Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1991-02-26
1992-07-07
Hannaher, Constantine
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25023113, 25023114, 25023117, 25023118, G01D 534
Patent
active
051285363
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an encoder which is used to detect the position and velocity of an object.
BACKGROUND ART
Hitherto, for instance, a rotary encoder has been used to detect the revolution angle and revolution speed of a motor or the like; rotary encoders are mainly classified as incremental encoders and absolute encoders. In the incremental encoder generates pulses of the number corresponding to the number of divided sections which are obtained by dividing one revolution range of a motor or the like at regular intervals, and a signal processing circuit counts the number of pulses, so that the rotational position or revolution speed of the motor or the like can be determined. The incremental encoder ordinarily outputs pulse signals of two phases, A and B, having a phase difference of 90.degree.; the direction of rotation (forward rotation or reverse rotation) of the motor or the like is discriminated by the phase relation (advance or delay). On the other hand, generally, one origin pulse (Z-phase pulse signal) is output during one revolution as a reference signal indicative of one revolution. The absolute encoder uses a code plate in which the absolute position in one revolution range of a motor or the like is expressed by a binary code. A parallel output type, an output type of A and B phases, and the like are known as output types. On the other hand, there are also an absolute encoder of the memory backup type in which the number of revolutions of a motor or the like is recorded by using a memory which uses a battery as a backup power source and an absolute encoder of the multi-rotation type in which an absolute position of one revolution or more of a motor or the like is also produced by using a reduction mechanism using a gear or the like.
DISCLOSURE OF INVENTION
The above-mentioned conventional encoders have the following drawbacks. In the case where an abnormality such that part of signals in the encoder are missing, the output signal generally become abnormal. However, whether an abnormality has occurred or not cannot be discriminated from the outside of the encoder. On the other hand, a case where no abnormality appears in the output signal also occurs on rare occasions. Further, even in the case where an instantaneous power failure has occurred, although the output signal generally becomes abnormal, such an abnormality of the output signal is usually momentary and, after that, the signal falsely becomes a normal signal. Consequently, the abnormality of the encoder cannot be detected from the outside. In the above cases, a runaway of the apparatus and, further, a breakdown of the apparatus are eventually caused. Particularly, in the multi-rotation type absolute encoder of the memory backup type using a battery, there is a drawback such that if the content of the memory is interfered with a disconnection of the battery or the like, the amount of errors increases and a serious problem is caused.
It is an object of the invention to provide an encoder which can prevent a runaway and a breakdown of the apparatus by informing the occurrence of abnormality to the outside when an abnormality occurrs.
A first encoder of the invention comprises: an encoder main body for producing and outputting pulse signals of a plurality of phases in association with a linear movement or a revolution of an object; an abnormality detecting circuit for detecting an abnormality of the encoder main body and outputting an abnormality detection signal; and a gate circuit for receiving the pulse signal of a certain phase among the pulse signals, for outputting the pulse signal when the encoder main body is normal, and for inverting the pulse signal and outputting the inverted pulse signal when the abnormality detection signal is output.
A second encoder of the invention comprises: an encoder main body for producing and outputting pulse signals of a plurality of phases in association with a linear movement or a revolution of an object; an abnormality detecting circuit for detecting an abnormali
REFERENCES:
patent: 4079251 (1978-03-01), Osann, Jr.
patent: 4233592 (1980-11-01), Leichle
patent: 4600835 (1986-07-01), Ishida et al.
patent: 4678948 (1987-07-01), Schmitt
Hannaher Constantine
Kabushiki Kaisha Yaskawa Denki Seisakusho
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