JP2006025508A - Motor for electric power steering system and electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor for an electric power steering system in which the slip of a permanent magnet can be prevented surely by a simple structure and a variation in loss torque can be reduced. <P>SOLUTION: Out of a plurality of electromagnetic steel plates (15, 16), at least one steel plate (16) at each end of a rotor core (17) has an outside diameter larger than the inside diameter of a rotor magnet (18). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor for an electric power steering (EPS) device and an electric power steering device that assist (assist) a manual steering force by a driver in a vehicle.

  The electric power steering apparatus includes a torque sensor that detects a steering torque applied to the steering wheel, and a steering assist motor, and drives the motor according to the steering torque detected by the torque sensor to thereby apply a steering force to the steering wheel. It is configured to assist.

  Specifically, when the steering wheel is slowly rotated at high speed and the steering torque is lower than a predetermined value, the motor is not driven. When the steering wheel is further moved and the steering torque exceeds a predetermined value, the motor is driven to rotate. At this time, if there is a large loss torque fluctuation, which is a friction loss based on the motor structure and a loss based on electromagnetic factors, in the output torque of the motor, this torque fluctuation is transmitted to the steering wheel and becomes a vibration to the driver's hand. It is transmitted. Therefore, the motor is required to have very little loss torque fluctuation.

One cause of the loss torque is scattering and deviation of a rotor magnet fixed to the rotor. As a measure to prevent the magnet from scattering and shifting, the magnet is fixed to the rotor core by a technique for fixing the magnet by installing a cover on the outer periphery of the magnet, the magnetic attractive force of the magnet itself, adhesion, or a complicated structure. Various techniques have been proposed (see, for example, Patent Documents 1 and 2).
JP 2003-70193 A (page 5, FIG. 1) JP 2003-333774 A (page 3-4, FIG. 4)

  However, in the techniques described in Patent Documents 1 and 2, although the safety of the magnet in the circumferential direction is maintained against the loosening of the magnet during high-speed rotation and operation in a high-temperature atmosphere, The countermeasures are insufficient, and the magnet may be displaced in the axial direction to increase motor lock or loss torque fluctuation. Further, there is a problem that the structure of the rotor is complicated, the number of parts is large, and the assembly process is complicated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to reliably position the rotor magnet in the axial direction with a simple structure, reduce loss torque fluctuation, and lock the motor. It is an object of the present invention to provide a motor for an electric power steering apparatus and an electric power steering apparatus that are free from electric power.

The above-mentioned subject concerning the present invention is attained by the following composition.
(1) a rotor having a rotor core formed by laminating a plurality of electromagnetic steel plates around a rotating shaft, and a rotor magnet provided on the outer peripheral surface of the rotor core;
A stator having a stator core and an excitation coil provided to face the rotor;
A motor for an electric power steering device comprising:
The motor for an electric power steering apparatus, wherein at least one of the plurality of electromagnetic steel sheets has an outer diameter larger than an inner diameter of the rotor magnet.
(2) An electric power steering apparatus using the motor according to (1) as a drive motor.

  According to the present invention, among the plurality of electromagnetic steel plates, at least one electromagnetic steel plate at each end of the rotor core has an outer diameter larger than the inner diameter of the rotor magnet, so that the shaft of the rotor magnet has a simple structure. The motor for an electric power steering device and the electric power steering device can be prevented in which the motor lock and the loss torque fluctuation are prevented from increasing due to the displacement in the direction.

  Hereinafter, a motor for an electric power steering apparatus and an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory view for explaining an electric power steering apparatus according to an embodiment of the present invention, FIG. 2 is a cross-sectional view for explaining an electric power steering apparatus motor, and FIG. 3 is an enlarged cross section of the rotor of FIG. 4 is a perspective view of the rotor of FIG. 3, FIG. 5 is a cross-sectional view showing an intermediate portion of the rotor, FIG. 6 is a front view of both ends of the rotor, and FIG. 7 is an enlarged view of both ends of the rotor of FIG. is there.

  First, an electric power steering apparatus will be described with reference to FIG. In the electric power steering device 1, a steering column that surrounds a steering shaft 4 that is connected to a steering device (not shown) at both ends and moves in the left-right direction in FIG. 1 and a steering shaft 4 having a steering wheel 3 attached to the upper end. 5 are connected by a rod 6. The motor 7 for the electric power steering device is connected to the steering shaft 4 via a worm wheel (not shown) and a worm (not shown), and is controlled by a controller 8 to which information such as the steering angle of the vehicle and the steering wheel 3 is input. Is done.

  As shown in FIG. 2, in the motor 7, the rotating shaft 14 is rotatably supported with respect to the housing 11 via a pair of bearings 12 and 13. A rotor core 17 formed by laminating a plurality of disk-shaped electromagnetic steel plates 15 and 16 is mounted around the rotary shaft 14 between the pair of bearings 12 and 13. A magnet 18 is fixed. The rotor magnet 18 uses a segment magnet as a permanent magnet for generating a field. Further, as shown in FIG. 3, on the outside of the rotor magnet 18, a flange portion 19 a formed at one end is brought into contact with the end surface of the rotor magnet 18 to prevent the rotor magnet 18 from scattering and shifting. A magnet cover 19 is provided. The rotating shaft 14, the rotor core 17, the rotor magnet 18, and the magnet cover 19 constitute a rotor 20.

  A stator 21 is configured in the housing 11 so as to face the rotor 20 in the radial direction, and an annular stator core 22 fixed to the inner peripheral surface of the housing 11 and an excitation coil wound around the stator core 22. 23.

  Further, a phase detector 24 of the rotor 20 is disposed in the vicinity of the one bearing 12. The phase detection unit 24 includes an annular phase detection permanent magnet 25 attached to the rotary shaft 14 and a phase detection element 26 that faces the permanent magnet 25 and is fixed to the housing 11 side. Since the motor 7 is a brushless motor in which the motor 7 does not include a mechanical commutator (brush and commutator), the phase detection unit 24 detects the phase of the rotor 20 and controls the excitation coil 23 according to the phase under the control of the controller 8. It is for energizing. In operation, the rotation of the rotary shaft 14 is decelerated by a reduction gear composed of a worm and a worm wheel, and the direction of motion is changed to assist (assist) the manual steering force.

  Here, as shown in FIG. 3, at least one rotor core 17 is disposed at each of the electromagnetic steel plates 15 stacked in correspondence with the axial length of the rotor magnet 18 and at both ends of the rotor core 17. And an electromagnetic steel plate 16.

  As shown in FIG. 5, each electromagnetic steel plate 15 includes a plurality of arc-shaped magnet installation portions 15 a where a plurality of rotor magnets 18 are installed, and an outer periphery of the magnet installation portion 15 a provided between adjacent magnet installation portions 15 a. A plurality of protrusions 15b protruding in a radial direction from the surface are provided on the outer peripheral surface, and the protrusions 15b of the respective electromagnetic steel plates 15 are laminated so that the positions thereof coincide with each other.

  As shown in FIGS. 4, 6, and 7, the electromagnetic steel plate 16 has an outer diameter larger than the inner diameter of the rotor magnet 18, and partially contacts the axial end surface of the rotor magnet 18. . Therefore, by using the electromagnetic steel plates 15 and 16, each rotor magnet 18 is reliably positioned in the circumferential direction and the axial direction.

  In the electric power steering apparatus motor 7 and the electric power steering apparatus 1 of the present embodiment configured as described above, the electromagnetic steel plates 16 provided at both ends of the rotor core 17 have an outer diameter larger than the inner diameter of the rotor magnet 18. Therefore, it is possible to easily position the rotor magnet 18 in the axial direction with a simple configuration, and to provide a motor for an electric power steering device and an electric power steering device with little loss torque fluctuation.

The present invention is not limited to the present embodiment, and appropriate modifications and improvements can be made.
For example, in the present embodiment, the electromagnetic steel plates 16 having an outer diameter larger than the inner diameter of the rotor magnet 18 are provided on both ends of the rotor core 17 one by one. In the present embodiment, the electromagnetic steel plate 16 is circular, but may be various shapes including polygons as long as the rotor magnet 18 can be pressed.

Further, the number of poles of the rotor magnet 18 can be arbitrarily set. Further, the rotor magnet 18 may have a ring shape instead of a segment shape, and the axial positioning of the rotor magnet 18 can be achieved by making the outer diameters of the electromagnetic steel plates 16 at both ends larger than those of the other electromagnetic steel plates 15. It can be done reliably.
Furthermore, the electric power steering apparatus motor may be used as a drive motor, and the mounting position may be connected to the steering shaft as shown in FIG. 1 or to the rack shaft.

It is explanatory drawing for demonstrating the electric power steering apparatus which concerns on one Embodiment of this invention. It is sectional drawing for demonstrating the motor for electric power steering apparatuses. It is an expanded sectional view of the rotor of FIG. FIG. 4 is a perspective view of the rotor of FIG. 3. It is sectional drawing which shows the intermediate part of a rotor. It is a front view in the both ends of a rotor. It is an enlarged view in the both ends of a rotor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 7 Motor for electric power steering apparatuses 14 Rotating shafts 15, 16 Electrical steel sheet 15b Protrusion part 17 Rotor core 18 Rotor magnet 20 Rotor 21 Stator 22 Stator core 23 Excitation coil

Claims (2)

A rotor core having a rotor core formed by laminating a plurality of electromagnetic steel plates around a rotating shaft, and a rotor magnet provided on the outer peripheral surface of the rotor core;
A stator having a stator core and an excitation coil provided to face the rotor;
A motor for an electric power steering device comprising:
A motor for an electric power steering apparatus, wherein among the plurality of electromagnetic steel sheets, at least one electromagnetic steel sheet at each end of the rotor core has an outer diameter larger than an inner diameter of the rotor magnet.   An electric power steering apparatus using the motor according to claim 1 as a drive motor.

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