JPH01152314A - Absolute encoder - Google Patents

Abstract

PURPOSE:To obtain an absolute encoder small and easy to adjust, by arranging a plurality of detectors in one row in the direction of relative movement while an absolute pattern is made as 1-track pattern corresponding to the number of the detectors. CONSTITUTION:An absolute pattern 2 has the circumference thereof divided in 16 and areas divided are formed as such transparent or non-transparent. The array of the areas is so determined that signals of the same combination will not be generated over one rotation of a code disc 1 from four light receiving elements 3a, 4a, 5a and 6a arranged corresponding to continuous four divided area along the circumference of a code disc 1. Thus, the light receiving element 3a is made to correspond to 2<0>, the light receiving element 4a to 2<1>, the light receiving element 5a to 2<2> and the light receiving element 6a to 2<3> thereby obtaining a 4-bit absolute signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an absolute encoder.

(Background of the Invention) Conventional absolute encoders include optical and magnetic types, but absolute encoders with a resolution of 2'' have n or more tracks as the absolute pattern of the code plate. If the code plate is disc-shaped, as shown in Figure 2, multiple tracks are required in the radial direction.Figure 2 (a) shows the code plate 8.
2(b) is a schematic side view of the encoder. Four concentric tracks forming an absolute pattern 9 are formed on the code plate 8, and four detection sensors are provided corresponding to each track. The vessels 10, 11, 12, and 13 are arranged. In addition, 14 in FIG. 2(b) is the rotation axis of the code plate 8.

In addition, FIGS. 4(a), (b), (c), and (d) show rectangular waves obtained by shaping the signals obtained from the detectors 1O111, 12, and 13, respectively, at arbitrary rotational positions of the code plate 8. The combination of rectangular waves obtained in corresponds to the decimal number shown in FIG. 4(e), and the rotational position of the code plate 8 can be detected absolutely.

Therefore, if the resolution is to be increased, the number of tracks (the number of detectors) must be increased, and as a result, the diameter of the code plate must be increased.

Furthermore, if the code plate is cylindrical or flat, the direction (width) perpendicular to the measurement direction becomes large.

Furthermore, it is troublesome to adjust the phase relationship between one track.

(Objective of the Invention) The object of the present invention is to solve these drawbacks and provide an absolute encoder that is compact and easy to adjust.

(Summary of the Invention) The present invention provides an absolute pattern formed on a code plate that is read by a plurality of detectors to detect an absolute position in a direction of relative movement between the code plate and the detector. The absolute encoder is characterized in that the plurality of detectors are arranged in a line in the relative movement direction, and the absolute pattern is a -track pattern depending on the number of the detectors.

In order to create a 2" absolute pattern, a computer generates a combination of 2""0" and "1" pulse trains in sequence, and when they are read by n sensors, this absolute encoder is The computer may select from 2n/n combinations of patterns so that the same output pattern does not appear from n sensors during rotation.

(Embodiment) FIGS. 1(a) and 1(b) are diagrams showing an embodiment in which the present invention is applied to a photoelectric absolute encoder, and FIG. 1(a) shows the plane of the code disk. FIG. 1(b) is a side view taken in the direction of arrow A in FIG. 1(a).

Absolute patterns 2 are formed in a row in the circumferential direction on the code disk l. The absolute pattern 2 is formed by dividing the circumference into 16 areas and making each divided area a transparent area or an opaque area.As shown in FIG. 1(b), the circumferential direction of the code plate l is , four light-receiving elements 3a, 4 arranged corresponding to four consecutive divided areas.
The arrangement is determined so that the same combination of signals does not occur from a, 5a, and 6a over one revolution of the code disk 1. In other words, transparency is 1. If opacity is represented by 0, the array (absolute code) of absolute pattern 2 in Figure 1 is 000011010111100.
It is 1.

Therefore, by making the light receiving element 3a correspond to 2 degrees, the light receiving element 4a to 2', the light receiving element 5a to 28, and the light receiving element 6a to 23, a 4-bit absolute signal can be obtained.

Note that the symbols 3b, 4b, and 5b in FIG. 1(b).

Reference numeral 6b indicates a light source corresponding to each of the light receiving elements 3a, 4a, 5a, and 6a, and reference numeral 7 indicates a rotation axis of the code disk 2.

With such a structure, by rotating the rotation axis 7, the four light sources 3b, 4b, 5b, 6b and the four light receiving elements 3
When the code disk l is rotated with respect to the light receiving elements 3a, 4a, 5a, and 6a, the light receiving elements 3a, 4a, 5a, and 6a detect whether there is a transparent area of the absolute pattern 2 between the corresponding light source or not. Signals with different levels are obtained depending on the presence of the region, and by waveform shaping these signals in a well-known manner, a rectangular signal as shown in FIG. 3 is obtained. Figure 3 (a
) is 2° (according to the output of the light receiving element 3a), Fig. 3(b
) is 2' (according to the output of the light receiving element 4a), Fig. 3 (
c) is 2 (according to the output of the light receiving element 5a), Fig. 3 (
d) indicates 23 (according to the output of the light-receiving element 6a), and the child hole number shown in FIG. 3(e) is 2@, 2I,
2! , 23.

Therefore, if we convert the rectangular wave in Figure 3 directly into numerical values, it will be 15
However, when the code disk l is rotated once,
Since the same combination does not appear at any one location, an absolute encoder is constructed.

Next, a method for determining the arrangement of absolute patterns will be explained. When the number of bits is small, it may be performed sequentially by trial and error, but when the number of bits becomes large, it is necessary to perform calculations using a computer. To explain in the case of 4 bits mentioned above, for example, there is always a case where each bit is O, so first consider 0.0.0.0, and if there are 5 consecutive 0's, the same combination will occur consecutively. Since it will be stored away, it is assumed that l will always come after four consecutive 0's.

In this way, 0 or 1 can be added one after another, and adjustments can be made so that the same combinations do not occur.

The results of the computer calculations are shown in FIGS. 5(a), (b), (c), and (d). Figure 5 (
a) is the absolute code for 5 bits, i.e., n=5, and FIG. 5(b) is the absolute code for 6 bits, i.e., n=5.
This is the absolute code when =6, and is shown in Figure 5 (C
) is the absolute code for 8 bits, that is, n=8, and FIG. 5(d) is the absolute code for 10 bits, that is, n
This is the absolute code when =10.

The absolute codes shown in FIGS. 5(b), (c), and (d) are constructed by connecting the last bit of the previous (upper) row to the first bit of the next (lower) row.

When this absolute code is used in a rotary encoder, the last bit of the bottom row is made to be continuous with the first bit of one row.

Although the above-described embodiments were mainly considered as absolute encoders for reading rotational positions, they can also be used in exactly the same way as absolute encoders for reading linear positions. In that case, the absolute pattern of the longevity track as described above may be formed linearly in the direction of relative movement of the code plate.

Furthermore, in the above explanation, an example was given of a transmissive photoelectric encoder in which an absolute pattern consisting of a transparent area and an opaque area was formed on the code plate. Not only can it be used as a reflective photoelectric encoder, but it can also be made into a magnetic encoder by making the transparent area correspond to a part with a magnet and the opaque area to a part without a magnet.

In addition, in the above explanation, an example was given in which detectors such as light-receiving elements and magnetic detection elements are arranged in correspondence with continuous divided areas, but it is also possible to arrange detectors in continuous divided areas as the pattern becomes finer. If it is physically difficult to do so, by devising an absolute pattern, it is possible to
The detectors can be arranged in parallel, and other arrangements are also possible. - As an example, an absolute code corresponding to an absolute pattern in which detectors can be arranged in correspondence with every other divided area is shown.

(Effects of the Invention) As described above, according to the present invention, it is possible to make the absolute pattern ≠ a track pattern, so not only can an absolute encoder with almost no difference in size from a so-called incremental encoder be created, but also It is possible to obtain an absolute encoder that is lightweight and can significantly reduce costs.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing a photoelectric absolute encoder according to a first embodiment of the present invention, and FIGS. 2(a) and (b)
) is a diagram showing a conventional photoelectric absolute encoder,
FIG. 3 is a waveform diagram showing a set of rectangular waves obtained by the configuration of FIGS. 1(a) and (b), and FIG.
A waveform diagram showing a set of rectangular waves obtained by the configuration shown in FIG. FIG. 6 is a diagram showing another example of the absolute code. (Explanation of symbols of main parts) 1... Code disk, 2... Absolute pattern, 3a, 4a, 5a, 6a... Light receiving element. Applicant Nippon Kogaku Kogyo Co., Ltd.

Claims (1)

[Claims] In the absolute encoder, an absolute pattern formed on a code plate is read by a plurality of detectors to detect an absolute position in a direction of relative movement between the code plate and the detector. An absolute encoder characterized in that the absolute pattern is arranged in a moving direction and that the absolute pattern is a one-track pattern corresponding to the number of the detectors.