JP5953059B2 - Electric motor - Google Patents

Description

  The present invention relates to an electric motor that can prevent a decrease in insulation resistance.

  An electric motor with a brush has a rotor rotatably supported via a bearing in a yoke (case) to which a permanent magnet is fixed. The rotor is applied by applying current from the brush to a commutator provided in the rotor. It is intended to rotate.

  In such an electric motor, the brush is worn by the commutator as the rotor rotates, and this wear powder accumulates in the electric motor. Since the wear powder is conductive, if it adheres to the periphery of the brush or commutator, there may be a problem that the insulation resistance between the bearing supporting the rotor shaft and the brush or commutator decreases.

  In order to solve such a problem, there is known a motor provided with a partition sheet provided between a bearing and a commutator to partition an internal space of the motor into a bearing chamber and a commutator chamber (see Patent Document 1). .

JP 2004-350457 A

  The prior art of Patent Document 1 prevents the wear powder generated by sliding between the brush and the commutator from entering the bearing chamber and the like, and ensures the insulation between the brush or the commutator and the rotor. Yes.

  Incidentally, the insulation resistance between the brush or commutator and the yoke is generally ensured by forming a coating or the like on the surface of the yoke.

  On the other hand, conventionally, the surface of the permanent magnet has not been insulated. Therefore, when the brush is worn by the commutator and this wear powder accumulates in the electric motor, a conduction path is formed between the brush and the permanent magnet, and the insulation resistance decreases between the brush and the permanent magnet. Resulting in. In such a situation, if the permanent magnet rubs the inner peripheral surface of the yoke by an operation such as press-fitting the permanent magnet into the inner peripheral surface of the yoke, and the coating on the inner peripheral surface of the yoke is scraped off, The insulation resistance between the permanent magnet in contact with the portion and the yoke is lowered. As a result, there is a problem that the insulation resistance between the brush and the yoke is lowered.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an electric motor capable of preventing a decrease in insulation resistance due to brush abrasion powder.

The present invention includes a yoke, a permanent magnet fixed in the yoke, a rotor having a commutator and rotatably supported in the yoke, and a brush that slidably contacts the commutator and supplies current to the commutator. , An electric insulating film is formed on the surface of the permanent magnet, and a low friction resistance film having a lower dynamic friction coefficient than the electric insulating film on the electric insulating film The electrically insulating film is thicker than the low friction-resistant film.

  According to the present invention, on the surface of the permanent magnet, the electrically insulating coating and the low friction resistant coating are sequentially laminated from the permanent magnet side. The electrically insulating coating insulates the surface of the permanent magnet to ensure insulation resistance with the brush. Also, the low friction resistance coating reduces the frictional resistance between the permanent magnet and the yoke, so that when the permanent magnet is inserted inside the yoke, the surface of the yoke (for example, the insulation applied to the surface) by the permanent magnet. Is prevented from being scraped. With such a configuration, the insulation resistance between the permanent magnet and the yoke can be secured, so that the insulation resistance between the brush and the yoke is reduced even when brush abrasion powder accumulates inside the yoke. Can be prevented.

It is sectional drawing of the rotating shaft direction of the electric motor of embodiment of this invention. It is AA sectional drawing in FIG. 1 of the electric motor of embodiment of this invention. It is a perspective view of BB sectional drawing in Drawing 2 of an electric motor of an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a sectional view of the electric motor 1 according to the embodiment of the present invention in the direction of the rotation axis.

  The electric motor 1 of the present embodiment includes a metallic yoke 10 that has a cylindrical shape and has a bottomed shape with one end opened, and a rotor 20 that is rotatably supported by the yoke 10. The yoke 10 constitutes a case of the electric motor 1.

  A permanent magnet 11 is mounted on the inner peripheral surface of the yoke 10. A bracket 12 made of an insulating material such as resin is attached to the opening of the yoke 10.

  The rotor 20 includes a rotor shaft 21, a commutator 22 fixed to the rotor shaft 21, and a rotor core 23. The rotor core 23 is configured by laminating thin electromagnetic steel plates in the rotation axis direction. A winding 24 is wound around the rotor core 23. The rotor shaft 21 is rotatably supported with respect to the yoke 10 via a bearing 13 fixed to the bottom side of the yoke 10 and a bearing 14 fixed to the bracket 12.

  A plurality of electrodes 22 a are fixed on the outer peripheral side of the commutator 22. A winding 24 is connected to each electrode 22a. In the electric motor 1, the brush 15 attached to the bracket 12 and the electrode 22 a of the commutator 22 are in sliding contact, and current is supplied to the winding 24 through the brush 15. As a result, a current flows through the winding 24, and a repulsive force between the magnetic force generated in the rotor core 23 and the magnetic force of the permanent magnet 11 acts in the rotation direction, and the rotor 20 is rotationally driven.

  The brush 15 is supported by a brush holder 31 formed on the bracket 12. The brush 15 is pressed against the commutator 22 by a spring 32 built in the brush holder 31 and is in sliding contact with the electrode 22a. A current from a power source (not shown) is supplied to the brush 15 via the harness 33, the lead plate 34, and the copper braided wire 35, and is supplied to the winding 24 via the electrode 22 a of the commutator 22 that is in sliding contact with the brush 15. The brush 15 is generally formed of a conductive material mainly composed of carbon or carbon and copper. The number of brushes 15 and the number of poles of the electrodes 22a of the commutator 22 are appropriately set according to the characteristics and performance of the electric motor 1.

  The bracket 12 is made of, for example, resin. The bracket 12 is formed with a brush holder 31 and a bearing mounting portion 12a into which an outer race (outer ring) 41 of the bearing 14 is fitted. An inner race (inner ring) 42 of the bearing 14 is fitted to the outer peripheral surface of the rotor shaft 21, and the tip end portion of the rotor shaft 21 protrudes outside through the shaft hole of the bracket 12.

  As shown in FIG. 2, a pair of segment-shaped permanent magnets 11 (11a, 11b) are mounted on the inner peripheral surface of the yoke 10 so as to face each other. The permanent magnet 11 is press-fitted and fixed inside the yoke 10 while being attached to the magnet holder 50. The permanent magnet 11 is composed of, for example, a ferrite magnet. As will be described later, an electrically insulating film 110a and a low friction resistance film 110b are formed on the surface of the permanent magnet 11.

  Next, the configuration of the electric motor 1 will be described with reference to FIGS.

  2 is a cross-sectional view of the electric motor 1 according to the embodiment of the present invention taken along the line AA in FIG. 1, and FIG. 3 is a perspective view of the electric motor 1 taken along the line BB in FIG. 2 and 3, the rotor 20 is omitted.

  The outer shape of the magnet holder 50 has a cylindrical shape that follows the shape of the inner peripheral surface of the yoke 10. A pair of window-shaped magnet mounting portions 51 a and 51 b on which the segment-shaped permanent magnet 11 is mounted are formed on the side wall portion of the magnet holder 50. The permanent magnets 11a and 11b are fixed to the magnet holder 50 by mounting the pair of permanent magnets 11a and 11b on the magnet mounting portions 51a and 51b.

  Each of the permanent magnets 11a and 11b has a segment shape (C shape) having substantially the same shape. The curved surfaces on the outer peripheral side (segment-shaped bulging side) of the permanent magnets 11 a and 11 b are shaped so as to follow the inner peripheral surface shape of the yoke 10. As will be described later, an electrically insulating coating 110a and a low friction resistant coating 110b are formed on the surfaces of the permanent magnets 11a and 11b.

  When a pair of permanent magnets 11 a and 11 b are attached to the magnet holder 50, the shape of the outer peripheral surface of the magnet holder 50 substantially matches the shape of the inner peripheral surface of the yoke 10. By setting it as such a shape, the magnet holder 50 is press-fitted and fixed to the inner peripheral surface of the yoke 10.

  Note that one end side of the magnet holder 50 has a throttle structure toward the bottom of the yoke 10 (see FIG. 1), and is fitted to the outer peripheral surface of the outer race 43 of the bearing 13 at the center of the throttle structure. A bearing mounting portion 50a is formed.

  The electric motor 1 of the present embodiment is assembled by the following procedure.

  First, the permanent magnets 11a and 11b are mounted on the magnet mounting portions 51a and 51b of the magnet holder 50, respectively. Then, the magnet holder 50 to which the permanent magnets 11 a and 11 b are attached is inserted into the yoke 10.

  As shown by the dotted line in FIG. 3, the magnet holder 50 is inserted into the yoke 10 from the opening of the yoke 10. The magnet holder 50 is inserted until the bottom of the magnet holder 50 abuts against the bottom of the yoke 10. At this time, the outer peripheral surfaces of the magnet holder 50 and the permanent magnet 11 are inserted until they abut against the bottom of the yoke 10 while sliding on the inner peripheral surface of the yoke 10.

  When the magnet holder 50 with the permanent magnet 11 mounted inside the yoke 10 is press-fitted, the outer peripheral surface of the permanent magnet 11 is in close contact with the inner peripheral surface of the yoke 10. As a result, the magnetic force of the pair of permanent magnets 11 a and 11 b is coupled by the yoke 10. An adhesive may be applied in advance between the magnet holder 50 and the yoke 10.

  Next, the rotor 20 on which the bearing 13 is mounted in advance is inserted into the yoke 10. The bearing 13 is mounted on the bearing mounting portion 50 a at the bottom of the magnet holder 50.

  Next, the bracket 12 on which the lead plate 34, the copper braided wire 35, the brush 15, the bearing 14 and the like are mounted in advance is mounted on the opening of the yoke 10. Thereafter, the bracket 12 and the yoke 10 are fixed by, for example, bolts and nuts.

  Conventionally, the following problems have occurred in the electric motor 1 configured as described above.

  Since the electrode 22a of the commutator 22 and the brush 15 are in sliding contact when the electric motor 1 rotates, the brush 15 that is a softer material than the electrode 22a is worn. Wear powder generated by the wear of the brush 15 accumulates inside the yoke 10.

  When the electric motor 1 is assembled, the magnet holder 50 is press-fitted while its outer surface slides on the inner surface of the yoke 10. Since the yoke 10 is made of a conductive metal, an electrically insulating film (for example, a film formed by cationic electrodeposition coating) is formed in advance on the surface of the yoke 10 in order to prevent leakage. Here, conventionally, when the magnet holder is press-fitted into the yoke, the tolerance of the shape of the inner peripheral surface of the yoke, the fine unevenness of the coating on the surface, the tolerance of the outer peripheral surface of the magnet holder or permanent magnet, The permanent magnet mounted on the magnet holder may scrape the coating on the inner peripheral surface of the yoke due to a tilt or the like.

  In such a conventional configuration, when the coating on the inner peripheral surface of the yoke is scraped, the metal forming the yoke is exposed, so that the insulation resistance between the portion where the metal portion of the yoke is exposed and the permanent magnet decreases. . Since the permanent magnet is made of a conductive material such as ferrite, the insulation resistance between the yoke and the permanent magnet is lowered. Under such circumstances, when the abrasion powder of the brush accumulates, an electrical conduction path is generated between the brush and the permanent magnet, and there is a possibility that the insulation resistance between the brush and the yoke is lowered.

  Therefore, in the embodiment of the present invention, when the magnet holder 50 is press-fitted into the yoke 10, the metal part of the yoke 10 is configured not to be exposed as follows.

  Prior to the assembly of the electric motor 1 described above, an electrically insulating coating 110a and a low friction resistance coating 110b are laminated on the surface (outer circumferential surface and inner circumferential surface) of the permanent magnet 11. First, the electrically insulating coating 110 a is formed by performing cationic electrodeposition coating on the surface of the permanent magnet 11.

  Cationic electrodeposition coating involves immersing an object to be coated in an electrodeposition layer filled with a water-soluble cationic paint, using the object to be coated as a cathode, and applying an electric current to the anode installed in the electrodeposition layer. As a result, the coating is deposited on the surface of the object to be coated to form a film. By using the electrically insulating cationic paint, the electrically insulating coating 110a can be formed on the object to be coated.

  On the surface of the permanent magnet 11, an electrically insulating coating 110a made of a cationic electrodeposition paint is formed. The thickness of the coating 110 a is set to a thickness that can sufficiently secure the insulation resistance between the permanent magnet 11 and the yoke 10. Specifically, it is a thickness necessary to ensure insulation against the rated voltage of the electric motor 1, and further, an appropriate thickness considering the cost and the efficiency of the manufacturing process (for example, 30 [μm]). And

  In addition, it is not limited to cationic electrodeposition coating, and any coating may be used as long as it forms an electrically insulating coating 110a on the surface of the permanent magnet 11. For example, an electrically insulating coating is sprayed onto the surface of the permanent magnet 11 to perform coating. 110a may be formed. Alternatively, the electrically insulating coating 110a may be formed by chemically treating the surface of the permanent magnet 11 like an aluminum oxide film.

  After the electrically insulating coating 110a is formed by cationic electrodeposition coating, a low friction resistance coating 110b is further laminated on the surface of the permanent magnet 11. In the present embodiment, a film 110b made of a fluororesin is formed on the electrically insulating film 110a formed on the surface of the permanent magnet 11.

  Examples of the fluororesin that forms the low-friction-resistant film 110b include tetrafluoroethylene resin (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer resin (FEP), and tetrafluoroethylene / barfluoroalkyl. Vinyl ether copolymer resin (PFA), tetrafluoroethylene copolymer resin (ETFE), or the like is used.

  By further forming such a coating 110b made of a fluororesin on the surface of the permanent magnet 11, the frictional resistance (dynamic friction coefficient) of the outer peripheral surface of the permanent magnet 11 is reduced. In particular, the fluororesin can form a coating 110b having a lower frictional resistance than the electrically insulating coating 110a by cationic electrodeposition coating. Further, it is possible to form the coating 110b having a surface hardness higher than that of the electrically insulating coating 110a by cationic electrodeposition coating.

  By reducing the frictional resistance of the outer peripheral surface of the permanent magnet 11, the frictional resistance between the outer peripheral surface of the permanent magnet 11 and the inner peripheral surface of the yoke 10 is reduced, and slipping occurs when the magnet holder 50 is press-fitted into the yoke 10. Increases nature. As a result, the outer peripheral surface of the permanent magnet 11 can easily slide on the inner peripheral surface of the yoke 10, and the coating on the inner peripheral surface of the yoke 10 is scraped, or the coating on the outer peripheral surface of the permanent magnet 11 (110 a, 110b) is prevented from being shaved.

  The fluororesin coating 110b is desirably formed to a thickness that can reduce the frictional resistance of the surface of the electrically insulating coating 110a. Specifically, it is set to an appropriate thickness (for example, 1 [μm] to 5 [μm]) depending on the cost and the efficiency of the manufacturing process. The fluororesin coating 110b may be formed by any method as long as it can form the low-friction-resistant coating 110b on the surface of the permanent magnet 11, such as spraying or coating.

  In this way, by forming the electrically insulating film 110a by the cationic electrodeposition coating on the surface of the permanent magnet 11 and further laminating the low friction resistance film 110b, the slip when the magnet holder 50 is press-fitted is formed. The outer peripheral surface of the permanent magnet 11 held by the magnet holder 50 scrapes the coating on the inner peripheral surface of the yoke 10, and the coating (110a, 110b) on the outer peripheral surface of the permanent magnet 11 is scraped. Is prevented.

  As described above, the electric motor 1 according to the embodiment of the present invention has a brush that includes the yoke 10, the permanent magnet 11 fixed to the yoke 10, and the rotor 20 that is rotatably supported in the yoke 10. It is an electric motor. On the surface of the permanent magnet 11, an electrically insulating coating 110 a and a low friction resistance coating 110 b are sequentially laminated from the permanent magnet 11 side. By forming the electrically insulating coating 110 a on the surface of the permanent magnet 11, the insulation resistance between the permanent magnet 11 and the yoke 10 is ensured. Further, the low frictional resistance coating 110 b is formed on the outer peripheral surface of the permanent magnet 11, thereby reducing the frictional resistance when the permanent magnet 11 is press-fitted into the yoke 10, and the outer peripheral surface of the permanent magnet 11. However, it is possible to prevent the coating on the inner peripheral surface of the yoke 10 from being shaved and the coatings (110a, 110b) on the surface of the permanent magnet 11 from being shaved.

  With this configuration, the abrasion powder of the brush 15 is placed inside the yoke 10 without damaging the coating on the inner circumferential surface of the yoke 10 and the electrically insulating coating 110a formed on the outer circumferential surface of the permanent magnet 11. Even if accumulated, it is possible to prevent the insulation resistance between the brush 15 and the yoke 10 from decreasing.

  The electrically insulating film 110a is a film formed by cationic electrodeposition coating, and the low frictional resistance film 110b is a film of a fluororesin. Since these films can be formed by using a conventional method, the manufacturing cost of the electric motor 1 is not increased.

  Further, the permanent magnet 11 is held by a magnet holder 50 having an outer surface shape that conforms to the inner surface shape of the yoke 10 and is press-fitted into the yoke 10. Since the plurality of permanent magnets 11 can be inserted into the yoke 10 by a single operation by the magnet holder 50, the manufacturing cost of the electric motor 1 can be reduced.

  In the embodiment of the present invention, the electric motor 1 has been described as an example.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 1 Electric motor 10 Yoke 11a, 11b Permanent magnet 12 Bracket 13 Bearing 14 Bearing 15 Brush 20 Rotor 21 Rotor shaft 22 Commutator 22a Electrode 23 Rotor core 24 Winding 50 Magnet holder 51a, 51b Magnet mounting part 110a Coating 110b Coating

Claims (3)

A yoke, a permanent magnet fixed in the yoke, a rotor having a commutator and rotatably supported in the yoke, and a brush that is in sliding contact with the commutator and supplies current to the commutator An electric motor comprising:
An electric insulating film is formed on the surface of the permanent magnet, and a low friction resistance film having a lower dynamic friction coefficient than the electric insulating film is formed on the electric insulating film. The electric motor is characterized in that the insulating film is formed thicker than the low frictional resistance film. The electric motor according to claim 1, wherein the low friction-resistant coating is a fluororesin coating. An outer surface shape conforming to the inner surface shape of the yoke, and further comprising a magnet holder inserted into the yoke;
The electric motor according to claim 1, wherein the permanent magnet is held by the magnet holder and provided in the yoke.

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