JP3195117B2 - Rotary encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incremental encoder used for detecting a rotational position and a speed of a machine.

[0002]

2. Description of the Related Art Generally, encoders are classified into an absolute type and an incremental type. The absolute type is highly reliable, but has a complicated structure and is expensive. Therefore,
Incremental encoders, which have a simple structure and are inexpensive, are widely used. FIGS. 6A and 6B show the configuration of a conventional optical incremental rotary encoder. The rotor 1 is mounted on a rotating shaft 2, and a bright and dark pattern 1a is engraved on the surface of the rotor 1 at an equal pitch. A stator 3 having a light and dark pattern 3a having the same pitch as that of the rotor 1 is provided at a very small gap in parallel with the rotor 1. The light emitting diode (L) is disposed on one side with the rotor 1 and the stator 3 sandwiched therebetween.
A light emitting element (light source) 4 using ED) or the like, a collimator lens 5 for converting a light beam from the light emitting element 4 into a parallel light beam, and a light receiving element 6 on the other side are provided.

According to this encoder, a periodic change in brightness that occurs each time the rotor 1 rotates by one pitch is converted into an electric signal by the light receiving element 6 and extracted as a sine wave signal. Next, the extracted signal is shaped into a rectangular wave signal 7 by a waveform shaping circuit (FIG. 7). Then, the rotation angle is determined by counting the rectangular wave signals 7 corresponding to the rotation angle of the rotor 2. In such an encoder, the rotor 1
In order to eliminate the eccentricity error component (FIG. 8A) with respect to the rotating shaft 2, the same pattern 3 b as the light and dark pattern is cut on the stator 3 at 180 ° facing position, and the light emitting elements 4 each having the same configuration as described above are respectively formed. , A collimator lens 5 and a light receiving element 6 are provided. The eccentricity error component is eliminated by taking the sum of these two sets of electric signals (FIG. 8B) (FIG. 8C).

[0004]

The eccentricity error component described above is a sinusoidal waveform of one cycle per one rotation of the rotor (FIG. 7 (a)).
And occupies most of the entire error amount. However, in order to realize a high-precision encoder, it is not possible to ignore an error component of two cycles or more generated by a scale error, a surface deviation of a protractor, or the like. In view of the above problems, the present invention removes error components of two or more cycles,
An object is to provide a high-precision encoder.

[0005]

According to the present invention, there is provided a rotary encoder having a code pattern for detection, a light emitting element and a light receiving element for reading the code pattern, and a rotary encoder comprising the light emitting element, the code pattern and the light receiving element. One set of light emitting units, two sets of opposing light receiving and emitting units as one pair, at least a plurality of pairs are arranged on the circumference, and each pair is at a position where the circumference is divided at equal intervals. It is a rotary encoder characterized by being provided. An embodiment of the present invention is characterized in that, in the precise measurement, the light-emitting elements constituting the light receiving / emitting unit are measured by pulse lighting or pulse lighting, and the measurement is performed only when the rotation of the rotary encoder is stopped. .

[0006]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an optical incremental rotary encoder according to the present invention. The rotary shaft 11 of the encoder is fitted on a bearing 12, and a thrust load acting in the axial direction is received by a ball bearing 13 disposed between the rotary shaft 11 and the bearing 12. Rotary axis 1
The stator 14 is attached to the first flange portion.
Further, a rotor 15 is attached to a flange portion of the bearing 12. The gap between the stator 14 and the rotor 15 is so small that they do not contact each other. A light emitting element 16 and a collimator lens 17 for converting a light beam from the light emitting element 16 into parallel light are mounted inside a holder 18. Holder 1
The tip of 8 is suspended on the tip of the flange of the rotating shaft 11. Each light receiving element 20 is mounted on the rotating shaft 11 via a printed circuit board 19.

FIG. 2 is a perspective view schematically showing the arrangement of the light receiving / emitting unit of the rotary encoder according to the present invention.
Eight light and dark patterns 14a to 14h are engraved on the stator 14 equally at 45 ° intervals. The light emitting element 16 and the collimator lens 1 correspond to the respective light and dark patterns.
7. Eight light receiving / emitting units including light receiving elements 20 to 27 are concentrically arranged. Therefore, two sets of light receiving / emitting units located opposite each other are paired, and
That is, four pairs are provided at an interval of °. The reason why the light and dark patterns are arranged at equal intervals on the stator 14 is that
This is because the most advantageous effect is obtained in removing a periodic error component with respect to the rotation of the rotor 15. The light receiving element 2
0 is composed of two parts 20a and 20b so as to obtain a sine wave signal having a phase difference of 90 ° from each other (see FIG. 5). The light receiving elements 21 to 27 have the same configuration.

FIG. 3 is a block diagram of a signal processing system according to the present invention. Sine wave signals and cosine wave signals having a phase difference of 90 ° obtained from the light receiving elements 20a and 20b are amplified and then converted into rectangular waves by the rectangular wave conversion circuits 30 and 31. After being converted into pulses by the pulse conversion circuits 50 and 51, the pulses are counted by the counter 36.
The direction of rotation of each rectangular wave is determined by a direction discriminating circuit 34, and the increase / decrease of a counter 36 is controlled based on the direction of rotation. Signals obtained from the light receiving elements 21a and 21b located opposite to the light receiving elements 20a and 20b are processed in the same manner and counted by the counter 37. Further, the sine wave signal and the cosine wave signal obtained by the light receiving elements 20a and 20b are subdivided in the pulse by the interpolation circuit 40. In this interpolation circuit, fine measurement is similarly performed on the signals obtained from the respective light receiving elements 21 to 27 by the interpolation circuits 41 to 47.

FIG. 4 is a waveform diagram of a sine wave signal (cosine wave signal) for explaining an example of the interpolation method according to the present invention.
From the sine wave signal A and the cosine wave signal B obtained from the light receiving elements 20a and 20b, the sine wave A
Waveforms C, D, and E having a phase difference of 35 ° and 180 ° are created. Further, the sine wave A is divided into eight portions, and interpolation is performed at each portion by using a waveform near the center that can be regarded as a linear approximation by a ratio of the distance from the center. In the example of FIG. 4, when the user is at the position of θ, it is at the third position in the eight divisions, and the interpolation is performed using the sine wave waveforms B and D by the ratio of a: b. The interpolation values obtained by the interpolation circuits 40 to 47 are
Through the multiplexer 48, the microcomputer 3
8, is converted into an accurate measurement value by averaging processing, processed with the values obtained from the counters 36 and 37, converted into an angle, and displayed on a display 39.

Further, the microcomputer 38 controls blinking of the light emitting element for precise measurement. FIG.
As described above, since the precise measurement is performed by the ratio of the waveforms, it is not necessary to always detect the waveform, and the measurement is performed by the pulse lighting or the pulse lighting only when the rotation of the encoder is stopped. In this embodiment, the precise measurement is read into the microcomputer 38 through the multiplexer 48 after obtaining the interpolated value. However, each signal for the precise measurement is taken into one interpolation circuit through the multiplexer and each interpolation is performed. You can also determine the value. Further, after synthesizing the respective sine waves and cosine waves, an interpolation value can be obtained by an interpolation circuit. In this case, there is an advantage that the synthesis of the waveform is equivalent to the averaging, and the obtained signal is increased by the signal synthesis.

Further, here, the description has been given of the example of eight light receiving / emitting elements. However, the main factors of the error component in the rotary encoder are many factors of two period components or less, such as eccentricity, surface runout of the scale error dividing plate. , To get rid of these,
A set of light receiving and emitting elements can sufficiently cope.

[0012]

According to the present invention, the following excellent effects are exhibited. (1) In addition to the eccentricity error of the rotor with respect to the rotating shaft, which has been removed by the conventional technology, errors due to scale errors and rotor runout are removed, so that the angle measurement accuracy can be improved and a high-precision encoder can be obtained. it can. (2) Conventionally, when a theodolite or the like is used in the surveying work, it is necessary to remove the scale error of the vertical axis.
Although the observation is performed more than once, the use of the present invention eliminates the need for this observation. For example, when the eight sets of light receiving and emitting elements shown in the above-described embodiment are equally arranged on the rotor, this corresponds to four pairs of observations of the surveying work, and the work can be saved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an optical incremental rotary encoder according to the present invention.

FIG. 2 is a perspective view showing a configuration of an optical incremental rotary encoder according to the present invention.

FIG. 3 is a block diagram of a signal processing system.

FIG. 4 is an explanatory diagram showing an example of an interpolation method.

FIG. 5 is a perspective view schematically showing an internal configuration of a light receiving element.

6A is a perspective view showing a configuration of a conventional optical incremental rotary encoder, and FIG. 6B is an explanatory view.

FIG. 7 shows a rectangular wave signal obtained by shaping a sine wave signal taken out by a light receiving element by a waveform shaping circuit.

FIGS. 8A, 8B, and 8C are waveform diagrams for explaining elimination of an eccentric error component.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Rotating shaft 12 ... Bearing 13 ... Ball bearing 14 ... Stator 14a-14h ... Light-dark pattern 15 ... Rotor 16 ... Light emitting element 17 ... Collimator lens 18 ... Holder 19 ... Printed circuit board 20-27 ... Light receiving element 40 ... Insertion circuit

Continuation of front page (56) References JP-A-61-280574 (JP, A) JP-A-62-55504 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) G01D 5 / 00-5/62 G01B 11/00-11/30 G01B 7/00-7/32 G01P 1/00-3/80

Claims (2)

(57) [Claims] 1. A rotary encoder having a code pattern for detection and a light emitting element and a light receiving element for reading the code pattern, comprising: a light receiving / emitting element comprising the light emitting element, the code pattern and the light receiving element.
The unit is one set, and two sets of light receiving and emitting units
As a pair, a plurality of pairs are arranged on the circumference,
In addition, each pair is placed at a position where the circumference is divided at equal intervals.
A rotary encoder, characterized in that it is set. 2. In the precise measurement, the light receiving and emitting unit is used.
2. The rotary encoder according to claim 1, wherein the measurement is performed by pulse lighting or pulse lighting of the light emitting element constituting the light emitting element , and only when the rotation of the rotary encoder is stopped. 3.