JP2013225953A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix a resolver rotor to a shaft of an electric motor by press fitting through a coupling, thereby preventing the deterioration of characteristics of the resolver rotor due to its distortion and improving the detection accuracy.SOLUTION: An electric motor includes a shaft 52 outputting a rotational force, provides a resolver stator 82 and a resolver rotor 81 which form a rotation position detection sensor 80 and a coupling 101 transmitting the rotational force at a tip of the shaft 52. Further, the electric motor includes a flange 51 fixing the resolver stator 82 at an opening of a stator case 15 where one end is formed into a closed structure and fixes the resolver rotor 81 to an outer diameter part 101A of the coupling 101. The resolver rotor 81 is fixed to the outer diameter part of a fixed part of the shaft 52 in the coupling 101.

Description

  The present invention relates to an electric motor, and more particularly to an improvement in a resolver fixing structure of an electric motor that is preferably used in an electric power steering apparatus (EPS) or the like.

  Conventionally, various motors such as a brushless motor have been proposed as electric motors. For example, a structure is disclosed in which a resolver rotor is press-fitted and fixed to a shaft of an electric motor, and a boss connected to a steering mechanism is press-fitted and fixed to the tip side thereof. (For example, refer to Patent Document 1).

JP 2003-204654 A

  However, in the method of fixing the resolver rotor of the electric motor described in Patent Document 1 described above, the resolver rotor is generally configured by laminating thin plates. The axial position of the press-fitted boss is not stable. Further, since the press fitting is fixed to the small-diameter shaft, the friction radius must be small and the press-fitting must be increased, and there is a problem that the resolver rotor is distorted and the accuracy of the resolver signal is deteriorated.

  In order to achieve this object, the present invention includes a resolver stator and a resolver rotor that constitute a rotational position detection sensor having a shaft that outputs rotational force, and a coupling that transmits rotational force is provided at the distal end of the shaft. An electric motor having a flange for fixing a resolver stator at an opening of a stator case having a closed structure and having a resolver rotor fixed to an outer diameter portion of a coupling.

  In the electric motor according to the present invention, preferably, the resolver rotor is fixed to an outer diameter portion of the shaft fixing portion of the shaft of the coupling, and preferably, the resolver rotor is configured such that the step portion of the shaft and the coupling step. It is an electric power steering apparatus having an electric motor that is sandwiched between the portions to regulate the axial position and more preferably applies a steering assist force to the steering via a speed reduction mechanism.

  The electric motor according to the present invention can increase the inner diameter of the press-fit fixing portion of the resolver rotor, so that the friction radius of the press-fit fixing portion can be increased and the press input can be reduced. Accordingly, since the distortion due to the press-fitting of the resolver rotor can be reduced, the accuracy of the resolver signal can be improved, so that the electric motor can be controlled with high reliability. In addition, since the positional accuracy of the boss to be coupled with the electric power steering mechanism is improved, it is possible to make the thickness accuracy of the thin plate on which the resolver rotor is laminated, so that an inexpensive product is provided. be able to. As a result, it is possible to provide an electric power steering apparatus that has no sense of incongruity and is suitable for steering feeling.

It is explanatory drawing which shows the outline of a structure of an electric power steering apparatus. It is sectional drawing of the deceleration mechanism part of the electric power steering device concerning embodiment of this invention. It is sectional drawing of the motor concerning embodiment of this invention. It is sectional drawing of the motor used for the 2nd example of embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of the configuration of an electric power steering apparatus 1 having a motor according to the present embodiment. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[First example of embodiment]
The electric power steering apparatus 1 is, for example, of a column type, and corresponds to a steering shaft 10 to which a vehicle steering wheel H is fixed, a rack and pinion motion conversion mechanism 11, and a steering torque applied to the steering wheel H. An electric motor 12 that generates auxiliary steering torque, and a worm reduction mechanism 13 that is interposed between the electric motor 12 and the steering shaft 10 and decelerates the rotation of the electric motor 12 are provided.

  The steering shaft 10 has a steering input shaft 10 a and a steering output shaft 10 b and is covered with a housing 20. A steering wheel H is fixed to the upper end of the steering input shaft 10a. The steering input shaft 10a and the steering output shaft 10b are connected via a torsion bar of the torque sensor 21. The steering torque generated by the operation of the steering wheel H is detected by the torque sensor 21 through the steering input shaft 10a, and the output of the electric motor 12 is controlled based on the detected steering torque. Details of the configuration of the electric motor 12 will be described later.

  The worm reduction mechanism 13 includes a worm wheel 30 attached to the steering output shaft 10b and a worm 31 that meshes with an outer peripheral gear of the worm wheel 30 (see FIG. 2). The worm 31 is supported by two bearings (bearings) 33 and 34 fixed to the housing 32. One end of the worm 31 is coupled to the shaft 52 (described later) of the electric motor 12 by a coupling structure 100 coaxially. Thereby, for example, the reaction force in the axial direction X of the shaft 52 received by the worm 31 by driving the steering output shaft 10 b and the worm wheel 30 can be absorbed by the worm reduction mechanism 13.

  As shown in FIG. 1, the steering output shaft 10 b and the rack and pinion motion conversion mechanism 11 are connected by two universal joints 40 and 41 and a connecting member 42. The rack and pinion motion conversion mechanism 11 connects the steering output shaft 10b and the tie rod of the operation wheel by a rack and pinion gear.

  The rotational force output by the electric motor 12 is transmitted to the steering output shaft 10b as auxiliary steering torque via the worm reduction mechanism 13, and the auxiliary steering torque is transmitted from the steering output shaft 10b to the rack and pinion motion conversion mechanism 11. To the tie rod of the operation wheel.

  Next, the configuration of the electric motor 12 will be described. For example, as shown in FIG. 3, the electric motor 12 includes a stator (stator) 54 and a flange 51 that closes one opening of the stator 54. A rotor (rotor) 53 that rotates a shaft (rotating shaft) 52 is provided inside the stator 54. Reference numeral 15 denotes a metal stator case that forms the casing of the stator 54.

  The stator 54 has a cylindrical stator core 60 constituted by any one of an integral, divided, and sintered core. Insulator 61 is inserted into the stator core 60 in which the necessary number of sheets are stacked after the tape is wound from the outside, and the coil 62 is wound in this state. In the present embodiment, a convex portion extending in the radial direction is provided on the yoke portion (back yoke) of the end core of the stator core 60, and after stacking the stator core 60, the convex portion of the intermediate portion is bent in the axial direction. It is in contact. The folding itself may be before or after the winding of the coil 62.

  Further, in the electric motor 12 used in the electric power steering apparatus 1 as in the present embodiment, although not shown in detail, the stator 54 is a convex portion extending in the radial direction on the joint surface back yoke portion of the split core. They are brought into contact with each other and integrated by laser welding or TIG welding before and after bending. A terminal block 90 is provided at one end of the stator 54, and the bus bar inserted into or inserted into the terminal block 90 and each phase coil are electrically connected by fusing, resistance welding, or the like. Further, the stator 54 is fixed to the stator case 15 by press fitting, bonding, shrink fitting or the like.

  In addition, since the electric motor 12 of the present embodiment is a three-phase motor, the 3n stator cores 60 are integrated by being press-fitted or welded for each yoke portion (back yoke). A flange 51 is fixed to the front side of the stator 54 in the axial direction X (the left side in FIG. 3 which is the motor output side) by press fitting, bonding, caulking, shrink fitting or the like. It is also preferable to interpose an elastic member between the stator 54 and the flange member 51. Although not shown in detail in detail, it is also preferable that a detent made of unevenness to prevent relative rotation between the stator 54 and the flange 51 is formed. Further, a bearing 70 is accommodated in a bearing housing on the rear side of the stator 54 (the motor end side on the right side in FIG. 3 opposite to the above-described front side).

  The flange 51 has a structure in which the stator case 15 is fixed to the opening side of the stator 54 by press fitting, bonding, caulking, or the like. A bearing 71 is accommodated in a bearing housing at a substantially central portion of the flange 51.

  The rotor 53 is installed inside the stator 54. The rotor 53 has a rotor core inside, and the shaft 52 is provided in a state in which the shaft 52 passes through the axis. A magnet and a magnet cover are provided on the outer peripheral surface of the rotor core. The rotor core is press-fitted with the shaft 52 or is integrally formed with the shaft 52. An even number of magnets are arranged on the outer peripheral surface of the core of the shaft 52 at equal intervals by adhesion or a holding member. When the magnet is an embedded magnet type, it is arranged in the rotor core. Further, a magnet scattering prevention cover is provided on the outer periphery of these magnets. The magnet scattering prevention cover is formed of, for example, a non-magnetic SUS material, aluminum, a heat shrinkable tube, or the like.

  The rear side of the shaft 52 is supported by a bearing 70. The front side of the shaft 52 penetrates the axis of the flange 51 and is supported by a bearing 71 fixed to the flange 51. The front end of the shaft 52 is coaxially connected to the worm 31 of the worm reduction mechanism 13 described above.

  A rotational position detection sensor 80 is provided on the front side of the bearing 71 of the shaft 52. The rotational position detection sensor 80 includes a cylindrical resolver rotor 81 press-fitted into the shaft 52 (for example, light press-fitting), and a resolver stator 82 that surrounds the outer periphery of the resolver rotor 81. The resolver stator 82 is attached to a resolver holder fixed to the flange 51 or to the flange 51. A sensor harness 84 communicating with the outside of the electric motor 12 is electrically connected to the resolver stator 82, coupled to a control device (not shown) that drives the electric motor 12, and a detection signal is fed back as a control result. The reliability of electric motor control is improved.

  The shaft 52 of the electric motor is press-fitted and fixed to the shaft press-fit fixing portion 101B of the coupling 101 constituting the coupling mechanism 100 at the tip of the shaft 52. The resolver rotor 81 is press-fitted and fixed to the coupling outer diameter portion 101 </ b> A where the shaft 52 is press-fitted on the lower side of the coupling 101. (See FIG. 3). Further, the axial position is regulated by being sandwiched between the stepped portion 52A of the shaft 52 and the coupling stepped portion 101C.

  As shown in FIG. 3, a terminal block 90 electrically connected to the coil 62 of the stator 54 is installed on the front side of the stator 54. In addition, a power harness (not shown) for supplying power to the coil 62 is electrically connected to the terminal block 90. The power harness passes through a hole of a grommet (not shown) provided in the flange 51 and communicates with the outside of the electric motor 12. The bus bar inserted or insert molded in the terminal block 90 and each phase coil are electrically connected by fusing, TIG welding, or the like.

  The housing 32 and the flange 51 of the worm speed reduction mechanism 13 to be fixed to the electric motor 12 are fixed by screwing screws into, for example, two through holes 51a in the circumferential direction.

  As in this embodiment, the resolver rotor 81 is press-fitted and fixed to the outer diameter portion of the portion into which the shaft 52 is press-fitted on the lower side of the coupling 101. The outer diameter of the coupling outer diameter portion 101A of the coupling 101 into which the resolver rotor 81 is press-fitted is larger than the shaft diameter of the shaft 52. Accordingly, since the friction radius by press-fitting increases as the diameter of the press-fitting portion increases, the press-fitting can be made lower than the direct press-fitting to the shaft 52 when the holding torque is kept equal. As a result, the strain due to the press-fitting stress of the resolver rotor 81 can be reduced. Further, it becomes unnecessary to strictly manage the tolerance of the press-fitting portion of the resolver rotor 81. Furthermore, since the press-fitting length of the shaft 52 and the coupling 101 can be increased, the tilting of the coupling can be suppressed and fluctuations in the torque transmission of the coupling can be prevented.

The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

[Second example of embodiment]
FIG. 4 is a sectional view of a second example of the embodiment showing the electric motor shown in FIG. 3. The shaft 52 of the electric motor is press-fitted and fixed to the shaft press-fit fixing portion 102B of the female spline boss 102 that transmits torque by spline coupling at the tip of the shaft 52. The resolver rotor 81 is press-fitted and fixed to the spline boss outer diameter portion 102 </ b> A where the shaft 52 is press-fitted on the lower side of the female spline boss 102. (See FIG. 4).

  As in this embodiment, the resolver rotor 81 is press-fitted and fixed to the outer diameter portion of the portion into which the shaft 52 is press-fitted on the lower side of the female spline boss 102. The outer diameter of the spline boss outer diameter portion 102A of the female spline boss 102 into which the resolver rotor 81 is press-fitted is larger than the shaft diameter of the shaft 52. Accordingly, since the friction radius by press-fitting increases as the diameter of the press-fitting portion increases, the press-fitting can be made lower than the direct press-fitting to the shaft 52 when the holding torque is kept equal. As a result, the strain due to the press-fitting stress of the resolver rotor 81 can be reduced. Further, it becomes unnecessary to strictly manage the tolerance of the press-fitting portion of the resolver rotor 81. Furthermore, since the press-fitting length of the shaft 52 and the female spline boss 102 can be increased, the fall of the spline can be suppressed and fluctuations in the torque transmission of the coupling can be prevented. Since the configuration and operation of the other parts are the same as those in the first example of the above-described embodiment, the description of the equivalent parts is saved.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 12 ... Electric motor (motor), 13 ... Worm deceleration mechanism (deceleration mechanism), 31 ... Worm, 52 ... Shaft, 80 ... Rotation position detection sensor, 81 ... Resolver rotor, 82 ... Resolver stator, 101 ... Coupling, 101A ... Coupling outer diameter portion, 102A ... Spline boss outer diameter portion

Claims (4)

Having a shaft that outputs rotational force,
A resolver stator and a resolver rotor constituting a rotational position detection sensor;
A coupling for transmitting rotational force is provided at the tip of the shaft,
A flange for fixing the resolver stator at the opening of the stator case having a closed structure at one end;
An electric motor, wherein the resolver rotor is fixed to an outer diameter portion of the coupling.   The motor according to claim 1, wherein the resolver rotor is fixed to an outer diameter portion of a shaft fixing portion of the shaft of the coupling.   The motor according to claim 1, wherein the resolver rotor is sandwiched between a stepped portion of the shaft and a coupling stepped portion to restrict an axial position. An electric power steering apparatus having an electric motor that applies a steering assist force to a steering via a deceleration mechanism,
An electric power steering apparatus having the motor according to claim 1 as the electric motor.

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