Harmonic Drive Systems Inc.

Other

Muneo Mitamura

Junji Koyama

Kunio Miyashita

Yasuo Sawamura

Yoshinori Ito

Toshiki Maruyama

Kozo Sasaki

Kazuhiro Hane

Toshiyuki Abe

Sadaharu Kanamori

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 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

In the magnetic absolute encoder, an ordinary operating circuit and an ordinary/backup operating circuit are actuated during ordinary operation in which power is supplied from the ordinary operating power supply; the single-rotation absolute value (1) and single-rotation absolute value (2) detected by these circuits are compared by the abnormality diagnosis circuit, and the presence or absence of an abnormality is automatically judged During backup in which the ordinary operating power supply is interrupted, only the low-power-consumption ordinary/backup operating circuit is actuated, and the multiple-rotation value (2) is detected At the point in time at which the system is returned to ordinary operation, the multiple-rotation value setting circuit sets the multiple-rotation value (2) as the multiple-rotation value (1) of the ordinary operating circuit. As a result, the calculation operation of the multiple-rotation value (1) can be restarted.

Magnetic absolute 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

A projection linear encoder has an SOQ substrate formed with transmission gratings and grid-like photodiode groups, and a reflecting grating plate with reflecting gratings that are formed facing thereto. A light-blocking film composed of a metal thin film or the like is formed on a surface of a glass substrate of the SOQ substrate, and the transmission gratings are formed by patterning the light-blocking film. The photodiodes are integrally formed by epitaxial growth on the silicon layer of the SOQ substrate. Transmission gratings with high mechanical strength can be formed inexpensively in comparison with cases in which through holes are formed by etching a silicon substrate to manufacture transmission gratings.

Projection encoder with moving side gratings and fixed side gratings

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

In an encoder signal interpolation divider () that automatically corrects errors in the offset and gain of an input signal at a high speed with a low cost circuit configuration, and can accurately generate an encoder signal having a predetermined resolution by interpolation division, analog input signals (A, B) are subjected to offset correction by a 0-point correction circuit () in adders () prior to being digitally converted by A/D converters (), and are subjected to gain correction by an amplitude correction circuit () in amplifiers (). The corrected analog signals are converted to digital values, angle data is calculated in an angle data lookup table (), and, based on these results, an encoder pulse signal having a predetermined resolution is generated and output from an encoder pulse signal generating circuit ().

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Azumino, Japan

Muneo Mitamura