Electricity: measuring and testing – Electrical speed measuring
Patent
1997-08-08
1999-12-14
Oda, Christine K.
Electricity: measuring and testing
Electrical speed measuring
25023114, G01P 342
Patent
active
060022493
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a rotation detection sensor for detecting a rotation stopped condition of a rotatable body, and in particular to a sensor technology for detecting such a rotation stopped condition of a rotatable body using a light beam.
BACKGROUND OF THE INVENTION
A conventional rotation detection sensor for detecting a rotation stopped condition of a rotatable body using a light beam comprises a single optical sensor and a rotatable disk (referred to hereunder simply as a disk) with an outer peripheral portion thereof having approximately equal width transparent portions which pass a light beam and opaque portions which do not pass a light beam. The optical sensor has a light source which generates an AC light beam by means of an AC signal from a signal generator, and a light receiving element for receiving the light beam from the light source, positioned facing each other on opposite sides of the outer peripheral portion of the disk, and generates from an output circuit, an output signal corresponding to a light received output from the light receiving element.
With such a construction, when the disk is rotating, the transparent portions and the opaque portions alternately intersect the light beam. Since the widths of the transparent portions and the opaque portions are approximately the same, then the output from the light receiving element of the optical sensor has an output form with a high level condition and a low level condition appearing alternately at approximately even interval following to the passing of the transparent portions and the opaque portions with rotation of the disk. Since the light source is driven by an AC signal from the signal generator, then in the case where the signal frequency of the signal generator is substantially higher than the rotational speed of the disk, the output signal from the optical sensor in the high level interval where the light beam is received, becomes an AC signal which is switched at the signal frequency of the signal generator.
When the disk stops rotating, then either a transparent portion or an opaque portion is positioned in the optical path of the light beam. Consequently, the output condition of the optical sensor is fixed at either a high level condition or a low level condition.
In this arrangement, when the disk stops rotating, an indicator lamp is illuminated, for example, for advising personnel that the vicinity of the disk is "not dangerous". In order to illuminate the indicator lamp with an output signal from the optical sensor, when the disk has stopped, a light beam is passed so that the output signal from the optical sensor becomes a high level condition, the indicator lamp can be illuminated directly by the output energy from the optical sensor. However, the disk will not always stop at a position where the light beam is passed. In the case where the disk stops at a position where the light beam is shut off, then the indicator lamp cannot be illuminated directly by the output signal from the optical sensor.
Therefore, it has been proposed that a rotation detection sensor has two indicator lamps, one having the output signal from the optical sensor input directly thereto, and the other having the output signal from the optical sensor input via a NOT circuit thereto, so that when the disk stops, one or the other of the two indicator lamps is continuously illuminated. In this case, when the disk is rotating the two indicator lamps flash alternately.
It has also been proposed that a rotation detection sensor has a circuit configuration with a single indicator lamp, which is devised such that the indicator lamp is continuously illuminated when the disk stops.
More specifically, the circuit configuration is such that a light received output from an optical sensor is rectified by a rectifying circuit, and a rectified output therefrom is then input to an on-delay circuit via a NOT circuit. An indicator lamp is then illuminated by an output from the on-delay circuit. The rectifying circuit in this case
REFERENCES:
patent: 5345138 (1994-09-01), Mukaidono et al.
patent: 5568131 (1996-10-01), Sakai
patent: 5619110 (1997-04-01), Sugimoto
Oda Christine K.
The Nippon Signal Co. Ltd.
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