JP2020162399A - Brushless motor - Google Patents

Abstract

To provide a brushless motor capable of being made thinner while being equipped with a magnetic rotary encoder.SOLUTION: The brushless motor has: a rotary shaft; a rotor including a rotor yoke located around the rotary shaft and a magnet holder for fixing a sensor magnet for generating a magnetic flux; a stator including a plurality of radial salient poles and a coil wound around the salient poles; and an encoder including a magnetic sensor for detecting a magnetic flux of the sensor magnet to acquire a rotation angle of the rotor. The magnet holder is fixed to the rotor yoke.SELECTED DRAWING: Figure 2

Description

The present invention relates to a brushless motor including a magnetic rotary encoder.

Conventionally, a brushless motor that accurately detects the rotation angle of a rotor using a rotary encoder has been known in order to perform highly accurate speed control and position control. Patent Document 1 discloses a motor using a detection magnet held by a magnet holder fixed to a rotating shaft of a rotor and a magnetic encoder including a magnetic sensor arranged coaxially with the detection magnet. ing.

Japanese Unexamined Patent Publication No. 2017-123731

In recent years, in order to perform speed control and position control in a state where the thickness is strictly regulated, a thin brushless motor having a function of detecting a necessary output and a rotation angle of a rotor is required. In the motor of Patent Document 1, by attaching a screwed protrusion provided on the magnet holder to a screw hole provided on the end face of the rotating shaft, the fixed portion between the magnet holder and the rotating shaft can be miniaturized and thickened in the axial direction. The thickness is thinned. However, in the configuration disclosed in Patent Document 1, since the thickness of the magnet holder in the axial direction is required, it is difficult to further reduce the thickness of the motor.

The present invention provides a brushless motor that can be made thinner while being provided with a magnetic rotary encoder.

The brushless motor as one aspect of the present invention includes a rotor having a rotating shaft, a rotor yoke arranged around the rotating shaft, and a magnet holder for fixing a sensor magnet that generates magnetic flux, and a plurality of radial protrusions. It has a stator with a pole and coils wound around a plurality of salient poles, and an encoder with a magnetic sensor that detects the magnetic flux of the sensor magnet and acquires the rotation angle of the rotor, and the magnet holder is fixed to the rotor yoke. It is characterized by being done.

According to the present invention, it is possible to provide a brushless motor that can be made thinner while being provided with a magnetic rotary encoder.

It is a perspective view of the motor which concerns on embodiment of this invention. It is sectional drawing of the motor which concerns on embodiment of this invention. It is sectional drawing of the rotor when the magnet holder and the rotor yoke are integrally formed. It is a figure which shows the main path of the magnetic field generated by the sensor magnet when magnetized in the direction parallel to the rotation axis. It is a figure which shows the main path of the magnetic field generated by the sensor magnet when magnetized in the direction perpendicular to the rotation axis.

Hereinafter, examples to which the present invention can be applied will be described in detail with reference to the drawings. In each figure, the same member is given the same reference number, and duplicate description is omitted.

FIG. 1 is a perspective view of the motor 50 according to the embodiment of the present invention. FIG. 2 is a cross-sectional view of the motor 50. The motor 50 is an inner rotor type brushless motor in which the rotor 70 is arranged on the inner peripheral side of the stator 60. A pinion 9 is attached to one end of the rotating shaft 11 of the rotor 70. In the following description, the pinion side is the output shaft side, and the side opposite to the pinion side is the non-output side.

First, the peripheral configurations of the stator 60 and the housing 1 will be described. The stator 60 is composed of a core 2, a coil 3, and an insulator 4, and is fixed to the housing 1. The core 2 is formed by laminating a plurality of soft magnetic steel plates, and includes a plurality of salient poles (not shown) extending in the radial direction. Each of the plurality of salient poles is insulated by the insulator 4. The coil 3 is wound around each of the plurality of salient poles from above the insulator 4.

The substrate 5 is fixed by being sandwiched between the housing 1 and the insulator 4. Each end of the winding start and winding end of the coil 3 is connected to the pattern of the substrate 5.

The housing 6 is fixed to the central portion of the housing 1. The housing 6 is provided with an upper bearing 7 and a lower bearing 8 for rotatably supporting the rotor 70. In this embodiment, deep groove ball bearings are used as the upper bearing 7 and the lower bearing 8.

Hereinafter, the configuration of the rotor 70 will be described. The rotor 70 is composed of a magnet holder 10, a rotating shaft 11, a sensor magnet 13, a rotor magnet 14, and a rotor yoke 15.

The magnet holder 10 is integrally formed in a cutting shape. The magnet holder 10 includes a fitting portion 10a fixed to the rotating shaft 11 on the inner peripheral surface, and rotates integrally with the rotating shaft 11. The outer peripheral surface of the fitting portion 10a and the rotating shaft 11 are radially fitted to the inner peripheral surfaces of the upper bearing 7 and the lower bearing 8, respectively. As a result, the rotor 70 is rotatably supported. With such a configuration, the joint portion between the magnet holder 10 and the rotating shaft 11 can be overlapped with the support portion of the upper bearing 7 in the axial direction, so that the thickness of the motor 50 in the axial direction can be reduced.

Further, the magnet holder 10 includes a recess 10b provided coaxially with the rotating shaft 11 on the counter-output shaft side. A sensor magnet 13 that generates magnetic flux is fixed in the recess 10b. The sensor magnet 13 rotates integrally with the magnet holder 10. By fitting and fixing the sensor magnet 13 in the recess 10b, the sensor magnet 13 can be easily attached at a position coaxial with the rotating shaft 11 at the time of assembly.

The rotor magnet 14 and the rotor yoke 15 are arranged on the outer peripheral side of the rotor 70. The rotor yoke 15 is arranged around the rotating shaft 11, and the rotor magnet 14 is arranged around the rotor yoke 15. The magnet holder 10 is fixed to the rotor yoke 15. As a result, the magnet holder 10 can be arranged closer to the output shaft side, so that the motor 50 can be made thinner in the axial direction.

Further, the magnet holder 10 may be formed integrally with the rotor yoke 15. FIG. 3 is a cross-sectional view of the rotor 70 when the magnet holder and the rotor yoke are integrally formed. The magnet holder 10 is integrally formed by press working, and also serves as a rotor yoke 15. Therefore, the magnet holder 10 needs to form a magnetic circuit with the rotor magnet 14, and needs to be a magnetic material. The recess 10b is bottomed, and the rotating shaft 11 is fixed to the surface on the output shaft side without penetrating the magnet holder 10. Therefore, the rotating shaft 11 can be fixed to the magnet holder 10 by a method such as welding, and the bonding strength can be secured without using a large amount of space in the axial direction. With such a configuration, the sensor magnet 13 can be held and the rotor magnet 14 and the rotating shaft 11 can be connected with one component, and the number of components can be reduced. In addition, in this embodiment, "the bottom" means "the bottom which does not have an opening".

Hereinafter, the configuration of the encoder 80 will be described. The encoder 80 is composed of a substrate 5a, a magnetic sensor 12, a sensor magnet 13, and a holding member 16. The substrate 5a is a flexible substrate, and as shown in FIG. 1, passes through a notched portion on the outer diameter side of the holding member 16 and the stator 60, and is integrated with the substrate 5. It is desirable that the surface of the substrate 5a on the anti-output shaft side is protected by a reinforcing plate or the like. The magnetic sensor 12 is mounted on the substrate 5a and is held by the holding member 16 so as to be arranged at a position facing the sensor magnet 13 with a predetermined gap on the rotation center axis of the rotor 70. The holding member 16 is fixed to the stator 60 and also functions as a rear lid of the motor 50.

Hereinafter, a method of detecting the rotation angle of the rotor 70 by the encoder 80 will be described. The magnetic sensor 12 is an absolute encoder IC that acquires an absolute rotation angle by detecting a magnetic flux in a direction perpendicular to the rotation axis 11 generated by the sensor magnet 13 that passes through a detection unit near the center. The sensor magnet 13 is magnetized in a direction parallel to the rotation shaft 11. In the present embodiment, the north pole and the south pole are formed on the surface of the sensor magnet 13 on the opposite output shaft side.

FIG. 4A shows the main path of the magnetic field created by the sensor magnet 13 when the magnet holder 10 is a non-magnetic material. When the magnet holder 10 is a non-magnetic material, the magnetic flux generated from the N pole passes through the magnetic sensor 12 in the direction perpendicular to the rotation axis 11 and enters the S pole. The magnetic sensor 12 can acquire the absolute rotation degree angle of the rotor 70 from the passing magnetic flux. Here, in order to accurately acquire the absolute rotation angle, it is necessary to secure a magnetic force passing through the magnetic sensor 12 with a predetermined strength or more.

FIG. 4B shows the main path of the magnetic field created by the sensor magnet 13 when the magnet holder 10 is a magnetic material. When the magnet holder 10 is a magnetic material, the magnet holder 10 serves as a back yoke, and a magnetic circuit is formed by the sensor magnet 13 and the magnet holder 10. Therefore, the magnetic force generated by the sensor magnet 13 on the magnetic sensor side can be strengthened. Therefore, when the magnetic force passing through the magnetic sensor 12 is constant in FIGS. 4A and 4B, the thickness of the sensor magnet 13 can be further reduced by using the magnet holder 10 as a magnetic material. Therefore, it is effective in reducing the thickness of the motor 50 in the axial direction.

Further, the sensor magnet 13 may be magnetized in a direction perpendicular to the rotation axis 11. In this case, one surface of the side surface of the sensor magnet 13 is the north pole, and the other surface is the south pole. FIG. 5 is a diagram showing a main path of a magnetic field created by the sensor magnet 13 when magnetized in a direction perpendicular to the rotation axis 11.

FIG. 5A shows the main path of the magnetic field created by the sensor magnet 13 when the magnet holder 10 is a non-magnetic material. When the magnet holder 10 is a non-magnetic material, the magnetic flux in the direction perpendicular to the rotation axis 11 from the N pole passes through the magnetic sensor 12 side and wraps around the S pole. The magnetic sensor 12 can acquire the absolute rotation degree angle of the rotor 70 from the passing magnetic flux.

FIG. 5B shows the main path of the magnetic field created by the sensor magnet 13 when the magnet holder 10 is a non-magnetic material. When the magnet holder 10 is a magnetic material, the magnet holder 10 serves as a back yoke, and a magnetic circuit is formed by the sensor magnet 13 and the magnet holder 10. Therefore, more magnetic flux wraps around the magnet holder side, and the magnetic flux passing through the magnetic sensor 12 decreases. Therefore, the magnetic force passing through the magnetic sensor 12 cannot be strengthened by the material of the magnet holder 10, and the motor 50 is not suitable for thinning.

As described above, according to the configuration of the present embodiment, the thickness of the magnetic rotary encoder structure required for detecting the rotation angle of the rotor 70 in the axial direction can be suppressed, so that the thin motor 50 is provided. be able to.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

3 Coil 10 Magnet holder 11 Rotating shaft 12 Magnetic sensor 13 Sensor magnet 15 Rotor yoke 50 Motor (brushless motor)
60 stator 70 rotor 80 encoder

Claims (8)

The axis of rotation and
A rotor having a rotor yoke arranged around the rotating shaft and a magnet holder for fixing a sensor magnet that generates magnetic flux, and a rotor.
A stator having a plurality of radial salient poles and a coil wound around the plurality of salient poles,
It has an encoder including a magnetic sensor that detects the magnetic flux of the sensor magnet and acquires the rotation angle of the rotor.
The magnet holder is a brushless motor characterized in that it is fixed to the rotor yoke. The brushless motor according to claim 1, wherein the magnet holder is provided coaxially with the rotation shaft and includes a recess for fixing the sensor magnet. The brushless motor according to claim 1 or 2, wherein the magnet holder is integrally formed in a cutting shape. The brushless motor according to claim 1 or 2, wherein the magnet holder is a magnetic material and is integrally formed with the rotor yoke. The brushless motor according to claim 4, wherein the magnet holder is integrally formed by press working. The magnet holder is provided coaxially with the rotation shaft and includes a recess for fixing the sensor magnet.
The brushless motor according to claim 4 or 5, wherein the recess is bottomed. The brushless motor according to any one of claims 1 to 6, wherein the magnet holder is radially fitted to an inner peripheral surface of a bearing that supports the rotor. The sensor magnet is magnetized in a direction parallel to the rotation axis.
The brushless motor according to any one of claims 1 to 7, wherein the magnetic sensor detects a magnetic flux in a direction perpendicular to the rotation axis to acquire an absolute rotation angle of the rotor.