JPS6291019A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent malfunction by forecasting it before an incident light pulse and an irradiated light pulse are overlapped when the period of the incident light pulse signal is longer than the period of the irradiated light pulse so as to neglect a noise light incident next. CONSTITUTION:A projecting section 3 generates a projected light beam in response to the irradiated light pulse having a prescribed period formed by a frequency divider 2. A light receiving section 4 converts the received signal into the incident light pulse signal and gives the result to a gate circuit 10 and a gate control circuit 5. The gate circuit 10 uses an irradiated light pulse so as to gate the incident light pulse signal from the light receiving section 4, and the gate control circuit 5 forecasts it before the incident light pulse and the irradiated light pulse are overlapped when the period of the incident light pulse signal is longer than the period of the irradiated light pulse to form a gate signal comprising pulses of the period being a natural number of multiple of the period of the irradiated light pulse thereby closing the gate of the gate circuit 10. Thus, the incident light noise having the period longer than the period of the irradiated light is prevented.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention, when a plurality of photoelectric switches are arranged side by side, can combine their own light emitting pulse with noise light caused by other photoelectric switches having a period longer than the period of this light emitting pulse. The present invention relates to a photoelectric switch that prevents malfunction by predicting the superposition of pulses immediately before the superposition of pulses and ignoring the noise light that enters next.

[Conventional technology]

Conventionally, in pulse-modulated light type photoelectric switches, the technology to prevent noise light from other light sources is to extract only the received light pulse input that is synchronized with the emitted light pulse and ignore the received light input that enters other periods. There is a gate method, which is effective against discontinuous noise light.

[Problem that the invention seeks to solve]

However, the above technology is photoelectric switch.

When using the switch alone, it is possible to eliminate noise light, but
As shown in FIG. 4, when a plurality of photoelectric switches are arranged side by side to continuously detect the position of an object to be detected, photoelectric switches A,
B's light projecting part IT, 2T's light projection range and light receiving part IR,
If the light receiving range of 2R is wide, even though the photoelectric switch A has not detected the detected object 3, the light from the light emitting part 2T of the photoelectric switch B will be reflected by the detected object 3, and the light will not reach the photoelectric switch. The light enters the light receiving section IR. And the light projector IT.

Pulsed light with different periods is projected from each 2T, but the periods of the pulses are often similar. In this case, a detection signal is output even though it does not receive the pulsed light from its own light emitter.In this case, the influence of the light projected by other photoelectric switches is affected by the synchronous gate method. cannot be eliminated alone.

Specifically, the operation of this conventional example will be explained by taking as an example a case where a photoelectric switch whose light emission repetition period is 11 clock pulses and a photoelectric switch whose light emission repetition period is 14 clock pulses are juxtaposed in close proximity.

When photoelectric switches such as those described above are arranged side by side, pulses of different periods will inevitably overlap at some point, as shown in FIG. If pulsed light from another photoelectric switch is received at the position of these overlapping pulses, the detected object will be detected even though the object to be detected is not detected.

For this reason, conventionally, the light emitter IT, 2T and the light receiver IR, 2
It has been considered to narrow the light projection range and light reception range of R so that the projection light from another photoelectric switch does not enter the light receiving section of another photoelectric switch. However, with so-called transmission-type photoelectric switches, it becomes difficult to align the optical axes of the corresponding light emitter and light receiver.
If the optical axis shifts even slightly due to vibration or shock, there is a drawback that it will cause inconvenience in operation.In addition, in the case of a so-called reflective photoelectric switch that uses reflected light, the roughness of the surface of the detected object 3 There is a drawback that if the initial operating conditions are changed even slightly depending on conditions such as the direction of entry into the sensitive area, the operation will be similarly inconvenient.

As another countermeasure, if multiple light emitting units are placed side by side,
Another idea is to sequentially emit light by shifting the light emitting timing so that they do not emit light at the same time, and to provide a gate circuit that selectively passes only the light reception signal at the corresponding timing to avoid mutual influence. However, a control circuit is required to shift the light emission timing and emit light sequentially, and an electrical connection is required to transmit a synchronization signal from this control circuit to each light emitting/receiving section, so the configuration is difficult. In addition to being complicated and requiring troublesome adjustment work, there is also the disadvantage that each photoelectric switch cannot be used independently.

The present invention solves the above-mentioned problems and has a light receiving range that allows easy adjustment of the optical axis, but does not require mutual electrical connection when multiple photoelectric switches are arranged side by side, and does not rely on the projection light of other photoelectric switches. The object of the present invention is to provide a photoelectric switch that can eliminate the influence and prevent malfunctions.

Means for Solving the Problems] The present invention that achieves this object will be explained based on the conceptual diagram of FIG. That is, a pulse oscillator 1 that generates a reference clock pulse, and a clock pulse generated by the oscillator 1 that is frequency-divided,
A frequency divider 2 that creates a light emission pulse with a constant repetition period; a light projector 3 that generates a light beam in accordance with the light emission pulse with a constant repetition period created by the frequency divider 2; a light receiving section 4 that converts the incident light pulse signal into a light pulse signal and transmits the incident light pulse signal to the gate circuit 10 and the gate control circuit 5; and a gate circuit that gates the incident light pulse signal transmitted from the light receiving section 4 with a light emission pulse. 10, if the period of the incident light pulse signal converted by the light receiving section 4 is longer than the repetition period of the light emitting pulse, the natural period of the light emitting pulse is predicted before the incident light pulse and the light emitting pulse overlap each other. A gate control circuit 5 that creates a gate signal consisting only of pulses with a period several times as large as that of the gate signal, and closes the gate of the gate circuit 10 using the gate signal; It is characterized by

[Effect]

According to the above configuration, how does it work when the photoelectric switch of the present invention whose light emission repetition period is, for example, 11 clock pulses and another photoelectric switch whose light emission repetition period is 14 clock pulses are juxtaposed in close proximity? Explain.

That is, the frequency divider 2 divides the frequency of the clock pulse generated by the pulse oscillator 1 as shown in FIG. The gate control circuit 5 detects the presence or absence of an incident light pulse signal f at a pulse b which is approximately 3 clocks ahead of this emission pulse e, and when the generation of an incident light pulse signal f is detected, the gate control circuit 5 detects the presence or absence of an incident light pulse signal f at the time of outputting the next emission pulse. A single pulse i having a pulse width equal to the period of the light emitting pulse e is created by predicting that the large light pulse f from another photoelectric switch will definitely overlap. If the gate circuit 10 is controlled using this single pulse i as a gate pulse, it becomes possible to ignore incident light information during the period when the self-emission pulse e and the incident light signal f from another photoelectric switch overlap. Here, the number of clocks by which the pulse b precedes the light emitting pulse e is set in consideration of the difference in the periods of the photoelectric switches arranged side by side.

〔Example〕

The photoelectric switch according to the present invention will be explained in more detail with reference to the circuit diagram of one embodiment shown in FIG. 2 and the operation waveform diagram of each part shown in FIG.

1 is a pulse oscillator that generates a reference clock pulse a.

2 inputs the clock pulse a and the reset pulse, starts operation by the reset pulse, divides the clock pulse a, and generates four types of pulses of the same period, b, c, d, as shown in FIG. This is a frequency divider that outputs e, and is composed of a hexadecimal counter IC and the like. Then, the setting of the counter advance number is changed in accordance with the cycle of the photoelectric switches arranged in parallel with each other.

Reference numeral 3 denotes a light projecting section which uses the output pulse e of the frequency divider 2 as a light emission pulse.

4 is a light receiving section that converts the received optical signal into a large optical pulse signal f.

5 is a gate control circuit, which includes an inverter 6 that inverts the large optical pulse signal f, an OR gate 7 that receives the inverted output and the output pulse b of the frequency divider 2, and an output pulse g of the OR gate 7. A D-type flip-flop 8 receives the output pulse d of the frequency divider 2 as the clock input, and the output of this D-type flip-flop 8 takes the D input, and the inverted signal of the output pulse d is used as the clock input. It consists of a D-type flip-flop 9 as an input.

Here, the D-type flip-flops 8 and 9 may be constructed of other types of flip-flops such as a J-type flip-flop.

Reference numeral 10 denotes a gate circuit which receives the output pulse e of the frequency divider 2, that is, the light emission pulse e, and outputs the output pulse and the light emission pulse e of the delay circuit 11, which is configured in series with a multi-stage structure or is composed of a capacitor and a resistor. Inverter 1
An AND gate 12 receives as input the pulse inverted by 6, an AND gate 13 receives as input the output pulse of this AND gate 12 and the incident light pulse f, and uses the output pulse of this AND gate 13 as a clock input. and a D-type flip-flop 14 whose reset input is the output pulse d of the frequency divider 2, and an N-type flip-flop whose inputs are the output pulse i of the flip-flop 9 and the output pulse C of the frequency divider 2.
It consists of an OR gate 15.

Reference numeral 17 denotes an integrating circuit, which is composed of a digital circuit and counts the output pulses of the gate circuit 10, and is a circuit having a configuration commonly used at present. Also, a linear circuit composed of a resistor and a capacitor may be used, but a digital circuit is better in order to make it compact.

With the above configuration, when an incident light pulse signal f having a period different from that of the emission pulse e is received, the above-mentioned OR which inputs the inverted signal of the incident light pulse f and the output pulse b of the frequency divider 2 Gate 7 outputs a single pulse like waveform g. This pulse g is given to the cent input of the D-type flip-flop circuit 8, and the output pulse d of the frequency divider 2 is given to the clock input, so that the pulse h of the output of the D-type flip-flop 8 is It becomes high level at the falling edge of pulse g, and becomes low level at the falling edge of the inverted signal of pulse d. A D-type flip-flop circuit 13 which receives this pulse h as an input and receives an inverted pulse of the output pulse d as a clock input has a pulse i which becomes high level at the rising edge of the inverted pulse d and becomes low level at the next rising edge.
Output.

That is, in order to ignore light information during a period in which the light emitting pulse e and the light incident pulse f having a period longer than the light emitting pulse e overlap, a single pulse i having a pulse width of the period of the light emitting pulse e is created. do.

Since this output signal 2 i and pulse C are given to the NOR gate 15, the output waveform becomes j. That is, it was possible to create a pulse j that excludes only the pulses that are output during a period in which the light emission pulse e and a pulse with a longer period than the light emission pulse e are predicted to overlap.

Next, the delayed pulse obtained by delaying the emitted light pulse e for a very short time in the delay circuit 11 and the inverted signal of the emitted light pulse e are given to the AND gate 12, so that the level becomes high at the fall of the emitted light pulse e, and the delayed pulse e is The repetition period is a light emitting pulse e with an extremely short pulse width that reaches a low level at the falling edge.
The AND gate 12 outputs the same waveform as . By delaying and reducing the pulse width in this manner, it is possible to detect the falling edge of the pulse that enters light slightly later than the emission pulse e, and to eliminate the influence of ambient light. That is, the output of this AND gate 12 and the large optical pulse f are AN
Since it is applied to the D gate 13, it is possible to detect the falling edge of the incident light pulse signal that is synchronized with its own light emitting pulse e.

The output pulse of this AND gate 13 is connected to the clock terminal of the D-type flip-flop 14, and the output pulse d of the frequency divider 2
Since it is applied to the recent terminal, an output signal having a predetermined pulse width can be obtained from the own large optical pulse.

The generated pulse J and the output signal of the flip-flop 14 are input to the AND gate of the next-stage integration circuit 17, this output is counted digitally, and this counted signal is passed through the waveform shaping circuit 18. The output circuit 19 outputs a detection signal of the object to be detected.

〔Effect of the invention〕

As described above, the present invention arranges a pair of photoelectric switches whose emission pulses have different periods, and detects when their own emission pulse overlaps with an incoming light pulse signal whose period is longer than that of their own emission pulse immediately before they overlap. It is possible to prevent malfunctions caused by the projected light of the other photoelectric switch by detecting the light emission pulse of the other photoelectric switch and ignoring the next light incident pulse signal, that is, the light incident signal of the mutually overlapping period. Since it is possible to detect only the incident light pulse signal that is synchronized with the light source, it is possible to eliminate noise light caused by other light sources and to detect only the incident light signal caused by the own light emission pulse.

Furthermore, since only the incident light information for the light emission pulse during the period that actually causes malfunction among the noise light is ignored, the detection accuracy can be improved without slowing down the response time.

Furthermore, for the above reasons, there is no need to narrow the light emitting and light receiving ranges, making it easy to align the optical axes, and when multiple photoelectric switches are arranged side by side, there is no need for electrical connection between them, which is a great effect. This makes it possible to provide a photoelectric switch.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an overview of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the invention, Fig. 3 is an operation waveform diagram of each part of the embodiment of the invention, and Fig. 4 is a conventional example. The schematic diagram shown in FIG. 5 is an operation waveform diagram of a conventional example. 1: Pulse oscillator, 2: Frequency divider, 3: Light emitter, 4: Light receiver, 5: Gate control circuit, 10: Gate circuit. Procedural amendment October 13, 1988 Commissioner of the Patent Office Black 1) Akio Yu 1, Indication of the case Japanese Patent Application No. 1988-232211 2, Name of the invention Photoelectric switch 3, Person making the amendment Relationship with the case 2 Patent Applicant Reed Electric Co., Ltd. 4, agent 5, date of amendment order spontaneous 6, claims of the specification to be amended, column for detailed description of the invention, and drawings. 7. Contents of correction. 2) On page 2 of the specification, line 12, the phrase "...predicts the superposition of pulses immediately before they overlap..." is replaced with "...predicts that the pulses will overlap immediately before they overlap..."・” is corrected. 3) Correct "detected object 3" on lines 9 and 11 on page 3 of the specification and lines 2 to 3 on page 5 to read "object D". 4) On the 6th line of page 7 of the specification, it is written that ``Light emission pulse...
.'' is corrected to ``The light emission pulse consists of...''. 5) In the second to third lines of page 10 of the specification, the phrase ``...inverter 16 is configured in multiple stages in series or with a capacitor and a resistor'' is replaced with ``...inverter 16 is configured in multiple stages in series or with a capacitor and resistor''. "With resistance," I corrected. 6) In the 20th line of page 10 of the specification cylinder, the phrase "Because of the above structure,..." is corrected to "Because of the above structure,...". 7) In the 20th line of page 12 of the specification, amend the phrase ``...because it is my own'' to ``...because it is my own.'' 8) On page 12, number 20 of the specification, it says "detection system",
Correct it as "detection accuracy". 9) Amend the drawings as shown in the attached attachment. 2. Claims (1) A pulse oscillator that generates a reference clock pulse;
A frequency divider that divides a reference clock pulse generated by the pulse oscillator to create a light emission pulse with a constant repetition period; and a frequency divider that creates a light emission pulse with a constant repetition period created by the frequency divider. A light emitting part that generates light, a light receiving part that converts the received light signal into an incident light pulse signal and transmits the incident light pulse signal to a gate circuit and a gate control circuit, and a large light pulse signal transmitted from the light receiving part. , when the period of the incoming light pulse signal converted by the gate circuit gated by the light emitting pulse and the light receiving section is longer than the repetition period of the light emitting pulse, the incoming light pulse and the light emitting pulse are predicted before they overlap each other. , a gate control circuit that creates a gate signal consisting only of pulses with a period that is a natural number multiple of the period of the light emission pulse, and closes the gate of the gate circuit with the gate signal; and a repetition period longer than the repetition period of the light emission pulse. A photoelectric switch that prevents light incident noise.

Claims (1)

[Claims] (1) A pulse oscillator that generates a reference clock pulse;
A frequency divider that divides the reference clock pulse generated by the pulse oscillator to create a light emission pulse with a constant repetition period; and a frequency divider that creates a light emission pulse with a constant repetition period created by the frequency divider. a light emitting section that generates light; a light receiving section that converts the received light signal into an incident light pulse signal and transmits the incident light pulse signal to a gate circuit and a gate control circuit; , a gate circuit that gates with the light emission pulse; and when the period of the incident light pulse signal converted by the light receiving section is longer than the repetition period of the light emission pulse, predicting the incident light pulse and the light emission pulse before they overlap each other; , the gate control circuit generates a gate signal consisting only of pulses with a period that is a natural number multiple of the period of the light emission pulse, and closes the gate of the gate circuit with the gate signal, and the repetition period is longer than the repetition period of the light emission pulse. A photoelectric switch that prevents periodic light incident noise.