JP2007082297A - Motor with magnetic encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shield a motor from magnetic noise generated from its magnet by means of a magnetic shield, and also to facilitate the assembly by keeping the engagement between the magnetic shield having a guide member and the brush cap of the motor having a guide member. <P>SOLUTION: This motor fitted with a magnetic encoder is coaxially equipped with a magnetic encoder. It comprises a motor which is composed of a rotating shaft pivoted within a housing, a rotor rotating by the rotating shaft, a magnet, a commutator, and a brush rest cap 15 having brush mounted on its one side and having a guide member on its other side, a magnetic shield 20 which has a guide member shielding it from the magnetic noise generated from the magnet of the motor, a magnetic drum which is magnetized so that magnetic poles may alternate, and rotates by the rotating shaft, and a board which is provided with a magnetic sensor being arranged in a position opposed to the magnetizing face of the magnetic drum. Furthermore, the guide member of the magnetic shield is engaged and retained in the guide member of the brush rest cap 15 of the motor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a motor with a magnetic encoder, and particularly shields magnetic noise (leakage magnetic flux) generated from a magnet of the motor with a magnetic shield, and also includes a magnetic shield having a guide member and a motor brush having the guide member. The present invention relates to a motor with a magnetic encoder that can be easily assembled by fitting and holding a base cap.

The rotary encoder (rotation position detection device) is a position sensor that detects a rotation angle, and an optical encoder that optically detects the rotation angle and a magnetic encoder that magnetically detects the rotation angle are provided. . The optical encoder has an advantage that high resolution can be obtained relatively easily. However, the high-resolution optical encoder has a problem that an error occurs because a signal is not detected when dust or oil adheres because the slit width carved into the rotating body is narrow.

The magnetic encoder is a method of detecting magnetic flux generated from a magnetic drum on which a predetermined magnetization pattern (S pole and N pole is magnetized) is formed by a magnetic sensor (for example, MR element). Compared to the advantages of being less susceptible to the effects of dust, oil, etc., the magnetic encoder has various advantages due to its small number of parts, simple structure, and excellent high-speed response. It is used for various purposes.

In general, the configuration of a magnetic encoder is provided with a magnetized surface in which a predetermined number of different magnetic poles are alternately magnetized on the surface of a magnetic drum. The magnetic drum is fixed to a rotating shaft, and rotates with the rotation of the rotating shaft. A magnetic sensor is disposed on the substrate in the vicinity of the rotating drum so as to face the magnetized surface. Such magnetic encoders are widely used as applications for detecting the exact position (movement amount) of a straight line and a rotating body in machine tools, industrial robots, and the like.

Recently, the use of the magnetic encoder described above as a motor with a magnetic encoder attached to a motor (for example, a coreless motor or the like) is increasing.
The magnetic encoder here is attached to the end of the motor housing and is coaxially attached to the rotating shafts pivotally supported at both ends of the motor.
The configuration of the coreless motor is general, for example, a rotating shaft supported by bearing metals (bearings) at both ends in the housing, a rotor rotating by the rotating shaft, a magnet, a commutator, And a brush base cap to which a brush is attached.

As a motor with a magnetic encoder, it is disclosed by the following patent document 1, for example. The motor of Patent Document 1 is a motor with a magnetic encoder to which a DC motor is attached.

JP-A-9-308171

In the case of a motor with a magnetic encoder, magnetic noise generated from a magnet provided in the motor invades the magnetic sensor of the magnetic encoder and has an adverse effect.
In order to shield the magnetic noise generated from the magnet, it has been proposed to prevent the magnetic noise from entering by covering with a magnetic shield plate or cover made of a magnetic material.
In Patent Document 1 described above, the magnetic encoder is covered with an encoder cover, and an internal pole magnet (magnetic drum) is attached to the surface of a back yoke made of a magnetic material. The back yoke has an outer peripheral edge located closer to the encoder cover than the Hall element (magnetic sensor). Therefore, since the magnetic noise generated from the motor main body is scattered from the outer peripheral edge of the back yoke toward the encoder cover, the magnetic noise does not enter the Hall element.
However, in such a structure, it is difficult to assemble, resulting in an increase in cost, and it is difficult to dispose the magnetic sensor closer to the outer peripheral edge, and the outer diameter of the magnetic drum cannot be increased. The resolution could not be improved by increasing the number of magnets.

  The present invention shields magnetic noise (leakage magnetic flux) generated from a magnet of a motor with a magnetic shield, and fits and holds a magnetic shield having a guide member and a brush base cap of the motor having the guide member. Accordingly, an object of the present invention is to provide a motor with a magnetic encoder that can be easily assembled.

The configuration of the present invention includes a rotating shaft supported in the housing, a rotor rotating by the rotating shaft, a magnet, a commutator, a brush on one side, and a guide member on the other side. A motor comprising a brush stand cap, a magnetic shield having a guide member for shielding magnetic noise generated from the magnet of the motor, a magnetic drum magnetized so that the magnetic poles are alternately changed, and rotated by a rotating shaft; In a motor with a magnetic encoder coaxially provided with a magnetic encoder comprising a substrate provided with a magnetic sensor arranged at a position facing the magnetized surface of the magnetic drum,
This is achieved by fitting and holding the guide member of the magnetic shield to the guide member of the brush base cap of the motor.

According to the configuration of the present invention, since the guide member of the magnetic shield can be fitted and held (contained) on the inner surface of the guide member provided on the other side of the brush base cap of the motor, the magnetism generated from the magnet of the motor The intrusion of noise is completely shielded and the magnetic sensor is not affected.
Further, since the guide member of the magnetic shield can be fitted and held on the guide member of the brush base cap, the number of assembling steps can be reduced and the manufacturing cost can be reduced. Furthermore, since the guide member of the brush base cap is integrally formed with the brush base cap of the motor, the number of parts is reduced.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a motor with a magnetic encoder of the invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing the whole motor with a magnetic encoder, FIG. 2 is an exploded sectional view showing the whole motor with a magnetic encoder, and FIG. 3 is a front view showing a magnetic shield.

The configuration of the motor 1 with a magnetic encoder will be described. The motor 1 with a magnetic encoder is obtained by connecting a front-stage motor 10 (for example, a coreless motor) and a rear-stage magnetic encoder 30.
In this way, the magnetic encoder 30 is connected to the end of the motor 10, and the rotating shaft 16 of the motor 10 is inserted into the magnetic encoder 30. Each of the coreless motor and the magnetic encoder here has a cylindrical shape (diameter: 16 mm) and a full length (about 40 mm).

First, the configuration of the coreless motor 10 will be described.
Here, the motor is described as the coreless motor 10, but the motor is not limited, and may be a DC motor with a core or the like.

In the coreless motor 10, a housing 11 is configured by a case main body 11 a and a case lid 11 b having a metal holder 12 that extends into the main body, and accommodates a rotor 18. A step portion 11 c is formed on the inner periphery of the edge opening on one side of the housing 11. A small diameter portion 15d of the edge of the brush base cap 15 described later is fitted into the step portion 11c. The rotor 18 is supported by the bearing metal 13 attached to both ends of the metal holder part 12, and the magnet 17 is fitted on the outer periphery of the metal holder part 12.

The rotor 18 includes a rotating shaft 16 and a cylindrical coreless winding 18a, and an end block 18b that connects the rotating shaft 16 and the rotor 18. The end block 18b includes a commutator 19. A rotating shaft 16 having a length reaching the shaft hole 31a of the magnetic drum 31 of the magnetic encoder 30 is rotatably supported on the bearing metal 13 at both ends. The coreless winding 18a is disposed in the gap between the magnet 17 and the inner wall of the case body 11a. A brush base cap 15 having a brush 14 that is in sliding contact with the commutator 19 is attached to an end of the housing 11.

Reference numeral 15 denotes a brush base cap, which has a terminal block on which the brush 14 is inserted and mounted on one side (brush side), and a guide member on the other side (the back side). Note that a small-diameter portion 15d is formed at the edge of one side (brush side).
The guide member of the brush base cap 15 has a U-shaped cross section in which an upper notch 15b with a part of the periphery cut out, and a lower curved part 15a and recesses 15c near the terminal holes 15f at both ends are connected along the periphery. A substantially cylindrical shape (substantially U-shaped cylinder) is formed integrally with the brush base cap 15.
The width of the notch 15b is a width that allows easy fitting with a second curved portion 20b of the magnetic shield 20 described later, and the width of the concave portions 15c at both ends is also easy to fit with the convex portions 20c protruding at both ends of the magnetic shield 20. It consists of.
A bottom surface having a U-shaped cross-section is a bottom portion 15g, and a rotation shaft hole 15e through which the rotation shaft 16 is inserted into the center of the bottom portion 15g of the brush base cap 15, and terminal holes 15f are formed at both ends thereof.
Thus, the magnetic shield 20 having a slightly smaller diameter, which will be described later, can be fitted and held in the space on the inner surface (inner side) of the guide member formed on the other side of the brush base cap 15.

Reference numeral 20 denotes a magnetic shield, which is formed in a cylindrical shape having a U-shaped cross section and is slightly smaller in diameter than the inner surface of the guide member of the brush base cap 15 described above.
As shown in FIG. 3, the magnetic shield 20 is formed of, for example, a magnetic material (metal material or the like) and has a guide member on the other side. The magnetic shield here is formed by MIM (metal powder injection molding) using a pure iron material. Use of pure iron material leads to the effect of preventing magnetic noise from entering. In addition to MIM (metal powder injection molding), sintering molding or molding with a resin mixed with metal powder may be used.
The guide member of the magnetic shield 20 is formed of a lower first curved portion 20a, an upper second curved portion 20b, and convex portions 20c (thickness) protruding in the vicinity of the terminal holes 22e at both ends along the periphery. ing. Accordingly, the first bending portion 20a and the second bending portion 20b can hold the up and down direction and the left and right protruding portions 20c can hold the left and right direction, and the four vertical and horizontal directions also serve as a detent. .
A bottom surface having a U-shaped cross section is a bottom portion 20f. A rotation shaft hole 20d is formed at the center of the bottom portion 20f of the magnetic shield 20, and terminal holes 20e are formed at both ends thereof.

In the configuration of the guide member of the magnetic shield 20 of the present invention, the space portion and the power supply member that are generated by being held outward by the thickness of the second curved portion 20b that is the guide member of the magnetic shield 20 The larger magnetic drum 31 than before can be disposed in the internal space generated by the shape of the left and right convex portions 20c avoiding (terminal / terminal hole). Therefore, by increasing the outer diameter of the magnetic drum 31, the number of magnetization can be increased, and as a result, the resolution can be improved.

When assembled and held, the second curved portion 20b of the magnetic shield 20 is aligned with the upper cutout portion 15b, which is a guide member of the brush base cap 15, and the lower portion is the guide member of the brush base cap 15. The first curved portion 20a of the magnetic shield 20 matches the curved portion 15a of the magnetic shield 20, and the convex portion 20c near the terminal hole 20e of the magnetic shield 20 is formed in the concave portion 15c near the terminal hole 15f, which is a guide member of the brush base cap 15. Each is matched and positioned by fitting and holding (the shaded portion in FIG. 5 is a magnetic shield).
Then, after the magnetic shield 20 is fitted and held on the inner surface of the guide member of the brush base cap 15, it is fixed by bonding (adhesive).
Further, each hole is positioned by fitting and holding the magnetic shield 20 to the brush base cap 15. That is, the positions of the terminal holes 15f at both ends of the bottom portion 15g of the brush base cap 15 and the terminal holes 20e at both ends of the bottom portion 20f of the magnetic shield 20 are matched, and the rotation shaft hole 15e of the bottom portion 15g of the brush base cap 15 The position of the rotary shaft hole 20d in the bottom 20f of the shield 20 also matches.
As described above, the magnetic shield 20 is formed in a cylindrical shape, and the magnetic noise generated from the magnet 17 of the motor 10 can be completely prevented by being fitted and held. Further, the entire magnetic shield 20 is accommodated and held in the inner surface (inner side) of the guide member of the brush base cap 15, whereby the overall length of the motor with a magnetic encoder is shortened and the size is reduced.

Next, the configuration of the magnetic encoder 30 will be described.
Each component described later of the magnetic encoder 30 is incorporated in a magnetic shield 20 (case) formed in a cylindrical shape having a U-shaped cross section. Since the magnetic shield 20 here is formed in a cylindrical shape, it can also serve as a case, and the number of parts is reduced.
The magnetic encoder 30 is supported by the rotary shaft 16 of the motor 10 described above and is magnetized so that the magnetic drum 31 is magnetized so that the magnetic poles are alternately changed along the circumference. A substantially disk-shaped substrate 33 provided with a magnetic sensor 32 (for example, an MR sensor) disposed at a position facing the surface is provided inside and is attached by an end cap 34. A plurality of lead wires 35 for outputting detection signals to the outside are attached to the substrate 33.

The motor with a magnetic encoder of the present invention is assembled by the following procedure.
The small diameter portion 15d on the other side of the brush base cap 15 is fitted into the step portion 11c of the edge opening portion on one side of the housing 11 of the motor 10 in which each component is incorporated. Next, the magnetic shield 20 is fitted and held on the guide member formed on the other side of the brush base cap 15 for positioning and attached with an adhesive.
In fitting and holding, the second curved portion 20b of the magnetic shield 20 is matched with the upper cutout portion 15b of the brush base cap 15, the first curved portion 20a of the magnetic shield 20 is matched with the lower curved portion 15a, and The convex portion 20c near the terminal hole 20e of the magnetic shield 20 is matched with the concave portion 15c near the terminal hole 15f of the brush base cap 15.
Next, the magnetic drum 31 is inserted into the rotating shaft 16 of the motor 10, the substantially disk-shaped substrate 33 provided with the magnetic sensor 32 is mounted, and finally the end cap 34 is attached to the magnetic shield 20 to complete.

The configuration of the guide member included in the brush base cap 15 and the configuration of the guide member included in the magnetic shield 20 are not limited to the above, and can be easily fitted and held (for example, fitted by a protrusion or the like provided on the bottom). (Holding) configuration, or any configuration in either the vertical direction or the horizontal direction.

It is sectional drawing which shows the whole motor with a magnetic encoder of this invention. It is an exploded sectional view showing the whole motor with a magnetic encoder of the present invention. It is a front view which shows a magnetic shield. It is a front view which shows a brush stand cap. It is a front view which shows the state by which the magnetic shield was fittingly hold | maintained at the brush stand cap.

Explanation of symbols

1 Motor with magnetic encoder 10 Motor (coreless motor)
11 Housing 15 Brush Stand Cap 15a Curved Part (Guide Member)
15b Notch (guide member)
15c recess (guide member)
17 Magnet 18 Rotor 19 Commutator 20 Magnetic shield 20a First curved portion (guide member)
20b 2nd bending part (guide member)
20c Convex part (guide member)
30 Magnetic encoder 31 Magnetic drum 32 Magnetic sensor 33 Substrate

Claims (3)

A rotating shaft supported in the housing, a rotor rotated by the rotating shaft, a magnet, a commutator, and a brush base cap having a brush mounted on one side and a guide member on the other side. A motor, a magnetic shield having a guide member for shielding magnetic noise generated from the magnet of the motor, a magnetic drum magnetized so that magnetic poles are alternately changed, and rotated by a rotating shaft; In a motor with a magnetic encoder coaxially provided with a magnetic encoder comprising a substrate provided with a magnetic sensor arranged at a position facing the surface,
A motor with a magnetic encoder, wherein the guide member of the magnetic shield is fitted and held on the guide member of the brush base cap of the motor. The motor with a magnetic encoder according to claim 1, wherein the guide member of the brush base cap is integrally formed on the other side of the brush base cap. The motor with a magnetic encoder according to claim 1 or 2, wherein the magnetic shield is integrally formed by metal powder injection molding.

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