JPS6291020A - 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 an incident pulse signal is shorter than the period of the irradiated light pulse so as to disregard the incident noise light next. CONSTITUTION:A projecting device 3 generates a projection beam in response to the irradiated light pulse having a prescribed period generated from a frequency divider 2. A light receiving 4 converts a received signal into an incident light pulse signal, which is sent to a gate circuit 10 and a gate control circuit 5. The gate circuit 10 uses the irradiated pulse to gate the incident light pulse signal sent from the light receiving 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 shorter than the period of the irradiated light pulse to form a gate signal compringing 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 shorter than the period of the irradiated light pulse is prevented.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a method for disposing a plurality of photoelectric switches in parallel, in which their own light emission pulse and noise light due to other photoelectric switches having a cycle shorter than that of the light emission pulse are combined. 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 caused by a thin light source 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, with the above technology, it is possible to eliminate noise light when a photoelectric switch is used alone, but as shown in Figure 4, it is possible to continuously detect the position of an object by arranging multiple photoelectric switches in parallel. In this case, if the light projection range of the light emitting parts LT and 2T of the photoelectric switches A and B and the light receiving range of the light receiving parts IR and 2R are wide, even though the photoelectric switch A has not detected the detected object 3. First, the light emitting part 2T of the photoelectric switch B
The light from is reflected by the detected object 3, and the photoelectric switch A
The light is incident on the light receiving section IR. And the light projector IT.

The 2T emits pulsed light with different periods, but the pulse periods are often similar, so the timing of the pulsed light from the light projector IT and 2T may overlap completely. In that case, a detection signal is output even though the pulsed light from its own light projecting unit is not received. In this case, the influence of the projected light from other photoelectric switches cannot be eliminated using only the synchronous gate method.

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

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 If the initial operating conditions are changed even slightly due to conditions such as the direction of entry into the sensitive area, there is a drawback that the operation will be similarly inconvenient.

As another countermeasure, if multiple light emitting units are placed side by side,
Another idea is to shift the light projection timing so that these light beams do not emit light at the same time and sequentially emit light, 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 to solve 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 basic clock pulse, and a frequency division of the clock pulse generated by the oscillator 1,
A frequency divider 2 that generates a light emission pulse with a constant repetition cycle; a light projector 3 that generates a projected beam according to the light emission pulse with a constant repetition cycle created by the frequency divider 2; and a received signal. a light receiving section 4 that converts the incident light pulse signal into an incident light pulse signal and transmits the incident light pulse signal to the gate circuit 10 and the gate control circuit 5; and gates the large light pulse signal transmitted from the light receiving section 4 with a light emission pulse. If the period of the incident light pulse signal converted by the gate circuit 10 and the light receiving section 4 is shorter than the repetition period of the light emitting pulse, the period of the light emitting pulse is predicted before the incident light pulse and the light emitting pulse overlap each other. A gate control 1 circuit 5 which creates a gate signal consisting only of pulses with a period that is a natural number multiple of , and closes the gate of the gate circuit 10 with the gate signal; It is characterized by noise prevention.

[Effect]

According to the above configuration, for example, how does it work when the photoelectric switch of the present invention whose light emission repetition period is 14 clock pulses and another photoelectric switch whose light emission repetition period is 11 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 using a pulse b that is delayed by approximately 3 clocks from 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 r generated by 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 r from another photoelectric switch overlap. Here, the number of clocks by which the pulse b lags behind the light emitting pulse e is set in consideration of the difference in period between the photoelectric switches arranged in parallel.

〔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 rc, etc. 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.

Reference numeral 4 denotes a light receiving section that converts the received optical signal into an incident light pulse signal r.

5 is a gate control circuit, which includes an inverter 6 that inverts the incident light 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 which uses the output pulse d of the frequency divider 2 as a clock input as well as a set input;
It consists of a D-type flip-flop 9 which receives an inverted signal of the output pulse d as a clock input.

Here, the D-type flip-flop 8.9 may be constructed with another type of flip-flop 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 ND gate 12 inputs the pulse inverted by 6, an AND gate 13 inputs the output pulse of the ND gate 12 and the incident light pulse f, and an output pulse of the 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;
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 with a period different from that of the emitted light pulse e is received, the above-mentioned OR which inputs the inverted signal of the large 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 that goes to a high level at the rising edge of the inverted pulse of the pulse d, and goes to a low level at the next rising edge. i
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 shorter period 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.

This output signal i and pulse C are given to the NOR gate 15, so the output waveform becomes j. That is, the emission pulse e
It was possible to create a pulse J that excludes only the pulses that are output during the period in which the period pJl(7) pulse, which is shorter than the light emission pulse e, is 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. In other words, the output of this AND gate 12 and the large optical pulse "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 pulses of this AND game 1-13 are
Since the output pulse d of the frequency divider 2 is applied to the clock terminal of the flop 14 and the reset terminal, an output signal having a predetermined pulse width can be obtained from the own incident light pulse.

The pulse j created above and the output signal of the flip-flop 14 are input to the AND gate of the integrating circuit 17 at the next stage, 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, in the present invention, a pair of photoelectric switches with different light emission pulse cycles are arranged in parallel, and self-light emission is achieved.

The overlap between a pulse and an incident light pulse signal with a shorter cycle than its own emission pulse is detected by the emission pulse immediately before the overlap, and the next incident light pulse signal, that is, the incident light signal in the period in which they overlap is ignored, and the This makes it possible to prevent malfunctions caused by light projected by other photoelectric switches, and also to detect only incoming light pulse signals that are synchronized with the own light emission pulse, eliminating light noise caused by other light sources. , it is possible to detect only the incident light signal due to its 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 easier to align the optical axes. This makes it possible to provide large photoelectric switches.

[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 wholesale circuit, 10: Gate circuit. Procedural amendment October 13, 1988 Commissioner of the Japan Patent Office Black 1) Yu Akira 1, Indication of the case Japanese Patent Application No. 1988-232212 2, Name of the invention Photoelectric switch 3, Person making the amendment Relationship to the case: Patent Applicant Reed Electric Co., Ltd. 4, attorney 5, date of amendment order voluntary 6, subject to amendment. 2) On page 2, line 12 of the specification, the phrase "...predicting the superposition of pulses immediately before they overlap..." has been replaced with "...predicting 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, it says "...inverter 16 in series in multiple stages or with a capacitor and resistor" instead of "...inverter] 6 in series in multi-stage configuration or in capacitor. and resistance.'' 6) On page 10 of the specification cylinder, line 20, 100, the phrase ``As the structure is as described above,...'' is corrected to ``As the structure is as described above,...''. 7) In the 20th line of page 12 of the specification, amend the phrase [...because it is done, it is my own] to "...it is my own because it is done". 8) On the 4th line of page 14 of the specification tube, there is a line that 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 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; , when the period of the light input pulse signal converted by the gate circuit gated by the light emission pulse and the light receiving section is shorter than the repetition period of the light emission pulse, the light input pulse and the light emission 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 shorter than the repetition period of the light emission pulse. A photoelectric switch that prevents light incident noise. Figure 1

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 shorter 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 shorter than the repetition period of the light emission pulse. A photoelectric switch that prevents periodic light incident noise.