Motor with brush

Abstract

To provide a motor with a brush capable of achieving extended service life and high reliability.SOLUTION: A motor 1 with a brush includes a stator 20 generating a magnetic field, an armature 31 having multiple coils 31b and a rotary shaft 15, for rotating within the magnetic field, a commutator 32 having multiple commutator segments 72 electrically connected to the multiple coils 31b, for rotating integrally with the armature 31, and multiple brushes 52, 62 that contact the commutator segments 72 while being biased toward the commutator 32, for supplying power to the coils 31b via the commutator segments 72. The brushes 52, 62 have a contact portion 81 contacting the commutator segment 72, a non-contact portion 82 separated from the commutator segment 72, and a discharge protrusion 83 projecting from the non-contact portion 82 toward the commutator segment 72 to generate spark discharge with the commutator segment 72.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A conventional brushed motor is disclosed in Patent Document 1. This brushed motor includes a stator, an armature, a commutator, and brushes.

[0003] The stator generates a magnetic field. The armature has multiple coils and a rotating shaft and rotates within the magnetic field. The commutator has multiple commutator bars electrically connected to the multiple coils and rotates integrally with the armature. The brushes are biased toward the commutator and come into contact with the commutator bars, supplying electricity to the coils via the commutator bars. The armature and commutator form the rotor.

[0004] In such a brushed motor, when electricity is supplied from the brushes to the coils via the commutator segments, an electromagnetic force is generated in the coils, and the rotor rotates due to the magnetic field lines in the magnetic field generated by the stator and the electromagnetic force generated in the coils. During this time, the direction of the electromagnetic force generated in the coils is switched due to the commutation of electricity by the brushes and commutator as the rotor rotates, causing the rotor to rotate continuously. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-153969 Summary of the Invention [Problem to be solved by the invention]

[0006] In this type of brushed motor, when the brushes and commutator segments come into contact with each other and are interrupted as the rotor rotates, spark discharges can occur between the brushes and the commutator segments as the brushes separate from the commutator segments. Such spark discharges can damage the brushes and commutator segments, shortening the lifespan of the brushed motor.

[0007] Furthermore, if silicon is present in the air in the environment in which a brushed motor is installed, the heat from spark discharges between the brushes and the commutator segments can produce silicon dioxide, an insulator, which can adhere to the surfaces of the commutator segments and the brushes. This can disrupt electrical conduction between the brushes and the commutator segments, resulting in poor electrical conduction and potentially causing the brushed motor to malfunction. This can result in a shorter lifespan and reduced reliability for the brushed motor.

[0008] The present invention has been made in view of the above-mentioned conventional circumstances, and an object to be achieved by the present invention is to provide a brushed motor that can achieve a long life and high reliability. [Means for solving the problem]

[0009] The brushed motor of the present invention comprises: a stator that generates a magnetic field; an armature having a plurality of coils and a rotating shaft, the armature rotating in the magnetic field; a commutator having a plurality of commutator bars electrically connected to the plurality of coils and rotating integrally with the armature; a plurality of brushes that are biased toward the commutator and contact the commutator segments, and that supply current to the coils via the commutator segments; The brush is characterized by having a contact portion that contacts the commutator segments, a non-contact portion that is spaced apart from the commutator segments, and a discharge protrusion that protrudes from the non-contact portion toward the commutator segments and generates a spark discharge between the brush and the commutator segments.

[0010] In a brushed motor of the present invention, contact between the brush contacts and the commutator segments causes current to flow from the brushes to the coils via the commutator segments. An electromagnetic force corresponding to the direction of the current is then generated in the coils. The magnetic field generated by the stator and the electromagnetic force generated in the coils generate torque that rotates the armature, causing the armature to rotate. As the armature rotates, the direction of the electromagnetic force generated in the coils is switched by the commutation of electricity between the brush contacts and the commutator segments, resulting in continuous rotation of the armature.

[0011] As mentioned above, when the commutator segments separate from the brush contacts during armature rotation, spark discharges may occur between the contacts and the commutator segments. In this regard, in the brush motor of the present invention, the discharge protrusions protruding from the non-contact portions of the brushes toward the commutator segments act as lightning rods, allowing spark discharges to occur between the discharge protrusions and the commutator segments preferentially over those between the contacts and the commutator segments. This prevents spark discharges from occurring between the contacts and the commutator segments. As a result, even in an environment where silicon is present in the air, the adhesion of silicon dioxide insulators, which are generated by the heat of spark discharges, to the surfaces of the commutator segments in contact with the contacts or to the surfaces of the contacts can be prevented. Therefore, this brush motor prevents malfunctions caused by the presence of silicon dioxide insulators between the brush contacts and the commutator segments.

[0012] Therefore, the brushed motor of the present invention can achieve a long life and high reliability.

[0013] It is preferable that the discharge projections include first projections, the distance between the tip and the commutator segments being a first distance, and second projections, the distance between the tip and the commutator segments being a second distance that is longer than the first distance.

[0014] In this case, spark discharges are more likely to occur between the first projections and the commutator segments than between the second projections and the commutator segments. As a result, an insulator such as silicon dioxide is more likely to adhere to the surface of the first projections before the second projections. Spark discharges are less likely to occur between the first projections and the commutator segments with the insulator attached. Therefore, the first projections no longer effectively function as lightning rods due to the insulator's attachment. However, the second projections can still effectively function as lightning rods. This allows this brushed motor to achieve an even longer lifespan.

[0015] The commutator may have a cylindrical body that covers the circumferential surface of the rotating shaft and a plurality of commutator segments arranged in a circumferential direction on the outer circumferential surface of the cylindrical body. The contact portion may have a contact surface that makes surface contact with the commutator segments from the radially outer side of the cylindrical body. The contact surface may have an arc shape that follows the shape of the outer circumferential surface of the cylindrical body. Preferably, the non-contact portion includes an extension portion that extends from the contact portion in the axial direction of the cylindrical body, and the discharge projection is provided on the extension portion.

[0016] In this case, the contact surfaces of the brush contact parts and the commutator segments are in surface contact, which is advantageous for supplying a large current from the brush to the commutator segments. Furthermore, because the discharge protrusions are provided on the extensions that extend axially from the contact parts, a brush that integrally has the contact parts with arc-shaped contact surfaces and the discharge protrusions can be easily formed by molding. [Effects of the Invention]

[0017] The brushed motor of the present invention can achieve a long life and high reliability. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing a brushed motor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the brushed motor of the embodiment taken along line AA in FIG. [Figure 3] FIG. 3 is a partial cross-sectional view of the brushed motor of the embodiment, taken along line BB in FIG. [Figure 4]FIG. 4 is a schematic diagram illustrating the positions of the discharge projections provided on the extension portion of the brushed motor according to the embodiment. [Figure 5] FIG. 5 is a partially enlarged cross-sectional view of the brush motor of the embodiment taken along another part of the area indicated by line BB in FIG. 2, showing the state before use. [Figure 6] FIG. 6 is a partially enlarged cross-sectional view similar to FIG. 5 of the brushed motor according to the embodiment, showing a state in which an insulator is formed at the tip of the first projection due to use. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0020] As shown in Figure 1, the brushed motor 1 of this embodiment is an example of a specific aspect of the "brushed motor" of the present invention. This brushed motor 1 is a brushed DC motor with a two-pole, three-slot structure in which three-phase armature coils are formed using a concentrated winding method.

[0021] The left side of the paper in Fig. 1 is defined as the front of the brushed motor 1, and the right side of the paper in Fig. 1 is defined as the rear of the brushed motor 1. The front-to-rear and up-to-down directions shown in Fig. 2 and subsequent figures are all shown in accordance with Fig. 1. Note that these directions are examples for the sake of convenience, and the position of the brushed motor 1 will be changed as appropriate depending on how it is mounted on a vehicle or the like.

[0022] Although not shown, the brushed motor 1 is connected to a locking member in a door lock device mounted on an automobile, and is used to displace the locking member between a locked position and an unlocked position.

[0023] The brush motor 1 includes a case 10, a stator 20, a rotor 30, a brush assembly 40, and a rotating shaft 15. The axial direction of the rotating shaft 15 corresponds to the front-to-rear direction, with one axial direction being the front and the other being the rear. The axial, radial, and circumferential directions of the rotating shaft 15 correspond to the axial, radial, and circumferential directions of a commutator 32, respectively, as described below. The axial, radial, and circumferential directions of the commutator 32 correspond to the axial, radial, and circumferential directions of a cylindrical body 71 of the commutator 32, respectively. In the following description, the term "axial direction" refers to the axial direction of the rotating shaft 15 or the commutator 32, the term "radial direction" refers to the radial direction of the rotating shaft 15 or the commutator 32, and the term "circumferential direction" refers to the circumferential direction of the rotating shaft 15 or the commutator 32.

[0024] The case 10 has a metal case body 11 and a metal cover body 12. The case body 11 is formed in a generally cylindrical shape with a bottom that is open at the rear and has a bottom wall 11a at the front. The cover body 12 is formed in a generally circular plate shape. A flange portion 11b extending radially outward from the rear end of the case body 11 is fastened to the outer peripheral edge of the cover body 12 by a fastening member (not shown).

[0025] A first support portion 11c is formed at the center of the bottom wall 11a, protruding cylindrically forward from the bottom wall 11a. A second support portion 12a is formed at the center of the cover body 12, protruding cylindrically rearward from the cover body 12. The rear of the second support portion 12a is open. A rotating shaft 15 is supported by the first support portion 11c and the second support portion 12a via a first bearing 13 and a second bearing 14 so as to be rotatable about a rotation axis O. The rotating shaft 15 functions as an output shaft of the motor. A rear portion of the rotating shaft 15 protrudes rearward from the case 10, and the locking member is connected to the rear portion of the rotating shaft 15.

[0026] The stator 20 has a first permanent magnet 21 and a second permanent magnet 22. Both the first permanent magnet 21 and the second permanent magnet 22 are formed in a partially cylindrical shape. The first permanent magnet 21 and the second permanent magnet 22 are fixed to the inner circumferential surface of the case body 11 so as to face each other. The first permanent magnet 21 and the second permanent magnet 22 form two field poles. A magnetic field is formed in the space between the first permanent magnet 21 and the second permanent magnet 22, and an armature 31, which will be described later, is rotatably disposed in this space.

[0027] The rotor 30 includes an armature 31 and a commutator 32 .

[0028] The armature 31 has a core 31a, a plurality of coils 31b wound around the core 31a, and the rotating shaft 15. The core 31a is fixed to the rotating shaft 15. Although not shown, the core 31a is made of a laminated core formed by stacking a plurality of magnetic steel plates in the axial direction of the rotating shaft 15, and has three teeth with three slots formed between each tooth. The coil 31b has three-phase coils housed in the three slots.

[0029] 1 and 2, the commutator 32 is cylindrical and fixed to the rotary shaft 15. The commutator 32 has a cylindrical body 71 and a plurality of commutator segments 72.

[0030] The cylindrical body 71 is fixed to the rotating shaft 15 at a position rearward and away from the core 31a. The cylindrical body 71 covers the circumferential surface of the rotating shaft 15, and the axis of the cylindrical body 71 coincides with the rotation axis O. The cylindrical body 71 is made of insulating synthetic resin.

[0031] Three metal commutator segments 72 are fixed to the outer peripheral surface of the cylindrical body 71. Each commutator segment 72 is partially cylindrical with a thin radial thickness. The commutator segments 72 are arranged in parallel in the circumferential direction on the outer peripheral surface of the cylindrical body 71. The commutator segments 72 are arranged at predetermined equal intervals in the circumferential direction of the cylindrical body 71. Each commutator segment 72 is longer in the axial direction than the cylindrical body 71. The portion of each commutator segment 72 that is longer in the axial direction than the cylindrical body 71 protrudes forward from the cylindrical body 71 in one axial direction, and the coil 31b is electrically connected to a hook portion 72a (see FIG. 1) at the tip of the portion.

[0032] 1 and 2, the brush device 40 has a first brush device 41 and a second brush device 42. The first brush device 41 and the second brush device 42 are arranged opposite each other at positions 180 degrees apart in the circumferential direction of the commutator 32.

[0033] The first brush device 41 includes a first brush holder 51 , a first brush 52 , and a first spring 53 .

[0034] The first brush holder 51 is rectangular and made of insulating synthetic resin. The first brush holder 51 is fixed to the inner circumferential surface of the case body 11. The first brush 52 is made of a sintered body of metal powder. The first brush 52 is accommodated in the first brush holder 51 so as to be able to reciprocate in the radial direction of the commutator 32. One end of a first spring 53 is fixed to the first brush holder 51, and the other end of the first spring 53 is fixed to the first brush 52. The first spring 53 biases the first brush 52 radially inward toward the commutator 32. As shown in FIG. 2 , on a line L passing through the rotation axis O, the first brush 52 is biased by the first spring 53 in a biasing direction P toward the commutator 32 (a direction radially inward of the commutator 32) and is in contact with the commutator segments 72. Although not shown in the drawings, the first brush 52 is connected to the positive electrode of an external DC power supply via a power supply line.

[0035] Similarly, the second brush device 42 has a second brush holder 61, a second brush 62, and a second spring 63. The second brush holder 61 is rectangular box-shaped and made of insulating synthetic resin. The second brush holder 61 is fixed to the inner circumferential surface of the case body 11. The second brush 62 is made of a sintered body of metal powder. The second brush 62 is housed in the second brush holder 61 so as to be able to reciprocate in the radial direction of the commutator 32. One end of the second spring 63 is fixed to the second brush holder 61, and the other end of the second spring 63 is fixed to the second brush 62. The second spring 63 biases the second brush 62 radially inward toward the commutator 32. 2, on a line L passing through the rotation axis O, the second brush 62 is biased by the second spring 63 in a biasing direction P toward the commutator 32 (a direction toward the radially inward direction of the commutator 32) and is in contact with the commutator segments 72. Although not shown in the figure, the second brush 62 is connected to the negative pole of an external DC power supply via a power supply line.

[0036] The first brush device 41 and the second brush device 42 have the same configuration. Below, the configuration of the first brush 52 in the first brush device 41 will be described, and a description of the configuration of the second brush 62 in the second brush device 42 will be omitted.

[0037] As shown in FIGS. 2 and 3, the first brush 52 has a partially cylindrical overall shape and includes a contact portion 81, a non-contact portion 82, and discharge projections 83.

[0038] The contact portion 81 has a partial cylindrical shape that is relatively thick in the radial direction and whose circumferential length is longer than the radial thickness. The contact portion 81 has a contact surface 81a that is arc-shaped and conforms to the shape of the outer circumferential surface of the cylindrical body 71. The contact surface 81a corresponds to the inner circumferential surface of the partial cylindrical contact portion 81. The first brush 52 is urged by the first spring 53 toward the commutator 32 in the urging direction P, so that the contact surface 81a of the contact portion 81 comes into surface contact with one or two of the three commutator segments 72 from the radially outer side of the cylindrical body 71 of the commutator 32.

[0039] The non-contact portion 82 has a pair of extension portions 84 that extend from the contact portion 81 to one side and the other side in the axial direction of the cylindrical body 71 .

[0040] As shown in FIG. 3 , each extension portion 84 faces the commutator segments 72 and the commutator 32 in the radial direction. Each extension portion 84 is spaced from the commutator segments 72 in the radial direction of the commutator 32, and the inner circumferential surface 84a of each extension portion 84 does not contact the commutator segments 72. Each extension portion 84 has a partially cylindrical shape whose circumferential length is longer than its radial thickness. The axial length of each extension portion 84 is shorter than the axial length of the contact portion 81. The circumferential length of each extension portion 84 is equal to the circumferential length of the contact portion 81. The radial thickness of each extension portion 84 is thinner than the radial thickness of the contact portion 81. The axial centers of the partially cylindrical first brush 52 and the second brush 62 coincide with the rotation axis O.

[0041] The discharge projections 83 are provided on the inner peripheral surface 84a of each extension portion 84. The discharge projections 83 project toward the commutator segments 72, and generate spark discharges between the discharge projections 83 and the commutator segments 72. Each discharge projection 83 projects in a conical shape from the extension portion 84 toward the radially inward direction of the commutator 32.

[0042] 4, the discharge projections 83 are arranged on the inner circumferential surface 84a of the extension portion 84 on the circumferential center line C of the first brush 52. The circumferential center line C here refers to a straight line on the inner circumferential surface 84a of the extension portion 84 that is parallel to the rotation axis O, which is also the axis of the first brush 52, and that passes through the circumferential center of the partially cylindrical first brush 52.

[0043] 5, each discharge projection 83 has a first projection 83a and a second projection 83b. The distance between the tip of the first projection 83a and the commutator segment 72 in the urging direction P is a first distance D1. The distance between the tip of the second projection 83b and the commutator segment 72 in the urging direction P is a second distance D2 that is longer than the first distance D1. The first projection 83a and the second projection 83b are arranged adjacent to each other on the inner circumferential surface 84a of the extension portion 84 and on the circumferential center line C of the first brush 52. The first projection 83a is arranged closer to the contact portion 81 than the second projection 83b.

[0044] As shown in Figure 2, any two of the three commutator segments 72 are in contact with the first brush 52 and the second brush 62, respectively, and as the commutator 32 rotates together with the armature 31, the two commutator segments 72 in contact with the first brush 52 and the second brush 62 switch.

[0045] In this manner, in this brushed motor 1, power is supplied to the three-phase coils 31b from the first brush 52 and the second brush 62 via the commutator segments 72, causing current to flow through each coil 31b. The rotor 30 rotates due to torque generated by magnetic field lines in the magnetic field generated by the first permanent magnets 21 and the second permanent magnets 22 of the stator 20 and electromagnetic force generated in each coil 31b according to the direction of the current. At this time, as the rotor 30 rotates, electrical commutation occurs between the contact portions 81 of the first brush 52 and the contact portions 81 of the second brush 62 and each commutator segment 72, switching the direction of the electromagnetic force generated in each coil 31b, causing the rotor 30 to rotate continuously.

[0046] In this brushed motor 1, the first brush 52 and the second brush 62 are each provided with a conical discharge protrusion 83 that protrudes toward the commutator segments 72 at one axial end and the other axial end. Therefore, due to the lightning rod effect of the discharge protrusion 83, a spark discharge is expected to occur between the discharge protrusion 83 and the commutator segments 72 preferentially over between the contact portions 81 and the commutator segments 72, thereby preventing a spark discharge from occurring between the contact portions 81 and the commutator segments 72. As a result, even if the air inside the vehicle cabin contains silicon, for example, and the brushed motor 1 is used in an environment containing silicon, the generation of silicon dioxide due to the heat of the spark discharge can be prevented, and the deposition of silicon dioxide insulators on the surfaces of the commutator segments 72 that come into contact with the contact portions 81 and the surfaces of the contact portions 81 can be prevented. Therefore, in this brushed motor 1, malfunctions caused by the presence of silicon dioxide insulators between the contact portions 81 of the first brush 52 and the contact portions 81 of the second brush 62 and the commutator segments 72 can be suppressed.

[0047] Therefore, this brushed motor 1 can achieve a long life and high reliability.

[0048] Furthermore, each discharge projection 83 in this brush motor 1 has a first projection 83a that is a short first distance D1 from the commutator segment 72 and a second projection 83b that is a long second distance D2 from the commutator segment 72. Spark discharges occurring between the commutator segment 72 and the discharge projection 83 occur preferentially between the first projection 83a, which is a short first distance D1 from the commutator segment 72, and the commutator segment 72, rather than between the second projection 83b, which is a long second distance D2 from the commutator segment 72, and the commutator segment 72. As a result, as shown in FIG. 6 , if silicon dioxide insulator 90 adheres near the tip of the first projection 83a during use of the brush motor 1, it becomes difficult to expect the lightning rod effect of the first projection 83a. In this regard, with this brush motor 1, the lightning rod effect of the second projection 83b can be expected even after the lightning rod effect of the first projection 83a can no longer be expected. Therefore, the brushed motor 1 can achieve an even longer lifespan.

[0049] Furthermore, in this brushed motor 1, the first brush 52 has contact portions 81 having contact surfaces 81a whose cross sections perpendicular to the axis are arc-shaped and correspond to the shape of the outer peripheral surface of the partially cylindrical commutator 32, and extension portions 84 extending axially from the contact portions 81, on which discharge protrusions 83 are provided, and the first brush 52 having the discharge protrusions 83 integrally formed on the circumferential center line C of the first brush 52 at the extension portions 84 can be easily formed by molding. The same applies to the second brush 62.

[0050] Although the present invention has been described above with reference to the examples, it goes without saying that the present invention is not limited to the above examples and can be modified and applied as appropriate within the scope of the invention.

[0051] In the embodiment, first and second discharge projections are provided on each of a pair of extension portions of the brush, but the present invention is not limited to this, and the number and positions of the discharge projections can be set as desired. Furthermore, the shape of the discharge projections is not limited to a cone shape, and they may be elongated rod-like or needle-like.

[0052] In the embodiment, the brush has a partially cylindrical shape, but the present invention is not limited to this, and the brush may have a polygonal prism shape such as a square prism shape, or a cylindrical shape.

[0053] In the embodiment, the brush is formed from a sintered body of metal powder, but the present invention is not limited to this. In addition to a sintered body of carbon powder, the brush may also be formed from a material in which metal powder or carbon powder is solidified with resin or pitch, or the brush may be formed by punching a metal plate.

[0054] In the embodiment, a brushed motor with two poles and three slots is used, but the present invention is not limited to this, and the number of poles and the number of slots in the brushed motor can be selected arbitrarily, and the brushed motor may have a multi-pole structure, for example, four poles or six poles.

[0055] In the embodiment, the number of coils and commutator segments is three, but the present invention is not limited to this, and the number of coils and commutator segments can be set arbitrarily.

[0056] In the embodiment, the magnetic field is generated by a permanent magnet, but the present invention is not limited to this, and the magnetic field may be generated by an electromagnet.

[0057] In the embodiment, the brush that faces radially from the cylindrical commutator is pressed into contact with the commutator from the radially outer side, but the present invention is not limited to this, and the brush that faces axially from the disc-shaped commutator may also be pressed into contact with the commutator from the axial direction. [Industrial Applicability]

[0058] The brushed motor of the present invention can be used as a drive source for automotive electrical equipment such as door lock devices, power windows, power seats, and sunroofs. [Explanation of symbols]

[0059] 1... Brushed motor 15...Rotation axis 20...Stator 31...Armature 31b...Coil 32... Commutator 52...First brush (brush) 62...2nd brush (brush) 71...Cylindrical body 72... Commutator piece 81...Contact part 82...Non-contact part 83…Discharge projection 83a...first protrusion 83b…Second protrusion 84...Extension part D1: First distance D2…Second distance

Claims

1. a stator that generates a magnetic field; an armature having a plurality of coils and a rotating shaft, the armature rotating in the magnetic field; a commutator having a plurality of commutator bars electrically connected to the plurality of coils and rotating integrally with the armature; a plurality of brushes that are biased toward the commutator and contact the commutator segments, and that supply current to the coils via the commutator segments; A brush motor characterized in that the brush has a contact portion that contacts the commutator segments, a non-contact portion that is spaced from the commutator segments, and a discharge protrusion that protrudes from the non-contact portion toward the commutator segments and generates a spark discharge between the brush and the commutator segments.

2. 2. The brushed motor according to claim 1, wherein the discharge projections include first projections whose tips are spaced a first distance from the commutator segments, and second projections whose tips are spaced a second distance from the commutator segments that is longer than the first distance.

3. the commutator includes a cylindrical body that covers a peripheral surface of the rotary shaft, and the plurality of commutator segments that are arranged in parallel in a circumferential direction on the outer peripheral surface of the cylindrical body, the contact portion has a contact surface that comes into surface contact with the commutator segments from the radially outer side of the cylindrical body, the contact surface has an arc shape that follows the shape of the outer circumferential surface of the cylindrical body, the non-contact portion includes an extension portion extending from the contact portion in the axial direction of the cylindrical body, 3. The brushed motor according to claim 1, wherein the discharge projections are provided on the extensions.

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