JP4077066B2 - Electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor suitable for various controls, and more particularly to a small electric motor having excellent noise resistance.
[0002]
[Prior art]
A brushless electric motor in which an armature winding is provided on the stator side and the rotor is composed of a high-performance permanent magnet is known. In this electric motor, the position of the rotor is detected by a non-contact type position detector, a current is supplied to the stator winding corresponding to the position, and the current value is controlled to control the rotation. ing.
A small electric brake in which a non-contact electric motor of the above type is incorporated in a disc brake for an automobile is also known (see, for example, PCT application international publication number WO / 03301).
[0003]
[Problems to be solved by the invention]
By the way, the electric motor requires a position sensor for detecting the position of the rotor and a magnetic pole sensor for detecting the magnetic pole. These sensors are usually provided on the side of the stator or rotor constituting the electric motor. On the other hand, for example, because it is arranged at the bearing portion of the shaft on the rotor side, the sensor portion has a shape that protrudes to the side of the motor body, which has been an obstacle to downsizing the electric motor. In addition, since the sensor is arranged on the side of the motor body or the like, it is easily affected by external magnetic noise. For this reason, it is necessary to provide a shield means around the sensor as a noise countermeasure, and the structure becomes complicated. There are problems such as.
[0004]
Therefore, the present invention provides noise resistance without providing special shielding means by providing a position sensor for detecting the position of the rotor and a magnetic pole sensor for detecting the magnetic pole inside the rotor constituting the electric motor. An object of the present invention is to provide an electric motor that can reduce the overall size of the motor and solve the above problems.
In the present invention, since the sensor is provided inside the rotor, the electric motor can be reduced in size compared to the case where the sensor is provided on the side of the stator or the rotor, as in the conventional electric motor. Furthermore, since the sensor is provided inside the rotor, the periphery of the sensor is surrounded by a magnetic material, and durability against external magnetic noise can be increased.
[0005]
Therefore, the technical solution adopted by the present invention is:
A bottomed circumferential groove 4 having a predetermined width is formed concentrically with the axis of the rotor 3 in the rotor constituting the electric motor, and a cylindrical shape separated from the rotor 3 in the groove 4. Are arranged concentrically with the axis, and a first ring magnet 10 for magnetic pole detection and a second ring magnet 11 for position detection are arranged in either one of the circumferential groove and the support. The first and second Hall elements 12 and 13 are arranged on the other side corresponding to each of the ring magnets to constitute the magnetic pole sensor 9 and the position sensor 8, and the position sensor 8 is further connected to the magnetic pole sensor 9. Is an electric motor characterized in that it is arranged on the back side of the circumferential groove.
[0006]
Embodiment
1 is a schematic cross-sectional view of a three-phase 8-pole brushless electric motor according to the first embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a cross-sectional view taken along the line BB in FIG.
[0007]
In the figure, reference numeral 1 denotes a motor casing 1 in which a rotating shaft 2 is rotatably supported. The rotating shaft 2 in the casing 1 is formed with a large-diameter portion 3a that forms the rotor 3 of the electric motor. The large-diameter portion 3a is concentric with the shaft 2 and has a predetermined width. A bottom-shaped circumferential groove 4 is formed. A cylindrical portion on the free end side of a cylindrical support body 5 having a bottom fixed to the casing 1 is disposed in the circumferential groove 4, and an inner peripheral surface 6 of the cylindrical support body 5 and the inner peripheral surface 6 thereof are arranged. A position sensor 8 and a magnetic pole sensor 9 to be described later are arranged on the inner peripheral surface 7 of the circumferential groove 4 facing the peripheral surface 6.
[0008]
A first ring magnet 10 and a position sensor 8 constituting a magnetic pole sensor 9 are formed on the inner peripheral surface 7 of the circumferential groove 4 facing the inner peripheral surface 6 of the cylindrical support 5 from the opening side toward the back. The second ring magnets 11 are sequentially arranged as shown in the figure. On the other hand, on the inner peripheral surface 6 of the cylindrical support 5, a first Hall element 12 is provided at a position corresponding to the first ring magnet 10, and A second Hall element 13 is disposed at a position corresponding to the two-ring magnet 11.
[0009]
Since the electric motor of this example is a three-phase 8-pole electric motor composed of a U-phase, a V-phase, and a W-phase, the first ring magnet 10 has four N and S poles alternately as shown in FIG. The first hall element 12 corresponding to the first ring magnet 10 is arranged with three hall elements 12a, 12b, and 12c for U phase, V phase, and W phase as shown in the figure. .
As shown in FIG. 3, the second ring magnet 11 is provided with a large number of N and S alternately arranged in order to perform a position detecting function, and a second Hall element corresponding to the second ring magnet 11 is provided. As shown in FIG. 13, two Hall elements 13a and 13b are arranged for the A phase and the B phase. In addition, if the number of magnetic poles of the second ring magnet 11 is large, the accuracy of position detection can be increased accordingly.
[0010]
The first ring magnet 10 and the first hall element 12 constitute a magnetic pole sensor 9, and the second ring magnet 11 and the second hall element 13 constitute a position sensor 8. These sensors are connected to an external control circuit by lead wires (not shown).
On the outer periphery of the large-diameter portion 3a of the rotary shaft 2, as shown in FIG. 2, a permanent magnet 14 for generating torque of the electric motor is alternately S and N poles so that the first ring magnet 10 of the magnetic pole sensor 9 and the magnetic pole correspond to each other. The U-phase, V-phase, and W-phase each forming a stator yoke (stator) 16 around which a coil 15 is wound around the casing 1 corresponding to the permanent magnet 14. Four phases are arranged in order, and a three-phase eight-pole electric motor is constituted by these.
[0011]
The operation of the electric motor configured as described above will be described.
The electric motor rotates according to a conventionally known principle. At this time, the magnetic pole sensor 9 responds to magnetism only in the normal direction, but the U phase, V phase, and W phase correspond to the corresponding Hall elements 12a, 12b, It is controlled at 12c. For example, the U-phase hall element is controlled to be turned on when the N pole is detected, and turned off when the S pole is detected. The other hall elements are similarly turned on and off for the corresponding phase. The rotational force of the motor is generated by the control.
[0012]
The position sensor 8 detects the rotation position and rotation direction of the electric motor.
Specifically, as shown in FIG. 3, the output signal from the Hall element for the A phase and the output signal from the Hall element for the B phase are 90 ° depending on the arrangement of the Hall elements, as shown in FIG. The rotation direction is detected by the direction of the phase shift, and the rotational position can be detected by detecting the number of N poles or S poles.
[0013]
The method of controlling the motor and detecting the position and the rotation direction by the Hall element as described above is the same as that conventionally performed.
As described above, in the present electric motor, since the magnetic pole sensor 9 and the position sensor 8 are arranged inside the rotor 3, the entire motor can be reduced in size. Further, in the above example, since the position sensor that requires high accuracy is disposed deeper in the circumferential groove of the rotor than the magnetic pole sensor that requires less accuracy, noise resistance can be improved.
[0014]
Next, a second embodiment of the present invention will be described with reference to FIG. In addition, the code | symbol in a figure respond | corresponds to the member of 1st Embodiment.
In this embodiment, the first ring magnetic pole 10 and the second ring magnetic pole 11 are disposed on the outer circumferential inner surface 18 of the circumferential groove 4 of the rotor-side large-diameter portion 3a, and the Hall elements 12 and 13 are disposed on the cylindrical support 5. The second embodiment is different from the first embodiment in that it is attached to the outer peripheral surface 17, and the other configurations and functions are the same as those of the first embodiment, so that the description thereof is omitted.
[0015]
Although the above embodiment has described an example in which a position sensor and a magnetic pole sensor are provided in the rotor of a three-phase eight-pole electric motor, it goes without saying that the same configuration can be applied to other types of electric motors. Of course, the positions of the magnetic pole sensor and the position sensor arranged in the rotor can be changed as necessary.
[0016]
【The invention's effect】
As described above in detail, according to the present invention, since the magnetic pole sensor and the position sensor are arranged inside the rotor of the electric motor, the electric motor can be downsized as compared with the conventional electric motor, and the sensor is further provided inside the motor. Therefore, the sensor is surrounded by a magnetic material, and it is possible to obtain excellent effects such as an increase in durability against external magnetic noise without providing a shielding means. In addition, by placing a position sensor that requires high accuracy in the rotor (at the back of the groove) than a magnetic pole sensor that requires low accuracy, noise resistance can be improved and an efficient sensor unit can be configured. And the like.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a three-phase 8-pole electric motor according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
3 is a cross-sectional view taken along the line BB in FIG.
FIG. 4 is a schematic cross-sectional view of an electric motor according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Casing 2 Rotating shaft 3 Rotor 3a Large diameter part 4 Circumferential groove 5 Cylindrical support body 6 Inner peripheral surface 7 of a cylindrical support body Inner peripheral surface 8 of a circumferential groove Position sensor 9 Magnetic pole sensor 10 First magnetic pole ring 11 2nd magnetic pole ring 12 1st Hall element 13 2nd Hall element 14 Permanent magnet 15 Coil 16 Stator yoke 17 The outer peripheral surface 17 of the cylindrical support body 5
18 Outer diameter inner circumferential surface of circumferential groove

Claims (1)

A bottomed circumferential groove 4 having a predetermined width is formed concentrically with the axis of the rotor 3 in the rotor constituting the electric motor, and a cylindrical shape separated from the rotor 3 in the groove 4. Are arranged concentrically with the shaft center, and a first ring magnet 10 for magnetic pole detection and a second ring magnet 11 for position detection are arranged in either one of the circumferential groove and the support. The first and second Hall elements 12 and 13 are arranged on the other side corresponding to each of the ring magnets to constitute the magnetic pole sensor 9 and the position sensor 8, and the position sensor 8 is further connected to the magnetic pole sensor 9. The electric motor is also arranged on the back side of the circumferential groove.

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