JP2006217672A - Small motor with encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small motor with an encoder in which detection of a magnetic pole of a driving magnet of a small motor such as an AC servo motor with high assembly accuracy and detection of a rotational position of a rotary shaft are integrated.
A motor main body having a driving magnet, a driving coil facing the driving magnet, a magnetic signal at a magnetic pole position corresponding to each magnetic pole of the driving magnet of the motor main body, and rotation of the motor main body A motor comprising a signal magnet in which a magnetic signal at a rotational position of a shaft is formed on the same surface, and an encoder formed on a surface orthogonal to the rotational shaft.
[Selection] Figure 1

Description

  The present invention relates to a small motor such as an AC servomotor, and more particularly to an encoder for a rotation axis position of a rotation axis.

  In a small motor such as an AC servo motor, a magnetic rotary encoder is used to detect a rotation angle of a rotating shaft and a magnetic pole position of a rotor. FIG. 5 is a side sectional view showing an example of a conventional magnetic rotary encoder described in Patent Document 1. As shown in FIG. In the figure, reference numeral 1 denotes a disk-shaped signal recording medium, which is attached to a rotating shaft 11 of a motor body 10.

A disk-shaped signal recording magnet 3 is placed on the signal recording medium 1 via a blocking plate 4 and attached to the upper end of the rotating shaft 11. The signal magnet 3 is magnetized corresponding to the magnetic pole position of a rotor (not shown) of the motor body 10. Reference numeral 5 denotes a circuit board 5 made of a non-magnetic material such as glass epoxy, and magnetic sensors 6a to 6c made up of magnetoresistive elements or Hall elements are disposed on the facing surface 5S against the signal magnet 3. In addition, a detection circuit (not shown) is provided.
On the outer peripheral surface of the signal recording medium 1, N poles and S poles are alternately magnetized at regular intervals over the entire circumference. A magnetic sensor (in the drawing, a magnetoresistive element) 2 is disposed opposite to the outer peripheral surface of the signal recording medium 1 with a certain distance. The magnetic sensor 2 receives a change in the magnetic field due to the magnetic poles magnetized on the outer peripheral surface at constant intervals by the rotation of the signal recording medium 1 (that is, the rotation of the rotating shaft 11), and outputs a rotation detection signal.

  When the motor body 10 is driven and the signal recording medium 1 rotates with the rotation of the rotating shaft 11, the magnetic sensor 2 detects the rotation by the change in the magnetic field of the magnetic poles magnetized on the outer peripheral surface of the signal recording medium 1 at a constant interval. Output a signal. The rotation detection signal is taken into a detection circuit (not shown), and the rotation position of the rotation shaft 11 is detected.

When the signal magnet 3 rotates with the rotation of the rotating shaft 11, the position of the magnetic pole changes relative to the magnetic sensors 6 a to 6 c on the circuit board 5. Thereby, each magnetic sensor 6a-6c outputs the detection signal of 3 phases, U phase, V phase, and W phase. These three-phase detection signals are taken into the detection circuit in the circuit board 5 and the magnetic pole position of the rotor (not shown) of the motor body 10 is detected.
Patent Document 2 proposes a method of attaching an encoder in a predetermined positional relationship to a servo motor attached to the airframe.

JP 06-88705 JP 2001-293276 A

  However, the conventional configuration has the following problems. The signal magnet for detecting the magnetic pole and the signal recording medium for detecting the rotational position of the rotating shaft are separate, and it is difficult to reduce the size of the motor. In addition, the cost of the encoder is increased, which increases the cost. Since the positioning of the magnetic pole position of the drive magnet and the signal magnet of the encoder unit and the positioning of the rotating shaft and the rotating position recording medium of the rotating shaft are performed in separate processes, the positioning work is complicated. In addition, to attach the encoder to the servo motor attached to the machine frame in a predetermined positional relationship, after fixing the rotating shaft to the external drive body, the motor or the motor was attached with the rotation position of the encoder aligned The work requires skill to attach to the machine frame.

The present invention has been made under the above-mentioned background, and is small with an encoder in which detection of the magnetic pole of a drive magnet and detection of the rotational position of a rotary shaft of a small motor such as an AC servo motor that is small and has high assembly accuracy are integrated. The purpose is to provide a motor.

  The first embodiment of the present invention for solving the above-described problem corresponds to a driving magnet, a motor body having a driving coil opposed to the driving magnet, and each magnetic pole of the driving magnet of the motor body. The magnetic signal of the magnetic pole position and the magnetic signal of the rotational position of the rotation shaft of the motor body have a signal magnet formed on the same plane, and the magnetic signal of the signal magnet is orthogonal to the rotation shaft. It is a motor comprising an encoder formed on a surface.

  With this configuration, the magnetic signal at the magnetic pole position corresponding to each magnetic pole of the driving magnet and the magnetic signal at the rotational position of the rotating shaft are formed on the same surface of one signal magnet. Thus, unlike the prior art, it is not necessary to separately provide the magnetic signal magnet at the magnetic pole position and the magnetic signal magnet at the rotational position of the rotating shaft. As a result, the encoder can be reduced in size, and the magnetic pole detection of the drive magnet and the rotational position detection of the rotary shaft can be performed at a time.

  Since the magnetic signal of the signal magnet is formed on a surface perpendicular to the rotation shaft, a magnetic sensor for detecting the magnetic pole position on one sensor substrate facing the signal magnet, and for detecting the rotational position. A magnetic sensor can be formed. Since it is not necessary to provide a sensor substrate for each magnetic sensor, the size can be reduced.

  As a second aspect of the present invention, in the motor of the first aspect, the rotation shaft of the motor main body provided with the reference position mark, and the magnetic signal of the rotation position of the rotation shaft have an N pole and an S pole. A line segment connecting the center of the rotation axis and the center of the reference position mark on a surface perpendicular to the rotation axis, and the rotation axis and the signal magnet. It is preferable that the angle formed by the line segment connecting the switching points from the north pole to the south pole of the magnetic signal at the rotation position is constant.

With this configuration, the magnetic signal of the rotational position at the center of the reference position mark of the rotational axis on the surface orthogonal to the rotational axis is the same between different motors. Thus, when the motor is connected to an external drive system, the reference position mark of the rotating shaft is attached as a reference, so that the magnetic signal at the rotating position can be in the same phase even in different motors.

  In the present invention, a driving magnet, a motor body having a driving coil facing the driving magnet, a magnetic signal at a magnetic pole position corresponding to each magnetic pole of the driving magnet of the motor body, and rotation of the motor body Because the magnetic signal of the rotational position of the shaft has a signal magnet formed in the same plane, and the magnetic signal of the signal magnet is a motor comprising an encoder formed on the surface orthogonal to the rotational shaft. Since the magnetic signal magnet at the magnetic pole position and the magnetic signal magnet at the rotational position of the rotating shaft do not need to be provided separately as in the prior art, the encoder can be reduced in size.

  Since both of the above signals are formed in one signal magnet, the positional relationship between the two signals does not go wrong during assembly work. Further, it is not necessary to perform a work for matching the magnetic signal at the magnetic pole position and the magnetic signal at the rotational position of the rotary shaft to a predetermined position.

Since the driving magnet and the signal magnet are configured separately, the configuration is not easily affected by electromagnetic noise from the driving coil or noise of a braking electromagnetic coil used in a servo motor with a brake. Therefore, a highly reliable motor can be configured.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  1A and 1B show a motor according to a first embodiment of the present invention. FIG. 1A is a cross-sectional view of a main part of the motor, and FIG. 1B is a schematic view of an arrangement of sensors attached to a sensor board. Is shown. FIG. 2 is a schematic diagram of the magnetization pattern of the magnetic signal for the magnetic pole position of the signal magnet and the magnetic signal for the rotational position. FIG. 3 shows an output signal from the magnetic pole detection magnetic sensor and a rotation position detection signal obtained by waveform shaping from the output signal of the rotation position detection magnetic sensor when the rotation shaft relative to the mechanical angle of the rotation shaft rotates.

  As shown in FIG. 1, the motor 30 includes a motor body 10 and an encoder unit 20. The motor main body 10 has a cover case 14 in which a drive magnet 12 fixed to the rotary shaft 11 and a drive coil 13 concentrically surrounding the outer periphery of the drive magnet 12 are accommodated. Yes. The distal end portion of the rotating shaft 11 protrudes on the encoder unit 20 side and on the opposite side of the encoder unit 20.

  The encoder unit 20 is covered with a cup-shaped cover 8 made of a magnetic material in order to prevent magnetic noise from entering from the outside. An end of the rotary shaft 11 protrudes inside the cover 8, and an aluminum disk-shaped holder 9 is fixed to the outer periphery thereof. A back yoke 15 made of a magnetic material is fixed to the rotary shaft 11 or the holder 9 on the protruding end side of the rotary shaft 11 of the holder 9. A signal magnet 3 is attached to the surface of the back yoke 15. The sensor substrate 5 is fixed with screws in parallel to the back yoke 15 at a position away from the signal magnet 3 on the rotation axis. A magnetic pole position detecting magnetic sensor 6 (comprising 6 a, 6 b, 6 c) and a rotational position detecting magnetic sensor 7 are fixed to the sensor substrate 5 at positions facing the signal magnet 3. As the magnetic sensor, a Hall element or an MR element is used. In this embodiment, since the AC servomotor is based on three-phase AC, the number of magnetic sensors for detecting the magnetic pole position is three, but the number can be selected according to the number of phases of the drive current.

  As shown in FIG. 2, the signal magnet 3 has a ring shape, and a hole 33 is formed at the center. The rotating position magnetized portion 31 and the magnetic pole position magnetized portion 32 are formed on the same surface perpendicular to the rotating shaft 11. Since the magnetized part is provided on the same surface, the magnetic signal at the magnetic pole position and the magnetic signal at the rotational position can be magnetized simultaneously, and there is no deviation in the magnetization position of both signals compared to the method of magnetizing both signals separately. There is a feature that a magnetized pattern can be formed. As the signal magnet 3, a ferrite magnet or a rare earth magnet can be used.

  The magnetic pole position magnetized portion 32 has the same number of magnetic poles as the number of magnetic poles of the driving magnet 12 of the motor unit 10. Magnetic pole position detection magnetic sensors 6a to 6c are fixed at positions facing the magnetic pole position magnetized portion 32 on the sensor substrate 5. The rotating position magnetized portion 31 is magnetized by 180 ° in N and S poles. A rotational position detecting magnetic sensor 7 is fixed at a position facing the rotation detecting magnetized portion 31 on the sensor substrate 5.

(Operation)
The operation of the motor of Example 1 will be described. When U-phase, V-phase, and W-phase signals Su, Sv, and Sw shown in FIG. 3 are output, U-phase, V-phase, and W-phase drive coils are output from a motor drive circuit (not shown) based on these signals. Are sequentially energized to rotate the rotating shaft 11.
Due to the rotation of the rotating shaft 11, the magnetic sensors 6a to 6c for detecting the magnetic pole receive a change in the magnetic field of the magnetic pole position magnetizing portion 32 of the signal magnet 3, and this three-phase signal is taken into a detection circuit (not shown). The magnetic pole position of the driving magnet of the motor body 10 is detected.

  Further, the rotation position detecting magnetic sensor 7 receives the change of the magnetic field of the rotation position magnetizing portion 31 of the signal magnet 3 by the rotation of the rotating shaft 11, and outputs the signal Sr shown in FIG. Since the rotation position magnetized portion 31 of this embodiment has N poles and S poles formed in 180 ° increments, the signal Sr has a phase of one cycle per rotation. Also, since switching from N pole to S pole and switching from S pole to N pole is 1 pulse each per rotation, one of the previous magnetic pole switching points is used as a rotation position origin and is identified by a detection circuit (not shown). can do. In this embodiment, the switching point from one N pole to the S pole of the magnetic pole detection magnetizing portion 32 of the signal magnet 3 and the switching from the N pole to the S pole of the rotational position detecting magnetizing portion 31 are performed. The points are matched as shown in FIG. 2 (A in FIG. 2), but can be shifted in the rotation direction.

  A predetermined positional relationship (rotation angle) necessary for rotating the rotating shaft 11 when the motor body 10 is attached to the encoder unit 20 will be described. In this embodiment, the drive coil 13 of the motor body 10 is composed of three coils of U phase, V phase, and W phase, and it is necessary to flow a sine wave current whose phase is shifted by 120 ° to each. When the magnetic pole position of the magnetic pole position detection magnetizing part 32 of the encoder unit 20 is coincident with the magnetic pole position of the drive magnet 12 in the rotation direction, the output signals (rotor phase signals) of the magnetic sensors 6a to 6c for detecting the magnetic pole position Even if the drive coil 13 is energized through a drive circuit (not shown) in this state, the rotating shaft 11 does not rotate, does not rotate smoothly, or does not produce a desired torque. Therefore, the phase of the magnetic pole of the rotational position detecting magnetizing portion 32 of the signal magnet 3 needs to be shifted from the phase of the magnetic pole of the drive magnet 12 by a predetermined mechanical angle (or electrical angle). The predetermined mechanical angle (or electrical angle) mentioned here is an angle required for normal rotation control of the number of rotor poles of the motor to be driven, the number of phases of the drive current, the drive circuit, etc. This is the angle that changes when changes.

(Effect of this embodiment)
In the first embodiment, the magnetic signal of the magnetic pole position corresponding to each magnetic pole of the driving magnet and the magnetic signal of the rotational position of the rotating shaft are formed on the same surface of one signal magnet. There is no need to separately provide a magnetic signal magnet at the magnetic pole position and a magnetic signal magnet at the rotational position of the rotating shaft as in the prior art. As a result, the encoder can be reduced in size, and the magnetic pole detection of the drive magnet and the rotational position detection of the rotary shaft can be performed at a time.

  In FIG. 4, the inside of the motor 30 from the encoder part 20 side of the 2nd Example of this invention is shown. Further, the sectional view in the axial direction of the motor of the second embodiment is the same as FIG.

  In FIG. 4, a reference position mark 41 is formed on the rotary shaft 11. The reference position marker 41 may be any marker that can be visually discriminated, such as D-plane cut, groove, or laser marking. In this embodiment, the D plane cut is illustrated as the reference position marker 41.

A driving magnet 12 is fixed to the rotating shaft 11, and a driving coil 13 that concentrically surrounds the outer periphery thereof is disposed. The positioning of the reference position mark 41 and the signal magnet 3 is based on the line segment connecting the center of the rotation shaft 11 and the center of the reference position mark 41 and the N pole of the magnetic signal at the rotation position of the rotation shaft 11 and the signal magnet 3. The angle formed by the line segment connecting the switching points to the south pole is shifted and fixed by the predetermined mechanical angle (or electrical angle) described in the first embodiment. The driving magnet 12 is fixed to the rotating shaft 11 so as to satisfy the relationship of the magnetic pole positions of the rotation detecting magnetized portion 32 of the driving magnet 12 and the signal magnet 3 described in the first embodiment.
With this configuration, the phase difference between the reference position marker 41 of the rotating shaft 11 and the rotation position origin of the encoder is the same even in different motors.

(Effect of this embodiment)
In this embodiment, the magnetic signal at the rotation position of the signal magnet 3 is magnetized by 180 ° in N and S poles, and the rotation shaft 11 of the motor main body 10 provided with the reference position mark 41 is connected to the rotation shaft. A line connecting the center of the rotation axis and the center of the reference position mark on the orthogonal surface, and a line connecting the switching point from the N pole to the S pole of the magnetic signal at the rotation position of the rotation axis and the signal magnet. Since the divided angle is constant, even in different motors, the phase difference between the center of the reference position mark 11 of the rotating shaft 11 and the rotation position origin of the encoder is the same.

  As a result, when the rotational position of the rotary shaft 11 is matched and fixed to the external drive body, the rotational position of the rotary shaft 11 (rotational position signal of the encoder) becomes the same if the reference position mark 41 is fixed as a reference. As in the prior art, after fixing the fixed shaft 11 and the external driving body, it is not necessary to adjust and attach while monitoring the rotation position signal of the encoder, so that assembly adjustment can be simplified and the installation space can be reduced.

  A specific example is a sewing needle driving motor of a sewing machine with an encoder assembly function. When attaching the rotating shaft and the sewing machine needle drive shaft constituting the motor, it is important to attach the motor and the rotating shaft fixed to the machine frame of the sewing machine so as to have a predetermined positional relationship (phase). When the motor of this embodiment is used as a drive source for one rotation of the motor to raise and lower the sewing needle once, the sewing needle is above the fabric to be sewn (above the bobbin) or below the fabric (within the bobbin). Whether or not there is can be determined by the rotation position origin of the rotation detection signal Sr. In general, the sewing needle is controlled to stop at a position above the fabric to be sewn. In this embodiment, if the angle between the reference position mark 41 and the rotation position origin is set so that the signal of the rotation position origin is on the upper side of the fabric, the control can be performed by the rotation position origin of the encoder. Further, since the rotation origin of the rotary shaft 11 is in an accurate positional relationship, workability is improved because it is only necessary to attach the sewing machine drive body with the reference position marker 41 as a reference.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

As described above, according to the present invention, there is provided a small motor with an encoder in which the magnetic pole detection of the driving magnet of a small motor such as an AC servo motor with high assembly accuracy is integrated with the rotational position detection of the rotary shaft. can do.

1A is a side sectional view of a motor according to an embodiment of the present invention, and FIG. 1B is a layout view of magnetic sensors disposed on a sensor substrate. It is a schematic diagram of the magnetization pattern of the signal magnet of an encoder part in one Embodiment concerning this invention. It is a diagram of a magnetic pole signal and a rotational position signal from a magnetic sensor of an encoder unit in an embodiment according to the present invention. It is a schematic front view of the motor from the encoder part side in 2nd Embodiment concerning this invention. It is a part sectional view of the motor with an encoder of the conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Signal magnet 5 Board | substrate 6 Magnetic sensor 6a, 6b, 6c Magnetic sensor 7 Magnetic sensor 10 Motor main body 11 Rotating shaft 12 Drive magnet 13 Drive coil 15 Back yoke 20 Encoder part 30 Motor 31 Rotation position magnetizing part 32 For magnetic pole position Magnetized part 41 Reference alignment marker

Claims (2)

A motor main body having a driving magnet, a driving coil facing the driving magnet, a magnetic signal at a magnetic pole position corresponding to each magnetic pole of the driving magnet of the motor main body, and a rotational position of the rotation shaft of the motor main body The motor includes a signal magnet formed on the same surface, and the magnetic signal of the signal magnet includes a detection mechanism formed on a surface orthogonal to the rotation shaft. The rotating shaft of the motor main body provided with a reference position mark, and the magnetic signal of the rotating position of the rotating shaft have the signal magnet in which the N pole and the S pole are magnetized by 180 °, and the rotation A line segment connecting the center of the rotation axis and the center of the reference position mark on a plane orthogonal to the axis, and a switching point from the N pole to the S pole of the magnetic signal at the rotation position of the rotation axis and the signal magnet are connected. 2. The motor according to claim 1, wherein an angle formed by the ellipse line is constant.

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