Harmonic Drive Systems Inc.

Kunio Miyashita

Junji Koyama

Muneo Mitamura

Toshiki Maruyama

Yasuo Sawamura

Tsukasa Koto

Nozomu Tanioka

Akira Akahane

Yuki Kato

Yoshikazu Yajima

Shunichi Tezuka

Yukitoshi Kobayashi

A magnetic absolute encoder includes: a board-holding assembly mounted to a motor case assembly side; and a flexible printed wiring board which is held, by the board-holding assembly, in the shape of a loop surrounding multipolar and bipolar ring magnets. On the flexible printed wiring board, multipolar-side hall elements and bipolar-side hall elements are mounted and a wiring pattern relating to the hall elements are printed. The assembling work and wiring work of the magnetic absolute encoder provided with a multipolar magnetic encoder and a bipolar magnetic encoder can be performed simply in a short time.

Magnetic absolute encoder and motor

First to fourth magnetic detection units (-) are arranged in opposition to a multipole magnetized surface () of a multipole magnet () of a magnetic encoder (). The first and second magnetic detection units () are placed on positions separated from each other by 180 degrees on the periphery of the center of the multipole magnet and output an A-phase signal and a B-phase signal. The third and fourth magnetic detection units () are placed on positions separated from each other by nearly 180 degrees on the periphery of the center of the multipole magnet and output an A-phase reverse signal and a B-phase reverse signal. Detection signals of the same phase are synthesized and averaged, and consequently a detection error generated by an outer magnetic flux extending in the diameter direction of the multipole magnet can be removed. The signal obtained by synthesizing the detection signals of the same phase and averaging the same and the reverse signal of a signal obtained by synthesizing reverse signals of the reverse phase and averaging the same are synthesized and averaged, and consequently the detection error generated by the outer magnetic flux radially extending in one direction along the radius direction of the multipole magnet can be removed.

Magnetic encoder and actuator

A magnetic encoder includes a multi-pole magnetic detecting unit having a multi-pole magnet. In the multi-pole magnetic detecting unit, first and second magnetic detecting elements that output sinusoidal signals having a 90&#xb0; phase difference are arranged apart from third and fourth magnetic detecting elements at a mechanical angle of 180&#xb0; . The first and third magnetic detecting elements are disposed at the same position represented by an electrical angle and output sinusoidal signals of a same phase. The second and fourth magnetic detecting elements are arranged at the same position represented by an electrical angle and output sinusoidal signals of a same phase. A sum signal of the output signals of the first and third magnetic detecting elements and that of the output signals of the second and fourth magnetic detecting elements are obtained, thereby eliminating or remarkably reducing error components of detection signals of the first to fourth magnetic detecting elements caused by the magnetic flux of a two-pole magnet and those of the detection signals caused by rotational run out of the multi-pole magnet. A rotational angle can be detected with high accuracy.

Magnetic encoder and method of detecting absolute rotational position

A magnetic absolute sensor for a geared motor comprises a dipole magnet and hall elements. The dipole magnet is fixed to a hollow portion of a hollow rotor shaft. A bracket attached to an end plate of a motor housing is coaxially inserted from the rear end side of the hollow portion. The dipole magnet is inserted from the front side in a cylindrical portion of the bracket. The hall elements are arranged at an interval of 90 degree on the circular inner periphery surface of the cylindrical portion. The hall elements face the circular outer periphery surface of the dipole magnet with a fixed gap therebetween. It is not necessary to increase a motor shaft length in order to incorporate the magnetic absolute sensor. The flux of a motor driven magnet is blocked by the hollow rotor shaft and the hall elements are not adversely affected.

Apparatus for detecting position of rotation of motor

A multiple-rotation absolute-value encoder of a geared motor, wherein the geared motor () reduces the rotational speed of a motor shaft () and takes it out from a gear shaft () to drive a machine device () in an operating range corresponding to two rotations of the gear shaft (). The multiple-rotation absolute-value encoder () fitted to the geared motor () is made up of a gear shaft absolute value encoder () for detecting the absolute position of the gear shaft () and a load side absolute value encoder () having a two-pole magnet () and a magnetic sensor () rotating at a rotational speed reduced to half the rotational speed of the gear shaft () through the magnetic gear ().

Multiple-rotation absolute-value encoder of geared motor

An insert member () having an identical permeability is fitted in the circular center hole() of a magnetic ring () which is then fitted in the circular hollow section () of a fitting-over member () having an identical permeability. Under that state, the magnetic ring () is placed in a parallel magnetic field. Lines of magnetic flux passing through the magnetic ring () held between the insert member () and the fitting-over member () become linear without substantially inclining against the parallel magnetic field. Under that state, harmonic noise causing a deterioration in detection precision will scarcely appear in the output of a magnetic sensor for detecting the rotating magnetic field of a ring magnet () obtained by performing two-pole magnetization on the magnetic ring (). When the ring magnet () is employed, a deterioration in the detection precision of a magnetic encoder () due to the magnetization state of the ring magnet () can be avoided, and the deterioration in detection precision can be suppressed.

Method for magnetizing ring magnet and magnetic encoder

A motor encoder is mounted on a motor shaft of a geared motor, and the origin position is detected by using a Z-phase signal. An absolute value encoder with a precision that allows the number of motor rotations to be determined is mounted on an output shaftof a reduction gear, and the absolute rotational position thereof is detected. When the first Z-phase signal generated in conjunction with the rotation of the motor shaftis obtained at startup and at other times, the mechanical starting point at which the motor shaft and output shaft are both positioned at the origin can be calculated based on the absolute rotational position of the reduction-gear output shaft obtained from the output-side absolute value encoder. Since the mechanical starting point is obtained by rotating the motor shaft a single rotation at most, the time required to calculate the mechanical starting point is short in comparison with conventional examples, and extraneous rotational movements can be avoided.

Geared motor

An encoder mounted on a motor axle of an AC servomotor has a single bipolarly magnetized rotational disk, magnetic sensors for outputting X- and Y-signals that differ in phase by 90&#xb0; in association with the rotation thereof, and a signal processing unit. The signal processing unit computes at predetermined cycles a rotor angle &#x3b8;a of a motor rotor on the basis of the X- and Y-phase signals, generates three-phase magnetic pole signals U, V, and W that differ in phase by 120&#xb0; on the basis of the number M of magnetic poles of a motor, a magnetic pole reference angle &#x3b8;o, and the rotor angle &#x3b8;a; and generates A- and B-phase signals with predetermined pulse cycles that differ in phase by 90&#xb0; on the basis of the rotor angle &#x3b8;a. An encoder that is advantageous for reducing the size and weight of an AC servomotor can be realized because it is sufficient to provide a single assembly composed of a rotational disk and magnetic sensors.

Motor encoder

The encoder rotor of an absolute magnetic encoder mounted on a servomotor shaft has a first drum of a bipolar magnet, and a second drum with a Q-bit multipolar magnetic pole track and a reference track. A signal processor generates absolute signals on the basis of detected signals, which differ in phase by 90&#xb0; and in which a single rotation represents a single period, from X-phase and Y-phase magnetic sensors disposed facing the first drum, and on the basis of A- and B-phase signals, which differ in phase by 90&#xb0;, and a reference signal obtained from A-, B-, and Z-phase magnetic sensors disposed facing the second drum. Even if the number of bits Q of the multipolar magnetic pole track is increased in order to enhance the resolution, the number of magnetic pole tracks does not need to be increased, and higher resolution can therefore be obtained without increasing the axial length.

Absolute magnetic encoder

An actuator has a housing, a motor and a wave gear reduction drive arranged axially in the housing, and a rotational shaft extending through the centers of these portions. The rotational shaft is supported at its rear side by a first bearing and at its front side by a boss of a flexible external gear of the wave gear reduction drive via a second bearing. The rotational shaft is formed integrally on its outer peripheral portion with a cam plate of a wave generator of the wave gear reduction drive. The actuator thus configured does not require a coupling mechanism between the motor and the wave gear reduction drive and needs fewer bearings to support the rotational shaft, making it possible to reduce the axial length of the actuator.

Actuator having a wave gear reduction drive

A DC motor of a galvanometer-type scanner has four poles, and compared to a conventional DC motor with a bipolar construction, the armature inductance L can be reduced to half or less for a case where the external diameter of the rotor and the induced voltage constant K are the same. Since K /L, which is the index for the rise of torque of the motor, is increased by a factor of two or more, the responsiveness of the motor can be improved without increasing the exciting current of the winding. Accordingly, it is possible to provide a galvanometer-type scanner that can set minute angles of around one degree within several hundred microseconds.

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Azumino, Japan

Kunio Miyashita