JPH064618U - Photoelectric 1-track absolute encoder - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the size and increase the resolution of the photoelectric 1-track absolute encoder without damaging the sensor. A code string in which codes representing two types of minimum reading units having different optical properties are arranged in a predetermined order is formed on a track of the main scale 1, and four sensors 3a are arranged so as to face the track. In the photoelectric one-track type absolute encoder having a special code string in which the n-bit code detected in step 1 is different in every absolute position, four light transmitting parts having a length equal to the minimum reading unit length λ of the main scale 1 The subscale 2 in which 2a is arranged so as to face the four sensors 3a is arranged between the main scale 1 and the sensor 3a. The gap between the main scale 1 and the sub-scale 2 is set to a predetermined value as the detection gap G for obtaining a clear pattern image.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a photoelectric one-track absolute encoder, and more particularly to a photoelectric one-track absolute encoder that can be assembled without damaging the sensor.

[0002]

[Prior art]

 FIG. 4 is an overall configuration diagram showing a conventional photoelectric one-track type absolute encoder (Japanese Patent Laid-Open No. 3-285114).

The code plate (or main scale) 21 has a minimum reading unit of length λ, which is represented by a white section “0” and a hatched section “1” along the circumference. A track 21A is formed by arranging clockwise from the mark to form a special code string. A sensor head 22 that is movable relative to the code plate 21 is arranged below the code plate 21, and four sensors 23 are arranged on the sensor head 22 along the track 21A at a pitch mλ. . The memory element 24 also converts the irregular code signal detected by the four sensors 23 into a BCD (binary ordinal) code.

The special code string Bj of the track 21A is obtained by re-creating the reference code string Aj: 000010100111101011, which is composed of the minimum reading units of 16 per round, according to the following expression: B _{1 + 3 · (j−1)} = Aj (mod.16). The arrangement is such that 0000110010111110 ↑ ↑ ↑ ↑ ↑ ↑ → the moving direction forms a code string of 16 minimum reading units for one round, and the following code signals are generated by using every two codes as indicated by arrows ↑. Assembly, first absolute position: 0000 → 0001 Second absolute position: 0101 → 0010 Third absolute position: 0111 → 0011 Fourth absolute position: 0001 → 0100 Fifth absolute position: 1011 → 0101 Sixth Absolute position: 1111 → 0110 7th absolute position: 0010 → 0111 8th absolute position: 0110 → 100 9th absolute position: 1110 → 1001 10th absolute position: 0100 → 1010 11th absolute position: 1010 → 1011 12th absolute position: 1101 → 1100 13th absolute position: 1001 → 1101 14th absolute position : 0100 → 1110 Fifteenth absolute position: 1010 → 1111 Sixteenth absolute position: 0011 → 0000 Immediately, each code signal is converted by the memory element 24 into a binary ordinal code signal indicated by an arrow. It is output to the output terminal 25.

[0005]

[Problems to be solved by the device]

 In order to reduce the size and increase the resolution of the photoelectric 1-track absolute encoder described above, the length λ of the minimum reading unit of the code plate 21 must be reduced, but considering the light diffraction phenomenon, the code plate 21 Since the detection gap between the sensor 23 and the sensor 23 must also be narrow (less than or equal to λ), the sensor 23 comes into contact with the code plate 21 at the time of assembly, and the sensor 23 is damaged. There is also a problem that the sensor 23 is easily damaged in the work of setting or confirming the detection gap value of 1.

The present invention has been made in view of such circumstances, and an object thereof is to realize miniaturization and high resolution of the photoelectric one-track absolute encoder without damaging the sensor. .

[0007]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the photoelectric one track type absolute encoder of the present invention is a main scale track in which a code string formed by arranging codes representing two kinds of minimum reading units having different optical properties in a predetermined order. In the photoelectric 1-track absolute encoder, which has a special code string formed in n and the n-bit code detected by n sensors arranged facing the track is different at any absolute position, A sub-scale in which n light-transmitting portions having a length equal to the length of the minimum reading unit of the main scale were disposed so as to face the n sensors, respectively, was disposed between the main scale and the sensor.

[0008]

[Action]

 As described above, a sub-scale in which n light transmissive parts of the same length as the minimum reading unit of the main scale are arranged facing the n sensors, respectively, is installed between the main scale and the sensor. Since it is arranged, the gap between the main scale and the sub-scale can be used as the detection gap for obtaining a clear pattern image, and the sub-scale exerts the diaphragm function, which influences the diffracted light from the adjacent minimum reading unit. The distance between the main scale and the sensor can be increased more than the length of the minimum reading unit of the main scale, and at the same time, the distance between the sub scale and the sensor can be increased sufficiently.

[0009]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall configuration diagram showing a photoelectric one-track type absolute encoder according to an embodiment of the present invention, and FIG. 1 is a conceptual diagram in which a part of the encoder is enlarged.

This photoelectric one-track absolute encoder is composed of a disk-shaped main scale 1 and a detection unit (unit part) 6 that can move relative to the main scale 1. The detection unit 6 includes a detector 12 formed by mounting four sensors (for example, photosensors) 3a and one memory element 4 on the substrate 3, and between the detector 12 and the main scale 1. The subscale 2 to be arranged is integrally assembled.

The main scale 1 includes a code string (absolute pattern) in which codes representing two types of minimum reading units having different optical properties (for example, transmittance) are arranged in a predetermined order along the circumferential direction. Tracks are formed. The white section (minimum reading unit) in FIG. 1 is the transparent part and the code “0”, and the shaded section (minimum reading unit) is the light-shielding part and the code “1”. A rotary shaft 8 is joined to the center of the main scale 1, and the rotation of the rotary shaft 8 causes the main scale 1 to rotate.

A housing 7 is attached to the rotary shaft 8 via a bearing 9.

As shown in FIG. 2, a light source 10 such as a light emitting diode is arranged above the main scale 1, and the light from the light source 10 is collimated between the light source 10 and the main scale 1. The collimator lens 11 is arranged.

A detection unit 6 fixed to a housing 7 is located below the main scale 1. The four sensors 3a of the detector 12 assembled in the detection unit 6 are arranged on the substrate 3 at an mλ pitch as shown in FIG. 1, and each sensor 3a is connected to the main scale 1 via the subscale 2. Facing the truck.

The subscale 2 is provided with light transmitting portions 2a having a pitch of mλ and a length of λ, and the light transmitting portions 2a face the sensor 3a. Both the sub-scale 2 and the main scale 1 are made of glass.

The detection gap G between the main scale 1 and the sub-scale 2 is set to be equal to or smaller than the minimum reading unit λ. For example, if λ is 20 μm, the detection gap G is set to about 20 μm or less. If this is not done, the pattern image of the main scale 1 will be blurred and accurate detection will not be possible.

As shown in FIG. 1, the sensors 3 a are connected to the memory elements 4, respectively.

The light from the light source 10 is collimated by the collimator lens 14 and is radiated to the main scale 1. The brightness information of the main scale 1 reaches the sub-scale 2, and further reaches the sensor 3a of the detector 12 from the light transmitting portion 2a of the sub-scale 2.

The sensor 3 a receiving the light / dark information outputs the light / dark information to the memory element 4, and the memory element 4 converts the light / dark information into a BCD code and outputs the BCD code to the output terminal 5.

In assembling the photoelectric one-track type absolute encoder of this embodiment, first, the dimension between the main scale 1 and the housing 7 is measured in advance. Then, the subscale 2 and the detector 12 are integrally assembled to assemble the detection unit 6. At this time, the thickness of the detection unit 6 is set so that the value of the detection gap G becomes λ or less. Since the light transmitting portions 2a of the sub-scale 2 are arranged at the mλ pitch, the distance between the sub-scale 2 and the sensor 3a can be made sufficiently longer than the detection gap G, and the sub-scale at the time of assembly It is possible to avoid contact between the scale 2 and the sensor 3a.

Finally, the detection unit 6 is fixed to the housing 7. Since the sensor 3a is inside the detection unit 6, when the detection unit 6 is fixed to the housing 7, the sensor 3a does not come into contact with the main scale 1 and be damaged. Further, since the main scale 1 and the subscale 2 facing each other are both made of glass, the detection gap G can be easily confirmed by a jig or the like after the detection unit 6 is fixed. Although the distance between the main scale 1 and the sensor 3a is increased by disposing the sub-scale 2 between the main scale 1 and the sensor 3a, the light transmitting portions 2a are arranged in the sub-scale 2 at the mλ pitch. Since it is possible to prevent light interference, the pattern image will not be blurred.

Although a disk-shaped main scale 1 is used in this embodiment, a long plate-shaped one or a cylindrical one may be used instead. The light transmitting portion 2a of the subscale 2 may be a hole or an opening.

FIG. 3 is an overall configuration diagram showing a photoelectric one-track absolute encoder according to a modification of the present invention.

The same parts as those of the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the length of the sensor 13a is set to λ which is n times, for example, twice the minimum reading unit of the main scale 1. Since the sub-scale 2 is arranged between the main scale 1 and the sensor 13a, if the minimum limit of the sensor 13a is 2λ, the minimum reading unit of the main scale can be λ which is half the sensor width. As a result, downsizing and higher resolution can be realized.

[0026]

[Effect of device]

 As described above, according to the photoelectric one-track type absolute encoder of the present invention, the sensor does not come into contact with the main scale to be damaged during assembly, and the measurement gap is measured between the main scale and the subscale. The sensor does not have to be damaged when setting or checking the detection gap.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a photoelectric one-track type absolute encoder according to an embodiment of the present invention.

2 is an overall configuration diagram of the photoelectric one-track type absolute encoder of FIG.

FIG. 3 is an overall configuration diagram of a photoelectric one-track absolute encoder according to a modified example of the present invention.

FIG. 4 is an overall configuration diagram of a conventional photoelectric one-track type absolute encoder.

[Explanation of symbols]

 1 Main Scale 2 Sub Scale 2a Light Transmission Part 3a Sensor 4 Memory Element 6 Detection Unit (Unit Parts)

Claims (2)

[Scope of utility model registration request] 1. A main scale track is formed with a code string in which codes representing two types of minimum reading units having different optical properties are arranged in a predetermined order, and n sensors are arranged to face the track. In the photoelectric 1-track absolute encoder having a special code string in which the n-bit code detected by the above is different at any absolute position, n light transmitting parts having a length equal to the length of the minimum reading unit of the main scale are provided. A photoelectric one-track absolute encoder, characterized in that sub-scales arranged so as to face each of n sensors are arranged between the main scale and the sensor. 2. The photoelectric type device according to claim 1, wherein the sub-scale and the sensor are integrally assembled with each other with a predetermined gap therebetween to form one unit component.
Track type absolute encoder.