JP2013198369A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor in which holing power of a stator core having a split stator structure can be secured and simplification of assembly can be achieved.SOLUTION: Stator cores 8 are constituted by a configuration in which a plurality of split cores 12 in which many T-shaped plates 38 are laminated and integrally connected are annularly arranged at equal intervals in a circumferential direction. A dovetail-shaped engaging projection 44 whose width in the circumferential direction gradually increases radially outwardly is provided on a central part of an outer circumferential surface of a yoke part 10 of the plate 38 so as to extend in a rotary center direction. A dovetail-shaped engaging groove 43 which is engaged with the engaging projection 44 whose width in the circumferential direction gradually increases radially outwardly is provided on an inner circumferential surface of a motor housing 5. The inner circumferential surface of the motor housing 5 and the outer circumferential surface of the stator core 8 are engaged by press-fitting and the engaging projection 44 and the engaging groove 43 are pressure-welded by both side edge parts on the outer circumferential side having the dovetail shape with a gap between the top face of the engaging projection 44 and the bottom face of the engaging groove 43.

Description

  The present invention relates to an electric motor.

  Conventionally, an electric motor in which a stator core is constituted by a plurality of divided cores is known, and is applied to, for example, an electric power steering device (EPS). The stator of this electric motor has a structure in which a plurality of stator cores are arranged in an annular shape. In the stator structure in which the outer periphery of the annular stator core is held by a cylindrical motor housing, the electric motor that prevents rotation of the stator core is provided. It has been proposed (see, for example, Patent Document 1). According to the technique of Patent Document 1, a recess is formed along the axial direction on the outer periphery of the stator core, and the stator core is held by the motor housing by deforming a portion of the motor housing that faces the recess. .

JP 2007-43845 A

  In the electric motor in which the motor housing is deformed, distortion may occur in the motor housing and the roundness of the motor housing may not be maintained. Since the motor used in the electric power steering device is particularly required to have a low cogging torque, the electric motor having the above-described split stator structure has a staticity such as roundness and outer diameter when the stator core is annular. It is necessary to ensure accuracy. That is, in order to maintain the optimum holding force by fitting with the motor housing, the outer diameter of the annular stator core is measured to ensure the accuracy of the outer diameter, that is, the fitting dimension of the stator core. However, in this measurement, there may be a case where the outer diameter dimension changes due to a displacement or elastic deformation of the stator core due to a binding force applied to the stator core from the outside during the measurement. Further, when the holding force of the stator core varies, the output torque of the electric motor may become unstable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric motor that can secure a holding force of a stator core having a split stator structure and can simplify assembly.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided with a plurality of stator cores having a housing, an arc-shaped yoke portion, and a teeth portion protruding radially inward from the yoke portion, and the stator cores are mutually connected. A stator that is arranged in an annular shape so that circumferential end surfaces of adjacent yoke portions are in contact with each other, a coil is wound around each tooth portion of the stator core, and is fixed in the housing, and the tooth portion of the stator An electric motor comprising: a rotor supported on the housing so as to be rotatable around a rotation center while facing an inner peripheral surface formed by a tip portion; and the stator core has a diameter from an outer peripheral surface of the yoke portion. A dovetail-shaped engagement protrusion is provided with a gradually increasing width in the circumferential direction toward the outer side, and a radial direction is formed on the inner peripheral surface of the housing. The width of the circumferential direction gradually increases toward the side, a dovetail-shaped engagement groove that fits the engagement protrusion is formed, and the yoke portion of the stator core that is annularly disposed on the inner peripheral surface of the housing A cylindrical outer peripheral surface is press-fitted, and the engagement protrusion is provided in the engagement groove with a gap between a top surface of the engagement protrusion and a bottom surface of the engagement groove, and the engagement groove and the engagement The gist is that the protrusions are pressed into contact with the outer peripheral side edges of the dovetail shape.

  According to a second aspect of the present invention, in the electric motor according to the first aspect, the engagement protrusion is formed at a center of an outer peripheral surface of the yoke portion of the stator core having a predetermined length from both axial end portions. The gist is that

  According to the first aspect of the present invention, the engagement protrusion provided on the outer peripheral surface of the yoke portion and the dovetail-shaped engagement groove that fits with the engagement protrusion provided on the inner peripheral surface of the housing are the engagement protrusions. A gap is provided between the top surface and the bottom surface of the engagement groove, and the dovetail-shaped outer peripheral side press-fit is press-fitted between the inner peripheral surface of the housing and the outer peripheral surface of the stator core. Thus, the rotation direction of the stator is restricted, and the holding force of the stator core can be easily secured. Further, since the outer peripheral side edges of the dovetail shape are in pressure contact with each other, it is possible to prevent the engagement protrusion and the engagement groove from coming into contact with an excessive force around the rotation center. As a result, the process of measuring the outer diameter of the stator can be omitted, the dimensional management can be simplified, and the outer diameter accuracy can be ensured.

  According to the second aspect of the present invention, the engaging protrusion at the center of the outer periphery of the stator core is formed with a predetermined length at both ends in the axial direction, so that the engaging protrusion is formed by the portion where the engaging protrusion is not formed. The pressure input to be fitted into the engagement groove of the housing is weakened, and the stator core can be easily press-fitted into the housing, so that the assembly process of the stator can be simplified.

1 is a longitudinal sectional view showing a schematic configuration of an electric motor according to an embodiment of the present invention. The front view which shows the structure of the stator core of the electric motor by embodiment of this invention. The enlarged view which shows the shape of the engagement protrusion of the stator core engaged with the housing of FIG. The top view which looked at the stator core of FIG. 2 from the outer peripheral surface side arrow A direction.

Next, as an example of an embodiment of the present invention, an electric motor used in an electric power steering apparatus (EPS) will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an electric motor according to an embodiment of the present invention. An electric motor (hereinafter referred to as a brushless motor) 1 is an inner rotor type brushless motor. As shown in FIG. 1, the brushless motor 1 includes an annular rotor 3 that is connected to a rotating shaft 2 so as to be able to rotate together, an annular stator 4 that surrounds the periphery of the rotor 3, and a first housing that accommodates the rotor 3 and the stator 4. A cylindrical housing (hereinafter referred to as a motor housing) 5 including a single housing 16 and a second housing 17 is provided. For example, in the case of a column assist type EPS motor, a worm speed reducer (not shown) is arranged on the left side in the axial direction of the brushless motor 1 in FIG. 1, and a controller (hereinafter referred to as ECU) (not shown) is arranged on the right side.

  The rotor 3 includes an annular rotor core 6 coaxially connected to the rotating shaft 2 and a plurality of permanent magnets 7 fixed to the outer periphery of the rotor core 6. The permanent magnet 7 is a multipolar magnet having a plurality of segment magnetic poles. The magnetic poles on the outer peripheral surface of the permanent magnet 7 have N and S poles alternately switched in the circumferential direction of the permanent magnet 7. The permanent magnet 7 has, for example, 10 segment magnetic poles.

  The stator 4 includes an annular stator core 8 and a plurality of coils 9 wound around the stator core 8. The stator core 8 is a laminate in which a plurality of thin plates formed by punching out electromagnetic steel plates into a predetermined shape are laminated and fixed in the axial direction of the stator core 8. That is, the stator core 8 is made of a material containing iron. As the electromagnetic steel plate, for example, a silicon steel plate whose surface is insulated can be used.

  Referring to FIG. 1, the motor housing 5 includes a cylindrical first housing 16 having one end opened, and a cylindrical second housing 17 fitted to the first housing 16. The first housing 16 and the second housing 17 are each made of a material containing iron such as carbon steel or aluminum.

  The first housing 16 includes a first tubular portion 19, a first flange portion 20 that protrudes radially outward from the first tubular portion 19 from one end of the first tubular portion 19, and An annular portion 22a having a first insertion hole 21a extending from the other end of the first tubular portion 19 inward in the radial direction of the first tubular portion 19 and through which the rotary shaft 2 is inserted. . A bearing holding portion 23 that holds the bearing 41 is formed on the inner peripheral portion of the annular portion 22a.

  The first cylindrical portion 19 of the first housing 16 is longer than the stator core 8 in the axial direction. The stator core 8 is fixed to the inner periphery of the first cylindrical portion 19 by shrink fitting or press fitting. That is, the first housing 16 and the stator core 8 are joined by fitting.

  The second housing 17 includes a second cylindrical portion 24 connected along the outer peripheral portion of the first cylindrical portion 19 of the first housing 16, and a rear end portion of the second cylindrical portion 24. A second annular portion 22b having a second insertion hole 21b extending inward in the radial direction of the second cylindrical portion 24 and through which the rotary shaft 2 is inserted is formed at the center, and the second cylindrical portion 24 And a flange portion 25 protruding outward in the radial direction of the second cylindrical portion 24 from the outer peripheral surface. A bearing holding portion 29 that holds the bearing 42 is formed at the center portion of the annular portion 22b of the second housing 17 on the stator core 8 side. A resolver 32 attached to the rotary shaft 2 is disposed on the opposite side of the annular portion 22b as a rotation angle sensor that detects the rotational position of the rotor 3. The rotating shaft 2 is rotatably held by the motor housing 5 via a bearing 41 held by the bearing holding portion 23 and a bearing 42 held by the bearing holding portion 29.

  The second flange portion 25 is overlapped with the first flange portion 20. The first flange portion 20 and the second flange portion 25 are fastened and fixed by a plurality of bolts (not shown) as fixing means (for example, three locations in the present embodiment) and screw portions provided on the second flange 25. Has been.

  Thereby, one end of the first housing 16 and one end of the second housing 17 are fixed, and the rotation of the second housing 17 with respect to the first housing 16 is prevented. That is, the plurality of bolts and nuts, and the first flange portion 20 and the second flange portion 25 function as rotation preventing means for preventing the rotation of the second housing 17 with respect to the first housing 16.

  Further, an ECU (not shown) for controlling the brushless motor 1 is attached to the rear end surface (right side in FIG. 1) of the annular portion 22b of the second housing 17 and fixed to the second flange 25 with screws. A metal bus bar 30 that is an output terminal of each phase of the brushless motor 1 that is connected to each coil 9 and insulated and supported by the insulator 31 is inserted into the board of the ECU and screwed to the inverter circuit section on the board. Has been. With the above configuration, the drive current controlled by the ECU is supplied to each coil 9 of the brushless motor 1. Thereby, a rotating magnetic field is generated in the coil 9, torque is generated in the permanent magnet 7, and the rotor 3 is rotationally driven. Similarly, the resolver 32 is connected to the ECU board by soldering lead wires as signal input / output terminals.

  The brushless motor 1 includes, for example, a column cyst type electric power steering device by a third flange portion 28 protruding from the left end in the axial direction of the first cylindrical portion 19 to the outside in the radial direction of the first cylindrical portion 19. The worm shaft is connected to a worm shaft rotating shaft via a boss 33 which is fixedly attached to a worm speed reducer (not shown) and transmits torque attached to the rotating shaft 2.

  Next, FIG. 2 is a front view showing the structure of the stator core of the brushless motor according to the embodiment of the present invention, and FIG. 3 is an enlarged view showing the shape of the engaging protrusion of the stator core that engages with the motor housing in the broken line of FIG. FIG.

  As shown in FIG. 2, the stator core 8 includes a plurality of (for example, 12 in the present embodiment) divided cores 12 in which a large number of T-shaped plates 38 are stacked and connected together at equal intervals in the circumferential direction. It consists of a structure arranged annularly at a distance. The split core 12 includes an arcuate yoke portion 10 and a teeth portion 11 extending radially inward from the yoke portion 10, and circumferential end surfaces of adjacent yoke portions 10 abut against each other in the radial direction. It is configured as follows. Further, a dovetail-shaped engagement protrusion 44 whose width in the circumferential direction gradually increases outward in the radial direction is provided at the center of the outer peripheral surface of the yoke portion 10 of the plate 38 so as to extend in the direction of the rotation center. A dovetail-shaped engagement groove 43 is provided on the inner peripheral surface of the housing 5 so as to be engaged with the engagement protrusion 44 whose width in the circumferential direction gradually increases toward the radially outer side. The inner peripheral surface of the motor housing 5 and the outer peripheral surface of the stator core 8 are press-fitted, and the engagement protrusion 44 and the engagement groove 43 are spaced between the top surface of the engagement protrusion 44 and the bottom surface of the engagement groove 43. And is in pressure contact with the outer peripheral edge portions on both sides of the outer peripheral side of the dovetail shape.

  At this time, the annular front end portion is pressed and fixed with a ring or the like to maintain a perfect circle, and the annular stator core 8 is formed. This ring can be easily positioned by providing a groove (for example, one location). Slots are formed between adjacent divided cores 12. In the present embodiment, the number of slots is 12. That is, the brushless motor 1 is a 10 pole 12 slot motor. In addition, the inner peripheral side core portion of the stator core 8 has an open slot 46 in order to suppress a reduction in output torque of the brushless motor 1 due to leakage magnetic flux generated between adjacent teeth portions 11. In the present embodiment, the engagement protrusions 44 and the engagement grooves 43 facing the inner peripheral surface of the motor housing 5 are provided in all slots (for example, 12 slots).

  As shown in FIG. 3, the engagement protrusion 44 of the split core 12 has a tip width dimension w and a height dimension h, and is formed at a predetermined angle radially inward from the outer peripheral surface. Further, an engagement groove 43 larger than the width w and height h of the engagement protrusion 44 is formed on the inner peripheral surface side of the motor housing 5 to be press-fitted. Here, the inclination toward the inner peripheral side of the engagement groove 43 is formed with an angle smaller than the inclination of the engagement protrusion 44. By attaching this angle difference, even if the w dimension and the h dimension vary, it is sure to be press-fitted somewhere. Here, a large stress is generated in the radial direction by press-fitting the inner peripheral surface of the motor housing 5 and the outer peripheral surface of the split core 12. Further, the engagement protrusion 44 and the engagement groove 43 are in pressure contact with both side edges on the outer peripheral side of the dovetail shape, and are held in a state where they do not contact with an excessive force in the circumferential direction (around the rotation center). .

  Next, FIG. 4 is a top view of the stator core of FIG. 2 as viewed from the direction of the arrow A on the outer peripheral surface side. As shown in FIG. 4, the split core 12 is configured such that a large number of plates 38 are laminated in the axial direction with the teeth portions 11 aligned, and are integrally connected and fixed by caulking. An engagement protrusion 44 having a predetermined width w is formed at the outer peripheral side central portion of the yoke portion 10 extending in an arc shape from the teeth portion 11 (see FIG. 2). Here, in order to reduce the pressure input of the split core 12 and facilitate press-fitting, the engagement protrusions 44 are provided in a predetermined length only at a part of both ends of the outer peripheral surface in the axial direction of the split core 12. Further, the engaging projections 44 at both ends are formed symmetrically in the axial direction.

  Next, operations and effects of the brushless motor 1 according to the present embodiment configured as described above will be described.

  According to the above configuration, a dovetail shape extending in the rotation center direction of the plurality of stator cores 8 and provided at the center portion of the outer peripheral surface of the arc-shaped yoke portion 10 and gradually increasing in the circumferential direction toward the radially outer side. The engagement protrusions 44 and the dovetail-shaped engagement grooves 43 that fit the engagement protrusions 44 gradually increase in the circumferential width toward the radially outer side on the inner peripheral surface of the motor housing 5. A gap is provided between the top surface of the groove and the bottom surface of the engaging groove 43, and the dovetail-shaped outer peripheral side edges are pressed against each other. The inner peripheral surface of the motor housing 5 and the outer peripheral surface of the stator core 8 are press-fitted, and the engaging protrusion 44 and the engaging groove 43 are pressed against each other so as not to contact with an excessive force around the rotation center. The tip of the outer peripheral surface of the stator core 8 is pressed and fixed by a ring or the like to maintain a perfect circular state, and the outer peripheral surface of the annular stator core 8 is formed in a cylindrical shape. At this time, the engaging projection 44 at the center of the outer periphery of the stator core 8 is formed to have a predetermined length at both ends in the axial direction.

  Thereby, since the rotation direction of the stator 4 is restrained by the engaging protrusion 44, the holding force of the stator core 8 can be easily secured. Further, since the outer peripheral side edges of the dovetail shape are in pressure contact with each other, it is possible to prevent the engagement protrusion 44 and the engagement groove 43 from coming into contact with an excessive force around the rotation center. As a result, the process of measuring the outer diameter of the stator 4 can be omitted, the dimensional management can be simplified, and the outer diameter accuracy can be ensured. Further, the portion where the engagement protrusion 44 is not formed weakens the pressure input for fitting the engagement protrusion 44 into the engagement groove 43 of the motor housing 5, and the stator core 8 can be easily press-fitted into the motor housing 5. . Furthermore, a cylindrical stator 4 is formed by fitting and pressing a ring-shaped holding member on the outer periphery of the stator core 8. Thereby, the stator core 8 can be press-fitted into the motor housing 5 after the stator 4 is assembled without a welding process. As a result, the assembly process of the stator 4 can be simplified.

  Further, since it is not necessary to guarantee the holding force in the fitting, the outer diameter measuring process of the stator 4 is abolished, the inner diameter measuring process of the motor housing 5 is abolished, dimensional management is simplified, and the outer diameter welding of the stator core 8 is performed. The process can be abolished. Further, by providing the engagement protrusions 44 and the engagement grooves 43 in all the slots, the effect of reducing the cogging torque particularly required for the electric power steering apparatus can be obtained.

  As described above, according to the present embodiment, it is possible to provide a brushless motor that can secure the holding force of the stator core having the divided stator structure and can simplify the assembly.

As mentioned above, although embodiment which concerns on this invention was described, this invention can also be implemented with another form.
In the above embodiment, the engaging protrusion 44 is integrally formed on the yoke portion 10 side. However, the present invention is not limited to this, and the engaging protrusion 44 may be provided anywhere, and other parts may be press-fitted. Good. Further, although the engagement protrusions 44 are provided in all the slots, they may be provided in some slots depending on the effect of reducing the cogging torque or the like. The engagement protrusion 44 may be provided on the motor housing 5 side, and the engagement groove 43 may be provided on the stator core 8 side. Furthermore, when the material of the motor housing 5 is softer than the stator core 8, the stator core 8 may be bitten while crushing the motor housing 5 side. Conversely, the engagement protrusion 44 on the stator core 8 side is bitten by the motor housing 5. It is also possible to make it.

  In the above embodiment, the brushless motor 1 is applied to a so-called column assist type of an electric power steering device (EPS). You may apply to an apparatus and may apply to the other apparatus using the same brushless motor.

  Moreover, although the case where ECU was arrange | positioned on the opposite side to the worm reduction gear of the axial direction of the brushless motor 1 and integrated with the brushless motor 1 was shown in the said embodiment, it is not limited to this, ECU is attached. You may install adjacent to the radial direction of the brushless motor 1 according to space. Further, the ECU may be disposed between the brushless motor 1 in the axial direction and the worm reducer.

  The permanent magnet 7 fixed to the outer periphery of the rotor core 6 may be another permanent magnet such as a ring magnet. Further, the stator core 8 may be a green compact made of a powder material containing a soft magnetic material, for example. Examples of soft magnetic materials include iron, ferrite, permalloy, and the like.

1: brushless motor (electric motor), 2: rotating shaft, 3: rotor, 4: stator, 5: motor housing (housing), 6: rotor core, 7: permanent magnet, 8: stator core, 9: coil, 10: yoke Part, 11: teeth part, 12: split core, 16: first housing, 17: second housing, 19: first cylindrical part, 20, 25, 28: flange part, 21a, 21b: insertion hole 22a, 22b: annular portion, 23, 29: bearing holding portion, 24: second cylindrical portion, 30: bus bar, 31: insulator, 32: resolver, 33: boss, 35: laminated yoke portion, 38: plate 41, 42: bearing, 43: engagement groove, 44: engagement protrusion, 45: laminated tooth portion, 46: open slot, w: engagement protrusion width, h: engagement protrusion height

Claims (2)

A housing;
A plurality of stator cores having an arcuate yoke portion and teeth portions projecting radially inward from the yoke portion; A stator in which a coil is wound around each tooth portion of the stator core and fixed in the housing;
An electric motor comprising: a rotor supported on the housing so as to be rotatable around a rotation center while facing an inner peripheral surface formed at a tip portion of the teeth portion of the stator.
The stator core is provided with a dovetail-shaped engagement protrusion that gradually increases in the circumferential width from the outer peripheral surface of the yoke portion toward the radially outer side,
On the inner peripheral surface of the housing, a circumferential width gradually increases toward the outer side in the radial direction, and a dovetail-shaped engagement groove that fits the engagement protrusion is formed. A cylindrical outer peripheral surface of the yoke portion of the stator core arranged in an annular shape is press-fitted, and the engagement protrusion is inserted into the engagement groove with a gap between the top surface of the engagement protrusion and the bottom surface of the engagement groove. The electric motor is characterized in that the engagement groove and the engagement protrusion are pressed against each other at both side edges on the outer peripheral side of the dovetail shape. The electric motor according to claim 1,
The electric motor is characterized in that the engaging protrusion is formed at a center of an outer peripheral surface of the yoke portion of the stator core with a predetermined length from both axial end portions.

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