JPH0315851B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an effective self-check mechanism applied to various photoelectronic switches such as transmission type, reflection type, and radiation type.

[Conventional technology and its problems]

In general, photoelectronic switches are used when the level when receiving light falls below the upper limit of the operating level due to optical axis misalignment or dirt on the lens surface, or when the level when not receiving light does not reach the lower limit of the operating level due to unnecessary reflections, unnecessary radiation, etc. In this case, sufficient detection function cannot be achieved. In order to prevent this, conventional optoelectronic switches were simply equipped with a margin display function, which required maintenance and inspection that took a lot of time and money, and if a malfunction was discovered late, Suddenly the automatic control device stopped,
Huge losses were often incurred.

[Problem to be solved by the invention]

The photoelectronic switch of the present invention, which was devised in view of the above circumstances, is designed to immediately issue an alarm and obtain an abnormal output when an abnormality is found in the level of light reception or non-reception with respect to the operating level. By providing a self-check function, the above-mentioned problems are solved.

To this end, in the present invention, in a photoelectronic switch equipped with a photoelectric conversion element, an amplifier, an output circuit, an output terminal, etc., a first comparison circuit that compares a received light signal with a lower limit light reception level and another upper limit lower than the lower limit light reception level are provided. A second comparison circuit that compares with the non-light receiving level, an OR circuit that receives both outputs of these comparison circuits as input, and a preset that uses the light reception signal as a counter input and resets by the high output of the OR circuit. The output of this preset counter is connected to a lighting circuit that controls the safety indicator light and an abnormality output circuit that outputs an abnormality, and when the count value of the preset counter reaches the preset value, an abnormality is output. In addition to doing
A method of flashing the safety indicator light was used.

[Effect]

For the two comparison circuits, lower and upper limits are determined as reference levels of the allowable range, and a range outside these, ie, an intermediate value, is judged to be in an unstable state. Further, the preset counter performs a function to increase the reliability value of the abnormal output, and is determined to be abnormal only after an unstable state is accumulated a predetermined number of times in succession.

〔Example〕

The configuration will be described in more detail below with reference to the drawings. 1 is a machine housing with a condensing lens on the front and a built-in level check circuit described below; 2 is a device connected to this level check circuit, and a stable area. This lamp (hereinafter referred to as a safety indicator lamp) is placed on the outer wall of the machine casing 1 to indicate that the safety indicator is on. Note that 3 is an operation indicator light that lights up when the signal is output, and 4 is one or more light emitting diodes (LEDs) that display the received light level at the time of detection.

Next, I will explain the configuration of the level check circuit.
a is a photoelectric conversion element such as a phototransistor,
b and b' are amplifiers for amplifying the light reception signal obtained from the photoelectric conversion element a, and c is an output circuit interposed between the amplifiers b and b' and the output terminal d. Also e,
e' is a comparison circuit connected to the amplifier b,
e is a first comparison circuit that determines whether the light reception level at the time of light reception (during operation) is equal to or higher than a predetermined lower limit value with respect to the operation level of the photoelectronic switch;
Reference numeral e' denotes a second comparison circuit that determines whether the light reception level during non-light reception (non-operation) is less than a predetermined upper limit value. In this embodiment, as shown in FIG. 2, if the predetermined operation level is 1, the reference level of the first comparison circuit is 2, and the reference level of the second comparison circuit is 0.5.

Subsequently, the outputs of these comparison circuits e and e' are input to an OR circuit f, and the output of this OR circuit f is connected to a reset terminal k of a preset counter j.
Then, the output of the preset counter j controls the lighting circuit g to turn on the safety indicator lamp 2.
Further, the abnormality output circuit h is driven to output a signal from the abnormality output terminal i. Note that the output of amplifier b' is connected to count input terminal l.

Note that a photoelectronic switch with these configurations detects light or heat from a detection object with a photoelectric conversion element a, and after amplifying this electric signal with amplifiers b and b',
Obtaining the detection output from the output terminal d via the output circuit c is the same as in the conventional photoelectronic switch of this type.

Next, the self-check function of the present invention uses comparison circuits e and e' to determine whether or not the light reception level when receiving light and when not receiving light satisfies predetermined requirements. Sometimes output circuit c
At the same time as the normal output is performed from the lighting circuit g
This keeps the safety indicator light 2 lit. On the other hand, due to optical axis misalignment, dirt on the lens surface, etc., the level when receiving light may not reach the lower limit value of comparator circuit e, or due to unnecessary reflection or unnecessary radiation, etc., the level when not receiving light may be lower than the lower limit of comparator circuit e'. When the value exceeds the upper limit of
The abnormality output circuit h operates and an abnormality output is sent from the abnormality output terminal i.

By the way, with only the above-mentioned configuration, each light reception signal is judged by the comparison circuits e and e', and if there is an abnormality each time, an abnormal output is performed. Even in this case, abnormal output will occur, resulting in a lack of reliability. Therefore, in the present invention, a preset counter j is provided between the OR circuit f, the lighting circuit g, and the abnormal output circuit h in the level check circuit, and its reset terminal k is connected to the output side of the OR circuit f, and the count input terminal l is connected to the output side of the OR circuit f. are connected to amplifier b′ respectively.

In other words, the preset counter j has a function to keep the display of the safety indicator light 2 lit during this period because the reset input continues from the reset terminal k when there is margin at the upper or lower limit of the received light level. I do. On the other hand, if the level of the received light signal deviates from the reference level of the two comparison circuits e and e', no reset input is performed;
Since the count input is integrated, when it reaches a preset value, the preset counter output is performed, and the lighting circuit g causes the safety indicator light 2 to flash to issue an alarm, and at the same time, an abnormality output is issued. The circuit h operates and an output is sent from the abnormal output terminal i (see Fig. 2).

〔Effect of the invention〕

As described above, the photoelectronic switch of the present invention has a self-check function for abnormalities in light reception and non-light reception levels, so that in the field, you can simply check the blinking state of the safety display. In addition, in remote locations, abnormal output operation allows early prediction of repair/inspection due to abnormality of the photoelectric switch or deterioration of the photoelectric element, eliminating the need for emergency repairs or sudden interruption of processes due to breakdowns. You can obtain the special effect of being In addition, since the preset counter is used to output the abnormality detection only after it continues for a certain period of time, it is possible to prevent the output from being caused by noise, etc., and this has the effect of increasing reliability. It became possible.

Furthermore, when installing a photoelectronic switch on-site, it is important to take into account optical axis misalignment for transmissive optoelectronic switches, and for reflective and radiation type switches, to ensure that the safety indicator light has a margin of light intensity due to the object on which it is mounted. It has many excellent advantages, including the fact that it can be confirmed immediately by lighting it up, and the position can be adjusted extremely easily during installation.

[Brief explanation of the drawing]

FIG. 1 shows the circuit section of the optoelectronic switch of the present invention, and FIG. 2 shows its waveform diagram. In addition, in the figure, 1...Machine housing, 2...Safety indicator light, a...Photoelectric conversion element, b, b'...Amplifier, c
...Output circuit, d...Output terminal, e, e'...Comparison circuit, f...OR circuit, g...Lighting circuit, h...
Output circuit, i...output terminal, j...preset counter.

Claims (1)

[Claims] 1. In a photoelectric switch equipped with a photoelectric conversion element, an amplifier, an output circuit, an output terminal, etc., a first comparison circuit that compares a received light signal with a lower limit light receiving level and an upper limit non-light receiving level that is lower than the lower limit light receiving level. a second comparison circuit, an OR circuit which receives both outputs of these comparison circuits as input, and a preset counter which receives the light reception signal as a counter input and is reset by the high output of the OR circuit, The output of this preset counter is connected to a lighting circuit that controls the safety indicator light and an abnormality output circuit that outputs abnormality, and when the count value of the preset counter reaches the preset value, it outputs abnormality and also outputs the safety signal. A photoelectronic switch characterized by a blinking indicator light.