 is not limited in any dimension, including width, length, and depth.

[0045] (Variant) Figure 6A is a perspective view showing a brush 180 in which a support shaft hole 84 extending along axis C2 is formed by two holes 84a, 84b with different inner diameters connected along the axis C2 direction, and a support pin 170 in which two shaft portions 75, 74 with different outer diameters are connected along the axis C2 direction, and Figure 6B is a plan view of the surface 86 of brush 180 viewed from the front.

[0046] 6A is a modified version of brush 80 in motor 100, and support pin 170 shown is a modified version of support pin 70 in motor 100. A motor in which brush 80 in motor 100 is replaced with brush 180 and support pin 70 is replaced with support pin 170 is a modified version of motor 100.

[0047] Similar to the brush 80, the brush 180 has a recess 88 formed in a bent portion 85 on the surface 86. As shown in FIGS. 6A and 6B , the support shaft hole 84 formed in the one end portion 81 of the brush 180 is a stepped hole in which two holes 84a, 84b with different inner diameters (a large-diameter hole 84a with a relatively large inner diameter and a small-diameter hole 84b with a relatively small inner diameter) are connected along the axis C2. The support pin 170 is a stepped pin in which two shaft portions 75, 74 with different outer diameters are connected along the axis C2. Similarly to the recess 88, the large-diameter hole 84a has a higher density than the rest of the brush 180. As a result, the large-diameter hole 84a formed by sintering has a higher strength than the rest of the brush 180.

[0048] Here, the shaft portion 75, which has an outer diameter larger than that of the shaft portion 74, can be passed through the large-diameter hole 84a, which has an inner diameter larger than that of the small-diameter hole 84b, but cannot be passed through the small-diameter hole 84b, which has a smaller inner diameter. The shaft portion 74, which has an outer diameter smaller than that of the shaft portion 75, can be passed through the small-diameter hole 84b, which has a smaller inner diameter. Then, by passing the shaft portion 75 through the large-diameter hole 84a and the shaft portion 74 through the small-diameter hole 84b, the brush 180 is allowed to swing (rotate) freely around the axis C2 by the support pin 170.

[0049] The modified motor configured in this manner also exhibits the same functions and effects as the motor 100 of the embodiment. Moreover, in the modified motor, the support shaft hole 84 of the brush 180 is formed with a step, increasing the strength of the support shaft hole 84. Therefore, the modified motor can prevent or suppress damage to the brush support shaft hole 84. Furthermore, in the modified motor, the support shaft hole 84 of the brush 180 and the support pin 170 that passes through the support shaft hole 84 are each formed with a step. Therefore, the modified motor can prevent the brush 180 from coming off the support pin 170 when the support pin 170 is fixed to the cap 20.

[0050] In the motors of the above-described embodiment and modified examples, the spring grooves 89 of the brush 80 and the holes 84a of the brush 180 have the function of increasing the brush density, but they may not have the function of increasing the brush density. Also, in the motors of the above-described embodiment and modified examples, the brushes 80, 180 are formed by sintering, but the brushes 80, 180 may be formed by a method other than sintering. In that case, it is also sufficient that the recesses 88 that increase the density of the bent portions 85 are formed within the range of the bent portions 85 of the brush 80.

Claims

1. A brush motor comprising: a commutator fixed to a rotating shaft; and a brush having one end supported by a shaft and the other end in contact with the commutator, the brush having a bent portion between the one end and the other end, wherein the brush has recesses formed in the area of ​​the bent portion on at least one of its front and back surfaces to increase the density of the bent portion.

2. A brushed motor according to claim 1, further comprising a spring member that presses the brush against the commutator, wherein the brush has a groove formed on the surface on which the recess is formed that catches the spring member, and the recess is connected to the groove.

3. A brushed motor as claimed in claim 1, comprising: a spring member that presses the brush against the commutator; and a brush base that supports the brush, wherein the brush has a groove formed on the surface opposite to the surface facing the brush base for engaging the spring member, and the recess is formed on the surface facing the brush base.

4. A brushed motor as described in claim 1, wherein the brush has a through hole formed in the supported portion for passing the support shaft, the through hole being formed with a step consisting of a large diameter hole with a large inner diameter and a small diameter hole with a small inner diameter, and the large diameter hole is a hole that increases the density of the supported portion of the brush.

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