electric motor

Abstract

An electric motor comprising: a rotor having a rotary shaft and a commutator attached to the rotary shaft; brushes each including a front end portion (first end portion) in contact with the commutator and a back end portion (second end portion) positioned on the opposite side to the first end portion; and constant load springs each of which is formed from a belt-shaped wire material and which is for pressing the brush against the commutator, wherein the constant load spring has a spiral portion formed by winding the belt-shaped wire material, and the spiral portion and the second end portion are in contact with each other at two or more positions.

Description

Technical Field

[0001] This disclosure relates to an electric motor.

Background Art

[0002] As electric motors, there are a commutator motor with brushes or a brushless motor without brushes. In a commutator motor, a brush spring is used to press the brush against the commutator. The brush spring applies pressure to the brush by utilizing spring elasticity. Conventionally, a coil spring or a torsion spring has been used as the brush spring of a commutator motor.

[0003] However, in a coil spring or a torsion spring, the difference between the pressing force before brush wear (initial pressure) and the pressing force after brush wear (final pressure) is large. Therefore, in order to ensure a final pressure above a certain level, it is necessary to set the initial pressure high. For this reason, at the initial stage, the friction between the brush and the commutator increases when the rotor rotates, and the sliding loss of the brush may increase. As a result, the efficiency of the electric motor and the brush life are reduced.

[0004] Therefore, in order to reduce the difference between the initial pressure and the final pressure and apply a uniform pressing force (load) to the brush, a technique of using a constant load spring as the brush spring has been proposed. For example, Patent Document 1 discloses an electric motor that applies a constant load to a brush by bringing a spiral portion of a spiral spring, which has a spiral portion formed by winding a strip-shaped wire as a constant load spring, into contact with the rear end surface of the brush.

[0005] However, it has been found that with conventional spiral springs, the spiral portion moves from side to side as the brush wears down. In this case, the contact point between the rear end face of the brush and the spiral portion also moves from side to side as the brush wears down. This can cause the load applied to the brush by the spiral spring to become unstable. In particular, when the spiral portion moves from side to side, the spiral portion of the spiral spring may come into contact with the inner surface of the brush holder, since the spiral spring is housed in the brush holder together with the brush. In this case, the load applied to the brush by the spiral spring is significantly reduced.

[0006] As described above, if the spiral part of the spiral spring moves from side to side, it becomes impossible to apply a stable load to the brush. As a result, the efficiency of the electric motor decreases, and the lifespan of the brush is reduced due to unstable mechanical wear. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 61-118987 [Overview of the Initiative]

[0008] This disclosure was made to solve these problems. The purpose of this disclosure is to provide an electric motor that can suppress a decrease in the efficiency of the electric motor and the lifespan of the brushes by applying a stable load to the brushes even when a constant-load spring is used.

[0009] To achieve the above objective, one embodiment of the electric motor according to the present disclosure comprises a rotor having a rotating shaft and a commutator attached to the rotating shaft; a brush including a first end in contact with the commutator and a second end located on the opposite side of the first end; and a constant-load spring made of a strip-shaped wire for pressing the brush against the commutator, wherein the constant-load spring has a spiral portion around which the strip-shaped wire is wound, and the spiral portion and the second end are in contact at two or more points.

[0010] It is preferable that a recess is formed at the second end, and that the spiral portion is in contact with the recess at two or more points.

[0011] In the cross-section obtained by cutting with a plane perpendicular to the axial direction of the rotation axis, the recess may have a V-shape, an arc shape, a U-shape, or a U-shape.

[0012] In the cross-section obtained by cutting with a plane perpendicular to the axial direction of the rotation axis, the spiral portion and the second end portion are in contact at two points, a first point and a second point, and it is preferable that the line connecting the first point and the second point is parallel to the direction perpendicular to the longitudinal direction of the brush.

[0013] In a circle centered on the center of the spiral portion, if θ is the central angle with respect to the chord between the first point and the second point, it is preferable that θ ≥ 40°.

[0014] In a circle centered on the center of the spiral portion, if θ is the central angle with respect to the chord between the first point and the second point, then it is even more preferable that θ ≥ 48°.

[0015] The second end may be provided with a restricting portion that restricts the movement of the spiral portion in the axial direction of the rotation axis.

[0016] The brush comprises a carbon brush and a mounting component attached to the rear end of the carbon brush, and the second end may be the rear end of the mounting component.

[0017] Furthermore, the device may be equipped with a brush holder for holding the brush, the brush holder having a cylindrical portion surrounding the brush, the constant-load spring having a folded structure in which one end drawn out from the spiral portion is folded back outwards, the folded structure having a first folded portion in which one end is folded back outwards, and an opposing portion facing the first folded portion, and the constant-load spring may be fixed to the cylindrical portion by inserting the folded structure into the open end of the cylindrical portion so as to sandwich the open end of the cylindrical portion between the first folded portion and the opposing portion.

[0018] The first folded portion has a first slit extending along the insertion direction of the folded structure, the brush holder has a protruding portion erected on the outer surface of the outer wall of the cylindrical portion and extending along the insertion direction, and the constant load spring may be fixed to the cylindrical portion by the folded structure being inserted into the open end of the cylindrical portion and the first slit being inserted into the protruding portion.

[0019] The folded structure further includes a second folded portion erected on the first folded portion, and the second folded portion has a second slit that is continuous with the first slit, and the second slit may be formed without cutting out to the tip of the second folded portion.

[0020] Preferably, the gap between the first folded portion and the opposing portion becomes narrower as it moves away from the folding position of the folded structure.

[0021] Furthermore, it is preferable that the conductive wire has one end connected to the brush and the other end connected to an electrode terminal that supplies power to the brush, and that the length of the conductive wire is set so that the constant-load spring applies a pressing force to the brush even when the brush is at its maximum wear.

[0022] According to this disclosure, a stable load can be applied to the brush even when a constant-load spring is used. Therefore, a decrease in the efficiency of the electric motor and the lifespan of the brush can be suppressed. [Brief explanation of the drawing]

[0023] [Figure 1] Figure 1 is an external perspective view of an electric blower according to an embodiment. [Figure 2] Figure 2 is an exploded perspective view of an electric blower according to an embodiment. [Figure 3] Figure 3 is a cross-sectional view of an electric blower according to an embodiment, when cut through a plane passing through the axis of rotation. [Figure 4] FIG. 4 is a cross-sectional view of the electric blower according to the embodiment when cut along a plane passing through the axis of the rotating shaft. [Figure 5] FIG. 5 is a cross-sectional view of the electric blower according to the embodiment when cut along a plane passing through a pair of brushes and orthogonal to the axis of the rotating shaft. [Figure 6] FIG. 6 is a perspective view of the brush holder with the brushes and the constant load springs housed therein as viewed from the front. [Figure 7] FIG. 7 is a perspective view of the brush holder with the brushes and the constant load springs housed therein as viewed from the rear. [Figure 8] FIG. 8 is an exploded perspective view of the brush, the brush holder, and the constant load spring. [Figure 9] FIG. 9 is a perspective view showing the contact portion between the brush and the constant load spring. [Figure 10] FIG. 10 is a cross-sectional view showing the contact portion between the brush and the constant load spring. [Figure 11] FIG. 11 is a view showing the shape of the outer end portion before forming the folded-back structure in the constant load spring according to the embodiment. [Figure 12A] FIG. 12A is a diagram for explaining the state when the constant load spring and the brush are incorporated into the brush holder in the electric motor according to the embodiment. [Figure 12B] FIG. 12B is a diagram for explaining the state when the constant load spring and the brush are incorporated into the brush holder in the electric motor according to the embodiment. [Figure 12C] FIG. 12C is a diagram for explaining the state when the constant load spring and the brush are incorporated into the brush holder in the electric motor according to the embodiment. [Figure 13A] FIG. 13A is a diagram for explaining the state when the constant load spring is incorporated into the brush holder in the electric motor according to the embodiment. [Figure 13B] FIG. 13B is a diagram for explaining the state when the brush is incorporated into the brush holder in the electric motor according to the embodiment. [Figure 13C]Figure 13C is a diagram illustrating the relationship between the brush and the conductive wire during brush wear in an electric motor according to an embodiment. [Figure 14A] Figure 14A is a diagram illustrating the behavior of a comparative example electric motor as the brushes wear down and the constant-load spring moves simultaneously. [Figure 14B] Figure 14B is a diagram illustrating the behavior of the motor in the comparative example, where the brushes slide and the constant-load spring moves as the brushes wear down. [Figure 14C] Figure 14C is a diagram illustrating the behavior of the motor in the comparative example, where the brushes slide and the constant-load spring moves as the brushes wear down. [Figure 15A] Figure 15A is a diagram illustrating the process in an electric motor according to an embodiment, where the brushes slide and the constant-load spring moves as the brushes wear down. [Figure 15B] Figure 15B is a diagram illustrating the process in an electric motor according to an embodiment, where the brushes slide and the constant-load spring moves as the brushes wear down. [Figure 15C] Figure 15C is a diagram illustrating the process in an electric motor according to an embodiment, where the brushes slide and the constant-load spring moves as the brushes wear down. [Figure 16] Figure 16 shows experimental results regarding the relationship between the groove width of the recess in the V-shaped groove and the lateral movement of the spiral part of the constant-load spring. [Figure 17] Figure 17 shows the shape of the outer end of the metal plate before the folded structure is formed in a modified constant-load spring. [Figure 18A] Figure 18A is a perspective view of a modified constant-load spring. [Figure 18B] Figure 18B is a top view of a constant-load spring related to a modification. [Figure 19A] Figure 19A is a diagram illustrating how a modified constant-load spring and brush are incorporated into a brush holder. [Figure 19B] Figure 19B is a diagram illustrating how a modified constant-load spring and brush are incorporated into a brush holder. [Figure 19C] Figure 19C is a diagram illustrating how a modified constant-load spring and brush are incorporated into a brush holder. [Figure 20A] Figure 20A shows the configuration of a constant-load spring according to a modified example. [Figure 20B] Figure 20B shows the configuration of a constant-load spring related to a modified example. [Figure 21A] Figure 21A is an enlarged view of the contact area between the brush and the constant-load spring in the modified example. [Figure 21B] Figure 21B is an enlarged view of the contact area between the brush and the constant-load spring in the modified example. [Figure 22A] Figure 22A is an enlarged view of the contact area between the brush and the constant-load spring in the modified example. [Figure 22B] Figure 22B is an enlarged view of the contact area between the brush and the constant-load spring in the modified example. [Figure 23] Figure 23 is an enlarged view of the contact area between the brush and the constant-load spring in the modified example. [Figure 24] Figure 24 is a cross-sectional view showing a modified example in which the brush and constant-load spring are housed in the brush holder. [Modes for carrying out the invention]

[0024] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the following embodiments are examples and are not intended to limit this disclosure. Accordingly, components in the following embodiments that are not described in an independent claim will be described as optional components.

[0025] Furthermore, in this specification and drawings, the X, Y, and Z axes represent the three axes of a three-dimensional Cartesian coordinate system. The X and Y axes are mutually orthogonal and both are orthogonal to the Z axis. In this embodiment, the Z axis direction is the direction of the axis C of the rotation axis 13.

[0026] Please note that each figure is a schematic diagram and not necessarily a strictly accurate representation. Furthermore, the same reference numerals are used for substantially identical components in each figure, and redundant explanations are omitted or simplified.

[0027] (Embodiment) First, the overall configuration of the electric blower 1 according to the embodiment will be explained using Figures 1 to 4. Figure 1 is an external perspective view of the electric blower 1 according to the embodiment. Figure 2 is an exploded perspective view of the same electric blower 1. Figures 3 and 4 are cross-sectional views of the electric blower 1 when cut by a plane passing through the axis C of the rotating shaft 13. Figure 3 shows a cross-section (XZ section) when cut through a cross-section passing through a pair of brushes 60. Figure 4 shows a cross-section (YZ section) when cut through a cross-section passing through a pair of magnets 21 of the stator 20. Figures 3 and 4 illustrate the parts that appear in the cross-section. In Figures 3 and 4, the airflow inside the electric blower 1 when the rotating fan 3 rotates is indicated by arrows.

[0028] As shown in Figures 1 to 4, the electric blower 1 comprises an electric motor 2, a rotating fan 3, an air guide 4, and a fan case 5. The electric motor 2 has a rotor 10 and a stator 20. The rotating fan 3 is attached to the rotating shaft 13 of the electric motor 2. Air discharged from the rotating fan 3 flows into the air guide 4. The fan case 5 houses the rotating fan 3. The electric blower 1 is used, for example, in a vacuum cleaner.

[0029] Motor 2 is a fan motor that rotates the rotating fan 3. For example, motor 2 is a DC motor that takes a DC power supply as input. Motor 2 is a commutator motor with brushes.

[0030] As shown in Figures 2 to 4, the electric motor 2 comprises a rotor 10, a stator 20, a yoke 30, a frame 40, a bracket 50, brushes 60, a brush holder 70, and a constant-load spring 80. The rotor 10, stator 20, and yoke 30 are arranged within the frame 40. The detailed configuration of each component of the electric motor 2 will be described later.

[0031] The rotating fan 3 draws air into the outer shell (housing) which is composed of a frame 40 and a fan case 5. For example, the rotating fan 3 is a centrifugal fan that can obtain high suction pressure. When the rotating fan 3 rotates, air pressure is generated, and air is drawn in from the intake port 5c of the fan case 5 and discharged from the rotating fan 3. The air discharged from the rotating fan 3 flows into the air guide 4. The rotating fan 3 is made of, for example, a resin material or a metal material such as aluminum.

[0032] As an example, the rotating fan 3 has a first side plate with an intake port, a second side plate facing the first side plate separated by a predetermined gap, and a plurality of fan blades sandwiched between the first and second side plates. Each of the plurality of fan blades is plate-shaped and curved in an arc. The plurality of fan blades are arranged radially in a swirling pattern.

[0033] The air guide 4 has the function of forming an airflow path. For example, the air guide 4 straightens and discharges the air drawn in from the intake port 5c of the fan case 5 by the rotation of the rotating fan 3. The air discharged from the air guide 4 flows into the inside of the frame 40 via the bracket 50. In this embodiment, the air discharged from the air guide 4 is not only discharged into the inside of the frame 40, but also discharged to the outside of the frame 40 via the bracket 50.

[0034] The air guide 4 has a main body 4a, an annular section 4b, and a plurality of connecting plates 4c. The annular section 4b surrounds the main body 4a with a gap between them. The plurality of connecting plates 4c connect the main body 4a and the annular section 4b. The gap between the main body 4a and the annular section 4b serves as a ventilation passage.

[0035] The main body portion 4a is a disc-shaped body having a through hole for fixing to the bracket 50. The annular portion 4b functions as a support portion that supports the end of the rotation axis 13 in the direction of the axis C (thrust direction) on the side wall portion 5b of the fan case 5. Each of the plurality of connecting plates 4c functions as a guide plate for forming an airflow path. Specifically, each of the plurality of connecting plates 4c is a plate shape that is curved in an arc. The plurality of connecting plates 4c are arranged radially so as to swirl outward from the through hole in the main body portion 4a. The air guide 4 is made of, for example, a resin material. However, the air guide 4 may be made of a metal material.

[0036] The fan case 5 is an enclosure that houses the rotating fan 3. The fan case 5 is a cover that encloses the rotating fan 3 and the air guide 4. For example, the fan case 5 is a metal cover made of a metal material. However, it may also be a resin cover made of a resin material.

[0037] The fan case 5 has a lid portion 5a and a side wall portion 5b. The lid portion 5a covers the upper portion of the rotating fan 3 and the air guide 4. The side wall portion 5b covers the lateral portion of the rotating fan 3 and the air guide 4. The fan case 5 has an air intake port 5c for drawing in outside air. The air intake port 5c is a circular through-hole provided in the center of the lid portion 5a.

[0038] The fan case 5 is fixed to the bracket 50. The fan case 5 is fixed to the bracket 50 via the air guide 4. A fan case spacer having an opening corresponding to the air intake 5c may be attached to the air intake 5c of the fan case 5.

[0039] In the electric blower 1 configured as described above, when the rotor 10 of the electric motor 2 rotates, the rotating fan 3 rotates, and air is drawn into the fan case 5 from the intake port 5c of the fan case 5. As a result, air flows into the rotating fan 3. The air drawn into the rotating fan 3 is compressed to high pressure by the fan blades of the rotating fan 3 and discharged radially outward from the outer circumference of the rotating fan 3. The air discharged from the rotating fan 3 flows along the side wall 5b of the fan case 5 into the air guide 4, and reaches the bracket 50 through the air passage of the air guide 4.

[0040] A portion of the air that reaches the bracket 50 flows into the frame 40 via the bracket 50, passes through the inside of the frame 40, and is discharged to the outside through the exhaust port 40b of the frame 40. In other words, the air that flows into the inside of the frame 40 cools the heat-generating components (windings, etc.) of the electric motor 2, and is then discharged outside the electric blower 1.

[0041] On the other hand, the remaining portion of the air that reaches the bracket 50 is discharged directly to the outside of the electric blower 1 via the bracket 50 without passing through the inside of the frame 40. This allows the airflow to be discharged to the outside of the electric blower 1 without incurring losses by passing through the inside of the frame 40.

[0042] Next, the detailed configuration of each component of the electric motor 2 will be explained with reference to Figures 2 to 4.

[0043] As shown in Figures 3 and 4, the rotor 10 of the electric motor 2 is positioned between it and the stator 20 with a small air gap between them. In this embodiment, the rotor 10 is an inner rotor and is positioned inside the stator 20. The rotor 10 has a rotation shaft 13 and rotates around the axis C of the rotation shaft 13 as the center of rotation due to the magnetic force generated by the stator 20.

[0044] The rotor 10 generates a magnetic force that acts on the stator 20. Specifically, the direction of the main magnetic flux generated by the rotor 10 is perpendicular to the direction of the axis C of the rotation shaft 13. In this embodiment, the rotor 10 is the armature. The rotor 10 has a rotor core 11, a winding coil 12, a rotation shaft 13, and a commutator 14. The rotor core 11 is attached to the rotation shaft 13. The winding coil 12 is wound around the rotor core 11. Note that the winding coil 12 is schematically shown in Figures 2 to 4.

[0045] The rotor core 11 is an armature core around which the winding coil 12 is wound. The rotor core 11 is a laminate in which multiple electromagnetic steel sheets are stacked in the direction in which the axis C of the rotation shaft 13 extends. The rotor core 11 is not limited to a laminate of electromagnetic steel sheets. The rotor core 11 may be a bulk body made of magnetic material.

[0046] The rotor core 11 has multiple teeth, each protruding radially outward from the axis of rotation 13. The multiple teeth extend radially in a direction perpendicular to the axis C of the axis of rotation 13 (radial direction). The multiple teeth are magnetic poles. The multiple teeth generate a magnetic force that acts on the stator 20 when current flows through the winding coils 12 wound around each tooth.

[0047] The winding coil 12 is wound around the rotor core 11. Specifically, the winding coil 12 is wound around multiple teeth of the rotor core 11. The winding coil 12 may also be wound around the rotor core 11 via an insulator. The winding coil 12 is electrically connected to the commutator segments 14a of the commutator 14. When current flows through the winding coil 12 via the commutator 14, a magnetic force acting on the stator 20 is generated on each tooth of the rotor core 11.

[0048] A rotating shaft 13 is fixed to the center of the rotor core 11. The rotating shaft 13 is a shaft having an axis C. The rotating shaft 13 is a long, rod-shaped member such as a metal rod. The axis C of the rotating shaft 13 is the center when the rotor 10 rotates. The longitudinal direction (extension direction) of the rotating shaft 13 is the direction of the axis C (axial direction).

[0049] The rotating shaft 13 is fixed to the rotor core 11 in such a way that it extends on both sides of the rotor core 11 in the direction of the axis C of the rotating shaft 13, and penetrates the rotor core 11. Specifically, the rotating shaft 13 is inserted into a through hole provided in the center of the rotor core 11 and fixed to the rotor core 11. The rotating shaft 13 is fixed to the rotor core 11, for example, by press-fitting or shrink-fitting into the through hole of the rotor core 11.

[0050] The rotating shaft 13 is rotatably supported by a first bearing 15 and a second bearing 16. Specifically, a first portion 13a of the rotating shaft 13, which protrudes to one side from the rotor core 11, is supported by the first bearing 15. A second portion 13b of the rotating shaft 13, which protrudes to the other side from the rotor core 11, is supported by the second bearing 16. For example, the first bearing 15 and the second bearing 16 are bearings such as ball bearings. In this way, the rotating shaft 13 is supported by the first bearing 15 and the second bearing 16 in a rotatable state. The first bearing 15 is fixed to a bracket 50. The second bearing 16 is fixed to the bottom of a frame 40. In other words, the bracket 50 is the first bracket, and the frame 40 is the second bracket.

[0051] The first portion 13a of the rotating shaft 13 protrudes from the first bearing 15. A rotating fan 3 is attached to the tip of the first portion 13a of the rotating shaft 13 that protrudes from the first bearing 15.

[0052] The commutator 14 is attached to the rotating shaft 13. Therefore, the commutator 14 rotates together with the rotating shaft 13. The commutator 14 is attached to the second portion 13b of the rotating shaft 13. Specifically, the commutator 14 is positioned between the rotor core 11 and the second bearing 16 on the rotating shaft 13.

[0053] The commutator 14 is composed of a plurality of commutator segments 14a arranged in a ring shape around the rotating shaft 13. The plurality of commutator segments 14a are insulated from each other in the direction of rotation of the rotating shaft 13. As described above, each of the plurality of commutator segments 14a is electrically connected to the winding coil 12.

[0054] As shown in Figure 4, the stator 20 faces the rotor 10. Specifically, the stator 20 faces the rotor core 11. The stator 20 is located on the radial outer circumference of the rotor core 11. The stator 20 consists of a plurality of magnets 21 arranged at intervals from each other along the circumferential direction of the rotor 10. The magnets 21 are field magnets that create magnetic flux for generating torque. The magnets 21 are, for example, permanent magnets having a south pole and a north pole. The plurality of magnets 21 are arranged such that the north poles and south poles alternate along the rotational direction (circumferential direction) of the rotation axis 13.

[0055] The stator 20 is composed of two magnets 21 facing each other via the rotor 10. A small air gap exists between the inner surface of each magnet 21 and the outer surface of the rotor 10 (rotor core 11). The magnets 21 are fixed to the yoke 30.

[0056] As shown in Figure 4, the yoke 30 surrounds the magnet 21. The yoke 30, together with the magnet 21, constitutes a magnetic circuit (field). Therefore, the yoke 30 may be considered part of the stator 20. The yoke 30 is cylindrical with a constant thickness and surrounds the entire rotor 10 and stator 20 (magnet 21). The yoke 30 is made of a magnetic material such as iron.

[0057] As shown in Figures 1 and 2, the frame 40 is a housing (case) that contains the components of the electric motor 2, such as the rotor 10 and the stator 20. In this embodiment, the frame 40 is the outer shell of the electric blower 1 and the electric motor 2. The frame 40 can be made of a metal material such as aluminum.

[0058] As shown in Figures 1 to 4, multiple exhaust ports 40b are formed in the side walls and bottom of the frame 40 to discharge the air drawn in by the rotation of the rotating fan 3. For example, a pair of opposing exhaust ports 40b are formed in the side walls of the frame 40. A pair of opposing exhaust ports 40b are formed in the bottom of the frame 40.

[0059] As shown in Figures 3 and 4, multiple gaps G are formed between the outer surface of the yoke 30 and the inner surface of the frame 40, serving as ventilation passages in the direction of the axis C of the rotation shaft 13 (rotation axis direction).

[0060] As shown in Figures 1 to 3, the frame 40 has a bulge 41 in which a portion of the side wall of the frame 40 bulges radially outward. The gap G is the space between the bulge 41 and the yoke 30. The bulge 41 is a rib formed in the shape of a protrusion, and can be formed, for example, by press-forming the side wall of the frame 40.

[0061] As shown in Figures 3 and 4, the bracket 50 covers the opening 40a of the frame 40. The bracket 50 partially covers the opening 40a of the frame 40 without completely blocking it. In other words, with the bracket 50 attached to the frame 40, the air rectified by the air guide 4 flows into the frame 40.

[0062] The bracket 50 is provided with multiple through holes as openings through which the air rectified by the air guide 4 passes. Specifically, as shown in Figures 2 to 4, the bracket 50 is provided with four first through holes 51 and four second through holes 52. The four first through holes 51 are located radially inward. The four second through holes 52 are located radially outward from the first through holes 51.

[0063] The bracket 50 is fixed to the frame 40. For example, the bracket 50 and the frame 40 are fixed together by joining the bracket 50 to the portion (recess) between two adjacent bulges 41 on the side wall of the frame 40.

[0064] Next, the brush 60, brush holder 70, and constant-load spring 80 will be described using Figures 5 to 10, with reference to Figures 2 and 3. Figure 5 is a cross-sectional view (XY cross-sectional view) of the electric blower 1 according to an embodiment in which the pair of brushes 60 are cut by a plane passing through the pair of brushes 60 and perpendicular to the axis C of the rotating shaft 13. Figure 6 is a perspective view of the brush holder 70 with the brushes 60 and constant-load spring 80 housed inside, viewed from the front. Figure 7 is a perspective view of the brush holder 70 with the brushes 60 and constant-load spring 80 housed inside, viewed from the rear. Figure 8 is an exploded perspective view of the brush 60, brush holder 70, and constant-load spring 80. Figure 9 is a perspective view showing the contact portion between the brush 60 and the constant-load spring 80. Figure 10 is a cross-sectional view showing the contact portion between the brush 60 and the constant-load spring 80.

[0065] As shown in Figures 3 and 5, the brush 60 is in contact with the commutator 14 in a direction (radial direction) intersecting the direction of the axis C of the rotating shaft 13. The brush 60 is pressed against the commutator 14 by the pressing force from the constant-load spring 80. Specifically, the brush 60 is mounted so as to be movable in the radial direction and so as to be in sliding contact with the commutator 14 by the pressing force from the constant-load spring 80.

[0066] A pair of brushes 60 are provided. The pair of brushes 60 are positioned opposite each other so as to sandwich the commutator 14. In other words, the pair of brushes 60 are positioned opposite each other with the commutator 14 in between. Specifically, the pair of brushes 60 are positioned symmetrically with respect to the axis C of the rotation axis 13. Each of the pair of brushes 60 is an elongated member, and is positioned such that its longitudinal direction is the radial direction. As an example, the brush 60 is essentially an elongated rectangular parallelepiped.

[0067] The brush 60 is a power supply brush that supplies power to the rotor 10 by contacting the commutator 14. Specifically, the brush 60 is electrically connected to an electrode terminal 92 that receives an input voltage from a power source via a conductive wire 91. When the brush 60 contacts the commutator segment 14a of the commutator 14, the armature current supplied from the power source to the brush 60 via the conductive wire 91 and the electrode terminal 92 flows through the commutator segment 14a to the winding coil 12 of the rotor 10. The power source is an external power source located outside the motor 2. The power source supplies a predetermined input voltage to the motor 2.

[0068] The brush 60 is composed of a conductive material. In this embodiment, the brush 60 is composed solely of a conductive material. Specifically, the brush 60 is composed solely of a long, substantially rectangular carbon brush made of carbon. As an example, the brush 60 is a metallic graphite brush containing a metal such as copper and carbon. In this embodiment, the brush 60 is a carbon brush containing copper. The brush 60 can be manufactured by crushing a mixture of graphite powder, copper powder, binder resin, and hardener, compressing it into a rectangular prism, and firing it.

[0069] As shown in Figures 3 and 5, the brush 60 includes a front end 61 which is a first end that contacts the commutator 14, and a rear end 62 which is a second end located on the opposite side from the front end 61.

[0070] The front end 61 of the brush 60 is one end of the brush 60 in the longitudinal direction. The front end 61 is the tip of the brush 60 on the side of the rotation axis 13 (radially inward). The front end 61 has a front end surface 61a that is the contact surface that contacts the commutator segment 14a of the commutator 14.

[0071] On the other hand, the rear end 62 of the brush 60 is the other end in the longitudinal direction of the brush 60. The rear end 62 is the tip of the brush 60 on the side opposite to the rotation axis 13 (radially outward). The rear end 62 has a rear end surface 62a that is the contact surface that comes into contact with the constant load spring 80.

[0072] A recess 63 is formed at the rear end 62 of the brush 60. The recess 63 is formed such that a part of the rear end surface 62a is recessed toward the front end 61. In this embodiment, the recess 63 is formed by cutting out the rear end surface 62a in a V-shape. The recess 63 is a V-groove with a uniform V-shaped cross-section. Therefore, the recess 63 has a V-shape in the cross-section (XY cross-section) when cut by a plane perpendicular to the direction of the axis C of the rotation axis 13. The recess 63, being a V-groove, has a line-symmetric V-shape in the XY cross-section. The recess 63, being a V-groove, is formed such that the bottom line of the V-groove is substantially parallel to the direction of the axis C of the rotation axis 13.

[0073] The recess 63 can be formed, for example, by drilling out a triangular prism-shaped portion from the flat end face of a rectangular brush and making an incision in the end face. The shape of the recess 63 may be formed by the shape of the mold used when sintering the brush 60, rather than by cutting the flat end face of the brush 60.

[0074] As shown in Figure 3, the brush 60 is held in the brush holder 70 so as to move in a direction (radial direction) intersecting the direction of the axis C of the rotation axis 13. The brush holder 70 is a holder that holds the brush 60. The brush holder 70 is fixed to the frame 40. Specifically, the brush holder 70 is inserted into an opening provided in the frame 40 and fixed to the frame 40 by screws 100. The number of brush holders 70 is determined according to the number of brushes 60. In this embodiment, since there are two brushes 60, there are also two brush holders 70.

[0075] As shown in Figures 6 and 7, the brush holder 70 houses the brush 60. The brush holder 70 has a first holder 71 for housing the brush 60 and a second holder 72 for holding the first holder 71.

[0076] The first holder 71 is a cylindrical section surrounding the brush 60. The first holder 71 is a long, essentially rectangular tube shape extending in a direction (radial direction) intersecting the axis C of the rotating shaft 13. Both ends of the first holder 71 in the longitudinal direction are open. The brush 60 is placed inside the first holder 71 with its front end 61 exposed. Alternatively, the brush 60 may be placed inside the first holder 71 while housed in a brush box made of metal plate.

[0077] A constant-load spring 80 is fixed to the front open end 71a of the cylindrical first holder 71. The specific method of fixing the first holder 71 and the constant-load spring 80 will be described later.

[0078] As shown in Figures 6 to 8, the brush holder 70 has a protruding portion 71b. The protruding portion 71b is used to fix the constant-load spring 80 to the brush holder 70. In other words, the constant-load spring 80 is fixed to the first holder 71 not only using the open end 71a of the first holder 71, but also using the protruding portion 71b. The protruding portion 71b is erected on the outer surface of the outer wall of the first holder 71. Specifically, the protruding portion 71b is flat and is provided in a screen-like manner on the lateral outer wall of the first holder 71. The protruding portion 71b is elongated and extends along the longitudinal direction of the first holder 71. In other words, the protruding portion 71b extends along the direction (radial direction) that intersects with the direction of the axis C of the rotation axis 13.

[0079] The second holder 72 has a fitting hole 72a into which the first holder 71 is fitted. The first holder 71 is held by the second holder 72 by being inserted into the fitting hole 72a. The second holder 72 is provided with a screw hole 72b through which a screw 100 is inserted. The second holder 72 can be attached to the frame 40 by inserting the second holder 72, which holds the first holder 71, into the opening of the frame 40 and screwing the screw 100 into the screw hole 72b. In other words, the brush holder 70 can be attached to the frame 40.

[0080] The first holder 71 and the second holder 72 are made of, for example, an insulating resin material. In this embodiment, each of the first holder 71 and the second holder 72 is a resin molded product formed by integral molding using a resin material.

[0081] An electrode terminal 92 is fixed to the rear end of the first holder 71. The electrode terminal 92 is positioned to close the rear opening of the first holder 71. The electrode terminal 92 and the brush 60 are connected by a conductive wire 91.

[0082] The conductive wire 91 is, for example, a pigtail wire. One end of the conductive wire 91 is connected to the brush 60. The other end of the conductive wire 91 is connected to the electrode terminal 92. As shown in Figure 8, one end of the conductive wire 91 is connected to the rear end face 62a of the brush 60. The conductive wire 91 may also be connected to the side of the brush 60.

[0083] The conductive wire 91 is routed in such a way that it does not interfere with the brush 60 even when the brush 60 wears down due to sliding. This prevents the conductive wire 91 from hindering the sliding of the brush 60. The length of the conductive wire 91 is set to be long enough to account for the movement of the brush 60 due to wear. For this reason, as shown in Figure 7, in the initial state before the brush 60 wears down, the conductive wire 91 protrudes from the opening formed on the upper surface of the first holder 71.

[0084] The electrode terminal 92, connected to the conductive wire 91, receives power to energize the winding coil 12 of the rotor 10. In other words, the electrode terminal 92 supplies power to the brush 60. The power supplied to the electrode terminal 92 is supplied to the brush 60 via the conductive wire 91 and then to the winding coil 12 via the commutator piece 14a.

[0085] As shown in Figure 5, the brush holder 70 houses the constant-load spring 80. In other words, the brush holder 70 holds not only the brush 60 but also the constant-load spring 80. The constant-load spring 80, together with the brush 60, is housed in the first holder 71 of the brush holder 70. That is, the brush 60 and the constant-load spring 80 are arranged inside the first holder 71.

[0086] The constant-load springs 80 are arranged according to the number of brushes 60. In this embodiment, since there are two brushes 60, there are also two constant-load springs 80. Specifically, the electric motor 2 is provided with two brush holders 70 that house the constant-load springs 80 and the brushes 60.

[0087] The constant-load spring 80 is a brush spring that presses the brush 60 against the commutator 14. Specifically, the constant-load spring 80 presses the brush 60 against the commutator 14 by applying pressure to it. The constant-load spring 80 is a spring that applies a uniform load to the brush 60. In other words, the constant-load spring 80 applies a uniform pressing force to the brush 60.

[0088] As shown in Figures 5 and 8, the constant-load spring 80 is made of a strip of wire. The constant-load spring 80 is a spiral spring and has a spiral section 81 (coil section) in which the strip of wire is wound in a spiral shape. The constant-load spring 80 is made of a single strip of wire made of, for example, a metal material.

[0089] Specifically, the constant-load spring 80 is composed of a long, strip-shaped metal plate. Therefore, the spiral portion 81 is the part of the constant-load spring 80 in which the long, strip-shaped metal plate is wound spirally multiple times in only one direction. The shape of one rotation of the spiral portion 81 is circular in cross-section (XY cross-section) when cut by a plane perpendicular to the direction of the axis C of the rotation axis 13. The spiral portion 81, configured in this way, has a spring elastic force (spring restoring force) that causes the spirally wound metal plate to return to its original shape.

[0090] The constant-load spring 80 has an outer end 80a, which is one end of a strip-shaped metal plate, and an inner end 80b, which is the other end of the strip-shaped metal plate. The outer end 80a is one tip of the strip-shaped metal plate that is drawn outward from the outermost circumference of the spiral portion 81. The inner end 80b is the other tip of the strip-shaped metal plate located at the innermost circumference of the spiral portion 81.

[0091] As shown in Figure 5, the constant-load spring 80 presses the brush 60 against the commutator 14 with its spiral portion 81. Specifically, the spiral portion 81 of the constant-load spring 80 is in contact with the rear end portion 62 of the brush 60. The constant-load spring 80 applies a load to the brush 60 through the spring elastic force of the spiral portion 81. In other words, the constant-load spring 80 applies a pressing force (spring pressure) to the brush 60 with its spiral portion 81. As a result, the brush 60 is biased toward the commutator 14.

[0092] As shown in Figures 9 and 10, the spiral portion 81 of the constant-load spring 80 and the rear end portion 62 of the brush 60 are in contact at two or more points. A recess 63 is formed in the rear end portion 62 of the brush 60. The spiral portion 81 is in contact with this recess 63 at two or more points. Specifically, the recess 63 is a V-shaped groove with a uniform V-shaped cross-section. As a result, the spiral portion 81, which is made of a strip-shaped metal plate, and the recess 63 are in line contact at two points. In other words, as shown in Figure 10, in a cross-section cut in a plane perpendicular to the direction of the axis C of the rotation axis 13 (the Z-axis direction in this embodiment), the spiral portion 81 and the rear end portion 62 are in contact at two points, a first point P1 and a second point P2. The first point P1 and the second point P2 are the contact points between the spiral portion 81 and the rear end portion 62. Thus, the spiral portion 81 and the recess 63 are in line contact at two points, the first point P1 and the second point P2. Furthermore, the spiral portion 81 is in contact with the inner surface of the recess 63, and a part of the spiral portion 81 extends inward into the recess 63.

[0093] In the XY cross-section, the recess 63 is a V-shape with line symmetry, and the spiral portion 81 is circular. Therefore, the line connecting the first point P1 and the second point P2 is parallel to the direction perpendicular to the longitudinal direction of the brush 60. In other words, the line connecting the first point P1 and the second point P2 is parallel to the short direction of the brush 60.

[0094] As described above, the constant-load spring 80 is housed in the brush holder 70. Specifically, as shown in Figure 5, the constant-load spring 80 is housed in the first holder 71 of the brush holder 70 such that the spiral portion 81 is located behind the rear end portion 62 of the brush 60. The outer end portion 80a of the constant-load spring 80 is positioned in the first holder 71 so as to be pulled out from the side of the brush 60 toward the front end portion 61 (commutator 14 side) of the brush 60.

[0095] The constant-load spring 80 is fixed to the brush holder 70. Specifically, as shown in Figure 5, the outer end 80a of the constant-load spring 80 is fixed to the first holder 71 of the brush holder 70. The constant-load spring 80 is fixed to the first holder 71 by the outer end 80a of the constant-load spring 80 engaging with the first holder 71.

[0096] Specifically, as shown in Figure 8, the constant-load spring 80 has a folded structure 82 in which the outer end 80a drawn out from the spiral portion 81 is bent back on the outside. As shown in Figures 6 and 7, the constant-load spring 80 is fixed to the first holder 71 by inserting the folded structure 82 into the open end 71a of the first holder 71. The open end 71a of the first holder 71 is part of the side wall of the cylindrical first holder 71.

[0097] As shown in Figure 8, the folded structure 82 has a first folded portion 82a formed by folding the outer end 80a of the constant-load spring 80 outwards, and an opposing portion 82b that faces the first folded portion 82a. The first folded portion 82a and the opposing portion 82b are metal pieces that are part of the metal plate constituting the constant-load spring 80. The first folded portion 82a (first folded piece) is a portion formed by folding the end of the metal plate outwards by 180 degrees. The first folded portion 82a is the tip portion of the outer end 80a. The opposing portion 82b (opposing piece) is the portion of the metal plate that faces the first folded portion 82a.

[0098] The constant-load spring 80 is fixed to the first holder 71 by inserting the folded structure 82 into the open end 71a of the first holder 71 (cylindrical portion) of the first holder 71, such that the open end 71a of the first holder 71 is sandwiched between the first folded portion 82a and the opposing portion 82b of the folded structure 82. In other words, the open end 71a of the first holder 71 is inserted into the gap between the first folded portion 82a and the opposing portion 82b of the folded structure 82.

[0099] In this way, by forming a folded structure 82 on the constant-load spring 80, the constant-load spring 80 can be fixed to the brush holder 70 simply by inserting the folded structure 82 into the open end 71a of the first holder 71. Therefore, compared to the case where the outer end 80a is fixed to the brush holder 70 with rivets or screws without forming a folded structure 82 on the outer end 80a, the number of man-hours and parts can be reduced.

[0100] In this embodiment, the first folded portion 82a has a first slit 83a that extends along the insertion direction of the folded structure 82. The first slit 83a is formed along the longitudinal direction of the metal plate constituting the constant-load spring 80. Figure 11 shows the shape of the outer end portion 80a before the formation of the folded structure 82 in the constant-load spring 80 according to this embodiment. As shown in Figure 11, the tip portion of the first slit 83a is open. In other words, the tip portion on one side of the metal plate before the formation of the folded structure 82 is separated into two thin pieces by the formation of the first slit 83a. The folded structure 82 is formed by bending the metal plate on which the first slit 83a is formed so as to fold it back 180 degrees at the folding position Pb. The folding position Pb is the connection portion between the first folded portion 82a and the opposing portion 82b. As shown in Figure 11, the folding position Pb is set in the middle of the first slit 83a, but it may be set at a different position from the first slit 83a.

[0101] As described above, a protruding portion 71b is provided on the outer wall of the first holder 71. The protruding portion 71b extends along the insertion direction when the folded structure 82 is inserted into the open end 71a of the first holder 71. In this embodiment, the constant load spring 80 is fixed to the first holder 71 using the protruding portion 71b as well.

[0102] Figures 12A, 12B, and 12C illustrate how the constant-load spring 80 and brush 60 are assembled into the brush holder 70 in the electric motor 2 according to the embodiment. Figure 13A illustrates how the constant-load spring is assembled into the brush holder in the electric motor according to the embodiment. Specifically, when fixing the constant-load spring 80 to the first holder 71, as shown in Figures 12A and 12B, the folded structure 82 of the constant-load spring 80 is inserted into the open end 71a of the first holder 71, and the first slit 83a of the constant-load spring 80 is inserted into the protruding portion 71b. In this case, the open end 71a of the first holder 71 is sandwiched between the first folded portion 82a and the opposing portion 82b of the folded structure 82. As a result, as shown in Figure 13A, the constant-load spring 80 is set in the front portion of the first holder 71 with its outer end 80a fixed to the first holder 71.

[0103] In this way, the constant-load spring 80 is fixed to the first holder 71 by inserting the folded structure 82 into the open end 71a of the first holder 71 and inserting the first slit 83a into the protruding portion 71b. In other words, the constant-load spring 80 is fixed to the first holder 71 not only by the folded structure 82 but also by utilizing the first slit 83a. By inserting the protruding portion 71b into the first slit 83a, the first folded portion 82a constituting the first slit 83a can be prevented from moving in the vertical direction (in the direction of the axis C of the rotation axis 13) by the protruding portion 71b. This prevents the constant-load spring 80 attached to the first holder 71 from moving in the vertical direction. Therefore, the constant-load spring 80 can be fixed to the brush holder 70 in a stable state.

[0104] In this embodiment, the constant-load spring 80 is fixed to the brush holder 70 only at its outer end 80a. The constant-load spring 80 is not fixed anywhere other than the outer end 80a. In other words, the parts of the constant-load spring 80 other than the outer end 80a are not supported and are free. That is, the constant-load spring 80 is supported at only one point, the outer end 80a.

[0105] After fixing the constant-load spring 80 to the brush holder 70, the brush 60 is inserted into the brush holder 70 as shown in Figure 12C. Specifically, the brush 60 is inserted into the back of the first holder 71 while pressing the rear end 62 of the brush 60 against the spiral portion 81 of the constant-load spring 80. As a result, as shown in Figure 13B, the brush 60 is housed in the first holder 71 while biased by the spring elastic force of the spiral portion 81 of the constant-load spring 80. Figure 13B is a diagram illustrating how the brush 60 is assembled into the brush holder 70 in the electric motor 2 according to this embodiment.

[0106] Figure 13C is a diagram illustrating the relationship between the brush 60 and the conductive wire 91 when the brush wears down in the electric motor 2 according to this embodiment. In this embodiment, as shown in Figure 13C, the length of the conductive wire 91 is set so that the constant-load spring 80 applies a pressing force to the brush 60 even when the brush 60 is at its maximum wear. Furthermore, the length of the conductive wire 91 is set so that the brush 60 is positioned to receive the load of the constant-load spring 80 from the initial position of the constant-load spring 80 before the brush 60 is assembled. In other words, the conductive wire 91 is fixed at a position where the brush 60 applies a load to the spiral portion 81 of the constant-load spring 80.

[0107] With this configuration, as shown in Figure 13C, the conductive wire 91 will remain taut even when the brush 60 is completely worn out. This suppresses vibration of the brush 60, even if there is a gap between the brush 60 and the brush holder 70. By setting the length of the conductive wire 91 as described above, the constant-load spring 80 can always apply pre-tension to the brush 60 by utilizing the spring properties of the constant-load spring 80. As a result, a reaction force from the brush 60 is applied to the constant-load spring 80, which prevents the constant-load spring 80 from coming out of the brush holder 70 once it has been installed in the brush holder 70.

[0108] In the electric motor 2 configured as described above, the armature current supplied to the brushes 60 flows through the commutator 14 to the winding coils 12 of the rotor 10. This generates a magnetic flux in the rotor 10, and the magnetic force generated by the interaction between the magnetic flux from the rotor 10 and the magnetic flux from the magnets 21 of the stator 20 becomes the torque that rotates the rotor 10. As a result, the rotor 10 rotates. And as the rotor 10 rotates, the rotating shaft 13 rotates. As a result, the rotating fan 3 attached to the rotating shaft 13 rotates.

[0109] As the rotor 10 rotates in this manner, the front end 61 of the brush 60 that contacts the commutator 14 wears down. At this time, the brush 60 is constantly subjected to a constant load (pressing force) from the constant-load spring 80 and pressed against the commutator 14. As a result, as the front end 61 of the brush 60 wears down due to friction with the commutator segments 14a, the brush 60 slides towards the commutator 14 within the first holder 71 of the brush holder 70. At this time, the wire constituting the constant-load spring 80 is wound up as the brush 60 shortens due to wear. In other words, the spiral portion 81 moves closer to the outer end 80a.

[0110] Here, the effects of the electric motor 2 according to this embodiment will be explained in comparison with the electric motor of the comparative example. Figures 14A, 14B, and 14C are diagrams illustrating the behavior of the electric motor of the comparative example as the brush 60X slides and the constant load spring 80X moves as the brush 60X wears down. Figures 15A, 15B, and 15C are diagrams illustrating the behavior of the electric motor 2 according to this embodiment as the brush 60 slides and the constant load spring 80 moves as the brush 60 wears down.

[0111] In the comparative example motor, the rear end portion 62 of the brush 60X does not have a recess 63. The rear end surface 62a of the rear end portion 62 is a flat surface. The spiral portion 81 of the constant-load spring 80X is in contact with the rear end surface 62a. The brush 60X is pressed against the commutator segment (not shown) by a constant pressing force from the spiral portion 81. In this case, in the comparative example motor, the rear end surface 62a of the brush 60X and the spiral portion 81 of the constant-load spring 80X are in contact at only one point. That is, in the XY cross-section, the rear end surface 62a of the brush 60X and the spiral portion 81 of the constant-load spring 80X are in contact at only one point.

[0112] In the comparative example motor configured in this way, similar to the motor motor 2 according to this embodiment, as the front end portion 61 of the brush 60X wears down due to friction with the commutator segments, the brush 60X slides toward the commutator segment. The spiral portion 81 of the constant-load spring 80X that applies pressure to the brush 60X moves toward the commutator segment as the brush 60X slides.

[0113] In this case, as shown in Figures 14A, 14B, and 14C, in the comparative example motor, the rear end surface 62a of the brush 60X and the spiral portion 81 of the constant-load spring 80X are in contact at only one point. Therefore, the spiral portion 81 that applies load to the brush 60X moves from side to side at the rear end surface 62a of the brush 60X as the brush 60X wears down due to the expansion and contraction of the spring caused by the spiral portion 81 itself during movement. In other words, the contact point between the rear end surface 62a of the brush 60X and the spiral portion 81 moves from side to side as the brush 60X wears down.

[0114] Specifically, as shown in Figure 14A, in the initial state before the brush 60X wears down, the center line of the spiral portion 81 and the center line of the brush 60X coincide. However, as shown in Figure 14B, as the brush 60X wears down, the spiral portion 81 shifts to the opposite side (right side in the figure) from which the outer end 80a was pulled out. As the brush 60X wears down further, as shown in Figure 14C, the spiral portion 81 shifts to the side (left side in the figure) from which the outer end 80a was pulled out, and eventually returns to its initial position.

[0115] As the brush 60X wears down, the spiral portion 81 moves from side to side, causing the load applied by the spiral portion 81 to the brush 60X to become unstable. Consequently, the pressing force applied by the spiral portion 81 to the brush 60X may become unstable. In particular, when the spiral portion 81 moves from side to side, the spiral portion 81 of the constant-load spring 80X may come into contact with the inner surface of the brush holder that holds the constant-load spring 80X and the brush 60X. In this case, the load applied by the constant-load spring 80X to the brush 60X decreases significantly.

[0116] In contrast, in the electric motor 2 according to this embodiment, the spiral portion 81 of the constant-load spring 80 and the rear end portion 62 of the brush 60 are in contact at two or more points. Specifically, a recess 63 is formed in the rear end portion 62 of the brush 60, and the spiral portion 81 is in contact with the recess 63 at two points.

[0117] In the electric motor 2 configured in this way, as described above, the front end 61 of the brush 60 wears down due to friction with the commutator segment 14a, causing the brush 60 to slide toward one side of the commutator. The spiral portion 81 of the constant-load spring 80 that applies pressure to the brush 60 moves toward one side of the commutator as the brush 60 slides.

[0118] In this case, as shown in Figures 15A, 15B, and 15C, the motor 2 has contact at two points between the rear end surface 62a of the brush 60 and the spiral portion 81 of the constant-load spring 80. Therefore, even if the spiral portion 81 itself expands and contracts during movement, the spiral portion 81 can be prevented from moving from side to side even as the brush 60 wears down. In other words, the contact points between the rear end surface 62a of the brush 60 and the spiral portion 81 do not move from side to side even as the brush 60 wears down.

[0119] Specifically, as shown in Figures 15A, 15B, and 15C, even as the brush 60 wears down, the center line of the spiral section 81 and the center line of the brush 60 remain aligned without shifting. In other words, the spiral section 81 does not move from side to side from the initial state before the brush 60 wears down to the final state after the brush 60 has worn down.

[0120] Therefore, by using a constant-load spring 80 with a small difference between the initial and final pressures, a constant pressing force can be continuously applied to the brush 60 even as the brush 60 wears down. In other words, a stable load can be continuously applied to the brush 60. This helps to suppress a decrease in the efficiency of the electric motor 2 and the lifespan of the brush 60.

[0121] Here, we conducted an experiment to determine the relationship between the groove width of the recess 63 of the V-shaped groove formed on the rear end surface 62a of the brush 60 and the left-right movement of the spiral portion 81 of the constant-load spring 80. The experimental results will be explained using Figure 16. Figure 16 shows the experimental results regarding the relationship between the groove width of the recess 63 of the V-shaped groove and the left-right movement of the spiral portion 81 of the constant-load spring 80.

[0122] In this experiment, five types of brushes 60, from Examples 1 to 5, were fabricated, each with a different groove width in the recess 63, as well as a conventional brush 60X with a flat rear end surface. The lateral movement of the spiral portion 81 of the constant-load spring 80 during the sliding motion of the brushes 60 and 60X was then evaluated.

[0123] As the constant-load spring 80, one having a spiral section 81 with a diameter of φ5.50 mm was used. The groove width of the V-shaped groove recess 63 was evaluated by the angle θ between the two points where the inner surface of the recess 63 and the spiral section 81 are in contact and the center of the spiral section 81. The angle θ is the central angle of a circle centered at the center O of the spiral section 81, with the first point P1 and the second point P2 as the chords. In this case, the first point P1 and the second point P2 are the points of contact between the spiral section 81 and the recess 63 in a cross-section when cut by a plane perpendicular to the direction of the axis C of the rotation axis 13.

[0124] As a result, in the case of the conventional brush 60X, the spiral portion 81 moved significantly from side to side as the brush 60X slid.

[0125] On the other hand, with respect to the brush 60 of Example 1 (θ=20.95°, groove width 1.0 mm), although the spiral portion 81 did not move significantly from side to side, the spiral portion 81 sometimes detached from the recess 63 and moved from side to side.

[0126] In the case of the brush 60 of Example 2 (θ=31.65°, groove width 1.5 mm) and the brush 60 of Example 3 (θ=37.11°, groove width 1.75 mm), although the spiral portion 81 did not move significantly from side to side, similar to the brush 60 of Example 1, the spiral portion 81 sometimes came out of the recess 63 and moved from side to side.

[0127] In the case of the brush 60 of Example 4 (θ=42.65°, groove width 2.0 mm), when the brush 60 was slid repeatedly, the spiral portion 81 occasionally moved from side to side, but the spiral portion 81 never came out of the recess 63.

[0128] In the case of the brush 60 of Example 5 (θ=48.30°, groove width 2.25 mm), the spiral portion 81 did not move from side to side no matter how many times the brush 60 was slid, and the spiral portion 81 did not come out of the recess 63.

[0129] From the above experimental results, in order for the constant-load spring 80 to continuously apply a stable load to the brush 60, θ ≥ 40° is desirable, and more preferably θ ≥ 48°. In particular, θ ≥ 48.30° is desirable.

[0130] As described above, the electric motor 2 according to this embodiment comprises a rotor 10 having a rotating shaft 13 and a commutator 14 attached to the rotating shaft 13, a brush 60 including a first end that contacts the commutator 14 and a second end 62 located on the opposite side of the first end 61, and a constant-load spring 80 made of a strip-shaped wire for pressing the brush 60 against the commutator 14. The constant-load spring 80 has a spiral portion 81 around which a strip-shaped wire is wound, and the spiral portion 81 and the second end 62 are in contact at two or more points.

[0131] This allows a stable load to be applied to the brush 60 even when using a constant-load spring 80. Therefore, a decrease in the efficiency of the electric motor 2 and the lifespan of the brush 60 can be suppressed.

[0132] The electric motor 2 has a recess 63 formed in the second end 62, and it is preferable that the spiral portion 81 is in contact with the recess 63 at two or more points.

[0133] The spiral portion 81 and the second end portion 62 are in contact at two points, a first point and a second point, in a cross-section obtained by cutting with a plane perpendicular to the axial direction of the rotation axis 13, and it is preferable that the line connecting the first point and the second point is parallel to the direction perpendicular to the longitudinal direction of the brush 60.

[0134] In a circle centered at the center of the spiral portion 81, if θ is the central angle between the first and second points on the chord, then it is preferable that θ ≥ 40°.

[0135] In a circle centered at the center of the spiral portion 81, if θ is the central angle with respect to the chord between the first and second points, then it is even more preferable that θ ≥ 48°.

[0136] The electric motor 2 further includes a brush holder 70 for holding the brush 60, the brush holder 70 having a cylindrical portion surrounding the brush 60, and the constant-load spring 80 having a folded structure 82 in which one end drawn out from the spiral portion 81 is folded back outwards, the folded structure 82 having a first folded portion 82a with one end folded back outwards and an opposing portion 82b facing the first folded portion 82a, and the constant-load spring 80 may be fixed to the cylindrical portion by inserting the folded structure 82 into the open end 71a of the cylindrical portion so that the open end 71a is sandwiched between the first folded portion 82a and the opposing portion 82b.

[0137] The first folded portion 82a has a first slit 83a that extends along the insertion direction of the folded structure 82, the brush holder 70 has a protruding portion 71b that is erected on the outer surface of the outer wall of the cylindrical portion and extends along the insertion direction, and the constant load spring 80 may be fixed to the cylindrical portion by the folded structure 82 being inserted into the open end 71a of the cylindrical portion and the first slit 83a being inserted into the protruding portion 71b.

[0138] The electric motor 2 further has a conductive wire 91, one end of which is connected to the brush 60 and the other end of which is connected to an electrode terminal 92 that supplies power to the brush 60, and it is preferable that the length of the conductive wire 91 is set so that the constant-load spring 80 applies a pressing force to the brush 60 even when the brush 60 is at its maximum wear.

[0139] (modified version) The electric motor 2 and electric blower 1 related to this disclosure have been described above based on embodiments. However, this disclosure is not limited to the embodiments described above.

[0140] For example, the folded structure 82 of the constant-load spring 80 is not limited to the structure shown in Figure 8. Specifically, in the above embodiment, the folded structure 82 of the constant-load spring 80 was formed by bending a metal plate in which a first slit 83a was formed with one end of the longitudinal direction open, as shown in Figure 11. However, with such a shape, there is a risk that the metal plate will deform during bending due to insufficient strength. Therefore, as shown in Figure 17, the metal plate is bent in which a slit is formed without opening one end of the longitudinal direction of the metal plate. This can form an L-shaped folded structure 82A as shown in Figures 18A and 18B. Figure 17 is a diagram showing the shape of the outer end 80a of the metal plate before the folded structure is formed in the modified constant-load spring 80A. Figure 18A is a perspective view of the modified constant-load spring 80A. Figure 18B is a top view of the constant-load spring 80A.

[0141] As shown in Figures 18A and 18B, the folded structure 82A of the constant-load spring 80A has a first folded portion 82a and an opposing portion 82b, as well as a second folded portion 82c erected on the first folded portion 82a. The second folded portion 82c has a second slit 83b formed therein, which is continuous with the first slit 83a. The second slit 83b is formed without cutting out to the tip of the second folded portion 82c. In other words, as shown in Figures 17 and 18A, in the folded structure 82A, the tips of the two thin pieces at the outer end 80a are not separated but connected by a bridge portion 82c1.

[0142] The folded structure 82A configured in this way can be formed by bending the metal plate shown in Figure 17 so that it is folded 180 degrees outward at the first folding position Pb1, and then bending it so that it is folded 90 degrees to the opposite side at the second folding position Pb2. At this time, the tip portion of the outer end 80a is not separated, and the tips of the two thin pieces at the outer end 80a are connected by the bridge portion 82c1. Therefore, deformation of the metal plate during the bending process can be suppressed.

[0143] The constant-load spring 80A manufactured in this manner can be fixed to the first holder 71 by inserting the folded structure 82A into the open end 71a of the first holder 71, as shown in Figures 19A, 19B, and 19C. Figures 19A, 19B, and 19C are diagrams illustrating how the modified constant-load spring 80A and brush 60 are assembled into the brush holder 70. Specifically, as shown in Figures 19A and 19B, the folded structure 82A of the constant-load spring 80A is inserted into the open end 71a of the first holder 71, and the first slit 83a and second slit 83b of the constant-load spring 80A are inserted into the protruding portion 71b. At this time, the open end 71a of the first holder 71 is sandwiched between the first folded portion 82a and the opposing portion 82b of the folded structure 82A. As a result, the constant-load spring 80A is set in the front portion of the first holder 71 with its outer end 80a fixed to the first holder 71.

[0144] Thus, the constant-load spring 80A is fixed to the first holder 71 not only by the folded structure 82A but also by utilizing the first slit 83a and the second slit 83b. By inserting the protruding portion 71b into the first slit 83a and the second slit 83b, the first folded portion 82a constituting the first slit 83a and the second folded portion 82c constituting the second slit 83b can be prevented from moving in the vertical direction (in the direction of the axis C of the rotation axis 13) by the protruding portion 71b. As a result, the constant-load spring 80A can be prevented from moving in the vertical direction compared to the constant-load spring 80 in the above embodiment. Therefore, the constant-load spring 80A can be fixed to the brush holder 70 in an even more stable state.

[0145] Then, after fixing the constant-load spring 80A to the brush holder 70, the brush 60 is inserted into the brush holder 70 as shown in Figure 19C. Specifically, the brush 60 is inserted into the back of the first holder 71 while pressing the spiral portion 81 of the constant-load spring 80A against the rear end 62 of the brush 60. As a result, the brush 60 is housed in the first holder 71 while biased by the spring elastic force of the spiral portion 81 of the constant-load spring 80A.

[0146] Figure 20A shows the configuration of a modified constant-load spring 80A. In the constant-load spring 80A, as shown in Figure 20A, a folded structure 82A having a first folded portion 82a and an opposing portion 82b is formed by bending a metal plate 180 degrees. In other words, the folding angle of the folded structure 82A between the first folded portion 82a and the opposing portion 82b was 180 degrees.

[0147] With this configuration, the constant-load spring 80A can be easily attached to the first holder 71 by the folded structure 82A. However, while it can be easily attached, there is a risk that the constant-load spring 80A may easily detach from the first holder 71. For example, if the folded structure 82A is in an oblique position, the folded structure 82A may easily detach from the open end 71a of the first holder 71. In this regard, while incorporating the brush 60 with conductive wire 91 can suppress the constant-load spring 80A from easily detaching, there is a risk that the constant-load spring 80A may detach before the brush 60 with conductive wire 91 is incorporated.

[0148] Figure 20B shows the configuration of a modified constant-load spring 80B. In the folded structure 82B, as shown in Figure 20B, the gap between the first folded portion 82a and the opposing portion 82b should narrow as it moves away from the folded position of the folded structure 82B. Specifically, the gap between the first folded portion 82a and the opposing portion 82b gradually narrows as it moves away from the connection point between the first folded portion 82a and the opposing portion 82b. For example, the folding angle of the folded structure 82B between the first folded portion 82a and the opposing portion 82b should be between 181° and 185°.

[0149] In this way, by making the gap between the first folded portion 82a and the opposing portion 82b narrower as it moves away from the folded position of the folded structure 82B, the spring elastic force of the leaf spring between the first folded portion 82a and the opposing portion 82b in the folded structure 82B can be used to clamp the open end 71a of the first holder 71 between the first folded portion 82a and the opposing portion 82b. Therefore, by inserting the folded structure 82B into the open end 71a of the first holder 71, the constant load spring 80B can be temporarily held or temporarily fixed to the brush holder 70. Note that the configuration of the first folded portion 82a and the opposing portion 82b in the folded structure 82B may also be applied to the constant load spring 80 in the above embodiment.

[0150] In the above embodiment, the shape of the recess 63 of the brush 60 was a V-shaped groove with a triangular cross-sectional shape of the notched portion, but is not limited to this. Figures 21A and 21B are enlarged views of the contact portion between the brush 60A and the constant-load spring 80 according to a modified example. For example, as shown in Figures 21A and 21B, the recess 63A of the brush 60A may be an arc-shaped groove. In this case, as shown in Figure 21B, the recess 63A has an arc shape in the cross-section (XY cross-section) when cut by a plane perpendicular to the direction of the axis C of the rotation axis 13. Figure 22A is an enlarged view of the contact portion between the brush 60B and the constant-load spring 80 according to a modified example. Figure 22B is an enlarged view of the contact portion between the brush 60B and the constant-load spring 80 according to a modified example. Alternatively, as shown in Figures 22A and 22B, the recess 63B of the brush 60B may be a rectangular groove with a rectangular cross-sectional shape of the notched portion. In this case, as shown in Figure 22B, the recess 63B is U-shaped in the cross-section (XY section) when cut by a plane perpendicular to the direction of the axis C of the rotation axis 13. The shape of the brush recess is not limited to these shapes. The brush recess may have a curved shape such as U-shape, C-shape, or parabola, a polygonal shape such as a trapezoid, or a shape with multiple straight lines, or a shape with one or more curves and one or more straight lines in the cross-section (XY section) when cut by a plane perpendicular to the direction of the axis C of the rotation axis 13. As shown in Figures 21A and 21B, if the recess 63A is an arc groove, the curvature of the arc of the recess 63A should be greater than the curvature of the circle that makes up the spiral section 81 in order for the recess 63A and the spiral section 81 to be in contact at two places.

[0151] As described above, the recess 63 of this embodiment may have a V-shape, an arc shape, a U-shape, or a U-shape in cross-section when cut by a plane perpendicular to the axial direction of the rotation axis 13.

[0152] The folded structure 82 further has a second folded portion 82c erected on the first folded portion 82a, and a second slit 83b continuous with the first slit 83a is formed in the second folded portion 82c, and the second slit 83b may be formed without cutting out to the tip of the second folded portion 82c.

[0153] Preferably, the gap between the first folded portion 82a and the opposing portion 82b becomes narrower as it moves away from the folded position of the folded structure 82.

[0154] Furthermore, in the above embodiment, the spiral portion 81 of the constant-load spring 80 and the rear end portion 62 of the brush 60 were in contact at only two points, but this is not limited to this. For example, the spiral portion 81 of the constant-load spring 80 and the rear end portion 62 of the brush 60 may be in contact at three or four points, or three or more points. In this way, by having the spiral portion 81 and the rear end portion 62 in contact at three or more points, a more stable load can be applied to the brush 60 compared to the above embodiment. In this case, the spiral portion 81 and the rear end portion 62 are not limited to being in contact at three or more points in only one cross-section of the XY cross-section, but may be in contact at three or more points in multiple cross-sections of the XY cross-section. For example, the spiral portion 81 and the rear end portion 62 may be in contact at only two points in one cross-section of the XY cross-section as in the above embodiment, and may also be in contact at one or more points in one or more other cross-sections of the XY cross-section. In this case, the notched portion of the recess formed on the rear end face of the brush 60 does not necessarily have to have the same cross-sectional shape along the direction of the axis C of the rotation shaft 13.

[0155] In the above embodiment, the recess 63 of the brush 60 was formed to cut out the entire area in the direction of the axis C of the rotation shaft 13 (Z-axis direction) on the rear end surface 62a, but is not limited to this. Figure 23 is an enlarged view of the contact area between the brush 60C and the constant-load spring 80. For example, as shown in Figure 23, the recess 63C of the brush 60C may be formed to cut out a portion of the area in the direction of the axis C of the rotation shaft 13 on the rear end surface 62a. In other words, the recess 63C may be formed only in the area where the spiral portion 81 of the constant-load spring 80 makes contact. In this case, the rear end portion 62 of the brush 60C is provided with a restricting portion 64 that restricts the movement of the spiral portion 81 of the constant-load spring 80 in the direction of the axis C of the rotation shaft 13 (Z-axis direction). By providing restricting portions 64 above and below the spiral portion 81 in this way, it is possible to suppress the movement of the spiral portion 81 in the vertical direction (Z-axis direction). Therefore, compared to the electric motor 2 in the above embodiment, a more stable load can be applied to the brush 60C. Consequently, a decrease in the efficiency of the electric motor and the lifespan of the brush can be further suppressed. Moreover, when the upper and lower surfaces of the spiral portion 81 are in contact with the restricting portion 64, not only is the movement of the spiral portion 81 in the vertical direction suppressed, but the movement of the spiral portion 81 in the horizontal direction when the brush 60C slides can be further suppressed. This makes it possible to apply a more stable load to the brush 60C. In this modified example, the restricting portion 64 is the part of the rear end surface 62a of the brush 60C that is not cut out when forming the recess 63C, but it is not limited to this. For example, the restricting portion 64 may be formed to protrude outward from the rear end surface 62a. Also, in Figure 23, restricting portions 64 are provided on both the upper and lower sides of the spiral portion 81, but the restricting portion 64 may be provided on only one of the upper or lower sides of the spiral portion 81.

[0156] As described above, the second end portion 62 of this embodiment may be provided with a restricting portion 64 that restricts the movement of the spiral portion 81 in the axial direction of the rotation axis 13.

[0157] In the above embodiment, the brush 60 was composed solely of a carbon brush. The recess 63 was formed on the rear end surface of the carbon brush. However, it is not limited to this. The recess 63 may be composed of a carbon brush that forms the conductive brush body and several other separate parts. Figure 24 is a cross-sectional view showing a modified brush 60D and a constant-load spring 80 housed in a brush holder 70. For example, as shown in Figure 24, the brush 60D may have a carbon brush 60a and a mounting part 60b attached to the rear end of the carbon brush 60a. In this case, the rear end 62 of the brush 60D is the rear end of the mounting part 60b. Therefore, the recess 63D of the brush 60D is provided at the rear end of the mounting part 60b. The material of the mounting part 60b may be a metal material or a resin material, or it may be the same material as the carbon brush 60a.

[0158] As described above, the brush 60 of this embodiment has a carbon brush 60a and a mounting part 60b attached to the rear end of the carbon brush 60a, and the second end 62 may be the rear end of the mounting part 60b.

[0159] In the above embodiment, the stator 20 was composed of magnets 21. However, it is not limited to this. For example, the stator 20 may be composed of a stator core and a winding coil wound around the stator core.

[0160] In the above embodiment, the electric blower 1 was described in the context of use in a vacuum cleaner. However, it is not limited to this. For example, the electric blower 1 may be used in an air towel or the like.

[0161] In the above embodiment, an example was described in which the electric motor 2 is used in the electric blower 1. However, the electric motor 2 is not limited to this and may be used in electrical equipment other than the electric blower 1. The electric motor 2 may be used not only in household equipment but also in industrial equipment.

[0162] Furthermore, this disclosure also includes forms obtained by applying various modifications to the above embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of this disclosure. [Industrial applicability]

[0163] The electric motors and electric blowers described herein can be used in a variety of electrical appliances, including household electrical appliances such as vacuum cleaners. [Explanation of Symbols]

[0164] 1 electric blower 2 electric motor 3 Rotating Fans 4 Air Guides 4a Main body 4b Annular section 4c connecting plate 5 Fan Case 5a Lid 5b Side wall part 5c air intake 10 rotors 11 Rotor core 12-winding coil 13 Rotation axis 13a Part 1 13b 2nd part 14 Commutator 14a Commutator piece 15. First bearing 16. Second bearing 20 Stator 21 Magnets 30 York 40 frames 40a opening 40b Exhaust port 41 Bulge 50 brackets 51 First through hole 52 Second through hole 60, 60A, 60B, 60C, 60D brushes 60a carbon brush 60b Mounting parts 61 Front end (first end) 61a Front end surface 62 Rear end (second end) 62a Rear end surface 63, 63A, 63B, 63C, 63D recess 64 Regulatory Department 70 Brush holders 71 First holder 71a Open end 71b Projection 72 Second holder 72a Fitting hole 72b Screw hole 80, 80A, 80B constant load springs 80a outer end 80b inner edge 81 Spiral section 82, 82A, 82B Folded structure 82a First Fold-Over Section 82b Opposite part 82c Second Folding Section 82c1 Bridge section 83a First Slit 83b Second Slit 91 Conductive wire 92 Electrode terminal 100 screws

Claims

1. A rotor having a rotating shaft and a commutator attached to the rotating shaft, A brush including a first end that contacts the commutator and a second end located on the opposite side of the first end, It consists of a strip-shaped wire material, a constant-load spring for pressing the brush against the commutator, Equipped with, The constant-load spring has a spiral section around which the strip-shaped wire is wound, The spiral portion and the second end are in contact at two or more points. Furthermore, it includes a brush holder for holding the brush, The brush holder has a cylindrical portion that surrounds the brush, The constant-load spring has a folded structure in which one end drawn out from the spiral portion is bent so as to fold back on the outside. The folded structure has a first folded portion in which one end is folded outward, and an opposing portion facing the first folded portion. The constant-load spring is fixed to the cylindrical portion by inserting the folded structure into the open end of the cylindrical portion so that the open end of the cylindrical portion is sandwiched between the first folded portion and the opposing portion. The first folded portion has a first slit that extends along the insertion direction of the folded structure. The brush holder has a protruding portion that is erected on the outer surface of the outer wall of the cylindrical portion and extends along the insertion direction, The constant-load spring is fixed to the cylindrical portion by the folding structure being inserted into the open end of the cylindrical portion and the first slit being inserted into the protruding portion. Electric motor.

2. The aforementioned folded structure further includes a second folded portion erected on the first folded portion, The second folded portion has a second slit formed therein, which is continuous with the first slit. The second slit is formed without cutting out to the tip of the second folded portion. The electric motor according to claim 1.

3. The gap between the first folded portion and the opposing portion narrows as it moves away from the folding position of the folded structure. The electric motor according to claim 1 or 2.

4. A recess is formed at the second end, The spiral portion is in contact with the recess at two or more points. The electric motor according to claim 1 or 2.

5. In a cross-section obtained by cutting the rotation axis with a plane perpendicular to the axial direction, the recess has a V-shape, an arc shape, a U-shape, or a U-shape. The electric motor according to claim 4.

6. In the cross-section obtained by cutting with a plane perpendicular to the axial direction of the rotation axis, the spiral portion and the second end are in contact at two points, the first point and the second point. The line connecting the first point and the second point is parallel to the direction perpendicular to the longitudinal direction of the brush. The electric motor according to claim 1 or 2.

7. In a circle centered at the center of the spiral portion, if the central angle between the first and second points is θ, θ ≥ 40° The electric motor according to claim 6.

8. In a circle centered at the center of the spiral portion, if the central angle between the first and second points is θ, θ ≥ 48° The electric motor according to claim 6.

9. The second end is provided with a restricting portion that restricts the movement of the spiral portion in the axial direction of the rotation axis. The electric motor according to claim 1 or 2.

10. The brush comprises a carbon brush and a mounting component attached to the rear end of the carbon brush. The second end is the rear end of the mounting part. The electric motor according to claim 1 or 2.

11. Furthermore, it has a conductive wire, one end of which is connected to the brush and the other end of which is connected to an electrode terminal that supplies power to the brush. The length of the conductive wire is set so that the constant-load spring applies a pressing force to the brush even when the brush is at its maximum wear. The electric motor according to claim 1 or 2.

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