JPS6113109A - Absolute encoder - Google Patents

Abstract

PURPOSE:To enable correspondence to all possible division numbers without outputting erroneous code, by providing a code disc which adds an identification bit varying in the state once each turn to change the other bit state within the unit division of the resulting signal output position. CONSTITUTION:The code of a code disc 2 corresponds to a gray code from the lowest order bit A0 to bit A2 and the highest order bit A3 is added as identification bit. In other words, with changes in number from 0-5, the corresponding cord varies as the normal gray code does but with changes from 5 to 6, the identification bit A3 alone inverts from 0 to 1. And the identification bit A3 is maintained as it is from the number 6-0 and remains unchanged except for this range of number. In short, the code disc 2 changes the state of the identification bit A3 to 1 in the divisions L6 and L0 once each turn. Moreover, among the divisions L6 and L0 of the signal output position where the identification bit A3 is 1, the states of the lowest order bit A0 and the bit A1 change from 1 to 0 in the unit division L6.

Description

[Detailed description of the invention] <Field of invention> The present invention relates to an absolute encoder.

<Prior art and its problems> In conventional absolute encoders, if two or more bits change simultaneously when the code changes, if there is a misalignment of the optical axis of each component or variations in detection characteristics of elements or circuits, electrical The signal cannot follow this and change at the same time, and as a result, a code other than the originally required code is output.
Misreading of the code may occur. For example, the fifth
As shown in figure (a), when the number of divisions is 7, in a normal binary code, the numbers range from 1 to 2.3 to 4.5 to 6.
．． When changing from 6 to 0, two or more bits of each code corresponding to these changes simultaneously. Therefore, the wrong food is output. In order to avoid this problem, a gray code is used in the hood arrangement of the conventional absolute encoder code disk. In this Gray code, as shown in FIG. 5(b) in the above-mentioned seven-division example, when the number changes from 0 to 6, the code sequentially changes one bit at a time. However, two or more bits change at the same time when the most significant number changes from the lowest number, that is, from 6 to 0. In this way, even in the case of the Gray code, when there is an odd number of divisions, two or more bits change at one place at the same time, and there is still a problem that an incorrect code is output.

<Objective of the Invention> The present invention aims to solve the above-mentioned conventional problems and provide an absolute encoder that does not output erroneous codes and can handle any number of divisions.

<Configuration and Effects of the Invention> In order to achieve the above object, the present invention provides an absolute encoder that converts mechanical displacement into an electrical signal and outputs the code as a code, in which an identification bit whose state changes only once per rotation is added, The absolute encoder includes a code disk in which codes are arranged so that the states of other bits change within the unit division section of the signal output position of the identification bit.

Since the present invention is configured as described above, an erroneous code will not be output even when the hood changes, and it has the excellent effect of being able to cope with any number of divisions.

<Description of Examples> Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

As shown in FIG. 1, the absolute encoder E of this embodiment has a code disk 2 fixed to a shaft 1 whose one end is attached to a mechanical part, and a fixed slit 3 arranged opposite to the hood disk 2. A light projecting element 4 and a light receiving element 5 are provided on the left and right sides of the code disk 2 and the fixed slit 3, respectively. As the code disk 2 is displaced with the rotation of the shaft 1, the positional relationship with the fixed slit 3 changes, so that the light emitted from the light emitting element 4 is transmitted through the fixed slit 3 and the code disk 2. The light receiving element 5 receives the light, and the code detection signal of the light receiving element 5 is outputted through the signal processing circuit 6.

As shown in FIG. 2, the code disk 2 has A,...
-A, with a 4-bit configuration, and one rotation. ~
A hood is formed by dividing into seven units up to L6. In this code, each beep)A. %AI, A2, A3
The least significant bit A. The digits YA2 to 3rd digit correspond to the Gray code, and the highest pitch A] is added to this gray hood as an identification pitch. That is, as shown in Figure 3, the numbers range from 0 to 5.
When the code changes to 1, the corresponding code also changes to 1 like the normal Greyhood, but the number changes from 5 to 6.
When changing from 0 to 1, only the identification bit is inverted from 0 to 1.

This identification bit A3 is maintained until the number changes from 6 to 0, and the code of this identification bit A3 does not change at any other time. Tsum 1), this food disk 2 has 1
1 degree per rotation, divided sections 1, 6, and L.

The state of the odor identification bit A changes to 1.

Furthermore, in this food disk 2, there are divided sections L6 and L of the signal output position which are the identification pits A3 and power bows. Among them, the hood is arranged so that the state of the least significant bit Ao and the second digit bit YA1 changes from 1 to O within the unit division interval (the interval indicated by reference numerals 1-6 in Fig. 1). .

FIG. 4 is a block diagram of a 2[' conversion circuit for converting the code signal output encoded by the code disk 2 into a binary code. This code conversion circuit 9 is included in the signal processing circuit 6 and has input terminals A t+ to A3 corresponding to each bit of the code of the code disk 2 and an output terminal B corresponding to each bit of the binary code. -B, and two first and second AND circuits 10.
．． 12. One OR circuit 14. Two exclusive OR circuits 16, 18 and one Inno\'-Y20
Consisting of

The relationship between the input signal and the output signal of the code conversion circuit 9 is expressed by the following logical expression.

B2=A2 Bl-(A20A1)+A3゛Bo-(B, (E)A,)・A3'A3'=A2・l\3 In other words, the first AND circuit 10 has the identification pins of the code disk 2) A3 and The signal corresponding to the third bit A2 is input, but the signal A31 output from the first AND circuit 10 is 1 in the unit interval of L6, that is, the number is 6. Only when. When this signal A3' output is 1, the output of the hood conversion circuit 9 is always set to 110, which corresponds to the number 6, and does not depend on the state of other codes Y'. That is, the least significant bit A6 . Even if the second digit bit A1 changes from 1 to 0, the output of the open code conversion circuit 9 does not change. Then, when the number changes from 6 to 0, only the third bit A of code disk 2 changes from 1 to 0. Also, during this time, the output of the $1 AND circuit 10 becomes O, so the output latched state is released.

In this embodiment, the case where the number of divisions is 7 with 4 bits has been explained, but the present invention is not limited to this, and the present invention can be applied to cases where the number of divisions is larger than this. Of course, it is possible to

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, and FIG. 5 shows a conventional example. FIG. 1 is a schematic configuration diagram of an absolute encoder, FIG. 2 is a plan view of a code disk, and FIG. The figure shows the code relationship between the code of the code disk and the code of the signal output of the hood conversion circuit. (1)) is a diagram showing the relationship between decimal numbers and Gray codes. E...Absolute encoder, 2...
...Code disk, A3...Identification bit.

Claims (1)

[Claims] (1) In an absolute encoder that converts mechanical displacement into an electrical signal and outputs it as a code, an identification bit whose state changes only once per rotation is added, and within the unit division interval of the signal output position of this identification bit. An absolute encoder characterized by comprising a code disk in which codes are arranged so that the states of other bits change at a certain time.