Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1986-04-03
1988-04-26
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250237G, G01D 534
Patent
active
047406917
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to an optical rotary encoder and, more particularly, to an optical rotary encoder which allows easy alignment to a light receiving element and a fixed slit.
2. Background Art
An optical rotary encoder is already known. FIGS. 1(A) to 1(D) show an example of such an optical rotary encoder. FIG. 1(A) is a partial cutaway view, in which a fixed encoding plate 13 is fixed to a lower portion of a rotating encoding disk 12 fixed to a rotating shaft 11, and a light receiving element array 14 is fixed below the plate 13. A light emitting diode 15 fixed to a printed circuit board 16 is arranged above the rotating encoding disk 12. FIG. 1(B) is a plan view of the rotating encoding disk. Light-transmitting portions (slits) and light-shielding portions (indicated by hatched portions) are formed along the outer periphery of the rotating encoding disk 12 at equal intervals. Light emitting diodes 15a and 15b (in FIG. 1(A), generally indicated by reference numeral 15), emit light downward onto the light-transmitting and light-shielding portions. FIGS. 1(C) and 1(D) are plan views showing the fixed encoding plate 13 and the light receiving element array 14. The fixed encoding plate 13 derives an A-phase signal and an A-phase signal (the inverted signal thereof), and a B-phase signal and B-phase signal (the inverted signal thereof), which have a 90.degree. phase difference from the A- and A-phase signals, respectively. Note that the patterns of the fixed encoding plate and the light receiving element array must completely overlap each other. In addition, the pattern of the fixed encoding plate 13 and that of the light-transmitting and light-shielding portions of the rotating encoding disk 12 must be completely concentric with each other.
For this reason, in the conventional encoder, the assembly and alignment are performed as shown in Figs. 2(A) to 2(F). Note that FIGS. 2(A), 2(C), and 2(E) are partial plan views of the encoder shown in FIGS. 1(A) to 1(D), and FIGS. 2(B), 2(D), and 2(F) are sectional views corresponding to those plan views.
Referring to FIGS. 2(A) and 2(B), the fixed encoding plate 13 is mounted on a fixing base 17 having a groove 17a. Next, referring to FIGS. 2(C) and 2(D), the light receiving element array 14 is inserted in the groove 17a, and is mounted on the fixing base 17. In this case, the patterns of the fixed encoding plate and the light receiving element array are aligned accurately using a microscope. Referring to FIGS. 2(E) and 2(F), the fixing base 17 is mounted on a flange 18, the patterns of the rotating encoding disk 12 and the fixed encoding plate 13 are aligned to be concentric with each other, and then the fixing base 17 is fixed to the flange 18 by screws.
Since the above components must be moved in X and Y directions, i.e., two directions, so as to be aligned, alignment of the light receiving element array and the fixed encoding plate, and that of the fixing base and the flange are cumbersome and the number of assembling steps of the encoder is undesirably increased.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an encoder which allows easy alignment of an encoder, and reduces the number of assembling steps.
According to the present invention, there is provided an optical rotary encoder for detecting a rotating position of a rotating shaft by exposing and obscuring an optical path formed between a light emitting element and an opposing light receiving element upon rotation of the rotating shaft, characterized by comprising: a fixing base having a cylinder concentric with an axis of the rotating shaft, and fixed to a flange; a light receiving element plate having a hole of a proper size to be engaged with the cylinder of the fixing base and be rotatable relative thereto during assembly, and a light receiving element precisely aligned from the center of the hole in the radial direction thereof; and a fixed encoding plate, in which an encoding portion is formed so that emitted light is radiated on
REFERENCES:
patent: 4184071 (1980-01-01), Fryer et al.
patent: 4345149 (1982-08-01), Blaser
patent: 4375592 (1983-03-01), Cox et al.
patent: 4512184 (1985-04-01), Ernst et al.
patent: 4644158 (1987-02-01), Taillebois
Fanuc Ltd.
Nelms David C.
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