JPH02285277A - Photoelectric switch equipped with mutual interference preventing function - Google Patents

Abstract

PURPOSE:To certainly operate mutual interference preventing function by directly inputting the signal from other switch to the light detection means of a photoelectric switch. CONSTITUTION:A photoelectric switch equipped with mutual interference preventing function contains the first and second switch circuits and the respective switch circuits emit pulse lights to the outside corresponding to the output signal of an oscillation circuit to receive said lights and the pulse cycle of the oscillation circuit is changed by a control circuit responding to a light detection signal immediately before the oscillation circuit generates a pulse. A means transmitting the drive state of the light emitting means of the first switch circuit is provided to the light detection means of the second switch circuit. Herein, the floodlight projector of one photoelectric switch 11 emits a floodlight signal from a window 21 to allow the same to be incident to the window 52 of the other photoelectric switch 11 and this light is reflected by mirror surfaces 53, 54 to be incident to the photodetector 5 of the other photoelectric switch 11. As mentioned above, by directly inputting the signal from the other switch to the light detection means of the photoelectric switch, mutual interference preventing function can be certainly operated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a photoelectric switch that turns on and off depending on the presence or absence of an object to be detected, and in particular, further strengthens the mutual interference prevention function that prevents mutual interference between multiple switches. This invention relates to a photoelectric switch with mutual interference prevention function.

[Prior Art] A pulse modulation type photoelectric switch employs a so-called synchronization gate method in which only the light receiving input synchronized with the light emitting pulse is extracted, and the light receiving input in other periods is prohibited. This method has the effect of preventing malfunctions against discontinuous noise light. However, when a plurality of photoelectric switches are arranged in parallel, malfunction may occur due to the influence of the projected light from other photoelectric switches. A photoelectric switch with a mutual interference prevention function that solved this problem was published in Japanese Patent Application Laid-Open No. 58-73.
This method is disclosed in Japanese Patent Publication No. 888 and Japanese Patent Application Laid-open No. 73889/1989.

FIG. 5 is a schematic block diagram showing the electrical configuration of a conventional photoelectric switch with a mutual interference prevention function. FIG. 6 is a signal waveform diagram at points A, B, and C shown in FIG. Next, a conventional photoelectric switch with a mutual interference prevention function will be described with reference to FIGS. 5 and 6. The photoelectric switch 1 includes a light emitting element 2. Light projecting element drive circuit 39 oscillation circuit 4. Light receiving element 5. A signal processing circuit 6 and an output circuit 7 are provided.

The light projecting element 2 is for emitting detection light to an object to be detected. The oscillation circuit 4 outputs a pulse signal. The light projecting element driving circuit 3 receives a pulse signal from the oscillation circuit 4 and drives the light projecting element 2 so that pulsed light synchronized with the pulse signal is emitted. The light receiving element 5 converts reflected light from an object to be detected into an electrical signal. Of the output signals of the light receiving element 5, the signal processing circuit 6
Shapes only signals with peak values above a certain level,
A pulse signal is output by a waveform shaping circuit that converts it into a rectangular wave, a gate circuit that extracts only the light receiving input synchronized with the light emitting pulse, an integrating circuit that integrates the light receiving signal extracted by the gate circuit, and an oscillation circuit 4. It also includes a control circuit that temporarily stops the pulse output of the oscillation circuit 4 when a light reception signal is applied immediately before. The output circuit 7 outputs a signal indicating that the target object has been detected to the cable 8 in response to a predetermined number of successive light reception signals counted by the integrating circuit included in the signal processing circuit 6. .

In the photoelectric switch shown in FIG. 5, the front of the light emitting element 2 is covered to prevent the light from the light emitting element 2 from entering the light receiving element 51; Assume that pulsed light is incident on the light receiving element 5.

The light reception signal of the light receiving element 5 is shown in FIG. 6(b).

Oscillation circuit 4 includes a capacitor 41. The signal waveform of the capacitor 41 is shown in FIG. 6(c). Capacitor 41 is photocharged to a predetermined voltage level and then discharged. During the discharge period, a pulsed current is applied to the light projecting element 2 so that pulsed light is emitted. The signals given to the light projecting element 2 are shown in FIG. 6(a).

The control circuit included in the signal processing circuit 6 detects the timing immediately before light emission based on the voltage level of the capacitor 41, and generates a light reception signal B1 immediately before light emission as shown in FIG. 6(b).
In response to the detection, the light emission timing is adjusted by temporarily stopping the photoelectric output of the capacitor 41 and making the light emission period T of the light emitting element 2 longer than the period TO when no light is received immediately before light emission. I'm trying to shift it.

In this way, when the light projected from another photoelectric switch is received, the operation of the oscillation circuit 4 is temporarily stopped, so the light projection timing is delayed and the timing of the projected light of the other photoelectric switch is delayed. It will generate pulsed light,
Therefore, there is less chance that the projected light beams overlap with each other. Therefore, the photoelectric switch 1 operates in accordance with the detection of the target object by the light from its own light projecting element 2 without being affected by the projection light of other photoelectric switches.

Note that there is a control circuit that speeds up the photoelectricity of the capacitor 41 to shorten the period of light projection. Waveform diagrams corresponding to FIGS. 6(a), (b) and (C) in this case are shown in FIGS. 7(a), (b) and (c).

[Problem WJ to be Solved by the Invention] By the way, it is assumed that the photoelectric switch having the above-mentioned mutual interference prevention function is arranged as shown in FIG. When the relationship between the photoelectric switches la and lb, the sensing object 10, and the background object 12 is as shown in FIG.
The light receiving element 5b of b is emitted from its own light projecting element 2b,
Two optical signals are received: the light M reflected by the background object 1-2, and the light emitted from the light projecting element 2a of the photoelectric switch 1a and reflected by the detection object 10.

In this way, when there is a background object 12 immediately behind the sensing object 10, the sensitivity adjustment volume (not shown) of the photoelectric switch is adjusted so that only the sensing object 10 can be detected. That is, as shown in FIG. 9, the background signal M caused by the light projection signal of the photoelectric switch 1b has a light incident detection level V.
2 and only when there is a sensing object 10, the input signal N of the photoelectric switch 1a exceeds V2 and the sensing object 10 is detected. make a clause

However, when a plurality of photoelectric switches are placed close to each other as shown in FIG. 8, the signal from the photoelectric switch 1a enters the light receiving element 5b of the photoelectric switch 2b, as described above. , the light reception level of the photoelectric switch 1b becomes L+M, which exceeds the above v2. At this time, if the signal exceeds the detection level v1 that activates the mutual interference prevention function of the photoelectric switch 1b, the photoelectric switch 1b
b's oscillation period changes and mutual interference can be prevented, but depending on how the sensitivity adjustment volume is adjusted and the position of the sensing object 10, the signal level may drop to the detection level V1 as shown in FIG.
may not exceed. In such a case, the mutual interference prevention function of the photoelectric switch 1b does not work, so the photoelectric switch 1b malfunctions.

Therefore, it is an object of the present invention to provide a photoelectric switch with a mutual interference prevention function in which the mutual interference prevention function works reliably.

[Means for Solving the Problems] A photoelectric switch with a mutual interference prevention function according to the present invention has the following features:
A pulse oscillation circuit that outputs a pulse signal, a light emitting means for emitting pulsed light to the outside according to the output pulse signal of the pulse oscillation circuit, and a light receiver for receiving light from the outside and outputting a light reception signal. and a control circuit that changes the pulse period of the pulse oscillation circuit in response to the generation of a light reception signal in the light reception means during a period immediately before the pulse generation of the pulse oscillation circuit. A first transmission means for transmitting light from the light emitting means of the photoelectric switch to another photoelectric switch, and a second transmission means for transmitting light from the other photoelectric switch to the light receiving means of the photoelectric switch. and a transmission means.

The photoelectric switch with mutual interference prevention function according to the present invention includes:
Each switch circuit includes a first and a second switch circuit, and each switch circuit includes a pulse oscillation circuit that outputs a pulse signal, and a light emitting unit that emits pulsed light to the outside in accordance with the output pulse signal of the pulse oscillation circuit. A light receiving means for receiving external light and outputting a light receiving signal, and a pulse period of the pulse oscillation circuit in response to a light receiving signal generated in the light receiving means in a period immediately before the pulse generation of the pulse oscillation circuit. and a transmission means for transmitting a signal representing a driving state of the light emitting means of the first switch circuit from the light emitting means of the first switch circuit to the light receiving means of the second switch circuit. Be prepared.

[Function] In this invention, since the light emitted from another switch used at the same time as the photoelectric switch or a signal based on the light is directly input to the light receiving means of the photoelectric switch, the mutual interference prevention function is ensured. Therefore, there is no possibility of malfunction.

[Embodiments of the Invention] In the following explanation of the embodiments, the electrical configuration of the photoelectric switch is the same as that shown in FIG. 5 except for the third embodiment, so the explanation will be omitted.

(1) First Embodiment FIGS. 1A and 1B are diagrams showing a photoelectric switch according to an embodiment of the present invention. In particular, FIG. 1A shows two photoelectric switches placed close to each other developed. FIG. 1B is a sectional view taken along line I B-I B shown in FIG. 1A. As shown in Figures 1A and 1B,
A box side 111 of the photoelectric switch 11 in which the light projecting element 2 is housed is provided with a window 21 for taking out the light of the light projecting element 2 to the outside. Side part 112 opposite to side part 111
A window 52. is provided for introducing light from the outside into the photoelectric switch 11. A cavity 50 serving as an optical path and a window 51 for providing the taken-in light to the light receiving element 5 are provided. An upper surface 53 of the cavity 50 inclined toward the window 52 and a lower surface 54 inclined toward the window 51 are mirror surfaces.

The light emitting signal output from the light emitting element 2 of one photoelectric switch 11 is emitted from the window 21, and the light emitting signal is emitted from the window 21 of the other photoelectric switch 11.
2. This light passes through the window 52, is reflected by the mirror surfaces 53 and 54, passes through the window 51, and enters the light receiving element 5 of the other photoelectric switch 11. With this configuration, it is possible to stably operate the mutual interference prevention function of the photoelectric switch.

Note that when the photoelectric switch 11 is used alone, a sticker is pasted on the windows 21 and 52 and removed only when necessary to prevent the influence of ambient light.

(n) Second Embodiment FIG. 2 is a diagram showing a photoelectric switch according to another embodiment of the present invention. In FIG. 2, the light emitting element 2a of one photoelectric switch lla and the light receiving element 5 of the other photoelectric switch 11b are shown.
b by an optical fiber 60, and the optical signal from the light emitting element 2a is directly transmitted to the light receiving element 5b. With this configuration, it is possible to stably operate the mutual interference prevention function of the photoelectric switch.

(m) Third Embodiment FIG. 3 shows a photoelectric switch according to still another embodiment of the present invention. In FIG. 3, one switch case 110 is provided with two switch circuits 11a and llb. A light projecting element drive signal from the light projecting element driving circuit 3a of one switch circuit 11a is electrically inputted via wiring 70 to the signal processing circuit 6b of the other switch circuit 11b.

By doing the second thing, the mutual interference prevention function of the photoelectric switch can work stably.

(IV) Fourth Embodiment FIG. 4 is a diagram showing an optical fiber type photoelectric switch to which the present invention is applied. In the case of a fiber optic photoelectric switch, unlike the photoelectric switches shown in Figures ffllA and 1B, the shapes of the light emitting part and the light receiving part are small.
As shown in FIG. 4, the shielding wall 80 between the light emitting element 2 and the light receiving element 5 can be arranged diagonally, so that the side part 111
By simply providing the windows 25 and 55 in and 112, respectively, the mutual interference prevention function can work stably.

Note that in each of the above embodiments, the photoelectric switch can be applied not only to a reflective type that detects reflected light from a sensing object, but also to a transmissive type that detects the presence or absence of transmitted light.

[Effects of the Invention] As described above, according to the present invention, light emitted from another switch used at the same time as the photoelectric switch or a signal based on the illumination can be directly input to the light receiving means of the photoelectric switch. Therefore, the mutual interference prevention function can be operated reliably, and malfunctions can be prevented.

[Brief explanation of drawings]

FIGS. 1A and 1B are diagrams showing a photoelectric switch according to a first embodiment of the present invention. FIG. 2 is a diagram showing a photoelectric switch according to a second embodiment of the invention. FIG. 3 is a diagram showing a photoelectric switch according to the m3 embodiment of the present invention. Fourth
The figure shows an optical fiber type photoelectric switch according to a fourth embodiment of the present invention. FIG. 5 is a schematic block diagram showing the electrical configuration of a conventional photoelectric switch with a mutual interference prevention function. Figure 6 shows A and B shown in Figure 5. It is a signal waveform diagram of 0 point. FIG. 7 is a signal waveform diagram of another conventional photoelectric switch. FIG. 8 is a diagram showing how a conventional photoelectric switch is used. FIG. 9 is a waveform diagram of a received signal of the photoelectric switch shown in FIG. 8. In the figure, 2, 2a and 2b are light projecting elements, 3.3a
and 3b are light emitting element drive circuits, 4, 4a and 4b are oscillation circuits, 5, 5a and 5b are light receiving elements, 6, 6a and 6b are signal processing circuits, 7.7a and 7b are output circuits, 11. lla and llb are photoelectric switches; 21.
25.51° 52 and 55 are windows, 53 and 54 are mirror surfaces, 60 is an optical fiber, and 70 is a wiring. 2nd name 3 concave 1A 40 6th 7th 8th

Claims (2)

[Claims] (1) A pulse oscillation circuit that outputs a pulse signal, a light emitting means for emitting pulsed light to the outside according to the output pulse signal of the pulse oscillation circuit, and a light emitting means that receives light from the outside and outputs a light reception signal. and a control circuit that changes the pulse period of the pulse oscillation circuit in response to a light reception signal generated in the light reception means during a period immediately before the pulse generation of the pulse oscillation circuit. A photoelectric switch with an interference prevention function, comprising: a first transmission means for transmitting light from the light emitting means of the photoelectric switch to another photoelectric switch; and a first transmission means for transmitting light from the light emitting means of the photoelectric switch to the light receiving means of the photoelectric switch. A photoelectric switch with a mutual interference prevention function, comprising a second transmission means for transmitting. (2) A photoelectric switch with a mutual interference prevention function having a first and a second switch circuit, the first and second switch circuits having a mutual interference prevention function.
Each of the switch circuits includes: a pulse oscillation circuit that outputs a pulse signal; a light emitting unit that emits pulsed light to the outside according to the output pulse signal of the pulse oscillation circuit; and a light emitting unit that receives light from the outside. a control circuit for changing the pulse period of the pulse oscillation circuit in response to the generation of the light reception signal in the light reception means during a period immediately before the pulse generation of the pulse oscillation circuit; further comprising a transmitting means for transmitting a signal representing a driving state of the light emitting means of the first switch circuit from the light emitting means of the first switch circuit to the light receiving means of the second switch circuit. Photoelectric switch with mutual interference prevention function.