JP2013219948A - Electric motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor having a magnet-embedded rotor capable of securely fixing a permanent magnet.SOLUTION: On a rotor core 24, a plurality of substantially rectangular magnet insertion holes 26 are formed in a circumferential direction around the shaft center of a revolving shaft 25. A permanent magnet 27 is coated with a resin member 28 with a predetermined thickness on an outer peripheral surface that faces the inner peripheral surfaces of the magnet insertion holes 26. On the outer diameter side of the inner peripheral surface in the radial direction of each magnet insertion holes 26, there is formed a projection 29 for preventing the release of the permanent magnet 27. The permanent magnet 27 having the coating of the resin member 28 formed on the outer peripheral surface is press fit and fixed into the magnet insertion hole 26.

Description

  The present invention relates to an electric motor.

  As an electric motor, there is a magnet-embedded motor (IPM motor) in which a permanent magnet is inserted and fixed in a plurality of magnet insertion holes formed in a rotor core. There is also an electric power steering device (EPS) equipped with this IPM motor. In the conventional IPM motor, an adhesive is applied to the surface of the permanent magnet, and the adhesive is fixed in the magnet insertion hole. Alternatively, there has been proposed a method in which a permanent magnet is inserted into a magnet insertion hole and then the position of the permanent magnet is fixed without reducing the magnetic force by filling the magnet insertion hole with a conductive resin (for example, see Patent Document 1). .

JP 2008-182824 A

  However, in the IPM motor as described above, when resin molding is performed on the outer peripheral surface of the permanent magnet in order to fix the permanent magnet in the magnet insertion hole, the manufacturing and inspection processes are performed for cleaning before resin molding and cooling after molding. Increases, and the productivity and manufacturing costs increase. In addition, since it is difficult to make the filling amount of the resin constant, the fixing position of the permanent magnet may vary in each magnet insertion hole.

  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 including an embedded magnet rotor that can securely fix a permanent magnet.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a rotor core provided on a rotating shaft, a plurality of circumferentially formed insertion holes in the rotor core, and a permanent magnet inserted and embedded in the insertion hole. And a resin member that covers the outer peripheral surface of the surface of the permanent magnet that faces the inner peripheral surface of the insertion hole, and the permanent magnet covered with the resin member is press-fitted into the insertion hole. And

  According to the first aspect of the invention, since the outer peripheral surface that contacts the insertion hole on the surface of the permanent magnet is covered with the resin member and is press-fitted into the plurality of insertion holes provided in the rotor core, the permanent magnet is securely attached. Can be fixed.

  According to a second aspect of the present invention, in the electric motor according to the first aspect, a protrusion that presses the permanent magnet covered with the resin member is formed on a part of the inner peripheral surface of the insertion hole. Is the gist.

  According to the second aspect of the present invention, the protrusion is provided on a part of the inner peripheral surface of the insertion hole so as to be in contact with the outer peripheral surface of the permanent magnet covered with the resin member. Can be done.

  ADVANTAGE OF THE INVENTION According to this invention, the electric motor provided with the magnet embedded type rotor which can fix a permanent magnet reliably can be provided.

The schematic diagram which shows schematic structure of an electric power steering apparatus. Sectional drawing orthogonal to the rotating shaft direction of the rotor of the electric motor which concerns on one Embodiment of this invention. The enlarged view of the permanent magnet vicinity in the rotor of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of the electric power steering apparatus 1. Specifically, the electric power steering apparatus 1 is configured as a so-called column assist type electric power steering apparatus that rotationally drives a column shaft. As shown in FIG. 1, the electric power steering apparatus 1 is used as a steering member. Steering wheel 2, a steering mechanism 4 that steers the steered wheels 3 in conjunction with the rotation of the steering wheel 2, and a steering assist mechanism (EPS actuator) that applies assist force to assist the steering operation to the steering system And 5. For example, a rack and pinion mechanism is used as the steering mechanism 4.

  The steering wheel 2 and the steering mechanism 4 are mechanically connected via a steering shaft 6, an intermediate shaft 7, and the like. The rotation of the steering wheel 2 is transmitted to the steering mechanism 4 via the steering shaft 6, the intermediate shaft 7, and the like. Thereby, the steered wheel 3 is steered.

  The steering shaft 6 extends linearly. Steering shaft 6 includes an input shaft 8 connected to steering wheel 2 and an output shaft 9 connected to intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected via a torsion bar 10 so as to be relatively rotatable on the same axis. That is, when a steering torque greater than a certain value is input to the steering wheel 2, the input shaft 8 and the output shaft 9 rotate in the same direction while rotating relative to each other.

  A torque sensor 11 disposed around the steering shaft 6 detects the steering torque input to the steering wheel 2 based on the relative rotational displacement amounts of the input shaft 8 and the output shaft 9. The torque detection result of the torque sensor 11 is input to an ECU (control device) 12 as a control device. The intermediate shaft 7 connects the steering shaft 6 and the steering mechanism 4.

  The steering mechanism 4 includes a pinion shaft 13 and a rack shaft 14. A steered wheel 3 is connected to each end of the rack shaft 14 via a tie rod 15 and a knuckle arm (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13 (the lower end in FIG. 1).

  The rack shaft 14 extends linearly along the left-right direction of the vehicle. A rack 17 that meshes with the pinion 16 is formed in the middle of the rack shaft 14 in the axial direction. By the pinion 16 and the rack 17, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. The steered wheel 3 can be steered by moving the rack shaft 14 in the axial direction.

  The steering assist mechanism 5 includes an electric motor 18 and a speed reducer 19 as a transmission mechanism for transmitting the output torque of the electric motor 18 to the steering mechanism 4. In this embodiment, a worm gear is used as the speed reducer 19. That is, the speed reducer 19 includes a worm shaft 20 as a drive gear and a worm wheel 21 as a driven gear that meshes with the worm shaft 20 and is accommodated in a gear housing 22 as a housing of a transmission mechanism.

  The worm shaft 20 is connected to a rotating shaft 25 (see FIG. 2) of the motor 18 through a power transmission joint (not shown). The worm shaft 20 is rotationally driven by the electric motor 18. The worm wheel 21 is coupled to the steering shaft 6 so as to be able to rotate together. The worm wheel 21 is rotationally driven by the worm shaft 20.

  An electric motor 18 serving as a drive source for the steering assist mechanism 5 is drivingly connected to the output shaft 9 of the steering shaft 6 via a speed reducer 19. The rotation of the electric motor 14 is decelerated by the speed reduction mechanism 15 and transmitted to the output shaft 9 so that the motor torque is applied to the steering system as an assist force.

  When the electric motor 18 rotationally drives the worm shaft 20, the worm wheel 21 is rotationally driven by the worm shaft 20, and the worm wheel 21 and the steering shaft 6 rotate together. The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. Thereby, the steered wheel 3 is steered. That is, by rotating the worm shaft 20 by the electric motor 18, the steered wheels 3 are steered, and the driver's steering operation is assisted.

  The electric motor 18 is rotationally driven and controlled by the ECU 12. The ECU 12 controls the electric motor 18 based on a torque detection result from the torque sensor 11, a vehicle speed detection result from a vehicle speed sensor (not shown), and the like. Specifically, the ECU 12 determines the target assist amount using a map in which the relationship between the steering torque and the target assist amount is stored for each vehicle speed, so that the assist force generated by the electric motor 18 approaches the target assist amount. Control. In this embodiment, an IPM motor having an embedded magnet rotor is used as the electric motor 18.

  Next, FIG. 2 is a cross-sectional view orthogonal to the rotational axis direction of the rotor 23 of the IPM motor (electric motor) 18 according to an embodiment of the present invention, and FIG. 3 is the vicinity of the permanent magnet 27 in the rotor 23 of FIG. FIG. A laminated steel plate is used for the rotor core 24 of the rotor 23 in FIG. 2, and the rotor core 24 is formed by lamination. As shown in FIG. 2, a rotary shaft 25 is fitted in the center of the rotor core 24 of the IPM motor 18. A plurality of (for example, eight in the present embodiment) substantially rectangular magnet insertion holes (insertion holes) 26 are formed in the rotor core 24 in the circumferential direction around the axis of the rotation shaft 25. Further, a rectangular parallelepiped permanent magnet 27 whose outer peripheral surface is coated with a resin member 28 is inserted and embedded in each magnet insertion hole 26.

  As shown in FIG. 3, the permanent magnet 27 is coated with a resin member 28 with a predetermined thickness on the outer peripheral surface facing the inner peripheral surface of the magnet insertion hole 26. For example, a thermosetting resin having excellent heat resistance and insulation and high strength is used as the resin material. Further, a projection 29 for preventing the permanent magnet 27 from coming off is formed on one side of the radially inner circumferential surface of the magnet insertion hole 26. And the permanent magnet 27 in which the coating | coated of the said resin member 28 was formed is press-fitted in the magnet insertion hole 26, and is being fixed. At this time, the press-fit allowance is not more than a thickness (for example, 0.01 to 0.05 mm) at which the coating of the coated resin member 28 is not broken. After the press-fitting, the permanent magnet 27 is magnetized and fixed with a stronger magnetic force.

  Next, the operation and effect of the IPM motor 18 according to the present embodiment configured as described above will be described.

  According to the above configuration, the eight magnet insertion holes 26 are formed in the rotor core 24 of the rotor 23 of the IPM motor 18 in the circumferential direction around the axis of the rotation shaft 25. The permanent magnet 27 has a predetermined thickness on the outer peripheral surface facing the inner peripheral surface of the magnet insertion hole 26 and is coated with a resin member (for example, thermosetting resin) 28. A protrusion 29 for preventing the permanent magnet 27 from coming off is formed on one side of the radially inner circumferential surface of the magnet insertion hole 26. A permanent magnet 27 having an outer peripheral surface covered with a resin member 28 is press-fitted into the magnet insertion hole 26 and fixed.

  Accordingly, the permanent magnet 27 can be fixed with high accuracy by being press-fitted into the magnet insertion hole 26 of the rotor core 24, and the permanent magnet 27 can be prevented from coming off. As a result, the performance degradation of the IPM motor 18 is suppressed, and adverse effects on the steering feeling can be prevented when applied as a power source of the electric power steering apparatus 1. Moreover, since the process can be simplified by press-fitting the permanent magnet 27 without filling the resin, the equipment and manufacturing costs can be reduced.

  As described above, according to this embodiment, it is possible to provide an IPM motor including a magnet-embedded rotor that can securely fix a permanent magnet.

  Although one embodiment according to the present invention has been described above, the present invention can also be implemented in other forms.

  In the above embodiment, the protrusion 29 is provided on one (outer diameter side) of the radially inner peripheral surface of the magnet insertion hole 26. However, the present invention is not limited to this, and the position of the protrusion 29 is on the inner diameter side. Alternatively, the position, shape, and number of the protrusions 29 to which the permanent magnet 27 is stably fixed may be used.

  Moreover, although the cross-sectional shape of the permanent magnet 7 of the said embodiment was a rectangle, an inverted U-shape, a flat trapezoid shape, or another shape may be sufficient.

  Furthermore, in the above-described embodiment, the example in which the IPM motor 18 is applied to the column assist type electric power steering apparatus 1 has been described. However, the present invention is not limited to this, and the pinion assist has a structure that applies an assist force to the pinion shaft 13. The present invention can also be applied to a rack assist type electric power steering apparatus having a structure that applies an assist force to the rack shaft 14. Moreover, you may apply to the apparatus used for the other use using the same IPM motor 18. FIG.

1: electric power steering device (EPS), 2: steering wheel, 3: steered wheel,
4: steering mechanism, 5: steering assist mechanism (EPS actuator), 6: steering shaft, 7: intermediate shaft, 8: input shaft, 9: output shaft, 10: torsion bar, 11: torque sensor,
12: ECU (control device), 13: pinion shaft, 14: rack shaft, 15: tie rod,
16: Pinion, 17: Rack, 18: IPM motor (electric motor), 19: Reducer,
20: Worm shaft, 21: Worm wheel, 22: Gear housing, 23: Rotor,
24: Rotor core, 25: Rotating shaft, 26: Magnet insertion hole (insertion hole), 27: Permanent magnet,
28: Resin member, 29: Projection

Claims (2)

A rotor core provided on the rotating shaft;
A plurality of insertion holes formed in the circumferential direction in the rotor core;
A permanent magnet inserted and embedded in the insertion hole;
A resin member covering an outer peripheral surface of the surface of the permanent magnet facing the inner peripheral surface of the insertion hole,
An electric motor, wherein the permanent magnet covered with the resin member is press-fitted into the insertion hole. The electric motor according to claim 1,
An electric motor, wherein a protrusion for pressing the permanent magnet covered with the resin member is formed on a part of the inner peripheral surface of the insertion hole.

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