JP2008125308A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the reliability of a motor by enhancing insulation at the stator coil terminal of a brushless motor without causing cost increase. <P>SOLUTION: The brushless motor 1 comprises: a stator 11 having a coil 14 wound around the stator core 13; a terminal unit 52 fixed to the end of the stator core 13 and having a coil power supply terminal 53 connected with the end of the coil 14; and a rotor 21 arranged rotatably on the inside of the stator 11. On the outer circumference of the terminal unit 52, an insulation cover 56 formed of a synthetic resin heat shrinkage tube is arranged to cover the joint 55 of the coil power supply terminal 53 and the coil end 14a. The insulation cover 56 is applied tightly to the joint 55 by heat shrinkage thus assuring insulation in the vicinity of the joint 55. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a brushless motor used for an electric power steering apparatus and the like, and more particularly to an insulating structure of a stator coil terminal portion.

  In recent years, many vehicles have been equipped with so-called power steering devices for assisting steering force of automobiles and the like. As such power steering devices, in recent years, vehicles equipped with electric power steering devices (so-called electric power steering devices) are increasing from the viewpoint of reducing engine load and weight. In this electric power steering device (hereinafter abbreviated as EPS), the motor as a driving source thereof is required to be downsized and high in performance because the device is arranged in a narrow bonnet space. Conventionally, DC motors with brushes have been widely used as such motors, but recently, with the improvement of control technology, the adoption of brushless motors that are superior in terms of miniaturization and high performance has increased. is doing.

  FIG. 4 is an explanatory view showing the stator structure of such a brushless motor for EPS. As shown in FIG. 4, the stator 101 includes a stator core 102 formed by laminating many steel plates, and a coil 103 using a copper wire is wound around the stator core 102. A plurality of teeth and slots are alternately formed on the outer periphery of the stator core 102, and a coil 103 is wound around each tooth via an insulator 104 made of synthetic resin. A terminal unit 105 is attached to one end side of the stator core 102. The terminal unit 105 has a large number of coil feed terminals 106 protruding in the radial direction. Each coil feed terminal 106 has a terminal portion 103a of the coil 103 (a winding start portion or a winding end portion of the coil 103). It is connected. The terminal unit 105 performs not only electrical relay between the power input terminal and the coil 103 but also a function of connecting between arbitrary coil segments.

The electrical connection between the coil power supply terminal 106 and the coil terminal portion 103a is generally performed by soldering, spot welding (resistance welding), fusing, arc welding, or the like. Since EPS brushless motors require high output, arc welding with the least resistance drop at the connecting portion and high connection reliability is often used. In recent years, EPS motors have been increasingly demanded for miniaturization and high output, and as a result, the internal layout of the motor has become very highly integrated. Under such circumstances, electrical insulation inside the motor is an important theme, and various measures are taken. Also in the welded portion of the coil terminal, insulation from adjacent components (particularly the motor housing) is indispensable in terms of product quality, and it is necessary to ensure insulation between the coil power supply terminal and the housing during vibration or the like. For this reason, conventionally, a method of coating an insulating film on the housing, a method of disposing an insulating component between the housing and the welded portion, and the like have been tried.
JP 2004-48851 A

  However, in the case of the system in which the insulating coating is applied to the housing, there is a problem in the magnetic circuit, and it is not preferable to apply the coating to the entire inner periphery of the housing. For this reason, in the case of coating, the effort of partially masking etc. is needed, and there is a problem that the man-hour is increased and the cost increases. On the other hand, in the method of arranging insulating parts, a configuration in which resin molded products are arranged between the welded parts of the housing can be considered. However, since the mold cost for molding increases and the number of parts also increases, the increase in cost is also avoided. I can't. In addition, when considering a method for fixing an insulating component, the shape of the component is complicated, the unit price of the component is increased, and there is a possibility of affecting the surrounding component design.

  An object of the present invention is to improve the insulation of a stator coil terminal portion of a brushless motor without increasing the cost, and to improve the reliability of the motor.

  The brushless motor of the present invention is attached to a stator including a steel core and a coil wound around the core, and an axial end of the core, and is electrically connected to the end of the coil. A brushless motor having a terminal unit including a power supply terminal and a rotor rotatably disposed inside the stator, wherein an outer periphery of a joint portion between the power supply terminal and the coil end is synthesized. It is characterized by being covered with an insulating cover formed using a resin heat-shrinkable tube.

  In the brushless motor of the present invention, since the outer periphery of the joint portion between the power supply terminal and the coil end is covered with an insulating cover formed using a heat shrinkable tube made of synthetic resin, the vicinity of the joint portion and the motor housing Can be electrically insulated by a commercially available heat-shrinkable tube, and a necessary insulation function can be achieved at a low cost.

  In the brushless motor, the insulating cover may be contracted by heating so as to be in close contact with the joint and its vicinity. In addition, the coil may be coated with a thermosetting resin, and the thermosetting resin and the insulating cover may be heated in the same process, thereby utilizing an existing adhesive heat curing process. Thus, the insulating cover can be contracted and adhered.

  According to the brushless motor of the present invention, it has a stator around which a coil is wound, a terminal unit having a power feeding terminal electrically connected to the coil end, and a rotor that is rotatably arranged. With a brushless motor, the outer periphery of the joint between the power supply terminal and the coil end is covered with an insulating cover formed using a heat-shrinkable tube made of synthetic resin, so the area between the joint and the motor housing is commercially available. It is possible to electrically insulate by the heat shrinkable tube. As a result, the necessary insulation function can be achieved at a low cost, and the reliability of the motor can be improved without incurring an increase in cost.

  In addition, the coil is coated with a thermosetting resin, and the thermosetting resin and the insulating cover are heated in the same process, so that the insulating cover is contracted and adhered using the existing adhesive heat curing process. Can do. Therefore, it is possible to employ an insulating cover without adding man-hours, and it is possible to suppress an increase in cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a brushless motor to which the present invention is applied. A motor 1 shown in FIG. 1 is used as a power source for a rack-assisted EPS, and has a configuration in which a rack shaft 2 penetrates the motor 1. The rotation of the motor 1 is transmitted to the rack shaft 2 via the ball screw mechanism 3 and becomes a steering assist force.

  The motor 1 has an inner rotor type device configuration in which a stator 11 is disposed outside and a rotor 21 is disposed inside. The stator 11 includes a housing 12, a stator core 13 fixed to the inner peripheral side of the housing 12, and a coil 14 wound around the stator core 13. The housing 12 is formed of iron or the like, and the outer periphery thereof is suppressed to about 100 mm in response to a request for miniaturization of the motor. The stator core 13 has a structure in which a large number of steel plates are laminated, and a plurality (9 in this case) of teeth 16 project from the inner peripheral side of the stator core 13. A coil 14 is wound on a slot (nine slots) formed between the teeth 16 via an insulator made of synthetic resin, and insulation of the coil 14 wound between the slots is secured by the insulator. The coil 14 is connected to a battery (not shown) via a lead wire 15.

  As in the conventional brushless motor shown in FIG. 4, stator insulators 51 (hereinafter abbreviated as insulators 51) are attached to both ends of the stator core 13. A terminal unit 52 is attached to the left end of the left side (insulator 51a) in FIG. A large number of coil power supply terminals 53 protrude from the terminal unit 52 in the radial direction. Each coil power supply terminal 53 is connected to a terminal portion of the coil 14 (a winding start portion or a winding end portion of the coil 14). The terminal unit 52 is further provided with an external power supply terminal 54 electrically connected to the coil power supply terminal 53. A lead wire 15 is connected to the external power supply terminal 54, and power is appropriately supplied to each coil 14 from the lead wire 15 via the terminal unit 52.

  FIG. 2 is an explanatory diagram illustrating a configuration of a connection portion between the terminal portion 14 a of the coil 14 and the coil power supply terminal 53. As shown in FIG. 2, the coil terminal portion 14 a is pulled out from the coil 14 in the direction of the terminal unit 52 along the axial direction, and is welded and fixed to the coil power supply terminal 53 at the joint portion 55. The coil terminal portion 14a, the coil power supply terminal 53, and the joint portion 55 are close to the housing 12, and as described above, the insulation between them is extremely important in terms of motor quality. Therefore, in the motor 1 according to the present invention, the outer periphery in the vicinity of the joint portion 55 is covered with the insulating cover 56 to ensure insulation between the housing 12.

  In this case, a synthetic resin heat shrinkable tube is used for the insulating cover 56. FIG. 3 is an explanatory view showing a state in which the heat-shrinkable tube is arranged in the vicinity of the joint portion 55. A heat-shrinkable tube is a cylindrical sheet (tube) formed of polyolefin, polyvinylidene fluoride, ethylene propylene rubber, silicone rubber, fluororesin, elastic neoprene, vinyl chloride, etc. The dimensions in the radial direction and the axial direction are reduced to the state shown in FIG. That is, before heating, the insulating cover 56 that is loosely fitted as shown in FIG. 3 is in close contact with the insulating cover 56 so as to cover the vicinity of the joint 55 as shown in FIG. As a result, a cover by the insulating cover 56 is formed on the outer periphery in the vicinity of the joint portion 55, and the vicinity of the joint portion and the inner peripheral surface of the housing 12 are electrically insulated.

  On the other hand, the coil 14 is impregnated and fixed with an epoxy adhesive or the like between the wires in order to prevent the insulation film from being peeled off due to vibration. For example, in the motor 1, the coil 14 is coated with an epoxy adhesive 57. A thermosetting adhesive is generally used as such an adhesive, and an adhesive heating step is present when the stator is manufactured. Therefore, in the motor 1, the insulating cover 56 is contracted using this heating process, and the insulating cover 56 is tightly covered in the vicinity of the joint without setting a special contracting process.

  As described above, in the motor 1 of the present invention, a commercially available heat-shrinkable tube is used to cover the vicinity of the joint portion, so that the necessary insulating function can be achieved with inexpensive parts. At this time, since the coil power supply terminal 53 is provided so as to protrude in the radial direction, the coil power supply terminal 53 is likely to come into contact with the housing 12 due to vibration of the vehicle or the like, and at least the joint portion 55 located at the tip of the coil power supply terminal 53. The insulation of the motor is greatly improved by coating with an insulating material. Further, since the insulating cover 56 is contracted and adhered by utilizing the existing adhesive heat curing process, no extra man-hours are required. For this reason, it is possible to secure the insulation in the vicinity of the joint without incurring a cost increase, and to improve the reliability of the motor while taking advantage of the cost merit.

  The rotor 21 is disposed inside the stator 11 and has a configuration in which a cylindrical rotor shaft 22, a rotor core 23, a magnet 24, and a magnet cover 25 are arranged coaxially. The rack shaft 2 is inserted inside the rotor shaft 22. A cylindrical rotor core 23 is externally provided on the outer periphery of the rotor shaft 22. A magnet 24 having a 6-pole configuration is fixed to the outer periphery of the rotor core 23.

  The magnet 24 is a rare earth magnet such as a neodymium iron magnet that is small and has a high magnetic flux density. Thus, by using a rare earth magnet for the magnet 24, the motor can be miniaturized, the inertia of the rotor 21 is reduced, and the steering feeling is improved. The magnet 24 has a ring shape, and a plurality of magnetic poles are alternately arranged N and S in the circumferential direction. A plurality of segment magnets may be used as the magnet 24. A magnet cover 25 is externally provided on the outside of the magnet 24 so that even if the magnet is broken, the motor 1 is not locked by the broken piece.

  An aluminum die-cast housing 31 is attached to the right end side of the housing 12 in the figure. The housing 31 accommodates a bearing 32 that supports the right end side of the rotor 21 and a resolver 33 that detects the rotation of the rotor 21. The resolver 33 includes a resolver stator 34 fixed to the housing 31 side and a resolver rotor 35 fixed to the rotor 21 side. A coil 36 is wound around the resolver stator 34, and an excitation coil and a detection coil are provided.

  A resolver rotor 35 fixed to the rotor shaft 22 is disposed inside the resolver stator 34. The resolver rotor 35 has a configuration in which metal plates are laminated, and has convex portions in three directions. When the rotor shaft 22 rotates, the resolver rotor 35 also rotates in the resolver stator 34. A high frequency signal is given to the exciting coil of the resolver stator 34, and the phase of the signal output from the detection coil changes due to the proximity of the convex portion. The rotational position of the rotor 21 is detected by comparing the detection signal with the reference signal. Then, based on the rotational position of the rotor 21, the current to the coil 14 is appropriately switched, and the rotor 21 is rotationally driven.

  A housing 41 made of aluminum die casting is attached to the left end side of the housing 12 in the drawing. A ball screw mechanism 3 is incorporated in the housing 41. The ball screw mechanism 3 includes a nut portion 42, a screw portion 43 formed on the outer periphery of the rack shaft 2, and a large number of balls 44 interposed between the nut portion 42 and the screw portion 43. . The rack shaft 2 is supported so as to be reciprocable in the left-right direction by the nut portion 42 in a state where the rotation around the shaft is restricted, and moves in the left-right direction as the nut portion 42 rotates.

  The nut portion 42 is fixed to the left end portion of the rotor shaft 22 and is rotatably held by an angular bearing 45 fixed to the housing 41. The angular bearing 45 is fixed in a state where axial movement is restricted between bearing fixing rings 46 a and 46 b screwed into the opening of the housing 41 and a stepped portion 47 formed inside the housing 41. ing. The axial movement between the nut portion 42 and the angular bearing 45 is restricted by a bearing fixing ring 48 screwed into the left end of the nut portion 42 and a step portion 49 formed on the outer periphery of the nut portion 42. Is done.

  In an EPS equipped with such a motor 1, the steering handle is first operated to rotate the steering shaft, and the rack shaft 2 is moved in a direction corresponding to this rotation to perform a steering operation. When a steering torque sensor (not shown) is activated by this operation, electric power is supplied from the battery to the coil 14 via the lead wire 15 according to the detected torque. When electric power is supplied to the coil 14, the motor 1 operates and the rotor shaft 22 rotates. When the rotor shaft 22 rotates, the nut portion 42 coupled therewith rotates, and the steering assist force in the axial direction is transmitted to the rack shaft 2 by the action of the ball screw mechanism 3. Thereby, the movement of the rack shaft 2 is promoted, and the steering force is assisted.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, an example in which the stator according to the present invention is used for a brushless motor used as an EPS drive source has been described. However, the stator is not limited to an EPS brushless motor, and is used for other applications. Widely applicable to motors. Further, the present invention can be widely applied to general brushless motors as well as motors for EPS and various in-vehicle electric products. Furthermore, in the above-described embodiment, the brushless motor used for the rack assist type EPS is shown, but the present invention can also be applied to other types of EPS motors such as a column assist type.

It is sectional drawing which shows the structure of the brushless motor to which this invention is applied. It is explanatory drawing which shows the structure of the connection part of a coil terminal part and a coil electric power feeding terminal. It is explanatory drawing which shows the state which has arrange | positioned the heat contraction tube in the vicinity of the junction part. It is explanatory drawing which shows the stator structure of the brushless motor for EPS.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Rack shaft 3 Ball screw mechanism 11 Stator 12 Housing 13 Stator core 14 Coil 14a Terminal part 15 Lead wire 16 Teeth 21 Rotor 22 Rotor shaft 23 Rotor core 24 Magnet 25 Magnet cover 31 Housing 32 Resolver 34 Resolver stator 35 Resolver rotor 36 Coil 41 Housing 42 Nut portion 43 Screw portion 44 Ball 45 Angular bearings 46a and 46b Bearing fixing ring 47 Step portion 48 Bearing fixing ring 49 Step portion 51 Stator insulator 51a Stator insulator 52 Terminal unit 53 Coil feed terminal 54 External feed terminal 54 55 Junction 56 Insulation cover 57 Epoxy adhesive
101 stator
102 stator core
103 coil
103a terminal
104 Insulator
105 Terminal unit
106 Coil feed terminal

Claims (3)

A stator comprising a steel core and a coil wound around the core;
A terminal unit that is attached to an axial end of the core and includes a power feeding terminal that is electrically connected to the end of the coil;
A brushless motor having a rotor rotatably disposed inside the stator,
A brushless motor, wherein an outer periphery of a joint portion between the power supply terminal and the coil end portion is covered with an insulating cover formed using a heat shrinkable tube made of synthetic resin.   2. The brushless motor according to claim 1, wherein the insulating cover is contracted by heating and is in close contact with the joint and its vicinity.   3. The brushless motor according to claim 1, wherein the coil is coated with a thermosetting resin, and the insulating cover and the thermosetting resin are heated in the same process.

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